Optical laminates, polarizing plates, and image display devices

Abstract

To provide an optical laminate that can suppress the decrease in adhesion and the change in transmitted image clarity after lightfastness testing. [Solution] An optical laminate having a resin layer on a substrate, wherein the resin layer comprises a first resin layer and a second resin layer from the substrate side, the first resin layer comprises a region α1 independent of each other and a region α2 surrounding the region α1, the resin contained in region α1 and the resin contained in region α2 being different, and the second resin layer comprises a region β1 independent of each other and a region β2 surrounding the region β1, the resin contained in region β1 and the resin contained in region β2 being different, satisfying specific conditions.

Description

Technical Field

[0001] The present disclosure relates to an optical laminate, a polarizing plate, and an image display device.

Background Art

[0002] An optical laminate may be installed on the surface of an image display device such as a monitor of a television, a notebook PC, or a desktop PC in order to impart antifouling properties, antireflection properties, antiglare properties, etc.

[0003] An optical laminate has a basic configuration having an optical functional layer on a substrate. Since an optical laminate is often used as a surface member of an image display device or the like, it has many opportunities to come into contact with human fingers and objects. Therefore, the optical laminate preferably has good pencil hardness.

[0004] In order to improve the pencil hardness of the optical laminate, as the binder resin of the optical functional layer, a cured product of a curable resin composition is preferably used. The cured product of the curable resin composition tends to improve the pencil hardness of the optical laminate, but is inferior in adhesion to the substrate. In Patent Documents 1 and 2, an optical laminate using a cured product of a curable resin composition as the binder resin of the optical functional layer and having good adhesion has been proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The optical laminates of Patent Documents 1 and 2 have good initial adhesion. However, the optical laminates of Patent Documents 1 and 2 may experience a decrease in adhesion or a change in optical properties over time. Specifically, when a light resistance test by ultraviolet irradiation was performed on the optical laminates of Patent Documents 1 and 2, the adhesion may have decreased or the transmission image sharpness may have changed.

[0007] An object of the present disclosure is to provide an optical laminate that can suppress a decrease in adhesion and a change in transmission image sharpness after a light resistance test, a polarizing plate using the same, and an image display device.

Means for Solving the Problems

[0008] The present disclosure provides the following optical laminates, polarizing plates, and image display devices of [1] to [3]. [1] An optical laminate having a resin layer on a substrate, The resin layer has, from the substrate side, a first resin layer and a second resin layer, The first resin layer has mutually independent regions α1 and a region α2 surrounding the region α1, and the resin contained in the region α1 is different from the resin contained in the region α2, The second resin layer has mutually independent regions β1 and a region β2 surrounding the region β1, and the resin contained in the region β1 is different from the resin contained in the region β2, An optical laminate that satisfies the following Condition 1 or Condition 2. <Condition 1> θa1 indicating the average inclination angle of the surface of the substrate on the resin layer side and θa2 indicating the average inclination angle of the surface of the first resin layer on the second resin layer side have a relationship of θa2 < θa1. <Condition 2> Pa1 indicating the arithmetic mean height of the surface of the substrate on the resin layer side and Pa2 indicating the arithmetic mean height of the surface of the first resin layer on the second resin layer side have a relationship of Pa2 < Pa1. [2] A polarizing plate having a polarizer, a first transparent protective plate disposed on one side of the polarizer, and a second transparent protective plate disposed on the other side of the polarizer, wherein at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate described in [1]. [3] An image display device having the optical laminate described in [1] on a display element. [Effects of the Invention]

[0009] The optical laminate, polarizer, and image display device of this disclosure can suppress the decrease in adhesion and the change in transmitted image clarity after light resistance testing. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing one embodiment of the optical laminate of the present disclosure. [Figure 2] This figure illustrates a method for calculating the position of region α1 in the thickness direction of the first resin layer. [Figure 3] This is a cross-sectional view showing one embodiment of the image display device of the present disclosure. [Modes for carrying out the invention]

[0011] The embodiments of this disclosure are described below. [Optical laminate] The optical laminate disclosed herein has a resin layer on a substrate, The resin layer comprises a first resin layer and a second resin layer, starting from the substrate side. The first resin layer has a region α1 that is independent of each other and a region α2 that surrounds the region α1, and the resin contained in region α1 and the resin contained in region α2 are different. The second resin layer has a region β1 that is independent of each other and a region β2 that surrounds the region β1, and the resin contained in region β1 and the resin contained in region β2 are different. It must satisfy either condition 1 or condition 2 below. <Condition 1> The relationship between θa1, which represents the average inclination angle of the surface of the base material on the resin layer side, and θa2, which represents the average inclination angle of the surface of the first resin layer on the second resin layer side, is θa2 < θa1. <Condition 2> The relationship between Pa1, which represents the arithmetic mean height of the surface of the base material on the resin layer side, and Pa2, which represents the arithmetic mean height of the surface of the first resin layer on the second resin layer side, is Pa2 < Pa1.

[0012] FIG. 1 is a cross-sectional view showing one embodiment of the optical laminate 100 of the present disclosure. The optical laminate 100 in FIG. 1 has a resin layer 20 on a base material 10. Further, the resin layer 20 in FIG. 1 has a first resin layer 21 and a second resin layer 22 from the base material 10 side. Further, the first resin layer 21 in FIG. 1 has regions α1 independent of each other and a region α2 surrounding the region α1. Also, the second resin layer 22 in FIG. 1 has regions β1 independent of each other and a region β2 surrounding the region β1. In this specification, a structure having regions n1 independent of each other and a region n2 surrounding the region n1, like the first resin layer and the second resin layer in FIG. 1, may be referred to as a "sea-island structure". Note that FIG. 1 is a schematic cross-sectional view. That is, the scales of each layer constituting the optical laminate 100, the scales of each material, and the scales of surface irregularities are schematized for easy illustration and are different from the actual scales. The same applies to the figures other than FIG. 1, which are also different from the actual scales.

[0013] <Base material> The substrate is preferably one that has good light transmittance, smoothness, heat resistance, and mechanical strength. Examples of such substrates include resin substrates containing resins such as polyester, triacetylcellulose (TAC), cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyetherketone, acrylic resin, polycarbonate, polyurethane, and amorphous olefin (Cyclo-Olefin-Polymer: COP). The resin substrate may be formed by laminating two or more resin substrates together. The resin substrate is preferably stretched to improve its mechanical strength and dimensional stability.

[0014] Among resin substrates, acrylic resin substrates are preferred because they have low hygroscopicity, making it easy to achieve good dimensional stability, and low optical anisotropy, making it easy to achieve good visibility. Furthermore, by using an acrylic resin substrate with a predetermined composition for the resin layer coating liquid and predetermined drying conditions, conditions 1 and 2 can be satisfied, and the first and second resin layers can be easily formed into a sea-island structure. Because acrylic resin substrates are hard and brittle, it is difficult to achieve good adhesion when other layers are formed on them. In particular, when a hard resin layer, such as a resin layer containing a cured product of a curable resin composition, is formed on an acrylic resin substrate, the adhesion between the substrate and the resin layer tends to be insufficient. The optical laminate of this disclosure can suppress a decrease in adhesion and easily suppress changes in image clarity, even when a resin layer containing a cured product of a curable resin composition is formed on an acrylic resin substrate, by satisfying condition 1 or condition 2 and having a sea-island structure in the resin layer. In this specification, acrylic resin means acrylic resin and / or methacrylic resin.

[0015] The acrylic resin contained in the acrylic resin substrate is not particularly limited, but for example, one obtained by polymerizing one or more alkyl (meth)acrylates is preferred, and more specifically, one obtained using methyl (meth)acrylate is preferred. Examples of acrylic resins include those described in Japanese Patent Publication No. 2000-230016, Japanese Patent Publication No. 2001-151814, Japanese Patent Publication No. 2002-120326, Japanese Patent Publication No. 2002-254544, Japanese Patent Publication No. 2005-146084, etc. As the acrylic resin, one having a ring structure such as an acrylic resin having a lactone ring structure or an acrylic resin having an imide ring structure may be used.

[0016] The acrylic resin preferably has a glass transition temperature (Tg) of 100°C to 150°C, more preferably 105°C to 135°C, and even more preferably 110°C to 130°C. If the glass transition temperature of the acrylic resin is 100°C or higher, it becomes easier to suppress excessive melting of the acrylic resin substrate when forming the resin layer. If the glass transition temperature of the acrylic resin is 150°C or lower, it becomes easier to control the degree to which the acrylic resin substrate melts when forming the resin layer.

