JP6581464B2 - Adhesive composition and polarizing plate - Google Patents

Description

The present invention relates to an adhesive composition that can obtain a polarizing plate that is excellent in adhesive strength and excellent in resistance to color loss and water resistance. The present invention also relates to a polarizing plate using the adhesive composition.

Liquid crystal display devices are widely used as image display devices for liquid crystal televisions, computer displays, mobile phones, digital cameras and the like.
A liquid crystal display device visualizes a polarization state by switching of liquid crystal, and a polarizing plate having a polarizer is used from the display principle. In particular, in applications such as televisions, higher brightness, higher contrast, and wider viewing angles are required, and polarizing plates are also required to have high transmittance, high polarization degree, high color reproducibility, and the like.

As a polarizer, since it has high transmittance and high degree of polarization, an iodine-based polarizer having a stretched structure in which iodine is adsorbed to polyvinyl alcohol (hereinafter also referred to as “PVA”) is widely used. . Further, as a general polarizing plate, a polarizing plate in which a protective film is bonded to both surfaces is used. As the protective film, thermoplastic resins such as cellulose resin, polycarbonate resin, cyclic olefin resin, (meth) acrylic resin, and polyester resin are generally used because of excellent transparency, mechanical strength, moisture barrier property, isotropic property, and the like. In particular, protective films made of triacetyl cellulose (TAC) resin are widely used.

These protective films are bonded to the polarizer by an adhesive. As such an adhesive, since it has excellent adhesion to a polarizer having a hydrophilic surface, a so-called aqueous adhesive in which a material such as PVA is dissolved in water, in particular, a high ken similar to PVA used in a polarizer. A PVA aqueous adhesive mainly composed of a PVA resin having a degree of conversion is preferably used.

Further, in recent years, there has been a demand for thinner polarizing plates, and acrylic resin films and cyclic polyolefin resin films have come to be used in place of TAC films that have been generally used as protective films. I came. However, these protective films used in place of the TAC film have a problem of poor adhesion to a polarizer when a conventional PVA aqueous adhesive is used as an adhesive.

Furthermore, when using a water-based adhesive such as a PVA-based water-based adhesive when manufacturing a polarizing plate, a drying process is required after laminating the polarizer and the transparent protective film, resulting in a decrease in productivity. was there.
In addition, the moisture content of the polarizer is usually about 30%. However, when a water-based adhesive is used, it is necessary to make the moisture content of the polarizer relatively high in order to obtain a polarizing plate with good adhesion. was there. However, the polarizing plate obtained using a polarizer having a high moisture content as described above has a problem that the dimensional change under a high temperature environment or a high humidity environment is large and the optical properties are inferior.
On the other hand, in order to suppress the dimensional change, it is possible to reduce the moisture content of the polarizer or use a transparent protective film with low moisture permeability. When used together, there are problems that the drying efficiency is lowered, the polarization property is lowered, and the appearance is defective.

In response to such problems, ultraviolet curable adhesives and radical polymerizable adhesives have been proposed.
For example, Patent Document 1 describes an ultraviolet curable adhesive containing a plurality of radically polymerizable compounds having SP values in a predetermined range. However, when such an adhesive is used, there is a problem that the adhesive force decreases with time because the adhesive layer becomes hard.
Patent Document 2 describes an adhesive using a radically polymerizable composition. However, since such an adhesive is accompanied by curing shrinkage at the time of curing, there is a problem that the stability of initial adhesion is low and the adhesive force is insufficient.
Further, Patent Document 3 describes an ultraviolet curable adhesive in which a (meth) acrylamide compound having no hydroxyl group and a (meth) acrylic acid alkyl ester compound having a hydroxyl group are combined. However, although such an adhesive exhibits an adhesive force to the acrylic film, there is a problem that the adhesive force to the polarizer is not sufficient. In addition, since the color fading resistance is also inferior, there is a problem that the durability of the obtained polarizing plate is lowered.

JP 2012-144690 A JP 2010-282161 A JP2013-194082A

In view of the above-mentioned present situation, an object of the present invention is to provide an adhesive composition that can obtain a polarizing plate that is excellent in adhesive strength and excellent in resistance to color loss and water resistance. Moreover, it aims at providing the polarizing plate using this adhesive composition.

The present invention is an adhesive composition containing a polyvinyl acetal resin, and the polyvinyl acetal resin has a polymerization degree of 200 to 4000 and a hydroxyl group content of 20 to 70 mol%, and is represented by the following formula (1). It has a structural unit that is an adhesive composition having a structural unit having an imine structure.

In formula (1), X represents an integer of 1 or 2, R ¹ represents a single bond or an alkylene group, and R ² represents a hydrogen atom, an oxygen atom, a formyl group or a hydrocarbon group.
The present invention is described in detail below.

As a result of intensive studies, the present inventors have determined that the degree of polymerization and the amount of hydroxyl groups are within a predetermined range and that a polyvinyl acetal resin having a specific structural unit is used in the adhesive composition for polarizing plates, immediately after curing. The present inventors have found that the adhesive strength is excellent, the adhesive strength is less likely to decrease with time, and that the color fading resistance and water resistance can be improved, and the present invention has been completed.

The adhesive composition of the present invention contains a polyvinyl acetal resin.
Polyvinyl acetal resin is synthesized from polyvinyl alcohol, which is used as a polarizer material, so that it has good compatibility with the polarizer and can improve the adhesion at the bonding interface when producing a polarizing plate. it can.

The lower limit of the degree of polymerization of the polyvinyl acetal resin is 200, and the upper limit is 4000.
When the polymerization degree is 200 or more, the viscosity of the adhesive composition can be made sufficient. When the polymerization degree is 4000 or less, the viscosity does not become too high when dissolved in an organic solvent, and handling is improved, for example, the coating property is improved when the solution is applied and used.
A preferable lower limit of the degree of polymerization of the polyvinyl acetal resin is 300, and a preferable upper limit is 3000.

The minimum of the amount of hydroxyl groups of the said polyvinyl acetal resin is 20 mol%, and an upper limit is 70 mol%.
When the amount of the hydroxyl group is 20 mol% or more, the toughness of the polyvinyl acetal resin becomes good, and the strength when the adhesive composition is cured can be made sufficient. When the amount of the hydroxyl group is 70 mol% or less, the polarity of the polyvinyl acetal resin does not become too high, and the occurrence of cracks and the like when the adhesive composition is cured can be suppressed.
A preferable upper limit of the amount of hydroxyl groups in the polyvinyl acetal resin is 30 mol%.

