JPH0156111B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a pressure-sensitive adhesive sheet, and in detail,
The present invention relates to a pressure-sensitive adhesive sheet whose adhesive strength can be reduced by irradiation with ultraviolet rays. (Prior Art) Generally, pressure-sensitive adhesive sheets or pressure-sensitive adhesive sheets, which are made by coating a pressure-sensitive adhesive on a base sheet, are used for various purposes in general households and industry, but in recent years, pressure-sensitive The required characteristics of adhesive sheets are diverse and wide-ranging, and various functionalities are now required depending on the application. For example, when manufacturing integrated circuits, in order to cut a silicon wafer into predetermined dimensions, that is, to obtain dice by dicing, the silicon wafer is placed on a pressure-sensitive adhesive sheet called a dicing film. After fixing with a pressure sensitive adhesive onto a dicing film and cutting it, it is picked up, that is, peeled off, from the dicing film. Therefore, in order to accurately dice silicon wafers, the dicing film must have strong adhesion to the silicon wafer during dicing, while the dicing film must have a strong adhesive force when picking up the obtained dice from the dicing film. It is necessary that the adhesive strength be weak. For example, although there are no limitations,
When dicing silicon wafers, the dicing film has an adhesive strength of about 100 to 500 g/25 mm or more, while when picking up dice, the dicing film has an adhesive strength of about 20 to 500 g/25 mm or more.
It is said that it is desirable to have an adhesive force of about g/25 mm or less. However, a pressure-sensitive adhesive sheet whose adhesive force can be reduced as necessary after being applied to an adherend surface is not yet known. On the other hand, for example, generally in the field of adhesives,
Ultraviolet crosslinkable adhesives consisting of photopolymerizable oligomers, photopolymerizable monomers, photoinitiators, and other additives are already known, and are solvent-free, one-component adhesives that cure quickly. Although this adhesive is superior in that it is highly durable and does not require heating, irradiation with ultraviolet rays is originally carried out in order to make the adhesive develop the required adhesive strength. (Objective of the Invention) The present inventors have conducted intensive research to obtain an adhesive composition for pressure-sensitive adhesive sheets that initially has strong adhesive strength and can reduce the adhesive strength as needed. As a result, unexpectedly, when a pressure sensitive adhesive composition containing an elastic polymer and an ultraviolet crosslinkable acrylic ester as main components is irradiated with ultraviolet rays,
It has been found that the adhesive force is significantly reduced, and furthermore, when forming a layer of the pressure-sensitive adhesive composition on a base resin sheet that can transmit ultraviolet rays to form a pressure-sensitive adhesive sheet, the pressure-sensitive The adhesive sheet is
It has been found that by applying ultraviolet rays from the side of the base resin sheet after applying it to the desired surface, the adhesive strength is significantly reduced, so that it can be easily peeled off from the surface. However, when a plasticized vinyl chloride resin sheet is used as the base resin sheet, for example, the plasticizer contained in this resin sheet migrates into the pressure-sensitive adhesive composition. It has also been found that the UV crosslinkable acrylic ester transferred into the resin sheet causes the adhesive force reduction effect caused by UV irradiation to decrease over time. Therefore, as a result of intensive research in order to solve this problem, the present inventors discovered that the plasticizer and the ultraviolet crosslinkable acrylic ester are bonded between the plasticizer-containing base resin sheet and the pressure-sensitive adhesive composition. The inventors have discovered that by forming a barrier layer made of a resin that does not transmit ultraviolet rays to prevent their mutual migration, the effect of reducing adhesive strength caused by ultraviolet irradiation can be maintained for a long period of time, and the present invention has been made based on this discovery. It has been reached. Therefore, the present invention has a strong adhesive force when not irradiated with ultraviolet rays, and by irradiating it with ultraviolet rays, the adhesive force can be significantly reduced.
