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 optical sheet includes a base material and a functional layer in this order from the second surface toward the first surface. The functional layer contains a binder component and hollow silica particles. In a 10 [mu] m * 10 [mu] m region of the first surface, a pit having a width of 0.1 [mu] m or more and 1.5 [mu] m or less and a depth of 10 nm or more is included.

Description

Technical Field

[0001] This disclosure relates to optical sheets, sheet articles, polarizers, display devices, panels, methods for selecting optical sheets, and methods for manufacturing optical sheets. Background Technology

[0002] Conventional display devices typically have a glass cover as their outermost surface. This glass cover is designed to suppress the reflection of incident light. In recent years, from the perspective of thinness and lightweight design, resin-based optical sheets have been researched as an alternative to glass cover. These optical sheets have a low-refractive-index functional layer as their surface layer. This functional layer can be fabricated by sputtering inorganic materials. Alternatively, as disclosed in Patent Document 1, the functional layer can be fabricated by curing a coating film containing hollow silica particles. A low-refractive-index layer formed by curing a coating film containing low-refractive-index particles offers advantages such as minimal hue variation in obliquely reflected light, excellent chemical stability, and low manufacturing cost.

[0003] Besides smartphones and tablets, touch sensing is also widely used in display devices such as laptop computers. Optical films used in such displays require scratch resistance appropriate to their application. Functional layers containing hollow silica particles exhibit slightly lower scratch resistance than sputtered inorganic material layers.

[0004] Patent Document 1: WO2019 / 208786A Summary of the Invention

[0005] The purpose of this disclosure is to improve the scratch resistance of optical sheets containing hollow silica particles.

[0006] One embodiment of the optical sheet disclosed herein includes a first surface and a second surface opposite to the first surface, wherein... The optical sheet has a substrate and a functional layer sequentially from the second surface toward the first surface. The functional layer comprises an adhesive component and hollow silica particles. The first surface contains a 10μm×10μm region containing pits with a width of more than 0.1μm and less than 1.5μm and a depth of more than 10nm.

[0007] An embodiment of the present disclosure comprises a plurality of optical sheets according to an embodiment of the present disclosure.

[0008] A polarizer according to one embodiment of the present disclosure 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 comprises an optical sheet according to one embodiment of the present disclosure.

[0009] A display device according to one embodiment of the present disclosure includes: an image forming apparatus; and an optical sheet according to one embodiment of the present disclosure overlapping the image forming apparatus.

[0010] One embodiment of the panel of this disclosure includes: an article to be joined; and an optical sheet of one embodiment of the present disclosure joined to the article to be joined.

[0011] The method for selecting an optical sheet according to one embodiment of this disclosure includes the following steps: For an optical sheet comprising a first surface and a second surface opposite to the first surface, the step of acquiring an image of a 10 μm × 10 μm region of the first surface, wherein the optical sheet comprises a substrate and a functional layer sequentially from the second surface toward the first surface, the functional layer comprising an adhesive component and hollow silica particles; and The step of selecting an optical sheet containing a pit with a width of more than 0.1 μm and less than 0.15 μm and a depth of more than 10 nm in the region based on the image.

[0012] One embodiment of the present disclosure provides a method for manufacturing an optical sheet comprising the following steps: The steps of manufacturing an optical sheet, wherein the optical sheet includes a first surface and a second surface opposite to the first surface, and a substrate and a functional layer are sequentially formed from the second surface toward the first surface, the functional layer comprising an adhesive component and hollow silica particles; and The step of selecting an optical sheet containing a 10μm × 10μm region on the first surface, wherein the pit has a width of 0.1μm to 0.15μm and a depth of 10nm or more.

[0013] According to the present invention, the scratch resistance of optical sheets containing hollow silica particles can be improved. Attached Figure Description

[0014] Figure 1 This is a diagram used to illustrate one embodiment, and is a cross-sectional view showing an example of an optical sheet.

[0015] Figure 2 This is a top view showing an example of a recess formed on the first surface of an optical plate.

[0016] Figure 3 This is a cross-sectional view showing an example of the cross-sectional profile of a pit formed on the first surface of the optical plate, illustrating the direction along... Figure 2 of The cross-section of the line.

[0017] Figure 4 Is with Figure 3 The corresponding cross-sectional view shows other examples of the cross-sectional profile of the pit.

[0018] Figure 5 This is a top view showing the first side of the optical plate, and a diagram showing an example of the distribution of the pits.

[0019] Figure 6 This is a top view showing the first side of the optical plate, and a diagram showing an example of the distribution of the pits.

[0020] Figure 7 Is with Figure 1 The corresponding figure is a cross-sectional view showing other examples of optical sheets.

[0021] Figure 8 This is a perspective view showing an example of a sheet article containing optical plates.

[0022] Figure 9 This is a cross-sectional view showing an example of a polarizer containing optical plates.

[0023] Figure 10 This is a cross-sectional view showing an example of a display device including an optical sheet.

[0024] Figure 11 This is a cross-sectional view showing an example of a panel containing optical sheets.

[0025] Figure 12 This is an image showing the surface of Example 1.

[0026] Figure 13 This is an image showing the surface of Example 2.

[0027] Figure 14 This is an image showing the surface of Example 3.

[0028] Figure 15 This is an image showing the surface of Comparative Example 1. Detailed Implementation

[0029] One embodiment of this disclosure relates to the following <1> ~ <17> .

[0030] <1> An optical sheet comprising a first surface and a second surface opposite to the first surface, wherein, The optical sheet has a substrate and a functional layer sequentially from the second surface toward the first surface. The functional layer comprises an adhesive component and hollow silica particles. The first surface contains a 10μm×10μm region containing pits with a width of more than 0.1μm and less than 1.5μm and a depth of more than 10nm.

[0031] <2> according to <1> The optical sheet wherein the depth of the pit is less than 70 nm.

[0032] <3> according to <1> or <2> The optical sheet wherein the 10μm×10μm region on the first surface contains three or more pits.

[0033] <4> according to <1> ~ <3> The optical sheet according to any one of the following methods, wherein the pits contained in the 10μm×10μm region of the first surface are 11 or more.

[0034] <5> according to <1> ~ <4> The optical sheet according to any one of the following methods, wherein the number of pits contained in the 10μm×10μm region of the first surface is 50 or less.

[0035] <6> according to <1> ~ <5> The optical sheet in any one of the following embodiments, wherein the four smaller regions formed by dividing the 10μm×10μm region into two equal parts along each side respectively contain the pit.

[0036] <7> according to <1> ~ <6> The optical sheet according to any one of the following methods, wherein the arithmetic mean roughness Sa of the first surface is 8.0 nm or less.

[0037] <8> according to <1> ~ <7> The optical sheet in any one of the following embodiments, wherein the first surface includes a flat portion around the recess.

[0038] <9> according to <1> ~ <8> The optical sheet according to any one of the following methods, wherein the proportion of the pits in the 10μm×10μm region of the first surface is less than 15%.

[0039] <10> according to <1> ~ <9> In any one of the optical sheets, the ratio of the depth to the width of the recess is 0.030 or more.

[0040] <11> according to <1> ~ <10> The optical sheet according to any one of the following methods, wherein the optical sheet is resistant to a scratch resistance test performed on the first surface using steel wool under the following conditions.

[0041] Abrasion resistance test: Using steel wool #0000 as the sliding piece, the test was conducted 1000 times with a load of 1000g, a moving speed of 80mm / second, and a single-journey moving distance of 40mm.

[0042] <12> according to <1> ~ <11> The optical sheet according to any one of the following methods, wherein the optical sheet is resistant to a scratch resistance test performed on the first surface using felt under the following conditions.

[0043] Abrasion resistance test: Using the "Jumbo Wearaser (registered trademark), product number: CS-7" manufactured by TABER as the sliding piece, the test was conducted 10,000 times with a load of 200g, a moving speed of 200mm / second, and a single-journey moving distance of 50mm.

[0044] <13> according to <1> ~ <12> The optical sheet described in any one of the above statements includes a resin layer located between the substrate and the functional layer. The resin layer comprises a cured product of a curable resin composition.

[0045] <14> A type of sheet item, which has multiple sheets <1> ~ <13> The optical sheet as described in any one of the following.

[0046] <15> according to <14> The sheet article, wherein the sheet article is wound around the winding axis.

[0047] <16> A polarizer comprising a first protective plate, a polarizing element, and a second protective plate. At least one of the first protective sheet and the second protective sheet includes <1> ~ <13> The optical sheet as described in any one of the following.

[0048] <17> A display device comprising: Image forming apparatus; and Overlapping with the image forming apparatus <1> ~ <13> The optical sheet as described in any one of the following.

[0049] <18> A panel having: The joined items; and Engaged with the engagement item <1> ~ <13> The optical sheet as described in any one of the following.

[0050] <19> A method for selecting an optical sheet, comprising the following steps: For an optical sheet comprising a first surface and a second surface opposite to the first surface, the step of acquiring an image of a 10 μm × 10 μm region of the first surface, wherein the optical sheet comprises a substrate and a functional layer sequentially from the second surface toward the first surface, the functional layer comprising an adhesive component and hollow silica particles; and The step of selecting an optical sheet containing a pit with a width of more than 0.1 μm and less than 0.15 μm and a depth of more than 10 nm in the region based on the image.

[0051] <20> A method for manufacturing an optical sheet, comprising the following steps: The steps of manufacturing an optical sheet, wherein the optical sheet includes a first surface and a second surface opposite to the first surface, and a substrate and a functional layer are sequentially formed from the second surface toward the first surface, the functional layer comprising an adhesive component and hollow silica particles; and The step of selecting an optical sheet containing a 10μm × 10μm region on the first surface, wherein the pit has a width of 0.1μm to 0.15μm and a depth of 10nm or more.

[0052] The following is a detailed description of one embodiment of the present disclosure. In the accompanying drawings, for ease of illustration and understanding, the scale and aspect ratios have been appropriately altered and exaggerated relative to the actual object.

[0053] In this specification, terms such as “sheet,” “film,” and “plate” are not distinguished from each other solely based on the difference in their names. For example, “optical sheet” is not distinguished from components called optical films or optical plates solely by the difference in their names.

[0054] "Sheet surface (film surface, plate surface)" refers to a surface whose planar direction is aligned with that of the sheet-like (film-like, plate-like) component when viewed holistically and globally. The normal direction relative to the sheet-like (plate-like, film-like) component refers to the normal direction of that sheet-like (plate-like, film-like) component relative to the sheet surface (plate surface, film surface).

[0055] In this specification, multiple candidates for upper limits and multiple candidates for lower limits related to a numerical range are sometimes stated in different statements. In such statements, the numerical range can also be constructed by combining any candidate for an upper limit and any candidate for a lower limit. For example, consider the statement: "Parameter B can be above A1, above A2, or above A3. Parameter B can be below A4, below A5, or below A6." In this example, the numerical range of parameter B can be above A1 and below A4, above A1 and below A5, above A1 and below A6, above A2 and below A4, above A2 and below A5, above A2 and below A6, above A3 and below A4, above A3 and below A5, or above A3 and below A6.

[0056] To clarify directional relationships between figures, common directions are indicated by arrows labeled with common reference numerals across several figures. The side of the arrowhead points to the first direction, and the side opposite the arrowhead points to the second direction. For example... Figure 1 As shown, an "×" symbol is used inside a circle to indicate an arrow pointing inwards towards the paper in a direction perpendicular to the paper's surface. For example, as shown... Figure 2 As shown, a dotted circle is used to represent an arrow pointing from the paper toward the viewer in a direction perpendicular to the paper in the attached figure.

[0057] <<<Optical Plate 10>>>

[0058] like Figure 1 As shown, the optical sheet 10 of this embodiment includes a first surface 11 and a second surface 12. The optical sheet 10 includes a substrate 20 and a functional layer 40 sequentially from the first surface 11 toward the second surface 12. The functional layer 40 includes an adhesive component 41 and hollow silica particles 43. By including hollow silica particles 43, the refractive index of the functional layer 40 is lower than the refractive index of the adhesive component 41. Due to the low refractive index of the functional layer 40, reflection of light incident on the first surface 11 can be suppressed.

[0059] The functional layer with reflection suppression function is as thin as about 100 nm. In conventional optical films, the first surface is sometimes damaged due to friction with fingers, etc., against the low-refractive-index functional layer. To reduce the refractive index, the functional layer contains hollow silica particles. Due to their hollow structure, the hollow silica particles have a relatively large particle size. Therefore, the hollow silica particles are prone to disintegration and deformation, causing them to detach from the binder components. Consequently, the surface of the functional layer in conventional optical films has insufficient scratch resistance.

[0060] On the other hand, in this embodiment, studies were conducted to improve scratch resistance. Specifically, the 10μm × 10μm square measurement area of ​​the first surface 11 contains one or more pits with a width of 0.1μm or more and a depth of 10nm or more. The presence of pits 45 with a width of 0.1μm or more and a depth of 10nm or more improves scratch resistance. The detailed reason for the improved scratch resistance due to the presence of pits 45 is not yet clear. It is speculated that the exudation (precipitation) of the leveling agent affects the improvement of scratch resistance. The leveling agent is added to the coating liquid used to form the functional layer 40. The leveling agent floats near the surface of the functional layer 40 during the fabrication of the functional layer 40. The leveling agent reduces the surface tension of the functional layer 40, smoothing the surface of the functional layer 40. Based on the leveling agent, the sliding properties and antifouling properties of the first surface 11 are improved.

[0061] Various leveling agents were tested, and pits 45 were generated when a specific combination of leveling agents was used. Furthermore, the scratch resistance of the first surface 11 of the optical sheet 10 with pits 45 was improved. For example, by adding an organosilicon-based leveling agent to a fluorine-based leveling agent, the scratch resistance of the first surface 11 was improved. Based on this phenomenon, it is speculated that in a specific combination of leveling agents, the leveling agent seeps into the first surface 11. In this speculation, the pits 45 are considered to be traces of leveling agent seepage. It is believed that in the optical sheet 10 with pits 45, the sliding properties of the first surface 11 are significantly improved due to the leveling agent seeping from the functional layer 40, resulting in improved scratch resistance.

[0062] The pit 45 was confirmed using an atomic force microscope (AFM). Three test samples were cut from the optical sheet 10. Each of the three test samples was cut from an area at least 10 mm apart within the optical sheet. Each test sample was a 5 mm × 5 mm square. Visual inspection confirmed the absence of foreign matter attachments, damage, etc., in the test samples. For each test sample, an image of the first face of five mutually separated test areas was obtained using an atomic force microscope. Each test area was a 10 μm × 10 μm square. Images were obtained using an atomic force microscope for each of the five test areas of the three test samples, totaling 15 test sites. If the pit 45 was confirmed in 12 or more of the 15 images, it was determined that the 10 μm × 10 μm square test area of ​​the first face 11 contained the pit 45. If the pit 45 was not confirmed in 4 or more images, it was determined that the 10 μm × 10 μm square test area of ​​the first face 11 did not contain the pit 45.

[0063] As an atomic force microscope, the "SPM-9700" manufactured by Shimadzu Corporation can be used. As the cantilever, the NCHR (resonance frequency: 320 kHz, spring constant 42 N / m) manufactured by NanoWorld can be used. The surface shape of the sample can be measured using the "SPM manager" software included with the atomic force microscope in On-Line (measurement) mode. Measurement conditions can be set as follows.

[0064] - Measurement mode: Phase

[0065] - Scan range: 10μm × 10μm

[0066] - Scanning speed: 2.0~2.5Hz (using a 10μm scanner)

[0067] - Pixel count: 512×512

[0068] The width W and depth D of the pits 45 in each measurement region are determined as follows. First, a 10μm × 10μm square measurement region is observed from the normal direction of the optical sheet 10, and a top view image of the measurement region is obtained. The top view image is an image of the first surface 11 observed from the normal direction of the optical sheet 10 using an atomic force microscope. Based on the top view image of the measurement region, the maximum length L of the pits 45 existing in that measurement region is determined. MAX The longest indentation is 45. Maximum length L MAX This refers to the maximum length of the straight line connecting two points on the periphery of the pit 45 during observation in the measurement area along the normal direction of the optical plate 10. In other words, the maximum length L MAX It is equivalent to the maximum distance between two parallel straight lines sandwiching a 45-degree indentation. Figure 2 This is a top view showing an example of a recess 45 from the normal direction of the optical element 10. As an example, Figure 2 The pit 45 shown is the longest maximum length L in the measurement area. MAX 45.