The degree of acetalization of the polyvinyl acetal resin is not particularly limited, but a preferable lower limit is 60 mol% and a preferable upper limit is 90 mol%.
When the degree of acetalization is 60 mol% or more, the polyvinyl acetal resin can be easily precipitated in the synthesis step by precipitation. When the acetalization degree is 90 mol% or less, the solubility in a solvent can be improved.
The more preferable lower limit of the degree of acetalization of the polyvinyl acetal resin is 65 mol%, and the more preferable upper limit is 85 mol%.

The amount of acetyl groups in the polyvinyl acetal resin is not particularly limited, but a preferable lower limit is 0.0001 mol% and a preferable upper limit is 5 mol%.
The hydroxyl group amount, the acetalization degree, and the acetyl group amount can be measured by NMR or the like.

The polyvinyl acetal resin has a structural unit represented by the above formula (1).
By having the structural unit represented by the above formula (1), the adhesion between the polarizer and the protective film can be improved, and the anti-color loss property of the polarizing plate can be improved.

In formula (1), X represents an integer of 1 or 2, R ¹ represents a single bond or an alkylene group, and R ² represents a hydrogen atom, an oxygen atom, a formyl group or a hydrocarbon group.
In Formula (1), the case where X is 1 represents a state in which one R ² is bonded to the nitrogen atom via a double bond. That is, it means that having a structure in which a nitrogen atom and R ² are bonded via a double bond as in the following formula (2).
In Formula (1), the case where X is 2 represents a state in which two R ² are bonded to the nitrogen atom through a single bond. That is, it means that having a structure in which a nitrogen atom and two R ² are bonded via a single bond as in the following formula (3). When X is 2, two R ² may be the same or different from each other.

In the above formula (1), when R ¹ is an alkylene group, the preferred lower limit of the carbon number of the alkylene group is 1, and the preferred upper limit is 12. When the number of carbon atoms of the alkylene group exceeds 12, optimal strength may not be obtained. When R ¹ is an alkylene group, the more preferable lower limit of the carbon number of the alkylene group is 5.

In the above formula (1), when R ¹ is an alkylene group, examples of the alkylene group include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a pentamethylene group, a hexamethylene group, and an octamethylene group. Group, linear alkylene group such as decamethylene group, branched alkylene group such as methylmethylene group, methylethylene group, 1-methylpentylene group, 1,4-dimethylbutylene group, cyclopropylene group, cyclobutylene group, cyclohexane And cyclic alkylene groups such as a hexylene group. Especially, linear alkylene groups, such as a methylene group, ethylene group, n-propylene group, n-butylene group, are preferable, and a methylene group and ethylene group are more preferable.

In the above formula (1), when R ² is a hydrocarbon group, examples of the hydrocarbon group include a saturated hydrocarbon group, an unsaturated hydrocarbon group, and an aromatic hydrocarbon group. In addition, the said hydrocarbon group may consist only of a saturated hydrocarbon group, an unsaturated hydrocarbon group, and an aromatic hydrocarbon group, and may contain 2 or more types of these. The hydrocarbon group may have a carbonyl group, a carbonate group, or the like.

Examples of the saturated hydrocarbon group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, Examples include heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, octadecyl and the like. Of these, a methyl group, an ethyl group, and an n-propyl group are preferable.
Examples of the aromatic hydrocarbon group include a phenyl group, a toluyl group, a xylyl group, a t-butylphenyl group, and a benzyl group.
Examples of the unsaturated hydrocarbon group include methylidene group, ethylidene group, propylidene group, butylidene group, pentylidene group, hexylidene group, heptylidene group, octylidene group, nonylidene group, decylidene group, isopropylidene group, vinylidene group, and the like. Alkenylidene groups such as a group, arylidene group, butenylidene group and pentenylidene group, alkenyl groups such as ethenyl group, propenyl group, butenyl group and pentenyl group.

The polyvinyl acetal resin preferably has at least one of a structural unit having an imine structure and a structural unit having an amino group or an amide structure, and has a structural unit having an imine structure and an amino group or an amide structure. It is more preferable to have a structural unit.
By containing the polyvinyl acetal resin having such a structural unit, a crosslinked structure can be formed with the crosslinking agent when the resin is used alone or in combination with a crosslinking agent. For this reason, the crosslinked body obtained after crosslinking has moderate elasticity while having high mechanical strength. In addition, by having an amino group, an amide group, or an imino group that reacts with an epoxy group, a carbonyl group, a vinyl group, etc., the adhesion between the polarizer and the protective film having opposite polarities can be further improved. Further, the color loss resistance of the polarizing plate can be further improved.

In the present invention, the imine structure refers to a structure having a C═N bond.
As a structural unit which has the said imine structure, the structural unit represented by following formula (4) is mentioned, for example.

In the formula (4), R ¹ represents the same as in the above formula (1), and R ³ represents a group having an imine structure.

Examples of R ³ include a functional group represented by the following formula (5).

式（５）中、Ｒ^４は水素原子又は炭素数１〜１８の炭化水素基を表し、Ｒ^５は炭素数１〜１８の炭化水素基を表す。

In formula (5), R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and R ⁵ represents a hydrocarbon group having 1 to 18 carbon atoms.

As said hydrocarbon group, the thing similar to what was mentioned by said R < ² > is mentioned.

In the present invention, in the structural unit having an imine structure, R ¹ is preferably a single bond, R ⁴ is a hydrogen atom, a methyl group or an ethyl group, and R ⁵ is preferably a methyl group or an ethyl group.

In the polyvinyl acetal resin, the content of the structural unit having an imine structure (hereinafter also referred to as “imine structure content”) has a preferable lower limit of 0.1 mol% and a preferable upper limit of 20.0 mol%.
When the content of the imine structure is 0.1 mol% or more, the viscosity stability with time of the adhesive composition can be improved. If the imine structure content is 20.0 mol% or less, acetalization can be sufficiently advanced.
The imine structure content has a more preferable lower limit of 1.0 mol% and a more preferable upper limit of 15.0 mol%.
The imine structure content can be measured by NMR or the like.

