WO2012057358A1

WO2012057358A1 - Optical film, method for manufacturing same, polarization plate, and image display device

Info

Publication number: WO2012057358A1
Application number: PCT/JP2011/075233
Authority: WO
Inventors: 昌神崎; 篤志金澤
Original assignee: 住友化学株式会社
Priority date: 2010-10-29
Filing date: 2011-10-26
Publication date: 2012-05-03
Also published as: JP2012098368A; TW201232055A

Abstract

Disclosed is an optical film that is provided with a base material film (101), and a fine particle-containing layer (102), which is formed on the base material film, and which is formed of a resin liquid that contains fine particles (104). The rate of fine particles (coarse particles), each of which has a particle diameter larger than the average thickness (h) of the fine particle-containing layer (102), to the whole fine particles (104) contained in the resin liquid is 2 % or less, and the surface of the fine particle-containing layer (102) has a shape formed by pressing thereto the surface of a mold. Also disclosed are a polarization plate having the optical film applied thereto and an image display device. Generation of a protruding defect due to the coarse particles is sufficiently suppressed or eliminated without increasing the thickness of the fine particle-containing layer, and the optical film provided with the fine particle-containing layer having excellent surface uniformity, and a method for manufacturing the optical film efficiently at low cost are provided.

Description

Optical film and manufacturing method thereof, polarizing plate, and image display device

The present invention relates to an optical film having a fine particle-containing layer on a base film and a method for producing the same. The present invention also relates to a polarizing plate and an image display device using the optical film.

An image display device such as a liquid crystal display, a plasma display panel, a cathode ray tube (CRT) display, or an organic electroluminescence (EL) display has a significant loss of visibility when external light is reflected on its display surface. In order to prevent such reflection of external light, an anti-glare film that has fine irregularities on the surface and scatters incident light to blur the reflected image is conventionally disposed on the surface of the image display device. It is.

The antiglare film can be produced, for example, by applying a resin liquid in which fine particles are dispersed on a base film to form an antiglare layer. However, in the antiglare film provided with surface irregularities by containing such fine particles, there are convex defects due to the coarse particles with large particle diameters contained in the fine particles protruding from the surface of the antiglare layer There is. Such a convex defect causes excessive scattering of light incident on the surface of the antiglare layer, and causes so-called whitishness or contrast reduction in which the entire screen is felt whitish. In addition, the surface quality of the antiglare layer surface is deteriorated. Therefore, it is important not to generate as many convex defects as possible due to the coarse particles protruding from the surface of the antiglare layer.

JP2010-102291-A has a value R / H obtained by dividing the average particle diameter R of the particles by the average thickness H of the antiglare layer in order to prevent the formation of large convex portions derived from the particles on the surface of the antiglare layer. It is disclosed that the value is 0.8 or less. JP2010-159421-A includes coarse particles (from average particle diameter) as translucent fine particles contained in the light diffusion layer from the viewpoint of improving the surface uniformity of the light diffusion layer (antiglare layer). In which the ratio of particles having a particle diameter of 20% or more is 1% or less (more preferably 0.1% or less, and still more preferably 0.01% or less) of the total number of particles is obtained by classification operation or the like. It is described that it is preferable to do.

JP2010-102291-A proposes a method of reducing the average particle diameter R / average thickness H to 0.8 or less, particularly when the average particle diameter R and the average thickness H are close to each other, thereby eliminating the above convex defects. It is inadequate as a technique for doing this. On the other hand, if the average thickness H is sufficiently larger than the average particle size R in order to effectively eliminate the convex defects, the manufacturing cost increases due to the increase in the thickness of the antiglare layer, and there is a demand for thinning the optical film. It will not be along.

Further, in the method of controlling the particle size distribution of fine particles proposed by JP2010-159421-A, in order to reduce the content of coarse particles to such an extent that the occurrence of convex defects is sufficiently suppressed, classification operation is performed. Need to be repeated, resulting in an increase in manufacturing cost and a significant decrease in manufacturing efficiency.

An object of the present invention is an optical film including a fine particle-containing layer on a base film, and sufficiently suppresses or prevents the occurrence of convex defects due to coarse particles without increasing the thickness of the fine particle-containing layer. It is an object of the present invention to provide an optical film provided with a fine particle-containing layer having good surface homogeneity and a method for producing such an optical film efficiently and at low cost. Another object of the present invention is to provide a polarizing plate and an image display device to which the optical film is applied.

The present invention includes the following.
[1] An optical film comprising a base film and a fine particle-containing layer formed from a resin liquid containing fine particles on the base film, and having a particle diameter larger than the average thickness h of the fine particle-containing layer (coarse The ratio of the particles) to the total fine particles contained in the resin liquid is 2% or less, and the surface of the fine particle-containing layer has a shape formed by pressing the surface of the mold. .

[2] The optical film according to [1], wherein the ratio r / h of the weight average particle diameter r of the fine particles contained in the resin liquid to the average thickness h of the fine particle-containing layer is 0.3 or more.

[3] The optical film according to [1] or [2], wherein r / h is 0.9 or less.

[4] The optical film according to any one of [1] to [3], wherein the ratio R / h of the maximum particle size R of the fine particles contained in the fine particle-containing layer to the average thickness h of the fine particle-containing layer is 2 or less. .

[5] The optical film according to any one of [1] to [4], wherein the fine particles contained in the resin liquid have a weight average particle diameter r of 1 μm to 15 μm.

[6] The optical film according to any one of [1] to [5], wherein the average thickness h of the fine particle-containing layer is 3 μm or more and 20 μm or less.

[7] The optical film according to any one of [1] to [6], wherein the fine particle-containing layer is a cured product layer of the resin liquid.

[8] The optical film according to any one of [1] to [7], wherein a ratio of coarse particles to the entire fine particles contained in the resin liquid is 0.2% or less.

[9] The optical film according to any one of [1] to [8], wherein the mold is a mold having a mirror surface or a concavo-convex surface.

[10] The optical film according to any one of [1] to [9], further comprising an antireflection layer laminated on the fine particle-containing layer.

[11] A method for producing an optical film according to claim 1, wherein a coating layer is formed by applying a resin liquid containing fine particles on a base film, and the coating layer A step of pressing the surface of the mold against the surface, and a step of forming a fine particle-containing layer by fixing the coating layer on the substrate film in a state where the surface of the mold is pressed against the surface of the coating layer The manufacturing method of an optical film containing these.

[12] In the step of forming the fine particle-containing layer, the coating layer is formed by irradiating the coating layer with active energy rays from the base film side while pressing the surface of the mold against the surface of the coating layer. The production method according to [11], including a curing step.

[13] A polarizing plate comprising a polarizing film and the optical film according to any one of [1] to [10], which is laminated on the polarizing film so that the base film side faces the polarizing film.

[14] An image display device comprising the polarizing plate according to [13] and an image display element, wherein the polarizing plate is disposed on the image display element with the fine particle-containing layer side facing outside.

