Adhesive composition and adhesive sheet

Abstract

The present invention provides an adhesive composition capable of forming an adhesive layer or the like having excellent high-temperature properties. The adhesive composition of the present invention comprises a (meth)acrylic polymer (A), a rosin-based tackifying resin (B) having a glass transition temperature of 85°C or higher, a hydroxyl value of more than 45 mgKOH / g, and an acid value of 5 to 20 mgKOH / g, and a crosslinking agent (C).

Description

TECHNICAL FIELD

[0001] The present application relates to an adhesive composition and an adhesive sheet. BACKGROUND

[0002] In the acrylic adhesive commonly used for double-sided tapes, in order to exhibit good load-holding and peeling properties, it is essential to add a polymeric rosin tackifier.

[0003] In recent years, adhesive tapes used for automotive applications and the like are required to have high-temperature durability in a presumed in-vehicle environment. Generally, there is a correlation between the high-temperature properties of an adhesive and the glass transition temperature (Tg) of a tackifier contained in the adhesive, and the higher the Tg of the tackifier, the better the high-temperature properties of the adhesive. However, existing high-Tg tackifiers have poor compatibility with acrylic adhesives, and cannot be added in an amount that would improve the high-temperature properties.

[0004] For example, in an acrylic adhesive composition containing an acrylic copolymer having a hydroxyl group, a crosslinking agent, and a tackifier, as the tackifier, a rosin ester compound having a softening point of 130°C or higher and a hydroxyl value of 35 to 80 mgKOH / g is proposed (for example, refer to Patent Literature 1). Patent Literature 1 describes that the adhesion properties of the above-described acrylic adhesive composition are excellent from low temperatures to high temperatures, and in particular, have excellent peeling properties with respect to polyurethane foam and low-polarity adherends.

[0005] Prior Art Documents

[0006] Patent Literature

[0007] Patent Literature 1: Japanese Patent Laid-Open No. 2007-291299 SUMMARY

[0008] Problems to be Solved by the Invention

[0009] According to the inventors' studies, even the acrylic adhesive composition disclosed in Patent Literature 1 is not sufficient in terms of high-temperature properties.

[0010] The present application relates to an adhesive composition and an adhesive sheet.

[0011] Technical Solution to Solve the Problem

[0012] The inventors conducted intensive studies in order to solve the above-described problems. As a result, it was found that a specific rosin tackifier has good compatibility with a (meth)acrylic polymer (A), and by using an adhesive composition containing them, the high-temperature properties of an adhesive layer and the like are good.

[0013] The present application is, for example, the following [1] to [6].

[0014] [1] An adhesive composition comprising a (meth)acrylic polymer (A), a rosin-based tackifying resin (B) having a glass transition temperature of 85°C or higher, a hydroxyl value of more than 45 mgKOH / g, and an acid value of 5 to 20 mgKOH / g, and a crosslinking agent (C).

[0015] [2] The adhesive composition according to [1], wherein the weight average molecular weight of the (meth)acrylic polymer (A) is 700,000 to 2,000,000.

[0016] [3] The adhesive composition according to [1] or [2], wherein the (meth)acrylic polymer (A) is a polymer of a monomer component (a) comprising 60 to 99.5 mass% of an alkyl (meth)acrylate having 4 to 8 carbon atoms in the alkyl group and 0.1 to 15 mass% of a crosslinkable functional group-containing monomer.

[0017] [4] The adhesive composition according to any one of [1] to [3], which is a non-emulsified adhesive composition.

[0018] [5] The adhesive composition according to any one of [1] to [4], wherein the haze of an adhesive layer having a thickness of 25 μm obtained from the adhesive composition is less than 1%.

[0019] [6] An adhesive sheet having an adhesive layer prepared from the adhesive composition described in any one of [1] to [5].

[0020] Effects of the Invention

[0021] According to the present application, an adhesive composition capable of forming an adhesive such as an adhesive layer having excellent high-temperature properties can be provided. DETAILED DESCRIPTION

[0022] Hereinafter, the present application will be described in detail. Hereinafter, the adhesive composition of the present application will be simply referred to as "composition". In addition, acrylic acid and methacrylic acid will be collectively referred to as "(meth)acrylic acid", and acrylate and methacrylate will be collectively referred to as "(meth)acrylate".

[0023] [Adhesive composition]

[0024] The adhesive composition of one embodiment of the present application comprises a (meth)acrylic polymer (A), a rosin-based tackifying resin (B) having a glass transition temperature of 85°C or higher, a hydroxyl value of more than 45 mgKOH / g, and an acid value of 5 to 20 mgKOH / g, and a crosslinking agent (C).

[0025] According to the present inventors' studies, it has been found that the rosin-based tackifying resin (B) having the specific hydroxyl value and acid value described above has excellent compatibility with the (meth)acrylic polymer (A) compared to rosin-based tackifying resins that are currently in common use. In addition, the rosin-based tackifying resin (B) has a high Tg. Thus, the adhesive composition of the present application makes it possible to provide an adhesive such as an adhesive layer having excellent high-temperature properties.

[0026] In addition, the haze of an adhesive layer having a thickness of 25 μm obtained from the adhesive composition of an embodiment of the present application is preferably less than 1%, more preferably 0.9% or less. If the haze is within the range described above, the components in the adhesive composition are easily mixed uniformly, and thus it is preferable. The lower the haze, the more preferable it is, and as a lower limit thereof, there is no particular limitation, but the haze is generally 0.1% or more. In addition, the haze can be measured by the method described in the examples.

[0027] ((Meth)acrylic polymer (A))

[0028] As the (meth)acrylic polymer (A) contained in the adhesive composition described above, there is no particular limitation as long as it is a polymer of a monomer component of a (meth)acrylic type such as a (meth)acrylate.

