TW201300221A - Process for producing optical film, polarizing plate and image display device - Google Patents

Abstract

The present invention provides a process for producing an optical film which comprises coating step of forming coating layer by applying coating solution containing active energy ray curable resin on continuously carried base film; and curing step of irradiating the coating layer with active energy ray from the base film side with holding a surface of the coating layer to a surface of a mold, wherein, in the curing step, a pressure exerted to the both end area in width direction in the coating layer is smaller than to the center area in width direction located between the both end area. By the present invention, peeling off of resin and generation of adhesion of resin to mold can effectively be prevented. An optical film can effectively be produced continuously without occurrence of malfunctioning such as defect thereby.

Description

Optical film manufacturing method, polarizing plate and image display device

The present invention relates to a method for producing an optical film in which a coating liquid containing an active energy ray-curable resin is applied onto a base film and cured. Further, the present invention relates to a polarizing plate and an image display device using the optical film.

An optical film in which a resin layer having a specific optical function is formed on a base film by coating is used as an anti-glare film, a light-diffusing film, a hard coat film, or the like, for various image display devices such as a liquid crystal display device. in.

Usually, the resin layer provided in the optical film is formed by applying a coating liquid containing an active energy ray-curable resin onto a base film, and irradiating the obtained coating layer with an active energy ray to cure it. . Depending on the optical characteristics required for the optical film, in order to impart a desired shape to the surface of the resin layer, the surface of the coating layer is pressed against a mold having a specific surface shape and hardened in this state.

For example, JP 2007-76089-A discloses a method in which an ultraviolet curable resin is applied onto a substrate film, and the resin coated surface is adhered to a concave-convex roller (embossing roll) which rotates in synchronization with the substrate film. In the state of the film, ultraviolet rays are irradiated to cure the resin, and then the laminate of the cured resin and the base film is peeled off from the uneven roll.

In the case of the method described in JP2007-76089-A, the surface of the coating layer is pressed against a mold having a specific surface shape such as an embossing roll, and the coating layer is hardened to produce an optical film. Sometimes, sometimes When the obtained optical film is peeled off from the mold, a "resin peeling" or a hardened resin residue in which the hardened resin is peeled off from the base film or at least a part of the peeled hardened resin is detached at both end portions in the width direction of the coating layer "Resin residue" on the surface of the mold.

Not only the portion where the resin is peeled off may itself be a defect, but also when the peeled hardened resin is detached from the base film, there is a problem that causes step contamination or further defects in the continuously produced optical film. Further, the resin remaining on the surface of the mold remains in the continuous production of the optical film to cause continuous defects in the obtained optical film (transfer of the cured resin to the surface of the optical film, or defects in the surface shape or optical characteristics of the optical film, etc.) After that. Moreover, removing the cleaning each time a resin residue is generated greatly reduces the manufacturing efficiency.

It is described in JPH05-58788-B, JP3546485-B, and JP3710901-B which are provided on the roll (molding) for imparting irregularities on the surface of the coating layer, and are provided on the outer side of the concave-convex pattern (both ends in the width direction of the roll). The smooth surface improves the peelability between the coating layer and the mold.

The method of providing a smooth surface on both ends of the mold described in JPH05-58788-B, JP3546485-B, and JP3710901-B is effective to some extent to reduce the resin residue on the surface of the mold, but there is still room for improvement. Further, this method is not a method effective for peeling off the resin of the resin on the substrate film.

On the other hand, as a method of preventing resin residue, it is conceivable to add a release agent to the coating liquid for forming the coating layer, or to apply a release agent or the like to the surface of the mold in advance, but it may be damaged by the addition of the release agent. The mechanical strength or optical properties of the optical film.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a The method of effectively preventing the occurrence of resin peeling and resin residue, and thereby continuously and efficiently producing an optical film without causing defects such as defects.

The present invention encompasses the following.

[1] A method for producing an optical film, comprising: a coating step of applying a coating liquid containing an active energy ray-curable resin onto a substrate film that is continuously conveyed to form a coating layer; and a hardening step, The coating layer is irradiated with an active energy ray from the substrate film side in a state where the surface of the coating layer is pressed against the surface of the mold; and in the hardening step, the surface of the coating layer is pressed against On the surface of the mold, the pressure applied to the both end portions in the width direction of the coating layer is smaller than the central portion in the width direction between the end portions.

[2] The method according to [1] above, wherein in the hardening step, the surface of the coating layer is pressed against the nip which is disposed opposite to the mold via the substrate film having the coating layer On the surface of the mold, and the nip roller is applied to the surface of the coating layer by pressing the surface of the coating layer against the surface of the casting layer, the pressure applied to the both end portions in the width direction of the coating layer is smaller than the two The central portion of the width direction between the end regions is processed.

[3] The method according to [2] above, wherein the nip roller is processed in such a manner that a region corresponding to a central portion of the coating layer is protruded more outward than a region corresponding to the both end regions. By.

[4] A polarizing plate comprising: a polarizing film, and an optical film laminated on the polarizing film such that the substrate film side faces the polarizing film, and by [1] to [...] 3] manufactured by any of the methods.

[5] An image display device comprising the polarizing plate and the image display element according to [4] above, wherein the polarizing plate is disposed on the image display element such that the polarizing film is on the image display element side.

According to the method of the present invention, the resin peeling of the hardened resin and the resin residue of the mold when the optical film is peeled off from the mold can be effectively prevented. Thereby, in the continuous production of the optical film in which the resin layer is continuously formed on the long base film, the optical film can be continuously and efficiently produced without causing defects such as defects or contamination of the steps. The optical film obtained by the present invention can be preferably applied to an image display device such as a polarizing plate or a liquid crystal display device.

