JP2006188607A - Removable adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a removable adhesive sheet having excellent adhesiveness, peelability and restorability. <P>SOLUTION: This removable adhesive sheet 11 having a substrate 12 comprising a flexible vinyl chloride polymer and an adhesive layer 14 disposed on at least one side of the substrate 12 is characterized by disposing an intermediate layer 13 comprising a biaxially oriented polyester film between the substrate 12 and the adhesive layer 14, and satisfying expressions: (thickness of the substrate 12)/(thickness of the intermediate layer 13)≥30 and (thickness of the intermediate layer 13)≤5 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a re-peelable pressure-sensitive adhesive sheet provided with a re-peelable pressure-sensitive adhesive layer, and particularly when the work piece is processed during cutting or the like in the manufacturing process of an electronic component. The present invention relates to a re-peelable pressure-sensitive adhesive sheet used for temporary fixing.

  In recent years, semiconductor wafers such as silicon, germanium, and gallium arsenide have been increased in size, and semiconductor wafers have been made thinner for IC card applications. Thinning of a semiconductor wafer is usually performed by attaching a protective sheet (back grind tape) to the surface of the semiconductor wafer and grinding the back surface. Here, for the purpose of preventing warpage occurring after thin processing of a semiconductor wafer, a soft vinyl chloride film having excellent stress relaxation properties after being attached to the protective sheet may be used.

  In addition, these semiconductor wafers are subjected to dicing, cleaning, drying, expanding, picking up, and mounting processes in a state where they are attached to an adhesive sheet in advance. As a semiconductor wafer holding adhesive sheet (dicing tape) used in such a semiconductor wafer dicing process, in recent years, it has sufficient adhesive force in the manufacturing process from the dicing process to the expanding process, and the pickup process. However, there is a demand for an adhesive sheet having such an adhesive strength that the adhesive does not adhere to the chip. Even in this case, a dicing tape having a soft vinyl chloride film excellent in stress relaxation, extensibility in the expanding process, and subsequent restoration is widely used. Details of the re-peelable pressure-sensitive adhesive sheet using a soft vinyl chloride film are described in Patent Documents 1 and 2 below.

  Further, these pressure-sensitive adhesive sheets based on re-peeling are provided with a radiation curable pressure-sensitive adhesive layer for easy peeling. Generally, a radiation-curable pressure-sensitive adhesive layer is composed of a polymer compound called a base polymer, a radiation-polymerizable compound (monomer or oligomer) having a weight-average molecular weight of 20,000 or less and having a carbon-carbon double bond in the molecule, and radiation. A polymerization initiator is used as an essential constituent material, and various additives such as a crosslinking agent are appropriately added thereto.

  In such an adhesive sheet, in order to exhibit the characteristic of extremely reducing the adhesive strength after irradiation, a so-called radiation-polymerizable compound having two or more carbon-carbon double bonds in one molecule, so-called Many polyfunctional compounds are used. By irradiating this with radiation, the radiation-polymerizable compound reacts and a three-dimensional network structure is rapidly formed, so that the entire pressure-sensitive adhesive layer is rapidly cured by the reaction of the radiation-polymerizable compound. In other words, the adhesive strength of the pressure-sensitive adhesive layer is reduced. Details of such an adhesive composition are described in Patent Documents 3 and 4 below.

  However, various problems caused by various additives contained in the flexible vinyl chloride film widely used in the pressure-sensitive adhesive sheet have been pointed out. That is, for example, a plasticizer such as a phthalate ester easily penetrates into the pressure-sensitive adhesive layer, and as a result, after the pressure-sensitive adhesive sheet is peeled off, it often remains as a contaminant on the bonded surface of the wafer. In addition, when the pressure-sensitive adhesive layer is a radiation-curable pressure-sensitive adhesive layer, the curing function of the pressure-sensitive adhesive layer due to radiation irradiation is lost when the contained radiation-polymerizable compound or radiation polymerization initiator is transferred to the substrate. There is also a problem that the adhesive force cannot be reduced to a predetermined value after irradiation. Such a decrease in peelability cannot be peeled from the wafer in the case of a protective sheet (back grind tape), and small chips cannot be picked up in the case of a dicing tape. In order to solve these problems, the following Patent Documents 2 and 5 disclose a pressure-sensitive adhesive sheet in which an intermediate layer for preventing migration of additives is provided between a soft vinyl chloride film and a pressure-sensitive adhesive layer. Further, as the intermediate layer, Patent Document 2 discloses a material composed of modified nylon, urethanized photosensitive rubber or resin, ethylene / vinyl alcohol copolymer or polyvinylidene chloride, and Patent Document 5 discloses. Those made of polyethylene, polypropylene, polyalkylene terephthalate or modified alkyd resin are disclosed.

  However, it has been found that in the intermediate layer made of the above-mentioned constituent materials, the plasticizer often migrates after long-term storage, and the additive migration is insufficiently prevented. In addition, when the pressure-sensitive adhesive sheet is used for a dicing tape, there is a problem that chip pick-up failure occurs and the peelability is low when the additive is transferred in a small part of the pressure-sensitive adhesive sheet.

