JPH06118233A - Protective film for polarizing plate - Google Patents

Abstract

PURPOSE:To provide a protective film having no deterioration of the UV absorbing power and no coloring when exposed to a high temperature and high humidity for a long period and excellent in the adhesiveness to a polarization film by combining and containing a specific benzophenone UV absorbent and a specific compound in a cellulose ester film. CONSTITUTION:At least one of benzophenone UV absorbents expressed by the formula I and at least one compound selected among the compounds expressed by the formula II and formula III are combined and contained in a cellulose ester film. In the formula I, Y indicates hydrogen atom or halogen atom, A indicates hydrogen atom or alkyl group, and (m), (n) indicate 1 or 2. In the formula II, R1, R2 indicate hydrogen atom or alkyl group, R3, R4 indicate halogen atom or alkyl group, and (m), (n) indicate an integer of 0-4. In the formula III, R1 indicates aliphatic group or allyl group, and Y indicates nonmetal atom group required to form 5-8-membered heterocycle together with nitrogen atom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose ester film, and more specifically, to protect the durability of the cellulose ester film itself used for a polarizing plate of a liquid crystal display device and a liquid crystal substance, a UV (ultraviolet) ray is used. The present invention relates to a protective film for a polarizing plate, which is provided with absorption performance.

[0002]

BACKGROUND OF THE INVENTION Cellulose ester films are widely used in optical applications such as protective films for polarizing plates because they have excellent transparency and can easily form a film having a small anisotropy of refractive index. There is.

However, the cellulose ester film has a disadvantage inherent in the film that it turns yellow when it is exposed to ultraviolet rays for a long time.

In the case of a liquid crystal display which is generally used for instrumental display of automobiles, the polarizing plate is required to have severe moisture resistance and heat resistance.

For this reason, conventionally, a UV absorber is previously mixed in a cellulose ester solution and the solution is used to form a casting film, or a UV absorber as described in JP-A-61-98301. It is disclosed that the agent solution is applied or dipped on a cellulose ester film to impart UV absorbability to prevent yellowing.

[0006] However, in a severe environment of high temperature and high humidity, for example, in an atmosphere of a temperature of 80 ° C and a RH of 90% or more, 10
After a lapse of about 00 hours, the film produced by the above method contains the UV absorber uniformly dispersed, so that the optical characteristics deteriorate due to the bleeding phenomenon, and the UV absorption performance deteriorates significantly due to yellowing. Is not satisfied,
The improvement was strongly desired.

Further, in the use of these display elements, strong adhesion is required between the polarizing film and the protective film in order to exhibit high reliability and durability in various environments. As a method of improving this adhesiveness, in the case of a cellulose triacetate film most widely used as a protective film, the surface is saponified in advance with an alkaline solution, and then laminated with a polyvinyl alcohol adhesive or the like to obtain a polarizing film. There is.

However, since the above alkali treatment uses a high-concentration alkali solution, it is not preferable from the viewpoint of workability and safety and environmental protection. Further, the alkali treatment increases the bleed-out of plasticizer and the haze, and the quality is improved. May be dropped.

In addition, before the alkali treatment, antistatic treatment,
When the processing for imparting functionality such as hard coating is performed, the effect is diminished by the alkali treatment, so that there has been a problem that the functionalization of the protective film is limited after the alkali treatment.

[0010]

SUMMARY OF THE INVENTION Therefore, the first object of the present invention is to protect a polarizing plate which is not deteriorated in UV absorbing ability or colored even when exposed to severe conditions under high temperature and high humidity for a long time. To provide a film.

Another object of the present invention is to provide a cellulose ester film which is excellent in adhesiveness to a polarizing film and which omits a saponification treatment step to reduce costs.

[0012]

The above object of the present invention is to provide at least one benzophenone UV absorber represented by the following general formula [1] in a cellulose ester film and the following general formulas [2], [3] and [4]. ] It is achieved by a protective film for a polarizing plate characterized by containing at least one selected from the compounds represented by the following.

[0013]

[Chemical 5]

In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxy group and a phenyl group, and these alkyl group, alkenyl group and phenyl group may have a substituent. A represents a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group or a -CO (NH) n _-1 -D group, and D represents an alkyl group, an alkenyl group or a substituent. It represents a phenyl group which may be possessed.
m and n represent 1 or 2.

