JPH09201912A - Protective film for polarizing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent curl from occurring and suppress blocking phenomenon during handling such as winding by providing an active ray curable resin layer on one face of a transparent resin film and a layer with a function for preventing curl from occurring on the opposite side. SOLUTION: For a protective film for a polarizing sheet, an active ray curable resin layer wherein a resin curable by irradiating an active ray such as UV rays and electron beam through crosslinking reaction is a main ingredient is provided on one side of a transparent resin film which can be used as a protective film for a polarizing sheet. In addition, on the opposite side, a layer formed by applying a compsn. wherein a solvent for at least dissolving a layer with curl preventing function and a transparent resin film used for the protective film for the polarizing sheet, a solvent for swelling them and a solvent which does not dissolve them, is provided. When strengthening the curl preventing function is required, the mixing ratio of the dissolving solvent and/or swelling solvent is made large and the ratio of the non-dissolving solvent is made small.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a protective film for a polarizing plate, and more specifically, it imparts durability such as scratch resistance and chemical resistance to a film widely used for a polarizing plate of a liquid crystal display device, In addition, the present invention relates to a protective film for a polarizing plate that can be produced in high yield.

[0002]

2. Description of the Related Art Conventionally, in producing a protective film for a polarizing plate, a transparent resin is uniformly cast on a stainless steel band, dried, peeled off from the stainless steel band, and then wound with a core. It was used for the next step.

[0003]

In recent years, liquid crystal display devices have been used for various purposes, and there is a possibility that the liquid crystal display device may be placed in a severe environment of use. Therefore, a polarizing plate provided on the surface of the liquid crystal display element with durability has been desired. In order to protect the polarizing film, which is the main material of the polarizing plate, a protective film for polarizing plate is stuck on both sides. When the surface side of the liquid crystal display element is subjected to surface treatment for imparting scratch resistance and chemical resistance, one side of the transparent resin film used as the protective film for the polarizing plate has a hard surface such as an actinic ray curable resin. However, it has been found that it is very difficult to wind up the transparent resin film when such a surface treatment is performed. As a result of intensive studies to solve this problem, the present invention has been completed.

[0004]

According to the present invention, there is provided (1) a polarizing plate comprising a transparent resin film provided with an actinic ray curable resin layer on one surface and a layer having a curl preventing function on the opposite side. It is a protective film for use, and as a result, it is possible to impart not only the curl prevention property to the transparent resin film but also the antiblocking function.

Further, the present invention is (2) a protective film for a polarizing plate characterized in that an actinic ray curable resin layer is provided on one surface of a transparent resin film and a solvent layer is provided on the other side thereof. In addition to the anti-curl property being imparted to the polarizing plate protective film, the blocking phenomenon during handling, such as winding the film, can be suppressed.

In a particularly preferred embodiment of the invention shown in (2), (2a) an acetylcellulose film is used as a transparent resin film, an actinic ray curable resin layer is provided on one side of the film, and a solvent layer is provided on the opposite side. It is a protective film for a polarizing plate, which is provided. In the case of this embodiment, in addition to the effect of improving the anti-blocking effect, which is the effect of the present invention, having the anti-curl function, the effect of suppressing the dimensional change of the heat and humidity resistance of the produced polarizing plate protective film can be obtained. It turned out that there is a new effect that is remarkable.

The present invention also provides (3) a protective film for a polarizing plate, characterized in that an actinic ray curable resin layer is provided on one surface of a transparent resin film and an easy-adhesion layer is provided on the opposite side thereof. This not only enhances the adhesiveness between the protective film for a polarizing plate and the adjacent layer such as the polarizing film, but also has the function of preventing curling and imparts the anti-blocking property.

The present invention also provides (4) a protective film for a polarizing plate, characterized in that an actinic radiation curable resin layer is provided on one side of a transparent resin film and a transparent resin layer is provided on the opposite side thereof. Thus, in addition to providing an anti-curl function, it was possible to suppress a blocking phenomenon during handling such as winding when preparing a protective film for a polarizing plate.

A preferred embodiment of the invention shown in (1) is
(1b) A protective film for a polarizing plate, wherein the transparent resin film is a polycarbonate-based transparent resin film having an actinic ray curable resin layer on one side and a layer having a curl preventing function on the opposite side. It is a film. Using a polycarbonate-based resin film as a protective film for a polarizing plate has advantages such as improved dimensional stability and a reduced thickness, but when the curl-preventing treatment according to the present invention is applied, anti-blocking is also obtained in terms of the curl-preventing function. The results show that a more remarkable effect can be obtained in terms of the improvement of the sex as well, and in this respect, the present embodiment is preferred.

