JPH07133471A - Acrylic adhesive composition - Google Patents

Abstract

PURPOSE:To provide the composition comprising a specific acrylic polymer, a crosslinking agent, and a block copolymer, excellent in adhesion to glass plates, moisture resistance, and repeelability, and suitable for laminating and fixing a plastic optical sheet such as a reflecting plate to a glass cell. CONSTITUTION:This composition comprises (A) 100 pts.wt. of an acrylic polymer consisting mainly of an alkyl (meth)acrylate, having a weight-average mol.wt. of >=500000, and a weight-average mol.wt./number-average mol.wt. of <=4.0, (B) 0.001-5 pts.wt. of a crosslinking agent selected from an organic compound having multi-functional groups, an organic metal compound, and a metal salt, and (C) 0.01-10 pts.wt. of a block copolymer comprising hydrophilic segments and hydrophobic segments.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic pressure-sensitive adhesive composition, and more particularly to an acrylic pressure-sensitive adhesive for fixing a synthetic resin optical material such as a retardation plate to a transparent support such as glass. It relates to a composition.

[0002]

2. Description of the Related Art Conventionally, liquid crystal display panels have been used for display applications. As a material forming the liquid crystal display plate, a material in which a retardation plate made of stretched polycarbonate and a polarizing plate made of polyvinyl alcohol are sequentially laminated on the inner surface of a glass cell facing outward is used. Adhesives are used as a method of fixing each laminate in the liquid crystal display plate, but when the liquid crystal display plate is left under high temperature and high humidity, bubbles are generated in the adhesive layer or each layer is peeled off. As a pressure-sensitive adhesive that more firmly adheres to the glass cell surface, an acrylic pressure-sensitive adhesive containing an epoxy group-containing silane compound has been proposed (JP-A-4-268502).

The acrylic pressure-sensitive adhesive has the effect of suppressing the phenomena such as foaming and peeling of the pressure-sensitive adhesive layer under high temperature and high humidity. However, when sticking to the glass cell surface, if there is air or dust entrapped, it is necessary to peel off the retardation plate from the glass cell surface once and attach a new retardation plate again. Before peeling off the phase difference plate,
When stored for a long time, the adhesion layer of the pressure-sensitive adhesive layer progresses to the glass cell surface, the peeling strength becomes too high, and it is not only difficult to peel off, but adhesive residue is left on the glass cell surface even after peeling off. There was a problem.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to improve the adhesiveness between an optical resin plate such as a polarizing plate or a retardation plate and a glass cell. Excellent in foaming resistance and peeling resistance under high temperature and high humidity, and after being attached to a glass cell, even after a certain amount of time has passed, it is relatively easy from the glass cell surface to an optical resin plate such as a retarder. An object of the present invention is to provide a pressure-sensitive adhesive composition that can be peeled off and does not cause adhesive residue phenomenon and can be suitably used for fixing a glass plate and an optical resin plate.

[0005]

The acrylic pressure-sensitive adhesive composition of the present invention comprises an acrylic polymer (A) having an alkyl (meth) acrylate as a main component, a cross-linking agent (B), a hydrophilic segment and a hydrophobic segment. It consists of a block copolymer (C) consisting of segments.

The acrylic polymer (A) is a copolymer obtained by copolymerizing an alkyl (meth) acrylate as a main component with another vinyl monomer.
Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate,
Examples thereof include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate and benzyl (meth) acrylate.

As the vinyl monomer, a monomer having a carboxyl group such as (meth) acrylic acid, crotonic acid, maleic acid and itaconic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate. In addition to monomers having a hydroxyl group such as vinyl acetate, vinyl acetate, styrene, N-vinylpyrrolidone, acrylonitrile, tetrafurfuryl acrylate, polyethylene glycol acrylate and the like.

The compounding ratio of the above components is preferably 1 to 60 parts by weight of vinyl monomer to 100 parts by weight of alkyl (meth) acrylate. This is because if it is less than 1 part by weight, the adhesive strength will be insufficient, and if it exceeds 60 parts by weight, the initial adhesive strength will be impaired. The weight average molecular weight (M _W ) of the acrylic polymer must be 500,000 or more, and the ratio (M _W / M _n ) of the weight average molecular weight to the number average molecular weight must be 4.0 or less. When the weight average molecular weight (M _W ) is 500,000 or less, or the ratio of the weight average molecular weight to the number average molecular weight (M _W / M _n ) is 4.0 or less, heat resistance is poor. is there.

