JP3401682B2 - Protective film for polarizing plate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a polarizing plate, and more particularly to a protective film for a polarizing plate having excellent adhesiveness. 2. Description of the Related Art A polarizing film in which a cellulose triacetate film is bonded to a polarizer of a dyed uniaxially stretched polyvinyl alcohol film (PVA film) as a protective film is widely used as a liquid crystal display element, a display section of a calculator, It is used for personal computers, liquid crystal televisions, and automobile displays. [0003] In applications of display elements, strong adhesion is required between the polarizer and the protective film in order to exhibit high reliability and durability under various environments. As a method for 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 alkali solution, and then laminated with a polyvinyl alcohol-based adhesive or the like to form a polarizing film. I have. [0004] However, the above alkali treatment uses a high-concentration alkaline solution, which is not preferable in terms of work safety and environmental protection. In addition, the alkali treatment results in poor quality such as bleed out of the plasticizer and high haze. There is a risk of dropping. [0005] In addition, before the alkali treatment, antistatic treatment,
When a process for imparting functionality such as hard coating is performed, the effect is reduced by the alkali treatment, and thus there is a problem that the functional assignment of the protective film is limited after the alkali treatment. An object of the present invention is to provide a protective film for a polarizing plate which is easily adhered to a PVA film. Second
Another object of the present invention is to provide a protective film for a polarizing plate having excellent adhesiveness by a process which is safe in operation and does not adversely affect the environment. Third, it is an object of the present invention to provide a polarizing plate protective film having good productivity and high quality and excellent adhesiveness. The above object of the present invention is attained by the following constitutions. [0008] In a protective film bonded adjacent to a polarizer made of dyed uniaxially stretched polyvinyl alcohol, at least a surface bonded to the polarizer has a -COOM group-containing copolymer represented by the following general formula [I ]. the polymer compound is dissolved in a solvent having an affinity with the protective film, the coercive for設層the polarizing plate protecting film. [0009] Hereinafter, the present invention will be described in more detail. [0011] specific -COOM group-containing copolymer compounds to be used in the present invention is indicated above following general formula. In the above general formula [I] , A is a vinyl monomer ,
M represents a hydrogen atom or a cation , and R represents —O—R ′ or —N (R ″) (R ′) , wherein R ′ is an alkyl group, an aralkyl group, an aryl group, a heterocyclic residue or A non-metallic atom required to form a heterocyclic ring with R ″,
R "represents a hydrogen atom, a lower alkyl group or a nonmetal atom necessary for forming an heterocyclic ring in cooperation with R ' .
p, q, and r are values indicating mol% of each monomer, m is 40 to 55 , p is 2 to 55 , q is 10 to 58 ,
r is from 0 to 25 and an m + p + q + r = 10 0. In the above formula, examples of the vinyl monomer include styrene, nitro group, fluorine, chlorine, bromine, chloromethyl group, styrene substituted with a lower alkyl group and the like, vinyl methyl ether, vinyl ethyl ether, 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 and unsubstituted or substituted chlorine, phenyl, etc., phenyl acrylate or phenyl methacrylate There are acrylate, acrylonitrile, vinyl chloride, vinylidene chloride, ethylene, acrylamide, acrylamide substituted with an alkyl group having 1 to 5 carbon atoms or chlorine, phenyl group, etc., vinyl alcohol, chrysidyl acrylate, acrolein, etc. Styrene having a group, vinyl acetate, vinyl methyl ether, alkyl acrylate, acrylonitrile and the like. The alkyl group represented by R 'in the above formula is preferably an alkyl group having 1 to 24 carbon atoms.
