Adhesive composition and adhesive layer

Abstract

Provided is an adhesive composition which exhibits sufficient adhesiveness when an adherend is joined, and which can be easily peeled off when the adherend is peeled off without contaminating the surface of the adherend. The adhesive composition contains an acrylic polymer (A), a photopolymerizable compound (B), and a polyolefin resin (C).

Description

Technical Field

[0001] The present invention relates to an adhesive composition. In particular, the present invention relates to an adhesive composition that exhibits sufficient adhesive properties when bonding adherends and can be easily peeled off by irradiation with light without contaminating the adherend surface. The present invention also relates to an adhesive layer formed from the adhesive composition. Background Art

[0002] A pressure-sensitive adhesive layer used for bonding components is sometimes required to have a function of reducing the adhesive strength by light irradiation or heating after bonding to an adherend, thereby facilitating peeling and disassembly.

[0003] For example, in the case of an adhesive layer used in semiconductor processing, sufficient adhesion is required to fix the silicon wafer to the substrate during dicing. On the other hand, after dicing, it is necessary to be able to easily pick up from the adhesive layer without contaminating the surface of the diced silicon wafer (chip).

[0004] As such an adhesive layer, for example, Patent Document 1 discloses an adhesive sheet containing a (meth)acrylate copolymer, a photopolymerizable compound, a curing agent, and a photopolymerization initiator, as well as a softening agent. Furthermore, Patent Document 2 discloses an adhesive sheet for semiconductor wafer processing in which a plasticizer and a surfactant are added to a base polymer.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2016 / 009879

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-228502 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, with the recent trend toward further miniaturization and thinner films of semiconductors, chips are more likely to break during pickup if the adhesive force is not sufficiently reduced by light irradiation or the like.

[0011] Therefore, an object of the present invention is to provide a PSA composition that exhibits sufficient adhesiveness when bonding adherends and can be easily peeled off without contaminating the adherend surface, and a PSA layer formed from the PSA composition.

[0012] Technical means to solve the problem

[0013] The present inventors have conducted intensive studies and have found that the above-mentioned problems can be solved by further adding a polyolefin resin to an acrylic polymer and a photopolymerizable compound, thereby completing the present invention.

[0014] That is, the present invention has the following aspects.

[0015] Plan 1

[0016] A pressure-sensitive adhesive composition comprises an acrylic polymer (A), a photopolymerizable compound (B), and a polyolefin resin (C).

[0017] Plan 2

[0018] The adhesive composition according to "Aspect 1", comprising 1 part by mass or more and less than 50 parts by mass of the polyolefin resin (C) based on 100 parts by mass of the acrylic polymer (A).

[0019] Plan 3

[0020] The adhesive composition according to "Aspect 1" or "Aspect 2", further comprising a photopolymerization initiator (D) and a crosslinking agent (E).

[0021] Plan 4

[0022] The adhesive composition according to any one of "Aspect 1" to "Aspect 3", wherein the photopolymerizable compound (B) is contained in an amount of 50 to 150 parts by mass based on 100 parts by mass of the acrylic polymer (A).

[0023] Plan 5

[0024] The adhesive composition according to any one of <Scheme 1> to <Scheme 4>, which is used for semiconductor processing.

[0025] Plan 6

[0026] An adhesive layer, formed from the adhesive composition according to any one of "Scheme 1" to "Scheme 5", having a thickness of 1 to 80 μm, and used for semiconductor processing. DETAILED DESCRIPTION

[0027] Adhesive composition

[0028] The adhesive composition according to this embodiment comprises an acrylic polymer (A), a photopolymerizable compound (B), and a polyolefin resin (C). By including the polyolefin resin (C) in addition to the acrylic polymer (A) and the photopolymerizable compound (B), the adhesive composition exhibits sufficient adhesion when adhering adherends and can be easily peeled off without contaminating the adherend surface.

[0029] Although the detailed principle is still uncertain, it is believed that if the adhesive composition involved in the present embodiment is applied to the adherend and dried to form an adhesive layer, first, the polyolefin resin (C) is moderately biased near the bonding interface with the adherend, thereby reducing the adhesive force. In addition, it is believed that by using a photopolymerizable compound (B) having a polymerizable functional group (carbon-carbon double bond) in one molecule, if light is irradiated, the adhesive layer will shrink significantly, and the surface of the adhesive layer at the bonding interface with the adherend will become rough, thereby reducing the adhesive force. If the adhesive force is reduced by light irradiation, the small angle peel strength is reduced, and the chip can be picked up without damage.

[0030] The pressure-sensitive adhesive composition according to the present embodiment preferably contains at least one of a photopolymerization initiator (D) and a crosslinking agent (E) in addition to the above-mentioned components, and more preferably contains both.