In addition, the inventors of the present application have found that the releasability is also lowered when a specific component is transferred from the pressure-sensitive adhesive layer to the soft vinyl chloride film. For example, when the pressure-sensitive adhesive layer is made into a radiation curable type, the curing function of the pressure-sensitive adhesive layer due to radiation irradiation is lost due to the migration of the radiation-polymerizable compound and radiation polymerization initiator contained in the soft vinyl chloride film. After irradiation, the adhesive force cannot be reduced to a predetermined value. Therefore, as in the pressure-sensitive adhesive sheet disclosed in each of the following patent documents, it is possible to prevent the additive contained in the soft vinyl chloride film from moving into the pressure-sensitive adhesive layer, and to maintain stable adhesiveness. An adhesive sheet having releasability or the like cannot be obtained.
Japanese Patent No. 2703467 Japanese Patent No. 3060417 Japanese Patent No. 219328 Japanese Patent No. 2126520 No. 1-56111

  This invention is made | formed in view of the said problem, The objective is to provide the re-peeling type adhesive sheet excellent in adhesiveness, peelability, and recoverability.

  In order to solve the above-mentioned conventional problems, the inventors of the present application have made extensive studies on the re-peelable pressure-sensitive adhesive sheet. As a result, the inventors have found that the object can be achieved by adopting the following configuration, and have completed the present invention.

  That is, the re-peelable pressure-sensitive adhesive sheet according to the present invention includes a base material containing soft vinyl chloride and a pressure-sensitive adhesive layer provided on at least one surface of the base material in order to solve the above-described problem. An intermediate layer made of a biaxially stretched polyester film is provided between the base material and the pressure-sensitive adhesive layer, and (thickness of base material) / (intermediate layer) Thickness) ≧ 30 and (intermediate layer thickness) ≦ 5 μm.

  According to the said structure, by providing the intermediate | middle layer which consists of a biaxially stretched polyester film between a base material and an adhesive layer, additives, such as a plasticizer contained in a base material, for example in an adhesive layer Transition can be prevented over a long period of time. As a result, it is possible to suppress a decrease in adhesiveness of the pressure-sensitive adhesive layer due to softening due to a decrease in cohesive force.

  In the above structure, the intermediate layer is made of a hard material (biaxially stretched polyester film), but the thickness thereof is set to 5 μm or less so as to be thinner than the conventional one (for example, 10 to 20 μm). By making the ratio with the thickness of the intermediate layer to be 30 or more, the intermediate layer is inhibited from reducing the extensibility of the re-peelable pressure-sensitive adhesive sheet. As a result, when the re-peelable pressure-sensitive adhesive sheet is stretched, the intermediate layer is prevented from being peeled from the base material, and can be restored to its original state after stretching. Thereby, it is possible to prevent slack from occurring in the re-peelable pressure-sensitive adhesive sheet.

  Moreover, in the said structure, it is preferable that the said adhesive layer is a radiation curing type adhesive layer.

  The intermediate layer can also block radiation polymerization initiators and radiation polymerizable compounds that are about to migrate from the adhesive layer to the substrate. Thereby, even when trying to peel the re-peelable pressure-sensitive adhesive sheet from the adherend, a sufficient amount of the radiation polymerization initiator and the radiation-polymerizable compound remain in the pressure-sensitive adhesive layer to cure it. Yes. As a result, when the pressure-sensitive adhesive layer is irradiated with radiation, the pressure-sensitive adhesive layer is sufficiently cured, and the re-peelable pressure-sensitive adhesive sheet can be easily peeled from the adherend. Therefore, with the above-described configuration, it is possible to prevent deterioration of peelability over a long period of time.

  The present invention has the following effects by the means described above.

  That is, since the re-peelable pressure-sensitive adhesive sheet according to the present invention has an intermediate layer composed of a biaxially stretched polyester film between the base material and the pressure-sensitive adhesive layer, for example, the additive in the base material is the pressure-sensitive adhesive layer. Transition to the inside can be prevented over a long period of time, and deterioration of adhesiveness due to softening of the pressure-sensitive adhesive layer can be prevented.

  In addition, the thickness of the intermediate layer is set to 5 μm or less so that it is thinner than the conventional one, and the ratio of the thickness of the base material to the thickness of the intermediate layer is 30 or more so that a hard material (biaxially stretched polyester film) It suppresses that the intermediate | middle layer which consists of reduces the extensibility of a releasable adhesive sheet. As a result, when the re-peelable pressure-sensitive adhesive sheet is extended, it is possible to prevent the intermediate layer from peeling from the base material. Moreover, the restoring property can be improved and the occurrence of slack can be reduced.

  Furthermore, it is possible to prevent migration of specific components present in the pressure-sensitive adhesive layer to the base material. For example, even when the pressure-sensitive adhesive layer is a radiation curable type, the radiation-polymerizable compound or the radiation polymerization present in the pressure-sensitive adhesive layer. It is possible to prevent the initiator and the like from transferring to the base material. As a result, it is possible to provide a re-peelable pressure-sensitive adhesive sheet having good peelability over a long period of time.

  Embodiments of the present invention will be described below with reference to the drawings. However, parts that are not necessary for the description are omitted, and there are parts that are illustrated in an enlarged or reduced manner for ease of explanation.