[0029] As the (meth)acrylic polymer (A) described above, a polymer containing a (meth)acrylic alkyl ester having an alkyl group with a carbon number of 4 to 8 and a monomer component (a) containing a cross-linkable functional group-containing monomer is preferable. A monomer other than the monomer component (a) (other monomer) can also be contained in the monomer component (a).

[0030] As the (meth)acrylic alkyl ester having an alkyl group with a carbon number of 4 to 8 described above, for example, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate can be exemplified, and n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate are preferable, and n-butyl (meth)acrylate, which easily makes the (meth)acrylic polymer (A) high-molecular, is more preferable. As the (meth)acrylic alkyl ester having an alkyl group with a carbon number of 4 to 8 described above, one kind can be used alone, or two or more kinds can be used.

[0031] In 100 mass% of the monomer component (a), the content of the (meth)acrylic alkyl ester having an alkyl group with a carbon number of 4 to 8 described above is preferably 60 to 99.5 mass%, more preferably 70 to 99.5 mass%.

[0032] As the above-mentioned crosslinkable functional group-containing monomer, at least one monomer having a hydroxyl group and a carboxyl group as a crosslinkable functional group is preferable, and more preferably at least one monomer selected from a hydroxyl group-containing monomer and a carboxyl group-containing monomer.

[0033] As the above-mentioned hydroxyl group-containing monomer, for example, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, chloro-2-hydroxypropyl acrylate, diethylene glycol mono(meth)acrylate, allyl alcohol, preferably 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate can be exemplified. As the above-mentioned hydroxyl group-containing monomer, one kind can be used alone, or two or more kinds can be used.

[0034] As the above-mentioned carboxyl group-containing monomer, for example, (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, 3-carboxypropyl (meth)acrylate, 4-carboxybutyl (meth)acrylate, itaconic acid, crotonic acid, maleic acid, fumaric acid, and maleic anhydride, preferably (meth)acrylic acid can be exemplified. As the above-mentioned carboxyl group-containing monomer, one kind can be used alone, or two or more kinds can be used.

[0035] As the above-mentioned crosslinkable functional group-containing monomer, one kind can be used alone, or two or more kinds can be used, but simultaneous use of the above-mentioned hydroxyl group-containing monomer and the above-mentioned carboxyl group-containing monomer is one of preferable modes. When the above-mentioned hydroxyl group-containing monomer and the above-mentioned carboxyl group-containing monomer are used simultaneously, the molar ratio thereof is not particularly limited, but the hydroxyl group-containing monomer: carboxyl group-containing monomer (molar ratio) is preferably 1:10 to 10:1, more preferably 1:8 to 8:1.

[0036] In 100% by mass of the monomer component (a), the content of the above-mentioned crosslinkable functional group-containing monomer is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass.

[0037] As the above-mentioned other monomer, for example, an alkyl (meth)acrylate in which the carbon number of the alkyl group is 1 to 3 or 9 or more, an alicyclic hydrocarbon group-containing (meth)acrylate, a nitrogen atom-containing monomer, an alkoxyalkyl (meth)acrylate, an epoxy group-containing (meth)acrylate, an acetoacetyl group-containing (meth)acrylate, an aromatic ring-containing monomer, methacryloyloxypropyl methoxysilane, vinyl acetate, chloroethylene, (meth)acrylonitrile can be exemplified.

[0038] As the (meth)acrylic acid alkyl ester having 1 to 3 or 9 or more carbon atoms in the alkyl group, there are exemplified (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid n-propyl ester, (meth)acrylic acid isopropyl ester, (meth)acrylic acid n-nonyl ester, (meth)acrylic acid isononyl ester, (meth)acrylic acid isodecyl ester, (meth)acrylic acid lauryl ester, (meth)acrylic acid stearyl ester, (meth)acrylic acid isostearyl ester.

[0039] As the (meth)acrylic acid ester having an alicyclic hydrocarbon group, there are exemplified (meth)acrylic acid cyclohexyl ester, (meth)acrylic acid isobornyl ester, (meth)acrylic acid adamantyl ester.

[0040] As the monomer having a nitrogen atom, there are exemplified a monomer having at least one functional group of an amide group and an amino group, specifically exemplified are (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, acryloyl morpholine, N-vinyl acetamide, diacetone (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, vinyl pyrrolidone, hydroxymethyl (meth)acrylamide, methoxyethyl (meth)acrylamide and the like amide group-containing monomers; N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, aminoethyl (meth)acrylate and the like amino group-containing monomers.

[0041] As the (meth)acrylic acid alkoxyalkyl ester, there are exemplified (meth)acrylic acid methoxyethyl ester, (meth)acrylic acid ethoxyethyl ester.

[0042] As the (meth)acrylic acid ester having an epoxy group, there is exemplified (meth)acrylic acid glycidyl ester.

[0043] As the (meth)acrylic acid ester having an acetoacetyl group, there is exemplified (meth)acrylic acid acetoacetoxyethyl ester.

[0044] As the monomer having an aromatic ring, there are exemplified benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, styrene, methylstyrene, vinyltoluene.

[0045] When the monomer component (a) contains the other monomer, the content of the other monomer is 0.1 to 30 mass%, more preferably 0.2 to 25 mass% in 100 mass% of the monomer component (a). As the other monomer, one kind can be used alone, or two or more kinds can be used.

[0046] The weight average molecular weight (Mw) of the above (meth)acrylic polymer (A) based on gel permeation chromatography (GPC) is usually 500,000 to 2,500,000, and from the viewpoint of the coatability of the adhesive composition and the high-temperature properties of the resulting adhesive sheet, it is preferably 7,000,000 to 20,000,000, and more preferably 10,000,000 to 18,000,000.

