TWI853045B - Adhesive composition and adhesive processed product - Google Patents

Abstract

The object of the present invention is to provide an adhesive composition capable of obtaining a film-like adhesive layer having sufficient adhesiveness and high transparency. The present invention for achieving the above object is related to an adhesive composition, which contains 47 to 99 parts by weight of a (meth) acrylic resin (A) satisfying (A-1) and (A-2), 0.5 to 50 parts by weight of all (co) polymers (B) satisfying (B-1) to (B-5), and 0.5 to 3 parts by weight of a crosslinking agent (C). (A-1) Contains structural units derived from (meth) acrylic esters having an alkyl group of C1 to 12 or less and (meth) acrylic esters containing hydroxyl groups (A-2) Tg is -80°C to 0°C (B-1) Contains structural units derived from isopropenyltoluene at a content of 20 mol% or more. (B-2) Softening point is 90-130°C (B-3) Tg is 40-80°C (B-4) The content of compounds with a molecular weight of 400 or less is 10% by mass or less (B-5) Mn is 750-1000, Mz is 1200-2000, and Mw/Mn is 1.5 or less

Description

Adhesive composition and adhesive processed product

The present invention relates to an adhesive composition and an adhesive processed product.

Adhesives (also called pressure-sensitive adhesives) are easy to use and have good adhesion to various objects such as plastics, paper, metal, and glass. Therefore, they are used as adhesive layers in adhesive products such as tapes, labels, sheets, and double-sided tapes. As compositions (adhesive compositions) used as the above-mentioned adhesives, compositions using acrylic resins or styrene resins (styrene-based block copolymers, etc.) as base polymers are generally used.

In particular, it is known that an adhesive composition using an acrylic resin as a base polymer has excellent transparency and excellent adhesion to polar adherends such as paper, metal, and glass.

On the other hand, with the thinning of electronic devices, double-sided tapes for bonding internal components are also required to be thinner. Therefore, it is expected that the adhesive composition has better adhesion and adhesion when the adhesive layer is made thinner.

In response to the above requirements, a method has been proposed in which a tackifier resin such as a rosin resin, a terpene resin, and a petroleum resin is added to an acrylic adhesive composition to further improve the tackiness of the adhesive composition. For example, Patent Document 1 states that by adding a tackifier resin such as a rosin resin that has low compatibility with a (meth)acrylic polymer to an acrylic adhesive composition, adhesion at both room temperature and high temperature can be exerted. Patent Document 1 states that the tackifier resin is added in such a way that the haze value of the adhesive composition when it is film-formed becomes 15 to 95%. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Application No. 64-16882

[Problems to be solved by the invention] Patent document 1 states that by adding a tackifier resin such as the above-mentioned rosin-based resin, the tackiness of the adhesive composition can be further improved. However, as also stated in patent document 1, if the above-mentioned tackifier resin is added, the transparency of the adhesive composition is reduced.

The present invention is made in view of the above circumstances, and its purpose is to provide an adhesive composition capable of obtaining a thin film adhesive layer having sufficient adhesiveness and high transparency, and an adhesive processed product obtained by processing the adhesive composition. [Means for Solving the Problem]

