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

Abstract

The optical sheet has a first surface and a second surface facing the first surface. The substrate and the functional layer are provided in this order from the second surface toward the first surface. The functional layer contains a binder resin, hollow silica particles, and metal oxide particles other than silica particles. The arithmetic average roughness Sa of the first surface is 5.2 nm or less.

Description

Technical Field

[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. Background Art

[0002] As disclosed in Patent Document 1 and Patent Document 2, an optical sheet including a functional layer having a low refractive index is known. The functional layer contains hollow silica particles. The refractive index of the functional layer is adjusted by the hollow silica particles and thus reduced. The low-refractive-index functional layer has a reflection suppression function of suppressing light reflection. In Patent Document 1, in addition to the hollow silica particles, the low-refractive-index layer further contains inorganic oxide particles. The inorganic oxide particles form convex portions on the surface. The convex portions protect the hollow silica particles that are likely to be damaged or peeled off due to the hollow structure. In Patent Document 1, the convex portions protect the hollow silica particles, thereby achieving an improvement in scratch resistance.

[0003] Patent Document 1: WO2021 / 020504A

[0004] Patent Document 2: WO2019 / 208786A Summary of the Invention

[0005] The means disclosed in Patent Document 1 cannot sufficiently improve the scratch resistance of the optical sheet. An object of the present disclosure is to improve the scratch resistance of an optical sheet containing hollow silica.

[0006] The optical sheet according to the first embodiment of the present disclosure is an optical sheet having a first surface and a second surface facing the first surface, wherein

[0007] a substrate and a functional layer are provided in this order from the second surface toward the first surface,

[0008] the functional layer contains a binder component, hollow silica particles, and metal oxide particles other than silica particles,

[0009] the arithmetic mean roughness Sa of the first surface is 5.2 nm or less.

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

[0011] The polarizing plate according to the first embodiment of the present disclosure includes a first protective sheet, a polarizing element, and a second protective sheet,

[0012] at least one of the first protective sheet and the second protective sheet contains the optical sheet according to the first embodiment of the present disclosure.

[0013] The display device according to the first embodiment of the present disclosure includes:

[0014] An image forming apparatus; and

[0015] An optical sheet according to the first embodiment of the present disclosure that overlaps with the above-described image forming apparatus.

[0016] The panel according to the first embodiment of the present disclosure includes:

[0017] An article to be joined; and

[0018] An optical sheet according to the first embodiment of the present disclosure that is joined to the above-described article to be joined.

[0019] The method for selecting an optical sheet according to the first embodiment of the present disclosure includes the following steps for the following optical sheet,

[0020] The optical sheet has a first surface and a second surface facing the first surface, and includes a substrate and a functional layer in this order from the second surface toward the first surface. The functional layer contains a binder component, hollow silica particles, and metal oxide particles other than silica particles,

[0021] The steps are:

[0022] A step of measuring the arithmetic mean roughness Sa of the first surface; and

[0023] A step of selecting an optical sheet having an arithmetic mean roughness Sa of 5.2 nm or less.

[0024] The method for manufacturing an optical sheet according to the first embodiment of the present disclosure includes the following steps:

[0025] A step of producing an optical sheet, the optical sheet having a first surface and a second surface facing the first surface, and including a substrate and a functional layer in this order from the second surface toward the first surface. The functional layer contains a binder component, hollow silica particles, and metal oxide particles other than silica particles; and

[0026] A step of evaluating the arithmetic mean roughness Sa of the first surface and selecting an optical sheet having an arithmetic mean roughness Sa of 5.2 nm or less.

[0027] The optical sheet according to the second embodiment of the present disclosure is an optical sheet including a first surface and a second surface facing the first surface, wherein,

[0028] The substrate and the functional layer are provided in this order from the second surface toward the first surface,

[0029] The functional layer contains a binder component and hollow silica particles,

[0030] The indentation hardness of the first surface with an indentation depth of 100 nm is 0.45 GPa or more,

[0031] The standard deviation of the complex elastic modulus with an indentation depth of 30 nm at 10 different positions on the first surface described above is 1.1 GPa or less.

[0032] The sheet article of the second embodiment of the present disclosure includes a plurality of optical sheets of the second embodiment of the present disclosure.

[0033] The polarizing plate of the second embodiment of the present disclosure includes a first protective sheet, a polarizing element, and a second protective sheet.

[0034] At least one of the first protective sheet and the second protective sheet described above includes the optical sheet of the second embodiment of the present disclosure.

[0035] The display device of the second embodiment of the present disclosure includes:

[0036] An image forming device; and

[0037] The optical sheet of the second embodiment of the present disclosure that overlaps with the image forming device described above.

[0038] The panel of the second embodiment of the present disclosure includes:

[0039] An article to be joined; and

[0040] The optical sheet of the second embodiment of the present disclosure that is joined to the article to be joined described above.

[0041] The method for selecting an optical sheet of the second embodiment of the present disclosure has the following steps for the following optical sheet.

[0042] The optical sheet includes a first surface and a second surface facing the first surface, and includes a substrate and a functional layer in this order from the second surface toward the first surface. The functional layer includes a binder component and hollow silica particles.

[0043] The steps are:

[0044] A step of measuring the indentation hardness of the first surface with an indentation depth of 100 nm and the complex elastic modulus of the first surface with an indentation depth of 30 nm; and

[0045] A step of selecting an optical sheet based on the indentation hardness and the standard deviation of the complex elastic modulus at 10 different positions on the first surface.

[0046] The manufacturing method of the optical sheet of the second embodiment of the present disclosure has the following steps:

[0047] Steps for manufacturing an optical sheet, the above optical sheet includes a first surface and a second surface facing the above first surface, and has a substrate and a functional layer in the order from the above second surface toward the above first surface, the above functional layer includes a binder component and hollow silica particles; and

[0048] Steps for selecting an optical sheet in which the indentation hardness of the above first surface with an indentation depth of 100 nm is 0.45 GPa or more, and the standard deviation of the complex elastic modulus with an indentation depth of 30 nm at 10 different positions on the above first surface is 1.1 GPa or less.

[0049] According to the present disclosure, the scratch resistance of an optical sheet containing hollow silica can be improved. Description of the Drawings

[0050] Figure 1 It is a diagram for explaining the first embodiment, and is a cross-sectional view showing an example of an optical sheet.

[0051] Figure 2 It is a transmission electron micrograph showing the functional layer of the optical sheet.

[0052] Figure 3 It is corresponding to Figure 1 It is a cross-sectional view showing another example of the optical sheet.

[0053] Figure 4 It is a perspective view showing an example of a sheet article including the optical sheet.

[0054] Figure 5 It is a cross-sectional view showing an example of a polarizing plate including the optical sheet.

[0055] Figure 6 It is a cross-sectional view showing an example of a display device including the optical sheet.

[0056] Figure 7 It is a cross-sectional view showing an example of a panel including the optical sheet.

[0057] Figure 8 It is a grayscale image showing the surface of Example 1.

[0058] Figure 9 It is a grayscale image showing the surface of Example 2.

[0059] Figure 10 It is a grayscale image showing the surface of Example 3.

[0060] Figure 11 It is a grayscale image showing the surface of Comparative Example 1.

[0061] Figure 12 It is a grayscale image showing the surface of Comparative Example 2.

[0062] Figure 13 This is a diagram for explaining the second embodiment, and is a cross-sectional view showing an example of an optical sheet.

[0063] Figure 14 This is a graph showing an example of a load-displacement curve obtained by nanoindentation.

[0064] Figure 15 This is related to Figure 13 This is a corresponding diagram, and is a cross-sectional view showing another example of an optical sheet. Detailed implementation manners

[0065] The first embodiment and the second embodiment of the present disclosure relate to the following [1] to

[29] .

[0066] [1] An optical sheet having a first surface and a second surface facing the first surface, wherein

[0067] A substrate and a functional layer are provided in order from the second surface toward the first surface,

[0068] The functional layer contains a binder component, hollow silica particles, and metal oxide particles other than silica particles,

[0069] The arithmetic mean roughness Sa of the first surface is 5.2 nm or less.

[0070] [2] The optical sheet according to [1], wherein the arithmetic mean roughness Sa is 4.2 nm or less.

[0071] [3] The optical sheet according to [1] or [2], wherein the kinetic friction coefficient between the first surface and a felt to which a load of 500 g is applied is 0.20 or less.

[0072] [4] The optical sheet according to any one of [1] to [3], wherein the kinetic friction coefficient between the first surface and a steel wool to which a load of 500 g is applied is 0.25 or less.

[0073] [5] The optical sheet according to any one of [1] to [4], wherein the average particle size of the metal oxide particles is smaller than the average thickness of the functional layer.

[0074] [6] The optical sheet according to any one of [1] to [5], wherein the average particle size of the metal oxide particles is smaller than the average particle size of the hollow silica particles.

[0075] [7] The optical sheet according to any one of [1] to [6], wherein the metal oxide particles contain alumina.

[0076] [8] The optical sheet according to any one of [1] to [7], wherein the functional layer contains solid silica particles.

[0077] [9] The optical sheet according to any one of [1] to [8], which has a resin layer located between the base material and the functional layer,

[0078] The resin layer contains a cured product of a curable resin composition.

[0079]

[10] The optical sheet according to any one of [1] to [9], wherein the indentation hardness of the first surface with an indentation depth of 100 nm is 0.45 GPa or more,

[0080] The standard deviation of the complex elastic modulus at 10 different positions on the first surface with an indentation depth of 30 nm is 1.1 GPa or less.

[0081]

[11] An optical sheet comprising a first surface and a second surface facing the first surface, wherein,

[0082] It has a base material and a functional layer in order from the second surface toward the first surface,

[0083] The functional layer contains a binder component and hollow silica particles,

[0084] The indentation hardness of the first surface with an indentation depth of 100 nm is 0.45 GPa or more,

[0085] The standard deviation of the complex elastic modulus at 10 different positions on the first surface with an indentation depth of 30 nm is 1.1 GPa or less.

[0086]

[12] The optical sheet according to

[10] or

[11] , wherein the indentation hardness is 0.55 GPa or more.

[0087]

[13] The optical sheet according to any one of

[10] to

[12] , wherein the standard deviation of the complex elastic modulus is 0.80 GPa or less.

[0088]

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

[13] , wherein the average thickness of the functional layer is 80 nm or more and 150 nm or less.

[0089]

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

[14] , wherein the average particle diameter of the hollow silica particles is 50 nm or more and 100 nm or less.

[0090]

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

[15] includes a resin layer located between the base material and the functional layer and adjacent to the functional layer.

[0091] The resin layer contains a cured product of a curable resin composition.

[0092] The average thickness of the resin layer is 0.1 μm or more and 100 μm or less.

[0093]

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

[16] includes a second functional layer located between the base material and the functional layer and adjacent to the functional layer.

[0094] The second functional layer contains a binder component and particles.

[0095] The average thickness of the second functional layer is 50 nm or more and 200 nm or less.

[0096]

[18] The optical sheet according to

[17] includes a resin layer located between the base material and the second functional layer and adjacent to the second functional layer.

[0097] The resin layer contains a cured product of a curable resin composition.

[0098] The average thickness of the resin layer is 0.1 μm or more and 100 μm or less.

[0099]

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

[18] is resistant to a scratch resistance test of the first surface using steel wool under the following conditions.

[0100] Scratch resistance test: Use steel wool #0000 as the sliding sheet, with a load of 1000 g, a moving speed of 80 mm / second, a one-way moving distance of 40 mm, and reciprocate 1000 times.

[0101]

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

[19] is resistant to a scratch resistance test of the first surface using felt under the following conditions.

[0102] Scratch resistance test: Use "Jumbo Wearaser (registered trademark), product number: CS-7" manufactured by TABER as the sliding sheet, with a load of 200 g, a moving speed of 200 mm / second, a one-way moving distance of 50 mm, and reciprocate 10000 times.

[0103]

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

[20] .

[0104]

[22] The sheet article according to

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

[0105]

[23] A polarizing plate, which includes a first protective sheet, a polarizing element, and a second protective sheet,

[0106] At least one of the above-mentioned first protective sheet and the above-mentioned second protective sheet includes the optical sheet according to any one of [1] to

[20] .

[0107]

[24] A display device, which includes:

[0108] An image forming device; and

[0109] The optical sheet according to any one of [1] to

[20] that overlaps with the above-mentioned image forming device.

[0110]

[25] A panel, which includes:

[0111] An article to be joined; and

[0112] The optical sheet according to any one of [1] to

[20] that is joined to the above-mentioned article to be joined.

[0113]

[26] A method for selecting an optical sheet, which has the following steps for the following optical sheet,

[0114] The optical sheet has a first surface and a second surface facing the above-mentioned first surface, and includes a substrate and a functional layer in the order from the above-mentioned second surface to the above-mentioned first surface. The functional layer includes a binder component, hollow silica particles, and metal oxide particles other than silica particles,

[0115] The steps are:

[0116] A step of measuring the arithmetic mean roughness Sa of the above-mentioned first surface; and

[0117] A step of selecting an optical sheet with the arithmetic mean roughness Sa of 5.2 nm or less.

[0118]

[27] A method for manufacturing an optical sheet, which includes the following steps:

[0119] A step of manufacturing an optical sheet, the optical sheet has a first surface and a second surface facing the above-mentioned first surface, and includes a substrate and a functional layer in the order from the above-mentioned second surface to the above-mentioned first surface. The functional layer includes a binder component, hollow silica particles, and metal oxide particles other than silica particles; and

[0120] A step of evaluating the arithmetic mean roughness Sa of the above-mentioned first surface and selecting an optical sheet with the arithmetic mean roughness Sa of 5.2 nm or less.

[0121]

[28] A method for selecting an optical sheet, which comprises the following steps for the following optical sheet,

[0122] The optical sheet includes a first surface and a second surface facing the first surface, and has a substrate and a functional layer in the order from the second surface toward the first surface. The functional layer includes a binder component and hollow silica particles,

[0123] The steps are as follows:

[0124] A step of measuring the indentation hardness of the first surface with an indentation depth of 100 nm and the complex elastic modulus of the first surface with an indentation depth of 30 nm; and

[0125] A step of selecting an optical sheet based on the indentation hardness and the standard deviation of the complex elastic modulus at 10 different positions on the first surface.

[0126]

[29] A method for manufacturing an optical sheet, which comprises the following steps:

[0127] A step of manufacturing an optical sheet, the optical sheet includes a first surface and a second surface facing the first surface, and has a substrate and a functional layer in the order from the second surface toward the first surface. The functional layer includes a binder component and hollow silica particles; and

[0128] A step of selecting an optical sheet based on the indentation hardness of the first surface with an indentation depth of 100 nm and the standard deviation of the complex elastic modulus with an indentation depth of 30 nm at 10 different positions on the first surface.

[0129] Hereinafter, the details of the first embodiment and the second embodiment of the present disclosure will be described. In the accompanying drawings of this specification, for the convenience of illustration and understanding, the scale, the aspect ratio, etc. are appropriately changed and exaggerated compared with the actual object.

[0130] In this specification, terms such as "sheet", "film" and "plate" only have different names and are not distinguished from each other. For example, "optical sheet" and a member called an optical film or an optical plate cannot be distinguished only in terms of name difference.

[0131] In this specification, there are sometimes candidates for multiple upper limit values and candidates for multiple lower limit values of a numerical range described in different sentences. In this description, the numerical range can also be formed by combining any one candidate for the upper limit value and any one candidate for the lower limit value. As an example, the description "The value B can be equal to or greater than A1, can be equal to or greater than A2, and can also be equal to or greater than A3. The value B can be equal to or less than A4, can be equal to or less than A5, and can also be equal to or less than A6." is explained. In this example, the numerical range of the value B can be from A1 or more and A4 or less, can be from A1 or more and A5 or less, can be from A1 or more and A6 or less, can be from A2 or more and A4 or less, can be from A2 or more and A5 or less, can be from A2 or more and A6 or less, can be from A3 or more and A4 or less, can be from A3 or more and A5 or less, and can also be from A3 or more and A6 or less.

[0132] To clarify the directional relationship between the drawings, in several drawings, the common direction is indicated by arrows marked with the same reference numerals. The tip side of the arrow becomes the first side of each direction. The side opposite the tip of the arrow becomes the second side of each direction. For example, as Figure 1 shown, an arrow indicating the depth toward the paper surface along the direction perpendicular to the paper surface of the drawing is represented by a symbol with an "×" set in a circle. For example, as Figure 8 shown, an arrow indicating the depth from the paper surface toward the front along the direction perpendicular to the paper surface of the drawing is represented by a symbol with a dot set in a circle.

[0133] <<<<First Embodiment>>>>

[0134] The first embodiment will be described.

[0135] <<<Optical Sheet 10>>>

[0136] As Figure 1 shown, the optical sheet 10 of the first embodiment includes a first surface 11 and a second surface 12. The optical sheet 10 includes a substrate 20 and a functional layer 40A in this order from the second surface 12 to the first surface 11. The functional layer 40A includes a binder component 41, hollow silica particles 43, and metal oxide particles 45. The arithmetic mean roughness Sa of the first surface 11 is 5.2 nm or less. Based on the study of the reflection suppression function of the functional layer 40A, the refractive index of the functional layer 40A is lower than that of the binder component 41 by including the hollow silica particles 43. Due to the low refractive index functional layer 40A, the reflection of light incident on the first surface 11 can be suppressed.

[0137] The thickness of the functional layer 40A having an antireflection function is as thin as about 100 nm. In the case of a conventional optical sheet, the first surface sometimes gets damaged due to, for example, rubbing the low refractive index layer with a finger. In order to reduce the refractive index, the low refractive index layer contains hollow silica particles. The hollow silica particles have a relatively large particle size. On the other hand, since the hollow silica particles have a hollow structure, they are liable to be broken, and are also liable to be deformed and thus fall off from the binder component 41. Therefore, the abrasion resistance of the surface of the low refractive index layer of the conventional optical sheet is poor.

[0138] In contrast, according to the optical sheet 10 of the first embodiment in which the functional layer 40A contains metal oxide particles 45 in addition to the hollow silica particles 43 and the arithmetic mean roughness Sa of the first surface 11 is 5.2 nm or less, the first surface 11 has excellent abrasion resistance. Although the detailed reason for the improvement in the abrasion resistance is not clear, the following matters are presumed to contribute to the improvement in the abrasion resistance. However, the present disclosure is not limited to the following presumption.

[0139] First, in addition to the hollow silica particles 43, the functional layer 40A has metal oxide particles 45. In the binder component 41, in addition to the hollow silica particles 43, the metal oxide particles 45 are dispersed. The metal oxide particles 45 are interposed between the hollow silica particles 43 in the binder component 41. Thus, the hydroxyl groups of the metal oxide particles 45 can form hydrogen bonds with the hydroxyl groups of the hollow silica particles 43. In addition, the hydroxyl groups of the metal oxide particles 45 can also form hydrogen bonds with the hydroxyl groups of the binder component. It is presumed that, for example, in the binder component 41 as a binder resin, the metal oxide particles 45 are dispersed in addition to the hollow silica particles 43, whereby crosslinking in the functional layer 40A proceeds. The metal oxide particles 45 can connect the hollow silica particles 43 to the hollow silica particles 43. The metal oxide particles 45 can connect the hollow silica particles 43 to the binder component 41. It is presumed that in this way, due to the metal oxide particles 45, the strength and hardness of the functional layer 40A are enhanced, and the abrasion resistance of the first surface 11 formed of the functional layer 40A is enhanced.

[0140] <Arithmetic mean roughness Sa>

[0141] In addition, the arithmetic mean roughness Sa of the first surface 11 is 5.2 nm or less. By reducing it to 5.2 nm or less, excellent slidability is imparted to the first surface 11. By the combination of the improvement in slidability caused by the significant reduction in the arithmetic mean roughness Sa and the reinforcing effect brought about by the metal oxide particles 45, as confirmed in the examples described later, the abrasion resistance of the first surface 11 can be greatly improved. From the aspect of improving the abrasion resistance, the arithmetic mean roughness Sa can be 4.2 nm or less, or can be 3.5 nm or less.

[0142] The lower limit of the arithmetic mean roughness Sa of the first surface 11 is not particularly limited. The arithmetic mean roughness Sa of the first surface 11 can be 0 nm or more, or can be greater than 0 nm.

[0143] The arithmetic mean roughness Sa of the first surface 11 can be 0 nm or more and 5.2 nm or less, can be 0 nm or more and 4.2 nm or less, or can be 0 nm or more and 3.5 nm or less. The arithmetic mean roughness Sa of the first surface 11 can be greater than 0 nm and 5.2 nm or less, can be greater than 0 nm and 4.2 nm or less, or can be greater than 0 nm and 3.5 nm or less.

[0144] In the above-mentioned Patent Document 1 (WO2021 / 020504A), inorganic oxide particles are used to form convex portions on the surface. The metal oxide particles of Patent Document 1 are expected to protect the hollow silica particles by forming convex portions on the surface. In the first embodiment, the metal oxide particles 45 are used for an action quite different from that of Patent Document 1. As a result, the surface shape also has a configuration quite different from that of Patent Document 1, and excellent scratch resistance compared to Patent Document 1 can be achieved. In this regard, the effect of the first embodiment is a remarkable effect far beyond the range predicted by the technical level at the time of filing of this application.

[0145] The arithmetic mean roughness Sa is the three-dimensional arithmetic mean roughness defined in ISO25178. The three-dimensional arithmetic mean roughness is obtained by extending the arithmetic mean roughness Ra related to two-dimensional roughness to three dimensions. Regarding the arithmetic mean roughness Sa, orthogonal coordinate axes X and Y are set on the reference plane, the roughness surface is set as Z(x, y), the sizes of the reference plane are set as Lx and Ly, and it is calculated by the following formula (i). It should be noted that in formula (i), A = Lx × Ly.

[0146] [Equation 1]

[0147]

[0148] The arithmetic mean roughness Sa is a value obtained by an atomic force microscope (Atomic Force Microscope; AFM). A measurement sample is cut out from the optical sheet 10 as the object. The size of the measurement sample is a 5 mm × 5 mm square. It is visually confirmed that there is no foreign matter attachment, damage, etc. on the measurement sample. For five mutually separated measurement regions of the measurement sample, an atomic force microscope is used to measure the shape of the surface formed by the first surface of the optical sheet. The measurement region is a 10 μm × 10 μm square.

[0149] As the atomic force microscope, "SPM-9700" manufactured by Shimadzu Corporation can be used. As the cantilever, NCHR (resonance frequency: 320 kHz, spring constant 42 N / m) manufactured by NanoWorld can be used. The measurement of the surface shape of the sample can be carried out in the On-Line (measurement) mode using the software "SPM manager" attached to the atomic force microscope. The measurement conditions can be set as follows.

[0150] - Measurement mode: Phase

[0151] - Scanning range: 10 μm × 10 μm

[0152] - Scanning speed: 2.0 - 2.5 Hz (using a 10 μm scanner)

[0153] - Number of pixels: 512 × 512

[0154] <Scratch resistance>

[0155] In the optical sheet 10 of the first embodiment, the functional layer 40A contains a binder component 41, hollow silica particles 43, and metal oxide particles 45. The arithmetic mean roughness Sa of the first surface 11 is 5.2 nm or less. The optical sheet 10 of the first embodiment has excellent scratch resistance. The steel wool resistance and felt resistance of the optical sheet with excellent scratch resistance are both excellent. As an index indicating the scratch resistance of the surface of the optical sheet, pencil hardness is known. Pencil hardness is an index indicating the resistance when contacting a hard substance with a stress close to a point load. On the other hand, during repeated friction and long-term use, due to the stable application of a surface load, minute scratches can be generated. Regarding the resistance to this damage, it is appropriate to evaluate it as steel wool resistance and felt resistance. In the scratch resistance test of the first surface 11 using steel wool, the optical sheet 10 can have high resistance. In the scratch resistance test of the first surface 11 using felt, the optical sheet 10 can have high resistance.

