Antireflective film, and image display device using same

Abstract

Provided are: an antireflective film which has low haze and excellent antiglare properties and in which reductions in antiglare properties when viewed obliquely are suppressed; and an image display device using the antireflective film. An antireflective film in which at least one optical functional layer is laminated on a translucent substrate, wherein an uneven shape is formed on at least one surface of the optical functional layer, fine particles having a plurality of projections are contained in the optical functional layer, and a curvature radius r1 of the core of the fine particles and a curvature radius r2 of the projections of the fine particles satisfy (A) 0.75 μm≤r1≤4.0 μm, (B) 0.05 μm≤r2≤1.0 μm, and (C) 0.25 μm≤r1-r2.

Description

Anti-reflection film and image display device using the same

[0001] The present invention relates to an anti-reflection film and an image display device using the same.

[0002] When a display is used in a relatively bright location such as outdoors or under fluorescent lights, reflection of external light such as sunlight or fluorescent lights on the display can be a problem. To prevent this reflection, anti-glare films are used, which have fine irregularities on their surfaces and diffuse the reflected external light.

[0003] Antiglare films include those obtained by coating a transparent film with a transparent resin and then performing a shaping process using a shaping mold with irregularities, and those obtained by coating a transparent film with a paint in which inorganic or organic transparent fine particles are dispersed in a resin binder (for the latter, see, for example, Patent Documents 1 to 3).

[0004] Japanese Patent No. 4839212 Japanese Patent Application Laid-Open No. 2009-122490 Japanese Patent Application Laid-Open No. 2012-220898

[0005] When anti-glare films are designed to have high anti-glare properties, the haze tends to increase as well, resulting in a decrease in panel contrast and a loss of the luxurious feel due to cloudiness.

[0006] Furthermore, with anti-glare treatments using shaping treatments and the anti-glare films described in Patent Documents 1 to 3, even if the anti-glare performance is high when viewed from the front (in the range of 0 to 30 degrees relative to the normal to the screen), there is a problem in that the anti-glare performance is significantly reduced when viewed from an oblique angle (in the range of 45 degrees or more relative to the normal to the screen) compared to when viewed from the front.

[0007] Therefore, an object of the present invention is to provide an anti-reflection film that has low haze and high anti-glare properties and in which the deterioration of the anti-glare properties when viewed from an oblique angle is suppressed, and an image display device using the same.

[0008] The antireflection film according to the present invention is characterized in that at least one optical functional layer is laminated on a light-transmitting substrate, the optical functional layer has an uneven shape formed on at least one surface thereof, the optical functional layer contains fine particles having a plurality of protrusions, and the radius of curvature r1 of the core of the fine particles and the radius of curvature r2 of the protrusions of the fine particles satisfy the following formulas (A), (B), and (C): 0.75 μm≦r1≦4.0 μm (A), 0.05 μm≦r2≦1.0 μm (B), and 0.25 μm≦r1-r2 (C).

[0009] An image display device according to the present invention includes an image display panel and the above-described anti-reflection film.

[0010] The present invention can provide an anti-reflection film that has low haze and high anti-glare properties and in which the deterioration of the anti-glare properties when viewed from an oblique angle is suppressed, and an image display device using the same.

[0011] FIG. 1 is a cross-sectional view schematically showing an antireflection film according to an embodiment. FIG. 2 is an SEM image of a particle having a plurality of protrusions. FIG. 3 is a schematic diagram of a particle having a plurality of protrusions. FIG. 4 is a graph showing the relationship between the light-receiving angle and the relative value of the reflected light amount. FIG. 5 is a graph showing the relationship between the light-receiving angle and the relative value of the reflected light amount for the antireflection film according to Example 1. FIG. 6 is a graph showing the relationship between the light-receiving angle and the relative value of the reflected light amount for the antireflection film according to Comparative Example 1.

[0012] FIG. 1 is a cross-sectional view schematically illustrating an anti-reflection film according to an embodiment.

[0013] The anti-reflection film 1 includes a light-transmitting substrate 2 and an anti-glare layer 3 laminated on one surface of the light-transmitting substrate 2. The anti-glare layer 3 is an optically functional layer that scatters incident light with fine irregularities formed on the surface, thereby suppressing the glare of external light. The anti-reflection film 1 including the anti-glare layer 3 is also called an AG film.

[0014] The light-transmitting substrate 2 is a film that serves as the base of the anti-reflection film 1, and is made of a material that has excellent transmittance to visible light. Examples of materials that can be used to form the light-transmitting 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 polysulfones, as well as transparent resins and inorganic glass. The thickness of the light-transmitting substrate 2 is not particularly limited, but is preferably 10 to 200 μm.