The polyvinyl acetal resin preferably includes a structural unit having the amino group or amide structure, and more preferably has the amino group or amide structure in a side chain. Further, the amino group or amide structure may be directly bonded to carbon constituting the main chain of the polyvinyl acetal resin, or may be bonded through a linking group such as an alkylene group. Further, the amino group may be a primary amine or a secondary amine.
In particular, the amino group is preferably —NH ₂ .
Note that in the present invention, the amide structure refers to a structure having —C (═O) —NH—.
Especially, it is preferable that the structural unit which has the said amino group is a structure represented by following formula (6). Moreover, it is preferable that the structural unit which has the said amide structure is a structure represented by following formula (7).

In formula (7), R ⁶ represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.
Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, and a cycloalkenyl group.

When the content of the structural unit having the amino group or the amide structure is 0.1 mol% in a preferable lower limit and the content of the structural unit in which a preferable upper limit is 20 mol% is 0.1 mol% or more, adhesion is achieved. The effect of improving the color and the effect of improving the color loss resistance can be sufficiently exhibited. When the content of the structural unit having an amino group or amide structure is 20 mol% or less, the polyvinyl acetal resin powder can be easily taken out by the precipitation method with appropriate solubility.
In addition, content of the structural unit which has the said amino group or amide structure can be measured by NMR etc.

In the polyvinyl acetal resin, the total content of the structural unit having the imine structure and the structural unit having the amino group or the amide structure is preferably 0.2 mol%, and preferably 20 mol%. is there.
Adhesiveness with a polarizing plate protective layer can be improved as the said total content is 0.2 mol% or more. When the total content is 20 mol% or less, good heat resistance can be ensured.
The minimum with said more preferable total content is 0.5 mol%, and a more preferable upper limit is 9 mol%.

In the present invention, the ratio of the content of the structural unit having an imine structure and the content of the structural unit having an amino group or amide structure (structural unit having an imine structure / structural unit having an amino group or amide structure) is: It is preferably 0.5 / 99.5 to 99.5 / 0.5. When the ratio is 0.5 / 99.5 or more, the ratio of the structural unit having an imine structure is sufficient, and the reactivity with a compound having an ethylenically unsaturated double bond described later is sufficiently exhibited. be able to. When the ratio is 99.5 / 0.5 or less, the proportion of the structural unit having an imine structure does not increase excessively, and the handleability can be improved.
As for the said ratio, a more preferable minimum is 5/95 and a more preferable upper limit is 75/25.

When the polyvinyl acetal resin has at least one of the structural unit having an imine structure and the structural unit having an imine structure and the structural unit having an imine structure, as a method for producing the polyvinyl acetal resin, for example, Polyvinyl alcohol is produced by saponifying polyvinyl acetate obtained by copolymerizing a monomer having an amino group, an amide structure or an imine structure and vinyl acetate, and the obtained polyvinyl alcohol is produced by a conventionally known method. The method of acetalizing by is mentioned. Moreover, you may use the method of introduce | transducing an imine structure by acetalizing the polyvinyl alcohol which has a structural unit which has an amino group or an amide structure by a conventionally well-known method. A method of acetalizing polyvinyl alcohol having an imine structure obtained by post-modifying polyvinyl alcohol having a structural unit having an amino group or an amide structure by a conventionally known method may be used.
Furthermore, an amino group or an amide structure or an imine structure may be introduced by post-modifying the unmodified polyvinyl acetal resin.
Among them, a method of obtaining a polyvinyl acetal resin by introducing an imine structure by acetalizing polyvinyl alcohol having a structural unit having an amino group or an amide structure is preferable. In particular, when such a method is used, an imine structure can be obtained by adding an excessive amount of an aldehyde and an acid catalyst used for acetalization.
For example, it is preferable to add 1.0% by weight or more of the acid catalyst.
In the case of using such a method, as a method for confirming a structural unit having an amino group or an amide structure and a structural unit having an imine structure, for example, using FT-IR, the spectrum of the amino group ( 1600 cm < ^-1 > vicinity), the method of confirming the spectrum (160-170 ppm) of an imine structure using < ¹³ > C-NMR, etc. are mentioned.

The acetalization can be performed by a known method, and is preferably performed in an aqueous solvent, a mixed solvent of water and an organic solvent compatible with water, or an organic solvent.
As the organic solvent compatible with the water, for example, an alcohol-based organic solvent can be used.
Examples of the organic solvent include alcohol organic solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol; aromatic organic solvents such as xylene, toluene, ethylbenzene, and methyl benzoate; Aliphatic ester solvents such as ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, ethyl acetoacetate; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone Ketone solvents such as acetophenone; lower paraffin solvents such as hexane, pentane, octane, cyclohexane, decane; diethyl ether, tetrahydrofuran, ethylene glycol dimethyl Ether solvents such as ether, ethylene glycol diethyl ether, propylene glycol diethyl ether; amide solvents such as N, N-dimethylformamide, N, N-dimethyltecetamide, N-methylpyrrolidone, acetanilide, ammonia, trimethylamine, triethylamine, Examples thereof include amine solvents such as n-butylamine, di-n-butylamine, tri-n-butylamine, aniline, N-methylaniline, N, N-dimethylaniline, and pyridine. These can be used alone or in a mixture of two or more solvents. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferable from the viewpoints of solubility in resins and simplicity during purification.

The acetalization is preferably performed in the presence of an acid catalyst.
The acid catalyst is not particularly limited, hydrogen halides such as hydrochloric acid, mineral acids such as nitric acid and sulfuric acid, carboxylic acids such as formic acid, acetic acid and propionic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, Examples thereof include sulfonic acids such as paratoluenesulfonic acid, phosphoric acid and the like. These acid catalysts may be used alone or in combination of two or more compounds. Of these, hydrochloric acid, nitric acid and sulfuric acid are preferable, and hydrochloric acid is particularly preferable.

Examples of the aldehyde used for the acetalization include aldehydes having a chain aliphatic group having 1 to 10 carbon atoms, a cyclic aliphatic group, or an aromatic group. Conventionally known aldehydes can be used as these aldehydes. The aldehyde used in the acetalization reaction is not particularly limited. For example, formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde Aliphatic aldehydes such as 2-ethylhexylaldehyde, n-heptylaldehyde, n-octaldehyde, n-nonylaldehyde, n-decylaldehyde, amylaldehyde, benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropionaldehyde, etc. Aromatic aldehydes, and the like. These aldehydes may be used alone or in combination of two or more. Among the aldehydes, butyraldehyde, 2-ethylhexyl aldehyde, n-nonyl aldehyde, which are particularly excellent in acetalization reactivity, provide a sufficient internal plastic effect to the resulting resin, and as a result, impart good flexibility. And butyraldehyde is more preferable.