Another object of the present invention is to provide a pressure-sensitive adhesive sheet in which this effect does not substantially change over time. (Structure of the Invention) The pressure-sensitive adhesive sheet of the present invention whose adhesive strength can be reduced by ultraviolet irradiation contains a plasticizer, and
A pressure-sensitive adhesive layer containing an elastic polymer, an ultraviolet crosslinkable acrylic ester, and a polymerization initiator is placed on a base resin sheet that allows ultraviolet rays to pass through. It is characterized in that it is formed through a resin layer that does not transmit ultraviolet rays, but allows ultraviolet rays to pass therethrough. Conventionally, various pressure-sensitive adhesive compositions have been published, for example, in "Adhesive Handbook (2nd Edition)" (edited by Japan Adhesive Association,
A typical pressure-sensitive adhesive composition has an elastic polymer as its main component, and a compatible material Good tackifiers and plasticizers, as well as
It is a mixture made by uniformly mixing fillers, anti-aging agents, colorants, etc. as required. In the present invention, particularly preferred examples of such elastic polymers include saturated copolymerized polyester resins, polyacrylic esters, and copolymers of acrylic esters. First of all, saturated copolymerized polyester resins are usually composed of two or more different saturated dihydric carboxylic acids and saturated dihydric alcohols, as described in, for example, "Kogyo Zaizai" Vol. 25, No. 11, pages 101-106. It is a saturated copolymer resin with a relatively low glass transition point obtained by polycondensation of As the dihydric alcohol, an aliphatic or alicyclic dihydric alcohol, that is, a glycol is used. In particular, in the present invention, the molar ratio of aromatic divalent carboxylic acid/aliphatic divalent carboxylic acid to
80/20 to 20/80, preferably 70/30 to 50/50
A saturated copolymerized polyester resin obtained by polycondensing a saturated dicarboxylic acid mixture and glycol in equimolar amounts is preferably used. In the present invention, terephthalic acid is used as an aromatic divalent carboxylic acid, sebacic acid is used as an aliphatic polycarboxylic acid,
Saturated copolymerized polyester resins obtained using adipic acid and glycols such as ethylene glycol, 1,4-butanediol, and propylene glycol are preferably used. In addition, if necessary,
In the production of saturated copolymerized polyester resin,
As the carboxylic acid component, a saturated polyhydric carboxylic acid having a valence of 3 or more or a polyhydric alcohol having a valence of 3 or more may be partially used in combination. Further, the polyacrylic acid ester or acrylic acid copolymer includes any one that is used as an elastic polymer as a main component in adhesives conventionally known as acrylic adhesives. The polymer used as the elastic polymer in acrylic pressure-sensitive adhesives is usually substantially an acrylic ester copolymer. This copolymer usually has an acrylic acid alkyl ester as a main monomer, such as ethyl acrylate, butyl acrylate, or 2-ethylhexyl acrylate, which forms a polymer with a low glass transition temperature to provide adhesive properties. , comonomers that form hard polymers with a high glass transition temperature to provide cohesive properties, such as vinyl acetate, acrylonitrile, styrene, methyl acrylate, methyl methacrylate, etc., and to improve crosslinking and adhesion properties. Monomers having functional groups such as carboxylic acid groups, hydroxyl groups, amide groups, glycidyl groups, and hydroxylmethyl groups, such as acrylic acid, methacrylic acid, itaconic acid, hydroxylethyl methacrylate, hydroxylpropyl methacrylate, acrylamide, glycidyl methacrylate, etc. It is a copolymer obtained by copolymerizing monomers of The ultraviolet crosslinkable acrylic ester used in the present invention refers to an acrylic ester or methacrylic ester as an oligomer or monomer that crosslinks by irradiation with ultraviolet rays, and has at least two acryloyl or methacryloyl groups in the molecule. Specifically, such oligomers include, for example, oligoester acrylate, etc.
Examples of monomers include esters of polyhydric alcohol and acrylic acid such as 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, dipentaerythritol hexaacrylate, or 1,6- Examples include esters of polyhydric alcohol and methacrylic acid such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethanetetramethacrylate, and dipentaerythritol pentamethacrylate. In the present invention, the pressure-sensitive adhesive composition contains the ultraviolet crosslinkable acrylic ester in an amount of 15 to 200 parts by weight, preferably 50 to 150 parts by weight, based on 100 parts by weight of the elastic polymer. When the amount of the ultraviolet crosslinkable acrylic ester is less than 15 parts by weight per 100 parts by weight of the elastic polymer, even if the resulting adhesive composition is irradiated with ultraviolet rays, its adhesive strength will not substantially change. On the other hand, when the amount exceeds 200 parts by weight, the adhesive force can be reduced by UV irradiation, but for example, when picking up the dice after dicing a silicon wafer, adhesive may remain on the dice. can be,
This is because it is not desirable. 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 copolymerized polyester resin, it is preferable to use this tackifier in combination. The tackifier that can be used is not particularly limited,
Those conventionally generally used in the production of adhesives can be used as appropriate. Examples of such tackifiers include xylene resins, rosin, polymerized rosin, hydrogenated rosin, modified rosin resins such as rosin esters, terpene resins, terpene phenol resins, rosin phenol resins, and aliphatic resins. , aromatic and alicyclic petroleum resins,
Examples include coumaron resin, styrene resin, alkylphenol resin, and the like. The tackifier is usually used in an amount of 10 to 200 parts by weight per 100 parts by weight of the saturated copolymerized polyester resin.