[0015] The surface of the light-transmitting 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.

[0016] The antiglare layer 3 is a functional layer that forms a fine uneven shape on the outermost surface of the antireflection film 1 .

[0017] The antiglare layer 3 contains fine particles (filler) having a plurality of protrusions. The antiglare layer 3 is formed by applying a coating liquid containing an ultraviolet-curable compound, fine particles, and a photopolymerization initiator to the light-transmitting substrate 2 and curing the coating film.

[0018] As the ultraviolet-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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] FIG. 2 is an SEM image of a particle having a plurality of protrusions, and FIG. 3 is a schematic diagram of a particle having a plurality of protrusions.

[0026] The fine particles are a material that forms minute irregularities on the surface of the antiglare layer 3 and provides the function of diffusing external light. As shown in Fig. 2, the fine particles have a spherical core and a plurality of protrusions protruding from the surface of the core. The protrusions on the surface of the fine particles have a shape that approximates a portion of a sphere, and the outer surfaces of the protrusions are substantially spherical. The fine particles are made of a resin, and examples of the material that can be used for the fine particles include acrylic resins and polymethylsilsesquioxane (PMSQ).

[0027] Here, the radius of curvature of the core is r1, and the radius of curvature of the protrusion is r2 (see FIG. 3). The radii of curvature r1 and r2 are approximate values ​​measured assuming the core and protrusions to be spheres, and specifically, are values ​​calculated as the radius of a circle passing through any three points on the outline of the core and protrusions that appear on the SEM image. As an example, in FIG. 3, a circle passing through any three points on the outline of one protrusion is shown by a dashed line. The radii of curvature r1 and r2 of the fine particles used in the anti-reflection film according to this embodiment satisfy the following formulas (A), (B), and (C): 0.75 μm≦r1≦4.0 μm (A) 0.05 μm≦r2≦1.0 μm (B) 0.25 μm≦r1-r2 (C)

[0028] When the radius of curvature r1 of the core is less than 0.75 μm, the haze is small, but the antiglare properties are also reduced. When the radius of curvature r2 of the core is more than 4.0 μm, the antiglare properties are high, but the haze is also high. When the radius of curvature r1 of the core is within the range of formula (A), high antiglare properties and low haze can both be achieved. Note that the haze of the antireflection film according to the present invention should be 20% or less, and more preferably 15% or less.

[0029] If the curvature radius r2 of the protrusions is less than 0.05 μm, the shape of the fine particles becomes nearly spherical, resulting in a decrease in the anti-glare properties when the anti-reflection film is viewed obliquely. If the curvature radius r2 of the protrusions exceeds 1.0 μm, the anti-glare properties when the anti-reflection film is viewed obliquely are also decreased. Furthermore, if r2 is too large, it becomes difficult to produce the fine particles.

[0030] If the difference in the radii of curvature r1-r2 becomes too small, it becomes difficult to produce fine particles, so the practical lower limit of r1-r2 is 0.25 or more.

[0031] As the photopolymerization initiator, radical polymerization initiators such as acetophenone-based, benzophenone-based, thioxanthone-based, benzoin, benzoin methyl ether, and acylphosphine oxide can be used. Examples of the photopolymerization initiator 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 may be used alone, or two or more may be used in combination.

[0032] If necessary, inorganic fine particles (inorganic nanoparticles) having an average particle size of 10 to 200 nm may be added to the composition for forming the antiglare layer.

[0033] The inorganic fine particles function as a thickener that increases the viscosity of the antiglare layer-forming composition and are a material for adjusting the sedimentation and aggregation of 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 that can be used include alumina, zinc oxide, tin oxide, antimony oxide, indium oxide, titania, and zirconia. Examples of mineral fine particles that can be used 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. Among the mineral fine particles, layered organic clay is more preferred. Layered organic clay refers to a swelling clay in which organic onium ions are introduced between the layers. The organic onium ions are not limited as long as they can be organized by utilizing the cation exchange property of the swelling clay. When a layered organic clay mineral is used as the mineral fine particles, the above-mentioned synthetic smectite can be preferably used.

[0034] The antiglare layer-forming composition may also contain components for improving antifouling properties, such as an antifouling agent, a leveling agent, an oil repellent, a water repellent, or an antifingerprint agent. Fluorine-containing compounds and silicone compounds can be suitably used as these additives. Other additives, such as antistatic agents, antifoaming agents, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, and photosensitizers, may also be added as needed.