The inventors of the present invention have conducted intensive research and found that the above-mentioned problem can be solved by the following structure. That is, the present invention is related to the following [1] to [6]. [1] An adhesive composition comprising 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), and 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 set to 100 parts by mass), the (meth)acrylic resin (A) satisfies the following (A-1) and (A-2), and the (co)polymer (B) satisfies all of the following (B-1) to (B-5). (A-1) Contains structural units derived from (meth)acrylates having an alkyl group having 1 to 12 carbon atoms and structural units derived from (meth)acrylates 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 to 0°C. (B-1) Contains structural units derived from isopropenyltoluene in an amount of 20 mol% or more relative to the total amount of its structural units. (B-2) The softening point measured in accordance with JIS K2207 is in the range of 90°C to 130°C. (B-3) The glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) is in the range of 40°C to 80°C. (B-4) The content of compounds having a molecular weight of 400 or less in terms of polystyrene measured by gel permeation chromatography (GPC) is 10% by mass or less. (B-5) The number average molecular weight (Mn) in terms of polystyrene measured by gel permeation chromatography (GPC) is in the range of 750 to 1000, the z average molecular weight (Mz) is in the range of 1200 to 2000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e. the dispersion (Mw/Mn), is 1.5 or less. [2] The adhesive composition as described in [1], wherein the (co)polymer (B) satisfies the following (B-6). (B-6) Contains 1 mol% or more and 80 mol% or less of structural units derived from monomers selected from the group consisting of styrene, α-methylstyrene, indene, vinyltoluene and unsaturated aliphatic hydrocarbon compounds having 4 or 5 carbon atoms, relative to the total amount of its structural units. [3] An adhesive processed product, which is a tape, a label, a sheet or a double-sided tape, and is obtained by processing the adhesive composition described in [1] or [2]. [4] The adhesive processed product described in [3], having an adhesive layer having a thickness of 5 μm or more and 50 μm or less. [5] The adhesive processed product described in [3] or [4], wherein the total light transmittance measured in accordance with JIS K7361 is 87% or more. [6] An adhesive product as described in any one of [3] to [5], wherein SUS is used as the adherend and the adhesive force measured by a 180° peel test is 9N/25mm or more. [Effect of the invention]

According to the present invention, there are provided an adhesive composition capable of obtaining a film-like adhesive layer having sufficient adhesiveness and high transparency, and an adhesive processed product obtained by processing the adhesive composition.

One embodiment of the present invention relates to an adhesive composition containing a (meth)acrylic acid resin (A), a (co)polymer (B), and a crosslinking agent (C). In this specification, (meth)acrylic acid refers to "acrylic acid or methacrylic acid", (meth)acrylate refers to "acrylate or methacrylate", and (co)polymer refers to "a single polymer or a copolymer".

[(Meth)acrylic resin (A)] (Meth)acrylic resin (A) is a (co)polymer of acrylic monomers or methacrylic monomers.

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 or more and 12 or less 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 more and 0°C or less.

(Regarding requirement (A-1)) Requirement (A-1) is a requirement for improving the adhesiveness of the adhesive composition of this embodiment.

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 higher, and the adhesiveness of the adhesive composition is further improved.

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

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.

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

In addition, if the (meth)acrylic resin (A) contains a structural unit derived from a (meth)acrylate containing a hydroxyl group, the crosslinking points generated by the crosslinking agent (C) increase, so the crosslinking density of the adhesive composition increases, making it easy to increase the molecular weight. Such an adhesive composition is unlikely to follow the surface of the adherend even when it is press-bonded, and the adhesiveness is unlikely to decrease during press-bonding.

Examples of the hydroxyl group-containing (meth)acrylate include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and N-hydroxymethyl (meth)acrylamide, etc. Among these, from the above viewpoint, the hydroxyl group-containing (meth)acrylate is preferably hydroxyethyl (meth)acrylate.

In the (meth)acrylic resin (A), the content of the structural unit derived from the hydroxyl group-containing (meth)acrylate relative to the total amount of its structural units is preferably 0.1 mol % to 5 mol %, more preferably 0.2 mol % to 3 mol %, and even more preferably 0.3 mol % to 2 mol %.

Furthermore, the (meth)acrylic resin (A) may be a copolymer having a structural unit derived from a monomer (or oligomer) having a functional group capable of forming a crosslink, which is different from the above-mentioned (meth)acrylic acid ester having an alkyl group having 1 to 12 carbon atoms or the above-mentioned (meth)acrylic acid ester containing a hydroxyl group. Examples of the above-mentioned monomer having a functional group capable of forming a crosslink include (meth)acrylic acid and (meth)acrylamide.

In addition, the (meth)acrylic resin (A) may be a copolymer having a structural unit derived from a vinyl monomer other than the above, as required. Examples of such vinyl monomers include styrene and vinyl acetate.

(Regarding requirement (A-2)) Requirement (A-2) is a requirement for the adhesive composition of this embodiment to properly exhibit its adhesiveness in a wider temperature range.

