Optical sheet, sheet article, polarizing plate, display device, panel, optical sheet selection method, and optical sheet manufacturing method

Abstract

The optical sheet includes a first surface and a second surface facing a first direction. The optical sheet includes an antiglare layer and a functional layer in this order from the second surface to the first surface. The transmission haze is 10-70%. The functional layer includes a binder component and hollow silica particles. A proper coordination parameter based on the hollow silica particles observed on the first surface is 1.0-2.0. The proper coordination parameter is a value obtained by subtracting an improper coordination number from a proper coordination number. The proper coordination number is the number of other hollow silica particles having the center of gravity located at a distance of 55-75 nm from the center of gravity of one hollow silica particle. The improper coordination number is the number of other hollow silica particles having the center of gravity located at a distance of less than 55 nm from the center of gravity of the one hollow silica particle.

Description

Optical sheet, sheet article, polarizing plate, display device, panel, 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 display device, a panel, a method for selecting an optical sheet, and a method for manufacturing an optical sheet.

[0002] As disclosed in Patent Document 1 (JP2022-15702A), an optical sheet including an antiglare layer and a functional layer is known. The antiglare layer has an antiglare function. The antiglare layer suppresses reflection of a background image on the surface of the optical sheet. The functional layer contains hollow silica particles. The functional layer has a function of suppressing reflection.

[0003] The optical sheet can be applied to, for example, a display device, such as a television, a display device incorporated in a notebook PC or a desktop PC, a display device incorporated in a smartphone or a tablet, etc. The optical sheet forms the outermost surface of the display device.

[0004] As described in Patent Document 1, a tint may be observed in an optical sheet including a functional layer having a reflection suppressing function.

[0005] A tint may be observed in an optical sheet including a functional layer having a reflection suppressing function. In an optical sheet including both an antiglare layer and a functional layer, a tint is easily observed in the optical sheet when the back of the optical sheet is dark. For example, when a display element is not displaying, the optical sheet attached to the display element does not appear black, and a tint may be observed in the optical sheet.

[0006] The present disclosure aims to suppress the observation of color tint in an optical sheet including an antiglare layer and a functional layer.

[0007] In one embodiment of the present disclosure, an optical sheet includes a first surface and a second surface facing each other in a first direction, and includes an antiglare layer and a functional layer in this order from the second surface to the first surface, the transmitted haze being 10% or more and 70% or less, the functional layer including a binder component and hollow silica particles, the proper coordination parameter based on the hollow silica particles observed on the first surface being 1.0 or more and 2.0 or less, the proper coordination parameter being a value obtained by subtracting the mismatch number from the proper coordination number, the proper coordination number being the number of other hollow silica particles whose centers of gravity are located at a distance of 55 nm or more and less than 75 nm from the center of gravity of one hollow silica particle, and the mismatch number being the number of other hollow silica particles whose centers of gravity are located at a distance of less than 55 nm from the center of gravity of one hollow silica particle.

[0008] In one embodiment of the present disclosure, a method for selecting an optical sheet comprises the steps of: measuring a proper coordination parameter based on the hollow silica particles observed on the first surface; and selecting an optical sheet having a proper coordination parameter of 1.0 or more and 2.0 or less; wherein the proper coordination parameter is a value obtained by subtracting a mismatch number from a proper coordination number; and the proper coordination number is the number of hollow silica particles whose center of gravity is located at a distance of 55 nm or more and less than 75 nm from the center of gravity of one hollow silica particle. The mismatch number is the number of hollow silica particles whose center of gravity is located at a distance of 55 nm or more and less than 75 nm from the center of gravity of one hollow silica particle.

[0009] In one embodiment of the present disclosure, a method for manufacturing an optical sheet includes the steps of: manufacturing the optical sheet; and selecting the optical sheet using an optical sheet selection method according to one embodiment of the present disclosure.

[0010] According to the present disclosure, it is possible to prevent color from being observed in an optical sheet including an antiglare layer and a functional layer.

[0011] FIG. 1 is a diagram for explaining one embodiment and is a cross-sectional view showing an example of an optical sheet. FIG. 2A is a cross-sectional view showing an example of a functional layer that can be included in FIG. 1. FIG. 2B is a cross-sectional view showing another example of a functional layer that can be included in FIG. 1. FIG. 3A is a plan view showing an example of an optical sheet for explaining proper coordination parameters. FIG. 3B is a plan view showing another example of an optical sheet for explaining proper coordination parameters. FIG. 3C is a plan view showing yet another example of an optical sheet for explaining proper coordination parameters. FIG. 4A is an observation image showing a first surface of an example of an optical sheet that was actually manufactured. FIG. 4B is an image obtained by binarizing the observation image of FIG. 4A. FIG. 4C is an image showing the distribution of the centers of gravity of hollow silica particles included in the observation image of FIG. 4A. FIG. 5 is a cross-sectional view showing another example of an optical sheet. FIG. 6 is a perspective view showing an example of a sheet article including an optical sheet. FIG. 7 is a cross-sectional view showing an example of a polarizing plate including an optical sheet. FIG. 8 is a cross-sectional view showing an example of a display device including an optical sheet. FIG. 9 is a cross-sectional view showing an example of a panel including an optical sheet.

[0012] One embodiment of the present disclosure relates to the following <1> to <14>.

[0013] <1> An optical sheet including a first surface and a second surface opposing each other in a first direction, the optical sheet comprising an antiglare layer and a functional layer in this order from the second surface to the first surface, the transmission haze being 10% or more and 70% or less, the functional layer including a binder component and hollow silica particles, the proper coordination parameter based on the hollow silica particles observed on the first surface being 1.0 or more and 2.0 or less, the proper coordination parameter being a value obtained by subtracting a mismatch number from a proper coordination number, the proper coordination number being the number of other hollow silica particles whose centers of gravity are located at a distance of 55 nm or more and less than 75 nm from the center of gravity of one hollow silica particle, and the mismatch number being the number of other hollow silica particles whose centers of gravity are located at a distance of less than 55 nm from the center of gravity of one hollow silica particle.

[0014] <2> L measured by reflected light from the first surface ＊ a＊ b ＊ Color system a ＊ The L value is -4.0 or more and 4.0 or less, and is measured by reflected light from the first surface. ＊ a ＊ b ＊ Color system b ＊ The optical sheet according to <1>, wherein the value is −4.0 or more and 4.0 or less.

[0015] <3> The optical sheet according to <1> or <2>, wherein the standard deviation of the proper alignment parameters is 0.30 or less.

[0016] <4> Luminous reflectance on the first surface and L measured by reflected light ＊ a ＊ b ＊ Color system a ＊ the absolute value of the product of the luminous reflectance and the L measured by reflected light is 4.0 or less; ＊ a ＊ b ＊ Color system b ＊ <3> The optical sheet according to any one of <1> to <3>, wherein the absolute value of the product of the value and the absolute value is 4.0 or less.

[0017] <5> The optical sheet according to any one of <1> to <4>, wherein the luminous reflectance of the first surface is 2.0% or less.

[0018] <6> The optical sheet according to any one of <1> to <5>, wherein the antiglare layer includes a textured surface, the textured surface is closer to the first surface than the second surface in the first direction, the textured surface includes a reference portion and a convex portion protruding from the reference portion, and the proper orientation parameter is a value measured in a region of the first surface that faces the reference portion in the first direction.

[0019] <7> The optical sheet according to any one of <1> to <6>, wherein the antiglare layer contains a resin and particles, and the proper coordination parameter is a value measured in a region of the first surface facing a region of the antiglare layer where the particles are not present and the region of the first surface facing the first direction.

[0020] <8> A sheet article comprising a plurality of the optical sheets according to any one of <1> to <7>.

[0021] <9> The sheet article according to <8>, which is wound around a winding axis.

[0022] <10> A panel comprising the optical sheet according to any one of <1> to <7>.

[0023] <11> A polarizing plate comprising: the optical sheet according to any one of <1> to <7>; and a polarizer superimposed on the optical sheet.

[0024] <12> A display device comprising: the optical sheet according to any one of <1> to <7>; and a display element superimposed on the optical sheet.

[0025] <13> A method for selecting an optical sheet, the method comprising: a step of measuring a proper coordination parameter based on the hollow silica particles observed on the first surface; and a step of selecting an optical sheet having a proper coordination parameter of 1.0 or more and 2.0 or less; wherein the proper coordination parameter is a value obtained by subtracting a mismatch number from a proper coordination number; the proper coordination number is the number of hollow silica particles whose center of gravity is located at a distance of 55 nm or more and less than 75 nm from the center of gravity of one hollow silica particle; and the mismatch number is the number of hollow silica particles whose center of gravity is located at a distance of less than 55 nm from the center of gravity of one hollow silica particle.

[0026] <14> A method for manufacturing an optical sheet, comprising: a step of manufacturing the optical sheet; and a step of selecting the optical sheet by the selection method described in <13>.

[0027] In the drawings accompanying this specification, the scale and the aspect ratios of the dimensions are appropriately changed and exaggerated from those of the actual objects for the sake of convenience in illustration and understanding.

[0028] 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" cannot be distinguished from a member called an optical film or an optical plate solely on the basis of differences in name.

[0029] In this specification, the normal direction of a sheet-like (film-like, plate-like) member refers to a direction parallel to the normal or perpendicular to the sheet surface (film surface, plate surface) of the target sheet-like (film-like, plate-like) member. The "sheet surface (film surface, plate surface)" refers to the surface that coincides with the target sheet-like (film-like, plate-like) member when the target sheet-like (film-like, plate-like) member is viewed overall and globally.

[0030] 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.

[0031] In order to clarify the relationship between directions between drawings, some drawings use arrows with common symbols to indicate a common first direction D1, second direction D2, and 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. An arrow pointing away from the paper in a direction perpendicular to the paper surface of the drawing is indicated by a symbol with an x ​​in a circle, as shown in FIG. 1, for example. An arrow pointing toward the user in a direction perpendicular to the paper surface of the drawing is indicated by a symbol with a dot in a circle, as shown in FIG. 3A, for example.

[0032] <<<Optical Sheet>>> As shown in Fig. 1 , the optical sheet 10 according to the present embodiment includes a first surface 11 and a second surface 12. The first surface 11 and the second surface 12 face each other in a first direction D1. The first surface 11 faces the opposite side from the second surface 12 in the first direction D1. The first surface 11 may be located on a first side in the first direction D1. The second surface 12 may be located on a second side in the second direction D2. The optical sheet 10 includes an antiglare layer 30 and a functional layer 40. The antiglare layer 30 and the functional layer 40 are located in this order from the second surface 12 toward the first surface 11 in the first direction D1.

[0033] The transmission haze of the optical sheet 10 is 10% or more and 70% or less.

[0034] A D65 light source is used to measure the transmission haze (%). Before measuring the transmission haze, the D65 light source is turned on for 15 minutes to stabilize the output of the D65 light source. When measuring the transmission haze, the angle of incidence on the measurement sample is 0°. When measuring the transmission haze of the optical sheet 10, the incident surface is the second surface 12. The measurement environment for measuring the transmission haze is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The measurement sample is placed in the measurement environment for 16 hours before starting the measurement. Other measurement conditions for measuring the transmission haze are in accordance with JIS K7136:2000.

[0035] The transmission haze is the arithmetic mean value of five measurements taken at five measurement positions on the measurement sample, the five measurement positions being spaced at least 10 mm apart from each other.

[0036] Setting a lower limit for the transmission haze of optical sheet 10 makes it possible to impart an anti-glare function to optical sheet 10. Optical sheet 10 with an anti-glare function can prevent background images in the environment in which optical sheet 10 is installed from being reflected on optical sheet 10. The transmission haze of optical sheet 10 may be 10% or more, 12% or more, 20% or more, 30% or more, 31% or more, 35% or more, 40% or more, or 48% or more.

[0037] Setting an upper limit to the transmission haze of the optical sheet 10 can prevent the optical sheet 10 from becoming cloudy, thereby improving the contrast of an image observed through the optical sheet 10. The transmission haze of the optical sheet 10 may be 70% or less, 66% or less, 60% or less, or 50% or less.

[0038] The transmission haze of the optical sheet 10 may be 10% to 70% or less, 12% to 70% or less, 20% to 70% or less, 30% to 70% or less, 31% to 70% or less, 35% to 70% or less, 40% to 70% or less, or 48% to 70% or less. The transmission haze of the optical sheet 10 may be 10% to 66% or less, 12% to 66% or less, 20% to 66% or less, 30% to 66% or less, 31% to 66% or less, 35% to 66% or less, 40% to 66% or less, or 48% to 66% or less. The transmission haze of the optical sheet 10 may be 10% to 60% or less, 12% to 60% or less, 20% to 60% or less, 30% to 60% or less, 31% to 60% or less, 35% to 60% or less, 40% to 60% or less, or 48% to 60% or less. The transmission haze of the optical sheet 10 may be 10% to 50% or less, 12% to 50% or less, 20% to 50% or less, 30% to 50% or less, 31% to 50% or less, 35% to 50% or less, 40% to 50% or less, or 48% to 50% or less.

[0039] The antiglare layer 30 imparts antiglare properties to the optical sheet 10. The antiglare layer 30 may exhibit its antiglare function by diffusing at least a portion of transmitted light. By adjusting the antiglare function of the antiglare layer 30, the transmission haze of the optical sheet 10 can be adjusted.

[0040] The antiglare layer 30 may include a first surface 31 and a second surface 32. The first surface 31 and the second surface 32 face each other in a first direction D1. The first surface 31 is located on a first side in the first direction D1. The second surface 32 is located on a second side in the first direction D1.

[0041] As shown in FIG. 1 , the anti-glare layer 30 may include an uneven surface 31X. The uneven surface 31X enables the anti-glare layer 30 to exhibit an anti-glare function. The uneven surface 31X may be closer to the first surface 11 than to the second surface 12 in the first direction D1. The uneven surface 31X may face the first side in the first direction D1. The uneven surface 31X may face the same side as the first surface 11 in the first direction D1. The uneven surface 31X may face the opposite side to the second surface 12 in the first direction D1. In the illustrated example, the first surface 31 includes the uneven surface 31X. In the illustrated example, the first surface 31 is the uneven surface 31X.

[0042] As shown in FIG. 1 , the uneven surface 31X may include a reference portion 31A and a protruding portion 31B. The protruding portion 31B is a portion that protrudes from the reference portion 31A in the first direction D1. The protruding portion 31B protrudes from the reference portion 31A toward a first side in the first direction D1. The protruding portion 31B is located closer to the first side in the first direction D1 than the reference portion 31A. The protruding portion 31B protrudes toward the first surface 11 in the first direction D1. The protruding portion 31B protrudes on the opposite side from the second surface 12 in the first direction D1. The reference portion 31A may be a flat portion that extends along a plane perpendicular to the first direction D1. The reference portion 31A may be a flat portion that extends generally along a plane perpendicular to the first direction D1. The reference portion 31A may be a recessed portion.

[0043] 1, the antiglare layer 30 may include a resin 36 and particles 37. In the illustrated example, the reference portion 31A is located in a region of the antiglare layer 30 where no particles 37 are present when observed from the first direction D1. In the example shown in FIG. 1, the reference portion 31A is a flat portion.

[0044] The first surface 11 may include an uneven surface 11X. The uneven surface 11X may include unevenness corresponding to the unevenness of the uneven surface 31X. That is, the uneven surface 11X may include a convex portion at a position facing the convex portion 31B of the uneven surface 31X in the first direction D1. The uneven surface 11X may include a reference portion that is a flat portion or a concave portion at a position facing the reference portion 31A of the uneven surface 31X in the first direction D1.

