JP2018012751A - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet which, even after heating, has excellent detachability from an uneven surface and hardly generates adhesive residues after detachment.SOLUTION: There is provided an adhesive sheet 100 having an adhesive layer 20 formed from an adhesive containing a base polymer and capable of hardening by irradiation of an active energy ray, in which rigidity (the product between nanoindenter elastic modulus and thickness at 25°C) of the adhesive layer 20 before hardening by the active energy ray is 0.0013 to 0.008 N/m, the nanoindenter elastic modulus at 25°C of the adhesive layer 20 before active energy ray curing is 0.045 to 0.175 MPa, and the thickness of the adhesive layer 20 of 20 to 60 μm. Preferable is the adhesive sheet 100 in which the base polymer has a carbon-carbon double bond, and the adhesive layer 20 contains a radical scavenger, further contains a photoinitiator and moreover contains a crosslinking agent.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an adhesive sheet.

  In recent years, a semiconductor component manufactured by resin-sealing a semiconductor chip (electrode-attached semiconductor chip) on which an electrode is formed has been attracting attention from the viewpoint that it can be miniaturized. As a method of manufacturing such a semiconductor component, an adhesive sheet is attached to the electrode side of the semiconductor chip with electrodes to fix the semiconductor chip with electrodes, and the semiconductor chip is covered with resin on the adhesive sheet. A method of sealing (resin-on-sheet sealing method) has been studied.

  The pressure-sensitive adhesive sheet used in the above method has adhesiveness that can maintain the fixing position of the electrode-attached semiconductor chip, adhesion that can prevent the sealing resin from flowing around the electrode surface of the electrode-attached semiconductor chip, and a sealing step Heat resistance that does not change due to heating at high temperature, and releasability that can be easily peeled off from a workpiece after sealing and with little adhesive residue are required. As an adhesive sheet satisfying such characteristics, the adhesiveness changes by UV curing (that is, it is possible to achieve both adhesiveness and releasability), and has excellent heat resistance and does not easily cause adhesive failure during heating. It is possible to use an adhesive sheet provided with a layer (for example, patent document 1). However, even with such an adhesive sheet, the adhesive sheet that has been subjected to the heat treatment has a problem in that the adhesive residue that occurs at the time of peeling cannot be sufficiently reduced on an uneven surface such as the electrode surface of the electrode-attached semiconductor chip. .

JP2015-12084A

  The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is to provide a pressure-sensitive adhesive sheet that is excellent in releasability from an uneven surface even after heating and hardly causes adhesive residue after peeling. There is to do.

  As a result of intensive studies, the present inventors have found that the adhesive residue generated when the pressure-sensitive adhesive sheet is peeled from the concavo-convex surface is concentrated at the corners of the concavo-convex surface (for example, the corners of the electrode), and the post-curing stress is concentrated. It is found that this is due to the physical destruction of the pressure-sensitive adhesive layer, and furthermore, such a factor is a factor that has been focused on in the past (that is, the low molecular weight component in the pressure-sensitive adhesive layer, the adherend surface, and the like). It has been found that the influence is larger than the intermolecular force, etc.), and the present invention has been completed.

The pressure-sensitive adhesive sheet of the present invention comprises a pressure-sensitive adhesive layer that is formed from a pressure-sensitive adhesive containing a base polymer and can be cured by irradiation with active energy rays. The rigidity of the pressure-sensitive adhesive layer before curing of active energy rays (nanoin at 25 ° C.) The product of the denter elastic modulus and thickness) is 0.0013 N / m to 0.008 N / m, and the nanoindenter elastic modulus at 25 ° C. of the pressure-sensitive adhesive layer before curing with active energy rays is 0.045 MPa to The pressure-sensitive adhesive layer has a thickness of 20 μm to 60 μm.
In one embodiment, the base polymer has a carbon-carbon double bond, and the residual ratio of the carbon-carbon double bond (after heating) when the pressure-sensitive adhesive sheet is heated at 150 ° C. for 1 hour. The number of acrylic carbon-carbon double bonds / number of carbon-carbon double bonds before heating × 100) is 80% or more.
In one embodiment, the pressure-sensitive adhesive layer further contains a radical scavenger, and the content ratio of the radical scavenger is 1 part by weight or less with respect to 100 parts by weight of the base polymer.
In one embodiment, the pressure-sensitive adhesive layer further contains a photopolymerization initiator, and the photopolymerization initiator is used in an environment where the temperature rises from 23 ° C. to 300 ° C. at a temperature increase rate of 2 ° C./min in a nitrogen atmosphere. The 10% by weight reduction temperature is 220 ° C. or higher.
In one embodiment, the pressure-sensitive adhesive layer further contains a crosslinking agent, and the content of the crosslinking agent is 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the base polymer.
In one embodiment, the pressure-sensitive adhesive sheet is adhered to a SUS304BA plate, left in an environment of 150 ° C. for 1 hour, and then irradiated with ultraviolet rays (integrated light amount: 460 mJ / cm ² ). The adhesive strength is 0.4 N / 20 mm or less.
In one embodiment, the pressure-sensitive adhesive sheet of the present invention further includes a base material, and the pressure-sensitive adhesive layer is disposed on at least one surface of the base material.
In one embodiment, the pressure-sensitive adhesive sheet of the present invention further includes a base material and another pressure-sensitive adhesive layer, and includes the pressure-sensitive adhesive layer, the base material, and the other pressure-sensitive adhesive layer in this order.

  The pressure-sensitive adhesive sheet of the present invention is provided with a pressure-sensitive adhesive layer having a specific range of rigidity (the product of the nanoindenter elastic modulus and thickness at 25 ° C.), and thus has excellent peelability even after heating. It is possible to obtain a pressure-sensitive adhesive sheet that hardly causes adhesive residue after peeling.

