Adhesive composition and adhesive processed product

Abstract

To provide an adhesive composition capable of forming an adhesive layer that is highly transparent and has sufficient adhesiveness even as a thin film.SOLUTION: The adhesive composition contains: a (meth)acrylic resin (A) in an amount from 47 pts.mass to 99 pts.mass inclusive; a (co)polymer (B) different from the (meth)acrylic resin (A) in an amount from 0.5 pt.mass to 50 pts.mass inclusive; and a cross-linking agent (C) in an amount from 0.5 pt.mass to 3 pts.mass; where the total content of the (meth)acrylic resin (A), the (co)polymer (B) and the cross-linking agent (C) is 100 pts.mass. The (meth)acrylic resin (A) satisfies specific requirements (A-1) and (A-2), and the (co)polymer (B) satisfies all of specific requirements (B-1) to (B-5).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition and an adhesive processed product. [Background technology]

[0002] Pressure-sensitive adhesives (also called pressure-sensitive adhesives) are easy to use and have adhesive properties to various substrates such as plastics, paper, metals, and glass. Therefore, they are widely used as adhesive layers in adhesive-treated products such as tapes, labels, sheets, and double-sided tapes. The compositions (adhesive compositions) used in the pressure-sensitive adhesives are generally those containing acrylic resins or styrene resins (such as styrene-based block copolymers) as the base polymer.

[0003] In particular, adhesive compositions using acrylic resin as a base polymer are known to have excellent transparency and excellent adhesion to polar adherends such as paper, metal, and glass.

[0004] On the other hand, as electronic devices and the like become thinner, there is a growing demand for thinner double-sided tapes for bonding internal components, etc. Therefore, it is desirable for pressure-sensitive adhesive compositions to have sufficient adhesiveness and adhesion even when formed into a thin pressure-sensitive adhesive layer.

[0005] In response to the above demands, a method has been proposed in which a tackifier resin such as a rosin-based resin, a terpene-based resin, or a petroleum-based resin is added to an acrylic pressure-sensitive adhesive composition to further enhance the adhesiveness of the pressure-sensitive adhesive composition. For example, Patent Document 1 describes that adding a tackifier resin that has low compatibility with (meth)acrylic polymers, such as a rosin-based resin, to an acrylic pressure-sensitive adhesive composition can enhance adhesive strength at both room temperature and high temperature. Patent Document 1 also describes that the tackifier resin is added so that the haze value of the pressure-sensitive adhesive composition when formed into a film is 15 to 95%. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 16882 / 1982 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 describes that the addition of a tackifier resin such as the rosin-based resin can further increase the adhesiveness of the pressure-sensitive adhesive composition. However, as also described in Patent Document 1, the addition of the tackifier resin reduces the transparency of the pressure-sensitive adhesive composition.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide an adhesive composition that has sufficient adhesiveness even in a thin film and can provide an adhesive layer with high transparency, and an adhesive processed product having an adhesive layer obtained from the adhesive composition. [Means for solving the problem]

[0009] That is, the present invention provides the following pressure-sensitive adhesive composition. A pressure-sensitive adhesive composition comprising 47 to 99 parts by mass of a (meth)acrylic resin (A), 0.5 to 50 parts by mass of a (co)polymer (B) different from the (meth)acrylic resin (A), and 0.5 to 3 parts by mass of a crosslinking agent (C) (wherein the total content of the (meth)acrylic resin (A), the (co)polymer (B), and the crosslinking agent (C) is 100 parts by mass), wherein the (meth)acrylic resin (A) satisfies the following requirements (A-1) and (A-2), and the (co)polymer (B) satisfies all of the following requirements (B-1) to (B-5): (A-1) Contains a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and a structural unit derived from a (meth)acrylate containing a hydroxyl group. (A-2) The glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) is in the range of -80°C or higher and 0°C or lower. (B-1) The (co)polymer (B) contains structural units derived from isopropenyltoluene in an amount of 20 mol % or more and 99 mol % or less based on the total amount of structural units of the (co)polymer (B). (B-2) The (co)polymer (B) contains structural units derived from indene in an amount of 1 mol % to 30 mol % based on the total amount of all structural units in the (co)polymer (B). (B-3) The softening point measured in accordance with JIS K2207 is in the range of 110°C or higher and 160°C or lower. (B-4) The glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) is in the range of 60°C or higher and 100°C or lower. (B-5) The number average molecular weight (Mn) is in the range of 800 or more and 1500 or less, the z average molecular weight (Mz) is in the range of 2000 or more and 3500 or less, and the polydispersity (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is in the range of 1.5 or more and 1.8 or less, as measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0010] The present invention also provides the following adhesive processed products. An adhesive processed product has an adhesive layer obtained from the above adhesive composition, and is a tape, a label, a sheet or a double-sided tape. [Effects of the Invention]

[0011] The adhesive composition of the present invention can provide an adhesive layer that has sufficient adhesiveness even in a thin film and is highly transparent. Furthermore, adhesive processed products having an adhesive layer obtained from the adhesive composition can be used for various purposes. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graph showing the relationship between the total light transmittance of the adhesive products of Examples 1 and 2 and Comparative Examples 1 to 7 and the adhesive strength of the adhesive layer of the adhesive products. DETAILED DESCRIPTION OF THE INVENTION

[0013] One embodiment of the present invention relates to an adhesive composition containing a (meth)acrylic resin (A) that satisfies specific requirements, a (co)polymer (B) that satisfies specific requirements, and a crosslinking agent (C). In this specification, (meth)acrylic means "acrylic, methacrylic, or both," (meth)acrylate means "acrylate, methacrylate, or both," and (co)polymer means "homopolymer, copolymer, or both."

