Antireflection film and image display device using the same

Abstract

An antireflective film with low haze and high anti-glare performance, which suppresses the reduction of anti-glare performance when viewed from an oblique angle, and an image display device using the antireflective film are provided. An antireflective film is an antireflective film having at least one optical functional layer laminated on a light-transmitting substrate, characterized in that at least one surface of the optical functional layer has an uneven shape, the optical functional layer contains microparticles with multiple protrusions, the radius of curvature r1 of the microparticle nucleus and the radius of curvature r2 of the microparticle protrusion satisfying: (A) 0.75μm≤r1≤4.0μm, (B) 0.05μm≤r2≤1.0μm, (C) 0.25μm≤r1-r2.

Description

Technical Field

[0001] This invention relates to an anti-reflective film and an image display device using the anti-reflective film. Background Technology

[0002] When using a monitor in bright environments such as outdoors or under fluorescent lights, external light such as sunlight or fluorescent lamps can cause it to reflect back into the monitor. To prevent this, an anti-glare film is used, which has a surface with micro-textures that diffuse and reflect the reflected external light.

[0003] As an anti-glare film, there are anti-glare films obtained by coating a transparent resin onto a transparent film and then shaping it with a molding die having concave and convex shapes, or anti-glare films obtained by coating a transparent film with a coating in which inorganic or organic transparent microparticles are dispersed in a resin binder (for the latter, see, for example, Patent Documents 1 to 3).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 4839212

[0007] Patent Document 2: Japanese Patent Application Publication No. 2009-122490

[0008] Patent Document 3: Japanese Patent Application Publication No. 2012-220898 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] When an anti-glare film is designed to have high anti-glare performance, the haze can easily increase, leading to a decrease in panel contrast or a reduction in the premium feel due to cloudiness.

[0011] In addition, the anti-glare treatment based on shape processing and the anti-glare film described in Patent Documents 1 to 3 have the following problems: the anti-glare performance is high when viewed from the front (within the range of 0 to 30° relative to the normal of the screen), but when viewed from an oblique angle (within the range of 45° or more relative to the normal of the screen), the anti-glare performance is significantly reduced compared to when viewed from the front.

[0012] Therefore, the object of the present invention is to provide an anti-reflective film with low haze and high anti-glare performance, which suppresses the reduction of anti-glare performance when viewed from an oblique angle, and an image display device using the anti-reflective film.

[0013] Methods for solving problems

[0014] The antireflective film of the present invention is an antireflective film having at least one optical functional layer laminated on a light-transmitting substrate, characterized in that at least one surface of the optical functional layer has an uneven shape, and the optical functional layer contains microparticles with multiple protrusions, wherein the radius of curvature r1 of the nucleus of the microparticle and the radius of curvature r2 of the protrusion of the microparticle satisfy the following formulas (A), (B), and (C): 0.75μm ≤ r1 ≤ 4.0μm (A) 0.05μm ≤ r2 ≤ 1.0μm (B) 0.25μmm ≤ r1 - r2 (C).

[0015] The image display device of the present invention includes an image display panel and the aforementioned anti-reflective film.

[0016] The effects of the invention

[0017] The present invention provides an anti-reflective film with low haze and high anti-glare performance, which suppresses the reduction of anti-glare performance when viewed from an oblique angle, and an image display device using the anti-reflective film. Attached Figure Description

[0018] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view of the antireflective film according to the embodiment.

[0019] [ Figure 2 ] Figure 2 It is an SEM image of particles with multiple protrusions.

[0020] [ Figure 3 ] Figure 3 It is a schematic diagram of a particle with multiple protrusions.

[0021] [ Figure 4 ] Figure 4 It is a graph showing the relationship between the angle of light reception and the relative value of the amount of reflected light.

[0022] [ Figure 5 ] Figure 5 This is a graph showing the relationship between the light-receiving angle and the relative value of the reflected light amount of the anti-reflective film involved in Example 1.

[0023] [ Figure 6 ] Figure 6 This is a graph showing the relationship between the light-receiving angle and the relative value of the reflected light amount of the antireflective film involved in Comparative Example 1. Detailed Implementation

[0024] Figure 1 This is a schematic cross-sectional view of the antireflective film according to the embodiment.

