JPH0739565B2 - 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. The adhesive sheet has various and various 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, a silicon wafer is placed on a pressure-sensitive adhesive sheet called a so-called dicing film, pressure-sensitive adhesively fixed on the dicing film, cut, and then diced. The film is picked up, 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 limited in any way, for example, when dicing a silicon wafer, the dicing film has an adhesive force of about 100 to 500 g / 25 mm, while the dicing film has a dicing film of about 20 to 50 g / 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 anhydrous silica powder as a component in such a pressure-sensitive adhesive composition has a higher adhesive force when it is irradiated with ultraviolet rays. The present invention has been made by finding that the reduction is remarkable.

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 according to the present invention whose adhesive strength can be lowered by irradiation with ultraviolet rays is a base resin sheet capable of transmitting ultraviolet rays, and (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, and (d) 1 to 30 parts by weight of anhydrous silica powder together with (e) a polymerization initiator , And a layer of a pressure sensitive adhesive is formed.

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, as described in "Industrial Materials", Vol. 25, No. 11, pp. 101 to 106, the saturated copolyester resin is usually composed of two or more different saturated divalent carboxylic acids and saturated divalent carboxylic acids. It is a saturated copolymer resin having a relatively low glass transition point obtained by polycondensation with alcohol. Usually, an aromatic divalent carboxylic acid and an aliphatic divalent carboxylic acid are used in combination as the saturated divalent carboxylic acid, An aliphatic or alicyclic dihydric alcohol, that is, glycol is used as the saturated dihydric alcohol. Particularly, in the present invention, a saturated divalent carboxylic acid mixture and a glycol having an aromatic divalent carboxylic acid / aliphatic divalent carboxylic acid molar ratio of 80/20 to 20/80, preferably 70/30 to 50/50. A saturated copolyester resin obtained by polycondensing and with equimolar amounts is preferably used. In the present invention, a saturated copolymer obtained by using terephthalic acid as the aromatic divalent carboxylic acid, sebacic acid, adipic acid as the aliphatic polycarboxylic acid, ethylene glycol, 1,4-butadiyl, propylene glycol, etc. as the glycol. 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 alkyl 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 to impart cohesiveness, such as 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 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 150 parts by weight, of the above-mentioned UV-crosslinkable acrylic acid ester with respect to 100 parts by weight of the elastic polymer. With respect to 100 parts by weight of the elastic polymer, when the amount of the UV-crosslinkable acrylic acid ester is less than 15 parts by weight, even if the resulting adhesive composition is irradiated with ultraviolet rays, the adhesive strength thereof does not substantially change, On the other hand, when the amount exceeds 200 parts by weight, the adhesive strength can be reduced by irradiation with ultraviolet rays, but for example, when the die is picked up after dicing a silicon wafer, the adhesive may remain on the die. Because it 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 compounding amount of the tackifier is too small, the adhesive force or the adhesive force is insufficient. On the other hand, when the compounding amount is too large, the decrease in the adhesive force after irradiating the resulting adhesive composition with ultraviolet rays is small. Also, when such an adhesive composition is applied to a dicing film, the tackifier may remain in 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 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 added 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,
The polymerization inhibitor is used in the range of 0.1 to 1 part by weight, if necessary.

The pressure-sensitive adhesive composition used in the present invention further contains 1 to 30 parts by weight of anhydrous silica powder with respect to 100 parts by weight of the elastic polymer. Due to the presence of anhydrous silica, the pressure-sensitive adhesive composition has a greater 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 does not contain this. However, the blending amount of the elastic polymer 100
About 1 part by weight, when the amount is less than 1 part by weight, the effect of lowering the adhesive force after irradiation with ultraviolet rays is poor, and when it is more than 30 parts by weight, the resulting pressure-sensitive adhesive composition remarkably thickens. It becomes a gel and, for example, the coating operation becomes difficult.
A particularly preferable range of the compounding amount is 3 to 15 parts by weight with respect to 100 parts by weight of the elastic polymer.