The addition amount of the aldehyde can be appropriately set according to the degree of acetalization of the target polyvinyl acetal resin. What is necessary is just to set suitably as the addition amount of the said aldehyde according to the acetalization degree of the target polyvinyl acetal resin. In particular, 60 to 95 mol%, preferably 70 to 90 mol% with respect to 100 mol% of polyvinyl alcohol is preferable because an acetalization reaction is efficiently performed and unreacted aldehyde is easily removed.

Although content of the said polyvinyl acetal resin in the adhesive composition of this invention is not specifically limited, A preferable minimum is 2 weight% and a preferable upper limit is 50 weight%. Adhesiveness to a PET film, a PVOH film, etc. can be improved as content of the said polyvinyl acetal resin is 2 weight% or more. When the content of the polyvinyl acetal resin is 50% by weight or less, the adhesive composition has flexibility, and the handleability in the dyeing and bonding process is improved.
As for content of the said polyvinyl acetal resin, a more preferable minimum is 10 weight% and a more preferable upper limit is 40 weight%.

The adhesive composition of the present invention preferably further contains a crosslinking agent.
By containing the said crosslinking agent, it can be bridge | crosslinked by applying energy by UV irradiation, a heating, etc., and an adhesive composition can be hardened.
As the crosslinking agent, a compound having an ethylenically unsaturated double bond (hereinafter also referred to as “unsaturated double bond monomer”) is preferably used.
The unsaturated double bond monomer may be a compound having one ethylenically unsaturated double bond (hereinafter also referred to as “monofunctional monomer”), and has two or more ethylenically unsaturated double bonds. It may be a compound (hereinafter also referred to as “polyfunctional monomer”).

Examples of the monofunctional monomer include styrene, vinyl toluene, chlorostyrene, α-methyl styrene, methyl (meth) acrylate, ethyl (meth) acrylate, acrylonitrile, vinyl acetate, 2-hydroxyethyl (meth) acrylate, 2- Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-phenoxy-2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 3 -Chloro-2-hydroxypropyl (meth) acrylate, glycerin mono (meth) acrylate, glycidyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isovo Nyl (meth) acrylate, tricyclodecanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, n-butyl (meth) acrylate , Hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl (meth) acrylate, n-stearyl (meth) acrylate , Benzyl (meth) acrylate, phenol ethylene oxide modified (n = 2) (meth) acrylate, nonylphenol propylene oxide modified (n = 2.5) (meth) acrylate, 2- (meth) acrylo Half (meth) acrylate, furfuryl (meth) acrylate, carbitol (meth) acrylate, benzyl (meth) acrylate of phthalic acid derivatives such as yloxyethyl acid phosphate, 2- (meth) acryloyloxy-2-hydroxypropyl phthalate, Butoxyethyl (meth) acrylate, allyl (meth) acrylate, acryloylmorpholine, dimethylacrylamide, 2-hydroxyethylacrylamide, N-methylol (meth) acrylamide, N-vinylpyrrolidone, 2-vinylpyridine, polyoxyethylene secondary Examples include alkyl ether acrylate.

Examples of the polyfunctional monomer include a bifunctional monomer and a trifunctional or higher monomer.

Examples of the bifunctional monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and propylene. Glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide modified bisphenol A type di (meth) ) Acrylate, propylene oxide modified bisphenol A type di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, Xylated cyclohexanedimethanol di (meth) acrylate, dimethylol dicyclopentane di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) Acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, phthalic acid diglycidyl ester di (meth) acrylate, hydroxypivalic acid modified neopentyl glycol di (Meth) acrylate, isocyanuric acid ethylene oxide modified diacrylate and the like.

Examples of the tri- or higher functional monomer include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth). ) Acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly (meth) acrylate, isocyanuric acid ethylene oxide modified triacrylate, caprolactone modified dipentaerythritol penta (meth) acrylate, caprolactone modified dipentaerythritol hexa ( (Meth) acrylate, caprolactone-modified pentaerythritol tri (meth) acrylate, caprolact Modified pentaerythritol tetra (meth) acrylate, ethylene oxide modified dipentaerythritol penta (meth) acrylate, ethylene oxide modified dipentaerythritol hexa (meth) acrylate, ethylene oxide modified pentaerythritol tri (meth) acrylate, ethylene oxide modified pentaerythritol tetra (Meth) acrylate, ethoxylated glycerin triacrylate and the like can be mentioned.

In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

In addition, as the crosslinking agent, epoxy compounds such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether; halohydrin compounds such as epichlorohydrin and epibromohydrin; 1,2-dichloroethane, 1,3-dichloropropane, and the like Halogen compounds of the above; isocyanate compounds such as hexamethylene diisocyanate; bisacrylamide compounds such as N, N′-methylenebisacrylamide and N, N′-ethylenebisacrylamide; urea compounds such as urea and thiourea; guanidines such as guanidine and diguanide Compounds; dicarboxylic acid compounds such as oxalic acid and adipic acid; glyoxal, glutaraldehyde, malonaldehyde, succinaldehyde, adipine aldehyde, phthalaldehyde, isophthalaldehyde, Aldehyde compounds including dialdehydes, such as reflex glutaraldehyde and the like.
The said crosslinking agent may be used independently and may be used in combination of 2 or more type.

In the adhesive composition of the present invention, the ratio of the content of the polyvinyl acetal resin and the content of the unsaturated double bond monomer (content of the polyvinyl acetal resin / content of the unsaturated double bond monomer). Is preferably 10/90 to 50/50. When the ratio is 10/90 or more, the adhesion to the protective film is good. When the ratio is 50/50 or less, the polyvinyl acetal resin can be uniformly dissolved in the unsaturated double bond monomer, and the resulting polarizing plate can have sufficient transparency.
The ratio is more preferably 20/80 to 40/60.

Although content of the said unsaturated double bond monomer in the adhesive composition of this invention is not specifically limited, A preferable minimum is 1 weight% and a preferable upper limit is 90 weight%. When the content of the unsaturated double bond monomer is 1% by weight or more, handling properties in dyeing and punching processes are improved. Heat resistance improves that content of the said unsaturated double bond monomer is 90 weight% or less.
The content of the unsaturated double bond monomer is more preferably a lower limit of 5% by weight and a more preferable upper limit of 40% by weight.

