Hot melt adhesive composition and adhesive sheet

Abstract

Provided is a hot-melt adhesive composition that can form an adhesive layer without rapid gelation when heated and melted. The adhesive composition provided by the present invention is a solvent-free hot-melt adhesive composition. The adhesive composition comprises: a base polymer; an isocyanate crosslinking agent; and a tackifier T that is a reaction product of a compound X and a compound Y. The content of the tackifier T is 20 parts by weight or more and 40 parts by weight or less relative to 100 parts by weight of the base polymer.

Description

Technical Field

[0001] The present invention relates to a hot melt adhesive composition. The present invention also relates to an adhesive sheet comprising an adhesive layer formed from a hot melt adhesive composition. This application claims priority based on Japanese Patent Application No. 2020-26124 filed on February 19, 2020, the entire contents of which are incorporated herein by reference. Background Art

[0002] Generally, adhesives (also called pressure-sensitive adhesives. The same applies hereafter) are in a soft solid (viscoelastic) state at a temperature range near room temperature, and have the property of being easily bonded to the adherend by pressure. Taking full advantage of the above properties, adhesives are widely used in various industrial fields, from home appliances to automobiles, OA equipment, etc., as a bonding method with good workability and high bonding reliability.

[0003] Adhesive is typically formed into a film using an adhesive composition and used in the form of an adhesive sheet containing the film-like adhesive (adhesive layer). When manufacturing the adhesive sheet of the above-mentioned composition, an adhesive composition in the form of a solvent solution such as a toluene solution is usually used, and an adhesive layer can be formed by applying the solvent solution to a suitable surface. However, in recent years, in order to protect the environment, it is required to limit the use of solvents, and a hot-melt adhesive composition using a solvent-free in the adhesive layer formation has also been studied. As a technical document related to this hot-melt adhesive composition, Patent Document 1 can be cited.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-147655 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] A crosslinking agent may be added to the adhesive composition for the purpose of improving the adhesive properties of the adhesive layer. When the adhesive layer is formed using an adhesive composition used in a conventional solution form, the adhesive composition containing the crosslinking agent is formed into a film by coating and then heated, thereby simultaneously performing a crosslinking reaction and drying to form an adhesive layer.

[0009] On the other hand, when a solvent-free hot-melt adhesive composition is used to form an adhesive layer, the hot-melt adhesive composition is formed into a film under a heated and molten state. However, if the hot-melt adhesive composition to which a crosslinking agent is added is heated to a molten state in which the composition has sufficient fluidity, the reaction of the crosslinking agent added to the composition will proceed, and sometimes a gelled substance will be rapidly generated in the adhesive composition. In this way, if gelation proceeds at the stage of heating and melting the adhesive composition, it may become the main cause of the occurrence of defects in the subsequent process of forming a film, the uniformity of the thickness of the adhesive layer or even the adhesive sheet, and the poor appearance.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hot melt adhesive composition that can form an adhesive layer without rapid gelation when heated and melted. Another object of the present invention is to provide an adhesive sheet obtained by using the hot melt adhesive composition.

[0011] Solutions for solving problems

[0012] According to the specification, a solvent-free hot melt adhesive composition is provided. The hot melt adhesive composition comprises: a base polymer; an isocyanate crosslinking agent; and a tackifier T which is a reaction product of a compound X and a compound Y. Here, the compound X is at least one selected from the group consisting of the following formulas (A1) to (A6), and the compound Y is at least one selected from the group consisting of the following formulas (B) and (C). The content of the tackifier T is 20 parts by weight or more and 40 parts by weight or less relative to 100 parts by weight of the base polymer.

[0013]

[0014]

[0015] The hot-melt adhesive composition can suppress rapid gelation during heating and melting. If such a hot-melt adhesive composition is used, poor molding when the composition is molded into a film can be suppressed, and there is a tendency to obtain an adhesive layer with improved thickness uniformity and good appearance. In addition, if the hot-melt adhesive composition is used, an adhesive layer showing good adhesive properties can be easily obtained.

[0016] In a preferred embodiment of the technology disclosed herein, the compound X comprises: a compound represented by the formula (A1), a compound represented by the formula (A2), and a compound represented by the formula (A3), and the compound Y is a compound represented by the formula (B). That is, in a preferred embodiment, the hot melt adhesive composition comprises a tackifier T which is a reaction product of the compound X and the compound Y represented by the formula (B), and the compound X is a mixture comprising the compound represented by the formula (A1), the compound represented by the formula (A2), and the compound represented by the formula (A3). By including the adhesive composition of the tackifier T, it is easy to suppress rapid gelation during heating and melting.

[0017] In another preferred embodiment of the technology disclosed herein, the compound X comprises: a compound represented by the above formula (A4), a compound represented by the above formula (A5), and a compound represented by the above formula (A6), and the compound Y is a compound represented by the above formula (C). That is, in a preferred embodiment, the hot melt adhesive composition comprises a tackifier T which is a reaction product of the compound X and the compound Y represented by the above formula (C), and the compound X is a mixture comprising the compound represented by the above formula (A4), the compound represented by the above formula (A5), and the compound represented by the above formula (A6). By including the adhesive composition of the tackifier T, it is easy to suppress rapid gelation during heating and melting.

[0018] In a preferred embodiment of the technology disclosed herein, the hot melt adhesive composition contains an acrylic polymer as the base polymer. The adhesive composition having the above-mentioned structure is used in a hot melt form to easily form an adhesive layer having good adhesive properties.

[0019] In a preferred embodiment of the technology disclosed herein, the acrylic polymer is polymerized with an alkyl (meth)acrylate having an alkyl group having 4 or more and 12 carbon atoms at the ester terminal at a ratio of 50% by weight or more. When the acrylic polymer is used, it is used in a hot melt form to easily form an adhesive layer showing good adhesive properties.

[0020] In a preferred embodiment of the technology disclosed herein, the dispersity (Mw / Mn) of the acrylic polymer is 3.0 to 9.0. When an acrylic polymer having such a dispersity is used, it is easy to form an adhesive layer showing good adhesive properties by using it in a solvent-free hot melt form.

[0021] In a preferred embodiment of the technology disclosed herein, the content of the isocyanate crosslinking agent is 0.5 parts by weight or more and 8 parts by weight or less based on 100 parts by weight of the base polymer. According to the above configuration, the gelation suppression effect during heat melting can be further improved.

[0022] According to the specification, an adhesive sheet having an adhesive layer formed by any adhesive composition disclosed herein is provided. According to the above-mentioned constitution, an adhesive sheet having improved uniformity of thickness and having good appearance and good adhesive force is easily obtained. In addition, the adhesive sheet of the above-mentioned constitution is easy to reduce environmental burden.

[0023] It should be noted that suitable combinations of the above-mentioned features are also included in the claims to be protected by the present patent application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a cross-sectional view schematically showing a configuration example of a pressure-sensitive adhesive sheet.

[0025] Figure 2 It is a cross-sectional view schematically showing another configuration example of the pressure-sensitive adhesive sheet. DETAILED DESCRIPTION

[0026] The following is a description of suitable embodiments of the present invention. It should be noted that, for those skilled in the art, matters other than those specifically mentioned in this specification and matters required for implementing the present invention are understood to be based on the implications of the implementation of the invention described in this specification and the technical common sense at the time of application. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in this field. In addition, in the following drawings, the same symbols are sometimes marked for components / parts that play the same role, and repeated descriptions are sometimes omitted or simplified. In addition, the embodiments described in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the products actually provided.

