JPH09222501A - Protective film for polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevented the curling of a protective film for a polarizing plate, to enhance the production efficiency of this polarizing plate and to improve the durability of the polarizing plate by providing one surface of the protective film for the polarizing plate with an active ray curing resin layer and providing the other surface on the opposite side with an easily adhesive layer. SOLUTION: One surface of the transparent resin film is provided with the active ray curing resin layer and the surface on the other side with the easily adhesive layer. The transparent resin film of this case may be any films, insofar as the films are usable as the protective film for the polarizing plate. Such films include, for example, a cellulose acetate resin film, polyester film, polycarbonate film, norbornane resin film and polyarylate film. The active ray curing resin layer refers to a layer which consists essentially of the rein cured through the crosslinking reaction by irradiation with active rays, such as UV rays and electron beams. While UV curing resins and electron beam curing rays are exemplified by such active ray curing resin, resins to be cured by irradiation with active rays other than the UV rays and electron beams are equally well.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a protective film for a polarizing plate, and more particularly to a protective film for a polarizing plate which has excellent durability such as scratch resistance and chemical resistance and is easy to handle.

[0002]

2. Description of the Related Art Cellulose triacetate resin films have been used as protective films for polarizing plates.
In recent years, a polarizing plate has been used in various applications and in various environments, and a polarizing plate having a function capable of withstanding unprecedented severe use conditions has been expected.
A polarizing plate protective film is usually provided on the surface of the polarizing plate, and the durability of the polarizing plate is often improved by subjecting the film to a surface treatment.

[0003]

In order to improve the durability of a polarizing plate, a curl phenomenon in which the film is curled when a surface treatment such as an actinic ray curable resin layer is provided on one surface of the protective film for polarizing plate. Is likely to occur. If curled, it is difficult to handle when using this to make a polarizing plate, and it is also difficult to increase the production yield of the polarizing plate. The problem to be solved by the present invention is to find out a technique for solving the problem of curling without impairing the function of the actinic radiation curable resin layer.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides (1) a protective film for a polarizing plate characterized by having an actinic ray curable resin layer on one surface of a transparent resin film and an easy-adhesion layer on the opposite surface. Since it is a film, curling can be prevented without impairing the function expected to improve the durability of the actinic radiation curable resin layer, and without impairing the function that the easy-adhesion layer itself should play, thus producing a polarizing plate. The yield can be increased.

Further, the present invention is (2) a protective film for a polarizing plate characterized in that it has an actinic radiation curable resin layer on one surface of a polycarbonate-based transparent resin film and an easy-adhesion layer on the opposite surface. . Compared with other films such as cellulose triacetate-based resin film, the use of a polycarbonate-based transparent resin film has an advantage that thinning can be realized while maintaining the function as a protective film for polarizing plate. However, it is possible to remarkably prevent the severe curling that occurs when an actinic radiation curable resin layer is provided on one surface of such a polycarbonate-based transparent resin film, and it is possible to increase the production yield of the polarizing plate.

A preferred embodiment of the invention shown in (1) is
(1a) A protective film for a polarizing plate comprising a transparent resin film having a fine particle-containing actinic radiation curable resin layer on one surface and an easy-adhesion layer on the opposite surface, whereby the durability is improved. It is possible to significantly prevent curling without impairing the function and also to perform the easy-adhesion function, and thus to increase the production yield of the polarizing plate.

A preferred embodiment of the invention shown in (2) is
(2a) A protective film for a polarizing plate comprising a polycarbonate-based transparent resin film having a fine particle-containing active ray-curable resin layer on one surface and an easy-adhesion layer on the opposite surface. As a result, it is possible to remarkably prevent severe curling of the film having excellent durability (scratch resistance and adhesiveness) that has been made thin, and it is possible to increase the production yield of the polarizing plate.

The transparent resin film according to the invention shown in (1) and (1a) may be any as long as it can be used as a protective film for a polarizing plate. For example, cellulose acetate resin film, polyester film,
Examples thereof include a polycarbonate film, a norbornene resin film, a polyarylate film and a polysulfone film.

For example, since two polarizing plates are usually used for a liquid crystal display as a liquid crystal display device, four transparent resin films, which are protective films for polarizing plates, are in a stacked state, and thus each transparent film is used. It is preferable that the resin film is thin.

At this time, depending on the type of resin, there is a suitable one in that it forms a thin film having a required strength. To realize this thinning, for example, a polycarbonate film or a norbornene film is used. A resin film, a polyarylate-based film, a polysulfone-based film, and the like are mentioned as preferable ones, and a polycarbonate-based film is particularly preferable as described above.