According to the present invention, the occurrence of convex defects due to coarse particles in the fine particle-containing layer is sufficiently suppressed or prevented, and an optical film provided with a fine particle-containing layer having good surface uniformity can be provided. When such an optical film is used as, for example, an antiglare film or a light diffusion film, excessive scattering of light incident on the surface of the fine particle-containing layer can be effectively suppressed, A decrease in contrast can be prevented. Moreover, according to the manufacturing method of this invention, the above optical films can be manufactured efficiently and at low cost. The optical film of the present invention can be suitably applied to image display devices such as polarizing plates and liquid crystal display devices.

It is a schematic sectional drawing which shows a preferable example of the optical film of this invention. It is the schematic which shows an example of the apparatus for manufacturing the optical film of this invention.

<Optical film>
FIG. 1 is a schematic cross-sectional view showing a preferred example of the optical film of the present invention. The optical film 100 shown in FIG. 1 according to the present invention includes a base film 101 and a fine particle-containing layer 102 laminated on the base film 101. The fine particle-containing layer 102 is a layer having a translucent resin 103 as a base material, and translucent fine particles 104 are dispersed in the translucent resin 103. The fine particle-containing layer 102 is formed by applying a resin liquid containing the fine particles 104 onto the base film 101. The surface (outer surface) of the fine particle-containing layer 102 is formed by pressing the surface of the mold. Therefore, as shown in the drawing, in the optical film of the present invention, even when the fine particles 104 include coarse particles 110 (fine particles having a particle diameter larger than the average thickness h of the fine particle-containing layer 102). Since the portion of the coarse particle 110 that should protrude from the surface of the fine particle-containing layer 102 is in a state of being crushed by the pressing of the mold, the convex defect due to the protrusion of the coarse particle 110 is effectively suppressed or It is prevented and the surface uniformity is excellent.

The optical film of the present invention can be used as an optical film for an image display device for various purposes. For example, when a mold having a concavo-convex surface is used as the mold, since the concavo-convex structure is imparted to the surface of the fine particle-containing layer 102, it is disposed on the surface of the image display device, and glare or reflection of external light is reflected It can be used as an antiglare film to prevent (the fine particle-containing layer 102 functions as an antiglare layer). Further, when a mold having a mirror surface is used as the mold, the surface of the fine particle-containing layer 102 is a flat surface, and the image display device can be used regardless of whether the surface is an uneven shape or a flat surface. Placed on the viewing side (front surface) of the liquid crystal display as a light diffusing film that improves the viewing angle or the like, or on the backlight side of a liquid crystal display device, etc., diffuses light incident on the liquid crystal cell and prevents moiré, etc. It can be used as a diffusion plate (or a diffusion sheet) (the fine particle-containing layer 102 functions as a light diffusion layer).

Hereinafter, the optical film of the present invention will be described in more detail.
[Base film]
The base film 101 only needs to be translucent, and for example, glass or plastic film can be used. The plastic film only needs to have appropriate transparency and mechanical strength. Specific examples include cellulose acetate resins such as TAC (triacetylcellulose), acrylic resins, polycarbonate resins, polyester resins such as polyethylene terephthalate, and polyolefin resins such as polyethylene and polypropylene. The thickness of the base film 101 is, for example, 10 to 500 μm, and is preferably 10 to 300 μm, more preferably 20 to 300 μm from the viewpoint of thinning the optical film.

[Fine particle containing layer]
The optical film of the present invention includes a fine particle-containing layer 102 laminated on a base film 101. The fine particle-containing layer 102 is a layer having a translucent resin 103 as a base material, and translucent fine particles 104 are dispersed in the translucent resin 103. Note that another layer (including an adhesive layer) may be provided between the base film 101 and the fine particle-containing layer 102.

(1) Translucent resin The translucent resin 103 is not particularly limited as long as it has translucency. For example, an active energy ray curable resin such as an ultraviolet curable resin or an electron beam curable resin, A cured product of a thermosetting resin, a thermoplastic resin, a cured product of a metal alkoxide, or the like can be used. Among these, an active energy ray-curable resin is preferable because it has high hardness and can impart high scratch resistance as an antiglare film or a light diffusion film provided on the surface of the image display device. When an active energy ray curable resin, a thermosetting resin, or a metal alkoxide is used, the translucent resin 103 is formed by curing the resin by irradiation or heating with an active energy ray.

The active energy ray-curable resin can contain a polyfunctional (meth) acrylate compound. The polyfunctional (meth) acrylate compound is a compound having at least two (meth) acryloyloxy groups in the molecule.

Specific examples of the polyfunctional (meth) acrylate compound include, for example, ester compounds of polyhydric alcohol and (meth) acrylic acid, urethane (meth) acrylate compounds, polyester (meth) acrylate compounds, epoxy (meth) acrylate compounds, and the like. And a polyfunctional polymerizable compound containing two or more (meth) acryloyl groups.

Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, propanediol, butanediol, and pentanediol. , Divalent alcohols such as hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, 2,2′-thiodiethanol, 1,4-cyclohexanedimethanol; trimethylolpropane, glycerol, pentaerythritol, Examples thereof include trihydric or higher alcohols such as diglycerol, dipentaerythritol, and ditrimethylolpropane.

Specific examples of the esterified product of polyhydric alcohol and (meth) acrylic acid include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (Meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, tetramethylolmethanetetra (meta ) Acrylate, pentaglycerol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerin tri (meth) acrylate, di Pentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate.

Examples of the urethane (meth) acrylate compound include an urethanization reaction product of an isocyanate having a plurality of isocyanate groups in one molecule and a (meth) acrylic acid derivative having a hydroxyl group. Examples of the organic isocyanate having a plurality of isocyanate groups in one molecule include two in one molecule such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate. And organic isocyanates having three isocyanate groups in one molecule obtained by subjecting these organic isocyanates to isocyanurate modification, adduct modification or biuret modification. Examples of the (meth) acrylic acid derivative having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, Examples include 2-hydroxy-3-phenoxypropyl (meth) acrylate and pentaerythritol triacrylate.

Preferred as the polyester (meth) acrylate compound is a polyester (meth) acrylate obtained by reacting a hydroxyl group-containing polyester with (meth) acrylic acid. The hydroxyl group-containing polyester preferably used is a hydroxyl group-containing polyester obtained by an esterification reaction of a polyhydric alcohol, a carboxylic acid, a compound having a plurality of carboxyl groups, and / or an anhydride thereof. Examples of the polyhydric alcohol include the same compounds as those described above. Moreover, bisphenol A etc. are mentioned as phenols other than a polyhydric alcohol. Examples of the carboxylic acid include formic acid, acetic acid, butyl carboxylic acid, benzoic acid and the like. Examples of the compound having a plurality of carboxyl groups and / or anhydride thereof include maleic acid, phthalic acid, fumaric acid, itaconic acid, adipic acid, terephthalic acid, maleic anhydride, phthalic anhydride, trimellitic acid, and cyclohexanedicarboxylic acid. An acid anhydride etc. are mentioned.