[0017] The acrylic resin substrate may contain resins other than acrylic resin, but it is preferable that the proportion of acrylic resin to the total resin constituting the acrylic resin substrate is 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0018] Acrylic resin substrates can be manufactured, for example, by melt-extruding pellets made of humidified acrylic resin, then stretching them longitudinally while cooling, and subsequently stretching them transversely. In the melt extrusion process, single-screw, double-screw, or double-screw or more-screw devices can be used, and the direction of screw rotation, rotation speed, and melting temperature can be set arbitrarily. Stretching should preferably be performed to achieve the desired thickness after stretching. While the stretching ratio is not limited, a ratio of 1.2 to 4.5 is preferred. The temperature and humidity during stretching can be determined arbitrarily. A general stretching method may be used.

[0019] The resin, such as acrylic resin, contained in the resin substrate preferably has a weight-average molecular weight of 10,000 to 500,000, and more preferably 50,000 to 300,000. By setting the weight-average molecular weight of the resin within the above range, conditions 1 and 2, and the sea-island structure described above can be easily controlled.

[0020] The average thickness of the substrate is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 35 μm or more. By setting the average thickness of the substrate to 10 μm or more, it is possible to improve the handling properties of the optical laminate. The average thickness of the substrate is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less. By making the average thickness of the substrate 100 μm or less, it is easier to improve the flexibility of the optical laminate.

[0021] The average thickness of the substrate mentioned above refers to the average thickness of the substrate at the time the optical laminate is completed. As will be described later, the average thickness of the substrate at the time the optical laminate is completed may decrease from the initial average thickness of the substrate due to the dissolution of a portion of the substrate by the coating liquid for the resin layer. For this reason, it is preferable that the initial average thickness of the substrate be thicker than the average thickness of the substrate at the time the optical laminate is completed. The difference between the initial average thickness of the substrate and the average thickness of the substrate at the time the optical laminate is completed cannot be generalized as it varies depending on the thickness of the resin layer, the composition of the coating liquid for the resin layer, the drying conditions of the coating liquid, etc., but it is preferably 0.1 μm to 10 μm, and more preferably 1 μm to 5 μm.

[0022] The average thickness of the substrate can be calculated, for example, by selecting 20 arbitrary points from a cross-sectional image of the optical laminate taken with a scanning transmission electron microscope (STEM) and taking the average value. It is preferable that the STEM acceleration voltage be between 10kV and 30kV, and the STEM magnification be between 1000x and 7000x. To measure the average thickness of the substrate, the thickness of the first resin layer, the thickness of the second resin layer, the position of region α1 in the thickness direction of the first resin layer, the position of the first particle in the thickness direction of the resin layer, θa1, θa2, Pa1, Pa2, etc., it is necessary to prepare a sample for measurement in which the cross-section of the optical laminate is exposed. The sample can be prepared, for example, by the following steps (A1) to (A2). If the interface etc. is difficult to see due to insufficient contrast, the sample may be stained with osmium tetroxide, ruthenium tetroxide, phosphotungstic acid, etc., as a pretreatment.

[0023] (A1) After preparing cut samples by cutting the optical laminate to an arbitrary size, embedded samples are prepared by embedding the cut samples in resin. The size of the cut samples is, for example, a strip of 10 mm in length and 3 mm in width. Epoxy resin is preferred for embedding. An embedded sample can be obtained, for example, by placing a cut sample in a silicone embedding plate, pouring in embedding resin, and then, after the embedding resin has hardened, removing the cut sample and the embedding resin surrounding it from the silicone embedding plate. In the case of the epoxy resin manufactured by Storuas, as exemplified below, the hardening process described above is preferably carried out by leaving it at room temperature for 12 hours. The shape of the embedded sample is block-like. Silicone embedding plates can be found, for example, those manufactured by Dosaka EM Co., Ltd. Silicone embedding plates are sometimes also called silicone capsules. For embedding, epoxy resin can be used, for example, a mixture of "Epofix" (product name) and "Epofix Hardener" (product name) manufactured by Storuas Co., Ltd., in a ratio of 10:1.2.

[0024] (A2) A sample for measurement is prepared by vertically cutting the block-shaped embedded sample, exposing the cross-section of the optical laminate. The thin section cut from the block-shaped embedded sample is used as the sample for measurement (the conditions for the measurement sample will be described later). It is preferable to cut the embedded sample so that it passes through the center of the cut sample. It is preferable to cut the embedded sample with a diamond knife. One example of a device used to cut embedded samples is the "Ultramicrotome EM UC7" manufactured by Leica Microsystems. When cutting embedded samples, it is preferable to first roughly cut them (coarse trimming) and then finally trim them precisely under the conditions of "SPEED: 1.00 mm / s" and "FEED: 70 nm". As described above, sections cut from a block-shaped embedded sample that are free of defects such as holes and have a uniform thickness of 60 nm to 100 nm can be used as samples for measuring the average thickness of the substrate, the thickness of the first resin layer, the thickness of the second resin layer, the position of region α1 in the thickness direction of the first resin layer, the position of the first particle in the thickness direction of the resin layer, θa1, θa2, Pa1, Pa2, the particle diameter of the first particle, and the particle diameter of inorganic fine particles.

[0025] In this specification, unless otherwise specified, the atmosphere used for various measurements and evaluations, as well as for sampling for measurement and evaluation, shall be a temperature of 23±5°C and a relative humidity of 40% to 65%. Furthermore, the optical laminate to be measured shall be exposed to the aforementioned atmosphere for at least 30 minutes before performing the measurement, evaluation, and sampling.

[0026] The base material may contain additives such as antioxidants, UV absorbers, light stabilizers, and plasticizers. The surface of the substrate may be subjected to physical or chemical treatments, such as corona discharge treatment, or a readily adhesive layer may be formed to improve adhesion.

[0027] <Resin layer> The resin layer must have a first resin layer and a second resin layer, starting from the substrate side. By having a first resin layer and a second resin layer as the resin layer, adhesion can be improved while suppressing the decrease in pencil hardness.

[0028] When the resin layer is a single layer, it is difficult to achieve good flexibility or pencil hardness in the optical laminate. For example, with a single layer of high-hardness resin, it is difficult to achieve good flexibility in the optical laminate. Also, with a single layer of low-hardness resin, it is difficult to achieve good pencil hardness in the optical laminate.

[0029] The first and second resin layers can be formed, for example, by applying a resin coating solution containing resin components and a solvent onto a substrate, drying it, and curing it as necessary. The resin coating solution may further contain, as necessary, first particles, inorganic fine particles, and additives. In the above method, for example, the resin coating solution dissolves a portion of the substrate, and a first resin layer is formed in a region containing a small amount of the resin component of the resin coating solution, with the resin component eluted from the substrate as the main component. Furthermore, a second resin layer can be formed in a region where the amount of resin component eluted from the substrate is small and the resin component of the resin coating solution is the main component. In other words, with the above method, the first and second resin layers can be formed with a single application using one resin coating solution. In addition, because the second resin layer formed by the above method contains a small amount of resin component eluted from the substrate, it is easier to achieve good pencil hardness. In the above method, it is essential to use a coating solution for the resin layer with a predetermined composition and predetermined drying conditions. The predetermined composition and predetermined drying conditions will be described later. The method for applying the coating liquid for the resin layer onto the substrate is not particularly limited, and general coating methods such as spin coating, dip coating, spray coating, die coating, bar coating, gravure coating, roll coating, meniscus coating, flexographic printing, screen printing, and speed coating are examples of such methods. When curing the coating liquid for the resin layer, it is preferable to irradiate it with ionizing radiation such as ultraviolet light and electron beams. Specific examples of ultraviolet light sources include ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arc lamps, black light fluorescent lamps, and metal halide lamps. Furthermore, the wavelength of the ultraviolet light is preferably in the range of 190 nm to 380 nm. Specific examples of electron beam sources include various electron beam accelerators such as Cockcroftwald type, Van de Graft type, resonant transformer type, insulated core transformer type, linear type, Dynamitron type, and high-frequency type.

[0030] The first resin layer has a region α1 that is independent of each other and a region α2 that surrounds region α1, and the resin contained in region α1 and the resin contained in region α2 must be different. Furthermore, the second resin layer has a region β1 that is independent of each other and a region β2 that surrounds region β1, and the resin contained in region β1 and the resin contained in region β2 must be different. The first resin layer has regions α1 and α2, and the second resin layer has regions β1 and β2, which makes it easier to improve adhesion after light resistance testing.

[0031] When the resin contained in region α1 is different from the resin contained in region α2, it means that at least one of the resin's composition or molecular weight is different. Preferably, the resin contained in region α1 and the resin contained in region α2 have different compositions. Examples of different resin compositions include cases where region α1 and region α2 contain different types of resins, or cases where region α1 and region α2 contain the same type of resin but the mixing ratio of the resins is different. When the resin contained in region β1 is different from the resin contained in region β2, it means that at least one of the resin's composition or molecular weight is different. Preferably, the resin contained in region β1 and the resin contained in region β2 have different compositions. Examples of different resin compositions include cases where region β1 and region β2 contain different types of resins, or where region β1 and region β2 contain the same type of resin but the mixing ratio of the resins is different.