<Method of Manufacturing Optical Film>

The method for producing an optical film of the present invention comprises the following steps: [1] a coating step of applying a coating liquid containing an active energy ray-curable resin onto a substrate film that is continuously conveyed to form a coating layer; [2] A hardening step of irradiating the coating layer with an active energy ray from the substrate film side in a state where the surface of the coating layer is pressed against the surface of the mold to cure the coating layer.

Hereinafter, each step will be described in detail with reference to the drawings. Fig. 1 is a view schematically showing a preferred embodiment of a method for producing an optical film of the present invention and a manufacturing apparatus therefor. The arrows in the figure indicate the direction in which the film is conveyed or the direction in which the rolls are rotated.

[1] Coating step

In this step, a coating liquid containing an active energy ray-curable resin is applied onto a substrate film that is continuously conveyed to form a coating layer. The coating step is, for example, As shown in Fig. 1, the base film 11 can be continuously wound up from the original sheet (the wound product of the long base film) attached to the film take-up device 31, and the coating liquid can be applied using the coating device 32. It is apply|coated on the base film 11.

The application of the coating liquid to the substrate film 11 can be performed, for example, by a gravure coating method, a micro gravure coating method, a bar coating method, a doctor blade coating method, an air knife coating method, or the like. The coating method, the die coating method, and the like are carried out.

(substrate film)

The base film 11 may be any light transmissive member, and for example, a glass or a plastic film may be used. As the plastic film, it is sufficient as long as it has moderate transparency and mechanical strength. Specifically, for example, a cellulose resin such as TAC (triacetyl cellulose), a polyester resin such as an acrylic resin, a polycarbonate resin, or polyethylene terephthalate, or a poly A polyolefin resin such as ethylene or polypropylene. The thickness of the base film 11 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 of the optical film.

In order to improve the coating property of the coating liquid or to improve the adhesion to the coating layer, various surface treatments may be applied to the surface (coating layer side surface) of the base film 11. 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 an undercoat layer may be formed on the base film 11, and a coating liquid may be applied to the other layer.

Further, in the case where the optical film is used in the following polarizing film, in order to improve the adhesion between the base film and the polarizing film, it is preferred to previously apply the surface of the substrate film by various surface treatments (and coating). The opposite side of the cloth layer) hydrophilic Chemical. This surface treatment can also be carried out after the production of the optical film.

(coating liquid)

The coating liquid contains an active energy ray-curable resin, and usually further contains a photopolymerization initiator (radical polymerization initiator). Other components such as a light-transmitting fine particle, an organic solvent, a solvent, a leveling agent, a dispersing agent, an antistatic agent, an antifouling agent, and a surfactant may be contained as needed.

(1) Active energy ray-curable resin

The active energy ray-curable resin may be an ultraviolet curable resin or an electron beam curable resin. For example, a polyfunctional (meth) acrylate compound may be preferably used. The polyfunctional (meth) acrylate compound refers to a compound having at least two (meth) acryloxy groups in the molecule. Specific examples of the polyfunctional (meth) acrylate compound include a polyhydric alcohol and a (meth)acrylic acid ester compound, a (meth)acrylic acid urethane compound, and a (meth)acrylic polyester compound. A polyfunctional polymerizable compound containing two or more (meth)acryl fluorenyl groups, such as an epoxy (meth) acrylate compound.

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, and 1,3-propanediol. , butanediol, pentanediol, hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, 2,2'-thiodiethanol, 1,4-cyclohexanedimethanol, etc. a diol or a trihydric or higher alcohol such as trimethylolpropane, glycerin, pentaerythritol, diglycerin, dipentaerythritol or di-trimethylolpropane.

As an ester of a polyhydric alcohol and (meth)acrylic acid, specifically For example: ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylic acid Ester, trimethylolpropane tri(meth) acrylate, trimethylolethane tri(meth) acrylate, tetramethylol methane tri(meth) acrylate, 1,6-hexanediol (meth) acrylate, tetramethylol methane tetra (meth) acrylate, pentaglycerol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol (Meth) acrylate, dipentaerythritol tri(meth) acrylate, dipentaerythritol tetra(meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate.

The (meth)acrylic acid urethane compound may be 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 hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, naphthalene diisocyanate, diphenylmethane diisocyanate, and benzodimethyl group. Diisocyanate, dicyclohexylmethane diisocyanate is equal to an organic isocyanate having two isocyanate groups in one molecule, and the organic isocyanate is modified by isocyanurate modification, adduct modification, and biuret modification. An organic isocyanate having three isocyanate groups in one molecule. Examples of the (meth)acrylic acid derivative having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. 2-hydroxybutyl acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, pentaerythritol triacrylate.

A (meth)acrylic polyester obtained by reacting a hydroxyl group-containing polyester with (meth)acrylic acid is preferred as the (meth)acrylic polyester compound. The hydroxyl group-containing polyester which can be preferably used is a hydroxyl group-containing polyester obtained by esterification reaction of a polyhydric alcohol with a carboxylic acid or a compound having a plurality of carboxyl groups and/or an anhydride thereof. The polyhydric alcohol may, for example, be the same as the above compound. Further, examples of the phenols other than the polyhydric alcohol include bisphenol A and the like. Examples of the carboxylic acid include formic acid, acetic acid, butyl formic acid, and benzoic acid. Examples of the compound having a plurality of carboxyl groups and/or an anhydride thereof include maleic acid, phthalic acid, fumaric acid, itaconic acid, adipic acid, terephthalic acid, and maleic anhydride. , phthalic anhydride, trimellitic acid, cyclohexane dicarboxylic anhydride, and the like.

