JPH07333436A - Protective film for polarizing plate - Google Patents

Abstract

PURPOSE:To facilitate adhesion to a PVA film by successively forming a layer contg. a hydrophilic high molecular compd. and a layer contg. a high molecular compd. having COOM groups from the polarizer side. CONSTITUTION:A layer contg. at least one kind of hydrophilic high molecular compd. and a layer contg. at least one kind of high molecular compd. having -COOM groups represented by formula I or II are successively formed on at least a face bonded to a polarizer from the polarizer side. In the formulae I, II, A is a structural unit formed by polymerizing a vinyl monomer, B is H, -COOM, etc., M is H or a cation, R is-OR' or-NOR') (R'') (R' is alkyl, aryl, a residue of a hetero ring or nonmetallic atoms required to form a hetero ring in combination with R'' and R'' is H, lower alkyl or nonmetallic atoms required to form a hetero ring in combination with R'), each of R1 and R2 is H, etc., X is -COO-, etc., R3 is halogenoalkyl, etc., and (m), (p), (q), (r), (x), (y) and (z) are values showing the mol percentages of monomers, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate protective film, and more particularly to a polarizing plate protective film having excellent adhesiveness.

[0002]

2. Description of the Related Art A polarizing film obtained by laminating a cellulose triacetate film as a protective film on a polarizer of a polyvinyl alcohol film (PVA film) that has been dyed uniaxially stretched is widely used as a liquid crystal display device, such as a display portion of a calculator, a personal computer or a liquid crystal display. It is used for TVs, automobile displays, etc.

In the use of these display elements, strong adhesion is required between the polarizer 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-mentioned alkali treatment uses a high-concentration alkali solution, it is not preferable in terms of work safety and environmental protection. Further, the alkali treatment causes bleed-out of plasticizer and increase in haze, which leads to quality deterioration. It may be dropped.

Also, before the alkali treatment, antistatic treatment,
When the processing for imparting functionality such as hard coat processing is performed, the effect thereof is diminished by the alkali treatment, so that there is a problem that the functionalization of the protective film is limited after the alkali treatment.

[0006]

SUMMARY OF THE INVENTION The first object of the present invention is to provide a protective film for a polarizing plate, which is easily adhered to a PVA film. Secondly, it is to provide a protective film for a polarizing plate having excellent adhesiveness by processing that is safe in operation and does not adversely affect the environment. Thirdly, to provide a high-quality protective film for a polarizing plate, which is excellent in productivity and has excellent adhesiveness.

[0007]

The above object of the present invention can be achieved by the following constitutions.

1. In a protective film for a polarizing plate, which is adhered adjacent to a polarizer, a layer containing at least one kind of hydrophilic polymer compound from the polarizer side at least on the surface to be adhered to the polarizer, and then the hydrophilic polymer. In contrast, a protective film for a polarizing plate, which has a layer containing at least one of —COOM group-containing polymer compounds represented by the following general formula [1] or [2].

[0009]

[Chemical 2]

In the formula, A is a structural unit formed by polymerization of a vinyl monomer, B is a hydrogen atom, --CO--OM or --CO--R, M is a hydrogen atom or a cation, and z = 0. When,
B is a hydrogen atom. R is -O-R 'or -N (R') (R ")
Wherein R ′ represents an alkyl group, an aralkyl group, an aryl group, a heterocyclic residue or a non-metal atom necessary for forming a heterocycle in cooperation with R ″, and R ″ represents a hydrogen atom or a lower alkyl. Group or R'representing a non-metal atom necessary for forming a heterocycle together, R ₁ and R ₂ each represent a hydrogen atom or a lower alkyl group, and X represents -CO-O- or -O-. It represents CO-, R ₃ represents a halogenoalkyl group or halogenoalkyl alkyloxyalkyl group, m, p, q, r , x, y and z
Is a value showing mol% of each monomer, and m and x
Is 0 to 60, p, q, r, x, y and z are 0 to 10 respectively.
0, m + p + q + r = 100, x + y + z = 100.

2. 2. The polarizing plate according to claim 1, wherein the hydrophilic polymer compound is at least one selected from hydrophilic cellulose derivatives, polyvinyl alcohol derivatives, natural polymers, hydrophilic polyester derivatives and hydrophilic polyvinyl derivatives. Protective film.

The present invention will be described in more detail below.

