KR101587804B1 - Adhesive composition for polarizing plate and polarizing plate using the same - Google Patents

Abstract

It is an object of the present invention to provide a pressure-sensitive adhesive composition for a polarizing plate capable of forming a pressure-sensitive adhesive layer having excellent durability and light leakage prevention property by short-term aging. The pressure-sensitive adhesive composition for a polarizing plate comprises the following components (A) and (B): (A) 100 parts by mass of a (meth) acrylic polymer having a weight average molecular weight of 300,000 to 1,500,000 copolymerized with at least 10% by mass of a carboxyl group- And 4 to 20 parts by mass of a tolylene diisocyanate compound having an isocyanurate structure (B).

Description

[0001] The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate and a polarizing plate using the same.

The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate, and more particularly, to a pressure-sensitive adhesive composition for a polarizing plate capable of forming a pressure-sensitive adhesive layer having excellent optical properties due to short-term aging and a polarizing plate using the same.

A liquid crystal device has a structure in which a liquid crystal material is sandwiched between two substrates, and a polarizer is attached to the surface of the substrate through a pressure-sensitive adhesive layer. BACKGROUND ART In recent years, liquid crystal devices have been used for on-vehicle use, outdoor use, personal computer displays, televisions, and the like.

The polarizing plate has a multilayer structure of different materials, and the dimensional stability is deteriorated due to the characteristics of the constituent materials. Particularly under high temperature and high humidity heat use environments, the stress concentrates due to the shrinkage of the polarizing plate, which causes birefringence of the polarizing plate, and the pressure sensitive adhesive itself is oriented by stress concentration and birefringence occurs. Color irregularity (light leakage) occurs, and the display quality decreases. Under these circumstances, problems such as foaming at the interface between the polarizing plate and the glass and peeling of the polarizing plate are likely to occur. Therefore, the pressure-sensitive adhesive for a polarizing plate is required to have excellent light leakage prevention and durability.

On the other hand, in order to form the pressure-sensitive adhesive layer on the polarizing plate, it is necessary to cure the polarizing plate by applying a pressure-sensitive adhesive composition on the polarizing plate, for example, , There has been a problem that the productivity is lowered or the inventory amount is increased due to the ripening period of such organ.

To solve this problem, a method of accelerating curing by additionally containing a carboxyl group in a hydroxyl group-containing acrylic polymer in a mixture of a hydroxyl group-containing acrylic polymer and an isocyanate crosslinking agent has been proposed (Patent Document 1). However, in this technique, the amount of the isocyanate-based crosslinking agent to be added is small and sufficient light leakage prevention and durability can not be obtained due to short-term aging. Also disclosed is a pressure-sensitive adhesive composition for a surface protective film containing an acryl-based polymer containing a hydroxyl group and a carboxyl group, and an aliphatic or alicyclic polyfunctional isocyanate-based or isocyanurate-based compound and having a shortened curing period Document 2). However, the acrylic polymer used in this pressure-sensitive adhesive composition has a limited amount of carboxyl groups, and thus is not suitable for use in the conjugation of a polarizing plate and a glass. If the aliphatic or alicyclic polyfunctional isocyanate or isocyanurate compound is added to at least one carboxyl group-containing pressure sensitive adhesive of the present invention, the pot life tends to be shortened, so that it can not be practically used .

And a pressure-sensitive adhesive composition for an optical film in which an isocyanate compound is added to an acryl-based polymer having a carboxyl group (Patent Documents 3 and 4). However, these techniques are aimed at improving the reworkability and light leakage prevention property, and do not consider the reduction of the aging period at all. Therefore, all of the pressure-sensitive adhesive compositions disclosed in these documents can not obtain sufficient optical aptitude due to short-term aging.

Japanese Patent Application Laid-Open No. 2008-156513 Japanese Patent Application Laid-Open No. 2005-247909 Japanese Patent No. 4136524 Japanese Patent Application Laid-Open No. 2008-144126

Therefore, a pressure-sensitive adhesive composition for a polarizing plate capable of forming a pressure-sensitive adhesive layer having excellent durability and light leakage prevention property by short-term aging has been desired. The present invention provides a pressure-sensitive adhesive composition for a polarizing plate will be.