A preferred embodiment of the invention shown in (2) is
(2b) A protective film for a polarizing plate, characterized in that the transparent resin film is a polycarbonate-based transparent resin film, an actinic radiation curable resin layer is provided on one surface of the polycarbonate resin film, and a solvent layer is provided on the opposite side thereof. As a result, dimensional stability is improved, thinning is possible, and curling is prevented, and antiblocking, which is the effect of the present invention, can be more significantly achieved.

A preferred embodiment of the invention represented by (3) is
(3b) A protective film for a polarizing plate, characterized in that the transparent resin film is a polycarbonate-based transparent resin film, and an actinic ray curable resin layer is provided on one side of the transparent resin film and an easy-adhesion layer is provided on the opposite side. As a result, not only the dimensional stability can be improved, the film can be thinned, curling can be prevented, and the adhesiveness with a polarizing film or the like can be enhanced, but the anti-blocking property, which is the effect of the present invention, can be more significantly achieved.

In the invention described in (4), (4b) the transparent resin film is a polycarbonate-based transparent resin film, and an actinic radiation curable resin layer is provided on one surface of the polycarbonate resin film, and a transparent resin layer is provided on the opposite side thereof. A protective film for a polarizing plate characterized by the above, which can improve the dimensional stability, enable thinning, prevent curling, and more significantly achieve the antiblocking effect which is the effect of the present invention.

The transparent resin film according to the invention described in (1) to (4) may be any as long as it can be used as a protective film for a polarizing plate, for example, an acetyl cellulose resin film, a 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 therefore each transparent plate is transparent. It is preferable that the resin film is thin.

At this time, depending on the type of resin, it may be difficult to form a thin film having a required strength. In order to realize a thin film, for example, a polycarbonate-based film, a norbornene-based 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 actinic ray-curable resin layer according to the present invention is a layer containing a resin as a main component, which is cured by a crosslinking reaction or the like by irradiation with actinic rays such as ultraviolet rays and electron beams. 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 ultraviolet rays and electron beams 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, and UV-curable polyester acrylate. Examples of the resin include resins and UV curable polyol acrylate resins.

Examples of the UV-curable polyol acrylate resin used in the present invention include trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, Alkyl-modified dipentaerythritol A photopolymerizable monomer oligomer such as pentaerythritol. These polyol acrylate resins are characterized by high cross-linking property, high curability, high hardness and small curing shrinkage, low odor, low toxicity and relatively high safety.

The above UV-curable polyol acrylate resin may contain other UV-curable resin, for example, UV-curable epoxy resin, as long as the effect thereof is not impaired. Curing becomes strong due to curing shrinkage in the cured coating film that is applied thick film of acrylate resin,
It may interfere with handling work. 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.

As examples of the electron beam curable resin, those having an acrylate-based functional group are preferable, for example, polyester resin and polyether resin having a relatively low molecular weight,
Acrylic resin, epoxy resin, urethane resin, alkyd resin, spiro acetal resin, polybutadiene resin,
Examples thereof include polythiol polyene resin.

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

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. .

These actinic ray curable resin layers may contain inorganic or organic fine particle powder for the purpose of further improving the blocking property improving effect of the present invention.

Examples of the inorganic fine particle powder in this case include silicon oxide, titanium oxide, aluminum oxide, potassium oxide, sodium oxide, zinc oxide, tin oxide, calcium carbonate, barium sulfate, talc, kaolin, calcium sulfate and the like.

As the organic fine particle powder, polymethacrylic acid methyl acrylate resin powder, silicone resin powder, polystyrene resin powder, polycarbonate resin powder, acrylstyrene 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. To give anti-blocking property,
The volume average particle diameter is 0.1 to 1 μm, and 0.1 to 5 parts by weight is suitable for 100 parts by weight of the resin composition.

The layer having an anti-curl function according to the present invention shown in (1) means a layer having a function of suppressing the curling of the transparent resin film when the actinic radiation curable resin layer is provided on one surface of the film. Say.