[0031] Hereinafter, each component will be described.

[0032] <Acrylic polymer (A)>

[0033] As the acrylic polymer (A) in the present embodiment, a conventionally known material can be used as a pressure-sensitive adhesive composition.

[0034] The acrylic polymer (A) may be either an acrylic polymer or a methacrylic polymer, and may be a homopolymer or a copolymer, but is preferably a copolymer.

[0035] When the acrylic polymer (A) is a copolymer, its arrangement is not particularly limited, and any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be used. However, from the viewpoint of ease of production and adjustment of the small-angle peel strength before light irradiation, random copolymers and block copolymers are preferred, and random copolymers are more preferred.

[0036] The monomers constituting the acrylic polymer (A) are not particularly limited as long as they are polymers of (meth)acrylic acid monomer components such as (meth)acrylic acid and (meth)acrylic esters. The monomers may be a single monomer or two or more. It should be noted that, in this specification, (meth)acrylic acid refers to at least one of acrylic acid and methacrylic acid, and (meth)acrylic ester refers to at least one of acrylic ester and methacrylic ester. Furthermore, the monomers constituting the acrylic polymer (A) may partially contain monomers other than acrylic esters.

[0037] The weight average molecular weight (Mw) of the acrylic polymer (A) in this embodiment is preferably 50,000 to 1.5 million. From the perspective of easily obtaining moderate low-angle peel strength before light irradiation and good coating properties, the weight average molecular weight is preferably 50,000 or more, more preferably 100,000 or more, and even more preferably 150,000 or more. It is also preferably 1.5 million or less, more preferably 1 million or less, and even more preferably 800,000 or less. It should be noted that the weight average molecular weight in this specification is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0038] The glass transition temperature (Tg) of the acrylic polymer (A) in this embodiment is preferably -70°C or higher, more preferably -70 to 20°C. From the perspective of easily obtaining moderate small-angle peel strength before light irradiation, the glass transition temperature is preferably -70°C or higher, more preferably -55°C or higher, and even more preferably -40°C or higher. From the perspective of easily reducing the small-angle peel strength after light irradiation, the glass transition temperature is preferably 20°C or lower, more preferably 10°C or lower, and even more preferably 0°C or lower.

[0039] The Tg of the acrylic polymer (A) is calculated from the monomer units constituting the acrylic polymer (A) and their content ratios using the Fox equation shown below.

[0040] Fox formula: 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+…+(W m / Tg m )

[0041] W1+W2+…+W m =1

[0042] In the above formula, Tg is the glass transition temperature of the polymer (unit: K), Tg1, Tg2, ..., Tg m is the glass transition temperature (unit: K) of the homopolymer formed by each monomer (m types of monomers from monomer 1 to monomer m), W1, W2, ..., W m The mass fraction of the structural unit derived from each monomer in the entire copolymer can be expressed as the mass fraction of the structural unit derived from each monomer. The charge ratio of each monomer to the total monomers during copolymer synthesis can be used.

[0043] In the calculation of the Fox equation, the glass transition temperature (Tg) of the homopolymer formed from each monomer can be, for example, the value described in the Polymer Handbook Fourth Edition (Wiley-Interscience 2003).

[0044] Examples of the (meth)acrylate include alkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, alkoxypolyalkylene glycol mono(meth)acrylates, alicyclic group-containing (meth)acrylates, aromatic group-containing (meth)acrylates, hydroxyl group-containing (meth)acrylates, and carboxyl group-containing (meth)acrylates.

[0045] The alkyl (meth)acrylate preferably has an alkyl group with 1 to 20 carbon atoms, for example. The alkyl (meth)acrylate more preferably has 1 to 12 carbon atoms, and even more preferably has 1 to 8 carbon atoms.

[0046] More specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (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, lauryl (meth)acrylate, oleyl (meth)acrylate, n-stearyl (meth)acrylate, and isostearyl (meth)acrylate.

[0047] As the alkoxyalkyl (meth)acrylate, for example, preferably one in which the alkyl group has 2 to 20 carbon atoms, more preferably 2 to 10 carbon atoms, and even more preferably 2 to 6 carbon atoms.

[0048] More specific examples of the alkoxyalkyl (meth)acrylate include methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate.

[0049] Examples of the alkoxypolyalkylene glycol mono(meth)acrylate include methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, ethoxytriethylene glycol mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, and methoxytriethylene glycol mono(meth)acrylate.

[0050] Examples of the alicyclic group-containing (meth)acrylate or the aromatic group-containing (meth)acrylate include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate.

[0051] Examples of the hydroxyl group-containing (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

[0052] Examples of the carboxyl group-containing (meth)acrylate include β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(meth)acryloyloxyethyl succinate, and ω-carboxypolycaprolactone mono(meth)acrylate.