When the amount of the tackifier is too small, the adhesive strength or adhesion is insufficient, and on the other hand, when it is too large, the amount of decrease in adhesive strength after irradiating the resulting adhesive composition with ultraviolet rays is small. , and when such an adhesive composition is applied to a dicing film,
This is because the tackifier may remain on the dice when the dice are picked up after dicing the silicon wafer, which is undesirable. 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 promote crosslinking of the ultraviolet crosslinkable acrylic ester by ultraviolet irradiation. Such polymerization initiators are generally well known in the technical field of ultraviolet crosslinking polymerization, and in the present invention, conventionally known polymerization initiators can be used. Specific examples of such polymerization initiators 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. Thermal polymerization inhibitor is added as necessary in order to prevent the above-mentioned ultraviolet crosslinkable acrylic ester from polymerizing due to heat, for example, without ultraviolet irradiation, and as such a polymerization inhibitor. Also, conventionally known polymerization inhibitors can be used. As such a polymerization inhibitor, for example, picric acid, phenol, hydroquinone, hydroquinone monomethyl ether, etc. can be used. The amount of the polymerization initiator and polymerization inhibitor may be in accordance with what is generally used in the technical field of ultraviolet crosslinking polymerization. ~20 parts by weight, and a polymerization inhibitor is used in a range of 0.1 to 1 part by weight, if necessary. The pressure-sensitive adhesive composition used in the present invention contains a saturated copolymerized polyester resin,
UV cross-linkable acrylic ester and polymerization initiator, if necessary, along with tackifier, polymerization inhibitor, filler, anti-aging agent, coloring agent, etc., are dissolved in an appropriate organic solvent such as aromatic carbonization. hydrogen,
It can be obtained as a solution by dissolving it in ketones or a mixture thereof. As the solvent, for example, specifically, a mixed solvent of toluene and methyl ethyl ketone is preferably used, but the solvent is not limited thereto. Further, the content of the elastic polymer in the adhesive composition is appropriately selected depending on the application and the like, 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 as follows:
Although not limited in any way, elastic polymers and tackifiers are usually commercially available in the form of solutions, and it is convenient to use them. For example, by mixing these solutions, A UV crosslinkable acrylic ester, a polymerization initiator, and if necessary, a polymerization inhibitor, a filler, an antiaging agent, a coloring agent, etc. may be added and mixed to the mixture and uniformly dissolved. The pressure-sensitive adhesive sheet according to the present invention contains the above-mentioned elastic polymer, ultraviolet crosslinkable acrylic ester, and polymeric material, which contains a plasticizer and is transparent to ultraviolet rays, and is coated with a barrier layer on a base sheet that is transparent to ultraviolet rays. A layer of a pressure-sensitive adhesive composition containing an initiator as a main component and, if necessary, a tackifier, a polymerization inhibitor, etc., is formed. Here, the barrier layer is made of a transparent resin layer that does not allow the plasticizer and the ultraviolet crosslinkable acrylic ester to pass through, but allows ultraviolet light to pass through. That is, this barrier layer does not prevent the transmission of ultraviolet rays in any way, but it prevents the plasticizer contained in the base resin sheet from migrating into the pressure-sensitive adhesive composition. The ultraviolet crosslinkable acrylic ester contained therein is prevented from migrating to the base resin sheet, and in this way, the plasticizer contained in the base resin sheet is retained in the base resin sheet. , by retaining the ultraviolet crosslinkable acrylic ester contained in the pressure sensitive adhesive composition in the adhesive composition,
Prevents the adhesive strength of pressure-sensitive adhesive sheets from decreasing over time due to UV irradiation. As the base resin sheet containing the above-mentioned plasticizer, various sheets can be used without particular limitation as long as they can transmit ultraviolet rays, but usually transparent or translucent synthetic resin sheets are used. used. For example, polyvinyl chloride containing a plasticizer, vinyl chloride-vinylidene chloride copolymer resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-acrylic acid ester copolymer resin, polyvinylidene chloride, acetyl cellulose, etc. Suitably used. Examples of the plasticizer include, but are not limited to, phthalic acid diesters such as dibutyl phthalate, dioctyl phthalate, didecyl phthalate, ditridecyl phthalate, and butylbenzyl phthalate, tricresyl phosphate, and trioctyl. Phosphate, triphenyl phosphate, 2-ethylhexyl diphenyl phosphate, cresyl diphenyl phosphate, and other phosphoric acid esters; dioctyl adipate, dioctyl sebacate, dioctyl azelate, acetyl tri-2-ethylhexyl citrate, and other fatty acids; Polyester plasticizers such as diester, polypropylene adipate, polypropylene sebacate,
Examples include epoxy plasticizers such as epoxidized soybean oil, chlorine plasticizers such as chlorinated paraffin, and chlorinated fatty acid esters. As the barrier layer, a film of poly-α-olefin such as polyethylene or polypropylene, or polyalkylene terephthalate such as polyethylene terephthalate, or a resin coating layer such as a resin coating layer such as a modified polyacrylic resin is suitably used. Therefore, the barrier layer can be formed by pressing a film made of the above-mentioned resin onto a base resin sheet, or by applying a melt of this resin and cooling it, or by applying a solution of the above-mentioned resin and drying it. Therefore, it can be formed. Alternatively, for example, by applying a modified polyacrylic resin solution and heating and drying as necessary to form a coating film.