[0047] (Meth)acrylic polymer (A) production conditions

[0048] The above (meth)acrylic polymer (A) can be obtained by polymerizing the monomer component by a conventionally known polymerization method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, and a suspension polymerization method, but is preferably produced by a solution polymerization method and a bulk polymerization method that do not contain a polymerization stabilizer such as an emulsifier or a suspending agent. The (meth)acrylic polymer (A) can be obtained as a polymer solution composed of the polymer and an organic solvent. As the organic solvent that can be used for polymerization, the following organic solvent (D) can be exemplified.

[0049] For example, by charging the polymerization solvent and the monomer component into a reaction vessel, adding a polymerization initiator under an inert gas atmosphere such as nitrogen, setting the reaction start temperature to usually 40 to 100°C, and preferably 50 to 90°C, and allowing the reaction system to be maintained at a temperature of usually 50 to 90°C, and preferably 60 to 90°C for 3 to 20 hours, the (meth)acrylic polymer (A) can be obtained.

[0050] As the polymerization initiator, for example, a peroxide-based polymerization initiator, an azo-based initiator can be exemplified.

[0051] As the peroxide-based polymerization initiator, for example, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, hexanoyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxyneodecanoate, 2,2-bis(peroxy-4,4-di-t-butylcyclohexyl)propane, 2,2-bis(peroxy-4,4-di-t-amylcyclohexyl)propane, 2,2-bis(peroxy-4,4-di-t-octylcyclohexyl)propane, 2,2-bis(peroxy-4,4-di-α-cumylcyclohexyl)propane, 2,2-bis(peroxy-4,4-di-t-butylcyclohexyl)butane, and 2,2-bis(peroxy-4,4-di-t-octylcyclohexyl)butane can be exemplified.

[0052] As the azo compound, for example, 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-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutyramide) dihydrate, 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionoate), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), and the like azo compounds can be exemplified.

[0053] The polymerization initiator can be used singly or two or more kinds can be used. In addition, it is not limited to adding the polymerization initiator several times in the polymerization.

[0054] The polymerization initiator is generally used in an amount within a range 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 component that forms the (meth)acrylic polymer (A). In addition, in the above polymerization reaction, the polymerization initiator, the chain transfer agent, the polymerizable monomer, and the polymerization solvent can be added as appropriate.

[0055] As the polymerization solvent used in the solution polymerization, for example, aromatic hydrocarbons such as benzene, toluene, xylene, and the like; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, n-octane, and the like; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, cyclooctane, and the like; ethers such as diethyl ether, isopropyl ether, 1,2-dimethoxyethane, butyl ether, tetrahydrofuran, dioxane, anisole, phenetol, diphenyl ether, and the like; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, chlorobenzene, and the like; esters such as ethyl acetate, propyl acetate, butyl acetate, methyl propionate, and the like; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone, and the like; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and the like; nitriles such as acetonitrile, benzonitrile, and the like; sulfoxides such as dimethyl sulfoxide, sulfolane, and the like can be exemplified.

[0056] The polymerization solvent can be used singly or two or more kinds can be used.

[0057] [Rosin-based tackifying resin (B)]

[0058] The rosin-based tackifying resin (B) contained in the above-mentioned adhesive composition is a rosin-based tackifying resin having a glass transition temperature of 85°C or higher, a hydroxyl value of more than 45 mgKOH / g, and an acid value of 5 to 20 mgKOH / g.

[0059] The glass transition temperature (Tg) is preferably 85°C or higher, more preferably 95°C or higher. In addition, the glass transition temperature is preferably 150°C or lower, more preferably 140°C or lower. The glass transition temperature of the rosin-based tackifying resin (B) can be measured by differential scanning calorimetry. When the Tg is within the above-mentioned range, the compatibility with the above-mentioned (meth)acrylic polymer (A) is good, and the high-temperature properties of the obtained adhesive sheet are excellent.

[0060] The hydroxyl value is preferably 50 mgKOH / g or more, more preferably 60 mgKOH / g or more. In addition, the hydroxyl value is preferably 100 mgKOH / g or less, more preferably 80 mgKOH / g or less. The hydroxyl value of the rosin-based tackifying resin (B) can be measured by potentiometric titration. When the hydroxyl value is within the above-mentioned range, the compatibility with the above-mentioned (meth)acrylic polymer (A) is good, and the haze of the obtained adhesive sheet can be suppressed to a low level. In addition, since the compatibility of the (meth)acrylic polymer (A) and the rosin-based tackifying resin (B) is excellent, after the adhesive sheet is manufactured, the rosin-based tackifying resin (B) can be suppressed from bleeding to the surface of the adhesive layer.

[0061] The acid value is preferably 5 mgKOH / g or more, more preferably 7 mgKOH / g or more. In addition, the acid value is preferably 20 mgKOH / g or less, more preferably 12 mgKOH / g or less. The acid value of the rosin-based tackifying resin (B) can be measured by potentiometric titration. When the acid value is within the above-mentioned range, the compatibility with the above-mentioned (meth)acrylic polymer (A) is good, and the adhesion of the obtained adhesive sheet is excellent.

[0062] The above-mentioned adhesive composition, by using the rosin-based tackifying resin (B) having the above-mentioned specific Tg, hydroxyl value, and acid value, can form an adhesive having excellent compatibility of the (meth)acrylic polymer (A) and the rosin-based tackifying resin (B), excellent high-temperature properties, and the like.

[0063] In addition, the weight average molecular weight (Mw) based on gel permeation chromatography (GPC) of the above-mentioned rosin-based tackifying resin (B) is preferably 1000 to 10000, more preferably 2500 to 5000.

[0064] As the blending amount of the rosin-based tackifying resin (B) in the above-mentioned adhesive composition, relative to 100 parts by mass of the (meth)acrylic polymer (A), it is generally 5 to 50 parts by mass, preferably 6 to 40 parts by mass, more preferably 10 to 30 parts by mass. If the blending amount of the rosin-based tackifying resin (B) is within the above-mentioned range, an adhesive sheet having excellent high-temperature properties can be obtained.