  FIG. 1 is a schematic cross-sectional view illustrating a schematic configuration of a re-peelable pressure-sensitive adhesive sheet (hereinafter simply referred to as a pressure-sensitive adhesive sheet) according to the present embodiment. As shown in the figure, the pressure-sensitive adhesive sheet 11 according to the present embodiment has a configuration in which an intermediate layer 13 and a pressure-sensitive adhesive layer 14 are sequentially laminated on a base material 12.

  The base 12 is a support base for the intermediate layer 13 and the pressure-sensitive adhesive layer 14 and is made of a film containing soft vinyl chloride. The substrate 12 may be composed of a single layer or may be composed of a laminate of two or more layers. When the substrate 12 is a laminate of two or more layers, at least one layer may be a soft vinyl chloride film. In addition, when the adhesive layer 14 is a radiation curing type, it is preferable that the base material 12 has a property of transmitting at least part of radiation such as X-rays, ultraviolet rays, and electron beams. Moreover, what has the softness | flexibility which can endure the expanding after dicing is preferable.

  The constituent material of the substrate 12 is not particularly limited. For example, polyvinyl chloride, urethane-vinyl chloride copolymer, ethylene-vinyl chloride copolymer, vinyl acetate-vinyl chloride copolymer, ethylene-acetic acid. Examples thereof include vinyl chloride copolymers such as vinyl copolymers and mixtures thereof, or mixtures with other resins and elastomers. The copolymer includes a kraft copolymer and the mixture includes a so-called alloy.

  In addition to the above-mentioned constituent materials, the base material 12 includes low density polyethylene, linear polyethylene, medium density polyethylene, high density polyethylene, ultra low density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolymer. Polypropylene, polybutene, polyolefins such as polymethylpentene, ionomer resin, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, Polymers such as ethylene-hexene copolymer, polyurethane, polyester such as polyethylene terephthalate, polyimide, polyether ether ketone, polyvinylidene chloride, fluororesin, cellulosic resin, and cross-linked products thereof were blended as required. Also It can also be used.

  Additives such as phthalic acid esters such as dibutyl phthalate, dioctyl phthalate, dinonyl phthalate, diisodecyl phthalate, other polyester plasticizers, epoxy plasticizers, or trimet plasticizers are added to the base material 12. May be. The epoxy plasticizer may be epoxidized soybean oil as a secondary plasticizer and stabilizer.

  Further, in the base material 12, softeners such as mineral oil, fillers such as calcium carbonate, silica, talc, mica, clay, antioxidants, light stabilizers, antistatic agents, lubricants, dispersants, neutralization Various known additives such as an agent, an α crystal nucleating agent, a β crystal nucleating agent, a processing aid, and an antiaging agent may be blended as necessary.

  The base material 12 may be used without stretching, or may be subjected to uniaxial or biaxial stretching treatment as necessary. The surface of the substrate 12 can be subjected to conventional physical or chemical treatment such as mat treatment, corona discharge treatment, primer treatment, and crosslinking treatment (chemical crosslinking (silane)) as necessary. The thickness of the substrate 12 (total thickness in the case of a laminate of two or more layers) is not particularly limited, and is preferably about 30 to 250 μm, more preferably about 60 to 230 μm. preferable.

  The substrate 12 can be formed by a conventionally known film forming method. Specifically, for example, a wet casting method, an inflation extrusion method, a T-die extrusion method, or the like can be used.

  The intermediate layer 13 is made of a biaxially stretched polyester film. The biaxially stretched polyester film is obtained by biaxially stretching a polyester mainly composed of polyethylene terephthalate or polyethylene naphthalate. Examples of the biaxial stretching method include simultaneous biaxial stretching and sequential biaxial stretching. A biaxially stretched polyester film is obtained as follows. That is, for example, after drying polyester as necessary, it is supplied to a melt extruder and extruded from a slit-shaped die into a sheet. Next, it is brought into close contact with the casting drum by a method such as electrostatic application, and solidified by cooling to obtain an unstretched sheet. As the stretching method, the above-described simultaneous biaxial stretching, sequential biaxial stretching, or the like can be employed. The unstretched sheet is stretched in the longitudinal direction and the width direction of the film and heat-treated. In the case of simultaneous biaxial stretching, the longitudinal direction and the width direction of the film are stretched almost simultaneously. In the case of sequential biaxial stretching, the film is stretched in the longitudinal direction and then stretched in the width direction. The draw ratio is 1.1 to 10 times, preferably 2.0 to 10 times in each direction. Any of the draw ratios in the longitudinal direction and the width direction may be increased or the same.

  The thickness of the intermediate layer 13 is preferably 5 μm or less, and more preferably in the range of 2 to 4 μm. However, in the present invention, (the thickness of the base material) / (the thickness of the intermediate layer) needs to be 30 or more, more preferably in the range of 48-50. By making the thickness of the intermediate layer 13 made of the biaxially stretched polyester film thinner than before, the extensibility of the pressure-sensitive adhesive sheet 11 is prevented from being lowered due to the intermediate layer. As a result, when the pressure-sensitive adhesive sheet 11 is stretched, the intermediate layer 13 is prevented from being peeled off from the base material 12 and can be restored to its original state after stretching. Thereby, it is possible to prevent the adhesive sheet 11 from being slackened.