In the polyfunctional (meth) acrylate compound as described above, hexanediol di(meth) acrylate or neopentyl glycol is preferred in terms of the strength of the cured product or the ease of obtaining it. Di(meth)acrylate, diethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylic acid An ester compound such as an ester or dipentaerythritol hexa(meth)acrylate; an adduct of hexamethylene diisocyanate and 2-hydroxyethyl (meth)acrylate; isophorone diisocyanate and (meth)acrylic acid 2 An adduct of hydroxyethyl ester; an adduct of toluene diisocyanate and 2-hydroxyethyl (meth)acrylate; an adduct-modified isophorone diisocyanate and 2-hydroxyethyl (meth)acrylate An adduct; and an addition product of a biuret-modified isophorone diisocyanate and 2-hydroxyethyl (meth)acrylate. Further, these polyfunctional (meth) acrylate compounds may be used singly or in combination of one or more kinds.

The active energy ray-curable resin may contain a monofunctional (meth) acrylate compound in addition to the above polyfunctional (meth) acrylate compound. Examples of the monofunctional (meth) acrylate compound include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and isobutyl (meth) acrylate. Base) butyl acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, glycidyl (meth)acrylate, propylene oxime Porphyrin, N-vinylpyrrolidone, tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid Ester, ethyl methacrylate, benzyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (Meth) acrylate, phenoxy (meth) acrylate, ethylene oxide modified phenoxy (meth) acrylate, propylene oxide (meth) acrylate, nonyl phenol (methyl) Acrylate, ethylene oxide modified (meth) acrylate, propylene oxide modified nonyl phenol (meth) acrylate, methoxy diethylene glycol (meth) acrylate, phthalic acid 2 -(Meth)acryloyloxyethyl-2-hydroxypropyl ester, (meth)acrylic acid dimethylaminoethyl ester, methoxytriethylene glycol (meth) acrylate, etc. (meth)acrylic acid Esters. These compounds may be used singly or in combination with one or more other kinds.

Further, the active energy ray-curable resin may contain a polymerizable oligomer. The hardness of the cured product can be adjusted by containing a polymerizable oligomer. The polymerizable oligomer may be, for example, the above polyfunctional (meth) acrylate compound, that is, a polyol (meth) acrylate ester compound or a (meth) acrylate urethane compound. An oligomer such as a dimer or a trimer such as a (meth)acrylic polyester compound or an epoxy (meth)acrylate.

As the other polymerizable oligomer, a (meth)acrylic acid amine group obtained by a reaction of a polyisocyanate having at least two isocyanate groups in the molecule and a polyol having at least one (meth) acryloxy group can be exemplified. Formate oligomer. Examples of the polyisocyanate include a polymer of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and benzodimethyl diisocyanate, and at least one (meth) group. The propylene oxy group-containing polyol may, for example, be a hydroxyl group-containing (meth) acrylate obtained by esterification reaction of a polyhydric alcohol with (meth)acrylic acid, and examples of the polyhydric alcohol include, for example, 1,3-butyl Alcohol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, trimethylolpropane, glycerin, pentaerythritol Dipentaerythritol and the like. The polyol having at least one (meth) acryloxy group is one in which an alcoholic hydroxyl group of a polyol is esterified with (meth)acrylic acid, and an alcoholic hydroxyl group remains in the molecule.

Further, examples of the other polymerizable oligomers include those obtained by a reaction of a compound having a plurality of carboxyl groups and/or an anhydride thereof with a polyol having at least one (meth)acryloxy group. ) Acrylic polyester oligomers. The compound having a plurality of carboxyl groups and/or an anhydride thereof is the same as those described for the (meth)acrylic polyester of the above polyfunctional (meth)acrylate compound. In addition, as the polyol having at least one (meth)acryl oxime group, the same as those described in the above (meth)acrylic acid urethane oligomer can be exemplified.

In addition to the polymerizable oligomer as described above, examples of the (meth)acrylic acid urethane oligomer include an isocyanate and a hydroxyl group-containing polyester, a hydroxyl group-containing polyether or a hydroxyl group. A compound obtained by reacting a hydroxyl group of a (meth) acrylate. The hydroxyl group-containing polyester which can be preferably used is a hydroxyl group-containing polyester obtained by esterification reaction of a polyhydric alcohol with a carboxylic acid or a compound having a plurality of carboxyl groups and/or an anhydride thereof. The polyhydric alcohol or a compound having a plurality of carboxyl groups and/or an anhydride thereof can be exemplified by the same as those described for the (meth)acrylic polyester compound of the polyfunctional (meth) acrylate compound. The hydroxyl group-containing polyether which can be preferably used is a hydroxyl group-containing polyether obtained by adding one or two or more kinds of alkylene oxides and/or ε-caprolactone to a polyol. The polyol may be the same as those usable for the above hydroxyl group-containing polyester. The hydroxyl group-containing (meth) acrylate which can be preferably used is the same as those described for the (meth)acrylic acid urethane oligomer of the polymerizable oligomer. The isocyanate is preferably a compound having one or more isocyanate groups in the molecule, and more preferably a toluene diisocyanate or a divalent isocyanate compound such as hexamethylene diisocyanate or isophorone diisocyanate.

These polymerizable oligomer compounds may be used singly or in combination of one or more kinds.