[0032] In this specification, the resins in regions α1, α2, β1, and β2 refer to so-called binder resins. Therefore, the particles such as the first particles described later do not refer to the resins in regions α1, α2, β1, and β2.

[0033] If the proportion of region α1 is large, the hardness tends to be insufficient, and if the proportion of region α2 is large, the adhesion tends to deteriorate. For this reason, the area ratio of region α1 to region α2 is preferably 1:99 to 10:90, and more preferably 2:98 to 5:95. If the proportion of region β1 is too high, the hardness tends to be insufficient, and if the proportion of region β2 is too high, the adhesion tends to deteriorate. For this reason, the area ratio of region β1 to region β2 is preferably 5:95 to 50:50, and more preferably 10:90 to 40:60. The above area ratio can be calculated from cross-sectional images of the optical laminate captured by a scanning transmission electron microscope (STEM). To improve the reliability of the numerical values, multiple cross-sectional images should be obtained, and the total number of regions α1 or β1 should be 50 or more before calculating the area ratio.

[0034] Preferably, the resin contained in region α1 and the resin contained in region β2 of the first resin layer and the second resin layer are substantially the same, and preferably the resin contained in region α2 and the resin contained in region β1 are substantially the same. By having the above configuration, it is possible to easily improve adhesion after the lightfastness test. The reason why the above configuration makes it easier to improve adhesion after the lightfastness test is thought to be that the affinity between the first resin layer and the second resin layer is increased, so that the adhesion at the interface between the first resin layer and the second resin layer does not easily deteriorate even in harsh environments such as lightfastness tests.

[0035] To facilitate the configuration of the first resin layer having regions α1 and α2, and to facilitate the configuration of the second resin layer having regions β1 and β2, it is preferable to reduce the compatibility between the components contained in the coating liquid for the resin layer, and to reduce the compatibility between the components contained in the coating liquid for the resin layer and the components eluted from the substrate. As described above, by lowering the compatibility, it is considered that the configuration of the first resin layer and the second resin layer of this disclosure can be easily formed by the events (1) to (4) below. (1) When the resin coating solution is applied to the substrate, a portion of the substrate dissolves. (2) The region containing a small amount of resin components from the resin coating solution for the resin layer, with resin components eluted from the substrate as the main component, becomes the first resin layer, while the region containing a small amount of resin components eluted from the substrate, with resin components from the resin coating solution for the resin layer as the main component, becomes the second resin layer. (3) Due to their low compatibility, in the case of (2) above, the resin components of the coating liquid for the resin layer contained in a small amount in the first resin layer form region α1, and the resin components eluted from the substrate form region α2. (4) Due to their low compatibility, in the case of (2) above, the resin components eluted from the substrate contained in small amounts in the second resin layer form region β1, and the resin components of the coating liquid for the resin layer form region β2.

[0036] When the area from the center of the first resin layer in the thickness direction toward the substrate is defined as the first region, and the area from the center of the first resin layer in the thickness direction toward the second resin layer is defined as the second region, it is preferable that 70% or more of region α1 is located in the second region. Having the above configuration makes it easier to improve adhesion after the light resistance test.

[0037] The proportion of region α1 present in the second region is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more, based on the number of regions.

[0038] In this specification, the location of region α1 in the thickness direction of the first resin layer shall be determined by the following methods (1) to (5). (1) A cross-sectional image of the optical laminate is taken using a scanning transmission electron microscope (STEM). Preferably, the acceleration voltage of the STEM is 10kV to 30kV, and the magnification of the STEM is 1000x to 7000x. (2) Based on the cross-sectional photograph, calculate the average elevation X1 of the ridges on the substrate side surface of the first resin layer and the average elevation X2 of the ridges on the second resin layer side surface of the first resin layer (see symbols X1 and X2 in Figure 2). (3) The midpoint between the elevations of X1 and X2 is defined as the center M in the thickness direction of the first resin layer (see symbol M in Figure 2). (4) Based on the cross-sectional photograph, the number of regions α1 located in the first region on the substrate side from the center of the first resin layer in the thickness direction, and the number of regions α1 located in the second region on the second resin layer side from the center of the first resin layer in the thickness direction are counted. Regions α1 that exist in both the first and second regions, straddling the center of the first resin layer in the thickness direction, are allocated to the first and second regions according to the area ratio of region α1. For example, if region α1 has an area ratio of 40% in the first region and an area ratio of 60% in the second region, 0.4 units are allocated to the first region and 0.6 units are allocated to the second region. (5) To improve the reliability of the numerical values, multiple cross-sectional images are obtained, and the total number of region α1 is set to 50 or more, and the ratio of the number of region α1 present in the first and second regions is calculated.

[0039] The total thickness of the resin layer (in other words, the sum of the first and second resin layers) is preferably 4.0 μm or more at the lower limit, more preferably 5.0 μm or more, and even more preferably 6.0 μm or more. The upper limit is preferably 15.0 μm or less, more preferably 12.0 μm or less, and even more preferably 10.0 μm or less. The average thickness t1 of the first resin layer is preferably 3.0 μm or more at the lower limit, more preferably 4.0 μm or more, and even more preferably 4.5 μm or more. The upper limit is preferably 10.0 μm or less, more preferably 8.0 μm or less, and even more preferably 7.0 μm or less. Setting t1 to 3.0 μm or more makes it easier to improve adhesion and flexibility, and setting t1 to 10.0 μm or less makes it easier to suppress the decrease in pencil hardness. The average thickness t2 of the second resin layer is preferably 0.3 μm or more at the lower limit, more preferably 0.5 μm or more, and even more preferably 1.0 μm or more. The upper limit is preferably 4.0 μm or less, more preferably 3.0 μm or less, and even more preferably 2.7 μm or less. Setting t2 to 0.3 μm or more makes it easier to improve pencil hardness, and setting t2 to 4.0 μm or less makes it easier to suppress the decrease in bending resistance.

[0040] The ratio of t1 / t2 is preferably 1.5 or higher, more preferably 1.8 or higher, and even more preferably 2.0 or higher, in order to help suppress the decrease in adhesion and bending resistance. Furthermore, the ratio of t1 / t2 is preferably 10.0 or lower, more preferably 5.0 or lower, and even more preferably 3.0 or lower, in order to help improve pencil hardness.

[0041] The average thickness of the first resin layer and the average thickness of the second resin layer can be calculated, for example, by selecting 20 arbitrary points from a cross-sectional image of the optical laminate taken with a scanning transmission electron microscope (STEM) and taking the average value. Preferably, the acceleration voltage of the STEM is 10kV to 30kV, and the magnification of the STEM is 1000x to 7000x.

[0042] Resin components The resin layer preferably contains a cured product of a curable resin composition as a resin component. Including a cured product of a curable resin composition in the resin layer makes it easier to improve the pencil hardness of the optical laminate.

[0043] The ratio of the curable resin composition to the total amount of resin components in the coating liquid for the resin layer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and most preferably 100% by mass.

[0044] Examples of cured products of curable resin compositions include cured products of thermosetting resin compositions and cured products of ionizing radiation-curable resin compositions. Among these, cured products of ionizing radiation-curable resin compositions are preferred because they easily achieve high pencil hardness and readily dissolve the substrate in their uncured state.

[0045] A thermosetting resin composition is a composition containing at least a thermosetting resin, and is a resin composition that hardens upon heating. Examples of thermosetting resins include acrylic resins, urethane resins, phenolic resins, urea-melamine resins, epoxy resins, unsaturated polyester resins, and silicone resins. A curing agent is added to these thermosetting resin compositions as needed.

[0046] An ionizing radiation-curable resin composition is a composition containing a compound having an ionizing radiation-curable functional group (hereinafter also referred to as "ionizing radiation-curable compound"). Examples of ionizing radiation-curable functional groups include ethylenically unsaturated bonding groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, as well as epoxy groups and oxetanyl groups. As the ionizing radiation-curable compound, a compound having an ethylenically unsaturated bonding group is preferred. Ionizing radiation refers to electromagnetic waves or charged particle beams that possess energy quanta capable of polymerizing or bridging molecules. While ultraviolet rays or electron beams are commonly used, other electromagnetic waves such as X-rays and gamma rays, as well as charged particle beams such as alpha rays and ion beams, can also be used. In this specification, (meth)acryloyl group refers to either an acryloyl group or a metacloyl group. Also, in this specification, (meth)acrylate refers to either an acrylate or a methacrylate.

