Optical laminate and image display device using same

Abstract

Provided is an antireflection film having excellent scratch resistance while a fluorine compound is used as a binder component of a low-refractive-index layer. An optical laminate according to the present invention comprises a low-refractive-index layer on the outermost surface on one surface side of a transparent base material. The low-refractive-index layer contains a binder resin, hollow particles, and solid particles. The average particle diameter D1 of the hollow particles and the average particle diameter D2 of the solid particles satisfy the condition of 1.4 ≤ D2 / D1 ≤ 2.8. The number of the solid particles in the low-refractive-index layer is 8 to 320 / 25 μm2.

Description

Optical laminate and image display device using the same

[0001] The present invention relates to an optical laminate in which a low refractive index layer is provided on the outermost surface of a transparent substrate, and an image display device using the same.

[0002] An anti-reflection film for suppressing reflection of external light is provided in image display devices such as liquid crystal display devices and organic EL display devices. The anti-reflection film is configured by laminating a low-refractive index layer (low-reflection (LR) layer) having a refractive index lower than that of an underlayer on a transparent substrate or an optical functional layer laminated on the transparent substrate.

[0003] A method for lowering the refractive index of a low refractive index layer by incorporating a fluorine compound into the low refractive index layer is known (Non-Patent Document 1). While this method can easily lower the refractive index of the low refractive index layer, the fluorine compound itself has soft properties, which causes a problem of reduced scratch resistance and makes the low refractive index layer more susceptible to scratches. Therefore, as in Patent Documents 1 and 2, methods have been proposed for improving scratch resistance by replacing or reducing the content of a fluorine compound in the low refractive index layer.

[0004] Hide Nakamura, Polymer, 1999, Vol. 48, June issue, pp. 438-439

[0005] Japanese Patent Application Laid-Open No. 2020-166236 Republished No. 2019-163829

[0006] However, methods for improving scratch resistance while adding a fluorine compound, rather than simply replacing or reducing the amount of the fluorine compound contained in the low refractive index layer, have not been fully investigated until now.

[0007] Therefore, an object of the present invention is to provide an anti-reflection film that uses a fluorine compound as a binder component in a low refractive index layer and has excellent scratch resistance.

[0008] An optical laminate comprising a low refractive index layer on the outermost surface of one side of a transparent substrate, the low refractive index layer containing a binder resin, hollow particles, and solid particles, wherein the average particle diameter D1 of the hollow particles and the average particle diameter D2 of the solid particles satisfy the condition of 1.4≦D2 / D1≦2.8, and the number of solid particles in the low refractive index layer is 8 to 320 particles / 25 μm.２ An optical laminate.

[0009] According to the present invention, an antireflection film having excellent scratch resistance can be provided, while using a fluorine compound as a binder component of a low refractive index layer.

[0010] Fig. 1 is a cross-sectional view showing the configuration of an optical laminate according to an embodiment. Fig. 2 is an STEM image of a cross section of the optical laminate. Fig. 3 is a cross-sectional view schematically showing a low refractive index layer according to an embodiment. Fig. 4 is a cross-sectional view schematically showing a low refractive index layer not containing solid particles.

[0011] FIG. 1 is a cross-sectional view schematically showing an example of an optical laminate according to an embodiment, FIG. 2 is an STEM image of a cross section of the optical laminate, and FIG. 3 is a cross-sectional view schematically showing a low refractive index layer according to an embodiment.

[0012] The optical laminate 11 includes a transparent substrate 2, an antiglare layer 3 laminated on one surface of the transparent substrate 2, and a low refractive index layer 4 laminated on the surface of the antiglare layer 3 and having a refractive index lower than that of the antiglare layer 3. The optical laminate 11 is an optical film (also referred to as an "AGLR film") that suppresses glare and reflection of external light by utilizing scattering of incident light and optical interference caused by fine irregularities on the outermost surface.

[0013] (Transparent Substrate) The transparent substrate 2 is a film that serves as the base of the optical laminate 11, and is made of a material that has excellent transparency to visible light. Examples of materials that can be used to form the transparent substrate 2 include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyacrylates such as polymethyl methacrylate, polyamides such as nylon 6 and nylon 66, polyimides, polyarylates, polycarbonates, triacetyl cellulose, polyacrylates, polyvinyl alcohol, polyvinyl chloride, cycloolefin copolymers, norbornene-containing resins, polyethersulfones, and transparent resins such as polysulfones, and inorganic glass. The thickness of the transparent substrate 2 is not particularly limited, but is preferably 10 to 200 μm.

