JP2011132403A - Adhesive for polarizing plate and polarizing plate using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive for a polarizing plate affording good adhesion in laminating a hydrophobic protective film and a polarizing film. <P>SOLUTION: The adhesive for a polarizing plate consists mainly of a polyvinyl alcohol resin and contains an ethylenic unsaturasted monomer and a polymerization initiator. The protective film is laminated on at least one side surface of the polarizing film via an adhesive layer, wherein the protective film has a contact angle of 20-90° with water at its adhesive surface and the adhesive layer consists mainly of a polyvinyl alcohol resin of 30-70 mol% in degree of saponification. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polarizing plate formed by bonding a polarizing film and a protective film, and to a polarizing plate formed by using the polarizing plate adhesive used for the bonding, and the polarizing plate adhesive. More specifically, the present invention relates to a polarizing plate adhesive having good adhesion to a protective film having a hydrophobic surface.

Liquid crystal display devices are widely used as image display devices for liquid crystal televisions, computer displays, mobile phones, digital cameras, and the like. Such a liquid crystal display device has a configuration in which a polarizing film is laminated on both sides of a glass substrate in which liquid crystal is sealed, and various optical functional films such as a retardation plate are laminated on this as necessary.
As a polarizing film, a dichroic material such as iodine is dispersed and adsorbed in a highly saponified polyvinyl alcohol resin (hereinafter, polyvinyl alcohol is abbreviated as PVA), and after stretching or simultaneously with stretching, boric acid or the like. A uniaxially stretched film cross-linked with a cross-linking agent is widely used.
A polarizing film using a uniaxially stretched film of this PVA resin tends to shrink under high humidity. Usually, a protective film is attached to at least one surface, preferably both surfaces to compensate for moisture resistance and strength. In addition, it is used as a polarizing plate.

  As such a protective film, a cellulose ester resin such as triacetyl cellulose is widely used because of its excellent transparency, mechanical strength, and moisture resistance. Furthermore, for applications that require higher heat resistance, protective films using cyclic olefin resins such as norbornene resins are used.

These protective films are bonded to the polarizing film by an adhesive, and as such an adhesive, the high saponification similar to that of the PVA-based resin, particularly the polarizing film, from the viewpoint of adhesion to the polarizing film having a hydrophilic surface. Those mainly composed of PVA-based resin are preferably used.
On the other hand, since a hydrophobic material is used for the protective film due to the requirement of moisture resistance, the adhesiveness with the adhesive mainly composed of the high saponification degree PVA resin is low. Has been hydrophilized.
For example, in the case of a cellulose ester-based resin film, a film obtained by treating the surface with an alkali solution and converting a part of the ester group to a hydroxyl group by hydrolysis is used. Moreover, also in the case of the protective film which consists of cyclic olefin resin, what improved hydrophilicity is used by the corona discharge treatment or the plasma treatment.

  Such a protective film should be hydrophilized only on the surface to be bonded to the polarizing film, but the influence on the opposite surface is affected by the fundamental problems of the processing method, restrictions on the equipment, and imperfections during processing. This may cause a decrease in moisture resistance of the polarizing plate.

In addition, the saponification treatment of cellulose ester resin requires a strong alkaline treatment liquid, so there are dangers during work and the problem of waste liquid treatment. Corona discharge treatment and plasma treatment used for cyclic olefin resin. Requires high-cost equipment and also requires a large amount of power during use, leading to an increase in manufacturing costs.
Therefore, there is a strong demand for an adhesive for polarizing plates that does not require hydrophilic treatment of the hydrophobic protective film.

As an adhesive for a polarizing film and a norbornene polymer film, an adhesive containing a PVA resin and a polymer component having a repeating unit derived from a (meth) acrylic acid ester having an alicyclic structure has been proposed. . (For example, see Patent Document 1)
However, the adhesive described in Patent Document 1 shows good adhesion to a norbornene-based polymer film that has been subjected to corona treatment as shown in the Examples, but has been subjected to a hydrophilic treatment. There is still room for improvement with respect to adhesion to non-hydrophobic films, for example, cellulose ester resin films not subjected to saponification treatment.

JP 2009-175721 A

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an adhesive for polarizing plate that can provide good adhesiveness in bonding a protective film having a hydrophobic surface and a polarizing film. It is.

As a result of intensive studies in view of the above circumstances, the present inventor has achieved the object of the present invention with an adhesive for polarizing plate containing a PVA resin as a main component and containing an ethylenically unsaturated monomer and a polymerization initiator. The present invention has been completed.
That is, the present invention is characterized by using an ethylenically unsaturated monomer and its polymerization initiator together with a PVA resin as an adhesive for polarizing plates. The effect obtained by such a configuration, that is, good adhesion between the polarizing film and the hydrophobic protective film is that the ethylenically unsaturated monomer in the adhesive slightly erodes the surface of the hydrophobic protective film. It is presumed that it contributes to the improvement of adhesiveness by enhancing the anchor effect and becoming a polymer at the interface with the hydrophobic protective film.

  The adhesive for polarizing plates of the present invention is excellent in adhesion to a polarizing film and a hydrophobic protective film, and in particular, it can be used without hydrophilizing the surface of the hydrophobic protective film. In addition, a polarizing plate excellent in moisture resistance can be obtained, and further, the manufacturing process can be shortened and the manufacturing cost can be reduced, which is industrially useful.

The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and is not limited to these contents.
Hereinafter, the present invention will be described in detail.
The polarizing plate adhesive of the present invention comprises a PVA resin as a main component, and is blended with an ethylenically unsaturated monomer and a polymerization initiator.