[0156] (Steel wool scratch resistance)

[0157] The test result of the steel wool scratch resistance test becomes an index indicating the resistance to defects such as damage generated when pressing steel wool against the test sample to be evaluated and causing relative movement. The optical sheet 10 can be resistant to the steel wool scratch resistance test carried out under the conditions described below.

[0158] The test sample of the optical sheet to be evaluated is rectangular in shape. The short side of the rectangular shape is set to 50 mm, and the long side is set to 100 mm. Visually confirm that the test sample has no abnormalities such as dust or damage. Unfold the rectangular sample on the testing machine along the horizontal plane in a manner that does not cause wrinkles or warping. Fix the four corners of the unfolded sample to the testing machine using repair tape. The repair tape can be the product named "810-3-18" manufactured by 3M Company.

[0159] Bring the steel wool, which serves as the sliding sheet, into contact with the surface of the sample formed by the first surface of the optical sheet. The steel wool is "BONSTAR B-204" of number #0000 manufactured by Nippon Steel Wool Co., Ltd. BONSTAR B-204 has a business size of length: approximately 390 mm, width: approximately 75 mm, and thickness: approximately 110 mm. The contact area between the test sample and the sliding sheet is 20 mm × 20 mm. Apply a load of 1000 g to the sliding sheet from directly above in the vertical direction, and press the test sample unfolded along the horizontal plane against the sliding sheet.

[0160] With the sliding sheet pressed against the test sample from directly above in the vertical direction, move the sliding sheet and the sample relative to each other in the horizontal direction. Move the sliding sheet and the test sample relative to each other in a direction parallel to the main extension direction of the fibers of the steel wool. The relative movement is a reciprocating motion along a straight path. The cycle of the reciprocating motion is 1000 times. The speed of the reciprocating motion is 80 mm / second. The stroke during the reciprocating motion is 40 mm for both the forward and return strokes. The reciprocating motion is in the direction parallel to the long side of the sample.

[0161] The test environment is set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The test sample is placed in the test environment for 16 hours before the start of the test.

[0162] The slider is an unused product. Before conducting the test on the evaluation object, rub the steel wool on the sample for preparation to perform pre-treatment of the steel wool. The testing machine used in the test of the sample as the evaluation object is also used for the pre-treatment of the steel wool. The sample for preparation is a polyethylene terephthalate film. The sample for preparation is rectangular with a short side of 50 mm and a long side of 100 mm. Rub the steel wool on the surface of the polyethylene terephthalate film that has not been surface-treated. Unfold the sample for preparation along the horizontal plane and fix the four corners of the sample for preparation to the testing machine with repair tape. Press the steel wool against the sample for preparation from above in the vertical direction. The contact area between the sample for preparation and the steel wool is 20 mm × 20 mm. Press the steel wool against the sample for preparation with a load of 300 g. Move the steel wool pressed against the sample for preparation relative to the sample for preparation in the horizontal direction. Move the steel wool and the sample for preparation relative to each other in a direction parallel to the direction in which the fibers of the steel wool mainly extend. The relative movement is a reciprocating motion. The cycle of the reciprocating motion is 300 times. The speed of the reciprocating motion is 80 mm / second. The stroke in the reciprocating motion is 40 mm for both the forward and return strokes. In this way, the steel wool pressed against the sample for preparation is used for the test of the evaluation object.

[0163] After the abrasion resistance test, visually observe the surface of the test sample composed of the first surface of the optical sheet. The observation distance is 30 cm. The illuminance on the surface of the sample as the observation object is 800 Lx or more and 1200 Lx or less.

[0164] In the case where damage and other defects of a degree that would cause problems when applied to a display device are observed in the test sample, it is determined that the optical sheet 10 as the evaluation object does not have resistance to the abrasion resistance test using steel wool for the first surface 11. Conduct the abrasion resistance test 5 times on one optical sheet 10 as the evaluation object. In the case where no defects of a degree that would cause problems when applied to a display device occur in all 5 tests, it is judged that the optical sheet 10 as the evaluation object has resistance to the abrasion resistance test using steel wool for the first surface 11. In the 5 tests, replace the steel wool each time. The above-mentioned pre-treatment of the steel wool is implemented before the start of each of the 5 tests.

[0165] (Felt resistance)

[0166] The test result of the felt abrasion resistance test becomes an index indicating the resistance to damage and other defects generated when pressing a felt against the test sample as the evaluation object and moving it relatively. The optical sheet 10 can have resistance to the abrasion resistance test under the following conditions with the "Jumbo Wearaser (registered trademark) CS-7" manufactured by TABER Company as the slider.

[0167] The test sample of the optical sheet to be evaluated is rectangular. The short side of the rectangular shape is set to 50 mm, and the long side is set to 100 mm. Visually confirm that there are no abnormalities such as dust or damage on the test sample. Unfold the rectangular sample on the testing machine along the horizontal plane without causing wrinkles or warping. Fix the four corners of the unfolded sample to the testing machine using repair tape. The repair tape can be the product named "810-3-18" manufactured by 3M Company.

[0168] Bring the felt, which is a sliding sheet, into contact with the surface of the sample formed by the first surface of the optical sheet. The felt is "CS-7" of "Jumbo Wearaser (registered trademark)" manufactured by TABER Company. The contact area between the test sample and the sliding sheet is a circle with a diameter of 12 mm. Apply a load of 200 g to the sliding sheet from above in the vertical direction, and press the test sample unfolded along the horizontal plane against the sliding sheet.

[0169] With the sliding sheet pressed against the test sample from above in the vertical direction, move the sliding sheet and the sample relative to each other in the horizontal direction. The relative movement is a reciprocating motion along a straight path. The cycle of the reciprocating motion is 10,000 times. The speed of the reciprocating motion is 200 mm / second. The stroke in the reciprocating motion is 50 mm for both the forward and return strokes. The reciprocating motion is in the direction parallel to the long side of the sample.

[0170] The test environment is set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The test sample is placed in the test environment for 16 hours before the start of the test.

[0171] Use an unused sliding sheet. Before conducting the test on the object to be evaluated, rub the felt against the preparation sample to perform the pre-treatment of the felt. The testing machine used in the test of the sample to be evaluated is also used for the pre-treatment of the felt. The preparation sample is "single-sided easy-bonding type: A4160" manufactured by Toyobo Company. The preparation sample is rectangular with a short side of 50 mm and a long side of 100 mm. Unfold the preparation sample along the horizontal plane, and fix the four corners of the surface of the preparation sample that has not been subjected to the easy-bonding treatment (the surface where PET is exposed) to the testing machine using repair tape. Rub the felt against the untreated surface of the preparation sample. Press the felt against the preparation sample from above in the vertical direction. The contact area between the preparation sample and the felt is a circle with a diameter of 12 mm. The load for pressing the felt against the preparation sample is 600 g. Move the felt pressed against the preparation sample relative to the preparation sample in the horizontal direction. The relative movement is a reciprocating motion. The cycle of the reciprocating motion is 150 times. The speed of the reciprocating motion is 220 mm / second. The stroke in the reciprocating motion is 50 mm for both the forward and return strokes. In this way, the felt pressed against the preparation sample is used for the test of the object to be evaluated. Confirm that there is no fuzz on the flattened surface of the pressed felt and it is flat, and then conduct the test.

[0172] After the abrasion resistance test, the surface of the test sample formed by the first surface of the optical sheet is observed with the naked eye. The observation distance is 30 cm. The illuminance on the surface of the sample to be observed is 800 Lx or more and 1200 Lx or less.

[0173] In the case where defects such as damage to the extent that it becomes a problem when applied to a display device are observed in the test sample, it is determined that the optical sheet 10 to be evaluated does not have resistance to the abrasion resistance test of the first surface 11 with CS-7 as the sliding sheet. The abrasion resistance test is performed 5 times on one optical sheet 10 to be evaluated. In the case where no defects to the extent that it becomes a problem when applied to a display device occur in all 5 tests, it is judged that the optical sheet 10 to be evaluated has resistance to the abrasion resistance test of the first surface 11 with CS-7 as the sliding sheet. In the 5 tests, the same CS-7 is used. The pretreatment of the above CS-7 is performed before the start of each of the 5 tests.

[0174] <Coefficient of kinetic friction>

[0175] The coefficient of kinetic friction of the first surface 11 can also be reduced. By reducing the coefficient of kinetic friction, the slidability of the first surface 11 is improved, and the abrasion resistance can be improved.

[0176] The coefficient of kinetic friction between the first surface 11 and the felt to which a load of 500 g is applied can be 0.20 or less, can be 0.19 or less, can be 0.18 or less, and can also be 0.16 or less. The coefficient of kinetic friction between the first surface 11 and the steel wool to which a load of 500 g is applied can be 0.25 or less, can be 0.24 or less, can be 0.20 or less, and can also be 0.15 or less. There is no particular limitation on the lower limit of the coefficient of kinetic friction of the first surface 11. The coefficient of kinetic friction of the first surface 11 can be 0 or more, and can also be greater than 0.

[0177] The coefficient of kinetic friction between the first surface 11 and the felt to which a load of 500 g is applied can be 0 or more and 0.20 or less, can be 0 or more and 0.19 or less, can be 0 or more and 0.18 or less, and can also be 0 or more and 0.16 or less. The coefficient of kinetic friction between the first surface 11 and the felt to which a load of 500 g is applied can be greater than 0 and 0.20 or less, can be greater than 0 and 0.19 or less, can be greater than 0 and 0.18 or less, and can also be greater than 0 and 0.16 or less.

[0178] The coefficient of kinetic friction between the first surface 11 and the steel wool applied with a load of 500 g can be 0 or more and 0.25 or less, can be 0 or more and 0.24 or less, can be 0 or more and 0.20 or less, or can be 0 or more and 0.15 or less. The coefficient of kinetic friction between the first surface 11 and the steel wool applied with a load of 500 g can be greater than 0 and 0.25 or less, can be greater than 0 and 0.24 or less, can be greater than 0 and 0.20 or less, or can be greater than 0 and 0.15 or less.

[0179] The coefficient of kinetic friction is determined as the average value of 20 measured values of the coefficient of kinetic friction obtained from a test sample cut out from the optical sheet to be measured and for the test sample. Visually confirm that the test sample has no abnormalities such as dust and damage. The coefficient of kinetic friction of the test sample is measured as follows.

[0180] Fix the test sample of the optical sheet to the coefficient of kinetic friction measuring device as follows. First, unfold the test sample on a table as a sample fixing table in a manner that does not cause wrinkles, warping, etc. The table is unfolded along the horizontal plane. The test sample is unfolded along the horizontal plane. The size of the test sample is 15 cm × 25 cm. Fix the four corners of the unfolded test sample to the table with repair tape. The repair tape can be the product named "810-3-18" manufactured by 3M Company. In the test sample of the optical sheet fixed to the table, the second surface contacts the table, and the first surface faces the side opposite to the table.

[0181] Next, prepare a sliding sheet as the object for measuring the coefficient of friction with the first surface 11. As described above, the sliding sheet is felt or steel wool. The felt is the "Polishing Felt Sheet (No. 56901)" with a thickness of 1.0 mm manufactured by Nakanishi Company in Japan. The steel wool is the "BONSTAR B-204" with the number #0000 manufactured by Nippon Steel Wool Co., Ltd. in Japan. The size of the sliding sheet is 5 cm × 5 cm. Prepare a glass plate with a size of 5 cm × 5 cm. Fix the sliding sheet to the glass plate. The sliding sheet fixed to the glass plate is arranged in a manner that contacts the first surface of the test sample fixed to the table. Fix the auxiliary plate to the glass plate with double-sided tape. A hook or nylon line connected to a weight can be installed on the auxiliary plate.

[0182] While pressing the sliding sheet from above in the vertical direction onto the first surface of the test sample with a 500 g weight, move the sliding sheet in the horizontal direction. The moving direction of the sliding sheet is along the long side of the sample. The moving speed of the sliding sheet with the weight is 10 cm / minute. The stroke of the sliding sheet is 10 cm. During the period when the sliding sheet moves one stroke, measure the kinetic friction force acting on the sliding sheet in the horizontal direction every 0.01 seconds. The value obtained by dividing the average value of the measured values of the kinetic friction force by the weight of the weight (500 g) is used as the coefficient of kinetic friction.

[0183] The test environment is set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The test samples are conditioned in the test environment for 16 hours before the start of the test.

[0184] Before conducting the test on the evaluation object, the slider is rubbed against the preparation sample to perform pre-treatment of the slider. The pre-treatment is performed on a 5 cm × 5 cm slider fixed to a 5 cm × 5 cm glass plate. The testing machine used for the test of the sample as the evaluation object is also used for the pre-treatment of the slider. The preparation sample is "Single-sided easy-bonding type: A4160" manufactured by Toyobo Co., Ltd. The preparation sample is spread out along the horizontal plane, and the four corners of the non-easy-bonding-treated surface (the surface where PET is exposed) of the preparation sample are fixed to the testing machine with repair tape. The slider is pressed against the preparation sample from above in the vertical direction. The load of the slider pressed against the preparation sample is 600 g. The slider pressed against the preparation sample is relatively moved in the horizontal direction with respect to the preparation sample. The relative movement is a reciprocating motion. The cycle of the reciprocating motion is 150 times. The speed of the reciprocating motion is 220 mm / second. The stroke in the reciprocating motion is 50 mm for both the forward and return strokes. In this way, the slider pressed against the preparation sample is used for the test of the evaluation object.

[0185] Twenty measurements are performed on one test sample. The average value of the dynamic friction coefficient measurement values calculated in the 20 tests is used as the value of the dynamic friction coefficient of the evaluation object. In the 20 tests on the evaluation object, the same slider is used. The pre-treatment of the slider is performed separately in each of the 20 tests.

[0186] The dynamic friction coefficient is measured according to JIS K7125:1999 under conditions other than the above.

[0187] <Relationship between the average particle size of metal oxide particles 45 and the average thickness of functional layer 40A>

[0188] The average particle size of the metal oxide particles 45 can be smaller than the average thickness of the functional layer 40A. The average particle size of the metal oxide particles 45 can be smaller than half of the average thickness of the functional layer 40A, can be smaller than 1 / 3 of the average thickness of the functional layer 40A, can be smaller than 1 / 4 of the average thickness of the functional layer 40A, or can be smaller than 1 / 5 of the average thickness of the functional layer 40A.

[0189] By setting the average particle diameter of the metal oxide particles 45 and the average thickness of the functional layer 40A as described above, it is possible to suppress the formation of large protrusions on the surface of the functional layer 40A by the metal oxide particles 45. In addition, the metal oxide particles 45 easily enter between adjacent hollow silica particles 43. The adjacent hollow silica particles 43 are connected by the metal oxide particles 45. Thus, the strength and hardness of the functional layer 40A are enhanced by the metal oxide particles 45. In addition, the detachment of the hollow silica particles 43 can also be suppressed. By adjusting the average particle diameter of the metal oxide particles 45 as described above, the slidability of the first surface 11 is improved, and the functional layer 40A is strengthened, and the scratch resistance of the first surface 11 can be improved.

[0190] The ratio of the average particle diameter of the metal oxide particles 45 to the average thickness of the functional layer 40A (average particle diameter of the metal oxide particles 45 / average thickness of the functional layer 40A) can be 0 or more and less than 1, can be 0 or more and less than 0.5, can be 0 or more and less than 1 / 3, can be 0 or more and less than 0.25, or can be 0 or more and less than 0.2. The ratio of the average particle diameter of the metal oxide particles 45 to the average thickness of the functional layer 40A can be greater than 0 and less than 1, can be greater than 0 and less than 0.5, can be greater than 0 and less than 1 / 3, can be greater than 0 and less than 0.25, or can be greater than 0 and less than 0.2.

[0191] The "average particle diameter" used for particles such as the metal oxide particles 45, the hollow silica particles 43, and the solid silica particles 44 described later is a value determined by the following (1) to (3).

[0192] (1) Observe the cross-section of the optical sheet containing the particles with a transmission electron microscope (TEM: Transmission Electron Microscope), and obtain an observation image by photographing.

[0193] (2) Extract any 10 particles from the observation image, and measure the particle diameter of each particle. The particle diameter (nm) is the distance between the two straight lines in the combination of the two straight lines with the largest distance between them when the cross-section of the particle is clamped by any two parallel straight lines. That is, the particle diameter is the maximum length of the particle in the observation image.

[0194] (3) Perform the operations of (1) and (2) on the same optical sheet to be measured 5 times, and measure the particle diameters of a total of 50 particles. The average value of the total 50 particle diameter measurement values is used as the average particle diameter (nm) of the particles.

[0195] Figure 2This is an example of an observation image of an optical sheet using a scanning transmission electron microscope (STEM), which is a type of transmission electron microscope. In this observation, the acceleration voltage was set to 10 kV to 30 kV, and the magnification was set to 50,000 to 300,000 times. Figure 2 The photograph shows the observation results at an acceleration voltage of 30 kV and a magnification of 200,000 times. As Figure 2 shown, the particles sometimes aggregate, but the particle size is determined as the particle size (maximum length) of each particle. That is, the particle size is the primary particle size, and the average particle size is the average primary particle size.

[0196] The "average thickness" of the functional layer 40A is a value determined by the following (4) to (6).

[0197] (4) Photograph the cross-section of the optical sheet containing the functional layer using a transmission electron microscope (TEM).

[0198] (5) Measure the thickness of the functional layer at the central position along the plane of the optical sheet and the thickness of the functional layer at positions 100 nm offset from the central position to both sides along the plane of the optical sheet in the photographed image. The thickness is the length (nm) of the functional layer in the direction orthogonal to the plane of the optical sheet.

[0199] (6) Perform the operations of (4) and (5) five times on the same optical sheet to be measured, and measure the thickness of the functional layer at a total of 15 positions. Take the average of the total 15 thickness measurement values as the average thickness (nm) of the functional layer.

[0200] <Relationship between the average particle size of metal oxide particles 45 and the average particle size of hollow silica particles 43>

[0201] The average particle size (nm) of the metal oxide particles 45 can be smaller than the average particle size (nm) of the hollow silica particles 43. The average particle size (nm) of the metal oxide particles 45 can be less than 1 / 2 of the average particle size (nm) of the hollow silica particles 43, can be less than 1 / 3 of the average particle size (nm) of the hollow silica particles 43, can be less than 1 / 4 of the average particle size (nm) of the hollow silica particles 43, or can be less than 1 / 5 of the average particle size (nm) of the hollow silica particles 43.

[0202] By adjusting the average particle diameter of the metal oxide particles 45 and the average particle diameter of the hollow silica particles 43 as described above, the metal oxide particles 45 can enter between the hollow silica particles 43 within the functional layer 40A. By the metal oxide particles 45 entering between the hollow silica particles 43, the bonding between the metal oxide particles 45 and the hollow silica particles 43 is promoted, crosslinking occurs within the functional layer 40A, and the functional layer 40A is further strengthened. In addition, while increasing the total blending amount of the particles within the functional layer 40A, the particles including the hollow silica particles 43 and the metal oxide particles 45 can be similarly dispersed within the functional layer 40A, and thus it is less likely to form protrusions on the first surface 11. As a result, the slidability of the first surface 11 is also improved. Thereby, the scratch resistance of the first surface 11 can be further improved.

[0203] The ratio of the average particle diameter of the metal oxide particles 45 to the average particle diameter of the hollow silica particles 43 (average particle diameter of the metal oxide particles 45 / average particle diameter of the hollow silica particles 43) can be 0 or more and less than 1, can be 0 or more and less than 0.5, can be 0 or more and less than 1 / 3, can be 0 or more and less than 0.25, or can be 0 or more and less than 0.2. The ratio of the average particle diameter of the metal oxide particles 45 to the average particle diameter of the hollow silica particles 43 can be greater than 0 and less than 1, can be greater than 0 and less than 0.5, can be greater than 0 and less than 1 / 3, can be greater than 0 and less than 0.25, or can be greater than 0 and less than 0.2.

[0204] When the ratio of the average particle diameter of the metal oxide particles 45 to the average particle diameter of the hollow silica particles 43 is small, as Figure 1 , Figure 2 shown, aggregation of the metal oxide particles 45 occurs. By the aggregated metal oxide particles 45, two adjacent hollow silica particles 43 are more firmly connected. By the aggregated metal oxide particles 45, the hollow silica particles 43 and the binder component 41 are more firmly connected. Thereby, the strength and hardness of the functional layer 40A are enhanced, and the scratch resistance of the first surface 11 can be further improved.

[0205] The metal oxide particles 45 may also include alumina particles 46. Alumina, which is an oxide of aluminum, can bind to the hollow silica particles 43 and the binder component 41 within the functional layer 40A. Therefore, crosslinking occurs within the functional layer 40A, and the functional layer 40A is further strengthened. The strength and hardness of the functional layer 40A are enhanced, and the scratch resistance of the first surface 11 can be further improved. In addition, alumina has a relatively low refractive index among the metal oxide particles. Therefore, the refractive index of the functional layer 40A can be reduced, and an excellent reflection suppression function can be imparted to the functional layer 40A.

[0206] The functional layer 40A may also contain solid silica particles 44. The solid silica particles 44 form hydrogen bonds with the metal oxide particles 45, which can promote crosslinking within the functional layer 40A. The particle size of the solid silica particles 44 is generally smaller than that of the hollow silica particles 43. Therefore, the solid silica particles 44 can enter between adjacent hollow silica particles 43 within the functional layer 40A. By including the solid silica particles 44 in the functional layer 40A, the strength and hardness of the functional layer 40A are enhanced, and the scratch resistance of the first surface 11 can be further improved. In addition, the refractive index of the solid silica particles 44 is lower than that of many metal oxide particles 45. Therefore, by including the metal oxide particles 45 and the solid silica particles 44 in the functional layer 40A, the refractive index of the functional layer 40A can be reduced. That is, by including the metal oxide particles 45 and the solid silica particles 44 in the functional layer 40A, the reflection suppression function of the functional layer 40A can be enhanced.

[0207] <Visual reflectance Y value>

[0208] The optical sheet 10 has a reflection suppression function for suppressing the reflection of light incident on the first surface 11. The visual reflectance Y value of the first surface 11 measured at an incident angle of 5° may be 1.0% or less, may be 0.8% or less, may be 0.7% or less, may be 0.6% or less, or may be 0.5% or less.

[0209] The lower limit of the visual reflectance is not particularly limited. The visual reflectance Y value of the first surface 11 measured at an incident angle of 5° may be 0% or more, or may be greater than 0%. The visual reflectance Y value of the first surface 11 may be 0% or more and 1.0% or less, may be 0% or more and 0.8% or less, may be 0% or more and 0.7% or less, may be 0% or more and 0.6% or less, or may be 0% or more and 0.5% or less. The visual reflectance Y value of the first surface 11 may be greater than 0% and 1.0% or less, may be greater than 0% and 0.8% or less, may be greater than 0% and 0.7% or less, may be greater than 0% and 0.6% or less, or may be greater than 0% and 0.5% or less.

[0210] The visual reflectance Y value refers to the visual reflectance Y value of the CIE1931 standard colorimetric system. The visual reflectance Y value is measured using a spectrophotometer as follows.

[0211] A sample is cut out from the optical sheet 10 that is the object of evaluation. Visually confirm that there are no abnormalities such as dust or damage in the sample. A black plate is adhered to the surface of the sample formed by the second surface of the optical sheet through an optically transparent adhesive sheet. The optically transparent adhesive sheet is "Panaclean PD-S1" manufactured by Panac company. The black plate is "COMOGLASDFA2CG502K (black) series" manufactured by KURARAY company. The thickness of the black plate is 2 mm. The total light transmittance of the black plate is 1% or less. Thus, an evaluation sample A including the optical sheet, the optically transparent adhesive sheet, and the black plate is produced.