[0014] The surface of the transparent substrate 2 may be subjected to a surface modification treatment in order to improve adhesion with other layers to be laminated thereon. Examples of surface modification treatments include alkali treatment, corona treatment, plasma treatment, sputtering treatment, application of a surfactant or a silane coupling agent, and Si vapor deposition.

[0015] (Anti-glare Layer) The anti-glare layer 3 is a functional layer that diffuses external light of the optical laminate 11 by forming minute irregularities on the surface.

[0016] The antiglare layer 3 is formed by applying a coating liquid containing an active energy ray-curable compound and organic fine particles and / or inorganic fine particles (filler) to the transparent substrate 2 and curing the coating film.

[0017] As the active energy ray-curable compound, for example, a monofunctional, difunctional, trifunctional or higher functional (meth)acrylate monomer can be used. In this specification, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acryloyl" is a general term for both acryloyl and methacryloyl.

[0018] Examples of monofunctional (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, glycidyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isobornyl (meth)acrylate. acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phosphate (meth)acrylate, ethylene oxide-modified phosphate (meth)acrylate, phenoxy (meth)acrylate, ethylene oxide-modified phenoxy (meth)acrylate, propylene oxide ethylene oxide-modified phenoxy (meth)acrylate, nonylphenol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, propylene oxide-modified nonylphenol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, ) acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydrohydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydrohydrogen phthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, 2-adamantane,adamantane derivative mono(meth)acrylates such as adamantyl acrylate having a monovalent mono(meth)acrylate derived from adamantanediol, etc.

[0019] Examples of bifunctional (meth)acrylates include di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and hydroxypivalic acid neopentyl glycol di(meth)acrylate.

[0020] Examples of tri- or higher functional (meth)acrylates include tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris-2-hydroxyethyl isocyanurate tri(meth)acrylate, and glycerin tri(meth)acrylate; trifunctional (meth)acrylate compounds such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate;

[0033] Examples of the polyfunctional (meth)acrylate include tri- or higher functional (meth)acrylate compounds such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrimethylolpropane hexa(meth)acrylate, as well as polyfunctional (meth)acrylate compounds in which a portion of these (meth)acrylates is substituted with an alkyl group or ε-caprolactone.

[0021] Urethane (meth)acrylates can also be used as polyfunctional monomers. Examples of urethane (meth)acrylates include those obtained by reacting a polyester polyol with an isocyanate monomer or a prepolymer, and then reacting the resulting product with a (meth)acrylate monomer having a hydroxyl group.

[0022] Examples of urethane (meth)acrylates include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer.

[0023] The polyfunctional monomers may be used alone or in combination of two or more. In addition, the polyfunctional monomers may be in the form of a monomer in the coating liquid, or may be in the form of a partially polymerized oligomer.

[0024] The organic fine particles are a material that mainly forms fine irregularities on the surface of the antiglare layer 3 and provides the function of diffusing external light. Resin particles made of a light-transmitting resin material such as acrylic resin, polystyrene resin, styrene-(meth)acrylic acid ester copolymer, polyethylene resin, epoxy resin, silicone resin, polyvinylidene fluoride, or polyethylene fluoride resin can be used as the organic fine particles. Two or more types of resin particles made of different materials (refractive indexes) may be mixed and used to adjust the refractive index and dispersion of the resin particles. The average particle diameter of the organic fine particles is preferably 0.5 to 10 μm.

[0025] The inorganic fine particles added to the composition for forming an antiglare layer are preferably nanoparticles having an average particle size of 10 to 200 nm.

[0026] The inorganic fine particles are primarily used to adjust the sedimentation and aggregation of the organic fine particles in the antiglare layer 3. Examples of inorganic fine particles that can be used include silica fine particles, metal oxide fine particles, and various mineral fine particles. Examples of silica fine particles include colloidal silica and silica fine particles surface-modified with reactive functional groups such as (meth)acryloyl groups. Examples of metal oxide fine particles include alumina, zinc oxide, tin oxide, antimony oxide, indium oxide, titania, and zirconia. Examples of mineral fine particles include mica, synthetic mica, vermiculite, montmorillonite, iron-montmorillonite, bentonite, beidellite, saponite, hectorite, stevensite, nontronite, magadiite, ilealite, kanemite, layered titanic acid, smectite, and synthetic smectite. The mineral fine particles may be natural or synthetic (including substituted or derivative) materials, or a mixture of both may be used. Among mineral fine particles, layered organic clay is more preferred. Layered organic clay refers to a swelling clay in which organic onium ions have been introduced between its layers. The organic onium ions are not limited as long as they can be organized by utilizing the cation exchange properties of the swelling clay. When a layered organic clay mineral is used as the mineral fine particles, the above-mentioned synthetic smectite can be suitably used. Synthetic smectite has the function of increasing the viscosity of the antiglare layer-forming composition, suppressing the settling of resin particles and inorganic fine particles, and adjusting the uneven shape of the surface of the optical functional layer.