DISCLOSURE OF THE INVENTION As a result of intensive investigations to solve the above problems, the present inventors have found that a tolylene diisocyanate compound having an isocyanurate structure is used as a cross-linking agent, and that a tolylene diisocyanate compound having a relatively large amount , It has been found that a pressure-sensitive adhesive layer having excellent durability and light leakage-preventing property can be formed even in a short-term aging, thereby completing the present invention.

That is,

The following components (A) and (B)

(A) 100 parts by mass of a (meth) acryl-based polymer having at least a carboxyl group-containing monomer copolymerized with 1 to 10% by mass and having a weight average molecular weight of 300,000 to 1,500,000

(B) 4 to 20 parts by weight of a tolylene diisocyanate compound having an isocyanurate structure

, And a pressure-sensitive adhesive composition for a polarizing plate.

Further, the present invention is a polarizing plate comprising a polarizing film provided with a pressure-sensitive adhesive layer formed on at least one surface thereof with the above-mentioned pressure-sensitive adhesive composition for a polarizing plate.

By using the pressure-sensitive adhesive composition of the present invention in a polarizing plate, occurrence of light leakage can be effectively prevented even under high-temperature and high-humidity conditions, and excellent durability and occurrence of foaming and peeling of the pressure-sensitive adhesive layer can be suppressed. In addition, since the curing speed is high and the aging period can be greatly shortened, the productivity can be remarkably improved and the inventory amount can be reduced.

The acrylic polymer of the component (A) used in the pressure-sensitive adhesive composition for a polarizing plate of the present invention is obtained by copolymerizing at least a carboxyl group-containing monomer.

Examples of the carboxyl group-containing monomer include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 3-carboxypropyl (meth) acrylate, 4-carboxybutyl (meth) acrylate, itaconic acid, crotonic acid, Malic acid and maleic anhydride.

Component (A) The content of the carboxyl group-containing monomer in the constituent monomers of the acrylic polymer is 1 to 10 mass% (hereinafter, referred to as "%"), preferably 2 to 8 mass%, more preferably 2 to 6 mass% %to be. If it is less than 1%, it is difficult to obtain a cohesive force, and if it is more than 10%, cohesive force is too high or adhesion increases.

Examples of other constituent monomers of the acrylic polymer of the component (A) include (meth) acrylic acid alkyl esters, hydroxyl group-containing monomers, benzene ring-containing monomers, (meth) acrylic acid alkoxy esters, amino group-containing monomers and amide-containing monomers.

Specific examples of the alkyl (meth) acrylate include alkyl (meth) acrylates, ethyl (meth) acrylates, propyl (meth) acrylates, isopropyl (Meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (Meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and lauryl (meth) acrylate. Of these, butyl acrylate and methyl acrylate are preferably used because of good balance of adhesion and durability.

Component (A) The content of the alkyl (meth) acrylate in the total monomer constituting the acrylic polymer is 10 to 99%, preferably 50 to 98.5%. If it is less than 10%, the adhesive force and durability may not be balanced. If more than 99%, durability may be deteriorated.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2- (Meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, chloro-2-hydroxypropyl acrylate, diethylene glycol mono (meth) acrylate and allyl alcohol And the gel fraction can be made higher by copolymerizing such hydroxyl group-containing monomers. Of these, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferably used because of their good copolymerization with (meth) acrylic acid alkyl ester.

Component (A) The content of the hydroxyl group-containing monomer with respect to the constituent monomers of the acrylic polymer is 0 to 1%, preferably 0.05 to 1%. If it is more than 1%, the gel fraction becomes excessively high, resulting in deterioration of adhesiveness and peeling off under high temperature and high humidity conditions.

The benzene ring-containing monomer has a definite intrinsic birefringence, and the birefringence of the (meth) acrylic polymer can be reduced by copolymerizing it. Specific examples thereof include phenylacrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide modified nonylphenol (meth) acrylate, Naphthol acrylate, biphenyl (meth) acrylate, styrene, vinyltoluene, and? -Methylstyrene. Of these, benzyl acrylate and phenoxyethyl acrylate are preferably used because they have good compatibility with the (meth) acrylic acid alkyl ester, good copolymerization and do not lower transparency.