A barrier layer can be obtained. Conventionally, the modified polyacrylic resin mentioned above is
Various materials are known, but in the present invention, alkyd-modified polyesters that generally have excellent solvent resistance and do not dissolve or swell in ultraviolet crosslinkable acrylic esters or plasticizers contained in the base resin sheet are used. Acrylic resin and thermosetting polyacrylic resin are suitable. As thermosetting polyacrylic resin,
For example, acid type, hydroxyl type, epoxy type, amide type, etc. are preferably used. The pressure-sensitive adhesive sheet according to the present invention can be obtained by, for example, laminating a barrier layer as described above on a base resin sheet, applying a solution of the pressure-sensitive adhesive composition as described above thereon, and drying. It can be obtained by After the pressure-sensitive adhesive sheet according to the present invention is applied to a desired surface, the means and method for irradiating it with ultraviolet rays are not particularly limited, and can be applied in the technical fields of ultraviolet curable resin paints and ultraviolet curable adhesives. This can be done by conventional means and methods. For example, as an irradiation means,
An ultraviolet light source such as a xenon lamp, low pressure, medium pressure, high pressure, or ultra-high pressure mercury lamp may be used for irradiation for several seconds to several minutes. (Effects of the Invention) As described above, the pressure-sensitive adhesive sheet according to the present invention has an elastic polymer, an ultraviolet crosslinkable acrylic ester, and a polymerization initiator as main components on a base resin sheet that can transmit ultraviolet rays. A layer of the pressure-sensitive adhesive contained therein is formed through a barrier layer, and the pressure-sensitive adhesive composition has a structure in which the adhesive strength of the pressure-sensitive adhesive composition is improved by irradiation with ultraviolet rays, although the reason for this is not necessarily clear. Therefore, after applying such a pressure-sensitive adhesive sheet to an adhered surface, the pressure-sensitive adhesive sheet can be easily peeled off from the adhered surface by irradiating ultraviolet rays from the side of the base resin sheet. can do. Moreover, in the pressure-sensitive adhesive sheet according to the present invention, since a barrier layer is interposed between the pressure-sensitive adhesive composition and the base resin sheet, the plasticizer contained in the base resin sheet is not contained in the pressure-sensitive adhesive composition. In addition, the ultraviolet crosslinkable acrylic ester does not transfer to the base resin sheet side, so the effect of reducing adhesive strength due to ultraviolet irradiation can be maintained for a long period of time. Therefore, the pressure-sensitive adhesive sheet according to the present invention can be suitably used, for example, as a film for dicing silicon wafers, as described above. (Example) Examples are shown below, but the present invention is not limited to these examples. Furthermore, in the examples, parts indicate parts by weight. Example 1 A pressure-sensitive adhesive having the composition shown in Table 1 was applied onto a release paper and dried at 120° C. for 1 minute to form a pressure-sensitive adhesive layer with a solid content of 10 μm thick. Here, the saturated copolymerized polyester resin has a glass transition point of about 10°C and is obtained by polycondensing a saturated dicarboxylic acid mixture with a terephthalic acid/sebacic acid molar ratio of 70/30 and ethylene glycol in equimolar amounts. Using resin. In addition, when polyacrylic ester or a copolymer of acrylic ester is used as an elastic polymer, a predetermined amount of ultraviolet crosslinkable acrylic ester and a polymerization initiator are added to a commercially available acrylic adhesive solution. A pressure-sensitive adhesive composition was prepared, and this was applied onto release paper in the same manner as above, and dried to form a pressure-sensitive adhesive layer having a solid content of 10 μm in thickness. Next, 100 parts of polyvinyl chloride with an average degree of polymerization of 1300,
A barrier layer shown in Table 1 was formed on a 0.1 mm thick sheet formed from a vinyl chloride resin composition containing 35 parts of a dioctyl phthalate or polyester plasticizer as a plasticizer and an appropriate amount of a stabilizer. The pressure-sensitive adhesive layer was laminated and laminated on the surface of the barrier layer of this base resin sheet to obtain a pressure-sensitive adhesive sheet according to the present invention. For comparison, a pressure-sensitive adhesive sheet was prepared in exactly the same manner as described above except that no barrier layer was provided (Comparative Example 1). After leaving each of the pressure-sensitive adhesive sheets obtained in this way at a predetermined temperature for a predetermined time, the release paper was peeled off and the adhesive strength was measured as it was, and separately from the vinyl chloride resin sheet side. Dominant wavelength
After irradiating with ultraviolet rays at 365 mμ and 120 W/cm for 7 seconds, the adhesive strength was measured. The results are shown in Table 1. According to the pressure-sensitive adhesive sheet of the present invention, even after a long period of time, the adhesive strength decreases significantly due to ultraviolet irradiation,
Initially 250-800g/25mm depending on appropriate mix design
It has adhesive strength of several tens of g/25 after UV irradiation.
