Optical sheet, sheet article, polarizing plate, touch panel member, display device, method for selecting optical sheet, and method for manufacturing optical sheet

Abstract

This optical sheet includes a first surface and a second surface facing the first surface. The optical sheet includes a base material layer and a functional layer in order from the second surface to the first surface. The functional layer includes a cured product of a curable resin composition, and an ultraviolet absorber. The spectral transmittance at a wavelength of 380 nm is 1% or less. The spectral transmittance at a wavelength of 440 nm is 70% or more. An indentation hardness HA1 at a first position in a cross section of the functional layer, an indentation hardness HA2 at a second position in the cross section of the functional layer, and an indentation hardness HA3 at a third position in the cross section of the functional layer satisfy the following relationships. The first position is located in a surface layer part close to the first surface in the cross section. The third position is located in a surface layer part close to the second surface in the cross section. The second position is located midway between the first position and the second position. HA3 < HA2 < HA1 HA1 / HA2 ≤ HA2 / HA3

Description

Optical sheet, sheet article, polarizing plate, touch panel member, display device, method for selecting optical sheet, and method for manufacturing optical sheet

[0001] The present disclosure relates to an optical sheet, a sheet article, a polarizing plate, a touch panel member, a display device, a method for selecting an optical sheet, and a method for manufacturing an optical sheet.

[0002] Patent Documents 1 and 2 disclose optical sheets including a functional layer. The functional layer includes a cured product of an ultraviolet-curable resin composition. The functional layer functions as a so-called hard coat layer. The functional layer imparts high hardness to the surface of the optical sheet. The optical sheet including the functional layer can be incorporated into various display devices. By using an optical sheet including the functional layer, it is possible to suppress the occurrence of scratches due to rubbing.

[0003] In Patent Documents 1 and 2, the functional layer is further provided with a blue light blocking function. Blue light can increase the strain and fatigue of the viewer, such as eye strain. Blue light can also deteriorate the polarizers of liquid crystal display panels and the EL elements of organic EL display panels.

[0004] The functional layer described in Patent Document 1 contains a yellow pigment. The yellow pigment can absorb some blue light. However, the yellow pigment cannot provide the optical sheet with sufficient blue-cutting functionality. Furthermore, an optical sheet containing a yellow pigment changes the color of an image observed through the optical sheet.

[0005] The functional layer described in Patent Document 2 contains an ultraviolet absorber. The ultraviolet absorber can absorb blue light. The functional layer described in Patent Document 2 blocks light of about 410 nm as blue light. Therefore, problems caused by blue light can be suppressed.

[0006] In Patent Document 2, an ultraviolet absorber that exhibits blue light blocking function is contained in an ultraviolet curable resin composition. The ultraviolet absorber can absorb ultraviolet light when a coating film of the curable resin composition is exposed to ultraviolet light. Therefore, ultraviolet irradiation of the coating film is inhibited, and the functional layer is not sufficiently cured.

[0007] Patent Document 1: JP6641105B Patent Document 2: JP6696562B

[0008] The present disclosure aims to improve the hardness of an optical sheet including a layer containing a cured product of a curable resin composition and an ultraviolet absorber.

[0009] an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on the cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer satisfy the following relationships: HA3 < HA2 ≦ HA1 HA1 / HA2 ≦ HA2 / HA3 The first position is located in a surface layer portion close to the first surface on the cross section, and the third position is located in a surface layer portion close to the second surface on the cross section, The second position is located at the center between the first position and the third position.

[0010] The sheet article according to the first embodiment of the present disclosure includes a plurality of optical sheets according to the first embodiment of the present disclosure.

[0011] The polarizing plate according to the first embodiment of the present disclosure includes: an optical sheet according to the first embodiment of the present disclosure; and a polarizer superimposed on the optical sheet.

[0012] The touch panel member according to the first embodiment of the present disclosure includes: an optical sheet according to the first embodiment of the present disclosure; and an electrode layer superimposed on the optical sheet.

[0013] The display device according to the first embodiment of the present disclosure includes: an optical sheet according to the first embodiment of the present disclosure; and a display element superimposed on the optical sheet.

[0014] A method for selecting an optical sheet according to a first embodiment of the present disclosure relates to an optical sheet including a first surface and a second surface opposite to the first surface, the optical sheet comprising, in order from the second surface to the first surface, a base layer and a functional layer, the functional layer including a cured product of a curable resin composition and an ultraviolet absorber, the method comprising the steps of measuring a spectral transmittance at a wavelength of 380 nm and a spectral transmittance at a wavelength of 440 nm, measuring an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on the cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer, and selecting an optical sheet based on the measured spectral transmittance and the measured indentation hardness, wherein the first position is located on a surface portion close to the first surface on the cross section, the third position is located on a surface portion close to the second surface on the cross section, and the second position is located at the center between the first position and the third position.

[0015] A method for manufacturing a first optical sheet according to a first embodiment of the present disclosure includes the steps of: preparing an optical sheet, the optical sheet including a first surface and a second surface opposite to the first surface, the optical sheet including a base layer and a functional layer in that order from the second surface toward the first surface, the functional layer including a cured product of a curable resin composition and an ultraviolet absorber; and selecting an optical sheet based on a spectral transmittance at a wavelength of 380 nm, a spectral transmittance at a wavelength of 440 nm, an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on a cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer, wherein the first position is located on a surface portion close to the first surface on the cross section, the third position is located on a surface portion close to the second surface on the cross section, and the second position is located at the center between the first position and the third position.

[0016] A method for manufacturing a second optical sheet according to the first embodiment of the present disclosure includes the steps of: applying a first curable resin composition containing an ultraviolet absorber onto a substrate film; curing the coating of the first curable resin composition to form a first portion on the substrate film; applying a second curable resin composition onto the first portion; and curing the coating of the second curable resin composition to form a second portion bonded to the first portion.

[0017] An optical sheet according to a second embodiment of the present disclosure comprises: a first layer; and a second layer adjacent to the first layer; the first layer includes a cured product of a curable resin composition and an ultraviolet absorber; a thickness ratio of 1.5 or more and 7.5 or less; the thickness ratio being the ratio of the thickness (μm) of the first layer to the thickness (μm) of the second layer; a spectral transmittance at a wavelength of 410 nm of 15% or less; and a spectral transmittance at a wavelength of 440 nm of 70% or more.

[0018] The sheet article according to the second embodiment of the present disclosure includes a plurality of optical sheets according to the second embodiment of the present disclosure.

[0019] A polarizing plate according to a second embodiment of the present disclosure includes: an optical sheet according to a second embodiment of the present disclosure; and a polarizer superimposed on the optical sheet.

[0020] A touch panel member according to a second embodiment of the present disclosure includes: an optical sheet according to a second embodiment of the present disclosure; and an electrode layer superimposed on the optical sheet.

[0021] A display device according to a second embodiment of the present disclosure includes: an optical sheet according to a second embodiment of the present disclosure; and a display element superimposed on the optical sheet.

[0022] A method for selecting an optical sheet according to a second embodiment of the present disclosure relates to an optical sheet comprising a first layer and a second layer adjacent to the first layer, wherein the first layer comprises a cured product of a curable resin composition and an ultraviolet absorber, and includes the steps of measuring a thickness ratio which is the ratio of the thickness (μm) of the first layer to the thickness (μm) of the second layer; measuring a spectral transmittance at a wavelength of 410 nm; measuring a spectral transmittance at a wavelength of 440 nm; and selecting an optical sheet based on the thickness ratio, the spectral transmittance at a wavelength of 410 nm, and the spectral transmittance at a wavelength of 440 nm.

[0023] A method for manufacturing a first optical sheet according to a second embodiment of the present disclosure includes the steps of: producing an optical sheet comprising a first layer and a second layer adjacent to the first layer, wherein the first layer comprises a cured product of a curable resin composition and an ultraviolet absorber; and selecting an optical sheet based on a thickness ratio, which is the ratio of the thickness (μm) of the first layer to the thickness (μm) of the second layer, a spectral transmittance at a wavelength of 410 nm, and a spectral transmittance at a wavelength of 440 nm.

[0024] A method for manufacturing a second optical sheet according to a second embodiment of the present disclosure includes the steps of: applying a first curable resin composition containing an ultraviolet absorber onto a substrate film; curing the coating of the first curable resin composition to form a first portion on the substrate film; applying a second curable resin composition onto the first portion; and curing the coating of the second curable resin composition to form a second portion bonded to the first portion.

[0025] an optical sheet according to a third embodiment of the present disclosure, comprising: a first layer; and a second layer adjacent to the first layer; the first layer comprising a cured product of a curable resin composition and an ultraviolet absorber; a thickness ratio of 1.2 or more and 7.5 or less; the thickness ratio being the ratio of the thickness (μm) of the first layer to the thickness (μm) of the second layer; a spectral transmittance at a wavelength of 380 nm being less than 1%; a spectral transmittance at a wavelength of 440 nm being 70% or more; the slope of the spectral transmittance at each wavelength at 0.5 nm intervals within the wavelength range of 380 nm or more and 440 nm or less having a maximum value within the wavelength range of 400 nm or more and 420 nm or less; and the slope (% / nm) of the spectral transmittance at wavelength X being a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

[0026] A sheet article according to the third embodiment of the present disclosure includes a plurality of optical sheets according to the third embodiment of the present disclosure.

[0027] A polarizing plate according to a third embodiment of the present disclosure includes: an optical sheet according to a third embodiment of the present disclosure; and a polarizer superimposed on the optical sheet.

[0028] A touch panel member according to a third embodiment of the present disclosure includes: an optical sheet according to a third embodiment of the present disclosure; and an electrode layer superimposed on the optical sheet.

[0029] A display device according to a third embodiment of the present disclosure includes: an optical sheet according to a third embodiment of the present disclosure; and a display element superimposed on the optical sheet.

[0030] A method for selecting an optical sheet according to a third embodiment of the present disclosure relates to an optical sheet comprising a first layer and a second layer adjacent to the first layer, wherein the first layer comprises a cured product of a curable resin composition and an ultraviolet absorber, the method comprising the steps of: measuring a thickness ratio which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer; measuring a spectral transmittance at each wavelength at 0.5 nm intervals within a wavelength range of 379.5 nm or more and 440.5 nm or less; and selecting an optical sheet based on the thickness ratio, the spectral transmittance at a wavelength of 380 nm, the spectral transmittance at a wavelength of 440 nm, and a slope of the spectral transmittance at wavelengths at 0.5 nm intervals within a wavelength range of 380 nm or more and 440 nm or less, wherein the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

[0031] A method for manufacturing a first optical sheet according to a third embodiment of the present disclosure includes: a step of producing an optical sheet comprising a first layer and a second layer adjacent to the first layer, wherein the first layer comprises a cured product of a curable resin composition and an ultraviolet absorber; and a step of selecting an optical sheet based on a thickness ratio which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer, a spectral transmittance at a wavelength of 380 nm, a spectral transmittance at a wavelength of 440 nm, and a slope of the spectral transmittance at each wavelength in 0.5 nm intervals within a wavelength range of 380 nm or more and 440 nm or less, wherein the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

[0032] A method for manufacturing a second optical sheet according to a third embodiment of the present disclosure includes the steps of: applying a first curable resin composition containing an ultraviolet absorber onto a substrate film; curing the coating of the first curable resin composition to form a first portion on the substrate film; applying a second curable resin composition onto the first portion; and curing the coating of the second curable resin composition to form a second portion bonded to the first portion.

[0033] According to the first to third embodiments of the present disclosure, the hardness can be improved in an optical sheet including a layer containing a cured product of a curable resin composition and an ultraviolet absorber.

[0034] FIG. 1 is a diagram illustrating a first embodiment and is a cross-sectional view showing an example of an optical sheet. FIG. 2A is an enlarged view of FIG. 1 and is a diagram illustrating a measurement position of indentation hardness. FIG. 2B is a graph showing an example of a load-displacement curve obtained by nanoindentation. FIG. 3 is a perspective view showing an example of a sheet article including an optical sheet. FIG. 4 is a cross-sectional view showing an example of a polarizing plate including the optical sheet shown in FIG. 1. FIG. 5 is a cross-sectional view showing an example of a touch panel member including the optical sheet shown in FIG. 1. FIG. 6 is a cross-sectional view showing an example of a display device including the optical sheet shown in FIG. 1. FIG. 7 is a graph showing an example of the spectral transmittance and slope of the spectral transmittance of an optical sheet. FIG. 8 is a diagram illustrating a second embodiment and is a cross-sectional view showing an example of an optical sheet. FIG. 9 is a diagram illustrating a third embodiment and is a cross-sectional view showing an example of an optical sheet. FIG. 10 is a graph showing another example of the spectral transmittance and slope of the spectral transmittance of an optical sheet.

[0035] The first to third embodiments of the present disclosure relate to the following [1] to

[75] .

[0036] [1] An optical sheet including a first surface and a second surface opposite to the first surface, comprising, in order from the second surface to the first surface, a base layer and a functional layer, the functional layer including a cured product of a curable resin composition and an ultraviolet absorber, a spectral transmittance at a wavelength of 380 nm of 1% or less, and a spectral transmittance at a wavelength of 440 nm of 70% or more, an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on the cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer satisfy the following relationships: HA3 < HA2 ≦ HA1 HA1 / HA2 ≦ HA2 / HA3 the first position is located in a surface portion close to the first surface on the cross section the third position is located in a surface portion close to the second surface on the cross section the second position is located in the middle of the first position and the third position.

[0037] [2] The optical sheet according to [1], wherein the indentation hardness HA1 at the first position and the indentation hardness HA2 at the second position satisfy the following relationship: HA1 / HA2≦1.7

[0038] [3] The optical sheet according to [1] or [2], wherein the indentation hardness HA2 at the second position and the indentation hardness HA3 at the third position satisfy the following relationship: 1.2≦HA2 / HA3

[0039] [4] The optical sheet according to any one of [1] to [3], wherein the indentation hardness HA1 at the first position and the indentation hardness HA3 at the third position satisfy the following relationship: 1.4≦HA1 / HA3

[0040] [5] The optical sheet according to any one of [1] to [4], wherein the indentation hardness HA1 at the first position, the indentation hardness HA2 at the second position, the indentation hardness HA3 at the third position, and the indentation hardness HC at the cross section of the base layer satisfy the following relationship: (HA1 + HA2 + HA3) / 3 = HA HA / HC ≦ 1.2

[0041] [6] The optical sheet according to any one of [1] to [5], wherein the indentation hardness HA2 at the second position and the indentation hardness HC at the cross section of the base layer satisfy the following relationship: HA2 / HC≦1.3

[0042] [7] The optical sheet according to any one of [1] to [6], wherein the indentation hardness HA1 at the first position and the indentation hardness HC at the cross section of the base layer satisfy the following relationship: HA1 / HC≦1.5

[0043] [8] The optical sheet according to any one of [1] to [7], wherein the indentation hardness HA1 at the first position is 340 MPa or more.

[0044] [9] The optical sheet according to any one of [1] to [8], wherein the indentation hardness HA2 at the second position is 240 MPa or more.

[0045]

[10] The optical sheet according to any one of [1] to [9], wherein the indentation hardness HA3 at the third position is 120 MPa or more.

[0046]

[11] The optical sheet according to any one of [1] to

[10] , further comprising an intermediate layer located between the functional layer and the base material layer, wherein the indentation hardness HB of the intermediate layer in a cross section is smaller than the indentation hardness HC of the base material layer in a cross section, and the thickness of the intermediate layer is 4.2 μm or less.

[0047]

[12] The optical sheet according to any one of [1] to

[11] , further comprising an intermediate layer located between the functional layer and the base layer, wherein the indentation hardness HB of the cross section of the intermediate layer is 120 MPa or more.

[0048]

[13] The optical sheet according to any one of [1] to

[12] , wherein the slope of the spectral transmittance at each wavelength at 0.5 nm intervals within a wavelength range of 380 nm to 440 nm has a maximum value within a wavelength range of 400 nm to 420 nm, and the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X−0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

[0049]

[14] The optical sheet according to

[13] , wherein the slope of the spectral transmittance has a maximum value within a wavelength range of 410 nm or more and 420 nm or less.

[0050]

[15] The optical sheet according to

[13] or

[14] , wherein the slope of the spectral transmittance at each wavelength in 0.5 nm intervals within a wavelength range of 380 nm to 440 nm is greater than 0.

[0051]

[16] The optical sheet according to any one of [1] to

[15] , which has a spectral transmittance of 15% or less at a wavelength of 410 nm.

[0052]

[17] The optical sheet according to any one of [1] to

[16] , wherein the ratio of silicon element to carbon element measured on the first surface by X-ray photoelectron spectroscopy is 0.02 or more.

[0053]

[18] The optical sheet according to any one of [1] to

[17] , wherein the ratio of elemental fluorine measured on the first surface by X-ray photoelectron spectroscopy is 0.1% or less.

[0054]

[19] L measured by transmitted light ＊ a ＊ b ＊ Color system a ＊ The value is -3.0 or more and -1.6 or less, and the L measured by transmitted light ＊ a ＊ b ＊ Color system b ＊

[19] The optical sheet according to any one of [1] to

[18] , wherein the value is 3.5 or more and 6.0 or less.

[0055]

[20] The optical sheet according to any one of [1] to

[19] , wherein the intermediate layer contains at least one of an acrylic resin and a cellulose resin.

[0056]

[21] The optical sheet according to any one of [1] to

[20] , wherein the base layer contains one or more of an acrylic resin and a cellulose resin.

[0057]

[22] The optical sheet according to any one of [1] to

[21] , wherein the thickness (μm) of the base layer is greater than the sum of the thickness (μm) of the functional layer and the thickness (μm) of the intermediate layer.

[0058]

[23] The optical sheet according to any one of [1] to

[22] , wherein the intermediate layer contains the same resin component as at least a part of the resin component contained in the base layer.

[0059]

[24] The optical sheet according to any one of [1] to

[23] , wherein the intermediate layer contains the same resin component as at least a part of the resin component contained in the functional layer.

[0060]

[25] The optical sheet according to any one of [1] to

[24] , wherein the intermediate layer contains a monomer.

[0061]

[26] The optical sheet according to any one of [1] to

[25] , wherein the pencil hardness of the first surface measured in accordance with JIS K 5600-5-4:1999 at a load of 500 g and a speed of 1.4 mm / sec is 2H or more.

[0062]

[27] The optical sheet according to any one of [1] to

[26] , wherein the load capacity of the first surface in a steel wool scratch resistance test under the following conditions is 100 g or more: Steel wool scratch resistance test: Steel wool #0000 is used, and the sheet is moved back and forth 10 times at a moving speed of 100 mm / sec and a one-way moving distance of 120 mm.

[0063]

[28] An optical sheet comprising: a first layer; and a second layer adjacent to the first layer; wherein the first layer contains a cured product of a curable resin composition and an ultraviolet absorber; a thickness ratio of 1.5 to 7.5, the thickness ratio being the ratio of the thickness (μm) of the first layer to the thickness (μm) of the second layer; a spectral transmittance at a wavelength of 410 nm of 15% or less; and a spectral transmittance at a wavelength of 440 nm of 70% or more.

[0064]

[29] The optical sheet according to

[28] , wherein the thickness ratio is 2.6 or more and 5.0 or less.

[0065]

[30] The optical sheet according to

[28] or

[29] , wherein the thickness of the second layer is 1.2 μm or more and 3.2 μm or less.

[0066]

[31] The optical sheet according to any one of

[28] to

[30] , wherein the thickness of the first layer is 5.0 μm or more and 9.0 μm or less.

[0067]

[32] The optical sheet according to any one of

[28] to

[31] , comprising a first surface and a second surface opposite to the first surface, the first layer and the second layer are disposed in this order from the first surface toward the second surface, and the ratio of silicon element to carbon element measured on the first surface by X-ray photoelectron spectroscopy is 0.02 or more.

[0068]

[33] The optical sheet according to any one of

[28] to

[32] , comprising a first surface and a second surface opposite to the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the ratio of elemental fluorine measured on the first surface by X-ray photoelectron spectroscopy is 0.1% or less.

[0069]

[34] L measured by transmitted light ＊ a ＊ b ＊ Color system a ＊ The value is -3.0 or more and -1.6 or less, and the L measured by transmitted light ＊ a ＊ b ＊ Color system b ＊

[28] The optical sheet according to any one of

[28] to

[33] , wherein the value is 3.5 or more and 6.0 or less.

[0070]

[35] The optical sheet according to any one of

[28] to

[34] , wherein the indentation hardness measured on a cross section of the first layer is greater than the indentation hardness measured on a cross section of the second layer.

[0071]

[36] The optical sheet according to any one of

[28] to

[35] , wherein the second layer contains one or more of an acrylic resin and a cellulose resin.

[0072]

[37] The optical sheet according to any one of

[28] to

[36] , further comprising a base layer adjacent to the second layer, the second layer being located between the first layer and the base layer, and the base layer containing one or more of an acrylic resin and a cellulose resin.

[0073]

[38] The optical sheet according to

[37] , wherein the thickness (μm) of the base layer is greater than the sum of the thickness (μm) of the first layer and the thickness (μm) of the second layer.

[0074]

[39] The optical sheet according to

[37] or

[38] , wherein the second layer contains the same resin component as at least a part of the resin component contained in the base layer.

[0075]

[40] The optical sheet according to any one of

[28] to

[39] , wherein the second layer contains the same resin component as at least a part of the resin component contained in the first layer.

[0076]

[41] The optical sheet according to any one of

[28] to

[40] , wherein the second layer contains a monomer.

[0077]

[42] The optical sheet according to any one of

[28] to

[41] , comprising a first surface and a second surface opposite to the first surface, the first layer and the second layer being arranged in this order from the first surface toward the second surface, and the indentation hardness of a cross section of the first layer at an indentation depth of 100 nm is 350 MPa or more.

[0078]

[43] The optical sheet according to any one of

[28] to

[42] , comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the pencil hardness of the first surface measured in accordance with JIS K 5600-5-4:1999 at a load of 500 g and a speed of 1.4 mm / sec is 2H or more.

[0079]

[44] The optical sheet according to any one of

[28] to

[43] , comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the load capacity of the first surface in a steel wool scratch resistance test under the following conditions is 200 g or more: Steel wool scratch resistance test: Using steel wool #0000, the sheet is moved back and forth 10 times at a moving speed of 100 mm / sec and a one-way moving distance of 120 mm.

[0080]

[45] An optical sheet comprising: a first layer and a second layer adjacent to the first layer, wherein the first layer comprises a cured product of a curable resin composition and an ultraviolet absorber; a thickness ratio of 1.2 or more and 7.5 or less, wherein the thickness ratio is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer; a spectral transmittance at a wavelength of 380 nm is less than 1%; a spectral transmittance at a wavelength of 440 nm is 70% or more; the slope of the spectral transmittance at each wavelength at 0.5 nm intervals within a wavelength range of 380 nm to 440 nm has a maximum value within a wavelength range of 400 nm to 420 nm; and the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X−0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

[0081]

[46] The optical sheet according to

[45] , wherein the slope of the spectral transmittance has a maximum value within a wavelength range of 410 nm or more and 420 nm or less.

[0082]

[47] The optical sheet according to

[45] or

[46] , wherein the slope of the spectral transmittance at each wavelength in 0.5 nm intervals within the wavelength range of 380 nm to 440 nm is greater than 0.

[0083]

[48] ​​The optical sheet according to any one of

[45] to

[47] , wherein the thickness ratio is 2.6 or more and 5.0 or less.

[0084]

[49] The optical sheet according to any one of

[45] to

[48] , wherein the second layer has a thickness of 1.2 μm or more and 3.5 μm or less.

[0085]

[50] The optical sheet according to any one of

[45] to

[49] , wherein the thickness of the first layer is 3.2 μm or more and 9.2 μm or less.

[0086]

[51] The optical sheet according to any one of

[45] to

[50] , comprising a first surface and a second surface opposite to the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the ratio of silicon element to carbon element measured on the first surface by X-ray photoelectron spectroscopy is 0.02 or more.

[0087]

[52] The optical sheet according to any one of

[45] to

[51] , comprising a first surface and a second surface opposite to the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the ratio of elemental fluorine measured on the first surface by X-ray photoelectron spectroscopy is 0.1% or less.

[0088]

[53] L measured by transmitted light ＊ a ＊ b ＊ Color system a ＊ The value is -3.0 or more and -1.6 or less, and the L measured by transmitted light ＊ a ＊ b ＊ Color system b ＊

[45] to

[52] , wherein the value is 3.5 or more and 6.0 or less.

[0089]

[54] The optical sheet according to any one of

[45] to

[53] , wherein the indentation hardness measured on a cross section of the first layer is greater than the indentation hardness measured on a cross section of the second layer.

[0090]

[55] The optical sheet according to any one of

[45] to

[54] , wherein the second layer contains one or more of an acrylic resin and a cellulose resin.

[0091]

[56] The optical sheet according to any one of

[45] to

[55] , further comprising a base layer adjacent to the second layer, the second layer being located between the first layer and the base layer, and the base layer containing one or more of an acrylic resin and a cellulose resin.

[0092]

[57] The optical sheet according to

[56] , wherein the thickness (μm) of the base layer is greater than the sum of the thickness (μm) of the first layer and the thickness (μm) of the second layer.

[0093]

[58] The optical sheet according to

[56] or

[57] , wherein the second layer contains the same resin component as at least a portion of the resin component contained in the base layer.

[0094]

[59] The optical sheet according to any one of

[45] to

[58] , wherein the second layer contains the same resin component as at least a part of the resin component contained in the first layer.

[0095]

[60] The optical sheet according to any one of

[45] to

[59] , wherein the second layer contains a monomer.

[0096]

[61] The optical sheet according to any one of

[45] to

[60] , comprising a first surface and a second surface opposite to the first surface, the first layer and the second layer being arranged in this order from the first surface toward the second surface, and the indentation hardness of the first surface at an indentation depth of 100 nm is 330 MPa or more.

[0097]

[62] The optical sheet according to any one of

[45] to

[61] , comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the pencil hardness of the first surface measured in accordance with JIS K 5600-5-4:1999 at a load of 500 g and a speed of 1.4 mm / sec is 2H or more.

[0098]

[63] The optical sheet according to any one of

[45] to

[62] , comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the load capacity of the first surface in a steel wool scratch resistance test under the following conditions is 150 g or more: Steel wool scratch resistance test: Using steel wool #0000, the sheet is moved back and forth 10 times at a moving speed of 100 mm / sec and a one-way moving distance of 120 mm.

[0099]

[64] A sheet article comprising a plurality of the optical sheets according to any one of [1] to

[63] .

[0100]

[65] The sheet article according to

[64] , which is wound around a winding axis.

[0101]

[66] A polarizing plate comprising: the optical sheet according to any one of [1] to

[63] ; and a polarizer superimposed on the optical sheet.

[0102]

[67] A touch panel member comprising: the optical sheet according to any one of [1] to

[63] ; and an electrode layer superimposed on the optical sheet.

[0103]

[68] A display device comprising: the optical sheet according to any one of [1] to

[63] ; and a display element superimposed on the optical sheet.

[0104]

[69] A method for selecting an optical sheet, the optical sheet including a first surface and a second surface opposite to the first surface, comprising, in order from the second surface to the first surface, a base layer and a functional layer, the functional layer including a cured product of a curable resin composition and an ultraviolet absorber, the method comprising the steps of measuring a spectral transmittance at a wavelength of 380 nm and a spectral transmittance at a wavelength of 440 nm, measuring an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on the cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer, and selecting an optical sheet based on the measured spectral transmittance and the measured indentation hardness, wherein the first position is located on a surface portion close to the first surface on the cross section, the third position is located on a surface portion close to the second surface on the cross section, and the second position is located midway between the first position and the third position.

[0105]

[70] A method for manufacturing an optical sheet, comprising: a step of producing an optical sheet including a first surface and a second surface opposite to the first surface, the optical sheet comprising, in order from the second surface toward the first surface, a base layer and a functional layer, the functional layer including a cured product of a curable resin composition and an ultraviolet absorber; and a step of selecting an optical sheet based on a spectral transmittance at a wavelength of 380 nm, a spectral transmittance at a wavelength of 440 nm, an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on a cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer, wherein the first position is located on a surface portion close to the first surface on the cross section, the third position is located on a surface portion close to the second surface on the cross section, and the second position is located midway between the first position and the third position.

[0106]

[71] A method for manufacturing an optical sheet, comprising: a step of applying a first curable resin composition containing an ultraviolet absorber onto a substrate film; a step of curing the coating film of the first curable resin composition to form a first portion on the substrate film; a step of applying a second curable resin composition onto the first portion; and a step of curing the coating film of the second curable resin composition to form a second portion bonded to the first portion.

[0107]

[72] An optical sheet comprising a first layer and a second layer adjacent to the first layer, wherein the first layer contains a cured product of a curable resin composition and an ultraviolet absorber, comprising the steps of: measuring a thickness ratio, which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer; measuring a spectral transmittance at a wavelength of 410 nm; measuring a spectral transmittance at a wavelength of 440 nm; and selecting an optical sheet based on the thickness ratio, the spectral transmittance at a wavelength of 410 nm, and the spectral transmittance at a wavelength of 440 nm.

[0108]

[73] A method for manufacturing an optical sheet, comprising: a step of producing an optical sheet comprising a first layer and a second layer adjacent to the first layer, wherein the first layer contains a cured product of a curable resin composition and an ultraviolet absorber; and a step of selecting an optical sheet based on a thickness ratio which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer, a spectral transmittance at a wavelength of 410 nm, and a spectral transmittance at a wavelength of 440 nm.

[0109]

[74] A method for selecting an optical sheet, comprising: a step of measuring a thickness ratio, which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer; a step of measuring a spectral transmittance at each wavelength at 0.5 nm intervals within a wavelength range of 379.5 nm to 440.5 nm; and a step of selecting an optical sheet based on the thickness ratio, the spectral transmittance at a wavelength of 380 nm, the spectral transmittance at a wavelength of 440 nm, and a slope of the spectral transmittance at wavelengths at 0.5 nm intervals within a wavelength range of 380 nm to 440 nm, wherein the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

[0110]

[75] A method for manufacturing an optical sheet, comprising: a step of preparing an optical sheet comprising a first layer and a second layer adjacent to the first layer, wherein the first layer comprises a cured product of a curable resin composition and an ultraviolet absorber; and a step of selecting an optical sheet based on a thickness ratio which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer, a spectral transmittance at a wavelength of 380 nm, a spectral transmittance at a wavelength of 440 nm, and a slope of the spectral transmittance at each wavelength in 0.5 nm intervals within a wavelength range of 380 nm to 440 nm, wherein the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

[0111] The following describes the details of the first to third embodiments of the present disclosure. In the drawings accompanying this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual objects for the sake of ease of illustration and understanding.

[0112] In this specification, terms such as "sheet," "film," and "plate" are not distinguished from one another solely on the basis of differences in name. For example, an "optical sheet" is not distinguished from a member called an optical film or an optical plate solely on the basis of differences in name.

[0113] In this specification, multiple upper limit candidate values ​​and multiple lower limit candidate values ​​for a numerical range may be described in separate sentences. In this description, the numerical range may be constructed by combining any one upper limit candidate value and any one lower limit candidate value. As an example, consider the description, "Parameter B may be A1 or more, A2 or more, or A3 or more. Parameter B may be A4 or less, A5 or less, or A6 or less." In this example, the numerical range of parameter B may be A1 or more and A4 or less, A1 or more and A5 or less, A1 or more and A6 or less, A2 or more and A4 or less, A2 or more and A5 or less, A2 or more and A6 or less, A3 or more and A4 or less, A3 or more and A5 or less, or A3 or more and A6 or less.

