JP2019048927A - Resin composition, adhesive, adhesive for polarizer and polarizer using the same - Google Patents

Abstract

To provide a resin composition excellent in viscosity stability when made a solution, and excellent in long term water-resistant adhesive when used as an adhesive.SOLUTION: There is provided a resin composition containing a modified group-containing polyvinyl alcohol resin having an active methylene group (A), a glyoxylic acid salt (B) and a compound containing an amino group and an acid group.SELECTED DRAWING: None

Description

  The present invention relates to a resin composition, an adhesive, an adhesive for a polarizing plate, and a polarizing plate using the same. More specifically, it is suitable as an adhesive for a polarizing plate because it has crosslinking reactivity, is excellent in viscosity stability (pot life) when made into an aqueous solution, and is further excellent in water resistance after crosslinking, especially long-term water-resistant adhesion. The present invention relates to a resin composition.

Polyvinyl alcohol-based resins (hereinafter referred to as PVA-based resins) are known as water-soluble resins, and are widely used as water-based adhesives, particularly because of their good affinity and cohesion with hydrophilic materials.
Moreover, when water-resistant adhesiveness and water resistance are calculated | required as this adhesive agent, it is common to use a crosslinking agent suitably together. However, the aqueous solution of the PVA-based resin composition in which the crosslinking agent is blended may increase in viscosity over time depending on the use environment and storage environment, so that the viscosity may increase and eventually gelation may make coating difficult. And viscosity stability are also important characteristics.

On the other hand, in recent years, liquid crystal display devices (image display devices such as liquid crystal televisions, computer displays, mobile phones and digital cameras) have been widely used, but in liquid crystal display devices, polarizing films are provided on both sides of a glass substrate in which liquid crystal is enclosed. It has a laminated structure, and various optical functional films such as a retardation plate are laminated thereon as required.
As a polarizing film, a uniaxially stretched film in which a dichroic material such as iodine is dispersed and adsorbed in a PVA resin having a high degree of saponification, and which is crosslinked by a crosslinking agent such as boric acid after stretching or simultaneously with stretching is widely used It is done.
A polarizing film using a uniaxially stretched film of this PVA-based resin is easily shrunk under high humidity, and usually, a protective film is attached to at least one surface, preferably both surfaces, to compensate for moisture resistance and strength, Together as a polarizing plate.

Moreover, as a protective film, cellulose ester-type resin, such as a triacetyl cellulose, is widely used from the point which is excellent in transparency, mechanical strength, and moisture resistance.
The protective film is bonded to the polarizing film by an adhesive, and the adhesive composition constituting the adhesive is mainly composed of a PVA-based resin from the viewpoint of adhesion to the polarizing film having a hydrophilic surface. The thing is used.

  A polarizing plate obtained by laminating a protective film and a polarizing film is transported to the world through land, air and sea. In the process of transportation, it often passes through areas of high temperature and high humidity, and may be stored in such areas, and at that time it has been a problem that the adhesion between the protective film and the polarizing film is lowered. .

In order to solve such problems, for example, it has been proposed to use, as an adhesive layer, a crosslinked polymer obtained by crosslinking an acetoacetyl group-containing PVA resin with glyoxylate (see, for example, Patent Document 1). .
Further, it has been proposed to use an acetoacetyl group-containing PVA-based resin as a polyvinyl alcohol-based resin used as an adhesive for polarizing plate, and to use a crosslinking agent in combination therewith (for example, see Patent Document 2). The patent document 2 exemplifies a glyoxylate salt and amino acids having a basic group and an acidic group, as well as a large number of compounds as a crosslinking agent.

Unexamined-Japanese-Patent No. 2010-077385 JP, 2013-101251, A

Although an acetoacetyl group-containing PVA resin described in Patent Document 1 and an adhesive using a glyoxylate as its crosslinking agent exhibit good pot life and water resistance, they are exposed to high humidity conditions for a long time, or moisture In the state of contact with the adhesive, the adhesion may be lowered, and in the recent increase in the required performance of the adhesive for polarizing plate, further improvement is required in terms of long-term water-resistant adhesion. .
An object of the present invention is to provide a resin composition excellent in long-term water-resistant adhesion, in which the adhesiveness does not decrease even when immersed in water for a long time under such a background.

  However, as a result of intensive studies conducted by the present inventors in view of the above circumstances, the composition of the modified group-containing PVA resin having an active methylene group and the glyoxylate further contains a compound containing an amino group and an acid group. As a result, it has been found that an adhesive excellent in long-term water-resistant adhesion can be obtained, thereby completing the present invention.

  That is, the gist of the present invention is a resin composition comprising a modified group-containing PVA resin (A) having an active methylene group, a glyoxylate (B), and a compound (C) containing an amino group and an acid group. It is about

  Furthermore, in the present invention, an adhesive containing such a resin composition, an adhesive for a polarizing plate, and a polarizing plate formed by bonding a polarizing film and a protective film using the above-mentioned adhesive are also provided.