[0027] <Adhesive Composition>

[0028] The adhesive composition disclosed herein is a solvent-free hot-melt adhesive composition. Here, in this specification, "hot-melt adhesive composition" refers to an adhesive composition used in a hot-melt (hot-melting) manner when forming an adhesive layer. In addition, in this specification, "solvent-free" means that it does not substantially contain a solvent. In this specification, the adhesive composition "solvent-free" or "substantially does not contain a solvent" means that the solvent content in the entire adhesive composition is 1% by weight or less, more preferably 0.1% by weight or less, and further preferably 0.01% by weight or less, including the case where the solvent content is 0% by weight. In this specification, the hot-melt adhesive composition is sometimes referred to as an "adhesive composition".

[0029] (Base polymer)

[0030] The adhesive composition disclosed herein includes a base polymer. The type of base polymer is not particularly limited. The adhesive composition disclosed herein may be, for example, an adhesive composition comprising one or more of various polymers selected from acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixed systems thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluorine polymers, etc., which exhibit rubber elasticity at room temperature as a base polymer (i.e., a component accounting for more than 50% by weight of the polymer component).

[0031] (Glass transition temperature (Tg))

[0032] The base polymer contained in the adhesive composition disclosed herein can be set, for example, in such a manner that the glass transition temperature (Tg) calculated based on the composition of the monomer components constituting the base polymer is lower than 0°C. Here, the Tg calculated based on the composition of the monomer components refers to the Tg obtained based on the composition of the above-mentioned monomer components and using the Fox formula. As shown below, the Fox formula is a relationship between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing the monomers constituting the copolymer.

[0033] 1 / Tg=Σ(Wi / Tgi)

[0034] In the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0035] As the glass transition temperature of the homopolymer used in the calculation of Tg, the value recorded in the known data is used. Specifically, the numerical values ​​in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be cited. For monomers with multiple values ​​recorded in the above-mentioned Polymer Handbook, the highest value is adopted. As the glass transition temperature of the homopolymer of the monomer not recorded in the above-mentioned Polymer Handbook, the value obtained by the measurement method recorded in the gazette of Japanese Patent Application Publication No. 2007-51271 can be used.

[0036] The Tg calculated based on the composition of the above-mentioned monomer component can be grasped as the Tg of the polymer of the monomer component (typically, the base polymer in the adhesive composition disclosed herein). The Tg of the above-mentioned polymer is preferably below -10°C, can be below -20°C, can be below -30°C, can be below -40°C. When the above-mentioned Tg becomes lower, there is a tendency to improve the adhesion to the adherend. In some embodiments, the Tg of the above-mentioned polymer can be below -50°C, can be below -55°C, can be below -60°C. The lower limit of the Tg of the above-mentioned polymer is not particularly limited. From the viewpoint of the ease of obtaining the material and the improvement of the aggregation of the adhesive layer, it is usually suitable to be above -80°C, preferably above -70°C.

[0037] (Acrylic polymer)

[0038] The adhesive composition disclosed herein can be preferably implemented in a manner in which more than 50% by weight of the above-mentioned monomer components are (meth) acrylic acid monomers. The adhesive composition disclosed herein is preferably an adhesive composition comprising an acrylic acid polymer as a polymer of the above-mentioned monomer components as a base polymer, i.e., an acrylic acid adhesive composition. In some preferred adhesive compositions, more than 70% by weight, more than 80% by weight, or more than 90% by weight of the polymer components contained in the composition can be acrylic acid polymers. More than 95% by weight or more than 98% by weight of the above-mentioned polymer components can be acrylic acid polymers.

[0039] It should be noted that in this specification, "acrylic polymer" refers to a polymer containing monomer units derived from (meth)acrylic monomers in the polymer structure, and typically refers to a polymer containing monomer units derived from (meth)acrylic monomers in a ratio of more than 50% by weight. In addition, in this specification, (meth)acrylic monomers refer to: a monomer having at least one (meth)acryloyl group in one molecule. Here, "(meth)acryloyl" means including acryloyl and methacryloyl. Therefore, the concept of (meth)acrylic monomers here can include both monomers having acryloyl groups (acrylic monomers) and monomers having methacryloyl groups (methacrylic monomers). Similarly, in this specification, "(meth)acrylic acid" means including acrylic acid and methacrylic acid, and "(meth)acrylate" means including acrylate and methyl acrylate.

[0040] The acrylic polymer may be, for example, a polymer containing 50% by weight or more of a monomer unit derived from an alkyl (meth)acrylate, i.e., a polymer in which 50% by weight or more of the total amount of monomer components used to prepare the acrylic polymer is an alkyl (meth)acrylate. As the alkyl (meth)acrylate, preferably used is a polymer having 1 to 20 carbon atoms at the ester terminal (i.e., C1-20 (meth)acrylic acid alkyl ester having a linear or branched alkyl group. In order to easily obtain a balance of properties, the total amount of the monomer component (meth)acrylic acid C 1-20 The proportion of the alkyl ester may be, for example, 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more. 1-20 The proportion of the alkyl ester may be, for example, 99.9 wt % or less, preferably 98 wt % or less, and more preferably 95 wt % or less. In some embodiments, the total amount of the monomer components is (meth) acrylic acid C 1-20 The ratio of the alkyl ester may be, for example, 80% by weight or more, or 85% by weight or more.

[0041] As (meth)acrylic acid C 1-20 Specific non-limiting examples of the alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0042] Among these, it is preferred to use at least (meth)acrylic acid C 1-18 Alkyl esters, more preferably at least (meth) acrylic acid C 1-14 In some embodiments, the acrylic polymer may contain a (meth)acrylic acid C 4-12 Alkyl ester (preferably (meth) acrylic acid C 4-10 As a monomer unit, at least one of (meth)acrylic acid (meth)acrylate ... 1-18Examples of alkyl esters include methyl acrylate, methyl methacrylate (MMA), n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (ISTA), etc. Suitable examples of the acrylic polymers include (meth)acrylic acid C 4-8 An acrylic polymer containing at least one monomer unit of an alkyl ester of (meth)acrylic acid C 4-6 An acrylic polymer containing at least one monomer unit of an alkyl ester of (meth)acrylic acid C 6-10 An acrylic polymer having at least one kind of alkyl ester as a monomer unit, and the like.

[0043] The monomer units constituting the acrylic polymer may contain other secondary monomers (copolymerizable monomers) copolymerizable with the (meth) alkyl acrylate as the main component as needed. As secondary monomers, monomers having functional groups (e.g., carboxyl, hydroxyl, amide, etc.) may be suitably used. Functional group-containing monomers may be used to introduce crosslinking points into the acrylic polymer or to improve the cohesive force of the acrylic polymer.

[0044] As the secondary monomer, for example, the following functional group-containing monomers may be used alone or in combination of two or more.

[0045] Hydroxyl-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether.

[0046] Carboxyl group-containing monomers: for example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid, isocrotonic acid, etc.; ethylenically unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, etc.

