JPH108000A - Tacky adhesive composition and tacky adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tacky adhesive sheet which is used outdoors, is resistant to dicoloration due to ultraviolet rays, sunlight, a fluorescent lamp, etc., and has tacky adhesive power hardly changing even after exposure to light and to provide a tacky adhesive compsn. for preparing the same. SOLUTION: This compsn. is an emulsion-type acrylic compsn. which contains as the main component a (meth)acrylic acid copolymer contg. 60-99wt.% units derived from 4-18C alkyl ester of (meth)acrylic acid and also contains 0.1-20 pts.wt. (based on 100 pts.wt. methacrylic acid copolymer) ultraviolet absorber added in the form of a water dispersion or emulsion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsion-type pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using the same, and in particular, has good light-fast discoloration against ultraviolet rays, sunlight, fluorescent lamps and the like, and has an adhesive strength even after exposure to light. A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet having little change.

[0002]

2. Description of the Related Art Adhesive sheets are widely used in the form of labels, stickers, patches, delivery slips and the like for commercial use, office work, process management, distribution management, home use, and the like. To explain the general structure of this adhesive sheet,
The adhesive is sandwiched between the surface substrate and the release sheet, and paper, foil, film, or the like is used as the surface substrate. High-density base paper such as glassine paper, clay-coated paper,
Polyamide base paper obtained by laminating a resin film such as polyethylene on kraft paper or high-quality paper, or a barrier layer mainly containing a water-soluble polymer such as polyvinyl alcohol or starch and a pigment on kraft paper or high-quality paper is provided. A resin-coated base paper coated with a release agent such as a silicone compound or a fluorine compound is used. As the pressure-sensitive adhesive, various types of pressure-sensitive adhesives of rubber type, acrylic type, vinyl ether type and the like, solvent type or non-solvent type are used.

However, in the conventional pressure-sensitive adhesive sheet, if an opaque material such as paper, PVC film, synthetic paper, or vapor-deposited PET is used as a base material, for example, a label or the like can be applied to a transparent adherend such as a film, plastic, or glass. When sticking, when exposed to ultraviolet rays, sunlight, fluorescent light, etc. for a long period of time indoors and outdoors, the appearance of the adherend and the contents, etc. will be noticeable due to the discoloration of the adhesive due to the discoloration of the adhesive. There were drawbacks such as damage. When a transparent substrate such as polyethylene, polypropylene, or PET is used as the substrate, regardless of whether the adherend is transparent or opaque, when exposed to ultraviolet light, sunlight, fluorescent lights, etc. Discoloration of the agent significantly impairs the appearance of adherends and contents,
Discoloration of the adhesive may reduce the transparency of the label.
Lamination on printed matter has drawbacks such as discoloration of the print and long-term exposure to light, preventing the fading of the print from being prevented. Furthermore, after sticking a label or the like to an adherend, when exposed for a long period of time, the label attached to the adherend peels off, and has a drawback that the adhesive strength decreases with time. .

[0004]

The present invention relates to a pressure-sensitive adhesive sheet used indoors and outdoors, in particular, has good light discoloration resistance to ultraviolet rays, sunlight, fluorescent lamps and the like, and changes in adhesive strength even after exposure to light. The present invention provides a low-pressure-sensitive adhesive composition and a sheet thereof.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a pressure-sensitive adhesive composition for a pressure-sensitive adhesive sheet used indoors and outdoors, and as a result, a pressure-sensitive adhesive composition obtained by adding a specific form of an ultraviolet absorber to an acrylic emulsion type pressure-sensitive adhesive. It has been found that the article and the pressure-sensitive adhesive sheet have good light discoloration resistance to ultraviolet rays, sunlight, fluorescent lamps and the like, and that the adhesive strength after exposure to light is little reduced.

(1) That is, the present invention mainly comprises (a) a (meth) acrylic acid copolymer containing at least 60 to 99% by weight of a C _{4 to} C ₁₈ alkyl ester monomer of (meth) acrylic acid. The emulsion-type acrylic pressure-sensitive adhesive composition is characterized in that 0.1 to 20 parts by weight of an ultraviolet absorber is added in the form of an aqueous dispersion or emulsion based on 100 parts by weight of the (meth) acrylic acid copolymer. It is an emulsion-type acrylic pressure-sensitive adhesive composition.