  The resin composition of the present invention can be used as an adhesive excellent in long-term water-resistant adhesion without impairing the conventional viscosity stability (pot life), and in particular, a polarizing plate obtained by using such an adhesive Can be applied to display devices used under severe conditions such as under high humidity.

  Such an effect is obtained by the carboxylate group of the glyoxylate (B), the amino group and the acid in the crosslinked structure formed by the modified group-containing PVA resin (A) having an active methylene group and the glyoxylate (B). By further reacting the amino group of the compound (C) containing a group, the growth of crystal nuclei is promoted, whereby the swelling of the adhesive layer is suppressed by the increase of the hardness of the adhesive layer, and the water adhesion is excellent. It is assumed that an adhesive layer is obtained.

  In addition, although the glyoxylate and an amino acid are illustrated together with many compounds as a crosslinking agent of acetoacetyl group containing PVA-type resin in patent document 2, when these are used together, both react and the crosslinkable functional group is consumed. It is assumed that those skilled in the art having ordinary chemical knowledge do not recall the combination since they are expected to lose the property as a crosslinker. It was found that the problem does not occur unexpectedly, probably because of the presence, but rather an unexpected effect is obtained.

The description of the configuration requirements described below is an example (representative example) of the embodiment of the present invention, and is not specific to these contents.
Hereinafter, the present invention will be described in detail.

The resin composition of the present invention comprises a modifying group-containing polyvinyl alcohol resin (A) having an active methylene group, a glyoxylate (B), and a compound (C) containing an amino group and an acid group. is there.
First, a modified group-containing PVA-based resin having an active methylene group (hereinafter, sometimes abbreviated as an active methylene-containing PVA-based resin) used in the present invention will be described (A).

[Modified Group-Containing PVA-Based Resin (A) Having Active Methylene Group]
The active methylene group as referred to in the present invention is, for example, a methylene group adjacent to a carbonyl group, which is a methylene group with increased acidity. That is, the crosslinking reaction occurs in the portion which is resonance stabilized between the methylene group and the carbonyl group.
The active methylene group-containing PVA resin (A) as described above is, for example, a PVA resin having a modifying group having a structure in which a carbonyl group such as a ketone, a carboxylic acid or a carboxylic ester is adjacent to a methylene group, Specifically, for example, a PVA-based resin having an acetoacetyl group or a diacetone group can be mentioned.
Among them, an acetoacetyl group-containing PVA-based resin (hereinafter sometimes abbreviated as AA-PVA-based resin) (A1) and a diacetone acrylamide structural unit-containing PVA-based resin are preferable, and further, in terms of water resistance. An AA-PVA-based resin (A1) is preferred.

In the present invention, the average degree of polymerization of the active methylene group-containing PVA-based resin (A) is usually 300 to 4000, preferably 400 to 3000, and more preferably 800 to 2000. If the average degree of polymerization is too small, sufficient water resistance may not be obtained or a sufficient crosslinking rate may not be obtained. On the contrary, if it is too large, the viscosity of the adhesive composition becomes too high. Tend to be difficult.
In addition, the said average degree of polymerization is measured based on JISK6726.

The degree of saponification of the active methylene group-containing PVA resin (A) is usually 80 to 100 mol%, preferably 85 to 99.9 mol%, particularly preferably 90 to 99.8 mol%. Used.
If the degree of saponification is too low, it may be difficult to form an aqueous solution, the stability of the aqueous solution may be reduced, and the water resistance of the resulting adhesive may be reduced.
The degree of saponification is measured in accordance with JIS K 6726.

The modified amount of the active methylene group-containing PVA resin (A) is usually 0.1 to 20 mol%, more preferably 1 to 15 mol%, and particularly preferably 2 to 10 mol%.
If the content is too small, the water resistance tends to decrease or a sufficient crosslinking rate can not be obtained. On the contrary, if the content is too large, the water solubility tends to decrease or the stability of the aqueous solution tends to decrease. .

  As a method for producing the active methylene group-containing PVA resin (A), for example, (i) copolymerizing a monomer having a modifying group containing an active methylene group with a vinyl ester compound, A method of saponifying the obtained copolymer, (ii) polymerizing a vinyl ester compound, saponifying the obtained polymer, and introducing a modified group having an active methylene group into the obtained PVA by post reaction The method is mentioned.

[AA-PVA-based resin (A1)]
Next, the AA-PVA-based resin (A1) preferably used in the present invention will be described.
The AA-PVA-based resin (A1) used in the present invention is a resin in which an acetoacetyl group (AA group) is bonded directly to the main chain of the PVA-based resin or via an oxygen atom or a linking group. The PVA-type resin containing the structural unit which has AA group represented by (1) is mentioned.
In addition, such AA-PVA-based resin (A1) has a vinyl alcohol structural unit in addition to the structural unit having an AA group, and further has a vinyl ester structural unit of an unsaponified part as necessary.