Specifically, if the (meth)acrylic resin (A) is a copolymer having a glass transition temperature (Tg) in the range of -80°C to 0°C as measured by a differential scanning calorimeter (DSC), the adhesive composition formed into a film-shaped adhesive layer can exhibit adhesiveness in a wide temperature range. From the above viewpoints, the glass transition temperature (Tg) of the (meth)acrylic resin (A) is preferably in the range of -70°C to -5°C, and more preferably in the range of -60°C to -10°C.

The glass transition temperature (Tg) of the (meth)acrylic resin (A) can be adjusted to the above range by changing the monomers to be polymerized and their ratios.

In the present invention, the glass transition temperature (Tg) of the (meth) acrylic resin (A) can be calculated from the theoretically calculated value obtained by the following FOX formula. 1/Tg=W1/Tg1+W2/Tg2+･･･+Wn/Tgn (wherein, Tg is the glass transition temperature (K) of the acrylic resin (A), W1, W2, ･･･, and Wn are the weight fractions of each monomer, and Tg1, Tg2, ･･･, and Tgn are the glass transition temperatures of the homopolymers of each monomer) The glass transition temperature of the homopolymer used for the above calculation can use the value described in the literature.

(Synthesis method) (Meth)acrylic resin (A) can be synthesized by a known polymerization method using a monomer (or oligomer) of a material that becomes each of the above-mentioned structural units. The above-mentioned polymerization method is not particularly limited as long as it is a free radical polymerization method including a block polymerization method, a solution polymerization method, and a suspension polymerization method. Among these, the solution polymerization method is preferred because it is easy to control the glass transition temperature (Tg) and other properties of the (meth)acrylic resin (A) and it is easy to synthesize a (meth)acrylic resin (A) having desired properties.

A polymerization initiator may also be used during the polymerization. Examples of the polymerization initiator include dicumyl peroxide, benzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, 1,1-bis(tert-butylperoxy)cyclohexane, α,α'-azobisisobutyronitrile, acetyl peroxide, tert-butyl peroxypivalate, tert-butyl hydroperoxide, isopropyl hydroperoxide, tert-hexyl peroxypivalate, 2,2'-azobis-(2,4-dimethylvaleronitrile), lauryl peroxide, tert-butyl peroxyneohexanoate, di-tert-butyl peroxide, azobiscyclohexyl nitrile, α,α-azobisisobutyric acid dimethyl ester, succinic acid peroxide, diisopropylbenzene peroxide, and dichloroperoxybenzoyl.

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

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

(B-1) Contains 20 mol% or more of structural units derived from isopropenyltoluene relative to the total amount of its structural units. (B-2) The softening point measured in accordance with JIS K2207 is within the range of 90°C or more and 130°C or less. (B-3) The glass transition temperature (Tg) measured by differential scanning calorimetry (DSC) is within the range of 40°C or more and 80°C or less. (B-4) The content of compounds having a molecular weight of 400 or less in terms of polystyrene measured by gel permeation chromatography (GPC) is 10% by mass or less. (B-5) The polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is in the range of 750 to 1000, the z-average molecular weight (Mz) is in the range of 1200 to 2000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., the dispersion (Mw/Mn), is 1.5 or less.

(Regarding requirement (B-1)) Requirement (B-1) is a requirement for improving the adhesiveness of the adhesive composition of this embodiment without reducing the transparency.

Although the reason is not certain, it is considered that the reason is that when the (co)polymer (B) contains 20 mol% or more of structural units derived from isopropenyltoluene (including isotopes of o-isopropenyltoluene, m-isopropenyltoluene, and p-isopropenyltoluene) relative to the total amount of its structural units, the (meth)acrylic resin (A) and the (co)polymer (B) are easily compatible, and the (co)polymer (B) is easily finely dispersed in the (meth)acrylic resin (A). The solubility parameter (SP value) of the (co)polymer (B) containing structural units derived from isopropenyltoluene becomes 8.7 to 8.9, and the SP value difference with the SP value (8.6 to 9.1) of the (meth)acrylic resin becomes small, so it is estimated that it is easily compatible with the (meth)acrylic resin (A).

In the (co)polymer (B), the content of the structural unit derived from isopropenyltoluene relative to the total amount of its structural units is preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably 85 mol% or more. The upper limit of the content of the structural unit derived from isopropenyltoluene is not particularly limited, and can be set to 100 mol% or less, preferably 98 mol% or less, more preferably 96 mol% or less, and more preferably less than 95 mol%.