(2) Photopolymerization initiator

As the photopolymerization initiator, for example, an acetophenone photopolymerization initiator, a benzoin photopolymerization initiator, a benzophenone photopolymerization initiator, and 9-oxosulfuric acid can be used. Photopolymerization initiator, three Photopolymerization initiator, A bisazole photopolymerization initiator or the like. Further, as the photopolymerization initiator, for example, 2,4,6-trimethylbenzimidyldiphenylphosphine oxide or 2,2'-bis(o-chlorophenyl)-4,4' may be used. 5,5'-tetraphenyl-1,2'-biimidazole, 10-butyl-2-chloroacridone, 2-ethyl hydrazine, diphenylethylenedione, 9,10-phenanthrenequinone, Camphorquinone, methyl phenylglyoxylate, titanocene compound, and the like. The amount of the photopolymerization initiator to be used is usually 0.5 to 20 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the active energy ray-curable resin.

(3) Translucent fine particles

The light-transmitting fine particles are not particularly limited, and for example, organic fine particles containing an acrylic resin, a melamine resin, polyethylene, polystyrene, an organic polyoxyn resin, an acrylic-styrene copolymer, or the like may be used. Inorganic fine particles such as cerium oxide, aluminum oxide, barium carbonate, barium sulfate, titanium oxide, glass, and the like. Further, an organic polymer balloon or hollow beads can also be used. These light-transmitting fine particles may be used alone or in combination of two or more. The shape of the light-transmitting fine particles may be any of a spherical shape, a flat shape, a plate shape, a needle shape, and an indefinite shape.

The particle diameter or refractive index of the light-transmitting fine particles is not particularly limited. However, when the optical film is a light-diffusing film or an anti-glare film, the particle diameter is preferably 0.5 μm in terms of effective internal haze. Within the range of 20 μm. Further, for the same reason, the difference between the refractive index of the active energy ray-curable resin after curing and the refractive index of the light-transmitting fine particles is preferably in the range of 0.04 to 0.15. The content of the light-transmitting fine particles is usually 3 to 60 parts by weight, preferably 5 to 50 parts by weight, per 100 parts by weight of the active energy ray-curable resin. When the content of the light-transmitting fine particles is less than 3 parts by weight based on 100 parts by weight of the active energy ray-curable resin, there is insufficient light diffusing property or anti-glare property. condition. On the other hand, when it exceeds 60 parts by weight, the transparency of the optical film may be impaired, and the anti-glare property or the light diffusibility may be excessively high, and the optical film may be applied to an image display device such as a liquid crystal display device. When the contrast of the display screen is lowered.

Further, in the case where the light-transmitting fine particles are used, in order to make the optical characteristics and the surface shape of the optical film homogeneous, the dispersion of the light-transmitting fine particles in the coating liquid is preferably dispersed in the same direction.

(4) Solvent

The coating liquid may contain a solvent such as an organic solvent. As the organic solvent, an aliphatic hydrocarbon such as hexane, cyclohexane or octane; an aromatic hydrocarbon such as toluene or xylene; ethanol, 1-propanol or isopropanol can be selected and used in consideration of viscosity and the like. , alcohols such as 1-butanol and cyclohexanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters such as ethyl acetate, butyl acetate and isobutyl acetate; Glycol ethers such as diol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate Esterified glycol ethers; cellosolve such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol; 2-(2-methoxyethoxy)ethanol, 2- a carbitol such as (2-ethoxyethoxy)ethanol or 2-(2-butoxyethoxy)ethanol. These solvents may be used singly or in combination of several kinds as needed. It is necessary to evaporate the above organic solvent after coating. Therefore, the boiling point is preferably in the range of 60 ° C to 160 ° C. Further, the saturated vapor pressure at 20 ° C is preferably in the range of 0.1 kPa to 20 kPa.

In the case where the coating liquid contains a solvent, it is preferred to provide a drying method for evaporating the solvent after the coating step and before the hardening step described below. Drying step. Drying can be carried out, for example, by passing the base film 11 including the coating layer through the drying furnace 33 as shown in FIG. The drying temperature can be appropriately selected depending on the type of solvent or substrate film to be used. It is usually in the range of 20 to 120 ° C, but is not limited thereto. Moreover, in the case of having a plurality of drying ovens, the temperature can also be changed for each drying oven.

[2] Hardening step

In this step, the coating layer is irradiated with an active energy ray from the substrate film side in a state where the surface of the coating layer is pressed against the surface of the mold having a specific surface shape, and the coating step is formed by the coating step. The step of hardening the cloth layer to form a hardened resin layer on the substrate film. By this step, the coating layer can be hardened, and the surface shape of the mold is transferred onto the surface of the coating layer.

In the present invention, when the surface of the coating layer is pressed against the surface of the casting mold, the both ends of the coating layer are oriented in the width direction (the direction orthogonal to the conveying direction of the substrate film). The pressure is smaller than the central portion of the width direction between the end portions. Thereby, the peeling of the resin of the hardening resin at the time of peeling the optical film from the mold and the generation of the resin residue of the mold can be effectively prevented.

The effect of the above-described effects is considered to be based on the following reasons. That is, when the surface of the coating layer is pressed against the surface of the mold, the coating layer is pushed and spread on both end portions in the width direction of the coating layer. In the portion where the diffusion layer is pushed, the time from the contact of the coating layer to the substrate film to the curing is short, and when the coating layer contains the solvent, the substrate film is not impregnated with the solvent, so the hardening is performed. Since the adhesion between the resin and the substrate film is relatively low, it is considered that resin peeling or resin residue is likely to occur. By the surface of the coating layer When the pressure is applied to the surface of the mold, the pressure applied to the both end portions in the width direction of the coating layer is smaller than the central portion, and the coating layer can be prevented from being pushed and diffused. Therefore, it is considered that the resin peeling can be effectively prevented. The production of resin residues in the mold.