[0069] The shape of the recess 45 when viewed from the normal direction of the optical plate 10, i.e., the planar shape of the recess 45, is not particularly limited. The planar shape of the recess 45 can have a curved outline, a straight outline, or an outline composed of a combination of curves and straight lines. The planar shape of the recess 45 can be circular, elliptical, or oblong. The planar shape of the recess 45 can also be a polygonal shape such as a triangle, quadrilateral, or pentagon.

[0070] Next, a measurement cross-sectional image is obtained using an atomic force microscope. The measurement cross-sectional image is an observation image of a plane parallel to the normal direction of the optical plate 10. The measurement cross-sectional image is an observation image of a plane that cuts across the pit 45 within the measurement area. The measurement cross-sectional image includes the maximum length L from which the pit 45 can be obtained. MAX An observation image of the surface at two points on the periphery of the pit 45. That is, the measured cross-sectional image is along... Figure 2 In The cross-section of the line. Figure 3 This represents an example of measuring a cross-sectional image.

[0071] according to Figure 3The cross-sectional profile 45x of the measured cross-sectional image of the pit 45 shown is used to determine the deepest part 45c of the pit 45. The deepest part 45c is the lowest position within the pit. Next, the high end 45a and the low end 45b, which are the two ends of the pit 45, are determined in the cross-sectional profile 45x of the pit 45. The high end 45a is the higher end of the two ends of the pit 45. The low end 45b is the lower end of the two ends of the pit 45. The high end 45a and the low end 45b are determined as the inflection points (maximum values) in the normal direction of the first optical element 10 located on both sides of the deepest part 45c in the cross-sectional profile 45x of the pit 45.

[0072] The width W of the pit 45 in each measurement area refers to the distance along the surface of the optical sheet 10 between the high end portion 45a and the low end portion 45b. Figure 3 In the example shown, the width W of the pit 45 refers to the distance between the higher end 45a and the lower end 45b along the first direction D1. The depth D of the pit 45 in each measurement region refers to the distance between the lower end 45b and the deepest part 45c along the normal direction of the optical sheet 10. Figure 3 In the example shown, the depth D of the pit 45 refers to the distance between the lower end 45b and the deepest part 45c along the third direction D3.

[0073] Among them, such as Figure 4 As shown, sometimes tiny protrusions 45e also exist within the recess 45. When the two ends of the recess 45 are determined using the method described above, located... Figure 4 The larger central depression is divided into two depressions 45 by the protrusion 45e. However, under the assumption that the increased slippage of the first surface 11 is due to the exudation of the leveling agent, the area located... Figure 4 The central depression should be interpreted as a depression 45. Even from the perspective that the structure of the depression physically reduces slippage, the area located... Figure 4 The central depression should also be interpreted as a depression 45.

[0074] Therefore, when the first distance LX1 between the provisional lower end (protrusion 45e) and the deepest part 45c along the normal direction of the optical sheet 10 is less than 30% of the second distance LX2 between the higher end 45a and the deepest part 45c along the normal direction of the optical sheet 10, the provisional lower end is treated as a protrusion 45e, not as a lower end 45b associated with the recess 45. Figure 4 In the example shown, the distance LX1 between the deepest part 45c and the protrusion 45e along the third direction D3 is less than 30% of the distance LX2 between the high end part 45a and the deepest part 45c along the third direction D3. Therefore, the protrusion 45e does not constitute the lower end part 45b.

[0075] As described above, the width W and depth D of the pit 45 in each measurement region are determined. Based on the determined width W and depth D of the pit 45, it is determined whether the pit corresponds to a pit with a width of 0.1 μm or more and a depth of 10 nm or more.

[0076] It should be noted that the maximum length L MAX The longest pit, 45, has a width W greater than 0.1 μm, but since its depth D is less than 10 nm, it does not meet the requirement of "a pit with a width greater than 0.1 μm and a depth greater than 10 nm". Maximum length L MAX The longest pit 45 has a depth D of 10 nm or more, but if the width W of this pit is less than 0.1 μm, it does not meet the requirement of "a pit with a width of 0.1 μm or more and a depth of 10 nm or more". In these cases, further investigation is conducted to determine whether a 10 μm × 10 μm square measurement area contains "a pit with a width of 0.1 μm or more and a depth D of 10 nm or more". Within the 10 μm × 10 μm square measurement area, the maximum length L is determined. MAX The width W and depth D of the second longest pit 45 are measured. Based on the measured values ​​of width W and depth D, it is determined whether the pit being measured corresponds to "a pit with a width W of 0.1 μm or more and a depth D of 10 nm or more". This determination is repeated until a "pit with a width of 0.1 μm or more and a depth of 10 nm or more" is found, or until the pit 45 being measured disappears.

[0077] In the optical sheet 10 of this embodiment, from the viewpoint of improving scratch resistance, as described above, the width W of the pit 45 is 0.1 μm or more. From the viewpoint of further improving scratch resistance, the width W of the pit 45 can be 0.2 μm or more, 0.3 μm or more, or 0.4 μm or more. From the viewpoint of improving scratch resistance, the depth D of the pit 45 is 10 nm or more. From the viewpoint of further improving scratch resistance, the depth D of the pit 45 can be 15 nm or more, 18 nm or more, 20 nm or more, or 23 nm or more.

[0078] In the optical sheet 10 of this embodiment, an upper limit can be set for the width W of the recess 45 formed on the first surface 11. An upper limit can also be set for the depth D of the recess 45 formed on the first surface 11. By setting an upper limit, the slipability of the first surface 11 can be ensured. This suppresses the reduction in slipability caused by the formation of a large recess on the first surface 11, i.e., the reduction in slipability caused by physical snagging, etc. Based on this, the width W of the recess 45 can be 2.0 μm or less, 1.5 μm or less, 1.4 μm or less, 1.1 μm or less, 1.0 μm or less, 0.8 μm or less, 0.6 μm or less, or less than 0.5 μm. The depth D of the recess 45 can be 70 nm or less, 61 nm or less, 60 nm or less, 55 nm or less, 50 nm or less, 40 nm or less, 38 nm or less, 30 nm or less, or 24 nm or less.

[0079] The width W of the pit 45 can be greater than 0.1 μm and less than 2.0 μm, greater than 0.2 μm and less than 2.0 μm, greater than 0.3 μm and less than 2.0 μm, or greater than 0.4 μm and less than 2.0 μm. The width W of the pit 45 can be greater than 0.1 μm and less than 1.5 μm, greater than 0.2 μm and less than 1.5 μm, greater than 0.3 μm and less than 1.5 μm, or greater than 0.4 μm and less than 1.5 μm. The width W of the pit 45 can be greater than 0.1 μm and less than 1.4 μm, greater than 0.2 μm and less than 1.4 μm, greater than 0.3 μm and less than 1.4 μm, or greater than 0.4 μm and less than 1.4 μm. The width W of the pit 45 can be greater than 0.1 μm and less than 1.1 μm, greater than 0.2 μm and less than 1.1 μm, greater than 0.3 μm and less than 1.1 μm, or greater than 0.4 μm and less than 1.1 μm. The width W of the pit 45 can be greater than 0.1 μm and less than 1.0 μm, greater than 0.2 μm and less than 1.0 μm, greater than 0.3 μm and less than 1.0 μm, or greater than 0.4 μm and less than 1.0 μm. The width W of the pit 45 can be greater than 0.1 μm and less than 0.8 μm, greater than 0.2 μm and less than 0.8 μm, greater than 0.3 μm and less than 0.8 μm, or greater than 0.4 μm and less than 0.8 μm. The width W of the pit 45 can be greater than 0.1 μm and less than 0.6 μm, greater than 0.2 μm and less than 0.6 μm, greater than 0.3 μm and less than 0.6 μm, or greater than 0.4 μm and less than 0.6 μm. The width W of the pit 45 can be greater than 0.1 μm and less than 0.5 μm, greater than 0.2 μm and less than 0.5 μm, greater than 0.3 μm and less than 0.5 μm, or greater than 0.4 μm and less than 0.5 μm.

[0080] The depth D of the pit 45 can be 10nm to 70nm, 15nm to 70nm, 18nm to 70nm, 20nm to 70nm, or 23nm to 70nm. The depth D of the pit 45 can be 10nm to 61nm, 15nm to 61nm, 18nm to 61nm, 20nm to 61nm, or 23nm to 61nm. The depth D of the pit 45 can be 10nm to 60nm, 15nm to 60nm, 18nm to 60nm, 20nm to 60nm, or 23nm to 60nm. The depth D of the pit 45 can be 10nm to 55nm, 15nm to 55nm, 18nm to 55nm, 20nm to 55nm, or 23nm to 55nm. The depth D of the pit 45 can be 10nm to 50nm, 15nm to 50nm, 18nm to 50nm, 20nm to 50nm, or 23nm to 50nm. The depth D of the pit 45 can be 10nm to 40nm, 15nm to 40nm, 18nm to 40nm, 20nm to 40nm, or 23nm to 40nm. The depth D of the pit 45 can be 10nm to 38nm, 15nm to 38nm, 18nm to 38nm, 20nm to 38nm, or 23nm to 38nm. The depth D of the pit 45 can be 10nm to 30nm, 15nm to 30nm, 18nm to 30nm, 20nm to 30nm, or 23nm to 30nm. The depth D of the pit 45 can be above 10nm and below 24nm, above 15nm and below 24nm, above 18nm and below 24nm, above 20nm and below 24nm, or above 23nm and below 24nm.

[0081] As described above, for a given measurement area, the maximum length L determined from the microscopic observation is... MAX The width W and depth D of the pit 45 are measured in the order of length. The width W and depth D of the pit 45 that are determined to be equivalent to "a pit with a width W of more than 0.1 μm and a depth D of more than 10 nm" are taken as the width W and depth D of the pit 45 in the measurement area.

[0082] As described above, for an optical sheet 10 to be evaluated, the presence or absence of a "dimple with a width W of 0.1 μm or more and a depth D of 10 nm or more" is determined in a total of 15 measurement areas. The arithmetic mean of the width W of the dimples 45 measured in 12 or more measurement areas that are determined to have a width W of 0.1 μm or more and a depth D of 10 nm or more is set as the width W of the dimple 45 of the optical sheet to be evaluated. The arithmetic mean of the depth D of the dimples 45 measured in 11 or more measurement areas that are determined to have a width W of 0.1 μm or more and a depth D of 10 nm or more is set as the depth D of the dimple 45 of the optical sheet to be evaluated. For example, if two of the 15 measurement areas of an optical sheet do not contain a dimple 45, the arithmetic mean of the measurements in the 13 measurement areas is used as the width W and depth D of the dimple 45 of the optical sheet.

[0083] A lower limit can be set for the ratio (D / W) of the depth D to the width W of the pit 45. By setting a lower limit for the ratio (D / W), the scratch resistance of the first surface 11 of the optical sheet 10 can be stably improved. The ratio (D / W) can be 0.030 or higher, 0.035 or higher, 0.040 or higher, 0.044 or higher, or 0.048 or higher.

[0084] There is no specific upper limit set for the ratio (D / W) of the depth D to the width W of the pit 45. The ratio (D / W) can be less than 0.15, less than 0.10, or less than 0.075.

[0085] The ratio (D / W) can be 0.030 or higher and 0.15 or lower, 0.035 or higher and 0.15 or lower, 0.040 or higher and 0.15 or lower, 0.044 or higher and 0.15 or lower, or 0.048 or higher and 0.15 or lower. The ratio of D to W can be 0.030 or higher and 0.10 or lower, 0.035 or higher and 0.10 or lower, 0.040 or higher and 0.10 or lower, 0.044 or higher and 0.10 or lower, or 0.048 or higher and 0.10 or lower. The ratio of D to W can be 0.030 or higher and 0.075 or lower, 0.035 or higher and 0.075 or lower, 0.040 or higher and 0.075 or lower, 0.044 or higher and 0.075 or lower, or 0.048 or higher and 0.075 or lower.

[0086] The ratio (D / W) of the depth D to the width W of the recess 45 is obtained by dividing the depth D of the recess 45 of the optical sheet 10 being evaluated, as determined by the method described above, by the width W of the recess 45 of the optical sheet 10 being evaluated, as determined by the method described above. When calculating the ratio, the units of the width W and the depth D of the recess 45 are kept consistent. The ratio (D / W) has no unit.

[0087] like Figure 5 , Figure 6 as well as Figures 12-14 As shown, in the example where the first surface includes multiple recesses 45, the multiple recesses 45 can be discretely arranged. In other words, the multiple recesses 45 can be located in mutually separated positions. Figure 5 , Figure 6 as well as Figures 12-14 As shown, the first surface 11 may have a flat portion 47 around the recess 45. The first surface 11 may include the flat portion 47 between recesses 45. The first surface 11 may form the area between recesses 45 by the flat portion 47. The flat portion 47 is a surface whose height difference along the normal direction of the optical sheet 10 is less than the depth D of the recess 45 of the optical sheet.

[0088] The presence or absence of the flat portion 47 is determined based on the observation images obtained by atomic force microscopy. Figures 12-14 An example of a top-view image of the measured area obtained by atomic force microscopy is shown. Figures 12-14 The image shown is an observation under an atomic force microscope. Darker areas in the image represent lower elevations within the measurement area, while lighter areas represent higher elevations. Figures 12-14 In the image shown, the color is represented by brown. Figures 12-14 The scale bar in the lower right corner of the image shows the relationship between color intensity and height. Corresponding to the scale bar, a histogram is shown in the lower right corner of the image. The histogram shows the frequency distribution of the regions represented by each color on the scale bar.

[0089] The inventors have confirmed that by positioning the flat portion 47 around the recess 45, the sliding properties at the first surface 11 of the optical sheet 10 can be improved. On the other hand, the functional layer 40 performs certain desired functions in the area outside the recess 45. The flat portion 47 performs certain desired functions. For example, the functional layer 40 can perform a low-reflection function or a reflection suppression function in the flat portion 47 outside the recess 45.

[0090] By having a flat portion 47 around the recess 45, physical snagging at the flat portion 47 can be suppressed. External contact objects rubbing against the optical plate 10 can contact the first surface 11 at the periphery of the recess 45, i.e., the boundary between the recess 45 and the flat portion 47. It is speculated that this promotes friction between the contact object at the periphery of the recess 45 and the first surface 11. Therefore, due to the increased slippage at the periphery of the recess 45, the scratch resistance of the optical plate 10 can be effectively improved.

[0091] An upper limit can also be set for the proportion of pits 45 in the 10μm × 10μm measurement area of ​​the first surface 11. By setting an upper limit, the functional layer 40 can fully perform its expected function in the optical sheet 10 with improved scratch resistance. In the 10μm × 10μm measurement area of ​​the first surface 11, the proportion of pits 45 can be less than 15%, less than 12%, less than 10%, or less than 5.0%.

[0092] A lower limit can be set for the proportion of pits 45 in a 10μm × 10μm measurement area on the first surface 11. By setting a lower limit, the scratch resistance of the first surface 11 of the optical sheet 10 can be stably improved. In the 10μm × 10μm measurement area on the first surface 11, the proportion of pits 45 can be 0.50% or more, 0.75% or more, 1.0% or more, 1.5% or more, or 2.0% or more.

[0093] The proportion of pits 45 in the measurement area can be 0.50% or more and less than 15%, 0.75% or more and less than 15%, 1.0% or more and less than 15%, 1.5% or more and less than 15%, or 2.0% or more and less than 15%. The proportion of pits 45 in the measurement area can be 0.50% or more and less than 12%, 0.75% or more and less than 12%, 1.0% or more and less than 12%, 1.5% or more and less than 12%, or 2.0% or more and less than 12%. The proportion of pits 45 in the measurement area can be 0.50% or more and less than 10%, 0.75% or more and less than 10%, 1.0% or more and less than 10%, 1.5% or more and less than 10%, or 2.0% or more and less than 10%. The proportion of pits 45 in the measurement area can be above 0.50% and below 5.0%, above 0.75% and below 5.0%, above 1.0% and below 5.0%, above 1.5% and below 5.0%, or above 2.0% and below 5.0%.

[0094] The proportion of the pit 45 in the 10μm × 10μm measurement area of ​​the first surface 11 refers to the proportion of the area occupied by the pit 45 when viewed from the normal direction of the optical plate 10. This proportion is a percentage, and the unit of proportion is "%". Regarding the proportion, it is based on the determination of the maximum length L mentioned above. MAX The scale is calculated using a top-view image of the measurement area used when the pit 45 is visible. Specifically, the scale is calculated based on an image obtained by atomic force microscopy, representing the first surface 11 from the normal direction of the optical slide 10. In image processing, ImageJ and Fiji can be used as image processing software. ImageJ is an open-source, public domain image processing software developed by the National Institutes of Health in the United States. Fiji is a plugin package for ImageJ.