[0045] The difference in height between the convex portions of the uneven surface 11X and the reference portion in the first direction D1 may be the same as the difference in height between the convex portions 31B of the uneven surface 31X and the reference portion 31A in the first direction D1. The difference in height between the convex portions of the uneven surface 11X and the reference portion in the first direction D1 may be equal to or less than the difference in height between the convex portions 31B of the uneven surface 31X and the reference portion 31A in the first direction D1. The difference in height between the convex portions of the uneven surface 11X and the reference portion in the first direction D1 may be less than the difference in height between the convex portions 31B of the uneven surface 31X and the reference portion 31A in the first direction D1.

[0046] 2A and 2B, the functional layer 40 includes a binder component 46 and hollow silica particles 47. Figures 2A and 2B are enlarged views showing the functional layer 40 in the same cross section as in Figure 1.

[0047] The hollow silica particles 47 are low refractive index particles. The refractive index of the hollow silica particles 47 may be lower than the refractive index of the binder component 46. In the example shown in FIG. 1 , the functional layer 40 may be configured as a layer with a refractive index lower than that of the anti-glare layer 30. The functional layer 40 has a reflection suppressing function that suppresses reflection. The functional layer 40 may be a low-reflection layer or a reflection suppressing layer that has a reflection suppressing function. The functional layer 40 suppresses reflection of ambient light from the environment in which the optical sheet 10 is installed on the first surface 11. As shown in FIG. 1 , the functional layer 40 may constitute the first surface 11.

[0048] As shown in FIG. 1 , the thickness of the functional layer 40 may be smaller than the height difference between the reference portion 31A and the convex portion 31B. The functional layer 40 extends along the unevenness of the uneven surface 31X. The uneven surface 11X has unevenness corresponding to the unevenness of the uneven surface 31X. The optical sheet 10 can change the traveling direction of incident light due to the uneven surfaces 11X and 31X. The optical sheet 10 may have a light diffusion function that diffuses incident light due to the uneven surfaces 11X and 31X. The optical sheet 10 may reflect incident light in a direction other than the specular reflection direction due to the uneven surfaces 11X and 31X. The optical sheet 10 may diffusely reflect at least a portion of incident light due to the uneven surfaces 11X and 31X. The optical effect of the uneven surfaces 11X and 31X allows the anti-glare layer 30 to exhibit anti-glare function.

[0049] The anti-glare and anti-reflection functions of the optical sheet 10 can prevent the background of the environment in which the optical sheet 10 is placed, such as a lighting device, from being reflected on the optical sheet. By preventing the reflection of the background, the area behind the optical sheet can be clearly observed. For example, when the optical sheet is positioned on the image forming surface of a display element, the optical sheet can prevent the reflected image from superimposing on the image formed by the display element. Therefore, the image displayed by the display element can be clearly observed.

[0050] However, coloring may be observed in optical sheets that include a functional layer with anti-reflection function. The reflectance of light with different wavelengths varies in the functional layer. The reflectance of light with the same wavelength varies depending on the thickness of the functional layer and the angle of incidence on the functional layer. These phenomena are thought to be one of the reasons why coloring is observed in optical sheets. The present inventors have confirmed that the problem of coloring is more pronounced in optical sheets that include both an anti-glare layer and a functional layer. One possible means of suppressing coloring is adjusting the thickness or refractive index of the functional layer. However, while adjusting the thickness and refractive index of the functional layer is somewhat effective for optical sheets that include a functional layer but not an anti-glare layer, it has not always worked sufficiently effectively for optical sheets that include both an anti-glare layer and a functional layer.

[0051] <<Feature A: Proper Coordination Parameter>> The optical sheet 10 according to the present embodiment has the following feature (A): (A): The proper coordination parameter based on the hollow silica particles 47 observed on the first surface 11 is 1.0 or more and 2.0 or less.

[0052] The proper coordination parameter defined in feature (A) is a value obtained by subtracting the miscoordination number from the proper coordination number. The proper coordination number is the number of other hollow silica particles 47 observed on the first surface 11 whose centers of gravity are located at a distance of 55 nm or more but less than 75 nm from the center of gravity of one hollow silica particle 47 observed on the first surface 11. The miscoordination number is the number of other hollow silica particles 47 observed on the first surface 11 whose centers of gravity are located at a distance of less than 55 nm from the center of gravity of the one hollow silica particle 47 observed on the first surface 11.

[0053] 3A to 3C are enlarged plan views showing the first surface 11. Fig. 3A shows the first surface 11 of the optical sheet 10 shown in Fig. 2A.

[0054] In the example shown in Figure 3A, the number of other hollow silica particles 47B observed on the first surface 11 whose centers of gravity 47BC are located at a distance of 55 nm or more but less than 75 nm from the center of gravity 47AC of one hollow silica particle 47A observed on the first surface 11 is 2. In the example shown in Figure 3A, the number of other hollow silica particles 47B observed on the first surface 11 whose centers of gravity 47BC are located at a distance of less than 55 nm from the center of gravity 47AC of one hollow silica particle 47A observed on the first surface 11 is 0. That is, in the example shown in Figure 3A, the proper coordination number is 2 and the miscoordination number is 0. In the example shown in Figure 3A, the proper coordination parameter is 2.

[0055] In the example shown in Figure 3B, the number of other hollow silica particles 47B observed on the first surface 11 whose centers of gravity 47BC are located at a distance of 55 nm or more but less than 75 nm from the center of gravity 47AC of one hollow silica particle 47A observed on the first surface 11 is 2. In the example shown in Figure 3B, the number of other hollow silica particles 47C observed on the first surface 11 whose centers of gravity 47CC are located at a distance of less than 55 nm from the center of gravity 47AC of one hollow silica particle 47A observed on the first surface 11 is 1. That is, in the example shown in Figure 3B, the proper coordination number is 2 and the mismatch number is 1. In the example shown in Figure 3B, the proper coordination parameter is 1.

[0056] In the example shown in Figure 3C, the number of other hollow silica particles 47B observed on the first surface 11 whose centers of gravity 47BC are located at a distance of 55 nm or more but less than 75 nm from the center of gravity 47AC of one hollow silica particle 47A observed on the first surface 11 is 4. In the example shown in Figure 3C, the number of other hollow silica particles 47C observed on the first surface 11 whose centers of gravity 47CC are located at a distance of less than 55 nm from the center of gravity 47AC of one hollow silica particle 47A observed on the first surface 11 is 1. That is, in the example shown in Figure 3C, the proper coordination number is 4 and the mismatch number is 1. In the example shown in Figure 3C, the proper coordination parameter is 3.

[0057] As will be demonstrated in the examples described below, feature (A) makes it possible to stably prevent color from being observed in the optical sheet 10 that includes both an antiglare layer and a functional layer.

[0058] According to feature (A), when observing the back of the optical sheet 10, it is possible to suppress a change in the hue of an image behind the optical sheet 10 due to a color produced by the optical sheet 10. For example, when the optical sheet 10 is positioned on the image forming surface of a display element, it is possible to suppress a change in the hue of an image formed by the display element.

[0059] Furthermore, according to the feature (A), even when the back of the optical sheet 10 including the antiglare layer and the functional layer is dark, it is possible to effectively prevent a color from being observed on the optical sheet 10. Therefore, a sense of luxury is imparted to the optical sheet 10, and the commercial value of the optical sheet 10 can be improved.

[0060] Although the details of why the characteristic (A) can prevent the color from being observed on the optical sheet 10 are unclear, the following is presumed to be one factor, although the present embodiment is not bound by the following presumption.

[0061] As the content of hollow silica particles in the functional layer increases, the refractive index of the functional layer decreases. As the refractive index of the functional layer decreases, the anti-reflection function of the functional layer is strengthened. Therefore, the content of hollow silica particles in the functional layer expected to have the anti-reflection function is usually high.

[0062] In a functional layer containing a large proportion of hollow silica particles, if the hollow silica particles are not uniformly dispersed, the in-plane variation in thickness of the functional layer may be large, as shown in Figure 2B. The central wavelength of light whose reflection is suppressed varies depending on the thickness of the functional layer. The central wavelength of light whose reflection is suppressed is the wavelength of light whose reflectance is the smallest.

[0063] In addition, if the hollow silica particles are not uniformly dispersed, the in-plane variation in the local refractive index of the functional layer may become large. The reflectance changes depending on the refractive index of the functional layer. This results in the reflection suppression function of the optical sheet 10 becoming locally insufficient.

[0064] As explained above, if the arrangement of hollow silica particles is non-uniform, the reflection characteristics of the optical sheet will be non-uniform within the plane. As a result, it is presumed that light in some wavelength ranges contained in ambient light, such as illumination light, is unintentionally reflected by the optical sheet, and the color may be observed due to the reflected light. The non-uniform arrangement of hollow silica particles may be more noticeable in functional layers overlaid on an anti-glare layer, especially in functional layers overlaid on an anti-glare layer including an uneven surface.

[0065] In an optical sheet 10 having characteristic (A), the hollow silica particles 47 can be uniformly dispersed in the functional layer 40. In a functional layer 40 containing a large proportion of hollow silica particles 47, the hollow silica particles 47 can be regularly arranged. As shown in FIGS. 2A and 3A , the hollow silica particles 47 can be uniformly dispersed along the sheet surface of the optical sheet 10. In addition, multiple layers containing uniformly dispersed hollow silica particles 47 can be stacked in the first direction D1. For example, the functional layer 40 may include two, three, or four layers of uniformly dispersed hollow silica particles 47. In other words, by satisfying characteristic (A), the in-plane variation in the thickness of the functional layer 40 is reduced. By satisfying characteristic (A), the in-plane variation in the content ratio of hollow silica particles 47 in the functional layer 40 is reduced. As a result, the optical sheet 10 having the characteristic (A) can effectively prevent color from being observed while ensuring excellent anti-reflection function and excellent anti-glare function.

[0066] By setting the lower limit of the appropriate configuration parameter, L ＊ a ＊ b ＊ b in the color system ＊ In other words, by setting the lower limit of the appropriate configuration parameter, it is possible to prevent the optical sheet 10 from being observed in blue.

[0067] As shown in Figures 2B and 3B, when the hollow silica particles 47 are unevenly dispersed, the appropriate coordination parameter becomes small. If the appropriate coordination parameter is small, the thickness of the functional layer 40 may become uneven. Furthermore, in areas where the functional layer 40 is thick, the content ratio of the hollow silica particles 47 becomes large, which may result in a small refractive index. In areas where the functional layer 40 is thin, the content ratio of the hollow silica particles 47 becomes small, which may result in a large refractive index. Therefore, it is inferred that the reflection suppression function for short-wavelength light such as blue light will be reduced. It can be thought that setting a lower limit for the appropriate coordination parameter can prevent the optical sheet 10 from being observed in blue.

[0068] From the above viewpoint, the appropriate configuration parameter may be 1.0 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, or 1.5 or more.

[0069] By setting the upper limit of the appropriate coordination parameter, L ＊ a ＊ b ＊ a in the color system ＊ In other words, by setting an upper limit for the appropriate configuration parameter, it is possible to prevent the optical sheet 10 from being observed in red.

[0070] As shown in Figure 3C, when the hollow silica particles 47 are arranged closely and uniformly, the appropriate coordination parameter becomes large. When the appropriate coordination parameter is large, the thickness of the functional layer 40 can be constant. Furthermore, the content ratio of the hollow silica particles 47 in the functional layer 40 can be high. In the example shown in Figure 3C, it is presumed that the reflectance of green light, which is in the central wavelength range of visible light, decreases in a concentrated manner. It can be thought that setting an upper limit on the appropriate coordination parameter can prevent the optical sheet 10 from being observed in red, which is the complementary color of green.

[0071] From the above viewpoint, the upper limit of the appropriate coordination parameter may be 2.0 or less, 1.8 or less, 1.6 or less, 1.5 or less, or 1.4 or less.

[0072] The proper coordination parameter may be 1.0 or more and 2.0 or less, 1.1 or more and 2.0 or less, 1.2 or more and 2.0 or less, 1.3 or more and 2.0 or less, 1.4 or more and 2.0 or less, or 1.5 or more and 2.0 or less. The proper coordination parameter may be 1.0 or more and 1.8 or less, 1.1 or more and 1.8 or less, 1.2 or more and 1.8 or less, 1.3 or more and 1.8 or less, 1.4 or more and 1.8 or less, or 1.5 or more and 1.8 or less. The proper coordination parameter may be 1.0 or more and 1.6 or less, 1.1 or more and 1.6 or less, 1.2 or more and 1.6 or less, 1.3 or more and 1.6 or less, 1.4 or more and 1.6 or less, or 1.5 or more and 1.6 or less. The proper coordination parameter may be 1.0 or more and 1.5 or less, 1.1 or more and 1.5 or less, 1.2 or more and 1.5 or less, 1.3 or more and 1.5 or less, or 1.4 or more and 1.5 or less. The proper coordination parameter may be 1.0 or more and 1.4 or less, 1.1 or more and 1.4 or less, 1.2 or more and 1.4 or less, or 1.3 or more and 1.4 or less.

[0073] <<Feature B: Standard Deviation of Proper Coordination Parameters>> The optical sheet 10 may further have feature (B) in addition to the above-described feature (A): (B): The standard deviation of the proper coordination parameters is 0.30 or less.

[0074] As will be described later, the appropriate configuration parameters are determined as the average values ​​of the 14 average appropriate configuration parameters. The values ​​of the 14 average appropriate configuration parameters are obtained by excluding the maximum and minimum values ​​from the values ​​of the 16 average appropriate configuration parameters measured based on the 16 images, respectively. The standard deviation of the appropriate configuration parameters is the standard deviation of the values ​​of the 14 average appropriate configuration parameters used to calculate the appropriate configuration parameters.

[0075] As described above, feature (A) can stably prevent the observation of color tints in the optical sheet 10 including both the antiglare layer and the functional layer. In addition to feature (A), setting an upper limit on the standard deviation of the appropriate coordination parameters can reduce color unevenness in the optical sheet. By reducing the standard deviation of the appropriate coordination parameters, color unevenness within the plane of the optical sheet can be made less noticeable.

[0076] The standard deviation of the proper configuration parameters may be 0.30 or less, 0.25 or less, 0.20 or less, 0.19 or less, 0.18 or less, 0.16 or less, or 0.14 or less.

[0077] The standard deviation of the appropriate configuration parameters may be equal to or greater than 0.

[0078] The standard deviation of the proper coordination parameters may be 0 to 0.30, 0 to 0.25, 0 to 0.20, 0 to 0.19, 0 to 0.18, 0 to 0.16, or 0 to 0.14. The standard deviation of the proper coordination parameters may be 0 to 0.30, 0 to 0.25, 0 to 0.20, 0 to 0.19, 0 to 0.18, 0 to 0.16, or 0 to 0.14.

[0079] In combination with feature (A), by setting an upper limit on the standard deviation of the proper configuration parameters, L ＊ a ＊ b ＊ a in the color system ＊ In other words, by setting an upper limit to the standard deviation of the appropriate configuration parameters, it is possible to more effectively prevent the optical sheet 10 from being observed as red.

[0080] The proper coordination parameter and the standard deviation of the proper coordination parameter can be adjusted by the solid content of the functional layer-forming coating liquid for forming the functional layer 40, the drying conditions of the coating film of the functional layer-forming coating liquid, the content of hollow silica particles 47 in the functional layer 40, the average thickness of the functional layer 40, the average particle diameter of the hollow silica particles 47, etc. For example, if the content of hollow silica particles 47 in the functional layer 40 is increased, the proper coordination parameter tends to increase. If the content of hollow silica particles 47 in the functional layer 40 is decreased, the proper coordination parameter tends to decrease. If the average thickness of the functional layer 40 is increased, the proper coordination parameter tends to decrease. If the average thickness of the functional layer 40 is decreased, the proper coordination parameter tends to increase. If the average thickness of the functional layer 40 is decreased, the proper coordination parameter tends to increase. If the average particle diameter of the hollow silica particles 47 is decreased, the proper coordination parameter tends to increase.