The solvent layer according to the invention shown in (2), (2a) and (2b) has the property of being rounded with the surface provided with the solvent layer facing inward. Is a layer formed by applying a composition containing at least a solvent for dissolving or swelling a transparent resin film used as a protective film for a polarizing plate. It may contain a solvent that does not dissolve in addition to a solvent that dissolves and / or a solvent that swells, and is formed using a composition and coating amount in which these are mixed in an appropriate ratio depending on the curl degree of the transparent resin film and the type of resin. It is a thing.

In order to enhance the curl prevention function, it is effective to increase the mixing ratio of the solvent to be dissolved and / or the solvent to swell and decrease the ratio of the solvent not to be dissolved.

This mixing ratio is preferably (solvent to be dissolved and / or solvent to be swollen): (solvent not to be dissolved)
= 10: 0 to 1: 9. Examples of the solvent contained in such a mixed composition for dissolving or swelling the transparent resin film include, for example, benzene, toluene, xylene, dioxane, acetone, methyl ethyl ketone, N,
N-dimethylformamide, methyl acetate, ethyl acetate,
Examples include trichloroethylene, methylene chloride, ethylene chloride, tetrachloroethane, trichloroethane and chloroform. Examples of the solvent that is not dissolved include methanol, ethanol, n-propyl alcohol, i-propyl alcohol, and n-butanol.

A gravure coater is used for these solvent compositions.
1 to 100 μm on the surface of the transparent resin film using a dip coater, reverse coater, extrusion coater, etc.
It is preferable to apply it, but especially 5 to 30 μm
Is good.

Each solvent of the solvent layer thus coated may be scattered after drying or may remain in a trace amount, but preferably, the solvent is not left on the coated surface. Is good.

As the acetylcellulose film according to the present invention shown in (2a), a known film can be used. Most preferably, it is triacetyl cellulose, and the acetic acid degree of triacetyl cellulose is 50 to 70.
% Is preferable, and 55 to 65% is more preferable. The weight average molecular weight is preferably 70,000 to 120,000, more preferably 80,000 to 100,000.

The acetyl cellulose may be partially esterified with a fatty acid such as propionic acid and butyric acid as long as the acetylation degree is satisfied, in addition to acetic acid, and the total amount satisfies the acetylation degree. As long as it contains cellulose ester such as cellulose propionate and cellulose butyrate.

The acetyl cellulose film constituting the protective film for polarizing plate generally contains a plasticizer. Examples of the plasticizer include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate and cresyl diphenyl phosphate, and phthalic acid esters such as diethyl phthalate and dimethyl phthalate.

The easily adhesive layer according to the present invention shown in (3) and (3b) is a layer having a function of adhering a protective film for a polarizing plate and its adjacent layer, typically a polarizing film. Say. 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 -COOM on the protective film side for a polarizing plate. A layer containing a polymer compound having a 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.

Preferred as the polymer compound having a --COOM group here is a vinyl acetate-maleic acid copolymer containing a --COOM group, which is used alone or in combination of two or more kinds, and a preferable weight average Molecular weight is 500 ~
It is about 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, etc.)
Polyvinyl indazole, polyvinyl pyrazole, etc.) can be used alone or in combination of two or more.

Particularly, as the hydrophilic polymer compound, --CO
Those containing an OM (M represents a hydrogen atom or a cation) group are preferable, and a vinyl acetate-maleic acid copolymer containing a -COOM group is more preferable. And the said -COOM group containing high molecular compound is independent or 2
It is used in combination of two or more kinds, and preferably has an average molecular weight of about 50.
The thing of about 0 to 500,000 (weight average) is used.

The transparent resin layer according to the invention shown in (4) and (4b) is a thermoplastic resin, a thermosetting resin, an electron beam curable resin, or any other reactive resin. Among them, the thermoplastic resin is preferable. Resins are preferred. Examples of the thermoplastic resin include vinyl chloride-vinyl acetate copolymer, vinyl chloride resin, vinyl acetate resin, copolymer of vinyl acetate and vinyl alcohol, partially hydrolyzed vinyl chloride-vinyl acetate copolymer, vinyl chloride. -Vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, ethylene-vinyl alcohol copolymer, chlorinated polyvinyl chloride, ethylene-
Vinyl-based copolymers or copolymers such as vinyl chloride copolymers and ethylene-vinyl acetate copolymers, cellulose derivatives such as nitrocellulose, cellulose acetate propionate and cellulose acetate butyrate resins, maleic acid and / or acrylic acid. Copolymer, acrylic ester copolymer, acrylonitrile-styrene copolymer, chlorinated polyethylene, acrylonitrile-chlorinated polyethylene-styrene copolymer, methyl methacrylate-butadiene-styrene copolymer, acrylic resin, polyvinyl acetal resin , Polyvinyl butyral resin,
Rubber resin such as polyester polyurethane resin, polyether polyurethane resin, polycarbonate polyurethane resin, polyester resin, polyether resin, polyamide resin, amino resin, styrene-butadiene resin, butadiene-acrylonitrile resin, silicone resin,
Fluorinated resins and the like can be mentioned. Particularly preferred is a cellulosic resin layer such as diacetyl cellulose.