  Examples of the vinyl ester structural unit include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and benzoic acid. Although structural units derived from vinyl, vinyl versatate and the like can be mentioned, vinyl acetate structural units are preferable from the viewpoint of economy.

  In addition to the vinyl ester structural unit, a structural unit derived from a compound copolymerizable with a vinyl ester compound can also be contained, and examples of such a copolymerizable compound include ethylene, propylene, isobutylene, and the like. Olefins such as α-octene, α-dodecene and α-octadecene; 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 3,4-dihydroxy-1-butene and the like Hydroxy group-containing α-olefins and derivatives thereof such as acylates thereof; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, undecylenic acid, salts thereof, monoesters, or Dialkyl esters; Nitriles such as acrylonitrile and methacrylonitrile; diacetone Amides such as chloramide, acrylamide, methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid or salts thereof; alkyl vinyl ethers, dimethyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl Vinyl compounds such as ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether and the like; substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate; vinylidene chloride, 1,1 4-diacetoxy -2- butene, 1, 4- dihydroxy -2- butene, vinylene carbonate, etc. are mentioned.

  The amount of such a copolymerizable compound to be introduced varies depending on the kind of the compound, but is usually 10% by mole or less, particularly 5% by mole or less of the total structural units. It may be damaged or the compatibility with the crosslinking agent may be reduced.

The average degree of polymerization of the AA-PVA-based resin (A1) may be appropriately selected depending on the application, but is usually 300 to 4000, and particularly preferably 400 to 3000, and more preferably 800 to 2000. If the average degree of polymerization is too small, sufficient water resistance may not be obtained or a sufficient crosslinking rate may not be obtained. On the other hand, if it is too large, the viscosity of the resin composition becomes too high, resulting in coating It tends to be difficult.
In addition, the said average degree of polymerization is measured based on JISK6726.

The saponification degree of the AA-PVA-based resin (A1) is usually 80 to 100 mol%, further 85 to 99.9 mol%, particularly 90 to 99.8 mol%, especially 95 to 99.8 mol% of what is used suitably. If the degree of saponification is too low, it may be difficult to form an aqueous solution, the stability of the aqueous solution may be reduced, and the water resistance of the resulting adhesive may be reduced.
The degree of saponification is measured in accordance with JIS K6726.

  Moreover, AA group content (Hereafter, AA conversion degree may be abbreviated.) In AA-ized PVA-type resin (A1) is 0.1-20 mol% normally, and also 1-15 mol. %, Particularly preferably 3 to 10 mol%. If the content is too small, the water resistance tends to decrease or a sufficient crosslinking rate can not be obtained. On the contrary, if the content is too large, the water solubility tends to decrease or the stability of the aqueous solution tends to decrease. .

In the present invention, it is preferable that all of the PVA resins used are AA-PVA-based resins (A1), but PVA-based resins other than AA-PVA-based resins (A1) may be used in combination, The content is usually 20 parts by weight or less, preferably 10 parts by weight or less, and more preferably 5 parts by weight or less, based on 100 parts by weight of the AA-PVA-based resin (A1).
As PVA-based resins other than the AA-PVA-based resin (A1), unmodified PVA-based resins, and various modified PVA-based resins obtained by copolymerizing various monomers having copolymerizability with vinyl ester-based monomers Can be mentioned.

  In addition, in the AA-PVA-based PVA resin (A1) used in the present invention, acetates of alkali metals such as sodium acetate used or by-produced in the production process (mainly alkali metal hydroxide used as a saponification catalyst and Organic acid (derived from a reaction product with acetic acid generated by saponification of polyvinyl acetate), organic acid such as acetic acid (at the time of reaction with diketene at the time of introducing acetoacetic ester group into PVA-based resin) Some organic solvents (derived from acids, etc.), organic solvents such as methanol, methyl acetate (derived from reaction solvents for PVA-based resins, cleaning solvents for AA-PVA-based resins, etc.) may remain.

  As a manufacturing method of this AA-ized PVA-type resin (A1), it can manufacture according to the method as described in specification paragraph-of Unexamined-Japanese-Patent No. 2010-077385.

[Glyoxylate (B)]
The glyoxylate (B) used in the present invention will be described.
The glyoxylate (B) used in the present invention is one which undergoes a crosslinking reaction with the active methylene group-containing PVA resin (A).
Examples of such glyoxylate (B) include metal salts and amine salts of glyoxylic acid, and metal salts include, for example, alkali metals such as lithium, sodium and potassium, alkaline earth metals such as magnesium and calcium, Transition metals such as titanium, zirconium, chromium, manganese, iron, cobalt, nickel and copper, other metals such as zinc and aluminum, and metal salts of glyoxylic acid, and as amine salts, ammonia, monomethylamine, dimethylamine, There may be mentioned salts of glyoxylic acid with amines such as trimethylamine.
In particular, metal salts are preferable from the viewpoint that an adhesive excellent in water resistance is obtained, among which salts of alkali metals or alkaline earth metals are preferably used, and particularly preferably alkali metal salts, particularly sodium salts from the viewpoint of water resistance. Certain sodium glyoxylate (B1) is preferably used.