[0025] The anti-reflective film 1 comprises a light-transmitting substrate 2 and an anti-glare layer 3 laminated on one side of the light-transmitting substrate 2. The anti-glare layer 3 is an optical functional layer that suppresses the reflection of external light by scattering incident light through the micro-unevenness formed on its surface. The anti-reflective film 1 with the anti-glare layer 3 is also called an AG film.

[0026] The light-transmitting substrate 2 is a film that serves as the base for the anti-reflective film 1, and is formed from a material with excellent visible light transmittance. The material forming the light-transmitting substrate 2 can be 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 light-transmitting substrate 2 is not particularly limited, but is preferably set to 10–200 μm.

[0027] To improve adhesion with other layers to be laminated, 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.

[0028] The anti-glare layer 3 is a functional layer with a fine, uneven shape forming the outermost surface of the anti-reflective film 1.

[0029] The anti-glare layer 3 contains microparticles (fillers) with multiple protrusions. The anti-glare layer 3 is formed by applying a coating liquid containing a UV-curable compound, microparticles, and a photopolymerization initiator onto a light-transmitting substrate 2 and then curing the coating.

[0030] As a UV-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.

[0031] 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.

[0032] Examples of difunctional (meth)acrylates include: ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, nonanediol dimethacrylate, ethoxylated hexanediol dimethacrylate, propoxylated hexanediol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, ethoxylated neopentyl glycol dimethacrylate, tripropylene glycol dimethacrylate, hydroxypentyl acid neopentyl glycol dimethacrylate, and other dimethacrylates.

[0033] Examples of trifunctional or higher (meth)acrylates include: trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane trimethacrylate, propoxylated trimethylolpropane trimethacrylate, tris(2-hydroxyethyl)isocyanurate trimethacrylate, glycerol trimethacrylate, etc.; and trifunctional (meth)acrylates such as pentaerythritol trimethacrylate, dipentaerythritol trimethacrylate, and di(trimethylolpropane)methacrylate. Acid ester compounds; polyfunctional (meth) acrylate compounds 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) acrylate compounds in which a portion of these (meth) acrylates is substituted with alkyl groups or ε-caprolactones.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Figure 2 It is an SEM image of particles with multiple protrusions. Figure 3 It is a schematic diagram of a particle with multiple protrusions.

[0038] The microparticles are materials that form fine irregularities on the surface of the anti-glare layer 3, giving it the function of diffusing external light. For example... Figure 2As shown, the microparticles have a spherical core and multiple protrusions extending from the core surface. The protrusions on the surface of the microparticles have a shape approximating a portion of a sphere, and the outer surface of the protrusions is approximately spherical. The microparticles are composed of resin, and the material used for the microparticles can be, for example, acrylic resins or polymethylsilsesquioxane (PMSQ).

[0039] Here, the radius of curvature of the core is set as r1, and the radius of curvature of the protrusion is set as r2 (refer to...). Figure 3 The radii of curvature r1 and r2 are approximations obtained by treating the nucleus and protrusions as spheres; specifically, they are values ​​calculated as the radii of a circle passing through any three points on the outer contour of the nucleus and protrusions appearing in the SEM image. As an example, in Figure 3 In the diagram, a dashed line represents a circle passing through any three points on the outer contour line of a protrusion. The radii of curvature r1 and r2 of the microparticles used in the antireflective film of this embodiment satisfy the following equations (A), (B), and (C).

[0040] 0.75μm ≤ r1 ≤ 4.0μm (A)

[0041] 0.05μm ≤ r2 ≤ 1.0μm (B)

[0042] 0.25μmm ≤ r1 - r2 (C)

[0043] When the radius of curvature r1 of the core is less than 0.75 μm, the haze decreases, but the anti-glare performance also decreases. When the radius of curvature r2 of the core is greater than 4.0 μm, the anti-glare performance increases, but the haze also increases. When the radius of curvature r1 of the core is within the range of formula (A), both high anti-glare and low haze can be achieved. It should be noted that the haze of the antireflective film of the present invention can be 20% or less, more preferably 15% or less.

