JP4506146B2 - Adhesive composition and adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet having a crosslinking system in a pressure-sensitive adhesive solution and crosslinking at the time of coating and drying, and having an improved balance between storage stability and cohesive force, and a method for producing the same. Is.

  Solvent-type pressure-sensitive adhesives have a relatively low molecular weight, so if they are used as they are, and the organic solvent is dried and used, the cohesive strength between the molecules is insufficient, and the desired physical properties (holding power, heat resistance, glue) The result of the overhang test etc. is not obtained. For this reason, polyfunctional isocyanates, epoxy compounds and the like have been used as crosslinking agents. These curing agents are added immediately before the adhesive is applied, and the adhesive is said to be a two-component type. However, when mixing the curing agent, it is difficult to verify the amount in the wrong amount, and if it is wrong, it is difficult to verify directly, and workability is difficult because the usable time (pot life) after charging is several hours. is there. Moreover, since the operator weighs isocyanate having a high reactivity, the one-component type is more preferable from the viewpoint of safety.

  On the other hand, in the one-pack type pressure-sensitive adhesive, it is considered that the crosslinking system or the crosslinking system used in paints may be applied as it is. However, since the molecular weight of the polymer used in the pressure-sensitive adhesive field is large, When the agent is added, there is a problem in storage stability (shelf life), and gelation occurs during long-term storage. That is, due to the length of the polymer chain, the effect of increasing the molecular weight is great even if a part of the polymer is crosslinked, and the viscosity is greatly increased.

  As one-pack type adhesives with storage stability, aluminum and titanium chelate cross-linking agents that are complex compounds blocked with alcoholic solvents are known. There were problems such as lack of power.

  A blocked isocyanate blocked with methyl ethyl ketone oxime or the like is also known as a crosslinking agent. However, in order to achieve both shelf life and reactivity, coating and drying at an extremely high temperature are required. In other words, those having a low deblocking temperature react at room temperature instead of high reactivity, and the shelf life is short. A high deblocking temperature has a long shelf life, but the temperature during coating and drying must be extremely high.

  Patent Document 1 describes a pressure-sensitive adhesive containing an acrylic polymer containing a benzotriazole-based and hindered amine-based UV absorber and also containing glycidyl methacrylate.

  Patent Document 2 describes a pressure-sensitive adhesive containing an acrylic polymer containing a benzotriazole-based compound and glycidyl methacrylate in a primer composition.

  However, Patent Document 1 does not contain a cyclic ether group and a carboxyl group as essential components. Further, the object of the invention itself is to improve light resistance, and the shelf life of the coating liquid important for realizing the pressure-sensitive adhesive is not described.

Patent Document 2 is a low molecular weight primer composition that does not function as an adhesive, and has not yet presented a technique for solving the problem of storage stability of an adhesive that easily gels due to its high molecular weight. .
As described above, a technology for improving the storage stability at a practical level has not been known for an adhesive using an acrylic polymer having a relatively large molecular weight.
Japanese Patent Laid-Open No. 10-279901 Japanese Patent Laid-Open No. 3-6282

  Therefore, an object of the present invention is to improve the storage stability of a solvent one-component pressure-sensitive adhesive while containing a crosslinking component which is a cohesive force improving component when it becomes a pressure-sensitive adhesive sheet.

  The present invention relates to (meth) acrylic acid alkyl ester having 1 to 14 carbon atoms in the alkyl group, ethylenic monomer having cyclic ether group of 0.2 to 1.8 phr, polymerizable unsaturated carboxylic acid of 4 to 8 phr, and necessary The pressure-sensitive adhesive composition comprises an acrylic polymer having a weight average molecular weight of 300,000 or more obtained by copolymerizing a copolymerizable ethylenically unsaturated monomer other than those described above.

Furthermore, this invention is the said adhesive composition whose cyclic ether group is a glycidyl group, an oxetane group, or an alicyclic epoxy group.
Furthermore, this invention is the said adhesive composition whose polymerizable unsaturated carboxylic acid is acrylic acid.

  Furthermore, this invention is the said adhesive composition containing the storage stabilizer chosen from a benzotriazole type compound, an amino ether type hindered amine compound, a hydroxyphenyl triazine compound, a polyphenol type compound, or an alkylphenol type compound.