[0027] A polymerization initiator may be added to cure the antiglare layer-forming composition by ultraviolet irradiation. Polymerization initiators that generate radicals upon ultraviolet irradiation can be used. Radical polymerization initiators such as acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, and acylphosphine oxides can be used as the polymerization initiator. Examples of polymerization initiators that can be used include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-phenylacetophenone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, and 2-chlorothioxanthone. One of these initiators may be used alone, or two or more may be used in combination.

[0028] Furthermore, it is preferable to add an antifouling agent, leveling agent, oil repellent, water repellent, or fingerprint inhibitor to the composition for forming the antiglare layer as a component for improving antifouling properties. Fluorine-containing compounds and silicone compounds can be suitably used as these additives. By adding an antifouling compound to the antiglare layer 3, which is the outermost layer, the ease of wiping off fingerprints can be further improved. In addition, various additives such as antistatic agents, antifoaming agents, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, and photosensitizers may be added as needed.

[0029] Furthermore, a solvent may be added to the antiglare layer-forming composition, if necessary. Examples of the solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropyl alcohol, and isobutanol; ketones such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ketone alcohols such as diacetone alcohol; aromatic hydrocarbons such as benzene, toluene, and xylene; glycols such as ethylene glycol, propylene glycol, and hexylene glycol; glycol ethers such as ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve, diethyl carbitol, and propylene glycol monomethyl ether; esters such as methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, and amyl acetate; ethers such as dimethyl ether and diethyl ether; and N-methylpyrrolidone and dimethylformamide, which may be used alone or in combination of two or more.

[0030] (Low Refractive Index Layer) The low refractive index layer 4 has a refractive index lower than that of the underlying antiglare layer 3, and is a functional layer that reduces the surface reflection of the optical laminate 11 by canceling out light reflected on the surface of the low refractive index layer 4 through interference with light reflected on the interface between the low refractive index layer 4 and the antiglare layer 3.

[0031] The low refractive index layer 4 can be formed by applying a coating liquid containing a binder resin 40, low refractive index fine particles added as needed, and solid particles 42 to the surface of the antiglare layer 3, and curing the coating film. The low refractive index layer 4 also has protruding portions 43 that protrude beyond portions of the low refractive index layer 4 where the solid particles 42 are present and where the solid particles 42 are not present.

[0032] The binder resin 40 used to form the low refractive index layer 4 can be, for example, any of the compounds exemplified as materials for the antiglare layer 3. However, it is preferable to use a fluorine-based compound, since the refractive index can be easily reduced by using a fluorine-based compound. As the fluorine-based compound, for example, perfluorodecanoic acid diurethane acrylate can be used.

[0033] Examples of low refractive index particles include LiF, MgF, 3NaF·AlF, and AlF (each having a refractive index of 1.4), and Na ３ AlF ６ Fine particles such as cryolite (refractive index 1.33) and silica fine particles having voids therein can be suitably used. Silica fine particles having voids therein (hollow particles 41) can have the refractive index of the voids equal to that of air (approximately 1), which is advantageous for lowering the refractive index of the low refractive index layer 4. Specific examples of hollow particles 41 that can be used include porous silica particles and silica particles with a shell structure. Note that, although this embodiment assumes that the low refractive index layer 4 contains hollow particles 41, low refractive index fine particles such as hollow particles 41 are not necessarily required. If the refractive index of the active energy ray-curable compound after curing is lower than the refractive index of the antiglare layer 3, the low refractive index fine particles may be omitted.

[0034] The solid particles 42 have a larger particle diameter than the hollow particles 41, and for example, silica fine particles without internal voids can be used. Therefore, the solid particles 42 are less likely to break than the hollow particles 41, which have internal voids. In Fig. 2, the particle diameters of the solid particles 42 are actually measured as 122 nm, 116 nm, and 117 nm, but are not limited to these values ​​and can be, for example, 110 nm to 210 nm.