Component (A) The content of the benzene ring-containing monomer relative to the constituent monomers of the acrylic polymer is 0 to 40%, preferably 0 to 30%. If it is more than 40%, appropriate adhesive force may not be obtained.

Examples of the (meth) acrylic acid alkoxy ester include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, 3-methoxypropyl ) 2-methoxybutyl acrylate, and 4-methoxybutyl (meth) acrylate. Component (A) The content of the (meth) acrylic acid alkoxy ester in the constituent monomers of the acrylic polymer is 0 to 90%, preferably 0 to 80%.

Examples of the amino group-containing monomer include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like.

Examples of the amide-containing monomer include (meth) acrylamide and (meth) N-methylol acrylamide. The amounts of these amino group-containing monomers and amide group-containing monomers to be used are about 0 to 1% with respect to the total monomers of the component (A) acrylic polymer.

The component (A) of the present invention can be produced by polymerizing a mixture of the above monomer components by a conventionally known polymerization method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method and a suspension polymerization method. Among them, those prepared by a solution polymerization method or a bulk polymerization method which do not contain a polymerization stabilizer such as an emulsifier or a suspending agent are more preferable.

The weight average molecular weight (Mw) of the component (A) obtained as described above is from 300,000 to 1,500,000, preferably from 400,000 to 1,200,000. When the weight average molecular weight is less than 300,000, the durability is deteriorated. When the weight average molecular weight is more than 1.5000,000, the viscosity is increased, which causes problems in handling. In the present specification, the weight average molecular weight means a value obtained by the measuring method described in the Examples.

The acrylic polymer of the component (A) preferably has a glass transition temperature of 0 ° C or lower, more preferably -20 ° C or lower, particularly preferably -80 ° C to -30 ° C. If the glass transition temperature is higher than 0 占 폚, the adhesiveness of the resultant pressure-sensitive adhesive to the base material and the flexibility of the pressure-sensitive adhesive layer may be deteriorated, resulting in peeling or peeling off from the base material. In the present specification, the glass transition temperature is a value calculated by the following FOX formula.

(Expression of FOX)

1 / Tg = Wa / Tga + Wb / Tgb +

Tg: glass transition temperature of the copolymer

Tga, Tgb, ...: monomer a, monomer b, ... Of glass transition temperature

Wa, Wb, ..., monomer a, monomer b, ... Weight fraction

The tolylene diisocyanate compound having an isocyanurate structure of the component (B) used in the present invention is a compound containing an isocyanurate ring formed by trimerization of tolylene diisocyanate in its structure and also includes various modified products do. The compound of the component (B) can be obtained by the method described in JP-A-8-193114 and WO2006 / 137307, and the compound corresponding to the component (B) is Coronate 342, Coronate 2030 All manufactured by Nippon Polyurethane Co., Ltd.) are commercially available.

The blending amount of the component (B) in the pressure-sensitive adhesive composition for a polarizing plate of the present invention is 4 to 20 parts, preferably 6 to 15 parts, per 100 parts by mass of the component (A). If the amount is less than 4 parts, the light leakage performance is not good, and if it is more than 20 parts, the cohesive force becomes too high.

Further, a crosslinking agent other than the above-mentioned component (B) may be used in combination with the pressure-sensitive adhesive composition for a polarizing plate of the present invention (component (C)). As such a crosslinking agent, there may be mentioned tolylene diisocyanate crosslinking agent (not having an isocyanurate structure), epoxy crosslinking agent and aziridine crosslinking agent, and one or more of these may be used.

Examples of the tolylene diisocyanate crosslinking agent (other than those having an isocyanurate structure) include tolylene diisocyanate and an isocyanate compound, a biuret type compound and a known poly (isocyanurate) compound obtained by reacting the tolylene diisocyanate with a polyhydric alcohol such as trimethylolpropane or pentaerythritol. And derivatives of urethane prepolymer type isocyanate compounds added in reaction with ether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol and the like. By using such a tolylene diisocyanate crosslinking agent (excluding those having an isocyanurate structure) in combination, adhesiveness to a substrate can be improved, and peeling and the like can be suppressed. Of these, tolylene diisocyanate and trimethylolpropane tolylene diisocyanate are preferred.