[0065] The rosin-based tackifying resin (B) can be obtained, for example, by polymerizing rosin acid, dimer of rosin acid, isomers of rosin acid. In order to adjust the hydroxyl value, acid value, it is also preferable to polymerize in the presence of a polyhydric alcohol such as pentaerythritol. As a method for obtaining the rosin-based tackifying resin (B), there is no particular limitation, and it can be obtained by appropriately adjusting the manufacturing method of the polymerized rosin which has been known conventionally, by adjusting the Tg, hydroxyl value, acid value to the above range.

[0066] (Crosslinking agent (C))

[0067] As the crosslinking agent (C) contained in the above-mentioned adhesive composition, there is no particular limitation as long as it can crosslink the (meth) acrylic polymer (A). As the crosslinking agent (C), for example, isocyanate compounds (C1), epoxy compounds (C2), metal chelate compounds (C3), and the like which can react with the above-mentioned (meth) acrylic polymer (A) can be used.

[0068] Since the above-mentioned adhesive composition contains the crosslinking agent (C), a crosslinked body is formed in the adhesive layer or the adhesive which is adhered to the adherend by pressure bonding, thermoforming, or the like, and the adhesion and heat resistance are excellent.

[0069] The above-mentioned crosslinking agent (C) can be used alone, or two or more kinds can be used.

[0070] (Isocyanate compound (C1))

[0071] As the isocyanate compound, an isocyanate compound in which the number of isocyanate groups in one molecule is 2 or more is generally used, and the number of isocyanate groups is preferably 2 to 8, and more preferably 3 to 6. If the number of isocyanate groups is within the above range, it is preferable in terms of the efficiency of the crosslinking reaction of the (meth) acrylic polymer (A) with the isocyanate compound, and in terms of maintaining the softness of the adhesive layer.

[0072] As the diisocyanate compound having the number of isocyanate groups in 1 molecule of 2, aliphatic diisocyanate, alicyclic diisocyanate, aromatic diisocyanate can be exemplified. As the aliphatic diisocyanate, ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, and the like aliphatic diisocyanate having a carbon number of 4 to 30 can be exemplified. As the alicyclic diisocyanate, isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylylene diisocyanate, and the like alicyclic diisocyanate having a carbon number of 7 to 30 can be exemplified. As the aromatic diisocyanate, phenylene diisocyanate, toluene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, diphenylpropane diisocyanate, and the like aromatic diisocyanate having a carbon number of 8 to 30 can be exemplified.

[0073] As the isocyanate compound having the number of isocyanate groups in 1 molecule of 3 or more, aromatic polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate can be exemplified. Specifically, 2,4,6-triisocyanatotoluene, 1,3,5-triisocyanatobenzene, 4,4',4"-triphenylmethane triisocyanate can be exemplified.

[0074] Further, as the isocyanate compound, the polymer (for example, dimer or trimer, biuret, isocyanurate) of the above isocyanate compound having the number of isocyanate groups of 2 or 3 or more, derivative (for example, addition reaction product of polyol and diisocyanate compound of 2 molecules or more), polymer can be exemplified. As the polyol in the above derivative, low molecular weight polyol can exemplify, for example, trimethylolpropane, glycerol, pentaerythritol, and the like alcohol of 3 or more; high molecular weight polyol can exemplify, for example, polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol.

[0075] As such isocyanate compound, for example, trimer of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, biuret or isocyanurate of hexamethylene diisocyanate or xylene diisocyanate, reaction product of trimethylolpropane and toluene diisocyanate or xylylene diisocyanate (for example, trimer of toluene diisocyanate or xylylene diisocyanate), reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, trimer of hexamethylene diisocyanate), polyether polyisocyanate, polyester polyisocyanate can be exemplified.

[0076] Among the isocyanate compounds, from the viewpoint of yellowing resistance, crosslinking agents of the xylylene diisocyanate type and the hexamethylene diisocyanate type are preferable, and from the viewpoint of stress relaxation, crosslinking agents of the toluene diisocyanate type are preferable. As the crosslinking agent of the xylylene diisocyanate type, for example, xylylene diisocyanate and its polymer or derivative, polymer can be exemplified; as the crosslinking agent of the hexamethylene diisocyanate type, for example, hexamethylene diisocyanate and its polymer or derivative, polymer can be exemplified; and as the crosslinking agent of the toluene diisocyanate type, for example, toluene diisocyanate and its polymer or derivative, polymer can be exemplified.

[0077] (Epoxy compound (C2))

[0078] As the epoxy compound, for example, a compound having two or more epoxy groups in the molecule can be exemplified, and for example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diaminoglycidyl amine, N,N,N',N'-tetraglycidyl-m-phenylenediamine, 1,3-bis(N,N'-diaminoglycidylaminomethyl) can be exemplified.

[0079] (Metal chelate compound (C3))

[0080] As the metal chelate compound, for example, a compound in which an alcoholate, acetylacetone, ethyl acetoacetate or the like coordinates with a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, zirconium or the like can be exemplified. Specifically, aluminum isopropoxide, aluminum sec-butyrate, ethyl aluminum acetoacetate diisopropyl, aluminum triacetoacetate, aluminum triacetylacetone can be exemplified.

[0081] The blending amount of the crosslinking agent (C) in the above-mentioned adhesive composition is usually 0.05 to 10 parts by mass, preferably 0.1 to 5 parts by mass, and more preferably 0.3 to 2.5 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0082] (Organic solvent (D))

[0083] In the above-mentioned adhesive composition, in order to adjust the coatability, an organic solvent (D) can be contained. As the organic solvent (D), the organic solvent mentioned above under the manufacturing conditions of the (meth)acrylic polymer (A) can be exemplified. In addition, the organic solvent used at the time of production of the (meth)acrylic polymer (A) and the organic solvent (D) contained in the adhesive composition can be the same kind of organic solvent or different kinds of organic solvent. As the organic solvent, one kind can be used alone, or two or more kinds can be used.