As the hydrophilic polymer compound according to the present invention,
Preferably hydrophilic cellulose derivatives (eg, methyl cellulose, carboxymethyl cellulose, hydroxy cellulose, etc.), polyvinyl alcohol derivatives (eg,
Polyvinyl alcohol, vinyl acetate-vinyl alcohol copolymer, polyvinyl acetal, polyvinyl formal, polyvinyl benzal, etc.), natural polymer compounds (eg, gelatin, casein, gum arabic, etc.), hydrophilic polyester derivatives (eg, partially) Sulfonated polyethylene terephthalate etc.) and polyvinyl derivatives (eg poly-N-vinyl pyrrolidone, polyacrylamide, polyvinyl indazole, polyvinyl pyrazole etc.).

The hydrophilic polymer compound according to the present invention may be used alone or in combination of two or more kinds.

In the above general formulas [1] and [2], A
As the vinyl monomer that generates the structural unit represented by,
For example, styrene substituted with a nitro group, a fluorine atom, a chlorine atom, a bromine atom, a chloromethyl group, a lower alkyl group, etc., vinyl methyl ether, vinyl ethyl ether, vinyl chloroethyl ether, vinyl acetate, vinyl chloroacetate, propione. Unsaturated acids such as vinyl acid, acrylic acid, methacrylic acid or itaconic acid, alkyl esters of acrylic acid or methacrylic acid (wherein the alkyl group is substituted with an unsubstituted alkyl group having 1 to 5 carbon atoms or a chlorine atom, a phenyl group, etc.) Alkyl group), phenyl ester of acrylic acid or methacrylic acid (wherein the phenyl group is an unsubstituted phenyl group or a phenyl group substituted with a chlorine atom or a phenyl group), acrylonitrile, vinyl chloride, vinylidene chloride, ethylene, acrylamide, carbon number 1 to 5 alkyl groups or Containing, acrylamide and substituted with a phenyl group or the like, vinyl alcohol, diglycidyl acrylate, there are acrolein, preferably styrene, styrene having a substituent, vinyl acetate, vinyl methyl ether, alkyl acrylates, acrylonitrile.

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

[0017]

[Chemical 3]

(In the formula, R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ and R ₁₀ each represent a hydrogen atom or a fluorine atom, and n is 1
Represents an 12 integer, n ₂ is 0 or 1, n ₁ when n ₁ is 0, n ₂ is 1 when n ₂ is 0, 2 or 3
And n ₃ represents an integer of 1 to 17. However, n ₁ + n ₃ is 1 to 17. When there are two or more R ₄ in the general formula [A], they may be different groups such that one is hydrogen and the other is a fluorine atom, and R ₅ , R ₆ and R _{7 are also the same.} When there are a plurality of each in the general formula [A], they may be different groups. ) Further, in the general formula [1] and the general formula [2],
When R'is a halogenoalkyl group or a halogenoalkyloxyalkyl group as described above, R in the general formulas [1] and [2] is preferably -O-R '.
Further, the aryl group represented by R ′ such as a phenyl group or the aralkyl group such as a benzyl group may have a substituent, and the substituent includes a halogen atom such as a fluorine atom, a chlorine atom and a bromine atom. A lower alkyl group substituted with
Examples thereof include a hydroxyl group, a hydroxycarbonyl group, a cationic oxycarbonyl group, a nitrile group and a nitro group.

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

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

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

[0022]

[Chemical 4]

[0023]

[Chemical 5]

[0024]

[Chemical 6]

[0025]

[Chemical 7]

[0026]

[Chemical 8]

Represented by the above general formula [1] or [2]-
The COOM group-containing polymer compound can be synthesized by a known method. That is, it is well known that a maleic anhydride copolymer is a very general polymer, and these derivatives are also prepared by reacting a maleic anhydride copolymer with an alcohol or amine compatible with them. 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 1,12
It is easily synthesized by the method for synthesizing monomers and polymers described in the specification of No. 1,357.

The amount of the polymer compound represented by the general formula [1] or [2] used is preferably 10 to 1000 mg / m ² , and more preferably 20 to 300 mg / m ^2. preferable.