It is a schematic sectional drawing of the adhesive sheet by one Embodiment of this invention. It is a schematic sectional drawing of the adhesive sheet by another embodiment of this invention.

A. Overall configuration diagram 1 of the adhesive sheet is a schematic sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. The pressure-sensitive adhesive sheet 100 includes a base material 10 and a pressure-sensitive adhesive layer 20 on at least one surface of the base material 10. The rigidity of the pressure-sensitive adhesive layer 20 (the product of the nanoindenter elastic modulus at 25 ° C. and the thickness) is 0.0013 N / m to 0.008 N / m. In FIG. 1, although the adhesive sheet 100 provided with the base material 10 is shown, the adhesive sheet of this invention may be provided with the base material and does not need to be provided. In this invention, in order to form the adhesive layer which has appropriate rigidity, even if it does not have a base material, the said effect can be exhibited. Although not shown, the pressure-sensitive adhesive sheet of the present invention may be provided with a release liner on the outside of the pressure-sensitive adhesive layer for the purpose of protecting the pressure-sensitive adhesive surface until it is used.

  FIG. 2 is a schematic cross-sectional view of an adhesive sheet according to another embodiment of the present invention. The pressure-sensitive adhesive sheet 100 includes a pressure-sensitive adhesive layer 20, a base material 10, and another pressure-sensitive adhesive layer 30 in this order. Such a pressure-sensitive adhesive sheet functions as a double-sided pressure-sensitive adhesive sheet, and the double-sided pressure-sensitive adhesive sheet is suitably used as a workpiece fixing sheet capable of improving workability in semiconductor chip processing (for example, resin sealing), for example. obtain. Another pressure-sensitive adhesive layer typically includes a pressure-sensitive pressure-sensitive adhesive.

  In the present invention, the nanoindenter elastic modulus and thickness of the pressure-sensitive adhesive layer are appropriately adjusted, and the rigidity of the pressure-sensitive adhesive layer 20 is set to 0.0013 N / m to 0.008 N / m, thereby following the uneven surface. Adhesive residue caused by a step on the uneven surface, that is, adhesive residue caused by concentration of peeling stress on the pressure-sensitive adhesive layer can be prevented while closely adhering. The pressure-sensitive adhesive sheet of the present invention is particularly advantageous in that it can be peeled off with little adhesive residue even after heating (for example, heating at 100 ° C. to 200 ° C.). The pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer can be suitably used as a pressure-sensitive adhesive sheet for fixing the electrode-attached semiconductor chip during the resin-on-sheet sealing method. More specifically, the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer can be adhered to the electrode surface (uneven surface) of the semiconductor chip with electrode with good adhesiveness and adhesion, so that the sealing resin wraps around the electrode surface. When peeling, it is difficult for adhesive residue to occur due to a step due to the electrode. In addition, when adhesive residue arises in the semiconductor chip with an electrode, when this semiconductor chip with an electrode is connected with another electric component, an adhesive residue causes a conduction defect. Moreover, the adhesive residue also causes soldering failure.

  The pressure-sensitive adhesive sheet of the present invention has a characteristic that the pressure-sensitive adhesive layer is cured by active energy rays (typically ultraviolet rays) and the pressure-sensitive adhesiveness is lowered. By irradiating active energy rays to reduce the adhesiveness of the pressure-sensitive adhesive layer, peeling from the adherend becomes easy. In this invention, it has one characteristic in the point that the adhesive residue inhibitory effect after adhesive layer hardening improves by making the said rigidity before adhesive layer hardening into a specific range.

B. As described above, the stiffness of the pressure-sensitive adhesive layer before curing with active energy rays (the product of the nanoindenter elastic modulus and thickness at 25 ° C.) is 0.0013 N / m to 0.008 N / m. The rigidity is preferably 0.002 N / m to 0.006 N / m, and more preferably 0.0025 N / m to 0.005 N / m. If it is such a range, the effect of this invention will become remarkable. Note that the nanoindenter elastic modulus is the load load to the indenter and the indentation depth when the indenter is pushed into the sample. It refers to the elastic modulus obtained from the height curve. Details of the method for measuring the nanoindenter elastic modulus will be described later.

  The nanoindenter elastic modulus at 25 ° C. before the active energy ray curing of the pressure-sensitive adhesive layer is preferably 0.045 MPa to 0.175 MPa, more preferably 0.1 MPa to 0.15 MPa. If it is such a range, the adhesive sheet excellent in adhesiveness and adhesiveness can be obtained. The pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having an elastic modulus of less than 0.045 MPa may follow the uneven surface too much when adhered to the uneven surface, and as a result, adhesive residue may be generated due to the uneven surface. There is. When the said elasticity modulus is larger than 0.175 MPa, there exists a possibility that the adhesiveness to an uneven surface may worsen. The nanoindenter elastic modulus can be controlled by, for example, the type of base polymer constituting the pressure-sensitive adhesive, the molecular weight of the base polymer, the degree of crosslinking of the base polymer, and the like.

  The nanoindenter elastic modulus at 25 ° C. after the active energy ray curing of the pressure-sensitive adhesive layer is preferably 1 MPa to 100 MPa, more preferably 5 MPa to 50 MPa. If it is such a range, the adhesive sheet which is excellent in peelability can be obtained.

  The thickness of the pressure-sensitive adhesive layer (thickness before active energy ray curing) is preferably 20 μm to 60 μm, more preferably 25 μm to 50 μm, and further preferably 30 μm to 45 μm. If it is such a range, the effect by making the said rigidity into a specific range will become remarkable.