[0015]

[Chemical 6]

In the formula, R ₁ and R ₂ each represent a hydrogen atom, an alkyl group, an alkenyl group or an aryl group. R ₃ and R ₄ are each a halogen atom, alkyl group, cycloalkyl group, alkenyl group, alkoxy group, aryl group, aryloxy group, alkylthio group, arylthio group, acyl group, acylamino group, sulfonyl group, sulfonamide group, hydroxyl group. Represents a group. m and n represent an integer of 0 to 4, and when m is an integer of 2 to 4, R ₃ may be the same or different. When n is an integer of 2 to 4,
R ₄ may be the same or different. A represents a divalent linking group.

[0017]

[Chemical 7]

In the formula, R ₁ represents an aliphatic group or an aryl group, and Y represents a nonmetallic atom group necessary for forming a 5- to 8-membered heterocycle with a nitrogen atom.

[0019]

[Chemical 8]

In the formula, R ₄ represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, a heterocyclic group or —Si (R _a ) (R _b ) (R _c ). Where (R _a ), (R _b ),
(R _c ) may be the same or different, and each is an alkyl group,
It represents an alkenyl group, an alkoxy group, an aryl group, an alkoxy group, an alkenoxy group or an aryloxy group.

R ₁ , R ₂ , R ₃ , R ₅ and R ₆ may be the same or different and each is a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an acylamino group, a sulfonamide group or an alkyl group. It represents an amino group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, an aryloxycarbonyl group, a halogen atom or -OR ₇ . R ₇ represents R ₄ group having the same meaning as, R ₄ and R _5, R ₅ and R ₆ or R ₁ and R ₆ may form a 5- or 6-membered ring or spiro ring bonded to each other .

The present invention will be described in detail below.

A plasticizer may be added to the cellulose ester film according to the present invention in order to improve the flexibility and moisture resistance of the film. Specific examples thereof include triphenyl phosphate, diethyl phthalate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like. The amount of these plasticizers used is 2 to 20% by weight relative to cellulose triacetate, but it is preferable to use the minimum amount that does not impair the flexibility of the membrane.

Examples of the solvent for the cellulose ester film according to the present invention include lower alcohols such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol and n-butanol, cyclohexanedioxane and lower fatty acids such as methylene chloride. Group hydrocarbons and the like can be used.

The solvent ratio is preferably 70 to 95% by weight of methylene chloride, and 30 to 5% by weight of other solvents. The concentration of cellulose ester is preferably 10 to 50% by weight. The heating temperature after the addition of the solvent is preferably not lower than the boiling point of the solvent used and in the range in which the solvent does not boil, and is preferably set to 60 ° C. or higher and 80 to 110 ° C., for example. The pressure is set so that the solvent does not boil at the set temperature.

For the purpose of accelerating the dissolution, for example, cellulose acetate and the above-mentioned solvent are placed in a pressure vessel and sealed, and at a temperature not lower than the boiling point of the solvent under normal pressure,
In addition, the solvent may be heated to a temperature in a range where it does not boil to dissolve with stirring.

After the dissolution, the product is taken out from the container while being cooled, or is taken out from the container with a pump or the like and cooled with a heat exchanger or the like, and is used for film formation.

The method for producing the cellulose ester film in the present invention is not particularly limited and may be a method generally used in the art, such as US Pat. No. 2,492,978.
2,739,070, 2,739,069, 2,492,977, 2,33
6,310, 2,367,603, 2,492,978, 2,607,704
No., British Patent No. 64071, No. 735892, Japanese Patent Publication No. 45-9074,
49-4554, 49-5614, 60-27562, 61-39890
No. 62-4208, etc. can be referred to.

In the general formula [1] of the present invention, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, and the alkoxy group represents, for example, an alkoxy group having up to 18 carbon atoms. As the alkenyl group, for example, an alkenyl group having up to 16 carbon atoms, an allyl group, 2-
Represents a butenyl group and the like.

The substituents on the alkyl group, alkenyl group and phenyl group include halogen atoms such as chlor, bromine and fluorine atom, hydroxyl group and phenyl group (the phenyl group includes alkyl group and halogen atom). May be substituted) and the like.

Next, specific examples of the benzophenone-based UV absorber represented by the general formula [1] of the present invention will be shown, but the present invention is not limited thereto.

[0032]

[Chemical 9]

[0033]

[Chemical 10]

[0034]

[Chemical 11]

Next, in the general formula [2] of the present invention, the alkyl group represents, for example, a linear or branched aliphatic group having up to 32 carbon atoms, and the cycloalkyl group represents
For example, an alkenyl group having 3 to 12 carbon atoms, particularly 5 to 7 carbon atoms, and an alkenyl group having, for example, 32 carbon atoms, such as an allyl group and a 2-butenyl group. Examples of the aryl group include a phenyl group.