[0114] In order to clarify the relationship between directions between drawings, several drawings use arrows with common symbols to indicate a first direction D1, a second direction D2, and a third direction D3. The tip of the arrow is the first side of each direction. The side opposite the tip of the arrow is the second side of each direction. Arrows pointing into the paper in a direction perpendicular to the paper surface of the drawing are indicated by a symbol of an x ​​in a circle, as shown in Figure 1, for example.

[0115] <<<<First Embodiment>>>> A first embodiment will be described.

[0116] <<<Optical Sheet 10>>> In the first embodiment, the optical sheet 10 includes a first surface 11 and a second surface 12. The optical sheet 10 includes, in order from the second surface 12 to the first surface 11, a base layer 40 and a functional layer 20. The functional layer 20 includes a cured product of a curable resin composition and an ultraviolet absorber. The functional layer 20 including the ultraviolet absorber can provide the optical sheet 10 with at least one of an ultraviolet blocking function and a blue light blocking function. In the first embodiment, the optical sheet 10 has the following characteristics (X) and (Y) regarding spectral transmittance: (X) The spectral transmittance of the optical sheet 10 at a wavelength of 380 nm is 1% or less. (Y) The spectral transmittance of the optical sheet 10 at a wavelength of 440 nm is 70% or more.

[0117] According to the characteristic (X), the optical sheet 10 can sufficiently block light with a wavelength of around 380 nm, thereby suppressing problems caused by ultraviolet rays and blue light.

[0118] When the optical sheet 10 is applied to a display device 60 (see FIG. 6 ), image light emitted from the display device 60 can be transmitted through the optical sheet 10. The optical sheet 10 can block light with a wavelength of around 380 nm from the image light. By sufficiently blocking light with a wavelength of around 380 nm from the image light, it is possible to alleviate strain on the observer of the image, such as eye strain.

[0119] External light such as sunlight can be incident on the optical sheet 10. By sufficiently blocking light with a wavelength of around 380 nm from external light, deterioration of the display element 61 (see FIG. 6) can be suppressed. For example, deterioration of the EL element (organic electroluminescence element) of an organic EL panel (organic electroluminescence panel) can be suppressed. By sufficiently blocking light with a wavelength of around 380 nm from external light, deterioration of the polarizer 52 of the polarizing plate 50 (see FIG. 4) can be suppressed.

[0120] The spectral transmittance of the optical sheet 10 at a wavelength of 380 nm may be 1% or less, or may be less than 1%. There is no particular lower limit for the spectral transmittance of the optical sheet 10 at a wavelength of 380 nm. The spectral transmittance of the optical sheet 10 at a wavelength of 380 nm may be 0% or more, or may be greater than 0%.

[0121] The spectral transmittance of the optical sheet 10 at a wavelength of 380 nm may be 0% or more and 1% or less, or may be 0% or more and less than 1%.The spectral transmittance of the optical sheet 10 at a wavelength of 380 nm may be greater than 0% or more and 1% or less, or may be greater than 0% or more and less than 1%.

[0122] According to the characteristic (Y), light having a wavelength of 440 nm or more can be transmitted through the optical sheet 10 with high transmittance. The optical sheet 10 may transmit light having a wavelength of 440 nm or more with high transmittance. This makes it possible to suppress changes and deterioration in the color of an image observed through the optical sheet 10.

[0123] The spectral transmittance of the optical sheet 10 at a wavelength of 440 nm may be 70% or more, 75% or more, 80% or more, or 85% or more. By setting the lower limit of the spectral transmittance of the optical sheet 10 at a wavelength of 440 nm in this manner, color changes in images transmitted through the optical sheet 10 can be effectively suppressed. No upper limit is particularly set for the spectral transmittance of the optical sheet 10 at a wavelength of 440 nm. The spectral transmittance of the optical sheet 10 at a wavelength of 440 nm may be 100% or less, or may be less than 100%.

[0124] The spectral transmittance of the optical sheet 10 at a wavelength of 440 nm may be 70% or more and 100% or less, 75% or more and 100% or less, 80% or more and 100% or less, or 85% or more and 100% or less. The spectral transmittance of the optical sheet 10 at a wavelength of 440 nm may be 70% or more and less than 100%, 75% or more and less than 100%, 80% or more and less than 100%, or 85% or more and less than 100%.

[0125] In relation to the ultraviolet ray blocking function and the blue light blocking function, the optical sheet 10 may have the following feature (Z) in addition to the above-described features (X) and (Y): (Z) The slope of the spectral transmittance at each wavelength at 0.5 nm intervals within a wavelength range of 380 nm or more and 440 nm or less has a maximum value within a wavelength range of 400 nm or more and 420 nm or less.

[0126] The spectral transmittance of the optical sheet 10 is measured at 0.5 nm intervals for each wavelength within the wavelength range of 379.5 nm to 440.5 nm. Using the spectral transmittance measurement results, it is determined whether or not characteristic (Z) is satisfied. Note that the above-mentioned characteristic (X) is evaluated based on the measured value of the spectral transmittance at a wavelength of 380.0 nm. The above-mentioned characteristic (Y) is evaluated based on the measured value of the spectral transmittance at a wavelength of 440.0 nm.

[0127] The slope of the spectral transmittance indicates the increase in transmittance (%) per 1 nm of wavelength. The slope of the spectral transmittance is calculated using the spectral transmittance measured for each wavelength in 0.5 nm increments within the wavelength range of 379.5 nm to 440.5 nm. For example, if the spectral transmittance at a wavelength of 409.5 nm is 41% and the spectral transmittance at a wavelength of 410.5 nm is 44%, the slope of the spectral transmittance at a wavelength of 410 nm is 3.0% / nm = (44.0 - 41.0) / (410.5 - 409.5). The slope (% / nm) of the spectral transmittance at wavelength X is the value obtained by subtracting the spectral transmittance (%) at wavelength X - 0.5 (nm) from the spectral transmittance (%) at wavelength X + 0.5 (nm).

[0128] If the wavelength at which the slope of the spectral transmittance is maximum is 400.0 nm or more and 420.0 nm or less, the optical sheet 10 is determined to have the characteristic (Z). If the wavelength at which the slope of the spectral transmittance is maximum is 395.5 nm or less, the optical sheet 10 is determined to not have the characteristic (Z). If the wavelength at which the slope of the spectral transmittance is maximum is 420.5 nm or more, the optical sheet 10 is determined to not have the characteristic (Z).

[0129] The characteristic (Z) defines the manner in which the spectral transmittance increases with increasing wavelength. The slope of the spectral transmittance has the same meaning as the value of the differential equation of the function representing the spectral transmittance. Therefore, at the wavelength at which the slope of the spectral transmittance is at its maximum and at wavelengths around that wavelength, the spectral transmittance increases rapidly with increasing wavelength. When the optical sheet 10 has the characteristic (Z) in addition to the characteristic (X), light in the wavelength range of 380 nm to 400 nm can be blocked by the optical sheet 10 with sufficient efficiency. When the optical sheet 10 has the characteristic (Z) in addition to the characteristic (Y), light in the wavelength range of 420 nm to 440 nm can be transmitted through the optical sheet 10 with sufficient transmittance.

[0130] The wavelength at which the maximum value of the slope of the spectral transmittance defined by the characteristic (Z) is obtained may be 405 nm or more, 408 nm or more, 410 nm or more, 412 nm or more, or 415 nm or more. By setting the lower limit of the wavelength at which the maximum value of the slope of the spectral transmittance is obtained in this manner, blue light can be blocked more effectively.

[0131] The wavelength at which the maximum value of the slope of the spectral transmittance defined by the characteristic (Z) is obtained may be 419 nm or less. By setting the upper limit of the wavelength at which the maximum value of the slope of the spectral transmittance is obtained in this manner, changes in the color of images, etc. observed through the optical sheet 10 can be more effectively suppressed.

[0132] The wavelength at which the maximum value of the slope of the spectral transmittance is obtained may be 400 nm or more and 420 nm or less, 405 nm or more and 420 nm or less, 408 nm or more and 420 nm or less, 410 nm or more and 420 nm or less, 412 nm or more and 420 nm or less, or 415 nm or more and 420 nm or less. The wavelength at which the maximum value of the slope of the spectral transmittance is obtained may be 400 nm or more and 419 nm or less, 405 nm or more and 419 nm or less, 408 nm or more and 410 nm or more and 419 nm or less, 412 nm or more and 415 nm or more and 419 nm or less.

[0133] A lower limit may be set for the maximum value of the slope of the spectral transmittance defined by characteristic (Z), i.e., the maximum value of the slope of the spectral transmittance at each wavelength in 0.5 nm increments within a wavelength range of 380 nm to 440 nm. By setting a lower limit for the maximum value of the spectral transmittance, the effects of blue light can be effectively suppressed. The maximum value of the slope of the spectral transmittance defined by characteristic (Z) may be 2.0 (% / nm) or more, 2.5 (% / nm) or more, 3.0 (% / nm) or more, 3.5 (% / nm) or more, or 4.0 (% / nm) or more.

[0134] An upper limit may be set for the maximum value of the slope of the spectral transmittance defined by characteristic (Z). By setting an upper limit for the maximum value of the spectral transmittance, changes in color and deterioration can be suppressed more naturally. The maximum value of the slope of the spectral transmittance defined by characteristic (Z) may be 8.0 (% / nm) or less, 7.0 (% / nm) or less, 6.0 (% / nm) or less, 5.5 (% / nm) or less, or 5.0 (% / nm) or less.

[0135] The maximum value of the slope of the spectral transmittance may be 2.0 (% / nm) or more and 8.0 (% / nm) or less, 2.5 (% / nm) or more and 8.0 (% / nm) or less, 3.0 (% / nm) or more and 8.0 (% / nm) or less, 3.5 (% / nm) or more and 8.0 (% / nm) or less, or 4.0 (% / nm) or more and 8.0 (% / nm) or less. The maximum value of the slope of the spectral transmittance may be 2.0 (% / nm) or more and 7.0 (% / nm) or less, 2.5 (% / nm) or more and 7.0 (% / nm) or less, 3.0 (% / nm) or more and 7.0 (% / nm) or less, 3.5 (% / nm) or more and 7.0 (% / nm) or less, or 4.0 (% / nm) or more and 7.0 (% / nm) or less. The maximum value of the slope of the spectral transmittance may be 2.0 (% / nm) or more and 6.0 (% / nm) or less, 2.5 (% / nm) or more and 6.0 (% / nm) or less, 3.0 (% / nm) or more and 6.0 (% / nm) or less, 3.5 (% / nm) or more and 6.0 (% / nm) or less, or 4.0 (% / nm) or more and 6.0 (% / nm) or less. The maximum value of the slope of the spectral transmittance may be 2.0 (% / nm) or more and 5.5 (% / nm) or less, 2.5 (% / nm) or more and 5.5 (% / nm) or less, 3.0 (% / nm) or more and 5.5 (% / nm) or less, 3.5 (% / nm) or more and 5.5 (% / nm) or less, or 4.0 (% / nm) or more and 5.5 (% / nm). The maximum value of the slope of the spectral transmittance may be 2.0 (% / nm) or more and 5.0 (% / nm) or less, 2.5 (% / nm) or more and 5.0 (% / nm) or less, 3.0 (% / nm) or more and 5.0 (% / nm) or less, 3.5 (% / nm) or more and 5.0 (% / nm) or less, or 4.0 (% / nm) or more and 5.0 (% / nm) or less.

[0136] 7 is a graph showing the spectral transmittance and the slope of the spectral transmittance of the optical sheets for Sample A1 and Sample A2. Sample A1 has the feature (Z) in addition to the feature (X) and the feature (Y).

[0137] 7, the spectral transmittance (%) may monotonically increase with increasing wavelength. The slope of the spectral transmittance at each wavelength in 0.5 nm intervals within the wavelength range of 380 nm to 440 nm may be greater than 0. According to these examples, changes and deterioration in the color tone of an image observed through the optical sheet 10 can be more naturally suppressed.

[0138] In relation to the blue light blocking function, the optical sheet 10 may have the following feature (W) in addition to the feature (X) and the feature (Y): (W) The spectral transmittance at a wavelength of 410 nm is 15% or less.

[0139] By satisfying the condition (W), light with a wavelength of 410 nm or less can be sufficiently blocked, thereby more effectively blocking ultraviolet rays and blue light.

[0140] The spectral transmittance of the optical sheet 10 at a wavelength of 410 nm may be 15% or less, 14% or less, 13% or less, 12% or less, or 10% or less. By setting the upper limit of the spectral transmittance of the optical sheet 10 at a wavelength of 410 nm in this manner, blue light can be effectively blocked. No particular lower limit is set for the spectral transmittance of the optical sheet 10 at a wavelength of 410 nm. The spectral transmittance of the optical sheet 10 at a wavelength of 410 nm may be 0% or more, greater than 0%, 2% or more, or 5% or more.

[0141] The spectral transmittance of the optical sheet 10 at a wavelength of 410 nm may be 0% to 15%, 0% to 14%, 0% to 13%, 0% to 12%, or 0% to 10%. The spectral transmittance of the optical sheet 10 at a wavelength of 410 nm may be greater than 0% to 15%, greater than 0% to 14%, greater than 0% to 13%, greater than 0% to 12%, or greater than 0% to 10%. The spectral transmittance of the optical sheet 10 at a wavelength of 410 nm may be 2% to 15%, greater than 2% to 14%, greater than 2% to 13%, greater than 2% to 12%, or greater than 2% to 10%. The spectral transmittance of the optical sheet 10 at a wavelength of 410 nm may be 5% or more and 15% or less, 5% or more and 14% or less, 5% or more and 13% or less, 5% or more and 12% or less, or 5% or more and 10% or less.

[0142] The spectral transmittance is the arithmetic mean of five measurements taken in accordance with JIS Z8722:2009. The geometric condition e specified in JIS Z8722:2009 is used in measuring the spectral transmittance. The five measurements are taken at five measurement positions on the sample of the optical sheet to be evaluated. The five measurement positions are located at least 10 mm apart from each other. The test environment for measuring the spectral transmittance is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before the start of the test. Before measuring the spectral transmittance, the light source of the measuring device is turned on for 15 minutes to stabilize the light source output.

[0143] The functional layer 20 further includes a cured product of the curable resin composition. In this specification, the cured product of the curable resin composition is also referred to as a cured resin product. The cured resin product can impart high hardness to the functional layer 20 and the optical sheet 10. The functional layer 20 functions as a so-called hard coat layer. The optical sheet 10 with improved hardness has excellent scratch resistance. Scratches on the optical sheet 10 can be suppressed during use. The optical sheet 10 is also suitable for a touch panel member 55 (see FIG. 5) that is expected to be touched by a finger or a pen during use.

[0144] However, in conventional optical sheets, it has sometimes been impossible to impart sufficient hardness to a functional layer containing a cured resin. This phenomenon is thought to be due to the UV absorber contained in the functional layer. A functional layer containing a cured resin is obtained by curing a coating film of a curable resin composition. The coating film can be cured by exposing the coating film to light, which promotes a crosslinking reaction. High-energy, short-wavelength light is usually used for exposure. The UV absorber added to the curable resin composition can absorb the light used in the curing treatment of the coating film. In other words, the UV absorber can inhibit the curing process of the curable resin composition.

[0145] If the hardness of the functional layer containing the cured resin is low, the scratch resistance may be significantly reduced. If the hardness of the functional layer containing the cured resin is low, the ultraviolet absorber may bleed out from the functional layer during use of the optical sheet. If the ultraviolet absorber bleeds out, the ultraviolet blocking function and blue light blocking function of the optical sheet 10 may also become insufficient.

[0146] In the first embodiment, the indentation hardness HA1, the indentation hardness HA2, and the indentation hardness HA3 satisfy the following conditions (A) and (B): (A) HA3<HA2≦HA1 (B) HA1 / HA2≦HA2 / HA3

[0147] The indentation hardnesses HA1 to HA3 are the indentation hardnesses of the functional layer 20 in the cross section of the optical sheet 10. As shown in Figure 2A, the cross section of the optical sheet 10 where the indentation hardness is measured is a cross section along the thickness direction of the optical sheet 10. In the illustrated example, the cross section of the optical sheet 10 where the indentation hardness is measured is a cross section along the first direction D1, which is the stacking direction of the functional layer 20 and the base layer 40.

[0148] The indentation hardness HA1 is the indentation hardness at a first position 26 in the cross section of the functional layer 20. As shown in FIG. 2A , the first position 26 is located in a surface portion of the functional layer 20 near the first surface 11 in the cross section of the functional layer 20. Specifically, the first position 26 is a position shifted 1.2 μm from the first side surface 21 to the second side surface 22 in the thickness direction of the optical sheet 10, i.e., along the normal direction of the optical sheet 10. The indentation hardness at the first position 26 is an indicator of the hardness of the functional layer 20 in the vicinity of the first side surface 21.

[0149] The first side surface 21 and the second side surface 22 are a pair of main surfaces of the functional layer 20. The first side surface 21 is located on a first side in a first direction D1, which is the normal direction of the functional layer 20. The first side surface 21 is a surface that is close to the first surface 11 in the first direction D1. In the example shown in FIG. 2A , the first side surface 21 of the functional layer 20 constitutes the first surface 11 of the optical sheet 10. The second side surface 22 is located on a second side in the first direction D1. The second side surface 22 is a surface that is close to the second surface 12 in the first direction D1.

[0150] The indentation hardness HA3 is the indentation hardness at a third position 28 in the cross section of the functional layer 20. As shown in FIG. 2A , the third position 28 is located in a surface portion of the functional layer 20 near the second surface 12 in the cross section of the functional layer 20. Specifically, the third position 28 is a position shifted 1.2 μm from the second side surface 22 to the first side surface 21 along the thickness direction of the optical sheet 10, i.e., the normal direction of the optical sheet 10. The indentation hardness at the third position 28 is an indicator of the hardness of the functional layer 20 in the vicinity of the second side surface 22.

[0151] The indentation hardness HA2 is the indentation hardness at a second position 27 in the cross section of the functional layer 20. The indentation hardness at the second position 27 is an indicator of the hardness at the center in the thickness direction of the functional layer 20. As shown in FIG. 2A , the second position 27 is located at the center between the first position 26 and the third position 28 along the thickness direction of the optical sheet 10, i.e., the normal direction of the optical sheet 10.

[0152] Indentation hardness is measured by the nanoindentation method using a nanoindenter. The nanoindentation method is a method for measuring hardness based on a load-displacement curve. In the nanoindentation method, the load-displacement curve is obtained by loading and unloading the evaluation object using an indenter. The load-displacement curve shows the relationship between the indentation load and the indentation depth. The nanoindentation method can evaluate the hardness of a microscopic area.

[0153] To measure the indentation hardness at the cross section of the functional layer 20 included in the optical sheet 10, a test piece made using the optical sheet to be evaluated is used. First, a sample is cut out from the optical sheet 10 to be evaluated. This sample is embedded in an embedding resin. The embedding resin is a cold-setting type two-component epoxy resin. The embedding resin is hardened by leaving it at room temperature for 24 hours or more to prepare an embedded sample. The embedded sample is cut using a microtome to expose the cross section of the optical sheet 10 along the first direction D1, which corresponds to the normal direction of the optical sheet. An indenter is pressed into the exposed cross section of the functional layer 20 to measure the indentation hardness at the cross section of the functional layer 20.

[0154] The indenter used to measure the indentation hardness at the cross section of the optical sheet 10 is a Berkovich indenter having a triangular pyramid shape. The indenter is pressed into the cross section of the sample to be evaluated from a direction perpendicular to the surface to be evaluated. The indenter is pressed at a pressing speed of 10 nm / sec. The indenter is pressed into the sample until the indentation depth reaches 100 nm. The indenter is held for 5 seconds in a state where it has been pressed 100 nm into the optical sheet 10 from the surface to be evaluated. Thereafter, the indenter is retracted from the surface to be evaluated, and the load is released from the optical sheet 10. When the load is released, the indenter is moved in a direction perpendicular to the surface to be evaluated. The indenter is retracted at a pressing speed of 10 nm / sec.

[0155] The above-described operation of the indenter results in a load-displacement curve C. The load-displacement curve C is a graph showing the magnitude of the load applied to the evaluation surface via the indenter and the indentation depth of the indenter. Fig. 2B shows an example of the load-displacement curve C.

[0156] Indentation hardness H ＩＴ is determined by the following equation (1) using the maximum load Fmax and the contact projection area Ap: ＩＴ = Fmax / Ap (1) The maximum load Fmax and the contact projection area Ap are obtained by analyzing the load-displacement curve. The maximum load Fmax is the maximum indentation load. The contact projection area Ap is the projected area on a plane perpendicular to the indentation direction of the region where the indenter and sample are in contact at the maximum indentation load. The contact projection area Ap is determined by a correction formula created using a standard sample of fused quartz in accordance with the instrument's standard method.

[0157] The indentation hardness is the arithmetic mean value of 10 measured values ​​measured at 10 measurement positions on the optical sheet to be evaluated.

[0158] Condition (A) requires that the indentation hardness of the cross section of the functional layer 20 increases from the second side to the first side in the first direction D1. In other words, condition (A) requires that the indentation hardness of the cross section of the functional layer 20 increases from the second surface 12 to the first surface 11.

[0159] Condition (B) requires that the gradient of change in indentation hardness in the cross section of the functional layer 20 be smaller on the first side than on the second side in the first direction D1. In other words, condition (B) requires that the indentation hardness in the cross section of the functional layer 20 change significantly near the second side surface 22 (second surface 12).

[0160] According to the combination of conditions (A) and (B), in a region of the functional layer 20 away from the first surface 11, the hardness increases rapidly from the first surface 11 toward the second surface 12. Sufficient hardness is ensured in a region of the functional layer 20 close to the first surface 11. Furthermore, even in a region of the functional layer 20 close to the first surface 11, the hardness can increase from the second surface 12 toward the first surface 11. Therefore, according to the combination of conditions (A) and (B), the hardness of the first surface 11 of the optical sheet 10 can be improved, and the scratch resistance of the first surface 11 of the optical sheet 10 can be improved. Furthermore, bleeding out of the ultraviolet absorber contained in the functional layer 20 from the first surface 11 can be suppressed. This allows the optical sheet 10 to stably exhibit its ultraviolet blocking function and blue light blocking function.

[0161] In the first embodiment in which the conditions (A) and (B) are satisfied, the following condition (C) including the indentation hardness HA1 and the indentation hardness HA2 may be further satisfied: (C) HA1 / HA2≦1.7

[0162] By satisfying condition (C), which sets an upper limit for "HA1 / HA2," the indentation hardness HA2 at the second position 27 can be made sufficiently larger than the indentation hardness HA1 at the first position 26. The indentation hardness at the cross section of the functional layer 20 increases from the second side surface 22 toward the first side surface 21. When condition (C) is satisfied, the indentation hardness at the cross section of the functional layer 20 increases sufficiently at the center of the second side surface 22 and the first side surface 21. The functional layer 20 has a sufficiently large indentation hardness in the region from the center in the thickness direction to the first side surface 21. This effectively improves the hardness at the first surface 11 of the optical sheet 10, and effectively improves the scratch resistance at the first surface 11.

[0163] The "HA1 / HA2" ratio specified in condition (C) may be 1.7 or less, 1.5 or less, 1.2 or less, or 1.1 or less. There is no particular lower limit for "HA1 / HA2". "HA1 / HA2" may be 1.0 or more, or may be greater than 1.0.

[0164] In the first embodiment in which the conditions (A) and (B) are satisfied, the following condition (D) including the indentation hardness HA2 and the indentation hardness HA3 may be further satisfied: (D) 1.2≦HA2 / HA3

[0165] By satisfying condition (D), which sets the lower limit of "HA2 / HA3," the indentation hardness HA2 at the second position 27 can be made sufficiently larger than the indentation hardness HA3 at the third position 28. The indentation hardness at the cross section of the functional layer 20 increases from the second side surface 22 toward the first side surface 21. When condition (D) is satisfied, the indentation hardness at the cross section of the functional layer 20 increases sufficiently at the center of the second side surface 22 and the first side surface 21. The functional layer 20 has a sufficiently large indentation hardness in the region from the center in the thickness direction to the first side surface 21. This effectively improves the hardness at the first surface 11 of the optical sheet 10, and effectively improves the scratch resistance at the first surface 11.

[0166] The "HA2 / HA3" defined in condition (D) may be 1.2 or more, 1.7 or more, 2.0 or more, 2.4 or more, or 2.7 or more. No upper limit is particularly set for "HA2 / HA3". "HA2 / HA3" may be 5.0 or less. "HA2 / HA3" may be 1.2 or more and 5.0 or less, 1.7 or more and 5.0 or less, 2.0 or more and 5.0 or less, 2.4 or more and 5.0 or less, or 2.7 or more and 5.0 or less.

[0167] In the first embodiment in which the conditions (A) and (B) are satisfied, the following condition (E) including the indentation hardness HA1 and the indentation hardness HA3 may be further satisfied: (E) 1.4≦HA1 / HA3

[0168] By satisfying condition (D), which sets the lower limit of "HA1 / HA3," the indentation hardness HA1 at the first position 26 can be made sufficiently larger than the indentation hardness HA3 at the third position 28. The indentation hardness at the cross section of the functional layer 20 becomes sufficiently larger from the second side surface 22 to the first side surface 21. This effectively improves the hardness at the first surface 11 of the optical sheet 10, and effectively improves the scratch resistance at the first surface 11.

[0169] The "HA1 / HA3" defined in condition (E) may be 1.4 or more, 2.0 or more, 2.5 or more, 3.0 or more, or 3.2 or more. No upper limit is particularly set for "HA1 / HA3". "HA1 / HA3" may be 5.5 or less. "HA1 / HA3" may be 1.4 or more and 5.5 or less, 2.0 or more and 5.5 or less, 2.5 or more and 5.5 or less, 3.0 or more and 5.5 or less, or 3.2 or more and 5.5 or less.

[0170] In the first embodiment in which the conditions (A) and (B) are satisfied, the following condition (F) including the indentation hardness HA2 and the indentation hardness HC may be further satisfied: (F) HA2 / HC≦1.3

[0171] The indentation hardness HC is the indentation hardness of the base layer 40 in a cross section of the optical sheet 10. As shown in Figure 2A, the cross section of the optical sheet 10 on which the indentation hardness HC is measured is a cross section along the thickness direction of the optical sheet 10. In the illustrated example, the cross section of the optical sheet 10 on which the indentation hardness HC is measured is a cross section along the first direction D1, which is the stacking direction of the functional layer 20 and the base layer 40.

[0172] The indentation hardness HC is the indentation hardness at a central position 41 of the base material layer 40 in the cross section of the base material layer 40. As shown in Fig. 2A, the central position 41 is located at the center in the thickness direction of the cross section of the base material layer 40.

[0173] If the indentation hardness at the cross section of the functional layer 20 becomes large, curling or warping may occur in the optical sheet 10. Deformation of the optical sheet 10 may occur due to cure shrinkage of the functional layer 20. By satisfying condition (F) that sets the upper limit of "HA2 / HC", deformation such as curling or warping of the optical sheet 10 can be suppressed.

[0174] The "HA2 / HC" defined in condition (F) may be 1.3 or less, 1.2 or less, or 1.1 or less. There is no particular lower limit for "HA2 / HC". "HA2 / HC" may be 0.73 or more, 0.90 or more, or 0.95 or more.

[0175] "HA2 / HC" may be 0.73 or more and 1.3 or less, 0.73 or more and 1.2 or less, or 0.73 or more and 1.1 or less. "HA2 / HC" may be 0.90 or more and 1.3 or less, 0.90 or more and 1.2 or less, or 0.90 or more and 1.1 or less. "HA2 / HC" may be 0.95 or more and 1.3 or less, 0.95 or more and 1.2 or less, or 0.95 or more and 1.1 or less.

[0176] In the first embodiment in which the conditions (A) and (B) are satisfied, the following condition (G) including the indentation hardness HA1 and the indentation hardness HC may be further satisfied. By satisfying the condition (G) that sets the upper limit of "HA1 / HC", deformation such as curling and warping of the optical sheet 10 can be suppressed. (G) HA1 / HC ≦ 1.5

[0177] The "HA1 / HC" defined in condition (G) may be 1.5 or less, 1.3 or less, or 1.2 or less. There is no particular lower limit for "HA1 / HC". "HA1 / HC" may be 1.0 or more, 1.1 or more, or 1.2 or more.

[0178] "HA1 / HC" may be 1.0 or more and 1.5 or less, 1.0 or more and 1.3 or less, or 1.0 or more and 1.2 or less. "HA1 / HC" may be 1.1 or more and 1.5 or less, 1.1 or more and 1.3 or less, or 1.1 or more and 1.2 or less. "HA1 / HC" may be 1.2 or more and 1.5 or less, or 1.2 or more and 1.3 or less.

[0179] In the first embodiment in which the conditions (A) and (B) are satisfied, the following condition (H) including the indentation hardness HA and the indentation hardness HC may be further satisfied: (H) HA / HC≦1.2

[0180] The indentation hardness HA is the arithmetic mean value of the indentation hardnesses HA1 to HA3, and is determined by the following formula: (HA1+HA2+HA3) / 3=HA When the condition (H) that sets the upper limit of "HA / HC" is satisfied, deformation of the optical sheet 10, such as curling or warping, can be suppressed.

[0181] The "HA / HC" ratio specified in condition (H) may be 1.2 or less, 1.1 or less, or 0.90 or less. There is no particular lower limit for "HA / HC". "HA / HC" may be 0.78 or more, 0.84 or more, or 0.86 or more.

[0182] "HA / HC" may be 0.78 or more and 1.2 or less, 0.78 or more and 1.1 or less, or 0.78 or more and 0.90 or less. "HA / HC" may be 0.84 or more and 1.2 or less, 0.84 or more and 1.1 or less, or 0.84 or more and 0.90 or less. "HA / HC" may be 0.86 or more and 1.2 or less, 0.86 or more and 1.1 or less, or 0.86 or more and 0.90 or less.

[0183] A lower limit for the indentation hardness HA1 at the first position 26 may be set. By setting a lower limit for the indentation hardness HA1, the hardness of the first surface 11 of the optical sheet 10 can be effectively improved, and the scratch resistance of the first surface 11 can be effectively improved. The indentation hardness HA1 at the first position 26 may be 340 MPa or more, 342 MPa or more, 387 MPa or more, 409 MPa or more, 414 MPa or more, 417 MPa or more, 483 MPa or more, 500 MPa or more, or 522 MPa or more.

[0184] The upper limit of the indentation hardness HA1 is not particularly set, and the indentation hardness HA1 may be 600 MPa or less.

[0185] The indentation hardness HA1 may be 340 MPa or more and 600 MPa or less, 342 MPa or more and 600 MPa or less, 387 MPa or more and 600 MPa or less, 409 MPa or more and 600 MPa or less, 414 MPa or more and 600 MPa or less, 417 MPa or more and 600 MPa or less, 483 MPa or more and 600 MPa or less, 500 MPa or more and 600 MPa or less, or 522 MPa or more and 600 MPa or less.

[0186] A lower limit may be set for the indentation hardness HA2 at the second position 27. By setting a lower limit for the indentation hardness HA2, the hardness of the first surface 11 of the optical sheet 10 can be effectively improved, and the scratch resistance of the first surface 11 can be effectively improved. The indentation hardness HA2 at the second position 27 may be 240 MPa or more, 243 MPa or more, 298 MPa or more, 313 MPa or more, 348 MPa or more, 360 MPa or more, 424 MPa or more, or 453 MPa or more.

[0187] The upper limit of the indentation hardness HA2 is not particularly set, and the indentation hardness HA2 may be 550 MPa or less.

