JPH10279901A - Adhesive sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive sheet, little discolored by ultraviolet ray, sunlight, fluorescence or the like, free of cracks, cleavages or the like in the base after being exposed to light, and little deteriorated in tackiness. SOLUTION: This adhesive sheet consists of a surface base laminated with one or more tack agent layers, wherein the tack agent layer is composed of (A) an acrylic tack agent composition, comprising a (metha)acrylic copolymer as the major ingredient which contains 60 to 99 wt.% of an alkyl ester monomer of (metha)acrylic acid, the monomer having a carbon number of 4 to 18, and (B) a coating solution for the tack agent layer, containing an ultraviolet ray absorber at 0.3 to 10 pts.wt. as the active ingredient per 100 pts.wt. of the (metha)acrylic copolymer, dissolved in an organic solvent in the case of the solid absorber or as it is or diluted with an inorganic solvent in the case of the liquid absorber, the tack agent layer containing the residual solvent at 10 to 2000 ppm after it is dried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive sheet used indoors and outdoors, in particular, there is little discoloration due to ultraviolet rays, sunlight, fluorescent lights, etc., and there is no crack or tear of a substrate even after exposure to light. The present invention also relates to a pressure-sensitive adhesive sheet having a small change in adhesive strength.

[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.

As a release sheet, high-density base paper such as glassine paper, clay-coated paper, kraft paper or high-quality paper, etc., laminated with a resin film such as polyethylene, or kraft paper or high-quality paper, etc. with polyvinyl alcohol, starch, etc. A resin-coated base paper provided with a barrier layer mainly composed of a water-soluble polymer or the like and a pigment is coated with a release agent such as a silicone compound or a fluorine compound.

As the pressure-sensitive adhesive, various pressure-sensitive adhesives such as rubber type, acrylic type and vinyl ether type, 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, the transparency of the adherend can be improved.
Regardless of opacity, when exposed to ultraviolet light, sunlight, fluorescent light, etc. for a long period of time indoors and outdoors, the discoloration of the adhesive significantly impairs the appearance of the adherend and the contents, and the label discolors the adhesive. Or the transparency of the film decreases. When such a label is affixed, there are disadvantages such as discoloration of the label and long-term exposure to light, which prevents the fading of the print. 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. .

[0007]

The present invention relates to a pressure-sensitive adhesive sheet used indoors and outdoors, and in particular, has little light discoloration due to ultraviolet rays, sunlight, fluorescent lights, and the like, and has cracks and tears in a substrate even after exposure to light. It is intended to provide a pressure-sensitive adhesive sheet having no adhesiveness and having little change in adhesive strength.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve such problems, and as a result, added an ultraviolet absorber to the adhesive composition in the form of an organic solvent solution to form a coating composition. It has been found that a pressure-sensitive adhesive sheet having excellent light resistance can be obtained by controlling the dried state of the pressure-sensitive adhesive layer and setting the residual solvent of the pressure-sensitive adhesive layer to 10 to 2000 ppm.

That is, the present invention relates to a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer laminated on a surface substrate, wherein the pressure-sensitive adhesive layer comprises (meth)
100 parts by weight of a (meth) acrylic acid copolymer was added to an acrylic pressure-sensitive adhesive composition containing a (meth) acrylic acid copolymer containing 60 to 99% by weight of an alkyl ester monomer of acrylic acid having 4 to 18 carbon atoms as a main component. 0.3 to 0.3% of active ingredient
An adhesive containing an ultraviolet absorber in an amount of 10 parts by weight, in the form of an organic solvent solution in the case of a solid ultraviolet absorber, or in the form of a liquid ultraviolet absorber as it is or diluted with an organic solvent. The pressure-sensitive adhesive layer has a residual solvent concentration of 10 to 2,000 after drying.
ppm.

The present invention is the pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has an absorbance at 340 nm of 0.2 to 10.0.

Further, the present invention is a pressure-sensitive adhesive sheet using a benzotriazole-based and / or benzophenone-based ultraviolet absorber as the ultraviolet absorber.