Examples of the alkyl component or aryl component in the alkoxy group, aryloxy group, alkylthio group, arylthio group include the above-mentioned alkyl group and aryl group. Further, as the acyl group, alkylcarbonyl, arylcarbonyl group and the like, as the acylamino group, alkylcarbonylamino, arylcarbonylamino group and the like, as the sulfonyl group, alkylsulfonyl, arylsulfonyl group and the like, as the sulfonamide group, alkylsulfonamino, An aryl sulfone amino group etc. are mentioned.

Next, specific examples of the compound represented by the general formula [2] of the present invention are shown, but the present invention is not limited thereto.

[0038]

[Chemical 12]

[0039]

[Chemical 13]

[0040]

[Chemical 14]

In the present invention, II-1 which is a typical example of the compounds described in JP-A No. 4-133055, pages 12 to 14 by the same applicant as the present invention, including the above compounds.
~ II-40 can be used.

Next, in the general formula [3] of the present invention, particularly preferable compounds are the following general formula [3]
a].

[0043]

[Chemical 15]

In the formula, R ₂ is an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, a heterocyclic group, an acyl group,
It represents an alkylsulfonyl group or an arylsulfonyl group, and R ₃ represents a group capable of substituting on the benzene ring. m is 0-4
And m is 2 or more, a plurality of R ₃ may be the same or different. R ₃ may form a ring together with R ₃ .

Y'has the same meaning as Y in formula [3].

In the general formula [3a], the alkyl group represented by R ₂ is preferably a linear or branched alkyl group having 1 to 24 carbon atoms.

The cycloalkyl group is preferably a cycloalkyl group having 5 to 24 carbon atoms.

The alkenyl group is preferably an alkenyl group having 3 to 24 carbon atoms.

Examples of the aryl group include phenyl and naphthyl groups.

Examples of the heterocyclic group include pyridyl, imidazolyl and thiazolyl groups.

Examples of the acyl group include acetyl and benzoyl groups.

Examples of the alkylsulfonyl group include a dodecylsulfonyl group and a hexadecylsulfonyl group, and examples of the arylsulfonyl group include a phenylsulfonyl group.

Each of these groups further includes those having a substituent, and examples of the substituent of the alkyl group include a halogen atom and hydroxyl, alkoxy, aryl, acylamino, sulfonamide, aryloxy, alkylthio, carbamoyl, sulfamoyl, alkyl. Examples thereof include sulfonyl, nitro, cyano, arylsulfonyl, carboxyl, amino, arylamino, alkylamino, alkoxycarbonyl, acyl and acyloxy groups, and the substituent of the group represented by R ₂ other than an alkyl group is the above. And the alkyl group.

Preferred as R ₂ is an alkyl group.

The group capable of substituting on the benzene ring represented by R ₃ is not particularly limited, but typical examples thereof include a halogen atom and alkyl, aryl, alkoxy, aryloxy, alkylthio, arylthio, acyl, acylamino, sulfonamide. (Eg, alkylsulfonamide, arylsulfonamide, etc.), alkoxycarbonyl, carbamoyl (eg, alkylcarbamoyl, arylcarbamoyl, etc.), ureido (eg, alkylureido, arylureido, etc.), sulfamoyl (eg, alkylsulfamoyl, arylsulfamoyl, etc.) ), Amino (including substituted amino), sulfonyl, nitro, cyano, carboxyl and the like. Among these, preferred as R ₃ are a halogen atom, an alkyl group and an alkyl group. An O group, an acylamino group, and a sulfonamide group.

The group represented by R ₃ may further have a substituent.

R ₂ O— can be in any position but is preferably in the para position.

Typical examples of the compound represented by the general formula [3] are shown below, but the present invention is not limited to these compounds.

[0059]

[Chemical 16]

[0060]

[Chemical 17]

[0061]

[Chemical 18]

In the present invention, III-1 to III of the typical compounds described in JP-A No. 4-133055, pages 16 to 19 by the same applicant as the present invention, including the above compounds, are included.
-70 can be used.

Next, as the alkyl group represented by R ₄ in the general formula [4], a linear or branched alkyl group having 1 to 24 carbon atoms can be mentioned.

Examples of the cycloalkyl group represented by R ₄ include cycloalkyl groups having 5 to 24 carbon atoms, such as cyclopentyl and cyclohexyl groups.

Examples of the alkenyl group include alkenyl groups having 2 to 24 carbon atoms.

Examples of the aryl group include a phenyl group and a naphthyl group. The heterocyclic group is preferably a 5- to 8-membered ring, for example, pyrrolidinyl, piperidyl, piperazinyl, morpholinyl, pyridyl, thiamorpholinyl, imidazolidinyl, thiazolidinyl, homopiperazinyl,
Each group such as 4-sulfopiperidyl can be mentioned.