[0188] The indentation hardness HA2 may be 240 MPa or more and 550 MPa or more, 243 MPa or more and 550 MPa or more, 298 MPa or more and 550 MPa or more, 313 MPa or more and 550 MPa or more, 348 MPa or more and 550 MPa or more, 360 MPa or more and 550 MPa or more, 424 MPa or more and 550 MPa or more, or 453 MPa or more and 550 MPa or more.

[0189] A lower limit may be set for the indentation hardness HA3 at the third position 28. By setting a lower limit for the indentation hardness HA3, the hardness of the first surface 11 of the optical sheet 10 can be effectively improved, and the scratch resistance of the first surface 11 can be effectively improved. The indentation hardness HA3 at the third position 28 may be 120 MPa or more, 122 MPa or more, 126 MPa or more, 129 MPa or more, 132 MPa or more, 147 MPa or more, 241 MPa or more, or 264 MPa or more.

[0190] The upper limit of the indentation hardness HA3 is not particularly set, and the indentation hardness HA3 may be 350 MPa or less.

[0191] The indentation hardness HA3 may be 120 MPa or more and 350 MPa or less, 122 MPa or more and 350 MPa or less, 126 MPa or more and 350 MPa or less, 129 MPa or more and 350 MPa or less, 132 MPa or more and 350 MPa or less, 147 MPa or more and 350 MPa or less, 241 MPa or more and 350 MPa or less, or 264 MPa or more and 350 MPa or less.

[0192] As demonstrated by the examples described below, satisfying conditions (A) and (B) regarding indentation hardness can improve the hardness of the first surface 11 of the optical sheet 10, and can also improve the scratch resistance of the first surface 11 of the optical sheet 10. Satisfying conditions (A) and (B) can make the pencil hardness of the first surface 11 2H or more. Satisfying conditions (A) and (B) can make the load capacity of the first surface 11 100 g or more in a steel wool scratch resistance test.

[0193] Pencil hardness is an index that indicates resistance to defects such as scratches that occur when a pencil lead is pressed against a sample to be evaluated and then moved. Pencil hardness is measured using a pencil hardness tester. The optical sheet sample to be evaluated is rectangular. The short side of the rectangle is 50 mm and the long side is 100 mm. The test environment is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before the start of the test. The rectangular sample is spread out on the pencil hardness tester so as not to cause wrinkles or warping. The two short sides of the spread sample are fixed to the pencil hardness tester using mending tape along the entire length of the short sides. The mending tape is not particularly limited. As an example, the mending tape may be "810-3-18" manufactured by 3M.

[0194] The load applied to the pencil during the test is 500 g. The pencil movement speed is 1.4 mm / sec. The pencil movement length is 10 mm. The pencil movement direction is parallel to the long side of the sample. The pencil is a uni made by MITSU-BISHI. Five tests are conducted on the same sample using pencils of the same hardness. The five tests are conducted at locations on the same sample that are at least 10 mm apart. A re-sharpened pencil is used for each of the five tests.

[0195] If the number of tests without defects on the first surface 11 is four or more, the evaluation object is deemed to have passed. A defect is a scratch of 3 mm or more. The presence or absence of defects is confirmed by visually observing the surface of the sample removed from the pencil hardness tester. The sample surface is observed under indoor lighting. The observation distance is 30 cm. The illuminance on the surface of the sample to be observed is 800 Lx or more and 1200 Lx or less.

[0196] The highest hardness of the pencils used in the tests that were judged to pass was used as the pencil hardness of the sample to be evaluated. Other conditions for the pencil hardness test were as per JIS K 5600-5-4:1999.

[0197] The steel wool scratch resistance test is an index showing resistance to defects such as scratches that occur when steel wool is pressed against a sample to be evaluated and moved relative to it. The optical sheet sample to be evaluated is rectangular. The short sides of the rectangle are 30 mm and the long sides are 250 mm. The rectangular sample is spread out on the testing machine so as not to cause wrinkles or warping. The two short sides of the spread sample are fixed to the testing machine using mending tape over the entire length of the short sides. The mending tape is not particularly limited. As an example, the mending tape may be "810-3-18" manufactured by 3M.

[0198] The steel wool used as the sliding piece is brought into contact with the surface of the sample, which is the first side of the optical sheet. The steel wool used is "Bonstar B-204" with a count of #0000 manufactured by Nippon Steel Wool Co., Ltd. The Bonstar B-204 is a commercial size with a width of approximately 390 mm, a length of approximately 75 mm, and a thickness of approximately 110 mm. The contact area between the test sample and the sliding piece is 20 mm x 20 mm. A load is applied to the sliding piece from the vertical direction, and the sample, which is spread out along a horizontal surface, is pressed against the sliding piece. With the sliding piece pressed against the sample, the sliding piece and the sample are moved relative to each other in the horizontal direction. The sliding piece and the test sample are moved relative to each other in a direction perpendicular to the main extension direction of the steel wool fibers. The load pressing the sliding piece against the sample is a minimum of 50 g. The relative movement is a reciprocating movement along a linear path. The reciprocating movement cycle is performed 10 times. The test environment is set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before the start of the test. The reciprocating speed is 100 mm / sec. The stroke of the reciprocating motion is 120 mm for both the forward and return paths. The reciprocating motion is parallel to the long side of the sample.

[0199] An unused sliding piece is used. Before conducting the test on the evaluation target, the steel wool is rubbed against the preparation sample to break it in. The testing machine used to test the sample to be evaluated is also used to break in the steel wool. The preparation sample is a polyethylene terephthalate film. The preparation sample is rectangular with short sides of 30 mm and long sides of 250 mm. The steel wool is rubbed against the untreated surface of the polyethylene terephthalate film. The preparation sample is spread along a horizontal plane, and the two short sides of the preparation sample are fixed to the testing machine with mending tape. The steel wool is pressed against the preparation sample from above in the vertical direction. The contact area between the preparation sample and the steel wool is 20 mm x 20 mm. The load pressing the steel wool against the preparation sample is 500 g. With the steel wool pressed against the preparation sample, the steel wool and the preparation sample are moved relative to each other in the horizontal direction. The steel wool and the preparation sample are moved relative to each other in a direction perpendicular to the direction in which the steel wool fibers mainly extend. The relative movement is a reciprocating movement. The reciprocating movement is performed 200 times. The reciprocating movement speed is 100 mm / sec. The reciprocating stroke is 120 mm for both the forward and backward movements. The steel wool pressed against the preparation sample in this manner is used for the test to be evaluated.

[0200] After completing the 10-cycle scratch resistance test, the sample is removed from the tester, and the surface of the sample, which is formed by the first side of the optical sheet, is observed with the naked eye. The sample surface is observed under indoor lighting. The observation distance is 30 cm. The illuminance on the surface of the sample to be evaluated is 800 Lx or more and 1200 Lx or less.

[0201] The steel wool scratch resistance test is conducted five times on the optical sheet to be evaluated. A test in which no scratches are observed on the first surface 11 four or more times is considered to have passed. The five tests are conducted on different samples cut out from the same optical sheet. The steel wool is replaced after each of the five tests. The above-mentioned break-in of the steel wool is conducted for each of the five tests.

[0202] If the test results are pass, the load applied by the slider to the sample is increased in 50g increments up to 300g. That is, the load applied by the slider to the sample is increased in 50g increments: 100g, 150g, 200g, 250g, and 300g. The maximum load in the test that is judged as pass is the load capacity of the steel wool scratch resistance test for that sample. For example, an evaluation object that is evaluated as having a load capacity of 200g is judged to pass in all tests with a pressing load of 50g, 100g, 150g, and 200g.

[0203] As described above, by satisfying other conditions in addition to condition (A) and condition (B), the hardness and scratch resistance of the first surface 11 of the optical sheet 10 can be improved. The pencil hardness of the first surface 11 may be 2H or more, 3H or more, or 4H or more. The load resistance of the first surface 11 in a steel wool scratch resistance test may be 100 g or more, 150 g or more, 200 g or more, 250 g or more, or 300 g or more.

[0204] There is no particular upper limit set for the pencil hardness of the first surface 11. The pencil hardness of the first surface 11 may be 2H or more and 8H or less, 3H or more and 8H or less, or 4H or more and 8H or less.

[0205] There is no particular upper limit set for the load capacity in a steel wool scratch resistance test on the first surface 11. The load capacity of the first surface 11 in a steel wool scratch resistance test may be 100 g or more and 300 g or less, 150 g or more and 300 g or less, 200 g or more and 300 g or less, or even 300 g.

[0206] The functional layer 20 may be in contact with the substrate layer 40. In this example, the functional layer 20 may be formed by applying a curable resin composition onto the substrate layer 40. In this example, the substrate layer 40 may be a substrate film.

[0207] 1 , the optical sheet 10 may further include an intermediate layer 30. The intermediate layer 30 is located between the functional layer 20 and the base layer 40 in a first direction D1, which is the thickness direction. The intermediate layer 30 is in contact with the functional layer 20. The intermediate layer 30 is in contact with the base layer 40.

[0208] The base material layer 40 and the intermediate layer 30 may both be constituted by a base material film 45 to which a curable resin composition for producing the functional layer 20 is applied. A portion of the base material film 45 that is permeated with the curable resin composition may constitute the intermediate layer 30. A portion of the base material film 45 that is not permeated with the curable resin composition may constitute the base material layer 40.

[0209] The intermediate layer 30 as a permeation layer may contain the same resin component as at least a portion of the resin component contained in the base material layer 40. According to this example, it is possible to improve the adhesion between the intermediate layer 30 and the base material layer 40. The adhesion between the intermediate layer 30 and the base material layer 40 can also contribute to improving the hardness of the first surface 11.

[0210] The intermediate layer 30 as a permeation layer may contain the same resin component as at least a portion of the resin component contained in the functional layer 20. According to this example, it is possible to improve the adhesion between the intermediate layer 30 and the functional layer 20. The adhesion between the intermediate layer 30 and the functional layer 20 can also contribute to improving the hardness of the first surface 11.

[0211] The intermediate layer 30 may contain an ultraviolet absorber that is the same as at least a portion of the ultraviolet absorber contained in the functional layer 20. When the intermediate layer 30 contains an ultraviolet absorber, the blue light blocking function can be strengthened.

[0212] Forming the intermediate layer 30 as a permeation layer improves the adhesion between the base film 45 and the functional layer 20. This improves the hardness of the first surface 11 of the optical sheet 10, and improves the scratch resistance of the first surface 11 of the optical sheet 10.

[0213] Fourier transform infrared spectroscopy (FT-IR) can quantitatively analyze the chemical bonds contained in each of the layers 20, 30, and 40. By using Fourier transform infrared spectroscopy, it is possible to determine whether the intermediate layer 30 contains the resin component contained in the functional layer 20. By using Fourier transform infrared spectroscopy, it is possible to determine whether the intermediate layer 30 contains the resin component contained in the base material layer 40.

[0214] The presence of the permeation layer can be confirmed by observing the cross section of the optical sheet along the first direction with a scanning transmission electron microscope (STEM). An observation image of the cross section of the optical sheet 10 to be evaluated is obtained by observing a thickness measurement sample (described later) with a scanning transmission electron microscope. The thickness measurement sample is stained before observation with the scanning transmission electron microscope. Osmium tetroxide, ruthenium tetroxide, phosphotungstic acid, or the like may be used for staining.

[0215] The substrate film 45 may contain one or more of an acrylic resin and a cellulose resin. The acrylic resin and the cellulose resin are easily permeated with the curable resin composition. Therefore, the intermediate layer 30, which is a mixed layer of the resin component of the functional layer 20 and the resin component of the substrate layer 40, can be easily produced. From this point of view, the substrate layer 40 may contain one or more of an acrylic resin and a cellulose resin. The intermediate layer 30 may contain one or more of an acrylic resin and a cellulose resin.

[0216] The indentation hardness HB of the intermediate layer 30 at a cross section may be smaller than the indentation hardness HC of the base layer 40 at a cross section. The intermediate layer 30 having a small indentation hardness can flexibly deform in accordance with the deformation of the functional layer 20 when the functional layer 20 shrinks upon curing. By positioning this intermediate layer 30 between the base layer 40 and the functional layer 20, deformation of the optical sheet 10 such as curling and warping can be suppressed.

[0217] The indentation hardness HB in the cross section of the intermediate layer 30 is the indentation hardness of the intermediate layer 30 in the cross section of the optical sheet 10. As shown in FIG. 2A , the cross section of the optical sheet 10 where the indentation hardness is measured is a cross section along the thickness direction of the optical sheet 10. In the illustrated example, the cross section of the optical sheet 10 where the indentation hardness is measured is a cross section along the first direction D1, which is the stacking direction of the functional layer 20 and the base layer 40. The indentation hardness HB is the indentation hardness at a central position 31 of the intermediate layer 30 in the cross section of the intermediate layer 30. As shown in FIG. 2A , the central position 31 is located at the center in the thickness direction in the cross section of the intermediate layer 30.

[0218] The intermediate layer 30 may contain a monomer. The intermediate layer 30 may contain at least a portion of the monomer contained in the curable resin composition for producing the functional layer 20. According to these examples, an intermediate layer 30 with low hardness can be stably formed. The intermediate layer 30 functions as a deformation absorbing layer, and can suppress deformation such as curling and warping of the optical sheet 10.

[0219] Whether the intermediate layer 30 contains a monomer is determined by staining with osmium tetroxide. First, a cross-sectional sample is cut out from the optical sheet 10 by cutting. The sample thickness is approximately 80 nm. The cut sample is collected on a Cu mesh. This sample is stained with osmium tetroxide for 30 minutes using a vapor-phase staining method. The portion of the stained sample corresponding to the intermediate layer 30 is observed using a scanning transmission electron microscope (STEM). The staining process stains unsaturated double bonds that may be contained in the intermediate layer 30. Therefore, if the observed sample is stained, it is determined that the intermediate layer 30 contains a monomer. Whether the monomer contained in the intermediate layer 30 is the same as the monomer contained in the curable resin composition used to produce the intermediate layer 30 is determined by quantitatively analyzing chemical bonds using Fourier transform infrared spectroscopy (FT-IR).

[0220] A lower limit may be set for the indentation hardness HB at the cross section of the intermediate layer 30. Setting a lower limit for the indentation hardness HB can effectively improve the hardness at the first surface 11 of the optical sheet 10. The indentation hardness HB at the cross section of the intermediate layer 30 may be 120 MPa or more, 124 MPa or more, 138 MPa or more, 142 MPa or more, 151 MPa or more, or 156 MPa or more.

[0221] An upper limit may be set for the indentation hardness HB at the cross section of the intermediate layer 30. Setting an upper limit for the indentation hardness HB can suppress deformation such as curling and warping of the optical sheet 10. The indentation hardness HB at the cross section of the intermediate layer 30 may be 240 MPa or less, 237 MPa or less, 200 MPa or less, or 180 MPa or less.

[0222] The indentation hardness HB may be 120 MPa or more and 240 MPa or less, 124 MPa or more and 240 MPa or less, 138 MPa or more and 240 MPa or less, 142 MPa or more and 240 MPa or less, 151 MPa or more and 240 MPa or less, or 156 MPa or more and 240 MPa or less. The indentation hardness HB may be 120 MPa or more and 237 MPa or less, 124 MPa or more and 237 MPa or less, 138 MPa or more and 237 MPa or less, 142 MPa or more and 237 MPa or less, 151 MPa or more and 237 MPa or less, or 156 MPa or more and 237 MPa or less. The indentation hardness HB may be 120 MPa or more and 200 MPa or less, 124 MPa or more and 200 MPa or less, 138 MPa or more and 200 MPa or less, 142 MPa or more and 200 MPa or less, 151 MPa or more and 200 MPa or less, or 156 MPa or more and 200 MPa or less. The indentation hardness HB may be 120 MPa or more and 180 MPa or less, 124 MPa or more and 180 MPa or less, 138 MPa or more and 180 MPa or less, 142 MPa or more and 180 MPa or less, 151 MPa or more and 180 MPa or less, or 156 MPa or more and 180 MPa or less.

[0223] A lower limit may be set for the thickness T20 of the functional layer 20. By setting a lower limit for the thickness of the functional layer 20, it is possible to stably improve the hardness of the first surface 11 of the optical sheet 10. The thickness T20 of the functional layer 20 may be 4.0 μm or more, 4.2 μm or more, 5.2 μm or more, or 5.5 μm or more.

[0224] An upper limit may be set for the thickness T20 of the functional layer 20. Setting an upper limit for the thickness of the functional layer 20 can stably suppress deformation such as curling and warping that occurs in the optical sheet 10. The thickness T20 of the functional layer 20 may be 10 μm or less, 9.5 μm or less, 8.7 μm or less, or 7.4 μm or less.

[0225] The thickness T20 of the functional layer 20 may be 4.0 μm or more and 10 μm or less, 4.2 μm or more and 10 μm or less, 5.2 μm or more and 10 μm or less, or 5.5 μm or more and 10 μm or less. The thickness T20 of the functional layer 20 may be 4.0 μm or more and 9.5 μm or less, 4.2 μm or more and 9.5 μm or less, 5.2 μm or more and 9.5 μm or less, or 5.5 μm or more and 9.5 μm or less. The thickness T20 of the functional layer 20 may be 4.0 μm or more and 8.7 μm or less, 4.2 μm or more and 8.7 μm or less, 5.2 μm or more and 8.7 μm or less, or 5.5 μm or more and 8.7 μm or less. The thickness T20 of the functional layer 20 may be 4.0 μm or more and 7.4 μm or less, 4.2 μm or more and 7.4 μm or less, 5.2 μm or more and 7.4 μm or less, or 5.5 μm or more and 7.4 μm or less.

[0226] An upper limit may be set for the thickness T30 of the intermediate layer 30. In particular, in an example in which the indentation hardness HB of the intermediate layer 30 at the cross section is smaller than the indentation hardness HC of the base layer 40 at the cross section, an upper limit may be set for the thickness T30 of the intermediate layer 30. By setting an upper limit for the thickness T30 of the intermediate layer 30, a decrease in hardness on the first surface 11 of the optical sheet 10 can be suppressed. Therefore, the hardness on the first surface 11 of the optical sheet 10 can be improved, and the scratch resistance on the first surface 11 of the optical sheet 10 can be improved. The thickness T30 of the intermediate layer 30 may be 4.2 μm or less, 3.1 μm or less, 2.7 μm or less, 2.4 μm or less, 2.3 μm or less, or 2.0 μm or less.

[0227] There is no particular lower limit set for the thickness T30 of the intermediate layer 30. The intermediate layer 30 is not essential and can be omitted from the optical sheet 10. The thickness T30 of the intermediate layer 30 may be greater than 0, 0.5 μm or more, 1.0 μm or more, or 1.4 μm or more.

[0228] The thickness T30 of the intermediate layer 30 may be 0.5 μm or more and 4.2 μm or less, 0.5 μm or more and 3.1 μm or less, 0.5 μm or more and 2.7 μm or less, 0.5 μm or more and 2.4 μm or less, 0.5 μm or more and 2.3 μm or less, or 0.5 μm or more and 2.0 μm or less. The thickness T30 of the intermediate layer 30 may be 1.0 μm or more and 4.2 μm or less, 1.0 μm or more and 3.1 μm or less, 1.0 μm or more and 2.7 μm or less, 1.0 μm or more and 2.4 μm or less, 1.0 μm or more and 2.3 μm or less, or 1.0 μm or more and 2.0 μm or less. The thickness T30 of the intermediate layer 30 may be 1.4 μm or more and 4.2 μm or less, 1.4 μm or more and 3.1 μm or less, 1.4 μm or more and 2.7 μm or less, 1.4 μm or more and 2.4 μm or less, 1.4 μm or more and 2.3 μm or less, or 1.4 μm or more and 2.0 μm or less.

[0229] 1 , the thickness T40 of the base layer 40 may be greater than the thickness T20 of the functional layer 20. The thickness T40 of the base layer 40 may be greater than the thickness T30 of the intermediate layer 30. The thickness T40 of the base layer 40 may be greater than the sum of the thickness T20 of the functional layer 20 and the thickness T30 of the intermediate layer 30. A base layer 40 having such a thickness T40 can stably support the functional layer 20 and the intermediate layer 30.

[0230] The intermediate layer 30 as a permeation layer is not essential to the optical sheet 10 of the first embodiment. The intermediate layer 30 itself is not essential to the optical sheet 10 of the first embodiment. Regardless of the presence or absence of the intermediate layer 30, the hardness and scratch resistance of the first surface 11 can be improved by satisfying the above-described conditions (A) and (B) regarding the indentation hardness in the cross section of the functional layer 20.

[0231] The thicknesses T20, T30, and T40 of the layers 20, 30, and 40 included in the optical sheet 10 are determined using a scanning transmission electron microscope (STEM). A cross section of the optical sheet 10 to be evaluated is observed with the STEM, and the thicknesses are measured from the images observed with the STEM. For each of the layers 20, 30, and 40, the thicknesses T20, T30, and T40 are determined as the arithmetic mean of ten thickness measurements taken at ten measurement positions.

[0232] An observation image of the cross section of the optical sheet 10 to be evaluated is obtained by observing a thickness measurement sample with a scanning transmission electron microscope. The thickness measurement sample is obtained by the following first and second steps.

[0233] (First step) A cut sample is cut out from the optical sheet to be evaluated. The cut sample is visually checked for any abnormalities such as dust or scratches. Next, the cut sample is embedded in resin to prepare an embedded sample.

[0234] The embedded sample is prepared in the following procedure. First, the cut sample is placed in a silicon embedding plate. Then, embedding resin is poured into the silicon embedding plate with the cut sample placed in it. Next, the embedding resin is hardened inside the silicon embedding plate. Next, the cut sample and the embedding resin that encases it are removed from the silicon embedding plate to obtain the embedded sample. The embedded sample is shaped like a block. The embedding resin is epoxy resin.

[0235] (Second step) The block-shaped embedded sample is cut to prepare a slice sample. The slice sample includes a surface along the first direction (thickness direction, stacking direction) of the target optical sheet. Among the slices cut from the block-shaped embedded sample, a slice sample that is free of defects such as holes and has a uniform thickness of approximately 60 nm to 100 nm is used as the thickness measurement sample.

[0236] When obtaining an observation image of the cross section of the optical sheet, the imaging conditions of the scanning transmission electron microscope are as follows: <Imaging conditions> Mode: Transmission mode TE, bright field Acceleration voltage: 10 kV to 30 kV Emission current: 10 μA WD (Working Distance): 8.8±0.1 mm Magnification: 5000 times

[0237] L of the optical sheet 10 measured by transmitted light ＊ a ＊ b ＊ Color system a ＊ The L value of the optical sheet 10 measured by transmitted light may be equal to or greater than -3.0 and equal to or less than -1.6. ＊ a ＊ b ＊ Color system b ＊ The value may be 3.5 or more and 6.0 or less. ＊ value and b ＊ By setting the value within the above range, it is possible to suppress changes and deterioration in the color of an image observed through the optical sheet 10 while maintaining the blue light blocking function.

[0238] L ＊ a ＊ b ＊ The color system is CIE 1976 L ＊ a ＊ b ＊ It is a color coordinate defined as a color space, and is also defined in JIS Z8781-4:2013. Using auxiliary illuminant C and a 2-degree visual field, the L is calculated based on the transmittance measured in 0.5 nm intervals in the range from 300 nm to 780 nm. ＊ a ＊ b ＊ a in the color system ＊ value and b ＊ Find the value. ＊ value and b ＊ Before measuring the value, the light source of the measuring device is turned on for 15 minutes to stabilize the light source output. ＊ value and b ＊ The incident surface when measuring the value is the second surface 12 of the optical sheet 10. ＊ value and b ＊ The test environment for measuring the values ​​is 23°C ± 2°C, and 50% ± 5% relative humidity. The sample is left in the test environment for 16 hours before the start of the test.

[0239] a ＊ The value is the arithmetic mean value of five measured values. The five measured values ​​are measured at five measurement positions on the optical sheet to be evaluated. The five measurement positions are located at least 10 mm apart from each other. ＊ The value is the arithmetic mean of five measurements. ＊ The five measurements for the value are a ＊ The five measurement values ​​for the value are taken as values ​​measured at the five measurement positions.

[0240] The yellowness index (YI value) of the optical sheet 10 may be 12 or less, 11 or less, 10 or less, or 9.0 or less. The yellowness index is an index showing the degree of yellow coloration of the optical sheet 10. By setting the above upper limit for the yellowness index (YI value), it is possible to limit the yellow coloration of the optical sheet 10. By achieving the above spectral transmittance without using a yellow pigment, it is possible to suppress color changes in images transmitted through the optical sheet 10.

[0241] There is no particular lower limit for the yellowness index (YI value) of the optical sheet 10. The yellowness index (YI value) of the optical sheet 10 may be 0 or greater, or may be greater than 0.

[0242] The yellowness index (YI value) of the optical sheet 10 may be 0 or more and 12 or less, 0 or more and 11 or less, 0 or more and 10 or less, or 0 or more and 9.0 or less. The yellowness index (YI value) of the optical sheet 10 may be 0 or more and 12 or less, 0 or more and 11 or less, 0 or more and 10 or less, or 0 or more and 9.0 or less.

[0243] Yellowness index is measured using transmitted light. Using spectrophotometric colorimetry, auxiliary illuminant C and a 2-degree visual field are used to measure transmittance in 0.5-nm intervals over the range of 300 nm to 780 nm. The tristimulus values ​​X, Y, and Z in the XYZ color system are calculated based on the calculated X, Y, and Z values. The yellowness index (YI value) is determined from the calculated X, Y, and Z values ​​using the following formula: YI = 100 (1.2769X - 1.0592Z) / Y. The geometrical optics condition e of JIS Z 8722:2009 is used as the geometrical optics condition for measuring yellowness index. To eliminate the influence of scattered light from the edge of the test piece, the diameter of the incident beam on the test piece is made smaller than the diameter of the aperture. Before measuring yellowness index, the light source of the measuring device is turned on for 15 minutes to stabilize the output of the D65 light source. The incident surface when measuring yellowness index is the second surface 12 of the optical sheet 10. The test environment for measuring yellowness is 23°C ± 2°C and 50% ± 5% relative humidity. The sample is placed in the test environment for 16 hours before the start of the test.

[0244] The yellowness index (YI value) is the arithmetic mean of five measured values. The five measured values ​​are measured at five measurement positions on the optical sheet to be evaluated. The five measurement positions are located at least 10 mm apart from each other. Other measurement conditions for measuring the yellowness index (YI value) are in accordance with JIS K7373-1:2006.

[0245] The total light transmittance of the optical sheet 10 may be 50% or more, 70% or more, 80% or more, or 90% or more. The total light transmittance of the optical sheet 10 has no particular upper limit. The total light transmittance of the optical sheet 10 may be 100% or less, or may be less than 100%.

[0246] The total light transmittance of the optical sheet 10 may be 50% or more and 100% or less, 70% or more and 100% or less, 80% or more and 100% or less, or 90% or more and 100% or less. The total light transmittance of the optical sheet may be 50% or more and less than 100%, 70% or more and less than 100%, 80% or more and less than 100%, or 90% or more and less than 100%.

[0247] A D65 light source is used to measure the total light transmittance. Before measuring the total light transmittance, the D65 light source is turned on for 15 minutes to stabilize the output of the D65 light source. The angle of incidence on the sample when measuring the total light transmittance is 0°. The incident surface when measuring the total light transmittance of the optical sheet 10 is the second surface of the optical sheet. The test environment when measuring the total light transmittance is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before starting the test. Other measurement conditions when measuring the total light transmittance are in accordance with JIS K7361-1:1997.

[0248] The total light transmittance is the arithmetic mean value of five measured values, which are measured at five measurement positions on the optical sheet to be evaluated, and which are located at least 10 mm apart from each other.

[0249] The transmission haze of the optical sheet 10 may be 1.1% or less, 0.5% or less, or 0.2% or less. The transmission haze of the optical sheet 10 has no particular lower limit. The transmission haze of the optical sheet 10 may be 0% or more, or may be greater than 0%.

[0250] The transmission haze of the optical sheet 10 may be 0% or more and 1.1% or less, 0% or more and 0.5% or less, or 0% or more and 0.2% or less. The transmission haze of the optical sheet 10 may be greater than 0% and 1.1% or less, greater than 0% and 0.5% or less, or greater than 0% and 0.2% or less.

[0251] A D65 light source is used to measure transmission haze. Before measuring transmission haze, the D65 light source is turned on for 15 minutes to stabilize the output of the D65 light source. The angle of incidence on the sample when measuring transmission haze is 0°. The incident surface when measuring transmission haze of the optical sheet 10 is the second surface 12 of the optical sheet 10. The test environment when measuring transmission haze is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before starting the test. Other measurement conditions when measuring transmission haze are in accordance with JIS K7136:2000.

[0252] The transmission haze is the arithmetic mean value of five measurements taken at five measurement positions on the optical sheet to be evaluated, the five measurement positions being spaced 10 mm or more apart from each other.

[0253] The ratio of silicon to carbon measured on the first surface 11 by X-ray photoelectron spectroscopy may be 0.02 or greater. In other words, the amount of silicon may be 0.02 or greater when the amount of carbon is 1 in the quantitative elemental analysis results by X-ray photoelectron spectroscopy. The silicon is the sum of an inorganic component (silica) and an organic component (silicone). The functional layer 20 may contain inorganic particles as a lubricant. By setting the ratio of silicon to carbon to 0.02 or greater, aggregation of inorganic particles added as a lubricant, such as silica aggregation, can be suppressed. In other words, by setting the ratio of silicon to carbon to 0.02 or greater, the lubricant functions effectively. The lubricant can prevent adjacent optical sheets 10 from sticking to each other when stacking or rolling up the optical sheets 10.

[0254] The curable resin composition for producing the functional layer 20 may contain a leveling agent. By using a Si-based leveling agent as the leveling agent added to the curable resin composition, the ratio of silicon element to carbon element can be set to 0.02 or more.

[0255] The ratio of elemental fluorine measured on the first surface 11 by X-ray photoelectron spectroscopy may be 0.1% or less. In other words, the ratio of the amount of elemental fluorine to the total amount of elements detected by X-ray photoelectron spectroscopy may be 0.001 or less. In this example, substantially no fluorine is detected in the surface layer portion of the optical sheet 10. By not using an F-based leveling agent as the leveling agent added to the curable resin composition, the ratio of elemental fluorine can be 0.1% or less.

[0256] By setting the fluorine element ratio to 0.1% or less, it is possible to suppress the generation of PFAS as an impurity. PFAS, an artificial organic fluorine compound, is a concern due to its bioaccumulation potential. Suppressing the generation of PFAS can contribute to reducing the environmental impact. Reducing the fluorine element ratio also improves the scratch resistance of the first surface 11.

[0257] X-ray photoelectron spectroscopy allows quantitative analysis of elements present in the surface layer of the optical sheet 10. X-ray photoelectron spectroscopy uses an X-ray photoelectron spectroscopy (XPS) device.