(Regarding requirement (B-2)) Requirement (B-2) is a requirement for making the viscosity of the adhesive composition of this embodiment to be excellent in coating properties on a substrate.

Specifically, if the softening point of the (co)polymer (B) measured by differential scanning calorimetry (DSC) is in the range of 90°C to 130°C, the adhesive composition containing the solvent has a suitable viscosity, so that the adhesive composition can be more easily applied to the substrate. From the above viewpoints, the softening point of the (co)polymer (B) is preferably in the range of 95°C to 125°C, more preferably in the range of 100°C to 120°C, and further preferably in the range of 105°C to 115°C.

The softening point of the (co)polymer (B) can be adjusted to the above range by adjusting the type, molecular weight and molecular weight distribution of the monomers to be copolymerized.

(Regarding requirement (B-3)) Requirement (B-3) is a requirement for improving the heat resistance of the adhesive composition of this embodiment while adjusting both transparency and adhesiveness to an appropriate range.

Specifically, if the glass transition temperature (Tg) of the (co)polymer (B) measured in accordance with JIS K2207 is 40°C or higher, the heat resistance of the adhesive composition is further improved. In addition, if the glass transition temperature (Tg) of the (co)polymer (B) is 80°C or lower, the transparency and adhesion of the adhesive composition are both likely to be within an appropriate range. From the above viewpoints, the glass transition temperature (Tg) of the (co)polymer (B) is preferably in the range of 45°C or higher and 78°C or lower, more preferably in the range of 50°C or higher and 75°C or lower, and further preferably in the range of 55°C or higher and 70°C or lower.

The glass transition temperature (Tg) of the (co)polymer (B) can be adjusted to the above range by adjusting the type, molecular weight, and molecular weight distribution of the monomers to be copolymerized.

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

(Regarding requirement (B-4)) Requirement (B-4) is a requirement for further improving the adhesiveness and heat resistance of the adhesive composition of this embodiment.

Specifically, if the content of compounds having a molecular weight of 400 or less in terms of polystyrene measured by gel permeation chromatography (GPC) in the (co)polymer (B) is 10% by mass or less, the content of extremely low molecular weight components is reduced, thereby being able to further improve heat resistance while maintaining the adhesiveness of the adhesive composition. From the above viewpoint, the content of compounds having a molecular weight of 400 or less in the (co)polymer (B) is preferably 8% by mass or less, and more preferably 6% by mass or less. The lower limit of the content of compounds having a molecular weight of 400 or less is not particularly limited, and can be set to 0% by mass (measurement limit) or more.

The content of compounds having a molecular weight of 400 or less can be determined by calculating the area of the region between the curve for compounds having a molecular weight of 400 or less and the base line by integrating the integrated molecular weight distribution curve measured by polystyrene conversion using the GPC method (gel permeation chromatography) method using tetrahydrofuran as a solvent.

The content of the compound having a molecular weight of 400 or less in the (co)polymer (B) can be adjusted to the above range by distilling the (co)polymer (B) under reduced pressure at a heating temperature of 250° C. or less.

(Regarding requirement (B-5)) Requirement (B-5) is a requirement for improving the adhesiveness of the adhesive composition of this embodiment without reducing the transparency.

Specifically, the number average molecular weight (Mn) of the (co)polymer (B) measured by gel permeation chromatography (GPC) in terms of polystyrene is within the range of 750 to 1000, the z average molecular weight (Mz) is within the range of 1200 to 2000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., the dispersion (Mw/Mn), is 1.5 or less. The molecular weight of the (co)polymer (B) satisfying the requirement (B-5) is relatively small, and thus it is estimated that the wettability of the adhesive composition to the substrate is improved, and the adhesiveness of the adhesive composition is improved. In addition, the molecular weight variation of the (co)polymer (B) satisfying the requirement (B-5) is small, and thus it is estimated that it is easily compatible with the (meth)acrylic resin (A), and an adhesive composition with higher transparency can be obtained.

From the above viewpoints, the number average molecular weight (Mn) of the (co)polymer (B) is preferably 770 or more and 980 or less, more preferably 790 or more and 950 or less, and further preferably 800 or more and 900 or less.