[0044] When the radius of curvature r2 of the protrusion is less than 0.05 μm, the shape of the microparticles is close to that of a true sphere, thus reducing the anti-glare performance when viewed from an oblique angle. When the radius of curvature r2 of the protrusion is greater than 1.0 μm, the anti-glare performance of the anti-reflective film also decreases when viewed from an oblique angle. Furthermore, when r2 is too large, the fabrication of the microparticles becomes difficult.

[0045] When the difference in curvature radii r1 - r2 is too small, it becomes difficult to produce particles. Therefore, the lower limit of r1 - r2 in reality is above 0.25.

[0046] As photopolymerization initiators, free radical polymerization initiators such as acetophenone-based, benzophenone-based, thioxanthone-based, benzoin, benzoin methyl ether, and phosphine oxide can be used. Examples of photopolymerization 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 individually or in combination of two or more.

[0047] If necessary, inorganic microparticles (inorganic nanoparticles) with an average particle size of 10 to 200 nm may also be added to the composition for forming the anti-glare layer.

[0048] Inorganic microparticles function as thickeners, increasing the viscosity of the composition used to form the anti-glare layer, and are used to regulate the settling and aggregation of microparticles in the anti-glare layer 3. As inorganic microparticles, silica microparticles, metal oxide microparticles, and various mineral microparticles can be used. For example, colloidal silica or silica microparticles surface-modified with reactive functional groups such as (meth)acryloyl groups can be used. For example, alumina, zinc oxide, tin oxide, antimony oxide, indium oxide, titanium dioxide, and zirconium oxide can be used. For example, mica, synthetic mica, vermiculite, montmorillonite, iron montmorillonite, bentonite, beidellite, saponite, hectorite, stevensite, nontronite, magadiite, illite, kanemite, layered titanate, smectite, and synthetic smectite can be used. 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 utilize the cation exchangeability of bentonite for organometallization. When using layered organoclay minerals as mineral microparticles, the aforementioned synthetic montmorillonite is preferred.

[0049] In addition, antifouling agents, leveling agents, oleophobic agents, hydrophobic agents, and anti-fingerprint agents can be added to the composition for forming the anti-glare layer as components to improve antifouling properties. Fluorinated compounds or organosilicon compounds are preferably used as these additives. Furthermore, various additives such as antistatic agents, defoamers, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, and photosensitizers can be added as needed.

[0050] Solvents may be added to the composition for forming the anti-glare layer as needed. Solvents may include one or a mixture of two or more of the following: 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.

[0051] Depending on the requirements, one or more layers of hard coating, high refractive index layer, medium refractive index layer, antistatic layer, electromagnetic wave shielding layer, infrared absorption layer, ultraviolet absorption layer, color correction layer, and other functional layers may be stacked between the light-transmitting substrate 2 and the anti-glare layer 3.

[0052] 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.

[0053] The transmitted image sharpness Ic and haze Ha of the antireflective film of the present invention preferably satisfy the following formula (D). Here, the transmitted image sharpness 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 according to JIS K7136.

[0054] (100 - Ic) / Ha ≥ 5 (D)

[0055] The value of (100 - Ic) / Ha is an indicator of the balance between anti-glare and haze. Under the condition (D), it can achieve both high anti-glare and low haze.

[0056] Figure 4 This is a graph showing the relationship between the angle of light reception and the relative amount of reflected light. It should be noted that... Figure 4The angle of light shown represents the angle of reflected light other than the orthogonal reflected light when the angle of orthogonal reflected light is taken as a reference (0°).

[0057] The maximum value of the relative amount of reflected light with respect to the amount of incident light incident at an angle of incidence of 30° is defined as x, and the maximum value of the relative amount of reflected light with respect to the amount of incident light incident at an angle of incidence of 60° is defined as y. Here, the relative amount of reflected light 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 ​​when the relative amount of reflected light is measured while changing the angle of illumination. In addition, the width of the angle of illumination where the relative amount of reflected light is more than 1 / 10 of the maximum value x (the 1 / 10 value width) is defined as α, and the width of the angle of illumination where the relative amount of reflected light is more than 1 / 10 of the maximum value y (the 1 / 10 value width) is defined as β. Figure 4 x, y, α, and β are shown.