  Furthermore, this invention is an adhesive composition which consists of the said adhesive composition and a solvent.

  Furthermore, this invention is an adhesive sheet formed by applying and drying the above-mentioned adhesive composition.

  Furthermore, this invention is a manufacturing method of the said adhesive sheet manufactured with the drying temperature of 100 to 150 degreeC.

  The present invention is a one-pack type pressure-sensitive adhesive having a cyclic ether group and a carboxyl group, the amount of the cyclic ether group and the carboxyl group, as additives, benzotriazole compounds, amino ether hindered amine compounds, hydroxyphenyl triazine compounds, polyphenol compounds, By using an alkylphenol compound and adjusting the amount thereof, the solid content of the pressure sensitive adhesive, and the molecular weight, the storage stability of the pressure sensitive adhesive and the conflicting properties such as the cohesive strength of the obtained pressure sensitive adhesive sheet were made compatible.

  Examples of the radically polymerizable (meth) acrylic acid ester having 1 to 14 carbon atoms in the alkyl group used in the present invention include linear or branched aliphatic alcohol acrylic acid esters and the corresponding methacrylic acid esters. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth ) Decyl acrylate, dodecyl (meth) acrylate, etc., and the content is preferably 60 to 95.8 phr. In addition, phr is an abbreviation for (part hundred resin) and represents a weight percentage with respect to the acrylic polymer.

  Examples of the ethylenic monomer having a cyclic ether group used in the present invention include glycidyl acrylate, glycidyl methacrylate (glycidyl methacrylate), allyl glycidyl ether, oxetane methacrylate, allyl oxetane, and 1.2-epoxy-4. -Vinylcyclohexane, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexylmethyl methacrylate tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate and the like.

  The content of ethylenic monomer having a cyclic ether group is 0.2 to 1.8 phr, preferably 0.6 to 1.2 phr. When it is 0.2 phr or less, the cohesive force and adhesive force when it becomes a pressure-sensitive adhesive sheet are insufficient, and when it is 1.8 phr or more, it may react with a carboxyl group during synthesis and gel. In addition, the storage stability of the pressure-sensitive adhesive solution is deteriorated, and it is difficult to control the crosslinking system.

  Examples of the polymerizable unsaturated carboxylic acid in the present invention include acrylic acid, methacrylic acid, maleic anhydride, maleic acid, itaconic acid, and crotonic acid. Its content is 4 to 8 phr, preferably 5 to 7 phr. When the content is 4 phr or less, the cohesive force and adhesive force when the pressure-sensitive adhesive sheet is obtained are insufficient. In addition, the storage stability of the pressure-sensitive adhesive solution is deteriorated, and it is difficult to control the crosslinking system.

  As the copolymerizable ethylenically unsaturated monomer in the present invention, there are functional group-containing monomers such as hydroxyl group, methylol group, amino group, amide group, ethyleneimine group and isocyanate group, Specific examples include 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, polyethylene glycol acrylate, vinyl isocyanate, N-methylol acrylamide, N-methylol methacryl. Amides, N-methylaminoethyl acrylate, N-tributylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N- Diethylaminoethyl methacrylate, acrylamide, methacrylamide, vinyl pyrrolidone, acryloyl morpho Emissions, N- vinylformamide, etc., and the content thereof is 5phr desirably from 0.

  Other copolymerizable ethylenically unsaturated monomers include vinyl esters, vinyl pyridine, vinyl acetate, vinyl propionate, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, isobornyl (meth) acrylate, butadiene Also, chloroprene can be used for copolymerization, and its content is preferably 0 to 40 phr.

  As the solvent of the pressure-sensitive adhesive composition in the present invention, ethyl acetate, butyl acetate, toluene, xylene, methanol, ethanol, isopropyl alcohol, isobutyl alcohol, methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone, acetone, hexane, cyclohexanone, etc. are used. be able to.

  The weight average molecular weight of the acrylic polymer of the present invention is preferably from 300,000 to less than 2,000,000, more preferably from 500,000 to 700,000. If the molecular weight is too low, the cohesive force and adhesive force when it becomes a pressure-sensitive adhesive sheet are insufficient. If the molecular weight is too large, gelation may occur during synthesis. In addition, since the viscosity increases more than necessary, the handling properties also deteriorate, and the storage stability of the pressure-sensitive adhesive solution also deteriorates.