[0212] Light is irradiated onto the surface of the evaluation sample A formed by the first surface of the optical sheet at an incident angle of 5°. Based on the specularly reflected light in the evaluation sample A, the reflectance (visual reflectance Y value) of the evaluation sample is measured. Using the auxiliary light source C and a 2-degree field of view, the visual reflectance Y (%) is obtained based on the specular reflectance measured at 0.5-nm intervals in the range from 300 nm to 780 nm. Before measuring the visual reflectance Y value of the optical sheet 10, the auxiliary light source C is lit for 15 minutes to stabilize the output of the auxiliary light source C. The test environment during the measurement of the visual reflectance is set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before the start of the test.

[0213] Other measurement conditions during the measurement of the visual reflectance are in accordance with JIS Z 8722:2009.

[0214] The visual reflectance is the arithmetic mean of 5 measurement values. The 5 measurement values are the measurement values measured at 5 measurement positions of the optical sheet that is the object of evaluation. The 5 measurement positions are located at positions separated from each other by 10 mm or more.

[0215] <Total light transmittance>

[0216] The total light transmittance of the optical sheet 10 can be 50% or more, can be 70% or more, can be 80% or more, or can be 90% or more. There is no particular upper limit for the total light transmittance of the optical sheet 10.

[0217] The total light transmittance of the optical sheet 10 can be 100% or less, or can be less than 100%. The total light transmittance of the optical sheet 10 can be 50% or more and 100% or less, can be 70% or more and 100% or less, can be 80% or more and 100% or less, or can be 90% or more and 100% or less. The total light transmittance of the optical sheet 10 can be 50% or more and less than 100%, can be 70% or more and less than 100%, can be 80% or more and less than 100%, or can be 90% or more and less than 100%.

[0218] In the measurement of the total light transmittance (%), a light source simulating the spectrum of the D65 standard light (referred to as the "D65 light source") is used. Before measuring the total light transmittance of the optical sheet 10, the D65 light source is turned on for 15 minutes to stabilize the output of the D65 light source. When measuring the total light transmittance, the incident angle of the sample is set to 0°. The incident surface when measuring the total light transmittance is the second surface 12 of the optical sheet 10. The test environment when measuring the total light transmittance is set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before the start of the test. Other measurement conditions when measuring the total light transmittance are in accordance with JIS K7361-1:1997.

[0219] The total light transmittance is the arithmetic mean of 5 measured values. The 5 measured values are the measured values obtained at 5 measurement positions of the optical sheet to be evaluated. The 5 measurement positions are located at positions separated from each other by more than 10 mm.

[0220] <Transmission haze>

[0221] The transmission haze of the optical sheet 10 can be 1.0% or less, can be 0.5% or less, or can be 0.2% or less. There is no particular lower limit for the transmission haze of the optical sheet 10. The transmission haze of the optical sheet 10 can be 0%, or can be greater than 0%.

[0222] The transmission haze of the optical sheet 10 can be 0% or more and 1.0% or less, can be 0% or more and 0.5% or less, or can be 0% or more and 0.2% or less. The transmission haze of the optical sheet 10 can be greater than 0% and 1.0% or less, can be greater than 0% and 0.5% or less, or can be greater than 0% and 0.2% or less.

[0223] In the measurement of the transmission haze (%), the D65 light source is used. Before measuring the transmission haze of the optical sheet 10, 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 incident angle of the sample is set to 0°. The incident surface when measuring the transmission haze is the second surface 12 of the optical sheet 10. The test environment when measuring the transmission haze is set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before the start of the test. Other measurement conditions when measuring the transmission haze are in accordance with JIS K7136:2000.

[0224] The transmission haze is the arithmetic mean of 5 measured values. The 5 measured values are the measured values obtained at 5 measurement positions of the optical sheet to be evaluated. The 5 measurement positions are located at positions separated from each other by more than 10 mm.

[0225] As Figure 1As shown, the optical sheet 10 may also include a resin layer 30 located between the substrate 20 and the functional layer 40A. The resin layer 30 may also include a cured product of a curable resin composition. The resin layer 30 containing the cured product of the curable resin composition has high strength and high hardness. By supporting the functional layer 40A by laminating it on the resin layer 30, the scratch resistance of the first surface 11 can be further improved.

[0226] Hereinafter, each layer of the optical sheet 10 shown will be further described in detail. Figure 1 in the Figure 1 In the example shown, the substrate 20, the resin layer 30, and the functional layer 40A are laminated in the third direction D3. That is, the third direction D3 is the lamination direction. The substrate 20, the resin layer 30, and the functional layer 40A extend in the first direction D1 and the second direction D2 orthogonal to the third direction D3. In the example shown, the first direction D1 and the second direction D2 are orthogonal to each other. In Figure 1 In the optical sheet 10 shown, the first surface 11 is constituted by the functional layer 40A. The second surface 12 is constituted by the substrate 20.

[0227] It should be noted that the optical sheet 10 sometimes also has an antistatic layer and an antifouling layer, and these layers are supported by the functional layer 40A to constitute the first surface 11. These antistatic layers, antifouling layers, etc. are very thin layers. Otherwise, the functional layer 40A cannot effectively exert the reflection suppression function. Therefore, in the example where the antistatic layer, the antifouling layer, etc. constitute the first surface 11, the scratch resistance of the first surface 11 is also affected by the functional layer 40A. That is, according to the above functional layer 40A, the scratch resistance of the first surface 11 can be significantly improved.

[0228] <<Substrate 20>>

[0229] The substrate 20 supports the resin layer 30 and the functional layer 40A. The substrate 20 may also be transparent. Transparent means that the total light transmittance according to JIS K7361-1:1997 is 50% or more, may be 70% or more, may be 80% or more, or may be 90% or more.

[0230] The material of the substrate 20 is not particularly limited, and the material of the substrate 20 may be resin or glass. Resin is preferred in terms of light weight and ease of manufacture.

[0231] The resin used in the base material 20 may be a polyolefin resin such as polyethylene or polypropylene. The resin used in the resin layer 30 may be a vinyl resin such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer. The resin used in the base material 20 may also be a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate. The resin used in the base material 20 may also be an acrylic resin such as poly(methyl)methacrylate, poly(methyl)acrylate. The resin used in the base material 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. As the resin used in the base material 20, a cycloolefin resin obtained from a resin such as polycarbonate, a polyimide resin, norbornene, dicyclopentadiene and the like may also be exemplified. The resin layer 30 may contain only one of the above resins, or may contain two or more of the above resins.

[0232] The thickness of the resin base material 20 is not particularly limited. From the viewpoint of operability, the thickness of the resin base material 20 may be 10 μm or more, may be 20 μm or more, or may be 50 μm or more. The thickness of the resin base material 20 may be 500 μm or less, may be 400 μm or less, or may be 300 μm or less. The thickness of the resin base material 20 may also be 500 μm or more.

[0233] When the optical sheet 10 is applied to a foldable use, the base material 20 may also have flexibility. In this case, the thickness of the resin base material 20 may also be 10 μm or more and 40 μm or less. When the optical sheet 10 is used in lamination with glass, from the viewpoint of preventing glass scattering, the thickness of the resin base material 20 may also be 40 μm or more and 100 μm or less.

[0234] The base material 20 may contain only a single layer, or may contain a plurality of layers. The base material 20 may also contain an undercoat layer such as an easy-bonding layer.

[0235] <<Functional layer 40A>>

[0236] The functional layer 40A contains a binder component 41, hollow silica particles 43, and metal oxide particles 45 other than silica particles. By containing the hollow silica particles 43, the functional layer 40A reduces the refractive index. The functional layer 40A can have a refractive index lower than that of the binder component 41. The refractive index of the functional layer 40A may be lower than the refractive index of the base material 20. The refractive index of the functional layer 40A may be lower than the refractive index of the layer adjacent to the functional layer 40A.

[0237] The functional layer 40A can function to suppress the reflection of incident light due to its refractive index and thickness. The antireflection function brought about by the functional layer 40A is based on the interference of light reflected from the two surfaces on both sides of the functional layer 40A. From the aspect of making this reflection suppression function effective, the refractive index of the functional layer 40A can be between the refractive indices of the two regions adjacent to the functional layer 40A on both sides. In addition, the thickness (nm) of the functional layer 40A can also be about 1 / 4 of the wavelength λ (nm) of the light whose reflection is to be suppressed.

[0238] From the aspect of the reflection suppression function, the refractive index of the functional layer and the average thickness of the functional layer can be set as follows.

[0239] The refractive index of the functional layer can be 1.10 or more and 1.48 or less, can be 1.20 or more and 1.48 or less, can be 1.26 or more and 1.48 or less, can be 1.28 or more and 1.48 or less, and can also be 1.30 or more and 1.48 or less. The refractive index of the functional layer can be 1.10 or more and 1.45 or less, can be 1.20 or more and 1.45 or less, can be 1.26 or more and 1.45 or less, can be 1.28 or more and 1.45 or less, and can also be 1.30 or more and 1.45 or less. The refractive index of the functional layer can be 1.10 or more and 1.40 or less, can be 1.20 or more and 1.40 or less, can be 1.26 or more and 1.40 or less, can be 1.28 or more and 1.40 or less, and can also be 1.30 or more and 1.40 or less. The refractive index of the functional layer can be 1.10 or more and 1.38 or less, can be 1.20 or more and 1.38 or less, can be 1.26 or more and 1.38 or less, can be 1.28 or more and 1.38 or less, and can also be 1.30 or more and 1.38 or less. The refractive index of the functional layer can be 1.10 or more and 1.35 or less, can be 1.20 or more and 1.35 or less, can be 1.26 or more and 1.35 or less, can be 1.28 or more and 1.35 or less, and can also be 1.30 or more and 1.35 or less. The refractive index used for the constituent elements constituting the optical sheet is the refractive index for a wavelength of 589.3 nm.

[0240] The thickness of the functional layer can be 80 nm or more and 150 nm or less, can be 85 nm or more and 150 nm or less, and can also be 90 nm or more and 150 nm or less. The thickness of the functional layer can be 80 nm or more and 110 nm or less, can be 85 nm or more and 110 nm or less, and can also be 90 nm or more and 110 nm or less. The thickness of the functional layer can be 80 nm or more and 105 nm or less, can be 85 nm or more and 105 nm or less, and can also be 90 nm or more and 105 nm or less.

[0241] <Binder component 41>

[0242] The binder component 41 is an element for holding the hollow silica particles 43. The binder component 41 can also function as a binder for forming a coating film. By having the binder component 41 hold the particles contained in the functional layer 40A, the functional layer 40A can maintain its film form. The binder component 41 may also contain a resin. The resin contained in the binder component 41 can be a natural resin or a synthetic resin. The binder component 41 may also wrap the particles contained in the functional layer 40A. The binder component 41 can completely surround each of the particles contained in the functional layer 40A, or may partially expose at least a part of the particles contained in the functional layer 40A.

[0243] The binder component 41 may also contain a cured product of a curable resin composition. The curable resin composition may also contain one or more of a thermosetting resin composition and a radiation-curable resin composition. The cured product of the curable resin composition can impart high strength and high hardness to the functional layer 40A and improve the scratch resistance of the first surface 11. From the viewpoint of improving scratch resistance, the radiation-curable resin composition is particularly useful.

[0244] The thermosetting resin composition contains a thermosetting resin. The thermosetting resin composition cures by heating. Examples of the thermosetting resin include acrylic resins, urethane resins, phenolic resins, urea-melamine resins, epoxy resins, unsaturated polyester resins, silicone resins, and the like. The thermosetting resin composition may also contain a curing agent.

[0245] The radiation-curable resin composition contains a radiation-curable compound. The radiation-curable compound contains a radiation-curable functional group. Examples of the radiation-curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl, vinyl, and allyl, and epoxy groups, oxetanyl groups, and the like. The radiation-curable compound may contain two or more radiation-curable functional groups. The radiation-curable compound may also be a compound having an ethylenically unsaturated bond group. The radiation-curable compound may also be a (meth)acrylate-based compound having a (meth)acryloyl group. The radiation-curable compound may also be a siloxane compound containing a siloxane bond.

[0246] Hereinafter, a (meth)acrylate-based compound having four or more ethylenically unsaturated bond groups will be referred to as a "polyfunctional (meth)acrylate-based compound". A (meth)acrylate-based compound having two to three ethylenically unsaturated bond groups will be referred to as a "low-functional (meth)acrylate-based compound".

[0247] (Meth)acrylate compounds can be monomers or oligomers. According to the radiation-curable compound containing a low-functional (meth)acrylate compound, uneven shrinkage during curing can be suppressed, and the surface of the functional layer 40A can be smoothed.

[0248] The proportion of the low-functional (meth)acrylate compound in the radiation-curable compound can be 60% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass. From the aspect of suppressing uneven shrinkage during curing and smoothing the uneven shape of the surface of the functional layer 40A, the low-functional (meth)acrylate compound can also be a (meth)acrylate compound containing two ethylenically unsaturated bond groups. When the radiation-curable compound contains a large amount of a polyfunctional (meth)acrylate compound, as described later, by appropriately adjusting the type of solvent and drying conditions, the surface of the functional layer can be smoothed.

[0249] Examples of the difunctional (meth)acrylate compound in the (meth)acrylate compound include polyalkylene glycol di(meth)acrylates such as di(meth)acryloyl isocyanurate, ethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, polybutylene glycol di(meth)acrylate, bisphenol A tetraethoxy diacrylate, bisphenol A tetrapropoxy diacrylate, 1,6-hexanediol diacrylate, etc. Examples of the trifunctional (meth)acrylate compound include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, isocyanuric acid-modified tri(meth)acrylate, etc. Examples of the polyfunctional (meth)acrylate compound having four or more functional groups include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, etc. The (meth)acrylate compound can be modified as described later.

[0250] Examples of the (meth)acrylate oligomer include acrylate polymers such as urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, and polyether (meth)acrylate. Urethane (meth)acrylate is obtained, for example, by the reaction of a polyol, an organic diisocyanate, and a hydroxy (meth)acrylate. The epoxy (meth)acrylate may also be a (meth)acrylate obtained by reacting an aromatic epoxy resin, an alicyclic epoxy resin, an aliphatic epoxy resin, etc. having 3 or more functional groups with (meth)acrylic acid. The epoxy (meth)acrylate may also be a (meth)acrylate obtained by reacting an aromatic epoxy resin, an alicyclic epoxy resin, an aliphatic epoxy resin, etc. having 2 or more functional groups with a polybasic acid and (meth)acrylic acid. The epoxy (meth)acrylate may also be a (meth)acrylate obtained by reacting an aromatic epoxy resin, an alicyclic epoxy resin, an aliphatic epoxy resin, etc. having 2 or more functional groups with a phenol and (meth)acrylic acid.

[0251] From the aspect of suppressing uneven shrinkage caused by crosslinking, the (meth)acrylate compound may modify a part of the molecular skeleton. The (meth)acrylate compound may be modified, for example, with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, an alkyl group, a cyclic alkyl group, an aromatic group, bisphenol, etc. The above (meth)acrylate compound may also be modified with an alkylene oxide such as ethylene oxide and propylene oxide. The proportion of the alkylene oxide-modified (meth)acrylate compound in the radiation-curable compound may be 60% by mass or more, may be 80% by mass or more, may be 90% by mass or more, may be 95% by mass or more, or may be 100% by mass. The alkylene oxide-modified (meth)acrylate compound may be a low-functional (meth)acrylate compound or a (meth)acrylate compound having 2 ethylenically unsaturated bond groups.

[0252] Examples of the alkylene oxide-modified (meth)acrylate compound having 2 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 repeating unit 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 the alkylene oxide-modified (meth)acrylate compound having 3 ethylenically unsaturated bond groups include trimethylolpropane alkylene oxide-modified tri(meth)acrylate and isocyanuric acid alkylene oxide-modified tri(meth)acrylate.

[0253] Examples of the siloxane compound include (poly)dimethylsiloxane, (poly)diethylsiloxane, (poly)diphenylsiloxane, (poly)methylphenylsiloxane, alkyl-modified (poly)dimethylsiloxane, azo group-containing (poly)dimethylsiloxane, dimethyl silicone, phenylmethyl silicone, alkyl-arylalkyl-modified silicone, fluorosilicone, polyether-modified silicone, fatty acid ester-modified silicone, methylhydrosilicone, silanol group-containing silicone, alkoxy group-containing silicone, phenol group-containing silicone, methacrylic acid-modified silicone, acrylic acid-modified silicone, amino group-modified silicone, carboxylic acid-modified silicone, methanol-modified silicone, epoxy-modified silicone, mercapto group-modified silicone, fluorine-modified silicone, polyether-modified silicone, etc.

[0254] One kind of radiation curable compound may be used alone, or two or more kinds of radiation curable compounds may be used in combination.

[0255] When the radiation curable compound is an ultraviolet curable compound, the curable resin composition forming the binder component 41 may also contain additives such as a photoinitiator and a photopolymerization accelerator. Examples of the photoinitiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzoin dimethyl ether, benzoyl benzoate, α-acyl oxime ester, α-aminoalkylphenone, thioxanthones, etc. The photopolymerization accelerator can reduce the polymerization hindrance caused by air during curing and accelerate the curing speed. Examples of the photopolymerization accelerator include one or more selected from isopentyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate, etc.

[0256] <Particles (hollow silica particles 43, solid silica particles 44, metal oxide particles 45)>

[0257] In addition to the binder component 41, the functional layer 40A further contains hollow silica particles 43 and metal oxide particles 45 other than silica particles. The functional layer 40A may also contain other particles. Examples of the other particles include inorganic particles such as magnesium fluoride particles and organic particles.

[0258] The functional layer 40A contains hollow silica particles 43 as silica particles. The hollow silica particles 43 have a shell layer made of silica. In the hollow silica particles 43, the particle interior surrounded by the shell layer becomes a cavity. Air may be contained inside the cavity. The hollow silica particles 43 have a refractive index lower than that of silica by including internal cavities. If the volume of the internal cavity is large, the refractive index of the hollow silica particles 43 becomes lower. The hollow silica particles 43 lower the refractive index of the entire functional layer 40A. By using large-sized hollow silica particles 43 with an increased internal space ratio, the refractive index of the functional layer 40A can be further reduced.

[0259] The hollow silica particles 43 can be uniformly dispersed in the functional layer 40A. By uniformly dispersing the hollow silica particles 43 in the functional layer 40A, the first surface 11 is smoothed, and the arithmetic mean roughness Sa of the first surface 11 can be reduced. Thereby, the slidability of the first surface 11 is improved, and the scratch resistance of the first surface 11 is enhanced. By reducing the particle size deviation of the hollow silica particles 43, adjusting the average particle size of the hollow silica particles 43 relative to the average film thickness of the binder component 41, adjusting the affinity between the hollow silica particles 43 and the binder component 41, adjusting the content ratio or average particle size ratio between the hollow silica particles 43 and other particles, adjusting the affinity between the hollow silica particles 43 and other particles, etc., the hollow silica particles 43 can be uniformly dispersed in the functional layer 40A.

[0260] As Figure 1 shown, in addition to the hollow silica particles 43, the functional layer 40A may further contain solid silica particles 44. The solid silica particles 44 are non-hollow silica particles. The solid silica particles 44 are particles without internal voids. The solid silica particles 44 may be solid silica particles. The solid silica particles, by being dispersed in the binder component 41, play a role in enhancing the scratch resistance of the functional layer 40A.

[0261] The solid silica particles 44 can be uniformly dispersed in the functional layer 40A together with the hollow silica particles 43. By uniformly dispersing the solid silica particles 44 in the functional layer 40A together with the hollow silica particles 43, the first surface 11 is smoothed, and the arithmetic mean roughness Sa of the first surface 11 can be reduced. Thereby, the slidability of the first surface 11 is improved, and the scratch resistance of the first surface 11 is enhanced. By adjusting the content ratio, average particle size ratio between the solid silica particles 44 and other particles, adjusting the affinity between the solid silica particles 44 and other particles, etc., the solid silica particles 44 can be uniformly dispersed in the functional layer 40A together with the hollow silica particles 43. In Figure 2 the example shown, the hollow silica particles 43 and the solid silica particles 44 are uniformly dispersed in the functional layer 40A.

[0262] The functional layer 40A contains metal oxide particles 45 other than silica particles. As described above, the metal oxide particles 45 other than silica particles enhance the strength and hardness of the functional layer 40A and improve the scratch resistance of the first surface 11. As the metal oxide particles 45, single substances or mixtures of oxides of any one of titanium, tantalum, zirconium, chromium, niobium, cerium, hafnium, and yttrium can be exemplified.

[0263] The metal oxide particles 45 may include alumina particles 46. The alumina particles 46 have a lower refractive index in the metal oxide. Alumina is alumina represented by Al2O3, and is known to have α-type, γ-type, σ-type, and mixtures thereof. The alumina particles 46 may also be modified alumina particles with a modified surface. Examples of the modified alumina particles include (meth)acrylic acid-modified alumina particles and silicone-modified alumina particles. The metal oxide particles 45 may be hollow particles having an internal space or solid particles not having an internal space.

[0264] The shapes of the particles such as the hollow silica particles 43, the solid silica particles 44, and the metal oxide particles 45 dispersed in the functional layer 40A are not particularly limited. The shapes of the particles such as the hollow silica particles 43, the solid silica particles 44, and the metal oxide particles 45 dispersed in the functional layer 40A may be spherical, ellipsoidal, polyhedral shapes approximating a sphere, etc., approximate spherical, rod-shaped, plate-shaped, fibrous, irregular shapes, etc. By making the shapes of the particles such as the hollow silica particles 43, the solid silica particles 44, or the metal oxide particles 45 dispersed in the functional layer 40A spherical, ellipsoidal, or approximately spherical, the slidability of the first surface 11 is improved and the scratch resistance of the first surface 11 is enhanced.

[0265] The particles such as the hollow silica particles 43, the solid silica particles 44, and the metal oxide particles 45 dispersed in the functional layer 40A may have their surfaces coated with a silane coupling agent. The silane coupling agent may include 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 and the particles are less likely to aggregate. As a result, the particles are more uniformly dispersed in the binder component.

[0266] Examples of the silane coupling agent 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-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 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, 3,3,3-trifluoropropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and the like. Particularly, it may be one or more selected from 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0267] As Figure 2 shown, the particles contained in the functional layer 40A such as the hollow silica particles 43 and the solid silica particles 44 may also be present at a high concentration in the functional layer 40A and uniformly dispersed in the functional layer 40A. According to such a configuration, as described above, the first surface 11 is smoothed and the coefficient of kinetic friction of the first surface 11 is reduced, whereby the scratch resistance of the first surface 11 can be improved. As Figure 1 and Figure 2 shown, the hollow silica particles 43 having a large average particle diameter are dispersed in the functional layer 40A at a high density. The metal oxide particles 45 and the solid silica particles 44 are dispersed in the functional layer 40A so as to fill the spaces between the hollow silica particles 43. The metal oxide particles 45 and the solid silica particles 44 are arranged in the functional layer 40A in proximity to the hollow silica particles 43.

[0268] In Figure 2In the example shown, the hollow silica particles 43 with high density and large average particle size are dispersed in the functional layer 40A at a high density. In addition, the solid silica particles 44 and metal oxide particles 45 with small average particle size are filled in the functional layer 40A so as to fill the spaces between the hollow silica particles 43. According to this example, the functional layer 40A has high hardness and the surface of the functional layer 40A becomes smooth. As a result, the arithmetic mean roughness Sa of the first surface 11 and the dynamic friction coefficient of the first surface 11 are reduced, and the scratch resistance of the first surface 11 can be improved.

[0269] The average particle size of the hollow silica particles 43 can be larger than the average particle sizes of the solid silica particles 44 and metal oxide particles 45. The average particle size of the hollow silica particles 43 can be 50 nm or more, and can also be 65 nm or more. The average particle size of the hollow silica particles 43 can be 100 nm or less, and can also be 80 nm or less.

[0270] The average particle size of the solid silica particles 44 can be 5 nm or more, and can also be 10 nm or more. The average particle size of the solid silica particles 44 can be 20 nm or less, and can also be 15 nm or less. The average particle sizes of the metal oxide particles 45 and alumina particles 46 can be 5 nm or more, and can also be 10 nm or more. The average particle sizes of the metal oxide particles 45 and alumina particles 46 can be 20 nm or less, and can also be 15 nm or less.