A layer containing at least one hydrophilic polymer compound according to the present invention (hereinafter sometimes referred to as "upper layer") and a polymer compound represented by the above general formula [1] or [2] As the protective film provided with a layer containing at least one kind (hereinafter sometimes referred to as “lower layer”),
In addition to the cellulose triacetate film that has been mainly used in the past, a film made of cellulose ester such as cellulose diacetate, cellulose acetate butyrate and cellulose propionate, polycarbonate, polyethylene terephthalate, polyacrylate and the like can be mentioned. The thickness of the protective film is not particularly limited, but is 10 to 500 μm, particularly 30 to 10 in terms of function and ease of handling.
300 μm is preferred. If desired, the protective film may contain an ultraviolet absorber, a plasticizer, a slip agent, a matting agent and the like.

The upper layer and the lower layer of the present invention are gravure coaters in the form of a coating solution prepared by dissolving or dispersing the above-described polymer compound and other additives, if necessary, in a solvent.
It can be formed by coating on the surface of the protective film by a known method such as a dip coater, a reverse roll coater or an extrusion coater. The amount of the hydrophilic polymer compound in the upper layer and the amount of the polymer compound in the lower layer are each preferably in the range of 10 to 1000 mg / m ² , and particularly from the viewpoint of stable adhesive force and finish after coating. 20 to 300 mg / m each
A range of ² is preferred.

There is no particular limitation on the method of applying the coating solution and then drying it, but the amount of residual solvent after drying is preferably 5 wt% or less. If the residual solvent amount is large, air bubbles may be generated at the adhesive interface in the drying process after being laminated with the polarizer, which is not preferable.

If desired, an ultraviolet absorber, a slip agent, a matting agent, an antistatic agent, a crosslinking agent, an activator and the like may be added to the coating liquid for the upper and lower layers of the present invention. A cross-linking agent is particularly 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 light vane and a boron compound.

Examples of the adhesive used for bonding the surface of the protective film having the upper layer and the lower layer of the present invention on the side of the upper layer to the polarizer include polyvinyl alcohol-based adhesives such as polyvinyl alcohol and polyvinyl butyral, A vinyl-based latex such as butyl acrylate can be used.

[0034]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these embodiments.

Example 1 On one side of a cellulose triacetate film having a thickness of 80 μm, a lower layer liquid (1) and an upper layer liquid (1) having the following compositions were applied in this order at a rate of 20 ml / m ² , and at 100 ° C. After drying for 10 minutes, a protective film sample 1 for polarizing plate according to the present invention was obtained.

Lower layer liquid (1) Exemplified compound (14) 0.5 g Acetone 60 ml Ethyl acetate 30 ml Toluene 10 ml Upper layer liquid (1) Polyvinyl alcohol 0.5 g (Nippon Gosei Chemical Co., Ltd., Gohsenol NH-26) Saponin (Merck) 0.03 g Water 50 ml Methanol 50 ml Example 2 A protective film for a polarizing plate according to the present invention was prepared in the same manner as in Example 1 except that the upper layer liquid (1) of Example 1 was replaced with the upper layer liquid (2) of the following composition. Sample 2 was obtained.

Upper layer liquid (2) Hydroxypropyl methylcellulose phthalate 0.5 g (HP-55 manufactured by Shin-Etsu Chemical Co., Ltd.) Methanol 60 ml Acetone 30 ml Isopropyl alcohol 10 ml Example 3 The upper layer liquid (1) of Example 1 was prepared according to the following composition. A protective film sample 3 for a polarizing plate according to the present invention was obtained in the same manner as in Example 1 except that the upper layer liquid (3) was used.

Upper layer liquid (3) Polyvinyl butyral 0.5 g (manufactured by Denki Kagaku Kogyo KK, S-REC # 2000-L) Methanol 70 ml Acetone 20 ml Toluene 10 ml Example 4 The upper layer liquid (1) of Example 1 was used as the upper layer of the following composition. A protective film sample 4 for a polarizing plate according to the present invention was obtained in the same manner as in Example 1 except that the liquid (4) was used.

Upper layer liquid (4) Gelatin 1 g Hardener (below) 0.15 g Water 70 ml Methanol 30 ml

[0040]

[Chemical 9]

Example 5 A protective film sample 5 for a polarizing plate according to the present invention was obtained in the same manner as in Example 1 except that the upper layer liquid (1) of Example 1 was replaced with the upper layer liquid (5) of the following composition. .