  Further, the solid content of the pressure-sensitive adhesive composition in the present invention is preferably 15% or more and less than 70%, and more preferably 25% or more and less than 40%.

  Although it does not specifically limit as a polymerization initiator used for a synthesis reaction, Specifically, alkyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, p-methane hydroperoxide, isobutyl peroxide, laurolyl peroxide 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1, 1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, di-isobutylperoxydicarbonate, Organic peroxides such as 2-ethylhexyl peroxydicarbonate and t-butylperoxyisobutyrate, azobisisobutyronitrile, dimethylazodiisobutyrate, 2,2-azobis (2,4-dimethylvaleronitrile) ), 2,2-azobis (2-methylbutyronitrile), potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, 4,4′-azobis-4-cyanovaleric acid ammonium (amine) salt 2,2′-azobis (2-methylamidooxime) dihydrochloride, 2,2′-azobis (2-methylbutanamidoxime) dihydrochloride tetrahydrate, 2,2′-azobis {2-methyl-N— [1,1-bis (hydroxymethyl) -2-hydroxyethyl] -propionamide} 2,2'-azobis [2-methyl-N-(2-hydroxyethyl) - propionamide], and the like.

For the purpose of improving the initial adhesive strength or the adhesive strength to a specific substrate, the pressure-sensitive adhesive composition of the present invention may contain a tackifier. For example, a rosin resin, a phenol resin, a polyterpene, an acetylene resin, a petroleum hydrocarbon resin, an ethylene vinyl acetate copolymer, a synthetic rubber, a natural rubber or the like may be included in the pressure-sensitive adhesive composition as a tackifier. Specifically, super ester A-75 (manufactured by Arakawa Chemical Co., Ltd.), super ester A-100 (manufactured by Arakawa Chemical Co., Ltd.), rosin ester such as super ester A-125 (manufactured by Arakawa Chemical Co., Ltd.), Pencel D125 (Arakawa Chemical Co., Ltd.) ), Pencel D160 (Arakawa Chemical Co., Ltd.), Ricacac PCJ (Rika Finetech Co., Ltd.) and other polymerized rosin esters, Nikanol HP-100 (Mitsubishi Gas Chemical Co., Ltd.), Nikanol HP-150 (Mitsubishi Gas Chemical Co., Ltd.) ), Xylene resins such as Nikanol H-80, terpene phenol resins such as YS Polystar T-115 (manufactured by Yashara Chemical Co., Ltd.), Mytec G125 (manufactured by Yashara Chemical Co., Ltd.), FTR-6120 (manufactured by Mitsui Petrochemical Co., Ltd.), FTR-6100 Petroleum resins such as Mitsui Petrochemical Co., Ltd., Coumarone Indene Resin, Terpene Tree , Styrene resin, an ethylene / vinyl acetate resins.
Examples of benzotriazole compounds include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-5'-di-tertbutylphenyl) benzotriazole, 3- (2H-benzotriazol-2-yl) -5- (1,1-dimethylethyl) -4-hydroxybenzenepropanoic acid C7-9 branched or straight chain alkyl ester (trade name TINUVIN384, manufactured by Ciba Specialty Chemicals) -2), 2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol.

  Examples of the hydroxyphenyl triazine compound include 2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1, 3 5-triazine and 2- [4-[(2-hydroxy-3-tridecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3, And a mixture of 5-triazines, 2,4-bis (2,4-dimethylphenyl) -6- (2-hydroxy-4-iso-octyloxyphenyl) -s-triazine.

  Examples of the amino ether hindered amine compound include TINUVIN123 manufactured by Ciba Specialty Chemicals.

Examples of the polyphenol compound include 2,5-di-tert-butylhydroquinone and 2,5-di-tert-butylamylhydroquinone.
Examples of alkylphenol compounds include 4,4′-butylidenebis (6-tert-butyl-3-methylphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,6-di-tert-butyl-4-methyl. Examples include phenol and 2,2-methylenebis (4-methyl-6-tert-butylphenol).