[0271] By setting the lower limits of the average particle sizes of the solid silica particles 44 and metal oxide particles 45, these particles can contribute to the enhancement of the strength and hardness of the functional layer 40A. By setting the upper limit of the average particle size of the hollow silica particles 43, the binder component 41 can stably hold the hollow silica particles 43. That is, the hollow silica particles 43 can be prevented from falling off from the functional layer 40A, and the scratch resistance can be improved. By setting the upper limits of the average particle sizes of the solid silica particles 44 and metal oxide particles 45 and setting the lower limit of the hollow silica particles 43, the solid silica particles 44 and metal oxide particles 45 can be arranged close to the hollow silica particles 43 with large average particle size. That is, the particles can be uniformly dispersed in the functional layer 40A at a high concentration. As a result, excellent scratch resistance can be stably imparted to the functional layer 40A and the optical sheet 10.

[0272] As described above, the average particle diameter (nm) of the metal oxide particles 45 can be less than 1 / 2 of the average particle diameter (nm) of the hollow silica particles 43, can be less than 1 / 3 of the average particle diameter (nm) of the hollow silica particles 43, can be less than 1 / 4 of the average particle diameter (nm) of the hollow silica particles 43, and can be less than 1 / 5 of the average particle diameter (nm) of the hollow silica particles 43. By setting the average particle diameters of the metal oxide particles 45 and the hollow silica particles 43 in this way, the particles 43 and 45 can be uniformly dispersed in the functional layer 40A at a high concentration. Thereby, excellent abrasion resistance can be stably imparted to the functional layer 40A and the optical sheet 10.

[0273] If the content of the hollow silica particles 43 increases, the refractive index of the functional layer 40A decreases, and the functional layer 40A can exhibit an excellent reflection suppression function. That is, from the aspect of the reflection suppression function of the functional layer 40A, a lower limit can be set for the content of the hollow silica particles 43. By setting a lower limit for the content of the particles other than the hollow silica particles 43, the smoothness, strength, and hardness of the functional layer 40A can be ensured. By setting a lower limit for the content of the binder component 41, the particles can be stably held by the binder component 41. Thereby, the detachment of the particles can be suppressed, and excellent abrasion resistance can be ensured. By setting an upper limit for the content of the binder component 41, the refractive index of the functional layer 40A decreases, and the functional layer 40A can exhibit an excellent reflection suppression function. By setting an upper limit for the content of each particle, the significant aggregation of the particle can be suppressed.

[0274] The content of the hollow silica particles can be 100 parts by mass or more and 300 parts by mass or less, can be 150 parts by mass or more and 300 parts by mass or less, and can also be 175 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the binder component. The content of the hollow silica particles can be 100 parts by mass or more and 250 parts by mass or less, can be 150 parts by mass or more and 250 parts by mass or less, and can also be 175 parts by mass or more and 250 parts by mass or less with respect to 100 parts by mass of the binder component.

[0275] The content of the metal oxide particles and the alumina particles can be 10 parts by mass or more and 200 parts by mass or less, can be 50 parts by mass or more and 200 parts by mass or less, can be 70 parts by mass or more and 200 parts by mass or less, or can be 100 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the binder component. The content of the metal oxide particles and the alumina particles can be 10 parts by mass or more and 150 parts by mass or less, can be 50 parts by mass or more and 150 parts by mass or less, can be 70 parts by mass or more and 150 parts by mass or less, or can be 100 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the binder component. The content of the metal oxide particles and the alumina particles can be 10 parts by mass or more and 100 parts by mass or less, can be 50 parts by mass or more and 100 parts by mass or less, or can be 70 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the binder component.

[0276] The content of the metal oxide particles and the alumina particles can be 30 parts by mass or more and 80 parts by mass or less, can be 35 parts by mass or more and 80 parts by mass or less, or can be 40 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the hollow silica particles. The content of the metal oxide particles and the alumina particles can be 30 parts by mass or more and 75 parts by mass or less, can be 35 parts by mass or more and 75 parts by mass or less, or can be 40 parts by mass or more and 75 parts by mass or less with respect to 100 parts by mass of the hollow silica particles. The content of the metal oxide particles and the alumina particles can be 30 parts by mass or more and 70 parts by mass or less, can be 35 parts by mass or more and 70 parts by mass or less, or can be 40 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the hollow silica particles.

[0277] The content of the solid silica particles can be 10 parts by mass or more and 200 parts by mass or less, can be 50 parts by mass or more and 200 parts by mass or less, can be 70 parts by mass or more and 200 parts by mass or less, or can be 100 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the binder component. The content of the solid silica particles can be 10 parts by mass or more and 150 parts by mass or less, can be 50 parts by mass or more and 150 parts by mass or less, can be 70 parts by mass or more and 150 parts by mass or less, or can be 100 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the binder component. The content of the solid silica particles can be 10 parts by mass or more and 100 parts by mass or less, can be 50 parts by mass or more and 100 parts by mass or less, or can be 70 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the binder component.

[0278] The content of the solid silica particles can be 30 parts by mass or more and 80 parts by mass or less, 35 parts by mass or more and 80 parts by mass or less, or 40 parts by mass or more and 80 parts by mass or less relative to 100 parts by mass of the hollow silica particles. The content of the solid silica particles can be 30 parts by mass or more and 75 parts by mass or less, 35 parts by mass or more and 75 parts by mass or less, or 40 parts by mass or more and 75 parts by mass or less relative to 100 parts by mass of the hollow silica particles. The content of the solid silica particles can be 30 parts by mass or more and 70 parts by mass or less, 35 parts by mass or more and 70 parts by mass or less, or 40 parts by mass or more and 70 parts by mass or less relative to 100 parts by mass of the hollow silica particles.

[0279] <Method for manufacturing the functional layer 40A>

[0280] The functional layer 40A can be manufactured using a coating liquid containing a curable resin composition and particles. The functional layer 40A can also be obtained by curing the coating film of the coating liquid. In this example, the coating liquid for the functional layer used to manufacture the functional layer 40A can also contain additives such as antistatic agents, antioxidants, surfactants, dispersants, and ultraviolet absorbers. In the curable resin composition forming the binder component 41, the coating liquid for the functional layer can also contain a silicone-based leveling agent (silicone-based compound) as an additive. By making the coating liquid for the functional layer contain a silicone-based leveling agent, the surface of the functional layer 40A can be made smoother. Depending on the silicone-based leveling agent, excellent slidability and excellent antifouling properties (fingerprint wiping property, large contact angles with pure water and hexadecane) can be imparted to the surface of the functional layer 40A.

[0281] <<Resin layer 30 (hard coat)>>

[0282] The optical sheet 10 can also include a resin layer 30 between the substrate 20 and the functional layer 40A. The resin layer 30 includes a cured product of a curable resin composition. The curable resin composition can include one or more of a thermosetting resin composition and a radiation-curable resin composition. The curable resin composition can include one or more of a thermosetting resin and a radiation-curable compound. The resin layer 30 can be a hard coat. The resin layer 30 imparts high strength and high hardness to the optical sheet 10 and the first surface 11, and can improve the scratch resistance of the first surface 11. The curable resin composition used in the formation of the resin layer 30 can be the same as the curable resin composition used to form the functional layer 40A. The resin layer 30 can be composed of the same resin as the resin constituting the binder component 41 of the functional layer 40A.

[0283] The thickness of the resin layer 30 can be 0.1 μm or more and 100 μm or less, can be 0.5 μm or more and 100 μm or less, and can also be 1 μm or more and 100 μm or less. The thickness of the resin layer 30 can be 0.1 μm or more and 20 μm or less, can be 0.5 μm or more and 20 μm or less, and can also be 1 μm or more and 20 μm or less. The thickness of the resin layer 30 can be 0.1 μm or more and 10 μm or less, can be 0.5 μm or more and 10 μm or less, and can also be 1 μm or more and 10 μm or less. By setting the thickness of the resin layer 30 in this way, excellent scratch resistance can be ensured, and the generation of cracks can be suppressed during processing such as cutting of the optical sheet 10.

[0284] From the aspect of obtaining the reflection suppression function through the functional layer 40A, the refractive index of the resin layer 30 can be lower than that of the functional layer 40A. The refractive index of the resin layer 30 can be 1.45 or more and 1.70 or less.

[0285] When the optical sheet 10 includes a high refractive index layer described later, the refractive index of the resin layer 30 can be lower than that of the high refractive index layer. In this example, the refractive index of the resin layer 30 can be 1.50 or more and 1.65 or less, can be 1.55 or more and 1.65 or less, can be 1.50 or more and 1.60 or less, and can also be 1.55 or more and 1.60 or less. By setting the refractive index of the resin layer 30 in this way, the resin layer 30 functions as a medium refractive index layer. The interference effect brought by the three layers of the resin layer 30 as the medium refractive index layer, the high refractive index layer, and the functional layer 40A as the low refractive index layer becomes possible, and the reflectance can be further reduced. The refractive index of the resin layer 30 can be adjusted by the resin and particles contained in the curable resin composition.

[0286] The refractive index is a value determined by fitting the reflection spectrum measured by a reflection photometer with the reflection spectrum calculated by the optical model of a multilayer thin film using Fresnel coefficients.

[0287] The resin layer 30 can be made using a coating liquid containing a curable resin composition. The resin layer 30 can also be obtained by curing the coating film of the coating liquid. In this example, the coating liquid for the resin layer used to make the resin layer 30 can also contain additives that can be applied to the coating liquid for the functional layer. That is, the coating liquid for the resin layer can also contain a photoinitiator and a photo - polymerization accelerator. The coating liquid for the resin layer can also contain a leveling agent.

[0288] <<Second functional layer 50 (high refractive index layer)>>

[0289] As Figure 3As shown, the optical sheet 10 may further include a second functional layer 50. The second functional layer 50 is located between the functional layer 40A and the resin layer 30 in the lamination direction, i.e., the third direction D3. As described before, the second functional layer 50 is configured to have a refractive index higher than that of the resin layer 30 and the functional layer 40A, and strengthens the reflection suppression function of the optical sheet 10.

[0290] From the aspect of the reflection suppression function, the refractive index and the average thickness of the second functional layer can be set as follows. The refractive index of the second functional layer can be 1.55 or more and 1.85 or less, can be 1.56 or more and 1.85 or less, can be 1.55 or more and 1.75 or less, or can be 1.56 or more and 1.75 or less. The thickness of the second functional layer can be 50 nm or more and 200 nm or less, or can be 50 nm or more and 180 nm or less.

[0291] As Figure 3 shown, the second functional layer 50 may also include a binder component 51 and particles 52. The binder component 51 is an element that holds the particles 52. The binder component 51 can also function as a binder for forming a coating film. By the binder component 51 holding the particles included in the second functional layer 50, the second functional layer 50 can maintain a film form. The binder component 51 may also include a resin. The binder component 51 can be configured in the same manner as the binder component 41 of the functional layer 40A.

[0292] The particles 52 are particles for adjusting the refractive index and may have an average particle size in the nanometer range. The second functional layer 50 can be made using a curable resin composition in the same manner as the functional layer 40A. The curable resin composition may include one or more of a thermosetting resin composition and a radiation-curable resin composition. The curable resin composition may include one or more of a thermosetting resin and a radiation-curable compound. The thermosetting resin and the radiation-curable compound used in the formation of the second functional layer 50 can be the same as those used in the formation of the functional layer 40A.

[0293] The particles 52 may also be particles having a refractive index higher than that of the binder component 51. Examples of the particles 52 include antimony pentoxide, zinc oxide, titanium oxide, cerium oxide, indium tin oxide, antimony-doped tin oxide, yttrium oxide, and zirconium oxide. Zirconium oxide, antimony pentoxide, and titanium oxide can impart high strength and high hardness to the second functional layer 50, contributing to an improvement in the scratch resistance of the first surface 11.

[0294] The average particle diameter of the particles 52 can be 5 nm or more and 200 nm or less, can be 10 nm or more and 200 nm or less, can be 5 nm or more and 100 nm or less, can be 10 nm or more and 100 nm or less, can be 5 nm or more and 80 nm or less, or can be 10 nm or more and 80 nm or less.

[0295] The content of the particles 52 can be set from the viewpoints of increasing the refractive index of the second functional layer 50 and the strength of the second functional layer 50. The content of the particles 52 can be 100 parts by mass or more and 2500 parts by mass or less, can be 300 parts by mass or more and 2500 parts by mass or less, or can be 500 parts by mass or more and 2500 parts by mass or less with respect to 100 parts by mass of the binder component 51. The content of the particles 52 can be 100 parts by mass or more and 2200 parts by mass or less, can be 300 parts by mass or more and 2200 parts by mass or less, or can be 500 parts by mass or more and 2200 parts by mass or less with respect to 100 parts by mass of the binder component 51. The content of the particles 52 can be 100 parts by mass or more and 2000 parts by mass or less, can be 300 parts by mass or more and 2000 parts by mass or less, or can be 500 parts by mass or more and 2000 parts by mass or less with respect to 100 parts by mass of the binder component 51.

[0296] The second functional layer 50 can also be formed by using a coating liquid containing a curable resin composition and the particles 52. The second functional layer 50 can be obtained by curing the coating film of the coating liquid. In this example, the coating liquid for the second functional layer used to form the second functional layer 50 can also contain additives applicable to the coating liquid for the functional layer. That is, the coating liquid for the second functional layer can also contain a photopolymerization initiator and a photopolymerization accelerator. The coating liquid for the second functional layer can also contain an antistatic agent, an antioxidant, a surfactant, a dispersant, an ultraviolet absorber, a leveling agent, and the like.

[0297] <<Manufacturing Method of Optical Sheet>>

[0298] The resin layer 30, the functional layer 40A, and the second functional layer 50 included in the optical sheet 10 can be formed by a wet method in which a coating liquid containing the components constituting each of the layers 30, 40A, and 50 is coated on the substrate 20 and then dried and cured. In addition to the resin composition and the particles used in the formation of each layer, the coating liquid can also contain a solvent. The resin composition can also contain solid components constituting each layer and additives such as a polymerization initiator.

[0299] The optical sheet 10 including the base material 20 and the functional layer 40A can be manufactured as follows. First, a coating liquid for the functional layer is prepared for forming the functional layer 40A. Next, the coating liquid for the functional layer is applied onto the base material 20 to form a coating film. Then, the coating film is dried and then cured. Thus, the functional layer 40A is manufactured on the base material 20, and the optical sheet 10 is obtained.

[0300] In the case where the optical sheet 10 further includes a resin layer 30 in addition to the functional layer 40A, the resin layer 30 is manufactured on the base material 20 before manufacturing the functional layer 40A. The coating liquid for the resin layer for forming the resin layer 30 is applied onto the base material 20, and the coating film is dried and cured, whereby the resin layer 30 is obtained. Next, the optical sheet 10 is obtained by manufacturing the functional layer 40A on the resin layer 30. It should be noted that the resin layer 30 can also be manufactured on the base material 20 in an uncured or semi-cured state, and when the functional layer 40A is cured, the resin layer 30 and the functional layer 40A can be completely cured together.

[0301] In the case where the optical sheet 10 further includes a second functional layer 50 in addition to the resin layer 30 and the functional layer 40A, the second functional layer 50 is manufactured on the resin layer 30 after manufacturing the resin layer 30 and before manufacturing the functional layer 40A. The coating liquid for the second functional layer for forming the second functional layer 50 is applied onto the resin layer 30, and the coating film is dried and cured, whereby the second functional layer 50 is obtained. Next, the optical sheet 10 is obtained by manufacturing the functional layer 40A on the second functional layer 50. It should be noted that when manufacturing one or more of the resin layer 30 and the second functional layer 50 in an uncured or semi-cured state and curing the functional layer 40A, one or more of the resin layer 30 and the second functional layer 50 can be completely cured together with the functional layer 40A.

[0302] By including a solvent in the coating liquid, the viscosity of the coating liquid can be adjusted, and each component can be dissolved or dispersed in the coating liquid. The solvent can be, for example, one or more of ketones (such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ethers (such as dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (such as hexane, etc.), alicyclic hydrocarbons (such as cyclohexane, etc.), aromatic hydrocarbons (such as toluene, xylene, etc.), halogenated carbons (such as dichloromethane, dichloroethane, etc.), esters (such as methyl acetate, ethyl acetate, butyl acetate, etc.), alcohols (such as butanol, cyclohexanol, etc.), cellosolves (such as methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetates, sulfoxides (such as dimethyl sulfoxide, etc.), glycol ethers (such as 1-methoxy-2-propyl acetate, etc.), amides (such as dimethylformamide, dimethylacetamide, etc.).

[0303] When the solvent evaporates too quickly, the solvent in the coating solution actively convects during drying. Particles contained in the coating solution such as hollow silica particles 43, solid silica particles 44, metal oxide particles 45, and particles 52 may be unevenly distributed due to the convection caused by the evaporation of the solvent during drying of the coating solution. That is, the particles in the coating film cannot be uniformly dispersed. From this point of view, the coating solution may also contain a solvent with a slow evaporation rate. The relative evaporation rate of the solvent contained in the coating solution may be 70 or less, or may be 30 or more and 60 or less. Regarding the relative evaporation rate, the evaporation rate of butyl acetate is set to 100, and the evaporation rate of the solvent as the object is expressed by comparison with the evaporation rate of butyl acetate. As an example, the relative evaporation rate of isobutanol is 64. The relative evaporation rate of 1-butanol is 47. The relative evaporation rate of 1-methoxy-2-propyl acetate is 44. The relative evaporation rate of ethyl cellosolve is 38. The relative evaporation rate of cyclohexanone is 32.

[0304] The solvent with a relative evaporation rate of 70 or less may be 10% by mass or more and 50% by mass or less of all the solvents, or may be 20% by mass or more and 40% by mass or less. In this example, as the solvent other than the solvent with a relative evaporation rate of 70 or less, a solvent with excellent solubility of the resin may be contained in the coating solution. The relative evaporation rate of the solvent with excellent solubility of the resin may also be 100 or more.

[0305] From the aspect of suppressing the convection of the solvent during drying of the coating solution, the drying temperature during drying of the coating solution can be lowered. In particular, the drying temperature during drying of the coating solution for the functional layer can be lowered. The drying temperature can be appropriately set in consideration of the type of solvent, the dispersibility of the particles, the production speed, etc.

[0306] As described above, by adjusting the type of solvent, the ratio, and the drying conditions of the coating film, it is possible to make the dispersion of particles such as hollow silica particles 43 and solid silica particles 44 in the functional layer 40A uniform.

[0307] As a means for curing the coating film used to form each layer, irradiation with ionizing rays such as ultraviolet rays and electron beams, and heating can be exemplified. The curing treatment using ionizing ray irradiation is excellent in productivity in terms of being able to cure in a short time.

[0308] According to the above-described method for manufacturing the optical sheet 10 using the wet method, as Figure 4 shown, it is possible to manufacture a long sheet article 5 including a plurality of optical sheets 10. By cutting the long sheet article 5 into a predetermined size, the optical sheet 10 is obtained. According to this example, it is possible to obtain optical sheets 10 with various sizes from the long sheet article 5 as needed. Therefore, it is possible to provide optical sheets 10 with various sizes in a timely manner. As Figure 4As shown, by treating the sheet article 5 as a wound object 7 wound around a winding core with a winding axis RA, the handleability of the sheet article 5 can be improved.

[0309] In addition to the above steps of manufacturing the optical sheet, the method for manufacturing an optical sheet may further include a step of selecting the manufactured optical sheet 10. The step of selecting the optical sheet 10 may further include: a step of measuring the arithmetic mean roughness Sa of the first surface 11 of the manufactured optical sheet 10; and a step of selecting an optical sheet having an arithmetic mean roughness Sa of a specified value or less. Here, the specified value may be 5.2 nm, may be 4.2 nm, or may be 3.5 nm. The functional layer 40A contains hollow silica particles 43 and metal oxide particles 45, and the optical sheet having an arithmetic mean roughness Sa of the first surface 11 of, for example, 5.2 nm or less has excellent scratch resistance. According to this selection step, an optical sheet having excellent scratch resistance can be selected with high precision without performing a scratch test using felt or steel wool.

[0310] The selection step may include a step of confirming that the functional layer 40A contains metal oxide particles 45 and a step of confirming that the functional layer 40A contains alumina particles 46. Whether the functional layer 40A contains metal oxide particles 45 and alumina particles 46 can be confirmed by energy dispersive X-ray spectroscopy (EDX), also known as EDX. According to EDX, in an image of a longitudinal section of the optical sheet obtained by a scanning transmission microscope (such as Figure 2 as shown, an image of a cross section along the third direction), the particles to be measured are determined, and the elements detected from the particles and their amounts can be determined. Based on the detected elements and their amounts, it can be confirmed that the functional layer 40A contains metal oxide particles 45 and alumina particles 46.

[0311] <<<Polarizing sheet 60>>>

[0312] The optical sheet 10 of the first embodiment and the optical sheet 10 of the second embodiment described later can also be applied to the polarizing sheet 60. In Figure 5 the example shown, the polarizing sheet 60 includes a first protective sheet 61, a polarizing element 62, and a second protective sheet 63. The first protective sheet 61 and the second protective sheet 63 sandwich the polarizing element 62 and cover it from both sides. At least one of the first protective sheet 61 and the second protective sheet 63 may contain the optical sheet 10. In the case where only one of the first protective sheet 61 and the second protective sheet 63 contains the optical sheet 10, the other protective sheet may also contain the substrate 20.

[0313] The polarization element 62 transmits one linearly polarized light component and blocks the other linearly polarized light component. The polarization element 62 may also be an absorption type polarization element that absorbs the other linearly polarized light component. The polarization element 62 may also be a reflection type polarization element that reflects the other linearly polarized light component. The polarization element 62 may also be a sheet type polarization element such as a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, or a saponified ethylene-vinyl acetate copolymer film that is dyed with iodine or the like and stretched. The polarization element 62 may also be a wire grid type polarization element composed of a plurality of parallel metal wires. The polarization element 62 may be a coating type polarization element coated with a lyotropic liquid crystal or a dichroic guest-host material, or a multilayer thin film type polarization element.

[0314] <<<Image display device 65>>>

[0315] The optical sheet 10 of the first embodiment and the optical sheet 10 of the second embodiment described later can also be applied to the display device 65. In Figure 6 the example shown, the display device 65 includes an image forming device 66 and an optical sheet 10. The image forming device 66 has a display surface 66a for displaying an image. The optical sheet 10 overlaps the image forming device 66 such that its second surface 12 faces the display surface 66a. The optical sheet 10 may also be joined to the image forming device 66 via a joining layer including an adhesive material, a bonding material, or the like. An observer can clearly observe the image displayed by the image forming device 66 through the optical sheet 10 while suppressing the reflection of the first surface 11 of the optical sheet 10. The image forming device 66 is not particularly limited. Examples of the image forming device 66 include a liquid crystal display element, an EL display element, a plasma display element, and an electronic paper element.

[0316] <<<Panel 70>>>

[0317] The optical sheet 10 of the first embodiment and the optical sheet 10 of the second embodiment described later can be applied to various uses. Figure 7 The panel 70 to which the optical sheet 10 is applied is shown. The panel 70 includes an optical sheet 10 and an article 71 to which the optical sheet 10 is joined. The panel 70 constitutes an anti-reflection article having an anti-reflection function through the optical sheet 10. The optical sheet 10 overlaps the article 71 such that its second surface 12 faces the article 71. The optical sheet 10 may also be joined to the article 71 via a joining layer including an adhesive material, a bonding material, or the like. Examples of the article 71 include an instrument panel, a clock, a display case, a window display, and a window.

[0318] [First Embodiment]

[0319] The first embodiment will be described in more detail by way of examples. The first embodiment is not limited by the following examples.

[0320] 1. Measurement and Evaluation

[0321] As described below, the optical sheets of the examples and comparative examples were measured and evaluated. The atmosphere for each measurement and evaluation was set to a temperature of 23 ± 5°C and a relative humidity of 50 ± 5%. Before each measurement and evaluation, the target sample was exposed to the above atmosphere for more than 30 minutes, and then the measurement and evaluation of the target sample were carried out.

