JPH07331209A - Acrylic tack agent composition - Google Patents

Abstract

PURPOSE:To obtain an acrylic tack agent composition causing no foaming and debonding even at elevated temperatures and humidities when a glass plate is laminated with an optical resin plate therethrough, also retaining its stable quality even after stored for a long period, and capable of easily re-releasing the optical resin plate when necessary for its laminating again because of developing no bonding enhancement to the glass plate surface. CONSTITUTION:This acrylic tack agent composition is such that the base polymer has a weight-average molecular weight (Mw) of >=500000 with the ratio of the weight-average molecular weight to number-average molecular weight (Mn):(Mw/Mn) being <=4.0 and is produced by copolymerization between (A) 100 pts.wt. of a (meth)acrylic 2-11C alkyl ester, (B) 1.0-60 pts.wt. of a monomer copolymerizable with the component A and (C) 0.1-4.9 pts.wt. of a (meth)acrylic >=12C alkyl ester.

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 fixing a synthetic resin optical material such as a polarizing plate and a retardation plate on a translucent support such as glass. The present invention relates to an 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 for forming the liquid crystal display plate, usually, a glass cell having an inner layer of a polarizing plate made of polyvinyl alcohol or the like, or a layered product of a retardation plate made of stretched polycarbonate or the like and the above polarizing plate are sequentially used. Has been.

In such a liquid crystal display plate, an adhesive is used as a method for fixing a retardation plate or a polarizing plate.
When this is left under high temperature and high humidity, there are problems that bubbles are generated in the pressure-sensitive adhesive layer and the layers are separated. Therefore, as a pressure-sensitive adhesive that adheres more strongly to the glass surface, a method has been adopted in which the polymer is adjusted to increase the glass transition temperature of the acrylic pressure-sensitive adhesive to increase the shear adhesive strength with the adherend.

However, when air or dust is entrained when the retardation plate or the polarizing plate is attached to the glass cell surface, the retardation plate or the like is peeled off from the glass cell surface and a new retardation is again provided. Although there is an inspection process for re-adhering plates etc., up to this process the laminated plate is stored at high temperature for a certain period of time, so adhesion of the adhesive layer to the glass cell surface progresses, not only difficult to peel off, but also peeled off There was a problem that an adhesive residue was left on the glass cell surface later.

Therefore, in order to enable re-peeling, a blooming layer is formed and a low-molecular-weight surfactant is added in order to suppress an increase in adhesive strength (Japanese Patent Publication No. 51-2005).
No. 3) or a plasticizer added. With these methods, the adhesive strength is reduced and removability can be imparted, but from the viewpoint of durability, the occurrence of foaming with the additive as the core, deterioration due to inhibition of cross-linking, and the adhesive / adhesive interface with time There was a problem with the quality during storage, such as the additive bleeding out.

As a countermeasure against this, carbon numbers of 2 to 8 and 12 to
A pressure-sensitive adhesive using a copolymer obtained by polymerizing two series of 22 acrylic acid esters having an aliphatic group and an acrylic compound having a functional group has been reported (JP-A-63-2).
No. 02682). However, this adhesive has 1 carbon
When the retardation plate or the polarizing plate is left under high temperature and high humidity, the interface between the pressure sensitive adhesive and the adherend is weak and the moisture content is high because the ratio of the acrylic ester having an aliphatic group of 2 to 22 is too large. Penetration of the tape is unavoidable and peeling of the tape occurs.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its purpose is to improve the adhesiveness between an optical resin plate such as a retardation plate or a polarizing plate and a glass cell. Under the storage conditions from the bonding to the inspection step, the retardation plate or the like can be peeled off from the glass cell surface relatively easily, and no adhesive residue is left on the glass cell surface. When used as a liquid crystal display board, foaming resistance under high temperature and high humidity,
An object is to provide a pressure-sensitive adhesive composition having excellent peel resistance.