[0047] Anhydride group-containing monomers: for example, maleic anhydride, itaconic anhydride.

[0048] Monomers having a ring containing a nitrogen atom: for example, N-vinyl-2-pyrrolidone, methyl-N-vinylpyrrolidone, vinylpyridine, vinylpyrazine, vinylpyrimidine, N-vinylpiperidone, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazine-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-(meth)acryloylmorpholine, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, and the like.

[0049] Amide group-containing monomers: for example, (meth)acrylamide; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl) (meth)acrylamide, N,N-di(tert-butyl) (meth)acrylamide and the like N,N-dialkyl (meth)acrylamide; N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N-n-butyl (meth)acrylamide and the like N-alkyl (meth)acrylamide; N-vinyl carboxylic acid amides such as N-vinyl acetamide; monomers having hydroxyl groups and amide groups, for example, N-(2-hydroxyethyl) (methyl)acrylamide N-hydroxyalkyl(meth)acrylamide, such as acrylamide, N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, and N-(4-hydroxybutyl)(meth)acrylamide; monomers having an alkoxy group and an amide group, such as N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide; N,N-dialkylaminoalkyl(meth)acrylamide, such as N,N-dimethylaminopropyl(meth)acrylamide, and the like.

[0050] Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate.

[0051] Monomers having a succinimide skeleton include, for example, N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyhexamethylenesuccinimide.

[0052] Maleimides: for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, etc.

[0053] Itaconimides: for example, N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide, N-cyclohexyl itaconimide, N-lauryl itaconimide and the like.

[0054] Epoxy group-containing monomers: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.

[0055] Cyano-containing monomers: for example, acrylonitrile, methacrylonitrile.

[0056] Ketone group-containing monomers: for example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.

[0057] Alkoxysilyl group-containing monomers: for example, alkoxysilyl group-containing (meth)acrylates such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, and alkoxysilyl group-containing vinyl compounds such as vinyltrimethoxysilane and vinyltriethoxysilane.

[0058] Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate.

[0059] Monomers containing sulfonic acid groups or phosphoric acid groups: for example, styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethylacryloyl phosphate, etc.

[0060] Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate, (meth)acryloyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0061] When using the above-mentioned monomer containing functional groups, its dosage is not particularly limited, and it is usually suitable for more than 0.01 weight % of the total monomer component. From the viewpoint of better exerting the effect brought by using the monomer containing functional groups, the dosage of the monomer containing functional groups can be set to more than 0.1 weight % of the total monomer component, or more than 1 weight %. In addition, the dosage of the monomer containing functional groups can be less than 50 weight % of the total monomer component, preferably less than 40 weight %. Thus, the cohesive force of the adhesive is prevented from becoming too high, and the adhesion of the adherend can be improved.

[0062] The adhesive composition disclosed herein may contain (meth)acrylic acid C as the above-mentioned monomer component. 4-10 The method of using a hydroxyl-containing monomer as an alkyl ester and further comprising one or both of acrylic acid and a hydroxyl-containing monomer is preferably implemented. As the hydroxyl-containing monomer, a hydroxyalkyl (meth)acrylate can be preferably used. In particular, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are preferred. 1-4 Alkyl esters.

[0063] The monomer component contains (meth) acrylic acid C 4-10 In the embodiment in which the (meth)acrylic acid C in the above monomer components further contains one or both of acrylic acid and a hydroxyl-containing monomer, 4-10 The content of the alkyl ester is preferably 60% by weight or more, more preferably 70% by weight or more, for example, 80% by weight or more, and preferably 99% by weight or less, more preferably 97% by weight or less, for example, 94% by weight or less. In addition, when the above-mentioned monomer component contains acrylic acid, its content is, for example, 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1.0% by weight or more, and, for example, 25% by weight or less, preferably 20% by weight or less, and may be 10% by weight or less. When the above-mentioned monomer component contains a hydroxyl-containing monomer, its content is, for example, 0.01% by weight or more, preferably 0.05% by weight or more, and, for example, 15% by weight or less, preferably 10% by weight or less, 5% by weight or less, 3% by weight or less, and 1% by weight or less. The above-mentioned monomer component more preferably contains (meth)acrylic acid C 4-10 The alkyl ester further includes both acrylic acid and a hydroxyl group-containing monomer.

[0064] The monomer raw material used for the preparation of the acrylic polymer may contain a secondary monomer other than the above-mentioned functional group-containing monomer for the purpose of improving the cohesive force of the acrylic polymer.

[0065] Specific non-limiting examples of the sub-monomer include the following monomers.

[0066] Alkoxy-containing monomers: for example, alkoxyalkyl (meth)acrylates (alkoxyalkyl (meth)acrylates) such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate; methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and alkoxy (poly)alkylene glycol (meth)acrylates.

[0067] Vinyl esters: for example, vinyl acetate, vinyl propionate, etc.

[0068] Vinyl ethers: For example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.

[0069] Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc.

[0070] Olefins: for example, ethylene, butadiene, isoprene, isobutylene, etc.

[0071] (Meth)acrylates having an alicyclic hydrocarbon group: for example, alicyclic hydrocarbon group-containing (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, and adamantyl (meth)acrylate.

[0072] Aromatic ring-containing (meth)acrylates include, for example, aryl (meth)acrylates such as phenyl (meth)acrylate, aryloxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate, and arylalkyl (meth)acrylates such as benzyl (meth)acrylate.

[0073] In addition, heterocyclic-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen-atom-containing monomers such as vinyl chloride and fluorine-containing (meth)acrylates, organosiloxane-chain-containing monomers such as silicone (meth)acrylates, and (meth)acrylates obtained from terpene compound derivative alcohols, etc.

[0074] Such secondary monomers can be used alone or in combination of two or more. The amount of the other secondary monomers can be appropriately selected according to the purpose and use, and is not particularly limited. For example, it is preferably less than 20% by weight (e.g., 2 to 20% by weight, typically 3 to 10% by weight) of the total monomer raw materials of the acrylic polymer.

[0075] The method for polymerizing the monomer raw material is not particularly limited, and various polymerization methods known as the synthesis methods of acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization, can be appropriately used. For example, solution polymerization can be preferably used. As a monomer supply method when performing solution polymerization, a one-time input method in which all monomer raw materials are supplied at one time, a continuous supply (drip) method, a batch supply (drip) method, etc. can be appropriately used. The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from existing well-known organic solvents. For example, any one solvent selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols with 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc. can be used, or a mixed solvent of two or more can be used. The polymerization temperature can be appropriately selected according to the types of monomers and solvents used, the types of polymerization initiators, etc., and can be, for example, about 20°C to 120°C (typically 40°C to 80°C). According to solution polymerization, a polymerization reaction liquid in the form of a polymer of a monomer raw material dissolved in a polymerization solvent can be obtained. The adhesive composition used in the formation of the adhesive layer can be preferably manufactured using the above-mentioned polymerization reaction liquid.

