Optical laminate and image display device using the same

Abstract

An antireflective film with excellent scratch resistance is provided, which uses a fluorine compound as the binder component of the low-refractive-index layer. An optical laminate is also provided, comprising a low-refractive-index layer on the outermost surface of one side of a transparent substrate. The low-refractive-index layer includes a binder resin, hollow particles, and solid particles. The average particle size D1 of the hollow particles and the average particle size D2 of the solid particles satisfy the condition 1.4 ≤ D2 / D1 ≤ 2.8. The number of solid particles in the low-refractive-index layer is 8–320 per 25 μm. 2 .

Description

Technical Field

[0001] The present invention relates to an optical laminate having a low refractive index layer disposed on the outermost surface of a transparent substrate, and an image display device using the optical laminate. Background Technology

[0002] In image display devices such as liquid crystal displays or organic EL displays, an anti-reflective film is provided to suppress the reflection of external light. The anti-reflective film is formed by stacking a low refractive index layer (low reflection (LR) layer) with a lower refractive index than the substrate layer on a transparent substrate or an optical functional layer stacked on a transparent substrate.

[0003] A method for reducing the refractive index of a low-refractive-index layer by including a fluorine compound in the low-refractive-index layer is known (Non-Patent Document 1). This method allows for easy reduction of the refractive index of the low-refractive-index layer; however, due to the soft nature of the fluorine compound itself, the scratch resistance of the low-refractive-index layer is reduced, making it more susceptible to damage. Therefore, as shown in Patent Documents 1 and 2, a method has been proposed to improve scratch resistance by replacing or reducing the content of the fluorine compound in the low-refractive-index layer.

[0004] Existing technical documents

[0005] Non-patent literature

[0006] Non-patent literature 1: Nakamura Hide, Polymer, 1999, Vol. 48, June, pp. 438-439

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2020-166236

[0009] Patent Document 2: Japanese Re-registration No. 2019-163829 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, to date, there has been insufficient research into methods that improve scratch resistance by adding fluorine compounds, rather than simply replacing or reducing the amount of fluorine compounds in the low-refractive-index layer.

[0012] Therefore, the object of the present invention is to provide an antireflective film that has excellent scratch resistance while using fluorine compounds as the binder component of the low refractive index layer.

[0013] Methods for solving problems

[0014] An optical laminate is disclosed, comprising a low-refractive-index layer on the outermost surface of one side of a transparent substrate. The low-refractive-index layer includes an adhesive resin, hollow particles, and solid particles. The average particle size D1 of the hollow particles and the average particle size D2 of the solid particles satisfy the condition 1.4 ≤ D2 / D1 ≤ 2.8. The number of solid particles in the low-refractive-index layer is 8–320 per 25 μm. 2 .

[0015] The effects of the invention

[0016] According to the present invention, an antireflective film with excellent scratch resistance can be provided while using fluorine compounds as the binder component of the low refractive index layer. Attached Figure Description

[0017] [ Figure 1 ] Figure 1 This is a cross-sectional view showing the structure of the optical laminate according to the embodiment.

[0018] [ Figure 2 ] Figure 2 It is a STEM image of the cross-section of an optical laminate.

[0019] [ Figure 3 ] Figure 3 This is a schematic cross-sectional view of the low refractive index layer involved in the embodiment.

[0020] [ Figure 4 ] Figure 4 It is a schematic cross-sectional view of a low-refractive-index layer that does not contain solid particles. Detailed Implementation

[0021] Figure 1 This is a cross-sectional view schematically illustrating an example of an optical laminate according to an embodiment. Figure 2 It is a STEM image of the cross-section of an optical laminate. Figure 3 This is a schematic cross-sectional view of the low refractive index layer involved in the embodiment.

[0022] The optical laminate 11 comprises a transparent substrate 2, an anti-glare layer 3 laminated on one side of the transparent substrate 2, and a low refractive index layer 4 laminated on the surface of the anti-glare layer 3 and having a lower refractive index than the anti-glare layer 3. The optical laminate 11 is an optical film (also known as an "AGLR film") that uses the scattering and optical interference of incident light caused by the fine irregularities of the outermost surface to suppress the reflection and reflection of external light.

[0023] (Transparent substrate)

[0024] The transparent substrate 2 is a film serving as the base of the optical laminate 11, and is formed from a material with excellent visible light transmittance. The transparent substrate 2 can be formed from 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; transparent resins such as polyimide, polyarylate, polycarbonate, triacetyl cellulose, polyacrylate, polyvinyl alcohol, polyvinyl chloride, cyclic olefin copolymers, norbornene-containing resins, polyethersulfone, and polysulfone, or inorganic glass. The thickness of the transparent substrate 2 is not particularly limited, but is preferably set to 10–200 μm.