[0095] In the optical sheet 10 of this embodiment, a lower limit can be set for the number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in a 10 μm × 10 μm square measurement area of ​​the first surface 11. By setting this lower limit, a certain number or more pits 45 of a predetermined size are contained in a measurement area. According to this example, the first surface 11 can be stably imparted with sliding properties, thereby stably imparting excellent scratch resistance to the first surface 11. Based on this, the number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in a measurement area can be 3 or more, 4 or more, 9 or more, 11 or more, 12 or more, 17 or more, or 20 or more.

[0096] An upper limit can be set for the number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in a 10 μm × 10 μm square measurement area of ​​the first surface 11. By setting this lower limit, a measurement area contains a certain number of pits 45 of a predetermined size. According to this example, the slipability of the first surface 11 can also be ensured. If too many pits are formed on the first surface 11, the slipability of the first surface 11 may be reduced due to physical hooking, etc. Based on this, the number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in a measurement area can be less than 50, less than 40, less than 35, or less than 32.

[0097] The number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in a measurement region can be 3 or more but less than 50, 4 or more but less than 50, 9 or more but less than 50, 11 or more but less than 50, 12 or more but less than 50, 17 or more but less than 50, or 20 or more but less than 50. The number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in a measurement region can be 3 or more and 35 or less, 4 or more and 35 or less, 9 or more and 35 or less, 11 or more and 35 or less, 12 or more and 35 or less, 17 or more and 35 or less, or 20 or more and 35 or less. The number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in a measurement region can be 3 or more and 32 or less, 4 or more and 32 or less, 9 or more and 32 or less, 11 or more and 32 or less, 12 or more and 32 or less, 17 or more and 32 or less, or 20 or more and 32 or less.

[0098] The number of pits 45 of a specified size contained in each measurement area is based on the determination of the maximum length L mentioned above. MAX The pits 45 are measured using images of the measurement areas used in the process. Specifically, based on images of the first surface 11 obtained using an atomic force microscope, the number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in each measurement area is measured. Whether the number of pits 45 with a width of 0.1 μm or more and a depth of 10 nm or more contained in a 10 μm × 10 μm square measurement area of ​​the first surface 11 meets the criteria is determined based on the average of the measured values ​​in the five measurement areas of each of the three measurement samples, i.e., the average of a total of 15 measured values. Similar to the width W and depth D of the pits 45, measurement areas deemed to lack pits 45 of the aforementioned specified dimensions are not considered. For example, if two of the 15 measurement areas of an optical sheet lack pits 45, the arithmetic mean of the measured values ​​in the 13 measurement areas is used as the number of pits 45 in that optical sheet.

[0099] The inventors of this case have confirmed that by dispersing smaller pits 45 more extensively, the scratch resistance of the first surface 11 can be stably improved.

[0100] Specifically, a 10μm × 10μm square measurement area containing 11 or more pits 45 with a width of 0.1μm or more and 0.8μm or less can stably improve scratch resistance. In this example, the width of the pits 45 contained in the measurement area can be 0.1μm or more and 0.6μm or less, or 0.1μm or more and less than 0.5μm. The number of pits 45 with a width of 0.1μm or more and 0.8μm or less contained in the measurement area can be 12 or more, 17 or more, or 20 or more. The number of pits 45 with a width of 0.1μm or more and 0.8μm or less contained in the measurement area can be 50 or less, 40 or less, 35 or less, or 32 or less.

[0101] In the optical sheet 10 of this embodiment, as Figure 5 As shown, pits can be included in four first small regions SS1, which are formed by dividing a 10μm × 10μm square measurement area DR into four equal parts along each side. In this example, the pits 45 are dispersed within the measurement area DR. Therefore, the slippage at various locations within the measurement area DR can be improved. Consequently, scratch resistance can be uniformly and stably improved within the optical sheet 10.

[0102] like Figure 6 As shown, the measurement area can also be divided into nine second smaller regions SS2 by trisecting each side of a 10μm × 10μm square measurement area, each containing a pit 45. According to... Figure 6 The example shown demonstrates a more uniform and stable improvement in scratch resistance within the optical sheet 10.

[0103] The optical sheet 10, which contains pits with a width of 0.1 μm or more and a depth of 10 nm or more in a 10 μm × 10 μm area on its first surface, exhibits excellent scratch resistance. The optical sheet, which imparts excellent scratch resistance, also demonstrates excellent resistance to both steel wool and felt. Pencil hardness is a known indicator of the scratch resistance of an optical sheet surface. Pencil hardness is an indicator of resistance to contact with a hard material under stress close to a point load. On the other hand, minor scratches may occur due to the steady application of surface loads during repeated friction or long-term use. It is appropriate to evaluate the resistance to such damage as steel wool resistance and felt resistance. In the steel wool scratch resistance test on the first surface 11, the optical sheet 10 exhibits high resistance. In the felt scratch resistance test on the first surface 11, the optical sheet 10 also exhibits high resistance.

[0104] The inventors of this case have confirmed that by including pits of a specified size in a 10μm × 10μm area on the first surface, the optical sheet 10 can be stably endowed with excellent abrasion resistance to felt. Previously, by adjusting the mechanical properties of the optical sheet 10, such as surface hardness, abrasion resistance to pencil hardness and steel wool could be improved. Recently, optical sheets have also been required to have abrasion resistance to fingers and pens when combined with touch panel functions, as well as abrasion resistance to wiping with cloths. However, while simply improving mechanical properties could improve pencil hardness and abrasion resistance to steel wool, it was difficult to consistently ensure excellent abrasion resistance to felt. By providing pits with a width of 0.1μm or more and a depth of 10nm or more in a 10μm × 10μm area on the first surface, excellent abrasion resistance to felt can be stably ensured; this effect is a significant one that exceeds the range predicted by current technology.

[0105] <Scratch resistance of steel wool>

[0106] The steel wool abrasion resistance test is an indicator of resistance to defects such as damage that occur when steel wool is pressed against a test sample and moved relative to it. The optical plate 10 is resistant to the steel wool abrasion resistance test performed under the conditions described below.

[0107] The test sample for the optical film being evaluated is rectangular. The shorter side of the rectangle is set to 50mm, and the longer side to 100mm. The sample is visually confirmed to be free of dust, damage, or other abnormalities. The rectangular sample is then unfolded horizontally on the testing machine in a manner that prevents wrinkles and warping. Repair tape is used to secure the four corners of the unfolded sample to the testing machine. The repair tape can be 3M product, trade name "810-3-18".

[0108] The steel wool, serving as a sliding plate, is brought into contact with the surface of the sample, which is formed by the first side of the optical plate. The steel wool is "BONSTAR B-204" with serial number #0000, manufactured by Japan Steel Wool Co., Ltd. Bonstar B-204 is a commercial size with a length of approximately 390 mm, a width of approximately 75 mm, and a thickness of approximately 110 mm. The contact area between the test sample and the sliding plate is 20 mm × 20 mm. A load of 1000 g is applied to the sliding plate from above in the vertical direction, pressing the sliding plate against the test sample, which is unfolded along a horizontal plane.

[0109] With the sliding plate pressed against the test sample from above in the vertical direction, the sliding plate and the sample are moved horizontally relative to each other. The relative movement is a reciprocating motion along a straight path. The reciprocating motion is repeated 1000 times. The speed of the reciprocating motion is set to 80 mm / s. The stroke of the reciprocating motion is 40 mm in both the forward and reverse directions. The reciprocating motion is parallel to the long side of the sample.

[0110] The test environment was set at a temperature of 23℃±2℃ and a relative humidity of 50%±5%. The test samples were prepared in the test environment for 16 hours before the start of the test.

[0111] Unused material is used for the sliding plate. Before testing the object to be evaluated, the sample is pretreated with steel wool by rubbing it with steel wool. The testing machine used in the test of the sample to be evaluated is also used for the steel wool pretreatment. The sample is a polyethylene terephthalate (PET) film. The sample is rectangular with a short side of 50 mm and a long side of 100 mm. Steel wool is rubbed onto the untreated surface of the PET film. The sample is unfolded horizontally, and the four corners are secured to the testing machine with repair tape. Steel wool is pressed onto the sample from the vertical direction. The contact area between the sample and the steel wool is 20 mm × 20 mm. The load applied by the steel wool to the sample is set to 300 g. The steel wool pressing against the sample is moved relative to the sample in the horizontal direction. The steel wool and the sample are moved relative to each other in a direction parallel to the main extension direction of the steel wool fibers. The relative movement is a reciprocating motion. The reciprocating motion cycle is set to 300 times. The speed of the reciprocating motion is set to 80 mm / s. The stroke of the reciprocating motion is 40 mm in both the forward and reverse directions. Thus, steel wool pressed against the prepared sample is used for the test of the evaluation object.

[0112] After the scratch resistance test, the surface of the test sample, consisting of the first side of the optical sheet, was observed with the naked eye. The observation distance was 30 cm. The illuminance on the surface of the sample being observed was set to be above 800 Lx and below 1200 Lx.

[0113] If damage is observed in the test sample to the extent that it would cause problems when applied to a display device, the optical sheet 10, as the evaluation object, is determined to be unresistant to the scratch resistance test using steel wool on the first surface 11. Five scratch resistance tests are performed on the optical sheet 10 as the evaluation object. If no damage occurs in any of the five tests to the extent that it would cause problems when applied to a display device, the optical sheet 10, as the evaluation object, is determined to be resistant to the scratch resistance test using steel wool on the first surface 11. The steel wool is replaced each time in the five tests. The aforementioned steel wool pretreatment is performed before the start of each of the five tests.

[0114] <Felt resistance>

[0115] The felt abrasion resistance test is an indicator of resistance to defects such as damage that occur when felt is pressed against a test sample and moved relative to it. The optical sheet 10 is resistant to abrasion resistance tests under the following conditions using TABER's "JumboWeaser CS-7" (registered trademark) as the sliding sheet.

[0116] The test sample for the optical film being evaluated is rectangular. The shorter side of the rectangle is set to 50mm, and the longer side to 100mm. The sample is visually confirmed to be free of dust, damage, or other abnormalities. The rectangular sample is then unfolded horizontally on the testing machine in a manner that prevents wrinkles and warping. Repair tape is used to secure the four corners of the unfolded sample to the testing machine. The repair tape can be 3M product, trade name "810-3-18".

[0117] The felt, which serves as the sliding plate, is brought into contact with the surface of the sample, which is formed by the first surface of the optical plate. The felt is "Jumbo Wearaser CS-7" manufactured by TABER Corporation (registered trademark). The contact area between the test sample and the sliding plate is 20mm × 20mm. A load of 200g is applied to the sliding plate from above in the vertical direction, pressing the sliding plate against the test sample which is unfolded along the horizontal plane.

[0118] With the sliding plate pressed against the test sample from above in the vertical direction, the sliding plate and the sample are moved horizontally relative to each other. This relative movement is a reciprocating motion along a straight path. The reciprocating motion is repeated 10,000 times. The speed of the reciprocating motion is set to 200 mm / s. The stroke of the reciprocating motion is 50 mm in both the forward and reverse paths. The reciprocating motion is parallel to the long side of the sample.

[0119] The test environment was set at a temperature of 23℃±2℃ and a relative humidity of 50%±5%. The test samples were prepared in the test environment for 16 hours before the start of the test.

[0120] Unused material was used for the sliding sheet. Before testing the evaluation object, the sample was pretreated with felt by wiping it with felt. The testing machine used for testing the sample as the evaluation object was also used for the felt pretreatment. The sample was a "single-sided easy-bond type: A4160" manufactured by Toyobo Co., Ltd. The sample was rectangular with a short side of 50 mm and a long side of 100 mm. The sample was unfolded horizontally, and the four corners of the untreated (exposed PET) side of the sample were fixed to the testing machine with repair tape. The felt was wiped on the untreated surface of the sample. The felt was pressed onto the sample from above in the vertical direction. The contact area between the sample and the felt was a circle with a diameter of 12 mm. The load of the felt pressing against the sample was set to 600 g. The felt pressed against the sample was moved horizontally relative to the sample. The relative movement was a reciprocating motion. The reciprocating motion cycle was set to 150 times. The reciprocating motion speed is 220 mm / s. The travel distance of the reciprocating motion is 50 mm in both the forward and reverse directions. The felt to be used as the sample is then pressed for testing the object being evaluated. The test is conducted after confirming that the flattened surface of the pressed felt is free of fuzz and is flat.

[0121] After the scratch resistance test, the surface of the test sample, consisting of the first side of the optical sheet, was observed with the naked eye. The observation distance was 30 cm. The illuminance on the surface of the sample being observed was set to be above 800 Lx and below 1200 Lx.

[0122] If, in the case where a problem is observed in the test sample when applied to a display device, the optical sheet 10, as the evaluation object, is determined to be unresistant to scratch resistance in the first surface 11 with CS-7 as the sliding sheet. Five scratch resistance tests are performed on the optical sheet 10 as the evaluation object. If no damage occurs in the five tests to the extent that it would cause a problem when applied to a display device, the optical sheet 10, as the evaluation object, is determined to be resistant to scratch resistance in the first surface 11 with CS-7 as the sliding sheet. The same CS-7 is used in all five tests. The aforementioned pretreatment of the CS-7 is performed before the start of each of the five tests.

[0123] Arithmetic mean roughness Sa

[0124] In the optical sheet 10 of this embodiment, the arithmetic mean roughness Sa of the first surface 11 can be 8.0 nm or less, 7.5 nm or less, 5.0 nm or less, 4.5 nm or less, or 4.1 nm or less. By reducing the arithmetic mean roughness Sa to 8.0 nm or less, excellent sliding properties are imparted to the first surface 11. By providing physical irregularities formed by the pits 45 on the first surface 11 and maintaining a low arithmetic mean roughness Sa, the sliding properties of the first surface 11 can be improved, and the scratch resistance of the first surface 11 can be improved. There is no particularly preferred lower limit for the arithmetic mean roughness Sa of the first surface 11. The arithmetic mean roughness Sa of the first surface 11 can be 0 nm or more, 0.1 nm or more, or 3.0 nm or more.

[0125] The arithmetic mean roughness Sa is the three-dimensional arithmetic mean roughness specified in ISO 25178. The three-dimensional arithmetic mean roughness is obtained by extending the two-dimensional arithmetic mean roughness Ra to three dimensions. With the orthogonal coordinate axes X and Y placed on a reference plane, the roughness surface defined as Z(x, y), and the size of the reference plane defined as Lx and Ly, the arithmetic mean roughness Sa is calculated using the following equation (i). It should be noted that in equation (i), A = Lx × Ly.

[0126] [Formula 1]

[0127] The arithmetic mean roughness Sa is a value obtained using an atomic force microscope (AFM). Three test samples are cut from the optical sheet 10, at a distance of at least 10 mm from each other. Each test sample is a 5 mm × 5 mm square. The absence of foreign matter attachments or damage is visually confirmed in the test samples. For each test sample, images of five separate test areas are obtained using the AFM. Each test area is a 10 μm × 10 μm square. For each of the five test areas of the three test samples, totaling 15 test sites, the arithmetic mean height Sa is calculated from the acquired images using the surface analysis software accompanying the AFM. The average of these 15 measurements is taken as the arithmetic mean roughness Sa (nm) of the optical sheet.

[0128] <Visual reflectivity>

[0129] The optical sheet 10 of this embodiment has a reflection suppression function that suppresses the reflection of light incident on the first surface 11. The apparent reflectance Y value of the first surface 11, measured at an incident angle of 5°, can be 1.5% or less, 1.0% or less, 0.8% or less, 0.7% or less, 0.6% or less, or 0.5% or less.

[0130] There is no specific lower limit for visual reflectance. The visual reflectance Y value of the first surface 11, measured at an incident angle of 5°, can be above 0% or greater than 0%.

[0131] The visual reflectance Y value is the visual reflectance Y value of the CIE 1931 standard colorimetric system. The visual reflectance Y value is measured using a spectrophotometer as follows.

[0132] A sample is cut from the optical sheet 10, which is to be evaluated. The sample is visually confirmed to be free of dust, damage, or other abnormalities. A black plate is attached to the sample surface, which is the second side of the optical sheet, through an optically transparent adhesive sheet. The optically transparent adhesive sheet is "PANACLEAN PD-S1" manufactured by PANAC Corporation. The black plate is "COMOGLASS DFA2CG502K (Black) series" manufactured by Kuraray Corporation. The thickness of the black plate is 2 mm. The total light transmittance of the black plate is less than 1%. Through the above operations, an evaluation sample A, comprising the optical sheet, the optically transparent adhesive sheet, and the black plate, is prepared.