  The pressure-sensitive adhesive force a1 of the pressure-sensitive adhesive layer at 23 ° C. when the pressure-sensitive adhesive sheet of the present invention is bonded to a SUS304BA plate is preferably 0.2 N / 20 mm or more, more preferably 0.5 N / 20 mm to 20 N / 20 mm. More preferably, it is 0.75 N / 20 mm to 10 N / 20 mm. If it is such a range, the adhesive sheet suitable as a fixing sheet used for the said resin sealing method on a sheet | seat can be obtained. In this specification, the adhesive strength refers to an adhesive strength measured by a method according to JIS Z 0237: 2000. A specific measuring method will be described later. The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet whose adhesive strength is reduced by irradiation with active energy rays. The “adhesive strength at 23 ° C.” means that the adhesive strength is reduced before irradiation with active energy rays. It means the adhesive strength before letting go.

  The pressure-sensitive adhesive strength a2 of the pressure-sensitive adhesive layer after the pressure-sensitive adhesive sheet of the present invention is adhered to a SUS304BA plate and left in an environment of 150 ° C. for 1 hour is preferably 1 N / 20 mm or more. / 20 mm is more preferable, and 5 N / 20 mm to 15 N / 20 mm is even more preferable. The adhesive strength a2 after being left for 1 hour in an environment of 150 ° C. is the adhesive strength before irradiation with active energy rays.

The pressure-sensitive adhesive strength b1 of the pressure-sensitive adhesive layer when irradiated with ultraviolet rays (integrated light amount: 460 mJ / cm ² ) after sticking the pressure-sensitive adhesive sheet of the present invention to a SUS304BA plate and leaving it in an environment of 150 ° C. for 1 hour It is preferably 2N / 20 mm or less, more preferably 1 N / 20 mm or less, and further preferably 0.4 N / 20 mm or less. If it is such a range, the adhesive sheet which is excellent in peelability can be obtained. The adhesive force b1 is preferably as small as possible, but the lower limit is, for example, 0.01 N / 20 mm.

  The pressure-sensitive adhesive layer contains a pressure-sensitive adhesive and an additive (for example, a crosslinking agent, a radical scavenger, and a photopolymerization initiator). The pressure-sensitive adhesive layer can be formed by applying a composition for forming a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive and additives by any appropriate method.

  Examples of the base polymer constituting the pressure-sensitive adhesive include acrylic polymers, rubber polymers (eg, natural rubber, chloroprene rubber, styrene-butadiene rubber, nitrile rubber, etc.), polyesters, urethane polymers, polyethers, and silicone polymers. Polymer, polyamide, fluorine polymer, ethylene-vinyl acetate polymer, epoxy resin, vinyl chloride polymer, cyanoacrylate polymer, cellulose polymer (nitrocellulose polymer, etc.), phenol resin, polyimide, polyolefin, styrene polymer , Polyvinyl acetate, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, polyvinyl butyral, polybenzimidazole, melamine resin, urea resin, resorcinol polymer, etc. And the like. These polymers may be used individually by 1 type, and may be used in combination of 2 or more type. From the viewpoints of adhesion and cost, acrylic polymers and rubber polymers are preferable, and acrylic polymers are more preferable. The “base polymer” refers to the main component of the polymer contained in the adhesive. The polymer is preferably a rubber-like polymer exhibiting rubber elasticity in a temperature range near room temperature. Further, in this specification, “main component” refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.

  As the acrylic polymer, for example, a polymer of a monomer raw material containing alkyl (meth) acrylate as a main monomer and a submonomer having copolymerizability with the main monomer is preferable. Here, the main monomer means a component occupying more than 50% by weight of the monomer composition in the monomer raw material. The content ratio of the main monomer is preferably 70 parts by weight to 100 parts by weight, and more preferably 90 parts by weight to 99.5 parts by weight with respect to 100 parts by weight of the total amount of monomers in the monomer raw material.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a branched or straight chain alkyl group having 1 to 20 carbon atoms (hereinafter, the range of such carbon atoms may be represented as “C1-20”). R ² is preferably a branched or linear C1-14 alkyl group, more preferably a branched or linear C6-14 alkyl group, and still more preferably a branched or linear C8. It is a -12 alkyl group.

  Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) Acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate Rate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, etc. Is mentioned. These alkyl (meth) acrylates can be used alone or in combination of two or more. Preferred alkyl (meth) acrylates include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and lauryl acrylate (LA). From the viewpoint of obtaining an appropriate peel strength, 2EHA and LA are particularly preferable.

In one embodiment, alkyl (meth) acrylate in which R ² is a branched or straight chain alkyl group having 8 or more carbon atoms is used. If such a monomer is used as a main monomer, a pressure-sensitive adhesive layer having a relatively low affinity with a metal can be formed. The pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer hardly causes adhesive residue when it is peeled from the semiconductor chip. Examples of the alkyl (meth) acrylate in which R ² is a branched or straight chain alkyl group having 8 or more carbon atoms include 2EHA, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, and isononyl. (Meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl (meth) acrylate and the like can be mentioned. The content ratio of the structural unit derived from alkyl (meth) acrylate in which R ² is a branched or straight chain alkyl group having 8 or more carbon atoms is preferably 70 to 95 parts by weight with respect to 100 parts by weight of the base polymer. Parts, more preferably 70 parts by weight to 90 parts by weight, still more preferably 75 parts by weight to 85 parts by weight. If it is such a range, the adhesive layer which is excellent in peelability can be formed.