(2) The emulsion-type acrylic pressure-sensitive adhesive composition according to (1), wherein the ultraviolet absorber is a benzotriazole-based and / or benzophenone-based ultraviolet absorber.

(3) The emulsion acrylic pressure-sensitive adhesive composition according to (1) or (2), wherein the ultraviolet absorber is a microencapsulated ultraviolet absorber.

(4) (meth) acrylic acid copolymer 100
The emulsion acrylic pressure-sensitive adhesive composition according to any one of (1) to (3), which contains 0.1 to 10 parts by weight of an antioxidant with respect to parts by weight.

(5) An adhesive sheet provided with a layer having the emulsion-type acrylic adhesive composition according to any one of (1) to (4) on a substrate.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The emulsion-type acrylic pressure-sensitive adhesive composition of the present invention contains a (meth) acrylic acid copolymer as a main component. The (meth) acrylic acid copolymer is
(A). (C) a C ₄ -C ₁₈ alkyl ester monomer of (meth) acrylic acid containing 60 to 99% by weight; 0 to 10% by weight of an ethylenically unsaturated carboxylic acid-containing monomer, and (c). It has 1 to 40% by weight of other monomers copolymerizable with the above (a) and (b).

The (meth) acrylic acid copolymer 100
It is characterized in that 0.1 to 20 parts by weight of an ultraviolet absorber is added in the form of an aqueous dispersion or an emulsion based on parts by weight. In a conventional pressure-sensitive adhesive sheet, the pressure-sensitive resin in the pressure-sensitive adhesive and an emulsifier, a polymerization initiator, a chain transfer agent, and the like added at the time of polymerization cause discoloration, decomposition, and the like when exposed to ultraviolet rays, sunlight, fluorescent lights, and the like. . Probably, the pressure-sensitive adhesive composition of the present invention is of an emulsion type, and since the ultraviolet absorber is added in the form of an aqueous dispersion or emulsion, the fine ultraviolet absorber can be efficiently dispersed in the pressure-sensitive adhesive composition. .
For this reason, the energy from ultraviolet rays, sunlight, fluorescent lamps and the like is absorbed by the fine ultraviolet absorber uniformly dispersed in the adhesive composition and converted into heat energy, so that the discoloration and adhesive force of the adhesive are changed. It seems to suppress the decrease in

The ultraviolet absorber used in the present invention may be a cyanoacrylate-based, benzotriazole-based, benzophenone-based, salicylic acid-based or hydroquinone-based ultraviolet absorber, or a reaction between a reactive ultraviolet absorber and a polymer. Alternatively, various known materials such as an ultraviolet absorbing polymer obtained by polymerizing a reactive ultraviolet absorber and a monomer can be used.

Specific examples of the benzotriazole-based ultraviolet absorber include, for example, 2- (2'-hydroxyphenyl) benzotriazole, 2- (2'-hydroxy-
5′-methylphenyl) benzotriazole, 2-
(2′-hydroxy-5′-tert-butylphenyl) benzotriazole, 2- (2′-hydroxy-
5'-tert-octylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-ter
t-butylphenyl) benzotriazole, 2- (2 ′
-Hydroxy-3'-di-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-
(2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole, 2-
(2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl)-
5-tert-butylbenzotriazole, 2,2′-
Methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-benzotriazolyl-phenol], 2,
2'-methylenebis (3-methoxy-6-benzoylphenol), 2,2'-octylidenebis [4-methyl-6- (5'-methylbenzotriazolyl) phenol] and the like.

Specific examples of the benzophenone type ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′-
Hydroxy-4,4'-dimethoxybenzophenone, 2
-Hydroxy-4-methoxy-5-sulfobenzophenone and the like.

Specific examples of the salicylic acid ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate,
2,4-di-tert-butylphenyl-3′5′-di-tert-butyl-4′-hydroxybenzoate and the like.

Specific examples of cyanoacrylate-based ultraviolet absorbers include 2-ethylhexyl-2-cyano-3,
3'-diphenyl acrylate, ethyl-2-cyano-
3,3′-diphenyl acrylate and the like.