As the alkyl group, alkenyl group and aryl group represented by R _a , R _b and R _c , the same groups as R ₄ can be mentioned, which constitutes an alkoxy group, an alkenoxy group or an aryloxy group. The alkyl, alkenyl or aryl component is also the same as described for R ₄ .

Examples of the alkyl group, cycloalkyl group, alkenyl group and aryl group represented by R ₁ , R ₂ , R ₃ , R ₅ and R ₆ are the same as those described for R _4. .

Examples of the halogen atom include chlor,
Brom and the like. Examples of the acylamino group include groups such as acetylamino and benzoylamino.

Examples of the sulfonamide group include groups such as methylsulfonylamino and benzenesulfonylamino.

Examples of the alkyl component constituting the alkylamino group and the alkylthio group include the same as the above-mentioned alkyl group. Examples of the aryl component constituting the arylthio group include the same as the above-mentioned aryl group.

Examples of the alkoxycarbonyl group include groups such as methoxycarbonyl group, ethoxycarbonyl and benzyloxycarbonyl, and examples of the aryloxycarbonyl group include phenoxycarbonyl group.

In the general formula [4], among the respective substituents, the alkyl group, the cycloalkyl group, the aryl group or the heterocyclic group, or the group which partially contains these groups may further have a substituent. Good.

Examples of the substituent of the alkyl group or cycloalkyl group include a halogen atom and hydroxyl, alkoxy, alkylthio, acylamino, sulfonamide, aryl, aryloxy, carboxyl, amino, alkylamino, arylamino, carbamoyl,
Examples thereof include sulfamoyl, alkylsulfonyl, arylsulfonyl, nitro, cyano, alkoxycarbonyl, acyl and acyloxy groups.

Examples of the substituent other than the alkyl group include the above-mentioned substituents and alkyl groups.

The substituent which the aryl group and the heterocyclic group may have include a halogen atom and alkyl, aryl, alkoxy, aryloxy, alkylthio, arylthio, acyl, acylamino, sulfonamide,
Examples thereof include carbamoyl, sulfamoyl, ureido, alkoxycarbonyl, amino, sulfonyl, nitro, cyano, and carboxyl groups.

The 5-membered ring and the 6-membered ring which may be formed by combining R ₄ and R ₅ with each other include a chroman ring and the like, and the spiro ring includes a spiropicumaran ring and the like.

Further, as a 5-membered ring or 6-membered ring which may be formed by combining R ₅ and R ₆ or R ₆ and R ₁ with each other, an indane ring, a coumaran ring, a naphthalene ring, a chroman ring and the like are spiro. Examples of the ring include a spirobiindane ring, a spirobicoumaran ring, a spirobichroman ring and the like.

These compounds are described in US Pat. No. 3,432,300
No., No. 3,573,050, No. 3,574,627, No. 3,700,455,
3,764,337, 3,935,016, 3,982,944, 4,2
54,216, JP-B-48-31625, 54-12337, JP-A-51
-152225, 53-17729, 53-17729, 53-20327
No. 54-145530, No. 55-6321, No. 55-21004, British Patent No. 1,347,556, British Patent Publication No. 2,062,888, No. 2,066,
975, 2,077,455 and the like.

Typical examples of the compound represented by the general formula [4] are shown below, but the invention is not limited thereto.

[0081]

[Chemical 19]

[0082]

[Chemical 20]

[0083]

[Chemical 21]

In the present invention, the compounds represented by IV-of the representative compounds described in JP-A No. 4-133055, pages 21 to 23 by the same applicant as the present invention, including the above compounds,
1 to IV-48 can be used.

In the present invention, at least one of the above general formulas [1] and at least one of the general formulas [2] to [4] are preferably used in combination, and the above general formulas [2] to [4] are used. The compounds [] may be used alone or in combination.

Further, in the present invention, together with the compound of the above-mentioned general formula [2], for example, an epoxy compound, a weak organic acid, a saturated polyhydric alcohol or an organic material conventionally known as a deterioration inhibitor for cellulose acetate is used. The known antioxidants such as hindered phenol compounds, thioether compounds, and phosphite compounds may be used in combination with the compounds of the general formulas [2] to [4] of the present invention.

In the present invention, the above general formulas [1] to
The amount of the compound [4] used is not uniform depending on the kind of the compound, the conditions of use, etc., but is usually 0.2 g to 3 g, preferably 0.5 g to ² g per m ² of the cellulose ester film.
g is particularly preferred.

