JPH09286808A - Photopolymerizable composition, acrylic pressure-sensitive adhesive, and method for manufacturing polarizing plate pressure-sensitive adhesive sheet - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a method for producing an acrylic pressure-sensitive adhesive and a polarizing plate pressure-sensitive adhesive sheet, which are not easily affected by reaction inhibition by oxygen, have a high degree of polymerization even in thin film polymerization, and do not impair anchorability with a polarizing plate. provide. [Structure] A photopolymerizable composition comprising a photopolymerizable monomer having an alkyl (meth) acrylate as a main component, a photoinitiator, and a phosphite compound having a boiling point of 160 ° C. or less, and the photopolymerizable composition is irradiated with light. Then, the acrylic pressure-sensitive adhesive obtained by polymerizing the photopolymerizable composition and the photopolymerizable composition are coated on a release sheet, irradiated with light to polymerize, and then heated to form an acrylic pressure-sensitive adhesive layer. A method for producing a polarizing plate pressure-sensitive adhesive sheet, comprising: obtaining a laminate, and sticking the pressure-sensitive adhesive surface side of the laminate to a polarizing plate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an acrylic pressure-sensitive adhesive obtained by photopolymerization and a polarizing plate pressure-sensitive adhesive sheet using the same.

[0002]

2. Description of the Related Art Liquid crystal display devices are used not only for simple display devices such as watches and electric appliances but also as display devices for small televisions, word processors, notebook computers, etc. Very harsh conditions are being demanded. In the liquid crystal display device, various optical films such as a polarizing plate and a retardation plate are used. However, since these optical films are bonded together, the transparency and weather resistance are excellent, and thus an allyl adhesive is used. Is used.

Among the above-mentioned allyl-based pressure-sensitive adhesives, a photopolymerization type acrylic-based pressure-sensitive adhesive containing an acrylate-based monomer as a main component is capable of increasing the molecular weight of the acrylic polymer as the main component, so that it has heat resistance and cohesive strength. It is expected that acrylic adhesives with high properties will be obtained.

However, in such a reaction system, the efficiency of the photoinitiator due to oxygen is deteriorated, and particularly in thin film polymerization, this effect is strongly influenced and the photopolymerization does not proceed, and a large amount of unreacted monomer remains. There is a problem that it ends up. As a method for solving the above problems, Japanese Patent Laid-Open No. 64-64-
Japanese Patent Publication No. 79213 discloses a photopolymerizable composition in which a phosphite compound or a thiophosphite compound is added to an unsaturated radical polymerization composition.

[0005]

However, when the pressure-sensitive adhesive layer obtained by polymerizing the photopolymerizable composition described in the above publication is formed on a plastic substrate such as a polarizing plate, Since the phosphite-based compound acts as an impurity, there is a problem that the anchoring property between the base material and the pressure-sensitive adhesive layer is lowered.

The present invention has been made in view of the above problems, and an object thereof is to be hardly affected by oxygen existing in the reaction system and to have a high degree of polymerization even in a thin film polymerization of 100 μm or less and to achieve high speed. Another object of the present invention is to provide an acrylic pressure-sensitive adhesive which is capable of various photopolymerizations and does not impair the anchoring property with a polarizing plate, and a polarizing plate pressure-sensitive adhesive sheet using the same.

[0007]

The first aspect of the present invention is a photopolymerizable composition comprising a photopolymerizable monomer, a photoinitiator, and a phosphite compound having a boiling point of 160 ° C. or less. The photopolymerizable monomer has an alkyl (meth) acrylate as a main component. The alkyl (meth) acrylate preferably has an alkyl group having 2 to 12 carbon atoms, more preferably 4 to 9 carbon atoms, and examples thereof include ethyl acrylate and n-propyl (meth). )
Acrylate, n-butyl (meth) acrylate, se
c-butyl (meth) acrylate, ter-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, (meth) lauryl acrylate, (Meth) isomisostyl acrylate etc. are mentioned.