[0322] 1-1. Visual Reflectance Y Value

[0323] Samples of 5 cm × 5 cm were cut from the optical sheets of the examples and comparative examples. Visually confirm that the samples have no abnormalities such as dust and damage. The visual reflectance Y (%) of the optical sheets of each example was measured by the above method. The measurement of the visual reflectance Y used the ultraviolet-visible-near-infrared spectrophotometer "V780" manufactured by JASCO Corporation. The measurement results are shown in the "Y value" column of Table 1.

[0324] 1-2. Total Light Transmittance and Haze

[0325] Samples of 10 cm × 5 cm were cut from the optical sheets of the examples and comparative examples. Visually confirm that the samples have no abnormalities such as dust and damage. The total light transmittance (%) and haze (%) of the optical sheets of each example were measured by the above method. The measurement of the total light transmittance and haze used the haze meter "HM-150" manufactured by Murakami Color Research Institute. The measurement results of the total light transmittance (%) are shown in the "Tt" column of Table 1. The measurement results of the haze (%) are shown in the "Hz" column of Table 1.

[0326] 1-3. Arithmetic Mean Roughness Sa

[0327] Samples of 5 cm × 5 cm were cut from the optical sheets of the examples and comparative examples. Visually confirm that the samples have no abnormalities such as dust and damage. For each of the examples and comparative examples, samples to be measured were prepared. The surface shape of each sample composed of the first surface of the optical sheet was measured using an atomic force microscope. As the atomic force microscope, "SPM-9700" manufactured by Shimadzu Corporation was used. The measurement of the surface shape of the sample was carried out in the On-Line (measurement) mode using the software "SPM manager" attached to the atomic force microscope. The measurement conditions are as described below.

[0328] (AFM Measurement Conditions)

[0329] - Measurement Mode: Phase

[0330] - Scanning Range: 5 μm × 5 μm

[0331] - Scanning speed: 2.0 - 2.5 Hz (using a 10 μm scanner)

[0332] - Number of pixels: 512 × 512

[0333] - Cantilever used: NCHR manufactured by NanoWorld (resonance frequency: 320 kHz, spring constant 42 N / m)

[0334] Using the Off - Line (analysis) mode of "SPM manager", tilt correction processing is performed by "line fitting" to obtain the surface shape of each sample in the form of a grayscale image. In the grayscale image, the position of 0 nm in height is shown in black, and as the height increases, the color is shown with a brightness approaching white. The position with the lowest height within the measurement range is taken as the position of 0 nm in height. The obtained grayscale image is analyzed, and the three - dimensional arithmetic mean roughness Sa is obtained for each sample. The average value of the five measurement values of the samples prepared for each of the examples and comparative examples is taken as the arithmetic mean roughness Sa of that example. The measurement results are shown in the "Sa" column of Table 1.

[0335] Figure 8 It is a grayscale image showing the first surface 11 of the optical sheet 10 of Example 1 described later. Figure 9 It is a grayscale image showing the first surface 11 of the optical sheet 10 of Example 2 described later. Figure 10 It is a grayscale image showing the first surface 11 of the optical sheet 10 of Example 3 described later. Figure 11 It is a grayscale image showing the first surface 11 of the optical sheet 10 of Comparative Example 1 described later. Figure 12 It is a grayscale image showing the first surface 11 of the optical sheet 10 of Comparative Example 2 described later.

[0336] 1 - 4. Coefficient of kinetic friction for steel wool

[0337] Samples of 15 cm × 25 cm are cut from the optical sheets of the examples and comparative examples. Visually confirm that the samples have no abnormalities such as dust and damage. The coefficient of kinetic friction of the optical sheets of each example for steel wool is measured by the above method. The measurement of the coefficient of kinetic friction uses a device that combines a small bench - type testing machine "EZ - LX" manufactured by Shimadzu Corporation with a coefficient - of - friction measuring device obtained from Shimadzu Corporation as a friction test fixture. The measurement results are shown in the "Resistance to SW" column of "Coefficient of kinetic friction" in Table 1.

[0338] 1 - 5. Coefficient of kinetic friction for felt

[0339] Samples measuring 15 cm × 25 cm were cut from the optical sheets of the examples and comparative examples. The samples were visually inspected to confirm that there were no abnormalities such as dust or damage. The dynamic friction coefficient of the optical sheets of each example was measured by the above method. The measurement of the dynamic friction coefficient was performed using a device that combined a small bench-top testing machine "EZ-LX" manufactured by Shimadzu Corporation with a friction coefficient measuring device obtained from Shimadzu Corporation as a friction test fixture. The measurement results are shown in the "Abrasion Resistance against Felt" column of "Dynamic Friction Coefficient" in Table 1.

[0340] 1-6. Abrasion Resistance against Steel Wool

[0341] Samples measuring 5 cm × 10 cm were cut from the optical sheets of the examples and comparative examples. The samples were visually inspected to confirm that there were no abnormalities such as dust or damage. The steel wool abrasion resistance test was performed on the optical sheets of each example by the above method. The steel wool abrasion resistance test was carried out using a Kagaku-shin model friction fastness tester "AB-301-S" manufactured by Tester Sangyo Co., Ltd.

[0342] The samples that had completed 1000 cycles of the steel wool abrasion resistance test under a load of 1000 g were removed from the testing machine, and the surface of the samples formed by the first surface of the optical sheet was observed under the above observation conditions. Based on the observation results, each sample was evaluated according to the following criteria. The evaluation results for each example of the examples and comparative examples are shown in the "Abrasion Resistance against SW" column of "Evaluation Results" in Table 1. Five samples were evaluated for each example, and the worst evaluation result in each example is shown in Table 1.

[0343] AA: No damage was observed on the surface.

[0344] A: Patterns of slight damage were observed on the surface, but the patterns were at a level that was acceptable for the product.

[0345] B: Damage was observed on the surface.

[0346] Among the above criteria, "AA" has the highest abrasion resistance. In "AA" and "A", no defects that would cause problems when applied to a display device were generated. "AA" and "A" were evaluated as being resistant to the steel wool abrasion resistance test. In "B", defects that would cause problems when applied to a display device were generated. "B" was evaluated as not being resistant to the steel wool abrasion resistance test. It should be noted that the test conditions of "load 1000 g, 1000 cycles" in the steel wool abrasion resistance test are more severe than the conditions usually required for anti-reflection films (AR films, LR films) applied to the display surface of a display device.

[0347] 1-7. Abrasion Resistance against Felt

[0348] Samples measuring 50 mm × 100 mm were cut out from the optical sheets of the examples and comparative examples. Visually confirm that the samples have no abnormalities such as dust and damage. The felt abrasion resistance test was performed on the optical sheets of each example by the above method. The felt abrasion resistance test used the "AB-301-S", a friction fastness tester of the Gakushin type manufactured by Tester Sangyo Co., Ltd.

[0349] The samples that had completed 10,000 cycles of the felt abrasion resistance test under a load of 200 g were removed from the testing machine, and the surface of the samples composed of the first surface of the optical sheet was observed under the above observation conditions. Based on the observation results, in the same manner as the evaluation criteria in the abrasion resistance test against steel wool, each sample of each example was evaluated using any one of "AA", "A", and "B". The evaluation results for each example of the examples and comparative examples are shown in the "Felt Resistance" column of "Evaluation Results" in Table 1. Five samples of each example were evaluated, and the worst evaluation result in each example is shown in Table 1.

[0350] 2. Fabrication of the optical sheet

[0351] [Comparative Example 1]

[0352] After coating a coating liquid 1 for resin layer (coating liquid 1 for HC layer) of the following formulation on a substrate made of triacetyl cellulose with a thickness of 80 μm, it was dried at 70 °C for 1 minute to volatilize the solvent. Then, ultraviolet irradiation was performed with an accumulated light amount of 100 mJ / cm 2 to fabricate a resin layer (hard coat) with a dry thickness of 10 μm.

[0353] Next, after coating a coating liquid 1 for the second functional layer (coating liquid 1 for high refractive index layer) of the following formulation on the resin layer, it was dried at 70 °C for 1 minute to volatilize the solvent. Then, ultraviolet irradiation was performed with an accumulated light amount of 100 mJ / cm 2 to form a second functional layer (high refractive index layer) with a dry thickness of 150 nm.

[0354] Next, after coating a coating liquid 1 for functional layer (coating liquid 1 for low refractive index layer) of the following formulation on the second functional layer, it was dried at 50 °C for 30 seconds (dry wind speed 0.5 m / s), and then further dried at 50 °C for 30 seconds (dry wind speed 5 m / s) to volatilize the solvent. Then, ultraviolet irradiation was performed with an accumulated light amount of 200 mJ / cm 2 to form a functional layer (low refractive index layer) with a dry thickness of 100 nm, obtaining the optical sheet of Example 1.

[0355] <Coating liquid 1 for resin layer (coating liquid 1 for hard coat)>

[0356] · 100 parts by mass of a composition containing a UV-curable acrylate

[0357] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M-450”, 100% solid content)

[0358] · 77 parts by mass of a composition containing a UV-curable acrylate

[0359] (Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name “New Frontier R-1403MB”, 80% solid content)

[0360] · 5 parts by mass of a fluorine-based leveling agent

[0361] (Manufactured by DIC Corporation, trade name “MEGAFACE F-568”)

[0362] · 5 parts by mass of a photoinitiator (manufactured by IGM Resins, trade name “Omnirad184”)

[0363] · 68 parts by mass of methyl isobutyl ketone

[0364] · 200 parts by mass of methyl ethyl ketone

[0365] <Coating liquid 1 for the second functional layer (coating liquid 1 for the high refractive index layer)>

[0366] · 100 parts by mass of PETA (manufactured by Toagosei Co., Ltd., trade name “Aronix M-305”, 100% solid content)

[0367] · 300 parts by mass of high refractive index particles (manufactured by Nippon Shokubai Co., Ltd., trade name “ZIRCOSTAR”, 70% solid content)

[0368] · 0.7 parts by mass of a fluorine-based leveling agent (manufactured by DIC Corporation, trade name “MEGAFACE F251”, 100% solid content)

[0369] · 9 parts by mass of a photoinitiator (manufactured by IGM Resins, trade name “Omnirad127”, 100% solid content)

[0370] · 3173 parts by mass of methyl isobutyl ketone

[0371] · 3173 parts by mass of propylene glycol monomethyl ether

[0372] <Coating liquid 1 for the functional layer (coating liquid 1 for the low refractive index layer)>

[0373] · 100 parts by mass of a polyfunctional acrylate composition (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name “NewFrontier MF-001”)

[0374] · 200 parts by mass of hollow silica particles (particles with an average particle size of 75 nm and surface-treated with a silane coupling agent having a methacryloyl group)

[0375] · 110 parts by mass of solid silica particles (particles with an average particle size of 12.5 nm and surface-treated with a silane coupling agent having a methacryloyl group) · 13 parts by mass of a silicone leveling agent (Shin-Etsu Chemical Co., Ltd., trade name “X-22-164E”, solid content 100%)

[0376] · 4.3 parts by mass of a photoinitiator (IGM Resins, trade name “Omnirad127”)

[0377] · 14,867 parts by mass of a solvent (a mixed solvent of methyl isobutyl ketone and 1-methoxy-2-propyl acetate. Mass ratio = 68 / 32)

[0378] [Example 1]

[0379] The resin layer coating liquid 2 (HC layer coating liquid 2) with the following formulation was coated onto a substrate, and the coating film was dried and cured to fabricate a resin layer (hard coat) with a dry thickness of 10 μm. The substrate used in Example 1 was the same as the substrate used in Comparative Example 1 above. The resin layer in Example 1 was different from that in Comparative Example 1 in that the resin layer coating liquid was changed, and the others were manufactured by the same method and under the same conditions as in Comparative Example 1.

[0380] Next, the functional layer coating liquid 2 (low refractive index layer coating liquid 2) with the following formulation was coated onto the resin layer, and the coating film was dried and cured to form a functional layer (low refractive index layer) with a dry thickness of 100 nm, obtaining the optical sheet of Example 1. That is, the optical sheet of Example 1 was different from the optical sheet of Comparative Example 1 and did not include the second functional layer. The functional layer in Example 1 was different from that in Comparative Example 1 in that the functional layer coating liquid was changed, and the others were manufactured by the same method and under the same conditions as in Comparative Example 1.

[0381] [Resin layer coating liquid 2 (Hard coat coating liquid 2)]

[0382] · 100 parts by mass of a composition containing a UV-curable acrylate

[0383] (manufactured by Toagosei Co., Ltd., trade name “Aronix M-450”, solid content 100%)

[0384] · 109 parts by mass of solid silica particles

[0385] (average particle size 12.5 nm, particles surface-treated with a silane coupling agent having a methacryloyl group, solid content 46%)

[0386] · 2 parts by mass of silicone leveling agent

[0387] (Manufactured by Dainichi Seika Kogyo Co., Ltd., trade name “10 - 301”, solid content 5%)

[0388] · 4 parts by mass of photoinitiator

[0389] (IGM Resins, trade name “Omnirad184”, solid content 100%)

[0390] · 69 parts by mass of methyl isobutyl ketone

[0391] · 297 parts by mass of methyl ethyl ketone

[0392] · 33 parts by mass of propylene glycol monomethyl ether

[0393] <Coating liquid 2 for functional layer (Coating liquid 2 for low refractive index layer)>

[0394] · 100 parts by mass of composition containing ultraviolet - curable siloxane - based compound

[0395] (Manufactured by Toagosei Co., Ltd., trade name “AS - SQ TA - 100”, solid content 100%)

[0396] · 43 parts by mass of composition containing ultraviolet - curable acrylate

[0397] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M - 305”, solid content 100%)

[0398] · 1111 parts by mass of hollow silica particles

[0399] (Particles with an average particle size of 65 nm, surface - treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0400] · 36 parts by mass of solid silica particles

[0401] (Particles with an average particle size of 9.0 nm, surface - treated with a silane coupling agent having a methacryloyl group, solid content 50%)

[0402] · 60 parts by mass of alumina particles

[0403] (Particles with an average particle size of 15.0 nm, surface - treated with a silane coupling agent having a methacryloyl group, solid content 30%)

[0404] · 201 parts by mass of leveling agent

[0405] (Shin-Etsu Chemical Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0406] · 6 parts by mass of photoinitiator

[0407] (IGM Resins, trade name "Omnirad127", solid content 100%)

[0408] · 15263 parts by mass of methyl isobutyl ketone

[0409] · 1819 parts by mass of propylene glycol monomethyl ether acetate

[0410] [Example 2]

[0411] Example 2 is different from Example 1 in that the coating liquid 2 for the functional layer is changed to the following coating liquid 3 for the functional layer, and the optical sheet of Example 2 is obtained by the same materials and the same method as in Example 1.

[0412] (Coating liquid 3 for functional layer (coating liquid 3 for low refractive index layer))

[0413] · 100 parts by mass of a composition containing a UV-curable silicone compound

[0414] (Manufactured by Toagosei Co., Ltd., trade name "AS-SQ TA-100", solid content 100%)

[0415] · 43 parts by mass of a composition containing a UV-curable acrylate

[0416] (Manufactured by Toagosei Co., Ltd., trade name "Aronix M-305", solid content 100%)

[0417] · 1111 parts by mass of hollow silica particles

[0418] (Particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0419] · 36 parts by mass of solid silica particles

[0420] (Particles with an average particle size of 9.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 50%)

[0421] · 60 parts by mass of alumina particles

[0422] (Particles with an average particle size of 15.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 30%)

[0423] · 201 parts by mass of leveling agent

[0424] (Shin-Etsu Chemical Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0425] · 54 parts by mass of a leveling agent

[0426] (Arakawa Chemical Industries, Ltd., trade name "Opstar TU2225", solid content 15%)

[0427] · 6 parts by mass of a photoinitiator

[0428] (IGM Resins, trade name "Omnirad127", solid content 100%)

[0429] · 15511 parts by mass of methyl isobutyl ketone

[0430] · 1851 parts by mass of propylene glycol monomethyl ether acetate

[0431] [Example 3]

[0432] Example 3 is different from Example 1 in that the coating liquid 2 for the functional layer is changed to the following coating liquid 4 for the functional layer, and the optical sheet of Example 3 is obtained by the same materials and the same method as in Example 1.

[0433] (Coating liquid 4 for the functional layer (coating liquid 4 for the low refractive index layer))

[0434] · 100 parts by mass of a composition containing an ultraviolet curable silicone compound

[0435] (Manufactured by Toagosei Co., Ltd., trade name "AS-SQ TA-100", solid content 100%)

[0436] · 43 parts by mass of a composition containing an ultraviolet curable acrylate

[0437] (Manufactured by Toagosei Co., Ltd., trade name "Aronix M-305", solid content 100%)

[0438] · 1143 parts by mass of hollow silica particles

[0439] (Particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0440] · 50 parts by mass of solid silica particles

[0441] (Particles with an average particle size of 9.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 50%)

[0442] · 83 parts by mass of alumina particles

[0443] (Particles with an average particle size of 15.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 30%)

[0444] · 633 parts by mass of a leveling agent

[0445] (Shin-Etsu Chemical Co., Ltd., trade name “X-71-1203M”, solid content 20%)

[0446] · 113 parts by mass of a leveling agent

[0447] (Arakawa Chemical Co., Ltd., trade name “Opstar TU2225”, solid content 15%)

[0448] · 6 parts by mass of a photoinitiator

[0449] (IGM Resins, trade name “Omnirad127”)

[0450] · 19354 parts by mass of methyl isobutyl ketone

[0451] · 2320 parts by mass of propylene glycol monomethyl ether acetate

[0452] [Comparative Example 2]

[0453] Comparative Example 2 is different from Example 1 above in that the coating liquid 2 for the functional layer is changed to the following coating liquid 5 for the functional layer. The optical sheet of Comparative Example 2 is obtained by the same materials and the same method as in Example 1.

[0454] (Coating liquid 5 for the functional layer (coating liquid 5 for the low refractive index layer))

[0455] · 100 parts by mass of a composition containing a UV-curable acrylate

[0456] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M-305”, solid content 100%)

[0457] · 800 parts by mass of hollow silica particles

[0458] (Particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0459] · 68 parts by mass of solid silica particles

[0460] (Particles with an average particle size of 12.5 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 37%)

[0461] · 143 parts by mass of a leveling agent

[0462] (Shin-Etsu Chemical Co., Ltd., trade name “X-71-1203M”, solid content 20%)

[0463] · 4 parts by mass of a photoinitiator

[0464] (IGM Resins, trade name “Omnirad127”, solid content 100%)

[0465] · 9504 parts by mass of methyl isobutyl ketone

[0466] · 1144 parts by mass of propylene glycol monomethyl ether acetate

[0467] [Table 1]

[0468] Table 1 Samples and evaluation results

[0469]

[0470] <<<<Second Embodiment>>>>

[0471] Next, a second embodiment of the present disclosure will be described. The second embodiment of the present disclosure includes features regarding the indentation hardness of the first surface of the optical sheet 10 and the complex elastic modulus of the first surface of the optical sheet 10. It should be noted that the above first embodiment may also include features regarding the indentation hardness of the first surface of the optical sheet 10 and the complex elastic modulus of the first surface of the optical sheet 10 in the same manner as the second embodiment. The above first embodiment may also include one or more of the features of the second embodiment described hereinafter.

[0472] In the second embodiment of the present disclosure, the functional layer 40B of the optical sheet 10 may, unlike the first embodiment, not contain metal oxide particles other than silica particles. In the second embodiment of the present disclosure, the functional layer 40B of the optical sheet 10 may, in the same manner as the first embodiment, contain metal oxide particles other than silica particles. In the second embodiment of the present disclosure, the functional layer 40B of the optical sheet 10 may also contain alumina.

[0473] In the second embodiment of the present disclosure, the arithmetic mean roughness Sa of the first surface of the optical sheet 10 may, unlike the first embodiment, be greater than 5.2 nm. In the second embodiment of the present disclosure, the arithmetic mean roughness Sa of the first surface of the optical sheet 10 may be within the same numerical range as in the first embodiment.

[0474] <<<Optical sheet 10>>>

[0475] As Figure 13As shown, the optical sheet 10 of the second embodiment includes a first surface 11 and a second surface 12. The optical sheet 10 includes a base material 20 and a functional layer 40B in this order from the second surface 12 to the first surface 11. The functional layer 40B includes a binder component 41 and hollow silica particles 43. By including the hollow silica particles 43, the refractive index of the functional layer 40B is lower than the refractive index of the binder component 41. According to the low-refractive-index functional layer 40B, reflection of light incident on the first surface 11 can be suppressed.

[0476] As already described in the first embodiment, the abrasion resistance of the surface of the functional layer of the existing optical sheet is insufficient.

[0477] <Indentation hardness H IT and complex elastic modulus E r standard deviation σ Er >

[0478] In the second embodiment, an attempt is made to improve the abrasion resistance. Specifically, a lower limit is set for the indentation hardness H IT (GPa) of the first surface 11, and an upper limit is set for the standard deviation σ r of the complex elastic modulus E Er of the first surface 11. The indentation hardness H IT and the complex elastic modulus E r are the hardness and elastic modulus measured by the nanoindentation method. The nanoindentation method is a method for measuring the hardness and elastic modulus based on the load-displacement curve. In the nanoindentation method, the load-displacement curve is obtained by loading and unloading the evaluation object using an indenter. The load-displacement curve shows the relationship between the indentation load and the indentation depth. The nanoindentation method can evaluate the hardness and elastic modulus of a small area.

[0479] In the second embodiment, the indentation hardness H IT of the first surface 11 with an indentation depth of 100 nm is 0.45 GPa or more, and the standard deviation σ r of the complex elastic modulus E Er at 10 different positions on the first surface 11 with an indentation depth of 30 nm is 1.1 GPa or less. By satisfying these conditions regarding the indentation hardness H IT and the complex elastic modulus E r and the standard deviation σ Er , the abrasion resistance can be improved.

[0480] By setting the indentation hardness of the first surface 11 with an indentation depth of 100 nm to 0.45 GPa or more, sufficient strength and sufficient hardness are imparted to the first surface 11 and the vicinity of the first surface 11. As a result, the abrasion resistance of the first surface 11 is improved.

[0481] From the aspect of improving the scratch resistance of the first surface 11, the indentation hardness of the first surface 11 with an indentation depth of 100 nm can be 0.55 GPa or more, can be 0.56 GPa or more, can be 0.57 GPa or more, can be 0.59 GPa or more, and can also be 0.60 GPa or more. There is no particular setting for the upper limit of the indentation hardness of the first surface 11 with an indentation depth of 100 nm. The indentation hardness can be, for example, 3.0 GPa or less, can be 2.0 GPa or less, and can also be 1.0 GPa or less.

[0482] The indentation hardness of the first surface 11 with an indentation depth of 100 nm can be 0.55 GPa or more and 3.0 GPa or less, can be 0.56 GPa or more and 3.0 GPa or less, can be 0.57 GPa or more and 3.0 GPa or less, can be 0.59 GPa or more and 3.0 GPa or less, and can also be 0.60 GPa or more and 3.0 GPa or less. The indentation hardness of the first surface 11 with an indentation depth of 100 nm can be 0.55 GPa or more and 2.0 GPa or less, can be 0.56 GPa or more and 2.0 GPa or less, can be 0.57 GPa or more and 2.0 GPa or less, can be 0.59 GPa or more and 2.0 GPa or less, and can also be 0.60 GPa or more and 2.0 GPa or less. The indentation hardness of the first surface 11 with an indentation depth of 100 nm can be 0.55 GPa or more and 1.0 GPa or less, can be 0.56 GPa or more and 1.0 GPa or less, can be 0.57 GPa or more and 1.0 GPa or less, can be 0.59 GPa or more and 1.0 GPa or less, and can also be 0.60 GPa or more and 1.0 GPa or less.