[0035] As described above, the refractive index of the low-refractive-index layer 4 can be easily reduced by incorporating a fluorine compound into the low-refractive-index layer 4. However, the fluorine compound itself is soft, which reduces the scratch resistance of the low-refractive-index layer 4. Furthermore, when the low-refractive-index layer 4 contains hollow particles 41, the cavities inside the hollow particles 41 can reduce the refractive index of the low-refractive-index layer 4. However, because the hollow particles 41 are fragile, increasing the content of hollow particles 41 reduces the scratch resistance of the low-refractive-index layer 4. Therefore, in this embodiment, as shown in FIGS. 2 and 3 , the scratch resistance is improved by incorporating solid particles 42 into the low-refractive-index layer 4. Specifically, assuming a rubbing test using steel wool 5 on the surface of the low-refractive-index layer 4, the solid particles 42 become contact points with the steel wool 5, thereby reducing the contact area between the hollow particles 41 and the binder resin 40 and the steel wool 5. This reduces the occurrence of scratches on the low-refractive-index layer 4 and improves scratch resistance. If the low refractive index layer 4 does not contain solid particles 42, the contact area between the hollow particles 41 and the binder resin 40 and the steel wool 5 becomes large as shown in Figure 4, making the low refractive index layer 4 more susceptible to scratches and reducing its scratch resistance.

[0036] In order to ensure sufficient scratch resistance of the low refractive index layer 4, the number of solid particles 42 in the low refractive index layer 4 is 8 to 320 particles / 25 μm. ２ The number of solid particles 42 is preferably 8 / 25 μm. ２ If the number of solid particles 42 is less than 320 / 25 μm, the number of solid particles 42 that form contact points is small, and no improvement in scratch resistance can be obtained. ２ If the refractive index exceeds 100%, the resin component of the low refractive index layer 4 will not be able to hold the solid particles 42, resulting in a decrease in scratch resistance.

[0037] Hereinafter, the average particle diameter of hollow particles 41 is defined as D1, the average particle diameter of solid particles 42 as D2, the average film thickness of portions of low refractive index layer 4 where solid particles 42 are not present as T1, and the average film thickness of protrusions 43 as T2. The average film thickness is the average value of film thicknesses at any three points on low refractive index layer 4.

[0038] When the low refractive index layer 4 contains hollow particles 41, the optical laminate 11 according to this embodiment preferably satisfies the following condition (1): 1.4≦D2 / D1≦2.8 (1)

[0039] If D2 / D1 is less than 1.4, the protrusions 43 do not adequately fulfill their role as contact points of the low refractive index layer 4, and therefore the effect of improving scratch resistance is small even if the low refractive index layer 4 contains solid particles 42. If D2 / D1 is more than 2.8, hollow particles 41, which have a relatively small particle size and low scratch resistance, pile up and protrude further than the solid particles 42, thereby deteriorating scratch resistance.

[0040] Furthermore, the optical laminate 11 according to this embodiment preferably satisfies the following condition (2): 1.0≦D2 / T1≦2.0 (2)

[0041] If D2 / T1 is less than 1.0, the average particle diameter D2 of the solid particles 42 will be equal to or less than the average film thickness T1 of the low refractive index layer 4, and the protrusions 43 will not adequately function as contact points of the low refractive index layer 4, resulting in little improvement in scratch resistance even if the low refractive index layer 4 contains the solid particles 42. If D2 / T1 is more than 2.0, the low refractive index layer 4 will no longer be able to retain the solid particles, causing them to fall off and resulting in no scratch resistance.

[0042] Furthermore, the optical laminate 11 according to this embodiment preferably satisfies the following condition (3): 1.1≦T2 / T1≦2.2 (3)

[0043] If T2 / T1 is less than 1.1, the surface of the low refractive index layer 4 becomes nearly flat, and the protrusions 43 do not fully fulfill their role as contact points on the outermost surface, resulting in little improvement in scratch resistance even if the low refractive index layer 4 contains solid particles 42. If T2 / T1 is more than 2.2, the balance of the low refractive index layer 4 deteriorates, causing an increase in reflectance or causing unevenness on the surface, deteriorating the appearance.

[0044] Furthermore, the optical laminate 11 preferably has an SCI reflectance Y of 1.5% or less, measured after blackening the other surface of the transparent substrate 2. The SCI reflectance is the reflectance of all reflected light, including specular reflected light, measured by the SCI (Specular Component Include) method, and can be measured in accordance with JIS Z 8722. If the SCI reflectance Y is 1.5% or less, the required characteristics for in-vehicle use can be satisfied.