Specific examples of the hindered amine-based ultraviolet absorber include bis (2,2,6,6-tetramethyl-4-
Piperidyl) sebacate, bis-succinate-bis (2,2,
6,6-tetramethyl-4-piperidyl) ester, 2
-(3,5-di-tert-butyl) malonic acid-bis-
(1,2,2,6,6-pentamethyl-4-piperidyl) ester and the like.

Above all, benzotriazole-based and benzophenone-based ultraviolet absorbers are preferably used because of their excellent light resistance to ultraviolet light, sunlight and the like. Of course, the ultraviolet absorber used is not limited to these, and one type may be used alone, or two or more types may be used in combination as needed.

In the present invention, the ultraviolet absorbent is added to the acrylic pressure-sensitive adhesive in the form of an aqueous dispersion or emulsion. For example, an ultraviolet absorber, for example, using water as a dispersion medium, adding an auxiliary agent such as a dispersant, a ball mill, a stirrer such as a sand mill, and pulverizing and dispersing using a pulverizer,
It is preferable to use an aqueous dispersion in which the average particle diameter of the ultraviolet absorber is about 0.5 to 3.0 μm. Further, an auxiliary agent such as a dispersant and an emulsifier may be added to the ultraviolet absorber to form an emulsion having an average particle diameter of the ultraviolet absorber of about 0.05 to 0.3 μm. In particular, the emulsion form is preferable because a sufficient improvement effect can be obtained with a small amount of addition.

Further, when an ultraviolet absorber (ultraviolet absorbing component) containing an ultraviolet absorber in a microcapsule is used,
It is particularly preferable because a large amount of an ultraviolet absorbing component can be contained in the adhesive composition. Above all, benzotriazole-based UV absorbers are preferred in terms of UV absorption efficiency. Particularly, those which are liquid at ordinary temperature are not necessary for dissolving the UV absorber in an organic solvent when synthesizing oil-in-water microcapsules. It can be contained in a capsule at a high concentration, the ultraviolet absorbing ability is also remarkably improved, and the microcapsule wall film agent used in the present invention has good compatibility with liquid benzotriazole at room temperature, so it is more preferably used. Can be

Specific examples of the benzotriazole-based ultraviolet absorber which is liquid at ordinary temperature include 2- (2'-hydroxy-3 ', 5'-di-n-aminophenyl) benzotriazole and 2- (2'-Hydroxy-3'-dodecyl-
Methylphenyl) benzotriazole, 2- [2′-hydroxy-4 ′-(2 ″ -ethylexyl) oxyphenyl] benzotriazole, methyl-3- [3-te
rt-butyl-5- (2H-benzotriazole-2-
Il) -4-hydroxyphenyl] propionate-condensate with polyethylene glycol (molecular weight about 300),
5-tert-butyl-3- (5-chloro-2H-benzotriazol-2-yl) -4-hydroxy-benzene-octyl propionate, 2- (2'-hydroxy-
sec-butyl-5'-tert-butylphenyl)-
5-tert-butylbenzotriazole and the like.

Microcapsules containing an ultraviolet absorber can be prepared by various known methods. Generally, a solution (oil-based liquid) containing the above-mentioned ultraviolet absorber as a main component is emulsified and dispersed in an aqueous medium. And a method of forming a wall film made of a polymer substance around an oily droplet. Among them, microcapsules having a wall film of a polyurethane resin or a polyurea resin formed from a polyisocyanate are preferably used because of their excellent heat resistance.

The method for producing microcapsules is not particularly limited. For example, microcapsules having a membrane wall made of polyurethane / polyurea resin may be a polyvalent isocyanate and a polyol that reacts with the polyisocyanate, or a polyvalent isocyanate and a polyol. The capsule wall film agent, such as an adduct with, is mixed with the core substance to be encapsulated, and emulsified and dispersed in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved. Manufactured by polymer formation.

In the preparation of microcapsules, various aqueous polymers, surfactants and the like are used as emulsifiers. The amount of the emulsifier used is not particularly limited, and is 1 to the microcapsule core substance and the wall film agent.
It is desirable to adjust so as to be in the range of about 50% by weight, more preferably about 3 to 30% by weight.

At the time of microencapsulation, a tin compound, a polyamide compound, an epoxy compound, a polyamine compound or the like can be used in combination as a reaction accelerator. When a polyamine compound is used, it is desirable to use an aliphatic polyamine compound from the viewpoint of light resistance.