Also, a solid ultraviolet absorber is mixed with the adhesive composition in the form of an organic solvent solution, or a liquid ultraviolet absorber is mixed, or the liquid ultraviolet absorber is diluted with an organic solvent and mixed. Then, the agitated coating solution for the pressure-sensitive adhesive layer was applied to a surface substrate or a release sheet, and the residual solvent concentration of the pressure-sensitive adhesive layer was 10%.
This is a method for producing a pressure-sensitive adhesive sheet, which is dried so as to have a concentration of about 2000 ppm and then bonded to a release sheet or a surface substrate.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylic pressure-sensitive adhesive composition used for the pressure-sensitive adhesive layer contains a (meth) acrylic acid copolymer as a main component. The (meth) acrylic acid copolymer is
(A). (Meth) acrylic acid containing 60 to 99% by weight of an alkyl ester monomer having 4 to 18 carbon atoms, and (b). Ethylenically unsaturated carboxylic acid-containing monomer
1 to 10% by weight, and (c). (A) and (b) above
And 0 to 39.9% by weight of other monomers copolymerizable with the above.

(A). (Meth) acrylic acid having 4 to 4 carbon atoms
Examples of the alkyl ester monomer 18 include:
Examples thereof include butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and stearyl (meth) acrylate. % By weight, preferably 70 to 98% 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. 0.1 to 10% by weight,
Preferably, the content is 0.1 to 5% by weight. By the way,
If the amount is less than 0.1% by weight, adhesive residue is apt to be left on the adherend, and if the amount exceeds 10% by weight, there is a problem that the peeling force increases with time. This component,
The cohesive force is improved when the adhesive force of the pressure-sensitive adhesive is applied and the functional group portion is crosslinked.

(C). Other monomers copolymerizable with (a) and (b) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and 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 may not be used, but when they are added, they may be appropriately blended in the copolymer up to about 39.9% by weight. This component is effective in improving the cohesive strength of the pressure-sensitive adhesive.

The above-mentioned copolymer can be produced by any method such as bulk polymerization, solution polymerization and suspension polymerization. The monomer concentration at the time of polymerization is usually 30 to 70% by weight, preferably about 40 to 60% by weight.
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 and 2,2′-azobis (2,4′-dimethylvaleronitrile), peroxides such as hydrogen peroxide, benzoyl peroxide and lauryl peroxide; A so-called redox-based polymerization initiator comprising a combination of ammonium persulfate, sodium sulfite, acidic sodium sulfite and the like can be mentioned. The amount of the polymerization initiator to be used is generally 0.2 to 2% by weight, more preferably 0.1 to 2% by weight, based on the total amount of monomers used for polymerization.
It is adjusted in the range of 3 to 1% by weight.

Further, as a 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 are 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.

In the present invention, in order to further improve the adhesive properties,
It is preferable to add a tackifier to the acrylic pressure-sensitive adhesive composition. By adding a tackifier, the adhesiveness to an adherend such as a polyolefin is also improved.
Examples of the tackifier used in the present invention include natural resins such as rosin, modified rosin, rosin and derivatives of modified rosin, polyterpene resins, modified terpene, aliphatic hydrocarbon resins, cyclopentadiene resins, and aromatic resins. Group petroleum resin, phenolic resin, alkyl-phenol-
Acetylene-based resin, cumarone-indene-based resin, vinyl toluene-α-methylstyrene copolymer and the like, but aliphatic hydrocarbon resin, from the viewpoint of the transparency of the adhesive,
Cyclopentadiene-based resins, aromatic petroleum resins, phenolic resins, and alkyl-phenol-acetylene-based resins are preferred. The mixing ratio of the tackifier is (meth)
1 to 100 parts by weight of the acrylate copolymer
50 parts by weight. By the way, if the amount is less than 1 part by weight, the effect of improving the adhesive strength and the adhesive strength is poor, and if it exceeds 50 parts by weight, the adhesive strength and the adhesive strength tend to be reduced.

The pressure-sensitive adhesive sheet of the present invention is prepared by adding an ultraviolet absorber of 0.3 to 10 parts by weight of an active ingredient to 100 parts by weight of a (meth) acrylic acid copolymer which is a main component of the acrylic pressure-sensitive adhesive composition. (Solid UV absorber in the form of an organic solvent solution, liquid UV absorber as it is or diluted with an organic solvent) to control the drying state of the applied adhesive layer, The residual solvent of the pressure-sensitive adhesive layer
It is characterized by being in the range of 0 to 2000 ppm. In the present invention, the absorbance of the pressure-sensitive adhesive layer at 340 nm is 0.2%.
Preferably, the adjustment is made to be 10.0 or less. This is performed by controlling the amount of addition according to the absorption capacity of the ultraviolet absorber used. The method for measuring the absorbance is described in the section of Examples.