  Further, as the solubility of the glyoxylate (B) used in the present invention in water, the solubility in water at 23 ° C. is 0.01 to 100%, particularly 0.1 to 50%, and further 0.5 to 20. % Is preferably used. If the solubility is too small, it tends to be difficult to prepare an aqueous solution.

  Although the manufacturing method of glyoxylate (B) can use a well-known method, For example, the method by the neutralization reaction of glyoxylic acid, (2) glyoxylic acid and an acid dissociation constant are larger than glyoxylic acid (3) methods by alkaline hydrolysis of glyoxylic acid esters (see, for example, JP-A-2003-300926) and the like. In particular, when the water solubility of the alkaline compound used for the neutralization reaction with glyoxylic acid is high, the method of (1) is also low in water solubility of the obtained glyoxylate, and the acid dissociation constant is larger than glyoxylic acid. When the water solubility of is high, the method of (2) is preferably used.

The method (1) is usually carried out using water as a medium, and the glyoxylic acid and an alkaline compound, for example, hydroxides of various metals or amine compounds are reacted in water, and the precipitated glyoxylate is separated by filtration. It can be dried and manufactured.
The method (2) is also generally carried out in water, and the glyoxylate can be obtained in the same manner as the method (1). Examples of salts of acids having a larger dissociation constant than glyoxylic acid used in the method (2) include alkali metal or alkaline earth metal salts of aliphatic carboxylic acids such as sodium acetate, calcium acetate and calcium propionate. It can be mentioned.

[Compound (C) containing an amino group and an acid group]
Next, the compound (C) containing an amino group and an acid group used in the present invention will be described.
Examples of the compound (C) containing an amino group and an acid group include taurine, aminomethanesulfonic acid, 3-sulfopropylamine, sulfanilic acid, 1-amino-2-naphthol-4-sulfonic acid, 1-aminonaphthalene -2-sulfonic acid, 1,4-phenylenediamine-2-sulfonic acid, 1,3-phenylenediamine-4-sulfonic acid, 1-amino-2-methoxy-5-methyl-4-benzenesulfonic acid, 2- Aminobenzenesulfonic acid, 2-aminophenol-4-sulfonic acid 2-aminonaphthalene-6,8-disulfonic acid, 2,5-dichlorosulfanilic acid, 2-amino-5-nitrobenzenesulfonic acid 2-amino-4-chloro Phenol-6-sulfonic acid, 2-phenylamino-5-aminobenzenesulfonic acid, 3,4-diaminoben Sulfonic acid, 3-aminobenzenesulfonic acid, 3-amino-4-hydroxy-1-naphthalenesulfonic acid, 3-methyl-4-aminobenzenesulfonic acid, 3-amino-4-chlorobenzenesulfonic acid, 3-amino-4 -Hydroxy-5-nitrobenzenesulfonic acid, 3- (4-amino-3-methoxyphenylazo) benzenesulfonic acid, 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid 3,5-diamino-4- Methylbenzenesulfonic acid, 4-amino-5-hydroxy-1,7-naphthalenedisulfonic acid 4-amino-1-naphthalenesulfonic acid, 4-acetamido-2-aminobenzenesulfonic acid, 4-aminoazobenzene-3-sulfonic acid , 5-amino-6-hydroxy-3-nitrobenzenesulfonic acid, 5-amino-2-c Rolotoluene-4-sulfonic acid, 5-amino-2-methylbenzenesulfonic acid, 5-amino-2-ethoxybenzenesulfonic acid, 6-amino-4-hydroxy-2-naphthalenesulfonic acid, 6-amino-1-naphthol -3-sulfonic acid, 6-amino-1-naphthalenesulfonic acid, 6-amino-1,3-naphthalenedisulfonic acid, 7-amino-1-naphthalenesulfonic acid, 8-amino-1-hydroxy-3.6- Naphthalenedisulfonic acid N- (2-acetamido) -2-aminoethanesulfonic acid, p-toluidine-2-sulfonic acid, p-anisidine-2-sulfonic acid, p-anisidine-3-sulfonic acid, O-anisidine-5 Sulfonic acid compounds (C1) having an amino group such as sulfonic acid, arginine, alanine, proline, cysteine, lidi , Threonine, asparagine, phenylalanine, serine, methionine, glycine, tyrosine, histidine, tryptophan, cystine, amino and carboxylic acid compounds such as theanine (amino acids) and the like. These may be used alone or in combination of two or more. Among these, from the viewpoint of water resistance, sulfonic acid compounds (C1) having an amino group are preferable, and taurine is particularly preferable.