[0008]

The acrylic pressure-sensitive adhesive composition of the present invention comprises an acrylic acid or methacrylic acid alkyl ester (A) 10 having an alkyl group having 2 to 11 carbon atoms.
0 parts by weight, 1.0 to 60 monomers (B) copolymerizable with the acrylic acid or methacrylic acid alkyl ester
Parts by weight, and acrylic acid or methacrylic acid alkyl ester (C) 0.1 having 12 or more carbon atoms in the alkyl group
The copolymer obtained by polymerizing 4.9 parts by weight is used as a base polymer. In the following, "acrylic acid or methacrylic acid" is abbreviated as "(meth) acrylic acid".

Examples of the (meth) acrylic acid alkyl ester (A) having an alkyl group having 2 to 11 carbon atoms used in the present invention include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (Meta)
Monomers such as isooctyl acrylate, isononyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, benzyl (meth) acrylate, ethyl (meth) acrylate, and methyl (meth) acrylate are used. To do. The (meth) acrylic acid alkyl ester (A) is not limited to one type, and two or more types may be used in combination.

As the unsaturated monomer (B) copolymerizable with the (meth) acrylic acid alkyl ester (A), (meth) acrylic acid, crotonic acid, maleic acid,
A monomer containing a carboxylic acid such as fumaric acid or itaconic acid is preferably used because it reacts with a crosslinking agent described later to improve the cohesive force of the pressure-sensitive adhesive. Further, in addition to the above, vinyl acetate, styrene, N-vinylpyrrolidone, 2-hydroxypropyl (meth) acrylate, (meth)
A hydroxyl group-containing monomer such as hydroxyethyl acrylate, tetrafurfuryl acrylate, polyethylene glycol acrylate or the like is used.

Examples of the (meth) acrylic acid alkyl ester (C) having an alkyl group having 12 or more carbon atoms used in the present invention include lauryl (meth) acrylate, stearyl (meth) acrylate, and (meth) acrylate. Examples include myristyl acrylate and behenyl (meth) acrylate.

The amount of the (meth) acrylic acid alkyl ester (C) added is limited to the range of 0.1 to 4.9 parts by weight with respect to 100 parts by weight of the (meth) acrylic acid alkyl ester (A). If the amount is less than 0.1 parts by weight, the re-peeling effect is not sufficient, and if the amount is more than 5.0 parts by weight, the adhesive strength is too low, and under the conditions of high temperature and high humidity, the contraction stress of the retardation plate or the polarizing plate cannot be endured. However, peeling occurs at the interface between the adhesive and the adherend.

As a method for polymerizing the above-mentioned monomers (A), (B) and (C), radical polymerization such as solution polymerization, bulk polymerization and emulsion polymerization can be adopted. As the polymerization initiator, conventionally known ones such as benzoyl peroxide and azobisisobutyronitrile are used. It may be polymerized by irradiation with light or radiation. Further, a chain transfer agent such as lauryl mercaptan may be added to adjust the molecular weight of the produced polymer.

The copolymer thus obtained has a weight average molecular weight (Mw) of 500,000 or more and a ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) of 4.0 or less. It is necessary to be. If the weight average molecular weight is less than 500,000 or the ratio of the weight average molecular weight to the number average molecular weight exceeds 4.0, the peeling resistance at high temperature becomes insufficient.

In the present invention, a cross-linking agent for cross-linking the acrylic polymer to enhance cohesive strength and heat resistance is added to the copolymer of the base polymer. The cross-linking agent is a polyfunctional group. Examples thereof include organic compounds, organometallic compounds, and metal salts.

Examples of the organic compound cross-linking agent include N,
N'-hexamethylene-1,6-bis (1-aziridinecarboxamide), trimethylolpropane-tri-
β-aziridinyl propionate, aziridine compound such as bisisophthaloyl-1- (2-methylaziridine), tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane adduct of tolylene diisocyanate, triphenylmethane Isocyanate compounds such as triisocyanate, methylenebis (4-phenylmethane) triisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, bisphenol A, epichlorohydrin type epoxy resin,
Ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine,
Examples thereof include N, N, N ′, N′-tetraglycidyl m-xylenediamine, epoxy compounds such as 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, and other amino resins and melamine resins.