[0053] Examples of monomers other than acrylic acid esters include N-vinylpyrrolidone, N-vinylcaprolactam, (meth)acryloylmorpholine, vinyl acetate, vinyl propionate, ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, styrene, α-methylstyrene, butadiene, isoprene, chloroprene, (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0054] The content of the acrylic polymer (A) in the adhesive composition of the present embodiment is preferably 30 to 70% by mass. From the perspective of easily obtaining a moderate low-angle peel strength before light irradiation, the content is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more. In addition, from the perspective of suitably obtaining the effects of other components, the content is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less.

[0055] When the acrylic polymer (A) contains a (meth)acrylate, the content of the (meth)acrylate in the acrylic polymer (A) is preferably 50 to 99% by mass. The content is preferably 50% by mass or greater, more preferably 65% ​​by mass or greater, and even more preferably 80% by mass or greater, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less.

[0056] In addition, the acrylic polymer (A) preferably contains a (meth)acrylate having an alkyl group with 1 to 3 carbon atoms. When the acrylic polymer (A) contains a (meth)acrylate having an alkyl group with 1 to 3 carbon atoms, the content of the (meth)acrylate having an alkyl group with 1 to 3 carbon atoms in the acrylic polymer (A) is preferably 30 to 90% by mass. Here, the above content is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0057] In addition, a portion of the monomers constituting the acrylic polymer (A) preferably includes a monomer having a crosslinkable functional group capable of reacting with the crosslinking agent (E) described below to form a crosslinked structure. Examples of monomers having a crosslinkable functional group include monomers having a hydroxyl group, a carboxyl group, an amino group, an amide group, and an epoxy group. Among these, monomers having a hydroxyl group and a carboxyl group are preferred.

[0058] Examples of the monomer having a hydroxyl group include the above-mentioned hydroxyl group-containing (meth)acrylates.

[0059] Examples of the monomer having a carboxyl group include the above-mentioned carboxyl group-containing (meth)acrylates, (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0060] When the acrylic polymer (A) contains a monomer having a crosslinkable functional group, the content of the monomer having a crosslinkable functional group in the acrylic polymer (A) is preferably 0.1 to 15% by mass. From the viewpoint of easily obtaining moderate small-angle peel strength before light irradiation and good stain resistance, the content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more. It is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 8% by mass or less.

[0061] The method for producing the acrylic polymer (A) is not particularly limited and a known method can be employed. For example, the acrylic polymer (A) can be produced by solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., with solution polymerization being preferred due to ease of molecular weight adjustment.

[0062] In the case of the solution polymerization method, for example, a polymerization solvent, the above-mentioned monomer components, and, if necessary, a chain transfer agent are placed in a reaction vessel, a polymerization initiator is added under an inert gas atmosphere such as nitrogen, the reaction initiation temperature is set to generally 40 to 100° C., preferably 50 to 90° C., the reaction system is maintained at a temperature generally 50 to 90° C., preferably 60 to 90° C., and the reaction is carried out for 3 to 20 hours to obtain the acrylic polymer (A).

[0063] Examples of the polymerization initiator include azo-based initiators and peroxide-based polymerization initiators.

[0064] Examples of the azo initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoyl azo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis Azo compounds such as (2-amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) dihydrate, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionate), and 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide).

[0065] Examples of the peroxide-based polymerization initiator include tert-butyl hydroperoxide, cumyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, hexanoyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, tert-butyl peroxypivalate, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)butane.

[0066] The polymerization initiator may be used alone or in combination of two or more. There is no limitation on adding the polymerization initiator multiple times during the polymerization.

[0067] The polymerization initiator is generally used in an amount of 0.001 to 5 parts by mass, preferably 0.005 to 3 parts by mass, relative to 100 parts by mass of the monomer components constituting the acrylic polymer (A).

[0068] Examples of the chain transfer agent include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, and dodecyl mercaptan; thioglycolates such as octyl thioglycolate, nonyl thioglycolate, and 2-ethylhexyl thioglycolate; 2,4-diphenyl-4-methyl-1-pentene; 1-methyl-4-isopropylidene-1-cyclohexene; α-pinene; and β-pinene. The chain transfer agent may be used alone or in combination of two or more.

[0069] Examples of the polymerization solvent used in the solution polymerization method include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethyl sulfoxide and sulfolane; and the like. The polymerization solvent may be used alone or in combination of two or more.

[0070] <Photopolymerizable compound (B)>

[0071] The photopolymerizable compound (B) in the present embodiment is a component added in order to peel the adherend without contamination when peeling by light irradiation after bonding the components.