[0045] Since the low refractive index layer 4 is a functional layer that serves as the outermost layer, it is preferable to add to the composition for forming the low refractive index layer components that improve antifouling properties, such as an antifouling agent, a leveling agent, an oil repellent, a water repellent, and an anti-fingerprint agent. Fluorine-containing compounds and silicone compounds can be suitably used as these additives. In addition, various additives such as antistatic agents, antifoaming agents, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, and photosensitizers may be added as needed.

[0046] Between the transparent substrate 2 and the antiglare layer 3, one or more other functional layers such as a hard coat layer, a high refractive index layer, a medium refractive index layer, an antistatic layer, an electromagnetic wave blocking layer, an infrared absorbing layer, an ultraviolet absorbing layer, or a color correction layer may be laminated.

[0047] The method for applying the antiglare layer-forming composition and the low refractive index layer-forming composition is not particularly limited, and for example, they can be applied using a spin coater, a roll coater, a reverse roll coater, a gravure coater, a microgravure coater, a knife coater, a bar coater, a wire bar coater, a die coater, a dip coater, a spray coater, an applicator, or the like.

[0048] The optical laminate 11 according to this embodiment can be used to configure an image display device by being attached to the outermost surface of an image display panel such as a liquid crystal panel or an organic EL panel. A touch panel may be provided between the optical laminate 11 and the image display panel.

[0049] Examples of specific implementations of the present invention will be described below.

[0050] Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3: A 40 μm-thick triacetyl cellulose film was used as the transparent substrate. A coating liquid for forming an antiglare layer was prepared, containing a binder resin, a filler, a photopolymerization initiator, and a solvent. The coating liquid for forming an antiglare layer was applied to the transparent substrate so that the film thickness after curing would be 5 μm, dried, and then polymerized and cured by ultraviolet irradiation to form an antiglare layer. Next, a coating liquid for forming a low refractive index layer was prepared on the antiglare layer, containing a binder resin blended in a ratio of 20 parts by weight of pentaerythritol triacrylate and 80 parts by weight of perfluorodecanoic acid diurethane acrylate, and solid silica particles and hollow silica particles having the average particle diameters shown in Table 1. The coating liquid for forming a low refractive index layer was applied to the antiglare layer so that the film thickness after curing would be as shown in Table 1, dried, and then polymerized and cured by ultraviolet irradiation to form a low refractive index layer.

[0051] (Comparative Examples 1-4 and 1-5) In Comparative Example 1-4, an optical laminate was prepared in the same manner as in Example 1-1, except that no solid silica particles were added to the coating liquid for forming the low refractive index layer. Comparative Example 1-5 was prepared in the same manner as Comparative Example 1-4, except that the average particle size of the hollow silica particles was changed to 57 nm.

[0052] The particle number of the solid silica particles shown in Table 1 is a value measured from an STEM image of the surface of the produced optical laminate, and is the average value of the number of particles in 10 arbitrary regions on the surface. In Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3, the content ratio of the solid silica particles in the coating liquid for forming the low refractive index layer was changed to obtain a particle size of 25 μm. ２ The number of solid silica particles per 1000 sieve was adjusted to the values ​​shown in Table 1.

[0053] The optical laminates according to the examples and comparative examples were evaluated as follows.

[0054] <Evaluation 1: Evaluation of Scratch Resistance> The optical laminates obtained in the examples and comparative examples were set in a Gakushin-type abrasion fastness tester (AB-301, manufactured by Tester Sangyo Co., Ltd.), and steel wool (Bonstar #0000) was applied to the surface of the optical laminate at a rate of 150 g / cm. ２After the scratch resistance test, the surface of the optical laminate was visually observed and evaluated according to the following criteria: ◯: no scratches ×: one or more scratches

[0055] <Evaluation 2: SCI Reflectance Y> In the optical laminates obtained in the examples and comparative examples, the other surface of the transparent substrate was blackened, and the SCI reflectance Y was measured. The SCI reflectance Y was measured in accordance with JIS Z 8722 using a spectrophotometer (CM-2600d, manufactured by Konica Minolta Japan, Inc.). The measurement conditions were a measurement diameter / illumination diameter of φ8 mm / φ11 mm, an observation condition of a 10° field of view, and an observation light source of D65. When measured with a measurement diameter (8 mm), areas with relatively high and low reflectance due to coating unevenness can be contained within a single field of view, allowing for an average SCI reflectance measurement to be obtained. In addition, a 10° field of view corresponds to viewing an area with a diameter of 8.8 cm at a distance of 50 cm. However, in the case of in-vehicle applications, a relatively wide area of ​​the image display device is often viewed at a close distance, so measurement with a 10° field of view is appropriate. D65 is the average noon light in Europe / Northern Europe defined by the International Commission on Illumination, and is suitable for measurement because it has a wavelength distribution similar to that of ambient light. The evaluation was carried out according to the following criteria: ◯: SCI reflectance Y≦1.5 ×: SCI reflectance Y>1.5