The fine particle-containing active ray-curable resin layer according to the invention shown in (1a) and (2a) contains fine particles exhibiting the blocking prevention and antiglare function of the cured coating film, such as ultraviolet rays and electron beams. It means a layer containing a resin which is cured through a crosslinking reaction or the like by actinic radiation as a main component.

The actinic ray curable resin layer according to the present invention means a layer containing a resin which is cured through a crosslinking reaction or the like by irradiation with actinic rays such as ultraviolet rays and electron beams as a main component.

Typical examples of the actinic ray curable resin include an ultraviolet curable resin and an electron beam curable resin, but a resin which is cured by irradiation with an actinic ray other than an ultraviolet ray or an electron beam may be used. Examples of the UV curable resin include UV curable polyester acrylate resin, UV curable acrylic urethane resin, UV curable acrylic ester resin, UV curable methacrylic ester resin, UV curable polyester acrylate resin and Examples thereof include UV curable polyol acrylate resins. As an example of the electron beam curable resin, one having an acrylate-based functional group is preferable, for example,
Examples include relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiro acetal resins, polybutadiene resins, polythiol polyene resins, and the like.

In order to exert the effect of the present invention remarkably and easily, it is preferable to use an ultraviolet curable resin.

The UV-curable polyol acrylate resin preferably used in the present invention is trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate. Photopolymerizable monomer oligomers such as acrylate and alkyl-modified dipentaerythritol. These polyol acrylate-based resins are highly crosslinkable and have a large curability, a large hardness, a small curing shrinkage,
It is also characterized by low odor, low toxicity, and relatively high safety.

The above UV-curable polyol acrylate-based resin may contain other UV-curable resin, for example, a UV-curable epoxy resin, as long as the effect thereof is not impaired. Curing of the acrylate-based resin, which has been applied as a thick film, causes particularly strong curling due to curing shrinkage, which may cause trouble in handling. Epoxy resins generally have a smaller curing shrinkage and curling of a cured coating film than acrylate resins. The ultraviolet-curable epoxy resin referred to here is a compound containing two or more epoxy groups in the molecule, contains a cationic polymerization initiator, and is an epoxy resin that undergoes a crosslinking reaction when irradiated with ultraviolet rays.

The fine particles according to the present invention shown in (1a) and (2a) exhibit an antiglare function, and include inorganic fine particle powder and organic fine particle powder. As the inorganic fine particle powder, silicon oxide, Titanium oxide, aluminum oxide,
Examples thereof include zinc oxide, tin oxide, calcium carbonate, barium sulfate, talc, kaolin and calcium sulfate.

As the organic fine particle powder, polymethacrylic acid methyl acrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, acrylic styrene resin powder, benzoguanamine resin powder, melamine resin powder, and further polyolefin resin. Resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, polyfluorinated ethylene resin powder and the like can be used.

The volume average particle size of these fine particle powders used for imparting the antiglare effect is 1 to 10 μm, and the ratio of the ultraviolet curable resin composition to the fine particle powder is 100 parts by weight of the resin composition. It is preferable to add 1 to 20 parts by weight.

In addition, fine particles having a volume average particle diameter of 0.01 to 1 μm may be added in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the resin composition in order to impart antiblocking property.

Further, when the above ultraviolet curable resin is used as an ultraviolet curable resin composition, acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, tetra Methyl thiuram monosulfide, thioxanthones, and n-butylamine, triethylamine, tri-n-butylphosphine and the like as a photosensitizer are mixed and used.

In the composition containing the ultraviolet curable resin according to the present invention, the polymerization initiator is generally preferably 0.1 to 1 relative to 100 parts by weight of the actinic radiation curable prepolymer.
5 parts by weight, more preferably 1 to 10 parts by weight.

The UV-curable resin composition that can be used in the present invention may contain a coloring agent such as a pigment or a dye, an antifoaming agent, a thickener, a leveling agent, if necessary, as long as the effect thereof is not impaired. Various additives such as a flame retardant, an ultraviolet absorber, an antioxidant, a filler, a modifying resin, etc. may be blended and used in an appropriate amount.

The composition containing the actinic radiation curable resin according to the present invention may be applied alone or by diluting it in an organic solvent to a solid content concentration of 10 to 95% by weight, a gravure coater, a spinner coater, a wire ba coater, and extrusion. Coater,
It is applied by a known method such as a reverse coater, dried, and then cured by ultraviolet light. The dry film thickness at this time is arbitrary, but is preferably about 0.1 to 30 μm. It is preferably 0.5 μm to 15 μm.