[0084] In the case where the adhesive composition contains the organic solvent (D), the content thereof is usually 30 to 90 mass%, preferably 40 to 90 mass% in 100 mass% of the adhesive composition.

[0085] (Additive (E))

[0086] The above-described adhesive composition can contain an additive (E) in addition to the above-described components (A) to (D) within a range not impairing the effects of the present application.

[0087] As the additive (E), tackifying resins other than the rosin-based tackifying resin (B), silane coupling agents, antistatic agents, antioxidants, light stabilizers, metal corrosion inhibitors, plasticizers, cross-linking accelerators, and rework agents can be exemplified. One kind of the additive (E) can be used alone, or two or more kinds thereof can be used. The amount of the additive (E) contained in the above-described adhesive composition varies depending on the kind of the additive (E) and is not particularly limited, but is usually 0.01 to 10 mass%, preferably 0.1 to 5 mass% in 100 mass% of the adhesive composition.

[0088] The above-described adhesive composition is preferably a non-emulsified adhesive composition. Since there is a tendency that the water resistance and the heat resistance are excellent as compared with an emulsified adhesive composition, the non-emulsified adhesive composition is preferred. The adhesive composition of the present application can be used as an adhesive such as an adhesive layer. In addition, the adhesive is a concept including an adhesive layer, and an adhesive formed in a layer shape is referred to as an adhesive layer.

[0089] (Preparation of Adhesive Composition)

[0090] The above-described adhesive composition can be prepared, for example, by mixing the above-described components by a conventionally known method. For example, the adhesive composition can be prepared by mixing a solution containing the (meth)acrylic polymer (A), the rosin-based tackifying resin (B), the cross-linking agent (C), and other components such as an additive, if necessary.

[0091] [Adhesive Sheet]

[0092] The adhesive sheet of one embodiment of the present application has an adhesive layer prepared from the adhesive composition.

[0093] As the adhesive sheet, an adhesive sheet formed only of an adhesive layer, a double-coated adhesive sheet having a substrate and adhesive layers formed on both surfaces of the substrate, and at least one of the adhesive layers being an adhesive layer formed from the adhesive composition of the present application, a single-coated adhesive sheet having a substrate and an adhesive layer formed on one surface of the substrate and formed from the adhesive composition of the present application, and an adhesive sheet having a substrate prepared on both surfaces of an adhesive layer formed from the adhesive composition of the present application can be exemplified.

[0094] As the above-mentioned base material, there is no particular limitation, and plastic base materials, nonwoven fabrics, woven fabrics, paper, metals, glass, ceramics, foams, and the like can be exemplified. The thickness of the base material varies depending on the use thereof and the like, and is not particularly limited, but is usually 5 to 200 μm.

[0095] As the plastic base material, plastic base materials selected from the group consisting of polyethylene terephthalate, polyvinyl chloride, polyolefin, polypropylene, polymethyl methacrylate, polycarbonate, polyimide, and ABS can be exemplified.

[0096] The base material can also be a release-treated base material. In the case where the adhesive sheet is provided with base materials on both sides of the adhesive layer formed of the adhesive composition of the present application, at least one of the base materials is a release-treated base material, which can be removed at the time of adhesion to an adherend.

[0097] From the viewpoint of maintaining the adhesive properties, the film thickness of the adhesive layer is usually 5 to 200 μm, and preferably 10 to 100 μm.

[0098] The adhesive layer can be crosslinked by causing the (meth)acrylic polymer (A) and the crosslinking agent (C) in the adhesive composition to react during the production thereof, thereby at least a part of the crosslinking.

[0099] As the production method of the adhesive sheet, there is no particular limitation, and the following method, for example, can be mentioned. The above-mentioned adhesive composition is applied to a base material. In the case where the above-mentioned adhesive composition contains a solvent, drying is performed at a temperature of usually 50 to 150°C, and preferably 60 to 100°C, for usually 1 to 10 minutes, and preferably 2 to 7 minutes, to remove the solvent, and a coating film is formed. Subsequently, the other base material is attached to the surface of the coating film on the side not having the base material. Subsequently, curing is performed in an environment of usually 1 day or more, and preferably 3 to 10 days, at a temperature of usually 5 to 60°C, and preferably 15 to 40°C, and at a humidity of usually 30 to 70% RH, and preferably 40 to 70% RH, to produce the adhesive sheet. The above-mentioned curing is also referred to as aging. If the aging is performed under the above-mentioned conditions, crosslinking occurs in the aging, and a crosslinked body can be efficiently formed.

[0100] As the application method of the adhesive composition, publicly known methods can be used, and for example, a method in which application and drying are performed in such a manner that a predetermined thickness is achieved by spin coating, knife coating, roll coating, bar coating, knife coating, die coating, gravure coating, and doctor blade coating can be mentioned.

[0101] The adhesive layer obtained from the above-mentioned adhesive composition is excellent in high-temperature properties, and is thus useful for various uses such as automobile uses.

[0102] Example

[0103] Hereinafter, the present application will be further explained by examples, but the present application is not limited thereto.

[0104] (Rosin-based resins)

[0105] The following rosin-based resins were used in the examples and comparative examples.

[0106] Rosin-based tackifying resin (B-1): synthesized from the following manufacturing example 1.

[0107] Rosin-based tackifying resin (B-2): synthesized from the following manufacturing example 2.

[0108] Rosin-based tackifying resin (B'-1): synthesized from the following manufacturing example 3.