[0047] As the ionizing radiation-curable compound, either a monofunctional ionizing radiation-curable compound having one ionizing radiation-curable functional group or a polyfunctional ionizing radiation-curable compound having two or more ionizing radiation-curable functional groups can be used. Furthermore, as the ionizing radiation-curable compound, either monomers or oligomers can be used. Note that monofunctional ionizing radiation-curable monomers tend to have good compatibility with other resin components, and therefore tend not to form sea-island structures in the first and second resin layers. When using monofunctional ionizing radiation-curable monomers, attention should be paid to the aforementioned characteristics. In order to dissolve a portion of the substrate, form a sea-island structure in the first and second resin layers, increase pencil hardness, and easily suppress curing shrinkage, it is preferable to use a mixture of the following (a) to (c) as the ionizing radiation-curable compound. The following (a) to (c) are preferably compounds having an ethylenically unsaturated bonding group as the ionizing radiation-curable functional group, and more preferably (meth)acrylate compounds. The (meth)acrylate compound may also be one in which part of the molecular skeleton has been modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, etc. (a) Bifunctional ionizing radiation-curable monomers (b) Trifunctional or more ionizing radiation-curable monomers (c) Polyfunctional ionizing radiation-hardening oligomer

[0048] By including the bifunctional ionizing radiation-curable monomer (a) as the ionizing radiation-curable compound, it is possible to make it easier to dissolve a portion of the substrate, thereby making it easier to increase θa1 or Pa1. However, if the amount of the bifunctional ionizing radiation-curable monomer (a) is too large, it may excessively dissolve the substrate, which may reduce the strength of the substrate or decrease the pencil hardness of the optical laminate. By including the trifunctional or more ionizing radiation-curable monomer of (b) as the ionizing radiation-curable compound, it is possible to improve the pencil hardness of the optical laminate. However, if the amount of the trifunctional or more ionizing radiation-curable monomer of (b) is too high, the hardness of the resin layer may become too high, which may reduce the flexibility of the optical laminate. By including the polyfunctional ionizing radiation-curable oligomer of (c) as the ionizing radiation-curable compound, it is possible to suppress curing shrinkage while maintaining the pencil hardness of the optical laminate. However, if the amount of the polyfunctional ionizing radiation-curable oligomer of (c) is too large, the pencil hardness of the optical laminate may decrease.

[0049] The amount of the bifunctional ionizing radiation-curable monomer of (a) relative to the total amount of the ionizing radiation-curable compound is preferably 10% by mass or more and 40% by mass or less, more preferably 13% by mass or more and 30% by mass or less, and even more preferably 15% by mass or more and 25% by mass or less. The amount of the trifunctional or more ionizing radiation-curable monomer of (b) relative to the total amount of the ionizing radiation-curable compound is preferably 25% by mass or more and 55% by mass or less, more preferably 30% by mass or more and 50% by mass or less, and even more preferably 35% by mass or more and 45% by mass or less. The amount of (c) polyfunctional ionizing radiation-curable oligomer relative to the total amount of ionizing radiation-curable compounds is preferably 25% by mass or more and 55% by mass or less, more preferably 30% by mass or more and 50% by mass or less, and even more preferably 35% by mass or more and 45% by mass or less.

[0050] Examples of the bifunctional ionizing radiation-curable monomers in (a) include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxydiaacrylate, bisphenol A tetrapropoxydiaacrylate, and 1,6-hexanediol diacrylate.

[0051] Examples of ionizing radiation-curable monomers with three or more functionalities in (b) include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and isocyanuric acid-modified tri(meth)acrylate. The number of functional groups in the three or more ionizing radiation-curable monomers in (b) is preferably 3 to 5, more preferably 3 to 4, and even more preferably 3, in order to increase pencil hardness while suppressing curing shrinkage.

[0052] Examples of polyfunctional ionizing radiation-curable oligomers in (c) include acrylate polymers such as urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, and polyether (meth)acrylate. Urethane (meth)acrylates can be obtained, for example, by the reaction of polyhydric alcohols and organic diisocyanates with hydroxy(meth)acrylates. Preferred epoxy (meth)acrylates are (meth)acrylates obtained by reacting trifunctional or higher aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. with (meth)acrylic acid; (meth)acrylates obtained by reacting bifunctional or higher aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. with polybasic acids and (meth)acrylic acid; and (meth)acrylates obtained by reacting bifunctional or higher aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. with phenols and (meth)acrylic acid.

[0053] The number of functional groups in the polyfunctional ionizing radiation-curable oligomer of (c) is preferably 4 to 8, more preferably 5 to 7, and even more preferably 6, in order to suppress curing shrinkage while maintaining pencil hardness. The weight-average molecular weight of the polyfunctional ionizing radiation-curable oligomer of (c) is preferably 1000 to 5000, more preferably 1100 to 3500, and even more preferably 1200 to 2000, in order to suppress curing shrinkage while maintaining pencil hardness. In this specification, weight-average molecular weight is the average molecular weight measured by GPC analysis and converted to standard polystyrene.

[0054] When the ionizing radiation-curable compound is an ultraviolet-curable compound, the ionizing radiation-curable composition preferably contains additives such as photopolymerization initiators and photopolymerization accelerators. Examples of photopolymerization initiators include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler ketone, benzoin, benzyldimethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthones, etc. Photopolymerization accelerators are those that can reduce polymerization inhibition by air during curing and accelerate the curing speed, and examples include one or more selected from p-dimethylaminobenzoate isoamyl ester, p-dimethylaminobenzoate ethyl ester, etc.

[0055] 《The First Particle》 The resin layer preferably contains first particles with an average particle diameter of 0.5 μm or more in order to facilitate good anti-glare properties. To further facilitate good anti-glare properties, it is even more preferable that the second resin layer contains the first particles.

[0056] To facilitate better anti-glare properties, it is preferable that 70% or more of the first particles, based on their number, are present on the second resin layer side. The aforementioned percentage is preferably 80% or more, and more preferably 90% or more.

[0057] The location of the first particle in the thickness direction of the resin layer can be determined, for example, from a cross-sectional image of the optical laminate taken with a scanning transmission electron microscope (STEM). The aforementioned ratio based on the number of particles can be calculated from the cross-sectional image. In order to improve the reliability of the numerical value, it is preferable to obtain multiple cross-sectional images and calculate the aforementioned ratio based on the number of particles after ensuring that the total number of first particles is 50 or more. Furthermore, if a first particle exists in both the first and second resin layers, spanning both layers, the number of particles in each layer is allocated according to the area ratio of each layer. For example, if a first particle occupies 40% of the area in the first resin layer and 60% of the area in the second resin layer, 0.4 particles are allocated to the first resin layer and 0.6 particles to the second resin layer. It is preferable that the acceleration voltage of the STEM be between 10kV and 30kV, and the magnification of the STEM be between 1000x and 7000x.

[0058] Examples of the first particles include organic particles formed from one or more resins such as polymethyl methacrylate, polyacrylic-styrene copolymer, melamine resin, polycarbonate, polystyrene, polyvinyl chloride, benzoguanamine-melamine-formaldehyde condensate, silicone, fluororesin, and polyester resin; and inorganic particles formed from one or more inorganic materials such as silica, alumina, zirconia, and titania. Among these, organic particles are preferred because they have excellent dispersion stability and a relatively low specific gravity, making it easy to position the first particles in the second resin layer.

[0059] The content of the first particles is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.3 parts by mass or more, with respect to 100 parts by mass of the resin component of the coating liquid for the resin layer. The upper limit is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. By setting the content of the first particle to 0.5 parts by mass or more, it is easier to improve the anti-glare properties. Furthermore, by setting the content of the first particle to 10.0 parts by mass or less, it is easier to suppress the decrease in flexibility.

[0060] The average particle size of the first particle is preferably 0.8 μm or larger, and more preferably 1.0 μm or larger, in order to facilitate good anti-glare properties. The average particle diameter of the first particles is preferably 3.0 μm or less, more preferably 2.7 μm or less, and even more preferably 2.5 μm or less, in order to help suppress the decrease in flexibility.