In a conventional pressure-sensitive adhesive sheet, the pressure-sensitive resin in the pressure-sensitive adhesive, and a polymerization initiator and a chain transfer agent added during polymerization are exposed to ultraviolet light, sunlight, fluorescent light, etc., so as to prevent discoloration and decomposition. Wake up. Possibly, the adhesive composition of the present invention is to disperse the ultraviolet absorber in a solvent such as toluene in a liquid form or powder evenly in the adhesive resin,
In order to absorb the energy from sunlight, fluorescent lamps, etc. efficiently with the adhesive composition and the UV absorber which is uniformly dispersed and convert it to heat energy, it is necessary to suppress the discoloration of the adhesive and the decrease in the adhesive strength. Seem. In order to exhibit this effect, at least 10 ppm of the residual solvent is required. If the residual solvent concentration is less than 10 ppm, the added ultraviolet absorber may precipitate or the adhesive strength of the adhesive may be reduced. There is. Conversely, if the content exceeds 2000 ppm, the solvent odor becomes severe, which not only poses a problem in use, but also tends to cause adhesive residue upon peeling after use. If the absorbance with respect to ultraviolet light at 340 nm is less than 0.2, the effect of ultraviolet light cannot be prevented due to insufficient capacity, and if the absorbance exceeds 10.0, the effect is saturated and becomes economically wasteful. .

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-benzotriazolylphenol], 2,
2'-methylenebis (3-methoxy-6-benzoylphenol), 2,2'-octylidenebis [4-methyl-6- (5'-methylbenzotriazolyl) phenol] and the like.

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 ″ -ethylhexyl) 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.

Specific examples of the benzophenone 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′-
Dihydroxy-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 type 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 rays, 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.

These ultraviolet absorbers are mixed with the acrylic pressure-sensitive adhesive composition in the form of an organic solvent solution to form a coating solution for the pressure-sensitive adhesive layer. Those having an action are preferred, and toluene, ethyl acetate and the like can be used alone or as a mixture of two or more.

The amount of the active ingredient of the ultraviolet absorber exemplified above is adjusted in the range of 0.3 to 10 parts by weight based on 100 parts by weight of the (meth) acrylic acid copolymer. By the way, if the amount is less than 0.3 parts by weight, discoloration of the adhesive cannot be prevented by exposure to ultraviolet rays and the like. If the amount exceeds 10 parts by weight, the initial adhesive performance is reduced, and the adhesive composition is colored. It is not preferable because there are problems such as
It is particularly preferred to keep the composition at about 5 to 8 parts by weight.

As the ultraviolet absorber, both solid and liquid can be used. However, a method in which the solid is dissolved in an organic solvent and mixed with the coating solution for the pressure-sensitive adhesive layer is preferable because the coating solution can be easily prepared. The coating solution for the pressure-sensitive adhesive layer is prepared, for example, by adding a solution obtained by dissolving an ultraviolet absorber in an organic solvent such as toluene to the acrylic pressure-sensitive adhesive composition and stirring with an agitator or the like. In addition, various auxiliaries such as a thickener, a wetting agent, a leveling agent, and an antifoaming agent are added before, after, or simultaneously with the addition of the solution containing the ultraviolet absorber, or included in the ultraviolet absorber solution. It may be added to the acrylic pressure-sensitive adhesive composition.

The acrylic pressure-sensitive adhesive composition is preferably used in combination with a crosslinking agent. As a cross-linking agent to be used in combination, an ionic cross-linking agent containing Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Al ^{3+ in a} resin, an epoxy resin, a melamine-formaldehyde resin,
Crosslinking agents such as amino-formaldehyde resin, urea resin and polyisocyanate resin can be exemplified. Examples of the ionic crosslinking agent include zinc acetate, magnesium acetate, calcium acetate and the like. Among them, an ionic cross-linking agent (metal chelate) and an epoxy-based cross-linking agent are preferable because they do not turn yellow.
The addition of the cross-linking agent is preferably performed after the mixing and stirring of the ultraviolet absorber because the pot life of the pressure-sensitive adhesive composition becomes longer. The crosslinking agent is an acrylic adhesive composition 10
It is advisable to add about 0.05 to 10 parts by weight to 0 part by weight. By the way, when the amount is less than 0.05 part by weight, the cohesive force is weak and glue residue is liable to be generated, and when it exceeds 10 parts by weight, the adhesive strength is reduced.