In the adhesive composition of the present invention, the content of the crosslinking agent with respect to 100 parts by weight of the polyvinyl acetal resin is preferably 100 parts by weight, more preferably 150 parts by weight, and more preferably 500 parts by weight. The upper limit is 400 parts by weight.

The cross-linking agent can be used by dissolving it in an organic solvent such as water or alcohol, if necessary.
The organic solvent used for dissolving the crosslinking agent is not particularly limited. For example, methanol, methyl acetate, tetrahydrofuran, ethylene glycol monophenyl ether, neopentyl glycol, benzyl alcohol, triethylene glycol, 1,4- Dioxane, propylene glycol, n-methylpyrrolidone, 3-methoxy-3-methyl-1-butanol and the like can be used. Of these, ethylene glycol monophenyl ether and neopentyl glycol are preferable. These organic solvents may be used independently and 2 or more types may be used together.

In the adhesive composition of the present invention, the content of the organic solvent with respect to 100 parts by weight of the crosslinking agent is preferably 10 parts by weight, preferably 500 parts by weight, and more preferably 200 parts by weight.

Moreover, the adhesive composition of this invention may contain the well-known photoinitiator and thermal polymerization initiator as needed. Since the transparent protective film having UV absorbing ability does not transmit light of 380 nm or less, it is preferable to use a photopolymerization initiator that is highly sensitive to light of 380 nm or more as the photopolymerization initiator.
Specific examples of the photopolymerization initiator include 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4- Morpholinophenyl) -butanone-1,2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2,4,6 -Trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro -3- (1H-pyrrol-1-yl) -phenyl) titanium and the like.

In particular, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholino), which are also commercially available as photopolymerization initiators. Phenyl) -butanone-1,2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, diethoxyacetophenone, 2-hydroxy 2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl- 2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- ( Acetophenones such as morpholinophenyl) butanone and 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone oligomer; benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin Benzoins such as isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3 ', 4,4'-tetra (t-butylperoxy Carbonyl) benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl] benzenemethananium bromide, (4-benzoylbenzene) Benzophenones such as (zyl) trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino Thioxanthones such as 2-hydroxy) -3,4-dimethyl-9H-thioxanthone-9-one mesochloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,6-dimethoxybenzoyl)- Examples thereof include acyl phosphine oxides such as 2,4,4-trimethyl-pentylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide.
In addition, these photoinitiators may be used independently and 2 or more types may be used together.
Moreover, when using the photopolymerization initiator, the adhesive composition is cured by irradiation with active energy rays, and when using a thermal polymerization initiator, the adhesive composition is cured by heating. It is also preferable to use both in combination.

These auxiliary agents include triethanolamine, triisopropanolamine, 4,4′-dimethylaminobenzophenone (Michler ketone), 4,4′-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, 4-dimethylaminobenzoic acid. Ethyl, 4-dimethylaminobenzoic acid (n-butoxy) ethyl, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone Etc. can be used in combination.

Among them, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoyl isopropyl ether, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, 2-hydroxy-2-methyl-1-phenyl It is preferable to use propan-1-one.

Although content of the said photoinitiator in the adhesive composition of this invention is not specifically limited, The preferable minimum with respect to 100 weight part of said polyvinyl acetal resins is 0.1 weight part, and a preferable upper limit is 5 weight part. When the content of the photopolymerization initiator is 0.1 parts by weight or more, sufficient adhesive force can be exhibited. Heat resistance etc. can be improved as content of the said photoinitiator is 5 weight part or less.

Examples of the thermal polymerization initiator include methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl cyclohexanone peroxide, methyl acetoacetate peroxide, acetyl acetate peroxide, 1,1-bis (t-hexylperoxy) -3. , 3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) -cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (T-butylperoxy) -2-methylcyclohexane, 1,1-bis (t-butylperoxy) -cyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 1,1-bis (t -Butylperoxy) butane, 2,2-bis (4,4-di- -Butylperoxycyclohexyl) propane, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t- Butyl hydroperoxide, α, α'-bis (t-butylperoxy) diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butyl cumi Ruperoxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, Octanoyl peroxide , Lauroyl peroxide, stearoyl peroxide, succinic acid peroxide, m-toluoyl benzoyl peroxide, benzoyl peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis (4-t-butylcyclohexyl) ) Peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethoxyhexyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-s-butyl peroxydicarbonate, di (3-Methyl-3-methoxybutyl) peroxydicarbonate, α, α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethyl Butyl peroxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate , T-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) Hexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-hexylper Oxyisopropyl monocarbonate, t-butyl peroxyisobutyrate, t-butyl Ruperoxymalate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropylmonocarbonate, t-butylperoxy-2-ethylhexylmono Carbonate, t-butylperoxyacetate, t-butylperoxy-m-toluylbenzoate, t-butylperoxybenzoate, bis (t-butylperoxy) isophthalate, 2,5-dimethyl-2,5-bis ( m-toluylperoxy) hexane, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxyallyl monocarbonate, t-butyltrimethylsilyl peroxide, 3, , 3 ', 4,4'-tetra (t-bu Organic peroxide initiators such as tilperoxycarbonyl) benzophenone and 2,3-dimethyl-2,3-diphenylbutane; 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 1-[(1 -Cyano-1-methylethyl) azo] formamide, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobisiso Butyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis (2-methyl-N-phenylpropylene) Onamidine) dihydrochloride, 2,2'-azobis [N- (4-chlorophenyl) -2-methylpropionamidine] dihydride Chloride, 2,2'-azobis [N- (4-hydrophenyl) -2-methylpropionamidine] dihydrochloride, 2,2'-azobis [2-methyl-N- (phenylmethyl) propionamidine] dihydrochloride, 2,2'-azobis [2-methyl-N- (2-propenyl) propionamidine] dihydrochloride, 2,2'-azobis [N- (2-hydroxyethyl) -2-methylpropionamidine] dihydrochloride, 2, , 2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2, , 2'-azobis [2- (4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl) propane Dihydrochloride, 2,2'-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (5-hydroxy-3,4) , 5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane] dihydrochloride, 2, , 2'-azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis [2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propion Amido], 2,2′-azobis [2-methyl-N- [1,1-bis (hydroxymethyl) ethyl] propionamide], 2,2′-azobis [2-methyl-N -(2-hydroxyethyl) propionamide], 2,2'-azobis (2-methylpropionamide), 2,2'-azobis (2,4,4-trimethylpentane), 2,2'-azobis (2 -Methylpropane), dimethyl-2,2-azobis (2-methylpropionate), 4,4'-azobis (4-cyanopentanoic acid), 2,2'-azobis [2- (hydroxymethyl) propio Nitrile] and the like; and the like. In addition, these thermal polymerization initiators may be used independently and 2 or more types may be used together.