(PVA resin)
First, the PVA resin used in the polarizing plate adhesive of the present invention will be described.
The PVA resin used in the present invention is obtained by saponifying a polyvinyl ester resin obtained by polymerizing a vinyl ester monomer represented by vinyl acetate, and has a vinyl alcohol structure corresponding to the degree of saponification. Consists of units and vinyl ester structural units.

As such a PVA-based resin, those having a saponification degree (measured in accordance with JIS K 6726) of 30 to 100 mol% can be used, but with the protective film having a hydrophobic surface which is the subject of the present invention. In order to obtain good adhesion, those having a saponification degree of 30 to 70 mol%, particularly 30 to 60 mol% are suitable.
If the degree of saponification is too high, the adhesion with the protective film surface having a hydrophobic surface will be insufficient, or the cohesive strength of the adhesive layer due to significant phase separation due to a decrease in compatibility with the ethylenically unsaturated monomer. However, if it is too low, the adhesion with the polarizing film surface tends to decrease.

  Moreover, the average degree of polymerization (measured according to JIS K 6726) of the PVA-based resin is usually 300 to 4000, preferably 400 to 3000, and more preferably 500 to 2000. If the average degree of polymerization is too small, sufficient adhesiveness may not be obtained due to insufficient cohesive strength of the adhesive layer. Conversely, if the average degree of polymerization is too large, the viscosity when the adhesive is used in a solution is increased, and workability is improved. It tends to be reduced or it becomes difficult to uniformly apply to the substrate.

The PVA-based resin used in the present invention is a PVA composed of only a vinyl alcohol structural unit, or only a vinyl alcohol structural unit and a vinyl acetate structural unit remaining in accordance with the degree of saponification, or a range that does not significantly impair the object of the present invention. Thus, it is possible to use various modified PVA resins having structural units other than these. Examples of such modified PVA resins include those obtained by copolymerization and saponification using other monomers during polymerization of vinyl ester monomers, and those obtained by introducing a functional group into PVA by post-reaction. Can be mentioned.
The modified amount of the modified PVA resin is usually in the range of 0.1 to 20 mol%, particularly in the range of 1 to 10 mol%, based on all structural units.

  Other monomers used for copolymerization with vinyl ester monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, and 3-buten-1-ol. , Derivatives of hydroxy group-containing α-olefins such as 4-penten-1-ol, 5-hexen-1-ol, 3,4-dihydroxy-1-butene and acylated products thereof, acrylic acid, methacrylic acid, croton Unsaturated acids such as acid, maleic acid, maleic anhydride and itaconic acid, salts, monoesters, or nitriles such as dialkyl esters, acrylonitrile and methacrylonitrile, amides such as diacetone acrylamide, acrylamide and methacrylamide, ethylene Sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, etc. Olefin sulfonic acids or salts thereof, alkyl vinyl ethers, dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, 3 Vinyl compounds such as 1,4-diacetoxy-1-butene, substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate, vinylidene chloride, 1,4-diacetoxy-2-butene, and vinylene carbonate. .

  Also, depending on the polymerization conditions (solvent, bath ratio, pressure, temperature, etc.) when polymerizing and copolymerizing vinyl ester monomers, 1,2-glycol bonds (usually, What adjusted the quantity of (1,3-glycol bond) suitably can also be used. The amount of 1,2-glycol bonds is usually 1.0 to 3.5 mol%. The smaller the value, the better the crystallinity, and the larger the reverse, the more stable the viscosity is when it is used as an aqueous solution. There is a tendency to improve.

  Examples of the functional group introduced into PVA by post reaction include a carboxyl group, an acetoacetyl group, a polyalkylene oxide group, a hydroxyalkyl group, a cyanoethyl group, and an acetal group.

By using these modified PVA-based resins, various functions can be imparted to the adhesive of the present invention. Among them, if the PVA-based resin is cross-linked by a reaction between functional groups or a combined use of a cross-linking agent, It is possible to improve the moisture resistance and water resistance of the adhesive layer. For this purpose, a modified PVA-based resin having a functional group rich in reactivity is preferable, and in particular, a modified PVA having an acetoacetyl group capable of utilizing a reaction with various crosslinking agents is preferable.
Hereinafter, the acetoacetyl group-containing PVA resin (hereinafter abbreviated as AA-PVA resin) will be described.

AA-PVA has a structural unit containing an acetoacetyl group in addition to a vinyl alcohol structural unit and a vinyl acetate structural unit.
Examples of a method for introducing an acetoacetyl group into a PVA resin include, for example, (i) a method in which a hydroxyl group of a PVA resin and a diketene are reacted to form an acetoacetate group, and (ii) an ester of a PVA resin and an acetoacetate ester. Examples include an exchange reaction method, (iii) a method of saponifying a copolymer of vinyl acetate and vinyl acetoacetate, and the like. Especially, since a manufacturing process is simple and AA-ized PVA-type resin with good quality is obtained, it is preferable to manufacture by the method of (i). Hereinafter, this method will be described.

  As a PVA resin used as a raw material, PVA consisting only of a vinyl alcohol structural unit and a remaining vinyl acetate structural unit depending on the degree of saponification is usually used, but the above-mentioned various modified PVA resins can also be used. . The production method, polymerization degree, saponification degree, etc. of such PVA-based resin are as described above.