[0081] The standard deviation of the appropriate coordination parameter can be adjusted by adjusting one or more of the average thickness of the functional layer 40, the content ratio of the hollow silica particles 47 in the functional layer 40, and the average particle diameter of the hollow silica particles 47. By incorporating an appropriate total volume of hollow silica particles 47 into an appropriate volume of the functional layer 40, the standard deviation of the appropriate coordination parameter can be reduced.

[0082] L for the optical sheet 10 ＊ a ＊ b ＊ a in the color system ＊ value and b ＊ The value is a value measured by reflected light with the first surface 11 as the incident surface. A black plate is attached to the surface of the sample formed by the second surface of the optical sheet using an optically transparent adhesive. The black plate is "Comoglass K, color number: 502K (thickness 2 mm)" manufactured by Kuraray. Light is irradiated at an incident angle of 8° onto the surface of the evaluation sample formed by the first surface 11 of the optical sheet 10. Using a 2-degree visual field, the L ＊ a ＊ b ＊ a in the color system ＊ value and b ＊ Find the value. ＊ value and b ＊The values ​​are measured using a D65 light source. ＊ 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 first surface 11 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.

[0083] a ＊ The value is the arithmetic mean of five measurements. ＊ The five measurement values ​​are measured at five measurement positions on the measurement sample, the five measurement positions being 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.

[0084] <Method for Measuring the Proper Coordination Parameter, Proper Coordination Number, Mismatch Number, and Standard Deviation of the Proper Coordination Parameter> The proper coordination parameter is obtained by subtracting the mismatch number from the proper coordination number. The proper coordination number and the mismatch number are measured by the following procedure. The procedure for measuring the proper coordination number and the mismatch number includes the steps of acquiring an observation image of the first surface 11, identifying the center of gravity of the hollow silica particles 47 from the observation image, and measuring the proper coordination number and the mismatch number from the center of gravity of each hollow silica particle 47.

[0085] (Step of Obtaining an Observation Image of the First Surface) A sample measuring 5 mm x 5 mm is cut out from the optical sheet 10 to be evaluated. Conductive double-sided tape is attached to the entire surface of the sample, which corresponds to the second surface 12 of the optical sheet 10. Furthermore, the conductive double-sided tape attached to the sample is attached to a planar sample stage. In this way, the sample is fixed to the planar sample stage using the conductive double-sided tape. The planar sample stage is an accessory of a scanning electron microscope (SEM) used to observe the sample. The conductive double-sided tape is not particularly limited. The conductive double-sided tape may be SEM carbon tape with an aluminum substrate manufactured by Nissin EM Co., Ltd.

[0086] Carbon paste is applied to the four corners of a sample fixed to a flat sample stage. The carbon paste is not particularly limited. Colloidal graphite No. 7141 (solvent: isopropanol) manufactured by Nissin EM Co., Ltd. may be used as the carbon paste.

[0087] Next, a PtPd vapor deposition film is formed on the sample using an ion sputtering device. The ion sputtering conditions are as follows: Ar gas is introduced into the chamber containing the sample; Target: PtPd; Vacuum level: 8 Pa; Discharge current value: 15 mA; Vapor deposition time: 15 seconds.

[0088] After forming the vapor-deposited film, the standard sample stage on which the sample is fixed is attached to the standard sample holder of a scanning electron microscope. The observation conditions for the scanning electron microscope are as follows, and an observation image of the surface of the sample corresponding to the first surface 11 of the optical sheet 10 to be evaluated is obtained. The scanning electron microscope used is an ultra-high resolution field emission scanning electron microscope SU-9000 from Hitachi High-Technologies Corporation. FIG. 4A shows an enlarged example of the observation image. Measurement mode: SE Acceleration voltage: 1.0 kV Emission current: 10 μA WD (working distance): 3 mm or more and 3.5 mm or less Lens mode: High Observation magnification: 10,000x Data size: 1,280 pixels x 960 pixels Pixel size: 3.96875 nm

[0089] Using the above procedure, 16 observation images are acquired. The 16 observation images are images of 16 rectangular divided areas obtained by dividing the rectangular measurement area of ​​the sample into four equal parts vertically and horizontally.

[0090] (Step of identifying the center of gravity of the hollow silica particle 47 from the observed image) From each of the observed images acquired above, only unnecessary parts such as the scale bar, which are not the image of the sample, are removed. By removing the unnecessary parts, image data for image processing is obtained. One image data is obtained from one observed image, so a total of 16 image data are obtained.

[0091] Next, the image data is binarized. Through the binarization process, light areas of the image data become white areas, and dark areas of the image data become black areas. An image is obtained in which circular white areas are dispersed within a background of black areas. The white areas appear at positions where hollow silica particles 47 are present. One piece of binarized image data is obtained from one piece of image data, so a total of 16 pieces of binarized image data are obtained.

[0092] ImageJ and Fiji were used as image processing software for the binarization process. ImageJ version 1.52e was used. ImageJ is open-source, public domain image processing software developed at the National Institutes of Health. Fiji is a plug-in package for ImageJ. The following Fiji commands were used for the binarization process. Under the following conditions, a white area was generated for each hollow silica particle 47 observed independently in the microscope image. Figure 4B shows the image obtained by binarizing the image in Figure 4A. In the "AutoLocal Threshold" command below, "Metod=Median" indicates that the median value of the local grayscale distribution is selected as the threshold value. "Radius=60" indicates that the radius of the local domain in which the threshold is calculated is 60 pixels. "Parameter1=-25" is a parameter for adjusting the threshold value, and indicates that the threshold value is determined by subtracting "-25" from the selected threshold value.・Enlarged vertically and horizontally by 2.5 times ・Noise removal: Despeckle ・Binarization processing: AutoLocal Threshold (Metod=Median, Radius=60, Parameter1=-25) ・White area separation: Watershed ・Noise removal: Open

[0093] The coordinates of the center of gravity of each white area representing the hollow silica particle 47 are identified by processing the binarized image data. A binary image is generated in which one pixel located at the center of gravity of each white area is white and the rest are black background. One binary image is obtained from one binarized image data, resulting in a total of 16 binary images. Information on the coordinates of the center of gravity of the hollow silica particle 47 is also obtained. The binary images are generated using Fiji's Analyze Particles function. Figure 4C is a binary image generated based on the image in Figure 4B.

[0094] (Step of measuring the proper coordination number and miscoordination number from the center of gravity of each hollow silica particle 47) Each hollow silica particle 47 included in the binary image is treated as one hollow silica particle 47A, and the proper coordination number and miscoordination number are measured. The proper coordination number and miscoordination number are measured for all hollow silica particles 47 included in the binary image. The proper coordination parameter is calculated from the measurement results of the proper coordination number and miscoordination number for all hollow silica particles 47 included in the binary image.

[0095] Specifically, for each particle identified in the binary image, the distances between the coordinates of the center of gravity of the particle and the coordinates of the centers of gravity of other particles located in the vicinity of the particle are listed, and then the number of particles in the list is counted to obtain the values ​​of the proper coordination number, improper coordination number, and proper coordination parameter for the particle.

[0096] The arithmetic mean value of the proper coordination parameters measured for each hollow silica particle 47 included in the binary image as one hollow silica particle 47A is set to the value of the average proper coordination parameter for the binary image. The maximum and minimum values ​​are removed from the 16 average proper coordination parameter values ​​calculated for each of the 16 binary images to obtain 14 average proper coordination parameter values. The arithmetic mean value of the 14 average proper coordination parameter values ​​is set to the proper coordination parameter of the optical sheet 10. The optical sheet 10 is evaluated based on whether the calculated proper coordination parameters of the optical sheet 10 satisfy the conditions specified in feature (A).

[0097] The standard deviation of the 14 average appropriate configuration parameter values ​​used to calculate the appropriate configuration parameters is set as the standard deviation of the appropriate configuration parameters of the optical sheet 10. The optical sheet 10 is evaluated based on whether the calculated standard deviation of the appropriate configuration parameters of the optical sheet 10 satisfies the condition defined in feature (B).

[0098] By aggregating data on the distances between the centers of gravity of all particles contained in a binary image, a radial distribution function can be created. The present inventors investigated the radial distribution functions related to the distances between the centers of gravity of hollow silica particles contained in the functional layers of various optical sheets and observed the arrangement of hollow silica particles within the functional layers. In the functional layers of optical sheets where the peak of the radial distribution function was 55 nm or more and less than 75 nm, hollow silica particles tended to be arranged regularly.

[0099] Whether or not the characteristic (A) is satisfied is determined based on an observation image acquired from any one of the measurement regions in the sample of the optical sheet 10. If the proper configuration parameters measured using the observation image acquired from any one of the measurement regions of the optical sheet 10 satisfy the characteristic (A), it is possible to sufficiently suppress the observation of a color tint on the optical sheet 10.

[0100] As described above, the antiglare layer 30 may include an uneven surface 31X. The thin functional layer 40 formed on the uneven surface 31X of the antiglare layer 30 may have different thicknesses depending on the reference portion 31A and the convex portion 31B of the uneven surface 31X of the antiglare layer 30. That is, the thickness of the functional layer on the reference portion 31A may be different from the thickness of the functional layer on the convex portion 31B. The thickness of the functional layer on the reference portion 31A may be thicker than the thickness of the functional layer on the convex portion 31B. Accordingly, the arrangement of the hollow silica particles 47 may also differ between the functional layer 40 located on the reference portion 31A and the functional layer 40 located on the convex portion 31B. However, by managing the optical sheet 10 with appropriate coordination parameters, the occurrence of coloring in the optical sheet 10 can be suppressed. In other words, by managing the optical sheet 10 with appropriate coordination parameters, an optical sheet 10 including an antiglare layer 30 and a functional layer 40 with suppressed coloring can be obtained.

[0101] The proper coordination parameter may be a value measured in a region of the first surface 11 facing the reference portion 31A in the first direction D1. The proper coordination parameter measured in the region of the first surface 11 facing the reference portion 31A in the first direction D1 means a proper coordination parameter measured using 16 observation images acquired from a measurement region including only the reference portion 31A or a measurement region centered on the reference portion 31A. When the proper coordination parameter measured based on the hollow silica particles 47 observed in the region of the first surface 11 facing the reference portion 31A in the first direction D1 satisfies feature (A), it is possible to stably suppress the observation of a color tint on the optical sheet 10.

[0102] The proper coordination parameter may be a value measured in a region of the first surface 11 facing in the first direction D1 to a region of the antiglare layer 30 where no particles 37 are present. The proper coordination parameter measured in a region of the first surface 11 facing the region of the antiglare layer 30 where no particles 37 are present means a proper coordination parameter measured using 16 observation images acquired from a measurement region including only the region where no particles 37 are present or a measurement region centered on the region where no particles 37 are present. When the proper coordination parameter measured based on the hollow silica particles 47 observed in the region of the first surface 11 facing the region of the antiglare layer 30 where no particles 37 are present satisfies feature (A), it is possible to stably suppress the observation of a color tint on the optical sheet 10.

[0103] <<L ＊ a ＊ b ＊ Color system a ＊ value and b ＊ Value >> L for optical sheet 10 ＊ a ＊ b ＊ a in the color system ＊ value and b ＊ The value may be within a predetermined range. ＊ The value may be between -4.0 and 4.0. ＊ The value may be between -4.0 and 4.0. ＊ value and b ＊ By setting the value within a predetermined range, it is possible to effectively prevent the optical sheet 10 from being perceived as having a color tint. ＊ a ＊ b＊ a in the color system ＊ value and b ＊ The values ​​are measured by the above-described method using reflected light with the first surface 11 as the incident surface.

[0104] L ＊ a ＊ b ＊ a in the color system ＊ By setting a lower limit to the value, it is possible to prevent the optical sheet 10 from being observed as green. ＊ a ＊ b ＊ a in the color system ＊ The value may be −4.0 or greater, −3.0 or greater, −2.0 or greater, −1.0 or greater, or 0 or greater.

[0105] L ＊ a ＊ b ＊ a in the color system ＊ By setting an upper limit to the value, it is possible to prevent the optical sheet 10 from being observed in red. ＊ a ＊ b ＊ a in the color system ＊ The value may be 4.0 or less, 3.6 or less, 3.5 or less, 3.0 or less, or 2.9 or less.

[0106] L ＊ a ＊ b ＊ a in the color system ＊ The value may be -4.0 or more and 4.0 or less, -3.0 or more and 4.0 or less, -2.0 or more and 4.0 or less, -1.0 or more and 4.0 or less, or 0 or more and 4.0 or less. L ＊ a ＊ b ＊ a in the color system ＊ The value may be -4.0 or more and 3.6 or less, -3.0 or more and 3.6 or less, -2.0 or more and 3.6 or less, -1.0 or more and 3.6 or less, or 0 or more and 3.6 or less. ＊ a ＊ b ＊ a in the color system ＊The value may be -4.0 or more and 3.5 or less, -3.0 or more and 3.5 or less, -2.0 or more and 3.5 or less, -1.0 or more and 3.5 or less, or 0 or more and 3.5 or less. ＊ a ＊ b ＊ a in the color system ＊ The value may be -4.0 or more and 3.0 or less, -3.0 or more and 3.0 or less, -2.0 or more and 3.0 or less, -1.0 or more and 3.0 or less, or 0 or more and 3.0 or less. L ＊ a ＊ b ＊ a in the color system ＊ The value may be -4.0 or more and 2.9 or less, -3.0 or more and 2.9 or less, -2.0 or more and 2.9 or less, -1.0 or more and 2.9 or less, or 0 or more and 2.9 or less.

[0107] L ＊ a ＊ b ＊ b in the color system ＊ By setting a lower limit to the value, it is possible to prevent the optical sheet 10 from being observed in blue. ＊ a ＊ b ＊ b in the color system ＊ The value may be -4.0 or greater, -3.0 or greater, -2.5 or greater, -2.0 or greater, or -1.7 or greater.

[0108] L ＊ a ＊ b ＊ b in the color system ＊ By setting an upper limit to the value, it is possible to prevent the optical sheet 10 from being observed as yellow. ＊ a ＊ b ＊ b in the color system ＊ The value may be 4.0 or less, 3.0 or less, 2.0 or less, 1.0 or less, or 0 or less.

[0109] L ＊ a ＊ b ＊ b in the color system ＊The value may be -4.0 or more and 4.0 or less, -3.0 or more and 4.0 or less, -2.5 or more and 4.0 or less, -2.0 or more and 4.0 or less, or -1.7 or more and 4.0 or less. ＊ a ＊ b ＊ b in the color system ＊ The value may be -4.0 or more and 3.0 or less, -3.0 or more and 3.0 or less, -2.5 or more and 3.0 or less, -2.0 or more and 3.0 or less, or -1.7 or more and 3.0 or less. ＊ a ＊ b ＊ b in the color system ＊ The value may be -4.0 or more and 2.0 or less, -3.0 or more and 2.0 or less, -2.5 or more and 2.0 or less, -2.0 or more and 2.0 or less, or -1.7 or more and 2.0 or less. ＊ a ＊ b ＊ b in the color system ＊ The value may be -4.0 or more and 1.0 or less, -3.0 or more and 1.0 or less, -2.5 or more and 1.0 or less, -2.0 or more and 1.0 or less, or -1.7 or more and 1.0 or less. ＊ a ＊ b ＊ b in the color system ＊ The value may be -4.0 or more and 0 or less, -3.0 or more and 0 or less, -2.5 or more and 0 or less, -2.0 or more and 0 or less, or -1.7 or more and 0 or less.

[0110] L ＊ a ＊ b ＊ a in the color system ＊ value and b ＊ Setting the value within the above-mentioned predetermined range can effectively prevent a color from being observed on the optical sheet 10. When observing the back of the optical sheet 10, it is possible to prevent a change in the hue of an image behind the optical sheet 10 due to a color occurring on the optical sheet 10. For example, when the optical sheet 10 is positioned on the image forming surface of a display element, it is possible to prevent a change in the hue of an image formed by the display element.