A submonomer having copolymerizability with the main monomer, alkyl (meth) acrylate, can be useful for introducing a crosslinking point into the acrylic polymer or increasing the cohesive strength of the acrylic polymer. Moreover, it is preferable to employ | adopt the monomer which has a functional group (functional group a) which can react with the functional group (functional group b) of the carbon-carbon double bond containing monomer mentioned later as a submonomer. As the submonomer, for example, the following functional group-containing monomer components can be used alone or in combination of two or more.
Carboxy group-containing monomers: ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA) and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid and citraconic acid and anhydrides thereof (Maleic anhydride, itaconic anhydride, etc.);
Hydroxyl group-containing monomer: For example, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate; Unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether;
Amino group-containing monomer: for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate;
Epoxy group-containing monomer: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether;
Cyano group-containing monomer: for example, acrylonitrile, methacrylonitrile;
Keto group-containing monomer: for example, diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate;
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl Pyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- (meth) acryloylmorpholine;
Alkoxysilyl group-containing monomer: For example, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxy Propylmethyldiethoxysilane;
Isocyanate group-containing monomer: (meth) acryloyl isocyanate, 2- (meth) acryloyloxyethyl isocyanate, m-isopropenyl-α, α-dimethylbenzyl isocyanate.
In addition, it is preferable not to use the amide group containing monomer which can produce | generate a polymer with high affinity with a metal from a viewpoint of maintaining peelability.

  As the submonomer, a carboxy group-containing monomer is preferably used from the viewpoint of improving cohesion, and the carboxy group-containing monomer is more preferably AA or MAA.

  The content ratio of the structural unit derived from the submonomer is preferably 0.1 to 40 parts by weight, more preferably 1 to 30 parts by weight with respect to 100 parts by weight of the base polymer. If it is such a range, the cohesive force is high and the adhesive layer which is excellent in adhesiveness can be formed.

  Moreover, when using the base polymer which has a carbon-carbon double bond as mentioned later as a base polymer, the functional group (functional group b) of the compound B which has a carbon-carbon double bond mentioned later as a submonomer. It is preferable to use a submonomer having a functional group capable of reacting with (functional group a). In such a case, the type of the submonomer is determined by the compound B type. As the submonomer having the functional group a, for example, a carboxy group-containing monomer, an epoxy group-containing monomer, a hydroxyl group-containing monomer, and an isocyanate group-containing monomer are preferable, and a hydroxyl group-containing monomer is particularly preferable. By using a hydroxyl group-containing monomer as a submonomer, the acrylic polymer has a hydroxyl group. On the other hand, by using an isocyanate group-containing monomer as the compound B having a carbon-carbon double bond, the hydroxyl group of the acrylic polymer and the isocyanate group of the compound react to generate carbon derived from the compound B. -A carbon double bond is introduced into the acrylic polymer.

  For the purpose of increasing the cohesive strength of the acrylic polymer, other copolymer components other than the above-mentioned secondary monomer can be used. Examples of such copolymer components include vinyl ester monomers such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), vinyltoluene; cyclohexyl (meth) acrylate, cyclopentyl di Cycloalkyl (meth) acrylates such as (meth) acrylate, isobornyl (meth) acrylate, etc .; aryl (meth) acrylate (eg, phenyl (meth) acrylate), aryloxyalkyl (meth) acrylate (eg, phenoxyethyl (meth) acrylate) Aromatic ring-containing (meth) acrylates such as arylalkyl (meth) acrylates (eg benzyl (meth) acrylate); olefins such as ethylene, propylene, isoprene, butadiene and isobutylene Monomers such as vinyl chloride and vinylidene chloride; alkoxy group-containing monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; . Other copolymerization components other than these submonomers can be used alone or in combination of two or more. The amount of such other copolymerization component is, for example, 2 to 20 parts by weight with respect to 100 parts by weight of the total amount of monomers in the monomer raw material.

  Furthermore, a polyfunctional monomer can be used as a copolymerizable component for the purpose of crosslinking treatment of an acrylic polymer. Examples of the multifunctional monomer include hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, and trimethylol. One or more of propanetri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate and the like can be used. The amount of the polyfunctional monomer is, for example, 30 parts by weight or less with respect to 100 parts by weight of the total amount of monomers in the monomer raw material.

  The acrylic polymer can be obtained by any appropriate polymerization method. For example, solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method and the like can be mentioned.

  Preferably, a carbon-carbon double bond is introduced into the base polymer (preferably an acrylic polymer). By using a base polymer having a carbon-carbon double bond, an adhesive layer that is cured by active energy rays (typically ultraviolet rays) can be formed. In the present invention, in addition to the method, it is possible to form a curable pressure-sensitive adhesive layer using a pressure-sensitive adhesive containing a polymerizable monomer or oligomer and an acrylic polymer. From the viewpoint of obtaining a pressure-sensitive adhesive sheet with a lower content, it is preferable to form a curable pressure-sensitive adhesive layer using a base polymer having a carbon-carbon double bond.

  Any appropriate method can be adopted as a method for producing the base polymer having a carbon-carbon double bond. For example, a method of reacting a polymer A having a functional group a with a compound B having a functional group capable of reacting with the functional group a (functional group b) and a carbon-carbon double bond may be mentioned. In this case, it is preferable to carry out the reaction so that the carbon-carbon double bond does not disappear. For example, a condensation reaction, an addition reaction or the like can be employed. As the polymer A, for example, as described above, a polymer obtained by copolymerizing an alkyl (meth) acrylate as a main monomer and a submonomer having a functional group a is used.