[0109] D-135, D-160: Polymerized rosin ester resin (manufactured by Arakawa Chemical Industry Co., Ltd.)

[0110] SEA-100: Rosin ester resin (manufactured by Arakawa Chemical Industry Co., Ltd.)

[0111] DP-2669: Rosin ester resin (manufactured by Halima Chemicals).

[0112] The physical properties of the above-mentioned rosin resins are shown in Table 1.

[0113] In addition, the physical properties of the rosin resins shown in Table 1 were determined by the following methods.

[0114] <Acid Value>

[0115] According to JIS K0070, the acid value is determined by potentiometric titration as the number of mg of potassium hydroxide required to neutralize 1g of rosin resin.

[0116] <Hydroxy value>

[0117] According to JIS K0070, the hydroxyl value is determined by potentiometric titration as the number of mg of potassium hydroxide required to neutralize the acetic acid bound to the hydroxyl group when acetylated 1g of rosin resin.

[0118] <Tg>

[0119] Rosin-based resins were sealed in a simple sealed dish, and measurements were performed using a differential scanning calorimeter (DSC). During the measurement, the temperature was increased from -100°C to 200°C at a rate of 10°C / min under a nitrogen flow, and the thermal changes were measured. A curve was plotted between "endothermic and calorific values" and "temperature," and the characteristic inflection point observed at this point was taken as Tg. Furthermore, Tg was obtained from the DSC curve using the midpoint method.

[0120] <GPC>

[0121] The determination of Mw (weight-average molecular weight) of the above-mentioned rosin resins based on GPC (gel permeation chromatography) was carried out under the following conditions.

[0122] Device name: Tosoh Corporation (manufactured by Tosoh Co., Ltd.), HLC-8120

[0123] Column: Made by Tosoh Co., Ltd., 1 G7000HXL (7.8mm ID×30cm), 2 GMHXL (7.8mm ID×30cm), 1 G2000HXL (7.8mm ID×30cm)

[0124] Sample concentration: to reach 1.5 mg / cm³ 3 The conditions were diluted with tetrahydrofuran.

[0125] Mobile phase solvent: tetrahydrofuran

[0126] Flow rate: 1.0 cm 3 / minute

[0127] Column temperature: 40℃.

[0128] [Table 1]

[0129]

[0130] [Manufacturing Example 1]

[0131] (Synthesis of rosin-based tackifying resin (B-1))

[0132] In a flask equipped with a stirrer, nitrogen inlet tube, thermometer, and reflux condenser, 50 parts by mass of rosin acid dimer and 840 parts by mass of dichloromethane were added, and 25 parts by mass of oxaloyl chloride were added dropwise while stirring. The mixture was allowed to react under a nitrogen stream at 25°C for 4 hours, after which the oxaloyl chloride and dichloromethane were removed using an evaporator. The resulting chloride intermediate was dissolved in 800 parts by mass of dichloromethane, and a mixture of 115 parts by mass of pentaerythritol, 10 parts by mass of 4-dimethylaminopyridine, and 13 parts by mass of pyridine was added dropwise to this solution under ice cooling. The mixture was allowed to react under a nitrogen stream at 40°C for 12 hours, and the reaction was terminated by adding 1000 parts by mass of 1 mol / L hydrochloric acid. After separating the oil and water layers, magnesium sulfate was added to the oil layer and stirred. The magnesium sulfate was filtered, the solvent was removed using an evaporator, and the mixture was dried under vacuum overnight to obtain a yellow solid rosin-based tackifying resin (B-1).

[0133] The rosin-based tackifying resin (B-1) has an acid value of 7.1 mgKOH / g, a hydroxyl value of 72 mgKOH / g, a Tg of 101℃, and a weight-average molecular weight (Mw) of 3100.

[0134] [Manufacturing Example 2] (Synthesis of Rosin-based Tackifying Resin (B-2))

[0135] In a flask equipped with a stirring device, a nitrogen introduction tube, a thermometer, and a reflux cooling tube, 50 parts by mass of a rosin acid dimer and 840 parts by mass of dichloromethane were put in, and 25 parts by mass of oxalyl chloride was added dropwise while stirring. After allowing it to react for 4 hours at 25°C under a nitrogen stream, the oxalyl chloride and dichloromethane were removed with an evaporator. The obtained chloride intermediate was dissolved in 800 parts by mass of dichloromethane, and a mixture of 85 parts by mass of pentaerythritol, 10 parts by mass of 4-dimethylaminopyridine, and 13 parts by mass of pyridine was added dropwise to the solution under ice cooling. After allowing it to react for 12 hours at 40°C under a nitrogen stream, 1000 parts by mass of 1 mol / L hydrochloric acid was added to terminate the reaction. After the oil layer and the water layer were separated, magnesium sulfate was added to the oil layer and stirred, and the magnesium sulfate was filtered, and the solvent was removed with an evaporator, and dried under vacuum overnight to obtain a rosin-based tackifying resin (B-2) as a yellow solid.

[0136] The rosin-based tackifying resin (B-2) had an acid value of 7.3 mgKOH / g, a hydroxyl value of 51 mgKOH / g, a Tg of 98°C, and a weight average molecular weight (Mw) of 3000.

[0137] [Manufacturing Example 3] (Synthesis of a rosin-based tackifying resin (B’-1))

[0138] In a flask equipped with a stirring device, a nitrogen introduction tube, a thermometer, and a reflux cooling tube, 50 parts by mass of a rosin acid dimer and 840 parts by mass of dichloromethane were put in, and 25 parts by mass of oxalyl chloride was added dropwise while stirring. After allowing it to react for 4 hours at 25°C under a nitrogen stream, the oxalyl chloride and dichloromethane were removed with an evaporator. The obtained chloride intermediate was dissolved in 800 parts by mass of dichloromethane, and a mixture of 85 parts by mass of pentaerythritol, 10 parts by mass of 4-dimethylaminopyridine, and 13 parts by mass of pyridine was added dropwise to the solution under ice cooling. After allowing it to react for 12 hours at 40°C under a nitrogen stream, 1000 parts by mass of 1 mol / L hydrochloric acid was added to terminate the reaction. After the oil layer and the water layer were separated, magnesium sulfate was added to the oil layer and stirred, and the magnesium sulfate was filtered, and the solvent was removed with an evaporator, and dried under vacuum overnight to obtain a rosin-based tackifying resin (B-2) as a yellow solid.

