JPH0834963A - Acrylic tacky agent composition - Google Patents

Abstract

PURPOSE:To obtain the composition useful in the field of optical parts, etc., having excellent adhesiveness to glass plates, excellent heat resistance and moisture resistance, providing a laminate free from foaming and peeling even under bad conditions of high temperature and high humidity, readily removable from a glass surface, comprising a specific acrylic polymer, a defoamer, a removing agent and a cross-linking agent. CONSTITUTION:This composition comprises (A) 100 pts.wt. of an acrylic polymer consisting essentially of an alkyl (meth)acrylate, having >=500,000 weight-average molecular weight and <=4.0 ratio (Mw/Mn) of weight-average molecular weight and number-average molecular weight, (B) 0.01-5 pts.wt. of a defoamer composed of a dimethylsilicone oil of formula I ((n) is 0-5,000) or a modified silicone oil obtained by replacing part of its side chain with another organic group, (C) 0.01-5 pts.wt. of a removing agent composed of a methylhydrogen silicone oil of formula II ((m) and (n) are >=1; R1 and R2 are each H or CH3) and (D) 0.001-5 pts.wt. of a cross-linking agent.

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 specifically, it is used for adhering and fixing a polarizing plate, a retardation plate or the like to a transparent adherend such as a glass plate. It relates to a suitable acrylic pressure-sensitive adhesive 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 laminated body in which a retardation plate and a polarizing plate are sequentially laminated on one surface of a glass cell is usually used. In this laminate, a pressure-sensitive adhesive having excellent transparency is used as a method for fixing the retardation plate and the polarizing plate, but when the liquid crystal display plate is left under high temperature and high humidity, bubbles are generated in the pressure-sensitive adhesive. There is a problem in that delamination occurs due to the occurrence of moisture or the intrusion of water from the interface between the glass plate and the pressure-sensitive adhesive layer.

Therefore, in order to solve this problem, a method of balancing the adhesive force and the elastic modulus by adjusting the molecular weight and the degree of crosslinking of the pressure-sensitive adhesive (JP-A-3-12471).
(See Japanese Patent Application Laid-Open No. 4-223403), or an acrylic pressure-sensitive adhesive containing a silane compound having an epoxy group to strengthen the adhesive force with a glass cell (see Japanese Patent Application Laid-Open No. 4-223403).

However, these conventional techniques have limitations, and when left for a long time in a more severe environment, for example, at a high temperature of 100 ° C. or higher, a low molecular weight component slightly contained in the adhesive or It was not possible to prevent bubbles from being generated by the residual solvent.

Further, after a retardation plate or a polarizing plate is attached to the glass cell surface to form a laminated body, in the inspection step, if there is entrainment of air or dust in the laminating step, the glass cell surface may be removed. Although the phase difference plate is peeled off and a new phase difference plate is attached again, it is stored at a high temperature for a certain time before the phase difference plate is peeled off, so the adhesion of the adhesive layer to the glass cell surface is promoted. However, there is a problem that the peeling strength becomes too high, the peeling is difficult, and the adhesive residue occurs.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, and in the adhesiveness between a glass cell and an optical component such as a polarizing plate or a retardation plate, an inspection process after bonding Under storage conditions up to, it is possible to relatively easily peel off the optical component from the glass cell surface, and there is no adhesive residue at that time, and especially when the above laminate is used as a liquid crystal display panel or the like, It is an object of the present invention to provide an acrylic pressure-sensitive adhesive composition that adheres strongly to an adherend without foaming even under adverse conditions of high temperature and high humidity and does not cause delamination.

[0007]

The acrylic pressure-sensitive adhesive composition of the present invention comprises (A) an acrylic polymer containing an alkyl (meth) acrylate as a main component, (B) an antifoaming agent, and
It consists of (C) a re-release agent and (D) a cross-linking agent.

The acrylic polymer (A) containing alkyl (meth) acrylate as a main component, which is the main component of the acrylic pressure-sensitive adhesive composition of the present invention, contains (meth) acrylic acid alkyl ester (a) as a main component. It is a copolymer obtained by copolymerizing with another vinyl monomer (b).

As the (meth) acrylic acid alkyl ester (a), methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate,
2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, octyl (meth) acrylate, decyl (meth)
Examples thereof include alkyl (meth) acrylates having an alkyl group having 11 or less carbon atoms, such as acrylate and benzyl (meth) acrylate.