  The reaction between the PVA resin and the diketene includes (α) a method in which a gaseous or liquid diketene is directly reacted with the powder of the PVA resin, and (β) the PVA resin powder is converted into an organic material such as acetic acid. Examples include a method of pre-swelling with an acid, a method of dissolving (γ) a PVA resin, and a method of dissolving both in an organic solvent such as DMSO that does not have reactivity with diketene, and the like. The method (β) is preferably used when the saponification degree is 90 mol% or more, and the method (γ) is preferably used when the saponification degree is 30 to 80 mol%.

  The polymerization degree and saponification degree of the AA-PVA resin used in the present invention are the same as those of the PVA resin used as a raw material. The content of acetoacetyl groups in the AA-PVA-based resin (hereinafter abbreviated as AA degree) is usually 0.1 to 20 mol%, further 1 to 10 mol%, especially 3 What is 5 mol% is used suitably. If the content is too small, the water resistance tends to be insufficient or a sufficient crosslinking rate may not be obtained. Conversely, if the content is too large, the water solubility tends to decrease or the stability of the aqueous solution tends to decrease. There is.

In addition, although it is preferable that all the PVA-type resin in an adhesive agent is AA-ized PVA-type resin, PVA-type resins other than AA-type PVA-type resin may be used together, and the content is 20 weight% normally. In particular, it is preferably 10% by weight or less.
Examples of various PVA resins other than the AA-modified PVA resin include unmodified PVA and the above-described various modified PVA resins.

(Ethylenically unsaturated monomer)
Next, the ethylenically unsaturated monomer used for the adhesive for polarizing plates of this invention is demonstrated. Examples of such ethylenically unsaturated monomers include vinyl ester monomers, acrylic acid or its ester monomers, acrylamide monomers, vinyl ether monomers, vinyl imidazole monomers, and the like. Can be mentioned.

  Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, Examples include vinyl versatate, 1-methoxyvinyl acetate, and isopropenyl acetate.

  As acrylic acid or its ester monomers, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, N-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, Examples include lauryl (meth) acrylate, octyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like. Here, (meth) acrylic acid means acrylic acid or methacrylic acid.

  Examples of the acrylamide monomer include (meth) acrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, t-butylacrylamide, acrylamide-2-methylpropanesulfonic acid, diacetone acrylamide and the like.

  Examples of vinyl ether monomers include methyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether and the like.

  Examples of the vinylimidazole monomer include 1-vinylimidazole and 2-methyl-1-vinylimidazole.

  Other olefin monomers such as hexene and octene; allyl monomers such as allyl acetate and allyl chloride; acrylonitrile monomers such as (meth) acrylonitrile; styrene monomers such as styrene and α-methylstyrene Mer: carboxyl group-containing compounds such as fumaric acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, trimetic anhydride, and esters thereof; ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamide-2- Examples of the sulfonic acid group-containing compound such as methylpropanesulfonic acid; vinylsilane compound such as vinyltrimethoxysilane; and the like include isopropenyl acetate and 3- (meth) acrylamidopropyltrimethylammonium chloride.

  As such an ethylenically unsaturated monomer, those that are excellent in affinity with the surface of the hydrophobic protective film and erodible to the surface and are liquid at room temperature are preferably used. Among these, acrylic acid or its ester monomers and vinyl imidazole monomers are effective in improving the adhesive strength of the adhesive layer.

  It is also a preferred embodiment to use monomers containing various functional groups, for example, monomers having an allyl group, a glycidyl group, a hydrolyzable silyl group, an acetoacetyl group, a vinyl group, or a carbonyl group. Can be mentioned.

  Examples of the allyl group-containing monomer include monomers having two or more allyl groups such as triallyloxyethylene, diallyl maleate, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, diallyl phthalate, and allyl glycidyl. Examples include ether and allyl acetate.

  Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate and 3,4-epoxycyclohexyl (meth) acrylate.

  Examples of the hydrolyzable silyl group-containing monomer include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, vinylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacrylate. Examples include loxypropylmethyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, and γ-methacryloxypropylmethyldiethoxysilane.

  Examples of the acetoacetyl group-containing monomer include acetoacetate vinyl ester, acetoacetate allyl ester, diacetoacetate allyl ester, acetoacetoxyethyl (meth) acrylate, acetoacetoxyethyl crotonate, acetoacetoxypropyl (meth) acrylate, acetoacetate Examples thereof include acetoxypropyl crotonate and 2-cyanoacetoacetoxyethyl (meth) acrylate.

The vinyl group-containing monomer is preferably a monomer having two or more vinyl groups in the molecular structure. For example, divinylbenzene, ethylene glycol di (meth) acrylate, 1,2-propylene glycol di (meth) Acrylate, 1,3-propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane Examples include tri (meth) acrylate and allyl (meth) acrylate.
Examples of the carbonyl group-containing monomer include diacetone acrylamide.

  Among them, a monomer having an acetoacetyl group, which is an excellent functional group having excellent affinity with a hydrophobic protective film and is highly reactive, is preferred, and acetoacetoxyethyl methacrylate is particularly preferably used.

Content of the ethylenically unsaturated monomer in the adhesive agent for polarizing plates of this invention is 10-1000 weight part normally with respect to 100 weight part of PVA-type resin, Especially 50-700 weight part, Furthermore, 100- A range of 500 parts by weight is preferably used. If the content of the ethylenically unsaturated monomer is too small, the adhesion to the surface of the protective film having a hydrophobic surface tends to be insufficient, and conversely if too large, the adhesion to the polarizing film surface is insufficient. There is a tendency to be sufficient.
Such ethylenically unsaturated monomers may be used alone or in combination with a plurality of monomers.