Examples of the surface substrate constituting the pressure-sensitive adhesive sheet of the present invention include paper, PVC film, synthetic paper, and vapor-deposited PE.
Opaque sheets such as T, cellulose triacetate,
Transparent sheets such as transparent films such as cellulose diacetate, polyethylene, polypropylene, soft polyvinyl chloride, hard polyvinyl chloride, polystyrene, polycarbonate, nylon, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and polyethylene terephthalate can be used as appropriate. . In particular, in the case of a transparent sheet, problems such as discoloration of the pressure-sensitive adhesive layer were remarkable, and the effect of the present invention was great.

The transparent film, when considering printability,
It is preferable to have an easy-adhesion coat layer on the surface where the pressure-sensitive adhesive layer is not provided. Such an easy-adhesion coat layer is not particularly limited, but an acrylic resin having a glass transition temperature of 70 ° C. or higher, such as a methyl methacrylate resin or a styrene-acrylic copolymer resin, is preferred because it has less blocking with the film substrate. Further, the surface on which the pressure-sensitive adhesive layer is formed is preferably subjected to a corona treatment or provided with an easy-adhesion coat layer, since the adhesiveness of the pressure-sensitive adhesive layer is excellent. In particular, the acrylic resin is preferable because it has excellent adhesion to the pressure-sensitive adhesive layer used in the present invention.

The method for forming the pressure-sensitive adhesive sheet of the present invention is as follows.
Using the pressure-sensitive adhesive layer coating liquid obtained as described above, except for adjusting the drying conditions so that the residual solvent concentration of the pressure-sensitive adhesive layer after drying is 10 to 2000 ppm, follow a conventional method. The adhesive composition is coated on the release agent surface of the release sheet,
A method of drying to provide an adhesive layer, and then laminating with the surface substrate, or coating the adhesive composition on the surface substrate, drying to provide an adhesive layer, and then applying a release sheet Finished in a matching way.

In this case, the base material of the release sheet may be a 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. A release base material provided with a filler layer containing a pigment as a main component, or a polylaminate paper obtained by laminating polyethylene or the like on kraft paper or woodfree paper, or a polypropylene, polyethylene terephthalate film or the like,
Solvent-type or non-solvent-type silicone resins or fluororesins are applied at a dry weight of about 0.05 to 3 g / m ² and then a release layer is formed by heat curing or ionizing radiation curing. 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. .

Examples of a coating device for coating the pressure-sensitive adhesive layer include a roll coater, a knife coater, a bar coater, and the like.
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 in the range of about 5 to 50 g / m ² by dry weight, preferably 10 to 40 g.
/ M ² . By the way, if it is less than 5 g / m ² ,
The adhesive performance of the obtained pressure-sensitive adhesive sheet was insufficient, while 5
If it exceeds 0 g / m ² , the pressure-sensitive adhesive may protrude at the time of laminating the pressure-sensitive adhesive sheets or cause cohesive failure at the time of peeling.

[0039]

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.

Example 1 [Preparation of pressure-sensitive adhesive composition]
A blended composition consisting of 80% by weight of 2-ethylhexyl, 19% by weight of butyl (meth) acrylate and 1% by weight of acrylic acid was copolymerized in toluene at 60 ° C. for 4 hours to obtain a solid composition having a solids concentration of 45% by weight. ) An acrylic acid copolymer was obtained. This was used as an adhesive composition.

[Preparation of Coating Solution for Pressure-Sensitive Adhesive Layer] With respect to 100 parts by weight of the obtained (meth) acrylic acid copolymer (45 wt%), 2- (2′-hydroxy-) was used as an ultraviolet absorber.
15 parts by weight of a 15 wt% toluene solution of 5'-tert-octylphenyl) benzotriazole was added and mixed, and stirred with an agitator to obtain a coating solution for an adhesive layer used in the present invention.