[0014] [(Meth)acrylic resin (A)] The (meth)acrylic resin (A) is a (co)polymer of an acrylic monomer or a methacrylic monomer.

[0015] The (meth)acrylic resin (A) satisfies the following requirements (A-1) and (A-2). (A-1) Contains a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and a structural unit derived from a (meth)acrylate containing a hydroxyl group. (A-2) The glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) is in the range of -80°C or higher and 0°C or lower.

[0016] (Regarding requirement (A-1)) The requirement (A-1) is a requirement for enhancing the adhesiveness of the adhesive composition according to this embodiment.

[0017] Specifically, when the (meth)acrylic resin (A) contains a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, the glass transition temperature (Tg) of the (meth)acrylic resin (A) becomes 0°C or lower, and the adhesiveness of the adhesive composition is increased.

[0018] From the above viewpoint, the (meth)acrylate having an alkyl group having from 1 to 12 carbon atoms is preferably a (meth)acrylate having an alkyl group having from 1 to 10 carbon atoms, and more preferably a (meth)acrylate having an alkyl group having from 2 to 8 carbon atoms. The alkyl group may be linear or branched.

[0019] Examples of the (meth)acrylate having an alkyl group having 1 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, and lauryl (meth)acrylate.

[0020] The amount of structural units derived from the (meth)acrylate having an alkyl group having 1 to 12 carbon atoms relative to the total amount of structural units in the (meth)acrylic resin (A) is preferably 50 mol % to 99 mol %, more preferably 55 mol % to 95 mol %, and even more preferably 60 mol % to 90 mol %.

[0021] Furthermore, when the (meth)acrylic resin (A) contains a structural unit derived from a (meth)acrylate containing a hydroxyl group, the number of crosslinking points by the crosslinking agent (C) increases, which increases the crosslinking density of the pressure-sensitive adhesive composition and makes it easier to achieve a high molecular weight. With such a pressure-sensitive adhesive composition, the entanglement between polymer molecules becomes strong, and the adhesiveness during compression bonding is less likely to decrease.

[0022] The (meth)acrylate containing a hydroxyl group may have only one hydroxyl group in its molecule, or may have two or more hydroxyl groups. Examples of the (meth)acrylate containing a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and N-methylol (meth)acrylamide. Among these, from the above viewpoint, the (meth)acrylate containing a hydroxyl group is preferably hydroxyethyl (meth)acrylate.

[0023] The content of the structural units derived from the (meth)acrylate containing a hydroxyl group relative to the total amount of structural units in the (meth)acrylic resin (A) is preferably from 0.1 mol % to 5 mol %, more preferably from 0.2 mol % to 3 mol %, and even more preferably from 0.3 mol % to 2 mol %.

[0024] The (meth)acrylic resin (A) may further contain structural units derived from a monomer (or oligomer) polymerizable with the (meth)acrylate having an alkyl group having 1 to 12 carbon atoms or the (meth)acrylate containing a hydroxyl group, as long as the purpose and effects of this embodiment are not impaired. Examples of such monomers include monomers (or oligomers thereof) capable of forming a crosslinked structure upon reaction with the crosslinking agent (C), and vinyl-based monomers (or oligomers thereof). Examples of monomers capable of forming a crosslinked structure include (meth)acrylic acid and (meth)acrylamide. On the other hand, examples of vinyl-based monomers include styrene and vinyl acetate.

[0025] (Regarding requirement (A-2)) Requirement (A-2) is a requirement for enabling the adhesive composition according to this embodiment to exhibit its adhesiveness suitably over a wider temperature range.

[0026] Specifically, when the (meth)acrylic resin (A) is a copolymer having a glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) in the range of -80°C to 0°C, the adhesive composition formed into a thin adhesive layer can exhibit adhesiveness over a wide temperature range. From the above viewpoint, the (meth)acrylic resin (A) preferably has a glass transition temperature (Tg) in the range of -70°C to -5°C, more preferably in the range of -60°C to -10°C.

[0027] The glass transition temperature (Tg) of the (meth)acrylic resin (A) can be adjusted by the type and ratio of the (meth)acrylate having an alkyl group with 1 to 12 carbon atoms or the (meth)acrylate containing a hydroxyl group, which are used when polymerizing the (meth)acrylic resin (A).

[0028] In the present embodiment, the glass transition temperature (Tg) of the (meth)acrylic resin (A) can be calculated from a theoretical value obtained by the following FOX formula. 1 / Tg=W1 / Tg1+W2 / Tg2++Wn / Tgn (In the formula, Tg is the glass transition temperature (K) of the acrylic resin (A), W1, W2, ..., Wn are the weight fractions of each monomer, and Tg1, Tg2, ..., Tgn are the glass transition temperatures of the homopolymers of each monomer.) The glass transition temperature of the homopolymer used in the above calculation can be a value given in the literature.

[0029] (synthesis method) The (meth)acrylic resin (A) satisfying the above requirements (A-1) and (A-2) can be obtained by synthesizing the monomers (or oligomers) that constitute the structural units by a known polymerization method. The polymerization method is not particularly limited as long as it is a radical polymerization method, including bulk polymerization, solution polymerization, and suspension polymerization. Among these, solution polymerization is preferred because it allows for easy control of the glass transition temperature (Tg) and other properties of the (meth)acrylic resin (A).

[0030] A polymerization initiator may be used during polymerization. Examples of the polymerization initiator include dicumyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, 1,1-bis(t-butylperoxy)cyclohexane, α,α'-azobisisobutyronitrile, acetyl peroxide, t-butyl peroxypivalate, t-butyl hydroperoxide, cumene hydroperoxide, t-hexyl peroxypivalate, 2,2'-azobis-(2,4-dimethylvaleronitrile), lauryl peroxide, t-butyl peroxyneohexanoate, di-t-butyl peroxide, azodicyclohexylcarbonitrile, α,α-dimethyl azodiisobutyrate, succinic acid peroxide, dicumene peroxide, and dichlorobenzoyl peroxide.