[0072] The photopolymerizable compound (B) has a carbon-carbon unsaturated bond as a polymerizable functional group in one molecule. Therefore, it is believed that the adhesive layer shrinks upon light irradiation, roughening the adhesive layer surface at the bonding interface, resulting in reduced adhesive strength and easy peeling of the adherend.

[0073] The number of polymerizable functional groups contained in one molecule of the photopolymerizable compound (B) is not limited, but is preferably 2 to 10, more preferably 3 to 8.

[0074] As the photopolymerizable compound (B), a conventionally known photopolymerizable compound can be used, and examples thereof include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, and ethylene glycol di(meth)acrylate.

[0075] The content ratio of the photopolymerizable compound (B) in the adhesive composition involved in the present embodiment is preferably 25 to 70 mass %. Here, from the viewpoint of easily reducing the small angle peel strength after light irradiation, the above-mentioned content ratio is preferably 25 mass % or more, more preferably 30 mass % or more, and further preferably 35 mass % or more. In addition, from the viewpoint of suitably obtaining the effect brought by other components, the above-mentioned content ratio is preferably 70 mass % or less, more preferably 65 mass % or less, and further preferably 60 mass % or less.

[0076] The content of the photopolymerizable compound (B) relative to 100 parts by mass of the acrylic polymer (A) is preferably 50 to 150 parts by mass. From the perspective of easily reducing the small-angle peel strength before and after appropriate light irradiation, the content is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 70 parts by mass or more. Furthermore, from the above perspective, the content is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 130 parts by mass or less.

[0077] <Polyolefin resin (C)>

[0078] The adhesive composition according to this embodiment includes a polyolefin resin (C). By intentionally including the polyolefin resin (C) having poor compatibility with the acrylic polymer (A) in addition to the acrylic polymer (A) and the photopolymerizable compound (B), it is believed that the polyolefin resin (C) is appropriately offset on the surface of the adhesive layer according to this embodiment, thereby achieving better releasability.

[0079] Examples of the polyolefin resin (C) include homopolymers or copolymers of α-olefins having 2 to 20 carbon atoms, such as ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 4-methyl-1-hexene, 1-octene, 4,4-dimethyl-1-hexene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene; and conjugated or non-conjugated dienes having 2 to 20 carbon atoms, such as butadiene, 1,5-hexadiene, ethylidene norbornene, and dicyclopentadiene. Furthermore, ethylene / ethyl acrylate copolymers, ethylene / vinyl acetate copolymers, styrene / butadiene copolymers, and styrene / isoprene copolymers may be used.

[0080] When using a copolymer, a random copolymer, a block copolymer, or a graft copolymer can be appropriately selected, but from the viewpoint of ease of production, a random copolymer or a block copolymer is preferred, and a random copolymer is more preferred. In addition, the polyolefin resin (C) can be used alone or in combination of two or more.

[0081] The polyolefin resin (C) is preferably a propylene copolymer such as polypropylene, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / ethylene / 1-butene copolymer, or propylene / ethylene / 1-octene copolymer, and more preferably a propylene copolymer. Furthermore, the propylene content of the propylene copolymer in the propylene copolymer is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on 100% by mass of the propylene copolymer.

[0082] The melting point of the polyolefin resin (C) is preferably 30 to 150° C. Here, from the viewpoint of exhibiting appropriate small-angle peel strength before light irradiation and readily reducing the small-angle peel strength after light irradiation to facilitate peeling, the melting point is preferably 30° C. or higher, more preferably 40° C. or higher, and even more preferably 50° C. or higher. It is preferably 150° C. or lower, more preferably 125° C. or lower, and even more preferably 100° C. or lower.

[0083] The weight average molecular weight (Mw) of the polyolefin resin (C) in this embodiment is preferably 5000 to 200,000. From the viewpoint of easily obtaining moderate small-angle peel strength before light irradiation and good coating properties, the weight average molecular weight is preferably 5000 or more, more preferably 7500 or more, and even more preferably 10,000 or more. It is also preferably 200,000 or less, more preferably 150,000 or less, and even more preferably 100,000 or less.

[0084] The polyolefin resin (C) may be a modified polyolefin resin or an unmodified polyolefin resin, but a modified polyolefin resin is preferred from the viewpoint of easily reducing the compatibility with the acrylic polymer (A) and the small-angle peel strength after light irradiation.

[0085] When the polyolefin resin (C) is a modified polyolefin resin, examples thereof include acid-modified polyolefin resins, chlorinated polyolefin resins, carbodiimide-modified polyolefin resins, urea-modified polyolefin resins, and imine-modified polyolefin resins, and may be a product having two or more modifications. Among these, acid-modified polyolefin resins can be preferably used. More specifically, polyolefin resins containing carboxylic acid or its anhydride can be used, with carboxylic anhydride-modified polyolefin resins being more preferred, and maleic anhydride-modified polyolefin resins being even more preferred.