In addition to the above monomers, if necessary, further vinyl monomers containing a carbosyl group such as (meth) acrylic acid, itaconic acid, maleic anhydride, fumaric anhydride, (meth) acrylonitrile, N-vinylpyrrolidone, N-vinyl. Copolymerizable vinyl monomers such as caprolactam, acryloylmorpholine, (meth) acrylamide, (meth) acrylic acid dimethylaminoethyl ester, (meth) acrylic acid diethylaminoethyl ester and dimethylaminovinyl acetate may be used in combination. If the blending amount of the vinyl monomer is too large, the cohesive force becomes too high, and the adhesiveness to the uneven surface of the adherend is lowered. Less than is preferred.

A polyfunctional vinyl monomer may be added to impart heat resistance and cohesive force at high temperature. Examples of such a monomer include hexamethylenediol di (meth) acrylate and (poly ) Ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate
Acrylates and trimethylolpropane tri (meth) acrylate are exemplified. As the compounding amount of the polyfunctional vinyl monomer, it becomes difficult to obtain a sufficient cohesive force when the amount is small, and when the amount is large, the cohesive force becomes too high and it becomes difficult to obtain adhesiveness to uneven surfaces and the like, so the alkyl (meth) 0.01 to 5 relative to 100 parts by weight of acrylate
Parts by weight are preferred.

The photoinitiator used in the present invention is one which generates radicals by ultraviolet rays and is, for example, 2,
4,6-Trimethylbenzoyldiphenylphosphine oxide (trade name "Lucirin TPO", manufactured by BASF), 2-benzyl-2-dimethylamino-1- (4-
Morifolinophenyl) -butanone-1 (trade name "Irgacure 369", manufactured by Ciba Geigy), 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (trade name "Darokyuya 2959", Merck) Company), α-hydroxy-α, α′-dimethylacetophenone (trade name “Darokyuya 1173”, manufactured by Merck), methoxyacetophenone, 2,2-dimethoxy-
2-Phenylacetone (trade name "Irgacure 65
1 ", manufactured by Ciba Geigy); 2-hydroxy-2-cyclohexylacetophenone (trade name" Irgacure 18 "
4 ", manufactured by Ciba-Geigy) and the like. If the amount of the photoinitiator added is small, the photopolymerization reaction rate will be slow and productivity will be lowered, and if it is large, the molecular weight reduction will be remarkable and the necessary initial cohesive force will be difficult to obtain. 0.01 to 2 parts by weight is preferable with respect to 100 parts by weight of the volatile monomer.

The phosphite compound used in the present invention has a boiling point of 160 ° C. or lower. By using one having a boiling point of 160 ° C. or less, the effect of oxygen existing in the reaction system is less likely to occur, and it can be easily removed by heating, so that the anchoring property with the polarizing plate is not impaired. Suitable examples of the phosphite compound include triethylphosphite (boiling point: 157 ° C.).

The second aspect of the present invention is an acrylic pressure-sensitive adhesive obtained by polymerizing the above photopolymerizable composition by irradiating it with light.

The lamps used for polymerizing the photopolymerizable composition of the present invention by irradiating it with light include low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultra high pressure mercury lamps, chemical lamps, black light lamps, and micro lamps. Examples include wave-excited mercury lamps and melarhalides. The light irradiation intensity of the photopolymerizable composition by the lamp is a factor that influences the degree of polymerization of the obtained polymer, and is appropriately controlled for each target product, in order to increase the degree of polymerization of the polymer, the light intensity is 0.1 to 10 mW / cm ² is preferable.

Although the photopolymerizable composition of the present invention is less susceptible to oxygen inhibition during the polymerization process, oxygen is added to the photopolymerizable composition in order to make it less susceptible to oxygen in the air and oxygen dissolved in the photopolymerizable composition. It is preferably carried out in a removable manner. As the above method, for example, a polyethylene terephthalate film (hereinafter, referred to as "PET
Film)) or a Teflon film, etc., and irradiate light through the above film, in an inert zone with a light-transmissive window in which oxygen is replaced by an inert gas such as nitrogen gas or carbon dioxide gas. And the like.