Among the polyfunctional (meth) acrylate compounds as described above, hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and diethylene glycol diene from the viewpoint of improving the strength of the cured product (coating film) and availability. Ester compounds such as (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate; hexamethylene diisocyanate and 2- Adduct of hydroxyethyl (meth) acrylate; adduct of isophorone diisocyanate and 2-hydroxyethyl (meth) acrylate; tolylene diisocyanate and 2-hydroxyethyl (meth) acrylate Adduct adduct modified isophorone diisocyanate with 2-hydroxyethyl (meth) acrylate; adducts and adducts of biuret of isophorone diisocyanate and 2-hydroxyethyl (meth) acrylate.
Further, the active energy ray-curable resin preferably contains a urethane (meth) acrylate compound because it exhibits good flexibility (a property showing flexibility) when it is thickened. Each of these polyfunctional (meth) acrylate compounds can be used alone or in combination with one or more other compounds.

The active energy ray-curable resin may contain a monofunctional (meth) acrylate compound in addition to the polyfunctional (meth) acrylate compound. Examples of the monofunctional (meth) acrylate compound include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, and 2-hydroxyethyl (meth) ) Acrylate, 2-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, glycidyl (meth) acrylate, acryloylmorpholine N-vinylpyrrolidone, tetrahydrofurfuryl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isobornyl (meth) acrylate, aceto (Meth) acrylate, benzyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxy (meth) acrylate, ethylene oxide modified phenoxy (meta ) Acrylate, propylene oxide (meth) acrylate, nonylphenol (meth) acrylate, ethylene oxide modified (meth) acrylate, propylene oxide modified nonylphenol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, 2- (meth) acryloyloxyethyl-2 -Hydroxypropyl phthalate, dimethylaminoethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, etc. Meth) acrylate and the like. Each of these compounds can be used alone or in combination with one or more other compounds.

The active energy ray curable resin may contain a polymerizable oligomer. By including the polymerizable oligomer, the hardness of the fine particle-containing layer 102 can be adjusted. The polymerizable oligomer is, for example, the polyfunctional (meth) acrylate compound, that is, an ester compound of a polyhydric alcohol and (meth) acrylic acid, a urethane (meth) acrylate compound, a polyester (meth) acrylate compound, or an epoxy (meth). It can be an oligomer such as a dimer, trimer or the like such as an acrylate.

Further, as other polymerizable oligomer, for example, urethane (meta) obtained by reaction of polyisocyanate having at least two isocyanate groups in the molecule and polyhydric alcohol having at least one (meth) acryloyloxy group. ) Acrylate oligomers. Examples of the polyisocyanate include hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, a polymer of xylylene diisocyanate, and the like. As the polyhydric alcohol having at least one (meth) acryloyloxy group, Hydroxyl group-containing (meth) acrylic acid ester obtained by esterification reaction of polyhydric alcohol and (meth) acrylic acid, wherein the polyhydric alcohol is, for example, 1,3-butanediol, 1,4-butanediol, 1 , 6-hexanediol, diethylene glycol, triethylene glycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, trimethylolpropane, glycerin, pentaerythritol Le, those dipentaerythritol and the like. In this polyhydric alcohol having at least one (meth) acryloyloxy group, a part of the alcoholic hydroxyl group of the polyhydric alcohol is esterified with (meth) acrylic acid, and the alcoholic hydroxyl group is present in the molecule. It remains.

Furthermore, as another example of the polymerizable oligomer, a polyester (meta) obtained by reacting a compound having a plurality of carboxyl groups and / or an anhydride thereof with a polyhydric alcohol having at least one (meth) acryloyloxy group. ) Acrylate oligomers. Examples of the compound having a plurality of carboxyl groups and / or anhydrides thereof are the same as those described for the polyester (meth) acrylate of the polyfunctional (meth) acrylate compound. Examples of the polyhydric alcohol having at least one (meth) acryloyloxy group include those described for the urethane (meth) acrylate oligomer.

In addition to the polymerizable oligomers as described above, examples of urethane (meth) acrylate oligomers are obtained by reacting isocyanates with hydroxyl groups of a hydroxyl group-containing polyester, a hydroxyl group-containing polyether or a hydroxyl group-containing (meth) acrylic acid ester. Compounds and the like. The hydroxyl group-containing polyester preferably used is a hydroxyl group-containing polyester obtained by an esterification reaction of a polyhydric alcohol, a carboxylic acid, a compound having a plurality of carboxyl groups, and / or an anhydride thereof. Examples of the polyhydric alcohol, the compound having a plurality of carboxyl groups, and / or the anhydride thereof are the same as those described for the polyester (meth) acrylate compound of the polyfunctional (meth) acrylate compound. The hydroxyl group-containing polyether preferably used is a hydroxyl group-containing polyether obtained by adding one or more alkylene oxides and / or ε-caprolactone to a polyhydric alcohol. The polyhydric alcohol may be the same as that which can be used for the hydroxyl group-containing polyester. Examples of the hydroxyl group-containing (meth) acrylic acid ester preferably used include the same as those described for the polymerizable oligomeric urethane (meth) acrylate oligomer. As the isocyanates, compounds having one or more isocyanate groups in the molecule are preferable, and divalent isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate are particularly preferable.

Each of these polymerizable oligomer compounds can be used alone or in combination with one or more other compounds.

Examples of the thermosetting resin include a phenol resin, a urea melamine resin, an epoxy resin, an unsaturated polyester resin, and a silicone resin, in addition to a thermosetting urethane resin composed of an acrylic polyol and an isocyanate prepolymer.

Examples of thermoplastic resins include cellulose derivatives such as acetylcellulose, nitrocellulose, acetylbutylcellulose, ethylcellulose, and methylcellulose; vinyl acetate and copolymers thereof, vinyl chloride and copolymers thereof, vinylidene chloride and copolymers thereof, and the like. Acetal resins such as polyvinyl formal and polyvinyl butyral; Acrylic resins and copolymers thereof, Acrylic resins such as methacrylic resins and copolymers; Polystyrene resins; Polyamide resins; Polyester resins; Polycarbonate resins Etc.

As the metal alkoxide, a silicon oxide matrix made of a silicon alkoxide material can be used. Specifically, it is tetramethoxysilane, tetraethoxysilane, or the like, and can be made into an inorganic or organic-inorganic composite matrix (translucent resin) by hydrolysis or dehydration condensation.

(2) Fine particles The fine particles 104 are not particularly limited as long as they have translucency, and conventionally known particles can be used. For example, organic fine particles made of acrylic resin, melamine resin, polyethylene, polystyrene, organic silicone resin, acrylic-styrene copolymer, calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, titanium oxide, glass, etc. And inorganic fine particles. Organic polymer balloons and glass hollow beads can also be used. One kind of these fine particles may be used alone, or two or more kinds may be mixed and used. The shape of the fine particles 104 may be any of a spherical shape, a flat shape, a plate shape, a needle shape, an indefinite shape, and the like, but a spherical shape or a substantially spherical shape is preferable.