[Other crosslinkers]
In the resin composition of the present invention, in addition to the glyoxylate (B) and the compound (C) containing an amino group and an acid group, another crosslinking agent may be blended, for example, a water-soluble titanium compound or Water-soluble zirconium compounds or polyvalent metal compounds represented by water-soluble aluminum compounds etc., boron compounds such as boric acid and borax, amine compounds (eg diamine compounds, polyamine compounds, polyallylamine etc.), silane compounds, aldehyde group-containing Compounds (for example, dimethoxyethanal, glutaraldehyde, glyoxylic acid and derivatives thereof such as hemiacetal or acetal thereof), thiol compounds, isocyanate compounds, polyisocyanate compounds (for example, “Hydran Assister, manufactured by Dainippon Ink Chemical Industry Co., Ltd. C1 etc.), blocky Cyanate compound (e.g., ketoxime block compounds, phenol-blocked products, etc.), water-soluble or water-dispersible oxetane resins or compounds, it can be used polyethyleneimine. These may be used alone or in combination of two or more.

[Resin composition]
The resin composition of the present invention contains an active methylene group-containing PVA resin (A), a glyoxylate (B), and a compound (C) containing an amino group and an acid group, and the active methylene group-containing PVA The content of the glyoxylate (B) is 0.1 to 20 parts by weight, in particular 1 to 10 parts by weight, and further 2 to 8 parts by weight with respect to 100 parts by weight of the resin (A) The content of the compound (C) containing an amino group and an acid group is preferably 1 to 100 parts by weight, particularly 10 to 70 parts by weight, and further preferably 20 to 60 parts by weight. If the content of glyoxylate (B) is too high or too low, long-term water-resistant adhesion tends to decrease, and the content of compound (C) containing an amino group and an acid group is too high or too low Even if it is too long, the long-term water-resistant adhesion tends to be lowered.

  The content of the compound (C) containing an amino group and an acid group is preferably 1 to 20 parts by weight, and more preferably 5 to 15 parts by weight, per 1 part by weight of the glyoxylate (B). .

  The form of the resin composition of the present invention is not particularly limited, but when it is used as an adhesive, particularly as an adhesive for polarizing plate, it is in the form of liquid to form a uniform adhesive composition layer on the substrate surface. It is preferable to use, and as a solvent, water which is a good solvent is suitably used for any of PVA-based resin (A), glyoxylate (B), and compound (C) containing an amino group and an acid group. .

Furthermore, after the adhesive composition is applied to a polarizing film or a protective film, a drying step is usually provided to remove the solvent contained in the adhesive composition, but for the purpose of shortening the drying step, the adhesive composition Water / alcohol containing an alcohol solvent which is easily miscible with water and has a boiling point lower than that of water, that is, a boiling point of 100 ° C. or less, particularly 80 ° C. or less, further 70 ° C. or less It is also a preferred embodiment to use a mixed solvent.
Specific examples of such alcohol solvents include, for example, lower alcohols having 1 to 3 carbon atoms such as methanol, ethanol, n-propanol and isopropanol, and among them, methanol having the lowest boiling point is preferably used. .

  The compounding amount of the alcohol-based solvent may be appropriately selected depending on the drying conditions and the type of alcohol used, but the content ratio (weight ratio) of both in water and alcohol mixed solvent is usually 99.99 / 0. The range of 0.1 to 20/80, preferably 99/1 to 30/70, particularly 90/10 to 40/60, and more preferably 80/20 to 50/50 is preferably used. If the blending amount of the alcohol is too large, the viscosity stability of the adhesive composition solution tends to decrease, and if too small, the shortening effect of the drying process tends not to be obtained.

  The solid content concentration of the adhesive composition solution can not generally be determined depending on the desired coating amount and the characteristics of the coating apparatus, but is usually 0.5 to 30% by weight, particularly 1 to 20% by weight, and further The range of 1.5 to 15% by weight is preferably used. If the concentration is too low, it takes a long time to dry, which impairs the productivity. On the contrary, if it is too high, the viscosity tends to be high, and uniform coating tends to be difficult.

The adhesive composition of the present invention usually contains 30% by weight or less, particularly 20% by weight or less of other resins within the range not impairing the object of the present invention, for example, polysaccharides such as starch and cellulose, polyethylene glycol Water-soluble resins such as polyvinyl pyrrolidone, polyoxazoline, water-soluble polyamide, water-soluble polyester, polyacrylamide, polyethylene imine and the like, and furthermore, urethane adhesives and emulsion adhesives can be used in combination.
Similarly, as various additives, for example, antifoaming agents, leveling agents, coloring agents, dyes, pigments, fluorescent brightening agents, pigments, UV absorbers, antioxidants, fillers, plasticizers, antistatic agents, A heat stabilizer, a surfactant, a desiccant, a deodorant, an antibacterial agent, an antiseptic, an antifoamer, etc. can be contained.