[0133] The surface of evaluation sample A, which is formed by the first surface of the optical sheet, is illuminated with light at an incident angle of 5°. The reflectance (apparent reflectance Y value) of the evaluation sample A is measured based on the positively reflected light. Using an auxiliary light source C and a 2-degree field of view, the apparent reflectance Y (%) is calculated based on the positive reflectance measured at 0.5 nm intervals in the range from 300 nm to 780 nm. Before measuring the apparent reflectance Y value of the optical sheet 10, the auxiliary light source C is illuminated for 15 minutes to allow its output to stabilize. The test environment for measuring the apparent reflectance is set to a temperature of 23℃ ± 2℃ and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before the start of the test.

[0134] Other measurement conditions for visual reflectance are based on JIS Z 8722:2009.

[0135] The perceived reflectance is the arithmetic mean of five measurements. These five measurements were taken at five locations on the optical sheet being evaluated, with each location at least 10 mm apart.

[0136] Total light transmittance

[0137] The total light transmittance of the optical sheet 10 can be above 50%, above 70%, above 80%, above 90%, or above 95%. There is no specific upper limit to the total light transmittance of the optical sheet 10. The total light transmittance of the optical sheet 10 can also be below 100% or less than 100%.

[0138] The total light transmittance (%) was measured using a light source simulating the spectrum of the D65 standard light (referred to as the "D65 light source"). Before measuring the total light transmittance of the optical sheet 10, the D65 light source was illuminated for 15 minutes to allow its output to stabilize. The incident angle of the sample was set to 0° during the total light transmittance measurement. The incident surface was the second surface 12 of the optical sheet 10. The test environment for measuring the total light transmittance was set to a temperature of 23℃ ± 2℃ and a relative humidity of 50% ± 5%. The sample was placed in the test environment for 16 hours before the test. Other measurement conditions for the total light transmittance were in accordance with JIS K7361-1:1997.

[0139] The total light transmittance is the arithmetic mean of five measurements. These five measurements were taken at five locations on the optical sheet being evaluated. Each of the five measurement locations is at least 10 mm apart.

[0140] <Transmitted Haze>

[0141] The transmission haze of the optical sheet 10 can be below 1.0%, below 0.5%, below 0.3%, or below 0.2%. There is no specific lower limit for the transmission haze of the optical sheet 10. The transmission haze of the optical sheet 10 can be 0% or greater than 0%.

[0142] The D65 light source was used to determine the transmitted haze (%). Before measuring the transmitted haze of the optical sheet 10, the D65 light source was lit for 15 minutes to stabilize its output. The incident angle of the sample was set to 0° during the transmitted haze measurement. The incident surface was the second surface 12 of the optical sheet 10. The test environment for measuring the transmitted haze was set to a temperature of 23℃±2℃ and a relative humidity of 50%±5%. The sample was placed in the test environment for 16 hours before the test. Other measurement conditions for the transmitted haze were in accordance with JIS K7136:2000.

[0143] Transmitted haze is the arithmetic mean of five measurements. These five measurements were taken at five locations on the optical sheet being evaluated. Each of the five measurement locations is at least 10 mm apart.

[0144] like Figure 1 As shown, the optical sheet 10 may include a resin layer 30 located between the substrate 20 and the functional layer 40. The resin layer 30 may contain a cured product of a curable resin composition. The resin layer 30 containing a cured product of a curable resin composition has high strength and high hardness. By laminating the functional layer 40 onto the resin layer 30 and supporting it, the scratch resistance of the first surface 11 can be further improved.

[0145] The following is a further detailed explanation. Figure 1The layers of the optical sheet 10 are shown. Figure 1 In the example shown, the substrate 20, resin layer 30, and functional layer 40 are stacked on a third direction D3, i.e., the third direction D3 is the stacking direction. The substrate 20, resin layer 30, and functional layer 40 extend in a first direction D1 and a second direction D2, which are 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 contained in the optical sheet 10. Figure 1 In the optical sheet 10 shown, the first surface 11 is composed of a functional layer 40. The second surface 12 is composed of a substrate 20.

[0146] It should be noted that the optical sheet 10 also has an antistatic layer or an antifouling layer, which are supported by the functional layer 40 to form the first surface 11. These antistatic layers, antifouling layers, etc., are very thin layers. Otherwise, the functional layer 40 would not be able to effectively perform its reflection suppression function. Therefore, in the example where the first surface 11 is formed by an antistatic layer, an antifouling layer, etc., the scratch resistance of the first surface 11 is also affected by the functional layer 40. That is, according to the aforementioned functional layer 40, the scratch resistance of the first surface 11 can be significantly improved.

[0147] <<Substrate 20>>

[0148] The substrate 20 supports the resin layer 30 and the functional layer 40. The substrate 20 can be transparent. Transparency means that the total light transmittance is 50% or more according to JIS K 7361-1:1997, which can be 70% or more, 80% or more, or 90% or more.

[0149] The material of the substrate 20 is not particularly limited; it can be resin or glass. Resin is preferred due to its lightweight and ease of manufacture.

[0150] The resin used in the substrate 20 can be a polyolefin resin such as polyethylene or polypropylene. The resin used in the substrate 20 can be a vinyl resin such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, or ethylene-vinyl alcohol copolymer. The resin used in the substrate 20 can also be a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate. The resin used in the substrate 20 can also be an acrylic resin such as poly(methyl methacrylate) or poly(ethyl methacrylate). The resin used in the substrate 20 can 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. Examples of resins used in the substrate 20 include cyclic olefin resins obtained from resins such as polycarbonate, polyimide resins, norbornene, dicyclopentadiene, etc. The substrate 20 may contain only one of the above-mentioned resins or may contain two or more of the above-mentioned resins.

[0151] The thickness of the resin substrate 20 is not particularly limited. From a processability point of view, the thickness of the resin substrate 20 can be 10 μm or more, 20 μm or more, or 50 μm or more. The thickness of the resin substrate 20 can be less than 500 μm, 400 μm or less, or 300 μm or less. The thickness of the resin substrate 20 can be 500 μm or more.

[0152] When the optical sheet 10 is used in a foldable application, the substrate 20 can also be flexible. In this example, the thickness of the resin substrate 20 can be 10 μm or more but less than 40 μm. When the optical sheet 10 is used in a laminate with glass, from the perspective of preventing glass from scattering, the thickness of the resin substrate 20 can also be 40 μm or more but less than 100 μm.

[0153] The substrate 20 may contain a single layer or multiple layers. The substrate 20 may include an adhesive layer or other base coating.

[0154] <<Functional Layer 40>>

[0155] Functional layer 40 includes adhesive component 41 and hollow silica particles 43. The inclusion of hollow silica particles 43 in functional layer 40 reduces the refractive index. Functional layer 40 can have a lower refractive index than adhesive component 41. The refractive index of functional layer 40 can be lower than the refractive index of substrate 20. The refractive index of functional layer 40 can be lower than the refractive index of layers adjacent to functional layer 40.

[0156] The functional layer 40, due to its refractive index and thickness, is able to suppress the reflection of incident light. The reflection suppression function of the functional layer 40 is based on the interference of light reflected from the surfaces on both sides of the functional layer 40. From the viewpoint of making this reflection suppression function effective, the refractive index of the functional layer 40 can be the magnitude between the refractive indices of the two regions adjacent to the functional layer 40 on both sides. Furthermore, the thickness (nm) of the functional layer 40 can be approximately 1 / 4 of the wavelength λ (nm) of the light whose reflection is to be suppressed.

[0157] From the perspective of reflection suppression, the refractive index and average thickness of the functional layer can be set as follows: The refractive index of the functional layer can be 1.10 or higher, 1.20 or higher, 1.26 or higher, 1.28 or higher, or 1.30 or higher. The refractive index of the functional layer can be 1.48 or lower, 1.45 or lower, 1.40 or lower, 1.38 or lower, or 1.35 or lower. The refractive index used for the constituent elements of the optical sheet is the refractive index relative to a wavelength of 589.3 nm. The thickness of the functional layer can be 80 nm or higher, 85 nm or higher, or 90 nm or higher. The thickness of the functional layer can be 150 nm or lower, 110 nm or lower, or 105 nm or lower.

[0158] <Adhesive component 41>

[0159] The binder component 42 is an element that retains the metal oxide particles 42. The binder component 42 can also function as a binder for forming a coating film. By retaining the particles contained in the functional layer 40 through the binder component 42, the functional layer 40 can maintain its film morphology. The binder component 42 may contain a resin. The resin contained in the binder component 42 can be a natural resin or a synthetic resin. The binder component 42 can encapsulate the particles contained in the functional layer 40. The binder component 42 can completely surround each particle contained in the functional layer 40, or it can leave at least a portion of the particles partially exposed.

[0160] The adhesive component 41 may also contain a cured product of the curable resin composition. The curable resin composition may also contain one or more of a thermosetting resin composition and an ionizing radiation-curable resin composition. The cured product of the curable resin composition can impart high strength and high hardness to the functional layer 40, improving the scratch resistance of the first surface 11. From the viewpoint of improving scratch resistance, the ionizing radiation-curable resin composition is particularly useful.

[0161] The thermosetting resin composition contains a thermosetting resin. The thermosetting resin composition is cured by heating. Examples of thermosetting resins include acrylic resins, urethane resins, phenolic resins, urea-melamine resins, epoxy resins, unsaturated polyester resins, and silicone resins. The thermosetting resin composition may also contain a curing agent.

[0162] The ionizing radiation-curable resin composition contains an ionizing radiation-curable compound. The ionizing radiation-curable compound contains an ionizing radiation-curable functional group. Examples of ionizing radiation-curable functional groups include olefinic unsaturated groups such as (meth)acryloyl, vinyl, and allyl, as well as epoxy and oxetyl groups. The ionizing radiation-curable compound may contain two or more ionizing radiation-curable functional groups. The ionizing radiation-curable compound may also be a compound having olefinic unsaturated groups. The ionizing radiation-curable compound may also be a (meth)acrylate compound having a (meth)acryloyl group. The ionizing radiation-curable compound may also be a siloxane compound containing a siloxane bond.

[0163] Hereinafter, (meth)acrylate compounds having four or more olefinic unsaturated groups are referred to as "polyfunctional (meth)acrylate compounds". (meth)acrylate compounds having two to three olefinic unsaturated groups are referred to as "low-functional (meth)acrylate compounds".

[0164] (Meth)acrylate compounds can be monomers or oligomers. Ionizing radiation-curable compounds containing low-functionality (meth)acrylate compounds can suppress uneven shrinkage during curing, thus smoothing the surface of the functional layer 40.

[0165] The proportion of low-functional (meth)acrylate compounds in the ionizing 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 even 100% by mass. From the perspective of suppressing uneven shrinkage during curing and smoothing the surface irregularity of the functional layer 40, the low-functional (meth)acrylate compound can also be a (meth)acrylate compound containing two olefinic unsaturated bond groups. When the ionizing radiation curable compound contains a large amount of polyfunctional (meth)acrylate compounds, as described later, the surface of the functional layer can be smoothed by appropriately adjusting the type of solvent and drying conditions.

[0166] Examples of difunctional (meth)acrylate compounds include dimethacrylate isocyanurate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polybutylene glycol dimethacrylate, and other polyalkylene glycol dimethacrylates, bisphenol A tetraethoxydimethacrylate, bisphenol A tetrapropoxydimethacrylate, and 1,6-hexanediol dimethacrylate. Examples of trifunctional (meth)acrylate compounds include trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, and isocyanuric acid-modified trimethacrylate. Examples of polyfunctional (meth)acrylate compounds with four or more functions include pentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, and dipentaerythritol tetramethacrylate. (Meth)acrylate compounds can be modified as described below.

[0167] Examples of (meth)acrylate oligomers include urethane (meth)acrylates, epoxy (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, and other acrylate polymers. Uramate (meth)acrylates are obtained, for example, by reacting a polyol and an organic diisocyanate with a hydroxyl (meth)acrylate. Epoxy (meth)acrylates can also be obtained by reacting a trifunctional or higher aromatic epoxy resin, alicyclic epoxy resin, or aliphatic epoxy resin with (meth)acrylic acid. Epoxy (meth)acrylates can also be obtained by reacting a difunctional or higher aromatic epoxy resin, alicyclic epoxy resin, or aliphatic epoxy resin with a polybasic acid and (meth)acrylic acid. Epoxy (meth)acrylates can also be obtained by reacting a difunctional or higher aromatic epoxy resin, alicyclic epoxy resin, or aliphatic epoxy resin with a phenol and (meth)acrylic acid.

[0168] From the perspective of suppressing uneven shrinkage caused by crosslinking, (meth)acrylate compounds can be modified by modifying a portion of their molecular backbone. For example, (meth)acrylate compounds can be modified using ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl groups, cyclic alkyl groups, aromatic groups, bisphenols, etc. From the viewpoint of improving affinity with silica particles, suppressing particle aggregation, and adjusting the C / Si ratio to the aforementioned range, the aforementioned (meth)acrylate compounds can also be modified using ethylene oxide, propylene oxide, or other epoxides. The proportion of epoxide-modified (meth)acrylate compounds in ionizing radiation-curable compounds 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. Epoxide-modified (meth)acrylate compounds can be low-functionality (meth)acrylate compounds or (meth)acrylate compounds having two olefinic unsaturated bond groups.

[0169] Examples of methacrylate compounds modified with alkylene oxide and having two olefinically unsaturated 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 in the polyalkylene glycol di(meth)acrylate can be 3 to 5. The alkylene glycol in the polyalkylene glycol di(meth)acrylate can be ethylene glycol and / or polyethylene glycol. Examples of methacrylate compounds modified with alkylene oxide and having three olefinically unsaturated groups include trimethylolpropane alkylene oxide-modified tri(meth)acrylate and isocyanuric acid alkylene oxide-modified tri(meth)acrylate.

[0170] Examples of siloxane compounds include (poly)dimethylsiloxane, (poly)diethylsiloxane, (poly)diphenylsiloxane, (poly)methylphenylsiloxane, alkyl-modified (poly)dimethylsiloxane, azo-containing (poly)dimethylsiloxane, dimethylsiloxane, phenylmethylsiloxane, alkyl-aralkyl-modified silicone, fluorosiloxane, polyether-modified silicone, fatty acid ester-modified silicone, methylhydrosiloxane, silanol-containing silicone, alkoxy-containing silicone, phenol-containing silicone, methacrylic acid-modified silicone, acrylic acid-modified silicone, amino-modified silicone, carboxylic acid-modified silicone, methanol-modified silicone, epoxy-modified silicone, mercapto-modified silicone, fluorinated silicone, and polyether-modified silicone.

[0171] One type of ionizing ray curing compound can be used alone, or two or more ionizing ray curing compounds can be used in combination.

[0172] When the ionizing radiation curable compound is an ultraviolet curable compound, the curable resin composition forming the adhesive component 41 may also include additives such as photopolymerization initiators and photopolymerization accelerators. Examples of photopolymerization initiators include one or more selected from acetophenone, benzophenone, α-hydroxyalkyl phenyl ketone, mischlerone, benzoin, benzoyl benzoate, benzoylbenzoate, α-acyl oxime ester, α-aminoalkyl phenyl ketone, and thioxanones. Photopolymerization accelerators can reduce polymerization hindrance caused by air during curing and accelerate the curing speed. Examples of photopolymerization accelerators include one or more selected from isoamyl p-dimethylaminobenzoate and ethyl p-dimethylaminobenzoate.

[0173] <Particles (Hollow silica particles 43, Solid silica particles 44)>

[0174] In addition to the adhesive component 41, the functional layer 40 also contains hollow silica particles 43. The functional layer 40 may also contain other particles. Examples of other particles include inorganic particles such as magnesium fluoride particles and organic particles.

[0175] The functional layer 40 includes hollow silica particles 43 as silica particles. The hollow silica particles 43 have an outer shell layer made of silica. Within the hollow silica particles 43, the interior of the particles surrounded by the outer shell layer is formed as voids. These voids may contain air. By including internal voids, the hollow silica particles 43 have a refractive index lower than that of silica. If the volume of the internal voids is large, the refractive index of the hollow silica particles 43 becomes lower. The hollow silica particles 43 reduce the overall refractive index of the functional layer 40. By using hollow silica particles 43 with a larger particle size that increase the internal space ratio, the refractive index of the functional layer 40 can be further reduced.

[0176] Hollow silica particles 43 can be uniformly dispersed within the functional layer 40. By uniformly dispersing the hollow silica particles 43 within the functional layer 40, the first surface 11 is smoothed, and the arithmetic mean roughness Sa of the first surface 11 can be reduced. As a result, the sliding properties of the first surface 11 are 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 of the hollow silica particles 43 to other particles, and adjusting the affinity between the hollow silica particles 43 and other particles, the hollow silica particles 43 can be uniformly dispersed within the functional layer 40.