The amount of the ultraviolet absorber exemplified above is adjusted in the range of 0.1 to 20 parts by weight based on 100 parts by weight of the (meth) acrylic acid copolymer. By the way,
If the amount is less than 0.1 part by weight, the pressure-sensitive adhesive will be discolored by exposure to ultraviolet rays or the like, and if it exceeds 20 parts by weight, the initial adhesive performance will be reduced and the pressure-sensitive adhesive composition will be colored, which is not preferable. It is preferable to keep the composition at about 3 to 15 parts by weight.

The emulsion-type acrylic pressure-sensitive adhesive composition preferably contains an antioxidant in addition to the ultraviolet absorber. Various known antioxidants such as hindered phenols and hindered amines can be used.

Specific examples of the hindered phenolic antioxidant include triethylene glycol-bis [3- (3
-Tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-
Bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,
2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,2′-ethylidenebis (4,6-di-tert-butylphenol) Butylphenol), 4,4'-thiobis (2-methyl-6-tert)
-Butylphenol), 4,4'-butylidenebis (6
-Tert-butyl-m-cresol), 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4
-[Α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-methyl-4
-Hydroxy-5-tert-butylphenyl) butane, 4,4′-thiobis (3-methylphenol),
4,4'-dihydroxy-3,3 ', 5,5'-tetrabromodiphenylsulfone, 4,4'-dihydroxy-
3,3 ′, 5,5′-tetramethyldiphenylsulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-
3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane and the like.

Specific examples of the hindered amine antioxidant include dimethyl succinate / 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate and poly [ポ リ 6 − (1,1,3,3-
(Tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene} (2
2,6,6-tetramethyl-4-piperidyl) imino}], N, N'-bis (3-aminopropyl) ethylenediamine.2,4-bis [N-butyl-N- (1,
2,2,6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3,5-triazine condensate, bis (2,2,6,6-tetramethyl-4-piperidyl)
Sebacate, 2- (3,5-di-tert-butyl-4)
-Hydroxybebenzyl) -2-n-butylmalonic acid bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like. Of course, the antioxidant used is not limited to these, and one kind may be used alone, or two or more kinds may be used in combination as needed.

The amount of the antioxidant exemplified above is adjusted in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the emulsion acrylic pressure-sensitive adhesive. By the way,
If the amount is less than 0.1 part by weight, the pressure-sensitive adhesive discolors due to heat and oxidation, and if it exceeds 10 parts by weight, the initial adhesive performance is lowered and the pressure-sensitive adhesive composition is colored. It is preferable to keep the composition at about 5 parts by weight.

The antioxidant generally uses water as a dispersion medium,
It may be prepared by a method of dispersing with a stirrer such as a ball mill or a sand mill, a pulverizer, or a method of emulsifying.

Next, the (meth) acrylic acid copolymer will be described in detail. Examples of the C ₄ -C ₁₈ alkyl ester monomer of (meth) acrylic acid include butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Stearyl (meth) acrylate and the like can be mentioned, and the copolymer preferably contains 60 to 99% by weight, preferably 70 to 95% by weight. By the way, if it is less than 60% by weight, the initial adhesive strength will be reduced, and if it is more than 99% by weight, the adhesive will stick out or cause cohesive failure when the label is applied. .

(B). Examples of the ethylenically unsaturated carboxylic acid-containing monomer include, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, monoalkyl maleic acid, monoalkyl itaconic acid, monoalkyl fumaric acid, and the like. 0 to 10% by weight, preferably 0.1 to 3% by weight. Incidentally, 0.
If the amount is less than 1% by weight, the emulsion becomes unstable and agglomerates tend to be easily generated during polymerization. Also one
Excessive compounding exceeding 0% by weight has a problem that the peeling force increases with time.

(C). Other monomers copolymerizable with (a) and (b) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, cyclohexyl (meth) acrylate ,
Methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate,
Glycidyl (meth) acrylate, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, styrene,
Divinylbenzene, ethylene, (meth) acrylonitrile, (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N'-methylenebis (meth)
Olefin unsaturated compounds such as acrylamide can be exemplified. These are about 0 to 40% by weight in the copolymer,
They can be appropriately blended.