  In addition, when what consists of a uniaxially stretched polyester film is used as the intermediate | middle layer 13, when extending | stretching a re-peeling type adhesive sheet, there exists a problem that it becomes non-uniform | heterogenous in the vertical direction or horizontal direction of a sheet | seat. Moreover, in the case of an unstretched polyester film, there exists a manufacturing problem that film formation is difficult.

  As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 14, various pressure-sensitive adhesive polymers such as rubber-based, acrylic-based, silicone-based, and vinyl ester-based are used. Among these adhesive polymers, (meth) acrylic polymers are used from the standpoints of easy molecular design and cleanability of electronic components that do not like contamination such as semiconductor wafers and glass with organic solvents such as ultrapure water and alcohol. Is particularly preferred.

  Examples of the acrylic polymer include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a heptyl group, and a cyclohexyl group. Carbon number such as 2-ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group, and dodecyl group Hereinafter, an alkyl (meth) acrylate having a linear or branched alkyl group having 4 to 18 carbon atoms is preferable. These alkyl (meth) acrylates may be used alone or in combination of two or more.

  Other monomer components and oligomer components include, for example, carboxyl groups such as acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Monomers, acid anhydride monomers such as maleic anhydride and itaconic anhydride, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (meth) acrylic 6-hydroxyhexyl acid, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl (meth) acrylate, etc. of Droxyl group-containing monomer, styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyloxynaphthalene sulfone Examples thereof include sulfonic acid group-containing monomers such as acids, and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate. These monomer components may be used alone or in combination of two or more.

  Moreover, a polyfunctional monomer etc. can also be used as a copolymerization monomer component as needed for the purpose of a crosslinking treatment of a (meth) acrylic polymer. Examples of polyfunctional monomers include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and pentaerythritol di (Meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and urethane (meth) acrylate Etc., and the like. These polyfunctional monomers may be used individually by 1 type, and may use 2 or more types together.

  The amount of the polyfunctional monomer used is preferably 30% by weight or less, more preferably 20% by weight or less of the total monomer components from the viewpoint of adhesive properties and the like.

  For the preparation of the (meth) acrylic polymer, an appropriate method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a suspension polymerization method is applied to a mixture containing one or more monomer components. It can be carried out.

  A carbon-carbon double bond may be introduced into the inner chain of the (meth) acrylic polymer to form a radiation curable polymer. In this case, it is not necessary to add a radiation-curable monomer component or oligomer component as a radiation-polymerizable compound described below, as long as the characteristics that reduce the adhesive force when irradiated with radiation can be sufficiently expressed. Its use is optional. As a method for introducing a carbon-carbon double bond, a conventionally known method can be employed. However, from the viewpoint of ease of molecular design, the following method is preferable. That is, a copolymer having a predetermined functional group is previously copolymerized with a (meth) acrylic polymer to obtain a copolymer. Next, this copolymer and another functional group capable of addition reaction with the above functional group and a monomer having a carbon-carbon double bond are condensed or added while maintaining the carbon-carbon double bond. React.

  Examples of the combination of the predetermined functional group and other functional group capable of addition reaction with the functional group include a carboxylic acid group and an epoxy group, a carboxylic acid group and an aziridyl group, a hydroxyl group and an isocyanate group, and the like. . Of these combinations, any combination may be used as long as the radiation-curable polymer can be produced after the reaction. However, a combination of a hydroxyl group and an isocyanate group is preferable from the viewpoint of easy reaction tracking.

  The case where a hydroxyl group and an isocyanate group are combined will be described in more detail. Examples of the monomer having an isocyanate group and a carbon-carbon double bond used in such a case include an isocyanate compound, and more specifically, methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl. -Α, α-dimethylbenzyl isocyanate and the like. Examples of the copolymer of a (meth) acrylic polymer and a monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxy (meth) acrylate. Ether bonds in the molecule such as butyl, 6-hydroxyhexyl (meth) acrylate having an ester bond in the molecule, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, etc. The compound which has is used suitably. However, it is not limited to the compounds exemplified above as long as the radiation curable polymer can be obtained.

  Examples of the polymerization initiator include peroxides such as hydrogen peroxide, benzoyl peroxide, and t-butyl peroxide. Although the polymerization initiator is preferably used alone, it can also be used as a redox polymerization initiator in combination with a reducing agent. Examples of the reducing agent include ionized salts such as sulfites, hydrogen sulfites, iron, copper, and cobalt salts, amines such as triethanolamine, and reducing sugars such as aldose and ketose. Azo compounds are also preferred polymerization initiators, and are 2,2′-azobis-2-methylpropioamidine, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis- Use N, N'-dimethyleneisobutylaminate, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methyl-N- (2-hydroxyethyl) propionamide, etc. Can do. Further, two or more kinds of the polymerization initiators can be used in combination.

  The reaction temperature is usually about 50 to 85 ° C., and the reaction time is about 1 to 8 hours. Among the production methods, a solution polymerization method is preferable, and a polar solvent such as ethyl acetate or toluene is generally used as a solvent for the (meth) acrylic polymer. The solution concentration is usually about 20 to 80% by weight.