Examples of the method for polymerizing the acrylic polymer include radical polymerization utilizing solution polymerization, bulk polymerization, emulsion polymerization and the like. As the polymerization initiator, conventionally known ones such as benzoyl peroxide and azobisisobutyronitrile can be used.

A chain transfer agent such as lauryl mercaptan may be added to adjust the molecular weight of the polymer.

The cross-linking agent (B) is used for cross-linking the acrylic polymer (A), and at least one selected from the group consisting of organic compounds having polyfunctional groups, organometallic compounds and metal salts. used. Examples of the organic compound include N, N'-hexamethylene-
Aziridine compounds such as 1,6 bis (1-aziridinecarboxamide), trimethylpropane-tri-β-aziridinylpropionate, bisisophthaloyl-1- (2-methylaziridine), tolylene diisocyanate, hydrogenation Isocyanate compounds such as tolylene diisocyanate, tolylene diisocyanate adduct of trimethylol propane, triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate, isophorone diisocyanate, bisphenol A, epichlorohydrin type epoxy resin, ethylene glycol diglycidyl Ether, triglycidyl ether, 1,6-hexanediol diglycidyl ether,
Trimethylpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine, N, N, N ',
N'-tetraglycidyl m-xylene diamine, 1,3
Examples include epoxy compounds such as -bis (N, N'-diglycidylaminomethyl) cyclohexane, aldehyde compounds such as glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardialdehyde, and melamine resin.

The above-mentioned organometallic compound is a coordination compound of acetylacetone or acetoacetate ester of polyvalent metal such as aluminum, iron, copper, tin, zinc, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium. Is mentioned.

Further, as the metal salt, cupric chloride,
Examples thereof include aluminum chloride, ferric chloride, aluminum sulfate, copper sulfate, stannic chloride, zinc chloride, nickel chloride, magnesium chloride, chromium acetate, and copper acetate.

The amount of the crosslinking agent (B) added is 0.001 to 5 parts by weight based on 100 parts by weight of the acrylic polymer.
When the amount is less than 0.001 part by weight, the heat resistance is poor, and when the amount is more than 5 parts by weight, the releasability deteriorates.

The block copolymer (C) is composed of a hydrophilic segment and a hydrophobic segment. The hydrophilic segment is, for example, a polymer composed of a monomer having a hydroxyl group such as polyvinyl alcohol and 2-hydroxyethyl (meth) acrylate, and the hydrophobic segment is a polymer having an alkyl (meth) acrylate as a main component.

As the block copolymer (C), MODIPER HM18 (manufactured by NOF CORPORATION) and MODIPER HM5
00 (manufactured by Nippon Oil & Fats Co., Ltd.) is on the market. The amount of the block copolymer (C) added is the acrylic polymer (A) 10
It is 0.01 to 10 parts by weight with respect to 0 parts by weight. 0.0
If the amount is less than 1 part by weight, the removability from glass is deteriorated, and if it exceeds 10 parts by weight, the heat resistance is deteriorated.

[0017]

The acrylic pressure-sensitive adhesive of the present invention has a weight average molecular weight of 500,000 or more and a ratio (M _W / M _n ) of the weight average molecular weight to the number average molecular weight of 4.0 or less, and therefore has an adhesive force. The drop in the elastic modulus of the adhesive at high temperatures can be suppressed without dropping it. In addition, since the block copolymer consisting of the hydrophilic segment and the hydrophobic segment is added, the progress of adhesion of the pressure-sensitive adhesive layer to the glass surface can be suppressed, and re-peeling from the glass surface can be easily performed.

[0018]

EXAMPLES Examples of the present invention will be described below.

Examples 1 to 3 and Comparative Examples 1 to 4 (Preparation of Acrylic Polymers A to E) According to the blending composition shown in Table 1, 2-ethylhexyl acrylate, n-
A prescribed number of parts of butyl acrylate, acrylic acid, lauryl mercaptan and ethyl acetate as a solvent were charged, dissolved by stirring, and the temperature was maintained at 70 ° C., and then 0.03 part by weight of benzoyl peroxide was added. Then, the mixture was reacted at 70 ° C. to obtain an acrylic polymer. The weight average molecular weight (M _W ) and number average molecular weight (M _n ) of the acrylic polymer were determined by gel permeation chromatography using standard crosslinked polystyrene as a standard, tetrahydrofuran as a separating agent, and detection using a refractometer. . The results are also shown in Table 1.