[0025] To improve adhesion with other layers, the surface of the transparent substrate 2 can be modified. Examples of surface modification treatments include alkali treatment, corona treatment, plasma treatment, sputtering treatment, coating with surfactants or silane coupling agents, and Si evaporation.

[0026] (Anti-glare layer)

[0027] The anti-glare layer 3 is a functional layer that scatters external light from the optical laminate 11 by forming fine irregularities on its surface.

[0028] The anti-glare layer 3 is formed by coating a coating liquid containing an active energy ray curable compound, organic microparticles and / or inorganic microparticles (fillers) onto a transparent substrate 2 and then curing the coating.

[0029] As an active energy ray-curable compound, monofunctional, difunctional, or trifunctional (meth)acrylate monomers can be used, for example. It should be noted that 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 groups.

[0030] 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, tert-butyl (meth)acrylate, glycidyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, and so on. Isodecanyl acrylate, lauryl acrylate, tridecyl acrylate, hexadecyl acrylate, octadecyl acrylate, benzyl acrylate, 2-ethoxyethyl acrylate, 3-methoxybutyl acrylate, ethyl carbitol acrylate, methacrylate, ethylene oxide modified methacrylate, phenoxy(meth)acrylate, ethylene oxide modified phenoxy(meth)acrylate, propylene 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 acrylate, hydrogenated 2-(meth)acryloyloxyethyl phthalate, hydrogenated 2-(meth)acryloyloxyethyl phthalate 2-(meth)acryloyloxypropyl ester, 2-(meth)acryloyloxypropyl hexahydrogenated phthalic acid, 2-(meth)acryloyloxypropyl tetrahydrogenated phthalic acid, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, and adamantane derivatives of mono(meth)acrylates derived from 2-adamantane and adamantanediol, such as adamantane acrylate and other adamantane derivatives of mono(meth)acrylates.

[0031] Examples of difunctional (meth)acrylate compounds include: 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, hydroxypentyl acid neopentyl glycol di(meth)acrylate, and other di(meth)acrylates.

[0032] Examples of trifunctional or higher (meth)acrylate compounds include: trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, glycerol tri(meth)acrylate, etc.; and trifunctional (meth)acrylates such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and di(trimethylolpropane)acrylate. Acrylates; polyfunctional (meth)acrylates such as pentaerythritol tetra(meth)acrylate, di(trimethylolpropane)tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, di(trimethylolpropane) penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and di(trimethylolpropane) hexa(meth)acrylate; and polyfunctional (meth)acrylates such as those with three or more functions, wherein a portion of these (meth)acrylates is replaced by alkyl groups or ε-caprolactones.

[0033] Alternatively, urethane (meth)acrylates can also be used as multifunctional monomers. Examples of urethane (meth)acrylates include those obtained by reacting a product obtained by reacting an isocyanate monomer or prepolymer with a polyester polyol with a (meth)acrylate monomer having hydroxyl groups.

[0034] 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.

[0035] One or more of the aforementioned multifunctional monomers can be used. Furthermore, the aforementioned multifunctional monomers in the coating liquid can be monomers or oligomers formed by partial polymerization.

[0036] Organic microparticles are materials that primarily form fine irregularities on the surface of the anti-glare layer 3, thereby imparting the function of scattering external light. As organic microparticles, resin particles composed of light-transmitting resin materials such as acrylic resin, polystyrene resin, styrene-(meth)acrylate copolymer, polyethylene resin, epoxy resin, silicone resin, polyvinylidene fluoride, and polyvinyl fluoride-based resins can be used. To adjust the refractive index and the dispersion of the resin particles, two or more resin particles with different materials (refractive indices) can also be mixed and used. The average particle size of the organic microparticles is preferably 0.5–10 μm.

[0037] The inorganic microparticles added to the composition for forming the anti-glare layer are preferably nanoparticles with an average particle size of 10 to 200 nm.