(Polymerization initiator)
Next, the polymerization initiator used for the adhesive agent for polarizing plates of this invention is demonstrated. As such a polymerization initiator, known initiators such as a thermal polymerization initiator, a photopolymerization initiator, and an electron beam polymerization initiator can be used.

 Examples of the thermal polymerization initiator include methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxy octoate, t-butyl peroxy benzoate, Organic peroxides such as lauroyl peroxide; azo compounds such as azobisisobutyronitrile; and amines such as N, N-dimethylaniline and N, N-dimethyl-p-toluidine combined with the organic peroxide. Examples include redox polymerization initiators.

  Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl, benzophenone, p-methoxybenzophenone, 2,2-diethoxyacetophenone, α, α- Carbonyl such as dimethoxy-α-phenylacetophenone, methylphenylglyoxylate, ethylphenylglyoxylate, 4,4′-bis (dimethylamino) benzophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one Compounds; sulfur compounds such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, benzoyldiethoxyphosphine Down oxide, and the like. These may be used alone or in combination of two or more.

  Examples of the electron beam polymerization initiator include benzophenone, 4,4-bis (diethylamino) benzophenone, 2,4,6-trimethylbenzophenone, methyl orthobenzoylbenzoate, 4-phenylbenzophenone, t-butylanthraquinone, 2-ethylanthraquinone. Thioxanthone such as 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone; diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1-hydroxycyclohexyl -Phenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, etc. Acetophenone; benzoin ether such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4- Examples include acylphosphine oxides such as trimethylpentylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; methylbenzoylformate, 1,7-bisacridinylheptane, and 9-phenylacridine. These may be used alone or in combination of two or more.

  The content of the polymerization initiator is usually 0.1 to 10 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated monomer, particularly 1 to 5 parts by weight, and further 2 to 3 parts by weight. Preferably used. If the content of the polymerization initiator is too small, the ethylenically unsaturated monomer remains without being polymerized, and tends to cause the adhesiveness to be inhibited. Moreover, even if there is too much this content, the effect has an upper limit and is economically disadvantageous.

(Adhesive for polarizing plate)
Next, the polarizing plate adhesive of the present invention will be described.
Although it does not specifically limit as a form of an adhesive agent, In order to form a uniform adhesive bond layer on the surface of the polarizing film or protective film which is a to-be-adhered body, it is preferable that it is liquid, The adhesive agent for polarizing plates of this invention In order to make the liquid into a liquid, it is necessary to use various solvent solutions or dispersions. In order to obtain an adhesive layer having uniform characteristics, it is desirable that the adhesive is a solution, but even a dispersion can be used without problems if the dispersion state is good.
The solvent used in such a solution or dispersion is a mixture of water and an organic solvent having high miscibility with water from the viewpoint of safety and solubility in PVA-based resins and ethylenically unsaturated monomers. Are preferably used. As such an organic solvent, those having a boiling point of 100 ° C. or lower, particularly 80 ° C. or lower are preferable from the viewpoint of shortening the drying process. For example, methanol, ethanol, n-propanol, isopropanol and the like have 1 to 3 carbon atoms. A lower alcohol solvent or a ketone solvent such as acetone or methyl ethyl ketone is preferably used. Among them, a low boiling point PVA resin having a low saponification degree and methanol having excellent solubility of an ethylenically unsaturated monomer are used. Preferably used.

  The content ratio of both in the water / organic solvent mixed solvent is not particularly limited, and may be appropriately selected depending on the drying conditions and the type of the organic solvent used. Usually, the water / organic solvent (weight ratio) is 80. / 20 to 20/80, particularly 70/30 to 30/70, and more preferably 60/40 to 40/60. If the content ratio of the organic solvent is too high, the viscosity stability of the adhesive solution tends to be lowered, and if it is too low, the solubility of the adhesive component is insufficient, or is deposited or separated during storage or use. There is a case.

  The solid content concentration of such an adhesive solution cannot be generally specified 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 3 to 3%. A range of 10% is preferably used. If the concentration is too low, drying takes a long time, so that productivity is impaired. On the other hand, if the concentration is too high, the viscosity tends to be high, and uniform coating tends to be difficult.

The adhesive layer in the polarizing plate of the present invention shows a good adhesive strength in the adhesion between the polarizing film and the protective film, but for the purpose of further improving the adhesive strength, or improving the water resistance and moisture resistance, It is also a preferred embodiment to use a crosslinking agent for As this crosslinking agent, a well-known thing can be used as a crosslinking agent of PVA-type resin.
In particular, when an AA-PVA-based resin is used as the PVA-based resin, excellent water resistance and moisture resistance can be obtained by using a crosslinking agent in combination, which is a preferred embodiment.

  Examples of such crosslinking agents include polyvalent metal compounds, boron compounds, amine compounds, hydrazine compounds, silane compounds, methylol group-containing compounds, aldehyde group-containing compounds, epoxy compounds, thiol compounds, isocyanate compounds, polyamide resins, and the like. However, polyvalent metal compounds, aldehyde group-containing compounds, amine compounds, hydrazine compounds, and isocyanate compounds are particularly suitable.