[0076] When performing polymerization, known or commonly used thermal polymerization initiators and photopolymerization initiators can be used according to the polymerization method, polymerization mode, etc. As examples of thermal polymerization initiators, azo polymerization initiators, peroxide-based initiators, redox-based initiators composed of a combination of peroxide and a reducing agent, substituted ethane-based initiators, etc. can be used. As examples of photopolymerization initiators, α-ketol-based photoinitiators, acetophenone-based photoinitiators, benzoin ether-based photoinitiators, ketal-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzophenone-based photoinitiators, thioxanthone-based photoinitiators, acylphosphine oxide-based photoinitiators, etc. can be listed. The polymerization initiator can be used alone or in combination of two or more.

[0077] The amount of the polymerization initiator used may be a common amount, and for example, can be selected from the range of about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) based on 100 parts by weight of all the monomer raw materials.

[0078] The adhesive composition disclosed herein may further contain a polymer other than an acrylic polymer as a secondary polymer as needed. As the above-mentioned secondary polymer, various polymers exemplified as polymers that may be contained in the adhesive layer, except for acrylic polymers, can be cited as suitable examples. When the adhesive composition disclosed herein contains a secondary polymer in addition to an acrylic polymer, it is suitable that the content of the secondary polymer is less than 100 parts by weight relative to 100 parts by weight of the acrylic polymer, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and further preferably 10 parts by weight or less. The content of the secondary polymer may be 5 parts by weight or less, or 1 part by weight or less relative to 100 parts by weight of the acrylic polymer. The technology disclosed herein can be preferably implemented, for example, in a manner in which 99.5 to 100% by weight of the polymer contained in the adhesive composition is an acrylic polymer.

[0079] The molecular weight of the base polymer (typically, an acrylic polymer) is not particularly limited and can be set to an appropriate range according to the required performance. The weight average molecular weight (Mw) of the base polymer (typically, an acrylic polymer) is 5×10 4 The above are suitable, and can be appropriately selected and used, preferably about 15×10 4 More preferably, about 30×10 4 More preferably, about 45×10 4 More than (e.g. about 50×10 4 The upper limit of the Mw is not particularly limited, but may be about 150×10 4 Less than (preferably about 100×10 4 Below, for example, about 80×10 4 By setting the Mw within the above range, it is easy to adjust the elastic modulus of the adhesive to a preferred range, and it is easy to exert good cohesive force.

[0080] There is no particular limitation, but the dispersity (Mw / Mn) expressed by the ratio of the weight average molecular weight (Mw) of the base polymer (typically, an acrylic polymer) to the number average molecular weight (Mn) is in principle more than 1, and from the viewpoint of ease of synthesis and productivity, it can be more than 2.0, and more preferably more than 3.0. In some preferred embodiments, the dispersity of the base polymer can be, for example, more than 4.0, more than 4.5, and further more than 4.8. By setting the dispersity (Mw / Mn) of the base polymer to a prescribed value or more, it is easy to obtain an adhesive layer that exerts good adhesion (adhesive force, viscosity, etc.) at a melt viscosity that is easy to apply without a solvent. The upper limit of the dispersity of the base polymer is not particularly limited. In some embodiments, it is suitable for the dispersity of the base polymer to be less than 10 (for example, less than 9.0), preferably less than 8.0, more preferably less than 7.0, less than 6.0, and less than 5.5. By setting the dispersion degree (Mw / Mn) of the base polymer to a predetermined value or less, an increase in melt viscosity due to the presence of high molecular weight substances can be suppressed, and a pressure-sensitive adhesive layer showing good cohesiveness can be formed.

[0081] It should be noted that Mw and Mn of the base polymer (typically, acrylic polymer) here refer to polystyrene-equivalent values ​​determined by gel permeation chromatography (GPC) measurement. As a GPC measuring apparatus, for example, a model "HLC-8120GPC" manufactured by Tosoh Corporation can be used.

[0082] (Thickener)

[0083] The pressure-sensitive adhesive composition disclosed herein contains a tackifier T. The tackifier T is a product obtained by reacting a compound X having a predetermined structure with a compound Y having another predetermined structure.

[0084] The compound X is a carboxylic acid having one or two carboxyl groups in the molecule. Specifically, the compound X is at least one selected from the group consisting of the following formulas (A1) to (A6). As the compound X, one selected from the group consisting of the following formulas (A1) to (A6) may be used alone or in combination of two or more.

[0085]

[0086]

[0087] The compound represented by the above formula (A2) and the compound represented by the above formula (A3) are obtained by adding hydrogen to the compound represented by the above formula (A1). In addition, the compound represented by the above formula (A4), the compound represented by the above formula (A5) and the compound represented by the above formula (A6) are obtained by reacting two molecules of the compound represented by the above formula (A1).

[0088] The compound Y is an alcohol having 3 or 4 hydroxyl groups in the molecule. Specifically, the compound Y is at least one selected from the group consisting of the following formulas (B) and (C). As the compound Y, one selected from the group consisting of the following formulas (B) and (C) may be used alone or in combination of two or more.

[0089]

[0090] Typically, the tackifier T is an ester of the compound X and the compound Y. When the tackifier T obtained by reacting (typically esterifying) the compound X represented by the above formula (A1) to (A6) with the compound Y represented by the above formula (B) and (C) is used, it is easy to achieve an adhesive composition that suppresses rapid gelation during heating and melting. In particular, by using the tackifier T in combination with the isocyanate crosslinking agent described later, it is easy to exert the gelation suppression effect during heating and melting.

[0091] The reason why the tackifier T suppresses the rapid gelation when the adhesive composition is heated is not particularly limited, and can be explained as follows, for example. The crosslinking reaction AB when a crosslinking agent (typically an isocyanate crosslinking agent) is used includes: a reaction A in which the crosslinking agent crosslinks with the base polymer, and a reaction B in which the crosslinking agents combine with each other in the presence of water to form a polymer network. On the other hand, the crosslinking agent may also react with the tackifier T. The reaction between the crosslinking agent and the tackifier T is hereinafter referred to as reaction X.

[0092] It is believed that when the adhesive composition containing a crosslinking agent and a tackifier T is heated, the crosslinking reaction AB and the reaction X proceed in a competitive state. Here, under relatively high temperature conditions such as when the adhesive composition melts, typically about 90 to 110°C, for example, under temperature conditions around about 100°C, the reaction X proceeds preferentially. On the other hand, it is believed that under lower temperature conditions, typically about 30 to 50°C, for example, under temperature conditions around about 40°C, the crosslinking reaction AB proceeds preferentially. Therefore, when the adhesive composition is heated and melted at a relatively high temperature, typically about 90 to 110°C, for example, at about 100°C, the reaction X proceeds preferentially, thereby suppressing the progress of the crosslinking reaction AB and suppressing the generation of gelled products. In addition, it is believed that after the heated and melted adhesive composition is formed into a film by melt extrusion, when it is aged at a relatively low temperature, typically about 30 to 50°C, for example, at about 40°C, the crosslinking reaction AB of the adhesive composition proceeds, and an adhesive layer with a sufficient degree of crosslinking can be formed.