[0056] <Overall Evaluation> An overall evaluation was made based on the results of Evaluation 1 and Evaluation 2. This evaluation was made according to the following criteria: ◯: The evaluation results of Evaluation 1 and Evaluation 2 were both ◯; ×: Either the evaluation result of Evaluation 1 or Evaluation 2 was ×.

[0057] Table 1 also shows the average particle size of the solid silica particles, the average particle size of the hollow silica particles, the number of solid silica particles, the ratio D2 / D1 of the average particle size of the solid silica particles to the average particle size of the hollow silica particles, and the evaluation results of the scratch resistance and SCI reflectivity.

[0058]

[0059] As shown in Table 1, the optical laminates according to Examples 1-1 to 1-7 all had a particle number of 8 to 320 particles / 25 μm ２The ratio D2 / D1 of the average particle size of the solid silica particles to the average particle size of the hollow silica particles satisfied the condition (1). Therefore, in the scratch resistance evaluation, the contact area between the binder and hollow silica particles of the optical laminate and the steel wool was small, and the scratch resistance was good. In addition, the SCI reflectance Y was 1.5 or less, and the low reflectivity was also good.

[0060] In the optical laminates according to Comparative Examples 1-1 and 1-2, the average particle diameter of the solid silica particles was too small to be observed, and the average particle diameter of the optical laminate was 25 μm. ２ It was not possible to count the number of solid silica particles within the region. In addition, because the average particle size of the solid silica particles was equal to or smaller than the average particle size of the hollow silica particles, the contact area between the low refractive index layer and the steel wool increased, resulting in poor scratch resistance.

[0061] In the optical laminate according to Comparative Example 1-3, the average particle size of the solid silica particles was too large compared to the average particle size of the hollow silica particles, so the hollow silica particles piled up, resulting in poor scratch resistance.

[0062] In the optical laminate according to Comparative Example 1-4, since no solid silica particles were added to the low refractive index layer, the contact area between the low refractive index layer and the steel wool was large, and the scratch resistance was low, similar to Comparative Examples 1-1 and 1-2. On the other hand, in Comparative Example 1-5, since the particle size of the hollow silica particles was small, the hollow ratio decreased and the refractive index of the hollow particles increased, so the SCI reflectance Y exceeded 1.5 and the low reflectivity was poor.

[0063] From the above, it was confirmed that, when the ratio D2 / D1 of the average particle size of the solid silica particles to the average particle size of the hollow silica particles satisfies the condition (1), an optical laminate having excellent scratch resistance and low reflectivity can be realized even when a fluororesin is used as the binder resin of the low refractive index layer.

[0064] Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-3: A 40 μm-thick triacetyl cellulose film was used as the transparent substrate. A coating liquid for forming an antiglare layer was prepared, containing a binder resin, a filler, a photopolymerization initiator, and a solvent. The coating liquid for forming an antiglare layer was applied to the transparent substrate so that the film thickness after curing would be 5 μm, dried, and then polymerized and cured by ultraviolet irradiation to form an antiglare layer. Next, a coating liquid for forming a low refractive index layer was prepared on the antiglare layer, containing a binder resin blended in a ratio of 20 parts by weight of pentaerythritol triacrylate and 80 parts by weight of perfluorodecanoic acid diurethane acrylate, and solid silica particles having the average particle size shown in Table 2. The coating liquid for forming a low refractive index layer was applied to the antiglare layer so that the film thickness after curing would be as shown in Table 2, dried, and then polymerized and cured by ultraviolet irradiation to form a low refractive index layer.

[0065] (Comparative Examples 2-4 and 2-5) In Comparative Example 2-4, an optical laminate was prepared in the same manner as in Example 1-1, except that no solid silica particles were added to the coating liquid for forming the low refractive index layer. Comparative Example 2-5 was prepared in the same manner as Comparative Example 2-4, except that the average particle size of the hollow silica particles was changed to 57 nm.