[0086] The amount of maleic anhydride or the like added to the acid-modified polyolefin resin is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, relative to the total mass of the acid-modified polyolefin resin, from the viewpoint of easily reducing compatibility and small-angle peel strength after light irradiation.

[0087] The content ratio of the polyolefin resin (C) in the adhesive composition involved in the present embodiment is preferably 1 to 15% by mass. Here, from the viewpoint of easily reducing the small-angle peel strength before and after appropriate light irradiation, the above-mentioned content ratio is preferably 1% by mass or more, more preferably 1.5% by mass or more, and further preferably 2% by mass or more. In addition, from the viewpoint of suitably obtaining the effects brought about by other components, the above-mentioned content ratio is preferably 15% by mass or less, more preferably 12% by mass or less, and further preferably 10% by mass or less.

[0088] The content of the polyolefin resin (C) relative to 100 parts by mass of the acrylic polymer (A) is preferably 1 to 50 parts by mass, more preferably 2 to 40 parts by mass, and even more preferably 3 to 30 parts by mass. From the perspective of easily reducing the small-angle peel strength after light irradiation, the above content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. Furthermore, from the perspective of staining, the above content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0089] <Photopolymerization initiator (D)>

[0090] The adhesive composition involved in this embodiment may further contain a photopolymerization initiator (D). The photopolymerization initiator (D) can use a conventionally known photopolymerization initiator. For example, acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-cyclohexylacetophenone and other acetophenones, benzophenone, 2-chlorobenzophenone, p,p'-dichlorobenzophenone, p,p'-bisdiethylaminobenzophenone, N,N'-tetramethyl-4,4'-diaminobenzophenone, 4-(2-hydroxy)-2-cyclohexylacetophenone, Ketones such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzyl methyl ketal; benzoyl benzoate; bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; α-acyl oxime esters; and thioxanthones. The photopolymerization initiator (D) may be used alone or in combination of two or more.

[0091] When the adhesive composition involved in this embodiment includes a photopolymerization initiator (D), the content of the photopolymerization initiator (D) in the adhesive composition is preferably 0.1 to 5% by mass. From the perspective of easily reducing the small-angle peel strength after light irradiation, the above-mentioned content is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. In addition, from the above-mentioned perspective, the above-mentioned content is preferably 5% by mass or less, more preferably 4.5% by mass or less, and even more preferably 4% by mass or less.

[0092] The content of the photopolymerization initiator (D) relative to 100 parts by mass of the acrylic polymer (A) is preferably 0.1 to 15 parts by mass. From the perspective of easily reducing the small-angle peel strength after light irradiation, the content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more. Furthermore, from the above perspective, the content is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 8 parts by mass or less.

[0093] Cross-linking agent (E)

[0094] The adhesive composition according to this embodiment may further include a crosslinking agent (E). A conventionally known crosslinking agent can be used as the crosslinking agent (E). Among them, the crosslinking agent is appropriately selected from a type that can react with the crosslinkable reactive group in the monomer constituting the acrylic polymer (A).

[0095] Examples of the cross-linking agent include isocyanate compounds, epoxy compounds, and metal chelate compounds.

[0096] As the isocyanate compound, for example, an isocyanate compound having two or more isocyanate groups in one molecule can be used. More specific examples thereof include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates.

[0097] Examples of the aliphatic diisocyanate include aliphatic diisocyanates having 4 to 30 carbon atoms, such as ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate.

[0098] Examples of the alicyclic diisocyanate include alicyclic diisocyanates having 7 to 30 carbon atoms, such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate.

[0099] Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms, such as phenylene diisocyanate, toluene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.

[0100] Examples of the isocyanate compound having three or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specifically, 2,4,6-triisocyanatotoluene, 1,3,5-triisocyanatobenzene, 4,4',4"-triphenylmethane triisocyanate, and the like can be cited. Furthermore, examples of the isocyanate compound include trimers of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, biuret / biuret bodies or isocyanurate bodies of hexamethylene diisocyanate or toluene diisocyanate, reaction products of trimethylolpropane with toluene diisocyanate or xylylene diisocyanate (e.g., 3-molecule adducts of toluene diisocyanate or xylylene diisocyanate), reaction products of trimethylolpropane with hexamethylene diisocyanate (e.g., 3-molecule adducts of hexamethylene diisocyanate), polyether polyisocyanates, and polyester polyisocyanates.

[0101] Examples of epoxy compounds include epoxy compounds having two or more epoxy groups per molecule. Examples include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N,N',N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, m-N,N-diglycidylaminophenylglycidyl ether, N,N-diglycidyltoluidine, and N,N-diglycidylaniline.