[0139] The rosin-based tackifying resin (B’-1) had an acid value of 10 mgKOH / g, a hydroxyl value of 31 mgKOH / g, a Tg of 69°C, and a weight average molecular weight (Mw) of 2000.

[0140] [Manufacturing Example 4]

[0141] (Synthesis of an acrylic polymer (A-1) solution)

[0142] A reaction vessel was charged with 94 parts by mass of n-butyl acrylate, 5 parts by mass of acrylic acid, 1 part by mass of 2-hydroxyethyl acrylate, 90 parts by mass of ethyl acetate, and 0.1 part by mass of 2,2'-azobisisobutyronitrile, and the air in the reaction vessel was replaced with nitrogen. Subsequently, the temperature was raised to 65°C with stirring, and the mixture was allowed to react for 8 hours to obtain a solution of acrylic polymer (A-1).

[0143] The GPC-based Mw of the resulting acrylic polymer (A-1) was 1.8 million.

[0144] [Manufacturing Example 5]

[0145] (Synthesis of a solution of acrylic polymer (A-2))

[0146] A reaction vessel was charged with 94 parts by mass of n-butyl acrylate, 5 parts by mass of acrylic acid, 1 part by mass of 2-hydroxyethyl acrylate, 160 parts by mass of ethyl acetate, and 0.1 part by mass of 2,2'-azobisisobutyronitrile, and the air in the reaction vessel was replaced with nitrogen. Subsequently, the temperature was raised to 70°C with stirring, and the mixture was allowed to react for 8 hours to obtain a solution of acrylic polymer (A-2). The GPC-based Mw of the resulting acrylic polymer (A-2) was 8 million.

[0147] [Manufacturing Example 6]

[0148] (Synthesis of a solution of acrylic polymer (A-3))

[0149] A reaction vessel was charged with 94 parts by mass of n-butyl acrylate, 5 parts by mass of acrylic acid, 1 part by mass of 2-hydroxyethyl acrylate, 110 parts by mass of ethyl acetate, and 0.1 part by mass of 2,2'-azobisisobutyronitrile, and the air in the reaction vessel was replaced with nitrogen. Subsequently, the temperature was raised to 65°C with stirring, and the mixture was allowed to react for 8 hours to obtain a solution of acrylic polymer (A-3). The GPC-based Mw of the resulting acrylic polymer (A-3) was 15.2 million.

[0150] (GPC)

[0151] The GPC-based Mw (weight average molecular weight) of the above-described acrylic polymers (A-1) to (A-3) was measured under the following conditions.

[0152] Apparatus name: HLC-8120, manufactured by Tosoh Corporation

[0153] Column: G7000HXL (7.8 mm I.D. x 30 cm) 1, GMHXL (7.8 mm I.D. x 30 cm) 2, G2000HXL (7.8 mm I.D. x 30 cm) 1, manufactured by Tosoh Corporation

[0154] Sample concentration: to achieve 1.5 mg / cm 3 Diluted with tetrahydrofuran under the conditions

[0155] Mobile phase solvent: tetrahydrofuran

[0156] Flow rate: 1.0 cm 3 / minute

[0157] Column temperature: 40°C.

[0158] [Example 1]

[0159] To an acrylic polymer (A-1) solution (100 parts by mass, calculated as solid content (acrylic polymer)), 20 parts by mass of a rosin-based tackifying resin (B-1) and 0.72 parts by mass of an isocyanate-based crosslinking agent L-45 (manufactured by Sanko Chemical Industry Co., Ltd.), calculated as solid content, were added, and stirred with a glass rod for 5 minutes to obtain an adhesive composition.

[0160] <Manufacture of Adhesive Sheet>

[0161] The obtained adhesive composition was coated on a polyethylene terephthalate (PET) film having a thickness of 25 μm after deaeration with a doctor blade so as to have a dried thickness of 25 μm, and dried at 80°C for 3 minutes to remove the solvent, thereby forming a coating film.

[0162] A release-treated PET film was attached to the surface on the opposite side of the surface of the adhesive layer that was in contact with the PET film. Thereafter, aging was performed by standing under conditions of 23°C / 50% RH for 7 days, and an adhesive sheet (1) having an adhesive layer with a thickness of 25 μm was manufactured.

[0163] (Physical Property Evaluation)

[0164] <Haze>

[0165] The obtained adhesive composition was coated on a release-treated PET film after deaeration with a doctor blade so as to have a dried thickness of 25 μm, and dried at 80°C for 3 minutes to remove the solvent, thereby forming a coating film.

[0166] A release-treated PET film was attached to the surface on the opposite side of the surface of the adhesive layer that was in contact with the release-treated PET film. Thereafter, aging was performed by standing under conditions of 23°C / 50% RH for 7 days, and an adhesive sheet (2) having an adhesive layer with a thickness of 25 μm was manufactured.

[0167] The release-treated PET film was peeled off from one side of the adhesive sheet (2), and the exposed adhesive layer was attached to a glass plate (manufactured by AGC Fabric Tech Co., Ltd., alkali glass FL, 1.1 mm thick).

[0168] Then, the remaining peeled PET film was peeled off, and the haze value of the test piece having only the adhesive layer on the above glass plate was measured as the haze (%) of the adhesive layer.