[0111] L ＊ a ＊ b＊ a in the color system ＊ value and b ＊ By setting the value within the above-mentioned range, even when the back of the optical sheet 10 including the antiglare layer and the functional layer is dark, it is possible to effectively prevent a color from being observed on the optical sheet 10. Therefore, a sense of luxury is imparted to the optical sheet 10, and the commercial value of the optical sheet 10 can be improved.

[0112] <<Total Light Transmittance>> 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 does not have a particular upper limit. The total light transmittance of the optical sheet 10 may be 100% or less, or may be less than 100%.

[0113] 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 10 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%.

[0114] 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 measurement 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 12 of the optical sheet 10. 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 measurement 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.

[0115] The total light transmittance is the arithmetic mean value of five measurements taken at five measurement positions on the measurement sample, the five measurement positions being spaced at least 10 mm apart from each other.

[0116] <<Luminous Reflectance>> The luminous reflectance of the optical sheet 10 may be 2.0% or less, 1.5% or less, 1.4% or less, or 1.2% or less. The luminous reflectance of the optical sheet 10 has no particular lower limit. The luminous reflectance of the optical sheet 10 may be 0% or more, or may be greater than 0%.

[0117] The luminous reflectance of the optical sheet 10 may be 0% or more and 2.0% or less, 0% or more and 1.5% or less, 0% or more and 1.4% or less, or 0% or more and 1.2% or less. The luminous reflectance of the optical sheet 10 may be greater than 0% and 2.0% or less, greater than 0% and 1.5% or less, greater than 0% and 1.4% or less, or greater than 0% and 1.2% or less.

[0118] Luminous reflectance is the Y value of the tristimulus values ​​XYZ in the CIE 1931 standard color system. Luminous reflectance is an SCI reflectance that includes specular reflection. Luminous reflectance (%) is measured using a spectrophotometer as follows.

[0119] A sample is cut out from the optical sheet 10 to be evaluated. The sample is visually checked for any abnormalities such as dust or scratches. A black plate is attached to the surface of the sample, which is the second surface of the optical sheet, using an optically transparent adhesive. The total light transmittance of the black plate is set to 1% or less. In this way, evaluation sample A is prepared, which includes the optical sheet, the optically transparent adhesive layer, and the black plate.

[0120] Light is irradiated onto the surface of evaluation sample A, which is formed by the first surface of the optical sheet, at an incident angle of 8°. The luminous reflectance of the evaluation sample A is measured based on the total reflected light from evaluation sample A. Using a 2-degree visual field, the luminous reflectance (%) is calculated based on the reflectance measured at 10 nm intervals in the range of 400 nm to 700 nm. A D65 light source is used to measure the luminous reflectance (%). Before measuring the luminous reflectance of the optical sheet 10, the light source of the measuring device is turned on for 15 minutes to stabilize the light source output. The test environment for measuring the luminous reflectance 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.

[0121] Other measurement conditions for measuring the luminous reflectance are in accordance with JIS Z 8722: 2009. The geometric condition in JIS Z 8722: 2009 is condition c, which includes a specular reflection component.

[0122] The luminous reflectance is the arithmetic mean value of five measurements taken at five measurement positions on the measurement sample, the five measurement positions being at least 10 mm apart from each other.

[0123] <<Luminous reflectance and color coordinate a ＊ The product of the values, luminous reflectance and color coordinate b ＊ Product of values>> From the viewpoint of more effectively suppressing the occurrence of color tint, the optical sheet 10 may satisfy the following characteristic (x) and characteristic (y).

[0124] Feature (x): The luminous reflectance at the first surface 11 and the L measured by the reflected light at the first surface 11 ＊ a ＊ b ＊ Color system a ＊ The absolute value of the product of the luminous reflectance at the first surface 11 and the L measured by the reflected light at the first surface 11 is 4.0 or less. ＊ a ＊ b ＊ Color system b ＊ The absolute value of the product of the values ​​is 4.0 or less.

[0125] The luminous reflectance used to calculate the absolute values ​​defined by the feature (x) and the feature (y) is a numerical value in the unit of "%".

[0126] a ＊ Even if the absolute value of the value can be reduced, if the luminous reflectance is large, a tint may be observed on the optical sheet 10. ＊ If the absolute value of the value is large, a tint may be observed in the optical sheet 10. ＊ a ＊ b ＊ Color system a ＊By setting an upper limit to the absolute value of the product of the value and the color, it is possible to more effectively prevent a color from being observed in the optical sheet 10. According to the feature (x), it is possible to more effectively prevent the optical sheet 10 from being observed as red or green, in particular.

[0127] Luminous reflectance and L ＊ a ＊ b ＊ Color system a ＊ The absolute value of the product of the luminous reflectance and the L value may be 4.0 or less, 3.7 or less, 3.5 or less, or 3.4 or less. ＊ a ＊ b ＊ Color system a ＊ The lower limit of the absolute value of the product of the luminous reflectance and the L ＊ a ＊ b ＊ Color system a ＊ The absolute value of the product with the value may be equal to or greater than 0.

[0128] Luminous reflectance and L ＊ a ＊ b ＊ Color system a ＊ The absolute value of the product of the luminous reflectance and the L value may be 0 or more and 4.0 or less, 0 or more and 3.7 or less, 0 or more and 3.5 or less, or 0 or more and 3.4 or less. ＊ a ＊ b ＊ Color system a ＊ The absolute value of the product with the value may be greater than 0 and less than or equal to 4.0, greater than 0 and less than or equal to 3.7, greater than 0 and less than or equal to 3.5, or greater than 0 and less than or equal to 3.4.

[0129] b ＊ Even if the absolute value of the value can be reduced, if the luminous reflectance is large, a tint may be observed on the optical sheet 10. ＊ If the absolute value of the value is large, a tint may be observed in the optical sheet 10. ＊ a ＊ b ＊ Color system a ＊By setting an upper limit to the absolute value of the product of the value and the color, it is possible to more effectively prevent a color from being observed in the optical sheet 10. According to the feature (y), it is possible to more effectively prevent the optical sheet 10 from being observed to be blue or yellow.

[0130] Luminous reflectance and L ＊ a ＊ b ＊ Color system b ＊ The absolute value of the product of the luminous reflectance and the L value may be 4.0 or less, 3.0 or less, 2.8 or less, 2.5 or less, 2.0 or less, or 1.7 or less. ＊ a ＊ b ＊ Color system b ＊ The lower limit of the absolute value of the product of the luminous reflectance and the L ＊ a ＊ b ＊ Color system b ＊ The absolute value of the product with the value may be equal to or greater than 0.

[0131] Luminous reflectance and L ＊ a ＊ b ＊ Color system b ＊ The absolute value of the product of the luminous reflectance and the L value may be 0 to 4.0, 0 to 3.0, 0 to 2.8, 0 to 2.5, 0 to 2.0, or 0 to 1.7. ＊ a ＊ b ＊ Color system b ＊ The absolute value of the product with the value may be greater than 0 and less than or equal to 4.0, greater than 0 and less than or equal to 3.0, greater than 0 and less than or equal to 2.8, greater than 0 and less than or equal to 2.5, greater than 0 and less than or equal to 2.0, or greater than 0 and less than or equal to 1.7.

[0132] <<Layers Included in Optical Sheet>> Each layer included in the optical sheet 10 will be described in further detail with reference to the illustrated optical sheet 10. The optical sheet 10 shown in Fig. 1 includes, in this order from the second surface 12 to the first surface 11 in the first direction D1, a substrate 20, an antiglare layer 30, and a functional layer 40.

[0133] The optical sheet 10 may further include other layers. In the example shown in FIG. 5 , the optical sheet 10 includes a substrate 20, an antiglare layer 30, a second functional layer 50, and a functional layer 40, in this order from the second surface 12 to the first surface 11. The second functional layer 50 may include a binder component and particles. The particles may be high-refractive-index particles. The refractive index of the particles may be higher than the refractive index of the binder component. In the example shown in FIG. 5 , the functional layer 40 may be configured as a layer with a lower refractive index than the second functional layer 50. The second functional layer 50 may be configured as a layer with a higher refractive index than the antiglare layer 30. The functional layer 40 and the second functional layer 50 exhibit a reflection-suppressing function. The functional layer 40 and the second functional layer 50 may form a low-reflection layer or a reflection-suppressing layer having a reflection-suppressing function.

[0134] 1 and 5, the first surface 11 is formed by the functional layer 40. The functional layer 40 and the second functional layer 50 are thin layers that extend along the uneven surface 31X of the antiglare layer 30. In the example shown in Figures 1 and 5, the first surface 11 is an uneven surface 11X having unevenness corresponding to the uneven surface 31X of the antiglare layer 30. In the example shown in Figures 1 and 5, the second surface 12 is formed by the substrate 20.

[0135] Each layer included in the optical sheet 10 may further have a function as another functional layer. The optical sheet 10 may further include another functional layer different from the example shown in the drawings. Examples of the other functional layer include an antifouling layer, a hard coat layer, and an antistatic layer.

[0136] In the illustrated example, the first direction D1 is the stacking direction. The layers 20, 30, 40, and 50 included in the optical sheet 10 are stacked in the first direction D1. Each of the layers 20, 30, 40, and 50 has a normal direction parallel to the first direction D1. Each of the layers 20, 30, 40, and 50 extends in a second direction D2 and a third direction D3 that are perpendicular to the first direction D1. In the illustrated example, the second direction D2 and the third direction D3 are perpendicular to each other.

[0137] The substrate 20, the antiglare layer 30, the functional layer 40, and the second functional layer 50 will be described below.

[0138] <Substrate> The substrate 20 supports the antiglare layer 30 and the functional layer 40. As shown in Figures 1 and 5 , the substrate 20 may constitute the second surface 12 of the optical sheet 10. The second surface 12 may be a flat surface. The second surface 12 may be a surface perpendicular to the first direction D1.

[0139] The substrate 20 may be transparent. Transparent means that the total light transmittance is 50% or more, and may be 70% or more, 80% or more, or 90% or more.

[0140] The material of the substrate 20 is not particularly limited, and may be resin or glass. Resin is preferable because it is lightweight and easy to manufacture.

[0141] The resin used for the substrate 20 may be a polyolefin resin such as polyethylene or polypropylene. The resin used for the substrate 20 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 20 may be a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate. The resin used for the substrate 20 may be an acrylic resin such as polymethyl(meth)acrylate or polyethyl(meth)acrylate. The resin used for the substrate 20 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 20 include resins such as polycarbonate, polyimide resins, and cycloolefin resins derived from cycloolefins such as norbornene and dicyclopentadiene. The antiglare layer 30 may contain only one of the above-mentioned resins, or two or more of the above-mentioned resins.

[0142] A substrate containing a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate may be stretched. The stretching may be uniaxial stretching. The stretching may be biaxial stretching. The stretched substrate containing a polyester-based resin has birefringence. The retardation Re of the stretched substrate containing a polyester-based resin may be adjusted.

[0143] The thickness of the resin substrate 20 is not particularly limited. From the viewpoint of ease of handling, the thickness of the resin substrate 20 may be 10 μm or more, 20 μm or more, or 50 μm or more. The thickness of the resin substrate 20 may be 500 μm or less, 400 μm or less, or 300 μm or less. The thickness of the glass substrate 20 may be 500 μm or more. The thickness of the glass substrate 20 may be 5 mm or less.

[0144] When the optical sheet 10 is used for foldable applications, the substrate 20 may be flexible. In this example, the thickness of the resin substrate 20 may be 10 μm or more and 40 μm or less. When the optical sheet 10 is used laminated with glass, the thickness of the resin substrate 20 may be 40 μm or more and 100 μm or less from the viewpoint of preventing the glass from shattering.

[0145] The substrate 20 may include only a single layer or multiple layers. The substrate 20 may include a primer layer such as an easy-adhesion layer.

[0146] <Functional Layer> The functional layer 40 includes a binder component 46 and hollow silica particles 47. The functional layer 40 may further include particles other than the hollow silica particles 47. The functional layer 40 has a reduced refractive index due to the inclusion of the hollow silica particles 47. The functional layer 40 may have a refractive index lower than that of the binder component 46. The refractive index of the functional layer 40 may be lower than that of the antiglare layer 30. The refractive index of the functional layer 40 may be lower than that of a layer adjacent to the functional layer 40.

[0147] The functional layer 40 has a reflection suppression function that suppresses reflection of incident light due to its refractive index and thickness. The reflection suppression function of the functional layer 40 is based on the interference of light reflected on both surfaces of the functional layer 40. To make this reflection suppression function effective, the refractive index of the functional layer 40 may be between the refractive indices of the two regions adjacent to the functional layer 40 on both sides. In the illustrated example, the refractive index of the functional layer 40 may be greater than the refractive index of air and less than the refractive index of the anti-glare layer 30. The thickness (nm) of the functional layer 40 may be approximately 1 / 4 of the wavelength λ (nm) of the light whose reflection is to be suppressed.

[0148] From the viewpoint of the anti-reflection function, the refractive index and average thickness of the functional layer can be set as follows: The refractive index of the functional layer may be 1.10 or more, 1.20 or more, 1.26 or more, 1.28 or more, or 1.30 or more. The refractive index of the functional layer may be 1.48 or less, 1.45 or less, 1.40 or less, 1.38 or less, or 1.35 or less. The refractive index used for the components that make up the optical sheet 10 is the refractive index for a wavelength of 589.3 nm.

[0149] The thickness of the functional layer may be 80 nm or more, 85 nm or more, or 90 nm or more. The thickness of the functional layer may be 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, or 105 nm or less.

[0150] The thickness of the functional layer may be 80 nm or more and 150 nm or less, 85 nm or more and 150 nm or less, or 90 nm or more and 150 nm or less. The thickness of the functional layer may be 80 nm or more and 140 nm or less, 85 nm or more and 140 nm or less, or 90 nm or more and 140 nm or less. The thickness of the functional layer may be 80 nm or more and 130 nm or less, 85 nm or more and 130 nm or less, or 90 nm or more and 130 nm or less. The thickness of the functional layer may be 80 nm or more and 120 nm or less, 85 nm or more and 120 nm or less, or 90 nm or more and 120 nm or less. The thickness of the functional layer may be 80 nm or more and 110 nm or less, 85 nm or more and 110 nm or less, or 90 nm or more and 110 nm or less. The thickness of the functional layer may be 80 nm or more and 105 nm or less, 85 nm or more and 105 nm or less, or 90 nm or more and 105 nm or less.

[0151] (Binder Component) The binder component 46 is an element that holds the hollow silica particles 47. The binder component 46 may function as a binding agent for forming a coating film. The binder component 46 may hold the particles contained in the functional layer 40, thereby allowing the functional layer 40 to maintain a film form. The binder component 46 may contain a resin. The resin contained in the binder component 46 may be a natural resin or a synthetic resin. The binder component 46 may encapsulate the particles contained in the functional layer 40. The binder component 46 may encapsulate the particles contained in the functional layer 40. The hollow silica particles 47 may completely surround each particle contained in the functional layer 40, or may partially expose at least some of the particles contained in the functional layer 40.

[0152] The binder component 46 may include a cured resin. The cured resin is a cured product of a curable resin composition. The curable resin composition may be a thermosetting resin composition. The curable resin composition may be an ionizing radiation curable resin composition. The binder component 46 may include at least one of a cured product of a thermosetting resin composition and a cured product of an ionizing radiation curable resin composition. The cured resin imparts high strength and high hardness to the functional layer 40, and can improve the scratch resistance of the first surface 11. The ionizing radiation curable resin composition is particularly useful from the viewpoint of improving scratch resistance.

[0153] The thermosetting resin composition contains a thermosetting resin. The thermosetting resin composition is cured by heating. Examples of the thermosetting resin include acrylic resin, urethane resin, phenolic resin, urea melamine resin, epoxy resin, unsaturated polyester resin, and silicone resin. The thermosetting resin composition may contain a curing agent.