[0102] Examples of metal chelate compounds include compounds in which alkoxides, acetylacetone, ethyl acetoacetate, and the like are coordinated to polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Specific examples include aluminum isopropoxide, aluminum sec-butyrate, ethyl acetoacetate-aluminum diisopropoxide, aluminum trisacetoacetate, and aluminum trisacetylacetonate.

[0103] When the adhesive composition involved in the present embodiment includes a crosslinking agent (E), the crosslinking agent (E) in the adhesive composition preferably has a content of 0.1 to 10% by mass. From the perspective of easily obtaining a moderate low-angle peel strength before light irradiation and good contamination resistance, the content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.3% by mass or more. In addition, from the above-mentioned perspective, the content is preferably 10% by mass or less, more preferably 9% by mass or less, and further preferably 8% by mass or less.

[0104] The content of the crosslinking agent (E) relative to 100 parts by mass of the acrylic polymer (A) is preferably 0.1 to 30 parts by mass. From the perspective of easily achieving moderate low-angle peel strength before light irradiation and good stain resistance, the content is preferably 0.1 parts by mass or greater, more preferably 0.5 parts by mass or greater, and even more preferably 1 part by mass or greater. Furthermore, from the aforementioned perspective, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less.

[0105] The pressure-sensitive adhesive composition according to this embodiment may further contain at least one of the above-mentioned photopolymerization initiator (D) and crosslinking agent (E) in addition to the acrylic polymer (A), the photopolymerizable compound (B), and the polyolefin resin (C).

[0106] 〈Other optional ingredients〉

[0107] The adhesive composition of this embodiment may further include any other components within the scope of not impairing the effects of the present invention. Examples of such other components include solvents, tackifiers, silane coupling agents, antistatic agents, antioxidants, light stabilizers, metal corrosion inhibitors, plasticizers, crosslinking accelerators, and rework agents.

[0108] It should be noted that the component ratios in the adhesive composition shown above represent the ratios excluding other optional components. That is, for example, a solvent may be added as another optional component to adjust the viscosity to a suitable coating viscosity. However, the amount of solvent added is not considered in the calculation of the component ratios in the adhesive composition shown above.

[0109] <use>

[0110] The adhesive composition according to this embodiment is preferably used for semiconductor processing and fixing green sheets of multilayer ceramic capacitors due to its adhesiveness and releasability, and is more preferably used for semiconductor processing. More specifically, semiconductor processing includes fixing and peeling semiconductor wafers in the dicing process.

[0111] The adhesive composition according to this embodiment is also preferably used for fixing an optical lens in an optical lens polishing process or a cutting process.

[0112] Preparation method

[0113] The method for producing the adhesive composition according to the present embodiment is not particularly limited, and a conventionally known method can be employed. For example, the adhesive composition can be prepared by mixing the components, and the mixing method is not particularly limited.

[0114] The components may be mixed simultaneously or sequentially. For example, the adhesive composition may be a so-called one-component adhesive composition containing a crosslinking agent (E) in advance, or a so-called two-component adhesive composition may be used in which the first liquid containing the adhesive composition according to the present embodiment and the second liquid containing the crosslinking agent (E) are preliminarily separated and the first and second liquids are mixed at least immediately before application.

[0115] Adhesive layer

[0116] The adhesive layer involved in this embodiment is formed by an adhesive composition. The adhesive composition can use the one described in the above-mentioned "Adhesive Composition", and the preferred embodiment is the same. Specifically, for example, when the adhesive composition is a mixture containing a solvent, the mixture is applied to a PET (polyethylene terephthalate) film or the like and dried to obtain it. In this case, the drying conditions vary depending on the type of solvent. Generally, the drying temperature is 50 to 150°C and the drying time is 1 to 10 minutes.

[0117] Examples of a method for applying the adhesive composition include spin coating, blade coating, roll coating, bar coating, knife coating, die coating, and gravure coating.

[0118] A release-treated PET film or the like may be attached as a pressure-sensitive adhesive sheet to the side of the pressure-sensitive adhesive layer opposite to the side to be bonded to the PET film.

[0119] The thickness of the adhesive layer according to this embodiment is preferably 1 to 80 μm. Here, the thickness is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, and is preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 40 μm or less.

[0120] When the adhesive composition contains a crosslinking agent (E), it can crosslink the acrylic polymer (A), resulting in excellent low-angle peel strength and stain resistance before light irradiation. To ensure sufficient crosslinking reactions, the adhesive layer is typically cured for at least one day after formation, preferably for 2 to 10 days. The curing temperature is typically 5 to 60°C, preferably 15 to 50°C.

[0121] The pressure-sensitive adhesive layer according to this embodiment exhibits sufficient adhesiveness before light irradiation and can be easily peeled off after light irradiation without contaminating the adherend surface.