[0093] In a preferred embodiment of the technology disclosed herein, the thickener T is a reaction product (typically an ester) of one or more compounds X selected from the group consisting of the above-mentioned formula (A1), the above-mentioned formula (A2) and the above-mentioned formula (A3) and the compound Y shown in the above-mentioned (B). The above-mentioned thickener T can easily suppress the rapid gelation during heating and melting. For example, the above-mentioned thickener T can be a reaction product of a mixture of two or more of the compounds represented by the above-mentioned formula (A1), the compound represented by the above-mentioned formula (A2) and the compound represented by the above-mentioned formula (A3), and the compound Y shown in the above-mentioned (B). In a preferred embodiment, the above-mentioned thickener T is a reaction product of a mixture of a compound represented by the above-mentioned formula (A1), a compound represented by the above-mentioned formula (A2) and a compound represented by the above-mentioned formula (A3), and the compound Y shown in the above-mentioned (B).

[0094] In a preferred embodiment of the technology disclosed herein, the thickener T is a reaction product (typically an ester) of one or more compounds X selected from the group consisting of the above-mentioned formula (A4), the above-mentioned formula (A5) and the above-mentioned formula (A6) and the compound Y shown in the above-mentioned (C). The above-mentioned thickener T can easily suppress the rapid gelation during heating and melting. For example, the above-mentioned thickener T can be a reaction product of a mixture of two or more of the compounds shown in the above-mentioned formula (A4), the compound shown in the above-mentioned formula (A5) and the compound shown in the above-mentioned formula (A6), and the compound Y shown in the above-mentioned (C). In a preferred embodiment, the above-mentioned thickener T is a reaction product of a mixture of a compound shown in the above-mentioned formula (A4), a compound shown in the above-mentioned formula (A5) and a compound shown in the above-mentioned formula (A6), and the compound Y shown in the above-mentioned (C).

[0095] From the viewpoint of suppressing the gelation when the adhesive composition is heated and melted, it is suitable that the content of the tackifier T is usually more than 1 part by weight relative to 100 parts by weight of the base polymer, preferably more than 5 parts by weight, more preferably more than 10 parts by weight, and more preferably more than 20 parts by weight. In some preferred embodiments, the content of the tackifier T can be more than 23 parts by weight relative to 100 parts by weight of the base polymer, can exceed 25 parts by weight, can be more than 27 parts by weight, and can be more than 30 parts by weight. From the viewpoint of improving the adhesion of the adhesive layer, it is suitable that the content of the tackifier T is usually less than 70 parts by weight relative to 100 parts by weight of the base polymer, preferably less than 60 parts by weight, more preferably less than 40 parts by weight, and more preferably less than 25 parts by weight. When the content of the tackifier T is too much, there is a concern that the cross-linking reaction during aging is hindered and the adhesive properties of the adhesive layer are reduced.

[0096] As the tackifier T, a tackifier having a softening point of about 50°C or higher (more preferably about 70°C or higher, for example, about 80°C or higher) can be preferably used. The upper limit of the softening point is not particularly limited, and may be, for example, about 180°C or lower (more preferably about 150°C or lower, typically 130°C or lower). It should be noted that the softening point of the tackifier T can be measured according to the softening point test method (ring and ball method) specified in JIS K2207.

[0097] The adhesive composition disclosed herein may further contain other tackifiers as tackifiers in addition to the above-mentioned tackifier T. Such other tackifiers are not particularly limited, and examples thereof include rosin-based tackifiers, terpene-based tackifiers, phenol-based tackifiers, hydrocarbon-based tackifiers, ketone-based tackifiers, polyamide-based tackifiers, epoxy-based tackifiers, and elastic-based tackifiers, etc., in addition to the tackifier T. The tackifiers may be used alone or in combination of two or more.

[0098] Examples of rosin-based tackifiers other than the tackifier T include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, modified rosins obtained by modifying these unmodified rosins by polymerization, disproportionation, hydrogenation, etc. (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, other chemically modified rosins, etc.), and various rosin derivatives.

[0099] Examples of the rosin derivatives include rosin phenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and thermally polymerizing the rosin;

[0100] Rosin ester resins such as rosin ester compounds obtained by esterifying unmodified rosin with alcohols (unmodified rosin esters), polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, and modified rosin ester compounds obtained by esterifying modified rosin with alcohols (polymerized rosin esters, stabilized rosin esters, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, and the like);

[0101] Unsaturated fatty acid-modified rosin resins obtained by modifying unmodified rosin or modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.) with unsaturated fatty acids;

[0102] Unsaturated fatty acid-modified rosin ester resin obtained by modifying rosin ester resin with unsaturated fatty acid;

[0103] A rosin alcohol resin obtained by reducing the carboxyl groups in unmodified rosin, modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.), unsaturated fatty acid-modified rosin resin, and unsaturated fatty acid-modified rosin ester resin;

[0104] Metal salts of rosin-based resins (particularly rosin ester-based resins) such as unmodified rosin, modified rosin, and various rosin derivatives; and the like.

[0105] Examples of the terpene thickener include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers, and modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.) (for example, terpene phenol resins, styrene-modified terpene resins, aromatic-modified terpene resins, hydrogenated terpene resins, etc.), and the like.

[0106] Examples of the phenolic thickener include condensates of various phenols (e.g., phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcinol, etc.) and formaldehyde (e.g., alkylphenol resins, xylene formaldehyde resins, etc.), resol resins obtained by an addition reaction of the above phenols with formaldehyde using an alkali catalyst, and novolacs obtained by a condensation reaction of the above phenols with formaldehyde using an acid catalyst.

[0107] Examples of hydrocarbon-based thickeners include various hydrocarbon-based resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone indene resins.

[0108] When other tackifiers are used in addition to the tackifier T, the ratio of the tackifier T in the total tackifier is not particularly limited. The ratio of the tackifier T in the total tackifier is usually more than 50% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more.

[0109] When other tackifiers are used in addition to the tackifier T, the amount of the tackifier as a whole is not particularly limited and can be set according to the purpose and use to exert suitable adhesive performance. The content of the tackifier as a whole can be, for example, 20 parts by weight or more, more than 25 parts by weight, or more than 30 parts by weight relative to 100 parts by weight of the base polymer, and can also be 80 parts by weight or less, 70 parts by weight or less, or 60 parts by weight or less. The adhesive composition disclosed herein may contain a tackifier other than the tackifier T.

[0110] (Crosslinking agent)

[0111] In the technology disclosed herein, the adhesive composition contains an isocyanate crosslinking agent as a crosslinking agent. The isocyanate crosslinking agent is used together with the above-mentioned tackifier T to suppress rapid gelation when the adhesive composition is heated and melted, and tends to increase the crosslinking degree of the adhesive in the aging process of the adhesive layer under lower temperature conditions.

[0112] As the isocyanate crosslinking agent, a polyfunctional isocyanate compound having two or more functions can be used. For example, aromatic isocyanates such as toluene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris (p-isocyanatophenyl) thiophosphate, and diphenylmethane diisocyanate can be listed; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate; etc. As commercially available products, isocyanate adducts such as trimethylolpropane / toluene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate HL"), and isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX") can be cited.