[0031] Examples of the solvent used in the solution polymerization include ethyl acetate, butyl acetate, benzene, toluene, xylene, cyclohexane, and methyl ethyl ketone.

[0032] [(Co)polymer (B)] The (co)polymer (B) is a (co)polymer different from the (meth)acrylic resin (A) and satisfies all of the following requirements (B-1) to (B-5).

[0033] (B-1) The (co)polymer (B) contains structural units derived from isopropenyltoluene in an amount of 20 mol % or more and 99 mol % or less based on the total amount of structural units of the (co)polymer (B). (B-2) The (co)polymer (B) contains structural units derived from indene in an amount of 1 mol % to 30 mol % based on the total amount of all structural units in the (co)polymer (B). (B-3) The softening point measured in accordance with JIS K2207 is in the range of 110°C or higher and 160°C or lower. (B-4) The glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) is in the range of 60°C or higher and 100°C or lower. (B-5) The number average molecular weight (Mn) is in the range of 800 or more and 1500 or less, the z average molecular weight (Mz) is in the range of 2000 or more and 3500 or less, and the polydispersity (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is in the range of 1.5 or more and 1.8 or less, as measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0034] (Regarding requirement (B-1)) The requirement (B-1) is a requirement for increasing the adhesiveness of the adhesive composition of this embodiment without decreasing the transparency.

[0035] Specifically, when the (co)polymer (B) contains structural units derived from isopropenyltoluene (including isotopes of o-isopropenyltoluene, m-isopropenyltoluene, and p-isopropenyltoluene) in an amount of 20 mol% to 99 mol% based on the total amount of its structural units, the solubility parameter (SP value) of the (co)polymer (B) becomes close to the SP value (8.6 to 9.1) of the (meth)acrylic resin (A). Therefore, it is thought that the (meth)acrylic resin (A) and the (co)polymer (B) become more compatible with each other, and the (co)polymer (B) becomes more easily finely dispersed in the (meth)acrylic resin (A).

[0036] The content of structural units derived from isopropenyl toluene relative to the total amount of structural units of the (co)polymer (B) is preferably 40 mol% or more and 98.5 mol% or less, more preferably 50 mol% or more and 98 mol% or less, and even more preferably 60 mol% or more and 97 mol% or less.

[0037] (Regarding requirement (B-2) The requirement (B-2) is a requirement for improving the transparency and adhesiveness of the adhesive composition of this embodiment.

[0038] Specifically, when the (co)polymer (B) contains 1 mol % or more and 30 mol % or less of structural units derived from indene relative to the total amount of its structural units, it is considered that the transparency of the adhesive composition becomes good and further the adhesiveness becomes good due to compatibility reasons.

[0039] The content of structural units derived from indene relative to the total amount of structural units of the (co)polymer (B) is preferably 1.2 mol% or more and 25 mol% or less, more preferably 1.5 mol% or more and 20 mol% or less, and even more preferably 2.0 mol% or more and 15 mol% or less.

[0040] (Regarding requirement (B-3)) Requirement (B-3) is a requirement for adjusting the viscosity of the pressure-sensitive adhesive composition of the present embodiment to a desired range.

[0041] Specifically, when the softening point of the (co)polymer (B), measured in accordance with JIS K2207, is in the range of 110°C or higher and 160°C or lower, the viscosity of the pressure-sensitive adhesive composition can be easily adjusted to an appropriate range. In other words, the pressure-sensitive adhesive composition can be easily applied to a substrate. From the above viewpoints, the softening point of the (co)polymer (B) is preferably 115°C or higher and 150°C or lower, more preferably 120°C or higher and 145°C or lower, and even more preferably 125°C or higher and 140°C or lower.

[0042] The softening point of the (co)polymer (B) can be adjusted by the type of copolymerizable monomer, molecular weight, molecular weight distribution, and the like.

[0043] (Regarding requirement (B-4)) Requirement (B-4) is a requirement for adjusting both the transparency and adhesiveness within suitable ranges while increasing the heat resistance of the adhesive composition of this embodiment.

[0044] Specifically, when the glass transition temperature (Tg) of the (co)polymer (B) measured by a differential scanning calorimeter (DSC) is 60°C or higher, the heat resistance of the pressure-sensitive adhesive composition is further improved. Furthermore, when the glass transition temperature (Tg) of the (co)polymer (B) is 100°C or lower, both the transparency and adhesiveness of the pressure-sensitive adhesive composition tend to fall within suitable ranges. From the above viewpoints, the glass transition temperature (Tg) of the (co)polymer (B) is preferably 62°C or higher and 95°C or lower, more preferably 64°C or higher and 90°C or lower, and even more preferably 66°C or higher and 85°C or lower.

[0045] The glass transition temperature (Tg) of the (co)polymer (B) can be adjusted by the type of copolymerizable monomer, the molecular weight, the molecular weight distribution, and the like.

[0046] In the present invention, the glass transition temperature (Tg) of the (co)polymer (B) can be calculated from the theoretical value obtained by the above-mentioned FOX formula.

[0047] (Regarding requirement (B-5)) Requirement (B-5) is a requirement for increasing the adhesiveness of the adhesive composition according to this embodiment without decreasing the transparency.