In the present invention, the adhesive composition of the present invention is uniformly coated on a polarizing film and a protective film, or both of them, and after bonding both, pressure bonding and heat drying are carried out.
When coating such an adhesive composition on a polarizing film or a protective film, the roll coater method, air doctor method, blade coater method, spraying method, immersion method, or the polarizing film and the protective film may be prepared immediately before bonding. A known method such as pasting together after supplying an appropriate amount between films and pouring can be used.
For lamination and pressure bonding, for example, a roll laminator can be used, and the pressure is selected from the range of 0.1 to 10 MPa. The heating and drying conditions are usually 5 to 150 ° C., particularly 30 to 120 ° C., for 10 seconds to 60 minutes, further 30 seconds to 30 minutes, and particularly 1 minute to 20 minutes.

  In the present invention, the adhesive composition is crosslinked to form an adhesive layer, and the thickness of the adhesive layer is usually 0.01 to 10 μm, particularly preferably 0.05 to 5 μm. If the thickness is too thin, the adhesion tends to be insufficient, and if it is too thick, uniform coating may be difficult, or thickness unevenness may occur to deteriorate the appearance.

(Polarizer)
There is no restriction | limiting in particular as a polarizer used by this invention, A well-known thing can be used.
For example, a dichroic material such as iodine or a dichroic dye is adsorbed to a vinyl alcohol-based resin film such as (i) PVA-based film, partially-formalized PVA-based film, ethylene-vinyl acetate copolymer saponified film or the like And uniaxially stretched (see, for example, JP-A-2001-296427 and JP-A-H07-333426), (ii) vinyl materials having birefringence as well as dichroic materials in (i) above. A film obtained by uniaxially stretching a thermoplastic norbornene resin film containing a dichroic material (for example, see JP-A-2001-72203) 356213), (iv) PVA resin or ethylene-vinyl alcohol resin is dehydrated or deacetateed. And a polyene-based film (see, for example, JP-A-2007-17845) obtained by introducing a continuous polyene structure and stretching it.
Among them, a uniaxially stretched film in which iodine is adsorbed to a PVA-based film is preferable from the viewpoint of excellent polarization characteristics.

The thickness of the polarizer is usually 0.1 to 100 μm, and particularly preferably 0.5 to 80 μm, and more preferably 1 to 60 μm.
The moisture content of the polarizer is usually 15% by weight or less, preferably 14% by weight or less, and particularly preferably 0.2 to 13% by weight.

(Protective film)
The protective film used in the present invention can compensate for the lack of durability under high humidity, which is a problem of the polarizer, by bonding it to at least one surface, preferably both surfaces of the polarizer.
Furthermore, as the characteristics required for the protective film used in the present invention, transparency, mechanical strength, thermal stability, water blocking property, optical isotropy and the like can be mentioned.

As the material of the protective film, cellulose ester resins, cyclic olefin resins, and (meth) acrylic resins are preferably used in terms of optical properties and durability.
Other materials include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polystyrene resins such as polystyrene and acrylonitrile / styrene copolymer, polyolefin resins such as polyethylene and polypropylene, polyarylate resins, and polycarbonate resins. , Vinyl chloride resin, amide resin such as nylon and aromatic polyamide, (fluorine-containing) polyimide resin, polyetheretherketone resin, polyphenylene sulfide resin, polyvinylidene chloride resin, polyvinyl acetal resin such as polyvinyl butyral And polyoxymethylene resins and epoxy resins. These may be used alone or in combination of two or more.

  As cellulose ester resin used for the above-mentioned cellulose ester resin film, triacetyl cellulose and diacetyl cellulose are representative, but in addition, lower fatty acid ester of cellulose, cellulose acetate propionate, cellulose acetate butyrate, etc. Mixed fatty acid esters of can be used.

  As cyclic olefin resin used for the said cyclic olefin resin film, norbornene resin can be mentioned. The norbornene resin is, for example, a ring-opened (co) polymer of a norbornene monomer, a resin obtained by addition polymerization of a norbornene monomer, or an addition copolymer of the norbornene monomer and an olefin monomer such as ethylene or α-olefin. It includes resins and the like.

  Specific examples of norbornene-based monomers include dimers such as norbornene and norbornadiene; tricycles such as dicyclopentadiene and dihydroxypentadiene; and heptacycles such as tetracyclopentadiene; such as methyl, ethyl, propyl and butyl Alkyl, alkenyl such as vinyl, alkylidene such as ethylidene, substituted such as aryl such as phenyl, tolyl and naphthyl; further, these ester group, ether group, cyano group, halogen, alkoxycarbonyl group, pyridyl group, hydroxyl group, carbonic acid Examples thereof include carbons such as an acid group, an amino group, an anhydride group, a silyl group, an epoxy group, an acryloyl group and a methacryloyl group, and substituted substances having a group containing an element other than hydrogen.