[0177] like Figure 1As shown, in addition to hollow silica particles 43, the functional layer 40 may also include solid silica particles 44. The solid silica particles 44 are non-hollow silica particles. The solid silica particles 44 are particles without internal cavities. The solid silica particles 44 can be solid silica particles. The solid silica particles, by being dispersed in the binder component 41, thereby improve the scratch resistance of the functional layer 40.

[0178] Solid silica particles 44 can be uniformly dispersed together with hollow silica particles 43 within the functional layer 40. By uniformly dispersing solid silica particles 44 and hollow silica particles 43 within the functional layer 40, the first surface 11 is smoothed, and the arithmetic mean roughness Sa of the first surface 11 can be reduced. This improves the sliding properties of the first surface 11 and enhances its scratch resistance. By adjusting the ratio of the content of solid silica particles 44 to other particles such as hollow silica particles 43, and the ratio of their average particle size, the affinity between solid silica particles 44 and other particles such as hollow silica particles 43 can be adjusted, allowing the solid silica particles 44 and hollow silica particles 43 to be uniformly dispersed together within the functional layer 40. Figure 1 In the example shown, hollow silica particles 43 and solid silica particles 44 are uniformly dispersed within the functional layer 40.

[0179] The functional layer 40 may contain metal oxide particles other than silicon dioxide particles. These metal oxide particles enhance the strength and hardness of the functional layer 40 and improve the scratch resistance of the first surface 11. Examples of metal oxide particles include single oxides or mixtures of oxides of any one of titanium, tantalum, zirconium, chromium, niobium, cerium, hafnium, and yttrium.

[0180] Metal oxide particles can include alumina particles. Alumina particles have a low refractive index among metal oxides. Alumina, represented by Al₂O₃, is known to exist in α-type, γ-type, σ-type, and mixtures thereof. Alumina particles can also be surface-modified alumina particles. Examples of modified alumina particles include (meth)acrylic acid-modified alumina particles and silicone-modified alumina particles. Metal oxide particles can be hollow particles with internal spaces or solid particles without internal spaces.

[0181] The shape of the hollow silica particles 43 or solid silica particles 44 dispersed within the functional layer 40 is not particularly limited. The shape of the particles can be spherical, ellipsoidal, polyhedral (approximately spherical), rod-shaped, plate-shaped, fibrous, or irregular. By making the shape of the hollow silica particles 43 or solid silica particles 44 dispersed within the functional layer 40 spherical, ellipsoidal, or approximately spherical, the sliding properties of the first surface 11 are improved, and the scratch resistance of the first surface 11 is enhanced.

[0182] Hollow silica particles 43 or solid silica particles 44, dispersed within the functional layer 40, can have their surfaces coated with a silane coupling agent. The silane coupling agent may contain (meth)acryloyl groups or epoxy groups. By subjecting the particles to surface treatment with a silane coupling agent, the affinity between the particles and the binder components is improved, and the particles are less prone to aggregation. Consequently, the particles are more uniformly dispersed within the binder components.

[0183] Silane coupling agents can include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-epoxypropoxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- Triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, tris(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, trifluoropropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane, etc. The silane coupling agent may be one or more selected from 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane and 3-methacryloxypropyltriethoxysilane.

[0184] like Figure 1 As shown, the particles contained in the functional layer 40, such as hollow silica particles 43 and solid silica particles 44, can exist in a high concentration within the functional layer 40 and be uniformly dispersed within it. According to this configuration, as described above, the first surface 11 is smoothed and its coefficient of kinetic friction is reduced, thereby improving the scratch resistance of the first surface 11. Figure 1 As shown, hollow silica particles 43 with a large average particle size are uniformly dispersed within the functional layer 40. Solid silica particles 44 are dispersed within the functional layer 40 in a manner that fills 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 40.

[0185] exist Figure 1In the example shown, hollow silica particles 43 with a large average particle size are uniformly dispersed within the functional layer 40. Additionally, solid silica particles 44 with a small average particle size are filled within the functional layer 40 in a manner that buries the hollow silica particles 43. According to this example, the functional layer 40 has high hardness and its surface becomes smooth. Consequently, the arithmetic mean roughness Sa of the first surface 11 and the coefficient of kinetic friction of the first surface 11 are reduced, and the scratch resistance of the first surface 11 is improved.

[0186] The average particle size of the hollow silica particles 43 can be greater than 50 nm or greater than 65 nm. The average particle size of the hollow silica particles 43 can be less than 100 nm or less than 80 nm.

[0187] The average particle size of the solid silica particles 44 can be greater than 5 nm or greater than 10 nm. The average particle size of the solid silica particles 44 can be less than 20 nm or less than 15 nm. The average particle size of the solid silica particles 44 can be smaller than the average particle size of the hollow silica particles 43.

[0188] By setting a lower limit for 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 40. By setting an upper limit for the average particle size of the hollow silica particles 43, the adhesive component 41 can stably hold the hollow silica particles 43. That is, it can suppress the detachment of the hollow silica particles 43 from the functional layer 40 and improve scratch resistance. By setting an upper limit for the average particle size of the solid silica particles 44 and a lower limit for the hollow silica particles 43, the solid silica particles 44 can be configured close to the hollow silica particles 43 with a larger average particle size. That is, it can make the hollow silica particles 43 and solid silica particles 44 uniformly dispersed in the functional layer 40 at a high concentration. As a result, excellent scratch resistance can be stably imparted to the functional layer 40 and the optical sheet 10.

[0189] The "average particle size" used for particles such as hollow silica particles 43 and solid silica particles 44 is set to the value determined by the following (1) to (3).

[0190] (1) Observe the cross section of the optical sheet containing particles using a transmission electron microscope (TEM) and obtain the observation image by taking pictures.

[0191] (2) Extract any 10 particles from the observed image and measure the particle size of each particle. The particle size (nm) is defined as the distance between the two lines that make the observed particle in the image the largest when the distance between the two lines is between them. That is, the particle size is the maximum length of the particle in the observed image.

[0192] (3) Perform the above operations (1) and (2) five times on the same optical sheet as the test object, and measure the particle size of a total of 50 particles. Take the average value of the total 50 particle size measurements as the average particle size (nm).

[0193] The "average thickness" of functional layer 40 is set to a value determined by the following (4) to (6).

[0194] (4) Use a transmission electron microscope (TEM) to photograph the cross section of the optical sheet containing the functional layer.

[0195] (5) Measure the thickness of the functional layer at the center position along the surface of the optical sheet in the captured image, and the thickness of the functional layer at a position offset 100 nm from the center position to both sides along the surface of the optical sheet. The thickness is set as the length (nm) of the functional layer along the direction orthogonal to the surface of the optical sheet.

[0196] (6) Perform the above operations (4) and (5) five times on the same optical sheet as the measurement object, and measure the thickness of the functional layer at a total of 15 locations. The average value of the total 15 thickness measurements is taken as the average thickness (nm) of the functional layer.

[0197] The average particle size and the thickness of the functional layer can be measured using a scanning transmission electron microscope (STEM), a type of transmission electron microscope, specifically the H-7650 electron microscope manufactured by Hitachi High Technology Corporation.

[0198] If the content of hollow silica particles 43 increases, the refractive index of functional layer 40 decreases, and functional layer 40 can exert excellent reflection suppression function. That is, from the perspective of the reflection suppression function of functional layer 40A, a lower limit can be set for the content of hollow silica particles 43. By setting a lower limit for the content of particles other than hollow silica particles 43, the smoothness, strength, and hardness of functional layer 40 can be ensured. By setting a lower limit for the content of binder component 41, the particles can be stably held by binder component 41. Thus, particle shedding can be suppressed, ensuring excellent scratch resistance. By setting an upper limit for the content of binder component 41, the refractive index of functional layer 40 decreases, and functional layer 40 can exert excellent reflection suppression function. By setting an upper limit for the content of each particle, significant aggregation of the particles can be suppressed.

[0199] The content of hollow silica particles relative to 100 parts by weight of the adhesive component can be more than 100 parts by weight, more than 150 parts by weight, or more than 175 parts by weight. The content of hollow silica particles relative to 100 parts by weight of the adhesive component can be less than 400 parts by weight, less than 300 parts by weight, or less than 250 parts by weight.

[0200] The content of solid silica particles relative to 100 parts by weight of the binder can be 10 parts by weight or more, 50 parts by weight or more, 70 parts by weight or more, or 100 parts by weight or more. The content of solid silica particles relative to 100 parts by weight of the binder can be less than 200 parts by weight, less than 150 parts by weight, or less than 100 parts by weight.

[0201] The content of solid silica particles relative to 100 parts by weight of hollow silica particles can be 30 parts by weight or more, 35 parts by weight or more, or 40 parts by weight or more. The content of solid silica particles relative to 100 parts by weight of binder components can be less than 80 parts by weight, less than 75 parts by weight, or less than 70 parts by weight.

[0202] <How to create Functional Layer 40>

[0203] The functional layer 40 can be made using a coating liquid containing a curable resin composition and particles. Alternatively, the functional layer 40 can be obtained by curing a coating film made from the coating liquid. The coating liquid used to make the functional layer 40 may contain additives such as antistatic agents, antioxidants, surfactants, dispersants, and ultraviolet absorbers.

[0204] The coating liquid for the functional layer contains a leveling agent. The leveling agent is an additive that smooths the surface of the functional layer 40. The leveling agent suppresses defects such as shrinkage, depressions, pinholes, and orange peel caused by uneven surface tension of the functional layer 40. The inclusion of a leveling agent in the coating liquid for the functional layer prevents the surface of the functional layer from becoming a Bénard cell structure. During the drying of a coating film composed of a coated functional layer and a coating solution, a surface tension difference arises between the surface and inner surfaces of the coating film, thereby inducing multiple convection currents within the film. The structure generated by this convection is called a Bénard cell structure, which produces an orange peel-like defect on the surface of the functional layer. By using a leveling agent, the unevenness of surface tension can be suppressed, thus inhibiting the formation of Bénard cell structures.

[0205] The leveling agent contained in the coating liquid for the functional layer is not particularly limited. Examples of leveling agents include compounds having polyether, polyurethane, epoxy, carboxyl, acrylate, methacrylate, methanol, or hydroxyl groups. These leveling agents may have polyether, polyurethane, epoxy, carboxyl, acrylate, methacrylate, methanol, or hydroxyl groups at the ends (single or double ends) of the main chain, or they may have the above-mentioned groups on the side chain, or they may have the above-mentioned groups at both the ends of the main chain and the side chain. As a leveling agent, there is no particular limitation as long as the compound has polyether, polyurethane, epoxy, carboxyl, acrylate, methacrylate, methanol, or hydroxyl groups. Examples of leveling agents include silicone-based, fluorine-based, silicone / fluorine-based, acrylic-based, methacrylate-based, vinyl-based, and aromatic-based leveling agents. From the viewpoint of suppressing coating defects such as shrinkage, the coating liquid for the functional layer may contain fluorine-based or silicone-based leveling agents. From the perspective of improving recoatability, the coating liquid for functional layers may contain acrylic leveling agents or vinyl leveling agents.

[0206] As described above, the scratch resistance of the first surface 11 is improved by forming pits 45 on the first surface 11. It is speculated that the pits 45 on the first surface 11 can be formed by the exudation of leveling agents. According to experimental results, by including two or more leveling agents in the coating liquid for the functional layer, the formation of pits 45 on the first surface 11 can be promoted. In particular, by including two or more of fluorine-based leveling agents, silicone-based leveling agents, and silicone / fluorine-based leveling agents in the coating liquid for the functional layer, the formation of pits 45 on the first surface 11 can be promoted. Although the details are unclear, pits 45 are more likely to form on the first surface 11 when two or more leveling agents are used. In particular, pits 45 are more likely to form on the first surface 11 when both fluorine-based leveling agents and silicone / fluorine-based leveling agents are used.

[0207] Depending on the leveling agent content, the formation of pits 45 on the first surface 11 can be promoted. Increasing the leveling agent content relative to the adhesive component 41 can promote the formation of pits 45 on the first surface 11. If the leveling agent content relative to the adhesive component 41 is too high, the width and depth of the pits 45 become too large, and the number of pits 45 becomes too large. Based on these aspects, the leveling agent content relative to 100 parts by mass of the adhesive component can be 1 part by mass or more, 2 parts by mass or more, 5 parts by mass or more, or 8 parts by mass or more. The leveling agent content relative to 100 parts by mass of the adhesive component can be 45 parts by mass or less, 40 parts by mass or less, 35 parts by mass or less, or 20 parts by mass or less. In addition, by reducing the particle content relative to the adhesive component 41, it is also easier to form pits 45 on the first surface 11. Specifically, as described above, by determining the particle content relative to the adhesive component 41, it is easier to form pits 45 on the first surface 11.

[0208] When the leveling agent comprises both fluorinated leveling agents and silicone / fluorinated leveling agents, from the viewpoint of promoting the formation of pits on the first surface 11, the content of each leveling agent can be set as follows: The fluorinated leveling agent can be 5 parts by mass or more, 8 parts by mass or more, or 10 parts by mass or more relative to 100 parts by mass of the adhesive component. The fluorinated leveling agent can be 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less relative to 100 parts by mass of the adhesive component. The silicone / fluorinated leveling agent can be 5 parts by mass or more, 8 parts by mass or more, or 10 parts by mass or more relative to 100 parts by mass of the fluorinated leveling agent. The silicone / fluorinated leveling agent can be less than 100 parts by mass, 35 parts by mass or less, 30 parts by mass or less, or 25 parts by mass or less relative to 100 parts by mass of the fluorinated leveling agent.

[0209] <<Resin Layer 30 (Hard Coating)>>

[0210] The optical sheet 10 may include a resin layer 30 between the substrate 20 and the functional layer 40. The resin layer 30 may be adjacent to the functional layer 40 on a third direction D3. The resin layer 30 comprises a cured product of a curable resin composition. The curable resin composition may comprise one or more of a thermosetting resin composition and an ionizing radiation curable resin composition. The curable resin composition may comprise one or more of a thermosetting resin and an ionizing radiation curable compound. The resin layer 30 may be a hard coating. The resin layer 30 can impart high strength and high hardness to the optical sheet 10 and the first surface 11, improving the scratch resistance of the first surface 11. The curable resin composition used in the formation of the resin layer 30 may be the same as the curable resin composition used to form the functional layer 40. The curable resin composition used in the formation of the resin layer 30 may include cured products of thermosetting resins and ionizing radiation curable compounds contained in the curable resin composition used to form the functional layer 40.

[0211] The thickness of the resin layer 30 can be 0.1 μm or more, 0.5 μm or more, or 1 μm or more. The thickness of the resin layer 30 can be less than 100 μm, less than 20 μm, or less than 10 μm. By setting the thickness of the resin layer 30 in this way, excellent scratch resistance can be ensured, and crack formation can be suppressed during processing such as cutting of the optical sheet 10.

[0212] From the perspective of achieving reflection suppression through functional layer 40, the refractive index of resin layer 30 can be lower than that of functional layer 40. The refractive index of resin layer 30 can be above 1.45 and below 1.70.

[0213] 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 higher, or 1.55 or higher. In this example, the refractive index of the resin layer 30 can be 1.65 or lower, or 1.60 or lower. 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 between the three layers—the resin layer 30 as a medium refractive index layer, the high refractive index layer, and the functional layer 40 as a low refractive index layer—becomes possible, further reducing reflectivity. The refractive index of the resin layer 30 can be adjusted by the resin and particles contained in the curable resin composition.

[0214] The refractive index is set to a value determined by fitting the reflection spectrum measured by a reflectance spectrophotometer to the reflection spectrum calculated based on an optical model of a multilayer thin film using Fresnel coefficients.

[0215] The resin layer 30 can be made using a coating liquid containing a curable resin composition. Alternatively, the resin layer 30 can be obtained by curing a coating film made from the coating liquid. In this example, the coating liquid used to make the resin layer 30 may contain additives suitable for use in coating liquids for functional layers. That is, the coating liquid for the resin layer may contain a photopolymerization initiator and a photopolymerization accelerator. The coating liquid for the resin layer may also contain a leveling agent.

[0216] <<Second Functional Layer 50 (High Refractive Index Layer)>>

[0217] like Figure 7 As shown, the optical sheet 10 may further include a second functional layer 50. The second functional layer 50 is located between the functional layer 40 and the resin layer 30 in a third direction D3, which is the stacking direction. The second functional layer 50 may be adjacent to the functional layer 40 in the third direction D3. As described above, the second functional layer 50 is configured to have a refractive index higher than that of the resin layer 30 and the functional layer 40, and enhances the reflection suppression function of the optical sheet 10.