From the above viewpoints, the z average molecular weight (Mz) of the (co)polymer (B) is preferably 1300 or more and 1900 or less, and more preferably 1400 or more and 1800 or less.

In addition, from the above viewpoint, the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the (co)polymer (B), i.e., the dispersion (Mw/Mn), is preferably 1.45 or less, and more preferably 1.4 or less. The lower limit of the Mw/Mn is not particularly limited and can be set to 1 or more.

The number average molecular weight (Mn), z average molecular weight (Mz), and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., the dispersity (Mw/Mn), of the (co)polymer (B) can be adjusted to the above ranges by adjusting the type of monomers to be copolymerized and performing reduced pressure distillation.

(Regarding other requirements) The (co)polymer (B) is preferably a (co)polymer further satisfying the following (B-6).

(B-6) containing 1 mol% or more and 80 mol% or less of a structural unit derived from a monomer selected from the group consisting of styrene, α-methylstyrene, indene, vinyltoluene and an unsaturated aliphatic hydrocarbon compound having 4 or 5 carbon atoms.

The structural units derived from these monomers improve the compatibility of the (co)polymer (B) with the (meth)acrylic resin (A), thereby making it possible to easily adjust the molecular weight distribution (Mw/Mn) of the (co)polymer (B) to the above range while maintaining the transparency of the adhesive composition.

Examples of the unsaturated aliphatic hydrocarbon compounds having 4 or 5 carbon atoms include _C4 distillate fractions and _C5 distillate fractions containing, as main components, unsaturated aliphatic hydrocarbon compounds having 4 or 5 carbon atoms additionally generated during the purification and decomposition of petroleum.

The _C4 distillate and the _C5 distillate are distillate components having a boiling point range of generally -15 to +45° C. at normal pressure. The _C4 distillate and the _C5 distillate 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.

The _C4 distillate and _C5 distillate may be used directly as petroleum distillate components including light oil distillate components including gaseous distillate components generated by atmospheric distillation (direct distillation) of crude oil in oil refineries, light oil distillate components generated by cracking or reforming of petroleum, and light oil distillate components including gaseous distillate components obtained by decomposing petroleum naphtha in petrochemical plants, or may be used after distillation, extraction or other treatment to obtain desired distillate components.

From the above viewpoints, in the (co)polymer (B), the content of structural units derived from styrene, α-methylstyrene, indene, vinyltoluene or unsaturated aliphatic hydrocarbon compounds having 4 or 5 carbon atoms, relative to the total amount of its structural units, is preferably from 2 mol % to 60 mol %, more preferably from 4 mol % to 40 mol %, and even more preferably from 5 mol % to 20 mol %.

(For other monomers) The (co)polymer (B) may also be a copolymer having structural units derived from other monomers other than the above-mentioned isopropenyltoluene, etc., as required. By using a copolymer containing structural units derived from the above-mentioned other monomers, it is easy to adjust the softening point and glass transition temperature (Tg) of the (co)polymer (B).

Examples of the other monomers include vinyl aromatic compounds and unsaturated aliphatic hydrocarbon compounds other than those having 4 or 5 carbon atoms.

Examples of the vinyl aromatic compound include styrene monomers including substituted styrenes having substituents on the aromatic ring and substituted α-methylstyrene having substituents on the aromatic ring. Examples of the substituents on the aromatic ring include alkyl groups having 1 to 20 carbon atoms, alkoxy groups having 1 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, and halogen atoms. The vinyl aromatic compound may have one substituent on the aromatic ring, or may have two or more substituents on the aromatic ring.

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

(Synthesis method) The (co)polymer (B) can be synthesized by a known polymerization method using isopropenyltoluene and any other copolymerizable monomers. The above polymerization is preferably cationic polymerization, and more preferably carried out in the presence of a Friedel process catalyst.

The Friedel process catalyst is not particularly limited as long as it is a known Friedel process catalyst including various complexes such as aluminum chloride, aluminum bromide, monoethylaluminum dichloride, titanium tetrachloride, tin tetrachloride, boron trifluoride, and ether complexes or phenol complexes of boron trifluoride. Among them, phenol complexes of boron trifluoride are preferred. The amount of the Friedel process catalyst used can be set to 0.05 mass parts or more and 5 mass parts or less, preferably 0.1 mass parts or more and 2 mass parts or less, relative to 100 mass parts of the total raw material monomers.

