JPH0635569B2 - Pressure sensitive adhesive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet, and more particularly to a pressure-sensitive adhesive sheet capable of reducing its adhesive force by irradiation with ultraviolet rays.

(Prior Art) Generally, a pressure-sensitive adhesive sheet or pressure-sensitive adhesive sheet obtained by applying a pressure-sensitive adhesive on a base sheet is used for various purposes in general households and industries. The adhesive sheet has a wide variety of required characteristics, and various functionalities are required depending on the application.

For example, when manufacturing an integrated circuit, a silicon wafer is cut into a predetermined size, that is, in order to obtain a dice by performing dicing, the silicon wafer is placed on a pressure-sensitive adhesive sheet called a so-called dicing film. After pressure-sensitive adhesive fixing on the dicing film and cutting, this is picked up from the dicing film, that is, peeled off and taken up. Therefore, in order to accurately dice the silicon wafer, the dicing film has a strong adhesive force to the silicon wafer during dicing,
On the other hand, when picking up the obtained dice from the dicing film, the dicing film needs to have a weak adhesive force. Although not particularly limited, for example, when dicing a silicon wafer, the dicing film has an adhesive force of about 100 to 800 g / 25 mm, while the dicing film has about 20 to 50 g / d when picking up the dice. It is said that it is desirable to have an adhesive force of about 25 mm or less.

However, as described above, a pressure-sensitive adhesive composition capable of reducing the adhesive force after application to the adherend and a pressure-sensitive adhesive sheet having such characteristics have not yet been known.

On the other hand, for example, generally in the field of adhesives, a UV-crosslinkable adhesive comprising a photopolymerizable oligomer, a photopolymerizable monomer, a photopolymerization initiator and other additives is already known, which is a solventless type, It is a one-pack type adhesive that is fast-curing and is excellent in that it does not require heating.
In this adhesive, irradiation of ultraviolet rays is originally performed in order to make the adhesive exhibit a required adhesive force.

(Object of the invention) As a result of intensive research to obtain a pressure-sensitive adhesive that initially has a strong adhesive force and can reduce the adhesive force as needed, the present inventors unexpectedly found that the elastic It has been found that the pressure-sensitive adhesive composition comprising a mixture containing a polymer and an ultraviolet-crosslinkable acrylic ester as a main component has a significantly reduced adhesive force when the composition is irradiated with ultraviolet rays.

As a result of further studies, the present inventors have found that a pressure-sensitive adhesive composition obtained by further containing polyisocyanate as a component in such a pressure-sensitive adhesive composition has a more remarkable adhesive force when it is irradiated with ultraviolet rays. It is found that the adhesive strength is reduced after application to the adherend by forming a layer of such an adhesive composition on an appropriate base resin sheet, if necessary. The present invention has been accomplished by finding that the pressure-sensitive adhesive sheet to be obtained can be obtained.

Therefore, the present invention has a strong adhesive force when not irradiated with ultraviolet rays, and by irradiating it with ultraviolet rays, an object thereof is to provide a pressure-sensitive adhesive sheet capable of significantly reducing the adhesive force. To do.

(Structure of the Invention) A pressure-sensitive adhesive sheet capable of reducing an adhesive force by irradiation with ultraviolet rays of the present invention is a substrate sheet capable of transmitting ultraviolet rays, (a) with respect to 100 parts by weight of an elastic polymer, A layer of a pressure-sensitive adhesive containing (b) 15 to 200 parts by weight of a UV-crosslinkable acrylic ester and (c) 1 to 100 parts by weight of polyisocyanate together with (d) a polymerization initiator is formed. And

Conventionally, various pressure-sensitive adhesive compositions are known as described in, for example, "Adhesive Handbook (2nd Edition)" (edited by Japan Adhesive Association, published by Nikkan Kogyo Shimbun, 1980), pages 398 to 414. However, a typical pressure-sensitive adhesive composition contains an elastic polymer as a main component, a tackifier or a plasticizer having good compatibility with the elastic polymer, and further, if necessary, a filler or an antioxidant. , A colorant and the like are uniformly mixed. In the present invention, a saturated copolymer polyester resin, a polyacrylic acid ester and a copolymer of acrylic acid ester can be preferably used as the elastic polymer.