[0258] In the quantitative analysis of elements present in the surface layer by X-ray photoelectron spectroscopy, the X-ray photoelectron spectra of the C1s orbital, O1s orbital, Si2p orbital, and F1s orbital on the surface of the low refractive index layer of each measurement sample are measured under the conditions described below. Peak separation is performed on each X-ray photoelectron spectrum to determine the ratio of F element to all elements. (Measurement conditions) Measurement method: Wide / Narrow X-ray source: Monochrome A1Kα X-ray output: 150 W Emission current: 10 mA Acceleration voltage: 15 kV Charge neutralization mechanism: ON Measurement area: 300 μm x 700 μm Pass Energy: Survey: 160 eV, Narrow: 40 eV Photoelectron acceptance angle: 90° Auto Z: ON Peak shift correction: Corrected so that the C-C peak is 285.0 eV in the C1s peak Waveform separation of narrow peak: Performed using the GL function in the analysis software attached to the device Etching ions: Ar monatomic ions

[0259] Each layer of the optical sheet 10 shown in FIG. 1 will be described in more detail below. In the example shown in FIG. 1, the base layer 40, the intermediate layer 30, and the functional layer 20 are stacked in a first direction D1. The first direction D1 is the stacking direction. The base layer 40, the intermediate layer 30, and the functional layer 20 extend in a second direction D2 and a third direction D3 that are perpendicular to the first direction D1. In the example shown, the second direction D2 and the third direction D3 are perpendicular to each other. The first direction D1 is the thickness direction and normal direction of the optical sheet 10. The first direction D1 is also the thickness direction and normal direction of each layer 40, 30, and 20 included in the optical sheet 10. In the optical sheet 10 shown in FIG. 1, the first surface 11 is formed by the functional layer 20. The second surface 12 is formed by the base layer 40. The functional layer 20 and the intermediate layer 30 are adjacent to each other in the first direction D1. The intermediate layer 30 and the base layer 40 are adjacent in the first direction D1.

[0260] The optical sheet 10 may include layers other than the functional layer 20, the intermediate layer 30, and the substrate layer 40. The optical sheet 10 may include one or more layers such as a low-reflection layer, an antistatic layer, and an antifouling layer. In this example, a layer other than the functional layer 20 may form the first surface 11. The other layers, such as the low-reflection layer, the antistatic layer, and the antifouling layer, are thin layers. Therefore, even in an example in which the first surface 11 is formed by other layers such as a low-reflection layer, an antistatic layer, and an antifouling layer, the combination of the functional layer 20 and the intermediate layer 30 can improve the hardness of the first surface 11 of the optical sheet 10 and the scratch resistance of the first surface 11 of the optical sheet 10.

[0261] <<Substrate Layer 40>> The substrate layer 40 supports the functional layer 20 together with the intermediate layer 30. The substrate layer 40 may be transparent. Transparent means that the total light transmittance in accordance with JIS K7361-1:1997 is 50% or more, and may be 70% or more, 80% or more, or 90% or more.

[0262] There are no particular limitations on the material of the base layer 40. The material of the base layer 40 may be resin or glass. Resin is preferable because it is lightweight and easy to manufacture.

[0263] The resin used for the substrate layer 40 may be a polyolefin resin such as polyethylene or polypropylene. The resin used for the substrate layer 40 may be a vinyl resin such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, or ethylene-vinyl alcohol copolymer. The resin used for the substrate layer 40 may be a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate. The resin used for the substrate layer 40 may be an acrylic resin such as polymethyl(meth)acrylate or polyethyl(meth)acrylate. The resin used for the substrate layer 40 may be a styrene resin such as polystyrene, a polyamide resin such as nylon 6 or nylon 66, or a cellulose resin such as triacetyl cellulose. Further examples of resins used for the substrate layer 40 include resins such as polycarbonate, polyimide resins, and cycloolefin resins derived from cycloolefins such as norbornene and dicyclopentadiene. The substrate layer 40 may contain only one of the above-mentioned resins, or two or more of the above-mentioned resins.

[0264] The thickness of the resin substrate layer 40 is not particularly limited. From the viewpoint of ease of handling, the thickness of the resin substrate layer 40 may be 10 μm or more, 20 μm or more, or 50 μm or more. The thickness of the resin substrate layer 40 may be 500 μm or less, 400 μm or less, or 300 μm or less. The thickness of the glass substrate layer 40 may be 500 μm or more.

[0265] When the optical sheet 10 is used for foldable applications, the base layer 40 may be flexible. In this example, the thickness of the resin base layer 40 may be 10 μm or more and 40 μm or less. When the optical sheet 10 is used in a laminated state with glass, the thickness of the resin base layer 40 may be 40 μm or more and 100 μm or less from the viewpoint of preventing the glass from shattering.

[0266] The substrate layer 40 may be prepared as a substrate film 45. This substrate film 45 may include only a single layer or multiple layers. The substrate layer 40 may include a primer layer such as an easy-adhesion layer. The surface of the substrate film 45 may be subjected to one or more of sputtering, corona discharge, ultraviolet irradiation, electron beam irradiation, etching treatment such as chemical conversion or oxidation, and priming treatment. These treatments can improve the adhesion between the substrate film 45 and the layer adjacent to the substrate film 45. The surface of the substrate film 45 may be subjected to a cleaning treatment such as solvent cleaning or ultrasonic cleaning.

[0267] <<Functional Layer 20>> The functional layer 20 includes a binder resin 23 and an ultraviolet absorber. By including the ultraviolet absorber, the functional layer 20 exhibits a blue light blocking function. The binder resin 23 includes a cured product of a curable resin composition. By including the cured product of the curable resin composition, the functional layer 20 contributes to improving the hardness of the first surface 11 and the functional layer 20.

[0268] The curable resin composition may be an ionizing radiation-curable resin composition. The ionizing radiation-curable resin composition may include one or more of an ultraviolet-curable resin composition and an electron beam-curable resin composition. The ionizing radiation-curable resin composition may include an ionizing radiation-curable compound and a photopolymerization initiator. The ionizing radiation-curable compound may include one or more of an ultraviolet-curable compound and an electron beam-curable compound. The ultraviolet-curable compound is a resin that is cured by irradiation with ultraviolet light. The electron beam-curable compound is a resin that is cured by irradiation with an electron beam. The cured product of the curable resin composition may be a cured curable compound.

[0269] <Curable Compound> The ionizing radiation-curable compound contains an ionizing radiation-curable functional group. Examples of the ionizing radiation-curable functional group include ethylenically unsaturated bond groups such as a (meth)acryloyl group, a vinyl group, and an allyl group, as well as an epoxy group and an oxetanyl group. The ionizing radiation-curable compound may contain two or more ionizing radiation-curable functional groups. The ionizing radiation-curable compound may be a compound having an ethylenically unsaturated bond group. The ionizing radiation-curable compound may be a (meth)acrylate-based compound having a (meth)acryloyl group. The ionizing radiation-curable compound may be a siloxane compound containing a siloxane bond.

[0270] Hereinafter, a (meth)acrylate compound having four or more ethylenically unsaturated bond groups will be referred to as a "polyfunctional (meth)acrylate compound," and a (meth)acrylate compound having two to three ethylenically unsaturated bond groups will be referred to as a "low-functional (meth)acrylate compound."

[0271] The (meth)acrylate compound may be a monomer or an oligomer. An ionizing radiation curable compound containing a low-functional (meth)acrylate compound can suppress uneven shrinkage during curing and smooth the surface of the functional layer 20.

[0272] The proportion of the low-functional (meth)acrylate compound in the ionizing radiation-curable compound may be 60% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or even 100% by mass. From the viewpoint of suppressing uneven shrinkage during curing and smoothing the irregularities on the surface of the functional layer 20, the low-functional (meth)acrylate compound may be a (meth)acrylate compound containing two ethylenically unsaturated bond groups. When the ionizing radiation-curable compound contains a large amount of a polyfunctional (meth)acrylate compound, the surface of the functional layer can be smoothed by appropriately adjusting the type of solvent and drying conditions, as described below.

[0273] Among the (meth)acrylate compounds, examples of bifunctional (meth)acrylate compounds include polyalkylene glycol di(meth)acrylates such as isocyanuric acid di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, and polybutylene glycol di(meth)acrylate, bisphenol A tetraethoxydiacrylate, bisphenol A tetrapropoxydiacrylate, and 1,6-hexanediol diacrylate. Examples of trifunctional (meth)acrylate compounds include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and isocyanuric acid-modified tri(meth)acrylate. Examples of polyfunctional (meth)acrylate compounds having tetrafunctional or higher functionality include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and dipentaerythritol tetra(meth)acrylate. The (meth)acrylate compound may be modified as described below.

[0274] Examples of (meth)acrylate oligomers include acrylate polymers such as urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, and polyether (meth)acrylate. Urethane (meth)acrylate can be obtained, for example, by reacting a polyhydric alcohol and an organic diisocyanate with a hydroxy (meth)acrylate. The epoxy (meth)acrylate may be a (meth)acrylate obtained by reacting a trifunctional or higher aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, or the like with (meth)acrylic acid. The epoxy (meth)acrylate may be a (meth)acrylate obtained by reacting a difunctional or higher aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, or the like with a polybasic acid and (meth)acrylic acid. The epoxy (meth)acrylate may be a (meth)acrylate obtained by reacting a difunctional or higher aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, or the like with a phenol and (meth)acrylic acid.

[0275] The (meth)acrylate compound may have a portion of its molecular skeleton modified to suppress uneven shrinkage due to crosslinking. The (meth)acrylate compound may be modified with, for example, ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, an alkyl, a cyclic alkyl, an aromatic, a bisphenol, or the like. To increase affinity with silica particles, suppress particle aggregation, and adjust the C / Si ratio within the above range, the (meth)acrylate compound may be modified with an alkylene oxide such as ethylene oxide or propylene oxide. The proportion of the alkylene oxide-modified (meth)acrylate compound in the ionizing radiation-curable compound may be 60% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or even 100% by mass. The alkylene oxide-modified (meth)acrylate compound may be a low-functional (meth)acrylate compound or a (meth)acrylate compound having two ethylenically unsaturated bond groups.

[0276] Examples of alkylene oxide-modified (meth)acrylate compounds having two ethylenically unsaturated bond groups include bisphenol F alkylene oxide-modified di(meth)acrylate, bisphenol A alkylene oxide-modified di(meth)acrylate, isocyanuric acid alkylene oxide-modified di(meth)acrylate, and polyalkylene glycol di(meth)acrylate. The average number of repeating units of the alkylene glycol contained in the polyalkylene glycol di(meth)acrylate may be 3 to 5. The alkylene glycol contained in the polyalkylene glycol di(meth)acrylate may be ethylene glycol and / or polyethylene glycol. Examples of alkylene oxide-modified (meth)acrylate compounds having three ethylenically unsaturated bond groups include trimethylolpropane alkylene oxide-modified tri(meth)acrylate and isocyanuric acid alkylene oxide-modified tri(meth)acrylate.

[0277] One type of ionizing radiation-curable compound may be used alone, or two or more types of ionizing radiation-curable compounds may be used in combination. That is, the curable resin composition may contain one type of ionizing radiation-curable compound, or may contain two or more types of ionizing radiation-curable compounds.

[0278] The curable resin composition may contain a solvent-drying resin. A solvent-drying resin is a resin that becomes a coating simply by drying a solvent added to adjust the solid content during coating. An example of the solvent-drying resin is a thermoplastic resin. When the ionizing radiation-curable compound contains a solvent-drying resin, coating defects on the coating surface can be suppressed. The solvent-drying resin is not particularly limited. Examples of the solvent-drying resin include styrene-based resins, (meth)acrylic-based resins, alicyclic olefin-based resins, polyester-based resins, and cellulose derivatives such as cellulose esters. The curable resin composition may contain one or more of these solvent-drying resins.

[0279] The curable resin composition may contain a thermosetting compound. A thermosetting compound is a resin that hardens when heated. The thermosetting compound is not particularly limited. Examples of thermosetting compounds include phenolic resins, urea resins, diallyl phthalate resins, melamine resins, guanamine resins, unsaturated polyester resins, polyurethane resins, epoxy resins, aminoalkyd resins, melamine-urea co-condensation resins, and silicone resins. The curable resin composition may contain one or more of these thermosetting compounds.

[0280] <Photopolymerization initiator> The photopolymerization initiator is not particularly limited. Examples of the photopolymerization initiator include acetophenones, benzophenones, Michler's benzoyl benzoate, α-amyloxime ester, thioxanthones, propiophenones, benzils, benzoins, and acylphosphine oxides. The curable resin composition may contain one or more of these photopolymerization initiators.

[0281] The photopolymerization initiator may be an acetophenone, a benzophenone, a thioxanthone, benzoin, benzoin methyl ether, etc. The curable resin composition may contain one or more of these photopolymerization initiators together with an ionizing radiation-curable compound having a radically polymerizable unsaturated group.

[0282] The photopolymerization initiator may be an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, a benzoin sulfonate ester, etc. The curable resin composition may contain one or more of these photopolymerization initiators together with an ionizing radiation-curable compound having a cationically polymerizable functional group.

[0283] The curable resin composition may contain a photosensitizer. Examples of the photosensitizer include n-butylamine, triethylamine, poly-n-butylphosphine, etc. The curable resin composition may contain one or more of these photosensitizers.

[0284] The content of the photopolymerization initiator may be 1 part by mass or more, or 2 parts by mass or more, relative to 100 parts by mass of the ionizing radiation-curable compound. The content of the photopolymerization initiator may be 10 parts by mass or less, or 8 parts by mass or less, relative to 100 parts by mass of the ionizing radiation-curable compound. This content can improve the hardness of the functional layer 20.

[0285] <UV absorber> The UV absorber may be dispersed in the first direction D1, the second direction D2, and the third direction D3 in the functional layer 20. The UV absorber may be contained in a liquid curable resin composition. The UV absorber contained in the curable resin composition may be dispersed in the functional layer 20 after a coating film of the curable resin composition has been subjected to a drying treatment and a curing treatment.

[0286] The ultraviolet absorber imparts blue light blocking function to the functional layer 20 and the optical sheet 10. The characteristics of the blue light blocking function can be adjusted by the type and content of the ultraviolet absorber. Therefore, the blue light blocking function attributable to the ultraviolet absorber can make the spectral transmittance at a wavelength of 440 nm 70% or more, while making the spectral transmittance at a wavelength of 410 nm 15% or less. Depending on the type and content of the ultraviolet absorber, the L measured by transmitted light can be adjusted. ＊ a＊ b ＊ Color system a ＊ The value can be adjusted by changing the type and content of the ultraviolet absorber. ＊ a ＊ b ＊ Color system b ＊ The yellowness index YI value measured by transmitted light can be adjusted by the type and content of the ultraviolet absorber. The type and content of the ultraviolet absorber are not particularly limited. ＊ Value and b ＊ The type and content of the ultraviolet absorber can be selected so as to obtain a desired value.

[0287] Examples of ultraviolet absorbers include triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers. Examples of triazine-based ultraviolet absorbers include "TINUVIN 460" and "TINUVIN 477" available from BASF. Examples of triazine-based ultraviolet absorbers include "LA-46" available from ADEKA Corporation. Examples of benzophenone-based ultraviolet absorbers include "CHMASSORB 81 / FL" available from BASF. Examples of benzotriazole-based ultraviolet absorbers include "KEMISORB 71D" and "KEMISORB 79" available from Chemipro Chemical Co., Ltd. Examples of benzotriazole-based ultraviolet absorbers include "JF-80" and "JAST-500" available from Johoku Chemical Industry Co., Ltd. Examples of benzotriazole-based ultraviolet absorbers include "ULS-1933D" available from Lion Specialty Chemicals Co., Ltd. and "RUVA-93" available from Otsuka Chemical Co., Ltd.

[0288] The ultraviolet absorber contained in the curable resin composition may be polymerized or oligomerized. The curable resin composition may contain a polymer or oligomer having a benzotriazole, triazine, or benzophenone skeleton as the ultraviolet absorber. The curable resin composition may contain an ultraviolet absorber obtained by thermally copolymerizing a (meth)acrylate having a benzotriazole or benzophenone skeleton with methyl methacrylate (MMA) in any ratio.

[0289] The content of the ultraviolet absorber is not particularly limited. The content of the ultraviolet absorber may be 1 part by mass or more, or 2 parts by mass or more, relative to 100 parts by mass of the solid content of the curable resin composition. The content of the ultraviolet absorber may be 35 parts by mass or less, or 12 parts by mass or less, relative to 100 parts by mass of the solid content of the curable resin composition.

[0290] As a more specific example, the curable resin composition may contain a sesamol-type benzotriazole monomer represented by the following general formula (1):

[0291]

[0292] R in formula (1) １ represents a hydrogen atom or a methyl group. ２ represents a linear or branched alkylene group having 1 to 6 carbon atoms, or a linear or branched oxyalkylene group having 1 to 6 carbon atoms.

[0293] The detailed structure of the sesamol-type benzotriazole monomer is not particularly limited. Specific examples of the sesamol-type benzotriazole monomer include the following: 2-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]ethyl methacrylate, 2-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]ethyl acrylate, 3-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]propyl methacrylate, 3-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]propyl acrylate, 4-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]butyl methacrylate, 4-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]butyl acrylate, 2-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yloxy]ethyl methacrylate, 2-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yloxy]ethyl acrylate, 2-[3-{2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl}propanoyloxy]ethyl methacrylate, 2-[3-{2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl}propanoyloxy]ethyl acrylate, 4-[3-{2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl}propanoyloxy]butyl methacrylate, 4-[3-{2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl}propanoyloxy]butyl acrylate, 2-[3-{2-(6-hydroxybenzo[1,2-[3-{2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl}propanoyloxy]ethyl acrylate, 2-(methacryloyloxy)ethyl 2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazole-5-carboxylate, 2-(acryloyloxy)ethyl 2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazole-5-carboxylate, 4-(methacryloyloxy)butyl 2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazole-5-carboxylate, 4-(acryloyloxy)butyl 2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazole-5-carboxylate The functional layer 20 may contain one or more of these substances as ultraviolet absorbers.

[0294] The sesamol-type benzotriazole monomer may be contained in the functional layer 20 at a content of 5% by mass or more and 20% by mass or less. With such a content, it is easy to adjust the spectral transmittance to a preferred range.

[0295] The sesamol-type benzotriazole-based monomer may react with the resin component constituting the functional layer 20 and be included as part of the resin component. The sesamol-type benzotriazole-based monomer may also be included alone without reacting with the resin component constituting the functional layer 20.

[0296] <Additives> The curable resin composition may contain particles as a lubricant. The particles as a lubricant may be inorganic particles or metal oxide particles. The particles as a lubricant may be silica. The particles as a lubricant may be silica having no reactive groups. The average primary particle diameter of the silica having no reactive groups may be 100 nm or more and 600 nm or less, or 100 nm or more and 350 nm or less. By setting the average primary particle diameter of the particles as a lubricant to 100 nm or more, an excellent anti-blocking function can be exhibited. By setting the average primary particle diameter of the particles as a lubricant to 600 nm or more, transmission haze can be reduced.

[0297] The particle diameter of the particles contained in the functional layer 20 is determined by the following (1) to (3): (1) A cross section of the optical sheet containing the particles is observed using a scanning transmission electron microscope (STEM) to obtain an observation image. The observation image is obtained by preparing a sample similar to the thickness measurement sample described above and observing this sample using a scanning transmission electron microscope. (2) 30 particles are randomly selected from the observation image, and the particle diameter of each particle is measured. The particle diameter measurement values ​​of 10 particles are selected by excluding the measurement values ​​of the 10 largest particles and the 10 smallest particles from the measurement values ​​of the 30 particles. The particle diameter (nm) is defined as the distance between two parallel lines that sandwich the particle and maximize the distance between the two lines. In other words, the particle diameter is the maximum length of the particle in the observation image. (3) The above steps (1) and (2) are performed five times for the same optical sheet to be measured. The arithmetic mean value of the particle diameter measurements of a total of 50 particles is taken as the average particle diameter (nm) of the particles.

[0298] The curable resin composition may contain a silicon-based leveling agent as an additive. When the functional layer coating liquid contains a silicon-based leveling agent, the surface of the functional layer 20 can be made smoother. The silicon-based leveling agent can impart excellent slip properties and excellent antifouling properties to the surface of the functional layer 20.

[0299] The curable resin composition may contain other additives. Examples of additives include antistatic agents, antioxidants, surfactants, dispersants, silane coupling agents, thickeners, coloring inhibitors, colorants (pigments, dyes), defoamers, flame retardants, adhesion promoters, polymerization inhibitors, antioxidants, and surface modifiers. The curable resin composition may contain one or more of these additives.

[0300] <Solvent> The curable resin composition may contain a solvent. The solvent can be selected and used depending on the type and solubility of the resin component used. Examples of types of solvents include ketones, ethers, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated carbons, esters, water, alcohols, cellosolves, cellosolve acetates, sulfoxides, and amides. Examples of ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and diacetone alcohol. Examples of ether solvents include dioxane, tetrahydrofuran, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate. Examples of aliphatic hydrocarbon solvents include hexane. Examples of alicyclic hydrocarbon solvents include cyclohexane. Examples of aromatic hydrocarbon solvents include toluene and xylene. Examples of halogenated carbon solvents include dichloromethane and dichloroethane. Examples of ester solvents include methyl acetate, ethyl acetate, and butyl acetate. Examples of alcohol solvents include ethanol, isopropanol, butanol, and cyclohexanol. Examples of cellosolve solvents include methyl cellosolve and ethyl cellosolve. Examples of sulfoxide solvents include dimethyl sulfoxide. Examples of amide solvents include dimethylformamide and dimethylacetamide. The curable resin composition may contain one or more of the solvents listed above.

[0301] The content ratio of the raw materials in the curable resin composition, i.e., the solid content ratio, is not particularly limited. The content ratio of the raw materials in the curable resin composition may be 5% by mass or more, or 25% by mass or more. The content ratio of the raw materials in the curable resin composition may be 70% by mass or less, or 60% by mass or less.

[0302] <Method of Producing Functional Layer 20> The functional layer 20 is produced using a liquid curable resin composition containing an ultraviolet absorber. The prepared curable resin composition is applied to the surface on which the functional layer 20 is to be produced, forming a coating film of the curable resin composition. The coating film of the curable resin composition is dried, and the dried coating film is cured to obtain the functional layer 20.

[0303] The method for preparing the curable resin composition is not particularly limited. The curable resin composition may be prepared using a known device such as a paint shaker, a bead mill, a kneader, or a mixer.

[0304] The method for applying the curable resin composition is not particularly limited, and the curable resin composition may be applied by a known method such as spin coating, dipping, spraying, die coating, bar coating, roll coating, meniscus coating, flexographic printing, screen printing, or pad coating.

[0305] The curing treatment of the curable resin composition may be performed by irradiation with ionizing radiation. The ionizing radiation may be ultraviolet light or an electron beam. Examples of ultraviolet light sources include ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arc lamps, black light fluorescent lamps, and metal halide lamps. The wavelength of the ultraviolet light may be in the wavelength range of 190 nm or more and 420 nm or less. The wavelength of the ultraviolet light used in the curing treatment is preferably the central absorption wavelength of the photopolymerization initiator contained in the curable resin composition, or close to the central absorption wavelength. The wavelength of the ultraviolet light used in the curing treatment is preferably away from the central absorption wavelength of the ultraviolet absorber contained in the curable resin composition. According to such an example, the functional layer 20 can be sufficiently cured by the curing treatment using ultraviolet light irradiation.

[0306] <<Intermediate Layer 30>> The intermediate layer 30 is a layer adjacent to the functional layer 20 and the substrate layer 40. The intermediate layer 30 may be a resin layer. The intermediate layer 30 may be a layer that has high adhesion to the substrate layer 40. The intermediate layer 30 may be a layer that has high adhesion to the functional layer 20. The indentation hardness HB measured on the cross section of the intermediate layer 30 may be smaller than the indentation hardness HC measured on the cross section of the substrate layer 40. The indentation hardness HB measured on the cross section of the intermediate layer 30 may be smaller than the indentation hardness HA1 measured at a first position 26 on the cross section of the functional layer 20. The indentation hardness HB measured on the cross section of the intermediate layer 30 may be smaller than the indentation hardness HA2 measured at a second position 27 on the cross section of the functional layer 20. The indentation hardness HB measured on a cross section of the intermediate layer 30 may be smaller than the indentation hardness HA measured on a cross section of the functional layer 20. The indentation hardness HA is the arithmetic average of the indentation hardness HA1 at the first position 26, the indentation hardness HA2 at the second position 27, and the indentation hardness HA3 at the third position 28. As demonstrated in the examples, the presence of such an intermediate layer 30 can improve the hardness of the first surface 11 of the optical sheet 10, and can improve the scratch resistance of the first surface 11 of the optical sheet 10.

[0307] In order to satisfy the above-described relationship between the hardness and adhesion between the functional layer 20 and the intermediate layer 30, the material of the intermediate layer 30 may be selected as follows: The intermediate layer 30 may contain a thermoplastic resin. The intermediate layer 30 may contain the same resin component as at least a portion of the resin component contained in the functional layer 20. The intermediate layer 30 may contain one or more of an acrylic resin and a cellulose resin. The intermediate layer 30 may contain a monomer. The intermediate layer 30 may contain at least a portion of the monomer contained in the curable resin composition used to produce the functional layer 20.

[0308] The intermediate layer 30 may be a mixed layer of the resin component of the functional layer 20 and the resin component of the base layer 40. By forming the intermediate layer 30 as a mixed layer of the resin component of the functional layer 20 and the resin component of the base layer 40, the hardness of the first surface 11 of the optical sheet 10 can be improved, and the scratch resistance of the first surface 11 of the optical sheet 10 can be improved.

[0309] The intermediate layer 30 as a mixed layer may be a permeation layer in which the curable resin composition for producing the functional layer 20 is permeated into the base film 45. The base film 40 and the intermediate layer 30 may both be constituted by the base film 45 to which the curable resin composition for producing the functional layer 20 is applied. The intermediate layer 30 may be constituted by a portion of the base film 45 into which the curable resin composition has permeated (permeation layer). The base film 45 may be constituted by a portion of the base film 45 into which the curable resin composition has not permeated.

[0310] The solvent contained in the curable resin composition easily penetrates the substrate film 45, allowing for stable formation of the intermediate layer 30 as a penetration layer. Using a substrate film 45 with high water absorption (liquid absorption) allows for easy penetration of the solvent into the substrate film 45. The solvent easily penetrates cellulose-based resins, particularly triacetylcellulose (TAC). The solvent also easily penetrates acrylic resins. Therefore, the substrate layer 40 and the substrate film 45 may contain one or more of an acrylic resin and a cellulose resin. In this case, the intermediate layer 30, which is a mixed layer of the resin components of the functional layer 20 and the substrate layer 40, can be stably produced. The produced intermediate layer 30 contains one or more of an acrylic resin and a cellulose resin.

[0311] The ease of forming the penetration layer varies depending on the relationship between the curable resin compound and solvent contained in the curable resin composition and the substrate film 45. The ease of forming the penetration layer also varies depending on the viscosity of the curable resin composition, the drying conditions for the coating film of the curable resin composition, and the curing conditions for the coating film of the curable resin composition. Therefore, the thickness T30 of the intermediate layer 30 serving as the penetration layer can be adjusted by the materials contained in the curable resin composition, the materials for the substrate film 45, the preparation conditions for the curable resin composition, the drying conditions for the curable resin composition, the curing conditions for the curable resin composition, etc.

[0312] The intermediate layer may contain an ultraviolet absorber that is the same as at least a part of the ultraviolet absorber contained in the functional layer.

[0313] <<Manufacturing of Optical Sheet>> The manufacturing method of the optical sheet 10 may include the following four steps: a step of applying a first curable resin composition containing an ultraviolet absorber onto a base film 45; a step of curing the coating of the first curable resin composition to form a first portion 20A on the base film 45; a step of applying a second curable resin composition onto the first portion 20A; and a step of curing the coating of the second curable resin composition to form a second portion 20B bonded to the first portion 20A.

[0314] The production method may further include a step of drying the coating film of the first curable resin composition before a step of curing the coating film of the first curable resin composition. The production method may further include a step of drying the coating film of the second curable resin composition before a step of curing the coating film of the second curable resin composition.

[0315] In this manufacturing method, the first portion 20A and the second portion 20B can constitute the functional layer 20. As described above, the curable resin composition permeates the base film 45, thereby forming the intermediate layer 30 as a part of the base film 45. The base layer 40 can be constituted by the portion of the base film 45 that is not permeated with the curable resin composition.

[0316] 1 , the second portion 20B constitutes a surface portion of the functional layer 20. The surface portion of the functional layer 20 is located near the first surface 11 or constitutes the first surface 11. The first portion 20A constitutes a portion of the functional layer 20 that is bonded to the base film 45. The first portion 20A is spaced apart from the first surface 11. By having the first curable resin composition and the second curable resin composition have different compositions, the properties of the first portion 20A and the second portion 20B in the functional layer 20 can be changed.

[0317] The first curable resin composition and the second curable resin composition may be the same as the curable resin compositions described above. However, the second curable resin composition may not contain an ultraviolet absorber. The second curable resin composition may contain an ultraviolet absorber in a content less than that of the first curable resin composition. The second curable resin composition may contain an ultraviolet absorber in a content less than that of the first curable resin composition.

[0318] In this example, the first curable resin composition contains a larger amount of UV absorber. Therefore, the hardness of the first portion 20A is reduced. The second curable resin composition contains no UV absorber or only a small amount of UV absorber. By exposing the coating film from the first side surface 21 (first surface 11), the coating film of the second curable resin composition can be irradiated with a sufficient amount of ionizing radiation, such as UV radiation, with sufficient strength. Therefore, the crosslinking reaction in the second portion 20B is promoted, and the hardness of the second portion 20B is increased. This allows the functional layer 20 to have UV-blocking and blue-light-blocking functions due to the UV absorber, while improving the hardness of the functional layer 20 at the first side surface 21.

[0319] The first portion 20A to which the first curable resin composition is applied may contain an ultraviolet absorber, which may cause the crosslinking reaction to stagnate, resulting in low hardness. Therefore, the second curable resin composition may penetrate into the first portion 20A. The first curable resin composition and the second curable resin composition are mixed, making the interface between the first portion 20A and the second portion 20B less noticeable. This significantly improves the adhesion between the first portion 20A and the second portion 20B. Furthermore, the indentation hardness distribution defined by the above-mentioned condition (A) can be imparted to the functional layer 20.

[0320] When the optical sheet 10 produced by this manufacturing method was observed using a scanning transmission electron microscope S4800 manufactured by Hitachi High-Tech Corporation at an acceleration voltage of 10 kV to 30 kV and a magnification of 5000 times, no interface was found between the first portion 20A and the second portion 20B. In other words, no interface that could cause a decrease in hardness on the first surface 11 was present.

[0321] Furthermore, by adjusting the coating amount of the first curable resin composition relative to the coating amount of the second curable resin composition, the indentation hardness gradient characteristic defined by condition (B) can be imparted to the functional layer 20. Specifically, the coating amount of the second curable resin composition may be greater than the coating amount of the first curable resin composition.

[0322] In the obtained functional layer 20, the ultraviolet absorber is dispersed mainly in the first portion 20A. The first portion 20A is covered by the high-hardness second portion 20B. Therefore, the ultraviolet absorber can be effectively prevented from passing through the second portion 20B and bleeding out.

[0323] In the above manufacturing method, the second curable resin composition can permeate not only into the first portion 20A but also into the base material layer 40. The amount of permeation of the first and second curable resin compositions into the base material film 45 can be adjusted by the materials contained in the first and second curable resin compositions, the material of the base material film 45, the preparation conditions of the first and second curable resin compositions, the drying conditions of the first and second curable resin compositions, the curing conditions of the first and second curable resin compositions, etc. Therefore, the thickness T30 of the intermediate layer 30 as a permeation layer can be adjusted with a high degree of freedom.

[0324] According to the above-described manufacturing method, the spectral transmittance characteristics can be adjusted with a high degree of freedom. The spectral transmittance characteristics can be adjusted by factors other than the type and total content of the ultraviolet absorbers contained in the first and second curable resin compositions.