As the organometallic compound cross-linking agent, a coordination compound of acetylacetone or acetoacetic ester of a polyvalent metal such as aluminum, iron, copper, tin, zinc, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium. Can be mentioned.

Examples of the metal salt crosslinking agent include cupric chloride, aluminum chloride, ferric chloride, aluminum sulfate, copper sulfate, stannic chloride, zinc chloride, nickel chloride, magnesium chloride, chromium acetate, and copper acetate. To be

The cross-linking agent is at least one type or two types.
Add more than one kind. The amount of addition is 100
It is 0.001 to 5 parts by weight with respect to parts by weight. 0.00
If it is less than 1 part by weight, the heat resistance will be poor, and if it exceeds 5 parts by weight, the wet peeling resistance will be poor.

[0020]

Since the composition of the present invention uses the copolymer as a base polymer as described above, it has a stable adhesive force without causing additives and the like to move or change with time during storage. To maintain. Further, the long-chain alkyl portion of the base polymer suppresses the adhesion progress of the pressure-sensitive adhesive to the adherend and imparts removability, and addition of (meth) acrylic acid alkyl ester (C) having a long-chain alkyl portion Since the amount is limited, it does not foam or peel even under high temperature and high humidity.

[0021]

EXAMPLES Next, examples of the present invention will be described. (Preparation of acrylic polymer) In accordance with the compounding composition shown in Table 1, 2-ethylhexyl acrylate and acrylic acid n
-Butyl, acrylic acid, hydroxyethyl methacrylate, stearyl acrylate, lauryl methacrylate,
Lauryl mercaptan as a chain transfer agent and a predetermined number of ethyl acetate as a solvent were charged, dissolved with stirring, the air in the vessel was replaced with nitrogen, and benzoyl peroxide 0.1. An acrylic polymer was obtained by adding 03 parts by weight and reacting for 15 hours.

The weight average molecular weight and number average molecular weight of the acrylic polymer thus prepared were measured by gel permeation chromatography using standard crosslinked polystyrene as a standard, tetrahydrofuran as a separating agent, and detection using a refractometer. did. In all Examples and Comparative Examples, the weight average molecular weight was adjusted to 900,000, and the ratio of the weight average molecular weight to the number average molecular weight was adjusted to 3.1.

[0023]

[Table 1]

(Preparation of Acrylic Pressure-Sensitive Adhesive Composition) The above acrylic polymer was diluted with ethyl acetate so that the solid content was 40% by weight, and then all the operations were carried out for 100 parts by weight of the acrylic polymer solid content. In Examples and Comparative Examples, N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide) as a cross-linking agent (manufactured by Mutual Pharmaceutical Co., Ltd.)
Of 0.03 part by weight and 0.40 part by weight of a trimethylolpropane adduct of tolylene diisocyanate (manufactured by Nippon Polyurethane Co.) were mixed and stirred to obtain an acrylic pressure-sensitive adhesive composition. In addition, in Comparative Example 2, cations of lauryltrimethylammonium chloride, which is a cationic surfactant, are further added.
20 parts by weight were added.

(Preparation of Acrylic Pressure-Sensitive Adhesive Composition Laminate) A solution of each acrylic pressure-sensitive adhesive composition thus prepared was applied onto a silicone-treated 38 μm-thick polyester film with an applicator and dried to give a thickness. Formed an adhesive layer having a thickness of 25 μm. Then, the pressure-sensitive adhesive layer side, stretched polyvinyl alcohol-based polarizing plate (Sanritz Co. "LLC ₂ -9218") thick 150μm and draw polycarbonate-based thick 85μm retardation plate (Sanritz Co.), respectively The laminated layered product was laminated with a laminator, and the pressure-sensitive 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,
Cut into a size of 25 × 150 mm, peel off the silicone-treated polyester film, attach the pressure-sensitive adhesive layer side of the retardation plate to a glass plate, and further attach the pressure-sensitive adhesive layer side of the polarizing plate to the back of the retardation plate. The laminate was laminated with a laminator so that air bubbles would not enter, to prepare a laminate including a polarizing plate, a retardation plate, and a glass plate via an adhesive layer.