[0154] The ionizing radiation curable resin composition contains an ionizing radiation 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 (meth)acryloyl groups, vinyl groups, and allyl groups, as well as epoxy groups and oxetanyl groups. 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 compound having a (meth)acryloyl group. The ionizing radiation curable compound may be a siloxane compound containing a siloxane bond.

[0155] A (meth)acrylate compound having four or more ethylenically unsaturated bond groups is referred to as a "polyfunctional (meth)acrylate compound." A (meth)acrylate compound having two to three ethylenically unsaturated bond groups is referred to as a "low-functional (meth)acrylate compound."

[0156] 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 40.

[0157] The weight average molecular weight of the monomer may be greater than 0 and less than 1,000, greater than 0 and not greater than 800, or greater than 0 and not greater than 600. The weight average molecular weight of the oligomer may be 1,500 or greater and not greater than 20,000, 2,000 or greater and not greater than 15,000, or 3,000 or greater and not greater than 12,000. The weight average molecular weight is an average molecular weight measured by GPC analysis and converted into standard polystyrene.

[0158] Ionizing radiation may be electromagnetic waves or charged particle beams. Ionizing radiation has an energy quantum capable of polymerizing or crosslinking molecules. Examples of ionizing radiation include ultraviolet (UV) rays, electron beams (EB), X-rays, gamma rays, alpha rays, and ion beams.

[0159] 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 40, 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.

[0160] 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.

[0161] 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.

[0162] 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. 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.

[0163] 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.

[0164] Examples of siloxane compounds include (poly)dimethylsiloxane, (poly)diethylsiloxane, (poly)diphenylsiloxane, (poly)methylphenylsiloxane, alkyl-modified (poly)dimethylsiloxane, azo group-containing (poly)dimethylsiloxane, dimethylsilicone, phenylmethylsilicone, alkyl-aralkyl-modified silicone, fluorosilicone, polyether-modified silicone, fatty acid ester-modified silicone, methylhydrogen silicone, silanol group-containing silicone, alkoxy group-containing silicone, phenol group-containing silicone, methacrylic-modified silicone, acrylic-modified silicone, amino-modified silicone, carboxylic acid-modified silicone, carbinol-modified silicone, epoxy-modified silicone, mercapto-modified silicone, fluorine-modified silicone, polyether-modified silicone, and the like.

[0165] The binder component 46 may contain one type of ionizing radiation curable compound alone, or may contain two or more types of ionizing radiation curable compounds.

[0166] When the ionizing radiation curable compound is an ultraviolet curable compound, the curable resin composition forming the binder component 46 may contain additives such as a photopolymerization initiator or a photopolymerization accelerator. Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyl dimethyl ketal, benzoyl benzoate, α-acyloxime ester, α-aminoalkylphenone, thioxanthones, and the like. The photopolymerization accelerator reduces polymerization inhibition by air during curing and increases the curing rate. Examples of the photopolymerization accelerator include one or more selected from p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, and the like.

[0167] (Hollow Silica Particles and Other Particles) The hollow silica particles 47 have an outer shell layer made of silica. In the hollow silica particles 47, the interior of the particle surrounded by the outer shell layer is hollow. Air may be contained inside the cavity. Due to the inclusion of an internal cavity, the hollow silica particles 47 have a refractive index lower than that of silica. The refractive index of the hollow silica particles 47 decreases as the volume of the internal cavity increases. The hollow silica particles 47 reduce the refractive index of the entire functional layer 40. By using hollow silica particles 47 with a large particle diameter and a high ratio of internal space, the refractive index of the functional layer 40 can be further reduced.

[0168] The average particle diameter of the hollow silica particles 47 may be 50 nm or more and 100 nm or less, 50 nm or more and 90 nm or less, or 50 nm or more and 80 nm or less. The average particle diameter of the hollow silica particles 47 may be 55 nm or more and 100 nm or less, 55 nm or more and 90 nm or less, or 55 nm or more and 80 nm or less. The average particle diameter of the hollow silica particles 47 may be 60 nm or more and 100 nm or less, 60 nm or more and 90 nm or less, or 60 nm or more and 80 nm or less. The average particle diameter of the hollow silica particles 47 may be 65 nm or more and 100 nm or less, 65 nm or more and 90 nm or less, or 65 nm or more and 80 nm or less. When the average particle diameter of the hollow silica particles 47 is adjusted in this manner, in combination with the above-mentioned feature (A), the observation of a color tint in the optical sheet 10 can be more effectively suppressed.

[0169] From the viewpoint of uniformly dispersing the hollow silica particles 47 in the functional layer 40, the average particle diameter (nm) of the hollow silica particles 47 may be smaller than the average thickness (nm) of the functional layer 40. An upper limit may be set on the ratio (%) of the average particle diameter (nm) of the hollow silica particles 47 to the average thickness (nm) of the functional layer 40. By setting an upper limit on the ratio (%) of the average particle diameter of the hollow silica particles 47 to the average thickness of the functional layer 40, the hollow silica particles 47 can be uniformly dispersed in the functional layer 40. The ratio (%) of the average particle diameter of the hollow silica particles 47 to the average thickness of the functional layer 40 may be 80% or less, 75% or less, 70% or less, 60% or less, or 50% or less.

[0170] There is no particular lower limit for the ratio (%) of the average particle diameter of the hollow silica particles 47 to the average thickness of the functional layer 40. The ratio (%) of the average particle diameter of the hollow silica particles 47 to the average thickness of the functional layer 40 may be 10% or more, 20% or more, or 30% or more.

[0171] The ratio (%) of the average particle diameter of the hollow silica particles 47 to the average thickness of the functional layer 40 may be within the following ranges. This ratio (%) may be 10% to 80% inclusive, 10% to 75% inclusive, 10% to 70% inclusive, 10% to 60% inclusive, or 10% to 50% inclusive. This ratio (%) may be 20% to 80% inclusive, 20% to 75% inclusive, 20% to 70% inclusive, 20% to 60% inclusive, or 20% to 50% inclusive. This ratio (%) may be 30% to 80% inclusive, 30% to 75% inclusive, 30% to 70% inclusive, 30% to 60% inclusive, or 30% to 50% inclusive. When the ratio of the average particle diameter of the hollow silica particles 47 to the average thickness of the functional layer 40 is adjusted in this manner, in combination with the above-mentioned feature (A), the observation of color in the optical sheet 10 can be more effectively suppressed.

[0172] The "average particle diameter" used for particles such as hollow silica particles 47 is a value determined by the following (1) to (3). Although particles may aggregate, the average particle diameter is the average primary particle diameter. (1) The cross section of an optical sheet containing particles is observed using a transmission electron microscope (TEM), and an observation image is obtained by imaging. (2) Ten particles are randomly selected from the observation image, and the particle diameters of each particle are measured. The particle diameter (nm) is defined as the maximum distance between two parallel lines when the particle is sandwiched between the two lines. In other words, the particle diameter is the maximum length of the particle in the observation image. The particle diameter is determined as the particle diameter (maximum length) of each particle. In other words, the particle diameter is defined as the primary particle diameter. (3) Steps (1) and (2) above are performed five times for the same optical sheet to be measured, and the particle diameters of a total of 50 particles are measured. The average of the 50 particle diameter measurements is defined as the average particle diameter (nm) of the particles.

[0173] The "average thickness" of the functional layer 40 is a value determined by the following steps (4) to (6): (4) A cross section of the optical sheet including the functional layer is imaged using a transmission electron microscope (TEM). (5) In the image, the thickness of the functional layer at the center position along the surface of the optical sheet and at positions 100 nm shifted from the center position on both sides along the surface of the optical sheet are measured. The thickness is defined as the length (nm) of the functional layer along the direction perpendicular to the surface of the optical sheet. (6) For the same optical sheet to be measured, steps (4) and (5) above are performed five times to measure the thickness of the functional layer at a total of 15 positions. The average of the 15 thickness measurements is defined as the average thickness (nm) of the functional layer.

[0174] As the content ratio of the hollow silica particles 47 increases, the refractive index of the functional layer 40 decreases, and the functional layer 40 can exhibit excellent anti-reflection function. From the viewpoint of strengthening the anti-reflection function of the functional layer 40, a lower limit may be set for the content ratio of the hollow silica particles 47. The content ratio of the hollow silica particles 47 may be 100 parts by mass or more, 150 parts by mass or more, or 175 parts by mass or more per 100 parts by mass of the binder component 46.

[0175] By setting an upper limit to the content ratio of hollow silica particles 47, hollow silica particles 47 can be stably held by binder component 46. From the viewpoint of suppressing the dropping off of hollow silica particles 47, an upper limit may be set to the content ratio of hollow silica particles 47. The content ratio of hollow silica particles 47 may be 400 parts by mass or less, 300 parts by mass or less, or 250 parts by mass or less per 100 parts by mass of binder component.

[0176] The content of the hollow silica particles 47 may be 100 parts by mass or more and 400 parts by mass or less, 150 parts by mass or more and 400 parts by mass or less, or 175 parts by mass or more and 400 parts by mass or less, relative to 100 parts by mass of the binder component. The content of the hollow silica particles 47 may be 100 parts by mass or more and 300 parts by mass or less, 150 parts by mass or more and 300 parts by mass or less, or 175 parts by mass or more and 300 parts by mass or less, relative to 100 parts by mass of the binder component. The content of the hollow silica particles 47 may be 100 parts by mass or more and 250 parts by mass or less, 150 parts by mass or more and 250 parts by mass or less, or 175 parts by mass or more and 250 parts by mass or less, relative to 100 parts by mass of the binder component. When the content of the hollow silica particles 47 is adjusted in this manner, in combination with the above-mentioned feature (A), the observation of a color tint in the optical sheet 10 can be more effectively suppressed.

[0177] The hollow silica particles 47 may be uniformly dispersed in the functional layer 40. By uniformly dispersing the hollow silica particles 47 in the functional layer 40, the proper coordination parameter can be reduced. By uniformly dispersing the hollow silica particles 47 in the functional layer 40, protrusion of the hollow silica particles 47 from the first surface 11 is suppressed, and the first surface 11 is smoothed. By uniformly dispersing the hollow silica particles 47 in the functional layer 40, thickness variation of the functional layer 40 is suppressed.

[0178] From the viewpoint of uniformly dispersing the hollow silica particles 47 in the functional layer 40, the following adjustments are effective: The particle size variation of the hollow silica particles 47 may be reduced; The average particle size of the hollow silica particles 47 relative to the average film thickness of the binder component 46 may be adjusted as described above; The affinity between the hollow silica particles 47 and the binder component 46 may be adjusted; The content ratio of the hollow silica particles 47 may be adjusted as described above.

[0179] The functional layer 40 may include particles other than the hollow silica particles 47. The functional layer 40 may include inorganic particles other than the hollow silica particles 47. The functional layer 40 may include magnesium fluoride particles in addition to the hollow silica particles 47. The functional layer 40 may include metal oxide particles other than the hollow silica particles 47. The functional layer 40 may include solid silica particles in addition to the hollow silica particles 47. The functional layer 40 may include organic particles in addition to the hollow silica particles 47.

[0180] Solid silica particles are non-hollow silica particles. Solid silica particles are particles that do not have an internal cavity. Solid silica particles may be solid silica particles.

[0181] The average particle size of the solid silica particles is generally smaller than the average particle size of the hollow silica particles 47. Therefore, the solid silica particles can be embedded between adjacent hollow silica particles 47 in the functional layer 40. When the functional layer 40 contains solid silica particles at an appropriate content ratio, the hollow silica particles 47 can be uniformly dispersed in the functional layer 40.

[0182] The average particle size of the solid silica particles is not particularly limited, and may be 5 nm or more and 20 nm or less, or 5 nm or more and 15 nm or less.

[0183] The content of the solid silica particles may be 10 parts by mass or more, 50 parts by mass or more, 70 parts by mass or more, or 100 parts by mass or more, relative to 100 parts by mass of the binder component, and 200 parts by mass or less, 150 parts by mass or less, or 100 parts by mass or less, relative to 100 parts by mass of the binder component.

[0184] The functional layer 40 may contain particles other than silica particles. Examples of particles other than silica particles contained in the functional layer 40 include a single oxide or a mixture of oxides of any of alumina, titanium, tantalum, zirconium, chromium, niobium, cerium, hafnium, and yttrium. The particles other than silica particles contained in the functional layer 40 may be hollow particles having an internal space. The particles other than silica particles contained in the functional layer 40 may be solid particles having no internal space.

[0185] The functional layer 40 may contain alumina particles as particles other than silica particles. Alumina particles have a relatively low refractive index among metal oxides. Alumina is a metal oxide having a refractive index of Al ２ O ３ The aluminum oxide is represented by the formula: α-type, γ-type, σ-type, and mixtures thereof are known as alumina. The alumina particles may be surface-modified alumina particles. Examples of modified alumina particles include (meth)acrylic-modified alumina particles and silicone-modified alumina particles.

[0186] The average particle size of the particles other than silica particles and the average particle size of the alumina particles may be 5 nm or more and 20 nm or less, 5 nm or more and 15 nm or less, 10 nm or more and 20 nm or less, or 10 nm or more and 15 nm or less.

[0187] There are no particular limitations on the shape of the hollow silica particles 47, solid silica particles, alumina, and other particles dispersed in the functional layer 40. The shape of the particles contained in the functional layer 40 may be a nearly spherical shape such as a perfect sphere, a spheroid, or a polyhedral shape that can approximate a sphere, or a rod-like, plate-like, fibrous, or irregular shape.

[0188] The surfaces of the particles contained in the functional layer 40 may be coated with a silane coupling agent. The silane coupling agent may contain a (meth)acryloyl group or an epoxy group. By subjecting the particles to surface treatment with a silane coupling agent, the affinity between the particles and the binder component is improved, making the particles less likely to aggregate. By coating the hollow silica particles 47 with a silane coupling agent, the hollow silica particles 47 can be uniformly dispersed within the functional layer 40.

[0189] Silane coupling agents include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylethyl)

[0033] Examples of the silane derivatives include trimethylsilane, trimethylsilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, trifluoropropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane. In particular, it may be one or more selected from 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0190] (Method of Producing Functional Layer) The functional layer 40 may be produced using a functional layer coating liquid containing a curable resin composition and hollow silica particles 47. The functional layer 40 may be obtained by curing a coating film of the functional layer coating liquid. In this example, the functional layer coating liquid for producing the functional layer 40 may contain additives such as an antistatic agent, an antioxidant, a surfactant, a dispersant, and an ultraviolet absorber.

[0191] The functional layer coating liquid may contain a silicone-based leveling agent (a silicone-based compound) as an additive. When the functional layer coating liquid contains a silicone-based leveling agent, the hollow silica particles 47 are prevented from protruding from the first surface 11, resulting in a smooth first surface 11. When the functional layer coating liquid contains a silicone-based leveling agent, the hollow silica particles 47 can be uniformly dispersed within the functional layer 40. This reduces thickness variation in the functional layer 40, preventing coloring from appearing on the optical sheet 10. The silicone-based leveling agent can impart excellent slip properties and excellent antifouling properties (fingerprint wipeability, large contact angle with pure water and hexadecane) to the surface of the functional layer 40.

[0192] <Anti-glare Layer> The anti-glare layer 30 has an anti-glare function. The anti-glare layer 30 imparts anti-glare properties to the optical sheet 10. The anti-glare layer 30 includes a first surface 31 and a second surface 32. The first surface 31 faces a first side in the first direction D1. The second surface 32 faces a second side in the first direction D1. The first surface 31 may be an uneven surface 31X having unevenness. The second surface 32 may be a flat surface. The anti-glare layer 30 is located between the functional layer 40 and the substrate 20 in the first direction D1. The anti-glare layer 30 may be connected to the substrate 20 at the second surface 32. The anti-glare layer 30 may be bonded to the substrate 20 at the second surface 32.