The weight average particle diameter r of the fine particles 104 is preferably 1 μm or more and 15 μm or less, more preferably 4 μm or more and 10 μm or less. When the weight average particle size r is less than 1 μm, internal haze cannot be effectively expressed, and the glare reduction effect as an antiglare film becomes insufficient, or light diffusion as a light diffusion film or the like. Tend to be insufficient.
On the other hand, when the weight average particle diameter r exceeds 15 μm, the average thickness h of the fine particle-containing layer 102 tends to be increased accordingly (this will be described in detail later). It is easy to invite. Further, the antiglare property and the light diffusibility may become excessively high. For example, when an optical film is disposed on the viewing-side surface of the liquid crystal display device, excessive light diffusibility is such that light that leaks obliquely with respect to the front direction of the liquid crystal panel is strongly scattered in the front direction in black display. There is a risk of lowering the contrast due to reasons such as. The weight average particle diameter r of the fine particles 104 is measured by a Coulter counter method.

The fine particles 104 contained in the resin liquid for forming the fine particle-containing layer 102 (which will be contained in the fine particle-containing layer 102) typically have a fine particle-containing layer that can cause the above-described convex defects. The fine particles having a particle diameter larger than the average thickness h are contained, and the content ratio is a ratio of the number of particles and can be 2% or less with respect to the whole fine particles 104 contained in the resin liquid. Is 0.5% or less, more preferably 0.2% or less. According to the present invention, when the proportion of coarse particles is at least 2% or less with respect to the whole fine particles, the occurrence of convex defects can be sufficiently suppressed, and the fine particle-containing layer having good surface homogeneity is provided. Optical film can be obtained. Moreover, since the allowable range of the coarse particle content is relatively wide, the classification operation described in JP2010-159421-A can be made unnecessary or simplified. The ratio of the number of coarse particles in the entire fine particles 104 can be, for example, 1.0 × 10 ⁻⁹ % or more. Here, “coarse particles” in the present invention refers to fine particles having a particle diameter larger than the average thickness h of the fine particle-containing layer 102. Therefore, coarse particles are fine particles that can protrude from the surface of the fine particle-containing layer and generate convex defects when the fine particle-containing layer is formed using a resin liquid containing the coarse particle. The ratio of the number of coarse particles to the whole fine particles 104 is the number of particles (coarse particles) having a particle size larger than the average thickness h of the fine particle-containing layer, in which the particle size is measured for 50,000 particles by the Coulter counter method. Is calculated and divided by 50000.

The presence of convex defects can be confirmed by visual transmission or reflection observation. You may confirm by observing the surface or a cross section using an optical microscope, an electron microscope, etc. The size of the convex defect depends on the particle diameter of the coarse particles, and is usually approximately the same as or larger than the particle diameter of the coarse particles.

The refractive index difference between the fine particles 104 and the translucent resin 103 is preferably in the range of 0.04 to 0.15. By setting the refractive index difference within the above range, moderate internal scattering due to the refractive index difference occurs, and a sufficient glare reduction effect or appropriate light diffusibility can be obtained.

The content of the fine particles 104 in the fine particle-containing layer 102 (substantially the same as the content of the fine particles 104 in the resin liquid described later) is 3 parts by weight or more and 60 parts by weight with respect to 100 parts by weight of the translucent resin 103. Preferably, the amount is 5 parts by weight or more and 50 parts by weight or less. When the content of the fine particles 104 is less than 3 parts by weight with respect to 100 parts by weight of the translucent resin, the antiglare property becomes insufficient and sufficient internal haze for reducing glare cannot be obtained, or light The diffusibility tends to be insufficient. On the other hand, when the content of the fine particles 104 exceeds 60 parts by weight with respect to 100 parts by weight of the translucent resin, the antiglare property and the light diffusibility become excessively high and the contrast tends to be lowered.

(3) Average thickness h of the fine particle-containing layer The average thickness h of the fine particle-containing layer 102 is preferably 3 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less. According to the present invention, even when the average thickness h is as small as about 3 μm, the occurrence of convex defects can be satisfactorily suppressed. If the average thickness h is extremely small, the proportion of coarse particles in all fine particles becomes too large, and the occurrence of convex defects may not be sufficiently suppressed, and it is disadvantageous in terms of the mechanical strength of the optical film. . On the other hand, extremely increasing the average thickness h of the fine particle-containing layer 102 to an extent exceeding 20 μm, as described above, can reduce the production cost even if the occurrence of convex defects can be suppressed by such means. This results in an increase and does not meet the demand for thinning the optical film. Furthermore, when the average thickness h exceeds 20 μm, the amount of curl generated in the produced optical film becomes large, and the handleability in bonding to other films or substrates may be deteriorated. The “average thickness h” of the fine particle-containing layer 102 is an average value of the thicknesses of two or more fine particle-containing layers arbitrarily selected along the effective range width direction of the optical film. The value of each thickness is measured using a contact-type film thickness meter.

The ratio r / h of the weight average particle diameter r of the fine particles 104 to the average thickness h of the fine particle-containing layer 102 is preferably 0.3 or more, more preferably 0.5 or more. When the ratio r / h is less than 0.3, it means that the average thickness h is increased or the weight average particle diameter r is decreased. In the former case, it is not preferable for the reason described above. In the latter case, the effect of reducing glare as an antiglare film is insufficient, or the light diffusibility as a light diffusion film or the like tends to be insufficient.

On the other hand, the ratio r / h is preferably 0.9 or less, and more preferably 0.85 or less. When the ratio r / h exceeds 0.9, it means that the average thickness h is increased or the weight average particle diameter r is increased. In the former case, it is not preferable for the reason described above. In the latter case, the antiglare property and the light diffusibility may become excessively high. As described above, in the present invention, the ratio r / h is preferably in the range of 0.3 to 0.9. That is, the present invention relates to the weight average particle diameter r of the fine particles 104 and the average thickness h of the fine particle-containing layer 102. It is suitable when is relatively close. And this invention shows the special effect in the point that a convex defect can fully be suppressed also on the conditions where such a convex defect tends to occur frequently.

The maximum particle size R of the fine particles 104 contained in the fine particle-containing layer 102 (which can be said to be the maximum particle size of coarse particles contained in the fine particle-containing layer 102) is not particularly limited, but the average thickness of the fine particle-containing layer 102 is not limited. In relation to h, the ratio R / h between the maximum particle size R and the average thickness h is preferably 2 or less, and more preferably 1.8 or less. If the ratio is extremely large, the protrusion of coarse particles may not be sufficiently flattened, and good surface smoothness may not be obtained. The maximum particle size R of the fine particles 104 contained in the fine particle-containing layer 102 is a microscope of the surface of the fine particle-containing layer of the optical film produced by the same method except that the fine particle-containing layer is formed without pressing the surface of the mold. Observation is performed, and arbitrary 100 defects (protrusions of coarse particles from the surface of the fine particle-containing layer) are selected, and the largest particle size among the particle sizes of the fine particles forming these 100 defects is meant. .