The polyvalent metal compound is a compound containing an aluminum atom, a zinc atom, an iron atom, a zirconium atom, a titanium atom, a gallium atom, an indium atom, a ruthenium atom, or a hafnium atom, and a compound having a zirconium atom is particularly preferable. It is.
The compound having a zirconium atom may be any one of a single salt and a double salt of an inorganic acid or an organic acid, an organic metal compound, a metal complex, an oxide compound (zirconyl compound), etc. Zirconium, zirconium chloride, zirconium bromide, zirconate, zirconate, zirconyl chloride ("Zircosol ZC" manufactured by Daiichi Rare Element Chemical Co., Ltd.), basic zirconyl chloride ("Zircosol ZC-2" manufactured by Daiichi Elemental Chemical Co., Ltd.) , Zirconyl sulfate, zirconyl nitrate ("Zircosol ZN" manufactured by Daiichi Rare Element Chemical Co., Ltd.), zirconyl carbonate, ammonium zirconium carbonate ("Zircosol AC-7" manufactured by Daiichi Rare Element Chemical Co., Ltd.), potassium zirconium carbonate (first rare element chemistry) "Zircosol ZK-10"), zirconyl acetate, and stearic acid Nil, zirconyl octylate, zirconyl citrate, zirconyl lactate, zirconyl oxalate, zirconyl phosphate, zirconium tetraacetylacetonate ("Orgatrix ZC-150" manufactured by Matsumoto Pharmaceutical Co., Ltd.), zirconium monoacetylacetonate (Matsumoto Pharmaceutical "Orgatics ZC-540"), zirconium bisacetylacetonate (Matsumoto Pharmaceutical Co., Ltd. "Orgachix ZC-550"), zirconium monoethyl acetoacetate (Matsumoto Pharmaceutical Co., Ltd. "Orgatics ZC-560") , Zirconium acetate (“Orgachix ZC-115” manufactured by Matsumoto Pharmaceutical Co., Ltd.), and the like.
Among these compounds containing zirconium atoms, zirconyl compounds such as ammonium zirconium carbonate, zirconium potassium carbonate, zirconyl acetate, basic zirconyl chloride, zirconyl oxychloride, zirconyl nitrate, etc. are preferable, and basic zirconyl chloride and zirconyl nitrate are particularly preferred. It is preferably used in that the object of the invention can be remarkably exhibited.

  Examples of the aldehyde group-containing compound include monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, crotonaldehyde, and benzaldehyde, glyoxal, glutaraldehyde, malondialdehyde, terephthalaldehyde, and dialdehyde starch, among which glyoxal and An alkali (earth) metal salt of glyoxylic acid is preferably used.

  Such hydrazine compounds include hydrazine, hydrazine hydrochloride, sulfuric acid, nitric acid, sulfurous acid, phosphoric acid, thiocyanic acid, carbonic acid and other inorganic acid salts, and formic acid, oxalic acid and other organic acid salts, hydrazine methyl, ethyl, propyl, Hydrazine derivatives such as mono-substituted compounds such as butyl and allyl, symmetrical di-substituted compounds such as 1,1-dimethyl and 1,1-diethyl, carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, glutaric acid dihydrazide, succinic acid dihydrazide, Adipic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid hydride Zido, trihydrazide citrate, 1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin (such as “Amicure VDH” manufactured by Ajinomoto Finetechno Co., Ltd.), 7,11-octadecadien-1,18-di And hydrazide compounds such as carbohydrazide (“Amicure UDH” manufactured by Ajinomoto Fine Techno Co., Ltd.), polyacrylic acid hydrazide, N-aminopolyacrylamide, N-aminoacrylamide / acrylamide copolymer, and the like. Polyhydric hydrazide compounds such as dihydrazide, 1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin, N-aminopolyacrylamide, N-aminoacrylamide / acrylamide copolymer, and the like, remarkably achieve the object of the present invention. It is preferably used because it can be used That.

  Examples of such amine compounds include fats such as ethylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, tetraethylenepentamine, N-aminoethylpiperazine, bisaminopropylpiperazine, trimethylhexamethylenediamine, and polyoxypropylenediamine. Polyamines, alicyclic polyamines such as 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, 4,4′-diaminodicyclohexylmethane, isophoronediamine, 1,3-bisaminomethylcyclohexane, norbornanediamine, 4 , 4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, diaminodiphenyl sulfone, m-phenylenediamine, 2,4'-toluylene diene Examples include amino group-containing water-soluble polymers such as aromatic diamines such as amine and metaxylylenediamine, amino group-modified PVA resins, polyvinylamine, polyallylamine, and polyethyleneimine. Particularly, 1,3-bisaminomethylcyclohexane , Metaxylylenediamine, amino group-modified PVA resin, polyethyleneimine and the like are preferably used in that the object of the present invention can be remarkably exhibited.

  Among these cross-linking agents, they have excellent reactivity with AA groups and can impart water resistance efficiently by adding a small amount. Therefore, aldehyde group-containing compounds, especially alkali (earth) metal salts of glyoxal and glyoxylic acid, especially glyoxyl. Sodium acid is preferably used.

  The blending amount of such a crosslinking agent is not particularly limited and may be selected from desired water resistance, etc., but is usually 0.1 to 50 parts by weight, particularly 1 with respect to 100 parts by weight of the PVA resin. The range of -30 parts by weight, and further 3-20 parts by weight is preferably used. If the amount of such a crosslinking agent is too large, the viscosity stability of the adhesive solution tends to deteriorate.