  In order to increase the number average molecular weight of the (meth) acrylic polymer that is the base polymer, a crosslinking agent can be appropriately added to the pressure-sensitive adhesive. Examples of the crosslinking agent include polyisocyanate compounds, epoxy compounds, aziridine compounds, melamine resins, urea resins, anhydrous compounds, polyamines, and carboxyl group-containing polymers. In the case of using a crosslinking agent, the amount used is about 0.01-5 parts by weight with respect to 100 parts by weight of the base polymer, considering that the peeling adhesive strength does not decrease too much. Is preferred. In addition to the above-described components, the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer may contain conventionally known various additives such as tackifiers, anti-aging agents, fillers, and colorants. it can.

  In order to improve the peelability from the adherend, the pressure-sensitive adhesive layer is preferably a radiation-curing pressure-sensitive adhesive layer that is cured by radiation such as ultraviolet rays or electron beams. In this case, as the soft vinyl chloride film, it is preferable to use a film having a property of transmitting at least part of radiation such as X-rays, ultraviolet rays and electron beams in order to cure the pressure-sensitive adhesive layer 14 by radiation.

  In order to obtain a radiation curable pressure-sensitive adhesive layer, a radiation polymerizable compound is blended in the constituent material. Examples of such radiation polymerizable compounds include radiation curable monomer components and oligomer components. More specifically, for example, various monomer components such as urethane, polyether, polyester, polycarbonate, polybutadiene, and the like. The oligomer components can be selected and combined. Specifically, for example, urethane (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol mono Examples include hydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, or commercially available oligoester acrylate. . These may be used alone or in combination of two or more.

  What is necessary is just to set the addition amount of a radiation polymerizable compound suitably. Specifically, for example, a range of 0.1 to 200 parts by weight is preferable with respect to 100 parts by weight of a base polymer such as a (meth) acrylic polymer constituting the pressure-sensitive adhesive, and a range of 0.1 to 150 parts by weight. Is more preferable.

  In addition, when using a urethane-type oligomer component as a radiation-curable oligomer component, it is preferable that the weight average molecular weight exists in the range of 3000-30000, and it is more preferable that it exists in the range of 4000-8000. This is because, when the weight average molecular weight is within the range, even when the surface of the semiconductor wafer as the adherend is rough, it is possible to prevent the adhesive from adhering to the chip surface during chip pickup.

The pressure-sensitive adhesive layer 14 according to the present embodiment may contain a radiation polymerization initiator in order to be cured by radiation such as ultraviolet rays. The radiation polymerization initiator has a molar extinction coefficient of 1,000 mol ⁻¹ · cm ⁻¹ or more at 365 nm, which is a characteristic wavelength of a high pressure mercury lamp generally used in the manufacturing process of semiconductor devices, preferably 1,500 mol ⁻¹ · cm ⁻¹ or more (usually 30,000 mol ⁻¹ · cm ⁻¹ or less) and the maximum absorption wavelength on the long wavelength side is 420 nm or more, preferably 430 nm or more (usually 460 nm or less). Things are used. Specific examples include 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide. It is done. In addition, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α′-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, 1 Α-ketol compounds such as hydroxycyclohexyl phenyl ketone; methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1- [4- (methylthio)- Acetophenone compounds such as phenyl] -2-morpholinopropane-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether and anisoin methyl ether; ketal compounds such as benzyldimethyl ketal; 2-naphthalenesulfonyl chloride Aromatic sulfonyl chloride compounds such as: 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime and other photoactive oxime compounds; benzophenone, benzoylbenzoic acid, 3,3′-dimethyl- Benzophenone compounds such as 4-methoxybenzophenone; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2, Examples include thioxanthone compounds such as 4-diethylthioxanthone and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketone; acyl phosphinoxide; acyl phosphonate.

  The compounding quantity of a radiation polymerization initiator is about 1-10 weight part with respect to 100 weight part of base polymers, such as an acryl-type polymer which comprises an adhesive.

  The thickness of the pressure-sensitive adhesive layer 14 is not particularly limited, but is usually in the range of about 5 to 100 μm.

  The radiation curable pressure-sensitive adhesive layer is described in detail in JP-A No. 2000-312862.

  The pressure-sensitive adhesive sheet 11 according to the present embodiment can be suitably used for processing a semiconductor (Si, Ge, Ga-As, etc.) wafer, for example. That is, for example, when the adhesive sheet 11 is bonded to the circuit pattern forming surface of a semiconductor wafer, the semiconductor wafer is diced to produce a semiconductor chip, and then the adhesive sheet 11 is irradiated with radiation to pick up the semiconductor chip. Used. Here, since the adhesive sheet 11 according to the present embodiment suppresses a decrease in adhesiveness, a workpiece such as a semiconductor wafer can be reliably fixed. For this reason, chipping or chip jumping during dicing can be prevented, and damage to the semiconductor wafer or the like can be reduced. In addition, since a sufficient curing function is maintained for irradiation with radiation, the semiconductor chip can be easily peeled off without causing adhesive residue, and the pickup property is excellent. Furthermore, since the pressure-sensitive adhesive layer 14 continues to maintain a sufficient curing function against radiation irradiation, it is excellent in long-term storage stability. In addition, a biaxially stretched polyester film was used for the intermediate layer 13 by setting the thickness of the intermediate layer 13 made of a hard material and the ratio of the thickness of the base material 12 and the thickness of the intermediate layer 13 within a predetermined range. Since the fall of the extensibility of the adhesive sheet 11 resulting from that is prevented, it is excellent also in expandability and recoverability.