Since the adhesive force can be reduced to about 100 g/25 mm, it can be suitably used for dicing silicon wafers as described above. However, according to the pressure-sensitive adhesive sheet of Comparative Example 1, immediately after its preparation, the adhesive strength after UV irradiation is significantly reduced compared to the adhesive strength before UV irradiation, but the adhesive strength due to UV irradiation is reduced. The effectiveness decreases significantly over time and, in some cases, the adhesion strength increases over time. For further comparison, a pressure-sensitive adhesive composition containing no ultraviolet crosslinkable acrylic ester was used.
A pressure-sensitive adhesive sheet was similarly prepared (Comparative Example 2).
The adhesive force of this pressure-sensitive adhesive sheet does not substantially change even when irradiated with ultraviolet rays. The method for measuring adhesive strength is as follows. That is, a pressure-sensitive adhesive sheet was cut to a width of 25 mm and a length of 100 mm to make a test piece, which was stacked on a stainless steel plate as an adherend, and after being pressed back and forth 5 times with a 3 kg roller, it was placed on a shovel. A 180° peel test was conducted at a tensile speed of 300 mm/min. Example 2 Acrylic adhesive solution containing polyacrylic ester or copolymer of acrylic ester as an elastic polymer (Polysick manufactured by Sanyo Chemical Industries, Ltd.)
Dipentaerythritol hexaacrylate and benzoin isopropyl ether are dissolved in 100 parts by weight of 610SA (polyacrylic ester or acrylic ester copolymer content: approximately 40% by weight) in the amounts shown in Table 2 to prepare a pressure-sensitive adhesive. A composition was prepared. Apply this pressure-sensitive adhesive composition onto release paper,
It was dried at 120° C. for 1 minute to form a pressure-sensitive adhesive layer with a solid content of 10 μm thick. Next, the same modified acrylic resin as in Example 1 was applied onto a sheet with the same thickness of 0.1 mm as in Example 1, and after drying to form a barrier layer, the surface of the barrier layer of this base resin sheet was The pressure-sensitive adhesive layer according to the present invention is laminated and bonded to the pressure-sensitive adhesive layer.

【table】

【table】

【table】

[Table] An adhesive sheet was obtained. Regarding the pressure-sensitive adhesive sheet thus obtained, the adhesive strength after irradiation with ultraviolet rays was measured in the same manner as in Example 1. The results are shown in Table 2. For comparison, a pressure-sensitive adhesive sheet was similarly prepared using a pressure-sensitive adhesive composition containing no ultraviolet crosslinkable acrylic ester (Comparative Example 3). This pressure-sensitive adhesive sheet can be irradiated with ultraviolet rays.
Its adhesive strength remains virtually unchanged.

Claims (1)

[Scope of Claims] 1. An elastic polymer and an ultraviolet crosslinkable acrylic ester are placed on a base resin sheet made of polyvinyl chloride or a copolymer of vinyl chloride that contains a plasticizer and can transmit ultraviolet rays. A pressure-sensitive adhesive layer containing a polymerization initiator and a tackifier is made of polyethylene, polypropylene, polyalkylene terephthalate, and modified alkyd resins that do not transmit the plasticizer and UV-crosslinkable acrylic ester, but transmit UV light. A pressure-sensitive adhesive sheet whose adhesive strength can be reduced by irradiation with ultraviolet rays, characterized in that it is formed through a selected resin layer. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the elastic polymer is a saturated copolymerized polyester resin. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the elastic polymer is a polyacrylic ester or an acrylic ester copolymer.