The content of the thermal polymerization initiator in the adhesive composition of the present invention is not particularly limited, but a preferred lower limit with respect to 100 parts by weight of the polyvinyl acetal resin is 0.1 parts by weight, a more preferred lower limit is 1 part by weight, and a preferred upper limit. Is 5 parts by weight, and a more preferable upper limit is 2.5 parts by weight.

Moreover, the adhesive composition of this invention can mix | blend various additives as another arbitrary component in the range which does not impair the objective and effect of this invention.
Examples of the additive include epoxy resin, polyamide, polyamideimide, polyurethane, polybutadiene, polychloroprene, polyether, polyester, styrene-butadiene black copolymer, petroleum resin, xylene resin, ketone resin, cellulose resin, fluorine-based oligomer, Polymers or oligomers such as silicone oligomers and polysulfide oligomers; polymerization inhibitors such as phenothiazine and 2,6-di-t-butyl-4-methylphenol; polymerization initiation assistants; leveling agents; wettability improvers; Surfactant; Plasticizer; UV absorber; Silane coupling agent; Inorganic filler; Pigment;

The adhesive composition of the present invention is prepared by blending the polyvinyl acetal resin, the unsaturated double bond monomer added as necessary, other crosslinking agents, the photopolymerization initiator, and the like. Can do.

The adhesive composition of the present invention is not only excellent in adhesive force immediately after curing, but also can be used for various applications because the adhesive force hardly decreases with time. It can be suitably used for laminating a film and a polarizer. The polarizing plate obtained by using the adhesive composition of the present invention can shorten the drying process, has excellent productivity, and can have excellent resistance to color loss.

By laminating a polarizer and a protective film using the adhesive composition of the present invention, a polarizing plate comprising these laminates can be obtained.
The polarizing plate which consists of a laminated body containing the adhesive composition of this invention, a polarizer, and a protective film is also one of this invention.

There is no restriction | limiting in particular as said polarizer, A well-known thing can be used.
For example, (i) uniaxial stretching by adsorbing dichroic materials such as iodine and dichroic dyes to vinyl alcohol resin films such as PVA film, partially formalized PVA film, and ethylene-vinyl alcohol resin film (For example, refer to JP-A-2001-296427, JP-A-7-333426), (ii) a birefringent material having liquid crystallinity together with a dichroic material in the above (i) is 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 resin or ethylene-vinyl alcohol resin is dehydrated or deaceticated to be continuous. Introducing Lien 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 the polarizer is preferably 0.1 to 100 μm, more preferably 0.5 to 80 μm, and still more preferably 1 to 60 μm.

The protective film in the present invention can make up for deficiency in durability under high humidity, which is a problem of polarizers, by bonding to at least one surface, preferably both surfaces, of the polarizer.
Properties required for the protective film used in the present invention include transparency, mechanical strength, thermal stability, moisture barrier properties, optical isotropy, and the like.

As the material for the protective film, cellulose ester resins, cyclic olefin resins, and (meth) acrylic resins are preferably used from the viewpoints of optical properties, durability, and the like.
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, Examples include polyoxymethylene resins and epoxy resins. These may be used independently and 2 or more types may be used together.

Typical examples of the cellulose ester resin used in the cellulose ester resin film include 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 cyclic olefin resin film include norbornene resins. Such norbornene resins include, for example, ring-opening (co) polymers of norbornene monomers, addition-polymerized norbornene monomers, and addition-copolymerization of norbornene monomers and olefin monomers such as ethylene and α-olefins. Resin etc. are included.

Specific examples of the norbornene-based monomer include bicyclic compounds such as norbornene and norbornadiene, tricyclic compounds such as dicyclopentadiene and dihydroxypentadiene, heptacyclic compounds such as tetracyclopentadiene, their methyl group, ethyl group, propyl group, Alkyl substituents such as butyl groups, alkenyl substituents such as vinyl groups, alkylidene substituents such as ethylidene groups, aryl substituents such as phenyl groups, tolyl groups, and naphthyl groups, their ester groups, ether groups, It has a group containing an element other than carbon and hydrogen, such as cyano group, halogen, alkoxycarbonyl group, pyridyl group, hydroxyl group, carboxylic acid group, amino group, hydroxyl group-free, silyl group, epoxy group, acryloyl group, and methacryloyl group. Substituents and the like can be mentioned.

Examples of commercially available cyclic olefin resin films include “ARTON” manufactured by JSR, “ZEONOR”, “ZEONEX” manufactured by Nippon Zeon, “OPTOREZ” manufactured by Hitachi Chemical, “APEL” manufactured by Mitsui Chemicals, and the like. it can.

Examples of the (meth) acrylic resin used in the (meth) acrylic resin film include poly (meth) acrylic esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, and methyl methacrylate. -(Meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer, polymer having alicyclic hydrocarbon group [For example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.], (meth) having a high glass transition temperature obtained by intramolecular crosslinking or intramolecular cyclization reaction Acrylic resins, rubber-acrylic graft type core-shell polymers and the like can be mentioned.

As a commercial item of the said (meth) acrylic-type resin film, "Acrypet VRL20A" by Mitsubishi Rayon Co., Ltd., "Acrypet IRD-70", "MUX-60" by UMGABS, etc. are mentioned.

In addition, the protective film is subjected to surface hydrophilization treatment such as saponification treatment with an alkaline solution for a film made of a cellulose ester resin, corona discharge treatment or plasma treatment for a film made of a cyclic olefin resin, if necessary. It may be what you did.

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, An easy-adhesion layer or an anchor coat layer containing polyethyleneimine, polyurethane / polyester copolymer or the like can be provided, or surface treatment can be performed with a coupling agent such as a silane coupling agent or a titanium coupling agent. In addition, it is also possible to use together the above-mentioned various surface treatment methods.
Moreover, what coated the antistatic agent on the surface of the protective film or contained it in the film is also preferably used.