[0038] Inorganic microparticles are materials primarily used to adjust the sedimentation and aggregation of organic microparticles in the anti-glare layer 3. These inorganic microparticles can include silica microparticles, metal oxide microparticles, and various mineral microparticles. Examples of silica microparticles include colloidal silica or silica microparticles surface-modified with reactive functional groups such as (meth)acryloyl groups. Examples of metal oxide microparticles include alumina, zinc oxide, tin oxide, antimony oxide, indium oxide, titanium dioxide, and zirconium oxide. Examples of mineral microparticles include mica, synthetic mica, vermiculite, montmorillonite, iron montmorillonite, bentonite, beidellite, saponite, hectorite, stevensite, nontronite, magadiite, illite, kanemite, layered titanate, smectite, and synthetic smectite. The mineral microparticles can be either natural or synthetic (including substituted products and derivatives), or a mixture of both. Layered organoclay is more preferred among the mineral microparticles. Layered organoclay refers to a substance in which organonium ions are introduced into the interlayer of bentonite. There are no restrictions on the organonium ions as long as they can be organically converted using the cation exchange capacity of bentonite. When using layered organoclay minerals as mineral microparticles, the aforementioned synthetic montmorillonite is preferred. Synthetic montmorillonite has the function of increasing the viscosity of the composition for forming the anti-glare layer, inhibiting the sedimentation of resin particles and inorganic microparticles, thereby adjusting the surface irregularity of the optical functional layer.

[0039] To cure the composition for forming the anti-glare layer using ultraviolet (UV) irradiation, a polymerization initiator can also be added. As a polymerization initiator, a polymerization initiator that generates free radicals upon UV irradiation can be used. Examples of free radical polymerization initiators include acetophenone-based, benzophenone-based, thioxanthone-based, benzoin, benzoin methyl ether, and phosphine oxide. Examples of polymerization initiators include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-diethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-phenylacetophenone, bibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, and 2-chlorothioxanthone. These can be used alone or in combination of two or more.

[0040] Furthermore, in the composition for forming the anti-glare layer, anti-fouling agents, leveling agents, oleophobic agents, hydrophobic agents, and anti-fingerprint adhesion agents are preferably added as components to improve anti-fouling properties. Fluorinated compounds or organosilicon compounds are preferably used as these additives. By adding anti-fouling compounds to the outermost anti-glare layer 3, fingerprint wiping properties can be further improved. In addition, various additives such as antistatic agents, defoamers, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, and photosensitizers can be added as needed.

[0041] In addition, a solvent may be added to the composition for forming the anti-glare layer as needed. One or a mixture of two or more of the following may be used as a solvent: alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropanol, and isobutanol; ketones such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ketols such as diacetone alcohol; aromatic hydrocarbons such as benzene, toluene, and xylene; diols such as ethylene glycol, propylene glycol, and hexanediol; diol 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.

[0042] (Low refractive index layer)

[0043] The low refractive index layer 4 is a functional layer that has a lower refractive index than the lower anti-glare layer 3. It reduces surface reflection of the optical laminate 11 by interfering with the light reflected at the interface between the low refractive index layer 4 and the anti-glare layer 3 to cancel the light reflected on the surface of the low refractive index layer 4.

[0044] The low refractive index layer 4 can be formed by coating the surface of the anti-glare layer 3 with a coating liquid containing an adhesive resin 40, low refractive index microparticles and solid particles 42 as needed, and then curing the coating. Additionally, the low refractive index layer 4 has a protrusion 43 containing the solid particles 42 of the low refractive index layer 4, protruding beyond the portion of the low refractive index layer 4 where the solid particles 42 are not present.

[0045] The adhesive resin 40 used to form the low refractive index layer 4 can be, for example, a compound exemplified as a material for the anti-glare layer 3. However, since the refractive index can be easily reduced using fluorine-based compounds, it is preferable to use a fluorine-based compound. Examples of fluorine-based compounds include perfluorodecanoic acid diurethane acrylate.

[0046] As low-refractive-index microparticles, LiF, MgF, 3NaF·AlF, or AlF (all with a refractive index of 1.4), or Na3AlF6 (cryolite with a refractive index of 1.33) microparticles, or silica microparticles with internal voids can be preferred. Since silica microparticles with internal voids (hollow particles 41) can make the void portion have the refractive index of air (approximately 1), it is beneficial to make the low-refractive-index layer 4 low-refractive-index. Specifically, porous silica particles or shell-structured silica particles can be used as hollow particles 41. It should be noted that in this embodiment, it is assumed that the low-refractive-index layer 4 contains hollow particles 41, but low-refractive-index microparticles 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 anti-glare layer 3, the low-refractive-index microparticles can also be omitted.

[0047] The solid particles 42 have a larger particle size than the hollow particles 41; for example, silica microparticles without internal voids can be used. Therefore, compared to the hollow particles 41 with internal voids, the solid particles 42 are less prone to breakage. It should be noted that... Figure 2 In the study, the measured particle size of solid particles 42 is 122 nm, 116 nm, and 117 nm, but it is not limited to these values. For example, it can be 110 nm to 210 nm.