The above-mentioned copolymer is produced by a method of emulsion polymerization in an aqueous system in the presence of an emulsifier, a chain transfer agent, a polymerization initiator, a dispersant and the like. In addition, the monomer concentration at the time of polymerization is usually 30 to 70% by weight, preferably 4 to 70% by weight.
About 0 to 60% by weight is appropriate. Further, as the polymerization initiator used in the polymerization, for example, potassium persulfate,
Persulfates such as ammonium persulfate, azo compounds such as 2,2′-azobisbutyronitrile, 2,2′-azobis (2,4′-dimethylvaleronitrile), hydrogen peroxide,
Examples include peroxides such as benzoyl peroxide and lauryl peroxide, so-called redox polymerization initiators comprising a combination of ammonium persulfate with sodium sulfite, acidic sodium sulfite, and the like. The amount of the polymerization initiator used is usually 0.2 to the total amount of the monomers to be subjected to polymerization.
To 2% by weight, more preferably 0.3 to 1% by weight.

Further, as the chain transfer agent to be added in the copolymerization, alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, octyl thioglycolate, nonyl thioglycolate, and 2-ethylhexyl thioglycolate can be used. Thioglycolic acid esters such as 2-ethylhexyl β-mercaptopropionate, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-
Isopropylidene-1-cyclohexene and the like can be mentioned. In particular, thioglycolic acid esters, 2,4
When -diphenyl-4-methyl-1-pentene and 1-methyl-4-isopropylidene-1-cyclohexene are used, the obtained copolymer has a low odor, which is preferable. The amount of the chain transfer agent is adjusted in the range of about 0.001 to 3% by weight of all monomers to be polymerized. Incidentally, the polymerization reaction is usually carried out under a temperature condition of 40 to 100 ° C.
This takes up to 8 hours. Further, a thickener, a wetting agent, a leveling agent, an antifoaming agent and the like can be appropriately added.

Examples of the surface substrate constituting the pressure-sensitive adhesive sheet of the present invention include papers such as art paper, coated paper, woodfree paper, and thermal recording paper, cellulose triacetate, cellulose diacetate, polyethylene, polypropylene, and soft polyvinyl chloride. And films such as hard polyvinyl chloride, polystyrene, polycarbonate, nylon, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and polyethylene terephthalate.

The method for forming the pressure-sensitive adhesive sheet of the present invention comprises:
According to a conventional method, a pressure-sensitive adhesive composition is coated on the release agent surface of a release sheet, dried to form a pressure-sensitive adhesive layer, and then bonded to the surface substrate, or on the surface substrate. And then dried to form a pressure-sensitive adhesive layer, which is then finished by laminating a release sheet.

In this case, the base material of the release sheet may be, for example, casein, dextrin, starch, carboxymethylcellulose, methylcellulose, ethylcellulose, or high-density base paper such as glassine paper, clay-coated paper, kraft paper, or high-quality paper. With natural or synthetic resins such as ethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, acrylate copolymer, etc. Water, solvent-type or solvent-free on a release substrate provided with a filler layer containing a pigment as a main component, or on a polylaminate paper obtained by laminating polyethylene or the like on kraft paper or woodfree paper, or on a polypropylene, polyethylene terephthalate film, etc. Type Silicone resin and 0.05 to 3 g / m ² approximately after coated fluororesin or the like by dry weight, obtained by forming a release layer is used by thermosetting or ionizing radiation-curable and the like. The coating device for applying the release agent is not particularly limited, but, for example, a bar coater, a direct gravure coater, an offset gravure coater, an air knife coater, a multi-stage roll coater and the like are appropriately used. .

As a coating apparatus for applying the pressure-sensitive adhesive, for example, a roll coater, a knife coater, a bar coater, a die coater, a comma coater, a lip coater, a reverse gravure coater, a vario gravure coater and the like are appropriately used. The coating amount of the adhesive is 5% by dry weight.
It is adjusted within a range of about 50 g / m ² . By the way, 5g
/ In m less than ^2, the adhesion performance of the adhesive sheet obtained becomes insufficient, whereas 50 g / m ² and over the adhesive or sticking during lamination of the adhesive sheet, which may cause cohesive failure during peeling.