[Production of pressure-sensitive adhesive sheet] A commercially available polyethylene laminated release paper was coated with a pressure-sensitive adhesive layer coating solution in a dry weight of 15%.
g / m ^2, and the residual solvent concentration is 150 p.
After drying to pm, a polyester film (trade name “Lumirror” 50 μm, manufactured by Toray Industries, Inc.) having the pressure-sensitive adhesive layer surface and the easy-adhesion coat layer was bonded to each other to form a pressure-sensitive adhesive sheet. The polyethylene laminate release paper is obtained by heat-sealing a high-quality paper with a polyethylene layer to a thickness of about 15 μm, applying a release agent containing a silicone resin as a main component to the polyethylene layer, and drying.

Example 2 A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive sheet was dried so that the residual solvent concentration was 20 ppm.

Example 3 In the production of an adhesive sheet, the residual solvent concentration was 1500 pp.
m was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive sheet was dried so as to obtain m.

Comparative Example 1 An adhesive composition and an adhesive sheet were prepared in the same manner as in Example 1 except that a 15 wt% toluene solution of 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole was removed. I got

Comparative Example 2 A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive sheet was dried so that the residual solvent concentration was 5 ppm.

Comparative Example 3 In the production of an adhesive sheet, the residual solvent concentration was 2500 pp
m was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive sheet was dried so as to obtain m.

Example 4 Adhesion was carried out in the same manner as in Example 1 except that a 15 wt% toluene solution of 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole was changed to 1.5 parts by weight. A composition and a pressure-sensitive adhesive sheet were obtained.

Example 5 The procedure of Example 1 was repeated, except that 24 parts by weight of a 15 wt% toluene solution of 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole was used.
An adhesive sheet was obtained.

Comparative Example 4 Adhesion was carried out in the same manner as in Example 1 except that a 15 wt% toluene solution of 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole was changed to 0.3 part by weight. A composition and a pressure-sensitive adhesive sheet were obtained.

Comparative Example 5 The procedure of Example 1 was repeated, except that 45 parts by weight of a 15 wt% toluene solution of 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole was used.
An adhesive composition and an adhesive sheet were obtained.

Example 6 In Example 1, 2- (2'-hydroxy-5'-t
tert-octylphenyl) benzotriazole 15
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1, except that 15 parts by weight of a 15 wt% toluene solution of 2,4-dihydroxybenzophenone was changed to 15 parts by weight of a 15 wt% toluene solution.

Example 7 An adhesive sheet was obtained in the same manner as in Example 1 except that a 20 μm polypropylene film was used as a surface substrate.

Comparative Example 6 An adhesive sheet was obtained in the same manner as in Comparative Example 1, except that a 20 μm polypropylene film was used as a surface substrate.

Example 8 [Production of pressure-sensitive adhesive composition]
A blended composition consisting of 80% by weight of 2-ethylhexyl, 19% by weight of butyl (meth) acrylate and 1% by weight of acrylic acid was copolymerized in toluene at 60 ° C. for 4 hours to obtain a solid composition having a solids concentration of 45% by weight. ) An acrylate copolymer was obtained. To 100 parts by weight of the obtained (meth) acrylate copolymer, 5 parts by weight of an aromatic petroleum resin as a tackifier was added and mixed to obtain a pressure-sensitive adhesive composition.

[Preparation of Coating Liquid for Adhesive Layer] With respect to 100 parts by weight of the obtained (meth) acrylate copolymer,
2- (2′-hydroxy-5′-t) as an ultraviolet absorber
tert-octylphenyl) benzotriazole 15
15% by weight of a wt% toluene solution was added, mixed and stirred with an agitator to obtain a coating solution for an adhesive layer.

[Production of pressure-sensitive adhesive sheet] The above-mentioned pressure-sensitive adhesive composition was put on a commercially available polyethylene-laminated release paper at a dry weight of 25%.
g / m ^2, and the residual solvent concentration is 150 p.
After drying to pm, a polyester film (trade name “Lumirror” 50 μm, manufactured by Toray Industries, Inc.) provided with the pressure-sensitive adhesive layer surface and the easy-adhesion coat layer was laminated to form a pressure-sensitive adhesive sheet. The polyethylene laminate release paper is obtained by heat-sealing a polyethylene layer to a high-quality paper to a thickness of about 15 μm, applying a release agent containing a silicone resin as a main component to the polyethylene layer, and drying.

Example 9 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 8, except that 45 parts by weight of an aromatic petroleum resin was added and mixed as a tackifier.

Example 10 A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 8, except that 20 parts by weight of an aromatic petroleum resin was added and mixed as a tackifier.