The alkyl group may be any of an alkyl group such as a branched alkyl group and a cycloalkyl group, and the alkyl group may have a substituent. Examples of the substituent include a hydroxy group, a hydroxycarbonyl group, and a cationic oxycarbonyl group. Particularly, a halogenoalkyl group or a halogenoalkyloxyalkyl group substituted with halogen such as fluorine can obtain a desired result. In this case, a halogenoalkyl group having 2 to 18 carbon atoms, a halogenoalkyloxyalkyl group or a halogenocycloalkyl group is preferable. Thus, the halogen number is desirably from 1 to 37. [0016] Further, halogenoalkyl groups such as R 'are described above in the general formula (I) or when the halogenoalkyl alkyloxyalkyl group is, preferably R in general formula (I) -O −R ′. Further, such aryl groups phenyl group R 'or an aralkyl group such as benzyl group, it is rather good have a substituent, as the substituent, a halogen such as fluorine, chlorine, bromine lower alkyl, hydroxy Group, hydroxycarbonyl group, cationic oxycarbonyl group, nitrile group, nitro group and the like . Also, hetero ring formed De and R "'heterocyclic or R''R in the formula is an oxygen, a heterocyclic saturated or unsaturated containing sulfur or nitrogen, for example, aziridine- Pyrrole / pyrrolidine / pyrazole / imidazole /
It is a heterocycle selected from heterocycles such as imidazoline, triazole, piperidine, piperazine, oxazine, morpholine, and thiazine. Further, the cation of M in the formula is, for example, a cation such as an ammonium ion, a sodium ion, a potassium ion, and a lithium ion. The -COOM group-containing copolymer compound represented by the above general formula is used alone or in combination of two or more, and preferably has an average molecular weight of about 500 to 500,000 (weight average).
The degree 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. Embedded image Embedded image Embedded image Embedded image Embedded image 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 a maleic anhydride copolymer is an extremely general polymer, and these derivatives can also be obtained by reacting an alcohol or an amine compatible with them with the maleic anhydride copolymer. It can be easily obtained, or can be obtained by copolymerizing a purified product obtained by reacting an alcohol or an amine compatible with maleic anhydride monomer with another vinyl monomer. In addition, acrylates such as halogenoalkyl and halogenoalkyloxyalkyl are available from Journal of Polymer Science (Journal of Polymer Science).
Science. 15 515-574 (1955) or British Patent 1,121,
It can be easily synthesized by the method for synthesizing monomers and polymers described in the specification of Japanese Patent No. 357. According to the present invention, the amount of the copolymer compound used is 10 to
Is preferably 1000 mg / m ^2, even 20 to 300 mg / m ²
It is particularly good to be. The protective film used in the present invention is mainly made of cellulose triacetate. However, cellulose esters such as cellulose diacetate, cellulose acetate butyrate and cellulose propionate, polycarbonate, polyethylene terephthalate, polyacrylate and the like can also be used. . The thickness is not particularly limited, but is 10 to 500 μm, particularly 30 to
300 μm is preferred. If necessary, the protective film may contain an ultraviolet absorber, a plasticizer, a slipping agent, a matting agent, and the like. The polymer solution according to the present invention may be a gravure coater, a dip coater, a reverse roll coater,
It can be applied by a known method such as an extrusion coater. Amount with the polymer according to the present invention is in the range of 10 to 1000 mg / m ^2,
Especially stable adhesive strength and finish after application are 20-30
0 mg / m ² is preferred. The method of drying after applying the coating solution is not particularly limited, but the amount of residual solvent after drying is 5 wt%.
It is preferable to set the following. If the amount of the residual solvent is large, air bubbles may be generated at the bonding interface during the drying process after lamination with the polarizer, which is not preferable. The polymer solution according to the present invention may optionally contain an ultraviolet absorber, a slipping agent, a matting agent, an antistatic agent, a crosslinking agent, an activator, and the like. Particularly, a cross-linking agent is preferable for promoting the adhesion of the polarizer to the polyvinyl alcohol film. Examples of such a cross-linking agent include a polyvalent epoxy compound, an aziridine compound, an isocyanate compound, a bright van and a boron compound. Examples of the adhesive used to bond the treated surface of the protective film according to the present invention to the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, and vinyl latex such as butyl acrylate. Is raised. The present invention will be described in more detail with reference to the following Examples, which by no means limit the present invention. Example 1 A solution having the following composition was applied at a rate of 20 g / m ² to one surface of a cellulose triacetate film having a thickness of 125 μm,
After drying at 10 ° C. for 10 minutes, films A and B according to the present invention were obtained. [Table 1] Example 2 A solution having the following composition was applied at a rate of 20 g / m ² to one surface of a polycarbonate film having a thickness of 100 μm.