[0035] The antiglare layer-forming composition may contain a solvent, 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.

[0036] Between the light-transmitting 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 as necessary.

[0037] 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.

[0038] It is preferable that the transmitted image clarity Ic and haze Ha of the antireflection film according to the present invention satisfy the following formula (D). Here, the transmitted image clarity Ic is a value measured using an optical comb with a width of 0.5 mm. The haze (total haze) Ha is a value measured in accordance with JIS K7136. (100-Ic) / Ha≧5 (D)

[0039] The value of (100-Ic) / Ha is an index representing the balance between antiglare properties and haze, and when condition (D) is satisfied, high antiglare properties and low haze can both be achieved.

[0040] 4 is a graph showing the relationship between the light-receiving angle and the relative value of the amount of reflected light. The light-receiving angle shown in FIG. 4 represents the angle of reflected light other than specularly reflected light, with the angle of specularly reflected light being taken as the reference angle (0°).

[0041] Let x be the maximum relative value of the reflected light amount relative to the amount of incident light incident at an incident angle of 30°, and y be the maximum relative value of the reflected light amount relative to the amount of incident light incident at an incident angle of 60°. Here, the relative value of the reflected light amount is the ratio of the amount of reflected light to the amount of incident light, and the maximum values ​​x and y are the maximum values ​​measured while changing the light-receiving angle. Also, let α be the width (1 / 10 value width) of the light-receiving angle at which the relative value of the reflected light amount is 1 / 10 or more of the maximum value x, and let β be the width (1 / 10 value width) of the light-receiving angle at which the relative value of the reflected light amount is 1 / 10 or more of the maximum value y. Figure 4 shows x, y, α, and β.

[0042] The antireflection film of the present invention preferably satisfies the following formula (E): β / α≧0.95 (E)

[0043] The value of β / α is one of the indicators of the antiglare properties when the antireflection film is observed from an oblique direction. When the condition (E) is satisfied, the diffusion angle of the reflected light is maintained even when the antireflection film is observed from an oblique direction, and the scattering method is unlikely to change even when the angle of incidence increases, so that the antiglare properties when viewed from an oblique direction are good.

[0044] Furthermore, the antireflection film of the present invention preferably satisfies the following (F): y / x≦3.0 (F)

[0045] The value of y / x is one of the indicators of the antiglare properties when the antireflection film is observed from an oblique direction. When condition (F) is satisfied, an increase in the amount of specularly reflected light is required even when the angle of incidence is large, and the antiglare properties when viewed from an oblique direction are good.

[0046] As described above, the anti-reflection film according to this embodiment contains microparticles with multiple protrusions as a filler in the anti-glare layer. When microparticles with multiple protrusions are used, incident light is likely to be multiple-scattered at the protrusions of the microparticles. Although the scattering angle is small, the incident light can be scattered in complex directions in many directions, thereby achieving high anti-glare properties (low image clarity) while maintaining low haze. Furthermore, the microparticles with multiple protrusions multiple-scatter the incident light, thereby efficiently scattering the incident light even when the light is incident from an oblique direction. The anti-reflection film according to this embodiment can achieve both low haze and high anti-glare properties, and therefore, when used in an image display device, it is possible to suppress the effects of external light reflections and reduce the decrease in image contrast.

[0047] The anti-reflection film according to this embodiment can be used to construct 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 anti-reflection film and the image display panel. The anti-reflection film according to this embodiment has excellent anti-glare properties when viewed from an oblique angle, and therefore has high anti-glare properties, can display vivid images, and is suitable for large displays intended to be viewed from multiple directions, such as public information displays (PIDs).

[0048] Examples of specific implementations of the present invention will be described below.

[0049] A 40 μm-thick triacetyl cellulose (TAC) film was used as the light-transmitting substrate. A composition for forming an antiglare layer was prepared by diluting with a solvent a concentration suitable for coating, containing pentaerythritol triacrylate (a UV-curable compound), a filler (fine particles), Omnirad® 184 (a photopolymerization initiator), and an organically treated synthetic clay (an additive) in the proportions shown in Tables 1 and 2 below. The blending ratios shown in Table 1 are in mass %. The composition for forming an antiglare layer was applied to the light-transmitting substrate so that the film thickness after curing was approximately equal to the particle diameter of the fine particles and so that the fine particles were embedded in the antiglare layer. After drying, the coating film was polymerized and cured by UV irradiation to form an antiglare layer, and antireflection films according to each example and comparative example were obtained.