The irradiation time of ultraviolet rays to the ultraviolet curable composition which can be used in the present invention varies depending on the kind of the irradiation light source in the above-mentioned ultraviolet region, but is generally preferably 0.5.
Seconds to 5 minutes, more preferably 3 seconds to 2 minutes.

The actinic radiation curable resin according to the present invention is cured by
It can be cured by irradiation with electron beams or ultraviolet rays. For example, in the case of electron beam curing, 50 to 1000 keV emitted from various electron beam accelerators such as Cockloft-Walton type, Van de Graaff type, resonance transformer type, insulating core transformer type, linear type, dynamitron type, and high frequency type, Preferably, an electron beam or the like having an energy of 100 to 300 keV is used, and in the case of ultraviolet curing, ultraviolet rays or the like emitted from light rays of an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, carbon arc, xenon arc, a metal halide lamp, etc. can be used. .

The atmosphere for irradiating the ultraviolet rays may be air or an inert gas such as nitrogen gas or carbon dioxide gas.

The easily adhesive layer according to the present invention means a layer having a function of adhering a protective film for a polarizing plate and its adjacent layer, typically a polarizing film.

The easy-adhesion layer includes, for example, a layer containing a polymer compound having a —COOM (M represents a hydrogen atom or a cation) group, and a particularly preferred embodiment is on the side of the protective film for a polarizing plate. A layer containing a polymer compound having a —COOM group is provided, and a hydrophilic layer containing a hydrophilic polymer compound as a main component is provided adjacent to the layer on the polarizing film side.

Examples of the polymer compound having a --COOM group include a vinyl acetate-maleic acid copolymer having a --COOM group. Such polymer compounds are used alone or in combination of two or more, and the preferable weight average molecular weight is about 500 to 500,000.

The hydrophilic polymer compound is preferably a hydrophilic cellulose derivative (eg, methyl cellulose, carboxymethyl cellulose, hydroxy cellulose, etc.), a polyvinyl alcohol derivative (eg, polyvinyl alcohol, vinyl acetate-vinyl alcohol copolymer, polyvinyl). Acetal, polyvinyl formal, polyvinyl benzal, etc.), natural polymer compounds (for example,
Gelatin, casein, gum arabic, etc.), hydrophilic polyester derivatives (eg partially sulfonated polyethylene terephthalate etc.), polyvinyl derivatives (eg poly-N-vinylpyrrolidone, polyacrylamide, polyvinylindazole, polyvinylpyrazole etc.) And may be used alone or in combination of two or more.

Specific preferred examples of the polymer compound having a —COOM group which is preferably used in the present invention are represented by the general formula [1] or [2].

[0033]

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In the formula, A is a vinyl monomer, B is a hydrogen atom,
-COOM or-(CO) -R, when z = 0, B is a hydrogen atom, M is hydrogen or a cation, and R is-.
O-R 'or -N (R ") (R'), where R'is required to form an alkyl, aralkyl, aryl, heterocyclic ring residue or R" in combination to form a heterocyclic ring. A non-metal atom, R ″ is a hydrogen atom, a lower alkyl group or a non-metal atom necessary for forming a heterocyclic ring together with R ′, R ₁ and R ₂ are hydrogen atoms or a lower alkyl group, and X is − (C
O) -O- or -O- (CO)-, R ₃ is a halogenoalkyl or halogenoalkyloxyalkyl group,
m, p, q, r, x, y and z are values showing the mol% of each monomer, respectively, m is 0 to 60, p is 0 to 100,
q is 0 to 100, r is 0 to 100, x is 0 to 60, y is 0 to 100, z is 0 to 100, and m + p + q + r =
100 and x + y + z = 100.

Examples of the vinyl monomer in the above general formula include styrene, nitro group, fluorine atom, chlorine atom, bromine atom, styrene substituted with chloromethyl group, lower alkyl group and the like, vinyl methyl ether, vinyl ethyl ether, vinyl. Unsaturated acids such as chloroethyl ether, vinyl acetate, vinyl chloroacetate, vinyl propionate, acrylic acid, methacrylic acid or itaconic acid, alkyl esters of acrylic acid or methacrylic acid (wherein the alkyl group is unsubstituted with 1 to 5 carbon atoms) An alkyl group or an alkyl group substituted with a chlorine atom or a phenyl group), a phenyl ester of acrylic acid or methacrylic acid (the phenyl group is an unsubstituted phenyl group or a phenyl group substituted with a chlorine atom, a phenyl group or the like), acrylonitrile, chloride Vinyl, vinylidene chloride, ethylene, Acrylamides, alkyl or chlorine of 1 to 5 carbon atoms, acrylamides and substituted with a phenyl group or the like, vinyl alcohol, diglycidyl acrylate,
There is acrolein, etc., preferably styrene, styrene having a substituent, vinyl acetate, vinyl methyl ether,
Examples include alkyl acrylate and acrylonitrile.