[Surface shape of fine particle-containing layer]
The surface shape of the fine particle-containing layer 102 can be a flat surface, for example. Such a flat surface can be formed as a transfer structure in which a template having a mirror surface is used as a template and the mirror surface is transferred to the surface of the fine particle-containing layer 102. Since the transfer is performed by pressing the surface of the mold against the surface of the coating layer forming the fine particle-containing layer 102, the portion protruding from the coating layer of coarse particles is crushed, resulting in a convex shape. Defects are effectively suppressed or prevented. As described above, the optical film having such a flat surface can function as a light diffusion film or the like.

The fine particle-containing layer 102 may have surface irregularities. Such surface irregularities can be formed as a transfer structure in which a mold having an irregular surface is used as a mold and the irregular surface is transferred to the surface of the fine particle-containing layer 102. Since the transfer is performed by pressing the surface of the mold against the surface of the coating layer forming the fine particle-containing layer 102, the portion protruding from the coating layer of coarse particles is crushed, resulting in a convex shape. Defects are effectively suppressed or prevented. As described above, an optical film having such surface irregularities can function as an antiglare film or a light diffusion film.

[Haze of optical film]
In the optical film of the present invention, the total haze is preferably 10% or more and 70% or less, and the internal haze is also preferably 10% or more and 70% or less. The surface haze resulting from the surface shape of the fine particle-containing layer 102 is preferably 6% or less. Here, “total haze” refers to the total light transmittance (Tt) representing the total amount of light transmitted through irradiation of the optical film, and the diffused light transmittance (Td) diffused and transmitted by the optical film. From the ratio of the following formula (1):
Total haze (%) = (Td / Tt) × 100 (1)
Is required.

The total light transmittance (Tt) is the sum of the parallel light transmittance (Tp) and the diffuse light transmittance (Td) that are transmitted coaxially with the incident light. The total light transmittance (Tt) and the diffused light transmittance (Td) are values measured in accordance with JIS K 7361.

The “internal haze” of the optical film is a haze other than the haze (surface haze) caused by the surface shape of the fine particle-containing layer 102 among all the hazes.

When the total haze and / or internal haze is less than 10%, the antiglare property and the glare reduction effect or the light diffusibility tend to be insufficient. On the other hand, when the total haze and / or internal haze exceeds 70%, the antiglare property and the light diffusibility become excessively high, and the contrast tends to decrease. Further, the transparency of the optical film tends to be impaired. The total haze and internal haze are each preferably 20% or more and 65% or less. When the surface haze resulting from the surface shape of the fine particle-containing layer 102 exceeds 6%, it becomes easy to generate whitish that the entire screen feels whitish due to the irregular reflection of the surface of the fine particle-containing layer. In order to prevent whitening more effectively, the surface haze is preferably 3% or less.

The total haze, internal haze, and surface haze of the optical film are specifically measured as follows. That is, first, in order to prevent warping of the film, the optical film is bonded to a glass substrate with an optically transparent adhesive so that the fine particle-containing layer 102 becomes the surface. A measurement sample is prepared, and the total haze value of the measurement sample is measured. For the total haze value, the total light transmittance (Tt) and diffuse light transmittance are measured using a haze transmittance meter (for example, a haze meter “HM-150” manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K 7136. The rate (Td) is measured and calculated by the above formula (1).

Next, a triacetyl cellulose film having a haze of approximately 0% is bonded to the surface of the fine particle-containing layer 102 using glycerin, and the haze is measured in the same manner as the above-described measurement of all haze. The haze is almost countered by the triacetyl cellulose film to which the surface haze due to the surface shape of the fine particle-containing layer 102 is bonded, and thus can be regarded as “internal haze” of the optical film. Therefore, the “surface haze” of the optical film is expressed by the following formula (2):
Surface haze (%) = Total haze (%)-Internal haze (%) (2)
More demanded.

[Method for producing optical film]
Next, a method for producing the optical film of the present invention will be described. The optical film of the present invention can be suitably produced (effectively and at low cost) by a method including the following steps (A) to (C).
(A) A step of applying a resin liquid containing the fine particles 104 to form a coating layer on the base film 101,
(B) A step of pressing the surface of the mold against the surface of the coating layer, and (C) fixing the coating layer onto the base film 101 in a state where the surface of the mold is pressed against the surface of the coating layer. A step of forming the fine particle-containing layer 102.

The resin liquid used in the step (A) includes the fine particles 104, the translucent resin 103 or a resin forming the same (for example, an active energy ray curable resin, a thermosetting resin, or a metal alkoxide), and if necessary. Other components such as a solvent such as an organic solvent, a leveling agent, a dispersant, an antistatic agent, and an antifouling agent may be contained. Moreover, when using an ultraviolet curable resin as resin which forms the translucent resin 103, the said resin liquid contains a photoinitiator (radical polymerization initiator).

Examples of the photopolymerization initiator include acetophenone photopolymerization initiator, benzoin photopolymerization initiator, benzophenone photopolymerization initiator, thioxanthone photopolymerization initiator, triazine photopolymerization initiator, and oxadiazole photopolymerization initiator. An initiator or the like is used. Examples of the photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenyl-1,2 '-Biimidazole, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, benzyl, 9,10-phenanthrenequinone, camphorquinone, methyl phenylglyoxylate, titanocene compound and the like can also be used. The amount of the photopolymerization initiator used is usually 0.5 to 20 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of the resin contained in the resin liquid.

Examples of organic solvents include aliphatic hydrocarbons such as hexane, cyclohexane, and octane; aromatic hydrocarbons such as toluene and xylene; alcohols such as ethanol, 1-propanol, isopropanol, 1-butanol, and cyclohexanol; methyl ethyl ketone, methyl isobutyl Ketones such as ketone and cyclohexanone; esters such as ethyl acetate, butyl acetate and isobutyl acetate; glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether Ethers; ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, etc. Esterified glycol ethers; Cellsolves such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol; 2- (2-methoxyethoxy) ethanol, 2- (2-ethoxyethoxy) ethanol, 2- (2- It can be selected from carbitols such as butoxyethoxy) ethanol in consideration of viscosity and the like. These solvents may be used alone or as a mixture of several kinds as required. After coating, it is necessary to evaporate the organic solvent. Therefore, the boiling point is desirably in the range of 60 ° C to 160 ° C. The saturated vapor pressure at 20 ° C. is preferably in the range of 0.1 kPa to 20 kPa.

In addition, in order to make the optical characteristics and surface shape of the optical film uniform, the dispersion of the fine particles 104 in the resin liquid is preferably isotropic dispersion.

Application of the resin liquid onto the base film 101 can be performed by, for example, a gravure coating method, a micro gravure coating method, a rod coating method, a knife coating method, an air knife coating method, a kiss coating method, a die coating method, or the like. . In applying the resin liquid, as described above, preferably, the average thickness h of the fine particle-containing layer 102, the ratio r / h of the weight average particle size r to the average thickness h of the fine particles 104, and the maximum particle size of the fine particles 104 are as follows. The coating layer is formed by adjusting the coating thickness so that the ratio R / h of R to the average thickness h is within the above preferred range.