First, as described in "Industrial Materials" Vol. 25, No. 11, pp. 101 to 106, the saturated copolyester resin is usually two or more different saturated dicarboxylic acids and saturated dihydric alcohols. It is a saturated copolymer resin having a relatively low glass transition point obtained by polycondensation of and is usually a saturated divalent carboxylic acid in which an aromatic divalent carboxylic acid and an aliphatic divalent carboxylic acid are used in combination. An aliphatic or alicyclic dihydric alcohol, that is, glycol is used as the dihydric alcohol. Particularly, in the present invention, the aromatic divalent carboxylic acid / aliphatic divalent carboxylic acid molar ratio is 80/20.
To 20/80, preferably 70/30 to 50/50
A saturated copolyester resin obtained by polycondensing the saturated divalent carboxylic acid mixture and glycol in an equimolar amount is preferably used. In the present invention, aromatic 2
A saturated copolymerized polyester resin obtained by using terephthalic acid as the carboxylic acid, sebacic acid, adipic acid as the aliphatic polycarboxylic acid, ethylene glycol, 1,4-butanediol, propylene glycol as the glycol is preferably used. Incidentally, in the production of the saturated copolyester resin, a trivalent or higher polyvalent saturated carboxylic acid or a trivalent or higher polyhydric alcohol may be partially used in combination, if necessary.

The polyacrylic acid ester or acrylic acid copolymer includes any of those used as an elastic polymer as a main component in a pressure-sensitive adhesive conventionally known as an acrylic pressure-sensitive adhesive. The polymer used as the elastic polymer in the acrylic pressure-sensitive adhesive is usually
It is substantially an acrylic ester copolymer. This copolymer usually contains an acrylic acid alkyl ester such as ethyl acrylate, butyl acrylate, or 2-ethylhexyl acrylate, which forms a polymer having a low glass transition point for imparting tackiness, as a main monomer. , Comonomers that form a hard polymer having a high glass transition point to impart cohesiveness, such as vinyl acetate, acrylonitrile, styrene, methyl acrylate, methyl methacrylate, etc., and for improving crosslinkability and adhesiveness A carboxylic acid group, a hydroxyl group, an amide group, a glycidyl group, a monomer having a functional group such as a hydroxylmethyl group, for example, acrylic acid, methacrylic acid, itaconic acid, hydroxyethylmethitacrylate, hydroxylpropylmethacrylate,
It is a copolymer obtained by copolymerizing monomers such as acrylamide and glycidyl methacrylate.

The UV-crosslinkable acrylic acid ester used in the present invention refers to an acrylic acid ester or a methacrylic acid ester as an oligomer or a monomer which is crosslinked by irradiation of ultraviolet rays, and has at least two acryloyl groups or methacryloyl groups in the molecule. Specifically, such oligomers are, for example, oligoester acrylates, and the monomers are, for example, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, dipentaerythritol hexaacrylate. Ester of polyhydric alcohol such as acrylate and acrylic acid, or 1,6
Examples thereof include esters of methacrylic acid with polyhydric alcohols such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, and dipentaerythritol pentamethacrylate.

The pressure-sensitive adhesive composition used in the present invention contains 15 to 200 parts by weight, preferably 50 to 1 part by weight of the above-mentioned UV-crosslinkable acrylic ester, per 100 parts by weight of the elastic polymer.
It is contained in the range of 50 parts by weight. For 100 parts by weight of the elastic polymer, 1 part of the above-mentioned UV-crosslinkable acrylic ester is used.
When the amount is less than 5 parts by weight, even if the obtained adhesive composition is irradiated with ultraviolet rays, its adhesive force does not substantially change,
On the other hand, when the amount exceeds 200 parts by weight, the adhesive force can be reduced by irradiating with ultraviolet rays.
This is because the adhesive may remain on the dice when picking up the dice after dicing the silicon wafer, which is not preferable.

The pressure-sensitive adhesive composition used in the present invention preferably further contains a tackifier. In particular, when the elastic polymer used is a saturated copolyester resin, it is preferable to use this tackifier together. The tackifier that can be used is not particularly limited, and those conventionally used in the production of pressure-sensitive adhesives can be appropriately used. As such a tackifier, for example, xylene resin, rosin or polymerized rosin, hydrogenated rosin, modified rosin resin such as rosin ester, terpene resin, terpene phenol resin, terpene resin such as rosin phenol resin, aliphatic series , Aromatic and alicyclic petroleum resins, coumarone resins, styrene resins, alkylphenol resins and the like.

