JPH0655929B2 - Pressure sensitive adhesive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet that can reduce the 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. Adhesive sheets are required to have various and diverse characteristics, and various functionalities are required depending on applications.

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. 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 a tens of g / 25 mm when picking up the dice. It is said that it is desirable to have an adhesive force of a degree 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 earnest studies by the present inventors to obtain a pressure-sensitive adhesive composition that initially has a strong adhesive force and can reduce the adhesive force as needed, unexpectedly It has been found that a pressure-sensitive adhesive composition composed of a mixture containing an elastic polymer and an ultraviolet-crosslinkable acrylic ester as a main component has a significantly reduced adhesive force when it 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 and anhydrous silica powder as components in such a pressure-sensitive adhesive composition, when it is irradiated with ultraviolet rays, The present invention has been accomplished by finding that the adhesive force is more significantly reduced or is substantially reduced.

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 according to the present invention comprises a base sheet capable of transmitting ultraviolet rays, (a) with respect to 100 parts by weight of an elastic polymer, (b) 15 to 200 parts by weight of UV-crosslinkable acrylic ester, (c) 10 to 200 parts by weight of tackifier, (d) 1 to 100 parts by weight of polyisocyanate, and (e) anhydrous silica powder 1 to 30 And (f) a pressure-sensitive adhesive layer together with a polymerization initiator.

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 copolymerized polyester resin, a polyacrylic acid ester, and a copolymer of acrylic acid ester can be preferably used as the elastic polymer.

First, the saturated copolyester resin is usually a saturated divalent carboxylic acid and two or more different saturated divalent carboxylic acids, as described in "Industrial Materials" Vol. 25, No. 11, pp. 101-106, for example. A saturated copolymer resin having a relatively low glass transition point obtained by polycondensation with alcohol, and usually,
An aromatic divalent carboxylic acid and an aliphatic divalent carboxylic acid are used together as the saturated divalent carboxylic acid, and a resin group or an alicyclic divalent alcohol, that is, glycol is used as the saturated divalent alcohol. Particularly, in the present invention, aromatic 2
Carboxylic acid / aliphatic dicarboxylic acid molar ratio is 80/2
0 to 20/80, preferably 70/30 to 50/5
A saturated copolyester resin obtained by polycondensing a saturated divalent carboxylic acid mixture of 0 and glycol in an equimolar amount is preferably used. In the present invention, terephthalic acid is used as the aromatic divalent carboxylic acid, sebacic acid, adipic acid is used as the aliphatic polycarboxylic acid, ethylene glycol, 1,4-butanediol, propylene glycol, etc. are used as the glycol. Polymerized polyester resin 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 acrylic ester such as ethyl acrylate, butyl acrylate, and 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 for imparting cohesiveness, for example, vinyl acetate, acrylonitrile, styrene, methyl acrylate, methyl methacrylate, etc., and for improving crosslinkability and adhesiveness A monomer having a functional group such as a carboxylic acid group, a hydroxyl group, an amide group, a glycidyl group, and a hydroxylmethyl group, for example, acrylic acid, methacrylic acid, itaconic acid, hydroxylethyl methacrylate, hydroxypropyl methacrylate, acrylamide, glycidyl methacrylate, etc. Copolymerization of monomers It was a copolymer comprising.

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 include, for example, oligoester acrylates, and the monomers include, for example, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, dipentaerythritol hexaacrylate. Ester of polyhydric alcohol such as acrylate and acrylic acid, or ester of polyhydric alcohol such as 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, dipentaerythritol pentamethacrylate and methacrylic acid Can be mentioned.

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 further contains a tackifier. The tackifier used here 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 amount of the tackifier added is too small, the adhesive force or adhesive force 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 during dicing of the silicon wafer after dicing. 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 to accelerate the crosslinking of the above UV-crosslinkable acrylic acid ester by UV irradiation. 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 monomethyl ether or the like 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 and 1 to 30 parts by weight of anhydrous silica powder.

The present inventors have already added the polyisocyanate or anhydrous silica to the pressure-sensitive adhesive composition containing the elastic polymer, the UV-crosslinkable acrylic acid ester, and the polymerization initiator as the main components, respectively. When irradiating with ultraviolet rays, it has been found that the adhesive strength is significantly reduced, but when polyisocyanate and anhydrous silica powder are added together to the pressure-sensitive adhesive composition, polyisocyanate and anhydrous silica powder are added. It has been found that, by virtue of the synergistic effect of (1), the decrease in the adhesive force after ultraviolet irradiation becomes more remarkable as compared with the case where each of them is blended alone. The clear reason is not yet clear, and the present invention is not limited by the reason, but the presence of polyisocyanate does not significantly reduce the adhesive strength of the pressure-sensitive adhesive composition after ultraviolet irradiation. It is considered that the reaction between the polyisocyanate and the functional group of the elastic polymer, for example, in the case of the saturated copolyester resin, is a carboxyl group or a hydroxyl group.