As a method of addition, a preliminarily dissolved organic solvent (eg, methanol, ethyl acetate, etc.) may be added to the dope composition of the present invention such as cellulose acetate, or may be added directly.

In the protective film for a polarizing plate according to the present invention, an adhesive treatment layer containing a hydrophilic binder for imparting adhesiveness to the polarizing film may be coated on the side to be adhered to the polarizing film for the purpose of cost reduction. preferable.

Examples of the hydrophilic binder include a --COOM group-containing copolymer or a hydrophilic cellulose derivative (for example, methyl cellulose, carboxymethyl cellulose, hydroxyalkyl cellulose, etc.), a polyvinyl alcohol derivative (for example, a copolymer of vinyl acetate and vinyl alcohol). Polymers, polyvinyl acetal, polyvinyl formal, polyvinyl benzal, etc.), natural polymer compounds (eg gelatin, casein, gum arabic, etc.), hydrophilic group-containing polyester derivatives, sulfone group-containing polyester copolymers and the like.

The specific --COOM group-containing copolymer compound used in the present invention is represented by the following general formula.

[0092]

[Chemical formula 22]

In the formula, A is a vinyl monomer, B is a hydrogen atom,
--CO--OM or-(CO)-R, when z = 0, B is a hydrogen atom, when R is an alkyl group, B is a hydrogen atom, M is hydrogen or a cation, and R is --O--R '. Alternatively, —N (R ″) (R ′) where R ′ is an alkyl group, an aralkyl group, an aryl group, a heterocyclic ring residue or a nonmetallic atom necessary for forming a heterocyclic ring in cooperation with R ″, R ″ is a hydrogen atom,
A non-metal atom necessary for forming a heterocyclic ring in cooperation with a lower alkyl group or R ', R ₁ and R ₂ are hydrogen atoms or a lower alkyl group, and X is-(CO) -O- or -O- ( CO)
-, R ₃ is a halogenoalkyl or halogenoalkyloxyalkyl group, m, p, q, r, x, y, z are values each showing the mol% of each monomer, and m is 0 to 60, p Is 0 to 10
0, q is 0-100, r is 0-100, x is 0-60, y is 0-100, z is 0
˜100, m + p + q + r = 100, x + y + z = 100.

Examples of the vinyl monomer in the above general formula include styrene, nitro group, fluorine, chlorine, bromine, chloromethyl group, lower alkyl group-substituted styrene, vinyl methyl ether, vinyl ethyl ether and vinyl chloroethyl ether. , Vinyl acetate, vinyl chloroacetate,
Unsaturated acids such as vinyl propionate, acrylic acid, methacrylic acid or itaconic acid, alkyl acrylates or alkyl methacrylates having 1 to 5 carbon atoms, unsubstituted or substituted with chlorine, phenyl group, etc., phenyl acrylate or phenyl meta There are acrylate, acrylonitrile, vinyl chloride, vinylidene chloride, ethylene, acrylamide, acrylamide substituted with an alkyl group having 1 to 5 carbon atoms or chlorine, a phenyl group, vinyl alcohol, chrysidyl acrylate, acrolein, etc., preferably styrene, substituted Examples thereof include styrene having a group, vinyl acetate, vinyl methyl ether, alkyl acrylate, and acrylonitrile.

Further, as the alkyl group of R ′,
Those having 1 to 24 carbon atoms are preferable, and may be any of alkyl groups such as linear alkyl group, branched alkyl group, and cycloalkyl group, and the alkyl group may have a substituent. Is a hydroxy group, a hydroxycarbonyl group, a cationic oxycarbonyl group or the like, and particularly, a halogen-substituted halogenoalkyl group or a halogenoalkyloxyalkyl group such as fluorine gives desirable results. An alkyl group, a halogenoalkyloxyalkyl group or a halogenocycloalkyl group, wherein the number of halogens is preferably 1
~ 37. The halogenoalkyl group and the halogenoalkyloxyalkyl group, and the halogenoalkyl group and the halogenoalkyloxyalkyl group of R _{3 in} the above formula are preferably represented by the following general formula [A].