The tackifier is usually used in the range of 10 to 200 parts by weight with respect to 100 parts by weight of the saturated copolyester resin. When the blending amount of the tackifier is too small, the adhesive force or tackiness is insufficient, while when it is too large,
The decrease in the adhesive strength after irradiation of the obtained adhesive composition with ultraviolet rays is small, and when such an adhesive composition is applied to a dicing film, it sticks to the dice when the die is picked up after the dicing of a silicon wafer. This is because the imparting agent may remain, which is not preferable.

The pressure-sensitive adhesive composition used in the present invention further contains a polymerization initiator or a photosensitizer and, if necessary, a polymerization inhibitor. The polymerization initiator is used in order to accelerate the cross-linking due to the UV irradiation of the above-mentioned UV-crosslinkable acrylic ester. Such a polymerization initiator is generally well known in the technical field of ultraviolet cross-linking polymerization, and in the present invention, a conventionally known polymerization initiator can be used. Specific examples of such a polymerization initiator include benzoin alkyl ethers such as benzoin methyl ether and benzoin isopropyl ether, and aromatic oxyketones and aromatic ketones such as benzoin, benzyl and benzophenone. It is not limited to.

The thermal polymerization inhibitor, the ultraviolet-crosslinkable acrylic ester is not added by ultraviolet irradiation, for example, in order to prevent polymerization by heat, is added as necessary,
As such a polymerization inhibitor, a conventionally known ordinary polymerization inhibitor can be used. As such a polymerization inhibitor, for example, picric acid, phenol, hydroquinone, hydolquinone monoethyl ether, etc. can be used.

The amounts of the above-mentioned polymerization initiator and polymerization inhibitor to be blended may be those generally used in the technical field of ultraviolet cross-linking polymerization. For example, the polymerization initiator is 1 per 100 parts by weight of the above-mentioned ultraviolet cross-linkable acrylic ester. -20 parts by weight, and the polymerization inhibitor is used in a range of 0.1-1 part by weight, if necessary.

The pressure-sensitive adhesive composition used in the present invention further comprises polyisocyanate 1 to 100 parts by weight of the elastic polymer.
It contains 100 parts by weight. Due to the presence of the polyisocyanate, the pressure-sensitive adhesive composition has a larger degree of decrease in the adhesive force after ultraviolet irradiation, as compared with the pressure-sensitive adhesive composition having the same composition except that it is not included. The clear reason is not yet clear, and the present invention is not limited by the reason, but if it is a functional group of the polyisocyanate and the elastic polymer, for example, a saturated copolyester resin. It is considered that the reaction with the carboxyl group or the hydroxyl group contributes to a large decrease in the adhesive strength of the pressure-sensitive adhesive composition after ultraviolet irradiation. However, with respect to 100 parts by weight of the elastic polymer, when the amount of the polyisocyanate is less than 1 part by weight, the effect of decreasing the adhesive strength after ultraviolet irradiation is not sufficient, while when it is more than 100 parts by weight, The adhesive force of the obtained pressure-sensitive adhesive composition before irradiation with ultraviolet rays decreases with time. A particularly preferable range of the compounding amount is 3 to 40 parts by weight with respect to 100 parts by weight of the elastic polymer.

The polyisocyanate is not particularly limited, but in the present invention, diisocyanate and triisocyanate are preferable. Examples of the diisocyanate include 2,4-toluene diisocyanate and m-
Phenylene diisocyanate, m-xylylene diisocyanate, 4,4'-diphenyl diisocyanate, 4,4 '
Examples thereof include diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, and dianisidine diisocyanate hexamethylene diisocyanate. Also, various triisocyanates are commercially available, for example, trimethylolpropane toluene diisocyanate commercially available from Sumitomo Chemical Co., Ltd. as "SUMIDYULE L" is
In the present invention, it is an example of a triisocyanate that can be suitably used as a polyisocyanate.

Further, a so-called urethane prepolymer of terminal isocyanate obtained by reacting diisocyanate and polyol in the presence of an excess amount of diisocyanate can also be used as polyisocyanate.