[0066] The film thickness of the low refractive index layer shown in Table 2 is a value measured from an STEM image of the cross section of the produced optical laminate, and is the average value of film thicknesses at 10 arbitrary locations between protruding portions of the low refractive index layer where no solid particles are present. The particle number of solid silica particles shown in Table 2 is a value measured from an STEM image of the surface of the produced optical laminate, and is the average value of the number of particles at 10 arbitrary locations on the surface. In Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-3, the content ratio of solid silica particles in the coating liquid for forming the low refractive index layer was changed, and the thickness of the low refractive index layer was increased to 25 μm. ２ The number of solid silica particles per 1000 sieve was adjusted to the values ​​shown in Table 2.

[0067] The scratch resistance and SCI reflectance Y of the optical laminates according to each of the examples and comparative examples were evaluated in the same manner as in Example 1-1. In addition, a comprehensive evaluation was performed using the same criteria as in Example 1-1.

[0068] Table 2 also shows the average particle size of the solid silica particles, the film thickness of the low refractive index layer, the number of solid silica particles, the ratio D2 / T1 of the average particle size of the solid silica particles to the film thickness of the low refractive index layer, and the evaluation results of the scratch resistance and SCI reflectivity.

[0069]

[0070] As shown in Table 2, the optical laminates according to Examples 2-1 to 2-7 all had a particle number of 8 to 320 particles / 25 μm ２ The ratio D2 / T1 of the average particle size of the solid silica particles to the film thickness of the low refractive index layer satisfied the condition (2). Therefore, in the scratch resistance evaluation, the contact area between the binder and hollow silica particles of the optical laminate and the steel wool was small, and the scratch resistance was good. In addition, the SCI reflectance Y was 1.5 or less, and the low reflectivity was also good.

[0071] In the optical laminates according to Comparative Examples 2-1 and 2-2, the average particle diameter of the solid silica particles was too small to be observed, and the average particle diameter of the solid silica particles was 25 μm. ２ It was not possible to count the number of solid silica particles in the region. In addition, because the average particle size of the solid silica particles was sufficiently smaller than the film thickness of the low refractive index layer, the contact area between the low refractive index layer and the steel wool increased, resulting in low scratch resistance.

[0072] In the optical laminate of Comparative Example 2-3, the average particle size of the solid silica particles was large relative to the film thickness of the low refractive index layer, exceeding the upper limit of condition (2). Since the average particle size of the solid silica particles was too large compared to the film thickness of the low refractive index layer, the solid silica particles could not be retained, and scratch resistance was deteriorated.

[0073] In the optical laminate according to Comparative Example 2-4, since no solid silica particles were added to the low refractive index layer, the contact area between the low refractive index layer and the steel wool was large, and the scratch resistance was low, similar to Comparative Examples 2-1 and 2-2. On the other hand, in Comparative Example 2-5, since the particle size of the hollow silica particles was small, the hollow ratio decreased and the refractive index of the hollow particles increased, so the SCI reflectance Y exceeded 1.5 and the low reflectivity was poor.

[0074] From the above, it has been confirmed that, when the ratio D2 / T1 of the average particle size of the solid silica particles to the film thickness of the low refractive index layer satisfies the condition (2), an optical laminate having excellent scratch resistance and low reflectivity can be realized even when a fluororesin is used as the binder resin of the low refractive index layer.

[0075] Examples 3-1 to 3-7 and Comparative Examples 3-1 to 3-3 A 40 μm-thick triacetyl cellulose film was used as the transparent substrate. A coating liquid for forming an antiglare layer was prepared, containing a binder resin, a filler, a photopolymerization initiator, and a solvent. The coating liquid for forming an antiglare layer was applied to the transparent substrate so that the film thickness after curing would be 5 μm, dried, and then polymerized and cured by ultraviolet light irradiation to form an antiglare layer. Next, a coating liquid for forming a low refractive index layer was prepared on the antiglare layer, containing a binder resin and solid silica particles having an average particle size shown in Table 3. The coating liquid for forming a low refractive index layer was applied to the antiglare layer so that the film thickness after curing would be the film thickness shown in Table 3, dried, and then polymerized and cured by ultraviolet light irradiation to form a low refractive index layer.

[0076] Comparative Example 3-4 An optical laminate was prepared in the same manner as in Example 3-1, except that solid silica particles were not added to the coating liquid for forming the low refractive index layer, in which an antiglare layer and a low refractive index layer were laminated on a transparent substrate.

[0077] Comparative Example 3-5 Comparative Example 3-5 was prepared in the same manner as Comparative Example 3-4, except that the average particle size of the hollow silica particles was changed to 57 nm.