[0058] The antireflective film of the present invention preferably satisfies the following formula (E).

[0059] β / α ≥ 0.95 (E)

[0060] The value of β / α is one of the indicators of the anti-glare performance when the anti-reflective film is viewed from an oblique angle. When condition (E) is met, the diffusion angle of reflected light can be maintained even when the anti-reflective film is viewed from an oblique angle. Even if the incident angle increases, the scattering mode is difficult to change, and the anti-glare performance is good when viewed from an oblique angle.

[0061] In addition, the antireflective film of the present invention preferably satisfies the following (F).

[0062] y / x ≤ 3.0 (F)

[0063] The y / x value is one of the indicators of the anti-glare performance of the anti-reflective film when viewed from an oblique angle. Under the condition (F) that is met, even if the incident angle increases, the increase in the amount of positively reflected light can be suppressed, and the anti-glare performance is good when viewed from an oblique angle.

[0064] As described above, the anti-reflective film of this embodiment contains microparticles with multiple protrusions as fillers in the anti-glare layer. When using microparticles with multiple protrusions, incident light is easily scattered multiple times at the protruding portions of the microparticles. Although the scattering angle is small, the incident light can be scattered in multiple directions in a complex manner, thus achieving low haze and high anti-glare performance (low image sharpness). Furthermore, by causing multiple scattering of incident light through microparticles with multiple protrusions, the incident light can be effectively scattered even when it is incident from an oblique angle. The anti-reflective film of this embodiment can achieve both low haze and high anti-glare performance; therefore, when used in an image display device, it can suppress the influence of external light while suppressing the reduction in image contrast.

[0065] The anti-reflective film described in this embodiment can be adhered 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 anti-reflective film and the image display panel. The anti-reflective film described in this embodiment exhibits excellent anti-glare performance when viewed from an oblique angle, thus possessing high anti-glare properties and capable of displaying vivid images. It is suitable for large displays intended for viewing from multiple directions, such as public information displays (PIDs).

[0066] Example

[0067] The following describes specific embodiments of the present invention.

[0068] A 40 μm thick triacetyl cellulose (TAC) membrane was used as the light-transmitting substrate. Anti-glare layer forming compositions were prepared containing pentaerythritol triacrylate (UV-curable compound), filler (microparticles), Omnirad (registered trademark) 184 (photopolymerization initiator), and organically treated synthetic clay (additive) in the proportions shown in Tables 1 and 2 below, and diluted with solvent to a suitable concentration for coating. The proportions shown in Table 1 are by mass%. The anti-glare layer forming compositions were coated onto the light-transmitting substrate in such a manner that the cured film thickness was approximately equal to the particle size and that the particles were embedded in the anti-glare layer. After drying, the coating was polymerized and cured by UV irradiation to form an anti-glare layer, thereby obtaining the anti-reflective films according to the various examples and comparative examples.

[0069]

[0070] The radii of curvature r1 of the nuclei and r2 of the protrusions of the microparticles used in Examples 1-5 and Comparative Examples 3-5 were determined as follows. SEM images of the cross-section of the antireflective film were obtained. 100 nuclei and 100 protrusions of any microparticles contained in the SEM images were selected. The radii of the circles passing through any three points on the outer contour lines of the nuclei and protrusions were measured, and the average values ​​were taken as r1 and r2.

[0071] (Ha)

[0072] According to JIS K 7105, the haze was measured using a haze meter (NDH 4000, manufactured by Nippon Denshoku Co., Ltd.).

[0073] (Transmission image sharpness Ic)

[0074] According to JIS K 7105, the sharpness of the transmitted image was measured using a printability measuring instrument (ICM-1T, manufactured by Suga Test Instruments Co., Ltd.) in transmission mode with an optical comb width of 0.5 mm.

[0075] (Relative value of reflected light)

[0076] The relative value of reflected light was measured using a variable angle photometer (Gonio Photometer, GP-5, manufactured by Murakami Color Technology Research Institute Co., Ltd.). A black acrylic sheet was attached to the uncoated side of the antireflective film using optical adhesive, serving as the measurement sample. Additionally, as a reference, a sample in which a black acrylic sheet was attached to one side of a translucent substrate (the same side as the uncoated side of the antireflective film) using optical adhesive was used, with the side matching the coated side of the antireflective film serving as the measurement surface.