However, the amount of polyisocyanate compounded is 10
When the amount of 0 parts by weight is less than 1 part by weight, the effect of lowering the adhesive strength after irradiation with ultraviolet rays is not sufficient, while 10
When the amount is more than 0 parts by weight, the adhesive strength of the obtained pressure-sensitive adhesive composition before irradiation with ultraviolet rays decreases with time. A particularly preferable range of the compounding amount is 1 to 50 parts by weight, and particularly preferably 1 to 20 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 '
-Diphenyl methane diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, dianisidine diisocyanate hexamethylene diisocyanate, etc. can be illustrated. In addition, various triisocyanates are commercially available, and for example, trimethylolpropane toluene diisocyanate commercially available as "Sumidayur L" from Sumitomo Chemical Co., Ltd. is preferably used as a polyisocyanate in the present invention. It is an example of a triisocyanate capable of producing.

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.

Further, the compounding amount of anhydrous silica in the pressure-sensitive adhesive composition is in the range of 1 to 30 parts by weight with respect to 100 parts by weight of the elastic polymer. However, with respect to 100 parts by weight of the elastic polymer, when the amount is less than 1 part by weight, the effect of lowering the adhesive strength after irradiation with ultraviolet rays is poor, and when it is more than 30 parts by weight, the pressure-sensitive pressure-sensitive composition obtained is increased. The adhesive composition remarkably thickens and becomes a gel, and, for example, the coating operation becomes difficult. The preferable range of blending amount is in the range of 1 to 20 parts by weight with respect to 100 parts by weight of the elastic polymer, particularly preferably 1 to 15 parts by weight.
The range is parts by weight.

The anhydrous silica powder is not particularly limited, but in the present invention, it is preferably fine particles, and thus, for example, "Aerosil" by Degussa Co.
Can be preferably used.

The pressure-sensitive adhesive composition according to the present invention contains an elastic polymer, a UV-crosslinkable acrylic acid ester, a tackifier, a polymerization initiator, a polyisocyanate and an anhydrous silica powder in the above-described blending amount, if necessary. Agents, fillers, anti-aging agents, colorants, etc., along with an appropriate organic solvent that dissolves organic components other than anhydrous silica powder, for example, aromatic hydrocarbons, ketones, or dissolved in these mixtures, anhydrous silica powder By dispersing, it is possible to obtain a uniform liquid composition. 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 used in the present pressure as described above is not particularly limited, but usually,
Since the elastic polymer and the tackifier are commercially available in the form of a solution and it is convenient to use these, for example, these solutions are mixed, and then an ultraviolet crosslinkable acrylic ester, a polymerization initiator is added thereto. , Polyisocyanate and anhydrous silica powder, if necessary, a polymerization inhibitor, a filler,
An antiaging agent, a colorant, etc. may be added and mixed uniformly.

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 ultraviolet rays to pass therethrough. Therefore, for example, it can be obtained by applying the pressure-sensitive adhesive composition as the liquid 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 inexpensive, and is particularly preferable in the present invention. Can be used for. In addition to the vinyl chloride resin sheet, there are some that can be suitably used as the base material sheet containing the 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, but for example, dibutyl phthalate, dioctyl phthalate, didecyl phthalate, ditridecyl phthalate, phthalic acid diesters such as butylendyl phthalate, tricresyl phosphate, and trisyl phthalate. Phosphate esters such as octyl phosphate, triphenyl phosphate, 2-ethylhexyl diphenyl phosphate, cresyl diphenyl phosphate, dioctyl adipate, dioctyl sebacate, dioctyl azelate, tri-2-ethylhexyl acetylcitrate, etc. Polyester plasticizers such as fatty acid diesters, polypropylene adipates, polypropylene sebacates, epoxy plasticizers such as epoxidized soybean oil, chlorine plasticizers such as chlorinated paraffins and chlorinated fatty acid esters. be able to.

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 migrates from the resin sheet into the pressure-sensitive adhesive composition, Usually, since the plasticizer and the UV-crosslinkable acrylic ester have good compatibility, the UV-crosslinkable acrylic ester contained in the pressure-sensitive adhesive composition migrates into the resin sheet, and by such mutual migration, The effect of reducing the adhesive strength of the pressure-sensitive adhesive sheet after ultraviolet irradiation is 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. It prevents the UV-crosslinkable acrylic acid ester contained in the base resin sheet from migrating to the base resin sheet, thus holding the plasticizer contained in the base resin sheet 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 by applying a melt of the resin and cooling, or by 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, in the present invention, the barrier layer, as described above, unless it substantially permeates the UV-crosslinkable acrylic ester contained in the pressure-sensitive adhesive composition and the plasticizer contained in the base resin sheet, In particular, it will be readily understood that the material is not limited, and the selection will depend on the particular UV-crosslinkable acrylic ester ester and plasticizer used in the present invention.