  Further, the storage stabilizer is not limited to one type, and may be used by mixing within a predetermined part by weight. Further, when an amino ether-based hindered amine compound and a benzotriazole-based compound or a hydroxyphenyltriazine compound are mixed, a synergistic effect may be exhibited.

  The amount of the storage stabilizer is not particularly limited as long as it is within the solubility, but it is 0.001 to 0.02 times, more preferably 0.0015 to 0.005 times the whole pressure-sensitive adhesive composition. If the amount is less than 0.001 times, the effect of addition is small, and if added more than 0.02 times, depending on the type, the coloring of the pressure-sensitive adhesive increases, and the merchantability is impaired, or the crosslinking reaction between the cyclic ether group and the carboxyl group is promoted. It may be gelled.

  In order to give the pressure-sensitive adhesive layer itself a light-shielding property and density, or to give a specific color, dyes, pigments and fillers can be added to the pressure-sensitive adhesive.

  The polymerization conditions in the present invention are not particularly limited, and examples thereof include a reflux reaction at a boiling point of an organic solvent at about 60 to 85 ° C. in a polymerization tank equipped with a stirrer, a thermometer, a dropping funnel, and a reflux device. . First, a reaction monomer, a solvent, and a part of a reaction initiator are charged into a polymerization tank, and the temperature is raised to about 60 to 85 ° C. Stirring while maintaining the approximate temperature when refluxed, the remaining monomer, solvent, and reaction initiator were dropped or dividedly added over about 1 to 3 hours, and then 1 to 4 at the same temperature. Ripen for about an hour. Finally, a solvent left as a cooling component may be added. Various additives such as a tackifier and a storage stabilizer can be added during or after the above process.

The pressure-sensitive adhesive sheet of the present invention is a transfer coating in which a pressure-sensitive adhesive is coated on a release material with a comma coater, reverse coater, slot die coater, etc., dried, and then laminated and pressed on a pressure-sensitive adhesive layer. Can be obtained. The coating amount of the pressure-sensitive adhesive in the pressure-sensitive adhesive sheet is preferably ² to 50 g / m ² by dry weight, and more preferably 5 to 25 g / m ² .

Conversely, the adhesive can be applied on the substrate with a comma coater, reverse coater, slot die coater, etc., dried and then laminated with a release material on the adhesive layer and pressed to obtain it by direct coating. it can. The coating amount of the pressure-sensitive adhesive in the pressure-sensitive adhesive sheet is preferably ² to 50 g / m ² by dry weight, and more preferably 5 to 25 g / m ² . In the case of direct coating, the anchoring property of the pressure-sensitive adhesive to the base material is improved.

  Although the coating method of the adhesive of this invention is not limited, For example, a comma coater, a die coater, a slot die coater, a curtain coater, a roll coater, a reverse roll coater, a gravure coater etc. are mentioned.

  The coating speed is not particularly limited, but is preferably 3 m / min to 1000 m / min, more preferably 10 m / min to 60 m / min.

EXAMPLES Next, although an Example demonstrates this invention, this invention is not limited to these.
The molecular weight is measured using GPC (gel permeation chromatography). GPC is liquid chromatography that separates and quantifies substances dissolved in a solvent based on the difference in molecular size. The molecular weight was determined in terms of polystyrene.
Viscosity was measured on a BL type viscometer under conditions of rotor No. 4 and 60 revolutions per minute.
In the present invention, the holding force was measured by the following procedure. The pressure-sensitive adhesive sheet is cut to 100 × 25 mm, and a 25 × 25 mm area portion at one end thereof is attached to a stainless steel plate in an atmosphere of 23 ° C. and 65% RH. The test piece was left in an atmosphere of 40 ° C. for 20 minutes, then a 1 kg weight was suspended, and the time until dropping or the displacement (creep state) of the attached surface after a certain time was measured.