[0061] The average particle size of the first particle can be calculated, for example, by the following steps (B1) to (B3). (B1) Obtain a transmission image of the optical laminate using an optical microscope. A magnification of 500x to 2000x is preferred. (B2) Extract any 10 particles from the observation image and calculate the particle diameter of each particle. The particle diameter is measured as the distance between two parallel lines that maximizes the distance between the two lines when the cross-section of the particle is enclosed by those two lines. (B3) Perform the same procedure five times on observation images of the same sample on different screens, and the average particle diameter obtained from the number average of the particle diameters of a total of 50 particles is taken as the average particle diameter. However, if the first particle cannot be observed optically, the average particle diameter of the first particle is calculated using (B4) to (B6) below. (B4) A section is prepared from the optical laminate using a microtome so that it is a cross-section passing through the center of the first particle. The thickness of the section is preferably 60 nm to 100 nm. Multiple sections are prepared consecutively for each first particle, and the section from each section in which the particle diameter calculated by the process in (B5) is maximized can be used as the section that is a cross-section passing through the center of the first particle. (B5) Observe the obtained sections using a scanning transmission electron microscope (STEM) and calculate the particle size. The method for calculating the particle size is the same as in (B2). A magnification of 5000x to 20000x is preferred. Perform the steps in (B6), (B4), and (B5) for 20 particles, and the value obtained from the number average of the particle diameters of the 20 particles will be taken as the average particle diameter of the first particle.

[0062] The average particle diameter D1 of the first particles and the average thickness t2 of the second resin layer are preferably such that t2-D1 is -0.5 μm or greater and preferably 2.0 μm or less. When t2-D1 is -0.5 μm or greater, the first particles can easily impart an uneven surface to the optical laminate, thus improving its anti-glare properties. It is more preferable that t2-D1 be 0 μm or greater, and even more preferable that it be 0.1 μm or greater. When t2-D1 is 2.0 μm or less, the first particles are less likely to protrude from the surface of the second resin layer, which makes it easier to improve scratch resistance. More preferably, t2-D1 is 1.5 μm or less, and even more preferably 0.8 μm or less.

[0063] 《Inorganic fine particles》 The resin layer may contain inorganic fine particles. By including inorganic fine particles with a relatively high specific gravity in the resin layer, the first particles are less likely to sink to the bottom of the resin layer, making it easier to position the first particles in the second resin layer. In addition, the inorganic fine particles can improve the dispersibility of the first particles, making it easier to suppress the decrease in flexibility. In this specification, inorganic fine particles mean inorganic particles with an average primary particle diameter of 200 nm or less. The average particle size of the inorganic fine particles is preferably 1 nm to 200 nm, more preferably 2 nm to 100 nm, and even more preferably 5 nm to 50 nm.

[0064] The average particle size of inorganic microparticles can be calculated by the following steps (C1) to (C3). (C1) The cross-section of the optical laminate is imaged using TEM or STEM. Preferably, the acceleration voltage of the TEM or STEM is 10kV or more and 30kV or less, and the magnification is 50,000x or more and 300,000x or less. (C2) Ten arbitrary inorganic microparticles are extracted from the observation image, and the particle diameter of each inorganic microparticle is calculated. The particle diameter is measured as the distance between two arbitrary parallel lines that maximize the distance between the two lines when the cross-section of the inorganic microparticle is sandwiched between them. (C3) Perform the same procedure five times on observation images of the same sample on different screens, and the average particle size of the inorganic microparticles is taken from the number average of the particle sizes of a total of 50 particles.

[0065] Examples of inorganic fine particles include those made of silica, alumina, zirconia, and titania. Among these, silica is preferred because it is easier to suppress the generation of internal haze.

[0066] The inorganic fine particle content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.7 parts by mass or more, per 100 parts by mass of the resin component of the coating liquid for the resin layer, at the lower limit, and preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less, per 100 parts by mass of the resin component of the coating liquid for the resin layer. By setting the inorganic fine particle content to 0.1 parts by mass or more, it becomes easier to position the first particles in the second resin layer. Furthermore, by setting the inorganic fine particle content to 5.0 parts by mass or less, it is possible to suppress the first particles from floating excessively above the resin layer, thereby making it easier to suppress a decrease in flexibility.

[0067] Additives The coating liquid for the resin layer may contain additives such as leveling agents, refractive index modifiers, antistatic agents, antifouling agents, ultraviolet absorbers, light stabilizers, antioxidants, viscosity modifiers, and thermal polymerization initiators, as needed.

[0068] "solvent" The coating liquid for the resin layer preferably contains a solvent. It is preferable to select a solvent that can dissolve the substrate. The more easily a solvent that dissolves the substrate is used, the larger the values ​​of θa1 and Pa1 tend to be. However, if the substrate is dissolved too much, its strength will decrease, so it is preferable to select an appropriate solvent depending on the type of substrate. Furthermore, it is preferable to select the solvent considering not only its solubility in the substrate but also its inherent evaporation rate. The rate at which the solvent evaporates can also be controlled by the drying conditions. For example, increasing the drying temperature will increase the rate at which the solvent evaporates. Similarly, increasing the drying air velocity will also increase the rate at which the solvent evaporates. If the solvent dries slowly, the dissolution of the substrate progresses, and θa1 and Pa1 tend to increase. Also, if the solvent dries slowly and the drying temperature is high, the movement of resin components between the first and second resin layers becomes vigorous, and θa2 and Pa2 tend to increase. Based on the above, it is preferable to select a solvent considering the solubility of the substrate, the evaporation rate, and the drying conditions.

[0069] Examples of solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as dioxane and tetrahydrofuran; aliphatic hydrocarbons such as hexane; alicyclic hydrocarbons such as cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated carbons such as dichloromethane and dichloroethane; esters such as methyl acetate, ethyl acetate, and butyl acetate; alcohols such as isopropanol, butanol, and cyclohexanol; cellosolves such as methyl cellosolve and ethyl cellosolve; glycol ethers such as propylene glycol monomethyl ether acetate; cellosolve acetates; sulfoxides such as dimethyl sulfoxide; and amides such as dimethylformamide and dimethylacetamide. The solvent may be used alone or as a mixture of two or more.

[0070] Acrylic resin substrates are easily soluble in solvents. Therefore, when using an acrylic resin substrate as a base material, it is preferable to include a solvent that has a fast evaporation rate specific to that solvent. In this specification, a solvent with a fast evaporation rate means a solvent whose evaporation rate is 100 or more, with the evaporation rate of butyl acetate set to 100. In this specification, a solvent with a slow evaporation rate means a solvent whose evaporation rate is less than 100, with the evaporation rate of butyl acetate set to 100.

[0071] For solvents with a fast evaporation rate, the evaporation rate is more preferably between 120 and 450, and even more preferably between 140 and 400. Examples of solvents with a fast evaporation rate include isopropyl alcohol (evaporation rate 150), methyl isobutyl ketone (evaporation rate 160), toluene (evaporation rate 200), and methyl ethyl ketone (evaporation rate 370). The solvent with a fast evaporation rate is preferably present in an amount of 75% to 85% by mass of the total solvent volume.

[0072] Furthermore, in order to facilitate the formation of a sea-island structure in the first and second resin layers, it is preferable to include a solvent that has a slow evaporation rate, high polarity, and a large molecular weight. Solvents possessing the aforementioned properties increase the viscosity of the coating solution, making it easier for the coating solution to become gel-like. Therefore, solvents possessing the aforementioned properties can easily reduce the compatibility of the coating solution, thereby facilitating the formation of a sea-island structure. Examples of solvents possessing the aforementioned properties include cyclohexanone and diacetone alcohol. It is preferable that the solvent, which has a slow evaporation rate, high polarity, and a large molecular weight, constitutes 15% to 25% by mass of the total amount of the solvent.

[0073] Drying conditions When forming a resin layer from a coating liquid for resin layers, it is preferable to control the drying conditions. Furthermore, it is preferable to dry the coating liquid for the resin layer in two stages in the optical laminate of this disclosure. Specifically, it is preferable to use a low drying air velocity in the first drying stage and a high drying air velocity in the second drying stage. During the first drying stage, a first resin layer can be formed by regions that mainly contain resin components eluted from the substrate and a small amount of resin components from the coating liquid for the resin layer, and a second resin layer can be formed by regions that mainly contain resin components eluted from the substrate and a small amount of resin components from the coating liquid for the resin layer. Furthermore, by increasing the drying temperature in the first stage, the resin components can be made to migrate more easily, thereby making it easier to form a sea-island structure. Furthermore, by performing a second drying stage, excessive dissolution of the substrate can be suppressed, making it easier to prevent θa1 and Pa1 from becoming too large.

[0074] Furthermore, it is preferable to control the drying time in the first and second drying stages. A longer drying time for the resin coating solution means that there is a longer time before the resin components of the resin coating solution are irradiated with ionizing radiation. In other words, a longer drying time for the resin coating solution means that the resin components of the resin coating solution remain in an uncured and fluid state for a longer period of time. Therefore, if the drying time for the resin coating solution is long, the movement of resin components between the first and second resin layers becomes more vigorous, and θa2 and Pa2 tend to increase, making it difficult to satisfy conditions 1 and 2.