[0169] A haze meter (Model HM-150, Murakami Color Research Laboratory) was used in the measurement. The results are shown in Table 2.

[0170] <Adhesion Test>

[0171] The adhesive sheet (1) was cut into a size of 20 mm x 100 mm to produce a test piece. The resulting test piece was peeled off the peeled PET film, and the exposed adhesive layer was attached to a stainless steel plate (SUS) with an attachment area of 20 mm x 20 mm, and was pressure-bonded with a 2-kg roller for 3 passes. Thereafter, the test piece was left to stand for 20 minutes in a dry environment at 40°C, and the amount of deviation (mm) of the adhesive layer was measured 1 hour after the application of a load of 1 kg in the shearing direction in the same environment.

[0172] In Table 2, the amount of deviation (mm) after 1 hour is indicated as the 40°C adhesion (mm).

[0173] <Constant Load Peeling Test>

[0174] The adhesive sheet (1) was cut into a size of 80 mm x 20 mm, and the peeled PET film was peeled off, and the exposed adhesive layer was attached to the lower surface side of a PP (polypropylene) plate arranged in a manner parallel to the horizontal direction with an attachment area of 50 mm x 20 mm using a 2-kg roller for 3 passes. Then, the peeling distance (mm) in the longitudinal direction of the test piece or the time (minutes) until falling was measured when left to stand for 60 minutes in a state where a load was applied to the end portion of the one end side of the test piece attached to the PP plate in the longitudinal direction toward the lower side in the vertical direction. Further, the load was 100 g at a measurement temperature of 40°C, 50 g at 80°C, 50 g at 120°C, and 16 g at 150°C. The results were evaluated according to the following criteria.

[0175] In Table 2, the results of the constant load peeling test are indicated as the PP constant load, and the load for each temperature.

[0176] AA: The peeling distance was 5 mm or less

[0177] BB: The peeling distance was more than 5 mm and 10 mm or less

[0178] CC: The peeling distance was more than 10 mm and less than 50 mm

[0179] DD: Falling (peeling distance 50 mm).

[0180] Rolling ball tack

[0181] The measurement was performed according to the J. Dow method according to the following procedure.

[0182] The PET film subjected to the release treatment was peeled off from the above-mentioned adhesive sheet (1) and placed on an inclined surface at an inclination angle of 30 degrees in such a manner that the adhesive layer was exposed. Subsequently, a stainless steel ball was boosted from the upper side of the inclined surface in an environment at 23°C / 50% RH and caused to slide on the adhesive surface (boosting distance: 10 cm, sliding distance: 10 cm).

[0183] The sliding test was performed by changing the diameter of the steel ball, and the maximum diameter of the steel ball that stopped sliding on the adhesive surface was determined. The diameter of the stainless steel ball used was X / 32 inch (X is an integer in the range of 2 to 32). The value of X at the maximum diameter of the stainless steel ball is shown in Table 2 as the result of the rolling ball tack test.

[0184] [Examples 2 to 6, Comparative Examples 1 to 5]

[0185] The adhesive composition and the adhesive sheet were obtained in the same manner as in Example 1 except that the type of the acrylic polymer, the type of the rosin-based resin and the amount of the crosslinking agent were changed as described in Table 2.

[0186] The physical properties were evaluated by the same method as in Example 1 using the obtained adhesive sheet. The results are shown in Table 2.

[0187] [Table 2]

[0188]

[0189] According to Table 2, the adhesive sheet obtained from the adhesive composition described in Examples 1 to 6 had good compatibility between the (meth)acrylic polymer (A) and the rosin-based tackifying resin (B) and low haze. In addition, it showed good results in the load peeling from polypropylene at high temperature.

[0190] The adhesive sheet obtained from the adhesive composition in which the rosin-based tackifying resin having a Tg lower than 85°C and a hydroxyl value of 45 mgKOH / g or less was blended showed poor results in the evaluation of the load peeling from polypropylene at high temperature (Comparative Examples 1, 2, 4, 5). In particular, the adhesive sheet of Comparative Example 4 had low haze, but since the Tg of the rosin-based tackifying resin was low, it showed poorer results in the evaluation of the load peeling than Comparative Examples 1, 2, 5.

[0191] In Comparative Example 3, although the rosin-based tackifying resin having a Tg of 85°C or more was used, the hydroxyl value was 45 mgKOH / g or less, and therefore the compatibility with the (meth)acrylic polymer (A) was poor, and as a result, an adhesive sheet having high haze and poor results in the evaluation of the load peeling was obtained.

Claims

1. An adhesive composition comprising a (meth)acrylic polymer (A), a rosin-based tackifying resin (B) having a glass transition temperature of 85°C or higher, a hydroxyl value of 50 mgKOH / g or more, and an acid value of 7 to 12 mgKOH / g, and a crosslinking agent (C), the weight average molecular weight of the (meth)acrylic polymer (A) is 700,000 to 2,000,000, the (meth)acrylic polymer (A) is a polymer of a monomer component (a) comprising 60 to 99.5 mass% of an alkyl (meth)acrylate having 4 to 8 carbons in the alkyl group and 0.1 to 15 mass% of a crosslinkable functional group-containing monomer, the blending amount of the rosin-based tackifying resin (B) is 5 to 50 parts by mass per 100 parts by mass of the (meth)acrylic polymer (A), the blending amount of the crosslinking agent (C) is 0.05 to 10 parts by mass per 100 parts by mass of the (meth)acrylic polymer (A).

2. The adhesive composition of claim 1, wherein It is a non-emulsified adhesive composition.

3. The adhesive composition of claim 1, wherein The haze of an adhesive layer having a thickness of 25 μm obtained from the adhesive composition is less than 1%.

4. An adhesive sheet, characterized by An adhesive layer prepared from the adhesive composition of any one of claims 1 to 3.

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