[0122] Here, as the irradiated light, energy rays such as infrared rays, visible light, ultraviolet rays, X-rays, gamma rays, and electron rays can be mentioned. When electron rays are used, the photopolymerizable compound (B) can be reacted even without using a photopolymerization initiator (D). Among the above-mentioned light, ultraviolet rays are preferably used from the viewpoint of easy introduction into the equipment.

[0123] When ultraviolet light is used as the irradiation light, it is preferable to use a light source with a peak wavelength of 100 to 400 nm. Examples of the light source include high-pressure mercury lamps, low-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, electrodeless discharge lamps, and LEDs. The irradiation intensity is not limited, but is generally 1 to 3000 mW / cm 2 , preferably 3 to 1000 mW / cm 2 The irradiation time is not limited, but is usually 1 second to 1 hour, preferably 2 seconds to 30 minutes.

[0124] The adhesive layer according to this embodiment is preferably used in semiconductor processing, fixation of green sheets of multilayer ceramic capacitors, and fixation of optical lenses in optical lens polishing and cutting steps, and is more preferably used in semiconductor processing.

[0125] Example

[0126] The present invention is further described in detail in the following examples, but the present invention is not limited thereto.

[0127] Manufacturing Example

[0128] <Synthesis of Acrylic Polymers (A-1) to (A-3)>

[0129] In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 100 parts by mass of toluene and the monomer components listed in Table 1 in the proportions described were added, and the temperature was raised to 70°C while introducing nitrogen. Subsequently, 0.1 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was added, and polymerization reaction was carried out at 75-76°C for 4 hours under a nitrogen atmosphere to obtain acrylic polymers (A-1) to (A-3), respectively.

[0130] The symbols of the monomers in Table 1 are as follows.

[0131] MA: Methyl acrylate

[0132] 2EHA: 2-ethylhexyl acrylate

[0133] AA: Acrylic acid

[0134] HEA: 2-Hydroxyethyl Acrylate

[0135]

Table 1

[0136]

[0137] The weight average molecular weights of the acrylic polymers (A-1) to (A-3) were determined by the following method. The results are also shown in Table 1.

[0138] <Weight average molecular weight (Mw)>

[0139] The weight average molecular weight (Mw) of each acrylic polymer (A) was analyzed by gel permeation chromatography (GPC) and calculated in terms of polystyrene under the following conditions.

[0140] · Apparatus: GPC-8220 (manufactured by Tosoh Corporation)

[0141] Column: TSKgel G7000HXL / 7.8mmID×1+TSKgel GMHXL / 7.8mmID×2+TSKgel G2500HXL / 7.8mmID×1 (all manufactured by Tosoh Corporation)

[0142] Medium: Tetrahydrofuran

[0143] Flow rate: 1.0 mL / min

[0144] Concentration: 1.5 mg / mL

[0145] Injection volume: 300 μL

[0146] Column temperature: 40°C

[0147] <Examples 1 to 15 and Comparative Example 1>

[0148] An acrylic polymer (A), a photopolymerizable compound (B), a polyolefin resin (C), a photopolymerization initiator (D), and a crosslinking agent (E) were mixed in the proportions (parts by mass) listed in Table 2 or Table 3 to obtain an adhesive composition. The proportions of the components in Tables 2 and 3 represent the solid content. Blank columns indicate that no component was added.

[0149] The photopolymerizable compounds (B) in Tables 2 and 3 include the following compounds: photopolymerizable compounds (B-1) to (B-3).

[0150] Photopolymerizable compound (B-1): Pentaerythritol tetraacrylate (LIGHTACRYLATE PE-4A, manufactured by Kyoeisha Chemical Co., Ltd.)

[0151] Photopolymerizable compound (B-2): dipentaerythritol hexaacrylate (LIGHTACRYLATE DPE-6A, manufactured by Kyoeisha Chemical Co., Ltd.)

[0152] Photopolymerizable compound (B-3): trimethylolpropane triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat #295)

[0153] The polyolefin resins (C) in Tables 2 and 3, polyolefin resins (C-1) to (C-3) are the following compounds.

[0154] Polyolefin resin (C-1): Maleic anhydride-modified polyolefin resin (manufactured by TOYOBO MC Co., Ltd., Hardlen PMA-L, melting point 70°C, Mw 75,000, maleic anhydride addition amount 1.5% by mass)

[0155] Polyolefin resin (C-2): Maleic anhydride-modified polyolefin resin (manufactured by TOYOBO MC Co., Ltd., Hardlen PMA-T, melting point 95°C, Mw 55,000, maleic anhydride addition amount 1.5% by mass)

[0156] Polyolefin resin (C-3): Maleic anhydride-modified polyolefin resin (manufactured by TOYOBO MC Co., Ltd., Hardlen PMA-KH, melting point 80° C., Mw 90,000, maleic anhydride addition amount 1.0 mass %)

[0157] 1-Hydroxycyclohexyl-phenyl ketone (Omnirad 184 manufactured by IGM Resins) was used as a photopolymerization initiator (D), and an isocyanate crosslinking agent (L-45K manufactured by Soken Chemical Co., Ltd.) was used as a crosslinking agent (E).