  In addition, you may form another layer between the intermediate | middle layer 13 and the base material 12 for the purpose of improving adhesiveness and blocking the transfer component from the adhesive layer 14 or the base material 12. FIG. . Examples of such other layers include those made of acrylic adhesive, rubber adhesive, and the like.

(Other matters)
In the above description, the most preferred embodiment of the present invention has been described. However, the present invention is not limited to this embodiment, and various modifications can be made within the scope substantially the same as the technical idea described in the claims of the present invention.

  That is, the re-peelable pressure-sensitive adhesive sheet of the present invention may have a structure in which a release liner is laminated thereon for protecting the pressure-sensitive adhesive layer. The release liner is obtained by applying a general-purpose releasable material to at least one surface of a general-purpose resin film. The resin film is not particularly limited, and specifically, polyolefin film such as polyethylene, polypropylene, polybutene, polybutadiene or polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyethylene terephthalate, polybutylene terephthalate, Examples thereof include polyurethane, ethylene vinyl acetate copolymer, ionomer resin, ethylene / (meth) acrylic acid copolymer, ethylene / (meth) acrylic acid ester copolymer, polystyrene, and polycarbonate. These materials can be used alone or in combination of two or more. The release liner is not particularly limited as long as the release function and the protective function of the pressure-sensitive adhesive layer are exhibited. Usually, for example, silicone-based, long-chain alkyl-based, fluorine-based, fatty acid network clock, silica-based release agent, etc. A polyester film coated with is often used. In addition, a polyethylene film, a polypropylene film, a polytetrafluoroethylene film, and the like can be used alone because they have a high mold release property without being subjected to a special mold release treatment. In addition, the thickness of the said resin film is not specifically limited, Usually, it is about 10-100 micrometers.

  Moreover, you may provide an undercoat layer between the said base material and an intermediate | middle layer, and between an intermediate | middle layer and an adhesive layer in order to improve adhesiveness (anchoring property). The constituent material of the undercoat layer provided between the base material and the intermediate layer is preferably the same as the pressure-sensitive adhesive layer and mainly composed of an acrylate copolymer having excellent adhesion to the base material. What has sufficient adhesiveness and high elasticity modulus which can endure a process is preferable. More specifically, for example, butyl acrylate or a product obtained by crosslinking it with an isocyanate is exemplified. Also, from base materials such as polyethylene, polypropylene, polyalkylene terephthalate, modified alkyd resin, modified nylon, urethanated photosensitive resin, ethylene / vinyl alcohol copolymer, ethylene / (meth) acrylic acid copolymer, polyvinylidene chloride, etc. Examples of known materials that are not easily affected by the migration of plasticizers are also available.

  In the above description, an example in which the pressure-sensitive adhesive layer is provided only on one side of the base material has been described as an example, but the present invention is not limited to this. That is, it is good also as a double-sided adhesive sheet which provided the adhesive layer also on the other side of the base material. In this case, an intermediate layer can also be provided on the other side of the substrate.

  Moreover, the re-peelable pressure-sensitive adhesive sheet according to the present invention is not limited to the processing of the semiconductor wafer, and is also suitable as a pressure-sensitive adhesive sheet for dicing such as a semiconductor package or glass.

  Further, the re-peelable pressure-sensitive adhesive sheet according to the present invention can have any shape such as a tape shape and a label shape.

  Hereinafter, preferred embodiments of the present invention will be described in detail by way of example. However, the materials, blending amounts, and the like described in the examples are not intended to limit the scope of the present invention only to them, but are merely illustrative examples, unless otherwise specified.

Example 1
In a 50 wt% solution of ethyl acetate, 33 parts by weight of 2-ethylhexyl acrylate, 67 parts by weight of methyl acrylate, 7.5 parts by weight of acrylic acid, and 0.2 parts by weight of benzoyl peroxide are added and polymerized to obtain a weight average molecular weight of about 700,000. A solution containing an acrylic polymer was obtained. Further, 100 parts by weight of this solution, 80 parts by weight of dipentaerythritol hexaacrylate (trade name: Kayarad DPHA, manufactured by Nippon Kayaku Co., Ltd.), photopolymerization initiator (trade names: Irgacure 651, Ciga Specialty Chemicals) Acrylic pressure-sensitive adhesive solution was prepared by adding 6.5 parts by weight) and 3 parts by weight of a polyisocyanate compound (trade name “Coronate L”, manufactured by Nippon Polyurethane Co., Ltd.).

  This acrylic pressure-sensitive adhesive solution was applied and dried on a release-treated polyester liner (release liner) having a thickness of 50 μm to form a radiation-curable pressure-sensitive adhesive layer (thickness 5 μm).