[0325] The wavelength of the ultraviolet light used in the curing treatment is preferably away from the central absorption wavelength of the ultraviolet absorber contained in the curable resin composition, and therefore, in many conventional curable resin compositions, particularly ultraviolet-curable resin compositions, contain only one type of ultraviolet absorber.

[0326] In the above manufacturing method, the spectral transmittance characteristics can be adjusted by factors other than the type of UV absorber and the total content of the UV absorbers. For example, the spectral transmittance characteristics can be adjusted by the ratio of the content of the UV absorber in the first curable resin composition to the content of the UV absorber in the second curable resin composition. The spectral transmittance characteristics can also be adjusted by the ratio of the content of the UV absorber in the first curable resin composition to the content of the curable resin composition in the second curable resin composition. The spectral transmittance characteristics can also be adjusted by one or more of the thickness of the first portion 20A, the thickness of the second portion 20B, and the ratio of the thickness of the first portion 20A to the thickness of the second portion 20B.

[0327] Furthermore, by exposing the coating film of the second curable resin composition from the surface forming the first surface 11, the influence of the UV absorber contained in the first portion 20A can be avoided and the coating film of the second curable resin composition can be cured. That is, when the coating film of the second curable resin composition is cured, the influence of the UV absorber contained in the first curable resin composition can be suppressed. Therefore, the type, content, and content ratio of the UV absorber contained in the first curable resin composition and the first portion 20A of the functional layer 20 can be selected with a high degree of freedom. This allows the functional layer 20 and the optical sheet 10 to have desired spectral transmittance characteristics.

[0328] Furthermore, the ultraviolet absorber can be unevenly distributed in a portion of the functional layer 20 in the thickness direction, for example, in the first portion 20A. Therefore, the ultraviolet absorber can be effectively utilized to efficiently capture ultraviolet light and blue light. From this perspective, the desired spectral transmittance characteristics can be imparted to the functional layer 20 and the optical sheet 10. Furthermore, while imparting the desired spectral transmittance characteristics to the optical sheet 10, the hardness and scratch resistance of the first surface 11 can be improved.

[0329] As a result of the above, the spectral transmittance characteristics of the optical sheet 10 can be adjusted with a higher degree of freedom. Spectral transmittance characteristics that satisfy the combination of features (X), (Y), and (Z) can be realized. (X) The spectral transmittance of the optical sheet 10 at a wavelength of 380 nm is 1% or less. (Y) The spectral transmittance of the optical sheet 10 at a wavelength of 440 nm is 70% or more. (Z) The slope of the spectral transmittance at each wavelength in 0.5 nm intervals within the wavelength range of 380 nm to 440 nm has a maximum value within the wavelength range of 400 nm to 420 nm.

[0330] <Sheet Article and Roll> According to the above-described method for manufacturing the optical sheet 10, a long sheet article 5 including a large number of optical sheets 10 can be manufactured, as shown in FIG. 3 . The optical sheets 10 are obtained by cutting the long sheet article 5 to a predetermined size. According to this example, optical sheets 10 having various dimensions can be obtained from the long sheet article 5 according to needs. Therefore, optical sheets 10 having various dimensions can be provided in a timely manner. As shown in FIG. 3 , by handling the sheet article 5 as a roll 7 wound around a winding core 6 about a winding axis RA, the handling of the sheet article 5 can be improved.

[0331] <Selection Method and Selection Step> In addition to the step of manufacturing the optical sheet described above, the method of manufacturing the optical sheet may further include a step of selecting the manufactured optical sheet 10. The step of selecting the optical sheet 10 may include a step of measuring the spectral transmittance, a step of measuring the indentation hardness, and a step of selecting the optical sheet based on the measurement results.

[0332] In the step of measuring the spectral transmittance, the spectral transmittance at a wavelength of 380 nm and the spectral transmittance at a wavelength of 440 nm may be measured.

[0333] In the step of measuring the indentation hardness, the indentation hardness may be measured on a cross section of the functional layer 20. More specifically, the indentation hardness HA1 at a first position 26, the indentation hardness HA2 at a second position 27 on the cross section of the functional layer 20, and the indentation hardness HA3 at a third position 28 on the cross section of the functional layer 20 may be measured. The first position 26 is located on a surface portion close to a first surface on the cross section. The third position 28 is located on a surface portion close to a second surface on the cross section. The second position 27 is located midway between the first position 26 and the third position 28.

[0334] In the step of selecting an optical sheet based on the measurement results, the optical sheet may be selected based on the measured spectral transmittance and the measured indentation hardness. A spectral transmittance of 1% or less at a wavelength of 380 nm may be considered acceptable. A spectral transmittance of 70% or more at a wavelength of 440 nm may be considered acceptable. The following characteristics (X) and (Y) regarding the indentation hardness HA1 at a first position 26 on the cross section of the functional layer 20, the indentation hardness HA2 at a second position 27 on the cross section of the functional layer 20, and the indentation hardness HA3 at a third position 28 on the cross section of the functional layer 20 may be satisfied as a condition for acceptance: (X) HA3 < HA2 < HA1 (Y) HA1 / HA2 ≦ HA2 / HA3

[0335] The optical sheet 10 selected as a good product has excellent ultraviolet blocking function and excellent blue light blocking function, and also has high hardness on the first surface 11. According to this selection step, an optical sheet having excellent scratch resistance can be selected with high precision without performing an abrasion test using felt or steel wool.

[0336] 4, the optical sheet 10 according to the first embodiment may be applied to a polarizing plate 50. An optical sheet 110 according to a second embodiment and an optical sheet 210 according to a third embodiment, which will be described later, may also be applied to the polarizing plate 50.

[0337] The polarizing plate 50 includes a first protective sheet 51, a polarizer 52, and a second protective sheet 53. The first protective sheet 51 and the second protective sheet 53 sandwich the polarizer 52 and cover it from both sides. At least one of the first protective sheet 51 and the second protective sheet 53 may include an optical sheet 10, 110, or 210. In the example shown in FIG. 4 , the first protective sheet 51 includes the optical sheet 10, 110, or 210. The optical sheet 10, 110, or 210 may efficiently block light with a wavelength of 380 nm or less that is included in light that enters the polarizing plate 50. This can suppress deterioration of the polarizer 52 caused by blue light.

[0338] The polarizer 52 transmits one linearly polarized component and blocks the other linearly polarized component. The polarizer 52 may be an absorptive polarizer that absorbs the other linearly polarized component. The polarizer 52 may be a reflective polarizer that reflects the other linearly polarized component. The polarizer 52 may be a sheet-type polarizer such as a stretched polyvinyl alcohol film, polyvinyl formal film, polyvinyl acetal film, or saponified ethylene-vinyl acetate copolymer film dyed with iodine or the like. The polarizer 52 may be a wire-grid polarizer made of a large number of metal wires arranged in parallel. The polarizer 52 may be a coated polarizer coated with a lyotropic liquid crystal or a dichroic guest-host material. The polarizer 52 may be a multilayer thin-film polarizer.

[0339] The polarizing plate 50 is not limited to the configuration shown in Fig. 4. The polarizing plate 50 may include a quarter-phase plate in addition to the optical sheets 10, 110, and 210 and the polarizer 52. This polarizing plate 50 functions as a circular polarizing plate. The polarizing plate 50 as a circular polarizing plate has the function of suppressing reflection.

[0340] 5 , the optical sheet 10 according to the first embodiment may be applied to a touch panel member 55. An optical sheet 110 according to a second embodiment and an optical sheet 210 according to a third embodiment, which will be described later, may also be applied to the touch panel member 55 in the same manner.

[0341] The touch panel member 55 includes an optical sheet 10, 110, or 210 and an electrode layer 56. The touch panel member 55 is a component that constitutes a touch panel. The touch panel member 55 outputs the approach or contact of a detection object, such as a finger or pen, as an electrical state change. A controller electrically connected to the touch panel member 55 can identify the position of the detection object based on the output from the touch panel member 55. The first surface of the optical sheet 10, 110, or 210 has high hardness and excellent scratch resistance. Therefore, when a detection object is rubbed against the first surface, scratches on the first surface can be suppressed.

[0342] The electrode layer 56 includes a conductor for detecting a touch position. The configuration of the conductor is appropriately selected depending on the touch detection method of the touch panel. In a resistive touch panel, the electrode layer 56 may include a conductor that extends in a planar form without being divided into regions. In a capacitively coupled touch panel, the electrode layer 56 may include a plurality of conductors. The plurality of conductors may be arranged in one direction, and each conductor may extend in a direction perpendicular to the one direction.

[0343] The conductor included in the electrode layer 56 may be a film formed of a transparent conductive material. Examples of transparent conductive materials include metal oxides such as indium tin oxide (ITO). The conductor included in the electrode layer 56 may include metal wires arranged in a mesh pattern.

[0344] <<<Display Device 60>>> The optical sheet 10 according to the first embodiment may be applied to the display device 60. An optical sheet 110 according to a second embodiment and an optical sheet 210 according to a third embodiment, which will be described later, may also be applied to the display device 60.

[0345] In the example shown in Fig. 6, the display device 60 includes a display element 61 and optical sheets 10, 110, and 210. The display element 61 has a display surface 61a that displays an image. The optical sheets 10, 110, and 210 are overlaid on the display element 61 with their second surfaces facing the display surface 61a. The optical sheets 10, 110, and 210 may be bonded to the display element 61 via a bonding layer containing an adhesive, a sticky material, or the like. Unlike the example shown in Fig. 6, the optical sheets 10, 110, and 210 may be incorporated into the display device 60 as part of the polarizing plate 50 or the touch panel member 55.

[0346] Image light emitted from the display element 61 passes through the optical sheets 10, 110, and 210. The optical sheets 10, 110, and 210 may block light with wavelengths of 380 nm or less contained in the image light with high efficiency. This can reduce eye strain and other strain on the viewer. The optical sheets 10, 110, and 210 block light with wavelengths of 410 nm or less from external light entering the display device 60. This can prevent the polarizer 52 of the polarizing plate 50 and the EL elements of the organic EL panel from being deteriorated by blue light contained in the external light.

[0347] The first surfaces of the optical sheets 10, 110, and 210 have sufficiently high hardness. Therefore, the optical sheets 10, 110, and 210 can protect the display surface 61 a of the display device 60. Furthermore, since scratches on the first surface can be suppressed, the display device 60 can display high-quality images.

[0348] There is no particular limitation on the display element 61. Examples of the display element 61 include a liquid crystal display element, an EL display element, a plasma display element, and an electronic paper element.

[0349] <<<<<Examples of First Embodiment>>>> The present disclosure will be described in more detail with reference to examples. The present disclosure is not limited to the following examples.

[0350] <<<<1. Preparation of Optical Sheets>>> Optical sheets according to Examples 11 to 18 and Comparative Examples 11 to 15 were prepared.

[0351] <<Example 11>> A first curable resin composition 1A was applied to a substrate film made of triacetyl cellulose with a thickness of 80 μm, and a first coating film was formed on the substrate film. A method for producing the first curable resin composition 1A will be described later. Next, the first coating film was dried under the conditions of 50°C x 20 seconds (drying air speed 0.4 m / s). Thereafter, the first coating film was dried under the conditions of 50°C x 20 seconds (drying air speed 0.5 m / s). In this way, the solvent was volatilized. Next, an integrated light intensity of 66 mJ / cm was applied. ２ The first coating film was irradiated with ultraviolet light. The first coating film was cured by irradiation with ultraviolet light, and a first portion of the functional layer was formed on the substrate film. The amount of the first curable resin composition 1A applied was set to an amount that would result in a first portion with a dry thickness of 3.4 μm, assuming that the first curable resin composition 1A did not penetrate into the substrate film.

[0352] Next, a second curable resin composition 1A having the following formulation was applied to the first portion to form a second coating film on the substrate film. The solid content of the second curable resin composition 1A was 45%. The second curable resin composition 1A did not contain an ultraviolet absorber. Next, the second coating film was dried under the conditions of 60°C x 20 seconds (drying air speed 0.4 m / s). Thereafter, the second coating film was dried under the conditions of 70°C x 20 seconds (drying air speed 0.3 m / s). In this way, the solvent was volatilized. Next, an integrated light dose of 288 mJ / cm was applied. ２ The second coating film was irradiated with ultraviolet light. The second coating film was cured by irradiation with ultraviolet light, and a second portion of the functional layer was formed on the substrate film and the first portion. The amount of second curable resin composition 1A applied was determined to be an amount that would result in a second portion with a dry thickness of 5.0 μm, assuming that the second curable resin composition 1A would not penetrate into the substrate layer or the first portion.

[0353] In this way, an optical sheet according to Example 11 was obtained. In this optical sheet, the first portion and the second portion constituted a functional layer.

[0354] During the thickness measurement described below, the cross section of the optical sheet according to Example 11 was observed. A scanning transmission electron microscope S4800 manufactured by Hitachi High-Tech Corporation was used to observe the cross section. Observation of the cross section at an acceleration voltage of 10 kV to 30 kV and a magnification of 5000x revealed that the curable resin composition had penetrated the substrate film, causing the substrate film to swell, forming a permeation layer that constituted the intermediate layer. Furthermore, the interface between the first and second portions within the functional layer could not be observed.

[0355] <First Curable Resin Composition 1A> A sesamol-type benzotriazole monomer was synthesized, and then an acrylic polymer to which the sesamol-type benzotriazole monomer was reactively bonded was synthesized, thereby obtaining a first curable resin composition 1A.

[0356] (Synthesis of Sesamol-Type Benzotriazole Monomer) A 200 mL four-neck flask was equipped with a ball condenser, a mercury thermometer, and a stirrer. 4.0 g (0.013 mol) of 6-[5-(2-hydroxyethyl)-2H-benzotriazol-2-yl]benzo[1,3]dioxol-5-ol, 40 mL of toluene, 1.8 g (0.021 mol) of methacrylic acid, and 0.4 g (0.004 mol) of methanesulfonic acid were placed in the four-neck flask. The contents of the four-neck flask were refluxed and dehydrated at 110-115°C for 4 hours. Next, 30 mL of water and 0.6 g (0.006 mol) of sodium carbonate were added to the four-neck flask. The four-neck flask was then allowed to stand, and the lower aqueous layer was separated and removed. Next, 0.2 g of activated carbon was added to the four-neck flask, and the contents were refluxed and stirred to decolorize. The contents removed from the four-neck flask were then filtered. 40 mL of toluene was recovered from the resulting filtrate under reduced pressure. 100 mL of isopropyl alcohol was added to the filtrate from which toluene had been removed, and the precipitated crystals were filtered. The resulting crystals were washed with 40 mL of isopropyl alcohol. The crystals were then dried at 40°C under reduced pressure to obtain yellow crystals. 4.2 g of the resulting yellow crystals were repulped and washed using isopropyl alcohol. Next, the washed yellow crystals were dried at 40°C under reduced pressure to obtain 3.4 g of 2-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]ethyl methacrylate as a sesamol-type benzotriazole monomer.

[0357] (Synthesis of acrylic polymer having sesamol-type benzotriazole monomer reactively bonded) A four-necked flask was equipped with a Dimroth condenser, a mercury thermometer, a nitrogen gas inlet tube, and a stirrer. The following was placed in the four-necked flask and stirred. "X" is a value described below. 2-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]ethyl methacrylate X parts by mass (another monomer) methyl methacrylate (100-X) parts by mass (solvent) toluene 20 parts by mass, methyl ethyl ketone 20 parts by mass (polymerization initiator) 1,1'-azobis(cyclohexane-1-carbonitrile) 0.6 parts by mass

[0358] Next, the atmosphere in the flask was replaced with nitrogen at a nitrogen gas flow rate of 10 mL / min for 1 hour, and then the contents in the flask were polymerized at a reaction temperature of 90 to 96°C under reflux for 10 hours. After completion of the polymerization reaction, 10 parts by mass of toluene and 10 parts by mass of MEK were added to the flask. As a result, 160.6 parts by mass of a solution of acrylic polymer (1) in which the sesamol-type benzotriazole monomer had been reactively bonded was obtained.

[0359] An intermediate composition was prepared by mixing the following: - Polyfunctional monomer (PET-30 (pentaerythritol triacrylate) manufactured by Nippon Kayaku Co., Ltd.) - Acrylic polymer (1) to which sesamol-type benzotriazole-based monomer has been reactively bonded (polymer in which sesamol-type benzotriazole-based monomer has been reactively bonded to MMA and an ultraviolet absorber at a mass ratio X of 40 parts by mass) - Solvent (solvent in which MEK and toluene have been mixed at a mass ratio of 30:70) The polyfunctional monomer and acrylic polymer (1) were mixed at a solid mass ratio of 30:70.

[0360] Next, 360 parts by mass of the obtained intermediate composition was mixed with a photopolymerization initiator (4 parts by mass of Irgacure 819 manufactured by BASF) and a leveling agent (0.2 parts by mass of LE-304 manufactured by Kyoeisha) and stirred thoroughly to prepare a first curable resin composition 1A. The obtained first curable resin composition 1A contained a solids content of 25%.

[0361] <Second Curable Resin Composition 1A> - 50 parts by mass of ultraviolet-curable acrylate-containing composition (manufactured by Nippon Kayaku Co., Ltd., PET-30 (pentaerythritol triacrylate)) - 50 parts by mass of ultraviolet-curable urethane acrylate-containing composition (manufactured by Arakawa Chemical Industries, Ltd., trade name "Beamset 577") - 0.4 parts by mass of leveling agent (Kyoeisha, trade name "LE-304") - 4 parts by mass of photopolymerization initiator (IGM Resins, trade name "Omnirad 184") - 20 parts by mass of lubricant (manufactured by CIK Nanotech, SIRMIBK15WT%-E65) - Solvent (solvent obtained by mixing methyl isobutyl ketone and methyl ethyl ketone at a mass ratio of 55:48)

[0362] <<Example 12>> Example 12 differs from the above-described Example 11 in that the amount of first curable resin composition 1A applied was increased, but the optical sheet of Example 12 was otherwise obtained using the same materials and method as in Example 11. The amount of first curable resin composition 1A applied was set to an amount that would produce a first portion with a dry thickness of 4.0 μm, assuming that there was no penetration into the base film.

[0363] During thickness measurement, which will be described later, the cross section of the optical sheet according to Example 12 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the intermediate layer. The interface between the first and second portions in the functional layer could not be observed.

[0364] Example 13 Example 13 differs from Example 11 above in that the solid content of the first curable resin composition was changed, the solid content of the second curable resin composition was changed, and the coating amount of the second curable resin composition was increased. Otherwise, the optical sheet of Example 13 was obtained using the same materials and method as Example 11. In Example 13, a first curable resin composition with a solid content of 35% was used. The first curable resin composition used in Example 13 was obtained by adjusting the amount of solvent contained in the first curable resin composition 1A. In Example 13, a second curable resin composition with a solid content of 50% was used. The second curable resin composition used in Example 13 was obtained by adjusting the amount of solvent contained in the second curable resin composition 1A. The coating amount of the second curable resin composition was set to an amount that would produce a second portion with a dry thickness of 6.0 μm, assuming no penetration into the substrate film and the first portion.

[0365] During thickness measurement, which will be described later, the cross section of the optical sheet according to Example 13 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the intermediate layer. The interface between the first and second portions in the functional layer could not be observed.

[0366] <<Example 14>> Example 14 differs from Example 11 described above in that the solid content of the first curable resin composition and the solid content of the second curable resin composition were changed. Otherwise, the optical sheet of Example 14 was obtained using the same materials and method as Example 11. In Example 14, a first curable resin composition with a solid content of 20% was used. The first curable resin composition used in Example 14 was obtained by adjusting the amount of solvent contained in the first curable resin composition 1A. In Example 14, a second curable resin composition with a solid content of 40% was used. The second curable resin composition used in Example 14 was obtained by adjusting the amount of solvent contained in the second curable resin composition 1A.

[0367] During thickness measurement, which will be described later, the cross section of the optical sheet according to Example 14 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the intermediate layer. The interface between the first and second portions in the functional layer could not be observed.

[0368] Example 15 Example 15 differs from Example 11 above in that the coating amount of the first curable resin composition 1A and the coating amount of the second curable resin composition 1A were reduced. The optical sheet of Example 15 was obtained using the same materials and method as Example 11. The coating amount of the first curable resin composition 1A was an amount that would produce a first portion with a dry thickness of 1.7 μm, assuming no penetration into the substrate film. The coating amount of the second curable resin composition was an amount that would produce a second portion with a dry thickness of 3.5 μm, assuming no penetration into the substrate film and the first portion.

[0369] During thickness measurement, which will be described later, the cross section of the optical sheet according to Example 15 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the intermediate layer. The interface between the first and second portions in the functional layer could not be observed.

[0370] Example 16 Example 16 differs from Example 11 above in that the composition of the first curable resin composition was changed, the coating amount of the first curable resin composition was increased, and the coating amount of the second curable resin composition 1A was increased. The optical sheet of Example 16 was obtained using the same materials and method as Example 11. The first curable resin composition 1A used in Example 11 contained a polyfunctional monomer and an acrylic polymer (1) mixed in a solid content mass ratio of 30:70. The first curable resin composition used in Example 16 was obtained by mixing a polyfunctional monomer and an indole-based UV absorber mixed in a mass ratio of 95:5 instead of the polyfunctional monomer and acrylic polymer (1) of the first curable resin composition 1A. The polyfunctional monomer contained in the first curable resin composition used in Example 16 was the same as the polyfunctional monomer contained in the first curable resin composition 1A. The indole-based ultraviolet absorber contained in the first curable resin composition used in Example 16 was trade name "BONASORB UA-3912" manufactured by Orient Chemical Industry Co., Ltd. The solid content of the first curable resin composition used in Example 16 was 25%, which was the same as the solid content of the first curable resin composition 1A.

[0371] The amount of the first curable resin composition applied was an amount that would produce a first portion with a dry thickness of 4.0 μm, assuming no penetration into the base film. The amount of the second curable resin composition 1A applied was an amount that would produce a second portion with a dry thickness of 7.0 μm, assuming no penetration into the base film or the first portion.

[0372] During thickness measurement, which will be described later, the cross section of the optical sheet according to Example 16 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the intermediate layer. The interface between the first and second portions in the functional layer could not be observed.

[0373] Example 17 Example 17 differs from Example 11 above in that the coating amount of the first curable resin composition 1A was increased and the coating amount of the second curable resin composition 1A was decreased. The optical sheet of Example 15 was obtained using the same materials and method as Example 11. The coating amount of the first curable resin composition 1A was an amount that would produce a first portion with a dry thickness of 5.1 μm, assuming no penetration into the substrate film. The coating amount of the second curable resin composition was an amount that would produce a second portion with a dry thickness of 3.0 μm, assuming no penetration into the substrate film and the first portion.

[0374] During thickness measurement, which will be described later, the cross section of the optical sheet according to Example 17 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the intermediate layer. The interface between the first and second portions in the functional layer could not be observed.

[0375] <<Example 18>> Example 18 differs from Example 11 described above in that the leveling agent in the first curable resin composition 1A was omitted and the leveling agent in the second curable resin composition 1A was changed. The optical sheet of Example 18 was obtained using the same materials and method as in Example 11. In Example 18, the first curable resin composition used to form the first coating film differed from the first curable resin composition 1A described above in that the leveling agent "Kyoeisha Co., Ltd., LE-304, 0.2 parts by mass" was omitted, and the optical sheet was otherwise identical to the first curable resin composition 1A described above. In Example 18, the second curable resin composition used to form the second coating film differed from the second curable resin composition 1A described above in that the leveling agent "Kyoeisha Co., Ltd., LE-304, 0.4 parts by mass" was replaced with the leveling agent "DIC Co., Ltd., F-477, 0.3 parts by mass." In Example 18, the second curable resin composition used to form the second coating film was the same as the above-mentioned second curable resin composition 1A except for the leveling agent.

[0376] During thickness measurement, which will be described later, the cross section of the optical sheet according to Example 18 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the second layer. The interface between the first and second portions in the first layer could not be observed.

[0377] <<Comparative Example 11>> A functional layer was formed on a substrate film made of triacetyl cellulose with a thickness of 80 μm using the first curable resin composition used in Example 11. The amount of first curable resin composition 1A applied was determined to be an amount that would produce a first portion with a dry thickness of 5.7 μm, assuming that there was no penetration into the substrate film. In this way, an optical sheet according to Comparative Example 11 was obtained. That is, in the optical sheet according to Comparative Example 11, the functional layer was composed only of the first portion produced using the first curable resin composition 1A.

[0378] The thickness of the layer produced using the first curable resin composition 1A in Comparative Example 11 was different from the thickness of the layer produced using the first curable resin composition 1A in Example 11. In other respects, the method and conditions for producing the functional layer using the first curable resin composition 1A in Comparative Example 11 were the same as the method and conditions for producing the first part using the first curable resin composition 1A in Example 11.

[0379] During thickness measurement described below, the cross section of the optical sheet according to Comparative Example 11 was observed in the same manner as in Example 11. The first curable resin composition permeated into the substrate film, causing the substrate film to swell, thereby forming a permeation layer that constitutes the intermediate layer.

[0380] <<Comparative Example 12>> A first curable resin composition 1B having the following formulation was applied to a substrate film made of triacetyl cellulose and having a thickness of 80 μm, to form a first coating film on the substrate film. The solid content of the first curable resin composition 1B was 45%. The first curable resin composition 1B did not contain an ultraviolet absorber. Next, the first coating film was dried under the conditions of 50°C x 20 seconds (drying air speed 0.4 m / s). Thereafter, the first coating film was dried under the conditions of 50°C x 20 seconds (drying air speed 0.5 m / s). In this way, the solvent was volatilized. Next, an integrated light intensity of 66 mJ / cm was applied.２ The first coating film was irradiated with ultraviolet light. The first coating film was cured by the ultraviolet light irradiation, and a first portion of the functional layer was formed on the substrate film. The amount of first curable resin composition 1B applied was set to an amount that would result in a first portion with a dry thickness of 4.0 μm, assuming that the first curable resin composition 1B did not penetrate into the substrate film.

[0381] <First Curable Resin Composition 1B> 50 parts by mass of ultraviolet-curable acrylate-containing composition (PET-30 (pentaerythritol triacrylate) manufactured by Nippon Kayaku Co., Ltd.) 50 parts by mass of ultraviolet-curable urethane acrylate-containing composition (Beamset 577 manufactured by Arakawa Chemical Industries, Ltd.) 0.4 parts by mass of leveling agent (LE-304 manufactured by Kyoeisha Co., Ltd.) 4 parts by mass of photopolymerization initiator (Omnirad 184 manufactured by IGM Resins) Solvent (a mixture of methyl isobutyl ketone and methyl ethyl ketone in a mass ratio of 55:48)

[0382] Next, a second curable resin composition was applied to the first portion to form a second coating film on the substrate film. In Comparative Example 12, the first curable resin composition 1A used in Example 11 was used as the second curable resin composition. The solid content of the second curable resin composition used in Comparative Example 12 was 25%. The second curable resin composition used in Comparative Example 12 contained an ultraviolet absorber. Next, the second coating film was dried under the conditions of 60°C x 20 seconds (drying air speed 0.4 m / s). Thereafter, the second coating film was dried under the conditions of 70°C x 20 seconds (drying air speed 0.3 m / s). In this way, the solvent was volatilized. Next, an integrated light dose of 288 mJ / cm ２ The second coating film was irradiated with ultraviolet light. The second coating film was cured by irradiation with ultraviolet light, and a second portion of the functional layer was formed on the substrate film and the first portion. The amount of second curable resin composition 1A applied was determined to be an amount that would result in a second portion with a dry thickness of 3.5 μm, assuming that the second curable resin composition 1A would not penetrate into the substrate layer or the first portion.

[0383] In this way, an optical sheet according to Comparative Example 12 was obtained. In this optical sheet, the first portion and the second portion constituted a functional layer.

[0384] During thickness measurement, which will be described later, the cross section of the optical sheet according to Comparative Example 12 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the intermediate layer. The interface between the first and second portions in the functional layer could not be observed.

[0385] <<Comparative Example 13>> Comparative Example 13 differs from Comparative Example 11 in that the composition of the first curable resin composition was changed, the amount of the first curable resin composition applied was increased, and the cumulative amount of ultraviolet light irradiated during curing of the first coating film was increased. Otherwise, the optical sheet of Comparative Example 13 was obtained using the same materials and method as Comparative Example 11. The first curable resin composition 1A used in Comparative Example 11 and Example 11 contained a polyfunctional monomer and an acrylic polymer (1) mixed at a solid content mass ratio of 30:70. The first curable resin composition used in Comparative Example 13 contained a polyfunctional monomer and an acrylic polymer (1) mixed at a solid content mass ratio of 60:40. The polyfunctional monomer contained in the first curable resin composition used in Comparative Example 13 was the same as the polyfunctional monomer contained in the first curable resin composition 1A. The acrylic polymer (1) contained in the first curable resin composition used in Comparative Example 12 was the same as the acrylic polymer (1) contained in the first curable resin composition 1A. The solid content of the first curable resin composition used in Comparative Example 13 was 25%, which was the same as the solid content of the first curable resin composition 1A.

[0386] The amount of the first curable resin composition applied was determined to be an amount sufficient to produce a functional layer consisting of only the first portion and having a dry thickness of 7.5 μm, assuming that the first curable resin composition did not penetrate into the substrate film. The cumulative amount of ultraviolet light irradiated during curing of the first coating film was 132 mJ / cm. ２ It was decided.

[0387] During thickness measurement described below, the cross section of the optical sheet according to Comparative Example 13 was observed in the same manner as in Example 11. The first curable resin composition permeated into the substrate film, causing the substrate film to swell, thereby forming a permeation layer that constitutes the intermediate layer.

[0388] <<Comparative Example 14>> A first curable resin composition 1C having the following formulation was applied to a substrate film made of triacetyl cellulose and having a thickness of 80 μm, to form a first coating film on the substrate film. The solid content of the first curable resin composition 1C was 45%. The first curable resin composition 1C did not contain an ultraviolet absorber. Next, the first coating film was dried under the conditions of 50°C x 20 seconds (drying air speed 0.4 m / s). Thereafter, the first coating film was dried under the conditions of 50°C x 20 seconds (drying air speed 0.5 m / s). In this way, the solvent was volatilized. Next, an integrated light intensity of 132 mJ / cm was applied. ２ The first coating film was irradiated with ultraviolet light. The first coating film was cured by the ultraviolet light irradiation, and a first portion of the functional layer was formed on the substrate film. The amount of the first curable resin composition 1C applied was set to an amount that would result in a first portion with a dry thickness of 5.0 μm, assuming that the first curable resin composition 1C did not penetrate into the substrate film.

[0389] <First Curable Resin Composition 1C> 50 parts by mass of ultraviolet-curable acrylate-containing composition (manufactured by Nippon Kayaku Co., Ltd., DPHA (dipentaerythritol hexaacrylate)) 50 parts by mass of ultraviolet-curable urethane acrylate-containing composition (manufactured by Arakawa Chemical Industries, Ltd., trade name "Beamset 577") 0.4 parts by mass of leveling agent (Kyoeisha, trade name "LE-304") 4 parts by mass of photopolymerization initiator (IGM Resins, trade name "Omnirad 184") Solvent (a solvent obtained by mixing methyl isobutyl ketone and methyl ethyl ketone in a mass ratio of 55:48)

[0390] Next, a second curable resin composition was applied to the first portion to form a second coating film on the substrate film. In Comparative Example 14, the first curable resin composition 1A used in Example 11 was used as the second curable resin composition. The solid content of the second curable resin composition used in Comparative Example 14 was 25%. The second curable resin composition used in Comparative Example 14 contained an ultraviolet absorber. Next, the second coating film was dried under the conditions of 60°C x 20 seconds (drying air speed 0.4 m / s). Thereafter, the second coating film was dried under the conditions of 70°C x 20 seconds (drying air speed 0.3 m / s). In this way, the solvent was volatilized. Next, an integrated light dose of 288 mJ / cm ２The second coating film was irradiated with ultraviolet light. The second coating film was cured by irradiation with ultraviolet light, and a second portion of the functional layer was formed on the substrate film and the first portion. The amount of second curable resin composition 1A applied was determined to be an amount that would result in a second portion with a dry thickness of 3.5 μm, assuming that the second curable resin composition 1A would not penetrate into the substrate layer or the first portion.