[0050]

[0051]

[0052] The radius of curvature r1 of the core and the radius of curvature r2 of the protrusions of the fine particles used in Examples 1 to 5 and Comparative Examples 3 to 5 were measured as follows: An SEM image of the cross section of the anti-reflection film was obtained, and 100 cores and 100 protrusions of any fine particles included in the SEM image were selected. The radii of circles passing through any three points on the outline of the cores and protrusions were measured, and the average values ​​were taken as r1 and r2.

[0053] (Haze Ha) Haze was measured in accordance with JIS K 7105 using a haze meter (NDH 4000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0054] (Transmitted Image Clarity Ic) The transmitted image clarity was measured in accordance with JIS K 7105 using an image clarity measuring instrument (ICM-1T, manufactured by Suga Test Instruments Co., Ltd.) in transmission mode with an optical comb width of 0.5 mm.

[0055] (Relative Value of Reflected Light Amount) The relative value of reflected light amount was measured using a goniophotometer (goniophotometer, GP-5, manufactured by Murakami Color Research Laboratory Co., Ltd.). A black acrylic plate was attached to the uncoated surface of an antireflection film using an optical adhesive, and used as a measurement sample. In addition, as a reference, a black acrylic plate was attached to one side of a light-transmitting substrate (the same side as the uncoated surface of the antireflection film) using an optical adhesive, and the same side as the coated surface of the antireflection film was used as the measurement surface.

[0056] The measurement conditions for the goniophotometer were set as follows: <Measurement conditions> Measurement mode: Reflection Measurement item: Variable angle VS1 (aperture on the light source (light beam) side): 2.0 VS2 (aperture on the light receiving side): 3.0 IA (incident light angle): 30° or 60° FA (tilt angle): 0.0° Receiving angle range (RA): specular reflection angle ±20° (when incident angle is 30°, R1: 10°, R2: 50°; when incident angle is 60°, R1: 40°, R2: 80°) Sensitivity check: performed (start: R1, end: R2) Neutral density filter: not used ND filter: not used

[0057] The relative value of the reflected light amount was determined by the following method. First, using the measurement surface of the reference, the reflected light amount was measured at intervals of 0.1° within the above-mentioned light-receiving angle range, and the relative value of the reflected light amount (maximum value) at the light-receiving angle at which the actual measured value of the reflected light amount was maximum was defined as 100. Next, a coefficient was calculated by dividing the maximum value of the relative value of the reflected light amount (=100) of the reference by the actual measured value of the reflected light amount (maximum value). Next, using the coated surface of the antireflection film according to each example and each comparative example, the reflected light amount was measured at intervals of 0.1° within the above-mentioned light-receiving angle range, and the product of the measured reflected light amount and the coefficient determined from the reference was defined as the relative value of the reflected light amount.

[0058] The relative value of the reflected light amount was calculated for each of the incident angles of 30° and 60°, and the maximum value of the relative value of the reflected light amount at an incident light angle of 30° was designated x, and the maximum value of the relative value of the reflected light amount at an incident light angle of 60° was designated y. Furthermore, on a plane with the horizontal axis representing the light-receiving angle and the vertical axis representing the relative value of the reflected light amount, the light-receiving angle and the calculated relative value of the reflected light amount were plotted on a graph, and the ranges (absolute values) of the light-receiving angle that were equal to or greater than 1 / 10 of x and y were designated α and β.

[0059] (Anti-glare property evaluation) Samples were prepared by laminating a black acrylic plate to the uncoated surface of the anti-reflection film according to each example and comparative example using an optical pressure-sensitive adhesive. The anti-glare property when the anti-reflection film was observed from the front, with fluorescent light irradiated from the front of the anti-reflection film and a position 40 cm away from the anti-reflection film surface, was defined as "front anti-glare property." The anti-glare property when the anti-reflection film was observed from the specular reflection direction (a direction horizontal to the normal to the anti-reflection film and tilted 60 degrees toward the opposite side of the light source) with fluorescent light irradiated from a position 40 cm away from the anti-reflection film surface, was defined as "60-degree anti-glare property."