  A solution containing an acrylic polymer having a molecular weight of about 850,000 is obtained by adding 100 parts by weight of butyl acrylate, 6.5 parts by weight of acrylic acid, and 0.2 parts by weight of benzoyl peroxide to a 60 wt% ethyl acetate solution for polymerization. It was. Furthermore, 0.15 parts by weight of an epoxy compound (trade name: Tetrad C, manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a crosslinking agent and a polyisocyanate compound (trade name “Coronate L”, manufactured by Nippon Polyurethane Co., Ltd.) ) 2.4 parts by weight were added to prepare an acrylic pressure-sensitive adhesive solution.

  This acrylic pressure-sensitive adhesive solution was applied and dried on a biaxially stretched polyester film having a thickness of 2 μm to form an undercoat layer having a thickness of 2 μm, thereby producing an intermediate layer. A soft vinyl chloride film (base material, thickness 100 μm) containing 30 parts by weight of dioctyl phthalate as a plasticizer is superimposed on the undercoat layer side of this intermediate layer, and heat treatment (heating temperature 75 ° C., heating time 1 hour) ) And hot pressing (heating temperature 75 ° C., heating time 1 hour, press pressure 5 MPa).

  Next, the pressure-sensitive adhesive layer formed on the polyester liner was transferred onto an intermediate layer provided on the soft vinyl chloride film to produce a re-peelable pressure-sensitive adhesive sheet according to Example 1. The transfer was performed by performing a heat treatment at a heating temperature of 50 ° C. and a heating time of 48 hours, and performing a heat press treatment at a heating temperature of 50 ° C., a heating time of 12 hours, and a press pressure of 1.0 MPa.

(Example 2)
In this example, the biaxially stretched polyester film in Example 1 was changed to one having a thickness of 4 μm, and a soft vinyl chloride film containing 30 parts by weight of dioctyl phthalate as a plasticizer was thickened. A re-peelable pressure-sensitive adhesive sheet according to Example 2 was produced in the same manner as in Example 1 except that the thickness was changed to 190 μm.

(Example 3)
A solution containing an acrylic polymer having a weight average molecular weight of about 850,000, polymerized by adding 100 parts by weight of butyl acrylate, 7.5 parts by weight of acrylic acid, and 0.2 parts by weight of benzoyl peroxide to a 60 wt% solution of ethyl acetate Got. Furthermore, 0.15 parts by weight of an epoxy compound (trade name: Tetrad C, manufactured by Mitsubishi Gas Chemical Co., Ltd.) and a polyisocyanate compound (trade name “Coronate L”, Nippon Polyurethane (trade name) 2.6 parts by weight (manufactured by Co., Ltd.) was added to prepare an acrylic pressure-sensitive adhesive solution. In the same manner as in Example 1, this acrylic pressure-sensitive adhesive solution was applied and dried on a release-treated polyester liner (release liner) having a thickness of 50 μm, and a pressure-sensitive pressure-sensitive adhesive layer (thickness 5 μm). Formed.

  Further, in the same manner as in Example 1, a re-peelable pressure-sensitive adhesive sheet according to Example 3 was produced.

(Comparative Example 1)
In Comparative Example 1, a re-peelable pressure-sensitive adhesive sheet according to Comparative Example 1 was produced in the same manner as in Example 1 except that a low-density polyethylene film having a thickness of 20 μm was used as the intermediate layer. .

(Comparative Example 2)
First, in the same manner as in Example 1, an acrylic pressure-sensitive adhesive solution was prepared, and this was applied and dried on a 50 μm-thick polyester liner that had been subjected to a release treatment, and a radiation-curable pressure-sensitive adhesive layer (thickness) 5 μm) was formed.

  Next, the pressure-sensitive adhesive layer formed on the polyester liner was transferred onto a soft vinyl chloride film, and a re-peelable pressure-sensitive adhesive sheet according to Comparative Example 2 was produced. The transfer was performed by performing a heat treatment at a heating temperature of 50 ° C. and a heating time of 48 hours, and performing a heat press treatment at a heating temperature of 50 ° C., a heating time of 12 hours, and a press pressure of 1.0 MPa.

(Comparative Example 3)
In Comparative Example 3, a re-peelable pressure-sensitive adhesive sheet according to Comparative Example 3 was produced in the same manner as in Example 2 except that a low-density polyethylene film having a thickness of 4 μm was used as the intermediate layer. .

(Comparative Example 4)
In Comparative Example 4, a biaxially stretched polyester film having a thickness of 7 μm was used as the intermediate layer, and a soft vinyl chloride sheet having a thickness of 230 μm was used as the base material. A re-peelable pressure-sensitive adhesive sheet according to Comparative Example 4 was produced.

(Comparative Example 5)
In Comparative Example 5, a re-peelable pressure-sensitive adhesive sheet according to Comparative Example 5 was produced in the same manner as in Example 2 except that a soft vinyl chloride sheet having a thickness of 70 μm was used as the base material. .

(Evaluation)
The re-peelable pressure-sensitive adhesive sheet obtained as described above was bonded to the surface of a silicon mirror wafer (size 6 inches, thickness 650 μm), and the adhesive strength before and after irradiation with ultraviolet rays was measured. Moreover, the silicon mirror wafer which each bonded each adhesive sheet was diced and picked up, and the success rate was calculated. Furthermore, restoration property was examined for each pressure-sensitive adhesive sheet after pickup. These results are shown in Table 1 below. The adhesive strength measurement conditions, dicing conditions, pickup conditions, and restoration property evaluation methods are as follows.