The thickness of such a protective film is not particularly limited, but usually a thicker one than the polarizer is used, and it has a function of imparting strength as a base material of the polarizer, and is preferably 10 to 100 μm. More preferably, it is 80 μm.

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

The polarizing plate of the present invention is obtained by bonding the above polarizer and a protective film through an adhesive. Specifically, the protective film is bonded to at least one surface, preferably both surfaces of the polarizer, using the adhesive composition of the present invention. Usually, the liquid adhesive composition is used as the polarizer. Or after apply | coating uniformly to a protective film or both, both are bonded together, it crimps | bonds, and a polarizing plate is formed by performing active energy ray irradiation.

In coating the above adhesive composition on a polarizer or a protective film, for example, reverse coater, gravure coater (direct, reverse or offset), bar reverse coater, roll coater, die coater, bar coater, rod coater, etc. Or can be applied by dipping.

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.
In the active energy ray irradiation, rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, electromagnetic waves such as X-rays and γ rays, electron beams, proton rays, neutron rays, etc. can be used. Curing by ultraviolet irradiation is advantageous from the standpoint of availability of the device and price. In addition, when performing electron beam irradiation, it can harden | cure even if it does not use the said photoinitiator.

As the light source for the ultraviolet irradiation, a high pressure mercury lamp, an electrodeless lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, an LED, or the like is used.
The cumulative exposure amount when performing ultraviolet irradiation is preferably ^{2 to} 3000 mJ / cm ² , more preferably 10 to 2000 mJ / cm ² .

Especially in the case of the high-pressure mercury lamp, for example, preferably 5~3000mJ / cm ^2, more preferably at a condition of 50~2000mJ / cm ^2.
Moreover, in the case of the said electrodeless lamp, it is preferably performed on the conditions of 2-2000 mJ / cm < ² >, More preferably, 10-1000 mJ / cm < ² >, for example.

The irradiation time varies depending on the type of the light source, the distance between the light source and the coating surface, the coating thickness, and other conditions, but may be usually from several seconds to several tens of seconds, and in some cases, may be a fraction of a second. On the other hand, in the case of the electron beam irradiation, for example, an electron beam having an energy in the range of 50 to 1000 keV is preferably used, and an irradiation amount of 2 to 50 Mrad is preferable.

The irradiation direction of the active energy ray (electron beam, ultraviolet ray, etc.) can be irradiated from any appropriate direction, but it is preferable to irradiate from the transparent protective film side in terms of preventing the polarizer from deteriorating.

The thickness of the adhesive layer in the polarizing plate of the present invention obtained as described above is preferably 0.01 to 10 μm, more preferably 0.01 to 5 μm, still more preferably 0.01 to 2 μm, and particularly preferably 0.01. ˜1 μm. When the thickness of the adhesive layer in the polarizing plate is 0.01 μm or more, sufficient adhesive strength can be obtained, and when the thickness is 10 μm or less, cracking during punching is suppressed and the processing of the polarizing plate is performed. The property can be made excellent.

ADVANTAGE OF THE INVENTION According to this invention, while being excellent in adhesive force, the adhesive composition which can obtain the polarizing plate excellent also in the color loss resistance and water resistance can be provided. Moreover, the polarizing plate using this adhesive composition can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Synthesis of polyvinyl acetal resin A having a structural unit having an imine structure and a structural unit having an amino group)
240 g of polyvinyl alcohol containing a polymerization degree of 600, a saponification degree of 99 mol% and 1.7 mol% of a structural unit having an amino group (—NH ₂ ) represented by the above formula (6) was added to 1800 g of pure water, The solution was stirred at a temperature of about 2 hours for dissolution. The solution was cooled to 40 ° C., 170 g of 35% by weight hydrochloric acid and 275 g of n-butyraldehyde were added thereto, and the acetalization reaction was carried out while maintaining the liquid temperature at 40 ° C. to precipitate the reaction product. It was.
Thereafter, the liquid temperature was kept at 40 ° C. for 3 hours to complete the reaction, and neutralized, washed with water and dried by a conventional method to obtain a polyvinyl acetal resin A powder.
When the obtained polyvinyl acetal resin A was dissolved in DMSO-d ₆ (dimethylsulfoxide) and analyzed using ¹³ C-NMR (nuclear magnetic resonance spectrum), an amino group represented by the above formula (6) was obtained. And a structural unit (content: 1.5 mol%, R ⁴ and R ⁵ are methyl groups) having an imine structure represented by the following formula (8): ).
Table 1 shows the degree of acetalization, the amount of acetyl groups, and the amount of hydroxyl groups measured using ¹³ C-NMR.

(Synthesis of polyvinyl acetal resin B having a structural unit having an imine structure and a structural unit having an amino group)
The polyvinyl alcohol was changed to 250 g of polyvinyl alcohol containing a polymerization degree of 600, a saponification degree of 98 mol%, and a structural unit having an amino group represented by the above formula (6) of 9 mol%, and the amount of n-butyraldehyde added was changed. A polyvinyl acetal resin B was obtained in the same manner as in Example 1 except that the amount was 150 g.
When the obtained polyvinyl acetal resin B was dissolved in DMSO-d ₆ (dimethylsulfoxide) and analyzed using ¹³ C-NMR (nuclear magnetic resonance spectrum), an amino group represented by the above formula (6) was obtained. And a structural unit having an imine structure represented by the above formula (8) (content: 8.3 mol%, R ⁴ and R ⁵ are methyl groups) ).
Table 1 shows the degree of acetalization, the amount of acetyl groups, and the amount of hydroxyl groups measured using ¹³ C-NMR.

(Synthesis of polyvinyl acetal resin C)
Polyvinyl alcohol is mixed into 140 g of polyvinyl alcohol having a polymerization degree of 570 and a saponification degree of 98 mol%, 50 g of polyvinyl alcohol having a polymerization degree of 790 and a saponification degree of 98 mol%, and 60 g of polyvinyl alcohol having a polymerization degree of 1700 and a saponification degree of 99%. A polyvinyl acetal resin C was obtained in the same manner as in Example 1 except for the change.
When the obtained polyvinyl acetal resin was dissolved in DMSO-d ₆ (dimethylsulfoxide) and analyzed using ¹³ C-NMR (nuclear magnetic resonance spectrum), the structural unit having an amino group and the imine structure were obtained. It could not be confirmed that the structural unit had.
Table 1 shows the degree of acetalization, the amount of acetyl groups, and the amount of hydroxyl groups measured using ¹³ C-NMR.