[0077] The measurement conditions for the angle photometer are set as follows.

[0078] <Measurement Conditions>

[0079] Measurement mode: Reflectance

[0080] • Measurement item: Variable angle

[0081] • VS1 (Aperture on the light source (beam) side): 2.0

[0082] • VS2 (Aperture on the receiving side): 3.0

[0083] • IA (Incident Angle): 30° or 60°

[0084] • FA (Elevation Angle): 0.0°

[0085] • Light reception angle range (RA): Orthographic reflection angle ± 20° (when the incident angle is 30°, R1: 10°, R2: 50°; when the incident angle is 60°, R1: 40°, R2: 80°)

[0086] • Sensitivity check: Implementation (Start: R1, End: R2)

[0087] • Neutral density filter: Not used

[0088] • ND filter: Not used

[0089] The relative value of reflected light is calculated as follows. First, using a reference measurement surface, the amount of reflected light is measured in 0.1° increments within the aforementioned light-receiving angle range. The measured value of reflected light is taken as the relative value (maximum value) of reflected light at the maximum light-receiving angle, and set to 100. Next, a coefficient is calculated by dividing the maximum value (=100) of the reference relative value of reflected light by the measured value (maximum value) of reflected light. Then, using the coating surface of the antireflective film according to each embodiment and each comparative example, the amount of reflected light is measured in 0.1° increments within the aforementioned light-receiving angle range. The product of the measured value of reflected light and the coefficient calculated based on the reference is taken as the relative value of reflected light.

[0090] The relative values ​​of reflected light were calculated for incident angles of 30° and 60° respectively. The maximum value of the relative value of reflected light at an incident angle of 30° was set as x, and the maximum value of the relative value of reflected light at an incident angle of 60° was set as y. In addition, on a plane with the horizontal axis representing the angle of light reception and the vertical axis representing the relative value of reflected light, the angle of light reception and the calculated relative value of reflected light were plotted. The widths (absolute values) of the angles of light reception that are more than 1 / 10 of x and y were set as α and β.

[0091] (Anti-glare evaluation)

[0092] Samples were prepared by attaching a black acrylic sheet to the uncoated surface of the antireflective film involved in each embodiment and comparative example using optical adhesive. The anti-glare performance of the antireflective film when viewed from the front, with fluorescent light illuminating it from a position 40 cm away from the surface of the antireflective film, is defined as "frontal anti-glare performance". Furthermore, the anti-glare performance of the antireflective film when viewed from the positive reflection direction (a direction tilted 60 degrees relative to the normal of the antireflective film towards the horizontal and opposite to the light source) when illuminated from a position 40 cm away from the surface of the antireflective film with fluorescent light illuminating it at a 60-degree angle to the horizontal relative to the normal of the antireflective film, is defined as "60-degree anti-glare performance".

[0093] Twenty evaluators visually compared the anti-glare performance of the anti-reflective film at the front and at a 60-degree angle, and scored it according to the following criteria.

[0094] <Evaluation Criteria>

[0095] 4 points: The 60-degree anti-glare performance is the same as the frontal anti-glare performance.

[0096] 3 points: The 60-degree anti-glare performance is slightly lower compared to the frontal anti-glare performance.

[0097] 2 points: The 60-degree anti-glare performance is significantly reduced compared to the frontal anti-glare performance.

[0098] 1 point: Almost no 60-degree anti-glare capability

[0099] The average rating of the 20 participants was categorized according to the following criteria as an evaluation value. A rating of 5 or higher on the following criteria indicates good oblique glare reduction.

[0100] <Evaluation Value>

[0101] Level 6: Above 3.5 and below 4.0

[0102] Level 5: Above 3.0 and below 3.5

[0103] Level 4: Above 2.5 and below 3.0

[0104] Level 3: Above 2.0 and below 2.5

[0105] Level 2: Above 1.5 and below 2.0

[0106] Level 1: 1.0 or higher, 1.5 or lower

[0107] Table 3 also shows the shape and size of the organic filler used in the antireflective films of each embodiment and comparative example, as well as the evaluation values ​​of transmitted image clarity, haze, relative value of reflected light, and oblique anti-glare performance.