From the viewpoints of removing the reaction heat generated during the polymerization reaction, suppressing the viscosity of the reaction liquid, and adjusting the molecular weight, the polymerization reaction is preferably carried out using a solvent in a manner such that the concentration of the raw material monomer is about 10 to 60 mass %. Examples of the above-mentioned 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.

The above-mentioned polymerization can be carried out in a reactor, in the presence of the above-mentioned catalyst, and in the above-mentioned solvent by subjecting the raw material monomers to a polymerization reaction. The above-mentioned polymerization can also be carried out in one stage, but is preferably carried out in multiple stages. The polymerization temperature at this time varies depending on the raw material composition, the target molecular weight range, etc., and is preferably -50 to +50°C. In addition, the reaction time at this time is preferably 10 minutes to 10 hours. After the polymerization is completed, an alkaline compound including an alkaline aqueous solution or an alcohol such as methanol is used to decompose the catalyst, and then the catalyst is washed with water, and the unreacted raw materials and solvent are removed by stripping and distillation, so that the target (co)polymer (B) can be obtained.

The removal of the unreacted raw materials and solvents can be performed, for example, by operations including atmospheric distillation, reduced pressure distillation, water vapor distillation, etc., which utilize the vapor pressure difference of each substance for concentration; and methods including atmospheric pressure columns and rapid columns, etc., which utilize the affinity for fillers such as silica gel and the difference in molecular size for concentration. Among these, reduced pressure distillation is preferred from the perspective of thermal decomposition inhibition and concentration efficiency. The range of the above-mentioned pressure reduction is not particularly limited. On the other hand, from the perspective of inhibiting the thermal decomposition of the (co)polymer (B), the heating temperature is preferably below 250°C, more preferably below 230°C, and further preferably below 210°C.

[Crosslinking agent (C)] The crosslinking agent (C) crosslinks the (meth)acrylic resin (A), thereby improving the adhesiveness of the adhesive composition of this embodiment.

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, trihydroxymethylpropane toluene diisocyanate triadduct, and polyisocyanate; trihydroxymethylpropane-tri-isocyanate ... Aziridine compounds such as β-propidium aziridine, tetrahydroxymethylmethane-tri-β-propidium aziridine, N,N'-diphenylmethane-4,4'-bis(1-aziridine carboxyamide), N,N'-hexamethylene-1,6-bis(1-aziridine carboxyamide), N,N'-toluene-2,4-bis(1-aziridine carboxyamide), trihydroxymethylpropane-tri-β-(2-methylaziridine) propionic acid; and melamine compounds including hexamethoxyhydroxymethylmelamine, etc. The crosslinking agent (C) may be used alone or in combination of two or more.

The crosslinking agent (C) is preferably formulated such that the number of functional groups capable of bonding with the (meth)acrylic resin (A) (including the number of functional groups generated by the dissociation of the blocking agent when the crosslinking agent (C) contains blocked isocyanate) is not more than the number of functional groups possessed by the (meth)acrylic resin (A). However, a larger amount may be formulated when new functional groups are generated by the crosslinking reaction or when the crosslinking reaction proceeds slowly.

[Content ratio] When the total content of the (meth)acrylic resin (A), the (co)polymer (B) and the crosslinking agent (C) is set to 100 parts by mass, the adhesive composition of this embodiment contains 47 parts by mass or more and 99 parts by mass or less of the (meth)acrylic resin (A), 0.5 parts by mass or more and 50 parts by mass or less of the (co)polymer (B), and 0.5 parts by mass or more and 3 parts by mass or less of the crosslinking agent (C).

If the content of the (meth)acrylic resin (A) is 47 parts by mass or more, a larger amount of the (meth)acrylic resin (A) is contained in the adhesive composition, and the crosslinking density of the adhesive composition becomes higher, and the molecular weight is further increased, so that it is difficult for the adhesive composition to follow the surface of the adherend during compression and cause a decrease in adhesiveness. If the content of the (meth)acrylic resin (A) is 99 parts by mass or less, a larger amount of the (co)polymer (B) and the crosslinking agent (C) are contained in the adhesive composition, so that the adhesiveness of the adhesive composition can be further improved. From the above viewpoints, 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.