[0096]

[Chemical formula 23]

(In the formula, R ₄ , R ₅ , R ₆ , R ₇ , and R ₈ are hydrogen or fluorine, n ₂ is 0 or 1, and when n ₂ is 0, n ₁ is 0 and n ₂ is When 1, n ₁ is 2 or 3, n ₃ is an integer of 1 to 17, where n ₁ + n ₃ is 1 to 17. However, when R ₄ is 2 or more in the structural formula, 1 They may be different groups such that one is hydrogen and the other is fluorine,
Similarly, when a plurality of R ₅ , R ₆ and R ₇ are present in the structural formula, they may be different groups. ) Further, when R'in the general formula [I] and the general formula [II] is a halogenoalkyl group or a halogenoalkyloxyalkyl group as described above, preferably the general formula [I] and the general formula [II] ] In R] is -O-R '. Further, an aryl group such as a phenyl group of R ′ or an aralkyl group such as a benzyl group may have a substituent, and as the substituent, a halogen lower alkyl group such as fluorine, chlorine or bromine, and a hydroxy group can be used. , A hydroxycarbonyl group, a cationic oxycarbonyl group, a nitrile group, a nitro group and the like. In the formula, the heterocycle of R ′ or the heterocycle formed by R ′ and R ″ is a saturated or unsaturated heterocycle containing oxygen, sulfur, or nitrogen, such as aziridine or pyrrole. , Pyrrolidine, pyrazole, imidazole, imidazoline, triazole, piperidine, piperazine, oxazine, morpholine, thiazine and the like heterocyclic rings, and the cation of M is, for example, ammonium ion or sodium ion. ,
It is a cation such as potassium ion or lithium ion.

The --COOM group-containing copolymer compound represented by the above general formula is used alone or in combination of two or more kinds, and preferably has an average molecular weight of about 500 to 500,000 (weight average).
Something is used.

Typical examples of the above-mentioned copolymer compound used in the present invention include the following. However, the present invention is not limited to these.

[0100]

[Chemical formula 24]

[0101]

[Chemical 25]

The --COOM group-containing copolymer compound represented by the above general formula used in the present invention is synthesized by a known method. That is, it is well known that the maleic anhydride copolymer is a very general polymer, and these derivatives also can be obtained by reacting a maleic anhydride copolymer with an alcohol or amine compatible with them. It can be easily obtained, or can be obtained by reacting an alcohol or amine compatible with a maleic anhydride monomer and purifying it and copolymerizing it with another vinyl monomer. In addition, acrylates such as halogenoalkyl and halogenoalkyloxyalkyl are available in Journal of Polymer Science.
Science. 15 515-574 (1955) or British Patent 1,121,
It is easily synthesized by the method for synthesizing monomers and polymers described in the specification of No. 357. The amount of the copolymer compound according to the present invention is 10 to 1000.
It is preferably mg / m ² , more preferably ²⁰ to 300 mg / m ² .

The protective film used in the present invention is mainly composed of cellulose triacetate, but cellulose diacetate, cellulose acetate butyrate, cellulose ester such as cellulose propionate, polycarbonate, polyethylene terephthalate, polyacrylate and the like are also applicable. . The thickness is not particularly limited, but it is 10 to 500 μm, especially 30 to 10 in terms of function and ease of handling.
300 μm is preferred.

The polymer solution according to the present invention is a gravure coater, a dip coater, a reverse roll coater,
It can be applied by a known method such as an extrusion coater. The coating amount of the polymer according to the present invention is in the range of 10 to 1000 mg / m ² ,
20 to 30 in terms of particularly stable adhesive strength and finish after application
0 mg / m ² is preferred. The method of applying the coating solution and then drying it is not particularly limited, but the residual solvent amount after drying is 5% by weight.
The following is preferable. If the amount of residual solvent is large, air bubbles may be generated at the adhesive interface in the drying process after being laminated with the polarizing film, which is not preferable.

Examples of the adhesive used for bonding the treated surface of the protective film of the present invention and the polarizing film include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latex such as butyl acrylate, etc. Can be given.

[0106]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Example 1 UV absorbers shown in Table 1 were added to prepare the following dope composition.

Cellulose acetate (oxidation degree 61.0%) 100 parts by weight Triphenyl phosphate 12 parts by weight Exemplified compounds of the present invention (Table 1) 8 parts by weight Methylene chloride 430 parts by weight Methanol 90 parts by weight The above composition was placed in a closed container. The solution was heated to 80 ° C under pressure and completely dissolved with stirring.

The dope was then filtered, cooled and kept at 33 ° C. and rotated on two drums with a rotating length of 6 m (effective length 5.
(5m) cast evenly on an endless stainless steel band,
When the solvent was evaporated until peeling became possible, after peeling from the stainless steel band, the drying was completed while being conveyed by a number of rolls to obtain a film having a thickness of 80 μm.