In the method of reacting in the inert zone, the photopolymerizable composition is polymerized at a conversion rate of 99.7.
In order to sufficiently complete the oxygen content in the irradiation atmosphere, the oxygen concentration in the irradiation atmosphere is preferably 5000 ppm or less. The molecular weight of the polymer obtained by light irradiation of the photopolymerizable composition decreases as the atmospheric oxygen concentration increases, so that the atmospheric oxygen concentration should be the same as that in the case of polymerization under completely inert conditions. Is 1000p
It is more preferably pm or less. The surface layer portion of the photopolymerizable composition is more susceptible to oxygen inhibition than the inside of the polymer, and in order for the surface layer portion to have the same degree of cohesiveness as the inner layer portion, the atmospheric oxygen concentration may be 300 ppm or less. More preferable.

The third aspect of the present invention is to obtain a laminate having an acrylic pressure-sensitive adhesive layer formed by applying the above photopolymerizable composition onto a release sheet, irradiating it with light to polymerize it, and then heating. The method for producing a polarizing plate pressure-sensitive adhesive sheet is characterized in that the pressure-sensitive adhesive surface side of the laminate is attached to a polarizing plate.

The above-mentioned release sheet is a commonly used PET.
Examples thereof include those obtained by subjecting the surface of a synthetic resin film such as a film to release treatment.

As the polarizing plate, for example, a resin film such as a polyester film, a polyvinyl alcohol resin film or a polyvinyl butyral resin film is dyed with iodine or a two-color dye, stretched in a uniaxial direction, and a protective film such as a triacetate film. It can be manufactured by sticking from both sides.

The method for applying the photopolymerizable composition onto the release sheet is not particularly limited, and examples thereof include a coating machine such as a roll coater which is usually used when producing an adhesive tape.

The coating thickness range of the photopolymerizable composition is not particularly limited and can be appropriately set according to the purpose of use, but it is generally 10 to 10 from the viewpoint of ease of use as an adhesive sheet. 1000 μm is preferable.

In the present invention, heating is for removing the phosphite compound from the pressure-sensitive adhesive layer obtained by irradiating the photopolymerizable composition with light, and the heating is performed at 200 ° C. or lower, and further at about 160 ° C. The object can be achieved by heating for 3 minutes.

After the acrylic pressure-sensitive adhesive layer is formed, the pressure-sensitive adhesive surface side of the laminate is laminated on a polarizing plate to obtain a polarizing plate pressure-sensitive adhesive sheet comprising a polarizing plate, a pressure-sensitive adhesive layer and a release sheet.

Further, the method for laminating the laminate having the acrylic pressure-sensitive adhesive layer formed thereon and the polarizing plate is not particularly limited, and it can be achieved by using an ordinary laminator or the like.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A polymerizable monomer component consisting of 97 parts by weight of butyl acrylate, 3 parts by weight of acrylic acid and 0.03 part by weight of 1,6-hexanediol diacrylate was used as a photoinitiator with methoxyacetophenone and 2 parts. ，
0.05 parts by weight of 2-dimethoxy-2-phenylacetone (trade name "Irgacure 651", manufactured by Ciba-Geigy) and 3 parts by weight of triethylphosphite were added and uniformly mixed by stirring to obtain a photopolymerizable composition. Got The resulting photopolymerizable composition was applied on a PET film that had been subjected to release treatment to a thickness of 30 μm, and PE that had been subjected to release treatment
After coating with T film, irradiation was performed with a chemical lamp at a light intensity of 1.0 mW / cm ^{2 for} 10 minutes, and then 16
It heated at 0 degreeC for 2 minutes, and obtained the laminated body which formed the acrylic adhesive layer.

Example 2 A laminate having an acrylic pressure-sensitive adhesive layer formed was obtained in the same manner as in Example 1 except that the amount of triethylphosphite added was changed to 5 parts by weight.

Comparative Example 1 An acrylic pressure-sensitive adhesive layer was formed in the same manner as in Example 1 except that after irradiation with a chemical lamp at a light intensity of 1.0 mW / cm ^{2 for} 10 minutes and no heating. The formed laminated body was obtained.

(Comparative Example 2) The same procedure as in Example 1 was carried out except that triethylphosphite was not added, but the photopolymerization did not proceed and a large amount of unreacted monomer remained, resulting in an acrylic pressure-sensitive adhesive. No layer was obtained.