[0483] As an index indicating the scratch resistance of the surface of an optical sheet, pencil hardness is known. Pencil hardness is an index indicating the resistance when contacting a hard substance with a stress close to a point load. On the other hand, when an optical sheet is used for a long time, scratches can occur due to repeated application of a small surface load. Compared with pencil hardness, the scratch resistance during long-term use should be evaluated as steel wool resistance and felt resistance. In the evaluation of steel wool resistance and felt resistance, steel wool and felt as sliding sheets are repeatedly rubbed against the object to be evaluated. The thickness of the functional layer that exhibits a reflection suppression function is thin. If a surface load is repeatedly applied, the thin functional layer can be peeled off from the optical sheet. Considering the scratch resistance of the peeling of the functional layer, not only the hardness of the functional layer 40B but also the adhesion between the functional layer 40B and the layer adjacent to the functional layer 40B and the hardness of the layer adjacent to the functional layer 40B should be considered.

[0484] The indentation hardness is not measured by taking the maximum load as the measurement condition, but by setting the indentation depth to 100nm as the measurement condition. The functional layer 40B having the reflection suppression function usually has a thickness of about 100nm. In the measurement of the indentation hardness, the indentation depth is set to 100nm. Therefore, the indentation hardness becomes an evaluation index including not only the hardness of the functional layer 40B, but also the adhesion of the functional layer 40B and the layer adjacent to the functional layer 40B, and the hardness of the layer adjacent to the functional layer 40B. By setting the indentation hardness of the first surface 11 with the indentation depth to 100nm, the scratch resistance of the first surface 11 can be evaluated with high precision. The above is considered to be the reason that by making the indentation hardness of the first surface 11 with the indentation depth to 100nm be the above range, sufficient hardness and sufficient strength can be given to the vicinity of the first surface 11, and the scratch resistance of the first surface 11 can be improved.

[0485] It should be noted that the inventors of the present disclosure also investigated the relationship between the indentation hardness measured at an indentation depth other than 100 nm and the scratch resistance. As a result of the investigation, the indentation hardness with an indentation depth of 100 nm showed the strongest correlation with the scratch resistance. The above-mentioned reason for the inference also matches such an investigation result.

[0486] Indentation hardness H IT This is a value measured using a measuring device "TI-950 Tribo Indenter" manufactured by BRUKER. Indentation hardness H IT The indenter used in the measurement is "TI-0039" manufactured by BRUKER. The indenter is a Berkovich indenter having a triangular pyramid shape. The indenter is pressed into the first surface 11 along the normal direction of the optical sheet 10, and a load is applied to the optical sheet 10 of the evaluation object. The indenter's indentation speed is set to 10 mm / sec. The indenter is pressed into the optical sheet 10 until the indentation depth reaches 100 nm. While the indenter is pressed 100 nm into the optical sheet 10 from the first surface 11, the indenter is maintained for 5 seconds. Then, the indenter is retracted from the optical sheet 10 along the normal direction of the optical sheet 10 to remove the load from the optical sheet 10. The retraction speed of the indenter is set to 10 nm / sec.

[0487] The above-described operation of the indenter provides a graph showing the magnitude of the load applied to the first surface 11 by the indenter and the depth of penetration of the indenter, that is, a load-displacement curve C. Figure 14 This is an example of the load-displacement curve C obtained in this way. Figure 14 The depth hmax in the load displacement curve C is the maximum indentation depth during unloading. The maximum indentation depth hmax is usually the indentation depth measured by the measuring device at the beginning of unloading. Figure 14The depth hf in the load-displacement curve C is the depth of the deformation trace remaining on the first surface 11 after unloading using the indenter. The depth hf is the indentation depth measured by the measuring device at the end of unloading.

[0488] Figure 14 In the measurement using a Berkovich indenter, the contact depth hc in the load-displacement curve C is calculated by the following formula (1).

[0489] hc = hmax - 0.75 × (Fmax / S) ··· (1)

[0490] "Fmax" in formula (1) is the maximum load after residual stress relaxation. The maximum load Fmax is usually the load measured by the measuring device at the start of unloading. "S" in formula (1) is called the contact stiffness and is the slope of the load-displacement curve C at the start of unloading. In Figure 14 the example shown, the slope of the tangent TL to the load-displacement curve C at the start of unloading corresponds to the contact stiffness S.

[0491] Calculate the contact projected area Ap related to the deformation trace, which corresponds to the tip shape of the indenter formed on the surface of the first surface 11 by pressing the indenter. The contact projected area Ap is determined by a standard method in the measuring device. The indentation hardness H IT is determined by the following formula (2) as the value obtained by dividing the maximum load Fmax by the contact projected area Ap.

[0492] H IT = Fmax / Ap ··· (2)

[0493] The indentation hardness H IT is the arithmetic mean of 10 measured values measured at 10 measurement positions on the optical sheet as the evaluation object. The 10 measurement positions are 10 positions located on a straight line at an interval of 10 μm.

[0494] In the second embodiment, in addition to the lower limit of the absolute value of the indentation hardness, an upper limit value of the standard deviation σ r of the complex elastic modulus E Er is also set. Specifically, the standard deviation σ r (GPa) of the complex elastic modulus E Er (GPa) at 10 different measurement positions on the first surface 11 where the indentation depth is 30 nm is 1.1 GPa or less. That is, for the optical sheet as the evaluation object, the complex elastic modulus E r is measured at 10 measurement positions, and the standard deviation σ Er of the 10 measured values of the complex elastic modulus obtained is 1.1 GPa or less.

[0495] The complex elastic modulus E is obtained by setting the indentation depth at 10 different measurement positions on the first surface 11 to 30 nm. r The standard deviation σ Er When the pressure is 1.1 GPa or less, the sliding property of the first surface 11 is sufficiently uniform. Therefore, the scratch resistance of the first surface 11 is improved.

[0496] From the perspective of improving the scratch resistance of the first surface 11, the composite elastic modulus E is set to 30 nm when the indentation depth at 10 different measurement positions on the first surface 11 is 0.1 nm. r The standard deviation σ Er The composite elastic modulus E of the first surface 11 may be 0.90 GPa or less, 0.88 GPa or less, 0.87 GPa or less, 0.78 GPa or less, 0.69 GPa or less, 0.60 GPa or less, or 0.59 GPa or less. r The standard deviation σ Er There is no particular lower limit. The complex elastic modulus E of the first surface 11 r The standard deviation σ Er For example, it may be 0.010 GPa or more, 0.050 GPa or more, or 0.10 GPa or more.

[0497] Composite elastic modulus E r The standard deviation σ Er It can be 0.010 GPa to 0.90 GPa, 0.010 GPa to 0.88 GPa, 0.010 GPa to 0.87 GPa, 0.010 GPa to 0.78 GPa, 0.010 GPa to 0.69 GPa, 0.010 GPa to 0.60 GPa, or 0.010 GPa to 0.59 GPa. Composite elastic modulus E r The standard deviation σ Er It can be 0.050 GPa to 0.90 GPa, 0.050 GPa to 0.88 GPa, 0.050 GPa to 0.87 GPa, 0.050 GPa to 0.78 GPa, 0.050 GPa to 0.69 GPa, 0.050 GPa to 0.60 GPa, or 0.050 GPa to 0.59 GPa. Composite elastic modulus E r The standard deviation σ ErIt can be not less than 0.10 GPa and not more than 0.90 GPa, it can be not less than 0.10 GPa and not more than 0.88 GPa, it can be not less than 0.10 GPa and not more than 0.87 GPa, it can be not less than 0.10 GPa and not more than 0.78 GPa, it can be not less than 0.10 GPa and not more than 0.69 GPa, it can be not less than 0.10 GPa and not more than 0.60 GPa, or it can be not less than 0.10 GPa and not more than 0.59 GPa.

[0498] Composite elastic modulus E r (GPa) is an index indicating the ease of deformation of the first surface 11 and its vicinity. The composite elastic modulus E r (GPa) standard deviation σ Er becomes an index indicating the deviation of the ease of deformation. If the standard deviation σ Er (GPa) of the composite elastic modulus is large, the deviation of the ease of deformation also becomes large. By setting an upper limit on the standard deviation σ Er (GPa) of the composite elastic modulus, the deviation of the ease of deformation is restricted. By making the degree of the ease of deformation of the first surface 11 not have a large deviation, when the slider repeatedly moves on the first surface 11, the movement of the slider becomes smooth. Thereby, the frictional force between the slider and the first surface 11 does not change significantly, and it is possible to suppress a large load being locally applied to the first surface 11. That is, the standard deviation σ r (GPa) of the composite elastic modulus E Er becomes an index indicating the uniformity of the slidability of the first surface 11. For the above reasons, it is considered that by making the standard deviation σ r of the composite elastic modulus E at 10 different measurement positions on the first surface 11 with an indentation depth of 30 nm Er be within the above range, the scratch resistance of the first surface 11 is improved.

[0499] It should be noted that the inventors of the present disclosure investigated the correlation between the standard deviation of the composite elastic modulus measured at an indentation depth other than 30 nm and the scratch resistance. As a result of the investigation, the standard deviation of the composite elastic modulus measured at an indentation depth of 30 nm showed the strongest correlation with the scratch resistance. The composite elastic modulus measured at an indentation depth of 30 nm can effectively reflect the surface properties of the first surface 11, the dispersion of particles such as the hollow silica particles 43 in the functional layer 40B, etc., and shows the ease of deformation. That is, the composite elastic modulus measured at an indentation depth of 30 nm becomes an index indicating the local ease of deformation and the local slidability. Based on this, it is considered that the uniformity of the slidability of the first surface 11 can be evaluated with high precision by the standard deviation of the composite elastic modulus measured at an indentation depth of 30 nm.

[0500] The inventors of the present disclosure also investigated the correlation between the standard deviation of the indentation hardness and the scratch resistance instead of the complex elastic modulus. As a result of the investigation, the standard deviation of the complex elastic modulus showed a stronger correlation with the scratch resistance than the standard deviation of the indentation hardness. The complex elastic modulus is an index that more directly represents the ease of deformation compared to the indentation hardness. Based on this, it is considered that the uniformity of the slidability of the first surface 11 can be evaluated with high precision by the standard deviation of the complex elastic modulus.

[0501] The inventors of the present disclosure also studied using the surface roughness of the first surface 11 and the standard deviation of the surface roughness of the first surface 11 to evaluate the scratch resistance of the first surface 11 instead of the standard deviation of the complex elastic modulus. However, the surface roughness cannot reflect the ease of deformation caused by the dispersion of particles such as the hollow silica particles 43 in the functional layer 40B. On the other hand, the complex elastic modulus measured at an indentation depth of 30 nm can reflect not only the ease of deformation caused by the dispersion of particles in the functional layer 40B but also the ease of deformation corresponding to the surface properties. Considering from such aspects, it is considered that the uniformity of the slidability of the first surface 11 can be evaluated with high precision by the standard deviation of the complex elastic modulus measured at an indentation depth of 30 nm.

[0502] Complex elastic modulus E r Similar to the measurement of the indentation hardness H IT The measurement is carried out using a measuring instrument "TI-950 TriboIndenter" manufactured by BRUKER Corporation. The indenter used in the measurement of the complex elastic modulus E r is the same as the indenter used in the measurement of the indentation hardness H IT and is an indenter "TI-0039" manufactured by BRUKER Corporation. This indenter is a Berkovich indenter in the shape of a triangular pyramid. The indenter is pressed into the first surface 11 along the normal direction of the optical sheet 10, and a load is applied to the optical sheet 10 to be evaluated. The pressing speed of the indenter is set to 10 mm / second. The indenter is pressed into the optical sheet 10 until the indentation depth reaches 30 nm. In the state where the indenter is pressed into the optical sheet 10 by 30 nm from the first surface 11, the indenter is held for 5 seconds. Then, the indenter is retracted from the optical sheet 10 along the normal direction of the optical sheet 10, and the load is removed from the optical sheet 10. The retraction speed of the indenter is set to 10 nm / second.

[0503] Through the operation of the above indenter, similar to the measurement of the indentation hardness H IT a load-displacement curve C shown as an example in Figure 14 is obtained. Based on the load-displacement curve C, similar to the measurement of the indentation hardness H IT the contact projected area Ap and the contact stiffness S are calculated. The complex elastic modulus E is obtained from the following formula (4) using the contact projected area Ap and the contact stiffness Sr 。

[0504] [Number 2]

[0505]

[0506] Complex elastic modulus E r Measure the optical sheet to be evaluated at 10 measurement positions. The 10 measurement positions are 10 positions on a straight line at an interval of 10 μm. Calculate the complex elastic modulus E from the measurement values of the 10 complex elastic moduli E r measured at the 10 measurement positions r (GPa) standard deviation σ Er (GPa).

[0507] It should be noted that the indentation hardness can be adjusted by the surface shape of the first surface 11, the thickness of the functional layer 40B, the material and mixing ratio of the binder component 41 contained in the functional layer 40B, the material of the particles contained in the functional layer 40B, the mixing ratio, the average particle size, the dispersion, etc. The complex elastic modulus can also be adjusted by the surface shape of the first surface 11, the thickness of the functional layer 40B, the material and mixing ratio of the binder component 41 contained in the functional layer 40B, the material of the particles contained in the functional layer 40B, the mixing ratio, the average particle size, the dispersion, etc. The standard deviation of the complex elastic modulus can be adjusted by the surface shape of the first surface 11, the mixing ratio of the particles contained in the functional layer 40B, the average particle size, the standard deviation of the average particle size, the dispersion, etc.

[0508] <Scratch resistance>

[0509] In the optical sheet 10 of the second embodiment, a lower limit is set for the indentation hardness H IT (GPa) of the first surface 11, and an upper limit is set for the standard deviation σ r of the complex elastic modulus E Er of the first surface 11. The optical sheet 10 of the second embodiment has excellent scratch resistance. The wire wool resistance and felt resistance of the optical sheet with excellent scratch resistance are both excellent. As an index indicating the scratch resistance of the surface of the optical sheet, pencil hardness is known. Pencil hardness is an index indicating the resistance when contacting a hard substance with a stress close to a point load. On the other hand, during repeated friction and long-term use, due to the stable application of a surface load, minute scratches may occur. Regarding the resistance to this damage, it is appropriate to evaluate it as wire wool resistance and felt resistance. In the scratch resistance test of the first surface 11 using wire wool, the optical sheet 10 can have high resistance. In the scratch resistance test of the first surface 11 using felt, the optical sheet 10 can have high resistance.

[0510] (Wire wool scratch resistance)

[0511] The steel wool abrasion resistance test is an index indicating the resistance to damage and other defects generated when the steel wool is pressed against the test sample to be evaluated and relatively moved. The optical sheet 10 can be resistant to the steel wool abrasion resistance test carried out under the conditions described below.

[0512] Abrasion resistance test: Use steel wool #0000 as the sliding sheet, with a load of 1000 g, a moving speed of 80 mm / second, a one-way moving distance of 40 mm, and reciprocate 1000 times.

[0513] After the abrasion resistance test, visually observe the surface of the test sample formed by the first surface of the optical sheet. The observation distance is 30 cm. The illuminance on the surface of the sample to be observed is 800 Lx or more and 1200 Lx or less. In the case where damage and other defects of a degree that would cause problems when applied to a display device are observed in the test sample, it is determined that the optical sheet 10 to be evaluated does not have resistance to the steel wool abrasion resistance test for the first surface 11. Conduct the abrasion resistance test 5 times on one optical sheet 10 to be evaluated. In the case where no defects of a degree that would cause problems when applied to a display device occur in all 5 tests, it is judged that the optical sheet 10 to be evaluated has resistance to the steel wool abrasion resistance test for the first surface 11.

[0514] The method of the abrasion resistance test and the method of evaluating the sample after the abrasion resistance test are as described in the first embodiment.

[0515] (Felt resistance)

[0516] The felt abrasion resistance test is an index indicating the resistance to damage and other defects generated when the felt is pressed against the test sample to be evaluated and relatively moved. The optical sheet 10 can be resistant to the steel wool abrasion resistance test carried out under the conditions described below.

[0517] Abrasion resistance test: Use "Jumbo Wearaser (registered trademark), product number: CS-7" manufactured by TABER as the sliding sheet, with a load of 200 g, a moving speed of 200 mm / second, a one-way moving distance of 50 mm, and reciprocate 10000 times.

[0518] After the abrasion resistance test, the surface of the test sample formed by the first surface of the optical sheet is observed with the naked eye. The observation distance is 30 cm. The illuminance on the surface of the sample to be observed is 800 Lx or more and 1200 Lx or less. In the case where damage or other defects of a degree that would cause problems when applied to a display device are observed in the test sample, it is determined that the optical sheet 10 to be evaluated does not have resistance to the abrasion resistance test using a felt for the first surface 11. The abrasion resistance test is performed 5 times on one optical sheet 10 to be evaluated. In the case where no defects of a degree that would cause problems when applied to a display device occur in all 5 tests, it is determined that the optical sheet 10 to be evaluated has resistance to the abrasion resistance test using a felt for the first surface 11.

[0519] The method of the abrasion resistance test and the method of evaluating the sample after the abrasion resistance test are as described in the first embodiment.

[0520] <Visual reflectance Y value>

[0521] The optical sheet 10 has a reflection suppression function for suppressing the reflection of light incident on the first surface 11. The visual reflectance Y value of the first surface 11 measured at an incident angle of 5° can be 1.0% or less, can be 0.8% or less, can be 0.7% or less, can be 0.6% or less, or can be 0.5% or less.

[0522] There is no particular limitation on the lower limit of the visual reflectance. The visual reflectance Y value of the first surface 11 measured at an incident angle of 5° can be 0% or more, or can be greater than 0%. The visual reflectance Y value of the first surface 11 can be 0% or more and 1.0% or less, can be 0% or more and 0.8% or less, can be 0% or more and 0.7% or less, can be 0% or more and 0.6% or less, or can be 0% or more and 0.5% or less. The visual reflectance Y value of the first surface 11 can be greater than 0% and 1.0% or less, can be greater than 0% and 0.8% or less, can be greater than 0% and 0.7% or less, can be greater than 0% and 0.6% or less, or can be greater than 0% and 0.5% or less.

[0523] The visual reflectance Y value refers to the visual reflectance Y value of the CIE1931 standard colorimetric system. The visual reflectance Y value is measured by the method described in the first embodiment.

[0524] <Total light transmittance>

[0525] The total light transmittance of the optical sheet 10 can be 50% or more, can be 70% or more, can be 80% or more, or can be 90% or more. There is no particular upper limit on the total light transmittance of the optical sheet 10. The total light transmittance of the optical sheet 10 can be 100% or less, or can be less than 100%.

[0526] The total light transmittance of the optical sheet 10 may be 50% or more and 100% or less, may be 70% or more and 100% or less, may be 80% or more and 100% or less, or may be 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%, may be 70% or more and less than 100%, may be 80% or more and less than 100%, or may be 90% or more and less than 100%.

[0527] The total light transmittance is measured by the method described in the first embodiment.

[0528] <Transmission haze>

[0529] The transmission haze of the optical sheet 10 may be 1.0% or less, may be 0.5% or less, or may be 0.2% or less. There is no particular lower limit for the transmission haze of the optical sheet 10. The transmission haze of the optical sheet 10 may be 0%, or may be greater than 0%.

[0530] The transmission haze of the optical sheet 10 may be 0% or more and 1.0% or less, may be 0% or more and 0.5% or less, or may be 0% or more and 0.2% or less. The transmission haze of the optical sheet 10 may be greater than 0% and 1.0% or less, may be greater than 0% and 0.5% or less, or may be greater than 0% and 0.2% or less.

[0531] The transmission haze is measured by the method described in the first embodiment.

[0532] As Figure 13 shown, the optical sheet 10 may also include a resin layer 30 located between the substrate 20 and the functional layer 40B. The resin layer 30 is adjacent to the functional layer 40B. The resin layer 30 may also include a cured product of a curable resin composition. The resin layer 30 containing the cured product of the curable resin composition has high strength and high hardness. By laminating the functional layer 40B on the resin layer 30 and being supported, the indentation hardness of the first surface 11 increases, and the scratch resistance of the first surface 11 can be further improved.

[0533] Hereinafter, Figure 13 the layers that can be included in the optical sheet 10 shown will be described. In the example shown in Figure 13 the substrate 20, the resin layer 30, and the functional layer 40B are laminated in the third direction D3, that is, the third direction D3 is the lamination direction. The substrate 20, the resin layer 30, and the functional layer 40B are extended in the first direction D1 and the second direction D2 orthogonal to the third direction D3. In the illustrated example, the first direction D1 and the second direction D2 are orthogonal to each other. The third direction D3 is the normal direction of the optical sheet 10. The third direction D3 is also the normal direction of each layer included in the optical sheet 10. In Figure 13In the optical sheet 10 shown, the first surface 11 is constituted by the functional layer 40B. The second surface 12 is constituted by the base material 20.

[0534] It should be noted that the optical sheet 10 sometimes further has an antistatic layer and an antifouling layer, and these layers are supported by the functional layer 40B to constitute the first surface 11. These antistatic layers, antifouling layers, etc. are very thin layers. Otherwise, the functional layer 40B cannot effectively exert the reflection suppression function. Therefore, in the example where the antistatic layer, antifouling layer, etc. constitute the first surface 11, the abrasion resistance of the first surface 11 is also affected by the functional layer 40B. That is, according to the above-mentioned functional layer 40B, the abrasion resistance of the first surface 11 can be greatly improved.

[0535] In the second embodiment, the base material 20 included in the optical sheet may be the same as the base material 20 described in the first embodiment. In the second embodiment, the resin layer 30 included in the optical sheet may be the same as the resin layer 30 described in the first embodiment.

[0536] <<Functional layer 40B>>

[0537] The functional layer 40B includes a binder component 41 and hollow silica particles 43. The functional layer 40B reduces the refractive index by including the hollow silica particles 43. The functional layer 40B can have a refractive index lower than that of the binder component 41. The refractive index of the functional layer 40B may also be lower than the refractive index of the base material 20. The refractive index of the functional layer 40B may also be lower than the refractive index of the layer adjacent to the functional layer 40B.

[0538] The functional layer 40B can exert the function of suppressing the reflection of incident light due to its refractive index and thickness. The reflection suppression function brought by the functional layer 40B is based on the interference of the light reflected on the two surfaces on both sides of the functional layer 40B. From the aspect of making this reflection suppression function effective, the refractive index of the functional layer 40B can be between the refractive indices of the two regions adjacent to the functional layer 40B on both sides. In addition, the thickness (nm) of the functional layer 40B may also be about 1 / 4 of the wavelength λ (nm) of the light whose reflection is to be suppressed.

[0539] Considering the reflection suppression function, the refractive index and the average thickness of the functional layer can be set. The refractive index of the functional layer can be within the numerical range of the refractive index described in the first embodiment. The thickness of the functional layer can be within the numerical range of the thickness described in the first embodiment.

[0540] <Binder component 41>

[0541] The binder component 41 is an element for holding the hollow silica particles 43. The binder component 41 can also function as a binder for forming a coating film. By having the binder component 41 hold the particles contained in the functional layer 40A, the functional layer 40B can maintain its film form. The binder component 41 can also contain a resin. The resin contained in the binder component 41 can be a natural resin or a synthetic resin. The binder component 41 can also coat the particles contained in the functional layer 40B. The binder component 41 can completely surround each of the particles contained in the functional layer 40B, or can partially expose at least a part of the particles contained in the functional layer 40B.

[0542] The binder component 41 can also contain a cured product of a curable resin composition. The curable resin composition can also contain one or more of a thermosetting resin composition and a radiation curable resin composition. The cured product of the curable resin composition can impart high strength and high hardness to the functional layer 40B. Thereby, the indentation hardness of the first surface 11 increases, and the scratch resistance of the first surface 11 is further improved. From the viewpoint of improving scratch resistance, the radiation curable resin composition is particularly useful.