[0048] Specifically, the (co)polymer (B) has a polystyrene-equivalent number-average molecular weight (Mn) of 800 to 1500, a z-average molecular weight (Mz) of 2000 to 3500, and a dispersity (Mw / Mn), which is the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), of 1.5 to 1.8, as measured by gel permeation chromatography (GPC). When the number-average molecular weight (Mn) is within this range, the adhesiveness is less likely to decrease. Furthermore, when the z-average molecular weight (Mz) is within this range, transparency is maintained. Furthermore, when the dispersity (Mw / Mn) is within this range, the adhesiveness is improved.

[0049] The number average molecular weight (Mn) of the (co)polymer (B) is preferably 900 or more and 1,400 or less, more preferably 950 or more and 1,300 or less, and even more preferably 1,000 or more and 1,200 or less.

[0050] The z-average molecular weight (Mz) of the (co)polymer (B) is preferably 2,200 or more and 3,200 or less, and more preferably 2,500 or more and 3,000 or less.

[0051] Furthermore, the dispersity (Mw / Mn) of the (co)polymer (B), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.55 or more and 1.75 or less, more preferably 1.6 or more and 1.7 or less.

[0052] The number average molecular weight (Mn), z average molecular weight (Mz), and dispersity (Mw / Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) of the (co)polymer (B), can be adjusted to the above ranges by selecting the type of monomer to be copolymerized or by performing distillation under reduced pressure.

[0053] (For other monomers) The (co)polymer (B) may contain a structural unit other than the isopropenyl toluene-derived structural unit and the indene-derived structural unit, as long as the purpose and effects of the present invention are not impaired. When a structural unit derived from a compound other than isopropenyl toluene or indene is contained, the softening point and glass transition temperature (Tg) of the (co)polymer (B) can be easily adjusted.

[0054] Examples of the monomer other than those mentioned above include vinyl aromatic compounds and unsaturated aliphatic hydrocarbon compounds.

[0055] Examples of the vinyl aromatic compound include styrene-based monomers such as substituted styrene having a substituent on the aromatic ring and substituted α-methylstyrene having a substituent on the aromatic ring. Examples of the substituent on the aromatic ring include an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and a halogen atom. The vinyl aromatic compound may have one or more of the above substituents on the aromatic ring.

[0056] Specific examples of the substituted styrenes include methylstyrene (excluding α-methylstyrene), ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene.

[0057] On the other hand, examples of unsaturated fatty hydrocarbon compounds include C4 fractions and C5 fractions, which are by-produced during petroleum refining and cracking and contain unsaturated aliphatic hydrocarbon compounds with 4 or 5 carbon atoms as their main components.

[0058] The C4 fraction and C5 fraction have a boiling point range of −15 to +45° C. under normal pressure. The C4 fraction and C5 fraction contain polymerizable monomers such as 1-butene, isobutene, 2-butene, 1,3-butadiene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-pentene, isoprene, 1,3-pentadiene, and cyclopentadiene.

[0059] The C4 fraction and C5 fraction may be petroleum fractions including light oil fractions including gas fractions produced as a by-product during atmospheric distillation (topping) of crude oil or the like in refineries, similar light oil fractions produced as a by-product in petroleum cracking or reforming processes, and light oil fractions including gas obtained in petroleum naphtha cracking or the like in petrochemical plants, and may be used as is, or may be used as the desired fraction after distillation, extraction, or other processing.

[0060] (synthesis method) The (co)polymer (B) can be obtained by synthesizing isopropenyltoluene, indene, and other monomers by a known polymerization method. The polymerization is preferably cationic polymerization, and more preferably carried out in the presence of a Friedel-Crafts catalyst.

[0061] The Friedel-Crafts catalyst is not particularly limited as long as it is a known Friedel-Crafts catalyst, including aluminum chloride, aluminum bromide, dichloromonoethylaluminum, titanium tetrachloride, tin tetrachloride, boron trifluoride, and various complexes such as boron trifluoride ether complexes and phenol complexes. Of these, boron trifluoride phenol complexes are preferred. The amount of the Friedel-Crafts catalyst used can be 0.05 to 5 parts by mass, preferably 0.1 to 2 parts by mass, per 100 parts by mass of the total raw material monomers.

[0062] From the viewpoints of removing the heat of reaction generated during the polymerization reaction, suppressing the viscosity of the reaction solution, and adjusting the molecular weight, it is preferable to carry out the polymerization reaction using a solvent so that the concentration of the raw material monomer is about 10 to 60 mass%. Examples of the solvent include aliphatic hydrocarbons such as pentane, hexane, heptane, and octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and mesitylene. These solvents may be used alone or in combination.

[0063] The polymerization can be carried out in a reactor by polymerizing the raw material monomers in the solvent in the presence of the catalyst. The polymerization can be carried out in one stage, but is preferably carried out in multiple stages. The polymerization temperature varies depending on the raw material composition, the target molecular weight range, etc., but is preferably -50 to +50°C. The reaction time is preferably 10 minutes to 10 hours. After the polymerization is completed, the catalyst is decomposed using a basic aqueous solution or a basic compound containing an alcohol such as methanol, followed by washing with water, and unreacted raw materials and solvent are removed by stripping or distillation to obtain the desired (co)polymer (B).

[0064] The removal of the unreacted raw materials and solvents can be carried out by, for example, concentration procedures that utilize the difference in vapor pressure between substances, including atmospheric distillation, reduced-pressure distillation, and steam distillation, as well as concentration methods that utilize the difference in molecular size or affinity for packing materials such as silica gel, including open columns and flash columns. Of these, reduced-pressure distillation is preferred from the viewpoints of suppressing thermal decomposition and increasing concentration efficiency. The range of reduced pressure is not particularly limited. On the other hand, from the viewpoint of suppressing thermal decomposition of the (co)polymer (B), the heating temperature is preferably 250°C or less, more preferably 230°C or less, and even more preferably 210°C or less.