[0113] The content of isocyanate crosslinking agent is not particularly limited. Relative to 100 parts by weight of base polymer, the amount of isocyanate crosslinking agent is usually suitable for less than 15 parts by weight, preferably less than 10 parts by weight, more preferably less than 8 parts by weight, can be less than 5 parts by weight, can be less than 3 parts by weight. The lower limit of the content of isocyanate crosslinking agent is not particularly limited. From the viewpoint of improving adhesive properties, relative to 100 parts by weight of base polymer (e.g., acrylic polymer), the amount of isocyanate crosslinking agent is usually suitable for more than 0.01 parts by weight, preferably more than 0.05 parts by weight, more preferably more than 0.1 parts by weight, further preferably more than 0.2 parts by weight, can be more than 0.5 parts by weight, can be more than 0.1 parts by weight, can be more than 0.5 parts by weight, can be more than 1 part by weight, can be more than 1.2 parts by weight, can be more than 1.5 parts by weight, can be more than 1.8 parts by weight.

[0114] The adhesive composition disclosed herein may further include a crosslinking agent in addition to an isocyanate crosslinking agent. As crosslinking agents that can be used as other crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, melamine crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, hydrazine crosslinking agents, amine crosslinking agents, etc. can be exemplified. These can be used alone or in combination of two or more.

[0115] As the epoxy crosslinking agent, an epoxy crosslinking agent having two or more epoxy groups in one molecule can be used without limitation. An epoxy crosslinking agent having 3 to 5 epoxy groups in one molecule is preferred. Specific examples of the epoxy crosslinking agent include N,N,N',N'-tetraglycidyl meta-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. Commercially available products of epoxy crosslinking agents include "TETRAD-X" and "TETRAD-C" manufactured by Mitsubishi Gas Chemical Corporation, "EPICLON CR-5L" manufactured by DIC Corporation, "DENACOL EX-512", "DENACOL EX-411", and "DENACOL EX-321" manufactured by Nagase ChemteX Corporation, and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

[0116] The total amount of the cross-linking agent as a whole is not particularly limited, and can be appropriately set to obtain the desired effect of use. From the viewpoint of the closeness and joint reliability of the adherend, relative to 100 parts by weight of the base polymer (such as acrylic polymer), the overall amount of the cross-linking agent is usually suitable for about 15 parts by weight or less, preferably 10 parts by weight or less, more preferably 8 parts by weight or less, and can be 5 parts by weight or less. The lower limit of the total amount of the cross-linking agent as a whole is not particularly limited. From the viewpoint of improving adhesive properties, relative to 100 parts by weight of the base polymer (such as acrylic polymer), the overall amount of the cross-linking agent is usually suitable for more than 0.01 parts by weight, preferably more than 0.05 parts by weight, more preferably more than 0.1 parts by weight, further preferably more than 0.2 parts by weight, can be more than 0.5 parts by weight, can be more than 1 part by weight, can be more than 3 parts by weight.

[0117] In order to more effectively carry out the reaction of any of the above-mentioned cross-linking agents, a cross-linking catalyst may be used. As the cross-linking catalyst, for example, a tin catalyst (particularly dioctyltin dilaurate) or an amine catalyst (for example, 1-isobutyl-2-methylimidazole) may be preferably used. The amount of the cross-linking catalyst is not particularly limited, and for example, it may be about 0.0001 to 1 parts by weight relative to 100 parts by weight of the base polymer.

[0118] (Multifunctional monomer)

[0119] The adhesive composition disclosed herein may be prepared using a polyfunctional monomer as needed. The polyfunctional monomer may be used in place of the crosslinking agent described above or in combination with the crosslinking agent to contribute to the purpose of adjusting the cohesive force, etc. Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butanediol (meth)acrylate, and hexanediol di(meth)acrylate. Among them, as preferred multifunctional monomers, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate can be listed. The multifunctional monomers can be used alone or in combination of two or more. The amount of the multifunctional monomer varies depending on its molecular weight, the number of functional groups, etc., and is generally suitable for a range of about 0.01 to 3.0 parts by weight relative to 100 parts by weight of the base polymer. The adhesive composition disclosed herein can be preferably implemented in a manner that substantially does not contain a multifunctional monomer.

[0120] In addition, within the scope that does not significantly hinder the effects of the present invention, the adhesive composition in the technology disclosed herein may contain leveling agents, plasticizers, softeners, colorants (dyes, pigments, etc.), antistatic agents, antioxidants, ultraviolet absorbers, antioxidants, light stabilizers, preservatives and other known additives that can be used for adhesives as needed.

[0121] <Formation of Adhesive Layer>

[0122] The adhesive layer of the adhesive sheet disclosed herein may be an adhesive layer formed of a hot-melt adhesive composition, the hot-melt adhesive composition comprising a base polymer (e.g., an acrylic polymer), an isocyanate crosslinking agent, and a tackifier T, and optionally other optional components. The adhesive composition disclosed herein is a hot-melt adhesive composition that can form an adhesive layer after being molded in a heated molten state and undergoing a maturation process.

[0123] The method for molding the hot-melt adhesive composition disclosed herein into a film (or sheet) is not particularly limited and can be carried out by a known suitable method. The adhesive composition disclosed herein can be molded, for example, by a calendering method, a casting method, an inflation extrusion method, a T-die extrusion method, and the like. For example, when the adhesive composition disclosed herein is molded into a film by melt extrusion, the adhesive composition is heated to a relatively high temperature (typically about 90 to 110° C., for example, about 100° C.) and is in a molten state with high fluidity. Next, the molten adhesive composition is extruded from the die of the extrusion device to form a film. The adhesive composition molded into a film is then placed under a lower temperature condition (typically about 30 to 50° C., for example, about 40° C.) for a certain period of time or more (typically more than 12 hours, for example more than 24 hours), so that it can be matured and an adhesive layer with suitable adhesive properties can be formed.

[0124] In the adhesive sheet disclosed herein, the thickness of the adhesive layer is not particularly limited and can be appropriately selected according to the purpose. Generally, the thickness of the adhesive layer is suitable for about 5 to 1000 μm, and from the viewpoint of adhesion, it is preferably about 10 μm or more (e.g., 15 μm or more, typically 25 μm or more), preferably 750 μm or less, more preferably 500 μm or less, and further preferably 400 μm or less (e.g., 300 μm or less, typically 200 μm or less).

[0125] <Configuration Example of Pressure-Sensitive Adhesive Sheet>

[0126] According to the technology disclosed herein, an adhesive sheet having the above-mentioned adhesive layer is provided. The above-mentioned adhesive layer typically constitutes at least one surface of the adhesive sheet. The adhesive sheet can be an adhesive sheet with a substrate having an adhesive layer on one or both sides of a substrate (support), or an adhesive sheet (substrate-free adhesive sheet) not containing a substrate.

[0127] The concept of the so-called adhesive sheet here may include adhesive tapes, adhesive labels, adhesive films, etc. In addition, the adhesive sheet provided by this specification may be in the form of a roll or a single sheet. Alternatively, it may be an adhesive sheet that is further processed into various shapes.

[0128] Figure 1 and Figure 2 This is a diagram showing a configuration example in a preferred embodiment of the PSA sheet disclosed herein. Figure 1 The PSA sheet 1 shown has a structure in which one surface (first PSA surface) 21A and the other surface (second PSA surface) 21B of a PSA layer 21 without a substrate are protected by release liners 31 and 32 respectively, at least the PSA layer side of which serves as a release surface. Figure 2The adhesive sheet 2 shown has a structure in which one surface (first adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31 whose two sides serve as release surfaces. When it is rolled up, the other surface (second adhesive surface) 21B of the adhesive layer 21 contacts the back side of the release liner 31, thereby forming a structure in which the other side 21B is also protected by the release liner 31.