  Examples of the combination of the functional group a and the functional group b include a combination of a carboxy group and an epoxy group, a combination of a carboxy group and an aziridyl group, and a combination of a hydroxyl group and an isocyanate group. Of these, a combination of a hydroxyl group and an isocyanate group is preferable from the viewpoint of reaction traceability. From the viewpoint of polymer design and the like, a combination in which the acrylic polymer has a hydroxyl group and the above compound has an isocyanate group is particularly preferable.

  Examples of the compound having the carbon-carbon double bond and the functional group b include an isocyanate group-containing monomer (isocyanate group-containing compound). Of these, 2- (meth) acryloyloxyethyl isocyanate is more preferable.

  The amount of the isocyanate group-containing monomer is preferably 1 to 40 parts by weight, more preferably 100 parts by weight with respect to 100 parts by weight of the polymer (that is, polymer A) before the carbon-carbon double bond is introduced. 5 to 30 parts by weight, more preferably 10 to 15 parts by weight.

  Further, a carbon-carbon double bond may be introduced so that the hydroxyl group that the polymer A has remains. In this way, the degree of crosslinking can be increased when the pressure-sensitive adhesive layer is heated. In this case, the molar ratio (a / b) between the hydroxyl group as the functional group a and the isocyanate group as the functional group b is suitably more than 1, and is preferably 1.1 or more.

  The base polymer is configured to have excellent heat resistance, that is, configured to maintain active energy ray curability even after heating (for example, heating at 100 ° C. to 200 ° C.). preferable. More specifically, it is preferable to use a base polymer that hardly generates radicals due to hydrogen abstraction even when heated. Unnecessary radical generation due to heating causes the polymer chain scission (causes the weakening of the pressure-sensitive adhesive layer) and the disappearance of the carbon-carbon double bond.

  One of the heat resistance indicators is the residual ratio of carbon-carbon double bonds after heating. When the pressure-sensitive adhesive contains a base polymer having a carbon-carbon double bond, the residual rate of the carbon-carbon double bond (carbon-carbon double after heating) when the pressure-sensitive adhesive sheet is heated at 150 ° C. for 1 hour. The carbon-carbon double bond before bonding / heating × 100) is preferably 80% or more, and more preferably 90% or more. The higher the residual ratio, the better. However, the upper limit is, for example, 99.9%. When the residual ratio of carbon-carbon double bonds after heating is low, that is, when many carbon-carbon double bonds disappear due to heating (low heat resistance), the adhesive strength reduction due to irradiation with active energy rays is insufficient. There is a risk of becoming. On the other hand, if the residual ratio of the carbon-carbon double bond is in the above range, even after heating, the curing with the active energy ray can sufficiently proceed to form an adhesive layer in which the adhesive strength is appropriately reduced. The pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer can be peeled with good releasability even after undergoing a heating step (for example, the above-described resin sealing step). The residual ratio of carbon-carbon double bonds can be adjusted appropriately by selecting the type of crosslinking agent, the amount of crosslinking agent added, the use and amount of radical scavenger, and the choice of photopolymerization initiator type. it can. Details will be described later.

The weight average molecular weight Mw of the base polymer (preferably an acrylic polymer) is preferably 10 × 10 ^{4 to} 500 × 10 ⁴ , more preferably 20 × 10 ^{4 to} 100 × 10 ⁴ , and further preferably it is a ^{30 × 10 4 ~70 × 10 4} . Within such a range, an adhesive layer with little adhesive residue and excellent adhesion can be formed. In addition, in this specification, Mw means the value of standard polystyrene conversion obtained by GPC.

  The hydroxyl value of the base polymer is preferably 70 mgKOH / g to 140 mgKOH / g, more preferably 95 mgKOH / g to 135 mgKOH / g. Within such a range, the cross-linking agent added in a preferable amount and the base polymer react appropriately to provide excellent mechanical properties (high nanoindenter elastic modulus) and heat resistance, and appropriate adhesive strength. It is possible to form an adhesive layer having

  Preferably, the pressure-sensitive adhesive layer contains a crosslinking agent. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, Examples of the metal chelate-based crosslinking agent, metal salt-based crosslinking agent, carbodiimide-based crosslinking agent, and amine-based crosslinking agent. These crosslinking agents can be used alone or in combination of two or more.

  The content of the crosslinking agent is preferably 0.5 parts by weight to 1.5 parts by weight, more preferably 1 part by weight to 1.25 parts by weight with respect to 100 parts by weight of the base polymer of the pressure-sensitive adhesive. . If it is such a range, the adhesive layer by which the nanoindenter elastic modulus was adjusted appropriately can be formed. Furthermore, when the pressure-sensitive adhesive containing a base polymer having a carbon-carbon double bond is used, the content ratio of the crosslinking agent (preferably an isocyanate-based crosslinking agent) is set in the above range, so that the carbon-carbon two after heating The residual rate of the heavy bond can be increased. As a result, an adhesive layer that can be cured well even when heated can be obtained.

  In one embodiment, an isocyanate-based crosslinking agent is preferably used. Isocyanate-based crosslinking agents are preferred in that they can react with various functional groups. Particularly preferably, a crosslinking agent having 3 or more isocyanate groups is used. By using an isocyanate-based cross-linking agent as the cross-linking agent and making the content ratio of the cross-linking agent in the above range, it is possible to form a pressure-sensitive adhesive layer that is excellent in releasability and has little adhesive residue even after heating. it can.

  The isocyanate-based crosslinking agent is preferably added so that the number of functional groups of the isocyanate-based crosslinking agent is 10 mol% to 50 mol% with respect to the number of functional groups of the functional group capable of reacting with the isocyanate-based crosslinking agent in the base polymer. It is more preferable to add so that it may become 20 mol%-40 mol%. When added in such an amount, a pressure-sensitive adhesive layer having a properly adjusted nanoindenter elastic modulus can be formed.