[0218] From the perspective of reflection suppression, the refractive index and 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 higher, or 1.56 or higher. The refractive index of the second functional layer can be 1.85 or lower, or 1.75 or lower. The thickness of the second functional layer can be 50 nm or higher. The thickness of the second functional layer can be 200 nm or lower, or 180 nm or lower.

[0219] like Figure 7 As shown, the second functional layer 50 may comprise an adhesive resin 51 and particles 52. The particles 52 are particles used to adjust the refractive index and may have an average particle size in the nanometer range. The adhesive resin 51 may be made using a curable resin composition similar to the adhesive component 41 of the resin serving as the functional layer 40. The curable resin composition may comprise one or more of a thermosetting resin composition and an ionizing radiation curable resin composition. The curable resin composition may comprise one or more of a thermosetting resin and an ionizing radiation curable compound. The thermosetting resin and ionizing radiation curable compound used to form the second functional layer 50 may be the same as those used to form the functional layer 40.

[0220] Particle 52 can also be a particle with a higher refractive index than that of the adhesive resin 51. Examples of particles 52 include antimony pentoxide, zinc oxide, titanium oxide, cerium oxide, tin-doped indium oxide, antimony-doped tin oxide, yttrium oxide, and zirconium oxide. Zirconia, antimony pentoxide, and titanium oxide can impart high strength and high hardness to the second functional layer 50, which helps to improve the scratch resistance of the first surface 11.

[0221] The average particle size of particle 52 can be 5 nm or more, or 10 nm or more. The average particle size of particle 52 can be less than 200 nm, less than 100 nm, or less than 80 nm. The content of particle 52 can be set from the viewpoint of increasing the refractive index of the second functional layer 50 and increasing the strength of the second functional layer 50. The content of particle 52 relative to 100 parts by mass of adhesive resin 51 can be 100 parts by mass or more, 300 parts by mass or more, or 500 parts by mass or more. The content of particle 52 relative to 100 parts by mass of adhesive resin 51 can be less than 2500 parts by mass, less than 2200 parts by mass, or less than 2000 parts by mass.

[0222] The second functional layer 50 can be made using a coating liquid comprising a curable resin composition and particles 52. The second functional layer 50 is obtained by curing the coating film of the coating liquid. In this example, the coating liquid used to make the second functional layer 50 may contain additives suitable for use in functional layer coating liquids. That is, the coating liquid for the second functional layer may contain photopolymerization initiators and photopolymerization accelerators. The coating liquid for the second functional layer may contain antistatic agents, antioxidants, surfactants, dispersants, ultraviolet absorbers, leveling agents, etc.

[0223] <<Methods for Manufacturing Optical Sheets>>>

[0224] The resin layer 30, functional layer 40A, and second functional layer 50 included in the optical sheet 10 can be manufactured by a wet process, which involves applying a coating liquid containing the components constituting each layer 30, 40, and 50 onto the substrate 20 and then drying and curing it. In addition to the resin composition and particles used in the formation of each layer, the coating liquid may also contain a solvent. The resin composition may also contain solid components constituting each layer and additives such as polymerization initiators.

[0225] The optical sheet 10, comprising a substrate 20 and a functional layer 40, can be manufactured as follows: First, a coating liquid for forming the functional layer 40 is prepared. Next, the coating liquid for forming the functional layer is applied to the substrate 20 to form a coating film. Then, the coating film is dried, and then cured. Thus, the functional layer 40 is formed on the substrate 20, resulting in the optical sheet 10.

[0226] In the case where the optical sheet 10 includes a resin layer 30 in addition to the functional layer 40, the resin layer 30 is formed on the substrate 20 before the functional layer 40 is formed. The resin layer used to form the resin layer 30 is coated onto the substrate 20 with a coating liquid, and the coating is dried and cured to obtain the resin layer 30. Next, the functional layer 40 is formed on the resin layer 30 to obtain the optical sheet 10. It should be noted that the resin layer 30 can also be formed on the substrate 20 in an uncured or semi-cured state, and the resin layer 30 and the functional layer 40 can be completely cured together during the curing process.

[0227] In the case where the optical sheet 10 includes a second functional layer 50 in addition to the resin layer 30 and the functional layer 40, the second functional layer 50 is formed on the resin layer 30 after the resin layer 30 is formed and before the functional layer 40 is formed. The second functional layer for forming the second functional layer 50 is coated onto the resin layer 30 with a coating liquid, and the coating film is dried and cured to obtain the second functional layer 50. Next, the optical sheet 10 is obtained by forming the functional layer 40 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 formed in an uncured or semi-cured state and the functional layer 40 is cured, one or more of the resin layer 30 and the second functional layer 50 can be completely cured together with the functional layer 40.

[0228] By including a solvent in the coating solution, the viscosity of the coating solution can be adjusted, allowing the various components to dissolve or disperse within it. The solvent can be one or more of the following: ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ethers (dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), carbon halides (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), alcohols (butanol, cyclohexanol, etc.), cellosolvers (methyl cellosolvers, ethyl cellosolvers, etc.), cellosolver acetates, sulfoxides (dimethyl sulfoxide, etc.), glycol ethers (1-methoxy-2-propyl acetate, etc.), and amides (dimethylformamide, dimethylacetamide, etc.).

[0229] When the solvent evaporates too quickly, the unevenness of the functional layer 40 increases, making it difficult to form pits 45. It is believed that a major reason for this is that when the solvent evaporates too quickly, the leveling agent in the coating film of the coating liquid cannot sufficiently float to the vicinity of the surface. On the other hand, by reducing the evaporation rate of the solvent, the unevenness of the functional layer 40 decreases, making it easier to form pits 45. Based on this, the coating liquid can contain solvents with slow evaporation rates.

[0230] When the solvent evaporates too quickly, it undergoes active convection during the drying of the coating solution. Particles contained in the coating solution, such as hollow silica particles 43, solid silica particles 44, metal oxide particles, and other granules, may exist unevenly due to convection caused by solvent evaporation during the drying process. That is, the particles within the coating film become unevenly dispersed. From this perspective, the coating solution can also contain solvents with slow evaporation rates.

[0231] The relative evaporation rate of the solvent contained in the coating solution can be 70 or less, or between 30 and 60. Regarding the relative evaporation rate, the evaporation rate of butyl acetate is set to 100, and the evaporation rate of the solvent being studied is expressed as a comparison with the evaporation rate of butyl acetate. For 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.

[0232] The solvent with a relative evaporation rate of 70 or less can be 10% to 50% by mass or 20% to 40% by mass of the total solvent. In this example, as a solvent other than the one with a relative evaporation rate of 70 or less, a solvent with excellent resin solubility can be included in the coating solution. The relative evaporation rate of the solvent with excellent resin solubility can also be 100 or more.

[0233] From the perspective of suppressing solvent convection during coating liquid drying, the drying temperature during coating liquid drying can be lowered, thus slowing down the drying rate. In particular, the drying temperature of the coating liquid used for functional layers can be lowered. The drying temperature of the coating film formed by the coating liquid can be appropriately set taking into account factors such as the formation of pits 45, the type of solvent, particle dispersibility, and production speed.

[0234] As described above, by adjusting the type of solvent, the mixing process, and the drying conditions of the coating film, the presence, size, and number of pits 45 in the first surface 11 can be controlled. By adjusting the type of solvent, the mixing process, and the drying conditions of the coating film, the dispersion of particles such as hollow silica particles 43 and solid silica particles 44 within the functional layer 40 can be controlled.

[0235] Examples of methods for curing coatings that form various layers include irradiation with ionizing rays such as ultraviolet light and electron beams, and heating. Curing processes using ionizing ray irradiation offer excellent productivity in terms of enabling curing in a short time.

[0236] According to the above-described manufacturing method of the optical sheet 10 using a wet process, such as Figure 8As shown, a strip of sheet 5 containing multiple optical pieces 10 can be manufactured. Optical pieces 10 are obtained by cutting the strip of sheet 5 to a predetermined size. According to this example, optical pieces 10 of various sizes can be obtained from the strip of sheet 5 as needed. Therefore, optical pieces 10 of various sizes can be provided as needed. Figure 8 As shown, by processing the sheet article 5 as a roll 7 wound around the winding axis RA on the winding core, the processability of the sheet article 5 can be improved.

[0237] In addition to the steps described above for manufacturing an optical sheet, the method for manufacturing an optical sheet may also include a step of selecting the optical sheet 10 to be manufactured. The step of selecting the optical sheet 10 may include the following steps: obtaining an image of a 10μm × 10μm measurement area on the first surface; and selecting an optical sheet containing one or more pits of a predetermined size within the measurement area based on the image of the measurement area. Here, the predetermined size is a size with a width of 0.1μm or more and a depth of 10nm or more. An optical sheet 10 containing pits 45 of a predetermined size within the measurement area exhibits excellent scratch resistance. According to this selection step, an optical sheet with excellent scratch resistance can be selected with high precision without performing a scratch test using felt or steel wool.

[0238] The selection step may also include the following steps: determining whether one or more of the following conditions A to K are met, and selecting the optical sheet 10 that meets the conditions.

[0239] [A] The width of the pit is less than 1.5 μm.

[0240] [B] The depth of the pit is less than 70nm.

[0241] [C] The 10μm × 10μm measurement area on the first surface contains more than 3 pits.

[0242] [D] The 10μm × 10μm measurement area on the first surface contains more than 11 pits.

[0243] [E] The number of pits contained in the 10μm × 10μm measurement area on the first surface is less than 50.

[0244] [F] The four smaller regions, each containing more than one pit, are formed by dividing the 10μm×10μm measurement area into four equal parts along each side.

[0245] [G] The measurement area of ​​10μm×10μm is divided into 9 smaller regions along each side into three equal parts, each containing more than one pit.

[0246] [H] The arithmetic mean roughness Sa of the first surface is below 8.0 nm.

[0247] [I] The first surface includes a flat area around the pit.

[0248] [J] The proportion of pits in the 10μm×10μm region on the first surface is less than 15%.

[0249] [K] The depth-to-width ratio of the pit is 0.030 or higher.

[0250] <<<Polarizing Film 60>>>

[0251] The optical element 10 in this embodiment can be applied to the polarizer 60. Figure 9 In the example shown, 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 in the middle, covering it from both sides. At least one of the first protective sheet 61 and the second protective sheet 63 may include an optical sheet 10. If only one of the first protective sheet 61 and the second protective sheet 63 includes an optical sheet 10, the other protective sheet may also include a substrate 20.

[0252] Polarizing element 62 allows one linearly polarized light component to pass through while blocking another linearly polarized light component. Polarizing element 62 can also be an absorptive polarizing element that absorbs the other linearly polarized light component. Polarizing element 62 can also be a reflective polarizing element that reflects the other linearly polarized light component. Polarizing element 62 can also be a sheet-type polarizing element, such as a polyvinyl alcohol film, polyvinyl formal film, polyvinyl acetal film, or ethylene-vinyl acetate copolymer saponified film, which has been dyed and stretched using iodine or the like. Polarizing element 62 can also be a wire grid type polarizing element composed of multiple parallel metal wires. Polarizing element 62 can be a coated polarizing element coated with lyotropic liquid crystal or dichroic guest-host material, or a multilayer thin film type polarizing element.

[0253] <<<Image display device 65>>>

[0254] The optical sheet 10 of this embodiment can be applied to a display device 65. Figure 10 In the example shown, the display device 65 includes an image forming apparatus 66 and an optical sheet 10. The image forming apparatus 66 has a display surface 66a for displaying an image. The optical sheet 10 overlaps with the image forming apparatus 66 such that its second surface 12 faces the display surface 66a. The optical sheet 10 may also be bonded to the image forming apparatus 66 by a bonding layer containing an adhesive material, bonding agent, etc. An observer can clearly observe the image displayed by the image forming apparatus 66 through the optical sheet 10 while suppressing reflection from the first surface 11 of the optical sheet 10. The image forming apparatus 66 is not particularly limited. Examples of image forming apparatus 66 include liquid crystal display elements, EL display elements, plasma display elements, electronic paper elements, etc.

[0255] <<<Panel 70>>>

[0256] The optical sheet 10 of this embodiment can be applied to various purposes. Figure 11 A panel 70 with an optical sheet 10 is shown. The panel 70 includes the optical sheet 10 and a bonded article 71 to which the optical sheet 10 is bonded. The panel 70 constitutes a reflection-suppressing article with the function of suppressing reflection through the optical sheet 10. The optical sheet 10 overlaps with the bonded article 71 face-to-face with its second surface 12. The optical sheet 10 may also be bonded to the bonded article 71 by means of a bonding layer including adhesive material, bonding agent, etc. Examples of the bonded article 71 include dashboards, clocks, display cases, shop windows, and windows.

[0257] Example

[0258] This disclosure is illustrated in more detail by way of examples. This disclosure is not limited to the following examples.

[0259] 1. Measurement and Evaluation

[0260] As described below, the optical sheets of the Examples and Comparative Examples were measured and evaluated. The test environment for each measurement and evaluation was set at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. Before each measurement and evaluation, the sample to be tested was placed in the above test environment for 16 hours.

[0261] 1-1. Visual reflectance Y value

[0262] Samples measuring 5cm × 5cm were cut from the optical sheets of Examples 1-3 and Comparative Example 1. The samples were visually inspected to ensure they were free of dust, damage, or other abnormalities. The apparent reflectance Y (%) of the optical sheets in each example was measured using the method described above. The apparent reflectance Y was measured using a UV-Vis-NIR spectrophotometer "V780" manufactured by Nippon Spectrophotometer Co., Ltd. The results of the apparent reflectance Y measurement are shown in Table 1.

[0263] 1-2. Total light transmittance and transmitted haze

[0264] Samples measuring 5 cm × 10 cm were cut from the optical films of Examples 1-3 and Comparative Example 1. The samples were visually inspected to ensure they were free of dust, damage, or other abnormalities. The total light transmittance (%) of the optical films in each example was measured using the method described above. The total light transmittance was measured using a haze meter "HM-150" manufactured by Murakami Color Technology Research Institute. The results of the total light transmittance (Tt) measurement are shown in the "Tt" column of Table 1.

[0265] Samples measuring 5 cm × 10 cm were cut from the optical films of Examples 1-3 and Comparative Example 1. The samples were visually inspected to ensure they were free of dust, damage, or other abnormalities. The transmittance haze (%) of the optical films in each example was measured using the method described above. The transmittance haze was measured using a haze meter "HM-150" manufactured by Murakami Color Technology Research Institute. The results of the transmittance haze (Hz) measurements are shown in the "Hz" column of Table 1.

[0266] 1-3. Evaluation of pits

[0267] Three test samples were cut from the optical sheets of the examples and comparative examples. The test samples were 5mm × 5mm squares. Each sample was visually inspected to ensure it was free of dust, damage, or other abnormalities. The surface of each test sample, consisting of the first side of the optical sheet, was observed using an atomic force microscope (AFM). The surface of the test samples was observed using an "SPM-9700" manufactured by Shimadzu Corporation.

[0268] First, prepare several flat, circular metal plates, each 15 mm in diameter and 1 mm thick. Attach carbon double-sided tape (manufactured by Nisshin EM Co., Ltd.) to each metal plate. Place a sample to be measured on the double-sided tape and fix the sample to the metal plate. Ensure the surface of each sample, formed by the first side of the optical plate, faces upwards. To ensure reliable adhesion between the tape and the sample, place the metal plate with the sample in a desiccator overnight. After overnight placement, use a magnet to fix the metal plate with the sample onto the stage of an atomic force microscope (product name "SPM-9700", manufactured by Shimadzu Corporation). For each sample, use the tapping mode of the atomic force microscope to obtain an image relating to the surface of a 10 μm square measurement area. For each sample, select five 10 μm square measurement areas and obtain images of the five measurement areas.

[0269] The surface shape of the samples was measured using the "SPM Manager" software included with the atomic force microscope, in On-Line mode. The measurement conditions are as follows.

[0270] (AFM measurement conditions)

[0271] - Measurement mode: Phase

[0272] - Scan range: 10μm × 10μm

[0273] - Scanning speed: 2.0~2.5Hz (using a 10μm scanner)

[0274] - Pixel count: 512×512

[0275] -Cantilever used: NanoWorld NCHR (resonant frequency: 320kHz, spring constant 42N / m)

[0276] Figure 12 This is an image showing a measurement area of ​​Example 1. Figure 13 This is an image showing a measurement area of ​​Example 2. Figure 14 This is an image showing a measurement area of ​​Example 3. Figure 15 This is an image showing a measurement area of ​​Comparative Example 1.