[0129] A double-sided PSA sheet without a substrate or with a substrate can be used as a single-sided PSA sheet with a substrate by attaching a non-releasable substrate to one of the adhesive surfaces.

[0130] For example Figure 1 , 2 As shown, the adhesive sheet before use (before being pasted on the adherend) can be in the form of an adhesive sheet with a release liner whose adhesive surface is protected by a release liner. As the release liner, there is no particular limitation, for example, a release liner with a release treatment on the surface of a liner substrate such as a resin film or paper, a release liner formed by a low-adhesive material of a fluorine-based polymer (polytetrafluoroethylene, etc.), or a polyolefin-based resin (polyethylene, polypropylene, etc.), etc. can be used. For example, the above-mentioned release treatment can use a release treatment agent such as a silicone-based or long-chain alkyl-based. In some methods, a resin film with a release treatment can be preferably used as the release liner.

[0131] When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, the adhesive constituting the first adhesive surface (first adhesive) and the adhesive constituting the second adhesive surface (second adhesive) are optionally the same composition or different compositions. For example, a substrate-free double-sided adhesive sheet having different compositions of the first adhesive surface and the second adhesive surface can be realized by directly (without the aid of a substrate) laminating two or more adhesive layers of different compositions to form an adhesive layer having a multilayer structure.

[0132] <Base Material>

[0133] In the adhesive sheet with substrate of single-sided adhesive type or double-sided adhesive type, as the substrate supporting the adhesive layer, various sheet substrates such as resin film, paper, cloth, rubber sheet, foam sheet, metal foil, and their composite can be used. The above-mentioned substrate can be a single layer, or a laminate of the same type or different types of substrates. It should be noted that in this specification, a single layer refers to a layer composed of the same composition, including a form in which a plurality of layers composed of the same composition are laminated.

[0134] In a preferred embodiment, a substrate (resin film substrate) with a resin sheet as the main component can be used. As the resin constituting the substrate, for example, low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolymer polypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(methyl) acrylic acid copolymer, ethylene-(methyl) acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, ethylene-hexene copolymer and other polyolefin resins; polyurethane; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyetheretherketone; polyetherimide; polyamides such as aramid and wholly aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; silicone resin; etc. The above resins can be used alone or in combination of two or more to form the entirety or a portion of the substrate (for example, any layer in a substrate having a laminated structure of two or more layers).

[0135] The base material may be mixed with various additives such as fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, colorants (pigments, dyes, etc.) as needed.

[0136] The substrate can be manufactured by any suitable method. For example, it can be manufactured by known methods such as calendaring, casting, inflation extrusion, T-die extrusion, etc. In addition, it can also be manufactured by stretching treatment as needed.

[0137] For the purpose of improving the adhesion with the adhesive layer and the retention of the adhesive layer, for example, the adhesive layer side surface of the substrate may be subjected to physical treatments such as corona discharge treatment, plasma treatment, sand pad processing treatment, ozone exposure treatment, flame exposure treatment, high voltage electric shock exposure treatment, ionizing radiation treatment, etc.; chemical treatments such as acid treatment, alkali treatment, chromic acid treatment, etc.; easy adhesion treatment based on a coating agent (primer); and other well-known or customary surface treatments. In addition, for the purpose of imparting antistatic ability, a conductive vapor deposition layer containing metals, alloys, their oxides, etc. may also be provided on the substrate surface.

[0138] In some preferred embodiments, a primer layer is provided on the adhesive layer side surface of the substrate. In other words, a primer layer can be configured between the substrate and the adhesive layer. As the primer layer forming material, there is no particular limitation, and one or more of urethane (polyisocyanate) resins, polyester resins, acrylic resins, polyamide resins, melamine resins, olefin resins, polystyrene resins, epoxy resins, phenolic resins, isocyanurate resins, polyvinyl acetate resins, etc. can be used. In the case where an adhesive layer such as an acrylic acid system is provided on a resin film substrate by a primer layer, a primer layer of a polyester system, an urethane system, or an acrylic acid system is preferred. In the case where an acrylic adhesive layer is provided on a polyester substrate such as a PET film by a primer layer, a polyester primer layer is particularly preferred. The thickness of the primer layer is not particularly limited, and can generally be in the range of about 0.1 μm to 10 μm (e.g., 0.1 μm to 3 μm, typically 0.1 μm to 1 μm). The primer layer can be formed using a known or commonly used coating machine such as a gravure roll coater and a reverse roll coater.

[0139] The adhesive sheet disclosed herein is a single-sided adhesive sheet having an adhesive layer on one side of a substrate, and a release treatment may be applied to the non-adhesive layer-forming side (back side) of the substrate by a release treatment agent (back side treatment agent). The back side treatment agent that can be used to form the back side treatment layer is not particularly limited, and other known or commonly used treatment agents such as silicone-based back side treatment agents, fluorine-based back side treatment agents, and long-chain alkyl-based back side treatment agents may be used according to the purpose and application.

[0140] The thickness of the substrate is not particularly limited and can be appropriately selected according to the purpose, and can generally be about 2 μm to 800 μm. From the viewpoint of the processability and operability of the adhesive sheet, the thickness of the substrate is suitable to be 5 μm or more, preferably 10 μm or more or 20 μm or more, 30 μm or more, or 40 μm or more. In addition, from the viewpoint of flexibility, the thickness of the substrate is generally suitable to be 300 μm or less, preferably 200 μm or less, 150 μm or less, 125 μm or less, 80 μm or less, or 60 μm or less.

[0141] The total thickness of the adhesive sheet disclosed herein (which may include an adhesive layer and a substrate, but does not include a release liner) is not particularly limited, and a range of about 10 μm to 1200 μm is suitable. Considering adhesion and operability, the total thickness of the adhesive sheet is preferably in the range of about 15 μm to 300 μm, and more preferably in the range of about 20 μm to 200 μm.

[0142] Example

[0143] Some embodiments of the present invention are described below, but the examples shown in the above embodiments are not intended to limit the present invention. It should be noted that "parts" in the following description are based on weight unless otherwise specified.

[0144] The thickeners used in the following examples are as follows.

[0145] Tackifier T1: stabilized rosin ester, product name "HARITACK SE10", manufactured by Harima Chemicals Group, Inc., softening point 78-87° C. Tackifier T1 is obtained by esterifying a mixture containing a compound represented by the above formula (A1), a compound represented by the above formula (A2), and a compound represented by the above formula (A3) with a compound represented by the above formula (B).

[0146] Tackifier T2: polymerized rosin ester, trade name "HARITACK PCJ", manufactured by Harima Chemicals Group, Inc., softening point 118-128° C. Tackifier T2 is obtained by esterifying a mixture containing a compound represented by the above formula (A4), a compound represented by the above formula (A5), and a compound represented by the above formula (A6) with a compound represented by the above formula (C).