[0391] In this way, an optical sheet according to Comparative Example 14 was obtained. In this optical sheet, the first portion and the second portion constituted a functional layer.

[0392] During thickness measurement, which will be described later, the cross section of the optical sheet according to Comparative Example 14 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the intermediate layer. The interface between the first and second portions in the functional layer could not be observed.

[0393] <<Comparative Example 15>> Comparative Example 15 differs from the above-described Comparative Example 13 in that the leveling agent of the first curable resin composition was changed and the leveling agent of the second curable resin composition was changed. Otherwise, the optical sheet of Comparative Example 15 was obtained using the same materials and the same method as Comparative Example 13.

[0394] In Comparative Example 15, the first curable resin composition used to form the first coating film differed from the first curable resin composition used in Comparative Example 13 in that a leveling agent "0.2 parts by mass of F-568 manufactured by DIC" was used instead of the leveling agent "0.2 parts by mass of LE-304 manufactured by Kyoeisha." In Comparative Example 15, the first curable resin composition used to form the first coating film was the same as the first curable resin composition used in Comparative Example 13, except for the leveling agent.

[0395] In Comparative Example 15, the second curable resin composition used to form the second coating film differed from the second curable resin composition 1A used in Comparative Example 13 in that a leveling agent "F-477, manufactured by DIC, 0.4 parts by mass" was used instead of the leveling agent "LE-304, manufactured by Kyoeisha, 0.4 parts by mass." In Comparative Example 15, the second curable resin composition used to form the second coating film was the same as the second curable resin composition 1A used in Comparative Example 13, except for the leveling agent.

[0396] During thickness measurement, which will be described later, the cross section of the optical sheet according to Comparative Example 15 was observed in the same manner as in Example 11. The curable resin composition penetrated into the substrate film, causing the substrate film to swell, forming a permeation layer that constitutes the second layer. The interface between the first and second portions in the first layer could not be observed.

[0397] <<<2. Measurement and Evaluation>>> Measurement and evaluation were carried out on the optical sheets according to the examples and comparative examples as described below. The test environment for each measurement and evaluation was a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. Before starting each measurement and evaluation, the target sample was placed in the above-mentioned test environment for 16 hours.

[0398] <<2-1. Thickness>> A sample for thickness measurement was prepared by the following first and second steps.

[0399] (First step) Cut samples were cut out from the optical sheets according to the examples and comparative examples. The size of the cut samples was a strip of approximately 10 mm length x 3 mm width. The cut samples were visually inspected for any abnormalities such as dust or scratches. For the optical sheets according to each example, the thickness T20 (μm) of the functional layer and the thickness T30 (μm) of the intermediate layer were measured using the method described above. Next, the cut samples were embedded in resin to prepare embedded samples.

[0400] The embedded sample was prepared as follows: First, the cut sample was placed in a silicon embedding plate. Then, embedding resin was poured into the silicon embedding plate with the cut sample placed therein. Next, the embedding resin was hardened in the silicon embedding plate. Next, the cut sample and the embedding resin surrounding it were removed from the silicon embedding plate to obtain an embedded sample. The embedded sample was shaped like a block.

[0401] The silicone embedding plate used was manufactured by Dosaka EM Co., Ltd. Epoxy resin was used as the embedding resin. The epoxy resin was obtained by mixing "Epofix" (trade name) manufactured by Struers and "Epofix Hardener" (trade name) manufactured by the same company in a ratio of 10:1.2. The embedding resin was allowed to harden by leaving it at room temperature for 12 hours.

[0402] (Second step) The block-shaped embedded sample was cut with a diamond knife to prepare slice samples. The slice samples were aligned along the first direction (thickness direction, stacking direction) of the target optical sheet. Among the slices cut from the block-shaped embedded sample, slice samples that were free of defects such as holes and had a uniform thickness of approximately 60 nm to 100 nm were used as thickness measurement samples.

[0403] The embedded samples were cut using a microtome, manufactured by Leica Microsystems under the trade name "Ultramicrotome EM UC7." When cutting the block-shaped embedded sample, the sample was first roughly cut as coarse trimming, and then precisely trimmed with a diamond knife to obtain section samples.

[0404] As described above, the thickness of each layer was measured using an image of the thickness measurement sample observed with a scanning transmission electron microscope. Before observing the thickness measurement sample, the thickness measurement sample was stained. Osmium tetroxide was used for staining. The stained thickness measurement sample was imaged using a scanning transmission electron microscope to obtain an observation image of the thickness measurement sample. The scanning transmission electron microscope used was an S4800 manufactured by Hitachi High-Tech Corporation. The imaging conditions were as follows: <Imaging conditions> Mode: Transmission mode TE, bright field Acceleration voltage: 10 kV to 30 kV Emission current: 10 μA WD (Working Distance): 8.8±0.1 mm Magnification: 5000x

[0405] Ten observation images were taken from one thickness measurement sample for each example. The ten observation images were taken at ten observation positions (measurement positions) spaced at 10 μm intervals in a direction perpendicular to the first direction of the optical sheet in question. From each observation image of the thickness measurement sample, the thickness T20 (μm) of the functional layer and the thickness T30 (μm) of the intermediate layer for the optical sheet in each example were measured. The arithmetic mean value of the ten thickness measurements taken from the ten observation images was taken as the thickness of the target layer. The measurement results for the thickness T20 (μm) of the functional layer and the thickness T30 (μm) of the intermediate layer are shown in Table 1.

[0406] <<2-2. Spectral Transmittance>> Samples measuring 50 mm x 100 mm were cut out from the optical sheets according to the examples and comparative examples. The samples were visually inspected for the absence of dust, scratches, or other abnormalities. The spectral transmittance (%) of each optical sheet according to the examples was measured using the method described above. The spectral transmittance (%) was measured for each wavelength in 0.5 nm increments within the wavelength range of 379.5 nm to 440.5 nm. The spectral transmittance (%) was measured using a UV-2600 UV-Visible Spectrophotometer manufactured by Nippon Bunko Co., Ltd. The measured spectral transmittance values ​​were used to calculate the slope of the spectral transmittance at each wavelength in 0.5 nm increments within the wavelength range of 380 nm to 440 nm. The slope (% / nm) of the spectral transmittance at wavelength X was calculated by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

[0407] The measurement results of the spectral transmittance at 380.0 nm and the spectral transmittance at 440.0 nm are shown in Tables 1 and 2. Tables 1 and 2 show the wavelengths at which the slope of the spectral transmittance is maximum.

[0408] The optical sheets according to Examples 11 to 18 and Comparative Examples 11 to 15 were placed on the display surface of a commercially available organic EL display device, and the images displayed by the organic EL display device were observed through the optical sheets. For Examples 11 to 18 and Comparative Examples 11 to 15, there was no noticeable change in color between the images when the optical sheets were installed and the images when the optical sheets were not installed, and the results were within the range that could be considered acceptable products. For Examples 11 to 16, Example 18, and Comparative Examples 11 to 15, there was no noticeable change in color between the images when the optical sheets were installed and the images when the optical sheets were not installed.

[0409] <<2-3. Pencil Hardness>> Samples measuring 50 mm x 100 mm were cut out from the optical sheets according to the examples and comparative examples. The samples were visually inspected to ensure that there were no defects such as dust or scratches. The pencil hardness of the optical sheets according to each example was measured using the method described above. A pencil hardness tester manufactured by Toyo Seiki Seisakusho, Ltd. was used to measure the pencil hardness. The pencil hardness evaluated according to the evaluation criteria described above is shown in Table 1.

[0410] <<2-4. Load-bearing capacity in steel wool resistance test>> Samples measuring 30 mm x 250 mm were cut out from the optical sheets according to the examples and comparative examples. The samples were visually inspected for the absence of any abnormalities such as dust or scratches. Using the method described above, a steel wool scratch resistance test was conducted on the optical sheets according to each example, and the load-bearing capacity was measured. The load applied when pressing the slider against the sample was varied from 50 g, 100 g, 150 g, 200 g, 250 g, and 300 g. For the steel wool resistance test, an SW tester "SJTR-053" manufactured by SAM JEE TECH was used. The load-bearing capacity in the steel wool resistance test evaluated according to the evaluation criteria described above is shown in Table 1.

[0411] <<2-5. Deformation>> Square samples with sides of 10 cm were cut out from the optical sheets according to the examples and comparative examples. The square samples were cut out from the optical sheets so that each side of the square was inclined at 45° with respect to the longitudinal direction (in other words, the machine direction) of the produced optical sheet. The samples were visually inspected to ensure that there were no abnormalities such as dust or scratches.

[0412] The sample was placed on the surface plate so that the second surface of the optical sheet was in contact with the surface plate. The height of the four corners of the sample from the surface plate was measured as the lift (mm). The maximum value of the four lift measurements taken for one sample was taken as the lift of that sample. For each example of the optical sheet, the lift was measured for each of three samples. The arithmetic mean value of the three lift measurements was taken as the deformation amount for that example. The deformation amount measurement results are shown in Table 1.

[0413] In Comparative Example 12, the sample placed on the surface plate curled into a cylindrical shape, and the amount of deformation could not be measured.

[0414] <<2-6. Color a ＊ value and b ＊ Values>> Samples of 5 cm x 10 cm were cut out from the optical sheets according to the examples and comparative examples. The samples were visually inspected to ensure there were no defects such as dust or scratches. ＊ value and b ＊ The values ​​were measured. ＊ value and b ＊The values ​​were measured using an ultraviolet-visible spectrophotometer "UV-2600" manufactured by Shimadzu Corporation. ＊ value and b ＊ The measurement results are shown in Table 2.

[0415] <<2-7. X-ray Photoelectron Spectroscopy>> Samples measuring 50 mm x 50 mm were cut out from the optical sheets according to Examples 1, 5, and 8, and Comparative Example 5. The samples were visually inspected to ensure there were no defects such as dust or scratches. The element ratios on the first surface were quantitatively evaluated by X-ray photoelectron spectroscopy using the method described above. An AXIS-NOVA manufactured by Kratos was used for the X-ray photoelectron spectroscopy measurements. The following measurement conditions were selected.

[0416] (Measurement conditions) Measurement method: Wide / Narrow X-ray source: Monochrome A1Kα X-ray output: 150 W Emission current: 10 mA Acceleration voltage: 15 kV Charge neutralization mechanism: ON Measurement area: 300 μm x 700 μm Pass Energy: Survey: 160 eV, Narrow: 40 eV Photoelectron acceptance angle: 90° Auto Z: ON Peak shift correction: Corrected so that the C-C peak is 285.0 eV in the C1s peak Waveform separation of narrow peak: Performed using the GL function in the analysis software attached to the device Etching ions: Ar monatomic ions

[0417] Table 2 shows the percentage (%) of the amount of each element detected, with the amount of all elements detected being 100.

[0418] In Example 11, the ratio of silicon element to carbon element was 0.02 (2%) or more. A cross section of the functional layer of Example 11 was observed. A scanning transmission electron microscope S4800 manufactured by Hitachi High-Tech Corporation was used for cross-sectional observation. Observation of the cross section at an acceleration voltage of 10 kV to 30 kV and a magnification of 5000x revealed that the silica added as a lubricant was dispersed without aggregation or uneven distribution.

[0419] <<2-8. Indentation hardness at cross section of each layer>> Samples of 1 mm x 20 mm were cut out from the optical sheets according to the examples and comparative examples. The samples were visually inspected to ensure that there were no defects such as dust or scratches. Using the method described above, embedded samples with the cross section of each layer exposed were prepared.

[0420] The epoxy resin used for embedding was obtained by mixing Struers' "Epofix" (trade name) and "Epofix Hardener" (trade name), both manufactured by the same company, in a ratio of 10:1.2. A microtome, Leica Microsystems' "Ultramicrotome EM UC7" was used to cut the embedded samples.

[0421] For each example of optical sheet slice sample, the indentation hardness (MPa) of the cross section was measured by the method described above. The indentation hardness (MPa) was measured using a measuring device "TI-950 TriboIndenter" manufactured by BRUKER. The indenter used for measuring the indentation hardness (MPa) was "TI-0039" manufactured by BRUKER.

[0422] The following measurement results for indentation hardness (MPa) are shown in Table 1. The indentation hardness in the cross section of each layer was the arithmetic mean value of the indentation hardness measured at 10 measurement positions. The 10 measurement positions were 10 positions on one slice sample, spaced apart at a pitch of 5 μm in a direction perpendicular to the first direction of the optical sheet. - Indentation hardness HA1 at a first position in the cross section of the functional layer - Indentation hardness HA2 at a second position in the cross section of the functional layer - Indentation hardness HA3 at a third position in the cross section of the functional layer - Indentation hardness HB at a central position in the cross section of the intermediate layer - Indentation hardness HC at a central position in the cross section of the substrate layer

[0423] <<2-9. Total Light Transmittance>> Samples measuring 5 cm x 10 cm were cut out from the optical sheets according to the examples and comparative examples. The samples were visually inspected to ensure there were no defects such as dust or scratches. The total light transmittance of the optical sheets according to each example was measured using the method described above. The total light transmittance was measured using a haze meter "HM-150" manufactured by Murakami Color Research Laboratory. The measurement results of the total light transmittance are shown in Table 2.

[0424] <<2-10. Yellowness Index: YI Value>> Samples measuring 5 cm x 10 cm were cut out from the optical sheets according to the examples and comparative examples. The samples were visually inspected to ensure there were no abnormalities such as dust or scratches. The yellowness index YI value of the optical sheets according to each example was measured using the method described above. The yellowness index YI value was measured using an ultraviolet-visible spectrophotometer "UV-2600" manufactured by Shimadzu Corporation. The measurement results of the yellowness index YI value are shown in Table 2.

[0425]

[0426]

[0427] Second Embodiment A second embodiment will now be described.

[0428] <<<Optical Sheet 110>>> In the second embodiment, the optical sheet 110 includes a first layer 120. The first layer 120 includes a cured product of a curable resin composition and an ultraviolet absorber. The first layer 120 including the ultraviolet absorber provides the optical sheet 110 with a blue light blocking function. The spectral transmittance of the optical sheet 110 at a wavelength of 410 nm is 15% or less. The spectral transmittance of the optical sheet 110 at a wavelength of 440 nm is 70% or more. This optical sheet 110 may block light with a wavelength of 410 nm or less with high efficiency. The optical sheet 110 may transmit light with a wavelength of 440 nm or more with high transmittance.

[0429] The optical sheet 110 blocks light with wavelengths of 410 nm or less, thereby suppressing problems caused by blue light. When the optical sheet 110 is applied to a display device 60 (see FIG. 6), image light emitted from the display device 60 can be transmitted through the optical sheet 110. The optical sheet 110 can block light with wavelengths of 410 nm or less from the image light. As an example, by sufficiently blocking light with wavelengths of 410 nm or less from the image light, eye strain of an observer of the image can be alleviated. As another example, external light such as sunlight can be incident on the optical sheet 110. By sufficiently blocking external light with wavelengths of 410 nm or less, deterioration of the display element 61 (see FIG. 6) can be suppressed. For example, deterioration of the EL element (organic electroluminescence element) of an organic EL panel (organic electroluminescence panel) can be suppressed. By sufficiently blocking external light with wavelengths of 410 nm or less, deterioration of the polarizer 52 of the polarizing plate 50 (see FIG. 4) can be suppressed.

[0430] Light with a wavelength of 440 nm or more can be transmitted with high transmittance through the optical sheet 110. This makes it possible to suppress changes and deterioration in the color of an image observed through the optical sheet 110.

[0431] The spectral transmittance of the optical sheet 110 at a wavelength of 410 nm may be 15% or less, 14% or less, 13% or less, 12% or less, or 10% or less. By setting the upper limit of the spectral transmittance of the optical sheet 110 at a wavelength of 410 nm in this manner, blue light can be effectively blocked. No particular lower limit is set for the spectral transmittance of the optical sheet 110 at a wavelength of 410 nm. The spectral transmittance of the optical sheet 110 at a wavelength of 410 nm may be 0% or more, greater than 0%, 2% or more, or 5% or more.

[0432] The spectral transmittance of the optical sheet 110 at a wavelength of 410 nm may be 0% to 15%, 0% to 14%, 0% to 13%, 0% to 12%, or 0% to 10%. The spectral transmittance of the optical sheet 110 at a wavelength of 410 nm may be greater than 0% to 15%, greater than 0% to 14%, greater than 0% to 13%, greater than 0% to 12%, or greater than 0% to 10%. The spectral transmittance of the optical sheet 110 at a wavelength of 410 nm may be 2% to 15%, greater than 2% to 14%, greater than 2% to 13%, greater than 2% to 12%, or greater than 2% to 10%. The spectral transmittance of the optical sheet 110 at a wavelength of 410 nm may be 5% or more and 15% or less, 5% or more and 14% or less, 5% or more and 13% or less, 5% or more and 12% or less, or 5% or more and 10% or less.

[0433] The spectral transmittance of the optical sheet 110 at a wavelength of 440 nm may be 70% or more, 75% or more, 80% or more, or 85% or more. By setting the lower limit of the spectral transmittance of the optical sheet 110 at a wavelength of 440 nm in this manner, color changes in images transmitted through the optical sheet 110 can be effectively suppressed. No upper limit is particularly set for the spectral transmittance of the optical sheet 110 at a wavelength of 440 nm. The spectral transmittance of the optical sheet 110 at a wavelength of 440 nm may be 100% or less, or may be less than 100%.

[0434] The spectral transmittance of the optical sheet 110 at a wavelength of 440 nm may be 70% or more and 100% or less, 75% or more and 100% or less, 80% or more and 100% or less, or 85% or more and 100% or less. The spectral transmittance of the optical sheet 110 at a wavelength of 440 nm may be 70% or more and less than 100%, 75% or more and less than 100%, 80% or more and less than 100%, or 85% or more and less than 100%.

[0435] The method for measuring the spectral transmittance is the same as the method described in the first embodiment.

[0436] The first layer 120 further includes a cured product of a curable resin composition. In this specification, the cured product of the curable resin composition is also referred to as a cured resin product. The cured resin product can impart high hardness to the first layer 120 and the optical sheet 110. The first layer 120 functions as a so-called hard coat layer. The optical sheet 110 with improved hardness has excellent scratch resistance. Scratches on the optical sheet 110 can be suppressed during use. The optical sheet 110 is also suitable for a touch panel member 55 (see FIG. 5 ) that is expected to be touched by a finger or a pen during use.

[0437] However, in conventional optical sheets, it has sometimes been impossible to impart sufficient hardness to a resin layer containing a cured resin product. This phenomenon is thought to be due to the ultraviolet absorber contained in the resin layer. A resin layer containing a cured resin product is obtained by curing a coating film of a curable resin composition. The coating film can be cured by exposing the coating film to light, which promotes a crosslinking reaction. High-energy, short-wavelength light is usually used for exposure. The ultraviolet absorber added to the curable resin composition can absorb the light used in the curing treatment of the coating film. In other words, the ultraviolet absorber can inhibit the curing process of the curable resin composition.

[0438] If the hardness of the resin layer containing the cured resin is low, the scratch resistance may be significantly reduced. If the hardness of the resin layer containing the cured resin is low, the ultraviolet absorber may bleed out from the resin layer during use of the optical sheet. If the ultraviolet absorber bleeds out, the blue light blocking function of the optical sheet 110 will also be insufficient.

[0439] In the second embodiment, a measure is taken to improve the hardness of the first layer 120 and the optical sheet 110. The optical sheet 110 according to the second embodiment includes a second layer 130 adjacent to the first layer 120. The ratio of the thickness T120 (μm) of the first layer 120 to the thickness T130 (μm) of the second layer 130 is defined as the "thickness ratio" (= T120 / T130). The thickness ratio is 1.5 or more and 7.5 or less.

[0440] The thickness ratio is determined using a scanning transmission electron microscope (STEM). First, the thickness T120 of the first layer 120 and the thickness T130 of the second layer 130 are measured. The cross section of the optical sheet 110 to be evaluated is observed with a scanning transmission electron microscope, and the thicknesses T120 and T130 are measured from the image observed with the scanning transmission electron microscope. The thickness T120 of the first layer 120 and the thickness T130 of the second layer 130 are measured at the same position in a direction perpendicular to the thickness direction observed with the scanning transmission electron microscope, and the thickness ratio at that measurement position is calculated. The thickness T120 and the thickness T130 are measured at 10 measurement positions, and the 10 thickness ratios are calculated. The thickness ratio of the optical sheet 110 is determined as the arithmetic mean of the 10 thickness ratios.

[0441] An observation image of the cross section of the optical sheet 110 to be evaluated is obtained by observing a thickness measurement sample with a scanning transmission electron microscope. The thickness measurement sample is obtained by the following first and second steps.

[0442] (First step) A cut sample is cut out from the optical sheet to be evaluated. The cut sample is visually inspected to ensure there are no defects such as dust or scratches. Next, the cut sample is embedded in resin to prepare an embedded sample.

[0443] The embedded sample is prepared in the following procedure. First, the cut sample is placed in a silicon embedding plate. Then, embedding resin is poured into the silicon embedding plate with the cut sample placed in it. Next, the embedding resin is hardened inside the silicon embedding plate. Next, the cut sample and the embedding resin that encases it are removed from the silicon embedding plate to obtain the embedded sample. The embedded sample is shaped like a block. The embedding resin is epoxy resin.

[0444] (Second step) The block-shaped embedded sample is cut to prepare a slice sample. The slice sample includes a surface along the first direction (thickness direction, stacking direction) of the target optical sheet. Among the slices cut from the block-shaped embedded sample, a slice sample that is free of defects such as holes and has a uniform thickness of approximately 60 nm to 100 nm is used as the thickness measurement sample.

[0445] When obtaining an observation image of the cross section of the optical sheet, the imaging conditions of the scanning transmission electron microscope are as follows: <Imaging conditions> Mode: Transmission mode TE, bright field Acceleration voltage: 10 kV to 30 kV Emission current: 10 μA WD (Working Distance): 8.8±0.1 mm Magnification: 5000 times

[0446] 8, the optical sheet 110 may include a first surface 111 and a second surface 112 that face each other in a first direction D1. The first surface 111 and the second surface 112 constitute a pair of main surfaces of the optical sheet 110. The first direction D1 is the stacking direction of multiple layers included in the optical sheet 110. The first layer 120 and the second layer 130 are located in this order from the first surface 111 to the second surface 112 in the first direction D1.

[0447] As demonstrated in the examples described below, the hardness of the first layer 120 is improved by setting the thickness ratio to be 1.5 or more and 7.5 or less. This improves the hardness of the first surface 111, and also improves the scratch resistance of the first surface 111. With the optical sheet 110 according to the second embodiment, the pencil hardness of the first surface 111 can be 2H or more. With the optical sheet 110 according to the second embodiment, the load capacity of the first surface 111 in a steel wool scratch resistance test can be 200 g or more. With the optical sheet 110 according to the second embodiment, the indentation hardness of the cross section of the first layer 120 at an indentation depth of 100 nm can be 350 MPa or more.

[0448] The pencil hardness is an index showing resistance to defects such as scratches that occur when a pencil lead is pressed against a sample to be evaluated and then moved. The method for measuring the pencil hardness is the same as the measurement method described in the first embodiment.

[0449] The steel wool scratch resistance test is an index showing resistance to defects such as scratches that occur when steel wool is pressed against a sample to be evaluated and moved relative to the sample. The method for measuring the load capacity in the steel wool scratch resistance test is the same as the measurement method described in the first embodiment.

[0450] Indentation hardness H ＩＴ is the hardness measured by the nanoindentation method using a nanoindenter. ＩＴ The measurement position is a position shifted by 1.2 μm from the first side surface 121 to the second side surface 122 of the first layer 120 along the normal direction of the optical sheet 110. That is, assuming that the first layer 120 corresponds to the functional layer 20, the indentation hardness H ＩＴ The method for measuring the indentation hardness is the same as the method described in the first embodiment.

[0451] The first side surface 121 and the second side surface 122 are a pair of main surfaces of the first layer 120. The first side surface 121 is located on a first side in a first direction D1 that is a normal direction of the first layer 120. The first side surface 121 is a surface that is close to the first surface 111 in the first direction D1. In the example shown in FIG. 8 , the first side surface 121 of the first layer 120 constitutes the first surface 111 of the optical sheet 110. The second side surface 122 is located on a second side in the first direction D1. The second side surface 122 is a surface that is close to the second surface 112 in the first direction D1.

[0452] It is unclear in detail how the thickness ratio (T120 / T130) of the thickness T120 of the first layer 120 to the thickness T130 of the second layer 130 affects the hardness of the first layer 120 and the hardness at the first surface 111 of the optical sheet 110. As demonstrated in the examples described later, by providing the second layer 130 adjacent to the first layer 120 containing a cured resin and an ultraviolet absorber as a thin layer so as to satisfy the thickness ratio, the hardness of the first layer 120 and the hardness at the first surface 111 were improved.

[0453] One of the reasons for the improvement in hardness can be inferred as follows: The second layer 130 tends to have a lower hardness than the first layer 120 containing a cured resin. When the second layer 130 has an appropriate thickness that is thinner than the first layer 120, the adhesion of the first layer 120 to the optical sheet 110 is easily ensured, and in addition, the hardness of the second layer 130 is easily prevented from being reflected in the hardness of the first surface 111. The present disclosure is not bound by this inference.

[0454] It was also confirmed that the thickness ratio of the first layer 120 to the second layer 130 has the following relationship with the hardness of the first surface 111 of the optical sheet 110 and the first layer 120:

[0455] Setting a lower limit for the thickness ratio improves the hardness of the first layer 120 and the hardness of the first surface 111. The thickness ratio may be 1.5 or more, and may further be 1.7 or more, 2.6 or more, 2.9 or more, or 3.4 or more. Setting the lower limit for the thickness ratio in this manner improves the hardness of the first layer 120 and the hardness of the first surface 111. The pencil hardness of the first surface 111 may be 2H or more, 3H or more, or 4H or more. The load capacity of the first surface 111 in a steel wool scratch resistance test may be 200 g or more, 250 g or more, or 300 g or more. The indentation hardness at a cross section of the first layer 120 at an indentation depth of 100 nm may be 350 MPa or more, 380 MPa or more, 387 MPa or more, 410 MPa or more, 414 MPa or more, 420 MPa or more, 440 MPa or more, 442 MPa or more, or 480 MPa or more.

[0456] There is no particular upper limit set for the pencil hardness of the first surface 111. The pencil hardness of the first surface 111 may be 2H or more and 8H or less, 3H or more and 8H or less, or 4H or more and 8H or less.

[0457] There is no particular upper limit set for the load capacity in a steel wool scratch resistance test on the first surface 111. The load capacity of the first surface 111 in a steel wool scratch resistance test may be 200 g or more and 300 g or less, 250 g or more and 300 g or less, or even 300 g.

[0458] There is no particular upper limit to the indentation hardness at an indentation depth of 100 nm in a cross section of the first layer 120. The indentation hardness at an indentation depth of 100 nm in a cross section of the first layer 120 may be 350 MPa to 600 MPa, 380 MPa to 600 MPa, 387 MPa to 600 MPa, 410 MPa to 600 MPa, 414 MPa to 600 MPa, 420 MPa to 600 MPa, 440 MPa to 600 MPa, 442 MPa to 600 MPa, or 480 MPa to 600 MPa.

[0459] If the thickness ratio becomes too large, the hardness of the first layer 120 and the hardness at the first surface 111 may decrease. By setting an upper limit to the thickness ratio, the hardness of the first layer 120 and the hardness at the first surface 111 can be improved. As described above, the thickness ratio may be 7.5 or less.

[0460] It has been confirmed that if the thickness ratio becomes too large, other problems may occur. By setting a lower limit to the thickness ratio, the hardness of the first layer 120 and the hardness at the first surface 111 increase. However, if the thickness ratio becomes too large, curling or warping may occur in the optical sheet 110. By setting an upper limit to the thickness ratio, deformations such as curling and warping can be suppressed. The thickness ratio may be 7.5 or less, or may be 7.3 or less, 5.0 or less, 4.8 or less, or 3.9 or less. By setting the upper limit to the thickness ratio in this manner, deformations such as curling and warping of the optical sheet 110 can be suppressed. Furthermore, by setting the upper limit to the thickness ratio in this manner, the hardness of the first layer 120 and the hardness at the first surface 111 can be improved.

[0461] The details of why setting an upper limit on the thickness ratio can suppress deformation such as curling and warping are unclear. The following can be inferred as one reason for suppressing deformation. Because the first layer 120 contains a cured resin, it may shrink during a curing process. This curing shrinkage may cause deformation such as curling and warping in the optical sheet 110. By setting an upper limit on the thickness ratio, the second layer 130 adjacent to the first layer 120 has a thickness that is at least a certain percentage of the thickness of the first layer 120. Therefore, it is inferred that the second layer 130 at least partially absorbs deformation of the first layer 120, thereby suppressing deformation of the optical sheet 110. The present disclosure is not bound by this inference.

[0462] The thickness ratio may be 1.5 or more and 7.5 or less, further, 1.7 or more and 7.5 or less, 2.6 or more and 7.5 or less, 2.9 or more and 7.5 or less, or 3.4 or more and 7.5 or less. The thickness ratio may be 1.5 or more and 7.3 or less, further, 1.7 or more and 7.3 or less, 2.6 or more and 7.3 or less, 2.9 or more and 7.3 or less, or 3.4 or more and 7.3 or less. The thickness ratio may be 1.5 or more and 5.0 or less, further, 1.7 or more and 5.0 or less, 2.6 or more and 5.0 or less, 2.9 or more and 5.0 or less, or 3.4 or more and 5.0 or less. The thickness ratio may be 1.5 or more and 4.8 or less, further, 1.7 or more and 4.8 or less, 2.6 or more and 4.8 or less, 2.9 or more and 4.8 or less, or 3.4 or more and 4.8 or less. The thickness ratio may be 1.5 or more and 3.9 or less, further, 1.7 or more and 3.9 or less, 2.6 or more and 3.9 or less, 2.9 or more and 3.9 or less, or 3.4 or more and 3.9 or less.

[0463] A lower limit may be set for the thickness T120 of the first layer 120. Setting a lower limit for the thickness of the first layer 120 makes it possible to stably improve the hardness of the first layer 120 and the hardness at the first surface 111. The thickness T120 of the first layer 120 may be 5.0 μm or more, 5.2 μm or more, 6.2 μm or more, 6.6 μm or more, or 6.7 μm or more.

[0464] An upper limit may be set for the thickness T120 of the first layer 120. Setting an upper limit for the thickness of the first layer 120 can stably suppress deformation such as curling or warping that occurs in the optical sheet 110. The thickness T120 of the first layer 120 may be 9.0 μm or less, 8.7 μm or less, 7.6 μm or less, 7.5 μm or less, or 7.3 μm or less.