[0193] In the example shown in FIG. 1 , the functional layer 40 constitutes the first surface 11 of the optical sheet 10. The functional layer 40 is a very thin layer that extends along the uneven surface 31X. The first surface 11 is an uneven surface 11X that includes irregularities corresponding to the irregularities of the uneven surface 31X. Ambient light in the environment in which the optical sheet 10 is installed is diffusely reflected by the first surface 11 as the uneven surface 11X. This diffuse reflection prevents background images in the environment in which the optical sheet 10 is installed from being reflected on the optical sheet 10. In this way, the antiglare layer 30 and the optical sheet 10 exhibit their antiglare function.

[0194] (Method for Producing Antiglare Layer) The antiglare layer 30 can be produced, for example, by (X) shaping using an embossing roll, (Y) etching treatment, (Z) molding using a mold, or (W) forming a coating film by coating. The (Z) production method allows for stable production of the desired textured surface 31X. The (W) production method uses a coating liquid for forming the antiglare layer 30. The coating film of the coating liquid for the antiglare layer is dried and cured to obtain the antiglare layer 30. The (W) production method is excellent in productivity and compatibility with a wide variety of products. The following two methods may be employed for producing (W). The first method (W1) involves applying a coating liquid containing a binder resin and particles to form texture due to the presence of the particles. The second method (W2) involves applying a coating liquid containing a resin and a resin with poor compatibility with the resin to phase separate the resins to form texture. The first method (W1) makes it easy to control the textured surface 31X.

[0195] The average thickness of the antiglare layer 30 can be determined in consideration of the balance between curl suppression, mechanical strength, hardness, toughness, etc. The average thickness of the antiglare layer may be 2 μm or more and 10 μm or less, or 4 μm or more and 8 μm or less.

[0196] The "average thickness" of the antiglare layer 30 is a value determined by the following (7) to (9). (7) A cross section of an optical sheet including an antiglare layer is imaged using a transmission electron microscope (TEM). (8) In the image, the thickness of the antiglare layer at the center position along the sheet surface of the optical sheet and the thickness of the measurement target layer at positions 50 μm shifted from the center position on both sides along the sheet surface of the optical sheet are measured. The thickness is defined as the length (μm) of the measurement target layer along the direction perpendicular to the sheet surface of the optical sheet. (9) For the same optical sheet to be measured, the above steps (7) and (8) are performed five times to measure the thickness of the antiglare layer at a total of 15 positions. The average of the 15 thickness measurements is defined as the average thickness (μm) of the antiglare layer.

[0197] <Components> The antiglare layer mainly contains a resin component and may contain additives as needed. Examples of additives include particles such as organic particles and inorganic particles, refractive index modifiers, antistatic agents, antifouling agents, UV absorbers, light stabilizers, antioxidants, viscosity modifiers, and thermal polymerization initiators.

[0198] 1 and 5 , the antiglare layer 30 produced by the above-described production method (W) may contain a resin 36 and particles 37. The particles 37 may be organic particles. The particles 37 may be inorganic particles. The antiglare layer 30 may contain both organic particles and inorganic particles as the particles 37.

[0199] (Organic Particles) Examples of materials for organic particles include polymethyl methacrylate, polyacrylic-styrene copolymer, melamine resin, polycarbonate, polystyrene, polyvinyl chloride, benzoguanamine-melamine-formaldehyde condensate, silicone, fluorine-based resin, and polyester-based resin.

[0200] The average particle diameter of the organic particles 37 may be 1.0 μm or more and 7.0 μm or less, 1.5 μm or more and 6.0 μm or less, or 1.7 μm or more and 5.0 μm or less.

[0201] The ratio D / T of the average thickness T of the antiglare layer to the average particle diameter D of the organic particles may be 0.10 or more and 3.5 or less, 0.20 or more and 2.0 or less, 0.30 or more and 1.0 or less, or 0.50 or more and 0.70 or less.

[0202] The content of the organic particles may be 10 parts by mass or more and 200 parts by mass or less, 15 parts by mass or more and 170 parts by mass or less, or 20 parts by mass or more and 150 parts by mass or less, relative to 100 parts by mass of the binder resin. By setting the content of the particles to 200 parts by mass or less, it is possible to prevent the organic particles from falling off from the antiglare layer 30.

[0203] (Inorganic Particles) Examples of inorganic particle materials include silica, alumina, zirconia, and titania. The inorganic particles may be amorphous inorganic particles. An example of the amorphous inorganic particles is amorphous silica.

[0204] The average particle size of the inorganic particles may be 1 nm or more and 200 nm or less, 2 nm or more and 100 nm or less, or 5 nm or more and 50 nm or less.

[0205] The content of the inorganic particles may be 5 parts by mass or more and 100 parts by mass or less, 15 parts by mass or more and 150 parts by mass or less, or 20 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0206] (Resin) The resin component contained in the antiglare layer 30 may include a cured resin. The cured resin is a cured product of a curable resin composition. The curable resin composition may be a thermosetting resin composition. The curable resin composition may be an ionizing radiation curable resin composition. The resin 36 may include a cured product of a curable resin composition and a cured product of an ionizing radiation curable resin composition.

[0207] The cured resin contained in the antiglare layer 30 may be the same as the cured resin contained in the functional layer 40 described above.

[0208] When the resin 36 includes a cured product of an ionizing radiation curable resin composition, the resin 36 may have the following configuration (C1) or (C2).

[0209] The (C1) resin 36 includes a cured product of an ionizing radiation curable resin composition and a thermoplastic resin. The (C2) resin 36 includes substantially only a cured product of an ionizing radiation curable resin composition, and includes 70 mass% or more of a monomer component as the ionizing radiation curable compound contained in the ionizing radiation curable resin composition.

[0210] When the above configuration (C1) is adopted, the viscosity of the coating liquid for forming the antiglare layer 30 is increased by the thermoplastic resin, making it difficult for the particles 37 to sink in the coating liquid for the antiglare layer.

[0211] Examples of thermoplastic resins include polystyrene-based resins, polyolefin-based resins, ABS resins (including heat-resistant ABS resins), AS resins, AN resins, polyphenylene oxide-based resins, polycarbonate-based resins, polyacetal-based resins, acrylic-based resins, polyethylene terephthalate-based resins, polybutylene terephthalate-based resins, polysulfone-based resins, and polyphenylene sulfide-based resins.

[0212] The weight average molecular weight of the thermoplastic resin may be from 20,000 to 200,000, from 30,000 to 150,000, or from 50,000 to 100,000. The weight average molecular weight is an average molecular weight measured by GPC analysis and converted into standard polystyrene.

[0213] In the above structure (C1), the mass ratio of the cured product of the ionizing radiation-curable resin composition to the thermoplastic resin may be 60:40 to 90:10, or 70:30 to 80:20. By using 10 parts by mass or more of the thermoplastic resin per 90 parts by mass of the cured product of the ionizing radiation-curable resin composition, the effect of increasing the viscosity of the coating liquid for the antiglare layer can be effectively obtained. By using 40 parts by mass or less of the thermoplastic resin per 60 parts by mass of the cured product of the ionizing radiation-curable resin composition, the mechanical strength of the antiglare layer can be improved.

[0214] When the above-described configuration (C2) is adopted, the particles 37 are spread out on the bottom of the antiglare layer 30, and the particles 37 tend to be stacked in some regions. Furthermore, a very thin layer of the resin 36 covers the particles 37.

[0215] In the above structure (C2), the proportion of the cured product of the ionizing radiation-curable resin composition relative to the total amount of resin 36 may be 90% by mass or more, 95% by mass or more, or even 100% by mass. In the above structure (C2), the proportion of the monomer component relative to the total amount of the ionizing radiation-curable compound may be 70% by mass or more, or even 75% by mass or more. When the above structure (C2) is adopted, the monomer component may be a polyfunctional (meth)acrylate compound.

[0216] (Coating liquid for antiglare layer) In the above-described production method (W), the antiglare layer 30 can be produced by drying and curing a coating film of the coating liquid for antiglare layer. The coating liquid for antiglare layer used to produce the antiglare layer 30 may contain a curable resin composition and particles. The coating liquid for antiglare layer may contain additives such as an antistatic agent, an antioxidant, a surfactant, a dispersant, and an ultraviolet absorber.

[0217] The coating liquid for the antiglare layer may contain a silicone-based leveling agent (a silicone-based compound) as an additive. When the coating liquid for the antiglare layer contains the silicone-based leveling agent, protrusion of the particles 37 from the first surface 11 can be suppressed.

[0218] <Second Functional Layer> The optical sheet 10 shown in Fig. 5 includes a functional layer 40 and a second functional layer 50. In the example shown in Fig. 5, the functional layer 40 may be configured similarly to the above-described functional layer 40 included in the optical sheet 10 shown in Fig. 1. That is, the functional layer 40 constitutes the first surface 11. As shown in Figs. 2A and 2B, the functional layer 40 may include a binder component 46 and hollow silica particles 47. The functional layer 40 is a low refractive index layer. The low refractive index layer has a refractive index lower than that of the adjacent second functional layer 50.

[0219] The second functional layer 50 is located between the functional layer 40 and the antiglare layer 30 in the first direction D1. The second functional layer 50 has a refractive index higher than the refractive index of the antiglare layer 30 and the refractive index of the functional layer 40. The functional layer 40 as a low refractive index layer and the second functional layer 50 as a high refractive index layer function as a low reflection layer or anti-reflection layer and suppress reflection at the first surface 11.

[0220] Specifically, the second functional layer 50 may include a binder component and particles. The particles may be high-refractive-index particles. The refractive index of the particles may be higher than the refractive index of the binder component. The refractive index of the second functional layer 50 is increased by including the high-refractive-index particles. The refractive index of the second functional layer 50 is higher than the refractive index of the anti-glare layer 30.

[0221] From the viewpoint of the anti-reflection function, the refractive index of the second functional layer 50 and the average thickness of the second functional layer may be set as follows: The refractive index of the second functional layer may be 1.55 or more and 1.85 or less, 1.56 or more and 1.85 or less, 1.55 or more and 1.75 or less, or 1.56 or more and 1.75 or less. The thickness of the second functional layer 50 may be 50 nm or more and 200 nm or less, or 50 nm or more and 180 nm or less.

[0222] The binder component contained in the second functional layer 50 may be the same as the binder component contained in the functional layer 40. The binder component contained in the second functional layer 50 may include a cured product of a curable resin composition. The curable resin composition may include one or more of a thermosetting resin composition and an ionizing radiation curable resin composition.

[0223] The second functional layer 50 may contain one or more organic particles and inorganic particles, such as antimony pentoxide, zinc oxide, titanium oxide, cerium oxide, tin-doped indium oxide, antimony-doped tin oxide, yttrium oxide, and zirconium oxide.

[0224] The second functional layer 50 may be produced by a wet method, similar to the functional layer 40. The second functional layer 50 may be produced using a second functional layer coating liquid for forming the second functional layer 50. The second functional layer 50 may be produced by drying and curing a coating film of the second functional layer coating liquid. The second functional layer coating liquid for producing the second functional layer 50 may contain an additive that can be applied to the functional layer coating liquid.

[0225] <<Method of Manufacturing Optical Sheet>> The antiglare layer 30, functional layer 40, and second functional layer 50 included in the optical sheet 10 may be produced by a wet method. In the wet method, a coating liquid containing components constituting each layer 30, 40, and 50 is prepared. First, the coating liquid is applied to the surface on which each layer 30, 40, and 50 is to be produced. Next, the coating film of the coating liquid is dried and cured to obtain each layer 30, 40, and 50. The coating liquid may contain a solvent in addition to the resin composition and particles used to form each layer. The resin composition may contain solid components constituting each layer and additives such as a polymerization initiator.

[0226] The optical sheet 10 including the substrate 20, the antiglare layer 30, and the functional layer 40 may be produced as follows.

[0227] First, a coating liquid for forming the antiglare layer 30 is prepared. Next, the coating liquid for forming the antiglare layer is applied to the substrate 20 to form a coating film. Next, the coating film is dried. Next, the coating film is cured. In this manner, the antiglare layer 30 is formed on the substrate 20.

[0228] Next, a functional layer coating liquid for forming the functional layer 40 is prepared. Next, the functional layer coating liquid is applied onto the antiglare layer 30 to form a coating film. Next, the coating film is dried. Next, the coating film is cured. In this manner, the functional layer 40 is formed on the antiglare layer 30, and the optical sheet 10 is obtained.

[0229] The antiglare layer 30 may be formed on the substrate 20 in an uncured or semi-cured state, and when the functional layer 40 is cured, the antiglare layer 30 may be completely cured together with the functional layer 40 .

[0230] When manufacturing the optical sheet 10 shown in FIG. 5 , after the antiglare layer 30 is manufactured and before the functional layer 40 is manufactured, the second functional layer 50 is manufactured on the antiglare layer 30. A second functional layer coating liquid for forming the second functional layer 50 is applied to the antiglare layer 30, and the coating film is dried and cured to obtain the second functional layer 50. Next, the functional layer 40 is manufactured on the second functional layer 50 to obtain the optical sheet 10 shown in FIG. 5 . Note that one or more of the antiglare layer 30 and the second functional layer 50 may be manufactured in an uncured or semi-cured state, and one or more of the antiglare layer 30 and the second functional layer 50 may be completely cured together with the functional layer 40 when the functional layer 40 is cured.

[0231] The coating liquid may contain a solvent. The viscosity of the coating liquid can be adjusted by the solvent. The solvent can dissolve or disperse each component in the coating liquid. The solvent may be, for example, one or more of ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ethers (dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), alcohols (butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetates, sulfoxides (dimethyl sulfoxide, etc.), glycol ethers (1-methoxy-2-propyl acetate, etc.), amides (dimethylformamide, dimethylacetamide, etc.), etc.

[0232] If the solvent evaporates too quickly, the solvent will convect vigorously as the coating solution dries. Particles such as hollow silica particles 47 contained in the coating solution may migrate toward the surface of the coating film due to convection caused by solvent evaporation as the coating solution dries. Particles that migrate toward the surface of the coating film may protrude from the first surface or form convex portions on the first surface 11 in the produced optical sheet. In this optical sheet, a large number of hollow silica particles 47 are observed on the first surface 11. The appropriate coordination parameter may be greater than the predetermined range defined in feature (A). To reduce the appropriate coordination parameter, the coating solution may contain a solvent with a slow evaporation rate.

[0233] A solvent with a high boiling point may be used as a solvent with a slow relative evaporation rate. An example of a solvent with a high boiling point is PMA: propylene glycol monomethyl ether acetate. An example of a solvent with a higher boiling point than PMA is diacetone alcohol. An example of a solvent with a higher boiling point than diacetone alcohol is benzyl acetate.

[0234] The drying temperature during drying of the coating liquid may be adjusted. The air volume and air speed of the drying air during drying of the coating liquid may be adjusted. For example, by weakening the drying conditions, rapid evaporation of the solvent can be suppressed. In other words, by adjusting the drying conditions, it is possible to suppress the hollow silica particles 47 from moving toward the surface of the coating film during drying of the coating liquid. The appropriate coordination parameter can also be adjusted by adjusting the drying conditions.

[0235] Drying conditions can be selected appropriately depending on the characteristics of the material used. When using a coating liquid that easily penetrates the base layer, the drying time can be shortened. By reducing the amount of penetration into the base layer, it is possible to prevent the hollow silica particles 47 from gathering on the surface of the coating film. When using hollow silica particles 47 that tend to aggregate, it is possible to prevent the hollow silica particles 47 from gathering on the surface of the coating film by shortening the drying time. As a result, the hollow silica particles 47 can be uniformly dispersed within the functional layer 40.