[0048] As described above, by containing a fluorine compound in the low-refractive-index layer 4, the low-refractive-index layer 4 can be easily made to have a low refractive index. However, since the fluorine compound itself is soft, the scratch resistance of the low-refractive-index layer 4 is reduced. Furthermore, when the low-refractive-index layer 4 contains hollow particles 41, the low-refractive-index layer 4 can be made to have a low refractive index through the voids inside the hollow particles 41. However, since the hollow particles 41 are easily broken, the scratch resistance of the low-refractive-index layer 4 decreases as the content of hollow particles 41 increases. Therefore, in this embodiment, as... Figure 2 and Figure 3 As shown, the presence of solid particles 42 in the low refractive index layer 4 improves scratch resistance. Specifically, assuming a friction test is conducted on the surface of the low refractive index layer 4 using steel wool 5, the solid particles 42 become the contact points with the steel wool 5, while the contact area between the hollow particles 41 and the adhesive resin 40 and the steel wool 5 is reduced. Therefore, damage to the low refractive index layer 4 can be suppressed, and scratch resistance can be improved. It should be noted that if the low refractive index layer 4 does not contain solid particles 42, as... Figure 4 As shown, the contact area between the hollow particles 41 and the adhesive resin 40 and the steel wool 5 increases, making the low refractive index layer 4 more susceptible to damage and reducing its scratch resistance.

[0049] 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 preferably 8 to 320 per 25 μm. 2 The number of solid particles 42 is less than 8 per 25 μm. 2 In cases where the number of solid particles 42 at the contact points is small, no improvement in scratch resistance can be achieved. When the number of solid particles 42 exceeds 320 per 25 μm... 2 In this case, the resin component of the low refractive index layer 4 cannot maintain solid particles 42, thus reducing scratch resistance.

[0050] Hereinafter, the average particle size of the hollow particles 41 is set as D1, the average particle size of the solid particles 42 is set as D2, the average film thickness of the portion of the low refractive index layer 4 where there are no solid particles 42 is set as T1, and the average film thickness of the protrusions 43 is set as T2. The average film thickness is the average of the film thicknesses at any three locations in the low refractive index layer 4.

[0051] 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).

[0052] 1.4≤D2 / D1≤2.8…(1)

[0053] When D2 / D1 is less than 1.4, the protrusion 43 cannot fully function as a contact point of the low-refractive-index layer 4. Therefore, even if the low-refractive-index layer 4 contains solid particles 42, the improvement in scratch resistance is small. Furthermore, when D2 / D1 exceeds 2.8, the hollow particles 41, which have relatively small particle sizes and low scratch resistance, accumulate and protrude more than the solid particles 42, thus deteriorating scratch resistance.

[0054] In addition, the optical laminate 11 involved in this embodiment preferably satisfies the following condition (2).

[0055] 1.0≤D2 / T1≤2.0…(2)

[0056] When D2 / T1 is less than 1.0, the average particle size D2 of the solid particles 42 is equal to or less than the average film thickness T1 of the low-refractive-index layer 4. Therefore, the protrusions 43 cannot fully function as contact points in the low-refractive-index layer 4. Consequently, even if the low-refractive-index layer 4 contains solid particles 42, the improvement in scratch resistance is minimal. Furthermore, when D2 / T1 exceeds 2.0, the low-refractive-index layer 4 cannot retain the solid particles, causing them to detach and resulting in poor scratch resistance.

[0057] In addition, the optical laminate 11 involved in this embodiment preferably satisfies the following condition (3).

[0058] 1.1≤T2 / T1≤2.2…(3)

[0059] When T2 / T1 is less than 1.1, the surface of the low-refractive-index layer 4 is nearly flat, and the protrusions 43 cannot fully function as the outermost contact point. Therefore, even if the low-refractive-index layer 4 contains solid particles 42, the improvement in scratch resistance is small. Furthermore, when T2 / T1 exceeds 2.2, the low-refractive-index layer 4 deteriorates, its reflectivity increases, or it develops unevenness on the surface, resulting in a deteriorated appearance.

[0060] Furthermore, regarding the optical laminate 11, the SCI reflectance Y, measured by blackening the other side of the transparent substrate 2, is preferably 1.5% or less. SCI reflectance is the reflectance of all reflected light, including specular reflection, measured using the SCI (Specular Component Include) method, and can be measured according to JIS Z8722. If the SCI reflectance Y is 1.5% or less, it meets the requirements for automotive applications.