Further, other resins such as polysaccharides such as starch and cellulose, polyethylene glycol, polyvinyl pyrrolidone, polyoxazoline, water-soluble polyamide, in a range not impairing the object of the present invention, usually 30% by weight or less, particularly 20% by weight or less, Water-soluble resins such as water-soluble polyester, polyacrylamide, and polyethyleneimine, and urethane adhesives and emulsion adhesives can be used in combination.
Similarly, as various additives, antifoaming agents, leveling agents, colorants, dyes, pigments, fluorescent brighteners, pigments, UV absorbers, antioxidants, fillers, plasticizers, antistatic agents, thermal stability Agents, surfactants, desiccants, deodorants, antibacterial agents, preservatives, antifoaming agents, and the like can be included.

(Polarizing film)
Next, the polarizing film pasted with a protective film with the polarizing plate adhesive of this invention is demonstrated.
There is no restriction | limiting in particular as this polarizing film, A well-known thing can be used. For example, (i) A dichroic material such as iodine or a dichroic dye is adsorbed on a vinyl alcohol resin film such as a PVA film, a partially formalized PVA film, or an ethylene-vinyl alcohol resin film. A stretched one (see, for example, JP-A-2001-296427 and JP-A-7-333426), (ii) a birefringent material having liquid crystallinity together with a dichroic material, and a vinyl alcohol resin film (Iii) a uniaxially stretched thermoplastic norbornene resin film containing a dichroic material (for example, see JP-A-2001-356213) .), (Iv) PVA-based resin and ethylene-vinyl alcohol resin are dehydrated or deaceticated to continue Introduced polyene structure, a polyene-based film obtained by stretching them (e.g., see JP Patent 2007-17845.), And the like.
Among these, a uniaxially stretched film in which iodine is adsorbed on a PVA-based film is preferable because of excellent polarization characteristics.

  The thickness of such a polarizing film is usually 0.1 to 100 μm, particularly 0.5 to 80 μm, and further preferably 1 to 60 μm.

(Protective film)
Next, the protective film bonded with a polarizing film with the adhesive agent for polarizing plates of this invention is demonstrated.
Such a protective film compensates for the lack of durability under high humidity, which is a problem of the polarizing film, by adhering to at least one surface of the polarizing film, preferably both surfaces. The surface to be applied is hydrophobic, and the water contact angle of the adhesive surface is in the range of 20 to 90 degrees. Further, such a contact angle is preferably 30 to 80 degrees, particularly 30 to 60 degrees. The contact angle on the surface of the protective film was measured by the droplet method in an atmosphere of 23 ° C. and 50% RH. When the contact angle of water is too small or too large, the adhesion with the polarizing film tends to be insufficient.
Furthermore, the properties required for the protective film used in the present invention include transparency, mechanical strength, thermal stability, moisture shielding properties, optical isotropy, and the like.

The material of the protective film is not particularly limited as long as the contact angle with water described above exhibits hydrophobicity within the above range, but from the viewpoint of optical properties and durability, cellulose ester Resin, cyclic olefin resin, and (meth) acrylate resin are preferably used.
Other materials include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polystyrene resins such as polystyrene and acrylonitrile / styrene copolymers, polyolefin resins such as polyethylene and polypropylene, polyarylate resins, and polycarbonate resins. , Vinyl chloride resins, amide resins such as nylon and aromatic polyamide, (fluorine-containing) polyimide resins, polyether ether ketone resins, polyphenylene sulfide resins, vinylidene chloride resins, polyvinyl acetal resins such as polyvinyl butyral And polyoxymethylene resins and epoxy resins.

  Typical cellulose ester resins used in such cellulose ester resin films are triacetyl cellulose and diacetyl cellulose, but also other lower fatty acid esters of cellulose, cellulose acetate propionate, cellulose acetate butyrate, etc. The mixed fatty acid ester can be used.

Examples of the cyclic olefin resin used in the above-mentioned cyclic olefin resin film include norbornene resins. Such norbornene resins include, for example, ring-opening (co) polymers of norbornene monomers, addition-polymerized norbornene monomers, addition-copolymerized norbornene monomers and olefin monomers such as ethylene and α-olefins. Resin etc. are included.
Specific examples of norbornene-based monomers include dimers such as norbornene and norbornadiene; tricyclics such as dicyclopentadiene and dihydroxypentadiene; heptacyclics such as tetracyclopentadiene; these methyl, ethyl, propyl and butyl Substituents such as alkyl, alkenyl such as vinyl, alkylidene such as ethylidene, aryl such as phenyl, tolyl, and naphthyl; and ester groups, ether groups, cyano groups, halogens, alkoxycarbonyl groups, pyridyl groups, hydroxyl groups, carvone Examples include substituents having groups containing elements other than carbon and hydrogen, such as acid groups, amino groups, hydroxyl-free groups, silyl groups, epoxy groups, acryloyl groups, and methacryloyl groups.
Examples of commercially available cyclic olefin-based resin films include “ARTON” manufactured by JSR, “ZEONOR”, “ZEONEX” manufactured by Nippon Zeon, “OPTOREZ” manufactured by Hitachi Chemical Co., Ltd., “APEL” manufactured by Mitsui Chemicals, etc. Can do.

Moreover, as a (meth) acrylic-type resin used for the above-mentioned (meth) acrylic-type resin film, poly (meth) acrylic acid ester, such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, Methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer, alicyclic hydrocarbon group Polymer (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.), high Tg (meth) obtained by intramolecular crosslinking or intramolecular cyclization reaction Acrylic resins, rubber-acrylic graft type core-shell polymers, and the like can be mentioned.
Examples of such commercially available (meth) acrylic resin films include “Acrypet VRL20A”, “Acrypet IRD-70” manufactured by Mitsubishi Rayon Co., Ltd., “MUX-60” manufactured by UMGABS, and the like.