[Measurement of adhesive strength of re-peelable adhesive sheet]
The measurement of the adhesive strength of the re-peelable pressure-sensitive adhesive sheet was as follows. That is, the silicon mirror wafer was used as an adherend, and the pressure-sensitive adhesive sheets according to Examples 1 to 3 and Comparative Examples 1 to 5 were bonded to each other and held for 30 minutes. In the case of a pressure-sensitive adhesive sheet having a radiation-curable pressure-sensitive adhesive layer, irradiation with ultraviolet light having a center wavelength of 365 nm is performed so as to obtain an integrated light amount of 460 mJ / cm ² (Nitto Seiki Co., Ltd., irradiation device: NEL UM-810). Then, the pressure-sensitive adhesive layer was UV-cured. Furthermore, the adhesive force of each re-peelable pressure-sensitive adhesive sheet was measured using TENSILON: RTM-100 type manufactured by Orientec. The measurement conditions for the adhesive strength were as follows.

Sheet width: 20mm
Peel angle: 180 °
Peeling speed: 300mm / min
[Dicing condition of silicon mirror wafer]
The pressure-sensitive adhesive sheets according to Examples 1 to 3 and Comparative Examples 1 to 5 were bonded to a dicing ring, and a silicon mirror wafer (size 6 inches, thickness 650 μm) after back grinding was further applied to the re-peelable pressure-sensitive adhesive sheet. After bonding and fixing, dicing was performed under the following conditions.

Dicing machine: DFD651 manufactured by DISCO
Dicing speed: 120mm / sec
Dicing blade: NBC-ZH2050HECC made by DISCO
Dicing blade rotation speed: 40000 rpm
Dicing tape cutting depth: 30μm
Wafer chip size: 7mm x 7mm
Cut mode: Down cut In addition, the backside grinding of the silicon mirror wafer (size 6 inches, thickness 650 μm) is performed using a grinding device (DFG-840 manufactured by Disco Corporation) after bonding each adhesive sheet to the surface. This was performed until the thickness of the silicon mirror wafer reached 150 μm.

[Pickup conditions]
Pickup of each wafer chip after dicing was performed using CPS-100 manufactured by NES Machinery. That is, 100 chips were picked up and calculated as the pick-up success rate (number of defects / total number). The pickup conditions were as follows.

Number of needles: 5 Push-up amount: 400 μm
Push-up speed: 80 mm / sec. Amount of withdrawal: 10 mm
Heating after withdrawal: 50 ° C x 10 seconds
[Restorability evaluation]
After picking up, each adhesive sheet bonded to the dicing ring was removed from the CPS-100, and the amount of looseness of each adhesive sheet shown in FIG. 2 was measured with calipers.

(result)
As is apparent from Table 1, in the pressure-sensitive adhesive sheets according to Examples 1 and 2, the pressure-sensitive adhesive strength was sufficiently reduced before and after UV irradiation, whereas in the pressure-sensitive adhesive sheet according to Comparative Example 1, It was found that the adhesive strength after UV irradiation was greatly increased. Thereby, the pressure-sensitive adhesive sheets according to Examples 1 and 2 contain a sufficient amount of the radiation-polymerizable compound and the photopolymerization initiator in each pressure-sensitive adhesive layer even after UV irradiation, and the pressure-sensitive adhesive layer is irradiated with ultraviolet rays. It was confirmed that the curing function by is sufficient.

  Moreover, in the adhesive sheet which concerns on Comparative Examples 2-4, the pick-up rate of the chip | tip was 30%-100%, and the peelability in the whole surface of an adhesive sheet was inferior. On the other hand, in the pressure-sensitive adhesive sheets according to Examples 1 to 3, the chip pickup success rate is 100%, and the entire surface of the pressure-sensitive adhesive sheet has excellent peelability and expandability. Was confirmed.

  Furthermore, about the amount of looseness, in the adhesive sheet which concerns on Comparative Examples 1 and 3-5, the amount of looseness was 6-8 mm, but about the adhesive sheet which concerns on Examples 1-3, it suppresses to about 1-2 mm. It was confirmed that the restoration was excellent.

It is a cross-sectional schematic diagram which shows schematic structure of the re-peeling type adhesive sheet which concerns on embodiment of this invention. It is a schematic diagram for demonstrating the measuring method of the amount of slack of a releasable adhesive sheet.

Explanation of symbols

11 Adhesive sheet (removable adhesive sheet)
12 Base material 13 Intermediate layer 14 Adhesive layer

Claims (2)

A re-peelable pressure-sensitive adhesive sheet having a base material comprising soft vinyl chloride and a pressure-sensitive adhesive layer provided on at least one surface of the base material,
Between the base material and the pressure-sensitive adhesive layer, an intermediate layer made of a biaxially stretched polyester film is provided,
A re-peelable pressure-sensitive adhesive sheet satisfying (thickness of base material) / (thickness of intermediate layer) ≧ 30 and (thickness of intermediate layer) ≦ 5 μm. The re-peelable pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is a radiation curable pressure-sensitive adhesive layer.

Images