  Commercial products of cyclic olefin resin films include "ARTON" manufactured by JSR, "ZEONOR" manufactured by Nippon Zeon, "ZEONOR", "OPTOREZ" manufactured by Hitachi Chemical, "APEL" manufactured by Mitsui Chemicals, etc. it can.

  Examples of the (meth) acrylic resin used for the above (meth) acrylic resin film include poly (meth) acrylic acid esters such as poly (methyl methacrylate), methyl methacrylate- (meth) acrylic acid copolymer, methacrylic Acid methyl-(meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester-(meth) acrylic acid copolymer, methyl (meth) acrylic acid-styrene copolymer, with alicyclic hydrocarbon group Polymers (eg, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylic acid norbornyl copolymer, etc.), high glass transition temperature (cross-linked or intramolecular cyclization reaction) (Meth) acrylic resin, rubber-acrylic graft core-shell polymer, etc. may be mentioned

  As a commercial item of this (meth) acrylic-type resin film, Mitsubishi Rayon "Acripet VRL20A", "Acripet IRD-70", a UMGABS company "MUX-60" etc. are mentioned, for example.

  In addition, the said protective film performs surface-hydrophilization processing, such as a corona discharge treatment and plasma processing, with respect to the saponification process by the alkaline liquid with respect to the film which consists of cellulose ester-type resin, and the film which consists of cyclic olefin resin as needed. It may be

In addition, in order to enhance the affinity of the surface of the protective film with the adhesive, it is possible to perform various surface treatments other than hydrophilization, and the surface of the protective film is made of (meth) acrylate latex or styrenic latex, An easily adhesive layer containing a polyethyleneimine, a polyurethane / polyester copolymer or the like or an anchor coat layer may be provided, or a surface treatment method with a coupling agent such as a silane coupling agent or a titanium coupling agent may be mentioned.
In addition, it is also possible to use together the various surface treatment methods mentioned above.
In addition, those in which the antistatic agent is coated on the surface of the protective film or contained in the film are preferably used.

  The thickness of the protective film is not particularly limited, but usually thicker than the polarizer is used and has a function of imparting strength as a substrate of the polarizer, and is usually 10 to 100 μm, preferably 20 to 80 μm. is there.

In addition, such a protective film can be provided with a hard coat layer on the surface not laminated with the polarizer, or can be subjected to various treatments such as anti-sticking, anti-reflection and anti-glare.
Furthermore, it is also possible to laminate various optical functional films such as a retardation plate and a viewing angle widening film.

(Polarizer)
The polarizing plate of the present invention is formed by bonding a polarizing film and a protective film using the resin composition of the present invention, and the protective film is provided on at least one surface, preferably both surfaces of the polarizing film.
Thus, the obtained polarizing plate is excellent in water-resistant adhesiveness such that the adhesive layer does not dissolve even when immersed in water for a long time, and can be applied to a display device used under particularly severe conditions. It is a thing.

EXAMPLES Hereinafter, the present invention will be more specifically described by way of examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
In the examples, "part" and "%" mean weight basis.

Example 1
(1) Preparation of AA-PVA-Based PVA Resin (A1) In a temperature-controlled ribbon blender, 3600 parts of powdered unmodified PVA (average polymerization degree 1200, saponification degree 99.2 mol%, average particle diameter 200 μm) are charged To this, 1000 parts of acetic acid was added to cause swelling, and the temperature was raised to 60 ° C. while stirring at a rotation speed of 20 rpm, then, 550 parts of diketene was dropped over 3 hours, and reaction was further performed for 1 hour. After completion of the reaction, the resultant was washed with methanol to prepare an AA-PVA-based resin (A1). The degree of AA conversion was 5.3 mol%, and the degree of saponification and the average degree of polymerization were as the raw unmodified PVA.

(2) Preparation of resin composition aqueous solution 100 parts of a 4% aqueous solution of the AA-PVA-based resin (A1) obtained in the above (1), 4% aqueous solution of sodium glyoxylate (B1) as glyoxylate (B) An aqueous resin composition was prepared by mixing 4 parts of a 4% aqueous solution of taurine (C1) (manufactured by Kishida Chemical Co., Ltd.) as a compound (C) containing an amino group and an acid group.

(3) Preparation of Polarized Film A 50 μm-thick PVA film consisting of a PVA-based resin having a degree of polymerization of 2600 and a degree of saponification of 99.8 mol% is immersed in water at 30 ° C., and then iodine 0.2 g / L, iodide Immersing and stretching in a 30 ° C dyeing solution containing 20 g / L of potassium, and further dipping and stretching in a 53 ° C boric acid treatment solution containing 50 g / L of boric acid and 50 g / L of potassium iodide, and draw ratio of 4 A polarizing film having a thickness of 28 μm was obtained.