[0465] The thickness T120 may be 5.0 μm or more and 9.0 μm or less, 5.2 μm or more and 9.0 μm or less, 6.2 μm or more and 9.0 μm or less, 6.6 μm or more and 9.0 μm or less, or 6.7 μm or more and 9.0 μm or less. The thickness T120 may be 5.0 μm or more and 8.7 μm or less, 5.2 μm or more and 8.7 μm or less, 6.2 μm or more and 8.7 μm or less, 6.6 μm or more and 8.7 μm or less, or 6.7 μm or more and 8.7 μm or less. The thickness T120 may be 5.0 μm or more and 7.6 μm or less, 5.2 μm or more and 7.6 μm or less, 6.2 μm or more and 7.6 μm or less, 6.6 μm or more and 7.6 μm or less, or 6.7 μm or more and 7.6 μm or less. The thickness T120 may be 5.0 μm or more and 7.5 μm or less, 5.2 μm or more and 7.5 μm or less, 6.2 μm or more and 7.5 μm or less, 6.6 μm or more and 7.5 μm or less, or 6.7 μm or more and 7.5 μm or less. The thickness T120 may be 5.0 μm or more and 7.3 μm or less, 5.2 μm or more and 7.3 μm or less, 6.2 μm or more and 7.3 μm or less, 6.6 μm or more and 7.3 μm or less, or 6.7 μm or more and 7.3 μm or less.

[0466] A lower limit may be set for the thickness T130 of the second layer 130. Setting a lower limit for the thickness of the second layer 130 makes it possible to stably suppress deformation such as curling and warping that occurs in the optical sheet 110. Setting a lower limit for the thickness of the second layer 130 makes it possible to stably improve the hardness of the first layer 120 and the hardness at the first surface 111. The thickness T130 of the second layer 130 may be 1.2 μm or more, 1.5 μm or more, 1.6 μm or more, or 1.7 μm or more.

[0467] An upper limit may be set for the thickness T130 of the second layer 130. Setting an upper limit for the thickness of the second layer 130 makes it possible to stably improve the hardness of the first layer 120 and the hardness at the first surface 111. The thickness T130 of the second layer 130 may be 3.2 μm or less, 3.0 μm or less, 2.5 μm or less, 2.4 μm or less, 2.3 μm or less, or 2.1 μm or less.

[0468] The thickness T130 may be 1.2 μm or more and 3.2 μm or less, 1.5 μm or more and 3.2 μm or less, 1.6 μm or more and 3.2 μm or less, or 1.7 μm or more and 3.2 μm or less. The thickness T130 may be 1.2 μm or more and 3.0 μm or less, 1.5 μm or more and 3.0 μm or less, 1.6 μm or more and 3.0 μm or less, or 1.7 μm or more and 3.0 μm or less. The thickness T130 may be 1.2 μm or more and 2.5 μm or less, 1.5 μm or more and 2.5 μm or less, 1.6 μm or more and 2.5 μm or less, or 1.7 μm or more and 2.5 μm or less. The thickness T130 may be 1.2 μm or more and 2.4 μm or less, 1.5 μm or more and 2.4 μm or less, 1.6 μm or more and 2.4 μm or less, or 1.7 μm or more and 2.4 μm or less. The thickness T130 may be 1.2 μm or more and 2.3 μm or less, 1.5 μm or more and 2.3 μm or less, 1.6 μm or more and 2.3 μm or less, or 1.7 μm or more and 2.3 μm or less. The thickness T130 may be 1.2 μm or more and 2.1 μm or less, 1.5 μm or more and 2.1 μm or less, 1.6 μm or more and 2.1 μm or less, or 1.7 μm or more and 2.1 μm or less.

[0469] The thickness T120 of the first layer 120 and the thickness T130 of the second layer 130 are each measured using a scanning transmission electron microscope (STEM). As described above, a cross section of the optical sheet 110 to be evaluated is observed with a scanning transmission electron microscope, and the thicknesses T120 and T130 are measured from the image observed with the scanning transmission electron microscope. The image of the cross section of the optical sheet 110 to be evaluated is obtained by observing a thickness measurement sample with the scanning transmission electron microscope. The thickness measurement sample is obtained through the first and second steps described above. For the first layer 120, the thickness T120 is determined as the arithmetic mean value of ten thickness measurements measured at ten measurement positions. For the second layer 130, the thickness T130 is determined as the arithmetic mean value of ten thickness measurements measured at ten measurement positions.

[0470] The hardness of the first layer 120 may be greater than the hardness of the second layer 130. The indentation hardness H measured on the cross section of the first layer 120 ＩＴ is the indentation hardness H measured at the cross section of the second layer 130 ＩＴ According to these examples, in combination with the above-described conditions regarding the thickness ratio, the hardness of the first layer 120 and the hardness at the first surface 111 can be stably improved. Furthermore, in combination with the above-described conditions regarding the thickness ratio, deformation of the optical sheet 110, such as curling and warping, can be stably suppressed.

[0471] Indentation hardness H of the cross section of the second layer 130 ＩＴ The measurement position is the center in the thickness direction of the second layer 130. That is, assuming that the second layer 130 corresponds to the intermediate layer 30, the indentation hardness H ＩＴ By pressing the indenter into this measurement position, the indentation hardness H ＩＴ is measured. The indentation hardness H of the cross section of the second layer 130 ＩＴIn addition, the indentation hardness H of the cross section of the first layer 120 described above ＩＴ It is measured using the same measurement method as the measurement method of .

[0472] The second layer 130 may contain one or more of an acrylic resin and a cellulose resin. According to this example, a relationship in which the hardness of the first layer 120 is greater than the hardness of the second layer 130 is stably established. For example, the indentation hardness H ＩＴ is the indentation hardness H measured on the cross section of the second layer 130. ＩＴ By combining this hardness relationship with the above-mentioned conditions regarding the thickness ratio, the hardness of the first surface 111 of the optical sheet 110 becomes stable and high. As a result, the hardness of the first layer 120, the pencil hardness of the first surface 111, the load capacity in a steel wool scratch resistance test on the first surface 111, and the indentation hardness H ＩＴ In addition, by combining this with the above-described condition regarding the thickness ratio, deformation of the optical sheet 110 such as curling and warping can be stably suppressed.

[0473] The second layer 130 may contain the same resin component as at least a portion of the resin component contained in the first layer 120. According to this example, the adhesion between the second layer 130 and the first layer 120 can be improved. When the adhesion between the second layer 130 and the first layer 120 is improved, the hardness of the first layer 120 and the hardness at the first surface 111 can be stably improved. As a result, the pencil hardness at the first surface 111, the load capacity in a steel wool scratch resistance test at the first surface 111, and the indentation hardness H at the cross section of the first layer 120 can be improved. ＩＴ may rise.

[0474] Fourier transform infrared spectroscopy (FT-IR) allows quantitative analysis of the chemical bonds contained in each layer, and by using this Fourier transform infrared spectroscopy, it is possible to determine whether the second layer 130 contains the resin component contained in the first layer 120.

[0475] The second layer 130 may contain a monomer. According to this example, a relationship in which the hardness of the first layer 120 is greater than the hardness of the second layer 130 is stably established. For example, the indentation hardness H ＩＴ is the indentation hardness H measured on the cross section of the second layer 130. ＩＴ By combining this hardness relationship with the above-mentioned conditions regarding the thickness ratio, the hardness of the first layer 120 and the hardness of the first surface 111 of the optical sheet 110 can be stably improved. As a result, the pencil hardness of the first surface 111, the load resistance in a steel wool scratch resistance test on the first surface 111, and the indentation hardness H ＩＴ In addition, by combining this with the above-described condition regarding the thickness ratio, deformation of the optical sheet 110 such as curling and warping can be stably suppressed.

[0476] The second layer 130 may contain at least a portion of the monomer contained in the curable resin composition for producing the first layer 120. According to this example, a relationship in which the hardness of the first layer 120 is greater than the hardness of the second layer 130 is stably established. For example, the indentation hardness H ＩＴ is the indentation hardness H measured on the cross section of the second layer 130. ＩＴ This makes it possible to increase the hardness more stably, and also improves the adhesion between the second layer 130 and the first layer 120. As a result, the hardness of the first layer 120 and the hardness of the first surface 111 of the optical sheet 110 can be improved stably.

[0477] Whether the second layer 130 contains a monomer is determined by staining with osmium tetroxide. First, a cross-sectional sample is cut out from the optical sheet 110. The sample thickness is approximately 80 nm. The cut sample is collected on a Cu mesh. This sample is stained with osmium tetroxide for 30 minutes using a vapor-phase staining method. The portion of the stained sample corresponding to the second layer 130 is observed using a scanning transmission electron microscope (STEM). The staining process stains unsaturated double bonds that may be contained in the second layer 130. Therefore, if the observed sample is stained, it is determined that the second layer 130 contains a monomer. Whether the monomer contained in the second layer 130 is the same as the monomer contained in the curable resin composition used to produce the first layer 120 is determined by quantitatively analyzing chemical bonds using Fourier transform infrared spectroscopy (FT-IR).

[0478] 8 , the optical sheet 110 may include a base layer 140. The first layer 120, the second layer 130, and the base layer 140 may be arranged in this order from the first surface 111 to the second surface 112 in the first direction D1. In the illustrated example, the first layer 120 includes a first side surface 121 and a second side surface 122. The first side surface 121 and the second side surface 122 constitute a pair of main surfaces of the first layer 120. In the illustrated example, the first side surface 121 constitutes the first surface 111. The second side surface 122 is in contact with the second layer 130.

[0479] 8 , the thickness T140 of the base layer 140 may be greater than the thickness T120 of the first layer 120. The thickness T140 of the base layer 140 may be greater than the thickness T130 of the second layer 130. The thickness T140 of the base layer 140 may be greater than the sum of the thickness T120 of the first layer 120 and the thickness T130 of the second layer 130. The base layer 140 having such a thickness T140 can stably support the first layer 120 and the second layer 130.

[0480] The thickness T140 of the base layer 140, like the thickness T120 of the first layer 120 and the thickness T130 of the second layer 130, is measured using a scanning transmission electron microscope (STEM). A cross section of the optical sheet 110 to be evaluated is observed with a scanning transmission electron microscope, and the thickness T140 is measured from the image observed with the scanning transmission electron microscope. The image of the cross section of the optical sheet 110 to be evaluated is obtained by observing a thickness measurement sample with a scanning transmission electron microscope. The thickness measurement sample is obtained through the first and second steps described above. The thickness T140 of the base layer 140 is determined as the arithmetic mean value of ten thickness measurements taken at ten measurement positions.

[0481] The second layer 130 may contain the same resin component as at least a portion of the resin component contained in the base layer 140. According to this example, the adhesion between the second layer 130 and the base layer 140 can be improved. The adhesion between the second layer 130 and the base layer 140 can also contribute to improving the hardness of the first layer 120 and the hardness at the first surface 111. When the adhesion between the second layer 130 and the base layer 140 is improved, the hardness of the first layer 120 and the hardness at the first surface 111 can be improved. As a result, the pencil hardness at the first surface 111, the load capacity in a steel wool scratch resistance test at the first surface 111, and the indentation hardness H at the cross section of the first layer 120 can be improved. ＩＴ may rise.

[0482] The second layer 130 may contain at least a portion of the resin component contained in the first layer 120 and at least a portion of the resin component contained in the base layer 140. According to this example, a relationship in which the hardness of the first layer 120 is greater than the hardness of the second layer 130 is stably established. For example, the indentation hardness H ＩＴ is the indentation hardness H measured on the cross section of the second layer 130. ＩＴ By combining this hardness relationship with the above-described condition regarding the thickness ratio, the hardness of the first layer 120 and the hardness at the first surface 111 can be increased stably.

[0483] In addition, the adhesion between the first layer 120 and the second layer 130 can be improved, and the adhesion between the second layer 130 and the base material layer 140 can be improved. The improved adhesion can stably improve the hardness of the first layer 120 and the hardness at the first surface 111.

[0484] The second layer 130 may contain the same ultraviolet absorbing agent as at least a portion of the ultraviolet absorbing agent contained in the first layer 120. When the second layer 130 contains an ultraviolet absorbing agent, the blue light blocking function can be strengthened.

[0485] Furthermore, the second layer 130 may be a mixed layer of the resin component of the first layer 120 and the resin component of the base layer 140. The second layer 130 as a mixed layer of the resin component of the first layer 120 and the resin component of the base layer 140 can more effectively improve the hardness of the first layer 120 and the hardness at the first surface 111. The second layer 130 as a mixed layer may be a permeation layer in which the curable resin composition for producing the first layer 120 is permeated into the base film 145. The base layer 140 and the second layer 130 may both be constituted by the base film 145 to which the curable resin composition for producing the first layer 120 is applied. The portion of the base film 145 that is permeated with the curable resin composition may constitute the second layer 130. The portion of the base film 145 that is not permeated with the curable resin composition may constitute the base layer 140.

[0486] The presence of the permeation layer can be confirmed by observing the cross section of the optical sheet along the first direction with a scanning transmission electron microscope (STEM). An observation image of the cross section of the optical sheet 110 to be evaluated is obtained by observing the thickness measurement sample described above with a scanning transmission electron microscope. The thickness measurement sample is stained before observation with the scanning transmission electron microscope. Osmium tetroxide, ruthenium tetroxide, phosphotungstic acid, or the like may be used for staining.

[0487] The base layer 140 and the base film 145 may contain one or more of an acrylic resin and a cellulose resin. The acrylic resin and the cellulose resin are easily permeable with the curable resin composition. Therefore, the second layer 130, which is a mixed layer of the resin components of the first layer 120 and the resin components of the base layer 140, can be easily produced. According to this example, the hardness of the first layer 120 and the hardness of the first surface 111 can be stably improved.

[0488] The hardness of the substrate layer 140 may be greater than the hardness of the second layer 130. The indentation hardness H measured on the cross section of the substrate layer 140 ＩＴ is the indentation hardness H measured at the cross section of the second layer 130 ＩＴ According to these examples, in combination with the above-described conditions regarding the thickness ratio, the hardness of the first layer 120 and the hardness at the first surface 111 can be stably improved. Furthermore, in combination with the above-described conditions regarding the thickness ratio, deformation of the optical sheet 110, such as curling and warping, can be stably suppressed.

[0489] Indentation hardness H of the cross section of the base layer 140 ＩＴ The measurement position is the center in the thickness direction of the base material layer 140. That is, assuming that the base material layer 140 corresponds to the base material layer 40, the indentation hardness H ＩＴ By pressing the indenter into this measurement position, the indentation hardness H ＩＴ is measured. The indentation hardness H ＩＴ In addition, the indentation hardness H of the cross section of the first layer 120 described above ＩＴ It is measured using the same measurement method as the measurement method of .

[0490] The L of the optical sheet 110 measured by transmitted light ＊ a ＊ b ＊ Color system a ＊ The L value of the optical sheet 110 measured by transmitted light may be equal to or greater than -3.0 and equal to or less than -1.6. ＊ a ＊ b＊ Color system b ＊ The value may be 3.5 or more and 6.0 or less. ＊ value and b ＊ By setting the value within the above range, it is possible to suppress changes and deterioration in the color of an image observed through the optical sheet 110 while maintaining the blue light blocking function. ＊ value and b ＊ The method for measuring the value is the same as the method described in the first embodiment.

[0491] The yellowness index (YI value) of the optical sheet 110 may be 12 or less, 11 or less, 10 or less, or 9.0 or less. The yellowness index is an index showing the degree of yellow coloration of the optical sheet 110. By setting the above upper limit for the yellowness index (YI value), it is possible to limit the yellow coloration of the optical sheet 110. By achieving the above spectral transmittance without using a yellow pigment, it is possible to suppress color changes in images transmitted through the optical sheet 110.

[0492] There is no particular lower limit for the yellowness index (YI value) of the optical sheet 110. The yellowness index (YI value) of the optical sheet 110 may be 0 or greater, or may be greater than 0.

[0493] The yellowness index (YI value) of the optical sheet 110 may be 0 or more and 12 or less, 0 or more and 11 or less, 0 or more and 10 or less, or 0 or more and 9.0 or less. The yellowness index (YI value) of the optical sheet 110 may be 0 or more and 12 or less, 0 or more and 11 or less, 0 or more and 10 or less, or 0 or more and 9.0 or less.

[0494] The method for measuring the yellowness is the same as the method described in the first embodiment.

[0495] The total light transmittance of the optical sheet 110 may be 50% or more, 70% or more, 80% or more, or 90% or more. The total light transmittance of the optical sheet 110 has no particular upper limit. The total light transmittance of the optical sheet 110 may be 100% or less, or may be less than 100%.

[0496] The total light transmittance of the optical sheet 110 may be 50% or more and 100% or less, 70% or more and 100% or less, 80% or more and 100% or less, or 90% or more and 100% or less. The total light transmittance of the optical sheet 110 may be 50% or more and less than 100%, 70% or more and less than 100%, 80% or more and less than 100%, or 90% or more and less than 100%.

[0497] The method for measuring the total light transmittance is the same as the method described in the first embodiment.

[0498] The transmission haze of the optical sheet 110 may be 1.1% or less, 0.5% or less, or 0.2% or less. The transmission haze of the optical sheet 110 does not have a particular lower limit. The transmission haze of the optical sheet 110 may be 0% or greater than 0%.

[0499] The transmission haze of the optical sheet 110 may be 0% or more and 1.1% or less, 0% or more and 0.5% or less, or 0% or more and 0.2% or less. The transmission haze of the optical sheet 110 may be greater than 0% and 1.1% or less, greater than 0% and 0.5% or less, or greater than 0% and 0.2% or less.

[0500] The method for measuring the transmission haze is the same as the method described in the first embodiment.

[0501] The ratio of silicon to carbon measured on the first surface 111 by X-ray photoelectron spectroscopy may be 0.02 or greater. In other words, the amount of silicon may be 0.02 or greater when the amount of carbon is 1 in the quantitative elemental analysis results by X-ray photoelectron spectroscopy. The silicon is the sum of an inorganic component (silica) and an organic component (silicone). The first layer 120 may contain inorganic particles as a lubricant. By setting the ratio of silicon to carbon to 0.02 or greater, aggregation of inorganic particles added as a lubricant, such as silica aggregation, can be suppressed. In other words, by setting the ratio of silicon to carbon to 0.02 or greater, the lubricant functions effectively. The lubricant can prevent adjacent optical sheets 110 from sticking to each other when stacking or rolling up the optical sheets 110.

[0502] The curable resin composition for producing the first layer 120 may contain a leveling agent. By using a Si-based leveling agent as the leveling agent added to the curable resin composition, the ratio of silicon element to carbon element can be set to 0.02 or more.

[0503] The ratio of elemental fluorine measured on the first surface 111 by X-ray photoelectron spectroscopy may be 0.1% or less. In other words, the ratio of the amount of elemental fluorine to the total amount of elements detected by X-ray photoelectron spectroscopy may be 0.001 or less. In this example, substantially no fluorine is detected in the surface layer portion of the optical sheet 110. By not using an F-based leveling agent as the leveling agent added to the curable resin composition, the ratio of elemental fluorine can be 0.1% or less.

[0504] By setting the fluorine element ratio to 0.1% or less, it is possible to suppress the generation of PFAS as an impurity. PFAS, an artificial organic fluorine compound, is a concern due to its bioaccumulation potential. Suppressing the generation of PFAS can contribute to reducing the environmental impact. Reducing the fluorine element ratio also improves the scratch resistance of the first surface 11.

[0505] X-ray photoelectron spectroscopy allows quantitative analysis of elements present in the surface layer of the optical sheet 110. An X-ray photoelectron spectroscopy device (XPS) is used for X-ray photoelectron spectroscopy. The measurement method by X-ray photoelectron spectroscopy using the X-ray photoelectron spectroscopy device is the same as the measurement method described in the first embodiment.

[0506] Each layer of the optical sheet 110 shown in FIG. 8 will be described in more detail below. In the example shown in FIG. 8, the base layer 140, the second layer 130, and the first layer 120 are stacked in a first direction D1. The first direction D1 is the stacking direction. The base layer 140, the second layer 130, and the first layer 120 extend in a second direction D2 and a third direction D3 that are perpendicular to the first direction D1. In the example shown, the second direction D2 and the third direction D3 are perpendicular to each other. The first direction D1 is the thickness direction and normal direction of the optical sheet 110. The first direction D1 is also the thickness direction and normal direction of each layer 140, 130, and 120 included in the optical sheet 110. In the optical sheet 110 shown in FIG. 8, the first surface 111 is formed by the first layer 120. The second surface 112 is formed by the base layer 140. The first layer 120 and the second layer 130 are adjacent to each other in the first direction D1. The second layer 130 and the substrate layer 140 are adjacent to each other in the first direction D1.

[0507] The optical sheet 110 may include layers other than the first layer 120, the second layer 130, and the substrate layer 140. The optical sheet 110 may include one or more of a low-reflection layer, an antistatic layer, an antifouling layer, etc. In this example, a layer other than the first layer 120 may form the first surface 111. The other layers, such as the low-reflection layer, the antistatic layer, and the antifouling layer, are thin layers. Therefore, even in an example in which the first surface 111 is formed by another layer, such as a low-reflection layer, an antistatic layer, or an antifouling layer, the hardness of the first surface 111 can be improved by the combination of the first layer 120 and the second layer 130.

[0508] <<Substrate Layer 140>> The substrate layer 140 supports the first layer 120 and the second layer 130. The substrate layer 140 may be transparent. “Transparent” means that the total light transmittance in accordance with JIS K7361-1:1997 is 50% or more, and may be 70% or more, 80% or more, or 90% or more.

[0509] The substrate layer 140 may be the same as the substrate layer 40 described in the first embodiment. The substrate layer 140 may have the same configuration as the substrate layer 40 described in the first embodiment. The material of the substrate layer 140 may be the same as the material of the substrate layer 40 described in the first embodiment. The thickness T140 of the substrate layer 140 may be the same as the thickness T40 of the substrate layer 40 described in the first embodiment. The layer configuration of the substrate layer 140 may be the same as the layer configuration of the substrate layer 40 described in the first embodiment.

[0510] The base layer 140 may be prepared as a base film 145. This base film 145 may include only a single layer or multiple layers. The base layer 140 may include a primer layer such as an easy-adhesion layer. The surface of the base film 145 may be subjected to one or more of the following etching treatments: sputtering, corona discharge, ultraviolet irradiation, electron beam irradiation, chemical conversion, oxidation, and the like, and a primer treatment. These treatments can improve the adhesion between the base film 145 and the layer adjacent to the base film 145. The surface of the base film 145 may be subjected to a cleaning treatment such as solvent cleaning or ultrasonic cleaning.

[0511] <<First Layer 120>> The first layer 120 includes a binder resin 123 and an ultraviolet absorber. The inclusion of the ultraviolet absorber allows the first layer 120 to exhibit a blue light blocking function. The binder resin 123 includes a cured product of a curable resin composition. The inclusion of the cured product of the curable resin composition in the first layer 120 contributes to improving the hardness of the first surface 111 and the first layer 120.

[0512] The first layer 120 may have the same configuration as the functional layer 20 described in the first embodiment. The material of the first layer 120 may be the same as the material of the functional layer 20 described in the first embodiment. The layer configuration of the first layer 120 may be the same as the layer configuration of the functional layer 20 described in the first embodiment.

[0513] The curable resin composition may be an ionizing radiation-curable resin composition. The ionizing radiation-curable resin composition may include one or more of an ultraviolet-curable resin composition and an electron beam-curable resin composition. The ionizing radiation-curable resin composition may include an ionizing radiation-curable compound and a photopolymerization initiator. The ionizing radiation-curable compound may include one or more of an ultraviolet-curable compound and an electron beam-curable compound. The ultraviolet-curable compound is a resin that is cured by irradiation with ultraviolet light. The electron beam-curable compound is a resin that is cured by irradiation with an electron beam. The cured product of the curable resin composition may be a cured curable compound.

[0514] <Curable Compound> The ionizing radiation curable compound may be the same as the ionizing radiation curable compound used in the functional layer 20 described in the first embodiment.

[0515] <Photopolymerization Initiator> The photopolymerization initiator is not particularly limited, and may be the same as the photopolymerization initiator used in the functional layer 20 described in the first embodiment.

[0516] The content of the photopolymerization initiator may be the same as the content of the photopolymerization initiator described in the first embodiment.

[0517] <UV Absorber> The UV absorber may be dispersed in the first direction D1, the second direction D2, and the third direction D3 in the first layer 120. The UV absorber may be contained in a liquid curable resin composition. The UV absorber contained in the curable resin composition may be dispersed in the first layer 120 after a coating film of the curable resin composition has been subjected to a drying treatment and a curing treatment.

[0518] The ultraviolet absorber imparts blue light blocking capability to the first layer 120 and the optical sheet 110. The characteristics of the blue light blocking capability can be adjusted by the type and content of the ultraviolet absorber. Therefore, the blue light blocking capability attributable to the ultraviolet absorber can make the spectral transmittance at a wavelength of 440 nm 70% or more, while making the spectral transmittance at a wavelength of 410 nm 15% or less. Depending on the type and content of the ultraviolet absorber, the L measured by transmitted light can be adjusted. ＊ a ＊ b ＊ Color system a ＊The value can be adjusted by changing the type and content of the ultraviolet absorber. ＊ a ＊ b ＊ Color system b ＊ The yellowness index YI value measured by transmitted light can be adjusted by the type and content of the ultraviolet absorber. The type and content of the ultraviolet absorber are not particularly limited. ＊ Value and b ＊ The type and content of the ultraviolet absorber can be selected so as to obtain a desired value.

[0519] The type and content of the ultraviolet absorbent may be the same as the type and content of the ultraviolet absorbent described in the first embodiment.

[0520] <Additives> The curable resin composition may contain particles as a lubricant. The curable resin composition may contain the same particles as the particles contained as the lubricant in the curable resin composition for the functional layer described in the first embodiment. The particle diameter of the particles contained in the first layer 120 is a value specified in the same manner as the particle diameter of the particles contained in the functional layer 20 described in the first embodiment.

[0521] The curable resin composition may contain a silicon-based leveling agent as an additive. When the first layer coating liquid contains a silicon-based leveling agent, the surface of the first layer 120 can be made smoother. The silicon-based leveling agent can impart excellent slip properties and excellent antifouling properties to the surface of the first layer 120.

[0522] The curable resin composition may contain other additives. Examples of additives include antistatic agents, antioxidants, surfactants, dispersants, silane coupling agents, thickeners, coloring inhibitors, colorants (pigments, dyes), defoamers, flame retardants, adhesion promoters, polymerization inhibitors, antioxidants, and surface modifiers. The curable resin composition may contain one or more of these additives.

[0523] <Solvent> The curable resin composition may contain a solvent. The curable resin composition may contain the same solvent as the solvent contained in the curable resin composition for the functional layer described in the first embodiment.

[0524] The content ratio of the raw materials in the curable resin composition, i.e., the solid content ratio, is not particularly limited. The content ratio of the raw materials in the curable resin composition may be 5% by mass or more, or 25% by mass or more. The content ratio of the raw materials in the curable resin composition may be 70% by mass or less, or 60% by mass or less.

[0525] <Method of Producing First Layer 120> The first layer 120 is produced using a liquid curable resin composition containing an ultraviolet absorber. The prepared curable resin composition is applied to the surface on which the first layer 120 is to be produced, forming a coating film of the curable resin composition. The coating film of the curable resin composition is dried, and the dried coating film is cured, thereby obtaining the first layer 120.

[0526] The method for preparing the curable resin composition is not particularly limited. The curable resin composition may be prepared using a known device such as a paint shaker, a bead mill, a kneader, or a mixer.

[0527] The method for applying the curable resin composition is not particularly limited, and the curable resin composition may be applied by a known method such as spin coating, dipping, spraying, die coating, bar coating, roll coating, meniscus coating, flexographic printing, screen printing, or pad coating.

[0528] The curing treatment of the curable resin composition may be performed by irradiation with ionizing radiation. The ionizing radiation may be ultraviolet light or an electron beam. Examples of ultraviolet light sources include ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arc lamps, black light fluorescent lamps, and metal halide lamps. The wavelength of the ultraviolet light may be in the wavelength range of 190 nm to 420 nm. The wavelength of the ultraviolet light used in the curing treatment is preferably the central absorption wavelength of the photopolymerization initiator contained in the curable resin composition or close to the central absorption wavelength. The wavelength of the ultraviolet light used in the curing treatment is preferably away from the central absorption wavelength of the ultraviolet absorber contained in the curable resin composition. According to such an example, the first layer 120 can be sufficiently cured by the curing treatment using ultraviolet light irradiation.

[0529] <<Second Layer 130>> The second layer 130 is a layer adjacent to the first layer 120 and the base material layer 140. As described above, the second layer 130 is a layer whose thickness T130 is adjusted relative to the thickness T120 of the first layer 120. The thickness ratio, which is the ratio of the thickness T120 of the first layer 120 to the thickness T130 of the second layer 130, is 1.5 or more and 7.5 or less.

[0530] The second layer 130 may be a resin layer. The second layer 130 may be a layer that has high adhesion to the substrate layer 140. The second layer 130 may be a layer that has high adhesion to the first layer 120. The second layer 130 may have a hardness that is lower than that of the first layer 120. The indentation hardness measured on a cross section of the first layer 120 may be greater than the indentation hardness measured on a cross section of the second layer 130. As demonstrated in the examples, the presence of such a second layer 130 can improve the hardness of the first layer 120 and the hardness at the first surface 111.

[0531] In order to satisfy the above-described relationship between the hardness and adhesion between the first layer 120 and the second layer 130, the material of the second layer 130 may be selected as follows: The second layer 130 may include a thermoplastic resin. The second layer 130 may include the same resin component as at least a portion of the resin component contained in the first layer 120. The second layer 130 may include one or more of an acrylic resin and a cellulose resin. The second layer 130 may include the same resin component as at least a portion of the resin component contained in the first layer 120. The second layer 130 may include a monomer. The second layer 130 may include at least a portion of the monomer contained in the curable resin composition used to produce the first layer 120.

[0532] The second layer 130 may be a mixed layer of the resin component of the first layer 120 and the resin component of the base layer 140. By forming the second layer 130 as a mixed layer of the resin component of the first layer 120 and the resin component of the base layer 140, the hardness of the first surface 111 of the optical sheet 110 can be more effectively improved.

[0533] The second layer 130 as a mixed layer may be a permeation layer in which the curable resin composition for producing the first layer 120 has permeated into the base film 145. The base layer 140 and the second layer 130 may both be formed by the base film 145 to which the curable resin composition for producing the first layer 120 has been applied. The second layer 130 may be formed by a portion of the base film 145 that has been permeated with the curable resin composition (permeation layer). The base layer 140 may be formed by a portion of the base film 145 that has not been permeated with the curable resin composition.

[0534] The solvent contained in the curable resin composition easily penetrates the base film 145, allowing the second layer 130 to be stably formed as a permeation layer. Using a base film 145 with high water absorption (liquid absorption) allows the solvent to easily penetrate the base film 145. The solvent easily penetrates cellulose-based resins, particularly triacetylcellulose (TAC). The solvent also easily penetrates acrylic resins. Therefore, the base layer 140 and the base film 145 may contain one or more of an acrylic resin and a cellulose resin. In this case, the second layer 130, which is a mixed layer of the resin components of the first layer 120 and the base layer 140, can be stably produced. The produced second layer 130 contains one or more of an acrylic resin and a cellulose resin.

[0535] The ease of forming the penetration layer varies depending on the relationship between the curable resin compound and solvent contained in the curable resin composition and the substrate film 145. Furthermore, the ease of forming the penetration layer also varies depending on the viscosity of the curable resin compound, the drying conditions of the coating film of the curable resin compound, and the curing conditions of the coating film of the curable resin compound. Therefore, the thickness T130 of the second layer 130 as a penetration layer can be adjusted depending on the materials contained in the curable resin composition, the materials of the substrate film 145, the preparation conditions of the curable resin composition, the drying conditions of the curable resin composition, the curing conditions of the curable resin composition, and the like. Similarly, the penetration amount varies depending on the materials contained in the curable resin composition, the materials of the substrate film 145, the preparation conditions of the curable resin composition, the drying conditions of the curable resin composition, the curing conditions of the curable resin composition, and the like, so the thickness T120 of the first layer 120 can also be adjusted. That is, when preparing the second layer 130 as a penetration layer, the thickness ratio can be adjusted.