  Preferably, the pressure-sensitive adhesive layer contains a radical scavenger. In the present invention, the radical scavenger means a compound that can react with a radical under heating (for example, 100 ° C. to 200 ° C.). Examples of such radical scavengers include peroxides such as benzoyl peroxide and azo compounds such as azobisisobutyronitrile. Of these, benzoyl peroxide is preferable. By containing the radical scavenger, the residual rate of the carbon-carbon double bond after heating can be increased. As a result, an adhesive layer that can be cured well even when heated can be obtained. Of these, benzoyl peroxide is preferable. By appropriately adjusting the residual rate of double bonds using radicals generated from the scavenger during heating, and appropriately crosslinking (thermosetting) the carbon-carbon double bonds in the acrylic polymer, The tape floating can be suppressed. In addition, azobisisobutyronitrile is a scavenger that does not have thermosetting properties. If azobisisobutyronitrile is used, the residual rate of double bonds in the acrylic polymer can be increased. For example, when floating during heating does not become a problem, an azo-based scavenger can be preferably used.

  The content ratio of the radical scavenger is preferably 1 part by weight or less, more preferably 0.04 part by weight to 0.08 part by weight with respect to 100 parts by weight of the base polymer of the pressure-sensitive adhesive. If it is such a range, the said effect of raising the said residual rate of a carbon-carbon double bond will become remarkable.

  The pressure-sensitive adhesive layer may contain a photopolymerization initiator. Preferably, a photopolymerization initiator that hardly decomposes or generates radicals by heating is used. By using such a photopolymerization initiator, it is possible to form a pressure-sensitive adhesive layer in which curing by active energy rays sufficiently proceeds even after heating and the adhesive force is appropriately reduced. As a result, an adhesive layer that can be cured well even when heated can be obtained.

  In one embodiment, a photopolymerization initiator having a 10% by weight reduction temperature of 200 ° C. or higher is used as the photopolymerization initiator. By using such a photopolymerization initiator, it is possible to form a pressure-sensitive adhesive layer in which curing by active energy rays sufficiently proceeds even after heating and the adhesive force is appropriately reduced. The 10% by weight reduction temperature means that when the photopolymerization initiator is placed in a nitrogen atmosphere and the environmental temperature is increased from 23 ° C. to 300 ° C. at a rate of temperature increase of 2 ° C./min, Means the environmental temperature when the weight is reduced by 10% by weight with respect to the weight before the temperature rise (that is, the weight of the photopolymerization initiator is 90% by weight with respect to the weight before the temperature rise). To do. The 10% by weight reduction temperature of the photopolymerization initiator is more preferably 210 ° C. or higher, and further preferably 220 ° C. or higher. Examples of the photopolymerization initiator having a 10% by weight reduction temperature within such a range include trade names “Irgacure 369”, “Irgacure 379ex”, “Irgacure 819”, “Irgacure OXE2”, “Irgacure 127” manufactured by BASF. Trade names “Esacure one” and “Esacure 1001m” manufactured by Lamberti; trade names “Adeka optomer N-1414”, “Adeka optomer N-1606”, “Adeka optomer N-” manufactured by Asahi Denka Kogyo Co., Ltd. 1717 "and the like.

  The pressure-sensitive adhesive layer may further contain any appropriate additive as required. Examples of such additives include tackifiers, plasticizers (for example, trimellitic acid ester plasticizers, pyromellitic acid ester plasticizers), pigments, dyes, fillers, anti-aging agents, conductive materials, ultraviolet absorption. Agents, light stabilizers, release modifiers, softeners, surfactants, flame retardants, antioxidants, solvents and the like.

C. Base material The base material can be made of any appropriate material as long as the pressure-sensitive adhesive layer can be formed to be peelable. Examples of the substrate include fiber-based substrates such as woven fabrics and nonwoven fabrics; paper-based substrates; plastic-based substrates such as resin films. Moreover, you may use foams, such as a foam sheet, as a base material. Furthermore, the base material may be a multilayer structure. When a base material has a form of a multilayer, each layer may be the same base material and may combine a different base material.

  The thickness of the substrate is preferably 25 μm to 75 μm.

D. Another pressure-sensitive adhesive layer The pressure-sensitive adhesive force c2 of the pressure-sensitive adhesive layer after the pressure-sensitive adhesive sheet of the present invention having the pressure-sensitive adhesive layer is stuck to a SUS plate and left in an environment of 150 ° C. for 1 hour is: 2N / 20 mm or less is preferable, and 1N / 20 mm or less is more preferable. If it is such a range, the adhesive sheet which is excellent in peelability can be obtained. The adhesive force b1 is preferably as small as possible, but the lower limit is, for example, 0.05 N / 20 mm.

  Said another adhesive layer contains adhesives, such as an acrylic adhesive, a rubber adhesive, and a silicone adhesive, for example.

  The thickness of the other pressure-sensitive adhesive layer is, for example, 1 μm to 100 μm.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. The evaluation methods in the examples are as follows. In Examples, unless otherwise specified, “parts” and “%” are based on weight.

(1) Weight reduction of photopolymerization initiator 10 mg of photopolymerization initiator was set in a temperature-modulated TGA (manufactured by TA Instruments), and room temperature (25 ° C at a heating rate of 2 ° C / min in a nitrogen atmosphere). ) To 300 ° C., and the weight loss due to the temperature rise was measured.