The pressure applied to the central portion of the coating layer when the surface of the coating layer is pressed against the surface of the casting mold is preferably 0.2 MPa or more or more than 0.2 MPa, more preferably 0.25 MPa or more, and further preferably 0.4 MPa. the above. When the pressure is less than 0.2 MPa, when the mold is pressed against the mold, fine bubbles are mixed at the interface between the coating layer and the mold, or the surface shape of the mold cannot be transferred to the surface of the coating layer.

The pressure applied to the both end portions of the coating layer when the surface of the coating layer is pressed against the surface of the casting mold is preferably 0.2 MPa or less or less than 0.2 MPa, more preferably 0.15 MPa or less, and further preferably 0.1 MPa or less. By adjusting the pressure within the range, resin peeling and resin residue which can be generated at both end portions can be effectively prevented.

In the present hardening step, for example, as shown in FIG. 1, the base film 11 via the coating step can be used with the nip roller 13 disposed to face the roll-shaped mold 14 via the base film 11 having the coating layer. The surface of the coating layer of the laminate of the coating layer is pressed against the surface of the mold 14, and in this state, the active energy ray is irradiated from the substrate film 11 side by the active energy ray irradiation device 15 to coat the coating layer. Layer hardening. The nip roller 13 is a pressure bonding device for pressing the surface of the coating layer against the surface of the mold 14, and is also effective in that the coating layer of the nip roller 13 is pressed against the mold to prevent air bubbles from entering the interfaces. Further, the active energy ray irradiation device 15 may use one or a plurality of stages.

When the surface of the coating layer is pressed against the surface of the mold 14 by using the nip roller 13, by applying it to a specific shape as the nip roller 13, the both ends in the width direction of the coating layer can be applied. The pressure on the area is smaller than the central area. The nip roll processed into a specific shape may be processed such that a region corresponding to a central portion of the coating layer is protruded more outward than a region corresponding to both end regions of the coating layer. Specifically, the following are mentioned.

a) A nip roll having a shorter width (roll length) than the width (effective width) of the coating layer [the length in the direction orthogonal to the conveying direction of the substrate film] as shown in FIG. 2 . When such a nip roll is used, there is no nip roller in the region corresponding to the both end portions of the coating layer, and the nip roller does not contact the base film portion directly below the both end portions of the coating layer, so The pressure applied to the end portions is made smaller than the central portion.

b) A nip roller having a concave cut portion on a region corresponding to both end portions of the coating layer (a region immediately below the both end portions) as shown in FIG. 5 is a view showing a state in which the surface of the coating layer 12 on the base film 11 is pressed against the surface of the mold 14 by the nip rolls 13 having the slit portions in the regions corresponding to the end portions of the coating layer 12. A schematic cross-sectional view of the state. When the nip roll having the slit portion is used, the nip roller can be applied to the both end portions directly under the both end portions of the coating layer in the same manner as the nip roller of the above a). The pressure on the area is less than the central area.

c) The nip rolls processed at both ends by the crown as shown in Fig. 4. The term "crown processing" refers to a process in which the roll diameter gradually decreases toward the end of the roll. Figure 6 is a view showing the surface of the coating layer 12 on the substrate film 11 using the nip rolls 13 which are processed by both ends. A schematic cross-sectional view of a state in which it is pressed against the surface of the mold 14. By using such nip rolls which are processed by the crown at both ends, the pressure applied to the end portions of the coating layer can be made smaller than the central portion. In particular, the use of the nip rolls which are processed by the crown at both ends does not cause a sudden change in the pressure applied to the coating layer, and is gradually reduced as the distance from the central portion toward the both ends becomes effective. It is preferable in terms of resin residue generated at a portion where a change in film thickness is caused by a change portion or the like.

After the hardening of the coating layer in this step, referring to Fig. 1, the laminate of the base film and the cured resin layer is peeled off from the mold 14 with the nip roller 16 on the outlet side as a fulcrum. The obtained optical film comprising the substrate film and the hardened resin layer is usually taken up by the film winding device 34. In this case, in order to protect the resin layer, a protective film containing polyethylene terephthalate or polyethylene may be wound on the surface of the resin layer via an adhesive layer having removability.

Further, after the mold 14 is peeled off, additional active energy ray irradiation may be performed.

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, and the like depending on the type of active energy ray-curable resin contained in the coating liquid. Ultraviolet and electron beams are particularly good for use in terms of ease of operation and high energy.

As the light source of the ultraviolet light, 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. Also, ArF excimer laser, KrF excimer can also be used. Laser, excimer lamp or synchrotron radiation. Among these, it is preferred to use an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon arc lamp, or a metal halide lamp.

Further, examples of the electron beam include a Cockcroft-Walton type, a Van de Graaff type, a resonant transformer type, an insulating core transformer type, and a linear type. An electron beam having an energy of 50 to 1000 keV, preferably 100 to 300 keV, emitted by various electron beam accelerators such as a high-frequency high-voltage accelerator type and a high-frequency type.