In the above formula, the alkyl group represented by R'is preferably one having 1 to 24 carbon atoms, which may be a linear alkyl group, a branched alkyl group or a cycloalkyl group, and the alkyl group is It may have a substituent, and as the substituent, a hydroxyl group, a hydroxycarbonyl group, a --COOM '(M' represents a cation) group and the like, particularly a carbon atom substituted with a halogen atom such as a fluorine atom. Number 2-18 halogenoalkyl group or number 2 carbon atoms
The 18 halogenoalkyloxyalkyl groups give favorable results for the purposes of the present invention. The number of halogen atoms substituted on the halogenoalkyl group and the halogenoalkyloxyalkyl group is preferably 1 to 37. The halogenoalkyl group and the halogenoalkyloxyalkyl group, and the halogenoalkyl group and the halogenoalkyloxyalkyl group represented by R ₃ in the general formula [2] are preferably represented by the following general formula [A].

[0037]

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In the formula, R ₄ , R ₅ , R ₆ , R ₇ and R ₈ each represent a hydrogen atom or a fluorine atom, n represents an integer of 1 to 12, n ₂ represents 0 or 1. When n ₂ is 0, n ₁ is 0, when n ₂ is 1, n ₁ is 2 or 3, and n ₃ is an integer of 1 to 17. However, n ₁ + n ₃ is 1
~ 17. When there are two or more R ₄ in the general formula [A], they may be different groups such that one is hydrogen and the other is a fluorine atom, and R ₅ , R ₆ and R _{7 are also the same.} When there are a plurality of each in the general formula [A], they may be different groups.

Further, the above general formula [1] and general formula [2]
When R ′ is a halogenoalkyl group or a halogenoalkyloxyalkyl group as described above, R in the general formula [1] and general formula [2] is preferably —O—
R '. Further, an aryl group such as a phenyl group represented by R ′ or an aralkyl group such as a benzyl group may have a substituent, and the substituent is a fluorine atom,
Examples thereof include a lower alkyl group substituted with a halogen atom such as a chlorine atom and a bromine atom, a hydroxyl group, a hydroxycarbonyl group, a cation oxycarbonyl group, a nitrile group and a nitro group.

The heterocycle represented by R'or the heterocycle formed by R'and R "is a saturated or unsaturated heterocycle containing an oxygen atom, a sulfur atom or a nitrogen atom, such as aziridine or pyrrole. , Pyrrolidine, pyrazole, imidazole, imidazoline, triazole, piperidine, piperazine, oxazine, morpholine, thiazine, etc., and a cation represented by M is, for example, ammonium ion, sodium ion, potassium ion. , Cations such as lithium ions.

In the present invention, the —COOM group-containing polymer compound represented by the above general formula [1] or [2] is used alone or in combination of two or more kinds, preferably an average molecular weight of about 500 to 500, Approximately 000 (weight average) is used.

Typical examples of the easily adhering polymer compound that can be used in the present invention, including the polymer compound containing a —COOM group, are as follows. However, the present invention is not limited to these.

[0043]

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[0044]

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[0045]

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[0046]

[Chemical 6]

[0047]

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[0048]

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Represented by the above general formula [1] or [2]-
The COOM group-containing polymer compound can be synthesized by a known method. That is, it is well known that a maleic anhydride copolymer is a very general polymer, and these derivatives are also prepared by reacting a maleic anhydride copolymer with an alcohol or amine compatible with them. Easy to get,
It can also be obtained by reacting an alcohol or amines compatible with a maleic anhydride monomer and purifying it and copolymerizing it with another vinyl monomer. Acrylates such as halogenoalkyl and halogenoalkyloxyalkyl are also available in Journal of Polymer Science (Journal).
of Polymer Science, 15 51
5 to 574 (1955) or British Patent 1,121,
It is easily synthesized by the method for synthesizing the monomer and polymer described in the specification of No. 357.

[0050] The amount of the easily adhesive polymer compound according to the present invention is preferably 10 to 1000 mg / m ^2, and particularly preferably even at 20 to 300 mg / m ^2.