Conventionally, an adhesive mainly with a highly saponified PVA-based resin has been used as an adhesive with a polarizing film. Therefore, in order to improve the adhesiveness to such an adhesive, a film made of a cellulose ester-based resin is used. Surface saponification treatment such as saponification treatment with an alkaline solution, corona discharge treatment or plasma treatment on a film made of a cyclic olefin resin has been performed. However, the adhesive for polarizing plates of the present invention is not subjected to these treatments because the ethylenically unsaturated monomer is blended with the PVA resin and has a high affinity with a protective film having a hydrophobic surface. It is possible to use things.
However, as long as the contact angle with water after the treatment is within the range specified in the present invention, it does not prevent the protective film from being subjected to the various hydrophilization treatments described above. Plasma treatment is one of effective means for further improving the adhesion.

In addition, in order to improve the affinity with the adhesive on the surface of the protective film, it is possible to perform various surface treatments other than hydrophilization, and (meth) acrylic acid ester latex or styrene latex on the surface of the protective film, Examples thereof include an easy-adhesion layer and an anchor coat layer containing polyethyleneimine, polyurethane / polyester copolymer, etc., and a surface treatment method using a coupling agent such as a silane coupling agent and a titanium coupling agent. In addition, it is also possible to use together the above-mentioned various surface treatment methods.
Moreover, the thing which apply | coated the antistatic agent on the surface or contained in the film is used preferably.

  The thickness of such a protective film is not particularly limited, but usually a thicker one than the polarizing film is used, and it has a function of imparting strength as a base material of the polarizing film, 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 a surface not laminated with the polarizing film, or can be subjected to various treatments such as anti-sticking, anti-reflection, and anti-glare. Furthermore, various optical functional films such as a phase difference plate and a viewing angle widening film can be laminated.

(Polarizer)
The polarizing plate of the present invention is formed by laminating a protective film on at least one surface, preferably both surfaces, of the polarizing film with the polarizing plate adhesive of the present application. It is formed by uniformly applying to a polarizing film and / or a protective film, and bonding them together, followed by pressure bonding and heat drying.
In coating such a liquid adhesive on a polarizing film or a protective film, the roll coater method, the air doctor method, the blade coater method, the spraying method, the dipping method, or just before laminating the polarizing film and the protective film, the film A known method can be used such as supplying an appropriate amount in between and pouring them together, and then bonding them together.
For the bonding and pressure bonding, for example, a roll laminator or the like 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 to 60 minutes, further 30 seconds to 30 minutes, particularly 1 to 20 minutes.

In addition, when AA-PVA-based resin is used as the PVA-based resin in the adhesive for polarizing plates of the present invention and the cross-linking agent is used in combination, the cross-linking reaction of the AA-PVA-based resin in the heat drying process of the adhesive Progresses.
Further, when a thermal polymerization initiator is used as the polymerization initiator, similarly, the polymerization of the ethylenically unsaturated monomer proceeds at the time of heating and drying, and the polymerization is usually completed within the drying time. When the content of the polymerization initiator is small or when the drying temperature is low, it is preferable to extend the drying time to complete the polymerization.

  In addition, when a photopolymerization initiator or an electron beam polymerization initiator is used as the polymerization initiator, visible light, ultraviolet light, or electron beam is directly or indirectly applied to the obtained polarizing plate after heat drying. By appropriately irradiating, the ethylenically unsaturated monomer in the polarizing plate adhesive can be polymerized.

  The thickness of the adhesive layer in the polarizing plate of the present invention is usually selected from the range of 0.01 to 10 μm, particularly 0.05 to 5 μm. If the thickness is too thin, the adhesive force tends to be insufficient. If it is too thick, uniform coating tends to be difficult, or thickness unevenness may occur, resulting in a poor appearance. Therefore, the coating amount of the adhesive of the present invention cannot be generally specified depending on the concentration thereof, but may be an amount corresponding to the thickness of the adhesive layer.

Hereinafter, the present invention will be described with reference to examples. However, the present invention is not limited to the description of the examples unless it exceeds the gist.
In the examples, “parts” and “%” mean weight basis unless otherwise specified.

Example 1
(1) Preparation of Adhesive Methanol is added to a 10% aqueous solution of PVA having an average polymerization degree of 600 and a saponification degree of 35 mol%, and a solid content concentration of 5% by weight and a water / methanol ratio of 5/5 (weight ratio). 200 parts by weight of 1-vinylimidazole (1-VI) as an ethylenically unsaturated monomer (200% by weight with respect to PVA) and 1-hydroxy-cyclohexyl-phenylketone as a polymerization initiator An eutectic mixture of benzophenone (trade name “Irgacure 500”, manufactured by Nagase Sangyo Co., Ltd.) 6 parts by weight (3% by weight based on 1-VI) was added to obtain an adhesive.
(2) Production of polarizing film A 50 μm thick PVA film made of PVA resin having a polymerization degree of 2600 and a saponification degree of 99.8 mol% was immersed in water at 30 ° C., followed by iodine 0.2 g / L, iodination Immersion / stretching in a dyeing solution at 30 ° C. containing 20 g / L of potassium, and further dipping / stretching in a boric acid treatment solution at 53 ° C. containing 50 g / L of boric acid and 50 g / L of potassium iodide. A polarizing film having a thickness of 0.0 and a thickness of 28 μm was obtained.
(3) Production of polarizing plate The adhesive obtained in (1) is dropped on the polarizing film obtained in (2) in an amount necessary and sufficient to cover the adhesive surface, and from this 80 μm thick triacetyl cellulose. A protective film to be bonded was laminated, laminated under a pressure of 0.33 MPa, and dried at 70 ° C. for 10 minutes to obtain a polarizing plate.
The water contact angle of the protective film made of triacetylcellulose was measured by a droplet method using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.) in an atmosphere of 23 ° C. and 50% RH (n = 10). The average value was 60 degrees.