When the active energy ray is ultraviolet ray, the cumulative amount of ultraviolet light UVA (Ultraviolet A) is preferably 40 mJ/cm ² or more and 2000 mJ/cm ² or less, more preferably 70 mJ/cm ² or more and 1800 mJ/ Below cm ² . When the cumulative amount of light is less than 40 mJ/cm ² , the hardening of the coating layer is insufficient, the hardness of the obtained resin layer is lowered, or the unhardened resin adheres to the guide roller or the like to cause step contamination, etc. Case. Further, when the integrated light amount exceeds 2000 mJ/cm ² , there is a case where wrinkles are caused by shrinkage of the base film due to heat radiated from the ultraviolet irradiation device.

The mold used in this step is for imparting a desired shape to the surface of the resin layer formed on the base film, and has a surface shape including the transfer structure of the desired shape. The surface shape of the mold can be transferred onto the surface of the resin layer by hardening the coating layer while pressing the surface of the coating layer against one surface of the surface (or after pressing). Examples of the mold include a mold having a mirror-containing surface (for example, a mirror roll) and a mold having a concave-convex surface (for example, an emboss roll).

When the casting mold has a concave-convex surface, the pattern of the concave-convex shape may be a gauge The pattern may be a random pattern or a false irregular pattern which is filled with one or more irregular patterns of a specific size, and is prevented when the obtained optical film is applied to an image display device such as a liquid crystal display device. It is preferably a random pattern or a pseudo irregular pattern in terms of the reflection of the reflected light due to the surface shape to cause the reflected image to become iridescent.

The shape of the mold is not particularly limited, and may be a flat plate shape or a cylindrical or cylindrical roller as shown in Fig. 1, but in terms of continuous productivity, it is preferably a mirror roll or embossing. A cylindrical or cylindrical mold such as a roller. In this case, a specific surface shape is formed on the side surface of the cylindrical or cylindrical mold.

The material of the base material of the mold is not particularly limited, and may be appropriately selected from metal, glass, carbon, resin, or a composite thereof, but is preferably metal in terms of workability and the like. As a metal material which can be preferably used, from the viewpoint of cost, aluminum, iron, or an alloy mainly composed of aluminum or iron can be cited.

As a method of obtaining a mold, for example, a method of performing electroless nickel plating after polishing a substrate and performing sandblasting is described (Japanese Patent Laid-Open No. 2006-53371); after the substrate is subjected to copper plating or nickel plating, Grinding and performing sandblasting, and then performing a method of chrome plating (Japanese Patent Laid-Open Publication No. 2007-187952); performing copper plating or nickel plating, grinding and performing sandblasting, and then performing an etching step or a copper plating step, followed by chrome plating In the method of performing copper plating or nickel plating on the surface of the substrate, polishing is performed on the surface of the substrate, and a photosensitive resin film is formed on the surface to be polished, and the photosensitive resin film is formed on the surface of the substrate. Display on the pattern after exposure a method in which a developed photosensitive resin film is used as a mask to perform an etching treatment, a photosensitive resin film is peeled off, an etching process is performed, and a concave-convex surface is blunt, and then the formed uneven surface is chrome-plated; and a lathe is used. A method of cutting a tool into a substrate of a mold by a cutting tool (International Publication No. 2007/077892).

The surface uneven shape of the mold including the random pattern or the dummy irregular pattern can be formed, for example, by FM (Freguency Modulation), DLDS (Dynamic Low-Discrepancy Sequence) The method, the random pattern formed by the method of the microphase separation pattern of the block copolymer or the band pass filter method is exposed and developed on the photosensitive resin film, and the developed photosensitive resin film is used as a mask. An etching process is performed.

The optical film of the present invention obtained as described above can be preferably applied to an image display device such as a liquid crystal display device. For example, the resin layer on the substrate film can be used to prevent damage caused by various external forces. a hard coat film of a hard coat layer (sometimes containing light-transmitting fine particles); the resin layer is a light diffusion layer (containing light-transmitting fine particles as a light diffusing agent) for diffusing light emitted from the liquid crystal cell to improve a viewing angle The side light diffusion film is viewed; the resin layer is an anti-glare film having an anti-glare layer (sometimes containing light-transmitting fine particles) having surface irregularities for preventing external light from being reflected or glare; the resin layer is for incident to A light-diffusion layer (diffusion plate) containing a light-diffusion layer (including a light-transmitting fine particle as a light-diffusing agent) such as a light-diffusing agent caused by a light-diffusion of the liquid crystal cell. The hard coat film, the visible side light diffusing film, and the anti-glare film are generally used as a protective side protective film of the viewing side polarizing plate and attached to the polarizing film. (ie, disposed on the surface of the image display device). The back side light diffusion film is usually bonded to the polarizing film as a backlight side protective film of the backlight side polarizing plate.

The optical film of the present invention may further comprise an antireflection layer laminated on the resin layer (the side opposite to the substrate film). The antireflection layer is provided to minimize the reflectance, and by forming the antireflection layer, reflection on the display screen can be prevented. Examples of the antireflection layer include a low refractive index layer containing a material lower than a refractive index of the resin layer, a high refractive index layer containing a material higher than a refractive index of the resin layer, and a refractive index lower than the high refractive index layer. The laminate structure of the low refractive index layer of the material. The method of laminating the antireflection layer is not particularly limited, and may be directly laminated on the resin layer, or may be separately prepared by laminating an antireflection layer on the base film in advance, and bonded to the resin layer using an adhesive or the like.