[0108]

[0109] The anti-reflective films described in Examples 1 to 5 have multiple protruding microparticles that meet the above conditions (A) to (C) added to the anti-glare layer, thus suppressing haze and providing good frontal and 60-degree anti-glare performance.

[0110] While the anti-glare films in Comparative Examples 1 and 2 exhibit good frontal anti-glare performance, their 60-degree anti-glare performance is significantly reduced due to the use of spherical microparticles. Furthermore, compared to Examples 1-5, the amount of microparticles added is higher, resulting in a deterioration in haze.

[0111] Although the anti-reflective film involved in Comparative Example 3 has added microparticles with multiple protrusions to the anti-glare layer, it does not meet the above condition (B), so the anti-glare performance at 60 degrees is deteriorated and the haze is also high.

[0112] Although the anti-reflective films involved in Comparative Examples 4 and 5 have added microparticles with multiple protrusions to the anti-glare layer, they do not meet the above condition (A), and therefore the anti-glare performance deteriorates at 60 degrees and the haze is high.

[0113] Figure 5 and Figure 6 The figures shown are the relationship between the light-receiving angle and the relative value of the reflected light amount of the antireflective film involved in Example 1 and Comparative Example 1, respectively.

[0114] exist Figure 6 In Comparative Example 1 (using spherical microparticles), the proportion of reflected light components approaching positive reflection is higher when the incident angle of incident light is 60° compared to when the incident angle is 30°. In contrast, in... Figure 5 In the antireflective film of Example 1 (using microparticles with multiple protrusions), compared with Comparative Example 1, the amount of positively reflected light is suppressed, and the reflected light is dispersed over a wider range of light reception angles than in Comparative Example 1. In the antireflective film of Example 1, it was confirmed that even with a larger incident angle, positively reflected light can be suppressed through multiple scattering of incident light by microparticles, thus achieving high anti-glare performance.

[0115] Industrial applicability

[0116] This invention can be used as an anti-reflective film for image display devices, etc.

[0117] Explanation of symbols

[0118] 1. Anti-reflective film

[0119] 2. Translucent substrate

[0120] 3 Anti-glare layer

Claims

1. An antireflective film, comprising at least one optical functional layer laminated on a light-transmitting substrate, characterized in that, At least one surface of the optical functional layer has an uneven shape. The optical functional layer contains microparticles with multiple protrusions. The radius of curvature r1 of the nucleus of the particle and the radius of curvature r2 of the protrusion of the particle satisfy the following equations (A), (B), and (C): 0.75μm ≤ r1 ≤ 4.0μm (A) 0.05μm ≤ r2 ≤ 1.0μm (B) 0.25μmm ≤ r1 - r2 (C).

2. The antireflective film according to claim 1, characterized in that, For a 0.5mm comb width, the image sharpness Ic and haze Ha of the transmitted image satisfy the following formula (D): (100 - Ic) / Ha ≥ 5 (D).

3. The antireflective film according to claim 1 or 2, characterized in that, Let x be the maximum value of the relative value of the reflected light quantity with respect to the incident light quantity at an incident angle of 30°, let y be the maximum value of the relative value of the reflected light quantity with respect to the incident light quantity at an incident angle of 60°, let α be the width of the light-receiving angle whose relative value of the reflected light quantity is more than 1 / 10 of the maximum value x, and let β be the width of the light-receiving angle whose relative value of the reflected light quantity is more than 1 / 10 of the maximum value y. At this time, the following equation (E) is satisfied: β / α ≥ 0.95 （E）。 4. The antireflective film according to claim 1 or 2, characterized in that, Let x be the maximum value of the relative value of the reflected light quantity with respect to the incident light quantity incident at an incident angle of 30°, and let y be the maximum value of the relative value of the reflected light quantity with respect to the incident light quantity incident at an incident angle of 60°. Then the following equation (F) is satisfied: y / x ≤ 3.0 (F).

5. An image display device, comprising: Image display panel; and The antireflective film according to claim 1.

Images