If the content of the (co)polymer (B) is 0.5 parts by mass or more, the adhesiveness of the adhesive composition can be further improved. If the content of the (co)polymer (B) is 50 parts by mass or less, the transparency of the adhesive composition can be further improved. 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.

If the content of the crosslinking agent (C) is 0.5 parts by mass or more, the adhesive composition is easy to aggregate, and it is difficult for the adhesive composition to remain on the surface of the adherend after compression, i.e., the so-called paste residue. If the content of the crosslinking agent (C) is 3 parts by mass or less, a larger amount of (meth) acrylic resin (A) will be contained in the adhesive composition, and the crosslinking density of the adhesive composition will become higher, and the molecular weight will be further increased, so it is difficult for the adhesive composition to follow the surface of the adherend during compression, resulting in a decrease in adhesion. From the above viewpoint, 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.

Furthermore, the adhesive composition of the present embodiment preferably does not substantially contain rosin resin or terpene resin. Rosin resin or terpene resin may cause coloring or discoloration of the adhesive composition. Furthermore, in order to suppress the above-mentioned coloring, hydrogenated resins obtained by hydrogenating rosin resin or terpene resin are sometimes used in the adhesive composition, but these tend to reduce the adhesive retention. Furthermore, rosin resin or terpene resin has an acid value, so if the adhesive composition containing these is attached to metal, there is a risk of corroding the metal.

Furthermore, "substantially free of" means that the content of the rosin resin or the terpene resin is 0.1 mass % or less relative to the total mass of the adhesive composition.

[Manufacturing method] The adhesive composition of this embodiment can be prepared by mixing the above-mentioned (meth) acrylic resin (A), (co) polymer (B) and crosslinking agent (C) in a formulation amount corresponding to the above-mentioned content together with an optional solvent.

Examples of the solvent include ethyl acetate, butyl acetate, benzene, toluene, xylene, cyclohexane, and methyl ethyl ketone.

[Application] The adhesive composition of this embodiment can be used in various applications requiring adhesive properties in the form of adhesive processed products such as tapes, labels, sheets, and double-sided tapes.

Specifically, the adhesive processed product has a base layer and an adhesive layer, and the adhesive layer includes the adhesive composition of this embodiment.

The thickness of the adhesive layer is not particularly limited, but from the perspective of imparting the desired adhesiveness to the adhesive processed product and reducing the impact on the productivity of the adhesive processed product, it is preferably greater than 5 μm and less than 50 μm, more preferably greater than 5 μm and less than 40 μm, and further preferably greater than 10 μm and less than 30 μm.

The substrate is not particularly limited, but is preferably a transparent resin film when the adhesive processed product is used for applications requiring transparency.

The adhesive product has an adhesive layer containing the adhesive composition, and thus can have high transparency. For example, when the substrate is a transparent PET film, the adhesive product can have a total light transmittance of 87% or more as measured in accordance with JIS K7361.

The adhesive product has an adhesive layer containing the adhesive composition, and thus can have high adhesiveness. For example, the adhesive product can be an adhesive product in which SUS is used as a bonded body and the adhesive force measured by a 180° peel test is 9N/25mm or more.

The adhesive processed product can be produced by applying the adhesive composition to the surface of a substrate, drying the applied adhesive composition and cross-linking the components.

The coating method is not particularly limited, and any known method such as roller coating, reverse roller coating, gravure roller coating, rod coating, notch wheel coating, and die coating can be used. The drying conditions are also not particularly limited, and preferably, drying is performed at 80 to 200°C for 10 seconds to 10 minutes, and more preferably, drying is performed at 80 to 170°C for 15 seconds to 5 minutes. [Example]

The present invention is described below using examples and comparative examples, but the present invention is not limited to the following examples.