Upper layer liquid (5) Hydrophilic polyester (composition below) 1 g Water 70 ml Methanol 30 ml Composition of hydrophilic polyester Dimethyl terephthalate 20 mol% Dimethyl isophthalate 10 mol% 5-Sulfoisophthalic acid dimethyl Na salt 10 mol% 1, 4-Cyclohexanedicarboxylic acid 10 mol% Ethylene glycol 50 mol% Example 6 The present invention is carried out in the same manner as in Example 1 except that the upper layer liquid (1) of Example 1 is replaced with the upper layer liquid (6) of the following composition. A protective film sample 6 for polarizing plate was obtained.

Upper Layer Liquid (6) Polyvinylpyrrolidone 1 g Methanol 70 ml Acetone 30 ml Example 7 The present invention was carried out in the same manner as in Example 1 except that the lower layer liquid (1) of Example 1 was replaced with the lower layer liquid (2) of the following composition. A protective film sample 7 for polarizing plate according to was obtained.

Lower layer liquid (2) Exemplified compound (15) 0.5 g Acetone 60 ml Ethyl acetate 30 ml Toluene 10 ml Example 8 Example 1 except that the lower layer liquid (1) of Example 1 was changed to the lower layer liquid (3) of the following composition A protective film sample 8 for polarizing plate according to the present invention was obtained in the same manner as in 1.

Lower layer liquid (3) Exemplified compound (13) 0.5 g N, N-dimethylformamide 10 ml Acetone 40 ml Methanol 30 ml Ethyl acetate 20 ml Comparative Example 1 Comparative protective film in the same manner as in Example 1 except that the lower layer was not provided. Sample 9 was obtained.

Comparative Example 2 A comparative protective film sample 10 was obtained in the same manner as in Example 2 except that the lower layer was not provided.

Comparative Example 3 A protective film sample 11 for comparison was obtained in the same manner as in Example 3 except that the lower layer was not provided.

Comparative Example 4 A comparative protective film sample 12 was obtained in the same manner as in Example 4 except that the lower layer was not provided.

Comparative Example 5 A comparative protective film sample 13 was obtained in the same manner as in Example 5 except that the lower layer was not provided.

Comparative Example 6 A comparative protective film sample 14 was obtained in the same manner as in Example 6 except that the lower layer was not provided.

Comparative Example 7 A comparative protective film sample 15 was obtained in the same manner as in Example 1 except that the upper layer was not provided.

Comparative Example 8 A lower layer solution (4) and an upper layer solution (7) having the following compositions were applied in this order on one surface of a cellulose triacetate film having a thickness of 80 μm at a rate of 20 ml / m ² and then at 100 ° C. After drying for 10 minutes, a protective film sample for polarizing plate according to the present invention
Got 16.

Lower layer liquid (4) Polyvinyl alcohol (Nippon Gosei Kagaku Kogyo KK, Gohsenol KL-05) 0.5 g Water 10 ml Methanol 30 ml Acetone 50 ml N, N-Dimethylformamide 10 ml Upper layer liquid (7) Exemplified compound (4) 0.5 g Acetone 60 ml Ethyl acetate 30 ml Toluene 10 ml Comparative Example 9 2N of 80 μm thick cellulose triacetate film
Was dipped in the sodium hydroxide solution at 60 ° C. for 3 minutes, washed with water and dried to obtain a cellulose triacetate film whose surface was alkali-saponified. This is designated as Comparative Protective Film Sample 17.

Then, the protective film samples 1 to 17 produced in Examples 1 to 8 and Comparative Examples 1 to 9 were subjected to an adhesive strength test by the following method. The results are shown in Table 1.

Method of Adhesion Test First, a polarizing film was produced by laminating a polarizer and a protective film in the following steps.

A protective film sample having a size of 18 cm × 5 cm is placed on a glass plate with the coated surface facing upward.

A polarizer composed of a uniaxially stretched polyvinyl alcohol dye film of the same size as the protective film sample is immersed in a polyvinyl alcohol adhesive tank having a solid content of 2 wt% for 1 to 2 seconds (both sides of the polarizer).

The excess adhesive adhering to the above-mentioned polarizer is lightly removed, placed on the above-mentioned protective film sample, and the next protective film so that the coated surface of the same sample film as described above and the adhesive are in contact with each other. Samples are stacked and placed.

Excess adhesive and air bubbles are removed from the ends of the laminate of the polarizer and the protective film, which are laminated as described above, by a hand roller, and they are bonded together. The pressure of the hand roller was about ^{2 to 3} kg / cm ² , and the roller speed was about 2 m / min.