[0543] The material of the binder component 41 can be the same as the material of the binder component 41 described in the first embodiment. For example, the binder component 41 can also contain a cured product of one or more thermosetting resin compositions described in the first embodiment. The binder component 41 can also contain a cured product of one or more radiation curable resin compositions described in the first embodiment. The binder component 41 can also contain one or more radiation curable compounds exemplified in the first embodiment.

[0544] The binder component can also contain a (meth)acrylate compound as a radiation curable compound. The (meth)acrylate compound can be a monomer or an oligomer. According to the radiation curable compound containing a low-functional (meth)acrylate compound, uneven shrinkage during curing can be suppressed, and the surface of the functional layer 40B can be smoothed. By smoothing the surface of the functional layer 40B, the standard deviation of the complex elastic modulus of the first surface 11 decreases, and the scratch resistance of the first surface 11 improves.

[0545] When the radiation curable compound contains a large amount of a polyfunctional (meth)acrylate compound, by appropriately adjusting the type of solvent and drying conditions, the surface of the functional layer can be smoothed. By smoothing the surface of the functional layer 40B, the standard deviation of the complex elastic modulus of the first surface 11 decreases, and the scratch resistance of the first surface 11 improves.

[0546] <Particles (hollow silica particles 43, solid silica particles 44)>

[0547] In addition to the binder component 41, the functional layer 40B contains hollow silica particles 43. The functional layer 40B may also contain other particles. Examples of other particles include inorganic particles such as magnesium fluoride particles and organic particles.

[0548] The functional layer 40B contains hollow silica particles 43 as silica particles. The hollow silica particles 43 have a shell layer made of silica. In the hollow silica particles 43, the particle interior surrounded by the shell layer becomes a cavity. The cavity interior may contain air. By including the internal cavity, the hollow silica particles 43 have a refractive index lower than that of silica. If the volume of the internal cavity is large, the refractive index of the hollow silica particles 43 becomes lower. The hollow silica particles 43 lower the refractive index of the entire functional layer 40B. By using large-sized hollow silica particles 43 with an increased internal space ratio, the refractive index of the functional layer 40B can be further reduced.

[0549] The hollow silica particles 43 can be uniformly dispersed in the functional layer 40B. By uniformly dispersing the hollow silica particles 43 in the functional layer 40B, the first surface 11 is smoothed. As a result, the slidability of the first surface 11 is improved and the scratch resistance of the first surface 11 is enhanced. By reducing the particle size deviation of the hollow silica particles 43, adjusting the average particle size of the hollow silica particles 43 relative to the average film thickness of the binder component 41, adjusting the affinity between the hollow silica particles 43 and the binder component 41, adjusting the content ratio or average particle size ratio between the hollow silica particles 43 and other particles, adjusting the affinity between the hollow silica particles 43 and other particles, etc., the hollow silica particles 43 can be uniformly dispersed in the functional layer 40B. As a result, the standard deviation of the complex elastic modulus of the first surface 11 is reduced and the scratch resistance of the first surface 11 is enhanced.

[0550] As Figure 13 shown, in addition to the hollow silica particles 43, the functional layer 40B may also contain solid silica particles 44. The solid silica particles 44 are non-hollow silica particles. The solid silica particles 44 are particles without an internal cavity. The solid silica particles 44 may be solid silica particles. By dispersing the solid silica particles in the binder component 41, the indentation hardness of the first surface 11 increases and the scratch resistance of the functional layer 40B is enhanced.

[0551] The solid silica particles 44 can be uniformly dispersed in the functional layer 40B together with the hollow silica particles 43. By uniformly dispersing the solid silica particles 44 and the hollow silica particles 43 in the functional layer 40B, the first surface 11 is smoothed. As a result, the slidability of the first surface 11 is improved, the standard deviation of the complex elastic modulus of the first surface 11 is reduced, and the scratch resistance of the first surface 11 is enhanced. By adjusting the content ratio and the average particle size ratio of the solid silica particles 44 and other particles such as the hollow silica particles 43, and by adjusting the affinity between the solid silica particles 44 and other particles such as the hollow silica particles 43, etc., the solid silica particles 44 can be uniformly dispersed in the functional layer 40B together with the hollow silica particles 43. In Figure 13 In the example shown, the hollow silica particles 43 and the solid silica particles 44 are uniformly dispersed in the functional layer 40B.

[0552] The functional layer 40B may also contain metal oxide particles other than silica particles. The metal oxide particles other than silica particles may be the same as the metal oxide particles other than silica particles described in the first embodiment. For example, the metal oxide particles may also include alumina particles.

[0553] The shapes of the particles such as the hollow silica particles 43 and the solid silica particles 44 dispersed in the functional layer 40B may be the same as those in the first embodiment. The shapes of the particles dispersed in the functional layer 40B are not particularly limited. By making the shapes of the particles such as the hollow silica particles 43 and the solid silica particles 44 dispersed in the functional layer 40B spherical, ellipsoidal or approximately spherical, the slidability of the first surface 11 is improved. As a result, the standard deviation of the complex elastic modulus of the first surface 11 is reduced, and the scratch resistance of the first surface 11 is enhanced.

[0554] The particles such as the hollow silica particles 43 and the solid silica particles 44 dispersed in the functional layer 40B can be coated on the surface with a silane coupling agent in the same manner as in the first embodiment. The silane coupling agent may be the same as the silane coupling agent described in the first embodiment. For example, the silane coupling agent may also contain (meth)acryloyl or epoxy groups. By subjecting the particles to surface treatment with a silane coupling agent, the affinity between the particles and the binder resin is improved, and the particles are less likely to aggregate. As a result, the particles are more uniformly dispersed in the binder resin. As a result, the standard deviation of the complex elastic modulus of the first surface 11 is reduced, and the scratch resistance of the first surface 11 is enhanced.

[0555] As Figure 13As shown, the particles contained in the functional layer 40B such as the hollow silica particles 43 and the solid silica particles 44 can also exist at a high concentration within the functional layer 40B and be uniformly dispersed within the functional layer 40B. According to such a configuration, as described above, the first surface 11 is smoothed and the coefficient of kinetic friction of the first surface 11 is reduced. Thereby, the standard deviation of the complex elastic modulus of the first surface 11 is reduced and the scratch resistance of the first surface 11 is improved. As Figure 13 shown, the hollow silica particles 43 having a large average particle size are uniformly dispersed within the functional layer 40B. The solid silica particles 44 are dispersed within the functional layer 40B so as to fill the spaces between the hollow silica particles 43. The solid silica particles 44 are arranged close to the hollow silica particles 43 within the functional layer 40B.

[0556] In Figure 13 the example shown, the hollow silica particles 43 having a large average particle size are uniformly dispersed within the functional layer 40B. In addition, the solid silica particles 44 having a small average particle size are filled within the functional layer 40B so as to fill the spaces between the hollow silica particles 43. According to this example, the functional layer 40B has high hardness and the surface of the functional layer 40B becomes smooth. That is, the indentation hardness of the first surface 11 increases and the standard deviation of the complex elastic modulus of the first surface 11 is reduced. Thereby, the scratch resistance of the first surface 11 is improved.

[0557] The average particle size of the hollow silica particles 43 can be 50 nm or more and 100 nm or less, can be 65 nm or more and 100 nm or less, can be 50 nm or more and 80 nm or less, or can be 65 nm or more and 80 nm or less.

[0558] The average particle size of the solid silica particles 44 can be 5 nm or more and 20 nm or less, can be 10 nm or more and 20 nm or less, can be 5 nm or more and 15 nm or less, or can be 10 nm or more and 15 nm or less. The average particle size of the solid silica particles 44 can be smaller than the average particle size of the hollow silica particles 43.

[0559] By setting a lower limit on the average particle size of the solid silica particles 44, the solid silica particles 44 can contribute to enhancing the strength and hardness of the functional layer 40B. By setting an upper limit on the average particle size of the hollow silica particles 43, the binder component 41 can stably hold the hollow silica particles 43. That is, it is possible to suppress the hollow silica particles 43 from peeling off the functional layer 40B and improve the scratch resistance. By setting an upper limit on the average particle size of the solid silica particles 44 and a lower limit on the average particle size of the hollow silica particles 43, the solid silica particles 44 can be arranged close to the hollow silica particles 43 with a large average particle size. That is, the hollow silica particles 43 and the solid silica particles 44 can be uniformly dispersed at a high concentration within the functional layer 40B. As a result, the indentation hardness of the first surface 11 increases, and it is possible to stably impart excellent scratch resistance to the functional layer 40B and the optical sheet 10.

[0560] The "average particle size" used for particles such as the hollow silica particles 43 and the solid silica particles 44 is a value determined by the steps (1) to (3) described in the first embodiment.

[0561] The "average thickness" of the functional layer 40B is a value determined by the steps (4) to (6) described in the first embodiment.

[0562] The average particle size of the particles and the thickness of the functional layer can be measured using a scanning transmission electron microscope (STEM: Scanning Transmission Electron Microscope), which is a type of transmission electron microscope, and the electron microscope H-7650 manufactured by Hitachi High-Technologies Corporation.

[0563] If the content of the hollow silica particles 43 increases, the refractive index of the functional layer 40B decreases, and the functional layer 40B can exhibit an excellent reflection suppression function. That is, from the aspect of the reflection suppression function of the functional layer 40B, a lower limit can be set on the content of the hollow silica particles 43. By setting a lower limit on the content of particles other than the hollow silica particles 43, the smoothness, strength, and hardness of the functional layer 40B can be ensured. By setting a lower limit on the content of the binder component 41, the particles can be stably held by the binder component 41. As a result, it is possible to suppress the peeling off of the particles and ensure excellent scratch resistance. By setting an upper limit on the content of the binder component 41, the refractive index of the functional layer 40B decreases, and the functional layer 40B can exhibit an excellent reflection suppression function. By setting an upper limit on the content of each particle, significant aggregation of the particle can be suppressed.

[0564] The content of the hollow silica particles relative to 100 parts by mass of the binder component may also be within the numerical range described in the first embodiment. The content of the solid silica particles relative to 100 parts by mass of the binder component may also be within the numerical range described in the first embodiment. The content of the solid silica particles relative to 100 parts by mass of the hollow silica particles may also be within the numerical range described in the first embodiment.

[0565] <Method for manufacturing the functional layer 40B>

[0566] The functional layer 40B can be manufactured using a coating liquid containing a curable resin composition and particles. The functional layer 40B can also be obtained by curing the coating film of the coating liquid. The coating liquid for the functional layer used to manufacture the functional layer 40B may also contain additives such as antistatic agents, antioxidants, surfactants, dispersants, and ultraviolet absorbers. The coating liquid for the functional layer may also contain a silicone-based leveling agent (silicone-based compound) as an additive. By making the coating liquid for the functional layer contain a silicone-based leveling agent, the surface of the functional layer 40B can be made smoother. Depending on the silicone-based leveling agent, excellent slidability and excellent antifouling properties (fingerprint wiping property, large contact angles with pure water and hexadecane) can be imparted to the surface of the functional layer 40B. The coating liquid for the functional layer may also contain one or more of an acrylic-based leveling agent, a methacrylic-based leveling agent, a vinyl-based leveling agent, and an aromatic-based leveling agent instead of or in addition to the silicone-based leveling agent.

[0567] <<The second functional layer 50 (high refractive index layer)>>

[0568] As Figure 15 shown, the optical sheet 10 may further include the second functional layer 50. The second functional layer 50 is located between the functional layer 40B and the resin layer 30 in the lamination direction, i.e., the third direction D3. The second functional layer 50 may also be adjacent to the functional layer 40B in the third direction D3. As described before, the second functional layer 50 is configured as a layer having a refractive index higher than that of the resin layer 30 and the functional layer 40B, and strengthens the reflection suppression function of the optical sheet 10.

[0569] The second functional layer 50 may also be the same as the second functional layer 50 described in the first embodiment. The refractive index of the second functional layer 50 may also be within the range of the refractive index of the second functional layer 50 described in the first embodiment. The thickness of the second functional layer 50 may also be within the range of the thickness of the second functional layer 50 described in the first embodiment. The material of the second functional layer 50 may also contain one or more of the materials of the second functional layer 50 described in the first embodiment.

[0570] <<Manufacturing method of the optical sheet>>

[0571] The resin layer 30, the functional layer 40B, and the second functional layer 50 included in the optical sheet 10 can be produced by a wet method in which a coating liquid containing the components constituting each of the layers 30, 40B, and 50 is coated onto the substrate 20 and then dried and cured. In addition to the resin composition and particles for forming each layer, the coating liquid may also contain a solvent. The resin composition may also contain additives such as solid components and polymerization initiators constituting each layer.

[0572] The optical sheet 10 including the substrate 20 and the functional layer 40B can be produced as follows. First, a coating liquid for the functional layer for forming the functional layer 40B is prepared. Next, the coating liquid for the functional layer is coated onto the substrate 20 to form a coating film. Then, the coating film is dried, and then, the coating film is cured. Thereby, the functional layer 40B is produced on the substrate 20, and the optical sheet 10 is obtained.

[0573] In the case where the optical sheet 10 further includes the resin layer 30 in addition to the functional layer 40B, the resin layer 30 is produced on the substrate 20 before producing the functional layer 40B. The coating liquid for the resin layer for forming the resin layer 30 is coated onto the substrate 20, and the coating film is dried and cured, thereby obtaining the resin layer 30. Next, the optical sheet 10 is obtained by producing the functional layer 40B on the resin layer 30. It should be noted that the resin layer 30 may be produced on the substrate 20 in an uncured or semi-cured state, and when the functional layer 40B is cured, the resin layer 30 and the functional layer 40B may be completely cured together.

[0574] In the case where the optical sheet 10 further includes the second functional layer 50 in addition to the resin layer 30 and the functional layer 40B, the second functional layer 50 is produced on the resin layer 30 after producing the resin layer 30 and before producing the functional layer 40B. The coating liquid for the second functional layer for forming the second functional layer 50 is coated onto the resin layer 30, and the coating film is dried and cured, thereby obtaining the second functional layer 50. Next, the optical sheet 10 is obtained by producing the functional layer 40B on the second functional layer 50. It should be noted that when one or more of the resin layer 30 and the second functional layer 50 are produced in an uncured or semi-cured state and the functional layer 40B is cured, one or more of the resin layer 30 and the second functional layer 50 may be completely cured together with the functional layer 40B.

[0575] By including a solvent in the coating liquid, the viscosity of the coating liquid can be adjusted, and each component can be dissolved or dispersed in the coating liquid. The solvent may be the same as the solvent described in the first embodiment. As described in the first embodiment, the drying speed of the coating liquid can be adjusted according to the type and content of the solvent.

[0576] According to the manufacturing method of the optical sheet 10 using the wet method, as in the first embodiment, with reference to Figure 4As described, it is possible to manufacture a long sheet article 5 including a plurality of optical sheets 10. By cutting the long sheet article 5 into a specified size, the optical sheet 10 is obtained. According to this example, it is possible to obtain optical sheets 10 having various sizes from the long sheet article 5 as needed. Therefore, it is possible to timely provide optical sheets 10 having various sizes. As Figure 4 shown, by treating the sheet article 5 as a roll 7 wound around a winding core about a winding axis RA, the operability of the sheet article 5 can be improved.

[0577] In addition to the above steps of manufacturing the optical sheet, the method of manufacturing the optical sheet may further include a step of selecting the manufactured optical sheet 10. The step of selecting the optical sheet 10 may further include: a step of measuring the indentation hardness of the first surface 11 with an indentation depth of 100 nm and the complex elastic modulus of the first surface 11 with an indentation depth of 30 nm; and a step of selecting the optical sheet based on the standard deviation of the complex elastic modulus at 10 different positions of the first surface 11 with respect to the indentation hardness. According to the combination of the indentation hardness of the first surface 11 with an indentation depth of 100 nm and the standard deviation of the complex elastic modulus with an indentation depth of 30 nm at 10 different positions of the first surface 11, the scratch resistance of the first surface 11 of the optical sheet 10 can be evaluated with high precision. Therefore, according to the selection step, it is possible to select with high precision an optical sheet having excellent scratch resistance without performing a scratch test using felt or steel wool.

[0578] The selection step may further include the following steps: determining whether any one or more of the following conditions A to C are satisfied, and selecting the optical sheet 10 that satisfies the conditions.

[0579] [A] The indentation hardness of the first surface with an indentation depth of 100 nm is 0.45 GPa or more, and the standard deviation of the complex elastic modulus at 10 different positions of the first surface with an indentation depth of 30 nm is 1.1 GPa or less;

[0580] [B] The indentation hardness is 0.55 GPa or more;

[0581] [C] The above standard deviation of the complex elastic modulus is 0.80 GPa or less.

[0582] <<<Polarizing plate>>>

[0583] The optical sheet 10 of the second embodiment can be applied to the polarizing plate 60 in the same manner as the first embodiment. As Figure 5As shown, the polarizer 60 includes a first protective sheet 61, a polarizing element 62, and a second protective sheet 63. The first protective sheet 61 and the second protective sheet 63 sandwich the polarizing element 62 therebetween 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. In the case where only one of the first protective sheet 61 and the second protective sheet 63 includes the optical sheet 10, the other protective sheet may also include the base material 20.

[0584] <<<Image display device>>>

[0585] The optical sheet 10 of the second embodiment can be applied to the display device 65 in the same manner as the first embodiment. In Figure 6 the example shown, the display device 65 includes an image forming device 66 and the optical sheet 10. An observer can clearly observe the image displayed by the image forming device 66 through the optical sheet 10 while suppressing the reflection on the first surface 11 of the optical sheet 10.

[0586] <<<Panel>>>

[0587] The optical sheet 10 of the second embodiment can be applied to various uses in the same manner as the first embodiment. Figure 7 The panel 70 to which the optical sheet 10 of the second embodiment is applied is shown. The panel 70 includes the optical sheet 10 and an article 71 to which the optical sheet 10 is joined. The panel 70 constitutes an antireflection article having an antireflection function through the optical sheet 10. The optical sheet 10 overlaps the article 71 such that its second surface 12 faces the article 71. The optical sheet 10 may also be joined to the article 71 through a joining layer including an adhesive material, a bonding material, or the like. Examples of the article 71 include a dashboard, a clock, a display case, a window display, and a window.

[0588] [Second Embodiment]

[0589] The second embodiment will be described in more detail by way of examples. The second embodiment is not limited by the following examples.

[0590] 1. Measurement and Evaluation

[0591] As described below, the optical sheets of the examples and comparative examples were measured and evaluated. The atmosphere for each measurement and evaluation was a temperature of 23 ± 5°C and a relative humidity of 50 ± 5%. Before starting each measurement and evaluation, the target sample was exposed to the above atmosphere for 30 minutes or more, and then the measurement and evaluation of the target sample were performed.

[0592] 1-1. Visual reflectance Y value

[0593] Samples measuring 5 cm × 5 cm were cut from the optical sheets of the examples and comparative examples. The samples were visually inspected to confirm that there were no abnormalities such as dust or damage. The visual reflectance Y (%) of the optical sheets of each example was measured by the above method. The measurement of the visual reflectance Y was performed using a UV-visible near-infrared spectrophotometer “V780” manufactured by JASCO Corporation. The measurement results are shown in the column “Y value” in Table 2.

[0594] 1-2. Total light transmittance and haze

[0595] Samples measuring 10 cm × 5 cm were cut from the optical sheets of the examples and comparative examples. The samples were visually inspected to confirm that there were no abnormalities such as dust or damage. The total light transmittance (%) and haze (%) of the optical sheets of each example were measured by the above method. The measurement of the total light transmittance and haze was performed using a haze meter “HM-150” manufactured by Murakami Color Research Laboratory. The measurement results of the total light transmittance (%) are shown in the column “Tt” in Table 2. The measurement results of the haze (%) are shown in the column “Hz” in Table 2.

[0596] 1-3. Evaluation based on nanoindentation method

[0597] 1-3-1. Indentation hardness H IT

[0598] The indentation hardness of the first surface with an indentation depth of 100 nm was measured by the above method. The measurement results of the indentation hardness (GPa) are shown in the column “H IT ” in Table 2.

[0599] 1-3-2. Indentation hardness H IT

[0600] By the above method, the complex elastic modulus E with an indentation depth of 30 nm was measured at 10 different positions on the first surface r , and the standard deviation σ of the 10 measured values was calculated Er . The standard deviation σ of the complex elastic modulus Er is shown in the column “σ Er ” in Table 2.

[0601] 1-4. Steel wool resistance

[0602] Samples measuring 5 cm × 10 cm were cut from the optical sheets of the examples and comparative examples. The samples were visually inspected to confirm that there were no abnormalities such as dust or damage. The steel wool abrasion resistance test was performed on the optical sheets of each example by the above method. The steel wool abrasion resistance test was performed using a friction fastness tester “AB-301-S” of Gakushin type manufactured by Tester Sangyo Co., Ltd.

[0603] Samples that had completed 1,000 cycles of the wire wool abrasion resistance test under a load of 1,000 g were removed from the testing machine, and the surface of the samples formed by the first surface of the optical sheet was observed under the above observation conditions. Based on the observation results, each sample was evaluated according to the following criteria. The evaluation results for each example of the examples and comparative examples are shown in the "Abrasion Resistance to SW" column of "Evaluation Results" in Table 2. Five samples were evaluated for each example, and the worst evaluation result for each example is shown in Table 2.

[0604] AA: No damage was observed on the surface.

[0605] A: A pattern of slight damage was observed on the surface, but the pattern was such that there was no problem as a product.

[0606] B: Damage was observed on the surface.

[0607] Among the above criteria, "AA" has the highest abrasion resistance. In "AA" and "A", no defects that would cause problems when applied to a display device were generated. "AA" and "A" were evaluated as being resistant to the wire wool abrasion resistance test. In "B", defects that would cause problems when applied to a display device were generated. "B" was evaluated as not being resistant to the wire wool abrasion resistance test. It should be noted that the test conditions of "load 1,000 g, 1,000 cycles" in the wire wool abrasion resistance test are more severe than the conditions usually required for anti-reflection films (AR films, LR films) attached to the display surface of a display device.

[0608] 1-5. Felt Resistance

[0609] Samples of 50 mm × 100 mm were cut out from the optical sheets of the examples and comparative examples. The samples were visually confirmed to have no abnormalities such as dust or damage. The felt abrasion resistance test was performed on the optical sheets of each example by the above method. The felt abrasion resistance test used the Gakushin type friction fastness testing machine "AB-301-S" manufactured by Tester Sangyo Co., Ltd.

[0610] Samples that had completed 10,000 cycles of the abrasion resistance test for felt under a load of 200 g were removed from the friction measuring machine, and the surface of the samples formed by the first surface of the optical sheet was observed under the above observation conditions. The presence or absence of damage was evaluated. Based on the observation results, in the same manner as the evaluation criteria, each sample of each example was evaluated using any one of "AA", "A", and "B". The evaluation results for each example of the examples and comparative examples are shown in the "Felt Resistance" column of "Evaluation Results" in Table 2. Five samples were evaluated for each example, and the worst evaluation result for each example is shown in Table 2.

[0611] 2. Fabrication of Optical Sheet

[0612] [Comparative Example 11]

[0613] After coating the resin layer coating solution 11 (HC layer coating solution 11) of the following formulation on a substrate made of triacetyl cellulose with a thickness of 80 μm, it was dried at 70 °C for 1 minute to volatilize the solvent. Then, ultraviolet irradiation was performed with a cumulative light quantity of 100 mJ / cm 2 to produce a resin layer (hard coat) with a dry thickness of 10 μm.

[0614] Next, after coating the second functional layer coating solution 11 (high refractive index layer coating solution 11) of the following formulation on the resin layer, it was dried at 70 °C for 1 minute to volatilize the solvent. Then, ultraviolet irradiation was performed with a cumulative light quantity of 100 mJ / cm 2 to form a second functional layer (high refractive index layer) with a dry thickness of 150 nm.