As the vinyl monomer (b),
A carboxylic acid-containing monomer such as (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic acid,
Those that react with the crosslinking agent (D) described later to enhance the cohesive force of the pressure-sensitive adhesive are suitably used. In addition, monomers having a high glass transition point such as vinyl acetate, styrene, N-vinylpyrrolidone and acrylonitrile, hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate, and tetraflu Monomers having a low glass transition point such as furyl acrylate and polyethylene glycol acrylate are also used.

The composition of the above copolymer is preferably 1 to 60 parts by weight of the vinyl monomer (b) per 100 parts by weight of the (meth) acrylic acid alkyl ester (a), and less than 1 part by weight. In the case of, the adhesive strength is insufficient,
If it exceeds 60 parts by weight, the initial adhesive strength tends to decrease.

In the present invention, the acrylic polymer (A) has a weight average molecular weight (Mw) of 500,000 or more, and the ratio of the weight average molecular weight to the number average molecular weight (Mw /
Mn) needs to be 4.0 or less. If the weight average molecular weight (Mw) is less than 500,000 or the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) exceeds 4.0, the adhesiveness is poor under bad conditions of high temperature and high humidity. Because.

Examples of the method for polymerizing the acrylic polymer (A) include radical polymerization methods utilizing solution polymerization, bulk polymerization, emulsion polymerization and the like. Further, as the polymerization initiator at this time, conventionally known ones such as benzoyl peroxide and azobisisobutyronitrile can be used,
It may be a method of polymerizing by irradiation with light or radiation. A chain transfer agent such as lauryl mercaptan may be added to adjust the molecular weight of the acrylic polymer (A).

The defoaming agent (B) is used as one of the constituent components of the acrylic pressure-sensitive adhesive composition of the present invention. The defoaming agent (B) is an additive used to suppress entrainment of foam and to crush generated air bubbles during production or use of the pressure-sensitive adhesive composition, and is represented by the general formula (1). Dimethyl silicone oil or a modified silicone oil in which a part of its side chain is replaced with another organic group.
In this case, it is most effective to use a fluorine-modified silicone oil such as trifluoropropyl silicone or perfluorooctylmethyl silicone.

[0015]

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The amount of the defoaming agent (B) added should be within the range of 0.01 to 5 parts by weight when the acrylic polymer (A) is 100 parts by weight. If it is less than 0.01 parts by weight, the desired defoaming effect cannot be obtained, and if it exceeds 5 parts by weight, the silicone oil excessively present in the pressure-sensitive adhesive tends to warp and increase foaming. is there.

A removable agent (C) is used as one of the constituent components of the acrylic pressure-sensitive adhesive composition of the present invention. The re-peeling agent (C) is an additive used for ensuring ease of re-peeling and moisture resistance, and is composed of methyl hydrogen silicone oil represented by the general formula (2).
By using the re-peeling agent (C), a water-repellent thin film is formed between the pressure-sensitive adhesive layer and the adherend such as a glass cell, and water and moisture can be prevented from entering the interface.

[0018]

[Chemical 4]

The amount of the removable agent (C) added is 0.01 when the acrylic polymer (A) is 100 parts by weight.
It should be within the range of 5 parts by weight. If the amount is less than 0.01 part by weight, the removability from the glass cell, the moisture resistance and other effects are weakened, and if the amount exceeds 5 parts by weight, the heat resistance tends to decrease.

A crosslinking agent (D) is used as one of the constituent components of the acrylic pressure-sensitive adhesive composition of the present invention. This cross-linking agent (D) is used for enhancing the cohesive force and heat resistance of the pressure-sensitive adhesive layer, and is mainly one selected from the group consisting of organic compounds having a polyfunctional group, organometallic compounds and metal salts, or Two or more types are used.

The organic compound having a polyfunctional group is roughly divided into three groups, an aziridine compound, an isocyanate compound and an epoxy compound. Specific examples include N, N′-hexamethylene-1,6bis (1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, bisisophthaloyl-1 (2-methyl Aziridine compounds such as aziridine), tolylene diisocyanate, hydrogenated tolylene diisocyanate, tolylene diisocyanate adduct of trimethylolpropane, triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, etc. Isocyanate compound, bisphenol A, Epchlorhydrin type epoxy resin,
Ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine,
Epoxy compounds such as N, N, N ′, N′-tetraglycidyl m-xylenediamine, 1,3 bis (N, N′-diglycidylaminomethyl), and cyclohexane. In addition to these three groups, amino resins, melamine resins and the like are also included.