<Polarizing plate>

The polarizing plate of the present invention includes a polarizing film and an optical film which are laminated on the polarizing film so that the substrate film side faces the polarizing film, and are obtained by the above-described manufacturing method. The polarizing film has a function of extracting linearly polarized light from incident light, and the type thereof is not particularly limited. As a preferable example of the polarizing film, a polarizing film in which a dichroic dye is adsorbed and oriented in a polyvinyl alcohol-based resin can be mentioned. Examples of the polyvinyl alcohol-based resin include, in addition to the polyvinyl alcohol which is a saponified product of vinyl acetate, a partially formalized polyvinyl alcohol or a saponified product of an ethylene-vinyl acetate copolymer. As the dichroic dye, an organic dye of iodine or a dichroic property can be used. Further, the polyene oriented film of the dehydrated material of polyvinyl alcohol or the dehydrochlorinated product of polyvinyl chloride may 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, or a transparent protective layer may be laminated on one side of the polarizing film. The optical film of the present invention is laminated on the other side.

At this time, the optical film also functions as a transparent protective layer (protective film) of the polarizing film. The transparent protective layer can be formed on the polarizing film by a method of bonding a transparent resin film using an adhesive or the like or a method of applying a coating liquid containing a transparent resin. 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 which is a transparent protective layer is preferably excellent in transparency, mechanical strength, thermal stability, water repellency, etc., and examples of such a transparent resin film include a film containing triethyl sulfonium cellulose and diethyl phthalate. a cellulose resin such as cellulose acetate or cellulose acetate propionate; a polycarbonate resin; a (meth) acrylate resin such as polyacrylate or polymethyl methacrylate; and poly (terephthalic acid); Polyester resin such as ethylene glycol or polyethylene naphthalate; chain polyolefin resin such as polyethylene or polypropylene; cyclic polyolefin resin; styrene resin; polyfluorene; polyether oxime; A vinyl chloride resin or the like. The transparent resin film may be optically isotropic or may be optically anisotropic in order to compensate for the viewing angle when incorporated in an image display device.

<Image display device>

The image display device of the present invention combines the above-described polarizing plate of the present invention with an image display element that displays various kinds of information on a screen. The type of the image display device of the present invention is not particularly limited, except that a liquid crystal panel is used. In addition to LCD (Liquid Crystal Display), Braun tube (CRT, Cathode Ray Tube) display, plasma display panel (PDP), field emission display (FED, Field Emission) Display), Surface-conduction Electron-emitter Display (SED), Organic EL (Electroluminescence) display, laser display, projection screen, etc.

For example, when the liquid crystal panel is manufactured by disposing the polarizing plate of the present invention on a liquid crystal cell, the polarizing plate is disposed on the liquid crystal cell such that the polarizing film is on the liquid crystal cell side (the resin layer is located outside). The same applies to other image display devices. The optical film may be disposed on the viewing side of the image display element, may be disposed on the backlight side, or may be disposed on both of them. When the optical film is disposed on the viewing side, the optical film can function as a hard coat film, a light diffusion film, an anti-glare film, or an anti-reflection film. On the other hand, when the optical film is disposed on the backlight side, the optical film can function as a light diffusion film (diffusion plate) that diffuses light incident on the liquid crystal cell to prevent moiré or the like.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited to the examples.

<Example 1>

The following components were mixed to prepare an ultraviolet curable coating liquid. ̇UV curable resin: 60 parts by weight of pentaerythritol triacrylate and polyfunctional urethane acrylate (hexamethylene diisocyanate and penta 40 parts by weight of a reaction product of tetraol triacrylate, a photopolymerization initiator: "Lucirin TPO" (manufactured by BASF Corporation, chemical name: 2,4,6-trimethylbenzimidyldiphenylphosphine oxide 5 parts by weight, hydrazine dilution solvent: 100 parts by weight of ethyl acetate.

Then, the coating liquid was applied onto a triacetyl cellulose (TAC) film (base film) having a thickness of 80 μm by using a gravure coater so as to have a film thickness of 10 μm after curing. A laminate of a base film and a coating layer [coating step]. Next, the obtained laminate was dried by a drying oven. Then, a nip roller as shown in FIG. 4 which is disposed in parallel with the chrome-plated roller via the laminated body and which is subjected to crown processing at both ends is used (a roller is disposed directly below both end portions in the width direction of the coating layer). The crown-processed portion whose diameter gradually decreases toward the end portion of the roller is pressed against the surface of the coating layer to be in close contact with the chrome-plated roller (molding) which is subjected to the polishing treatment so that the surface becomes a mirror surface. At this time, the nip pressure in the central portion was 0.4 MPa, and the nip pressure at both end portions was set to 0 MPa, that is, no pressure was applied. In this state, ultraviolet rays were irradiated from the base film side so that the maximum illuminance of UVA became 700 mW/cm ² and the cumulative amount of UVA became 300 mJ/cm ^{2 to} cure the coating layer [curing step]. Thereafter, the laminate was peeled off from the chrome-plated roll, whereby an optical film having an average thickness of the resin layer containing the cured product of the ultraviolet curable resin of 10 μm was obtained.

<Example 2>

The nip roll processed as shown in FIG. 4 was used in the same manner as in Example 1 except that the nip pressure in the central portion was 0.4 MPa and the nip pressure at both end portions was 0.2 MPa. Optical film.

The nip roll processed as shown in FIG. 4 was used, and the nip pressure in the central portion was 0.2 MPa and the nip pressure at the both end portions was 0.1 MPa, except in the same manner as in Example 1. Make an optical film.

<Example 4>

A nip roller having a concave portion having a concave shape on a region corresponding to both end portions of the effective width of the coating layer (a region immediately below the both end portions) as shown in FIG. 3 is used, so that the central portion is An optical film was produced in the same manner as in Example 1 except that the nip pressure was 0.4 MPa (the nip pressure in the end portion was 0 MPa due to the slit).