[0060] Twenty evaluators visually compared the front anti-glare properties and 60-degree anti-glare properties of the anti-reflection films and assigned scores according to the following criteria: <Evaluation criteria> 4 points: 60-degree anti-glare properties are equivalent to the front anti-glare properties 3 points: 60-degree anti-glare properties are slightly inferior to the front anti-glare properties 2 points: 60-degree anti-glare properties are significantly inferior to the front anti-glare properties 1 point: Almost no 60-degree anti-glare properties

[0061] The average scores of 20 panelists were classified according to the following criteria to obtain an evaluation value. If the score is level 5 or higher on the following criteria, the oblique antiglare properties are good. <Evaluation Values> Level 6: More than 3.5 and 4.0 or less Level 5: More than 3.0 and 3.5 or less Level 4: More than 2.5 and 3.0 or less Level 3: More than 2.0 and 2.5 or less Level 2: More than 1.5 and 2.0 or less Level 1: 1.0 or more and 1.5 or less

[0062] Table 3 also shows the shape and size of the organic filler used in the antireflection films of each Example and Comparative Example, as well as the evaluation values ​​of transmitted image clarity, haze, relative value of reflected light amount, and oblique antiglare property.

[0063]

[0064] The anti-reflection films according to Examples 1 to 5 had the anti-glare layer containing fine particles having a plurality of protrusions that satisfied the above conditions (A) to (C), and therefore had good front anti-glare properties and good 60-degree anti-glare properties while suppressing haze.

[0065] The anti-reflection films according to Comparative Examples 1 and 2 had good front anti-glare properties, but the 60-degree anti-glare properties were significantly reduced because the particles used were spherical. Furthermore, the haze also worsened because the amount of particles added was larger than in Examples 1 to 5.

[0066] Although the anti-reflection film of Comparative Example 3 contains fine particles having a plurality of protrusions in the anti-glare layer, it does not satisfy the above condition (B), and therefore the 60-degree anti-glare property was deteriorated and the haze was also high.

[0067] Although the anti-reflection films of Comparative Examples 4 and 5 contained fine particles having multiple protrusions in the anti-glare layer, they did not satisfy the above condition (A), and therefore had poor 60-degree anti-glare properties and high haze.

[0068] 5 and 6 are graphs showing the relationship between the light-receiving angle and the relative value of the amount of reflected light for the antireflection films according to Example 1 and Comparative Example 1, respectively.

[0069] In the anti-reflection film of Comparative Example 1 (using spherical microparticles) shown in Figure 6, when the incident angle of incident light is 60°, the proportion of reflected light components close to specularly reflected light is higher than when the incident angle is 30°. In contrast, in the anti-reflection film of Example 1 (using microparticles having a plurality of protrusions) shown in Figure 5, the amount of specularly reflected light is suppressed more than in Comparative Example 1, and the reflected light is dispersed over a wider range of light-receiving angles than in Comparative Example 1. It was confirmed that the anti-reflection film of Example 1 can suppress specularly reflected light and exhibit high anti-glare properties even when the incident angle is large, as the microparticles multiple-scatter the incident light.

[0070] The present invention can be used as an anti-reflection film for image display devices and the like.

[0071] 1 Anti-reflection film 2 Transparent substrate 3 Anti-glare layer

Claims

1. An antireflection film comprising at least one optical functional layer laminated on a light-transmitting substrate, wherein an uneven shape is formed on at least one surface of the optical functional layer, and wherein the optical functional layer contains fine particles having a plurality of protrusions, and wherein the radius of curvature r1 of the core of the fine particles and the radius of curvature r2 of the protrusions of the fine particles satisfy the following formulas (A), (B), and (C): 0.75 μm≦r1≦4.0 μm (A), 0.05 μm≦r2≦1.0 μm (B), and 0.25 μm≦r1-r2 (C).

2. The anti-reflection film according to claim 1, wherein the transmitted image clarity Ic at a 0.5 mm comb width and the haze Ha satisfy the following formula (D): (100-Ic) / Ha≧5 (D) 3. The antireflection film according to claim 1 or 2, characterized in that the following formula (E) is satisfied: β / α≧0.95 (E), where x is the maximum relative value of the amount of reflected light relative to the amount of incident light incident at an incident angle of 30°, y is the maximum relative value of the amount of reflected light relative to the amount of incident light incident at an incident angle of 60°, α is the width of the light-receiving angle at which the relative value of the amount of reflected light is 1 / 10 or more of the maximum value x, and β is the width of the light-receiving angle at which the relative value of the amount of reflected light is 1 / 10 or more of the maximum value y.

4. The antireflection film according to claim 1 or 2, characterized in that the following formula (F) is satisfied, where x is the maximum relative value of the amount of reflected light relative to the amount of incident light incident at an incident angle of 30°, and y is the maximum relative value of the amount of reflected light relative to the amount of incident light incident at an incident angle of 60°: y / x≦3.0 (F).

5. An image display device comprising: an image display panel; and the anti-reflection film according to claim 1.

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