[0042]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. In the examples, all parts, weights, ratios, coating amounts, etc. are indicated by solid weight unless otherwise specified.

[0043]

Example 1 [Production of (meth) acrylic acid copolymer] As a monomer mixture, 85 parts by weight of 2-ethylhexyl acrylate, 0.2 parts by weight of acrylic acid, 14.8 parts by weight of methyl methacrylate, polymerization 0.4 parts by weight of sodium persulfate as an initiator,
1.0 parts by weight of sodium dodecylbenzenesulfonate, 1.0 part by weight of polyoxyethylene nonylphenyl ether and 40 parts by weight of water were prepared as emulsifiers. Water and a polymerization initiator were charged into an autoclave equipped with a stirrer, a temperature controller and a reflux condenser, and the temperature was raised to 70 ° C. Next, a monomer mixture and an emulsifier were added, followed by stirring and emulsification to prepare a pre-emulsion. While continuously adding the whole amount of the pre-emulsion over 3 hours, the mixture was stirred at 80 ° C. for emulsion polymerization. Thereafter, stirring was further continued at 80 ° C. for 2 hours to complete the copolymerization, thereby obtaining a (meth) acrylic acid copolymer.

[Production of pressure-sensitive adhesive composition] 2- (2'-hydroxy-3 ', 5'-di-ter) was used as an ultraviolet absorber with respect to 100 parts by weight of the obtained (meth) acrylic acid copolymer.
5 parts by weight of (t-amylphenyl) bensotriazole,
Addition and mixing in the form of an aqueous dispersion having an average particle size of 1.5 μm,
An adhesive composition used in the present invention was obtained.

[Production of adhesive sheet] Commercially available polyethylene
20 g / dry weight of the adhesive composition on the laminate release paper
m ^TwoAfter applying and drying so that it becomes
And a surface substrate (polyester film, 25μm)
Together, an adhesive sheet was prepared. The above polyethylene lami
Nate release paper is a high quality paper with a polyethylene layer of about 15 μm.
Heat-sealed with a thickness of
It is obtained by applying a release agent such as fat and drying.

[0046]

Example 2 Except that 0.5 parts by weight of 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) bensotriazole was added in the form of an aqueous dispersion, In the same manner as in Example 1, an adhesive composition and an adhesive sheet were obtained.

[0047]

Example 3 Except that 10 parts by weight of 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) bensotriazole was added in the form of an aqueous dispersion,
In the same manner as in Example 1, an adhesive composition and an adhesive sheet were obtained.

[0048]

Example 4 3- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) bensotriazole was added in an amount of 3 parts by weight in the form of an emulsion having an average particle diameter of 0.2 μm. Except for the above, an adhesive composition and an adhesive sheet were obtained in the same manner as in Example 1.

[0049]

Example 5 In Example 1, 5 parts by weight of an aqueous dispersion of 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) bensotriazole was added to 2- (2'-hydroxy-3 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1, except that the aqueous dispersion of (-5'-tert-octylphenyl) benzotriazole was changed to 5 parts by weight.

[0050]

Example 6 In Example 1, 5 parts by weight of an aqueous dispersion of 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) bensotriazole was added to 2,4-dihydroxybenzene. An adhesive composition and an adhesive sheet were obtained in the same manner as in Example 1 except that the aqueous dispersion of phenone was changed to 5 parts by weight.

[0051]

Example 7 The procedure of Example 1 was repeated, except that a 20 μm polypropylene film was used as the surface substrate.
An adhesive sheet was obtained.

[0052]

Example 8 An adhesive sheet was obtained in the same manner as in Example 1, except that high quality paper of 50 g / m ² was used as a surface substrate.

[0053]

Example 9 [Production of (meth) acrylic acid copolymer] As a monomer mixture, 85 parts by weight of 2-ethylhexyl acrylate, 0.2 parts by weight of acrylic acid, 14.8 parts by weight of methyl methacrylate, polymerization 0.4 parts by weight of sodium persulfate as an initiator,
A (meth) acrylic acid copolymer was prepared in the same manner as in Example 1 except that 1.0 part by weight of sodium dodecylbenzenesulfonate, 1.0 part by weight of polyoxyethylene nonylphenyl ether and 40 parts by weight of water were used as emulsifiers. Obtained.