The pressure-sensitive adhesive composition used in the present invention contains an elastic polymer, a UV-crosslinkable acrylic ester, a polymerization initiator and a polyisocyanate in the above-mentioned blending amounts, if necessary, a tackifier, a polymerization inhibitor, and a filling agent. To obtain a uniform solution-like composition by dissolving it with an agent, an antioxidant, a colorant, etc. in an appropriate organic solvent that dissolves them, for example, aromatic hydrocarbons, ketones, or a mixture thereof. You can As the solvent, for example, a mixed solvent of toluene and methyl ethyl ketone is preferably used, but the solvent is not limited thereto.
The content of the elastic polymer in the adhesive composition is appropriately selected depending on the application etc., but is usually in the range of 10 to 50% by weight. However, it is not limited to this.

The method for preparing the pressure-sensitive adhesive composition as described above is not particularly limited, but usually, the elastic polymer and the tackifier are commercially available in the form of a solution, and it is possible to use these. Since it is convenient, for example, these solutions are mixed, and then an ultraviolet-crosslinkable acrylic ester, a polymerization initiator and a polyisocyanate, and if necessary, a polymerization inhibitor, a filler, an antioxidant, a colorant, etc. It may be added and mixed and dissolved.

Furthermore, the pressure-sensitive adhesive composition used in the present invention optionally contains a plasticizer such as liquid polyacrylic acid ester, liquid polybutene, mineral oil and lanolin, and also a filler, an antiaging agent and the like. You may have.

In the pressure-sensitive adhesive sheet according to the present invention, a layer of the pressure-sensitive adhesive composition as described above is formed on a base sheet that allows transmission of ultraviolet rays. Therefore, for example, it can be obtained by applying the pressure-sensitive adhesive composition as the solution-like composition as described above on the substrate sheet and drying.

As the substrate sheet, as long as it can transmit ultraviolet rays,
Various sheets can be used without particular limitation, but a transparent or translucent synthetic resin sheet is usually used. For example, a resin sheet made of vinyl chloride resin, vinyl chloride-vinylidene chloride copolymer resin, vinyl chloride-vinyl acetate copolymer resin, vinylidene chloride resin, polyolefin, acetyl cellulose, polyvinyl alcohol, polyamide, polyester, polycarbonate or the like is preferable. Used for.

Among the various base resin sheets described above, a resin sheet made of polyvinyl chloride or a copolymer of vinyl chloride containing a plasticizer is flexible and is inexpensive, and thus is particularly preferable in the present invention. Can be used. In addition to the vinyl chloride resin sheet, there is a substrate sheet that can be suitably used as a base material sheet containing a plasticizer. For example, vinyl chloride-vinylidene chloride copolymer resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-acrylic acid ester copolymer resin, polyvinylidene chloride, acetyl cellulose and the like can be mentioned.

Here, the plasticizer is not particularly limited, for example, dibutyl phthalate, dioctyl phthalate, didecyl phthalate, ditridecyl phthalate, phthalic acid diesters such as butyl benzyl phthalate, tricresyl phosphate, trioctyl. Phosphates such as phosphate, triphenyl phosphate, 2-ethylhexyl diphenyl phosphate, cresyl diphenyl phosphate, dioctyl adipate, dioctyl sebacate, dioctyl azelate, tri-2-ethylhexyl acetylcitrate Polyester plasticizers such as diesters, polypropylene adipates, polypropylene sebacates, epoxy plasticizers such as epoxidized soybean oil, chlorine plasticizers such as chlorinated paraffins and chlorinated fatty acid esters, etc. It can gel.

However, as described above, when a resin sheet containing a plasticizer is used as the base resin sheet of the pressure-sensitive adhesive sheet, the plasticizer is transferred from the resin sheet into the pressure-sensitive adhesive composition, and usually, Since the plasticizer and the UV-crosslinkable acrylic ester have good compatibility with each other, the UV-crosslinkable acrylic ester contained in the pressure-sensitive adhesive composition migrates into the resin sheet, and by such mutual migration, In some cases, the effect of reducing the adhesive force of the pressure-sensitive adhesive sheet after irradiation with ultraviolet rays may be significantly reduced.