There are various resins used to prepare the polycarbonate transparent resin film according to the present invention shown in (1b)-(4b), and aromatic polycarbonate is preferable from the viewpoint of chemical properties and physical properties. Bisphenol A-based polycarbonate is particularly preferable. Among them, more preferable 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 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 23 ° C. water 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.

The anti-blocking property, which is the effect of the present invention, is reflected in the ease of handling during and after the production of the protective film for a polarizing plate, but if the blocking property is poor, the film is wound into a roll. At that time, winding disorder may occur, or the once wound roll may collapse.

[0046]

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

<Preparation of Comparative Sample A> An ultraviolet-curable resin composition A was applied to one side of a cellulose acetate film (Konica Cat 80UVSH manufactured by Konica Corp.) having a film thickness of 80 μm so as to have a dry film thickness of 3.5 μm. , At 80 ℃ 5
Dried for minutes. 60 W / cm high pressure mercury lamp 10 cm
Comparative sample A was prepared by irradiating from the distance of 4 seconds for 4 seconds to form an ultraviolet curable resin layer. The curl degree at this time is +4
It was 4.

<Preparation of Comparative Sample B> Comparative Sample B was prepared in the same manner as Comparative Sample A except that the ultraviolet curable resin composition A in Comparative Sample A was replaced with the ultraviolet curable composition B. The curl degree at this time was +41.

<Preparation of Comparative Sample C> Comparison was made in the same manner as Comparative Sample B except that the cellulose acetate film having a thickness of 80 μm in Comparative Sample B was replaced with a polycarbonate film having a thickness of 50 μm prepared as follows. Sample C was prepared. The curl degree at this time was +56.

<Preparation of Comparative Sample D> The procedure of Comparative Sample C was the same as that of Comparative Sample C except that the 80 μm thick cellulose acetate film in Comparative Sample B was replaced by a norbornene-based polyolefin film having a thickness of 70 μm prepared as follows. A comparative sample D was prepared. The curl degree at this time is +
It was 50.

<Preparation of Inventive Sample 1> In Comparative Sample A, the curl prevention layer coating liquid a was applied to the side opposite to the side where the ultraviolet curable resin layer was present in a film thickness such that the curl degree was +1 and dried (100 ° C.). Inventive Sample 1 was prepared.

<Preparation of Inventive Sample 2> In Comparative Sample B, the anti-curl layer coating liquid a was applied to the side opposite to the side where the ultraviolet curable resin layer was present in a film thickness such that the curl degree was +1 and dried (100 ° C.). Inventive Sample 2 was prepared.

<Preparation of Sample 3 of the Present Invention> An ultraviolet-curable resin composition A was formed on one surface of a cellulose acetate film (Konica Cat 80UVSH manufactured by Konica Corp.) having a thickness of 80 μm.
Was applied to give a dry film thickness of 7.0 μm, and dried at 80 ° C. for 5 minutes. Next, use a 60W / cm high pressure mercury lamp for 10c.
Irradiation was performed for 4 seconds from a distance of m to form an ultraviolet curable resin layer. On the opposite side, the coating liquid a for the anti-curl layer was dried to a curl degree of +2 (about 2 in the sample 2 of the present invention).
Inventive sample 3 after coating and drying (at 100 ° C.)
It was created.

<Preparation of Inventive Sample 4> The anti-curl layer coating liquid a in Inventive Sample 2 was replaced with the anti-curl layer coating liquid b.
Inventive sample 4 was prepared in the same manner as in inventive sample 2 except that the curl-preventing layer coating liquid was adjusted to a curl degree of +2 instead of the (upper layer liquid and lower layer liquid). It was created. The anti-curl layer coating liquid b was applied in the order of the lower layer liquid and the upper layer liquid, and dried at 100 ° C.