(4) Evaluation [Adhesive strength]
From the obtained polarizing plate, a 100 mm × 25 mm sample was cut out with the extending direction of the polarizing film as the long side, and the adhesive strength between the protective film and the polarizing film was evaluated. This evaluation was performed using an autograph AG-IS manufactured by Shimadzu at a 180 ° peel method and a test speed of 300 m / min. The results are shown in Table 1.

Comparative Example 1
In Example 1, a polarizing plate adhesive was prepared in the same manner as in Example 1 except that the ethylenically unsaturated monomer and the polymerization initiator were not blended, and a polarizing plate was similarly prepared and evaluated. The results are shown in Table 1.

Example 2
In Example 1, AA-modified PVA having an average polymerization degree of 2000, a saponification degree of 50 mol%, and an AA degree of 4.5 mol% was used as the adhesive, and the resulting solid content concentration was 5 wt%, and the ratio of water / methanol. To 2000 parts by weight of a 5/5 (weight ratio) solution, 10 parts by weight of sodium glyoxylate (GOA-Na) (10% by weight based on AA-PVA-based resin) was added as a crosslinking agent. 2-acetoxyethyl acrylate (AAEA) 100 parts by weight (100% by weight based on AA-modified PVA) as a monomer, methyl ethyl ketone peroxide (trade name “Percure HB”, dimethyl phthalate solution, manufactured by NOF Corporation) A polarizing plate adhesive was prepared in the same manner as in Example 1 except that 2 parts by weight (2% by weight with respect to AAEA) was added. Were made and evaluated. The results are shown in Table 2.

Comparative Example 2
In Example 2, a polarizing plate adhesive was prepared in the same manner as in Example 2 except that the ethylenically unsaturated monomer and the polymerization initiator were not blended, and a polarizing plate was similarly prepared and evaluated. The results are shown in Table 2.

Comparative Example 3
In Example 2, without using AA-PVA-based resin and sodium glyoxylate, 100 parts by weight of AAEA and methyl ethyl ketone peroxide (trade name “Percure”) were added to 2000 parts by weight of a solution of only water / methanol (5/5) (weight ratio). An adhesive for polarizing plate was prepared in the same manner as in Example 2 except that 2 parts by weight (2% by weight with respect to AAEA) was added ("HB", dimethyl phthalate solution, manufactured by NOF Corporation), and polarized light similarly. Plates were made and evaluated. The results are shown in Table 2.

Example 3
In Example 2, 2-acetoxyethyl methacrylate (AAEM) was used as the ethylenically unsaturated monomer, the addition amount was 200 parts by weight (200% by weight based on AA-PVA), and a polymerization initiator (Percure HB). ) Was added in an amount of 4 parts by weight (2% by weight based on AAEM), a polarizing plate adhesive was prepared in the same manner as in Example 2, and a polarizing plate was prepared and evaluated in the same manner. The results are shown in Table 2.

Example 4
In Example 3, the addition amount of AAEM was 500 parts by weight (500% by weight with respect to AA-modified PVA), and the addition amount of the polymerization initiator (percure HB) was 10 parts by weight (2% by weight with respect to AAEM). A polarizing plate adhesive was prepared in the same manner as in Example 2 except that a polarizing plate was prepared and evaluated in the same manner. The results are shown in Table 2.

Example 5
In Example 4, a polarizing plate adhesive was used in the same manner as in Example 4 except that a saponification degree of 60 mol%, an average polymerization degree of 2000, and an AA degree of polymerization of 4.2 mol% were used as the AA-PVA resin. A polarizing plate was similarly prepared and evaluated. The results are shown in Table 3.

Comparative Example 4
In Example 5, a polarizing plate adhesive was prepared in the same manner as in Example 5 except that the ethylenically unsaturated monomer and the polymerization initiator were not blended, and a polarizing plate was similarly prepared and evaluated. The results are shown in Table 3.

  The adhesive for polarizing plates of the present invention is excellent in adhesion to a polarizing film and a hydrophobic protective film, and in particular, it can be used without hydrophilizing the surface of the hydrophobic protective film. In addition, a polarizing plate excellent in moisture resistance can be obtained, and further, the manufacturing process can be shortened and the manufacturing cost can be reduced, which is industrially useful.

Claims (5)

A polarizing plate adhesive comprising a polyvinyl alcohol resin as a main component and containing an ethylenically unsaturated monomer and a polymerization initiator. The adhesive for polarizing plates according to claim 1, wherein the saponification degree of the polyvinyl alcohol-based resin is 30 to 70 mol%. The adhesive for polarizing plates according to claim 1 or 2, wherein the polyvinyl alcohol resin is an acetoacetate group-containing polyvinyl alcohol resin. A polarizing plate formed by laminating a polarizing film and a protective film with the adhesive for polarizing plates according to claim 1, and then polymerizing an ethylenically unsaturated monomer in the adhesive. The polarizing plate according to claim 4, wherein the protective film has a water contact angle of 20 to 90 degrees.