(Evaluation) Evaluation was carried out on five items: foaming property, peeling property, adhesive strength to glass plate and adhesive residue, and storage stability. As an evaluation of foamability, the above sample was heated to 80 ° C.
After being left in the constant temperature bath for 500 hours, the change in appearance due to foaming was evaluated according to the following evaluation points. That is, 10 μm in the pressure-sensitive adhesive layer of the glass plate and the polarizing plate or the retardation plate.
The case where the above bubbles were not recognized was set to 1 when a small number of bubbles of 20 to 40 μm was recognized, and the case where a large number of bubbles of 20 to 40 μm was recognized was set to 3.

As an evaluation of peelability, each sample was tested at 60 ° C.
After being left for 500 hours in a thermostat with a relative humidity of 90%, the appearance change due to peeling was evaluated according to the following evaluation points. That is, peeling from the glass plate near the edge of the polarizing plate or the retardation plate was not observed at all, 1 was peeling of 0.5 mm or less at the edge, 2 was 0.5 mm near the edge. The case where the above peeling was recognized was set to 3.

The adhesive strength to the glass plate and the adhesive residue were evaluated by leaving each sample in a constant temperature bath at 90 ° C. for 2 hours and then at room temperature for 3 days, and then 180 ° from the glass plate according to JIS-Z0237. Degree direction, pulling speed 300mm
The peeling adhesive strength was measured under the condition of / min, and the degree of adhesive residue on the glass surface after peeling was visually observed.

To evaluate the storage stability, each sample was stored in a thermostatic chamber at 23 ° C. and a relative humidity of 65% for 6 months, and then the foamability and peelability were evaluated. The evaluation results are shown in Table 2.

[0031]

[Table 2]

As can be seen from the evaluation results, all of the compositions of Examples have good foamability, peelability, adhesive strength, adhesive residue, storage stability, and the adhesive strength is a limit at which re-peelability is 1500 gf / It showed a suitable numerical value of less than 25 mm. In the comparative example, the copolymer is a (meth) acrylic acid alkyl ester (C) having an alkyl group having 12 or more carbon atoms.
Those without addition of have a high adhesive strength and cannot be removed again. Even if additives are added after the polymerization to lower the adhesive strength, the foamability, peeling property, adhesive residue and storage stability are poor. Further, it can be seen that when the (meth) acrylic acid alkyl ester (C) having an alkyl group having 12 or more carbon atoms is added in an amount of 10 parts by weight in excess of 5 parts by weight, there are problems in foamability and peelability.

[0033]

As described above and as can be seen from the evaluation of the examples, the acrylic pressure-sensitive adhesive composition of the present invention has excellent adhesiveness to a glass plate, heat resistance and moisture resistance, and a polarizing plate or a retardation plate. When the resin plate of 1 is laminated on a glass plate, a laminated body which does not foam or peel even under high temperature and high humidity can be obtained, and moreover,
Maintains stable quality even after long-term storage. Also,
Since there is no progress of adhesion to the glass surface, re-peeling from the glass surface etc. can be easily performed when re-adhesion is necessary.

Therefore, when re-adhering due to entrainment of bubbles or mixing of dust that occurs after the bonding, the necessary re-peeling can be easily performed and the glass cell can be reused. Since the acrylic pressure-sensitive adhesive composition of the present invention has the above-described properties, it can be suitably used as a pressure-sensitive adhesive composition for laminating and fixing an optical resin plate such as a polarizing plate or a retardation plate on a glass cell.

Claims (1)

[Claims] 1. A base polymer comprising 100 parts by weight of an acrylic acid or methacrylic acid alkyl ester (A) having an alkyl group having 2 to 11 carbon atoms, and a monomer (copolymerizable with the acrylic acid or methacrylic acid alkyl ester). B) A copolymer obtained by polymerizing 1.0 to 60 parts by weight and 0.1 to 4.9 parts by weight of an alkyl or methacrylic acid alkyl ester (C) having an alkyl group having 12 or more carbon atoms. The copolymer has a weight average molecular weight (Mw) of 500,000 or more, and the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) is 4.
An acrylic pressure-sensitive adhesive composition, which is 0 or less.