Each of the cellulose triacetate films thus obtained was cut into a 10 cm square,
After leaving for 1000 hours in a high temperature and high humidity atmosphere at 80 ° C and 90% RH, measure the spectral absorption characteristics of the transmittance of the protective film alone using a spectrophotometer, and measure the transmittance at wavelengths of 320 nm and 400 nm to 25
The degree of change was evaluated by comparison with the sample left in an atmosphere of 56 ° C and 56% RH.

A polarizing plate was prepared by using the above-mentioned cellulose acetate film as a protective film and adhering both sides of a polarizing plate film prepared by the following method with an acrylic adhesive.

How to make a polarizing plate film A polyvinyl alcohol film having a thickness of 120 μm was immersed in an aqueous solution containing 1 part by weight of iodine, 2 parts by weight of potassium iodide and 4 parts by weight of boric acid, and stretched 4 times at 50 ° C. A polarizing plate film was obtained.

Next, a portion of the cellulose acetate film prepared above was immersed in a sodium hydroxide aqueous solution having a temperature of 60 ° C. and a concentration of 8 wt% for 5 minutes and washed with water to form a saponification-treated layer, which was used as a comparative sample.

As a part of the cellulose acetate film prepared above, as shown in Table 1, as a sample of the present invention, one side of the film was coated with a coating solution containing the following composition at 25 ml / m ^2.
Apply using a double roll coater to
After drying at 5 ° C for 5 minutes, a protective film having an adhesive layer was obtained.

Exemplified Compound (P-1) 10 parts by weight Water 20 〃 Methanol 400 〃 Acetone 600 〃 Then, the protective film is laminated with the above polarizing plate film so that the adhesive layer side becomes the adhesive side to form a polarizing plate. Created.

The above polarizing plate was left in a high temperature and high humidity atmosphere of 80 ° C. and 90% RH for 1000 hours, and its degree of change in spectral absorption and the presence or absence of peeling between the polarizing film and the cellulose acetate protective film were evaluated. did.

Moisture and Heat Resistance Test of Polarizing Plates Polarizing plates were prepared by the following method using the protective films obtained in each of the examples and comparative examples, and each polarizing plate was 5 cm × 7 cm.
Cut to size. The cut pieces obtained are each 6 cm x 8 cm
Each of the cuts was attached to the glass plate by temporarily adhering it to the central part of the glass plate with an acrylic adhesive and then pressing them to completely remove the bubbles between each piece and the glass plate.

The test pieces thus prepared were placed vertically in a constant temperature and humidity oven set at 80 ° C. and 95% RH so as not to overlap each other, and fixed on a supporting frame for 1000 hours. went.

(A) Change in transmittance between protective film and polarizing plate (B) Adhesion between polarizing film and protective film (C) Change in polarization degree Evaluation of change in transmittance between the protective film and polarizing plate After leaving the sample in a high temperature and high humidity atmosphere of 80 ° C. and 90% RH for 1000 hours, the spectral absorption characteristic of 320 nm to 400 nm and the spectral absorption characteristic of 500 nm to 600 nm are measured using a spectrophotometer at 25 ° C. 56
% T change with spectral absorption characteristics in% RH atmosphere
(%) Was evaluated.

◯: Change rate of 2% or less △: 〃 2 to 5% × ・ ・ ・ 〃 5 to 11% XX · ・ ・ ・ to 11% The evaluation of the adhesiveness between the polarizing film and the protective film was performed at a high temperature. After the high humidity treatment, the state of peeling between the polarizing film and the protective film was evaluated by visual observation.

◯: The raised portion of the film is 1 mm or less on the periphery. Δ: The raised portion of the film is in the range of 1 to 5 on the periphery. × ... The raised portion of the film is 5 mm or more on the periphery. The value in the 700 nm region was calculated based on the following formula from the average value of the transmission at the time of parallel and at the time of going straight, and the degree of change in the polarization degree at 25 ° C. and 56% RH atmosphere was evaluated. However, the transmittance was corrected to 43%.

P = (HO-H90 / HO + H90) × 100 (where P is the degree of polarization, HO is the average parallel transmittance, and H90 is the average orthogonal transmittance) ..... Measured value before wet heat treatment ( 43%) within ± 2% △ ・ ・ ・ 〃 ± 2% ～ 5
% × ・ ・ ・ 〃 ± 5% 〜11
% × × ・ ・ 〃 ± 11% or more

[0122]

[Table 1]

As can be seen from the table, according to the method of the present invention, there is little change in transmittance at 400 nm or less even under severe conditions, and an excellent polarizing film without deterioration of spectral characteristics as a polarizing plate. It turns out that

Further, the sample of the present invention in which a treatment layer containing a hydrophilic binder is provided on the surface of the cellulose acetate film according to the present invention has excellent adhesiveness to the polarizing film, and the saponification treatment layer can be omitted. .