Further, these polymer solutions according to the present invention can be applied by a known method such as a gravure coater, a dip coater, a reverse roll coater and an extrusion coater. The coating amount of the polymer according to the present invention is 10 to 1,000 m.
It is in the range of g / m ² , and 20 to 300 mg / m ² is preferable in view of particularly stable adhesive force and finish after application.
The method of applying the coating liquid and then drying it is not particularly limited, but the residual solvent amount after drying is preferably 5 wt% or less.

There are various resins used for preparing the polycarbonate transparent resin film according to the invention shown in (2) and (2a), and aromatic polycarbonate is preferable from the viewpoint of chemical properties and physical properties, and particularly, Bisphenol A-based polycarbonate is preferred. Among them, more preferred are those using a bisphenol A derivative in which a benzene ring, a cyclohexane ring, or an aliphatic hydrocarbon group is introduced into bisphenol A. Particularly, these groups are introduced asymmetrically with respect to the central carbon. A polycarbonate having a structure in which the anisotropy in the unit molecule is reduced, which is obtained by using the above derivative, is preferable. For example, the one in which two methyl groups of the central carbon of bisphenol A are replaced by a benzene ring, and the one hydrogen of each benzene ring of bisphenol A is asymmetrically substituted with a methyl group or a phenyl group for the central carbon is used. The polycarbonate obtained by the above is preferable.

Specifically, it is obtained from a 4,4'-dihydroxydiphenylalkane or a halogen-substituted product thereof by a phosgene method or a transesterification method, for example, 4,4'-dihydroxydiphenylmethane,
4,4'-dihydroxydiphenylethane, 4,4'-
Examples thereof include dihydroxydiphenylbutane.

The protective film made of the polycarbonate resin used in the present invention may be used as a mixture with a transparent resin such as a polystyrene resin, a methyl methacrylate resin or a cellulose acetate resin. A polycarbonate resin may be laminated on at least one surface. The method for producing the polycarbonate resin film that can be used in the present invention is not particularly limited. That is, any of an extrusion film, a solvent casting film, a calendering film and the like may be used. In the present invention, a uniaxially stretched film or a biaxially stretched film may be used, but a solvent cast film is preferable because it has excellent surface accuracy and has small optical isotropy and anisotropy.

The polycarbonate resin film used in the present invention has a glass transition point (Tg) of 110 ° C. or higher and a water absorption rate (value measured in water at 23 ° C. for 24 hours) of 0.3% or less. It is better to use the one.
It is more preferable to use one having a Tg of 120 ° C. or higher and a water absorption rate of 0.2% or lower.

The polarizing plate according to the present invention refers to a portion including a polarizing film containing a polarizer and a protective film for polarizing plate attached thereto, and may include a retardation plate in addition to the portion. An adhesive is usually used for this attachment, and examples of the adhesive include polyvinyl alcohol, polyvinyl alcohol adhesives such as polyvinyl butyral, and the like.
Vinyl-based latex such as butyl alcohol can be used. Further, the polarizing film, which is the main constituent element of the polarizing plate according to the present invention, is an element that allows only light having a polarization plane in a fixed direction to pass therethrough, and a typical polarizing film currently known is a polyvinyl alcohol-based polarizing film. , This is a polyvinyl alcohol film dyed with iodine and a dichroic dye, but a polyvinyl alcohol aqueous solution is formed into a film and stretched uniaxially to dye it, or after dyeing it uniaxially. After being stretched, it is common to use the one which is preferably subjected to a durability treatment with a boron compound.

In addition to the easy-adhesion layer and the fine particle-containing actinic ray-curable resin layer described above, the protective film for a polarizing plate includes
You may give antistatic processing, antireflection processing, etc.

[0058]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

First, the composition and the like used in the examples will be described.

<Preparation of Polycarbonate Film> The following dope composition A was prepared.

<Dope composition A> Polycarbonate resin (viscosity average molecular weight 40,000, bisphenol A type) 100 parts 2- (2'hydroxy-3 ', 5'-di-t-butylphenyl) -benzotriazole 1.0 Parts Methylene chloride 430 parts Methanol 90 parts The above composition was placed in a closed container, kept at 80 ° C. under pressure and completely dissolved with stirring to obtain a dope composition A.

Next, this dope composition A was filtered, cooled and kept at 33 ° C., and uniformly cast on a stainless band.
It was dried at 33 ° C. for 5 minutes. Next, the drying time was adjusted so that the retardation was 5 nm at 65 ° C., after peeling from the stainless band, the drying was completed while being conveyed by a number of rolls to obtain a polycarbonate film having a thickness of 50 μm.