[0065] [Crosslinker (C)] The crosslinking agent (C) is not particularly limited as long as it can crosslink the (meth)acrylic resin (A) and further increase the adhesiveness of the adhesive composition according to this embodiment.

[0066] Examples of the crosslinking agent (C) include epoxy compounds including sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, and resorcinol diglycidyl ether; isocyanate compounds including tetramethylene diisocyanate, hexamethylene diisocyanate, a toluene diisocyanate triadduct of trimethylolpropane, and polyisocyanates; trimethylol Examples of the crosslinking agent (C) include aziridine compounds such as trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), N,N'-toluene-2,4-bis(1-aziridinecarboxamide), and trimethylolpropane-tri-β-(2-methylaziridine)propionate; and melamine compounds such as hexamethoxymethylolmelamine. The crosslinking agent (C) may be used singly or in combination.

[0067] The crosslinking agent (C) is preferably blended to such an extent that the number of functional groups in the crosslinking agent (C) that can bond with the (meth)acrylic resin (A) (when the crosslinking agent (C) contains a blocked isocyanate, this number includes the number of functional groups generated by dissociation of the blocking agent) does not exceed the number of functional groups possessed by the (meth)acrylic resin (A). However, when new functional groups are generated by the crosslinking reaction or when the crosslinking reaction proceeds slowly, the amount blended may exceed this value.

[0068] [Content ratio] The pressure-sensitive adhesive composition according to this embodiment contains 47 to 99 parts by mass of a (meth)acrylic resin (A), 0.5 to 50 parts by mass of a (co)polymer (B), and 0.5 to 3 parts by mass of a crosslinking agent (C), where the total content of the (meth)acrylic resin (A), the (co)polymer (B), and the crosslinking agent (C) is 100 parts by mass.

[0069] When the content of the (meth)acrylic resin (A) is 47 parts by mass or more, a relatively large amount of the (meth)acrylic resin (A) is contained in the pressure-sensitive adhesive composition, and the pressure-sensitive adhesive composition is likely to form a crosslinked structure. As a result, the pressure-sensitive adhesive composition has a high molecular weight, and the adhesiveness is less likely to decrease when the adhesive is bonded. On the other hand, when the content of the (meth)acrylic resin (A) is 99 parts by mass or less, sufficient amounts of the (co)polymer (B) and crosslinking agent (C) are contained in the pressure-sensitive adhesive composition. Therefore, the adhesiveness of the pressure-sensitive adhesive composition is likely to be good. The content of the (meth)acrylic resin (A) is preferably 57.2 parts by mass or more and 94 parts by mass or less, and more preferably 62.5 parts by mass or more and 88.5 parts by mass or less.

[0070] When the content of the (co)polymer (B) is 0.5 parts by mass or more, the adhesiveness of the pressure-sensitive adhesive composition is enhanced. On the other hand, when the content of the (co)polymer (B) is 50 parts by mass or less, the transparency of the pressure-sensitive adhesive composition is enhanced. From the above viewpoints, the content of the (co)polymer (B) is preferably 5 parts by mass or more and 40 parts by mass or less, and more preferably 10 parts by mass or more and 35 parts by mass or less.

[0071] When the content of the crosslinking agent (C) is 0.5 parts by mass or more, the pressure-sensitive adhesive composition is likely to aggregate appropriately, and the pressure-sensitive adhesive composition is unlikely to remain on the surface of the adherend after peeling off. When the content of the crosslinking agent (C) is 3 parts by mass or less, the (meth)acrylic resin (A) and (co)polymer (B) are contained in sufficient amounts, and therefore the adhesiveness is likely to be good. The content of the crosslinking agent (C) is preferably 1 part by mass or more and 2.8 parts by mass or less, and more preferably 1.5 parts by mass or more and 2.5 parts by mass or less.

[0072] It is preferable that the adhesive composition according to this embodiment substantially does not contain a rosin resin or a terpene resin. Rosin resins or terpene resins cause coloring or discoloration of the adhesive composition. Hydrogenated resins obtained by hydrogenating rosin resins or terpene resins are sometimes used in adhesive compositions to suppress the above-mentioned coloring, but these tend to reduce the adhesive holding power. Furthermore, since rosin resins or terpene resins have an acid value, there is a risk that adhesive compositions containing these resins may corrode the metal when applied to the metal.

[0073] The term "substantially free" means that the content of rosin resin or terpene resin relative to the total mass of the pressure-sensitive adhesive composition is 0.1 mass % or less.

[0074] [Manufacturing method] The adhesive composition according to this embodiment can be prepared by mixing the above-mentioned (meth)acrylic resin (A), (co)polymer (B), and crosslinking agent (C) in amounts corresponding to the above-mentioned contents, together with an optionally used solvent.

[0075] Examples of such solvents include ethyl acetate, butyl acetate, benzene, toluene, xylene, cyclohexane, and methyl ethyl ketone.

[0076] [Application] The adhesive composition according to this embodiment can be used in various applications requiring adhesiveness as adhesive processed products such as tapes, labels, sheets, and double-sided tapes.

[0077] The shape of the adhesive processed product is not particularly limited, but may be, for example, a configuration having a substrate and an adhesive layer obtained from the above-mentioned adhesive composition. The substrate may be provided on both sides of the adhesive layer.

[0078] The thickness of the adhesive layer is not particularly limited, but from the viewpoint of imparting the desired adhesiveness to the adhesive processed product and minimizing the impact on the productivity of the adhesive processed product, it is preferably 5 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, and even more preferably 10 μm or more and 30 μm or less. The above-mentioned adhesive composition can fully exhibit adhesiveness even in a thin film. Therefore, for example, even if the thickness of the adhesive layer is 30 μm or less, sufficient adhesive strength can be obtained.