[0078] The film thickness of the low refractive index layer shown in Table 3 is a value measured from an STEM image of the cross section of the produced optical laminate, and is the average value of film thicknesses at 10 arbitrary locations between protruding portions of the low refractive index layer where no solid particles are present. The film thickness of the protruding portions shown in Table 3 is a value measured from an STEM image of the cross section of the produced optical laminate, and is the average value of film thicknesses of the low refractive index layer at 10 arbitrary protruding portions. The particle number of solid silica particles shown in Table 3 is a value measured from an STEM image of the surface of the produced optical laminate, and is the average value of the number of particles at 10 arbitrary regions on the surface. In Examples 3-1 to 3-7 and Comparative Examples 3-1 to 3-3, the content ratio of solid particles in the coating liquid for forming a low refractive index layer was changed, and the thickness of the low refractive index layer was increased to 25 μm. ２The number of solid silica particles per 1000 sieve was adjusted to the values ​​shown in Table 3.

[0079] The scratch resistance and SCI reflectance Y of the optical laminates according to each of the examples and comparative examples were evaluated in the same manner as in Example 1-1. In addition, a comprehensive evaluation was performed using the same criteria as in Example 1-1.

[0080] Table 3 also shows the evaluation results of the film thickness of the low refractive index layer, the film thickness of the protrusions, the number of solid silica particles, the ratio T2 / T1 of the film thickness of the protrusions to the film thickness of the low refractive index layer, scratch resistance, and SCI reflectivity.

[0081]

[0082] As shown in Table 3, the optical laminates according to Examples 3-1 to 3-7 all had a particle number of 8 to 320 particles / 25 μm ２ The ratio T2 / T1 of the film thickness of the low refractive index layer to the film thickness of the protrusions satisfied the condition (3). Therefore, in the scratch resistance evaluation, the contact area between the binder and hollow silica particles of the optical laminate and the steel wool was small, and the scratch resistance was good. In addition, the SCI reflectance Y was 1.5 or less, and the low reflectivity was also good.

[0083] In the optical laminates according to Comparative Examples 3-1 and 3-2, the average particle diameter of the solid silica particles was too small to be observed, and the average particle diameter of the optical laminate was 25 μm. ２ It was not possible to count the number of solid particles within the region. In addition, the average particle size of the solid silica particles was too small to form protrusions on the surface of the low refractive index layer, which increased the contact area between the low refractive index layer and the steel wool, resulting in low scratch resistance.

[0084] In the optical laminate of Comparative Example 3-3, the film thickness of the protruding portion of the low refractive index layer was too large compared to the film thickness of the portion other than the protruding portion of the low refractive index layer, so the protruding portion could not be held, resulting in deterioration of scratch resistance and appearance.

[0085] In the optical laminate of Comparative Example 3-4, since no solid particles were added to the low refractive index layer, no protrusions were formed, as in Comparative Examples 3-1 and 3-2, the contact area between the low refractive index layer and the steel wool was large, and the scratch resistance was low.

[0086] In Comparative Example 3-5, the hollow silica particles had a small particle size, which reduced the hollowness and increased the refractive index of the hollow particles, resulting in an SCI reflectance Y exceeding 1.5 and poor low reflectivity.

[0087] From the above, it has been confirmed that, when the ratio T2 / T1 of the film thickness of the protrusion to the film thickness of the low refractive index layer satisfies condition (3), an optical laminate having excellent scratch resistance and low reflectivity can be realized even when a fluororesin is used as the binder resin for the low refractive index layer.

[0088] The present invention can be used as an optical laminate to be provided on the outermost surface of an image display device for in-vehicle use or the like.

[0089] 2 transparent substrate 3 antiglare layer 4 low refractive index layer 11 optical laminate 40 binder resin 41 hollow particles 42 solid particles 43 protrusions

Claims

1. An optical laminate comprising a low refractive index layer on the outermost surface of one side of a transparent substrate, wherein the low refractive index layer contains a binder resin, hollow particles, and solid particles, wherein the average particle diameter D1 of the hollow particles and the average particle diameter D2 of the solid particles satisfy the condition of 1.4≦D2 / D1≦2.8, and the number of the solid particles in the low refractive index layer is 8 to 320 particles / 25 μm. ２ An optical laminate.

2. The optical laminate according to claim 1, wherein the SCI reflectance Y measured after blackening the other surface of the transparent substrate is 1.5% or less.

3. An image display device comprising the optical laminate according to claim 1 or 2.

Images