<Preparation of Norbornene-based Polyolefin Resin Film> A reaction vessel having an internal volume of 1000 ml substituted with nitrogen was charged with a solution prepared by dissolving 1.5 g of Pd (CH ₃ CN) ₄ (BF ₄ ) ₂ in 100 ml of nitromethane. While stirring at room temperature, 8-carboxymethyltetracyclo [4.4.0.1 ^2.5 . 1 ^7.10 ] -3-Dodecene 15
A solution of 0 g dissolved in 150 ml of nitromethane was added,
After reacting for 1 hour, 500 ml of methanol was added,
The precipitated resin was collected by filtration. The obtained resin was washed with a mixed solution of 300 ml of methanol and 40 ml of concentrated hydrochloric acid. After further washing with methanol, it was vacuum dried at 60 ° C. to obtain a norbornene-based resin.

The following dope composition was prepared.

<Dope Composition> Norbornene-based resin 100 parts by weight 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole 1.0 part by weight Methylene chloride 430 parts by weight Methanol 90 parts by weight Parts The above composition was placed in a closed container, kept at 80 ° C. under pressure and completely dissolved while stirring.

Next, the dope composition was filtered, cooled and kept at 33 ° C., and uniformly cast on a stainless steel band,
Dry for 5 minutes at 3 ° C, then retardation 5 at 65 ° C.
The drying time was adjusted so that the thickness became nm, and after peeling from the stainless steel band, the drying was completed while being conveyed by a number of rolls to obtain a norbornene-based polyolefin film having a film thickness of 80 μm.

(Composition for UV curable resin layer (a)) Dipentaerythritol hexaacrylate monomer 60 parts Dipentaerythritol hexaacrylate dimer 20 parts Dipentaerythritol hexaacrylate trimer or more components 20 parts Diethoxy Benzophenone UV initiator 2 parts Silicone surfactant 1 part Aerosil R-972 (manufactured by Nippon Aerosil Co., Ltd.) 1 part Methyl ethyl ketone 50 parts Ethyl acetate 50 parts Isopropyl alcohol 50 parts Ultrasonic dispersion was carried out while stirring.

(Composition for UV curable resin layer (b)) Dipentaerythritol hexaacrylate monomer 50 parts Dipentaerythritol hexaacrylate dimer 20 parts Dipentaerythritol hexaacrylate trimer 20 parts or more 1, 4-Butanediol diglycidyl ether 10 parts Diethoxybenzophenone UV initiator 2 parts Aromatic sulfonium salt UV initiator 0.5 part Fluorosurfactant 1 part Aerosil R-972 (manufactured by Nippon Aerosil Co., Ltd.) 1 Parts Methyl ethyl ketone 50 parts Ethyl acetate 50 parts Isopropyl alcohol 50 parts The above was ultrasonically dispersed while stirring.

<Coating Liquid for Easy-Adhesion Layer (a)> (1) Liquid Exemplary Compound (14) 1.0 g Polymethylmethacrylate (Acrypet # 001S manufactured by Fujikura Kasei Co., Ltd.) 1.0 g Acetone 90 ml N-methylpyrrolidone 10 ml (2) liquid Completely saponified polyvinyl alcohol 0.5 g saponin (manufactured by Merck) 0.03 g water 55 ml methanol 40 ml 1-methoxy-2-propanol 5 ml <coating liquid for easy adhesion layer (b)> (1) liquid Exemplified Compound (9) 1.0 g Polymethylmethacrylate (Acrypet # 001S manufactured by Fujikura Kasei Co., Ltd.) 0.5 g Acetone 90 ml N-methylpyrrolidone 7 ml Tetrahydrofuran 3 ml (2) Liquid Completely saponified polyvinyl alcohol 0.5 g Saponin ( (Merck) 0.03g Water 55ml Methanol 40m 1-Methoxy-2-propanol 5 ml <Coating liquid for easy adhesion layer (c)> (1) liquid Exemplified compound (20) 2.0 g methanol 100 ml Glyoxal 0.1 g (2) liquid Exemplified compound (21) 2.0 g methanol 100 ml <Coating liquid for easy adhesion layer (d)> (1) Liquid Exemplary compound (4) 1.0 g Polymethylmethacrylate (Acrypet # 001S manufactured by Fujikura Kasei Co., Ltd.) 0.4 g Acetone 50 ml Ethyl acetate 50 ml (2) Liquid Completely saponified polyvinyl alcohol 0.5 g Saponin (manufactured by Merck) 0.03 g Water 55 ml Methanol 40 ml 1-Methoxy-2-propanol 5 ml Samples of the present invention and comparative samples were prepared according to the following.