[0236] Heating the substrate 20 during drying of the coating liquid promotes penetration of the coating liquid into the substrate 20. Therefore, the drying temperature may be gradually increased to dry the coating liquid while suppressing penetration of the coating liquid into the substrate 20. When drying the coating film, the drying conditions may be changed between the first half and the second half.

[0237] The solid content of the functional layer coating solution may be adjusted. As the solid content increases, the viscosity of the functional layer coating solution increases. This makes it easier to maintain the hollow silica particles 47 uniformly dispersed within the coating film. Therefore, the appropriate coordination parameter can be adjusted by adjusting the solid content of the functional layer coating solution.

[0238] Examples of means for curing the coating film for forming each layer include irradiation with ionizing radiation such as ultraviolet rays or electron beams, and heating. Curing treatment by irradiation with ionizing radiation is excellent in productivity because it allows curing in a short time.

[0239] In this manner, the optical sheet 10 can be manufactured.

[0240] As described above, the appropriate coordination parameter based on the hollow silica particles 47 observed on the first surface 11 can be adjusted by adjusting the formulation of the coating liquid, the type of solvent, the drying conditions of the coating film, and the like. Instead of or in addition to these techniques, other techniques may be used to adjust the appropriate coordination parameter. For example, the appropriate coordination parameter can also be adjusted by the affinity between the hollow silica particles 47 and the binder component 46. By using a binder component 46 that has a high affinity for the hollow silica particles 47, the binder component 46 can more easily surround the hollow silica particles 47. This allows the hollow silica particles 47 to be uniformly dispersed within the functional layer 40, making it easier to adjust the appropriate coordination parameter within the predetermined range defined by feature (A).

[0241] The method for manufacturing an optical sheet may further include a step of selecting the manufactured optical sheet 10 in addition to the step of manufacturing the optical sheet described above. The step of selecting the optical sheet 10 may include a step of measuring a proper coordination parameter based on the hollow silica particles 47 observed on the first surface 11, and a step of selecting an optical sheet having a proper coordination parameter of 1.0 or more and 2.0 or less. An optical sheet having a proper coordination parameter of 1.0 or more and 2.0 or less has a color that is difficult to observe. According to this selection method, an optical sheet having a color that is difficult to observe can be accurately selected without undergoing a sensory test by a large number of subjects.

[0242] <<<Sheet Article>>> According to the above-described wet method for producing an optical sheet 10, a long sheet article 5 including a large number of optical sheets 10 can be produced, as shown in FIG. 6 . The long sheet article 5 is cut to a predetermined size to obtain the optical sheets 10. According to this example, optical sheets 10 having various dimensions can be obtained from the long sheet article 5 in accordance with needs. Therefore, optical sheets 10 having various dimensions can be provided in a timely manner. As shown in FIG. 6 , handling the sheet article 5 as a roll 7 wound around a winding core about a winding axis RA improves the handleability of the sheet article 5.

[0243] <<<Polarizing Plate>>> The optical sheet 10 according to the present embodiment may be applied to a polarizing plate 60. In the example shown in Fig. 7 , the polarizing plate 60 includes a first protective sheet 61, a polarizer 62, and a second protective sheet 63. The first protective sheet 61 and the second protective sheet 63 sandwich the polarizer 62 and cover it from both sides. At least one of the first protective sheet 61 and the second protective sheet 63 may include the optical sheet 10. The first protective sheet 61 located on the first side (viewer side) in the first direction D1 may include the optical sheet 10. When only one of the first protective sheet 61 and the second protective sheet 63 includes the optical sheet 10, the other protective sheet may be a resin film.

[0244] The optical sheet 10 can effectively suppress the reflection of a background image onto the optical sheet 10. Therefore, the image behind the polarizing plate 60 can be clearly observed. Furthermore, as described above, the observation of a color on the optical sheet 10 is suppressed. Therefore, it is possible to effectively suppress the change in the hue of the image observed behind the polarizing plate 60 due to the color of the optical sheet 10.

[0245] The polarizer 62 transmits one linearly polarized component and blocks the other linearly polarized component. The polarizer 62 may be an absorptive polarizer that absorbs the other linearly polarized component. The polarizer 62 may be a reflective polarizer that reflects the other linearly polarized component. The polarizer 62 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 62 may be a wire-grid polarizer made of a large number of metal wires arranged in parallel. The polarizer 62 may be a coated polarizer coated with a lyotropic liquid crystal or a dichroic guest-host material, or a multilayer thin-film polarizer.

[0246] <<<Display Device>>> The optical sheet 10 according to the present embodiment may be applied to a display device 65. In the example shown in FIG. 8 , the display device 65 includes a display element 66 and the optical sheet 10. The display element 66 includes an image forming surface 66a that displays an image. The optical sheet 10 is overlaid on the display element 66 with its second surface 12 facing the image forming surface 66a. The optical sheet 10 may be bonded to the display element 66 via a bonding layer containing an adhesive, a pressure-sensitive adhesive, or the like. The display element 66 is not particularly limited. Examples of the display element 66 include a liquid crystal display element, an EL display element, a plasma display element, and an electronic paper element.

[0247] The anti-reflection function and anti-glare function of the optical sheet 10 can prevent background images located in the environment in which the display device 65 is installed from being reflected on the optical sheet 10. Therefore, the viewer can clearly observe the image displayed by the display element 66 through the optical sheet 10. As described above, the observation of a color on the optical sheet 10 is suppressed. Therefore, it is possible to effectively prevent the hue of the image displayed by the display element 66 from changing due to the color of the optical sheet 10. As described above, the display device 65 including the optical sheet 10 can effectively prevent the image displayed by the display device 65 from deteriorating. The viewer can observe a high-quality image.

[0248] <<<Panel>>> The optical sheet 10 according to this embodiment can be used in a variety of applications. FIG. 9 shows a panel 70 to which the optical sheet 10 is applied. The panel 70 includes the optical sheet 10 and a bonded article 71 to which the optical sheet 10 is bonded. The panel 70 constitutes a reflection-suppressing article that functions to suppress reflection by the optical sheet 10. The optical sheet 10 is overlaid on the bonded article 71 with its second surface 12 facing the bonded article 71. The optical sheet 10 may be bonded to the bonded article 71 via a bonding layer containing an adhesive, a pressure-sensitive adhesive, or the like. Examples of the bonded article 71 include an instrument panel, a clock, a showcase, a show window, and a window. The bonded article 71 may be a transparent substrate such as glass or a resin film.

[0249] The optical sheet 10 can effectively suppress the reflection of a background image onto the optical sheet 10. Therefore, the image behind the panel 70 can be clearly observed. Furthermore, as described above, the observation of a color on the optical sheet 10 is suppressed. Therefore, it is possible to effectively suppress the change in the hue of the image observed behind the panel 70 due to the color of the optical sheet 10.

[0250] The present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to the following examples.

[0251] <<<<1. Fabrication of Optical Sheets>>> Optical sheets according to Examples 1 to 4 and Comparative Examples 1 to 3 were fabricated.

[0252] Example 1 A triacetyl cellulose film (TAC film) having a thickness of 80 μm was used as a substrate. This substrate was TD80UL manufactured by Fujifilm Corporation.

[0253] Coating liquid 1 for antiglare layer having the following formulation was applied onto a substrate to form a coating film of coating liquid 1 for antiglare layer on the substrate. The solid content of coating liquid 1 for antiglare layer was 38%. Next, the coating film of coating liquid 1 for antiglare layer was dried under the drying conditions of 70°C x 30 seconds (drying air speed 5 m / s) to volatilize the solvent. Thereafter, the coating film was dried under the drying conditions of 70°C x 30 seconds (drying air speed 5 m / s) to volatilize the solvent. Then ... ２ The coating film was irradiated with ultraviolet light of 1000 kJ / cm. An antiglare layer made of the cured coating film was formed on the substrate. The thickness of the antiglare layer was 5 μm.

[0254] Next, functional layer coating liquid 1 (low refractive index layer coating liquid 1) having the following formulation was applied onto the antiglare layer to form a coating film of functional layer coating liquid 1 on the substrate. The solid content of functional layer coating liquid 1 was 5.0%. Thereafter, the coating film of functional layer coating liquid 1 was dried at 50°C for 30 seconds (drying air speed: 0.5 m / s), and further dried at 50°C for 30 seconds (drying air speed: 5 m / s) to volatilize the solvent. Next, in a nitrogen atmosphere with an oxygen concentration of 200 ppm or less, an integrated light intensity of 200 mJ / cm was applied. ２ The coating film was irradiated with ultraviolet light of 1000 nm. A functional layer made of the cured coating film was formed on the antiglare layer. The thickness of the functional layer was 100 nm. In this way, an optical sheet of Example 1 was obtained.

[0255] <Coating Solution 1 for Antiglare Layer> Pentaerythritol triacrylate 30 parts by weight (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Urethane acrylate oligomer 70 parts by weight (DIC Corporation, trade name "LUXYDIR V-4501") Organic particles 2 parts by weight (average particle size 2.0 μm, proportion of particles with a particle size of 1.8 to 2.2 μm of 90% or more, refractive index 1.515, spherical polyacrylic-styrene copolymer, Sekisui Plastics Co., Ltd.) Silica particles 4 parts by weight (average particle size 4.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Silica particles 10 parts by weight (average particle size 6.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Photopolymerization initiator 1.5 parts by weight (IGM Resins B.V., trade name "Omnirad 184") 0.3 parts by mass of photopolymerization initiator (IGM Resins B.V., trade name "Omnirad 907") 1.3 parts by mass of photopolymerization initiator (Lamberti, trade name "ESACUREONE") 0.1 parts by mass of silicone leveling agent (Momentive Performance Materials, trade name "TSF4460") 130.5 parts by mass of solvent (toluene) 32.6 parts by mass of solvent (MIBK: methyl isobutyl ketone)

[0256] <Coating Solution 1 for Functional Layer (Coating Solution 1 for Low Refractive Index Layer)> Pentaerythritol triacrylate 100 parts by mass (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Hollow silica particles 175 parts by mass (average particle diameter 75 nm, particles surface-treated with a silane coupling agent having a methacryloyl group) Photopolymerization initiator 7.0 parts by mass (IGM Resins B.V., trade name "Omnirad127") Silicone-based leveling agent 40.0 parts by mass (Momentive Performance Materials, trade name "TSF4460") Solvent (MIBK: methyl isobutyl ketone) 5563.2 parts by mass Solvent (PMA: propylene glycol monomethyl ether acetate) 744.8 parts by mass

[0257] <<Example 2>> Example 2 differs from the above-described Example 1 in that antiglare layer coating liquid 1 was changed to the following antiglare layer coating liquid 2, and functional layer coating liquid 1 was changed to the following functional layer coating liquid 2. Otherwise, an optical sheet of Example 2 having the same thickness as Example 1 was obtained using the same materials and method as Example 1. The solids content of antiglare layer coating liquid 2 was 35%. The solids content of functional layer coating liquid 2 was 5%.

[0258] <Coating Solution 2 for Antiglare Layer> Pentaerythritol triacrylate 30 parts by weight (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Urethane acrylate oligomer 70 parts by weight (DIC Corporation, trade name "LUXYDIR V-4501") Organic particles 2 parts by weight (average particle size 2.0 μm, proportion of particles with a particle size of 1.8 to 2.2 μm of 90% or more, refractive index 1.515, spherical polyacrylic-styrene copolymer, Sekisui Plastics Co., Ltd.) Silica particles 11 parts by weight (average particle size 4.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Silica particles 3 parts by weight (average particle size 6.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Photopolymerization initiator 3.0 parts by weight (IGM Resins B.V., trade name "Omnirad 184") 0.5 parts by mass of photopolymerization initiator (IGM Resins B.V., trade name "Omnirad 907") 0.7 parts by mass of photopolymerization initiator (Lamberti, trade name "ESACUREONE") 0.1 parts by mass of silicone leveling agent (Momentive Performance Materials, trade name "TSF4460") 130.5 parts by mass of solvent (toluene) 32.6 parts by mass of solvent (MIBK: methyl isobutyl ketone)

[0259] <Coating Solution 2 for Functional Layer (Coating Solution 2 for Low Refractive Index Layer)> Pentaerythritol triacrylate 100 parts by mass (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Hollow silica particles 210 parts by mass (average particle diameter 75 nm, particles surface-treated with a silane coupling agent having a methacryloyl group) Photopolymerization initiator 7.0 parts by mass (IGM Resins B.V., trade name "Omnirad127") Silicone-based leveling agent 40.0 parts by mass (Momentive Performance Materials, trade name "TSF4460") Solvent (MIBK: methyl isobutyl ketone) 5367.2 parts by mass Solvent (PMA: propylene glycol monomethyl ether acetate) 1675.8 parts by mass

[0260] <<Example 3>> Example 3 differs from the above-described Example 1 in that antiglare layer Coating Liquid 1 was changed to the following antiglare layer Coating Liquid 3, and functional layer Coating Liquid 1 was changed to the following functional layer Coating Liquid 3. Otherwise, an optical sheet of Example 3 having the same thickness as Example 1 was obtained using the same materials and method as Example 1. The solids content of antiglare layer Coating Liquid 3 was 38%. The solids content of functional layer Coating Liquid 3 was 5%.

[0261] <Coating Solution 3 for Antiglare Layer> Pentaerythritol triacrylate 30 parts by mass (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Urethane acrylate oligomer 70 parts by mass (DIC Corporation, trade name "LUXYDIR V-4501") Organic particles 2 parts by mass (average particle size 2.0 μm, proportion of particles with a particle size of 1.8 to 2.2 μm of 90% or more, refractive index 1.515, spherical polyacrylic-styrene copolymer, Sekisui Plastics Co., Ltd.) Silica particles 11 parts by mass (average particle size 4.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Photopolymerization initiator 3.0 parts by mass (IGM Resins B.V., trade name "Omnirad 184") Photopolymerization initiator 0.5 parts by mass (IGM Resins B.V., trade name "Omnirad 907") Photopolymerization initiator 0.7 parts by mass (Lamberti, trade name "ESACUREONE") Silicone leveling agent 0.1 parts by mass (Momentive Performance Materials, trade name "TSF4460") Solvent (toluene) 146.8 parts by mass Solvent (MIBK: methyl isobutyl ketone) 16.3 parts by mass

[0262] <Coating Solution 3 for Functional Layer (Coating Solution 3 for Low Refractive Index Layer)> Pentaerythritol triacrylate 100 parts by mass (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Hollow silica particles 210 parts by mass (average particle diameter 75 nm, particles surface-treated with a silane coupling agent having a methacryloyl group) Photopolymerization initiator 7.0 parts by mass (IGM Resins B.V., trade name "Omnirad127") Silicone-based leveling agent 40.0 parts by mass (Momentive Performance Materials, trade name "TSF4460") Solvent (MIBK: methyl isobutyl ketone) 6205.1 parts by mass Solvent (PMA: propylene glycol monomethyl ether acetate) 837.9 parts by mass

[0263] <<Example 4>> Example 4 differs from the above-described Example 1 in that antiglare layer coating liquid 1 was changed to the following antiglare layer coating liquid 4, and functional layer coating liquid 1 was changed to the above-described functional layer coating liquid 2. Otherwise, an optical sheet of Example 4 having the same thickness as Example 1 was obtained using the same materials and method as Example 1. The solids content of antiglare layer coating liquid 4 was 38%. The solids content of functional layer coating liquid 2 was 5%.