Example 2 The following dope composition was prepared in the same manner as in Example 1.

Cellulose acetate (acetylation degree 61.0%) 100 parts by weight Triphenyl phosphate 12 parts by weight Exemplified compounds of the present invention (Table 2) 10 parts by weight Methylene chloride 550 parts by weight Methanol 30 parts by weight n-butanol 60 parts by weight The dope was filtered, cooled and kept at 33 ° C. and uniformly cast from the first casting port shown in FIG. 1 located on a rotating 6 m long endless stainless band placed in two drums, then The dope described in Example 2 was finished from the second casting port to a thickness of 80 μm and 80% and 20%, respectively.
%, The solvent is evaporated until it can be peeled off from the stainless steel band, then peeled from the stainless steel band, and dried while being conveyed by multiple rolls to complete the film. A film having a thickness of 80 μm was obtained.

Further, a polarizing plate was prepared in the same manner as in Example 1, and the UV absorption characteristics of the protective film alone and the U of the polarizing plate were measured.
The V absorption properties and the adhesion between the polarizing film and the cellulose acetate were evaluated.

Regarding the adhesiveness, the sample obtained by providing a saponification treatment layer on one side of the sample of the cellulose acetate film according to the present invention obtained as in Example 1 and the adhesive layer containing a hydrophilic binder A sample coated with was prepared.

For the adhesive layer, the following solution was prepared,
It was applied under the following conditions.

Exemplified Compound (P-6) 5 parts by weight Ethyl acetate 500 〃 Acetone 500 〃 The obtained results are shown in Table 2 below. As is clear from the table, according to the method of the present invention, the change of the degree of polarization and the deterioration of the spectral characteristics of the polarizing plate are small even if the method is left in a harsh atmosphere for a long time.

[0131]

[Table 2]

[0132]

EFFECTS OF THE INVENTION According to the present invention, even when exposed to severe high temperature and high humidity for a long time, there is little change in transmittance of 400 nm or less, and UV
A protective film for polarizing plate without deterioration of absorption performance was obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a film forming machine used in Example 2.

[Explanation of symbols]

 1 First casting port 2 Endless stainless steel band 3 Second casting port 4 Separation position

Claims (1)

[Claims] 1. A cellulose ester film is selected from at least one of benzophenone UV absorbers represented by the following general formula [1] and compounds represented by the following general formulas [2], [3] and [4]. A protective film for a polarizing plate, which contains at least one in combination. [Chemical 1] In the formula, Y is a hydrogen atom, a halogen atom or an alkyl group,
It represents an alkenyl group, an alkoxy group and a phenyl group, and these alkyl group, alkenyl group and phenyl group may have a substituent. A is a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group or -CO (NH) n _-1 -D
Represents a group, and D represents an alkyl group, an alkenyl group or a phenyl group which may have a substituent. m and n represent 1 or 2. [Chemical 2] In the formula, R ₁ and R ₂ each represent a hydrogen atom, an alkyl group, an alkenyl group or an aryl group. R ₃ and R ₄ are each a halogen atom, alkyl group, cycloalkyl group, alkenyl group, alkoxy group, aryl group, aryloxy group, alkylthio group, arylthio group, acyl group, acylamino group, sulfonyl group, sulfonamide group, hydroxyl group. Represents a group. m and n represent an integer of 0 to 4, and when m is an integer of 2 to 4, R ₃ may be the same or different. When n is an integer of 2 to 4, R ₄ may be the same or different. A represents a divalent linking group. [Chemical 3] In the formula, R ₁ represents an aliphatic group or an aryl group, and Y represents a nonmetal atom group necessary for forming a 5- to 8-membered heterocycle with a nitrogen atom. [Chemical 4] In the formula, R ₄ is a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, a heterocyclic group or —Si (R
_a ) ( _Rb ) ( _Rc ). Here, (R _a ), (R _b ), and (R _c ) may be the same or different, and each is an alkyl group, an alkenyl group,
It represents an alkoxy group, an aryl group, an alkoxy group, an alkenoxy group, or an aryloxy group. R ₁ , R ₂ , R ₃ , R ₅ ,
R _{6 s} may be the same or different and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an acylamino group, a sulfonamide group, an alkylamino group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, an aryloxy group. It represents a carbonyl group, a halogen atom or -OR ₇ . R ₇ represents R ₄ group having the same meaning as, R ₄ and R _5, R ₅ and R ₆ or R ₁ and R ₆ may form a 5- or 6-membered ring or spiro ring bonded to each other .