As the organometallic compound, aluminum,
Examples thereof include coordination compounds of acetylacetone and acetoacetate of polyvalent metals such as iron, copper, tin, zinc, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium.

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

The amount of the crosslinking agent (D) added is 0.001 to 5 when the acrylic polymer (A) is 100 parts by weight.
It must be part by weight. If it is less than 0.001 part by weight, the heat resistance will be poor, and if it exceeds 5 parts by weight, the moisture resistance will be poor.

[0025]

The acrylic pressure-sensitive adhesive composition of the present invention comprises an acrylic polymer having a weight average molecular weight of 500,000 or more and a ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight of 4.0 or less. Since A) is the main component, high temperature,
It has excellent adhesiveness under adverse conditions of high humidity.

Further, since the defoaming agent (B) is contained as an additive, it exerts the function of crushing the foam generated under high temperature conditions, can prevent the generation of bubbles, and can further remove the re-peeling agent ( Since C) is included, a water-repellent layer is formed at the interface between the pressure-sensitive adhesive layer and the adherend, and water and moisture are prevented from entering the interface, which suppresses adhesion promotion and re-peeling. Easy and
Further, since the crosslinking agent (D) is contained, the cohesive force and heat resistance of the pressure-sensitive adhesive layer are improved, and the pressure-sensitive adhesive layer serves to further promote the above-mentioned excellent quality characteristics.

[0027]

EXAMPLES Examples of the present invention will be described in detail below.

(Examples 1 to 4 and Comparative Examples 1 to 4) (Preparation of acrylic polymers A to D) According to the blending composition shown in Table 1, a stirrer, a reflux condenser, a thermometer, a dropping funnel and nitrogen gas introduction. In a five-necked flask equipped with a neck,
Ethylhexyl acrylate, n-butyl acrylate, acrylic acid, lauryl mercaptan as a chain transfer agent, and ethyl acetate as a solvent were charged in a predetermined number of parts so that the total weight was 1 kg, stirred and dissolved, and then about 30 with nitrogen gas. Purge for a minute to eliminate oxygen dissolved in the monomer solution. Then, the air in the flask was replaced with nitrogen gas, and the temperature was maintained at 70 ° C., and then 0.03 parts by weight of benzoyl peroxide as a thermal polymerization initiator was added to 3 cc.
Dissolved in ethyl acetate and added dropwise with a dropping funnel. After the initiator was charged, the temperature was maintained at 70 ° C. for 15 hours to obtain an acrylic polymer.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the above acrylic polymer were determined by gel chromatography using standard crosslinked polystyrene as a standard, tetrahydrofuran as a separating agent, and a refractometer for detection. It was measured. Table 1 shows the results.

[0030]

[Table 1]

(Preparation of Acrylic Adhesive Composition) The above acrylic polymer solution was diluted with ethyl acetate so that the solid content was 40% by weight, and then the acrylic polymer, N, N'-hexamethylene-
1,6-bis (1-aziridinecarboxamide) (Mutual Yakuhin Co., Ltd.), trimethylolpropane adduct of tolylene diisocyanate (Nippon Polyurethane Co., Ltd.), dimethyl silicone oil (Shin-Etsu Silicone KF-9)
6,1000 cps / 25 ° C), methyl hydrogen silicone oil (KF-99, manufactured by Shin-Etsu Silicone Co., Ltd.)
1000 cps / 25 ° C.), [only in the case of Comparative Example 2, further, γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicone Co., Ltd.)] is added in a predetermined number and mixed and stirred to prepare an acrylic pressure-sensitive adhesive composition. Got

(Preparation of Acrylic Pressure-Sensitive Adhesive Composition Laminate) The obtained solutions of the respective acrylic pressure-sensitive adhesive compositions were applied on a silicon-treated polyethylene terephthalate film having a thickness of 38 μm and dried,
An adhesive layer having a thickness of 25 μm was formed.

Then, a thickness of 150 μm is provided on the pressure-sensitive adhesive layer side.
Polarizer (Sanritz Co., stretched polyvinyl alcohol, LLC ₂ -9,218) and a phase difference plate having a thickness of 85 .mu.m (Sanritz Co., stretching a polycarbonate-based) and with the bonded respectively laminator laminate polarizer And an adhesive layer was formed on the retardation plate.