In the pressure-sensitive adhesive composition for a polarizing plate of the present invention, it is preferable that the tolylene diisocyanate crosslinking agent (excluding those having an isocyanurate structure) is blended so that the blending ratio to the component (B) is 1: 3 to 3: 1 . If the compounding ratio is out of this range, aging may take a long period of time, and peeling may occur at high temperature and high humidity.

Examples of the epoxy crosslinking agent include bisphenol A epichlorohydrin type epoxy resin, ethylene diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol N, N ', N'-tetraglycidyl-m-xylylenediamine, 1, 2, 3, 4, And 3-bis (N, N'-diamine glycidylaminomethyl) cyclohexane. By using these epoxy crosslinking agents in combination, the gel fraction can be increased. Among these, N, N, N ', N'-tetraglycidyl-m-xylylenediamine and 1,3-bis (N, N'-diamine glycidylaminomethyl) cyclohexane are preferably used.

The blending amount of the epoxy cross-linking agent in the pressure-sensitive adhesive composition for a polarizing plate of the present invention is 0 to 1%, preferably 0.05 to 0.5% based on the component (B). If the blending amount is outside this range, a long period of time is required for aging, and peeling may occur at high temperature and high humidity.

Examples of the aziridine crosslinking agent include 1,1 '- (methylene-di p-phenylene) bis-3,3-aziridyl element, 1,1' - (hexamethylene) 4,6-triaziridinyl-1,3,5-triazine, and trimethylolpropane-tris- (2-aziridinyl propionate). By using these aziridine crosslinking agents in combination, the gel fraction can be increased.

The blending amount of the aziridine crosslinking agent in the pressure-sensitive adhesive composition for a polarizing plate of the present invention is 0 to 1%, preferably 0.05 to 0.5% based on the component (B). If the blending amount is out of this range, the aging period becomes long, and peeling may occur at high temperature and high humidity heat conditions.

The pressure-sensitive adhesive composition for a polarizing plate of the present invention is preferably blended with a silane coupling agent (D) containing a group reactive with a carboxyl group contained in the acrylic polymer of the component (A). By using this, the pressure-sensitive adhesive can be firmly adhered to the glass, and peeling can be prevented in a moist heat environment. Specific examples thereof include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, Containing silane coupling agents such as 3-aminopropyltrimethoxysilane and N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, and the like.

The blending amount of the silane coupling agent (D) in the pressure-sensitive adhesive composition for a polarizing plate of the present invention is 0.05 to 1 part, preferably 0.1 to 0.5 part, per 100 parts of the component (A). When the amount is less than 0.05 part, peeling easily occurs under a humid environment. If it is more than 1 part, the silane coupling agent bleeds under high temperature environment, and peeling easily occurs, which is not preferable.

The pressure-sensitive adhesive composition for a polarizing plate of the present invention is prepared by blending the components (A) and (B) with components (C) and (D) or other optional components as necessary and mixing them according to a conventional method. Examples of optional components that can be used include antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, and the like, and they can be compounded within a range that does not impair the effects of the present invention.

In order to obtain the pressure-sensitive adhesive sheet for a polarizing plate of the present invention from the pressure-sensitive adhesive composition for a polarizing plate thus obtained, the pressure-sensitive adhesive composition is applied to at least one surface of a support according to a conventional method, followed by drying and aging to form a pressure-sensitive adhesive layer. Drying is usually carried out at 80 to 110 ° C for 2 to 10 minutes. On the other hand, the pressure-sensitive adhesive composition of the present invention can significantly shorten the aging time as compared with the conventional one. For example, the pressure-sensitive adhesive composition is sufficiently cured at a temperature of 23 캜 and 50% RH under aging of 1 to 3 days, A pressure-sensitive adhesive layer having an adhesive property and an optical property can be obtained. The gel fraction of the pressure-sensitive adhesive layer after aging is preferably 60 to 90%, more preferably 65 to 85%. If it is outside this range, durability may be deteriorated and it may be easily peeled off. In the present specification, the gel fraction means a value obtained by the measuring method described in the examples. As the support, a polyester film that has been peeled off the surface may be used. The thickness of the pressure-sensitive adhesive layer is usually about 10 to 30 占 퐉, preferably about 15 to 25 占 퐉.