[0061] The low-refractive-index layer 4 is the outermost functional layer. Therefore, in the composition for forming the low-refractive-index layer, antifouling agents, leveling agents, oleophobic agents, hydrophobic agents, and anti-fingerprint agents are preferably added as components to improve antifouling properties. Fluorinated compounds or organosilicon compounds are preferably used as these additives. In addition, various additives such as antistatic agents, defoamers, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, and photosensitizers may be added as needed.

[0062] Between the transparent substrate 2 and the anti-glare layer 3, one or more other functional layers may be stacked, such as a hard coating layer, a high refractive index layer, a medium refractive index layer, an antistatic layer, an electromagnetic wave blocking layer, an infrared absorption layer, an ultraviolet absorption layer, and a color correction layer.

[0063] There are no particular limitations on the coating method for the above-mentioned anti-glare layer forming composition and low refractive index layer forming composition. For example, a spin coater, roller coater, reverse roller coater, gravure coater, micro-gravure coater, air knife coater, bar coater, wire bar coater, die coater, dip coater, sprayer, applicator, etc. can be used for coating.

[0064] The optical laminate 11 described in this embodiment can be attached to the outermost surface of an image display panel such as a liquid crystal panel or an organic EL panel to form an image display device. A touch panel can also be disposed between the optical laminate 11 and the image display panel.

[0065] Example

[0066] The following describes specific embodiments of the present invention.

[0067] (Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3)

[0068] A 40 μm thick triacetyl cellulose membrane was used as the transparent substrate. A coating solution for forming an anti-glare layer was prepared, containing a binder resin, filler, photopolymerization initiator, and solvent. The coating solution was applied to the transparent substrate to achieve a cured film thickness of 5 μm. After drying, the coating was polymerized and cured by ultraviolet irradiation to form an anti-glare layer. Next, a low-refractive-index layer coating solution was prepared on the anti-glare layer, containing a binder resin formulated in a ratio of 20 parts by weight of pentaerythritol triacrylate and 80 parts by weight of perfluorodecanoic acid diurethane acrylate, as well as solid silica particles and hollow silica particles with the average particle sizes shown in Table 1. The low-refractive-index layer coating solution was applied to the anti-glare layer to achieve a cured film thickness as shown in Table 1. After drying, the coating was polymerized and cured by ultraviolet irradiation to form a low-refractive-index layer.

[0069] (Compare Examples 1-4 and 1-5)

[0070] In Comparative Examples 1-4, solid silica particles were not added to the coating solution for forming the low refractive index layer. Otherwise, optical laminates with an anti-glare layer and a low refractive index layer stacked on a transparent substrate were fabricated in the same manner as in Examples 1-1. Comparative Examples 1-5 were the same as Comparative Examples 1-4, except that the average particle size of the hollow silica was further changed to 57 nm.

[0071] It should be noted that the number of solid silica particles shown in Table 1 is a value determined based on STEM images of the surface of the fabricated optical laminate, and is the average number of particles in any 10 regions of the surface. In Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3, by changing the content ratio of solid silica particles in the coating solution for forming the low refractive index layer, the number of particles per 25 μm was increased. 2 The number of solid silica particles was adjusted to the values ​​shown in Table 1.

[0072] The optical laminates involved in each embodiment and comparative example are evaluated below.

[0073] <Evaluation 1: Abrasion Resistance Evaluation>

[0074] The optical laminates obtained in the examples and comparative examples were placed on a vibration-type friction fastness testing machine (AB-301, manufactured by TESTER Sangyo Co., Ltd.) and subjected to a test at 150 g / cm. 2 The pressure was applied to the surface of the optical laminate, and an abrasion resistance test was conducted 10 times. After the abrasion resistance test, the surface of the optical laminate was visually observed and evaluated according to the following criteria.

[0075] 〇: No scars

[0076] ×: There is one or more scars

[0077] <Evaluation 2: SCI reflectance Y>

[0078] In the optical laminates obtained in the examples and comparative examples, the other side of the transparent substrate was blackened, and the SCI reflectance Y was measured. The SCI reflectance Y was measured according to JIS Z8722 using a spectrophotometer (CM-2600d, manufactured by Konica Minolta Japan Co., Ltd.). The measurement conditions were: measurement diameter / illumination diameter φ8mm / φ11mm, observation condition 10° field of view, and observation light source D65. When measuring with a measurement diameter of 8mm, the relatively high and low reflectance portions caused by uneven coating can be contained within a single field of view, thus obtaining an average measured value for the SCI reflectance. Furthermore, a 10° field of view corresponds to viewing an area with a diameter of 8.8cm at a distance of 50cm; however, in automotive applications, where larger areas of the image display device are viewed at close range, a 10° field of view measurement is more appropriate. D65 is the average midday light in Europe / Northern Europe as defined by the International Commission on Illumination, having a wavelength distribution close to external light, and is therefore suitable for measurement. This evaluation was conducted according to the following criteria.