<Preparation of Inventive Sample 5> In Comparative Sample C, the curl prevention layer coating liquid c was applied to the side opposite to the side where the ultraviolet curable resin layer was present in a film thickness such that the curl degree was +1 and dried (100 ° C.). Then, Sample 5 of the present invention was prepared.

<Preparation of Inventive Sample 6> The anti-curl layer coating solution c in Inventive Sample 5 was replaced with the anti-curl layer coating solution b.
Sample 6 of the present invention was prepared in the same manner as that of Sample 5 of the present invention, except that the curl degree was adjusted to +1 by adjusting the coating film thickness of the lower layer liquid.

<Preparation of Inventive Sample 7> The anti-curl layer coating liquid c in Inventive Sample 5 was replaced with the anti-curl layer coating liquid d.
Instead of this, Sample 7 of the present invention was prepared in the same manner as Sample 5 of the present invention, except that the coating film thickness was adjusted so that the curl degree was +3.

<Preparation of Inventive Sample 8> In Comparative Sample D, the curl prevention layer coating solution a was applied to the side opposite to the side where the ultraviolet curable resin layer was present in a film thickness such that the curl degree was +3, and dried (100 ° C.). Then, Sample 8 of the present invention was prepared.

(Ultraviolet curable resin composition A) Dipentaerythritol hexaacrylate monomer 60 parts Dipentaerythritol hexaacrylate dimer 20 parts Dipentaerythritol hexaacrylate trimer or more components 20 parts Diethoxybenzophenone UV start Agent 2 parts Silicone-based 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.

(Ultraviolet curable resin composition B) Dipentaerythritol hexaacrylate monomer 50 parts Dipentaerythritol hexaacrylate dimer 20 parts Dipentaerythritol hexaacrylate trimer 20 parts or more 1,4-butane Diol 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 part Methyl ethyl ketone 50 Part Ethyl acetate 50 parts Isopropyl alcohol 50 parts The above was ultrasonically dispersed while stirring.

<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 of 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 1
A solution prepared by dissolving 50 g in 150 ml of nitromethane was added and reacted for 1 hour, then 500 ml of methanol was added, and 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 to obtain 3
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.

(Coating liquid for curl prevention layer a) Acetone 41.0 liters Ethyl acetate 56.0 liters N, N-Dimethylformamide 3.0 liters (Coating liquid for curl prevention layer b) <Lower layer liquid> Water-soluble polymer shown below (M) 0.5 g Acetone 60 ml Ethyl acetate 30 ml Toluene 10 ml <Upper layer liquid> (Coating amount 20 ml / m ² ) Polyvinyl alcohol 0.5 g (Nippon Gosei Kagaku Kogyo Co., Ltd. Gohsenol NH-26) Saponin 0.03 g ( Surfactant manufactured by Merck) Pure water 50 ml Methanol 50 ml

[0069]

Embedded image

(Coating liquid for anti-curl layer c) Acetone 60.0 liter Ethyl acetate 30.0 liter Methylene chloride 10.0 liter (Coating liquid for anti-curl layer d) Dimethyl cellulose (number average molecular weight 50,000) 6 parts Acetone 60 parts Ethyl acetate 30 parts Toluene 10 parts <Curling degree measuring method> A sample cut into a lengthwise direction of 35 mm and a width direction of 1 mm is used as a curling degree measuring 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 measurement is JIS-K76
It was carried out according to Method A of 19-1988.

<Blocking property measurement and evaluation method> A sample (width 35 mm, length 950 mm) was wound around a core having a diameter of 50 mm for 6 turns with a load of 1 kg, and both ends of the sample were covered with double-sided tape (width 30 mm, length 5 m
Stick it with m).

After removing the core and leaving it in an atmosphere of 23 ° C. and 55% RH for 24 hours, the sample is placed on an electronic balance and pushed in for 10 minutes for 10 minutes, and the stress at that time is measured.

Next, the sample is unwound, wound one turn, and the stress is measured in the same manner.

The blocking force of the sample is calculated by subtracting 6 times the stress of one winding from the stress of six windings.