Therefore, in the present invention, when a resin sheet containing a plasticizer is used as the base sheet of the pressure-sensitive adhesive sheet, the plasticizer and the UV-crosslinking are present between the base sheet and the pressure-sensitive adhesive sheet. It is preferable to interpose a barrier layer made of a resin layer that does not allow the permeation acrylic ester to pass through.
However, this barrier layer must not prevent the transmission of ultraviolet rays.

That is, this barrier layer does not hinder the transmission of ultraviolet rays at all, but it prevents the plasticizer contained in the base resin sheet from migrating into the pressure-sensitive adhesive composition, and at the same time, the pressure-sensitive adhesive composition. The UV-crosslinkable acrylic acid ester contained in the base resin sheet is prevented from migrating to the base resin sheet, and thus, the plasticizer contained in the base resin sheet is retained in the base material, The UV-crosslinkable acrylic acid ester contained in the pressure-sensitive adhesive composition is retained in the adhesive composition to prevent the adhesive force of the pressure-sensitive adhesive sheet from decreasing with time due to UV irradiation.

Examples of the barrier layer include poly-α-olefin such as polyethylene and polypropylene, and a film of polyalkylene terephthalate such as polyethylene terephthalate,
A resin coating film, for example, a resin coating film layer such as a modified polyacrylic resin is preferably used. Therefore, the barrier layer is formed by pressing a film made of the above-exemplified resin on the base resin sheet, or applying a solution of this resin and cooling, or applying a solution of the above resin and drying. Therefore, it can be formed. The barrier layer can also be obtained by, for example, applying a modified polyacrylic resin solution, heating and drying it as necessary to form a coating film.

As the above-mentioned modified polyacrylic resin, various ones are conventionally known, but in the present invention, they are generally excellent in solvent resistance, and accordingly, are included in the ultraviolet-crosslinkable acrylic acid ester and the base resin sheet. An alkyd-modified polyacrylic resin that does not dissolve or swell in a plasticizer and a thermosetting polyacrylic resin are suitable. As the thermosetting polyacrylic resin, for example, acid type, hydroxyl group type, epoxy type, amide type and the like are preferably used.

However, as described above, the barrier layer is particularly preferable in the material thereof unless the ultraviolet-crosslinkable acrylic ester contained in the pressure-sensitive adhesive composition and the plasticizer contained in the base resin sheet are substantially permeated. It will be readily understood, without limitation, that the material of the barrier layer will be selected according to the particular UV-crosslinkable acrylate ester and plasticizer used in the present invention.

The means and method for irradiating the pressure-sensitive adhesive sheet with ultraviolet rays according to the present invention are not particularly limited, and may be according to means and methods that have been conventionally performed in the technical field of ultraviolet-curable resin coatings and ultraviolet-curable adhesives. be able to. For example, an ultraviolet source such as a xenon lamp, a low pressure, a medium pressure, a high pressure, or an ultrahigh pressure mercury lamp may be used as the irradiation means, and irradiation may be performed for several seconds to several minutes.

(Effects of the Invention) As described above, the pressure-sensitive adhesive sheet according to the present invention is mainly composed of an elastic polymer, a UV-crosslinkable acrylic ester, a polyisocyanate, and a polymerization initiator on a base sheet capable of transmitting UV rays. A layer of a pressure-sensitive adhesive contained as a component is formed, and the reason why the pressure-sensitive adhesive composition is not clear here, but its adhesive force is significantly reduced by irradiation of ultraviolet rays. Therefore, after applying the pressure-sensitive adhesive sheet to the adherend surface, by irradiating the base resin sheet side with ultraviolet rays, the pressure-sensitive adhesive sheet can be easily peeled from the adherend surface. it can.

Therefore, the pressure-sensitive adhesive sheet according to the present invention can be suitably used, for example, as a film for dicing a silicon wafer, as described above.

(Example) An example will be shown below, but the present invention is not limited to this example. In the examples, "parts" means "parts by weight".

Example 1 A release paper was coated with a pressure-sensitive adhesive having the composition shown in Table 1, and 1
After drying at 20 ° C. for 1 minute, the pressure-sensitive adhesive layer was formed as a solid content to have a thickness of 10 μm.

Here, as the saturated copolyester resin, a saturated divalent carboxylic acid mixture having a terephthalic acid / sebacic acid molar ratio of 70/30 and ethylene glycol are polycondensed in an equimolar amount and have a glass transition point of about 10 ° C. Resin was used.