[0075] Drying conditions can be controlled by the drying temperature and the airflow velocity inside the dryer. The preferred range for drying temperature and airflow velocity varies depending on the composition of the coating liquid for the resin layer and cannot be stated definitively, but the following conditions are preferable. <First stage of drying> The drying temperature is preferably between 75°C and 95°C, and the drying air velocity is preferably between 1 m / s and 10 m / s. The drying time is preferably between 20 seconds and 40 seconds. <Second stage of drying> The drying temperature is preferably 75°C or higher and 95°C or lower, the drying wind speed is preferably 15 m / s or higher and 30 m / s or lower, and the drying time is preferably 20 seconds or longer and 40 seconds or shorter.

[0076] In order to dissolve a part of the base material with the coating liquid for the resin layer and to facilitate sufficient mixing of the components eluted from the base material and the coating liquid for the resin layer, it is preferable to perform irradiation with ionizing radiation after drying the coating liquid.

[0077] <Other Layers> The optical laminate may have layers other than the base material and the resin layer. Examples of other layers include an antireflection layer, an antifouling layer, and an antistatic layer.

[0078] <Condition 1, Condition 2> The optical laminate of the present disclosure needs to satisfy the following Condition 1 or Condition 2. The optical laminate of the present disclosure only needs to satisfy at least one of Condition 1 and Condition 2, but it is preferable to satisfy both. <Condition 1> There is a relationship of θa2 < θa1 between θa1 indicating the average inclination angle of the surface of the base material on the resin layer side and θa2 indicating the average inclination angle of the surface of the first resin layer on the second resin layer side. <Condition 2> There is a relationship of Pa2 < Pa1 between Pa1 indicating the arithmetic mean height of the surface of the base material on the resin layer side and Pa2 indicating the arithmetic mean height of the surface of the first resin layer on the second resin layer side.

[0079] -Condition 1- When the relationship of θa2 < θa1 is not satisfied, it is difficult to improve the initial adhesion due to a small θa1, or it is difficult to suppress the change in the transmission image sharpness after the light resistance test due to a large θa2. The reason why the clarity of the transmitted image changes before and after the light resistance test is considered to be that the refractive index difference at the interface between the first resin layer and the second resin layer changes before and after the light resistance test. In the optical laminate of the present disclosure, there is not only an interface between the first resin layer and the second resin layer, but also an interface between the base material and the first resin layer. The base material (especially an acrylic resin base material) is relatively difficult to be deformed by the light resistance test. On the other hand, the resin component of the coating liquid for the resin layer is relatively easy to be deformed by the light resistance test. Therefore, the second resin layer with a small content of the resin component of the base material is likely to change in refractive index before and after the light resistance test. On the other hand, the base material and the first resin layer containing a large amount of the resin component of the base material are less likely to change in refractive index before and after the light resistance test. Therefore, when θa2 is large and the relationship θa2 < θa1 is not satisfied, it is considered difficult to suppress the change in the clarity of the transmitted image after the light resistance test.

[0080] -Condition 2- When the relationship Pa2 < Pa1 is not satisfied, if Pa1 is small, it is difficult to achieve good initial adhesion, and if Pa2 is large, it is difficult to suppress the change in the clarity of the transmitted image after the light resistance test. The reason why it is difficult to suppress the change in the clarity of the transmitted image after the light resistance test when the relationship Pa2 < Pa1 is not satisfied due to Pa2 being large is considered to be the same reason as in Condition 1.

[0081] For θa1, in order to easily achieve good initial adhesion, it is preferably 5.0 degrees or more, more preferably 8.0 degrees or more, and still more preferably 10.0 degrees or more. For θa1, in order to easily achieve good pencil hardness, it is preferably 20.0 degrees or less, more preferably 18.0 degrees or less, and still more preferably 17.0 degrees or less.

[0082] For θa2, in order to easily suppress the change in the clarity of the transmitted image after the light resistance test, it is preferably 10.0 degrees or less, more preferably 8.0 degrees or less, still more preferably six 6.0 degrees or less, and even more preferably 4.0 degrees or less. For θa2, in order to easily achieve good adhesion, it is preferably more than 0 degrees, more preferably 1.0 degrees or more, and still more preferably 2.0 degrees or more.

[0083] To facilitate good initial adhesion, Pa1 is preferably 0.05 μm or more, more preferably 0.07 μm or more, and even more preferably 0.10 μm or more. To facilitate good pencil hardness, Pa1 is preferably 0.25 μm or less, more preferably 0.23 μm or less, and even more preferably 0.20 μm or less.

[0084] To facilitate the suppression of changes in transmitted image clarity after the lightfastness test, the Pa2 particle size is preferably 0.15 μm or less, more preferably 0.13 μm or less, even more preferably 0.10 μm or less, and even more preferably 0.06 μm or less. To facilitate good adhesion, the thickness of Pa2 is preferably 0.02 μm or more, more preferably 0.04 μm or more, and even more preferably 0.05 μm or more.

[0085] θa1 and θa2, as well as Pa1 and Pa2, can be measured, for example, as follows. (1) A cross-sectional image of the optical laminate is taken using a scanning transmission electron microscope (STEM). Preferably, the acceleration voltage of the STEM is 10kV to 30kV, and the magnification of the STEM is 5000x to 10000x. (2) From the cross-sectional photograph, the edges of the interface between the substrate and the resin layer, and the edges of the interface between the first resin layer and the second resin layer are obtained, and height data is obtained. Specifically, this is done as follows: The interface between the substrate and the resin layer corresponds to the surface of the substrate on the resin layer side. The interface between the first resin layer and the second resin layer corresponds to the surface of the first resin layer on the second resin layer side. (a) Display the captured images using ImageJ (version 1.52a), an open-source, public-domain image processing software. (b) Determine the length per pixel from the scale displayed in the image. (c) Select “FreeHand Selections” to create an ROI that includes the interface, and adjust the Brightness so that the colors are clearly different on either side of the interface. (d) Run Process-Smooth twice. (e) Set Image-Type to 8bit. (f) Select “Straight” and draw a line along the interface. (g) Install and run the ABSnake plugin for ImageJ. Set the "Gradient threshold" to 10 and the Draw color to Red. Leave all other settings at their default values. (h) Visually confirm that the interface can be traced with Red. If it is not, start again from (f). (i) Run Image-Adjust-Color Threshold. Set the threshold to separate Red from the others. Specifically, set the Color space to RGB, check "Pass" for "Red," "Green," and "Blue," set the upper and lower limits of the Red range to the maximum value (255), and the upper and lower limits of the Green and Blue ranges to the minimum value (0). (j) Execute Process-Binary-Make Binary to binarize the interface into the trace line portion and the portion other than the trace line portion. (k) Save the binarized data as "Text Image" using File-Save As. (l) Convert the binarized data into a sequence of height data points for the interface. (3) From the height data point sequence, calculate the average slope angle and arithmetic mean height using the following procedure. (m) The center line of the height data is found using the least squares method of quadratic regression, and subtracted from the height data to transform the data so that the center line is 0, the upward direction is positive, and the downward direction is negative. The direction of the center line is defined as the x-axis, and the direction perpendicular to it (height direction) is defined as the y-axis. (n) Using the length per pixel obtained in (b), convert the height data into length. (o) Apply a Gaussian low-pass filter with a cutoff wavelength of 0.5 μm. (p)tan -1 ((y i+1 -y i-1 ) / 2Δx)[y iθa1 and θa2 are obtained by calculating the arithmetic mean of the absolute values ​​of the inclination angles of each point, which are obtained by [where Δx is the height at the i-th point in the height data point sequence, and Δx is the distance in the x-axis direction between adjacent points]. (q) Calculate the arithmetic mean heights Pa1 and Pa2 by calculating the arithmetic mean of the absolute values ​​of the heights of each point.

[0086] In this specification, θa1 and θa2, as well as Pa1 and Pa2, represent the average values ​​of measurements from 20 samples. In order to set θa1 and θa2, and Pa1 and Pa2 within the above ranges, it is important, as described above, to dissolve a portion of the substrate with the resin coating solution, to appropriately prepare the composition of the resin coating solution, and to set the drying conditions of the resin coating solution within an appropriate range.

[0087] <Optical properties, surface shape> The optical laminate preferably has a total light transmittance of 70% or more, more preferably 80% or more, and even more preferably 85% or more, according to JIS K7361-1:1997. When measuring total light transmittance and the haze described later, the light incident surface shall be the substrate side.

[0088] The optical laminate preferably has a haze of 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more, according to JIS K7136:2000. By setting the haze to 0.5% or more, it is easier to improve the anti-glare properties. Furthermore, in order to make it easier to suppress the decrease in image resolution, the optical laminate preferably has a haze of 20% or less, more preferably 10% or less, and even more preferably 5% or less.