Comparative Example 3 As a photoinitiator, 0.2 parts by weight of methoxyacetophenone and 2,2-dimethoxy-2-phenylacetone (trade name "Irgacure 651", manufactured by Ciba Geigy) were added, and triethylphosphite was added. A laminate having an acrylic pressure-sensitive adhesive layer formed was obtained by the same method as in Example 1 except that was not added.

(Comparative Example 4) Instead of triethyl phosphite, isodecyl phosphite (boiling point: 180 ° C /
0.1 mmHg) except that 2.0 parts by weight are added.
A laminate having an acrylic pressure-sensitive adhesive layer formed was obtained in the same manner as in Example 1.

[0031]

[Table 1]

<Evaluation Items and Evaluation Method> The samples obtained above were evaluated according to the following evaluation items and evaluation methods, and the results are shown in Table 1. (Weight average molecular weight) Dissolve in tetrahydrofuran,
The sample solution obtained by removing the insoluble matter was measured by Gelei permeation chromatography using a standard polystyrene as a reference and a refractometer. (Polymerization rate) Chro supporting polyethylene glycol
The amount of residual monomer was measured using a gas chromatograph (GC-6A, manufactured by Shimadzu Corporation) having a separation column obtained by treating mosorb-W (manufactured by Gaskuro Industrial Co., Ltd.) with an acid, and a hydrogen flame ion detector to calculate the polymerization rate. . (Anchor force) A polarizing plate was attached to the pressure-sensitive adhesive surface side of the laminates in the above Examples and Comparative Examples to obtain a polarizing plate pressure-sensitive adhesive sheet. A 20 mm-wide polarizing plate pressure-sensitive adhesive sheet was attached to an SUS plate that had been subjected to a polishing battle on the pressure-sensitive adhesive surface, and was allowed to cure at room temperature for 1 day, and then the peeling force when the polarizing plate was peeled at 180 mm in the direction of 300 mm / min was measured. (Heat-resistant adhesion) Polarizing plate adhesive sheet, 75 mm x 150
It was cut into a size of mm and was attached to a glass plate while holding it at a temperature of 50 ° C. and a pressure of 5 kg / cm ² for 20 minutes.
The obtained sample was visually observed and evaluated for the state of occurrence of foaming and peeling after standing in a constant temperature bath at 100 ° C. for 500 hours.

[0033]

The photopolymerizable composition of the present invention is hardly affected by oxygen existing in the reaction system, and therefore 100 μm.
Even in thin film polymerization of m or less, the degree of polymerization is high, and high-speed photopolymerization is possible. Further, since it is obtained by photopolymerization, the problems associated with organic solvents are eliminated. Furthermore, in the method for producing a polarizing plate pressure-sensitive adhesive sheet according to the present invention, by removing the phosphite compound from the pressure-sensitive adhesive layer, the anchoring property between the polarizing plate and the pressure-sensitive adhesive layer is not impaired, and heat resistance and adhesion are excellent.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09J 7/02 JJW C09J 7/02 JJW JKZ JKZ 133/06 JDC 133/06 JDC G02B 5/30 G02B 5/30 G02F 1/1335 510 G02F 1/1335 510

Claims (4)

[Claims] 1. A photopolymerizable monomer containing an alkyl (meth) acrylate as a main component, a photoinitiator, and a boiling point of 160.
A photopolymerizable composition comprising a phosphite compound having a temperature of not higher than 0 ° C. 2. The photopolymerizable composition according to claim 1, wherein the phosphite compound is triethylphosphite. 3. An acrylic pressure-sensitive adhesive obtained by irradiating light to polymerize the photopolymerizable composition according to claim 1 or 2. 4. A photopolymerizable composition according to claim 1 or 2 is coated on a release sheet and irradiated with light to be polymerized.
A method for producing a polarizing plate pressure-sensitive adhesive sheet, which comprises heating to obtain a laminate having an acrylic pressure-sensitive adhesive layer formed thereon, and laminating the pressure-sensitive adhesive surface side of the laminate to a polarizing plate.