(Production of polarizer)
A polyvinyl alcohol film having a thickness of 60 μm prepared using polyvinyl alcohol having an average polymerization degree of 2400 and a saponification degree of 99.9 mol% was immersed in warm water at 30 ° C. for 60 seconds to swell. Next, the film was dyed while immersed in an aqueous solution of iodine / potassium iodide (weight ratio 1: 7.5) (concentration 0.2 wt%) and stretched to 1.8 times. Then, it extended | stretched so that the draw ratio from the initial stage might be set to 6 times in 60 degreeC borate ester aqueous solution (3.0 weight% of potassium iodide containing). After stretching, drying was performed in an oven at 40 ° C. for 3 minutes to obtain a polyvinyl alcohol polarizer.

(Polarizing plate protective film)
The following were used as the polarizing plate protective film.
Cycloolefin polymer (COP, manufactured by Nippon Zeon Co., Ltd., “ZEONOR”, thickness 60 μm)
Triacetylcellulose (TAC, manufactured by Fuji Film, “Fujitac”, thickness 60 μm)

Example 1
(Preparation of adhesive composition)
20 g of the above polyvinyl acetal resin A, 70 g of 2-hydroxyethyl methacrylate which is an unsaturated double bond monomer as a crosslinking agent, and 10 g of ethylene glycol diacrylate are mixed, the resulting mixture is put into a sealed container, and the sealed container is placed on a roller bench to form polyvinyl Acetal resin A was dissolved in an unsaturated double bond monomer to obtain a resin solution. Furthermore, 1 g of 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF Japan, “Irgacure 184”) as a photopolymerization initiator was added to the resin solution and stirred to obtain a polarizing plate adhesive composition.

(Preparation of polarizing plate)
An acrylic film with an adhesive composition layer obtained by using COP as a polarizing plate protective film, cutting the protective film into 200 mm × 50 mm, and coating the obtained adhesive composition with a bar coater to a film thickness of 5 μm Two sheets were produced. Thereafter, the polarizer obtained in the above (preparation of the polarizer) is cut into 150 mm × 30 mm, the acrylic film is superposed on both surfaces of the polarizer, and bonded at a nip pressure of 2 MPa using a roll machine, and laminated film Got.
Next, from both sides of the laminated film on the acrylic film side, UV irradiation is performed with an ultraviolet irradiation device equipped with a high-pressure mercury lamp at a peak illuminance of 130 mW / cm ² and an integrated exposure amount of 900 mJ / cm ² (365 nm) to adhere. The agent composition was cured to produce a polarizing plate.

(Example 2)
In (Preparation of polarizing plate), a polarizing plate was prepared in the same manner as in Example 1 except that TAC was used as the polarizing plate protective film.

(Example 3)
In (Preparation of Adhesive Composition), 100 g of a mixed solvent of ethylene glycol monophenyl ether (EPE) / neopentyl glycol (NPG) (EPE: NPG = 60: 40) was used as an organic solvent for dissolving the crosslinking agent. An adhesive composition was prepared in the same manner as in Example 1 except that the formulation was changed to

In addition, using the obtained adhesive composition, before irradiating the laminated film with ultraviolet rays, the laminated film was dried in a blown oven at 100 ° C. for 10 minutes, and further dried in a vacuum oven for 1 hour. In the same manner as in Example 1, a polarizing plate was produced.

(Examples 4 and 5, Comparative Examples 1 and 2)
A polarizing plate was prepared in the same manner as in Example 1 except that the composition was as shown in Table 2 in (Preparation of adhesive composition) and the type of protective film used in (Preparation of polarizing plate) was changed as shown in Table 2. .

(Example 6 and Comparative Example 3)
A polarizing plate was produced in the same manner as in Example 3 except that the formulation was as shown in Table 2 in (Preparation of adhesive composition).

<Evaluation>
Using the polarizing plates obtained in Examples and Comparative Examples, performance evaluation was performed as follows.

(Adhesiveness)
The polarizing plate is cut into 120 mm x 25 mm, reinforced with kraft tape on two protective films, and the resulting resin laminate is tensioned using TENSILON (produced by ORIENTEC) according to JIS K 6829. The stress (N / 25 mm) was measured under the condition of 20 mm / min.
(Evaluation criteria)
A: 20 N or more (adhered firmly)
○: 10N or more and less than 20N (bonded)
×: Less than 10N (not bonded)

(Color loss resistance)
The polarizing plate was cut into 5 cm × 5 cm, immersed in warm water at 60 ° C., the color tone of the polarizing plate after 48 hours was observed, and evaluated according to the following criteria.
○: No change in color and condition before testing
Δ: Slightly discolored (discolored)
×: Completely missing (discolored)

(water resistant)
The polarizing plate was cut into 5 cm × 5 cm, immersed in warm water at 60 ° C., and the adhesion of the polarizing plate after 48 hours was observed and evaluated according to the following criteria.
○: No peeling from the end of the test piece was observed.
Δ: Peeling was observed in the range of less than 5 mm from the end of the test piece.
X: Peeling was observed in the range of 5 mm or more from the end of the test piece.

ADVANTAGE OF THE INVENTION According to this invention, while being excellent in adhesive force, the adhesive composition which can obtain the polarizing plate excellent also in the color loss resistance and water resistance can be provided. Moreover, the polarizing plate using this adhesive composition can be provided.

Claims (5)

An adhesive composition containing a polyvinyl acetal resin,
The polyvinyl acetal resin, a polymerization degree of 200 to 4000, a hydroxyl group amount from 20 to 70 mol%, characterized in that have a structural unit represented by the following formula (1), a structural unit having an imine structure An adhesive composition.

In formula (1), X represents an integer of 1 or 2, R ¹ represents a single bond or an alkylene group, and R ² represents a hydrogen atom, an oxygen atom, a formyl group or a hydrocarbon group. Polyvinyl acetal resin, the adhesive composition according to claim 1, characterized in that have a structural unit having an amino group or an amide structure. 3. The adhesive composition according to claim 2, wherein the polyvinyl acetal resin has a total content of 0.2 to 9 mol% of a structural unit having an imine structure and a structural unit having an amino group or an amide structure. object. The adhesive composition according to claim 1, 2 or 3, further comprising a compound having an ethylenically unsaturated double bond. A polarizing plate comprising a laminate comprising the adhesive composition according to claim 1, 2, 3 or 4, a polarizer, and a protective film.