[0079] 〇: SCI reflectance Y≤1.5

[0080] ×: SCI reflectance Y > 1.5

[0081] <Overall Evaluation>

[0082] A comprehensive evaluation will be conducted based on the results of Evaluation 1 and Evaluation 2. This evaluation is based on the following criteria.

[0083] 〇: The evaluation results for both Evaluation 1 and Evaluation 2 are 〇.

[0084] ×: Either the evaluation result of Evaluation 1 or Evaluation 2 is ×

[0085] Table 1 shows the evaluation results of the average particle size of solid silica particles, the average particle size of hollow silica particles, the number of solid silica particles, the ratio of the average particle size of solid silica particles to that of hollow silica particles (D2 / D1), scratch resistance, and SCI reflectivity.

[0086]

[0087] As shown in Table 1, in the optical laminates involved in Examples 1-1 to 1-7, the number of solid silica particles is 8 to 320 per 25 μm. 2 The ratio of the average particle size of solid silica particles to that of hollow silica particles, D2 / D1, both satisfy condition (1). Therefore, in the scratch resistance evaluation, the contact area between the adhesive of the optical laminate and the hollow silica particles and the steel wool is smaller, resulting in good scratch resistance. In addition, the SCI reflectivity Y is below 1.5, indicating good low reflectivity.

[0088] In the optical laminates involved in Comparative Examples 1-1 to 1-2, the average particle size of the solid silica particles was too small to be observed, thus making it impossible to observe the 25 μm diameter of the optical laminates. 2 The number of solid silica particles within the area is counted. Furthermore, since the average particle size of the solid silica particles is less than or equal to the average particle size of the hollow silica particles, the contact area between the low-refractive-index layer and the steel wool is increased, resulting in lower scratch resistance.

[0089] In Comparative Examples 1-3, the optical laminates exhibit reduced scratch resistance due to the accumulation of hollow silica particles caused by the larger average particle size of the solid silica particles compared to the average particle size of the hollow silica particles.

[0090] The optical laminates involved in Comparative Examples 1-4, because no solid silica particles were added to the low-refractive-index layer, exhibited similar characteristics to Comparative Examples 1-1 and 1-2, resulting in a larger contact area between the low-refractive-index layer and the steel wool, leading to lower scratch resistance. On the other hand, in Comparative Example 1-5, due to the small particle size of the hollow silica particles and the reduced hollowness, the refractive index of the hollow particles increased, resulting in an SCI reflectance Y exceeding 1.5 and poor low reflectivity.

[0091] It has been confirmed from the above that by making the ratio of the average particle size of solid silica particles to the average particle size of hollow silica particles, D2 / D1, satisfy condition (1), even when using fluororesin as the binder resin for the low refractive index layer, an optical laminate with excellent scratch resistance and low reflectivity can be achieved.

[0092] (Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-3)

[0093] A 40 μm thick triacetyl cellulose membrane was used as the transparent substrate. A coating solution for forming an anti-glare layer, containing binder resin, filler, photopolymerization initiator, and solvent, was prepared. The coating solution was applied to the transparent substrate to a cured film thickness of 5 μm. After drying, the coating was polymerized and cured by ultraviolet irradiation to form an anti-glare layer. Next, a low-refractive-index layer coating solution was prepared on the anti-glare layer, containing a binder resin formulated 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 with the average particle size shown in Table 2. The low-refractive-index layer coating solution was applied to the anti-glare layer to a cured film thickness as shown in Table 2. After drying, the coating was polymerized and cured by ultraviolet irradiation to form a low-refractive-index layer.

[0094] (Compare Examples 2-4 and 2-5)

[0095] In Comparative Examples 2-4, solid silica particles were not added to the coating solution for forming the low refractive index layer. Otherwise, an optical laminate with an anti-glare layer and a low refractive index layer stacked on a transparent substrate was fabricated in the same manner as in Examples 1-1. Comparative Examples 2-5 were the same as Comparative Examples 2-4, except that the average particle size of the hollow silica was further changed to 57 nm.