[Example 1]
In a polymerization tank equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, 180 g of 2-ethylhexyl acrylate, 57 g of butyl acrylate, 40 g of methyl acrylate, 18 g of acrylic acid, 2.75 g of glycidyl methacrylate, 0.45 azobisisobutylnitrile g and a raw material consisting of 274 g of ethyl acetate were divided in half and charged into a dropping funnel and a reaction kettle. The system was saturated with nitrogen gas and stirred, and the temperature of the reaction system was raised and refluxing was started. After completion of the dropwise addition, the mixture was further aged for 3 hours with stirring, and then cooled by adding ethyl acetate to obtain a solution containing an acrylic polymer having a solid content of 30% by weight. The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage.
The viscosity of the pressure-sensitive adhesive was measured and found to be 2100 mPa · s. The weight average molecular weight measured by GPC (gel permeation chromatography) was 590,000.
This pressure-sensitive adhesive composition was coated on a polyester substrate, dried at 110 ° C., and the pressure-sensitive adhesive surface was laminated with release paper to obtain a pressure-sensitive adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 2]
A pressure-sensitive adhesive composition was obtained in the same manner except that the amount of acrylic acid in Example 1 was 22 g. The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage.
The viscosity of the pressure-sensitive adhesive was measured and found to be 2200 mPa · s. The weight average molecular weight measured by GPC was 600,000.
This pressure-sensitive adhesive composition was coated on a polyester substrate, dried at 110 ° C., and the pressure-sensitive adhesive surface was laminated with release paper to obtain a pressure-sensitive adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 3]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the amount of glycidyl methacrylate was 4.8 g. The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage.
The viscosity of the pressure-sensitive adhesive was measured and found to be 2300 mPa · s. The weight average molecular weight measured by GPC was 610,000.
This pressure-sensitive adhesive composition was coated on a polyester substrate, dried at 110 ° C., and the pressure-sensitive adhesive surface was laminated with release paper to obtain a pressure-sensitive adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 4]
The charging and reaction were the same as in Example 1, and the amount of ethyl acetate used for cooling was changed to obtain a solution containing an acrylic polymer having a solid content of 35% by weight. Add 0.002 times the amount of 2-hydroxyphenyltriazine compound (trade name TINUVIN400, manufactured by Ciba Specialty Chemicals Co., Ltd.) to the (meth) acrylic acid copolymer solution, and stir at room temperature for 30 minutes. An adhesive composition was obtained. The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage.
The viscosity of the pressure-sensitive adhesive was measured and found to be 3000 mPa · s. The weight average molecular weight measured by GPC was 590,000.
This pressure-sensitive adhesive composition was coated on a polyester substrate, dried at 110 ° C., and the pressure-sensitive adhesive surface was laminated with release paper to obtain a pressure-sensitive adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 5]
In Example 4, a pressure-sensitive adhesive composition was obtained in the same manner except that the 2-hydroxyphenyltriazine compound was changed to a 2-hydroxyphenylbenzotriazole compound (trade name Tinuvin384-2, manufactured by Ciba Specialty Chemicals Co., Ltd.). . The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage. This composition was applied to a polyester substrate, dried at 110 ° C., and the adhesive surface was laminated with release paper to obtain an adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 6]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 4, except that the 2-hydroxyphenyltriazine compound was changed to an amino ether-based hindered amine compound (trade name Tinuvin123, manufactured by Ciba Specialty Chemicals Co., Ltd.). The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage. This composition was applied to a polyester substrate, dried at 110 ° C., and the adhesive surface was laminated with release paper to obtain an adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 7]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 4 except that the 2-hydroxyphenyltriazine compound was changed to a polyphenol compound (2,5-di-tert-butylhydroquinone). The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage. This composition was applied to a polyester substrate, dried at 110 ° C., and the adhesive surface was laminated with release paper to obtain an adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 8]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that oxetane methacrylate was used instead of glycidyl methacrylate. The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage. This composition was applied to a polyester substrate, dried at 110 ° C., and the adhesive surface was laminated with release paper to obtain an adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 9]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that 3,4-epoxycyclohexylmethyl acrylate was used instead of glycidyl methacrylate. The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage. This composition was applied to a polyester substrate, dried at 110 ° C., and the adhesive surface was laminated with release paper to obtain an adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Example 10]
In the same manner as in Example 1, except that the raw material composition was 180 g of 2-ethylhexyl acrylate, 97 g of methyl acrylate, 18 g of acrylic acid, 2.75 g of glycidyl methacrylate, 0.45 g of azobisisobutylnitrile, and 274 g of ethyl acetate. I got a thing. The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage.
The viscosity of the pressure-sensitive adhesive composition was measured and found to be 2200 mPa · s. The weight average molecular weight measured by GPC was 610,000.
This pressure-sensitive adhesive composition was coated on a polyester substrate, dried at 110 ° C., and the pressure-sensitive adhesive surface was laminated with release paper to obtain a pressure-sensitive adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Comparative Example 1]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the amount of glycidyl methacrylate was 6 g. The pressure-sensitive adhesive composition was thickened when stored at 50 ° C. for 2 weeks. The viscosity of the adhesive was measured and found to be 2400 mPa · s. The weight average molecular weight measured by GPC was 630,000.
This pressure-sensitive adhesive composition was coated on a polyester substrate, dried at 110 ° C., and the pressure-sensitive adhesive surface was laminated with release paper to obtain a pressure-sensitive adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Comparative Example 2]
A pressure-sensitive adhesive composition was obtained in the same manner except that the amount of acrylic acid in Example 1 was 28 g. The pressure-sensitive adhesive composition was thickened when stored at 50 ° C. for 2 weeks. The viscosity of the adhesive was measured and found to be 2400 mPa · s. The weight average molecular weight measured by GPC was 630,000.
This pressure-sensitive adhesive composition was applied to a polyester substrate, dried at 110 ° C., and the pressure-sensitive adhesive surface was laminated with release paper to obtain a pressure-sensitive adhesive sheet. When this sheet was used for a holding force test, the weight did not fall after 70000 seconds.