Example 11 Adhesion was carried out in the same manner as in Example 8, except that 2.5 parts by weight of a 15 wt% toluene solution of 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole was used. A composition and a pressure-sensitive adhesive sheet were obtained.

Example 12 The procedure of Example 8 was repeated except that a 15 wt% solution of 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole in toluene was used in an amount of 24 parts by weight.
An adhesive composition and an adhesive sheet were obtained.

Example 13 In Example 8, 2- (2'-hydroxy-5'-t
tert-octylphenyl) benzotriazole 15
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 8, except that 15 parts by weight of a 15 wt% toluene solution of 2,4-dihydroxybenzophenone was changed to 15 parts by weight of a 15 wt% toluene solution.

Comparative Example 7 An adhesive composition and an adhesive sheet were prepared in the same manner as in Example 8 except that a 15 wt% toluene solution of 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole was removed. I got

Comparative Example 8 A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 8, except that the pressure-sensitive adhesive sheet was dried so that the residual solvent concentration was 5 ppm.

Comparative Example 9 In the production of an adhesive sheet, the residual solvent concentration was 2500 pp.
m was obtained in the same manner as in Example 8 except that the pressure-sensitive adhesive sheet was dried so as to obtain m.

Comparative Example 10 Adhesion was carried out in the same manner as in Example 8 except that a 15 wt% toluene solution of 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole was changed to 0.3 part by weight. A composition and a pressure-sensitive adhesive sheet were obtained.

Comparative Example 11 The procedure of Example 8 was repeated except that 70 parts by weight of a 15 wt% toluene solution of 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole was used.
An adhesive composition and an adhesive sheet were obtained.

Example 14 As a surface substrate, a polypropylene film (trade name “155LL-534”, 50 μm,
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 10 except that Mobil) was used.

Comparative Example 12 As a surface substrate, a polypropylene film (trade name “155LL-534”, 50 μm,
(Comparative Example 7) except that Mobil) was used.
An adhesive sheet was obtained.

Comparative Example 13 2- (2'-hydroxy-5'-t was used as an ultraviolet absorber.
2.25 parts by weight of tert-octylphenyl) benzzotriazole powder was added, but was not uniformly dissolved in the (meth) acrylic acid copolymer, and undissolved substances were generated. Could not be obtained.

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

<Evaluation Items> Absorbance measurement: The absorbance at 340 nm of the adhesive layer was obtained by subtracting the absorbance of the surface substrate from the absorbance of the adhesive sheet using a self-recording spectrophotometer (U-3500, manufactured by Hitachi, Ltd.). Was calculated by

"Light fastness" A sample was stuck on art paper printed with three colors of red, black, and yellow, and white art paper, and the discoloration of the white paper after ultraviolet irradiation, cracking of the base material, and fading of the print were visually observed. Was evaluated. UV irradiation is performed on the substrate surface at 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:
(300-700 nm) for 720 hours.

[0074]

"Adhesion" Adhesion to a SUS plate before and after irradiation with ultraviolet rays was measured (unit: g / 25 mm) in accordance with the method for measuring normal adhesion in JIS-Z-0237. Ultraviolet radiation is applied from the substrate surface to the low-temperature cycle sunshine
Xenon Long Life Weather Meter (Product Name: WE
L-7XS-LHP-B.EcS, manufactured by Suga Test Instruments Co., Ltd.) with an irradiance of 390 W / m ² and an irradiation wavelength of 300 to
Irradiation was performed at 700 nm for 400 hours.

"Glue residue" The glue residue on the adherend after the measurement of the adhesive strength before the weather meter treatment was visually evaluated.

"Appropriate for PP container" Affixed to a household detergent container made of polypropylene and the floating of the label was evaluated. ：: Very good without label floating. Δ: The label is slightly lifted, but at a practical level. X: The level of the label is too large to be practical.