[0096] It should be noted that the film thickness of the low-refractive-index layer shown in Table 2 is a value measured from a STEM image of the cross-section of the fabricated optical laminate, and is the average film thickness at any 10 locations between the protrusions of the low-refractive-index layer where no solid particles are present. Furthermore, the number of solid silica particles shown in Table 2 is a value measured from a STEM image of the surface of the fabricated optical laminate, and is the average number of particles at any 10 locations on the surface. In Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-3, by changing the proportion of solid silica particles in the coating solution for forming the low-refractive-index layer, the thickness of each 25 μm layer was increased. 2 The number of solid silica particles was adjusted to the values ​​shown in Table 2.

[0097] The scratch resistance and SCI reflectivity Y of the optical laminates involved in each embodiment and comparative example were evaluated in the same manner as in Examples 1-1. Furthermore, a comprehensive evaluation was performed using the same criteria as in Examples 1-1.

[0098] Table 2 shows the evaluation results of the average particle size of solid silica particles, the film thickness of the low refractive index layer, the number of solid silica particles, the ratio of the average particle size of solid silica particles to the film thickness of the low refractive index layer (D2 / T1), scratch resistance, and SCI reflectivity.

[0099]

[0100] As shown in Table 2, in the optical laminates involved in Examples 2-1 to 2-7, the number of solid silica particles is 8 to 320 per 25 μm. 2 The ratio of the average particle size of the solid silica particles to the film thickness of the low refractive index layer, D2 / T1, both satisfy condition (2). Therefore, in the scratch resistance evaluation, the contact area between the adhesive of the optical laminate and the hollow silica particles and the steel wool is smaller, resulting in good scratch resistance. In addition, the SCI reflectivity Y is below 1.5, indicating good low reflectivity.

[0101] In the optical laminates involved in Comparative Examples 2-1 to 2-2, the average particle size of the solid silica particles is too small to be observed, thus making it impossible to observe the 25 μm diameter of the optical laminates. 2 The number of solid silica particles within the region was counted. Furthermore, compared to the film thickness of the low-refractive-index layer, the average particle size of the solid silica particles is sufficiently small, thus increasing the contact area between the low-refractive-index layer and the steel wool, resulting in low scratch resistance.

[0102] In the optical laminates involved in Comparative Examples 2-3, the average particle size of the solid silica particles is large relative to the film thickness of the low refractive index layer, exceeding the upper limit of condition (2). Compared with the film thickness of the low refractive index layer, the average particle size of the solid silica particles is too large, so the solid silica particles cannot be maintained, and the scratch resistance deteriorates.

[0103] In Comparative Examples 2-4, the optical laminate did not contain solid silica particles in the low-refractive-index layer. Therefore, similar to Comparative Examples 2-1 and 2-2, the contact area between the low-refractive-index layer and the steel wool was larger, resulting in lower scratch resistance. On the other hand, in Comparative Example 2-5, the hollow silica particles had small particle sizes, leading to a lower hollowness and an increased refractive index. Consequently, the SCI reflectance Y exceeded 1.5, resulting in poor low reflectivity.

[0104] The above confirms that by ensuring that the ratio of the average particle size of the solid silica particles to the film thickness of the low refractive index layer, D2 / T1, satisfies condition (2), an optical laminate with excellent scratch resistance and low reflectivity can be achieved even when using fluororesin as the binder resin for the low refractive index layer.

[0105] (Examples 3-1 to 3-7 and Comparative Examples 3-1 to 3-3)

[0106] A 40 μm thick triacetyl cellulose membrane was used as the transparent substrate. A coating solution for forming an anti-glare layer, containing binder resin, filler, photopolymerization initiator, and solvent, was prepared. The coating solution was applied to the transparent substrate to a cured film thickness of 5 μm. After drying, the coating was polymerized and cured by ultraviolet irradiation to form an anti-glare layer. Next, a coating solution for forming a low-refractive-index layer, containing binder resin and solid silica particles with the average particle size shown in Table 3, was prepared on the anti-glare layer. The low-refractive-index layer coating solution was applied to the anti-glare layer to a cured film thickness as shown in Table 3. After drying, the coating was polymerized and cured by ultraviolet irradiation to form a low-refractive-index layer.

[0107] (Comparative Examples 3-4)

[0108] Except that solid silica particles were not added to the coating liquid for forming the low refractive index layer, an optical laminate with an anti-glare layer and a low refractive index layer stacked on a transparent substrate was fabricated in the same manner as in Example 3-1.

[0109] (Comparative Examples 3-5)

[0110] Comparative Examples 3-5 are the same as Comparative Examples 3-4, except that the average particle size of the hollow silica is further changed to 57 nm.