[0079] In addition, the type of substrate is not particularly limited, and may be a resin film or the like, or a metal film or the like. The shape of the substrate is also not particularly limited, and may be flat or have a three-dimensional structure, and is appropriately selected depending on the application. In addition, the transparency is not particularly limited, but as described above, the pressure-sensitive adhesive composition has excellent transparency. Therefore, the pressure-sensitive adhesive processed product can be used for applications requiring transparency, and in this case, it is preferable that the substrate also has excellent transparency.

[0080] For example, when transparency is required for an adhesive product, the total light transmittance of the adhesive product measured in accordance with JIS K 7361 is preferably 87% or more. In such applications, it is preferable to use a transparent PET film or the like as the substrate.

[0081] Furthermore, when the adhesive processed product is attached to the SUS substrate via the adhesive layer, the adhesive strength measured by a 180° peel test is preferably 11 N / 25 mm or more, more preferably 11.5 N / 25 mm or more, and even more preferably 12 N / 25 mm or more.

[0082] The adhesive processed product can be produced by applying the adhesive composition to the surface of a substrate and drying the applied adhesive composition to crosslink each component.

[0083] The coating method is not particularly limited, and may be a known method such as a roll coater method, a reverse roll coater method, a gravure roll method, a bar coater method, a comma coater method, a die coater method, etc. The drying conditions are also not particularly limited, and drying at 80 to 200°C for 10 seconds to 10 minutes is preferred, and drying at 80 to 170°C for 15 seconds to 5 minutes is more preferred. [Example]

[0084] The present invention will be described below using examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0085] [Measurement of physical properties] <Structural unit content> The content (mol %) of the structural units of the (co)polymers (B1) to (B8) was measured under the following conditions: 13 It was determined by analyzing the C-NMR spectrum. Equipment: Bruker Biospin AVANCEIII cryo-500 nuclear magnetic resonance spectrometer Measurement nuclei: 13 C(125MHz) Measurement mode: Single pulse proton broadband decoupling Pulse width: 45° (5.00 μsec) Number of points: 64k Measurement range: 250 ppm (-55 to 195 ppm) Repeat time: 5.5 seconds Number of times accumulated: 128 Measurement solvent: orthodichlorobenzene / benzene-d6 (4 / 1 (volume ratio)) Sample concentration: 60 mg / 0.6 mL Measurement temperature: 120℃ Window function: exponential (BF: 1.0 Hz) Chemical shift reference: δδ signal 29.73 ppm

[0086] <Softening point> The softening points of the (co)polymers (B1) to (B8) were measured by the ring and ball method in accordance with JIS K2207.

[0087] <Glass transition temperature (Tg)> The glass transition temperatures (Tg) of the (meth)acrylic resin (A) and the (co)polymers (B1) to (B8) were determined by sealing these resins in a simple hermetic pan and heating them from -100°C to 200°C at a rate of 10°C / min under a nitrogen stream, and analyzing the DSC curves in accordance with JIS K7121.

[0088] <Number average molecular weight (Mn), z-average molecular weight (Mz), weight average molecular weight (Mw / Mn), and content of compounds with a molecular weight of 400 or less> The number-average molecular weight (Mn), weight-average molecular weight (Mw), z-average molecular weight (Mz), and molecular weight distribution (Mw / Mn) of the (meth)acrylic resin (A) and the (co)polymers (B1) to (B8) were determined by GPC measurement. The measurement was carried out under the following conditions. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) were then determined from a calibration curve using commercially available monodisperse standard polystyrene, and Mw / Mn was calculated. Apparatus: GPC HLC-8320 (Tosoh Corporation) Solvent: tetrahydrofuran Columns: TSKgel G7000 x 1, TSKgel G4000 x 2, TSKgel G2000 x 1 (all manufactured by Tosoh Corporation) Flow rate: 1.0ml / min Sample: 20 mg / mL tetrahydrofuran solution Temperature: 40℃

[0089] [Synthesis of (meth)acrylic resin (A)] The (meth)acrylic resin (A) was synthesized using the following monomers.

[0090] 2-Ethylhexyl acrylate (2EHA) Ethyl acrylate (EA) Vinyl Acetate (VA) Acrylic Acid (AA) Hydroxyethyl acrylate (HEA)

[0091] (Synthesis of (meth)acrylic resin (A1)) A temperature-controllable reactor equipped with a stirrer was charged with 350 parts by weight of ethyl acetate as a polymerization solvent and 40 parts by weight of toluene, purged with nitrogen, and heated. After heating to 75°C, a solution containing 316 parts by weight of 2EHA, 43 parts by weight of EA, 50 parts by weight of VA, 9 parts by weight of AA, 2 parts by weight of HEA, and 2 parts by weight of benzoyl peroxide as a polymerization initiator was continuously added to the reactor and reacted for 5 hours. After 5 hours, the mixture was diluted with 120 parts by weight of toluene to obtain an ethyl acetate / toluene solution containing (meth)acrylic resin (A1) with a solids content of 45%.

[0092] The solvent was evaporated from the resulting solution to give a (meth)acrylic resin (A1). The glass transition temperature (Tg) of the resulting resin was measured and found to be -60°C.

[0093] [Synthesis of (co)polymer (B)] (Co)polymers (B1) to (B8) were prepared as follows. Table 1 shows the composition, softening point, glass transition temperature (Tg), number average molecular weight (Mn), z-average molecular weight (Mz), dispersity (Mw / Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), and solubility parameter. In Table 1, "IPT" stands for isopropenyl toluene, and "IND" stands for indene.