[Comparative Example 3]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 4 except that the 2-hydroxyphenyltriazine compound was changed to a hindered amine compound (trade name Tinuvin292, manufactured by Ciba Specialty Chemicals Co., Ltd.). When this pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, it gelled.

[Comparative Example 4]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1. This composition was applied to a polyester substrate, dried at 80 ° C., and the adhesive surface was laminated with release paper to obtain an adhesive sheet. When this sheet was used for a holding force test, the weight dropped after 50000 seconds.

[Comparative Example 5]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that 274 g of ethyl acetate used in the polymerization was changed to 443 g of ethyl acetate and 111 g of toluene. The pressure-sensitive adhesive composition was stored at 50 ° C. for 2 weeks, and the viscosity was measured. As a result, no change in viscosity was observed compared to before storage.
When the viscosity of this pressure-sensitive adhesive was measured, it was 700 mPa · s, and when the weight average molecular weight was measured by GPC, it was 200,000.
When a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 and a holding power test was performed using the pressure-sensitive adhesive sheet, the weight dropped after 200 seconds.
The results of Examples and Comparative Examples are summarized in Table 1.

Viscosity evaluation over time ○: Thickness is less than 10% at 50 ° C for 2 weeks storage test ×: Thickness is 10% or more at 50 ° C for 2 weeks storage test ○: Does not fall for 70000 seconds in the retention strength test
×: Dropped within 70000 seconds in holding force test.

Claims (7)

(Meth) acrylic acid alkyl ester having 1 to 14 carbon atoms of alkyl group, ethylenic monomer having cyclic ether group of 0.2 to 1.8 phr, polymerizable unsaturated carboxylic acid of 4 to 8 phr, and, if necessary, the above A pressure-sensitive adhesive composition comprising an acrylic polymer having a weight average molecular weight of 300,000 or more obtained by copolymerizing a copolymerizable ethylenically unsaturated monomer other than the above. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the cyclic ether group is a glycidyl group, an oxetane group or an alicyclic epoxy group. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the polymerizable unsaturated carboxylic acid is acrylic acid. 2. The pressure-sensitive adhesive composition according to claim 1, further comprising a storage stabilizer selected from a benzotriazole compound, an amino ether hindered amine compound, a hydroxyphenyl triazine compound, a polyphenol compound, or an alkylphenol compound. 2. A pressure-sensitive adhesive composition comprising the pressure-sensitive adhesive composition according to claim 1 and a solvent. 6. A pressure-sensitive adhesive sheet obtained by coating and drying the pressure-sensitive adhesive composition according to claim 5. 7. The method for producing a pressure-sensitive adhesive sheet according to claim 6, which is produced at a drying temperature of 100 ° C. to 150 ° C.