[0089] To facilitate good anti-glare properties, the optical laminate preferably has an arithmetic mean roughness Ra of 0.03 μm or more, and more preferably 0.05 μm or more, on the resin layer side surface, according to JIS B0601:2001. Furthermore, to facilitate suppression of image resolution degradation, the optical laminate preferably has an Ra of 0.12 μm or less, and more preferably 0.10 μm or less, on the resin layer side surface. Ra refers to the value at a cutoff value of 0.8 mm.

[0090] <Size, shape, etc.> The optical laminate may be in the form of a single sheet cut to a predetermined size, or in the form of a roll formed by winding a long sheet into a roll. The size of the sheet is not particularly limited, but the maximum diameter is approximately 2 inches to 500 inches. "Maximum diameter" refers to the maximum length when connecting any two points on the optical laminate. For example, if the optical laminate is rectangular, the diagonal of the rectangle is the maximum diameter. If the optical laminate is circular, the diameter of the circle is the maximum diameter. The width and length of the roll are not particularly limited, but generally, the width is 500 mm to 3000 mm and the length is 500 m to 5000 m. The optical laminate in roll form can be cut into individual sheets to match the size of an image display device or the like. When cutting, it is preferable to remove the roll ends, which have unstable physical properties. The shape of the sheet is not particularly limited; for example, it may be a polygon such as a triangle, square, or pentagon, or it may be circular, or it may be a random, irregular shape. More specifically, if the optical laminate is rectangular, the aspect ratio is not particularly limited as long as it does not cause problems as a display screen. Examples include width:height = 1:1, 4:3, 16:10, 16:9, 2:1, 5:4, 11:8, etc.

[0091] [Polarizing plate] The polarizing plate of the present disclosure is a polarizing plate having a polarizer, a first transparent protective plate disposed on one side of the polarizer, and a second transparent protective plate disposed on the other side of the polarizer, wherein at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate of the present disclosure described above.

[0092] Polarizing plates are used, for example, to provide anti-reflective properties by combining them with λ / 4 phase difference plates. In this case, the λ / 4 phase difference plate is placed on the display element of an image display device, and the polarizing plate is placed on the viewer side of the λ / 4 phase difference plate. When a polarizing plate is used for a liquid crystal display device, the polarizing plate is used to provide the function of a liquid crystal shutter. In this case, the liquid crystal display device is arranged in the order of a lower polarizing plate, a liquid crystal display element, and an upper polarizing plate, and the absorption axis of the polarizer of the lower polarizing plate and the absorption axis of the polarizer of the upper polarizing plate are arranged orthogonally. In the above configuration, it is preferable to use the polarizing plate of this disclosure as the upper polarizing plate.

[0093] <Transparent protection plate> In the polarizing plate of this disclosure, at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate of this disclosure described above. A preferred embodiment is one in which the transparent protective plate on the light-emitting side of the first and second transparent protective plates is the optical laminate of this disclosure described above. It is preferable that the optical laminate is arranged such that the substrate-side surface of the optical laminate faces the polarizer side.

[0094] If one of the first transparent protective plate and the second transparent protective plate is the optical laminate of the present disclosure described above, the other transparent protective plate is not particularly limited, but an optically isotropic transparent protective plate is preferred. In this specification, optical isotropy refers to a plane phase difference of 20 nm or less, preferably 10 nm or less, and more preferably 5 nm or less. Acrylic films and triacetylcellulose (TAC) films are easily given optical isotropy.

[0095] <Polarizer> Examples of polarizers include sheet-type polarizers such as polyvinyl alcohol film, polyvinyl formal film, polyvinyl acetal film, and ethylene-vinyl acetate copolymer saponified film dyed with iodine or the like and stretched; wire grid-type polarizers consisting of numerous parallel metal wires; coated polarizers coated with lyotropic liquid crystal or dichroic guest-host materials; and multilayer thin-film polarizers. These polarizers may also be reflective polarizers that have the function of reflecting polarization components that do not transmit through them.

[0096] <Size, shape, etc.> Embodiments of the size and shape of the polarizing plate of this disclosure include the embodiments of the size and shape of the optical laminate of this disclosure described above.

[0097] [Image display device] The image display device of this disclosure has the optical laminate of this disclosure described above on a display element.

[0098] Figure 3 is a cross-sectional view showing an embodiment of the image display device 500 of the present disclosure. The image display device 500 in Figure 3 has an optical laminate 100 of the present disclosure on a display element 200. Within the image display device, it is preferable to arrange the optical laminate so that the substrate side faces the display element side.

[0099] Examples of display elements include liquid crystal display elements; EL display elements (organic EL display elements, inorganic EL display elements); plasma display elements; display elements using QD (Quantum Dot); LED display elements such as mini-LEDs and micro-LEDs; and others. These display elements may also have a touch panel function inside. Examples of liquid crystal display methods for liquid crystal display elements include IPS, VA, multi-domain, OCB, STN, and TSTN methods. When the display element is a liquid crystal display element, a backlight is required. The backlight is located on the side opposite to the side where the optical laminate of the liquid crystal display element is located.

[0100] Furthermore, the image display device of this disclosure may also be an image display device with a touch panel, having a touch panel between the display element and the optical laminate. In this case, it is preferable to place the optical laminate on the outermost surface of the image display device with a touch panel, and to position the optical laminate so that the substrate side faces the display element side.

[0101] The size of the image display device is not particularly limited, but it is preferable that the maximum diameter of the effective display area is between 2 inches and 500 inches. The effective display area of ​​an image display device is the area in which an image can be displayed. For example, if an image display device has a housing that surrounds the display element, the area inside the housing becomes the effective image area. The maximum diameter of the effective image area is defined as the maximum length between any two points within the effective image area. For example, if the effective image area is rectangular, the diagonal of the rectangle is the maximum diameter. If the effective image area is circular, the diameter of the circle is the maximum diameter. [Examples]

[0102] Next, the present disclosure will be described in more detail by examples, but the present disclosure is not limited in any way by these examples. Unless otherwise specified, "parts" and "%" refer to mass.

[0103] 1. Measurement and Evaluation The optical laminates of the examples and comparative examples were measured and evaluated as follows. The atmosphere during each measurement and evaluation was a temperature of 23±5°C and a relative humidity of 40% to 65%. In addition, before starting each measurement and evaluation, the target sample was exposed to the above atmosphere for 30 minutes or more. The results are shown in Table 2.

[0104] 1-1. Presence or absence of regions α1 and β1, and the proportion of region α1 present in the second region. In accordance with the description in the specification, samples with exposed cross-sections of the optical laminates of the examples and comparative examples were prepared. The presence or absence of regions α1 and β1 was confirmed from cross-sectional photographs of the samples taken with a scanning transmission electron microscope. Furthermore, the area ratio of region α1 to region α2 and the area ratio of region β1 to region β2 were calculated. The presence of an independent region α1 within the first resin layer 21, the difference between the resin contained in region α1 and the resin contained in region α2, the presence of an independent region β1 within the second resin layer 22, and the difference between the resin contained in region β1 and the resin contained in region β2 can be determined by the difference in brightness of the photographs. Furthermore, the proportion of region α present in the second region was calculated based on the number of regions. In calculating this proportion, multiple cross-sectional images were taken until the total number of regions α exceeded 50.

[0105] 1-2. θa1 and θa2, and Pa1 and Pa2 In accordance with the description in the specification, samples were prepared in which the cross-sections of the optical laminates of the examples and comparative examples were exposed. From the cross-sectional images of the samples taken with a scanning transmission electron microscope, θa1 and θa2, and Pa1 and Pa2 were calculated in accordance with the description in the specification.

[0106] 1-3. Average thickness of the first resin layer and the second resin layer In accordance with the description in the specification, samples with exposed cross-sections of the optical laminates of the examples and comparative examples were prepared. Twenty arbitrary points were selected from the cross-sectional photographs of the samples taken with a scanning transmission electron microscope, and the average thickness t1 of the first resin layer and t2, the average thickness of the second resin layer, were calculated from the average values ​​of these points.

[0107] 1-4. Total light transmittance (Tt) and haze (Hz) The optical laminates of the examples and comparative examples were cut into 10 cm squares. The cutting locations were selected randomly after visually confirming that there were no abnormalities such as dust or scratches. The total light transmittance according to JIS K7361-1:1997 and the haze according to JIS K7136:2000 were measured for each sample using a haze meter (HM-150, manufactured by Murakami Color Technology Laboratory). To ensure the light source stabilized, the device's power switch was turned ON and waited for at least 15 minutes. Calibration was performed with nothing in the inlet opening (where the measurement sample is placed), and then the measurement sample was placed in the inlet opening and measurements were taken. The light incidence surface was the substrate side.