[0264] <Coating Solution 4 for Antiglare Layer> Pentaerythritol triacrylate 30 parts by mass (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Urethane acrylate oligomer 70 parts by mass (DIC Corporation, trade name "LUXYDIR V-4501") Organic particles 2 parts by mass (average particle size 2.0 μm, proportion of particles with a particle size of 1.8 to 2.2 μm of 90% or more, refractive index 1.515, spherical polyacrylic-styrene copolymer, Sekisui Plastics Co., Ltd.) Silica particles 4 parts by mass (average particle size 4.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Photopolymerization initiator 3.0 parts by mass (IGM Resins B.V., trade name "Omnirad 184") Photopolymerization initiator 0.5 parts by mass (IGM Resins B.V., trade name "Omnirad 184") B.V., trade name "Omnirad 907") Photopolymerization initiator 0.7 parts by mass (Lamberti, trade name "ESACUREONE") Silicone leveling agent 0.1 parts by mass (Momentive Performance Materials, trade name "TSF4460") Solvent (toluene) 130.5 parts by mass Solvent (MIBK: methyl isobutyl ketone) 32.6 parts by mass

[0265] <<Comparative Example 1>> Comparative Example 1 differs from the above-described Example 1 in that Coating Liquid 1 for antiglare layer was changed to Coating Liquid 5 for antiglare layer described below, but an optical sheet of Comparative Example 1 having the same thickness as Example 1 was obtained using the same materials and method as Example 1. The solids content of Coating Liquid 5 for antiglare layer was 35%. The solids content of Coating Liquid 1 for functional layer was 5%.

[0266] <Coating Solution 5 for Antiglare Layer> Pentaerythritol triacrylate 30 parts by mass (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Urethane acrylate oligomer 70 parts by mass (DIC Corporation, trade name "LUXYDIR V-4501") Organic particles 2 parts by mass (average particle size 2.0 μm, proportion of particles with a particle size of 1.8 to 2.2 μm of 90% or more, refractive index 1.515, spherical polyacrylic-styrene copolymer, Sekisui Plastics Co., Ltd.) Silica particles 6 parts by mass (average particle size 6.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Photopolymerization initiator 1.5 parts by mass (IGM Resins B.V., trade name "Omnirad 184") Photopolymerization initiator 0.3 parts by mass (IGM Resins B.V., trade name "Omnirad 184") B.V., trade name "Omnirad 907") Photopolymerization initiator 1.3 parts by mass (Lamberti, trade name "ESACUREONE") Silicone leveling agent 0.1 parts by mass (Momentive Performance Materials, trade name "TSF4460") Solvent (toluene) 130.5 parts by mass Solvent (MIBK: methyl isobutyl ketone) 32.6 parts by mass

[0267] <<Comparative Example 2>> Comparative Example 1 differs from the above-described Example 1 in that antiglare layer coating liquid 1 was changed to the following antiglare layer coating liquid 6, and functional layer coating liquid 1 was changed to the above-described functional layer coating liquid 2. Otherwise, an optical sheet of Comparative Example 2 having the same thickness as Example 1 was obtained using the same materials and method as Example 1. The solids content of antiglare layer coating liquid 6 was 38%. The solids content of functional layer coating liquid 2 was 5%.

[0268] <Coating Solution 6 for Antiglare Layer> Pentaerythritol triacrylate 30 parts by mass (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Urethane acrylate oligomer 70 parts by mass (DIC Corporation, trade name "LUXYDIR V-4501") Organic particles 2 parts by mass (average particle size 2.0 μm, proportion of particles with a particle size of 1.8 to 2.2 μm of 90% or more, refractive index 1.515, spherical polyacrylic-styrene copolymer, Sekisui Plastics Co., Ltd.) Silica particles 15 parts by mass (average particle size 4.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Photopolymerization initiator 3.0 parts by mass (IGM Resins B.V., trade name "Omnirad 184") Photopolymerization initiator 0.5 parts by mass (IGM Resins B.V., trade name "Omnirad 907") Photopolymerization initiator 0.7 parts by mass (Lamberti, trade name "ESACUREONE") Silicone leveling agent 0.1 parts by mass (Momentive Performance Materials, trade name "TSF4460") Solvent (toluene) 146.8 parts by mass Solvent (MIBK: methyl isobutyl ketone) 16.3 parts by mass

[0269] <<Comparative Example 3>> Comparative Example 3 differs from the above-mentioned Example 1 in that Coating Liquid 1 for antiglare layer was changed to Coating Liquid 7 for antiglare layer described below, but an optical sheet of Comparative Example 2 having the same thickness as Example 1 was obtained using the same materials and method as Example 1. The solids content of Coating Liquid 6 for antiglare layer was 38%. The solids content of Coating Liquid 1 for functional layer was 5%.

[0270] <Coating Solution 7 for Antiglare Layer> Pentaerythritol triacrylate 30 parts by mass (Nippon Kayaku Co., Ltd., trade name "KAYARAD-PET-30") Urethane acrylate oligomer 70 parts by mass (DIC Corporation, trade name "LUXYDIR V-4501") Organic particles 2 parts by mass (average particle size 2.0 μm, proportion of particles with a particle size of 1.8 to 2.2 μm of 90% or more, refractive index 1.515, spherical polyacrylic-styrene copolymer, Sekisui Plastics Co., Ltd.) Silica particles 3 parts by mass (average particle size 4.0 μm, gel-process amorphous silica, Fuji Silysia Chemical Ltd.) Photopolymerization initiator 3.0 parts by mass (IGM Resins B.V., trade name "Omnirad 184") Photopolymerization initiator 0.5 parts by mass (IGM Resins B.V., trade name "Omnirad 184") B.V., trade name "Omnirad 907") Photopolymerization initiator 0.7 parts by mass (Lamberti, trade name "ESACUREONE") Silicone leveling agent 0.1 parts by mass (Momentive Performance Materials, trade name "TSF4460") Solvent (toluene) 130.5 parts by mass Solvent (MIBK: methyl isobutyl ketone) 32.6 parts by mass

[0271] <<<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 measurement environment during 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 measurement environment for 16 hours.

[0272] <<2-1. Transmission Haze>> Samples measuring 10 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 that they were free of any abnormalities such as dust or scratches. The transmission haze (%) of the samples according to each example was measured using the method described above. The transmission haze was measured using a haze meter "HM-150" manufactured by Murakami Color Research Laboratory. The measurement results of transmission haze are shown in the "Transmission Haze" column of Table 1.

[0273] <<2-2. Luminous Reflectance>> 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 for the absence of any abnormalities such as dust or scratches. As described above, a black plate was attached to the surface of the sample, which was the second surface of the optical sheet, using an optically transparent adhesive. The black plate was "Comoglass K, color number: 502K (thickness 2 mm)" manufactured by Kuraray. The luminous reflectance (%) of the samples according to each example was measured using the method described above. The luminous reflectance was expressed as an SCI Y value. A spectrophotometer "CM-600d" manufactured by Konica Minolta was used to measure the luminous reflectance. The light source was a D65 light source. The measurement results of the luminous reflectance are shown in the "Luminous Reflectance" column of Table 1.

[0274] <<2-3. 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. As described above, a black plate was attached to the surface of the sample that was made up of the second surface of the optical sheet using an optically transparent adhesive. The black plate was "Comoglass K, color number: 502K (thickness 2 mm)" manufactured by Kuraray. Using the method described above, the L ＊ a ＊ b ＊ a in the color system ＊ value and b ＊ The values ​​were measured. ＊ value and b ＊ The values ​​were measured using a spectrophotometer "CM-600d" manufactured by Konica Minolta. ＊ The measurement results of the values ​​are shown in Table 1 under "a ＊ The values ​​are shown in the "Value" column. ＊ The measurement results of the values ​​are shown in Table 1 under "b ＊ The values ​​are shown in the "Value" column.

[0275] <<2-4. Luminous reflectance and a ＊ The product of the luminous reflectance and b ＊ The product of the measured luminous reflectance and a value for each example ＊ The absolute value of the product of the luminous reflectance and a ＊ The absolute value of the product with the value is shown in Table 2 as "|Y a ＊The measured luminous reflectance and b for each example are shown in the "|" column. ＊ The absolute value of the product of the luminous reflectance and b ＊ The absolute value of the product of the value is shown in Table 2 as "|Y b ＊ |" column.

[0276] <<2-4. Proper Coordination Parameter>> Samples measuring 5 mm x 5 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, the proper coordination parameter based on the hollow silica particles observed on the first surface of the optical sheet according to each example was measured.

[0277] First, a scanning electron microscope (SEM) was used to obtain observation images of 16 partitioned regions arranged adjacently in four rows and four columns within the measurement area on the first surface. The scanning electron microscope used was an ultra-high resolution field emission scanning electron microscope SU-9000 manufactured by Hitachi High-Technologies Corporation. An example of an observation image obtained using the scanning electron microscope is shown in FIG. 4A.

[0278] Next, the 16 observation images acquired with the scanning electron microscope were binarized using the image processing software "ImageJ 1.52e" and "Fiji." As an example, the binarized binary image of the first surface is shown in FIG. 4B. The binary image shown in FIG. 4B was obtained by binarizing the observation image of the first surface shown in FIG. 4A.

[0279] Then, using "ImageJ 1.52e" and "Fiji," the positions of the centers of gravity of the hollow silica particles observed on the first surface 11 were identified based on the binarized binary image. As an example, the distribution of the centers of gravity of the identified hollow silica particles is shown in FIG. 4C. The distribution of the centers of gravity shown in FIG. 4C was generated based on the observed images of the first surface shown in FIGS. 4A and 4B.

[0280] Next, using the image processing software "ImageJ 1.52e" and "Fiji," the proper coordination number and the miscoordination number were measured for each of the 16 observation images. Furthermore, for each of the 16 observation images, the proper coordination parameters were calculated by subtracting the miscoordination number from the proper coordination number. The maximum and minimum proper coordination parameters were excluded from the calculated values ​​of the 16 proper coordination parameters measured for each of the 16 observation images, yielding 14 calculated values ​​of proper coordination parameters. The proper coordination parameter for each example was calculated as the arithmetic mean value of the calculated values ​​of the 14 proper coordination parameters. The calculated proper coordination parameters for each example are shown in the "Proper Coordination Parameter" column of Table 2.

[0281] The standard deviation of the proper coordination parameters for each example was calculated as the standard deviation of the calculated values ​​of the 14 proper coordination parameters. The standard deviation of the proper coordination parameters calculated for each example is shown in the "Standard Deviation" column of Table 2.

[0282] <<2-5. Sensory Evaluation of Antiglare Properties>> Samples measuring 10 cm x 5 cm were cut out from the optical sheets according to the Examples and Comparative Examples. A black plate was attached to the second surface of the sample to be evaluated in each Example using an optically transparent adhesive. The black plate was "COMOGLAS K, color number: 502K (thickness: 2 mm)" manufactured by Kuraray. The first surface of the evaluation sample, which was produced by adhering the black resin plate, was visually inspected for the absence of any abnormalities such as dust or scratches.

[0283] The first surface of the evaluation sample was observed from various directions in a bright room environment with the lighting device turned on, and it was confirmed whether a color was observed on the evaluation sample. The light-emitting part of the lighting device was an Hf32 straight-tube, three-wavelength, daylight white fluorescent lamp. The lighting device was positioned 2 m vertically above the floor. The illuminance on the first surface of the evaluation sample was 500 lux to 1000 lux. The evaluator's line of sight was approximately 170 cm from the floor. The evaluators were 20 healthy individuals in their 30s with eyesight of 0.7 or higher.

[0284] The observation results were evaluated according to the following evaluation criteria. The evaluation results are shown in the "Color" column of Tables 1 and 2. The evaluations "AA" and "A" were of a level that would be considered passable in a normal product inspection. The evaluation "B" was of a level that would be considered poor in a normal product inspection.

[0285] <Evaluation Criteria> AA: Two or fewer evaluators were able to observe the color of the evaluation sample. A: Three to seven evaluators were able to observe the color of the evaluation sample. B: Eight or more evaluators were able to observe the color of the evaluation sample.

[0286]

[0287]

[0288] D1: first direction, D2: second direction, D3: third direction, 5: sheet article, 6: winding core, 7: roll, RA: winding axis, 10: optical sheet, 11: first surface, 11X: uneven surface, 12: second surface, 20: substrate, 30: antiglare layer, 31: first surface, 31X: uneven surface, 31A: reference portion, 31B: convex portion, 32: second surface, 36: resin, 37: particles, 40: functional layer, 46: binder component, 47: hollow silica particles, 50: second functional layer, 60: polarizing plate, 61: first protective sheet, 62: polarizer, 63: second protective sheet, 65: display device, 66: display element, 66a: image forming surface, 70: panel, 71: bonded article

Claims

1. An optical sheet having a first surface and a second surface opposing each other in a first direction, comprising an antiglare layer and a functional layer in the order from the second surface to the first surface, the transmission haze being 10% or more and 70% or less, the functional layer including a binder component and hollow silica particles, the proper coordination parameter based on the hollow silica particles observed on the first surface being 1.0 or more and 2.0 or less, the proper coordination parameter being a value obtained by subtracting the mismatch coordination number from the proper coordination number, the proper coordination number being the number of other hollow silica particles whose centers of gravity are located at a distance of 55 nm or more and less than 75 nm from the center of gravity of one hollow silica particle, and the mismatch coordination number being the number of other hollow silica particles whose centers of gravity are located at a distance of less than 55 nm from the center of gravity of one hollow silica particle.

2. L measured by the reflected light from the first surface ＊ a ＊ b ＊ Color system a ＊ The L value is -4.0 or more and 4.0 or less, and is measured by reflected light from the first surface. ＊ a ＊ b ＊ Color system b ＊ The optical sheet according to claim 1, wherein the value is -4.0 or more and 4.0 or less.

3. The optical sheet according to claim 1, wherein the standard deviation of the proper alignment parameters is 0.30 or less.

4. The luminous reflectance and L measured by reflected light on the first surface ＊ a ＊ b ＊ Color system a ＊ the absolute value of the product of the luminous reflectance and the L measured by reflected light is 4.0 or less; ＊ a ＊ b ＊ Color system b ＊ The optical sheet according to claim 1 , wherein the absolute value of the product of the value is 4.0 or less.

5. The optical sheet according to claim 1, wherein the luminous reflectance of the first surface is 2.0% or less.

6. An optical sheet according to claim 1, wherein the antiglare layer includes a textured surface, the textured surface being closer to the first surface in the first direction than the second surface, the textured surface including a reference portion and a convex portion protruding from the reference portion, and the proper orientation parameter is a value measured in a region of the first surface facing the reference portion in the first direction.

7. The optical sheet according to claim 1, wherein the antiglare layer contains a resin and particles, and the proper coordination parameter is a value measured in a region of the first surface facing a region of the antiglare layer where the particles are not present in the first direction.

8. A sheet product comprising a plurality of optical sheets according to any one of claims 1 to 7.

9. The sheet product of claim 8, which is wound about a winding axis.

10. A panel comprising an optical sheet according to any one of claims 1 to 7.

11. A polarizing plate comprising: the optical sheet according to any one of claims 1 to 7; and a polarizer superimposed on the optical sheet.

12. A display device comprising: an optical sheet according to any one of claims 1 to 7; and a display element superimposed on the optical sheet.

13. A method for selecting an optical sheet, the optical sheet having a first surface and a second surface opposing each other in a first direction, comprising an antiglare layer and a functional layer in this order from the second surface to the first surface, the optical sheet having a transmission haze of 10% or more and 70% or less, the functional layer including a binder component and hollow silica particles, the method comprising the steps of measuring a proper coordination parameter based on the hollow silica particles observed on the first surface, and selecting an optical sheet having a proper coordination parameter of 1.0 or more and 2.0 or less, the proper coordination parameter being a value obtained by subtracting a mismatch number from a proper coordination number, the proper coordination number being the number of hollow silica particles whose centers of gravity are located at a distance of 55 nm or more and less than 75 nm from the center of gravity of one hollow silica particle, and the mismatch number being the number of hollow silica particles whose centers of gravity are located at a distance of less than 55 nm from the center of gravity of one hollow silica particle.

14. A method for manufacturing an optical sheet, comprising: a step of manufacturing the optical sheet; and a step of selecting the optical sheet by the selection method described in claim 13.

Images