(2) Double bond residual rate The pressure-sensitive adhesive sheet is oven-heated at 150 ° C. for 1 hour, and the residual rate of carbon-carbon double bonds (carbon after heating) of the pressure-sensitive adhesive (acrylic polymer) constituting the pressure-sensitive adhesive layer -Carbon double bond / carbon-carbon double bond before heating × 100) was evaluated. The residual ratio of the carbon-carbon double bond is determined by the formula of (peak area after heating / peak area before heating) from the peak area of 1620 to 1650 cm ⁻¹ obtained by analyzing the pressure sensitive adhesive by FT-IR. Asked.

(3) Adhesive strength of the adhesive layer at 23 ° C. Under an environment of 23 ° C., the adhesive layer surface of the adhesive sheet cut to a width of 20 mm was attached to a SUS304BA plate (adhesion condition: 2 kg roller 1 reciprocation). After 30 minutes passed, the pressure-sensitive adhesive sheet was peeled from the SUS304BA plate, and peel strength (peeling speed: 300 mm / min, peel angle: 180 °) was measured.

(4) Adhesive strength of the pressure-sensitive adhesive layer after being left in an environment of 150 ° C. for 1 hour and irradiating with ultraviolet rays In the same manner as in the above (3), the pressure-sensitive adhesive sheet was adhered to a SUS304BA plate.
Thereafter, the laminate of the pressure-sensitive adhesive sheet and the SUS304BA plate was left in a heating oven at 150 ° C. for 1 hour. Next, using a high-pressure mercury lamp, the laminate was irradiated with ultraviolet rays (43 mW / cm ² , 10.7 seconds, 460 mJ / cm ² ).
Subsequently, the adhesive sheet was peeled from the SUS304BA plate, and peel strength (peeling speed: 300 mm / min, peeling angle: 180 °) was measured.

(5) Another pressure-sensitive adhesive layer adhesive strength after standing for 1 hour in an environment of 150 ° C. Another pressure-sensitive adhesive layer surface of a pressure-sensitive adhesive sheet cut to a width of 20 mm was attached to a SUS304BA board (adhesion condition: 2 kg roller 1 round trip).
Thereafter, the laminate of the pressure-sensitive adhesive sheet and the SUS304BA plate was left in a heating oven at 150 ° C. for 1 hour. Subsequently, the adhesive sheet was peeled from the SUS304BA plate, and peel strength (peeling speed: 300 mm / min, peeling angle: 180 °) was measured.

(6) Adhesive residue and resin leakage The Au target was sputtered by inert gas plasma to form an Au metal film for electrode wiring on the surface of the silicone wafer, and a 0.75 mm square chip was obtained from the silicone wafer. The Au film was formed at a height of 3 μm at both ends of the chip surface so that a groove having a width of 0.25 mm was formed in the center of the chip.
The chips (625 pieces) produced as described above were arranged on the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet at intervals of 1 mm. Next, after the silicone sealant (trade name “OE-6336” manufactured by Toray Dow Co., Ltd.) was dropped to seal the chip, the chip was thermocompression bonded to the adhesive sheet (pressure: 2 MPa, temperature) : 100 ° C.).
Thereafter, post mold curing at 150 ° C. for 3 hours was performed. Next, a polyvinyl chloride film (manufactured by Nitto Denko Corporation, trade name “SPV-224”) was attached to the silicone sealant surface, and then the laminate was irradiated with ultraviolet rays using a high-pressure mercury lamp. After (43 mW / cm ² , 10.7 seconds, 460 mJ / cm ² ), the pressure-sensitive adhesive sheet was peeled off.
Presence of adhesive layer component remaining on chip and silicone sealant after peeling (presence of adhesive residue) and presence of adhesive layer in groove formed in chip (presence of adhesive leakage) Was confirmed visually. In Table 1, the case where no adhesive residue and adhesive layer leakage were confirmed was marked with ◯, and the case where it was confirmed was marked with x.

(7) Peelability Whether or not the chip is transferred to a polyvinyl chloride film (trade name “SPV-224”, manufactured by Nitto Denko Corporation) when the pressure-sensitive adhesive sheet is peeled off during the evaluation of (6) above. (Whether or not chips remain on the pressure-sensitive adhesive sheet side) was confirmed. In Table 1, the case where all the chips were transferred to the polyvinyl chloride film was marked as ◯, and the case where one or more chips remained on the adhesive sheet side was marked as x.

(8) Elastic modulus and rigidity of nanoindenter The elastic modulus of the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples was measured with a nanoindenter.
An elastic modulus was obtained by numerically processing a displacement-load hysteresis curve obtained by pressing a probe (indenter) against an object to be measured using software (triboscan) attached to the measuring device.
Moreover, rigidity was calculated | required from the measured nanoindenter elastic modulus and the thickness of an adhesive layer.
The nanoindenter apparatus and measurement conditions are as follows.
Apparatus and measurement conditions (i) Apparatus: Nanoindenter; Triboindenter manufactured by Hystron Inc.
(Ii) Measuring method: single indentation method (iii) Measuring temperature: 25 ° C
(Iv) Push-in speed: about 1000 nm / sec
(V) Indentation depth: about 800 nm
(Vi) Probe: Made of diamond, Berkovich type (triangular pyramid type)