(Preparation of Test Pieces for Measuring Physical Properties) Each of the obtained laminates was left at room temperature for 1 week, cut into a size of 75 × 150 mm, the siliconized polyester film was peeled off, and a retardation plate was prepared. 100 x 200 mm on the adhesive layer side
It was attached to a glass plate of the size. Furthermore, the pressure-sensitive adhesive layer side of the polarizing plate was attached to the back surface of the retardation plate with a laminator so that air bubbles would not enter. Thus, a test piece (No. 1) of a laminate including a retardation plate-glass plate with an adhesive layer interposed therebetween and a polarizing plate-retardation plate-glass plate with an adhesive layer interposed therebetween was obtained.

Each of the obtained laminates was allowed to stand at room temperature for 1 week, then cut into a size of 25 × 150 mm, the siliconized polyester film was peeled off, and the pressure-sensitive adhesive layer side of the retardation plate was attached to one end thereof. Was displaced inward from the edge of the glass plate, and the other end was offset from the edge of the glass plate to the outside, and the glass plate having a size of 40 × 100 mm was attached. Furthermore, the pressure-sensitive adhesive layer side of the polarizing plate was attached to the back surface of the retardation plate with a laminator so that air bubbles would not enter.
Thus, a test piece (No. 2) of a laminate composed of a retardation plate-glass plate with an adhesive layer interposed therebetween and a polarizing plate-retardation plate-glass plate with an adhesive layer interposed therebetween was obtained.

(Evaluation of Foaming, Peelability, Adhesiveness to Glass Plate, and Adhesive Remaining Property) As an evaluation of foaming property, a test piece (No. 1) was placed on a stainless steel stand and left in a thermostat at 100 ° C. for 500 hours. After that, the change in appearance due to foaming was evaluated according to the following evaluation points. 10 μm in the pressure-sensitive adhesive layer between the glass plate and the retardation plate or the retardation plate and the glass plate
When the above bubbles are not recognized = 1, when a small number of bubbles of 20 to 40 μm are recognized = 2, and when a large number of bubbles of 20 to 40 μm are recognized = 3.

As an evaluation of peelability, a test piece (1)
After being left for 500 hours in a thermostat at 60 ° C. and 90% relative humidity, the appearance change due to peeling was evaluated according to the following evaluation points. No peeling from the glass plate in the vicinity of the edge of the phase difference plate = 1, peeling of 0.5 mm or less at the edge = 2, peeling of 0.5 mm or more near the edge was observed Things = 3.

As an evaluation of the adhesive strength to the glass plate and the adhesive residue, the test piece (No. 2) was placed on a stainless steel stand, left in a constant temperature bath at 90 ° C. for 2 hours, and then left at room temperature for 3 days. 1 from glass plate using Tensilon
The peeling strength (g / 25 mm) was measured by peeling at an angle of 80 ° and a pulling speed of 300 mm / min, and the degree of adhesive residue on the glass surface after peeling was visually confirmed. The above evaluation results are shown in Table 2.

[0039]

[Table 2]

[0040]

Industrial Applicability The acrylic pressure-sensitive adhesive composition of the present invention has excellent adhesiveness to a glass plate, heat resistance and moisture resistance, and when an optical component such as a retardation plate is laminated on the glass plate, it is exposed to high temperature and high humidity. It is possible to obtain a laminate which does not foam or peel even under adverse conditions. 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 even when re-adhesion is necessary.

Therefore, it is possible to easily perform re-peeling necessary for re-bonding due to entrapment of air bubbles after mixing and mixing of dust, and it is possible to reuse the glass cell.

Since it has the above-mentioned properties, the acrylic pressure-sensitive adhesive composition of the present invention is particularly suitable as a pressure-sensitive adhesive composition for laminating and fixing optical components such as a retardation plate and a polarizing plate on a glass cell. Can be used.

Claims (1)

[Claims] 1. A main component of (A) an alkyl (meth) acrylate having a weight average molecular weight of 500,000 or more, and a ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight of 4.
100 parts by weight of an acrylic polymer of 0 or less, (B)
0.01 to 5 parts by weight of a defoaming agent represented by the general formula (1), which comprises dimethyl silicone oil or a modified silicone oil in which a part of the side chain thereof is replaced with another organic group, (C) the general formula ( An acrylic pressure-sensitive adhesive composition represented by 2) comprising 0.01 to 5 parts by weight of a re-release agent composed of methyl hydrogen silicone oil and 0.001 to 5 parts by weight of (D) a cross-linking agent. Embedded image Embedded image