[Production of Adhesive Composition] 2- (2′-Hydroxy-3 ′, 5′-di-tert-amylphenyl) benso was used with respect to 100 parts by weight of the obtained (meth) acrylic acid copolymer. 5 parts by weight of an aqueous dispersion of triazole and dimethyl succinate 1- (2-hydroxyethyl) -4-
One part by weight of an aqueous dispersion of hydroxy-2,2,6,6-tetramethylpiperidine polycondensate was mixed to obtain a pressure-sensitive adhesive composition. [Production of pressure-sensitive adhesive sheet] A pressure-sensitive adhesive sheet was obtained using the above-mentioned pressure-sensitive adhesive composition and a 25-μm polyester film as a surface substrate.

[0055]

Comparative Example 1 An adhesive composition was prepared in the same manner as in Example 1 except that the aqueous dispersion of 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) bensotriazole was omitted. And an adhesive sheet.

[0056]

Comparative Example 2 The procedure of Example 1 was repeated except that the aqueous dispersion of 2- (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) bensotriazole was 0.05 parts by weight. Thus, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained.

[0057]

Comparative Example 3 The procedure of Example 1 was repeated, except that the aqueous dispersion of 2- (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) bensotriazole was 25 parts by weight. An adhesive composition and an adhesive sheet were obtained.

[0058]

Comparative Example 4 Except that a 20 μm polypropylene film was used as the surface substrate,
An adhesive sheet was obtained.

[0059]

Comparative Example 5 An adhesive sheet was obtained in the same manner as in Comparative Example 1, except that high quality paper of 50 g / m ² was used as a surface substrate.

[0060]

Comparative Example 6 An adhesive composition was prepared in the same manner as in Example 8 except that the aqueous dispersion of 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) bensotriazole was omitted. And an adhesive sheet.

[0061]

Example 10 [Manufacture of UV absorber contained in microcapsule] Preparation of Microcapsule Wall Membrane Agent A 1,6-hexamethylene diisocyanate (hereinafter abbreviated as HDI) was placed in a 1-liter glass four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and Dimroth condenser tube under a nitrogen gas atmosphere. ) 500 g and 5-ethyl-2
-5 g of nonanol was charged, heated to 80 ° C, kept for 2 hours to form a homogeneous solution, and then cooled to 50 ° C. Next, 0.1 g of trimethyl-N-2-hydroxypropylammonium-2-ethylhexanoate and then 0.25 g of tetraphenyldipropylene glycol diphosphite were added as a catalyst for isocyanuration. This mixture is
The temperature was raised to 0 ° C., the reaction was continued for 3 hours, and the reaction was stopped by adding 0.05 g of benzoyl chloride as a catalyst deactivator. The obtained reaction solution is applied to a thin film distillation apparatus (0.7 mmHg vacuum, 150 ° C. temperature) to obtain unreacted HD.
The I monomer was removed to obtain 92.4 g of a pale yellow transparent product (conversion rate: 18.3%).

Solution A Preparation 220 parts of a 12% aqueous solution of acetoacetyl group-modified partially saponified polyvinyl alcohol (trade name: Gosefimer Z-210, manufactured by Nippon Synthetic Chemical Co., Ltd.) is added to a stirring and mixing vessel equipped with a heating device. And an aqueous medium for capsule production. Separately, 2- (2'-hydroxy-3'-dodecyl-5'-
A solution obtained by heating, mixing and stirring 77 parts of methylphenyl) benzotriazole and 33 parts of the microcapsule wall film agent obtained above at 40 ° C. in the aqueous medium for producing capsules was mixed with a TK homomixer [Model HV-M]. , Manufactured by Tokushu Kika Kogyo Co., Ltd.] while cooling so that the average particle size becomes 1.5 μm. Then, 175 parts of water was added to the emulsified dispersion, and the mixture was reacted at 90 ° C. for 5 hours with stirring to prepare a microcapsule dispersion having a wall film made of a polyurethane / polyurea resin containing an ultraviolet absorbent.

[Production of Adhesive Composition] To 100 polymer parts of the (meth) acrylic acid copolymer obtained in the same manner as in Example 1, 3 parts by weight of Liquid A was mixed to obtain an adhesive composition. [Production of pressure-sensitive adhesive sheet] A pressure-sensitive adhesive sheet was obtained using the above-mentioned pressure-sensitive adhesive composition and a 25-μm polyester film as a surface substrate.