[0094] (Synthesis of (co)polymer (B1)) A mixture of isopropenyltoluene, indene, and dehydrated and purified toluene (total monomer / toluene = 1 / 1 (volume ratio)) and a boron trifluoride phenolate complex (1.7 times the equivalent of phenol) diluted 10 times with dehydrated and purified toluene were continuously fed into the first plate of a 1270 ml autoclave equipped with a stirring blade, and a polymerization reaction was carried out at 5°C. The mass ratio of isopropenyltoluene to indene (isopropenyltoluene / indene) was 75 / 25, the feed rate of the monomer and toluene mixture was 1.0 liter / hour, and the feed rate of the diluted catalyst was 68 milliliters / hour.

[0095] The reaction mixture was transferred to the second autoclave and the polymerization reaction continued at 5°C. When the total residence time in the first and second autoclaves reached 2 hours, the reaction mixture was continuously discharged from the autoclave. When the residence time reached three times the normal residence time, 1 liter of reaction mixture was collected to terminate the polymerization. After the polymerization was completed, a 1N NaOH aqueous solution was added to the collected reaction mixture to deash the catalyst residue. The resulting reaction mixture was washed five times with a large amount of water, and the solvent and unreacted monomer were removed under reduced pressure using an evaporator to obtain (co)polymer (B1), an isopropenyltoluene-indene copolymer. The (co)polymer (B1) had a content of structural units derived from isopropenyl toluene of 98 mol%, a softening point of 134°C, a glass transition temperature (Tg) of 73°C, a number average molecular weight (Mn) of 1090, a z-average molecular weight (Mz) of 2700, and a dispersity (Mw / Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 1.63.

[0096] (Synthesis of (co)polymer (B2)) The isopropenyltoluene-indene copolymer (B2) was obtained by the same method as for (B1), except that the mass ratio of isopropenyltoluene to indene (isopropenyltoluene / indene) was 70 / 30 and the diluted catalyst feed rate was 78 mL / h. (B2) had a content of structural units derived from isopropenyltoluene of 95 mol%, a softening point of 137°C, a glass transition temperature (Tg) of 74°C, a number-average molecular weight (Mn) of 1130, a z-average molecular weight (Mz) of 2760, and a polydispersity (Mw / Mn) of 1.63.

[0097] (Synthesis of (co)polymer (B3)) The isopropenyltoluene-indene copolymer (B3) was obtained by the same method as for (B1), except that the mass ratio of isopropenyltoluene to indene (isopropenyltoluene / indene) was 60 / 40 and the feed rate of the diluted catalyst was 108 mL / h. (B3) had a content of structural units derived from isopropenyltoluene of 63 mol%, a softening point of 146°C, a glass transition temperature (Tg) of 80°C, a number-average molecular weight (Mn) of 1090, a z-average molecular weight (Mz) of 3060, and a polydispersity (Mw / Mn), which is the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), of 1.78.

[0098] (Synthesis of (co)polymer (B4)) (Co)polymer (B4), a homopolymer of isopropenyltoluene, was obtained in the same manner as in the synthesis of (co)polymer (B1), except that indene was not fed, the polymerization temperature was 25°C, and the feed rate of the diluted catalyst was 30 mL / h. (Co)polymer (B4) had a content of structural units derived from isopropenyltoluene of 100 mol%, a softening point of 102°C, a glass transition temperature (Tg) of 47°C, a number-average molecular weight (Mn) of 770, a z-average molecular weight (Mz) of 1330, and a polydispersity (Mw / Mn), which is the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), of 1.31.

[0099] (Synthesis of polymer (B5)) (Co)polymer (B5), a homopolymer of isopropenyl toluene, was obtained in the same manner as in the synthesis of (co)polymer (B4), except that the polymerization temperature was 5°C and the feed rate of the diluted catalyst was 105 mL / h. (Co)polymer (B5) had a content of structural units derived from isopropenyl toluene of 100 mol%, a softening point of 100°C, a glass transition temperature (Tg) of 45°C, a number average molecular weight (Mn) of 760, a z-average molecular weight (Mz) of 1700, and a polydispersity (Mw / Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 1.50.

[0100] (Synthesis of (co)polymer (B6)) (Co)polymer (B6), a homopolymer of isopropenyl toluene, was obtained in the same manner as in the synthesis of (co)polymer (B4), except that the polymerization temperature was 5°C and the feed rate of the diluted catalyst was 82 mL / h. (Co)polymer (B6) had a content of structural units derived from isopropenyl toluene of 100 mol%, a softening point of 118°C, a glass transition temperature (Tg) of 62°C, a number average molecular weight (Mn) of 980, a z-average molecular weight (Mz) of 2910, and a polydispersity (Mw / Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 1.80.

[0101] (Synthesis of (co)polymer (B7)) (Co)polymer (B7), a homopolymer of isopropenyl toluene, was obtained in the same manner as in the synthesis of (co)polymer (B4), except that the polymerization temperature was 5°C and the feed rate of the diluted catalyst was 68 mL / h. (Co)polymer (B7) had a content of structural units derived from isopropenyl toluene of 100 mol%, a softening point of 133°C, a glass transition temperature (Tg) of 72°C, a number average molecular weight (Mn) of 1110, a z-average molecular weight (Mz) of 3510, and a polydispersity (Mw / Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 1.89.

[0102] (Synthesis of (co)polymer (B8)) (Co)polymer (B8), a homopolymer of isopropenyl toluene, was obtained in the same manner as in the synthesis of (co)polymer (B4), except that the polymerization temperature was 5°C and the feed rate of the diluted catalyst was 53 mL / h. (Co)polymer (B8) had a content of structural units derived from isopropenyl toluene of 100 mol%, a softening point of 145°C, a glass transition temperature (Tg) of 78°C, a number average molecular weight (Mn) of 1520, a z-average molecular weight (Mz) of 4740, and a polydispersity (Mw / Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of 1.99.