[0147] <Example 1>

[0148] (Preparation of Adhesive Composition)

[0149] In a reaction vessel equipped with a Liebig condenser, a nitrogen inlet tube, a thermometer, a dropping funnel, and a stirring device, 100 parts of n-butyl acrylate (BA) as a monomer raw material, 2 parts of acrylic acid (AA), 8 parts of vinyl acetate, 0.1 parts of 2-hydroxyethyl acrylate (HEA), and 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) (10-hour half-life temperature: 65°C) as a polymerization initiator were added to 172 parts of a mixed solvent of toluene and ethyl acetate (toluene:ethyl acetate = 1:1 on a weight basis) as a polymerization solvent. Then, after nitrogen reflux was performed at room temperature for 1 hour, the temperature was raised and solution polymerization was performed at 58°C for 6 hours. Then, the temperature was further raised and the first aging reaction was performed at 65°C for 2 hours, and then the temperature was further raised and the second aging reaction was performed at 72°C for 2 hours. Then, it was naturally cooled to obtain a solution of acrylic polymer A. The weight average molecular weight (Mw) of the acrylic polymer A is 600,000, and the weight average molecular weight / number average molecular weight (dispersity) is 5.0. 4 The content of the following polymers was 20% by weight. The glass transition temperature (Tg) of the acrylic polymer A based on the composition of the above-mentioned monomer raw materials was -49°C.

[0150] A mixture solution is obtained by adding 20 parts of thickener T1 relative to 100 parts of acrylic polymer A to the solution of the acrylic polymer A. A solvent-free solid mixture is obtained by recovering the solvent component from the solution using a desolventizing process. Two parts of an isocyanate crosslinking agent (trimethylolpropane / toluene diisocyanate trimer adduct, manufactured by Tosoh Corporation, trade name "Coronate L", solid content concentration 75% by weight) are added to the solid mixture, and melt mixing is performed using a twin-screw extruder at a temperature of about 100°C. The molten resin is ejected from the coating section of the twin-screw extruder to form a sheet-like resin layer. The appearance state of the resin layer just after formation is observed and the gel fraction is measured.

[0151] The resin layer was aged at about 40° C. for 72 hours to obtain an adhesive layer with a thickness of about 50 μm. The adhesive layer was used as the adhesive sheet of Example 1. That is, the adhesive sheet of Example 1 was a double-sided adhesive sheet without a substrate composed of an adhesive layer.

[0152] <Examples 2 to 5 and 7 to 10>

[0153] A PSA sheet of this example was obtained in the same manner as in Example 1 except that tackifier T1 and / or tackifier T2 were added to the solution of the acrylic polymer A in amounts shown in Table 1 based on 100 parts of the acrylic polymer A.

[0154] <Example 6>

[0155] A PSA sheet of this example was obtained in the same manner as in the preparation of the PSA sheet of Example 1, except that no tackifier was added to the solution of the acrylic polymer A.

[0156] <Evaluation>

[0157] The adhesive composition of each example was heated at about 100°C, and the appearance of the resin layer just after melt extrusion (i.e., when the resin layer was formed) was visually observed to confirm the presence or absence of gelled products. In addition, the gel fraction (initial gel fraction) of the resin layer was measured. Furthermore, the gel fraction (gel fraction after aging) of the adhesive layer after heating the above-mentioned resin layer at about 40°C for 72 hours to mature it (i.e., when the adhesive layer was formed) was measured. Table 1 shows the results obtained. In addition, the case where melt extrusion can be performed well is ○, and the case where it is not good is ×, and they are shown in the corresponding columns of Table 1. It should be noted that the gel fraction is measured using the following method.

[0158] (Determination of gel fraction)

[0159] Collect about 0.1g (weight: W1[mg]) of sample from the resin layer or adhesive layer of the measurement object, wrap it into a waist bag with a porous membrane made of tetrafluoroethylene resin with an average pore size of 0.2μm (weight: W2[mg]), and tie the mouth with a kite string (weight: W3[mg]) to obtain a package. Put the package into a 50mL threaded tube and fill the threaded tube with ethyl acetate (one threaded tube is used for each package). After leaving it at room temperature (typically 23°C) for 7 days, take out the package from the threaded tube and dry it at 130°C for 2 hours. Then measure the weight of the package (W4[mg]). In addition, substitute the values ​​of W1 to W4 into the following formula to calculate the gel fraction of the resin layer or adhesive layer.

[0160] Gel fraction [%] = [(W4-W2-W3) / W1] × 100

[0161] As the tetrafluoroethylene resin porous membrane, a tetrafluoroethylene resin porous membrane manufactured by Nitto Denko Corporation (trade name: "NITOFLON (registered trademark) NTF1122") was used.

[0162] [Table 1]

[0163] Table 1

[0164]

[0165] *Content relative to 100 parts of base polymer

[0166] As shown in Table 1, the initial gel fraction of the adhesive compositions of Examples 1 to 5, 8, and 10 immediately after the resin layer was formed was 0%, and no gel was observed in the resin layer. In contrast, gel was observed in the resin layer of the adhesive compositions of Examples 6, 7, and 9. In addition, the adhesive compositions of Examples 1 to 5 were able to perform melt extrusion well.

[0167] In addition, the adhesive compositions of Examples 1 to 5, 8, and 10 had an increased gel fraction after aging, resulting in an adhesive layer showing improved adhesive properties. In particular, the adhesive compositions of Examples 1 to 5 had an increased gel fraction after aging, resulting in an adhesive layer showing further improved adhesive properties.

[0168] Although the specific examples of the present invention have been described in detail above, these are merely examples and do not limit the claims. The technology described in the claims includes various modifications and changes made to the specific examples described above.

[0169] Description of Reference Numerals

[0170] 1, 2 Adhesive sheet

[0171] 21 Adhesive layer

[0172] 21A First bonding surface

[0173] 21B Second adhesive surface

[0174] 31, 32 Release liner

Claims

1. A hot melt adhesive composition, which is a solvent-free hot melt adhesive composition, comprising: A base polymer, wherein the hot melt adhesive composition comprises, as the base polymer, an acrylic polymer obtained by polymerizing an alkyl (meth)acrylate having an alkyl group having 4 to 12 carbon atoms at the end of the ester at a ratio of 50% by weight or more; an isocyanate crosslinking agent, wherein the content of the isocyanate crosslinking agent is 0.5 parts by weight or more and 8 parts by weight or less relative to 100 parts by weight of the base polymer; and a tackifier T which is the reaction product of compound X and compound Y, The compound X is at least one selected from the group consisting of the following formulae (A1) to (A6), The compound Y is at least one selected from the group consisting of the following formulas (B) and (C), The content of the tackifier T is 20 parts by weight or more and 40 parts by weight or less relative to 100 parts by weight of the base polymer.

2. The hot melt adhesive composition according to claim 1, in, The compound X comprises: the compound represented by the formula (A1), the compound represented by the formula (A2) and the compound represented by the formula (A3), The compound Y is the compound represented by the formula (B).

3. The hot melt adhesive composition according to claim 1, in, The compound X comprises: a compound represented by the formula (A4), a compound represented by the formula (A5), and a compound represented by the formula (A6), The compound Y is the compound represented by the formula (C).

4. The hot melt adhesive composition according to any one of claims 1 to 3, in, The dispersion degree (Mw / Mn) of the acrylic polymer is 3.0 or more and 9.0 or less. 5 . An adhesive sheet comprising an adhesive layer formed from the hot-melt adhesive composition according to claim 1 .

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