<Example 5>

Using a nip roll having a shorter width (roll length) than the effective width of the coating layer as shown in Fig. 2, the clamping pressure in the central portion is made 0.4 MPa (since the width of the nip roller is more effective than the coating layer) An optical film was produced in the same manner as in Example 1 except that the width was narrow and the nip pressure at the end portion was 0 MPa.

<Comparative Example 1>

A cylindrical nip roll having a width (roll length) longer than the effective width of the coating layer (the roll surface including a smooth surface having no unevenness and not processed) was used, and otherwise the same as in Example 1. The optical film is produced in a manner.

(Evaluation of resin residue)

The surface of the chrome-plated roll after the production of the optical film was observed with a magnifying glass, and the position A corresponding to both end portions of the cured resin layer and the position B of the pressure change applied to the coating layer in Examples 1 to 5 were observed (implementation Example 1~3: The boundary between the central portion of the chrome-plated roll and the end portion of the crown processed Position, Example 4: Position of the step near the center on both slit portions, Example 5: Residual resin residue on both end portions in the width direction of the chrome-plated roller). In the case where the resin residue was not confirmed at any position, it was confirmed that the resin remained at any position, but the portion where the resin remained did not reach 1/3 of the entire circumference of the roll was set to Δ. The resin residue was confirmed at any position, and the portion where the resin remained was 1/3 or more of the entire circumference of the roll, and was set to ×. The results are shown in Table 1.

(Evaluation of resin peeling)

Adhesive tape ("Sellotape (registered trademark)", manufactured by Nichiban Co., Ltd., 24 mm wide) was attached to both end portions in the width direction of the hardened resin layer of the obtained optical film, and was repeated three times in relation to After the surface of the resin layer was peeled off at an angle of 45 degrees, the both end portions were observed with a magnifying glass, and the presence or absence of peeling of the resin (peeling of the resin layer from the base film or detachment of the resin layer from the base film) was confirmed. The case where the resin peeling was not confirmed was set to ○, and the case where it was confirmed was set to ×.

In addition, the operation using the above-mentioned tape is for the purpose of easily confirming the existence of the portion of the resin layer which is not detached from the base film but is peeled off from the base film and is in an easily detachable state (this portion is included in the category of resin peeling) . The results are shown in Table 1.

As shown in Table 1, by using a nip which is processed in such a manner that the pressure applied to the both end portions in the width direction of the coating layer is smaller than the central portion, it is possible to use a nip which is not subjected to any processing. In the case (Comparative Example 1), resin peeling and resin residue were effectively suppressed. In particular, when the nip rolls which are processed by the crown at both ends are used so that the clamping pressure at the both end portions is less than 0.2 MPa, the pressure applied to the coating layer gradually increases from the central portion toward the both ends. Further, the nip pressure applied to the both end portions is sufficiently low, so that the resin residue can be effectively prevented even at the position B where the pressure applied to the coating layer changes, and the resin peeling can be effectively prevented. In Examples 2, 4 and 5, no resin residue was observed at the position A, but a slight resin residue was confirmed at the position B.

11‧‧‧Base film

12‧‧‧ Coating layer

13‧‧‧Pinch roller

14‧‧‧Molding

15‧‧‧Active energy line irradiation device

16‧‧‧Pinch roller

31‧‧‧film roll-out device

32‧‧‧ Coating device

33‧‧‧ drying oven

34‧‧‧ film winding device

Fig. 1 is a view schematically showing a preferred embodiment of a method for producing an optical film of the present invention and a manufacturing apparatus therefor.

Figure 2 is a view showing an example of the shape of a nip roller which can be preferably used in the present invention. Schematic diagram.

Fig. 3 is a schematic view showing another example of the shape of a nip roll which can be preferably used in the present invention.

Fig. 4 is a schematic view showing still another example of the shape of a nip roll which can be preferably used in the present invention.

Fig. 5 is a schematic cross-sectional view showing a state in which the surface of the coating layer on the base film is pressed against the surface of the mold by using a nip roll having a notched portion in a region corresponding to both end portions of the coating layer.

Fig. 6 is a schematic cross-sectional view showing a state in which the surface of the coating layer on the base film is pressed against the surface of the mold by a crown-processed nip roll.

Claims (5)

A method for producing an optical film, comprising: a coating step of applying a coating liquid containing an active energy ray-curable resin onto a substrate film continuously conveyed to form a coating layer; and a hardening step of The coating layer is irradiated with an active energy ray from the substrate film side in a state where the surface of the coating layer is pressed against the surface of the mold; and in the hardening step, the surface of the coating layer is pressed against On the surface of the above-mentioned mold, the pressure applied to the both end portions in the width direction of the coating layer is smaller than the central portion in the width direction between the end portions. The method of claim 1, wherein in the hardening step, the surface of the coating layer is pressed against the nip which is disposed to face the mold via the base film having the coating layer And the nip roller is applied to a pressure applied to both end portions of the coating layer in the width direction when the surface of the coating layer is pressed against the surface of the casting mold by the surface thereof; It is processed so as to be smaller than the central portion in the width direction between the end portions. The method of claim 2, wherein the nip roller is processed so that a region corresponding to a central portion of the coating layer protrudes more outward than a region corresponding to the both end regions. A polarizing plate comprising: a polarizing film; The optical film is laminated on the polarizing film so that the substrate film side faces the polarizing film, and is produced by the method according to any one of claims 1 to 3. An image display device comprising the polarizing plate of claim 4 and an image display element; and the polarizing plate is disposed on the image display element such that a polarizing film thereof is on the image display element side.