<Preparation of Comparative Sample A> Using the dope composition A, a polycarbonate film having a thickness of 50 μm was prepared according to the above-mentioned <Preparation of polycarbonate film>.

One side of this polycarbonate film (a
Surface) with the composition for ultraviolet curable resin layer (a) as a dry film thickness 3.
It was applied so as to have a thickness of 5 μm and dried at 80 ° C. for 5 minutes. Next, a 60 W / cm high pressure mercury lamp was irradiated from a distance of 10 cm for 4 seconds to form an ultraviolet curable resin layer (a) to prepare a comparative sample A.

<Preparation of Comparative Sample B> The composition for ultraviolet curable resin layer (a) in Comparative Sample A was prepared by applying the ultraviolet curable resin layer (b).
Comparative sample B was prepared in the same manner as comparative sample A except that the composition for use was replaced.

<Preparation of Comparative Sample C> Comparative Sample C was prepared in the same manner as Comparative Sample A except that the polycarbonate film having a thickness of 50 μm in Comparative Sample A was replaced with a cellulose acetate film having a thickness of 80 μm.

<Preparation of Comparative Sample D> Comparative Sample D was prepared in the same manner as Comparative Sample B except that the polycarbonate film having a thickness of 50 μm in Comparative Sample B was replaced with a cellulose acetate film having a thickness of 80 μm.

<Preparation of Comparative Sample E> Comparative sample A was prepared in the same manner as comparative sample A except that the polycarbonate film having a thickness of 50 μm in comparative sample A was replaced by the norbornene-based polyolefin film having a thickness of 80 μm prepared by the above-mentioned method. Sample E was prepared.

<Preparation of Inventive Sample 1> On the surface b of Comparative Sample A, first, 20 ml of the coating liquid (1) for the easy-adhesion layer (a) was prepared.
/ M ^{2 and} dried at 100 ° C for 5 minutes. Next, 20 ml / m ^{2 of the} solution (2) was applied and dried at 100 ° C. for 10 minutes to prepare Sample 1 of the present invention.

<Preparation of Inventive Sample 2> On the surface b of Comparative Sample A, 20 ml / m of the coating liquid (1) for the easy-adhesion layer (b) was applied.
^Two coats were applied and dried at 100 ° C. for 5 minutes, then 20 ml / m ^{2 of the} solution (2) was applied and dried at 100 ° C. for 10 minutes to prepare Sample 2 of the present invention.

<Preparation of Inventive Sample 3> On the surface b of Comparative Sample A, 20 ml / m of the coating liquid (1) for the easy-adhesion layer (c) was applied.
² application and drying at 80 ° C for 10 minutes, then apply the same solution (2) at 20 ml / m ^{2 and} apply at 60 ° C for 5 minutes, then 100 ° C.
Then, the sample of the present invention 3 was prepared.

<Preparation of Sample 4 of the Present Invention> Sample 4 of the present invention was prepared by coating the coating solution for easy adhesion layer (a) on the surface b of Comparative Sample B in the order of Solution (1) and Solution (2) and drying. Created.

<Preparation of Sample 5 of the Present Invention> Sample 5 of the present invention was prepared by coating the coating solution for the easy-adhesion layer (b) on the surface b of the comparative sample B in the order of the solution (1) and the solution (2) and drying the solution. Created.

<Preparation of Sample 6 of the Present Invention> A composition for ultraviolet curable resin layer (a) was applied to one side (a side) of a polycarbonate film having a film thickness of 50 μm so as to have a dry film thickness of 7.0 μm, and the composition was dried at 80 ° C. And dried for 5 minutes. Next 60 W / cm
A high pressure mercury lamp was irradiated from a distance of 10 cm for 4 seconds to form an ultraviolet curable resin layer (a ′). Apply 40 ml / m ^{2 of the} coating liquid (1) for the easy-adhesion layer (a) to the surface b to make 1
It was dried at 00 ° C. for 5 minutes. Next, 40 ml of the same (2) liquid /
m ² applied and dried at 100 ° C. for 10 minutes to obtain sample 6 of the invention
It was created.

<Preparation of Inventive Sample 7> On the surface b of the comparative sample C, 20 ml / m of the coating liquid (1) for the easy-adhesion layer (d) was applied.
^Two coats were applied and dried at 100 ° C for 5 minutes. Next, 20 ml / m ^{2 of the} solution (2) is applied and dried at 100 ° C. for 10 minutes,
Inventive sample 7 was prepared.