[0158]

Table 2

[0159]

[0160]

Table 3

[0161]

[0162] "evaluate"

[0163] <Small angle peel strength: before light irradiation>

[0164] When evaluating the adhesive strength of the PSA composition, a PSA sheet was prepared according to the following procedure.

[0165] First, each adhesive composition was applied onto an 80 μm thick low-density polyethylene (LDPE) film and dried at 80°C for 3 minutes to form an adhesive layer. The dried film thickness of each adhesive layer is shown in Tables 2 and 3. Next, a release-treated PET film was laminated onto the formed adhesive layer and aged for 7 days at 23°C and 65% humidity to produce an adhesive sheet.

[0166] The PSA sheet obtained above was cut into 25 mm x 150 mm pieces. The release-treated PET film was peeled off and attached to an acrylic plate. The sheet was then left in an environment at 23°C and 50% humidity for 24 hours. Subsequently, one side of the PSA sheet was stretched at a rate of 600 mm / min and a peel angle of 30°. The force required for peeling was measured and evaluated based on the following criteria. The results are shown in Tables 2 and 3.

[0167] ◎: The peeling force is 15N / 25mm or more, which is very good.

[0168] ○: The force required for peeling is 10 N / 25 mm or more and less than 15 N / 25 mm, which is good.

[0169] △: The peeling force is 5N / 25mm or more and less than 10N / 25mm, which is acceptable.

[0170] <Small angle peel strength: after light irradiation>

[0171] The adhesive sheet obtained by the same method as described in the above "Small Angle Peel Strength: Before Light Irradiation" was cut into pieces of 25 mm x 150 mm. The peel-treated PET film was peeled off and attached to an acrylic plate. The plate was then left in an environment of 23°C and 50% humidity for 24 hours. Next, the plate was irradiated with light at a peak wavelength of 365 nm and an illumination of 30 mW / cm2 in an environment of 23°C and 50% humidity. 2 The adhesive sheet was then exposed to light for 5 seconds and then allowed to stand in an environment of 23°C and 50% humidity for 1 hour. One side of the adhesive sheet was then stretched at a rate of 600 mm / min and a peel angle of 30°. The force required for peeling was measured and evaluated based on the following criteria. The results are shown in Tables 2 and 3.

[0172] ◎: The peeling force is less than 1.5N / 25mm, which is very good.

[0173] ○: The force required for peeling is 1.5 N / 25 mm or more and less than 2.0 N / 25 mm, which is good.

[0174] △: The peeling force is 2.0N / 25mm or more and less than 2.5N / 25mm, which is acceptable.

[0175] ×: The force required for peeling is 2.5N / 25mm or more, defective

[0176] Pollution

[0177] After the above-mentioned <Small Angle Peel Strength: Before Light Irradiation> test, the surface of the acrylic plate from which the adhesive sheet was peeled was visually observed and evaluated based on the following criteria. The results are shown in Tables 2 and 3.

[0178] ○: No contamination, good

[0179] △: Observable traces of adhesion are minor, presenting no practical problems, thus passing. These results demonstrate that the inclusion of a polyolefin resin (C) in addition to the acrylic polymer (A) and the photopolymerizable compound (B) provides sufficient adhesion when adhering adherends, while reducing adhesion when peeling the adherends, resulting in a pressure-sensitive adhesive composition with excellent releasability. Furthermore, this effect is evident regardless of the type or proportion of the acrylic polymer (A) and the photopolymerizable compound (B).

Claims

1. An adhesive composition comprising an acrylic polymer (A), a photopolymerizable compound (B), and a polyolefin resin (C).

2. The adhesive composition according to claim 1, wherein The polyolefin resin (C) is contained in an amount of 1 part by mass or more and less than 50 parts by mass based on 100 parts by mass of the acrylic polymer (A). 3 . The adhesive composition according to claim 1 , further comprising a photopolymerization initiator (D) and a crosslinking agent (E).

4. The adhesive composition according to claim 1, wherein The photopolymerizable compound (B) is contained in an amount of 50 to 150 parts by mass relative to 100 parts by mass of the acrylic polymer (A). 5 . The adhesive composition according to claim 1 , which is used for semiconductor processing. 6 . An adhesive layer formed from the adhesive composition according to claim 1 , having a thickness of 1 μm to 80 μm, for use in semiconductor processing.

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