The polarizing plate of the present invention can be obtained by providing a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate on at least one surface of the polarizing film. The thickness of the pressure-sensitive adhesive layer provided on the polarizing film is usually about 10 to 30 占 퐉, preferably about 15 to 25 占 퐉.

When a pressure-sensitive adhesive layer is provided on a polarizing film, a pressure-sensitive adhesive composition is coated on a polarizing film, dried, aged, or coated on a support to form a pressure-sensitive adhesive layer . The conditions for drying, aging, and the range of the gel fraction are the same as described above.

As the polarizing film used in the present invention, layers having different functions may be laminated, and specifically, an elliptically polarizing film and a retardation film are also included.

A liquid crystal device is produced by providing the polarizing plate of the present invention obtained as described above on the surface of a substrate of a liquid crystal cell. The type of liquid crystal device in which the polarizing plate of the present invention is used is not particularly limited, and TN mode, VA mode, IPS mode, and OCB mode may be used. By appropriately attaching a component such as a backlight to the liquid crystal device, a liquid crystal display device with reduced light leakage is manufactured.

The polarizer-type pressure-sensitive adhesive composition of the present invention is capable of forming a pressure-sensitive adhesive layer having excellent light leakage prevention and durability due to short-term aging, for the following reasons.

That is, it is said that when an isocyanate compound is added to an adhesive in an excessive amount, a polyurethane originating from an isocyanate compound is produced. This polyolefin is intertwined with the main polymer of the pressure-sensitive adhesive to cause physical bonding and has a mesh structure similar to that of a general pressure-sensitive adhesive. In the case of a tolylene diisocyanate compound having an isocyanurate structure, It is thought to have a mesh structure. The polyolefins derived from a tolylene diisocyanate compound having an isocyanurate structure are highly elastic and can control the birefringence, so that the light leakage preventing property is improved, and the tolylene diisocyanate compound having an isocyanurate structure It is considered that the radical-isocyanate-based compound has a higher reactivity than other isocyanate-based compounds, and is quick in the cross-linking reaction and poly-urea formation reaction, thereby greatly shortening the aging period.

(Example)

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples at all.

(Production Example 1)

Preparation of acrylic polymer:

97 parts by mass of butyl acrylate, 3 parts by mass of acrylic acid, 100 parts by mass of ethyl acetate and 0.04 parts by mass of n-dodecyl mercaptan (NDM) were placed in a flask equipped with a stirrer, a nitrogen gas introducing tube, a thermometer and a reflux condenser, The contents of the flask were heated to 60 DEG C while introducing nitrogen gas. Then, 0.1 part by mass of a polymerization initiator azobisisobutyronitrile (AIBN) sufficiently purged with nitrogen gas was added to the flask under stirring. Heating and cooling were performed for 10 hours so that the temperature of the contents in the flask could be maintained at 60 DEG C, and finally 100 parts of ethyl acetate was added to obtain an acrylic polymer A1 solution. The weight average molecular weight (Mw) and the number average molecular weight (Mn) of this acrylic polymer A1 were measured according to the following GPC measurement conditions and the degree of dispersion (Mw / Mn) was determined. The nonvolatile fraction (nV) and viscosity were also measured by the following methods. The measurement results are shown in Table 1 together with the monomer composition.

≪ GPC measurement condition >

Measurement apparatus: HLC-8120GPC (manufactured by Tosoh Corporation)

GPC Column Composition: The following five continuous columns (all Tosoh Corporation)

(1) TSK-GEL HXL-H (Guard column)

(2) TSK-GEL G7000HXL

(3) TSK-GEL GMHXL

(4) TSK-GEL GMHXL

(5) TSK-GEL G2500HXL

Sample concentration: 1.0 mg / cm < ³ >, diluted with tetrahydrofuran

Mobile phase solvent: tetrahydrofuran

Flow rate: 1 ml / min

Column temperature: 40 DEG C

<Method of measuring non-volatile matter>

Approximately 1 g of the acrylic copolymer solution was placed in a precisely weighed quartz crystal (n1), and the total weight (n2) was precisely weighed and then heated at 105 DEG C for 3 hours. Thereafter, the quartz crystal was allowed to stand in a desiccator at room temperature for one hour, and then precisely weighed again to measure the total weight (n3) after heating. Using the obtained weight measurement values (n1 to n3), the non-volatile content was calculated from the following formula.