Various surface treatments may be applied to the surface of the base film 101 (surface on the fine particle-containing layer side) for the purpose of improving the coating property of the resin liquid or improving the adhesion with the fine particle-containing layer 102. Examples of the surface treatment include corona discharge treatment, glow discharge treatment, acid surface treatment, alkali surface treatment, and ultraviolet irradiation treatment. Further, another layer such as a primer layer may be formed on the base film 101, and the resin liquid may be applied on the other layer.

Moreover, when using the optical film of this invention as a protective film of the polarizing film mentioned later, in order to improve the adhesiveness of the base film 101 and a polarizing film, the surface (fine particle content layer) of the base film 101 is improved. It is preferable to hydrophilize the surface on the opposite side of the surface by various surface treatments.

Next, in the step (B), the surface of the mold is pressed against the surface of the coating layer (layer made of a resin liquid), and the shape of the surface is transferred to the surface of the coating layer. The mold is for imparting a desired shape to the surface of the fine particle-containing layer 102, and has a surface shape composed of a transfer structure of the desired shape. By fixing the coating layer onto the substrate film 101 while pressing the surface shape against the surface of the coating layer, the surface shape of the mold can be transferred and the protrusions of coarse particles are crushed. Examples of the mold include a mold having a mirror surface (for example, a mirror roll) and a mold having an uneven surface (for example, an emboss roll).

In the case where the mold has an uneven surface, the uneven pattern may be a regular pattern, a random pattern, or a pseudo random pattern in which one or more random patterns of a specific size are spread. Although it is good, it is preferably a random pattern or a pseudo-random pattern from the viewpoint of preventing the reflected image from becoming iridescent due to interference of reflected light caused by the surface shape.

The outer shape of the mold is not particularly limited, and may be a flat plate shape or a cylindrical or cylindrical roll. From the viewpoint of continuous productivity, a mirror surface roll, an emboss roll, etc. A columnar or cylindrical mold is preferred. In this case, a predetermined surface shape is formed on the side surface of the columnar or cylindrical mold.

The material of the base material of the mold is not particularly limited, and can be appropriately selected from metal, glass, carbon, resin, or a composite thereof, but metal is preferable from the viewpoint of workability. Suitable metal materials include aluminum, iron, or an alloy mainly composed of aluminum or iron from the viewpoint of cost.

As a method for obtaining a mold, for example, a method of polishing a substrate, sandblasting, and then applying electroless nickel plating (JP2006-53371-A); after applying copper plating or nickel plating to the substrate, Polishing, sand blasting, and chromium plating (JP2007-188952-A); copper plating or nickel plating, polishing, sand blasting, etching process or copper plating process And then applying chromium plating (JP 2007-237541-A); applying copper plating or nickel plating to the surface of the substrate, polishing, applying a photosensitive resin film on the polished surface, The pattern is exposed on the photosensitive resin film, then developed, and etched using the developed photosensitive resin film as a mask. A method of performing treatment, peeling the photosensitive resin film, further etching, dulling the uneven surface, and then plating the formed uneven surface with chrome; and a cutting tool using a machine tool such as a lathe And a method of cutting a base material to be a mold (WO2007 / 077892-A) and the like.

The surface irregularity shape of the template comprising a random pattern or a pseudo-random pattern is, for example, an FM screen method, a DLDS (Dynamic Low-Discretion Sequence) method, a method using a microphase separation pattern of a block copolymer, or a bandpass filter method. The random pattern generated by the above can be formed by exposing and developing on the photosensitive resin film, and performing an etching process using the developed photosensitive resin film as a mask.

Next, in the step (C), in a state where the surface of the mold is pressed against the surface of the coating layer, the coating layer is fixed on the base film 101 to form the fine particle-containing layer 102, and the optical film is formed. obtain. Specifically, when an active energy ray curable resin, a thermosetting resin, or a metal alkoxide is used as the resin for forming the translucent resin 103, drying (removing the solvent) is performed as necessary, and then coating is performed. In the state where the mold surface is pressed against the surface of the work layer, the active energy ray is irradiated from the base film 101 side to the coating layer (when an active energy ray-curable resin is used) or heated (thermosetting type). When the resin or metal alkoxide is used), the coating layer is cured. The active energy ray can be appropriately selected from ultraviolet rays, electron beams, near ultraviolet rays, visible light, near infrared rays, infrared rays, X-rays, etc. depending on the type of resin contained in the resin liquid. An electron beam is preferable, and ultraviolet rays are particularly preferable because of easy handling and high energy.

As the ultraviolet light source, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. An ArF excimer laser, a KrF excimer laser, an excimer lamp, synchrotron radiation, or the like can also be used. Among these, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon arc, and a metal halide lamp are preferably used.

As the electron beam, 50 to 1000 keV emitted from various electron beam accelerators such as Cockloft Walton type, Bande graph type, resonance transformation type, insulation core transformation type, linear type, dynamitron type, and high frequency type, preferably 100 An electron beam having an energy of ~ 300 keV can be mentioned.

On the other hand, when a thermoplastic resin is used as the translucent resin 103, after drying (removing the solvent) as necessary, the coating layer is softened or melted, and the mold surface is pressed against the coating layer surface. When the coating layer is cooled in this state, an optical film to which the surface shape of the mold is transferred can be produced.

According to the manufacturing method of the present invention described above, the fine particle-containing layer 102 is not thickened (when the average thickness h of the fine particle-containing layer 102 is relatively close to the weight average particle diameter r of the fine particles 104). In addition, convex defects can be effectively suppressed at low cost without performing additional operations such as classification of fine particles.

Next, a preferred embodiment for producing the optical film of the present invention will be described. The production method according to the preferred embodiment includes a step of continuously feeding the base film 101 wound in a roll shape, the fine particles 104 and the ultraviolet curable resin in order to continuously produce the optical film of the present invention. A step of applying a resin liquid to be applied and drying it as necessary, a step of curing the coating layer while pressing the mold surface against the surface of the coating layer, and a step of winding up the obtained optical film. Such a manufacturing method can be implemented, for example, using a manufacturing apparatus shown in FIG. Hereinafter, the manufacturing method according to the preferred embodiment will be described with reference to FIG.