<Preparation of Sample 8 of the Present Invention> On the surface b of Comparative Sample D, the coating liquid for easy adhesion layer (d) was applied in the order of liquid (1) and liquid (2) and dried to prepare sample 8 of the present invention. Created.

<Preparation of Sample 9 of the Present Invention> The sample b of Comparative Sample E was coated with the coating liquid for the easy-adhesion layer (a) in the order of the liquid (1) and the liquid (2) and dried to prepare the sample 9 of the present invention. Created.

The curl degree of each of the samples prepared as described above was measured, and the results are shown in Table 1.

<Curling degree measuring method> The sample is placed in the width direction 35.
mm, and cut in the longitudinal direction of 1 mm is used as a curl degree measurement sample. This is left to stand in an atmosphere of 25 ° C. and 55% RH for 3 days, and the curl degree is measured. Curling degree is J
It was carried out according to the method A of IS-K7619-1988.

<Measurement Method of Effective Width of Polarizing Plate> When the polarizing plate was prepared, the length of adhesion, excluding the peeled portion of the polarizing film and the protective film, was 10 in the longitudinal direction.
Measure for 2 m for each cm, and use the average value as the effective width. For each sample, the effective width of the polarizing plate with respect to the comparative sample A is shown as a relative value.

Using Comparative Samples A to E and Inventive Samples 1 to 9 as protective films for polarizing plates, polarizing plates were prepared according to the following method, and the effective width of the polarizing plates was measured.

<Preparation Method of Polarizing Plate> A protective film sample cut in a length direction of 30 cm and a width direction of 18 cm is placed on a glass plate with the a surface facing upward. Two
Immerse in a wt% polyvinyl alcohol adhesive tank for 1 to 2 seconds. Lightly remove excess adhesive adhering to the above polarizing film, place it on the above protective film sample, and use the same sample film as above b Instead of the UV curable resin layer on the surface, a sample film in which the same easy-adhesion layer as the surface a is applied to the surface b is prepared and laminated so that the surface a of the sample film is in contact with the adhesive. Excess adhesive and air bubbles are removed from the ends of the laminate of the polarizing film and the protective film, which have been laminated in step 1, and the layers are bonded together. Hand roller pressure is about 2-3 kg
/ Cm ² , and the roller speed was about 2 m / min. The sample obtained in a dryer at 80 ° C was left for 2 minutes.

[0090]

[Table 1]

As can be seen by comparing the sample of the present invention and the comparative sample, the curl phenomenon caused by providing the ultraviolet curable resin layer on one surface can be suppressed by providing the easily adhesive layer on the opposite surface. In addition, the effective width of the polarizing plate can be increased, and the production yield of the polarizing plate can be increased.

As can be seen by comparing Comparative Sample A and Comparative Sample B, when a transparent resin film is provided with an ultraviolet curable resin layer on one side and a polycarbonate film is used as the transparent resin film, other resins such as triacetyl are used. The degree of curl is much larger than that when a cellulose or norbornene-based resin film is used, and the effective width of the polarizing plate is also smaller. The present invention is extremely effective as a means for mastering such a polycarbonate film having a large curl degree. That is, when an ultraviolet curable resin layer is provided on one side of a polycarbonate film and an easy-adhesion layer is provided on the other side, a severe curl phenomenon can be remarkably suppressed, and the effective width of the polarizing plate can be remarkably increased, resulting in a polarizing plate production yield. Can be significantly increased.

As can be seen by comparing the sample 1 of the present invention and the sample 6 of the present invention, when the ultraviolet curable resin layer is thickened to improve the durability, an easy-adhesion layer having a thickness commensurate with that is applied. Similarly, curl can be suppressed and the effective width of the polarizing plate can be increased.

[0094]

EFFECTS OF THE INVENTION By providing an actinic ray curable resin layer on one surface of a protective film for a polarizing plate and an easy-adhesion layer on the opposite surface, curling of the protective film is prevented and the production yield of the polarizing plate is increased. At the same time, the durability of the polarizing plate can be improved.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hitoshi Nara 1 Konica Stock Company, Sakura-cho, Hino-shi, Tokyo

Claims (2)

[Claims] 1. A protective film for a polarizing plate, comprising an actinic radiation curable resin layer on one surface of a transparent resin film and an easy-adhesion layer on the opposite surface. 2. A protective film for a polarizing plate, which has an actinic radiation curable resin layer on one surface of a polycarbonate-based transparent resin film and an easy-adhesion layer on the opposite surface.