(4) Preparation of Polarizing Plate The aqueous solution of the resin composition obtained in the above (2) is applied to the polarizing film obtained in the above (3), and a protective film made of triacetyl cellulose having a thickness of 40 μm Were laminated under a pressure of 0.25 MPa, and dried at 80 ° C. for 5 minutes to obtain a polarizing plate.
The contact angle of water of the protective film consisting of such triacetyl cellulose is measured by a droplet method in an atmosphere of 23 ° C. and 50% RH using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.) (n = 10 Of 42 degrees when measured by the average value of

(5) Cast Film Preparation A 10% PVOH aqueous solution was prepared, and a predetermined amount of an additive aqueous solution was added to prepare a 10% concentration mixed solution. 13 g of this 10% solution was poured into a frame of 10 cm × 10 cm in size to prepare a cast film having a theoretical thickness of 100 μm, and was allowed to stand at 23 ° C. and 50% RH for 3 days.

(6) Evaluation [pot life]
The resin composition aqueous solution obtained in the above (2) was allowed to stand in a constant temperature and humidity chamber at 23 ° C. and 50% RH. The viscosity after 7 days was measured with a B-type viscometer (BROOKFIELD RHEOMETER DV3T), and the time until the aqueous solution viscosity doubled the initial one was taken as the pot life of the adhesive.

Long-term water-resistant adhesion
From the obtained polarizing plate, a sample of 60 mm × 40 mm was cut out with the stretching direction of the polarizing film as the long side, and attached to a glass plate with a double-sided tape to make a sample for evaluation. The sample for evaluation was immersed in water at 23 ° C. for 30 days, and the change in the adhesive layer was visually observed and evaluated as follows. The results are shown in Table 1.
○ · · No peeling point × · · Peeling point

[Water swelling rate of adhesive layer]
The cast film obtained in the above (5) was stapled to a paper frame, suspended in a drier, and heat-treated at 80 ° C. for 5 minutes. It was cut into a size of 4 cm × 4 cm and immersed in water at 23 ° C. for 1 day. The size of the film immediately after taking out from water was measured with a ruler to calculate the area swelling ratio. The formula for calculating the area swelling ratio is as follows.
Area swelling ratio (%) = 100 × (film area after water immersion) / (film area before water immersion)

Comparative Example 1
A polarizing plate was produced in the same manner as in Example 1 except that taurine (C1) was not blended in Example 1, and evaluated in the same manner. The results are shown in Table 1.

Comparative example 2
A polarizing plate was produced in the same manner as in Example 1 except that sodium glyoxylate (B1) was not blended in Example 1, and evaluated in the same manner. The results are shown in Table 1.

In Example 1 using the resin composition of the present invention as an adhesive, there was no peeling of the adhesive surface even after immersion in water at 23 ° C. for 30 days, and the appearance remained good. Furthermore, since the pot life was long, the viscosity stability was excellent, and the area swelling ratio of the adhesive layer after water immersion was small, the water resistance of the adhesive layer was excellent.
On the other hand, in Comparative Example 1 which did not contain the compound (C) containing an amino group and an acid group, peeling occurred on the adhesive surface in the long-term water-resistant adhesion test, and this is because swelling of the adhesive layer is large. It is guessed.

  The resin composition of the present invention can be suitably applied to adhesives, particularly to adhesives for polarizing plates, because it has excellent long-term water-resistant adhesion without impairing viscosity stability (pot life) when it is made into an aqueous solution. It is possible.

Claims (9)

  A resin composition comprising a modifying group-containing polyvinyl alcohol resin (A) having an active methylene group, a glyoxylate (B), and a compound (C) containing an amino group and an acid group.   The resin composition according to claim 1, wherein the modifying group-containing polyvinyl alcohol resin (A) having an active methylene group is an acetoacetyl group-containing polyvinyl alcohol resin (A1).   The content of the glyoxylate (B) is 0.1 to 20 parts by weight with respect to 100 parts by weight of the modifying group-containing polyvinyl alcohol resin (A) having an active methylene group. Or resin composition in any one of 2.   The resin composition according to any one of claims 1 to 3, wherein the compound (C) containing an amino group and an acid group is a sulfonic acid compound (C1) containing an amino group.   The content of the compound (C) containing an amino group and an acid group is 1 to 20 parts by weight with respect to 1 part by weight of the glyoxylate (B). Resin composition.   The content of the compound (C) containing an amino group and an acid group is 1 to 100 parts by weight with respect to 100 parts by weight of the modifying group-containing polyvinyl alcohol resin (A) having an active methylene group. The resin composition according to any one of claims 1 to 5.   An adhesive comprising the resin composition according to any one of claims 1 to 6.   The adhesive agent for polarizing plates characterized by containing the resin composition in any one of Claims 1-6.   A polarizing plate characterized in that the polarizing film and the protective film are bonded using the adhesive for polarizing plate according to claim 8.