"Comprehensive evaluation" A practical evaluation as a pressure-sensitive adhesive sheet was comprehensively evaluated. A: Very excellent as a light-resistant adhesive sheet. ：: Light resistance is slightly inferior, or there is some problem as an adhesive sheet, but at a practically usable level. Δ: Although light resistance was excellent, there was a problem as a pressure-sensitive adhesive sheet, and the level was not practical. ×: Poor light resistance, not practical

[0079]

[Table 1]

As is clear from the results in Table 1, (meta)
In the examples in which the effective component of the ultraviolet absorber is 0.3 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the acrylic acid copolymer (solid), discoloration of white paper, discoloration of printing, cracking of the substrate, Adhesive strength and glue residue are balanced. When the residual solvent is less than 10 ppm as in Comparative Examples 2 and 8, the adhesive strength before the treatment decreases, and when the residual solvent exceeds 2000 ppm as in Comparative Examples 3 and 9, glue residue occurs. In the case of each of the examples in which the residual solvent is 10 ppm or more and 2000 ppm or less, there is no decrease in adhesive strength before treatment and no adhesive residue. When the effective component of the ultraviolet absorber is less than 0.3 parts by weight as in Comparative Examples 4 and 10, discoloration of white paper, discoloration of printing, and cracking of the base material are inferior.
When the amount exceeds the weight part, the adhesive strength before the treatment is reduced. Also,
As shown in Examples 8 to 14, it is found that when a tackifier is blended, a pressure-sensitive adhesive sheet having excellent adhesion to a polypropylene (PP) container is obtained.

[0081]

As described above, the pressure-sensitive adhesive sheet of the present invention is excellent in prevention of discoloration due to light-fast exposure and discoloration of printing, and has no crack or tear of the substrate even after light-fast exposure, and has little change in adhesive strength. It was a sheet.

Claims (10)

[Claims] 1. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer laminated on a surface substrate, wherein the pressure-sensitive adhesive layer contains 60 to 99% by weight of a (meth) acrylic acid alkyl ester monomer having 4 to 18 carbon atoms. ) An acrylic pressure-sensitive adhesive composition containing an acrylic acid copolymer as a main component, a (meth) acrylic acid copolymer 1
The ultraviolet absorber is used in an amount of 0.3 to 10 parts by weight of the active ingredient with respect to 00 parts by weight. In the case of a solid ultraviolet absorber, it is in the form of an organic solvent solution, and in the case of a liquid ultraviolet absorber, it is as it is. Or a pressure-sensitive adhesive sheet characterized by being coated with a coating solution for a pressure-sensitive adhesive layer containing the same in a form diluted with an organic solvent, and having a residual solvent concentration of 10 to 2000 ppm after drying of the pressure-sensitive adhesive layer. . 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has an absorbance at 340 nm of 0.2 to 10.0. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the ultraviolet absorber is a benzotriazole-based and / or benzophenone-based ultraviolet absorber. 4. The pressure-sensitive adhesive sheet according to claim 1, wherein the organic solvent is toluene and / or ethyl acetate. 5. An acrylic pressure-sensitive adhesive composition comprising 1 to 5 tackifiers per 100 parts by weight of a (meth) acrylic acid copolymer.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, which contains 0 parts by weight. 6. The pressure-sensitive adhesive sheet according to claim 1, wherein the surface substrate is a transparent film having an easy-adhesion coat layer formed thereon. 7. The pressure-sensitive adhesive sheet according to claim 6, wherein the easy-adhesion coat layer is a layer mainly composed of an acrylic resin having a glass transition temperature of 70 ° C. or higher. 8. The adhesive composition is mixed with a solid ultraviolet absorber in the form of an organic solvent solution, a liquid ultraviolet absorber is mixed, or the liquid ultraviolet absorber is diluted with an organic solvent and mixed. A stir-coated pressure-sensitive adhesive layer coating solution is applied to a surface substrate or a release sheet, and the residual solvent concentration of the pressure-sensitive adhesive layer is 10 to 20.
A method for producing a pressure-sensitive adhesive sheet, characterized in that the pressure-sensitive adhesive sheet is dried so as to have a concentration of 00 ppm and then bonded to a release sheet or a surface substrate. 9. The pressure-sensitive adhesive composition is a (meth) acrylic acid copolymer containing 60 to 99% by weight of an alkyl ester monomer having 4 to 18 carbon atoms of (meth) acrylic acid.
9. The method for producing a pressure-sensitive adhesive sheet according to claim 8, wherein 0.3 to 10 parts by weight of an active ingredient is mixed with 100 parts by weight of the acrylic acid copolymer in the form of an organic solvent solution, liquid or diluted liquid. . 10. The method for producing a pressure-sensitive adhesive sheet according to claim 9, wherein a crosslinking agent is mixed with the coating solution for the pressure-sensitive adhesive layer, which has been mixed and stirred with an ultraviolet absorber, and then applied.