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 used in the present invention is an elastic polymer, a UV-crosslinkable acrylic acid ester, a tackifier polymerization initiator and anhydrous silica powder in the above-mentioned blending amount, if necessary, a polymerization inhibitor, Along with a filler, an antioxidant, a colorant and the like, an organic solvent other than silica is dissolved in an appropriate organic solvent, for example, an aromatic hydrocarbon, a ketone, or a mixture thereof is dissolved to disperse silica. As a result, a uniform liquid composition can be obtained. As a solvent,
For example, specifically, a mixed solvent of toluene and methyl ethyl ketone is preferably used, but it is not limited thereto. Further, the content of the elastic polymer in the adhesive composition is appropriately selected according to the application etc.,
Usually, it is 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 invention 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 them, for example, these solutions are mixed, and then the UV-crosslinkable acrylic ester, polymerization initiation The agent and anhydrous silica powder, and if necessary, a polymerization inhibitor, a filler, an antiaging agent, a colorant and the like may be added and mixed, and then 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 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 butylbenzyl 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, etc. Polyester plasticizers such as diesters, polypropylene adipates, polypropylene sebacates, epoxy plasticizers such as epoxidized soybean oil, chlorinated paraffins, chlorine plasticizers such as chlorinated fatty acid esters, etc. Rukoto can.

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 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. As a result, the effect of reducing the adhesive force 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 provided 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 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 being deteriorated 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.

Ultraviolet irradiation means and irradiation method for the pressure-sensitive adhesive sheet according to the present invention is not particularly limited, and by means and methods conventionally used conventionally 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 comprises an elastic polymer, a UV-crosslinkable acrylic acid ester, a polymerization initiator, and anhydrous silica powder on a base resin sheet that can transmit UV rays. A layer of a pressure-sensitive adhesive containing as a main component is formed, and the reason why the pressure-sensitive adhesive composition is not clear here, but its adhesive force is remarkably increased by irradiation of ultraviolet rays. After applying the pressure-sensitive adhesive sheet to the adherend, the pressure-sensitive adhesive sheet is easily peeled off from the adherend by irradiating ultraviolet rays from the base resin sheet side. be able to.

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
Dry at 0 ° C for 1 minute and apply a layer of pressure sensitive adhesive to a solid content of 10
It was formed to a thickness of μm.

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

Next, 100 parts of polyvinyl chloride having an average degree of polymerization of 1300, dioctyl phthalate or a polyester plasticizer as a plasticizer.
A modified acrylic resin was applied onto a 0.1 mm-thick sheet molded from a vinyl chloride resin composition consisting of 35 parts and an appropriate amount of a stabilizer, and dried to form a barrier layer. After this,
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.

For comparison, a pressure-sensitive adhesive composition containing no silica powder was prepared (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. The results are shown in Table 1.

First, according to the pressure-sensitive adhesive sheet of the present invention, the decrease in the adhesive force due to ultraviolet irradiation is remarkable even after a long period of time, and by an appropriate compounding design, the adhesive force of 250 to 800 g / 25 mm is initially provided. Since the adhesive force can be reduced to about several tens g / 25 mm to about 100 g / 25 mm after ultraviolet 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, and 3 kg.
After pressing back and forth five times with a roller, a 180 ° peel test was performed with a shocker at a pulling speed of 300 mm / min.

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 About 40
% By weight) 100 parts by weight of dipentaerythritol hexaacrylate and benzoin isopropyl ether were dissolved in the amounts shown in Table 2, and the same anhydrous silica powder as that used in Example 1 was added and mixed to obtain a pressure-sensitive composition. An adhesive composition was prepared.

This pressure-sensitive adhesive composition was coated on a release paper and
Dry for a minute and apply a layer of pressure sensitive adhesive to solids. Was formed to a thickness of 10 μm.

Then, the same modified acrylic resin solution as in Example 1 was applied onto a sheet having a thickness of 0.1 mm 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 (3)

[Claims] 1. A base resin sheet capable of transmitting ultraviolet rays, (b) 15 to 200 parts by weight of a UV-crosslinkable acrylic ester, and (c) an adhesive with respect to 100 parts by weight of an elastic polymer. A layer of a pressure-sensitive adhesive containing 10 to 200 parts by weight of an imparting agent and (d) 1 to 30 parts by weight of anhydrous silica powder together with (e) a polymerization initiator. Therefore, a pressure-sensitive adhesive sheet that can reduce the adhesive force. 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.