Nonvolatile matter (%) = 100 x [weight after heating (n3-n1) / weight before heating (n2-n1)]

<Method of measuring viscosity>

B type viscometer at room temperature.

(Production Examples 2 to 6)

Acrylic polymers A2 to A6 were obtained in the same manner as in Preparation Example 1 except that the monomer compositions shown in Table 1 were used. The Mw, Mn, non-volatile content and viscosity of the polymer were measured in the same manner as in Production Example 1. The results are shown in Table 1.

(Comparative Production Examples 1 to 4)

Acrylic polymers B1 to B4 were obtained in the same manner as in Preparation Example 1 except that the monomer compositions shown in Table 1 were used. The Mw, Mn, non-volatile content and viscosity of the polymer were measured in the same manner as in Production Example 1. The results are shown in Table 1.

The abbreviations in the table are as follows.

BA: butyl acrylate

AA: Acrylic acid

HEA: 2-hydroxyethyl acrylate

BzA: benzyl acrylate

POA: phenoxyethyl acrylate

MEA: methoxyethyl acrylate

(Example 1)

Preparation of a polarizing plate having a pressure-sensitive adhesive layer:

(Preparation of pressure-sensitive adhesive composition)

5 parts by mass of Coronate 342 (manufactured by Nippon Polyurethane Industry Co., Ltd.), which is an isocyanurate modification of tolylene diisocyanate (TDI), was added to 100 parts by mass of the acrylic polymer A1 (solid content) of the acrylic polymer A1 solution obtained in Production Example 1, And 0.2 parts by mass of KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent were added and thoroughly mixed to obtain a pressure-sensitive adhesive composition.

(Production of polarizing plate)

After the bubbles had disappeared, the coated film was applied to a peeled polyester film using a doctor blade, and dried at 90 ° C for 3 minutes. Dried, adhered to a polarizing plate, allowed to stand at a room temperature of 23 캜 and a humidity of 50%, and aged to obtain a polarizing plate having a pressure-sensitive adhesive layer. The aging period was 1 day, 3 days, and 7 days.

(Examples 2 to 12)

A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the acrylic polymer and the crosslinking agent were changed as shown in Table 2 below. Using the obtained pressure-sensitive adhesive composition, a polarizing plate having a pressure-sensitive adhesive layer was produced in the same manner as in Example 1.

(Comparative Examples 1 to 11)

A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the acrylic polymer and the crosslinking agent were changed as shown in Table 3 below. Using the obtained pressure-sensitive adhesive composition, a polarizing plate having a pressure-sensitive adhesive layer was produced in the same manner as in Example 1.

(Test Example 1)

Among the polarizers obtained in Examples 1 to 12 and Comparative Examples 1 to 11, the durability and the light leakage preventing property were evaluated by the following methods, with the aging period being one day and seven days. The results are summarized in Tables 2 and 3.

<Evaluation method of durability>

A polarizing plate having a pressure-sensitive adhesive layer was cut to a size of 150 mm x 250 mm, and the glass plate was attached to one side of the glass plate using a laminator roll and then maintained in an autoclave adjusted at 50 캜 and 5 atm for 20 minutes to prepare a test plate. Two sheets of the same test plates were prepared and left for 500 hours under the conditions of a temperature of 60 ° C and a humidity of 95% RH (humid heat resistance) and a temperature of 85 ° C (heat resistance), and the occurrence of peeling .

(standard)

○: No foaming, peeling, or cracks observed

△: Foaming, peeling, and cracks are somewhat visible

X: Foam, peeling, and crack appear on the front side

&Lt; Evaluation method of light leakage prevention property &

Two polarizer plates each having a pressure-sensitive adhesive layer were laminated on the front and back surfaces of a 19-inch wide TN monitor (model number: BenQ FP93VW) by using a laminator roll so as to be perpendicular to each other, and then placed in an autoclave Minute, and a trial version was prepared. The prepared test plate was allowed to stand under the condition of 70 캜 for 500 hours, and light leakage was visually observed and evaluated according to the following criteria.