[0277] like Figures 12-15 As shown, in atomic force microscopy images, height is represented by the intensity of color. Darker areas in the image indicate lower heights within the measurement area, while lighter areas indicate higher heights. Figures 12-15 In the image shown, the color is represented by brown. Figures 12-15 The scale bar in the lower right corner of the image shows the relationship between color intensity and height. Corresponding to the scale bar, a histogram is displayed in the lower right corner of the image. The histogram shows the frequency distribution of the regions represented by each color on the scale bar. The histogram is automatically acquired in conjunction with the acquisition of the image from the atomic force microscope.

[0278] according to Figures 12-14 In the image shown, the pits are identified as areas of darker color. That is, according to the... Figures 12-15 The images obtained by the atomic force microscope shown can determine whether there is a recess equivalent to a pit of a specified size.

[0279] Atomic force microscopy (AFM) acquires three-dimensional data of the surface of the measurement area corresponding to the first side of the optical slide, forming an image. AFM can also generate cross-sectional data of the pit in any direction. That is, it obtains... Figure 3 , Figure 4 The cross-sectional profile shown is 45x. As described above, the width and depth of the pit can be determined based on the top view image and the cross-sectional profile.

[0280] Using an atomic force microscope, images of five measurement regions were obtained for each of the three test samples in both the examples and comparative examples. That is, 15 images were obtained for each of the examples and comparative examples. Based on these images, the following measurements and evaluations were performed on each of the examples and comparative examples. The results are shown in Table 1.

[0281] (Evaluation 1) Presence or absence of pits

[0282] As an example, in Figures 12-15In the top view image shown, the longest pit was identified, and its width was determined to be 0.1 μm or more and its depth to be 10 nm or more based on the cross-sectional profile of the pit. A pit with a width of 0.1 μm or more and a depth of 10 nm or more is also referred to as a "pit with a specified size". If a pit with a specified size is present in 12 or more of the 15 measurement areas in each example, it is determined that the measurement area contains a pit with a specified size, and "A" is recorded in the "Evaluation 1: Presence or Absence of Pits" column of Table 1. If a pit with a specified size is not present in 4 or more of the 15 measurement areas in each example, it is determined that the measurement area does not contain a pit with a specified size, and "B" is recorded in the "Evaluation 1: Presence or Absence of Pits" column of Table 1. In each of the 15 measurement areas of Examples 1 to 6, the number of measurement areas containing pits with specified sizes is 15.

[0283] (Evaluation 2) Width of the pit

[0284] The measurement area where a pit of a specified size is identified is taken as the object. Based on the cross-sectional profile of the pit, the width of the pit of the specified size confirmed to exist in the measurement area is measured. For each example, the arithmetic mean of the measured pit widths is calculated, and the average of the calculated measured values ​​is taken as the pit width for that example. The pit widths for each example are recorded in the "Evaluation 2: Pits Width" column of Table 1. The base for calculating the arithmetic mean is the number of measurement areas in each example where the pit with the maximum length is identified as having a width of 0.1 μm or more and a depth of 10 nm or more (i.e., 15). This is also the same for the pit depth in (Evaluation 3) and the number of pits in (Evaluation 4) below.

[0285] Regarding Comparative Examples 2 and 3, in (Evaluation 1), the pits were determined to be of no specified size. In the "Evaluation 2: Width of the Pit" column of Table 1, the width of the pit determined to be the longest was recorded. Pits were confirmed on the first surface of the optical sheets of Comparative Examples 2 and 3. The pit formed in Comparative Example 2 has a larger top view shape than the pits formed in Examples 1-6. The pit formed in Comparative Example 3 has a smaller top view shape than the pits formed in Examples 1-6.

[0286] (Evaluation 3) Depth of the pit

[0287] The measurement area where a pit of a specified size is identified is selected as the object. Based on the cross-sectional profile of the pit, the depth of the pit of the specified size confirmed to exist within the measurement area is measured. The arithmetic mean of the measured pit depths for each example is calculated, and this average value is taken as the pit depth for that example. The pit depths for each example are recorded in the "Evaluation 3: Pits Depth" column of Table 1.

[0288] Regarding Comparative Examples 2 and 3, in (Evaluation 1), it was determined that there were no pits of the specified size. In the "Evaluation 3: Depth of Pit" column of Table 1, the depth of the pit determined to be the longest and largest is recorded. The pit formed in Comparative Example 2 has a deeper depth compared to the pits formed in Examples 1-6. The pit formed in Comparative Example 3 has a shallower depth compared to the pits formed in Examples 1-6.

[0289] (Evaluation 4) Number of pits

[0290] The measurement area identified as containing pits of a specified size was selected as the object. The number of pits present in this area was determined based on the top view image and cross-sectional profile. For each example, the arithmetic mean of the measured values ​​of the number of pits of the specified size was calculated, and this average value was taken as the number of pits in that example. The number of pits of the specified size for each example is recorded in the "Evaluation 4: Number of Pits" column of Table 1.

[0291] Regarding Comparative Examples 2 and 3, in (Evaluation 1), it was determined that there were no pits of the specified size. However, although they did not have the specified size, it was confirmed that pits were formed in Comparative Examples 2 and 3. In Comparative Example 2, an average of 12 pits of the specified size were identified in each measurement area. In Comparative Example 3, an average of 15 pits of the specified size were identified in each measurement area.

[0292] (Evaluation 5) Aspect Ratio

[0293] Divide the depth D of the pit calculated in (Evaluation 3) by the width W of the pit calculated in (Evaluation 2) to calculate the aspect ratio (D / W). The aspect ratios for each example are recorded in the "Evaluation 5: Aspect Ratio" column of Table 1. When calculating the aspect ratio, the units of depth D and width W are kept consistent.

[0294] (Evaluation 6) Area Ratio

[0295] For Examples 1-3, the area ratio of pits in a 10μm × 10μm region on the first surface was measured. The measurement regions where pits of a specified size were determined to exist were used as the objects, and the area ratio of pits in each measurement region was measured. The area ratio (%) was determined by image analysis of the top-view image. In Examples 1-3, the arithmetic mean of the area ratios measured for each measurement region where pits of a specified size were determined to exist was taken as the area ratio (%) of pits in the measurement region. The area ratio for Example 1 was 2.9%. The area ratio for Example 2 was 1.5%. The area ratio for Example 3 was 4.2%.

[0296] 1-4. Evaluation of Arithmetic Mean Roughness Sa

[0297] Three test samples were cut from the optical sheets of the examples and comparative examples. Each test sample was a 5mm × 5mm square. The samples were visually inspected for any abnormalities such as dust or damage. For each test sample, images of five mutually separated test areas were obtained using an atomic force microscope. The test area was defined as the surface of each sample formed by the first surface of the optical sheet.

[0298] The atomic force microscope used was a Shimadzu SPM-9700. The surface shape of the sample was measured using the SPM manager software included with the atomic force microscope, in On-Line (measurement) mode. The measurement conditions are as follows.

[0299] (AFM measurement conditions)

[0300] - Measurement mode: Phase

[0301] - Scan range: 10μm × 10μm

[0302] - Scanning speed: 2.0~2.5Hz (using a 10μm scanner)

[0303] - Pixel count: 512×512

[0304] -Cantilever used: NanoWorld NCHR (resonant frequency: 320kHz, spring constant 42N / m)

[0305] When acquiring data, for one test sample, five mutually separated test areas were selected; for three test samples × five test areas (a total of 15 test areas), relevant data on surface shape were acquired. For each of the examples and comparative examples, the arithmetic mean roughness Sa of the 15 test areas was measured, and the arithmetic mean of the 15 measurements was taken as the arithmetic mean roughness Sa for each example. The measurement results of the arithmetic mean roughness Sa were recorded in the "Arithmetic Mean Roughness Sa (nm)" column of Table 1.

[0306] 1-5. Steel wool toughness

[0307] Samples measuring 50mm × 100mm were cut from the optical films of the examples and comparative examples. The samples were visually inspected to ensure they were free of dust, damage, or other abnormalities. The evaluators were 20 healthy individuals around 30 years of age with visual acuity of 0.7 or better. The steel wool abrasion resistance test was performed on the optical films of each example using the method described above. The steel wool abrasion resistance test was conducted using a vibration-type friction fastness testing machine “AB-301-S” manufactured by TESTERSANGYO Co., Ltd.

[0308] The samples that have undergone 1000 cycles of the steel wool abrasion resistance test under a load of 1000g are removed from the testing machine, and the surface of the sample consisting of the first side of the optical sheet is observed under the above observation conditions. Each sample is evaluated according to the following criteria. The evaluators are 20 healthy individuals around 30 years of age with visual acuity of 0.7 or better. In the following criteria, "AA" indicates the highest abrasion resistance; "AA" and "A" are optical sheets evaluated as resistant to the steel wool abrasion resistance test. "B" is an optical sheet evaluated as not resistant to the steel wool abrasion resistance test. It should be noted that the test conditions of "1000g load, 1000 cycles" in the steel wool abrasion resistance test are more stringent than the conditions typically required for anti-reflective films (AR films, LR films) attached to the display surface of display devices.

[0309] The evaluation results for each of the examples and comparative examples are shown in the "SW Tolerance" column of "Evaluation Results" in Table 1.

[0310] AA: More than 18 evaluators observed no damage on the surface. Even when damage was observed, it was thin enough to be considered acceptable as a product without issues.

[0311] A: More than 12 evaluators observed no damage on the surface. Even where damage was observed, it was thin enough to be considered acceptable as a product without issues.

[0312] B: Less than 11 evaluators observed no damage on the surface. Alternatively, any evaluator found damage on the surface that indicated the extent to which the product was a problem.

[0313] 1-6. Felt durability

[0314] Samples measuring 50mm × 100mm were cut from the optical sheets of the examples and comparative examples. The samples were visually inspected to ensure they were free of dust, damage, or other abnormalities. The felt abrasion resistance test was then performed on the optical sheets of each example using the method described above. The felt abrasion resistance test was conducted using an AB-301-S vibration-type friction fastness tester manufactured by TESTER SANGYO Co., Ltd.

[0315] Samples that had undergone 10,000 cycles of the felt abrasion resistance test under a load of 200g were removed from the testing machine, and the surface of the sample, consisting of the first side of the optical sheet, was observed under the aforementioned observation conditions. Each sample was evaluated according to the following criteria. Evaluators were selected from 20 healthy individuals around 30 years of age with visual acuity of 0.7 or better. In the following criteria, "AA" indicates the highest abrasion resistance; "AA" and "A" are optical sheets evaluated as resistant to the felt abrasion resistance test. "B" is an optical sheet evaluated as not resistant to the felt abrasion resistance test.

[0316] The evaluation results for each of the examples and comparative examples are shown in the "Felt Durability" column of "Evaluation Results" in Table 1.

[0317] AA: More than 18 evaluators observed no damage on the surface. Even when damage was observed, it was thin enough to be considered acceptable as a product without issues.

[0318] A: More than 12 evaluators observed no damage on the surface. Even where damage was observed, it was thin enough to be considered acceptable as a product without issues.

[0319] B: Less than 11 evaluators observed no damage on the surface. Alternatively, any evaluator found damage on the surface that indicated the extent to which the product was a problem.

[0320] 2. Fabrication of optical sheets

[0321] [Comparative Example 1]

[0322] After coating a 80 μm thick triacetyl cellulose substrate with the resin layer coating solution 1 (HC layer coating solution 1) formulated below, the substrate was dried at 70°C for 1 minute to allow the solvent to evaporate. Then, the substrate was subjected to a cumulative light intensity of 100 mJ / cm². 2 By subjecting the material to ultraviolet light irradiation, a resin layer (hard coating) with a dry thickness of 10 μm is formed.

[0323] Next, after coating the resin layer with the second functional layer coating solution 1 (high refractive index layer coating solution 1) formulated below, it is dried at 70°C for 1 minute to allow the solvent to evaporate. Then, the cumulative light intensity is measured at 100 mJ / cm². 2 By irradiating with ultraviolet light, a second functional layer (high refractive index layer) with a dry thickness of 150 nm is formed.

[0324] Next, after applying the functional layer coating liquid 1 (low refractive index layer coating liquid 1) of the following formulation to the second functional layer, the coating film is dried at 50°C for 30 seconds (drying air velocity 0.5 m / s), and then dried at 50°C for 30 seconds (drying air velocity 5 m / s) to allow the solvent to evaporate. Then, the cumulative light intensity is measured at 200 mJ / cm². 2 By subjecting the material to ultraviolet irradiation, a functional layer (low refractive index layer) with a dry thickness of 100 nm is formed, resulting in the optical sheet of Comparative Example 1.

[0325] <Coating solution 1 for resin layer (Coating solution 1 for hard coating layer)>

[0326] · 100 parts by weight of a composition containing UV-curable acrylate

[0327] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-450", solid content 100%)

[0328] • 77 parts by weight of a composition containing UV-curable acrylate

[0329] (Made by First Industrial Corporation, trade name "NewFrontier R-1403MB", 80% solid content)

[0330] · 5 parts by weight of fluorine-based leveling agent

[0331] (DIC Corporation, product name "Megafac F-568")

[0332] · 5 parts by weight of photopolymerization initiator

[0333] (IGM Resins, trade name "Omnirad184", 100% solids)

[0334] 68 parts by weight of methyl isobutyl ketone

[0335] 200 parts by weight of methyl ethyl ketone

[0336] <Coating solution 1 for the second functional layer (Coating solution 1 for the high refractive index layer)>

[0337] ·PETA 100 parts by weight

[0338] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0339] · 300 parts by weight of high refractive index particles

[0340] (Nippon Shokubai Co., Ltd., product name "Zircostar", 70% solid content)

[0341] · 0.7 parts by weight of fluorine-based leveling agent

[0342] (DIC Company, trade name "Megafac F251", 100% solids)

[0343] · 9 parts by weight of photopolymerization initiator

[0344] (Product manufactured by IGM Resins under the brand name "Omnirad127", 100% solid content)

[0345] · 3173 parts by weight of methyl isobutyl ketone

[0346] ·Propylene glycol monomethyl ether 3173 parts by weight

[0347] <Coating solution 1 for functional layer (Coating solution 1 for low refractive index layer)>

[0348] 100 parts by weight of a multifunctional acrylate composition

[0349] (Made by Daiichi Kogyo Pharmaceutical Co., Ltd., trade name "New Frontier MF-001")

[0350] · 200 parts by weight of hollow silica particles

[0351] (Particles with an average primary particle size of 75 nm, surface-treated with a silane coupling agent containing methacrylyl groups)

[0352] 110 parts by weight of solid silica granules

[0353] (Particles with an average primary particle size of 12.5 nm, surface-treated with a silane coupling agent containing methacrylyl groups)

[0354] · 13 parts by weight of silicone-based leveling agent

[0355] (Shin-Etsu Chemical Co., Ltd., trade name "X-22-164E", 100% solids)

[0356] · 4.3 parts by weight of photopolymerization initiator

[0357] (IGM Resins, trade name "Omnirad127", 100% solids)

[0358] • Solvent 14,867 parts by weight

[0359] (A mixed solvent of methyl isobutyl ketone and 1-methoxy-2-propyl acetate. Mass ratio = 68 / 32)

[0360] [Example 1]

[0361] The resin layer of the following formulation was coated onto the substrate using coating liquid 2 (coating liquid 2 for HC layer), and the coating film was dried and cured to produce a resin layer (hard coating) with a dry thickness of 10 μm. The substrate used in Example 1 was the same as that used in Comparative Example 1. The resin layer in Example 1 differed from that in Comparative Example 1 in that the coating liquid used for the resin layer was changed; otherwise, it was manufactured using the same method and conditions as Comparative Example 1.

[0362] Next, the functional layer coating liquid 2 (low refractive index layer coating liquid 2) of the following formulation was applied 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, thus obtaining the optical sheet of Example 1. That is, the optical sheet of Example 1 is different from the optical sheet of Comparative Example 1 in that it does not contain a second functional layer. The functional layer in Example 1 differs from that in Comparative Example 1 in that the functional layer coating liquid was changed; otherwise, it was manufactured using the same method and conditions as Comparative Example 1.