The sample obtained in 80 ° C. oven is left for 2 minutes.

With respect to the polarizing film thus produced, the adhesion between the polarizer and the protective film was evaluated as follows.

Initial adhesion: After the polarizer and the protective film were bonded together, the peelability was measured by hand, and the degree of occurrence of material destruction was evaluated according to the following three grades.

Material destruction occurs. (Indicated by “◯” in Table 1.) Although some material destruction occurs, the peeling area between the sample film and the PVA film is large. (Indicated by “Δ” in Table 1.) Peeling occurs between the sample film and the PVA film.
(Indicated by "x" in Table 1.) Workability: Cutting was performed using a single blade, and the degree of floating of the adhesive surface was evaluated in the following three grades.

There is no floating of the adhesive surface. (Indicated by “◯” in Table 1.) Slight floating of the adhesive surface occurs. (Indicated by “Δ” in Table 1.) Floating of the adhesive surface occurs. (Indicated by "x" in Table 1.) Durability: Under conditions (A) of 75 ° C and 90% relative humidity, and 90
The sample was left under the condition (B) at 500 ° C. for 500 hours, the change in appearance was observed, and the width of peeling from the edge was measured. The meanings of the symbols in Table 1 are as follows.

○: Within 0.5 mm △: 0.6 to 1.5 mm ×: 1.6 mm or more If the adhesiveness is equal to or higher than that of Comparative Sample 17 (target of the present invention), there is no problem in practical use, and " ○ ”is given.

The transmittance of each of the samples of the polarizing film was measured by using MPS-2000 manufactured by Shimadzu Corp. at a wavelength of 35.
It was measured in the range of 0 to 700 nm. The results are shown in Table 1.

[0067]

[Table 1]

As is clear from the results shown in Table 1, the protective film sample of the present invention shows good adhesiveness without the alkali saponification treatment. In addition, it exhibits excellent light transmittance without bleeding out of the plasticizer.

[0069]

The protective film for polarizing plate according to the present invention comprises
It has excellent adhesiveness and transmittance to the PVA film of the polarizer, and in the manufacturing process thereof, it has a high saponification rate as compared with a protective film made of a cellulose triacetate film whose surface is saponified with an alkaline solution. Since it is not necessary to use a concentrated alkaline solution, work safety and environmental conservation are improved, productivity is good, and a plasticizer by alkali treatment for saponification of the surface of a conventional cellulose triacetate film. The problem of high bleedout and high haze is improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C09J 7/02 JHR JJA JLF

Claims (2)

[Claims] 1. A protective film for a polarizing plate, which is adhered adjacent to a polarizer, comprising a layer containing at least one hydrophilic polymer compound from at least the polarizer side on the surface to be adhered to the polarizer, and then the A protective film for a polarizing plate, which has a layer containing at least one kind of —COOM group-containing polymer compound represented by the following general formula [1] or [2], unlike a hydrophilic polymer. [Chemical 1] [In the formula, A is a structural unit formed by polymerization of a vinyl monomer, B is a hydrogen atom, -CO-OM or -CO-R, M is a hydrogen atom or a cation, and when z = 0. , B is a hydrogen atom. R represents -O-R 'or -N (R') (R "),
Here, R'is an alkyl group, an aralkyl group, an aryl group,
A heterocyclic residue or a non-metal atom necessary for forming a heterocycle in cooperation with R ″, R ″ is a hydrogen atom, a lower alkyl group or a non-metal atom necessary for forming a heterocycle in combination with R ′. Represents a metal atom, R ₁ and R ₂ each represent a hydrogen atom or a lower alkyl group, X represents —CO—O— or —O—CO—, and R ₃
Represents a halogenoalkyl group or a halogenoalkyloxyalkyl group, and m, p, q, r, x, y and z are each
It is a value showing the mol% of each monomer, and m and x are 0 respectively.
-60, p, q, r, x, y, and z are 0-100, respectively, and m + p + q + r = 100 and x + y + z = 100. ] 2. The hydrophilic polymer compound is at least one selected from hydrophilic cellulose derivatives, polyvinyl alcohol derivatives, natural polymers, hydrophilic polyester derivatives and hydrophilic polyvinyl derivatives. A protective film for a polarizing plate as described above.