[0064]

Example 11 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 10, except that the amount of the solution A was changed to 0.5 part by weight.

[0065]

Example 12 Example 1 was repeated except that the liquid A was changed to 7 parts by weight.
In the same manner as in Example No. 0, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained.

[0066]

Example 13 In Example 10, 5 parts by weight of microcapsules containing 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) bensotriazole were added to 2- (2'-hydroxy-3 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 10, except that the amount of microcapsules containing ', 5'-di-n-amylphenyl) bensotriazole was changed to 5 parts by weight.

[0067]

Comparative Example 7 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 10 except that the amount of the solution A was changed to 0.05 part by weight.

[0068]

Comparative Example 8 Example 1 was repeated except that the liquid A was 25 parts by weight.
In the same manner as in Example No. 0, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained.

The following evaluation was performed on the thus obtained pressure-sensitive adhesive sheet, and the results are shown in Table 1.

<Evaluation Items>"Lightfastness" A sample was stuck on art paper on which three colors of red, black and yellow were printed and on white art paper, and the discoloration of the white paper before and after the irradiation of ultraviolet rays, embrittlement of the base material and printing. Was visually evaluated (however, Example 8 and Comparative Example 5 were excluded). UV irradiation is applied to the substrate surface at low temperature cycle sunshine xenon long life weather meter (trade name: WEL-7XS)
-LHP-B · EcS, manufactured by Suga Test Instruments Co., Ltd.) (Irradiance:
(390 W / m ² , irradiation wavelength: 300 to 700 nm) for 720 hours. For Example 8 and Comparative Example 5, the sample was stuck to a 25 μm polyester film and irradiated with ultraviolet light from the polyester film surface.
The discoloration before and after the ultraviolet irradiation was visually evaluated.

[0071]

[Adhesion] Adhesion to glass before and after irradiation with ultraviolet rays was measured (unit: g / 25 mm) in accordance with the measuring method of normal adhesion in JIS-Z-0237. Irradiation of ultraviolet rays is performed on a substrate surface and a glass surface by applying a low-temperature cycle sunshine xenon long life weather meter (trade name: WEL-7XS-LHP-B.EcS, manufactured by Suga Test Instruments Co., Ltd.) (irradiance: 390 W / m ² , Irradiation wavelength: 30
(0 to 700 nm) for 400 hours (except for Example 8 and Comparative Example 5). In Example 8 and Comparative Example 5, ultraviolet light was irradiated from the glass surface, and the adhesive strength to glass before and after the irradiation of the ultraviolet light was measured.

[0073]

[Table 1]

[0074]

As is clear from the results shown in Table 1, the pressure-sensitive adhesive sheet of the present invention is excellent in preventing discoloration due to light-fast exposure and fading of printing, and has a small change in adhesive strength after light-fast exposure. Was.

Claims (5)

[Claims] C ₄ -C according to claim 1 wherein at least (meth) acrylic acid
_In an emulsion-type acrylic pressure-sensitive adhesive composition containing a (meth) acrylic acid copolymer containing 60 to 99% by weight of an ₁₈ alkyl ester monomer as a main component, 0.1 to 0.1 part by weight of the (meth) acrylic acid copolymer is used. An emulsion-type acrylic pressure-sensitive adhesive composition, characterized by adding up to 20 parts by weight of an ultraviolet absorber in the form of an aqueous dispersion or emulsion. 2. The emulsion-type acrylic pressure-sensitive adhesive composition according to claim 1, wherein the ultraviolet absorber is a benzotriazole-based and / or benzophenone-based ultraviolet absorber. 3. The emulsion-type acrylic pressure-sensitive adhesive composition according to claim 1, wherein the ultraviolet absorber is a microencapsulated ultraviolet absorber. 4. The emulsion type according to claim 1, which contains 0.1 to 10 parts by weight of an antioxidant based on 100 parts by weight of the (meth) acrylic acid copolymer. Acrylic adhesive composition. 5. A pressure-sensitive adhesive sheet provided with a layer having the emulsion-type acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 4 on a substrate.