[0108] 1-5. Adhesion The adhesion of the optical laminates of the examples and comparative examples was evaluated using the following method. Furthermore, the adhesion of the optical laminates of the examples and comparative examples was evaluated after conducting the following lightfastness tests. The evaluation sample was cross-cut into a grid pattern of 10 rows and 10 columns, totaling 100 squares. The cut interval was 1 mm. When cutting, the cutter blade was inserted from the second resin layer side, and the cross-cut was performed so that the cutter blade reached the top of the substrate. Adhesive tape (manufactured by Nichiban Co., Ltd., product name "Sellotape®") was applied to the surface of a cross-cut sample, and a peel test was performed in accordance with the cross-cut method specified in JIS K 5600-5-6:1999. Based on the results of the peel test, adhesion was evaluated according to the following evaluation criteria. <Evaluation Criteria> A: Less than 5% of the cross-cut areas where peeling can be confirmed by the grid pattern are less than 5%. B: The cross-cut areas where peeling can be confirmed in the grid pattern are between 5% and 15%. C: More than 15% of the area is a cross-cut section where peeling can be confirmed using a grid pattern.

[0109] <Lightfastness Test> A UV carbon arc lamp type lightfastness and weather resistance tester conforming to JIS B7751 (product name "FAL-AU·B" manufactured by Suga Test Instruments Co., Ltd., light source: UV carbon arc lamp, irradiance: 500W / m²) 2 The optical laminates of the examples and comparative examples were placed in a black panel (black panel temperature: 63°C) with the resin layer facing the light source, and a 200-hour test was conducted.

[0110] 1-6. Transmission image clarity (Transmission image clarity according to JIS K7374:2007) The transmitted image clarity of the optical laminates of the examples and comparative examples was measured. The light incident surface was the substrate side. The measuring device used was an image clarity meter (product name: ICM-1T) manufactured by Suga Test Instruments Co., Ltd. Table 2 shows the sum of the transmitted image clarity for the widths of the four optical combs (unit: "%"). The four comb widths used were 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm. Furthermore, the transmitted image clarity was measured for the optical laminates of the examples and comparative examples after the lightfastness test described above, in the same manner as above. The sum of the transmitted image clarity for the widths of the four optical combs is shown in Table 2 (unit: "%"). Table 2 shows the difference in transmitted image clarity before and after the lightfastness test (unit: "%"). A difference of 10.0% or less is considered acceptable, and among those that meet the acceptable criteria, a difference of 5.0% or less is more preferable.

[0111] 1-7. Anti-glare property Samples were prepared by laminating a black plate (Kuraray Co., Ltd., product name "Comoglass DFA2CG 502K (black) series", total light transmittance 0%, thickness 2 mm, refractive index 1.49) to the substrate side of the optical laminates of the examples and comparative examples (sample size: 20 cm vertically x 30 cm horizontally) via a 25 μm thick transparent adhesive layer (Panac Co., Ltd., product name "Panaclean PD-S1", refractive index 1.49). The samples were then evaluated by 20 subjects under bright room conditions (illuminance on the first main surface of the sample between 500 lux and 1000 lux; lighting: Hf32 type straight tube three-wavelength daylight white fluorescent lamp) from a straight-line distance of 50 cm above the center of the first main surface of the sample, according to the following criteria to determine whether sufficient anti-glare properties were obtained so that the observer's own reflection was not noticeable. The position of the lighting during evaluation was 2 m vertically above the horizontal table. The subjects were healthy individuals in their 30s with a visual acuity of 0.7 or better. A: More than 14 people answered "good". B: 7 to 13 people answered "good" C: Six or fewer people answered "good".

[0112] 2. Fabrication of optical stacks [Example 1] (Manufacturing of base materials) A copolymer of methyl methacrylate and methyl acrylate was kneaded at 260°C using a twin-screw extruder to obtain a pelletized composition (glass transition temperature: 134°C). The obtained pelletized composition was melt-extruded using a T-die (T-die temperature: 260°C) and discharged onto a cooling roll at 130°C. Next, it was sequentially biaxially stretched in the longitudinal and transverse directions at a stretching ratio of 1.5 times at a stretching temperature of 145°C. After cooling, an acrylic resin substrate with a thickness of 40 μm was obtained. (Formation of resin layer) On the aforementioned acrylic resin substrate, the resin layer coating solution of Example 1 in Table 1 was applied using the Meyer bar coating method at a rate of 6.0 g / m². 2 After applying the coating solution, the first stage of drying was performed by drying it for 30 seconds with hot air at a wind speed of 5 m / s and a temperature of 90°C. Furthermore, the second stage of drying was performed by drying the coating solution for 30 seconds with hot air at a wind speed of 20 m / s and a temperature of 90°C. Subsequently, under a nitrogen atmosphere with an oxygen concentration of 200 ppm or less, the cumulative light intensity was 100 mJ / cm². 2 By irradiating with ultraviolet light in such a manner, the ionizing radiation-curable resin composition of the resin layer coating liquid was cured to form a first resin layer and a second resin layer, obtaining the optical laminate of Example 1. In this specification, the coating amount refers to the coating amount after drying.

[0113] [Examples 2-4], [Comparative Examples 1-3] Optical laminates of Examples 2-4 and Comparative Examples 1-3 were obtained in the same manner as in Example 1, except that the composition of the coating solution for the resin layer, the amount of coating solution applied, and the drying conditions for the coating solution for the resin layer were changed to those listed in Table 1.

[0114] [Table 1]

[0115] In Table 1, the hexafunctional urethane acrylate oligomer is Mitsubishi Chemical's urethane acrylate oligomer (product name: Shiko UV-7600B, weight-average molecular weight: 1400), the bifunctional acrylate monomer is tetraethylene glycol diacrylate, the trifunctional acrylate monomer is pentaerythritol triacrylate, the monofunctional acrylate monomer is 4-hydroxybutyl acrylate, and the photopolymerization initiator is IGM Resins BV's product name "Omnirad 184".

[0116] [Table 2]

[0117] The results in Table 2 confirm that the optical laminates of the examples can suppress the decrease in adhesion and the change in transmitted image clarity after the light resistance test. On the other hand, the optical laminate of Comparative Example 1 has a first resin layer that does not have region α1. As a result, the optical laminate of Comparative Example 1 could not achieve good affinity between the first resin layer and the second resin layer, and the adhesion after the lightfastness test was reduced. It is thought that in Comparative Example 1, the coating liquid for the resin layer contains a monofunctional monomer, resulting in good compatibility, which makes it difficult for a sea-island structure to form, and thus region α1 was not formed. The optical laminate of Comparative Example 2 has large θa1 and Pa1 values ​​and does not satisfy either condition 1 or condition 2. As a result, the transmitted image clarity of the optical laminate of Comparative Example 2 fluctuated drastically after the lightfastness test. The reason why Comparative Example 2 does not satisfy conditions 1 and 2 is thought to be that the long drying time caused significant movement of resin components between the first and second resin layers, resulting in large θa2 and Pa2 values. The optical laminate of Comparative Example 3 has small θa1 and Pa1 values ​​and does not satisfy either condition 1 or condition 2. Therefore, the optical laminate of Comparative Example 3 could not achieve good adhesion after the lightfastness test. Furthermore, the optical laminate of Comparative Example 3 did not have sufficient adhesion even before the lightfastness test. The reason why Comparative Example 3 does not satisfy conditions 1 and 2 is thought to be that the coating liquid for the resin layer does not contain a difunctional monomer. [Explanation of symbols]

[0118] 10: Base material 20: Resin layer 21: First resin layer 22: Second resin layer 100: Optical laminate 200: Display element 500: Image display device

Claims

[Claim 1] An optical laminate having a resin layer on a substrate, The resin layer comprises a first resin layer and a second resin layer, starting from the substrate side. The first resin layer has a region α1 that is independent of each other and a region α2 that surrounds the region α1, and the resin contained in region α1 and the resin contained in region α2 are different. The second resin layer has a region β1 that is independent of each other and a region β2 that surrounds the region β1, and the resin contained in region β1 and the resin contained in region β2 are different. An optical laminate that satisfies either condition 1 or condition 2 below. <Condition 1> The relationship between θa1, which represents the average inclination angle of the surface of the substrate on the resin layer side, and θa2, which represents the average inclination angle of the surface of the first resin layer on the second resin layer side, is θa2 < θa1. <Condition 2> The relationship between Pa1, which represents the arithmetic mean height of the surface of the substrate on the resin layer side, and Pa2, which represents the arithmetic mean height of the surface of the first resin layer on the second resin layer side, is Pa2 < Pa1.

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