Next, 100 parts of polyvinyl chloride having an average degree of polymerization of 1300,
A modified acrylic resin solution is applied onto a sheet having a thickness of 0.1 mm formed from a vinyl chloride resin composition composed of 35 parts of a dioctyl phthalate or polyester plasticizer as a plasticizer and an appropriate amount of a stabilizer, and the barrier is dried. Layers were formed. After that, the pressure-sensitive adhesive layer was laminated on the surface of the barrier layer of the base resin sheet, and the pressure-sensitive adhesive sheet according to the present invention was obtained.

For comparison, a pressure-sensitive adhesive composition containing no polyisocyanate was prepared, and using this, pressure-sensitive adhesive sheets were obtained in the same manner (Comparative Examples 1 and 2).

Each pressure-sensitive adhesive sheet thus obtained was allowed to stand at a predetermined temperature for a predetermined time, the release paper was peeled off, the adhesive strength was measured as it was, and separately from the vinyl chloride resin sheet side. After irradiating with ultraviolet rays for 7 seconds at a main wavelength of 365 mμ and 120 W / cm, the adhesive strength was measured. First result
Shown in the table.

According to the pressure-sensitive adhesive sheet of the present invention, the adhesive strength is remarkably reduced by irradiation with ultraviolet rays even after a long period of time, and an adhesive composition of several hundred g / 25 mm is initially used to obtain an ultraviolet ray by an appropriate compounding design. Since the adhesive force can be reduced to about several tens g / 25 mm after irradiation, it can be suitably used for dicing a silicon wafer, as described above.

However, according to the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2,
Compared to the adhesive strength before UV irradiation, the degree of reduction after UV irradiation is small.

The measuring method of the adhesive force is as follows. That is, a pressure-sensitive adhesive sheet is cut into a width of 25 mm and a length of 100 mm to form a test piece, which is stacked on a stainless steel plate as an adherend.
After pressing back and forth 5 times with a 3 kg roller, a 180 ° peel test was carried out with a shocker at a pulling speed of 300 mm / min.

Example 2 Acrylic adhesive solution containing polyacrylic acid ester or copolymer of acrylic acid ester as elastic polymer (manufactured by Sanyo Chemical Industry Co., Ltd., Poly 610SA, polyacrylic acid ester or acrylic acid ester copolymer-containing 40 %) 100 parts by weight of dipentaerythritol hexaacrylate and benzoin isopropyl ether were dissolved in 100 parts by weight, and the same polyisocyanate as used in Example 1 was further added and mixed to obtain a pressure-sensitive adhesive. An agent composition was prepared.

This pressure-sensitive adhesive composition was applied onto a release paper and dried at 120 ° C. for 1 minute, and the pressure-sensitive adhesive layer had a solid content of 10 μm.
It was formed to a thickness.

Next, the same modified acrylic resin solution as in Example 1 was applied onto a sheet having the same thickness as in Example 1 and dried to form a barrier layer, and then the barrier layer of the base resin sheet was formed. The pressure-sensitive adhesive layer was laminated on the surface of and laminated to obtain a pressure-sensitive adhesive sheet according to the present invention.

With respect to the pressure-sensitive adhesive sheet thus obtained, the adhesive force after ultraviolet irradiation was measured in the same manner as in Example 1. The results are shown in Table 2.

Claims (5)

[Claims] 1. A base material sheet which allows ultraviolet rays to pass therethrough, (b) 15 to 200 parts by weight of an ultraviolet-crosslinkable acrylic acid ester, and (c) a polyisocyanate 1 with respect to 100 parts by weight of an elastic polymer. A pressure-sensitive adhesive sheet capable of reducing its adhesive force by irradiation with ultraviolet rays, characterized in that a layer of a pressure-sensitive adhesive containing (d) a polymerization initiator is contained in an amount of up to 100 parts by weight. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the elastic polymer is a saturated copolyester resin. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the elastic polymer is a polyacrylic acid ester or a copolymer of acrylic acid ester. 4. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive contains a tackifier. 5. The pressure-sensitive adhesive sheet according to claim 1, wherein the base sheet is a sheet made of polyvinyl chloride or a vinyl chloride copolymer containing a plasticizer.