(standard)

○: No light leakage observed

△: Light leakage partially observed

X: Light leakage is seen on the front side

The abbreviations in the table are as follows.

L-45: TDI-based isocyanate (manufactured by Soekenkagaku Co., Ltd.)

Coronate 342: TDI isocyanurate-modified product (manufactured by Nippon Polyurethane Industry Co., Ltd.)

Coronate 2030: TDI isocyanurate (manufactured by Nippon Polyurethane Industry Co., Ltd.)

Coronate 2041: Polymeric MDI (manufactured by Nippon Polyurethane Industry Co., Ltd.)

TD-75: XDI system (manufactured by Soweki Kagaku Co., Ltd.)

E-5XM: epoxy cross-linking agent (manufactured by Soekenkagaku Co., Ltd.)

Dyuranate TPA-100: HDI isocyanurate (manufactured by Asahi Chemical Industry Co., Ltd.)

KBM-403: Silane coupling agent (Shin-Etsu Chemical Co., Ltd.)

(Test Example 2)

The polarizing plates having the pressure-sensitive adhesive layers of aged 1, 3 and 7 days obtained in Examples 1 to 12 and Comparative Examples 1 to 11 were evaluated for adhesion by the following method. The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive compositions obtained in Examples 1 to 12 and Comparative Examples 1 to 11 was evaluated for gel fraction on aging 1, 3 and 7 by the following method. The results are shown in Table 4.

&Lt; Measurement method of adhesive force >

A polarizing plate having a pressure-sensitive adhesive layer was cut into a size of 70 mm x 25 mm to prepare a test piece. The polyester film was peeled off from the test piece and attached to one side of the glass plate using a laminator roll, and then held in an autoclave adjusted to 5 atmospheric pressure at 50 캜 for 20 minutes. Next, the substrate was left for one hour under an environment of 23 ° C and 50% RH, and pulled at a speed of 300 mm / min in a 90 ° direction to measure the peel strength.

<Method of measuring gel fraction>

The obtained pressure-sensitive adhesive composition was coated on the surface of the polyester subjected to the peeling treatment so as to have a thickness of 20 탆 after drying, and then the polyester film peeled off on the other surface was stuck together and dried at 23 캜 and 50% Aged for 3 or 7 days to prepare a test piece. Approximately 0.1 g of a pressure sensitive adhesive was taken from the test piece into a sample bottle, and 30 cc of ethyl acetate was added and shaken for 24 hours. The content of the sample bottle was filtered with a 200 mesh stainless steel net, Dried, and the dry weight was measured.

Gel fraction (%) = (dry weight / weight of the pressure-sensitive adhesive) x 100

In the polarizing plates of Comparative Examples 1 to 11, light leakage preventing properties and durability were not sufficient at one day of maturing at room temperature, whereas light leakage preventing properties and durability of the polarizing plates of Examples 1 to 12 were good at 1 day of maturing, Adhesion and gel fraction were also stable at 1 day of aging, and these performances remained stable.

The pressure-sensitive adhesive composition of the present invention can effectively prevent light leakage by aging in a short period of time, and can form a pressure-sensitive adhesive layer having excellent durability and capable of suppressing the occurrence of foaming and peeling even under high temperature and high humidity conditions. Therefore, it can be suitably used as a pressure-sensitive adhesive composition for a polarizing plate.