[0363] <Coating solution 2 for resin layer (coating solution 2 for hard coating layer)>

[0364] · 100 parts by weight of a composition containing UV-curable acrylate

[0365] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-450", solid content 100%)

[0366] · 109 parts by weight of solid silica granules

[0367] (Particles with an average primary particle size of 12.5 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 46%)

[0368] · 2 parts by weight of silicone-based leveling agent

[0369] (Manufactured by Dai Nippon Seika Co., Ltd., trade name "10-301", solid content 5%)

[0370] · 4 parts by weight of photopolymerization initiator

[0371] (IGM Resins, trade name "Omnirad184", 100% solids)

[0372] 69 parts by weight of methyl isobutyl ketone

[0373] · 297 parts by weight of methyl ethyl ketone

[0374] ·Propylene glycol monomethyl ether 33 parts by weight

[0375] <Coating solution 2 for functional layer (Coating solution 2 for low refractive index layer)>

[0376] • 100 parts by weight of a composition containing a UV-curable siloxane compound

[0377] (Manufactured by Toa Synthetic Co., Ltd., trade name "AS-SQ TA-100", 100% solids)

[0378] • 43 parts by weight of a composition containing UV-curable acrylate

[0379] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0380] · 1143 parts by weight of hollow silica particles

[0381] (Particles with an average primary particle size of 65 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 20%)

[0382] 50 parts by weight of solid silica granules

[0383] (Particles with an average primary particle size of 9.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 50%)

[0384] ·83 parts by weight of alumina particles

[0385] (Particles with an average primary particle size of 15.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 30%)

[0386] · 633 parts by weight of leveling agent

[0387] (Shin-Etsu Chemical Industry Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0388] · Leveling agent 113 parts by weight

[0389] (Shin-Etsu Chemical Industry Co., Ltd., trade name "KP-422", solid content 15%)

[0390] · 6 parts by weight of photopolymerization initiator

[0391] (IGM Resins, trade name "Omnirad127", 100% solids)

[0392] · 19354 parts by weight of methyl isobutyl ketone

[0393] ·Propylene glycol monomethyl ether acetate 2320 parts by weight

[0394] [Example 2]

[0395] Example 2 differs from Example 1 in that the functional layer coating liquid 2 is changed to the functional layer coating liquid 3 described below. Otherwise, the optical sheet of Example 2 is obtained using the same materials and the same method as in Example 1.

[0396] <Coating solution 3 for functional layers (Coating solution 3 for low refractive index layers)>

[0397] • 100 parts by weight of a composition containing a UV-curable siloxane compound

[0398] (Manufactured by Toa Synthetic Co., Ltd., trade name "AS-SQ TA-100", 100% solids)

[0399] • 43 parts by weight of a composition containing UV-curable acrylate

[0400] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0401] · 1111 parts by weight of hollow silica particles

[0402] (Particles with an average primary particle size of 65 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 20%)

[0403] · 36 parts by weight of solid silica granules

[0404] (Particles with an average primary particle size of 9.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 50%)

[0405] · 60 parts by weight of alumina granules

[0406] (Particles with an average primary particle size of 15.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 30%)

[0407] · Leveling agent 201 parts by weight

[0408] (Shin-Etsu Chemical Industry Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0409] · Leveling agent 54 parts by weight

[0410] (Shin-Etsu Chemical Industry Co., Ltd., trade name "KP-422", solid content 15%)

[0411] · 6 parts by weight of photopolymerization initiator

[0412] (IGM Resins, trade name "Omnirad127", 100% solids)

[0413] · 15511 parts by weight of methyl isobutyl ketone

[0414] ·Propylene glycol monomethyl ether acetate 1851 parts by weight

[0415] [Example 3]

[0416] Example 3 differs from Example 1 in that the functional layer coating liquid 2 is changed to the functional layer coating liquid 4 described below. Otherwise, the optical sheet of Example 3 is obtained using the same materials and the same method as in Example 1.

[0417] <Coating solution 4 for functional layers (Coating solution 4 for low refractive index layers)>

[0418] • 100 parts by weight of a composition containing a UV-curable siloxane compound

[0419] (Manufactured by Toa Synthetic Co., Ltd., trade name "AS-SQ TA-100", 100% solids)

[0420] • 11 parts by weight of a composition containing UV-curable acrylate

[0421] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0422] 777 parts by weight of hollow silica particles

[0423] (Particles with an average primary particle size of 65 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 20%)

[0424] · 39 parts by weight of solid silica granules

[0425] (Particles with an average primary particle size of 9.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 50%)

[0426] · 65 parts by weight of alumina granules

[0427] (Particles with an average primary particle size of 15.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 30%)

[0428] · Leveling agent 457 parts by weight

[0429] (Shin-Etsu Chemical Industry Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0430] · Leveling agent 82 parts by weight

[0431] (Shin-Etsu Chemical Industry Co., Ltd., trade name "KP-422", solid content 15%)

[0432] · 5 parts by weight of photopolymerization initiator

[0433] (IGM Resins, trade name "Omnirad127", 100% solids)

[0434] · 14107 parts by weight of methyl isobutyl ketone

[0435] 1580 parts by weight of propylene glycol monomethyl ether acetate

[0436] [Example 4]

[0437] Example 4 differs from Example 1 in that the functional layer coating liquid 2 is changed to the functional layer coating liquid 5 described below. Otherwise, the optical sheet of Example 4 is obtained using the same materials and the same method as in Example 1.

[0438] <Coating solution 5 for functional layers (Coating solution 5 for low refractive index layers)>

[0439] · 100 parts by weight of a composition containing UV-curable acrylate

[0440] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0441] · 650 parts by weight of hollow silica particles

[0442] (Particles with an average primary particle size of 65 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 20%)

[0443] · 67 parts by weight of solid silica granules

[0444] (Particles with an average primary particle size of 12.5 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 37%)

[0445] · Leveling agent 128 parts by weight

[0446] (Shin-Etsu Chemical Industry Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0447] · Leveling agent 34 parts by weight

[0448] (Shin-Etsu Chemical Industry Co., Ltd., trade name "KP-422", solid content 15%)

[0449] · 7 parts by weight of photopolymerization initiator

[0450] (IGM Resins, trade name "Omnirad127", 100% solids)

[0451] 8828 parts by weight of methyl isobutyl ketone

[0452] 1034 parts by weight of propylene glycol monomethyl ether acetate

[0453] [Example 5]

[0454] Example 5 differs from Example 1 in that the functional layer coating liquid 2 is changed to the functional layer coating liquid 6 described below. Otherwise, the optical sheet of Example 5 is obtained using the same materials and the same method as in Example 1.

[0455] <Coating solution 6 for functional layers (Coating solution 6 for low refractive index layers)>

[0456] • 100 parts by weight of a composition containing a UV-curable siloxane compound

[0457] (Manufactured by Toa Synthetic Co., Ltd., trade name "AS-SQ TA-100", 100% solids)

[0458] • 43 parts by weight of a composition containing UV-curable acrylate

[0459] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0460] · 1194 parts by weight of hollow silica particles

[0461] (Particles with an average primary particle size of 65 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 20%)

[0462] · 57 parts by weight of solid silica granules

[0463] (Particles with an average primary particle size of 9.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 50%)

[0464] · 96 parts by weight of alumina particles

[0465] (Particles with an average primary particle size of 15.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 30%)

[0466] · 660 parts by weight of leveling agent

[0467] (Shin-Etsu Chemical Industry Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0468] · Leveling agent 125 parts by weight

[0469] (Shin-Etsu Chemical Industry Co., Ltd., trade name "KP-422", solid content 15%)

[0470] · 6 parts by weight of photopolymerization initiator

[0471] (IGM Resins, trade name "Omnirad127", 100% solids)

[0472] ·Methyl isobutyl ketone 2020 7 parts by weight

[0473] ·Propylene glycol monomethyl ether acetate 2424 parts by weight

[0474] [Example 6]

[0475] Example 6 differs from Example 1 in that the functional layer coating liquid 2 is changed to the functional layer coating liquid 7 described below. Otherwise, the optical sheet of Example 6 is obtained using the same materials and the same method as in Example 1.

[0476] <Coating solution 7 for functional layers (Coating solution 7 for low refractive index layers)>

[0477] • 100 parts by weight of a composition containing a UV-curable siloxane compound

[0478] (Manufactured by Toa Synthetic Co., Ltd., trade name "AS-SQ TA-100", 100% solids)

[0479] • 44 parts by weight of a composition containing UV-curable acrylate

[0480] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0481] · 1148 parts by weight of hollow silica particles

[0482] (Particles with an average primary particle size of 65 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 20%)

[0483] 50 parts by weight of solid silica granules

[0484] (Particles with an average primary particle size of 9.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 50%)

[0485] · 84 parts by weight of alumina granules

[0486] (Particles with an average primary particle size of 15.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 30%)

[0487] · Leveling agent 847 parts by weight

[0488] (Shin-Etsu Chemical Industry Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0489] · Leveling agent 169 parts by weight

[0490] (Shin-Etsu Chemical Industry Co., Ltd., trade name "KP-422", solid content 15%)

[0491] · 6 parts by weight of photopolymerization initiator

[0492] (IGM Resins, trade name "Omnirad127", 100% solids)

[0493] · 21125 parts by weight of methyl isobutyl ketone

[0494] ·Propylene glycol monomethyl ether acetate 2538 parts by weight

[0495] [Comparative Example 2]

[0496] Comparative Example 2 differs from Example 1 in that the functional layer coating liquid 2 is changed to the functional layer coating liquid 8 described below. Otherwise, the optical sheet of Comparative Example 2 is obtained using the same materials and the same methods as in Example 1.

[0497] <Coating solution 8 for functional layers (Coating solution 8 for low refractive index layers)>

[0498] • 100 parts by weight of a composition containing a UV-curable siloxane compound

[0499] (Manufactured by Toa Synthetic Co., Ltd., trade name "AS-SQ TA-100", 100% solids)

[0500] • 42 parts by weight of a composition containing UV-curable acrylate

[0501] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0502] · 1137 parts by weight of hollow silica particles

[0503] (Particles with an average primary particle size of 65 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 20%)

[0504] · 49 parts by weight of solid silica granules

[0505] (Particles with an average primary particle size of 9.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 50%)

[0506] ·83 parts by weight of alumina particles

[0507] (Particles with an average primary particle size of 15.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 30%)

[0508] · Leveling agent 1049 parts by weight

[0509] (Shin-Etsu Chemical Industry Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0510] · Leveling agent 280 parts by weight

[0511] (Shin-Etsu Chemical Industry Co., Ltd., trade name "KP-422", solid content 15%)

[0512] · 5 parts by weight of photopolymerization initiator

[0513] (IGM Resins, trade name "Omnirad127", 100% solids)

[0514] · 22,851 parts by weight of methyl isobutyl ketone

[0515] ·Propylene glycol monomethyl ether acetate 2753 parts by weight

[0516] [Comparative Example 3]

[0517] Comparative Example 3 differs from Example 1 in that the functional layer coating liquid 2 is changed to the functional layer coating liquid 9 described below. Otherwise, the optical sheet of Comparative Example 3 is obtained using the same materials and the same methods as in Example 1.

[0518] <Coating solution 9 for functional layers (Coating solution 9 for low refractive index layers)>

[0519] • 100 parts by weight of a composition containing a UV-curable siloxane compound

[0520] (Manufactured by Toa Synthetic Co., Ltd., trade name "AS-SQ TA-100", 100% solids)

[0521] • 43 parts by weight of a composition containing UV-curable acrylate

[0522] (Manufactured by Toagosei Co., Ltd., trade name "ARONIX M-305", solid content 100%)

[0523] · 1138 parts by weight of hollow silica particles

[0524] (Particles with an average primary particle size of 65 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 20%)

[0525] · 49 parts by weight of solid silica granules

[0526] (Particles with an average primary particle size of 9.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 50%)

[0527] ·83 parts by weight of alumina particles

[0528] (Particles with an average primary particle size of 15.0 nm, surface-treated with a silane coupling agent containing methacrylamide groups, and a solid content of 30%)

[0529] · 104 parts by weight of leveling agent

[0530] (Shin-Etsu Chemical Industry Co., Ltd., trade name "X-71-1203M", solid content 20%)

[0531] · 13 parts by weight of leveling agent

[0532] (Shin-Etsu Chemical Industry Co., Ltd., trade name "KP-422", solid content 15%)

[0533] · 6 parts by weight of photopolymerization initiator

[0534] (IGM Resins, trade name "Omnirad127", 100% solids)

[0535] · 15312 parts by weight of methyl isobutyl ketone

[0536] 1825 parts by weight of propylene glycol monomethyl ether acetate

[0537] [Table 1]

[0538] Explanation of reference numerals in the attached figures

[0539] 5: Sheet article, 6: Winding core, 7: Roll, 10: Optical sheet, 11: First side, 12: Second side, 20: Substrate, 30: Resin layer, 40: Functional layer, 41: Adhesive component, 43: Hollow silica particles, 44: Solid silica particles, 45: Recess, 45a: High end, 45b: Low end, 45c: Deepest part, 45e: Protrusion, 45x: Cross-sectional profile, 50: Second functional layer, 51: Adhesive resin, 52: Particle, 60: Polarizer, 61: First protective sheet, 62: Polarizing element, 63: Second protective sheet, 65: Display device, 66: Image forming apparatus, 66a: Display surface, 70: Panel, 71: Article to be bonded

Claims

1. An optical sheet comprising a first surface and a second surface opposite to the first surface, wherein, The optical sheet has a substrate and a functional layer sequentially from the second surface toward the first surface. The functional layer comprises an adhesive component and hollow silica particles. The first surface contains a 10μm×10μm region containing pits with a width of more than 0.1μm and less than 1.5μm and a depth of more than 10nm.

2. The optical sheet according to claim 1, wherein, The depth of the pit is less than 70 nm.

3. The optical sheet according to claim 1, wherein, The first surface contains three or more pits within the 10μm×10μm region.

4. The optical sheet according to claim 1, wherein, The first surface contains 11 or more pits within the 10μm × 10μm region.

5. The optical sheet according to claim 1, wherein, The number of pits contained in the 10μm×10μm region of the first surface is 50 or less.

6. The optical sheet according to claim 1, wherein, The 10μm×10μm region is divided into four smaller regions along each side, each containing the pit.

7. The optical sheet according to claim 1, wherein, The arithmetic mean roughness Sa of the first surface is below 8.0 nm.

8. The optical sheet according to claim 1, wherein, The first surface includes a flat portion around the pit.

9. The optical sheet according to claim 1, wherein, The proportion of the pits in the 10μm×10μm region of the first surface is less than 15%.

10. The optical sheet according to claim 1, wherein, The ratio of the depth to the width of the pit is 0.030 or greater.

11. The optical sheet according to claim 1, wherein, The optical sheet is resistant to abrasion resistance tests performed on the first surface using steel wool under the following conditions. Abrasion resistance test: Using steel wool #0000 as the sliding piece, the test was conducted 1000 times with a load of 1000g, a moving speed of 80mm / second, and a single-journey moving distance of 40mm.

12. The optical sheet according to claim 1, wherein, The optical sheet is resistant to abrasion resistance tests performed on the first surface using felt under the following conditions. Abrasion resistance test: Using "Jumbo Wearaser (registered trademark), product number: CS-7" manufactured by TABER as the sliding piece, the test was conducted 10,000 times with a load of 200g, a moving speed of 200mm / second, and a single-journey moving distance of 50mm.

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

14. A sheet article comprising a plurality of optical sheets as described in any one of claims 1 to 13.

15. The sheet article according to claim 14, wherein, The sheet of material is wound up with the winding axis as the center.

16. A polarizer comprising a first protective sheet, a polarizing element, and a second protective sheet. At least one of the first protective sheet and the second protective sheet comprises the optical sheet according to any one of claims 1 to 13.

17. A display device comprising: Image forming apparatus; and The optical sheet according to any one of claims 1 to 13 that overlaps with the image forming apparatus.

18. A panel comprising: The joined items; and The optical sheet according to any one of claims 1 to 13 that is joined to the article being joined.

19. A method for selecting an optical sheet, comprising the following steps: For an optical sheet comprising a first surface and a second surface opposite to the first surface, the step of acquiring an image of a 10 μm × 10 μm region of the first surface, wherein the optical sheet comprises a substrate and a functional layer sequentially from the second surface toward the first surface, the functional layer comprising an adhesive component and hollow silica particles; and The step of selecting an optical sheet containing a pit with a width of more than 0.1 μm and less than 1.5 μm and a depth of more than 10 nm in the region based on the image.

20. A method for manufacturing an optical sheet, comprising the following steps: The steps of manufacturing an optical sheet, wherein the optical sheet includes a first surface and a second surface opposite to the first surface, and a substrate and a functional layer are sequentially formed from the second surface toward the first surface, the functional layer comprising an adhesive component and hollow silica particles; and The step of selecting an optical sheet containing a 10μm × 10μm region on the first surface, wherein the pit has a width of 0.1μm to 1.5μm and a depth of 10nm or more.

Images