[0536] The second layer may contain an ultraviolet absorber that is the same as at least a portion of the ultraviolet absorber contained in the first layer.

[0537] <<Manufacturing of optical sheets>>

[0538] <First Example> As a first example, a method for manufacturing the optical sheet 110 may include a step of producing an intermediate laminate including the base layer 140 and the second layer 130, and a step of producing the first layer 120 on the second layer 130.

[0539] The method for producing the intermediate laminate may be selected appropriately depending on the configuration of the second layer 130 to be produced. The intermediate laminate may be produced by laminating a film constituting the second layer 130 and a film constituting the base layer 140. The second layer 130 and the base layer 140 may be directly bonded by heat welding. The second layer 130 and the base layer 140 may also be bonded using a bonding layer containing an adhesive, a pressure-sensitive adhesive, or the like. The intermediate laminate may be produced by forming the second layer 130 on the base layer 140 as a base film by a wet method. In the wet method, a liquid composition is prepared. The liquid composition is applied to the base layer 140. The second layer 130 may be formed on the base layer 140 by drying a coating of the composition.

[0540] The first layer 120 may be produced by the wet method described above. In the wet method, a liquid curable resin composition is prepared. The liquid curable resin composition may contain solid components constituting the binder resin 123 of the first layer 120, additives such as an ultraviolet absorber and a polymerization initiator, and a solvent. The curable resin composition is applied onto the second layer 130 of the intermediate laminate, thereby forming a coating film of the curable resin composition on the second layer 130. Next, the coating film is dried and cured, thereby forming the first layer 120 on the second layer 130.

[0541] <Second Example> As a second example, the method for manufacturing the optical sheet 110 may include a step of producing an intermediate laminate including the second layer 130 and the first layer 120, and a step of laminating the intermediate laminate including the second layer 130 and the first layer 120 and the base layer 140.

[0542] In the process of producing the intermediate laminate, the first layer 120 may be formed on the second layer 130 by a wet method. In the process of laminating the intermediate laminate and the base material layer 140, the base material layer 140 and the second layer 130 of the intermediate laminate may be directly bonded by heat welding. The base material layer 140 and the second layer 130 of the intermediate laminate may also be bonded using a bonding layer containing an adhesive, a pressure-sensitive adhesive, or the like.

[0543] The intermediate laminate may include a release sheet, a first layer 120, and a second layer 130, in this order. The process of producing the intermediate laminate may include a process of forming the first layer 120 on the release surface of the release sheet by a wet method, and a process of forming the second layer 130 on the first layer 120. The second layer 130 may be formed on the first layer 120 by a wet method. The second layer 130 may be composed of a film laminated to the first layer 120. The release sheet may be peeled off from the second layer 130 and the first layer 120, which are transferred onto the substrate layer 140.

[0544] <Third Example> As a third example, a manufacturing method for the optical sheet 110 may include a step of forming the first layer 120 on the substrate film 145 by a wet method. This manufacturing method may include a step of applying a curable resin composition to the substrate film 145 and a step of curing the coating film of the curable resin composition. The manufacturing method may further include a step of drying the coating film of the curable resin composition before the step of curing the coating film. In this example, the first layer 120 may be formed by the coating film of the cured curable resin composition. The second layer 130 may be formed by a portion of the substrate film 145 into which the curable resin composition has permeated (i.e., a permeation layer). The substrate layer 140 may be formed by a portion of the substrate film into which the curable resin composition has not permeated.

[0545] As described above, the thickness T130 of the second layer 130 as a penetration layer can be adjusted depending on the material contained in the curable resin composition, the material of the base film 145, the preparation conditions of the curable resin composition, the drying conditions of the curable resin composition, the curing conditions of the curable resin composition, etc. Similarly, the amount of penetration into the base layer 140 changes depending on the material contained in the curable resin composition, the material of the base film 145, the preparation conditions of the curable resin composition, the drying conditions of the curable resin composition, the curing conditions of the curable resin composition, etc., so the thickness T120 of the first layer 120 can also be adjusted. In other words, when the second layer 130 is produced as a penetration layer, the thickness ratio can be adjusted.

[0546] For example, the thickness T130 of the second layer 130 can be increased by selecting a type of solvent that easily penetrates the base film 145 or by increasing the solvent content. The thickness T130 of the second layer 130 can be increased by selecting a base film 145 made of a resin material that is easily penetrated by the solvent of the curable resin composition. An example of a resin material that is easily penetrated by a solvent is a cellulose-based resin such as triacetylcellulose (TAC). The thickness of the second layer 130 can be increased by increasing the plasticizer content or content of the base film 145. The thickness T130 of the second layer 130 can be increased by decreasing the temperature of the heated air blown onto the coating film during the drying process or by decreasing the flow velocity or volume of the heated air. The thickness T130 of the second layer 130 can be decreased by increasing the solids content of the curable resin composition.

[0547] <Fourth Example> As a fourth example, a method for manufacturing the optical sheet 110 may include the following four steps: a step of applying a first curable resin composition containing an ultraviolet absorber onto the base film 145; a step of curing the coating of the first curable resin composition to form the first portion 120A on the base film 145; a step of applying a second curable resin composition onto the first portion 120A; and a step of curing the coating of the second curable resin composition to form the second portion 120B bonded to the first portion 120A.

[0548] In a fourth example, the production method may further include a step of drying the coating film of the first curable resin composition before a step of curing the coating film of the first curable resin composition. In the fourth example, the production method may further include a step of drying the coating film of the second curable resin composition before a step of curing the coating film of the second curable resin composition.

[0549] In a fourth example, the first portion 120A and the second portion 120B may constitute the first layer 120. The second layer 130 may be constituted by a portion of the base film 145 that has been permeated with the curable resin composition (i.e., a permeation layer). The base layer 140 may be constituted by a portion of the base film 145 that has not been permeated with the curable resin composition.

[0550] As shown by the two-dot chain line in Figure 8, the second portion 120B constitutes a surface portion of the first layer 120. The surface portion of the first layer 120 is located near or constitutes the first surface 111. The first portion 120A constitutes a portion of the first layer 120 that is bonded to the second layer 130. The first portion 120A is spaced apart from the first surface 111. The first curable resin composition and the second curable resin composition have different compositions, so that the properties of the first portion 120A and the second portion 120B in the first layer 120 can be changed.

[0551] In the fourth example, the first curable resin composition and the second curable resin composition may be the same as the curable resin compositions described above. However, the second curable resin composition may not contain an ultraviolet absorber. The second curable resin composition may contain an ultraviolet absorber in a content less than that of the first curable resin composition. The second curable resin composition may contain an ultraviolet absorber in a content less than that of the first curable resin composition.

[0552] In this example, the first curable resin composition contains a larger amount of UV absorber. Therefore, the hardness of the first portion 120A is reduced. The second curable resin composition contains no UV absorber or only a small amount of UV absorber. By exposing the coating film from the first side surface 121 (first surface 111), the coating film of the second curable resin composition can be irradiated with a sufficient amount of ionizing radiation, such as UV radiation, with sufficient intensity. Therefore, the crosslinking reaction in the second portion 120B is promoted, and the hardness of the second portion 120B is increased. This allows the first layer 120 to have blue light blocking properties due to the UV absorber while increasing the surface hardness of the first layer 120 at the first side surface 121.

[0553] In the obtained first layer 120, the ultraviolet absorber is dispersed mainly in the first portion 120A. The first portion 120A is covered by the second portion 120B, which has a higher hardness. Therefore, the ultraviolet absorber can be effectively prevented from passing through the second portion 120B and bleeding out.

[0554] The first portion 120A to which the second curable resin composition is applied may contain an ultraviolet absorber, which may slow the crosslinking reaction and result in low hardness. Therefore, the second curable resin composition may penetrate into the first portion 120A. The first and second curable resin compositions are mixed, making the interface between the first portion 120A and the second portion 120B less noticeable. This significantly improves the adhesion between the first portion 120A and the second portion 120B.

[0555] When the optical sheet 110 manufactured by the manufacturing method of the fourth example was observed using a scanning transmission electron microscope S4800 manufactured by Hitachi High-Tech Corporation at an acceleration voltage of 10 kV to 30 kV and a magnification of 5000 times, no interface was found between the first portion 120A and the second portion 120B. In other words, no interface that could cause a decrease in hardness was present on the first surface 111.

[0556] The second curable resin composition may permeate not only the first portion 120A but also the base material layer 140. In the manufacturing method according to the fourth example, the thickness T130 of the second layer 130 serving as a permeation layer can be adjusted by the materials contained in the first and second curable resin compositions, the material of the base material film 145, the preparation conditions of the first and second curable resin compositions, the drying conditions of the first and second curable resin compositions, the curing conditions of the first and second curable resin compositions, etc. According to the manufacturing method according to the fourth example, the thickness T130 and thickness ratio of the second layer 130 can be adjusted with a higher degree of freedom compared to the manufacturing method according to the third example described above.

[0557] According to the fourth example of the production method, the spectral transmittance can also be adjusted with a high degree of freedom. In the fourth example of the production method, the spectral transmittance can be adjusted by factors other than the type and total content of the ultraviolet absorbers contained in the first and second curable resin compositions.

[0558] The wavelength of the ultraviolet light used in the curing treatment is preferably away from the central absorption wavelength of the ultraviolet absorber contained in the curable resin composition, and therefore, in many conventional curable resin compositions, particularly ultraviolet-curable resin compositions, contain only one type of ultraviolet absorber.

[0559] In the manufacturing method according to the fourth example, the spectral transmittance characteristics can be adjusted by factors other than the type of UV absorber and the total content of the UV absorbers. For example, the spectral transmittance characteristics can be adjusted by the ratio of the content of the UV absorber in the first curable resin composition to the content of the UV absorber in the second curable resin composition. The spectral transmittance characteristics can also be adjusted by the ratio of the content of the UV absorber in the first curable resin composition to the content of the curable resin composition in the second curable resin composition. The spectral transmittance can also be adjusted by one or more of the thickness of the first portion 120A, the thickness of the second portion 120B, and the ratio of the thickness of the first portion 120A to the thickness of the second portion 120B. As a result, the manufacturing method according to the fourth example allows for greater flexibility in adjusting the spectral transmittance characteristics of the optical sheet 110.

[0560] Furthermore, by exposing the coating film of the second curable resin composition from the surface forming the first surface 111, the coating film of the second curable resin composition can be cured while avoiding the influence of the UV absorber contained in the first portion 120A. That is, when the coating film of the second curable resin composition is cured, the influence of the UV absorber contained in the first curable resin composition can be suppressed. Therefore, the type, content, and content ratio of the UV absorber contained in the first curable resin composition and the first portion 120A of the first layer 120 can be selected with a high degree of freedom. This allows the first layer 120 and the optical sheet 110 to be imparted with desired spectral transmittance characteristics.

[0561] Furthermore, the ultraviolet absorber can be unevenly distributed in a portion of the first layer 120 in the thickness direction, for example, the first portion 120A. Therefore, the ultraviolet absorber can be effectively utilized to efficiently capture blue light. From this perspective, the desired spectral transmittance characteristics can be imparted to the first layer 120 and the optical sheet 110. Furthermore, while imparting the desired spectral transmittance characteristics to the optical sheet 110, the hardness and scratch resistance of the first surface 111 can be improved.

[0562] <Sheet Article and Roll> According to the above-described method for manufacturing the optical sheet 110, a long sheet article 5 including a large number of optical sheets 110 can be manufactured, as shown in FIG. 3 . The long sheet article 5 is cut to a predetermined size to obtain the optical sheet 110. According to this example, optical sheets 110 having various dimensions can be obtained from the long sheet article 5 according to needs. Therefore, optical sheets 110 having various dimensions can be provided in a timely manner. As shown in FIG. 3 , by handling the sheet article 5 as a roll 7 wound around a winding core 6 about a winding axis RA, the handling of the sheet article 5 can be improved.

[0563] <Selection Method and Selection Process> The method for manufacturing an optical sheet may further include a step of selecting a manufactured optical sheet 110 in addition to the step of manufacturing the optical sheet described above. The step of selecting the optical sheet 110 may include a step of measuring a thickness ratio, a step of measuring a spectral transmittance at a wavelength of 410 nm, and a step of measuring a spectral transmittance at a wavelength of 440 nm. The thickness ratio is the ratio of the thickness T120 (μm) of the first layer 120 to the thickness T130 (μm) of the second layer 130. The step of selecting the optical sheet 110 may further include a step of selecting an optical sheet based on the thickness ratio, the spectral transmittance at a wavelength of 410 nm, and the spectral transmittance at a wavelength of 440 nm. A thickness ratio of 1.5 or more and 7.5 or less may be considered acceptable. A spectral transmittance of 15% or less at a wavelength of 410 nm may be considered acceptable. A spectral transmittance of 70% or more at a wavelength of 440 nm may be considered acceptable. The optical sheet 110 that passes all of the thickness ratio, the spectral transmittance at a wavelength of 410 nm, and the spectral transmittance at a wavelength of 440 nm may be selected as a good product. The optical sheet 110 selected as a good product has an excellent blue light blocking function and a high hardness on the first surface 111. This selection step makes it possible to select an optical sheet with excellent scratch resistance with high precision without performing a scratch test using felt or steel wool.

[0564] <<<Polarizing Plate 50, Touch Panel Member 55, Display Device 60>>> As described in the first embodiment with reference to FIGS. 4 to 6 , the optical sheet 110 can be applied to one or more of the polarizing plate 50, the touch panel member 55, and the display device 60.

[0565] <<<<<Examples of Second Embodiment>>>> The present disclosure will be described in more detail with reference to examples. The present disclosure is not limited to the following examples.

[0566] <<<<1. Preparation of Optical Sheets>>> Optical sheets according to Examples 21 to 27 and Comparative Examples 21 to 24 were prepared.

[0567] <<Example 21>> A first curable resin composition 2A was applied to a substrate film made of triacetyl cellulose with a thickness of 80 μm, and a first coating film was formed on the substrate film. A method for producing the first curable resin composition 2A will be described later. Next, the first coating film was dried under the conditions of 40°C x 20 seconds (drying air speed 0.4 m / s). Thereafter, the first coating film was dried under the conditions of 40°C x 20 seconds (drying air speed 0.5 m / s). In this way, the solvent was volatilized. Next, an integrated light intensity of 66 mJ / cm was applied. ２ The first coating film was irradiated with ultraviolet light. The first coating film was cured by the ultraviolet light irradiation, and a first portion of the first layer was formed on the substrate film. The amount of the first curable resin composition 2A applied was set to an amount that would result in a first portion with a dry thickness of 3.0 μm, assuming that the first curable resin composition 2A did not penetrate into the substrate film.

[0568] Next, a second curable resin composition 2A having the following formulation was applied to the first portion to form a second coating film on the substrate film. The second curable resin composition 2A had a solids content of 47%. The second curable resin composition 2A did not contain an ultraviolet absorber. Next, the second coating film was dried under the conditions of 60°C x 20 seconds (drying air speed 0.4 m / s). Thereafter, the second coating film was dried under the conditions of 70°C x 20 seconds (drying air speed 0.3 m / s). In this way, the solvent was volatilized. Next, an integrated light dose of 288 mJ / cm was applied. ２The second coating film was irradiated with ultraviolet light. The second coating film was cured by irradiation with ultraviolet light, and the second portion of the first layer was formed on the substrate film and the first portion. The amount of second curable resin composition 2A applied was set to an amount that would result in a second portion with a dry thickness of 5.0 μm, assuming that the second curable resin composition 2A would not penetrate into the substrate layer or the first portion.

[0569] In this way, an optical sheet according to Example 21 was obtained. In this optical sheet, the first portion and the second portion constituted a first layer.

[0570] During the thickness measurement described below, the cross section of the optical sheet according to Example 21 was observed. A scanning transmission electron microscope S4800 manufactured by Hitachi High-Tech Corporation was used to observe the cross section. Observation of the cross section at an acceleration voltage of 10 kV to 30 kV and a magnification of 5000x revealed that the curable resin composition had permeated the substrate film, causing the substrate film to swell, thereby forming a permeation layer constituting the second layer. Furthermore, the interface between the first and second portions in the first layer could not be observed.

[0571] <First Curable Resin Composition 2A> A sesamol-type benzotriazole-based monomer was synthesized, and then an acrylic polymer to which the sesamol-type benzotriazole-based monomer was reactively bonded was synthesized, thereby obtaining a first curable resin composition 2A.

[0572] (Synthesis of Sesamol-Type Benzotriazole Monomer) A 200 mL four-neck flask was equipped with a ball condenser, a mercury thermometer, and a stirrer. 4.0 g (0.013 mol) of 6-[5-(2-hydroxyethyl)-2H-benzotriazol-2-yl]benzo[1,3]dioxol-5-ol, 40 mL of toluene, 1.8 g (0.021 mol) of methacrylic acid, and 0.4 g (0.004 mol) of methanesulfonic acid were placed in the four-neck flask. The contents of the four-neck flask were refluxed and dehydrated at 110-115°C for 4 hours. Next, 30 mL of water and 0.6 g (0.006 mol) of sodium carbonate were added to the four-neck flask. The four-neck flask was then allowed to stand, and the lower aqueous layer was separated and removed. Next, 0.2 g of activated carbon was added to the four-neck flask, and the contents were refluxed and stirred to decolorize. The contents removed from the four-neck flask were then filtered. 40 mL of toluene was recovered from the resulting filtrate under reduced pressure. 100 mL of isopropyl alcohol was added to the filtrate from which toluene had been removed, and the precipitated crystals were filtered. The resulting crystals were washed with 40 mL of isopropyl alcohol. The crystals were then dried at 40°C under reduced pressure to obtain yellow crystals. 4.2 g of the resulting yellow crystals were repulped and washed using isopropyl alcohol. Next, the washed yellow crystals were dried at 40°C under reduced pressure to obtain 3.4 g of 2-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]ethyl methacrylate as a sesamol-type benzotriazole monomer.

[0573] (Synthesis of acrylic polymer having sesamol-type benzotriazole monomer reactively bonded) A...

Claims

1. An optical sheet including a first surface and a second surface opposite to the first surface, comprising, in the order from the second surface to the first surface, a base layer and a functional layer, the functional layer comprising a cured product of a curable resin composition and an ultraviolet absorber, a spectral transmittance at a wavelength of 380 nm being 1% or less, and a spectral transmittance at a wavelength of 440 nm being 70% or more, an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on the cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer satisfy the following relationships: HA3 < HA2 ≦ HA1 HA1 / HA2 ≦ HA2 / HA3 the first position is located on a surface portion close to the first surface on the cross section, the third position is located on a surface portion close to the second surface on the cross section, and the second position is located midway between the first position and the third position.

2. The optical sheet according to claim 1, wherein the indentation hardness HA1 at the first position and the indentation hardness HA2 at the second position satisfy the following relationship: HA1 / HA2≦1.7 3. The optical sheet according to claim 1, wherein the indentation hardness HA1 at the first position and the indentation hardness HA3 at the third position satisfy the following relationship: 1.4≦HA1 / HA3 4. The optical sheet according to claim 1, wherein the indentation hardness HA2 at the second position and the indentation hardness HC at the cross section of the base layer satisfy the following relationship: HA2 / HC≦1.3 5. The optical sheet according to claim 1, wherein the indentation hardness HA1 at the first position is 340 MPa or more.

6. The optical sheet according to claim 1, wherein the indentation hardness HA2 at the second position is 240 MPa or more.

7. The optical sheet according to claim 1, wherein the indentation hardness HA3 at the third position is 120 MPa or more.

8. The optical sheet according to claim 1, comprising an intermediate layer located between the functional layer and the base material layer, wherein an indentation hardness HB of the intermediate layer at a cross section is smaller than an indentation hardness HC of the base material layer at a cross section, and the thickness of the intermediate layer is 4.2 μm or less.

9. The optical sheet according to claim 1, further comprising an intermediate layer located between the functional layer and the base material layer, the intermediate layer having an indentation hardness HB of 120 MPa or more in a cross section.

10. The optical sheet according to claim 1, wherein the slope of the spectral transmittance at each wavelength in 0.5 nm intervals within the wavelength range of 380 nm or more and 440 nm or less has a maximum value within the wavelength range of 400 nm or more and 420 nm or less, and the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

11. The optical sheet according to claim 10, wherein the slope of the spectral transmittance has a maximum value within a wavelength range of 410 nm or more and 420 nm or less.

12. The optical sheet according to claim 1, which has a spectral transmittance of 15% or less at a wavelength of 410 nm.

13. The optical sheet according to claim 1, wherein the pencil hardness of the first surface is 2H or more when measured in accordance with JIS K 5600-5-4:1999 at a load of 500 g and a speed of 1.4 mm / sec.

14. The optical sheet according to claim 1, wherein the load resistance of the first surface in a steel wool scratch resistance test under the following conditions is 100 g or more: Steel wool scratch resistance test: using steel wool #0000, moving back and forth 10 times at a moving speed of 100 mm / sec and a one-way moving distance of 120 mm.

15. An optical sheet comprising a first layer and a second layer adjacent to the first layer, wherein the first layer contains a cured product of a curable resin composition and an ultraviolet absorber, wherein a thickness ratio is 1.5 or more and 7.5 or less, wherein the thickness ratio is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer, wherein a spectral transmittance at a wavelength of 410 nm is 15% or less, and wherein a spectral transmittance at a wavelength of 440 nm is 70% or more.

16. The optical sheet according to claim 15, wherein the thickness ratio is equal to or greater than 2.6 and equal to or less than 5.

0.

17. The optical sheet according to claim 15, wherein the second layer has a thickness of 1.2 μm or more and 3.2 μm or less.

18. The optical sheet according to claim 15, wherein the thickness of the first layer is not less than 5.0 μm and not more than 9.0 μm.

19. An optical sheet according to claim 15, comprising a first surface and a second surface opposite to the first surface, the first layer and the second layer being disposed in this order from the first surface to the second surface, and a ratio of silicon element to carbon element measured on the first surface by X-ray photoelectron spectroscopy is 0.02 or more.

20. An optical sheet as described in claim 15, comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface to the second surface, and a ratio of elemental fluorine measured on the first surface by X-ray photoelectron spectroscopy is 0.1% or less.

21. L measured by transmitted light ＊ a ＊ b ＊ Color system a ＊ The value is -3.0 or more and -1.6 or less, and the L measured by transmitted light ＊ a ＊ b ＊ Color space b ＊ The optical sheet according to claim 15, wherein the value is 3.5 or more and 6.0 or less.

22. The optical sheet according to claim 15, wherein an indentation hardness measured on a cross section of the first layer is greater than an indentation hardness measured on a cross section of the second layer.

23. The optical sheet according to claim 15, wherein the second layer includes one or more of an acrylic resin and a cellulose resin.

24. The optical sheet according to claim 15, further comprising a base layer adjacent to the second layer, the second layer being located between the first layer and the base layer, and the base layer including one or more of an acrylic resin and a cellulose resin.

25. The optical sheet according to claim 24, wherein the thickness (μm) of the base layer is greater than the sum of the thickness (μm) of the first layer and the thickness (μm) of the second layer.

26. An optical sheet according to claim 15, comprising a first surface and a second surface opposite to the first surface, the first layer and the second layer being disposed in this order from the first surface to the second surface, and the indentation hardness of a cross section of the first layer at an indentation depth of 100 nm is 350 MPa or more.

27. An optical sheet according to claim 15, comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface to the second surface, and the pencil hardness of the first surface, measured in accordance with JIS K 5600-5-4:1999 at a load of 500 g and a speed of 1.4 mm / sec, is 2H or greater.

28. The optical sheet according to claim 15, comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the load capacity of the first surface in a steel wool scratch resistance test under the following conditions is 200 g or more: Steel wool scratch resistance test: Using steel wool #0000, the sheet is moved back and forth 10 times at a moving speed of 100 mm / sec and a one-way moving distance of 120 mm.

29. An optical sheet comprising: a first layer and a second layer adjacent to the first layer, the first layer comprising a cured product of a curable resin composition and an ultraviolet absorber, a thickness ratio being 1.2 or more and 7.5 or less, the thickness ratio being a ratio of the thickness (μm) of the first layer to the thickness (μm) of the second layer, a spectral transmittance at a wavelength of 380 nm being less than 1%, a spectral transmittance at a wavelength of 440 nm being 70% or more, a slope of the spectral transmittance at each wavelength at 0.5 nm intervals within a wavelength range of 380 nm or more and 440 nm or less has a maximum value within a wavelength range of 400 nm or more and 420 nm or less, and a slope (% / nm) of the spectral transmittance at wavelength X being a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

30. The optical sheet according to claim 29, wherein the slope of the spectral transmittance has a maximum value within a wavelength range of 410 nm or more and 420 nm or less.

31. The optical sheet according to claim 29, wherein the thickness ratio is equal to or greater than 2.6 and equal to or less than 5.

0.

32. The optical sheet according to claim 29, wherein the thickness of the second layer is 1.2 μm or more and 3.5 μm or less.

33. The optical sheet according to claim 29, wherein the thickness of the first layer is 3.2 μm or more and 9.2 μm or less.

34. An optical sheet as described in claim 29, comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface to the second surface, and a ratio of silicon element to carbon element measured on the first surface by X-ray photoelectron spectroscopy is 0.02 or more.

35. An optical sheet as described in claim 29, comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface to the second surface, and the ratio of elemental fluorine measured on the first surface by X-ray photoelectron spectroscopy is 0.1% or less.

36. L measured by transmitted light ＊ a ＊ b ＊ Color system a ＊ The value is -3.0 or more and -1.6 or less, and the L measured by transmitted light ＊ a ＊ b ＊ Color space b ＊ The optical sheet according to claim 29, wherein the value is 3.5 or more and 6.0 or less.

37. The optical sheet of claim 29, wherein an indentation hardness measured on a cross-section of the first layer is greater than an indentation hardness measured on a cross-section of the second layer.

38. The optical sheet according to claim 29, wherein the second layer includes one or more of an acrylic resin and a cellulosic resin.

39. The optical sheet of claim 29, further comprising a base layer adjacent to the second layer, the second layer being located between the first layer and the base layer, and the base layer including one or more of an acrylic resin and a cellulose resin.

40. The optical sheet according to claim 39, wherein the thickness (μm) of the base layer is greater than the sum of the thickness (μm) of the first layer and the thickness (μm) of the second layer.

41. An optical sheet as described in claim 29, comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the indentation hardness of the first surface at an indentation depth of 100 nm is 330 MPa or more.

42. An optical sheet according to claim 29, comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface to the second surface, and the pencil hardness of the first surface, measured in accordance with JIS K 5600-5-4:1999 at a load of 500 g and a speed of 1.4 mm / sec, is 2H or greater.

43. The optical sheet according to claim 29, comprising a first surface and a second surface opposing the first surface, the first layer and the second layer being disposed in this order from the first surface toward the second surface, and the load capacity of the first surface in a steel wool scratch resistance test under the following conditions is 150 g or more: Steel wool scratch resistance test: Using steel wool #0000, the sheet is moved back and forth 10 times at a moving speed of 100 mm / sec and a one-way moving distance of 120 mm.

44. A sheet product comprising a plurality of optical sheets according to any one of claims 1 to 43.

45. The sheet article of claim 44, wound about a winding axis.

46. ​​A polarizing plate comprising: an optical sheet according to any one of claims 1 to 43; and a polarizer superimposed on the optical sheet.

47. A touch panel member comprising: an optical sheet according to any one of claims 1 to 43; and an electrode layer superimposed on the optical sheet.

48. A display device comprising: an optical sheet according to any one of claims 1 to 43; and a display element superimposed on the optical sheet.

49. A method for selecting an optical sheet comprising an optical sheet having a first surface and a second surface opposite to the first surface, the optical sheet comprising, in the order from the second surface toward the first surface, a base layer and a functional layer, the functional layer comprising a cured product of a curable resin composition and an ultraviolet absorber, the method comprising the steps of: measuring a spectral transmittance at a wavelength of 380 nm and a spectral transmittance at a wavelength of 440 nm; measuring an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on the cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer; and selecting an optical sheet based on the measured spectral transmittance and the measured indentation hardness, the first position being located on a surface portion close to the first surface on the cross section, the third position being located on a surface portion close to the second surface on the cross section, and the second position being located midway between the first position and the third position.

50. A method for manufacturing an optical sheet, comprising: a step of preparing an optical sheet including a first surface and a second surface opposite to the first surface, the optical sheet comprising, in the order from the second surface toward the first surface, a base layer and a functional layer, the functional layer comprising a cured product of a curable resin composition and an ultraviolet absorber; and a step of selecting an optical sheet based on a spectral transmittance at a wavelength of 380 nm, a spectral transmittance at a wavelength of 440 nm, an indentation hardness HA1 at a first position on a cross section of the functional layer, an indentation hardness HA2 at a second position on the cross section of the functional layer, and an indentation hardness HA3 at a third position on the cross section of the functional layer, the first position being located on a surface portion close to the first surface on the cross section, the third position being located on a surface portion close to the second surface on the cross section, and the second position being located midway between the first position and the third position.

51. A method for selecting an optical sheet comprising: a first layer and a second layer adjacent to the first layer, the first layer including a cured product of a curable resin composition and an ultraviolet absorber, the method comprising the steps of: measuring a thickness ratio which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer; measuring a spectral transmittance at a wavelength of 410 nm; measuring a spectral transmittance at a wavelength of 440 nm; and selecting an optical sheet based on the thickness ratio, the spectral transmittance at a wavelength of 410 nm, and the spectral transmittance at a wavelength of 440 nm.

52. A method for manufacturing an optical sheet, comprising: a step of preparing an optical sheet comprising a first layer and a second layer adjacent to the first layer, the first layer including a cured product of a curable resin composition and an ultraviolet absorber; and a step of selecting an optical sheet based on a thickness ratio which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer, a spectral transmittance at a wavelength of 410 nm, and a spectral transmittance at a wavelength of 440 nm.

53. A method for selecting an optical sheet comprising a first layer and a second layer adjacent to the first layer, the first layer comprising a cured product of a curable resin composition and an ultraviolet absorber, the method comprising the steps of: measuring a thickness ratio which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer; measuring a spectral transmittance at each wavelength at 0.5 nm intervals within a wavelength range of 379.5 nm to 440.5 nm; and selecting an optical sheet based on the thickness ratio, the spectral transmittance at a wavelength of 380 nm, the spectral transmittance at a wavelength of 440 nm, and a slope of the spectral transmittance at wavelengths at 0.5 nm intervals within a wavelength range of 380 nm to 440 nm, wherein the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

54. A method for producing an optical sheet comprising: a first layer and a second layer adjacent to the first layer, the first layer comprising a cured product of a curable resin composition and an ultraviolet absorber; and a step of selecting an optical sheet based on a thickness ratio which is a ratio of a thickness (μm) of the first layer to a thickness (μm) of the second layer, a spectral transmittance at a wavelength of 380 nm, a spectral transmittance at a wavelength of 440 nm, and a slope of the spectral transmittance at each wavelength at 0.5 nm intervals within a wavelength range of 380 nm to 440 nm, wherein the slope (% / nm) of the spectral transmittance at wavelength X is a value obtained by subtracting the spectral transmittance (%) at wavelength X-0.5 (nm) from the spectral transmittance (%) at wavelength X+0.5 (nm).

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