First, the base film 101 is continuously unwound by the unwinding device 201. Next, a resin liquid containing the fine particles 104 and the ultraviolet curable resin is applied onto the unwound base film 101 using the coating device 202 and the backup roll 203 facing the coating device 202. Next, when a solvent is contained in the resin liquid, the resin liquid is dried by passing it through a dryer 204. Next, the base film 101 provided with the coating layer is placed between the mirror metal roll or the embossing metal roll 205 and the nip roll 206, and the coating layer is a mirror metal roll or the embossing metal. It is wound around in close contact with the roll 205. Thereby, the mirror surface of the mirror surface metal roll or the uneven surface of the metal roll for embossing is pressed against the surface of the coating layer, and the surface shape is transferred. Next, in a state where the base film 101 is wound around a mirror surface metal roll or an embossing metal roll 205, the coating layer is cured by irradiating ultraviolet rays from the ultraviolet irradiation device 208 through the base film 101. Let Since the irradiated surface becomes hot due to ultraviolet irradiation, the mirror surface metal roll or the embossing metal roll 205 preferably includes a cooling device for adjusting the surface temperature to about room temperature to about 80 ° C. . Further, one or a plurality of ultraviolet irradiation devices 208 can be used. The substrate film 101 (optical film) on which the fine particle-containing layer 102 is formed is peeled off from the mirror surface metal roll or the embossing metal roll 205 by the peeling roll 207. The optical film produced as described above is taken up by the take-up device 209. At this time, for the purpose of protecting the fine particle-containing layer 102, a protective film made of polyethylene terephthalate or polyethylene or the like may be wound on the surface of the fine particle-containing layer 102 through a pressure-sensitive adhesive layer having removability. Good.

In addition, after peeling from the mirror surface metal roll or the embossing metal roll 205 by the peeling roll 207, additional ultraviolet irradiation may be performed.

[Other Embodiments of Optical Film]
The optical film of the present invention may further include an antireflection layer laminated on the fine particle-containing layer 102 (surface opposite to the base film 101). The antireflection layer may be directly formed on the fine particle-containing layer 102. An antireflection film in which an antireflection layer is formed on a transparent film is separately prepared, and this is applied to the fine particle-containing layer 102 using an adhesive or an adhesive. You may laminate. The antireflection layer is provided to reduce the reflectance as much as possible, and reflection on the display screen can be more effectively prevented by forming the antireflection layer. The antireflective layer includes a low refractive index layer composed of a material lower than the refractive index of the fine particle-containing layer 102; a high refractive index layer composed of a material higher than the refractive index of the fine particle-containing layer 102, and the high refractive index. A laminated structure with a low refractive index layer composed of a material lower than the refractive index of the layer can be exemplified. When an antireflection film is laminated on the fine particle-containing layer 102 using an adhesive or an adhesive, a commercially available antireflection film can be used.

<Polarizing plate>
The polarizing plate of this invention is equipped with a polarizing film and the above-mentioned optical film laminated | stacked on this polarizing film so that the base film 101 side may oppose this polarizing film. A polarizing film has a function which takes out linearly polarized light from incident light, The kind is not specifically limited. As an example of a suitable polarizing film, there can be mentioned a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin. Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol, which is a saponified product of vinyl acetate, partially formalized polyvinyl alcohol, and a saponified product of an ethylene / vinyl acetate copolymer. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, a polyene-oriented film of a polyvinyl alcohol dehydrated product or a polyvinyl chloride dehydrochlorinated product can also be a polarizing film. The thickness of the polarizing film is usually about 5 to 80 μm.

The polarizing plate of the present invention may be one in which the optical film of the present invention is laminated on one side or both sides (usually one side) of the polarizing film, and a transparent protective layer is laminated on one side of the polarizing film. And what laminated | stacked the optical film of this invention on the other surface may be sufficient. At this time, the optical film also has a function as a transparent protective layer of the polarizing film. When the surface irregularity shape is given to the fine particle-containing layer 102 of the optical film, the fine particle-containing layer also has a function as an antiglare layer. The transparent protective layer can be formed on the polarizing film by a method of laminating a transparent resin film using an adhesive or the like, a method of applying a transparent resin-containing coating solution, or the like. Similarly, the optical film of the present invention can be bonded to a polarizing film using an adhesive or the like.

The transparent resin film serving as the transparent protective layer is preferably excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, etc., and examples thereof include triacetyl cellulose, diacetyl cellulose, cellulose acetate propio Cellulose resins such as cellulose acetate such as nates; Polycarbonate resins; (Meth) acrylic resins such as polyacrylate and polymethyl methacrylate; Polyester resins such as polyethylene terephthalate and polyethylene naphthalate; Chains such as polyethylene and polypropylene Examples thereof include films made of polyolefin resin; cyclic polyolefin resin; styrene resin; polysulfone; polyether sulfone; polyvinyl chloride resin. These transparent resin films may be optically isotropic, or have optical anisotropy for the purpose of compensating the viewing angle when incorporated in an image display device. Also good.

<Image display device>
The image display device of the present invention is a combination of the polarizing plate of the present invention and an image display element that displays various information on a screen. The type of the image display device of the present invention is not particularly limited. In addition to a liquid crystal display (LCD) using a liquid crystal panel, a cathode ray tube (CRT) display, a plasma display (PDP), a field emission display (FED), a surface Examples thereof include a conduction electron-emitting device display (SED), an organic EL display, a laser display, and a projector television screen.

For example, when a liquid crystal panel is produced by disposing the polarizing plate of the present invention on a liquid crystal cell, the polarizing plate is disposed on the liquid crystal cell with the fine particle-containing layer 102 outside. The same applies to other image display apparatuses. The optical film may be disposed on the viewing side of the image display element, on the backlight side, or on both. When the optical film is arranged on the viewer side, the optical film functions as an antiglare film that prevents glare or reflection of external light, or a light diffusion film that improves the viewing angle. On the other hand, when the optical film is disposed on the backlight side, the optical film functions as a diffusion plate (or diffusion sheet) that diffuses light incident on the liquid crystal cell and prevents moiré or the like.

Since the image display device of the present invention includes an optical film in which the occurrence of convex defects is effectively suppressed or prevented, the occurrence of whitening and the decrease in contrast are effectively suppressed, and visibility is improved. Excellent.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The average thickness h of the fine particle-containing layer, the weight average particle size r, the standard deviation and the maximum particle size R of the fine particles, and the ratio of the number of coarse particles in the entire fine particles are measured as follows.

(A) Average thickness h of the fine particle-containing layer
The total thickness including the base film and the fine particle-containing layer every 5 cm along the effective range width direction of the optical film is measured by a contact-type film thickness meter [DIGIMICRO MH-15 (main body) and ZC-101 (counter) manufactured by NIKON The average value of these was calculated by subtracting 80 μm of the thickness of the base film from this average value to obtain the average thickness h of the fine particle-containing layer.

(B) Weight average particle diameter r and standard deviation of fine particles Measured by a Coulter counter method.

(C) Maximum particle size R of fine particles contained in the fine particle-containing layer
A microscopic observation of the surface of the fine particle-containing layer is performed on an optical film or the like of a comparative example which will be described later, and arbitrary 100 defects (protrusions of coarse particles from the surface of the fine particle-containing layer) are selected, and these 100 defects are formed. The maximum particle size of the particle sizes of the fine particles is defined as the maximum particle size R.