[0020]

[Table 1]

(Preparation of Acrylic Adhesive Composition) According to the composition shown in Table 2, the above acrylic polymer,
A block copolymer consisting of N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide), 2-hydroxyethylmethacrylate homopolymer segment and methylmethacrylate homopolymer segment (manufactured by NOF Corporation, trade name "MODIPA HM18" )) And a 2-hydroxyethylmethacrylate homopolymer segment and a block copolymer consisting of a copolymer segment of methylmethacrylate and acrylic acid (manufactured by NOF CORPORATION, trade name "MODIPER H500") are uniformly stirred to obtain an acrylic pressure-sensitive adhesive. A composition was obtained.

(Preparation of Acrylic Pressure-Sensitive Adhesive Composition Laminate) Each of the obtained acrylic pressure-sensitive adhesive compositions was coated on a silicon-treated polyester film having a thickness of 38 μm.
It was applied and dried with an applicator to form a pressure-sensitive adhesive layer having a thickness of 25 μm. Then, a thickness of 15 is applied to the pressure-sensitive adhesive layer surface side.
0 μm, stretched polyvinyl alcohol-based polarizing plate (LLC
₂ -9218, by Sanritz) and a thickness of 85μm,
Stretched polycarbonate type retarder (manufactured by Sanritz)
Laminate each with a laminator to make a laminated body,
An adhesive layer was formed on the polarizing plate and the retardation plate.

After leaving each of the obtained laminates at room temperature for 1 week,
The polyester film cut into a size of 75 × 150 mm and treated with silicon was peeled off, and the pressure-sensitive adhesive surface side of the retardation plate was attached to a glass plate. Further, the pressure-sensitive adhesive surface of the polarizing plate was attached to the back surface of the retardation plate with a laminator so that air bubbles did not enter, and a test piece of a laminated body composed of a polarizing plate, a retardation plate, and a glass plate via an adhesive layer was obtained. It was

(Evaluation of Foaming, Peelability, Adhesiveness to Glass Plate and Adhesive Remaining Property) As an evaluation of foaming property, after leaving the above test piece in a thermostat at 80 ° C. for 500 hours, the change in appearance due to foaming is as follows. It evaluated according to the evaluation point of.

10 in the adhesive layer of the glass plate and the retardation plate
1 to 20 to 40μ when bubbles above μm are not recognized
2 when the number of m bubbles is small, and 20 to 40
The case where a large number of air bubbles with a size of μm was recognized was set to 3.

Further, as an evaluation of the peeling property, each test piece was left in a thermostatic chamber at 60 ° C. and 90% relative humidity for 500 hours, and then the appearance change due to peeling was evaluated according to the following evaluation points.

No peeling from the glass plate near the edge of the retardation plate was observed at all, 1, peeling of 0.5 mm or less at the edge was observed at 2, and 0.5 m near the edge.
The case where peeling of m or more was recognized was set to 3.

Further, as an evaluation of removability from the glass plate, each test piece was left in a constant temperature bath at 90 ° C. for 2 hours,
Further, it was allowed to stand at room temperature for 3 days, and a peel test was performed in the direction of 180 ° C. from the glass plate, and the degree of adhesive residue on the glass surface after peeling was visually confirmed. Table 2 shows the above evaluation results.
It was shown to.

[0029]

[Table 2]

[0030]

The acrylic pressure-sensitive adhesive composition of the present invention has excellent adhesiveness to a glass plate, heat resistance and moisture resistance, and when a resin plate such as a retardation plate is laminated on the glass plate, it is exposed to high temperature and high humidity. However, a laminate without foaming or peeling can be obtained. Further, since there is no progress of adhesion to the glass surface, re-peeling from the glass surface or the like can be easily performed when re-adhesion is necessary.

Therefore, it is possible to eliminate the yield due to a defective product generated after the bonding and also reduce the yield of the defective product generated during the bonding. The acrylic pressure-sensitive adhesive composition of the present invention having the above-mentioned performance,
In particular, it can be suitably used as an adhesive composition for laminating and fixing a plastic optical sheet material such as a retardation plate or a polarizing plate on a glass cell.

Claims (1)

[Claims] 1. An alkyl (meth) acrylate as a main component
And its weight average molecular weight (M_W) Is more than 500,000 and the weight
Ratio of average molecular weight to number average molecular weight (M_W/ M _n) Is 4.
100 parts by weight of an acrylic polymer (A) of 0 or less
And organic compounds, organometallic compounds and
And at least one selected from the group consisting of metal salts
Crosslinking agent (B) 0.001 to 5 parts by weight, and hydrophilic segment
Block copolymer consisting of menthol and hydrophobic segment
(C) 0.01-10 parts by weight of acrylic adhesive
Composition.