Inventive Sample 1 is for Comparative Sample A, Inventive Samples 2, 3 and 4 is for Comparative Sample B, Inventive Samples 5, 6 and 7 is for Comparative Sample C, and With respect to Sample 8, the blocking property with respect to Comparative Sample D was evaluated.

<Measurement and Evaluation of Dimensional Change> Surface 2 of sample
Mark the cross with a cross and mark it with a factory microscope before and after heat treatment (conditions: 60 ° C, 95% RH for 100 hours).
The distance between two marks was measured.

Inventive sample 1 is for comparative sample A, inventive samples 2, 3 and 4 is for comparative sample B, inventive samples 5, 6 and 7 is for comparative sample C, and For sample 8, the amount of dimensional change relative to comparative sample D was evaluated.

The evaluation results are shown in Table 1.

[0079]

[Table 1]

<Effects of the Present Invention in Examples> From the results of comparing the present invention samples 1 to 8 with the comparative samples A to D, when the ultraviolet curable resin layer is provided on one side, curl prevention is performed on the opposite side. When the layer is provided, the blocking property becomes good.

Inventive sample 1 is compared with comparative sample A, inventive sample 2 is compared with comparative sample B, inventive sample 5 is compared with comparative sample C, and inventive sample 8 is compared with comparative sample D From the results, when an ultraviolet curable resin layer is provided on one side,
If a solvent layer is provided on the opposite side, curl is improved and blocking property is improved.

From the results of comparing the sample 4 of the present invention with the comparative sample B, and comparing the sample 6 of the present invention with the comparative sample C, when the ultraviolet curable resin layer was provided on one side, the easy-adhesion layer was formed on the opposite side. By providing, the curl is improved and the blocking property is improved.

From the result of comparison between the sample 7 of the present invention and the comparative sample C, when the ultraviolet curable resin layer is provided on one side, the transparent resin layer is provided on the opposite side, the curl is improved and the blocking property is improved. Get better

From the results of comparing the sample of the present invention and the comparative sample,
When the ultraviolet curable resin layer is provided on one side and the curl prevention layer is provided on the opposite side, the amount of dimensional change is reduced.

From the results of comparing Samples 1 to 4 of the present invention with Samples 5 to 8 of the present invention, when the transparent resin film is cellulose acetate, when the anti-curl layer is provided on the opposite side of the ultraviolet curable resin layer, The rate of dimensional change is less than in the case of resin film.

From the results of comparing the blocking improving effect between the present invention sample 5 and the present invention sample 2 and the blocking improving effect between the present invention sample 6 and the present invention sample 4, it was found that when the transparent resin film was polycarbonate When the curl prevention layer is provided on the opposite side of the curable resin layer, the effect of improving blocking property is more remarkable than in the case of other resin films.

From the results of comparing the blocking improving effect between the sample 5 of the present invention and the sample 2 of the present invention, when the transparent resin film is polycarbonate, if a solvent layer is provided on the side opposite to the ultraviolet curable resin layer, another resin is obtained. The effect of improving the blocking property is more remarkable than in the case of the film.

From the result of comparing the blocking improving effect between the sample 6 of the present invention and the sample 4 of the present invention, when the transparent resin film is polycarbonate, when the easily adhesive layer is provided on the opposite side of the ultraviolet curable resin layer, other The effect of improving the blocking property is more remarkable than in the case of the resin film.

From the results of comparing the blocking improving effect between Sample 7 of the present invention and Samples 5 and 6 of the present invention, when the transparent resin film is polycarbonate, when the transparent resin layer is provided on the side opposite to the ultraviolet curable resin layer, The effect of improving blocking property is more remarkable than in the case of other resin films.

[0090]

By the constitution of the present invention, curling is prevented and antiblocking property is remarkably improved.

Claims (4)

[Claims] 1. A protective film for a polarizing plate, comprising an actinic radiation curable resin layer provided on one side of a transparent resin film and a layer having a curl prevention function on the opposite side. 2. A protective film for a polarizing plate, wherein an actinic radiation curable resin layer is provided on one side of a transparent resin film and a solvent layer is provided on the opposite side. 3. A protective film for a polarizing plate, comprising an actinic ray curable resin layer provided on one surface of a transparent resin film and an easy-adhesion layer provided on the opposite side. 4. A protective film for a polarizing plate, wherein an actinic radiation curable resin layer is provided on one side of a transparent resin film, and a transparent resin layer is provided on the opposite side.