(D) The ratio of the number of coarse particles in the whole fine particles The particle size of 50,000 particles was measured by a Coulter counter method, and the number of particles (coarse particles) having a particle size larger than the average thickness h of the fine particle-containing layer. Was divided by 50000 to obtain the ratio of the number of coarse particles. In addition, when the said measuring method is applied about the polystyrene type particle | grains (same as what was used in Example 1) used in the following Example 3 and Comparative Example 2, the ratio of the number of coarse particles in which a particle diameter exceeds 13 micrometers is 0.00. However, even when the average thickness h of the fine particle-containing layer is 13 μm (Example 3 and Comparative Example 2), coarse particles having a particle diameter exceeding 13 μm can be confirmed by microscopic observation. It turns out that the convex defect by particle | grains becomes a problem.

<Example 1>
60 parts by weight of pentaerythritol triacrylate, 40 parts by weight of polyfunctional urethanized acrylate (reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate), polystyrene-based particles as fine particles (weight average particle diameter: 6.9 μm, standard deviation: 1.3 μm, the proportion of coarse particles with a particle diameter exceeding 10 μm in the entire fine particles: 0.12%, the proportion of coarse particles with a particle diameter exceeding 13 μm in the entire fine particles: 0.002% or less) 20 parts by weight, light A polymerization initiator “Lucirin TPO” (manufactured by BASF, chemical name: 2,4,6-trimethylbenzoyldiphenylphosphine oxide) 5 parts by weight and 80 parts by weight of propylene glycol monomethyl ether as a diluent solvent were mixed and coated. An ultraviolet curable resin liquid to be a work layer was prepared.

The resin solution is applied on a triacetyl cellulose (TAC) film (base film) having a thickness of 80 μm with a die coater to form a coating layer, and a laminate of the base film and the coating layer is obtained. It was. After the obtained laminate was dried in a drying furnace, a chromium plating roll that had been polished so that the surface became a mirror surface was pressed and adhered to the coating layer surface of the laminate using a nip roll.
In this state, the coating layer was cured by irradiating ultraviolet rays from the base film side so that the maximum illuminance in UVA was 700 mW / cm ² and the integrated light quantity in UVA was 300 mJ / cm ² . Thereafter, the laminate was peeled from the chromium plating roll to obtain an optical film having an average thickness h of the fine particle-containing layer of 10 μm.

<Example 2>
Implemented except that polystyrene particles (weight average particle size: 8.2 μm, standard deviation: 0.6 μm, ratio of coarse particles with a particle diameter exceeding 10 μm in the entire fine particles: 1.6%) were used as the fine particles. An optical film was produced in the same manner as in Example 1. The maximum particle size R of the optical film produced by the same method, except that the fine particle-containing layer was formed without pressing the surface of the mold, was measured and the maximum particle size R was measured. there were.

<Example 3>
An optical film was produced in the same manner as in Example 1 except that the average thickness h of the fine particle-containing layer was 13 μm.

<Comparative Example 1>
Except that the laminate of the base film and the coating layer produced in the same manner as in Example 1 was irradiated with ultraviolet rays from the coating layer side without carrying out the transfer step (pressing the chromium plating roll). An optical film was produced in the same manner as in Example 1. When the maximum particle size R of this optical film was measured, it was 13.5 μm (therefore, the maximum particle size R in the optical film of Example 1 was also 13.5 μm).

<Comparative Example 2>
An optical film was produced in the same manner as in Comparative Example 1 except that the average thickness h of the fine particle-containing layer was 13 μm. When the maximum particle size R of this optical film was measured, it was 13.5 μm (therefore, the maximum particle size R in the optical film of Example 3 was also 13.5 μm).

[Evaluation of convex defects in optical films]
About the obtained optical film, a fine particle-containing layer of coarse particles (particles having a particle diameter exceeding 10 μm for Examples 1 and 2 and Comparative Example 1, and particles having a particle diameter exceeding 13 μm for Example 3 and Comparative Example 2) The presence or absence of convex defects due to protrusion from the surface was confirmed by visual transmission or reflection observation. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 3 in which the ratio of coarse particles having a particle diameter larger than the average thickness h of the fine particle-containing layer was 2% or less and the transfer process was performed, the occurrence of convex defects was observed. In Comparative Examples 1 and 2 in which the transfer process was not performed, a convex defect occurred.

DESCRIPTION OF SYMBOLS 100 Optical film 101 Base film 102 Fine particle content layer 103 Translucent resin 104 Fine particle 110 Coarse particle 201 Unwinding device 202 Coating device 203 Backup roll 204 Dryer 205 Mirror surface metal roll or Embossing metal roll 206 Nip roll 207 Peeling roll 208 Ultraviolet irradiation device 209 Winding device

Claims

An optical film comprising a base film and a fine particle-containing layer formed from a resin liquid containing fine particles on the base film,
The ratio of fine particles (coarse particles) having a particle diameter larger than the average thickness h of the fine particle-containing layer to the total fine particles contained in the resin liquid is 2% or less,
The surface of the fine particle-containing layer is an optical film having a shape formed by pressing the surface of a mold.
2. The optical film according to claim 1, wherein the ratio r / h of the weight average particle diameter r of the fine particles contained in the resin liquid to the average thickness h of the fine particle-containing layer is 0.3 or more.
The optical film according to claim 1 or 2, wherein the ratio r / h of the weight average particle diameter r of the fine particles contained in the resin liquid to the average thickness h of the fine particle-containing layer is 0.9 or less.
4. The optical film according to claim 1, wherein the ratio R / h of the maximum particle size R of the fine particles contained in the fine particle-containing layer to the average thickness h of the fine particle-containing layer is 2 or less.
The optical film according to any one of claims 1 to 4, wherein the fine particles contained in the resin liquid have a weight average particle diameter r of 1 µm or more and 15 µm or less.
6. The optical film according to claim 1, wherein an average thickness h of the fine particle-containing layer is 3 μm or more and 20 μm or less.
7. The optical film according to claim 1, wherein the fine particle-containing layer is a cured product layer of the resin liquid.
The optical film according to any one of claims 1 to 7, wherein a ratio of the coarse particles to the whole fine particles contained in the resin liquid is 0.2% or less.
The optical film according to any one of claims 1 to 8, wherein the mold is a mold having a mirror surface or a mold having an uneven surface.
10. The optical film according to claim 1, further comprising an antireflection layer laminated on the fine particle-containing layer.
It is a manufacturing method of the optical film of Claim 1, Comprising:
On the base film, a process of coating a resin liquid containing fine particles to form a coating layer;
Pressing the surface of the mold against the surface of the coating layer;
Forming the fine particle-containing layer by fixing the coating layer on the base film in a state where the surface of the mold is pressed against the surface of the coating layer;
The manufacturing method of the optical film containing this.
The step of forming the fine particle-containing layer is performed by irradiating the coating layer with active energy rays from the base film side with the surface of the mold pressed against the surface of the coating layer. The manufacturing method of Claim 11 including the process of hardening a layer.
A polarizing film;
The optical film according to any one of claims 1 to 10, which is laminated on the polarizing film so that the base film side faces the polarizing film;
A polarizing plate comprising:
A polarizing plate according to claim 13 and an image display element,
The said polarizing plate is an image display apparatus arrange | positioned on the said image display element by making the fine particle content layer side into the outer side.