[0111] It should be noted that the film thickness of the low refractive index layer shown in Table 3 is a value measured from a cross-sectional STEM image of the fabricated optical laminate, and is the average film thickness at any 10 locations between the protrusions of the low refractive index layer where no solid particles are present. The film thickness of the protrusions shown in Table 3 is a value measured from a cross-sectional STEM image of the fabricated optical laminate, and is the average film thickness of the low refractive index layer at any 10 protrusions. Furthermore, the number of solid silica particles shown in Table 3 is a value measured from a STEM image of the surface of the fabricated optical laminate, and is the average number of particles at any 10 locations on the surface. In Examples 3-1 to 3-7 and Comparative Examples 3-1 to 3-3, by changing the proportion of solid particles in the coating solution for forming the low refractive index layer, the number of particles per 25 μm was increased. 2 The number of solid silica particles was adjusted to the values ​​shown in Table 3.

[0112] The scratch resistance and SCI reflectivity Y of the optical laminates involved in each embodiment and comparative example were evaluated in the same manner as in Examples 1-1. Furthermore, a comprehensive evaluation was performed using the same criteria as in Examples 1-1.

[0113] Table 3 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 of the film thickness of the protrusions to the film thickness of the low refractive index layer (T2 / T1), scratch resistance, and SCI reflectivity.

[0114]

[0115] As shown in Table 3, in the optical laminates involved in Examples 3-1 to 3-7, the number of solid particles is 8 to 320 per 25 μm. 2 The ratio of the film thickness of the low refractive index layer to the film thickness of the protrusion, T2 / T1, both satisfy condition (3). Therefore, in the scratch resistance evaluation, the contact area between the adhesive and hollow silica particles of the optical laminate and the steel wool is smaller, resulting in good scratch resistance. In addition, the SCI reflectivity Y is below 1.5, indicating good low reflectivity.

[0116] In the optical laminates involved in Comparative Examples 3-1 to 3-2, the average particle size of the solid silica particles was too small to be observed, thus making it impossible to observe the 25 μm diameter of the optical laminates. 2 The number of solid particles within the area is counted. Furthermore, because the average particle size of the solid silica particles is too small, no protrusions are formed on the surface of the low-refractive-index layer. Therefore, the contact area between the low-refractive-index layer and the steel wool is increased, resulting in low scratch resistance.

[0117] In the optical laminate involved in Comparative Example 3-3, the thickness of the protrusion of the low refractive index layer is too large compared with the film thickness of the portion of the low refractive index layer excluding the protrusion. Therefore, the protrusion cannot be maintained, resulting in scratch resistance and appearance degradation.

[0118] The optical laminate involved in Comparative Examples 3-4 did not have any protrusions formed, just like Comparative Examples 3-1 and 3-2, because no solid particles were added to the low refractive index layer. As a result, the contact area between the low refractive index layer and the steel wool increased, and the scratch resistance was low.

[0119] In addition, in Comparative Examples 3-5, due to the small particle size of the hollow silica particles, the hollowness ratio is reduced, and the refractive index of the hollow particles is increased. Therefore, the SCI reflectance Y exceeds 1.5, and the low reflectivity is also poor.

[0120] It has been confirmed from the above that by making the ratio of the thickness of the protrusion to the thickness of the low refractive index layer, T2 / T1, satisfy condition (3), even when using fluororesin as the binder resin for the low refractive index layer, an optical laminate with excellent scratch resistance and low reflectivity can be achieved.

[0121] Industrial applicability

[0122] This invention can be used as an optical laminate disposed on the outermost surface of an image display device such as an automotive application.

[0123] Explanation of symbols

[0124] 2 Transparent substrate

[0125] 3 Anti-glare layer

[0126] 4 Low-refractive-index layer

[0127] 11 Optical laminates

[0128] 40 Adhesive Resin

[0129] 41 Hollow particles

[0130] 42 solid particles

[0131] 43. Protrusion

Claims

1. An optical laminate comprising an optical laminate having a low-refractive-index layer on the outermost surface of one side of a transparent substrate, wherein, The low-refractive-index layer comprises adhesive resin, hollow particles, and solid particles. The average particle size D1 of the hollow particles and the average particle size D2 of the solid particles satisfy the condition 1.4 ≤ D2 / D1 ≤ 2.

8. The number of solid particles in the low-refractive-index layer is 8–320 per 25 μm. 2 .

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

3. An image display device comprising the optical laminate as described in claim 1 or 2.

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