[Example 1]
(Formation of adhesive layer (UV curable adhesive layer))
88.6 parts by weight of 2-ethylhexyl acrylate (2-EHA), 11.2 parts by weight of hydroxyethyl acrylate (HEA), and a polymerization initiator (trade name “Nyper BW” manufactured by NOF Corporation) 0.2 weight Part and toluene were mixed. The obtained mixture was polymerized at 60 ° C. under a nitrogen gas stream to obtain an acrylic copolymer having a weight average molecular weight (Mw) of about 600,000.
To a toluene solution containing 100 parts by weight of an acrylic copolymer, 11.9 parts by weight of methacryloyloxyethyl isocyanate (MOI) and 0.06 parts by weight of butyltin dilaurate are added to cause MOI to undergo an addition reaction. -An acrylic polymer having a carbon double bond was prepared. Furthermore, in a toluene solution of the above acrylic polymer, 100 parts by weight of the solid content of the acrylic polymer, 0.5 parts by weight of an isocyanate crosslinking agent (trade name “Coronate L”, manufactured by Nippon Polyurethane Industry Co., Ltd.), and photopolymerization Initiator (Ciba Specialty Chemicals, trade name “Irgacure 127” (Irg127): 2-hydroxy-1- {4- [2- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl}- 2 parts by weight of 2-methyl-propan-1-one) was added to prepare a coating solution. The coating liquid is applied to one surface of a PET base material (50 μm) to obtain a pressure-sensitive adhesive tape a (pressure-sensitive adhesive layer / PET base material) having an ultraviolet curable pressure-sensitive adhesive layer (thickness: 30 μm). It was. Further, when the photopolymerization initiator Irg127 contained in the pressure-sensitive adhesive layer was subjected to the evaluation (1), the weight loss at 200 ° C. was 5.78%, and the weight loss at 210 ° C. was 6.4%. The weight loss at 220 ° C was 7.47% and the weight loss at 230 ° C was 9.29%.
(Formation of another adhesive layer (pressure-sensitive adhesive layer))
96.9 parts by weight of butyl acrylate (BA), 2.7 parts by weight of acrylic acid (AA), 0.4 parts by weight of a polymerization initiator (trade name “Nyper BW” manufactured by NOF Corporation), toluene, Were mixed. The obtained mixture was polymerized at 60 ° C. under a nitrogen gas stream to obtain an acrylic copolymer having a weight average molecular weight (Mw) of about 500,000.
To a toluene solution containing 100 parts by weight of an acrylic copolymer, 1.5 parts by weight of an epoxy crosslinking agent (trade name “Tetrad C” manufactured by Mitsubishi Gas Chemical Company) was added to prepare a coating solution. The coating liquid is applied to the surface of the pressure-sensitive adhesive tape a opposite to the pressure-sensitive adhesive layer of the PET base material, and pressure-sensitive adhesive tape I (pressure-sensitive adhesive layer / PET base material / another pressure-sensitive adhesive layer (thickness: 50 μm)) was obtained.
The obtained adhesive tape I was used for the evaluations (2) to (8).

[Examples 2 to 12, Comparative Examples 1 to 6]
A pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the compounds used for forming the pressure-sensitive adhesive layer and another pressure-sensitive adhesive layer were changed to the compounds shown in Tables 1 and 2.
The obtained adhesive tape I was used for the evaluations (2) to (8). The results are shown in Table 1 or Table 2.
In Table 1, ACMO means acryloylmorpholine, LMA means lauryl methacrylate, INAA means isononyl acrylate, IOAA means isooctyl acrylate, and 2-HEMA means 2-ethylhexyl methacrylate.

10 Substrate 20 Adhesive layer 100, 200 Adhesive sheet

Claims (8)

A pressure-sensitive adhesive layer that is formed from a pressure-sensitive adhesive containing a base polymer and can be cured by irradiation with active energy rays,
The rigidity (product of nanoindenter elastic modulus at 25 ° C. and thickness) of the pressure-sensitive adhesive layer before active energy ray curing is 0.0013 N / m to 0.008 N / m,
The nanoindenter elastic modulus at 25 ° C. of the pressure-sensitive adhesive layer before active energy ray curing is 0.045 MPa to 0.175 MPa,
The pressure-sensitive adhesive layer has a thickness of 20 μm to 60 μm.
Adhesive sheet. The base polymer has a carbon-carbon double bond;
Residual rate of the carbon-carbon double bonds when the pressure-sensitive adhesive sheet is heated at 150 ° C. for 1 hour (number of acrylic carbon-carbon double bonds after heating / number of carbon-carbon double bonds before heating × 100) Is 80% or more,
The pressure-sensitive adhesive sheet according to claim 1. The pressure-sensitive adhesive layer further contains a radical scavenger,
The content ratio of the radical scavenger is 1 part by weight or less with respect to 100 parts by weight of the base polymer.
The pressure-sensitive adhesive sheet according to claim 1 or 2. The pressure-sensitive adhesive layer further contains a photopolymerization initiator,
Under an environment where the temperature rises from 23 ° C. to 300 ° C. at a temperature rising rate of 2 ° C./min in a nitrogen atmosphere,
10% by weight reduction temperature of the photopolymerization initiator is 220 ° C. or higher,
The pressure-sensitive adhesive sheet according to claim 1. The pressure-sensitive adhesive layer further comprises a crosslinking agent;
The content of the crosslinking agent is 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the base polymer.
The pressure-sensitive adhesive sheet according to claim 1. When the adhesive sheet was attached to a SUS304BA plate and left in an environment of 150 ° C. for 1 hour, and then irradiated with ultraviolet rays (integrated light amount: 460 mJ / cm ² ),
The adhesive strength of the adhesive layer is 0.4 N / 20 mm or less,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 5. A base material, and the pressure-sensitive adhesive layer is disposed on at least one surface of the base material;
The pressure-sensitive adhesive sheet according to claim 1. Further comprising a substrate and another adhesive layer,
The pressure-sensitive adhesive layer, the base material, and another pressure-sensitive adhesive layer are provided in this order.
The pressure-sensitive adhesive sheet according to claim 1.

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