[0615] Next, after coating the functional layer coating solution 11 (low refractive index layer coating solution 11) of the following formulation on the second functional layer, the coated film was dried under the conditions of 50 °C for 30 seconds (drying wind speed 0.5 m / s), and then the coated film was dried under the conditions of 50 °C for 30 seconds (drying wind speed 5 m / s) to volatilize the solvent. Then, ultraviolet irradiation was performed with a cumulative light quantity of 200 mJ / cm 2 to form a functional layer (low refractive index layer) with a dry thickness of 100 nm, and an optical sheet of Comparative Example 11 was obtained.

[0616] <Resin layer coating solution 11 (Hard coat coating solution 11)>

[0617] · 100 parts by mass of a composition containing a UV-curable acrylate

[0618] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M-450”, solid content 100%)

[0619] · 77 parts by mass of a composition containing a UV-curable acrylate

[0620] (Daiichi Kogyo Seiyaku Co., Ltd., trade name “New Frontier R-1403MB”, solid content 80%)

[0621] · 5 parts by mass of a fluorine-based leveling agent

[0622] (DIC Corporation, trade name “MEGAFACE F-568”)

[0623] · 5 parts by mass of a photoinitiator

[0624] (IGM Resins, trade name “Omnirad184”)

[0625] · 68 parts by mass of methyl isobutyl ketone

[0626] · 200 parts by mass of methyl ethyl ketone

[0627] <Coating liquid 11 for the second functional layer (coating liquid 11 for the high refractive index layer)>

[0628] · 100 parts by mass of PETA

[0629] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M-305”, solid content 100%)

[0630] · 300 parts by mass of high refractive index particles

[0631] (Manufactured by Nippon Shokubai Co., Ltd., trade name “ZIRCOSTAR”, solid content 70%)

[0632] · 0.7 parts by mass of fluorine-based leveling agent

[0633] (Manufactured by DIC Corporation, trade name “MEGAFACE F251”, solid content 100%)

[0634] · 9 parts by mass of photoinitiator

[0635] (Manufactured by IGM Resins B.V., trade name “Omnirad127”, solid content 100%)

[0636] · 3173 parts by mass of methyl isobutyl ketone

[0637] · 3173 parts by mass of propylene glycol monomethyl ether

[0638] <Coating liquid 11 for the functional layer (coating liquid 11 for the low refractive index layer)>

[0639] · 100 parts by mass of polyfunctional acrylate composition

[0640] (Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name “New Frontier MF-001”)

[0641] · 200 parts by mass of hollow silica particles

[0642] (Particles with an average particle size of 75 nm and surface-treated with a silane coupling agent having a methacryloyl group)

[0643] · 110 parts by mass of solid silica particles

[0644] (Particles with an average particle size of 12.5 nm and surface-treated with a silane coupling agent having a methacryloyl group)

[0645] · 13 parts by mass of silicone-based leveling agent

[0646] (Shin-Etsu Chemical Co., Ltd., trade name "X-22-164E", solid content 100%)

[0647] · 4.3 parts by mass of photoinitiator

[0648] (IGM Resins, trade name "Omnirad127")

[0649] · 14,867 parts by mass of solvent

[0650] (Mixed solvent of methyl isobutyl ketone and 1-methoxy-2-propyl acetate. Mass ratio = 68 / 32)

[0651] [Example 11]

[0652] The resin layer coating liquid 12 (HC layer coating liquid 12) with the following formulation was coated onto a substrate, and the coating film was dried and cured to fabricate a resin layer (hard coat) with a dry thickness of 10 μm. The substrate used in Example 11 was the same as the substrate used in Comparative Example 11 above. The resin layer in Example 11 differed from the above Comparative Example 11 in that the resin layer coating liquid was changed, and the others were manufactured by the same method and under the same conditions as in Comparative Example 11.

[0653] Next, the functional layer coating liquid 12 (low refractive index layer coating liquid 12) with the following formulation was coated onto the resin layer, and the coating film was dried and cured to form a functional layer (low refractive index layer) with a dry thickness of 100 nm, obtaining the optical sheet of Example 11. That is, the optical sheet of Example 11 differed from the optical sheet of Comparative Example 11 in that it did not contain the second functional layer. The functional layer in Example 11 differed from the above Comparative Example 11 in that the functional layer coating liquid was changed, and the others were manufactured by the same method and under the same conditions as in Comparative Example 11.

[0654] <Resin layer coating liquid 12 (Hard coat coating liquid 12)>

[0655] · 100 parts by mass of a composition containing a UV-curable acrylate

[0656] (Manufactured by Toagosei Co., Ltd., trade name "Aronix M-450", solid content 100%)

[0657] · 109 parts by mass of solid silica particles

[0658] (Particles with an average particle size of 12.5 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 46%)

[0659] · 2 parts by mass of a silicone leveling agent

[0660] (Manufactured by Dainichi Seika Kogyo Co., Ltd., trade name "10-301", solid content 5%)

[0661] · 4 parts by mass of photoinitiator

[0662] (IGM Resins, trade name "Omnirad184", solid content 100%)

[0663] · 69 parts by mass of methyl isobutyl ketone

[0664] · 297 parts by mass of methyl ethyl ketone

[0665] · 33 parts by mass of propylene glycol monomethyl ether

[0666] <Coating liquid 12 for functional layer (Coating liquid 12 for low refractive index layer)>

[0667] · 100 parts by mass of a composition containing an ultraviolet curable silicone compound

[0668] (Manufactured by Toagosei Co., Ltd., trade name "AS-SQ TA-100", solid content 100%)

[0669] · 12 parts by mass of a composition containing an ultraviolet curable acrylate

[0670] (Manufactured by Toagosei Co., Ltd., trade name "Aronix M-305", solid content 100%)

[0671] · 842 parts by mass of hollow silica particles

[0672] (Particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0673] · 27 parts by mass of solid silica particles

[0674] (Particles with an average particle size of 9.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 50%)

[0675] · 46 parts by mass of alumina particles

[0676] (Particles with an average particle size of 15.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 30%)

[0677] · 307 parts by mass of leveling agent

[0678] (Shin-Etsu Chemical Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0679] · 82 parts by mass of leveling agent

[0680] (Arakawa Chemical Industries, trade name "Opstar TU2225", solid content 15%)

[0681] · 4 parts by mass of a photoinitiator

[0682] (IGM Resins, trade name "Omnirad127", solid content 100%)

[0683] · 13126 parts by mass of methyl isobutyl ketone

[0684] · 1472 parts by mass of propylene glycol monomethyl ether acetate

[0685] [Example 12]

[0686] Example 12 is different from Example 11 above in that the coating liquid 12 for the functional layer is changed to the following coating liquid 13 for the functional layer, and the optical sheet of Example 12 is obtained by the same materials and the same method as in Example 11.

[0687] [Coating liquid 13 for functional layer (coating liquid 13 for low refractive index layer)]

[0688] · 100 parts by mass of a composition containing an ultraviolet curable silicone compound

[0689] (manufactured by Toagosei Co., Ltd., trade name "AS-SQ TA-100", solid content 100%)

[0690] · 42 parts by mass of a composition containing an ultraviolet curable acrylate

[0691] (manufactured by Toagosei Co., Ltd., trade name "Aronix M-305", solid content 100%)

[0692] · 1096 parts by mass of hollow silica particles

[0693] (average particle size 65 nm, particles surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0694] · 97 parts by mass of solid silica particles

[0695] (average particle size 12.5 nm, particles surface-treated with a silane coupling agent having a methacryloyl group, solid content 37%)

[0696] · 199 parts by mass of a leveling agent

[0697] (Shin-Etsu Chemical Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0698] · 5 parts by mass of photoinitiator

[0699] (manufactured by IGM Resins, trade name “Omnirad127”, 100% solid content)

[0700] · 15255 parts by mass of methyl isobutyl ketone

[0701] · 1696 parts by mass of propylene glycol monomethyl ether acetate

[0702] [Example 13]

[0703] Example 13 is different from Example 11 in that the coating liquid 12 for the functional layer is changed to the following coating liquid 14 for the functional layer, and the optical sheet of Example 13 is obtained by the same materials and the same method as in Example 11.

[0704] [Coating liquid 14 for functional layer (coating liquid 14 for low refractive index layer)]

[0705] · 100 parts by mass of a composition containing a UV-curable silicone compound

[0706] (manufactured by Toagosei Co., Ltd., trade name “AS-SQ TA-100”, 100% solid content)

[0707] · 43 parts by mass of a composition containing a UV-curable acrylate

[0708] (manufactured by Toagosei Co., Ltd., trade name “Aronix M-305”, 100% solid content)

[0709] · 1111 parts by mass of hollow silica particles

[0710] (particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, 20% solid content)

[0711] · 36 parts by mass of solid silica particles

[0712] (particles with an average particle size of 9.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, 50% solid content)

[0713] · 60 parts by mass of alumina particles

[0714] (particles with an average particle size of 15.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, 30% solid content)

[0715] · 201 parts by mass of a leveling agent

[0716] (Shin-Etsu Chemical Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0717] · 6 parts by mass of photoinitiator

[0718] (IGM Resins, trade name "Omnirad127", solid content 100%)

[0719] · 15263 parts by mass of methyl isobutyl ketone

[0720] · 1819 parts by mass of propylene glycol monomethyl ether acetate

[0721] [Example 14]

[0722] Example 14 is different from Example 11 in that the coating liquid 12 for the functional layer is changed to the following coating liquid 15 for the functional layer, and the optical sheet of Example 14 is obtained by the same materials and the same method as in Example 11.

[0723] (Coating liquid 15 for functional layer (coating liquid 15 for low refractive index layer))

[0724] · 100 parts by mass of a composition containing a UV-curable acrylate

[0725] (Manufactured by Toagosei Co., Ltd., trade name "Aronix M-305", solid content 100%)

[0726] · 650 parts by mass of hollow silica particles

[0727] (Particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0728] · 67 parts by mass of solid silica particles

[0729] (Particles with an average particle size of 12.5 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 37%)

[0730] · 128 parts by mass of leveling agent

[0731] (Shin-Etsu Chemical Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0732] · 34 parts by mass of leveling agent

[0733] (Arakawa Chemical Co., Ltd., trade name "Opstar TU2225", solid content 15%)

[0734] · 7 parts by mass of photoinitiator

[0735] (IGM Resins, trade name "Omnirad127", 100% solid content)

[0736] · 8828 parts by mass of methyl isobutyl ketone

[0737] · 1034 parts by mass of propylene glycol monomethyl ether acetate

[0738] [Example 15]

[0739] Example 15 is different from Example 11 in that the coating liquid 12 for the functional layer is changed to the following coating liquid 16 for the functional layer. The optical sheet of Example 15 is obtained by the same materials and the same method as those in Example 11.

[0740] <Coating liquid 16 for functional layer (coating liquid 16 for low refractive index layer)>

[0741] · 100 parts by mass of a composition containing an ultraviolet curable silicone compound

[0742] (Manufactured by Toagosei Co., Ltd., trade name "AS-SQ TA-100", 100% solid content)

[0743] · 11 parts by mass of a composition containing an ultraviolet curable acrylate

[0744] (Manufactured by Toagosei Co., Ltd., trade name "Aronix M-305", 100% solid content)

[0745] · 777 parts by mass of hollow silica particles

[0746] (Particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, 20% solid content)

[0747] · 39 parts by mass of solid silica particles

[0748] (Particles with an average particle size of 9.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, 50% solid content)

[0749] · 65 parts by mass of alumina particles

[0750] (Particles with an average particle size of 15.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, 30% solid content)

[0751] · 457 parts by mass of a leveling agent

[0752] (Shin-Etsu Chemical Co., Ltd., trade name "X-71-1203M", 20% solid content)

[0753] · 82 parts by mass of a leveling agent

[0754] (Arakawa Chemical Industries, trade name “Opstar TU2225”, solid content 15%)

[0755] · 5 parts by mass of a photoinitiator

[0756] (IGM Resins, trade name “Omnirad127”, solid content 100%)

[0757] · 14107 parts by mass of methyl isobutyl ketone

[0758] · 1580 parts by mass of propylene glycol monomethyl ether acetate

[0759] [Example 16]

[0760] Example 16 is different from Example 11 in that the coating liquid 12 for the functional layer is changed to the following coating liquid 17 for the functional layer, and the optical sheet of Example 16 is obtained by the same materials and the same method as in Example 11.

[0761] (Coating liquid 17 for functional layer (coating liquid 17 for low refractive index layer))

[0762] · 100 parts by mass of a composition containing an ultraviolet curable silicone compound

[0763] (Manufactured by Toagosei Co., Ltd., trade name “AS-SQ TA-100”, solid content 100%)

[0764] · 43 parts by mass of a composition containing an ultraviolet curable acrylate

[0765] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M-305”, solid content 100%)

[0766] · 1111 parts by mass of hollow silica particles

[0767] (Particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0768] · 36 parts by mass of solid silica particles

[0769] (Particles with an average particle size of 9.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 50%)

[0770] · 60 parts by mass of alumina particles

[0771] (Particles with an average particle size of 15.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 30%)

[0772] · 201 parts by mass of a leveling agent

[0773] (Shin-Etsu Chemical Co., Ltd., trade name “X-71-1203M”, solid content 20%)

[0774] · 54 parts by mass of a leveling agent

[0775] (Arakawa Chemical Industries, Ltd., trade name “Opstar TU2225”, solid content 15%)

[0776] · 6 parts by mass of a photoinitiator

[0777] (IGM Resins, trade name “Omnirad127”, solid content 100%)

[0778] · 15511 parts by mass of methyl isobutyl ketone

[0779] · 1851 parts by mass of propylene glycol monomethyl ether acetate

[0780] [Example 17]

[0781] Example 17 is different from Example 11 in that the coating liquid 12 for the functional layer is changed to the following coating liquid 18 for the functional layer, and the optical sheet of Example 17 is obtained by the same materials and the same method as in Example 11.

[0782] <Coating liquid 18 for functional layer (coating liquid 18 for low refractive index layer)>

[0783] · 100 parts by mass of a composition containing an ultraviolet curable silicone compound

[0784] (Manufactured by Toagosei Co., Ltd., trade name “AS-SQ TA-100”, solid content 100%)

[0785] · 43 parts by mass of a composition containing an ultraviolet curable acrylate

[0786] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M-305”, solid content 100%)

[0787] · 1143 parts by mass of hollow silica particles

[0788] (Particles with an average particle size of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0789] · 50 parts by mass of solid silica particles

[0790] (Particles with an average particle size of 9.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 50%)

[0791] · 83 parts by mass of alumina particles

[0792] (Particles with an average particle size of 15.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 30%)

[0793] · 633 parts by mass of a leveling agent

[0794] (Shin-Etsu Chemical Co., Ltd., trade name “X-71-1203M”, solid content 20%)

[0795] · 113 parts by mass of a leveling agent

[0796] (Arakawa Chemical Co., Ltd., trade name “Opstar TU2225”, solid content 15%)

[0797] · 6 parts by mass of a photoinitiator

[0798] (IGM Resins, trade name “Omnirad127”)

[0799] · 19354 parts by mass of methyl isobutyl ketone

[0800] · 2320 parts by mass of propylene glycol monomethyl ether acetate

[0801] [Example 18]

[0802] Example 18 is different from Example 11 in that the coating liquid 12 for the functional layer is changed to the following coating liquid 19 for the functional layer, and the optical sheet of Example 18 is obtained by the same materials and the same method as in Example 11.

[0803] (Coating liquid 19 for the functional layer (coating liquid 19 for the low refractive index layer))

[0804] · 100 parts by mass of a composition containing an ultraviolet curable silicone-based compound

[0805] (Manufactured by Toagosei Co., Ltd., trade name “AS-SQ TA-100”, solid content 100%)

[0806] · 43 parts by mass of a composition containing an ultraviolet curable acrylate

[0807] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M-305”, solid content 100%)

[0808] · 1135 parts by mass of hollow silica particles

[0809] (Particles with an average particle diameter of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0810] · 65 parts by mass of solid silica particles

[0811] (Particles with an average particle diameter of 9.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 50%)

[0812] · 109 parts by mass of alumina particles

[0813] (Particles with an average particle diameter of 15.0 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 30%)

[0814] · 651 parts by mass of a leveling agent

[0815] (Shin-Etsu Chemical Co., Ltd., trade name “X-71-1203M”, solid content 20%)

[0816] · 116 parts by mass of a leveling agent

[0817] (Arakawa Chemical Co., Ltd., trade name “Opstar TU2225”, solid content 15%)

[0818] · 6 parts by mass of a photoinitiator

[0819] (IGM Resins, trade name “Omnirad127”)

[0820] · 19935 parts by mass of methyl isobutyl ketone

[0821] · 2320 parts by mass of propylene glycol monomethyl ether acetate

[0822] [Comparative Example 12]

[0823] Comparative Example 12 is different from Example 11 above in that the coating liquid 12 for the functional layer is changed to the following coating liquid 20 for the functional layer. The optical sheet of Comparative Example 12 is obtained by the same materials and the same method as in Example 11 except for this point.

[0824] <Coating liquid 20 for functional layer (coating liquid 20 for low refractive index layer)>

[0825] · 100 parts by mass of a composition containing an ultraviolet-curable acrylate

[0826] (Manufactured by Toagosei Co., Ltd., trade name “Aronix M-305”, solid content 100%)

[0827] · 800 parts by mass of hollow silica particles

[0828] (Particles with an average particle diameter of 65 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 20%)

[0829] · 68 parts by mass of solid silica particles

[0830] (Particles with an average particle diameter of 12.5 nm, surface-treated with a silane coupling agent having a methacryloyl group, solid content 37%)

[0831] · 143 parts by mass of a leveling agent

[0832] (Shin-Etsu Chemical Co., Ltd., trade name “X-71-1203M”, solid content 20%)

[0833] · 4 parts by mass of a photoinitiator

[0834] (IGM Resins, trade name “Omnirad127”, solid content 100%)

[0835] · 9504 parts by mass of methyl isobutyl ketone

[0836] · 1144 parts by mass of propylene glycol monomethyl ether acetate

[0837] [Table 2]

[0838]

[0839] Explanation of reference numerals

[0840] 5: Sheet article, 6: Take-up core, 7: Roll, 10: Optical sheet, 11: First surface, 12: Second surface, 20: Substrate, 30: Resin layer, 40A: Functional layer, 41: Binder component, 43: Hollow silica particles, 44: Solid silica particles, 45: Metal oxide particles, 46: Alumina particles, 50: Second functional layer, 51: Binder component, 52: Particles, 60: Polarizing plate, 61: First protective sheet, 62: Polarizing element, 63: Second protective sheet, 65: Display device, 66: Image forming device, 66a: Display surface, 70: Panel, 71: Article to be joined.

Claims

1. An optical sheet, which is an optical sheet having a first surface and a second surface facing the first surface, wherein, in the order from the second surface toward the first surface, a substrate and a functional layer are provided, the functional layer contains a binder component, hollow silica particles, and metal oxide particles other than silica particles, the arithmetic mean roughness Sa of the first surface is 5.2 nm or less.

2. The optical sheet according to claim 1, wherein, The arithmetic mean roughness Sa is 4.2 nm or less.

3. The optical sheet according to claim 1, wherein, The kinetic friction coefficient between the first surface and a felt applied with a load of 500 g is 0.20 or less.

4. The optical sheet according to claim 1, wherein, The kinetic friction coefficient between the first surface and steel wool applied with a load of 500 g is 0.25 or less.

5. The optical sheet according to claim 1, wherein, The average particle size of the metal oxide particles is smaller than the average thickness of the functional layer.

6. The optical sheet according to claim 1, wherein The average particle size of the metal oxide particles is smaller than the average particle size of the hollow silica particles.

7. The optical sheet according to claim 1, wherein, The metal oxide particles contain alumina.

8. The optical sheet according to claim 1, wherein, The functional layer contains solid silica particles.

9. The optical sheet according to claim 1, which further comprises a resin layer located between the substrate and the functional layer, wherein the resin layer contains a cured product of a curable resin composition.

10. An optical sheet, which is an optical sheet comprising a first surface and a second surface facing the first surface, wherein, in the order from the second surface toward the first surface, a substrate and a functional layer are provided, the functional layer contains a binder component and hollow silica particles, the indentation hardness of the first surface with an indentation depth of 100 nm is 0.45 GPa or more, the standard deviation of the complex elastic modulus with an indentation depth of 30 nm at 10 different positions on the first surface is 1.1 GPa or less.

11. The optical sheet according to claim 10, wherein, The indentation hardness is 0.55 GPa or more.

12. The optical sheet according to claim 10, wherein, The standard deviation of the complex elastic modulus is 0.80 GPa or less.

13. The optical sheet according to claim 10, wherein, The average thickness of the functional layer is 80 nm or more and 150 nm or less.

14. The optical sheet according to claim 10, wherein, The average particle size of the hollow silica particles is 50 nm or more and 100 nm or less.

15. The optical sheet according to claim 10, which further comprises a resin layer located between the substrate and the functional layer and adjacent to the functional layer, wherein the resin layer contains a cured product of a curable resin composition, and the average thickness of the resin layer is 0.1 μm or more and 100 μm or less.

16. The optical sheet according to claim 10, which further comprises a second functional layer located between the substrate and the functional layer and adjacent to the functional layer, wherein the second functional layer contains a binder component and particles, and the average thickness of the second functional layer is 50 nm or more and 200 nm or less.

17. The optical sheet according to claim 16, which further comprises a resin layer located between the substrate and the second functional layer and adjacent to the second functional layer, wherein the resin layer contains a cured product of a curable resin composition, and the average thickness of the resin layer is 0.1 μm or more and 100 μm or less.

18. A sheet article, which comprises a plurality of the optical sheets according to any one of claims 1 to 17.

19. The sheet article according to claim 18, which is wound around a winding axis.

20. A polarizing plate, which includes a first protective sheet, a polarizing element, and a second protective sheet, wherein at least one of the first protective sheet and the second protective sheet includes the optical sheet according to any one of claims 1 to 17.

21. A display device, which includes: an image forming device; and the optical sheet according to any one of claims 1 to 17 that overlaps with the image forming device.

22. A panel, which includes: an article to be joined; and the optical sheet according to any one of claims 1 to 17 that is joined to the article to be joined.

23. A method for selecting an optical sheet, which includes the following steps for the following optical sheet, the optical sheet has a first surface and a second surface facing the first surface, and includes a substrate and a functional layer in the order from the second surface toward the first surface, and the functional layer includes a binder component, hollow silica particles, and metal oxide particles other than silica particles, and the steps are: a step of measuring the arithmetic mean roughness Sa of the first surface; and a step of selecting an optical sheet with the arithmetic mean roughness Sa of 5.2 nm or less.

24. A method for manufacturing an optical sheet, which includes the following steps: a step of manufacturing an optical sheet, the optical sheet has a first surface and a second surface facing the first surface, and includes a substrate and a functional layer in the order from the second surface toward the first surface, and the functional layer includes a binder component, hollow silica particles, and metal oxide particles other than silica particles; and a step of evaluating the arithmetic mean roughness Sa of the first surface and selecting an optical sheet with the arithmetic mean roughness Sa of 5.2 nm or less.

25. A method for selecting an optical sheet, which includes the following steps for the following optical sheet, the optical sheet includes a first surface and a second surface facing the first surface, and includes a substrate and a functional layer in the order from the second surface toward the first surface, and the functional layer includes a binder component and hollow silica particles, and the steps are: a step of measuring the indentation hardness of the first surface with an indentation depth of 100 nm and the complex elastic modulus of the first surface with an indentation depth of 30 nm; and a step of selecting an optical sheet based on the indentation hardness and the standard deviation of the complex elastic modulus at 10 different positions on the first surface.

26. A method for manufacturing an optical sheet, which includes the following steps: a step of manufacturing an optical sheet, the optical sheet includes a first surface and a second surface facing the first surface, and includes a substrate and a functional layer in the order from the second surface toward the first surface, and the functional layer includes a binder component and hollow silica particles; and a step of selecting an optical sheet based on the indentation hardness of the first surface with an indentation depth of 100 nm and the standard deviation of the complex elastic modulus with an indentation depth of 30 nm at 10 different positions on the first surface.

Images