[0103] [Table 1]

[0104] [Crosslinker (C)] As the crosslinking agent (C1), Takenate D-101E (an isocyanate compound, "Takenate" is a registered trademark of Mitsui Chemicals, Inc.) manufactured by Mitsui Chemicals, Inc. was used.

[0105] [Production and evaluation of adhesive processed products] An ethyl acetate / toluene solution containing the (meth)acrylic resin (A1), any one of the (co)polymers (B1) to (B8), and a crosslinking agent (C) were mixed at room temperature so that the ratio of the (meth)acrylic resin (A1), any one of the (co)polymers (B1) to (B8), and the crosslinking agent (C) in the solution was the mass ratio shown in Table 2, thereby obtaining an ethyl acetate / toluene solution of an adhesive composition.

[0106] The resulting ethyl acetate / toluene solution of the adhesive composition was applied to a release paper so that the film thickness after drying would be 10-50 μm, and after drying at 100°C for 10 minutes, a 25 μm PET film was pressed onto the coated surface to produce an adhesive sheet. The sheet was left at 50°C for 3 days to allow the adhesive composition to be fully crosslinked.

[0107] <Measurement of total light transmittance> The release paper of the adhesive sheet, whose adhesive layer had a thickness of 50 μm, was peeled off to expose the adhesive layer, and a 25 μm-thick PET film was pressed onto the exposed adhesive layer to obtain a test piece. The test piece had a configuration of PET film / adhesive layer / PET film = 25 μm / 50 μm / 25 μm. The total light transmittance of the test piece was measured according to JIS K7361.

[0108] <Adhesive strength measurement> The pressure-sensitive adhesive sheet, with an adhesive layer thickness of 30 μm, was cut into a width of 25 mm and a length of 150 mm to prepare a test piece. The release paper was peeled off from the test piece to expose the adhesive layer, and the exposed adhesive layer was brought into contact with a stainless steel plate (SUS) in an atmosphere of 23°C, and the test piece was pressure-bonded by rolling a 2 kg rubber roll back and forth twice. After leaving it for 20 minutes, the 180° peel strength was measured at a speed of 300 mm / min according to JIS Z0237.

[0109] The formulation of the adhesive composition constituting the produced adhesive processed products, as well as the total light transmittance and adhesive strength of the adhesive layer of the adhesive processed products, are shown in Table 2. Furthermore, the relationship between the total light transmittance and adhesive strength for Examples 1 and 2 and Comparative Examples 1 to 7 is shown in Figure 1.

[0110] [Table 2]

[0111] As shown in Table 2 and Figure 1, the pressure-sensitive adhesive compositions (Examples 1 and 2) containing a (co)polymer (B) satisfying all of the requirements (B-1) to (B-5) had significantly higher adhesive strength and superior transparency than the pressure-sensitive adhesive compositions (Comparative Examples 2 to 7) containing a (co)polymer (B) that did not satisfy any of the requirements (B-1) to (B-5). Furthermore, the pressure-sensitive adhesive composition (Comparative Example 1) that did not contain a (co)polymer (B) had a very low adhesive strength. [Industrial Applicability]

[0112] According to the present invention, a pressure-sensitive adhesive composition having both high transparency and high adhesiveness is provided. The present invention can be suitably implemented in various applications in which transparency of the pressure-sensitive adhesive composition is particularly required.

Claims

1. 47 parts by mass or more and 99 parts by mass or less of a (meth)acrylic resin (A); 0.5 parts by mass or more and 50 parts by mass or less of a (co)polymer (B) different from the (meth)acrylic resin (A); 0.5 parts by mass or more and 3 parts by mass or less of a crosslinking agent (C); (wherein the total content of the (meth)acrylic resin (A), the (co)polymer (B), and the crosslinking agent (C) is 100 parts by mass), The (meth)acrylic resin (A) satisfies the following requirements (A-1) and (A-2), and The (co)polymer (B) satisfies all of the following requirements (B-1) to (B-5): Adhesive composition. (A-1) Contains a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and a structural unit derived from a (meth)acrylate containing a hydroxyl group. (A-2) The glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) is in the range of −80° C. or higher and 0° C. or lower. (B-1) The (co)polymer (B) contains structural units derived from isopropenyltoluene in an amount of 60 mol % to 99 mol % based on the total amount of structural units. (B-2) The (co)polymer (B) contains structural units derived from indene in an amount of 1 mol % to 15 mol % based on the total amount of all structural units in the (co)polymer (B). (B-3) The softening point measured in accordance with JIS K2207 is in the range of 110°C or higher and 160°C or lower. (B-4) The glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) is in the range of 66° C. or higher and 85° C. or lower. (B-5) The number average molecular weight (Mn) is in the range of 800 or more and 1500 or less, the z average molecular weight (Mz) is in the range of 2000 or more and 3500 or less, and the polydispersity (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is in the range of 1.5 or more and 1.8 or less, as measured by gel permeation chromatography (GPC) in terms of polystyrene.

2. A pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition according to claim 1, a tape, label, sheet or double-sided tape; Adhesive processed products.

3. The thickness of the adhesive layer is 5 μm or more and 50 μm or less. The adhesive processed product according to claim 2.

4. The total light transmittance measured in accordance with JIS K7361 is 87% or more. The adhesive processed product according to claim 2 or 3.

5. When attached to an SUS substrate via the adhesive layer, the adhesive strength measured by a 180° peel test is 11 N / 25 mm or more. The adhesive processed product according to any one of claims 2 to 4.

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