Claims (8)

The following components (A) and (B)
(A) 100 parts by mass of a (meth) acrylic polymer having a weight average molecular weight of 300,000 to 1,500,000 copolymerized with at least 1% by mass of a carboxyl group-containing monomer and 0.05-1% by mass of a hydroxyl group-
(B) a tolylene diisocyanate compound having an isocyanurate structure in an amount of 6 to 20 parts by weight
And a gel fraction of 75 to 90% as determined by the following measuring method.
<Method of measuring gel fraction>
The pressure-sensitive adhesive composition for a polarizing plate was coated on the surface of the polyester which had been peeled to a thickness of 20 mu m after drying, and then the polyester film peeled off from the other surface was stuck to the surface of the polyester and dried at 23 DEG C and 50% The test pieces were aged for a day. Approximately 0.1 g of a pressure sensitive adhesive was taken from the test piece into a sample bottle, and 30 cc of ethyl acetate was added and shaken for 24 hours. The content of the sample bottle was filtered with a 200 mesh stainless steel net, Dried, and the dry weight was measured.
Gel fraction (%) = (dry weight / weight of the pressure-sensitive adhesive) x 100 The positive photosensitive resin composition according to claim 1, which further comprises one or more crosslinking agents selected from the group consisting of a tolylene diisocyanate crosslinking agent (excluding those having an isocyanurate structure), an epoxy crosslinking agent and an aziridine crosslinking agent By weight based on the total weight of the pressure-sensitive adhesive composition. The composition according to claim 2, wherein the component (C) is a tolylene diisocyanate crosslinking agent (except for having an isocyanurate structure) and the compounding ratio of the component (C) to the component (B) is from 1: 3 to 3: A pressure-sensitive adhesive composition for a polarizing plate. The pressure-sensitive adhesive composition for a polarizing plate according to any one of claims 1 to 3, further comprising a component (D) silane coupling agent. A pressure-sensitive adhesive sheet for a polarizing plate characterized by comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate according to any one of claims 1 to 5 on at least one surface of a support. Wherein a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate according to claim 1 is provided on at least one surface of the polarizing film. The following components (A) and (B)
(A) 100 parts by mass of a (meth) acrylic polymer having a weight average molecular weight of 300,000 to 1,500,000 copolymerized with at least 1% by mass of a carboxyl group-containing monomer and 0.05-1% by mass of a hydroxyl group-
(B) a tolylene diisocyanate compound having an isocyanurate structure in an amount of 6 to 20 parts by weight
And a polarizing plate provided on at least one surface of the polarizing film with a pressure-sensitive adhesive layer having a gel fraction of 75 to 90% determined by the following measuring method is formed on the substrate surface of the liquid crystal cell A method of manufacturing a liquid crystal device.
<Method of measuring gel fraction>
The pressure-sensitive adhesive composition for a polarizing plate was coated on the surface of the polyester which had been peeled to a thickness of 20 mu m after drying, and then the polyester film peeled off from the other surface was stuck to the surface of the polyester and dried at 23 DEG C and 50% The test pieces were aged for a day. Approximately 0.1 g of a pressure sensitive adhesive was taken from the test piece into a sample bottle, and 30 cc of ethyl acetate was added and shaken for 24 hours. The content of the sample bottle was filtered with a 200 mesh stainless steel net, Dried, and the dry weight was measured.
Gel fraction (%) = (dry weight / weight of the pressure-sensitive adhesive) x 100 The following components (A) and (B)
(A) 100 parts by mass of a (meth) acrylic polymer having a weight average molecular weight of 300,000 to 1,500,000 copolymerized with at least 1% by mass of a carboxyl group-containing monomer and 0.05-1% by mass of a hydroxyl group-
(B) a tolylene diisocyanate compound having an isocyanurate structure in an amount of 6 to 20 parts by weight
And a polarizing plate provided on at least one surface of the polarizing film with a pressure-sensitive adhesive layer having a gel fraction of 75 to 90% determined by the following measuring method is formed on the substrate surface of the liquid crystal cell (Method for Reducing Light Leakage in a Liquid Crystal Display).
<Method of measuring gel fraction>
The pressure-sensitive adhesive composition for a polarizing plate was coated on the surface of the polyester which had been peeled to a thickness of 20 mu m after drying, and then the polyester film peeled off from the other surface was stuck to the surface of the polyester and dried at 23 DEG C and 50% The test pieces were aged for a day. Approximately 0.1 g of a pressure sensitive adhesive was taken from the test piece into a sample bottle, and 30 cc of ethyl acetate was added and shaken for 24 hours. The content of the sample bottle was filtered with a 200 mesh stainless steel net, Dried, and the dry weight was measured.
Gel fraction (%) = (dry weight / weight of the pressure-sensitive adhesive) x 100