After drying for 10 minutes, a film C according to the invention was obtained. [Table 2] Example 3 A solution having the following composition containing a cationic activator (LATANAC-SN, manufactured by American Cyanamid Co.) as an antistatic agent was applied to the untreated surface of the sample film obtained in Example 1 at 20 g / m ² . The film was applied at a predetermined rate and dried at 100 ° C. for 10 minutes to obtain a film D according to the present invention. [Table 3] Comparative Sample Film A cellulose triacetate film having a thickness of 125 μm was applied to the film E, a polycarbonate film having a thickness of 100 μm was applied to the film F, and one side of the film E which was not bonded to the polarizer was subjected to only the antistatic treatment shown in Example 3. G film
And Further, the film D and the film E are added at 15 wt%.
Dipped in caustic soda solution at 70 ° C. for 180 seconds, washed with water and dried
And Next, all samples of Examples 1 to 3 and the comparative sample film, films A, B, C, D, E,
Adhesion tests were performed using F, G, H and I. At the same time, the light transmittance and the surface resistivity of the films D, E, F, G, H and I were measured. The results are shown in Table 4 below. <Evaluation Items, Methods and Criteria><AdhesionTest> A rectangular sample film having a width of 3.5 cm and a length of 15 cm was placed on a latex of butyl acrylate (solid content: 20%).
wt%), and laminated with a uniaxially stretched polyvinyl alcohol dyed film of the same size as the sample film, 90 ° C
The sample is dried for 3 minutes and left to cool for 24 hours to obtain a sample.
In the evaluation, about 3 cm of one end of the sample is left without applying an adhesive in advance, and the peeling force is obtained using the spring as a starting point. (Evaluation) ：: Latex can be applied uniformly, peeling force is 500 gr or more. ×: Latex partially forms cissing, peeling force is 300 g.
r: 50 to 100 g, Δ: less than 50 g, ×: <Transmissivity> One sample film, M, manufactured by Shimadzu Corporation
The transmittance was measured in the range of 350 to 700 nm using PS-2000, and the transmittance at that time is represented by%. <Surface resistivity> A sample film was heated at 23 ° C. and 55%
After controlling the humidity for at least 3 hours in an RH atmosphere, the measurement is performed under the same conditions using a micro current meter MODEL VE-30 manufactured by Kawaguchi Electric Works, Ltd. [Table 4] As shown in Table 4, only the sample film of the present invention has excellent adhesive strength and does not impair the light transmittance. E, F, and G have good light transmittance but poor adhesive strength, and H and I have good adhesive strength but poor transmittance, and have very poor antistatic properties. The protective film for a polarizing plate according to the present invention has excellent adhesion to the PVA film used for the polarizing film, is safe in operation, does not adversely affect the environment, and has good productivity and high productivity. It is excellent in quality and adhesiveness.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-171403 (JP, A) JP-A-3-130702 (JP, A) JP-A-59-111114 (JP, A) JP-A-58- 171008 (JP, A) JP-A-6-88907 (JP, A) JP-A-6-88908 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 5/30

Claims (1)

(57) [Claim 1] In a protective film bonded adjacent to a polarizer made of dyed uniaxially stretched polyvinyl alcohol, at least a surface bonded to the polarizer has the following general formula [ A protective film for a polarizing plate, comprising: dissolving a -COOM group-containing copolymer compound represented by I ] in a solvent having an affinity for the protective film and forming a layer. Embedded image (Where A represents a vinyl monomer , M represents a hydrogen atom or a cation , and R represents -O-R 'or -N (R ") (R') .
You. Here, R 'is an alkyl group, an aralkyl group, an aryl group, a heterocyclic ring residue or a nonmetal atom necessary for forming an heterocyclic ring together with R ", and R" is a hydrogen atom, a lower alkyl group or Represents a nonmetallic atom necessary for forming a heterocyclic ring in cooperation with ' . m, p, q, and r are values indicating mol% of each monomer, where m is 40 to 55 and p is 2 to 5
5 and q are 10 to 58 , r is 0 to 25 , and m + p + q
A + r = 10 0. )