The means for irradiating the pressure-sensitive adhesive sheet according to the present invention with ultraviolet rays and the irradiation method are not particularly limited, and the means and methods conventionally used for UV-curable resin coatings and UV-curable adhesives in the technical field are conventionally used. 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 comprises an elastic polymer, an ultraviolet-crosslinkable acrylic ester, a tackifier, and a polymerization initiator on a base resin sheet that can transmit ultraviolet rays. A layer of a pressure-sensitive adhesive containing polyisocyanate and anhydrous silica powder as a main component is formed, and the reason for the pressure-sensitive adhesive composition is not clear here. Since its adhesive force is remarkably reduced or substantially disappears, by applying such a pressure-sensitive adhesive sheet to the adherend surface and then irradiating ultraviolet rays from the base resin sheet side, The pressure-sensitive adhesive sheet can be easily peeled off from the adhered surface.

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 to obtain a pressure-sensitive adhesive sheet according to the present invention.

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 decrease of the adhesive force due to the irradiation of ultraviolet rays is particularly remarkable even after a long period of time, and the adhesive force of several hundred g / 25 mm is initially provided by an appropriate composition design. After UV irradiation, the adhesive strength can be reduced to about several tens of g / 25 mm, or it can be virtually eliminated.
As described above, it can be suitably used for dicing a silicon wafer.

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.

Comparative Example 1 For comparison, a representative example of a pressure-sensitive adhesive composition having the same composition as in Example 1 except that one of polyisocyanate and anhydrous silica powder was not contained was prepared and the same procedure as in Example 1 was performed. A pressure-adhesive sheet was prepared.

According to these pressure-sensitive adhesive sheets, as compared with the pressure-sensitive adhesive sheets according to the above-described examples, the degree of decrease in the adhesive force after ultraviolet irradiation with respect to the adhesive force before ultraviolet irradiation is small.

Furthermore, for comparison, a pressure-sensitive adhesive composition containing neither polyisocyanate nor anhydrous silica was prepared,
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1. It is clear that the adhesive strength of these pressure-sensitive adhesive sheets does not change practically even when exposed to the external rays of vinegar.

Example 2 Acrylic pressure-sensitive adhesive solution containing polyacrylic acid ester or copolymer of acrylic acid ester as an elastic polymer (manufactured by Sanyo Kasei Co., Ltd. Polysic 610SA, polyacrylic acid ester or acrylic acid ester copolymer content Dipentaerythritol hexaacrylate and benzoin isopropyl ether were dissolved in 100 parts by weight (about 40% by weight) in the amounts shown in Table 2, and the same polyisocyanate as used in Example 1 was further added and mixed to give a reaction mixture. A pressure-sensitive adhesive 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. The pressure-sensitive adhesive layer was laminated on the surface 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.

Comparative Example 2 For comparison, a representative example of a pressure-sensitive adhesive composition having the same composition as in Example 2 except that one of polyisocyanate and anhydrous silica powder was not included, was prepared. A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1.

According to these pressure-sensitive adhesive sheets, as compared with the pressure-sensitive adhesive sheets according to the above-described examples, the degree of decrease in the adhesive force after ultraviolet irradiation with respect to the adhesive force before ultraviolet irradiation is small.

Furthermore, for comparison, a pressure-sensitive adhesive composition containing neither polyisocyanate nor anhydrous silica was prepared,
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1. It is apparent that the adhesive force of these pressure-sensitive adhesive sheets does not substantially change even when irradiated with ultraviolet rays.

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Claims (5)

[Claims] 1. A base material sheet capable of transmitting ultraviolet rays, (b) 15 to 200 parts by weight of a UV-crosslinkable acrylic ester, and (c) a tackifier to 100 parts by weight of an elastic polymer. 10 to 200 parts by weight of the agent, (d) 1 to 100 parts by weight of polyisocyanate, and (e) 1 to 30 parts by weight of anhydrous silica powder, and (f) a layer of a pressure sensitive adhesive containing a polymerization initiator are formed. The pressure-sensitive adhesive sheet capable of reducing the adhesive force by ultraviolet irradiation. 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. A pressure sensitive adhesive comprising a base resin sheet containing a plasticizer and capable of transmitting ultraviolet rays, a barrier layer thereon, and a pressure sensitive adhesive composition layer thereon. The composition is (a) 100 parts by weight of the elastic polymer, (b) 15 to 200 parts by weight of a UV-crosslinkable acrylic ester, (c) 10 to 200 parts by weight of a tackifier, and (d) a polyisocyanate. 1 to 100 parts by weight and (e) 1 to 30 parts by weight of anhydrous silica powder together with (f) a polymerization initiator, the base resin sheet contains a plasticizer, and the barrier layer contains the plasticizer and ultraviolet rays. A pressure-sensitive adhesive sheet capable of reducing adhesive strength by irradiation of ultraviolet rays, which is made of a resin which does not allow passage of crosslinkable acrylic acid ester but allows transmission of ultraviolet rays. 5. The pressure-sensitive adhesive sheet according to claim 4, wherein the base resin sheet is made of polyvinyl chloride or a vinyl chloride copolymer containing a plasticizer.