[Measurement of Physical Properties] <Content of Structural Unit> The content ratio (mol %) of the structural unit of (co)polymer (B1) to (co)polymer (B3) was determined by analyzing the ¹³ C-NMR spectrum measured under the following conditions. Device: AVANCEIII cryo-500 NMR device manufactured by Bruker Daltonics Measurement nucleus: ¹³ C (125 MHz) Measurement mode: Single pulse proton broadband decoupling Pulse width: 45° (5.00 μsec) Point number: 64K Measurement range: 250 ppm (-55 to 195 ppm) Repeat time: 5.5 sec Accumulated times: 128 times Measurement solvent: o-dichlorobenzene/benzene-d ₆ (4/1 (volume ratio)) Sample concentration: 60 mg/0.6 mL Measurement temperature: 120°C Window function: exponential (BF: 1.0 Hz) Chemical shift reference: δδ signal 29.73 ppm

<Softening point> The softening points of (co)polymers (B1) to (co)polymers (B3) were measured by the cyclotron method in accordance with JIS K2207.

<Glass transition temperature (Tg)> The glass transition temperature (Tg) of the (meth)acrylic resin (A) and the (co)polymers (B1) to (co)polymers (B3) was determined by analyzing the DSC curve according to JIS K7121. The DSC curve was obtained when the resins were sealed in a simple sealed dish and heated from -100°C to 200°C at a rate of 10°C/min under a nitrogen flow.

<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 (meth)acrylic resin (A) and (co)polymers (B1) to (co)polymers (B3) were determined by GPC measurement. The measurement was performed under the following conditions. In addition, the number average molecular weight (Mn), weight average molecular weight (Mw), z average molecular weight (Mz), and Mw/Mn were determined based on the calibration line obtained using commercially available monodisperse standard polystyrene. In addition, the content of compounds with a molecular weight of 400 or less was calculated by integrating the obtained molecular weight distribution. Apparatus: GPC HLC-8320 (manufactured by Tosoh Corporation) Solvent: tetrahydrofuran Column: TSKgel G7000×1, TSKgel G4000×2, TSKgel G2000×1 (all manufactured by Tosoh Corporation) Flow rate: 1.0mL/min Sample: 20mg/mL tetrahydrofuran solution Temperature: 40℃

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

2-Ethylhexyl acrylate (2EHA) Ethyl acrylate (EA) Vinyl acetate (VA) Acrylic acid (AA) Hydroxyethyl acrylate (HEA)

(Synthesis of (meth)acrylic resin (A1)) Into a temperature-adjustable reactor equipped with a stirrer, 350 parts by mass of ethyl acetate and 40 parts by mass of toluene as a polymerization solvent were charged, and the temperature was raised while nitrogen substitution was performed. After the temperature was raised to 75°C, a solution in which 316 parts by mass of 2EHA, 43 parts by mass of EA, 50 parts by mass of VA, 9 parts by mass of AA, 2 parts by mass of HEA, and 2 parts by mass of benzoyl peroxide as a polymerization initiator were continuously added to the reactor and reacted for 5 hours. After 5 hours, the solution was diluted with 120 parts by mass of toluene to obtain an ethyl acetate/toluene solution containing (meth)acrylic resin (A1) with a solid content of 45%.

The glass transition temperature (Tg) of the (meth)acrylic resin (A1) obtained by evaporating the solvent from the obtained solution was measured and found to be -60°C.

[Synthesis of (co)polymer (B)] (Synthesis of (co)polymer (B1), (co)polymer (B4) and (co)polymer (B6)) A mixture of _C5 distillate obtained by thermal decomposition of isopropenyltoluene and petroleum naphtha and toluene purified by dehydration (total monomers/toluene = 1/1 (volume ratio)) and boron trifluoride phenolate complex diluted to 10 times with toluene purified by dehydration (1.7 times phenol equivalent) were continuously supplied to the first section of an autoclave having a true capacity of 1270 mL and equipped with a stirring blade, and a polymerization reaction was carried out at 5°C. The mass ratio of isopropenyltoluene to _C5 distillate (isopropenyltoluene/ _C5 distillate) was set to 90/10, the supply rate of the mixture of monomer and toluene was set to 1.0 L/hour, and the supply rate of the diluted catalyst was set to 105 mL/hour.

The reaction mixture was transferred to the second stage autoclave and the polymerization reaction was continued at 5°C. When the total residence time in the first and second stage autoclaves reached 2 hours, the reaction mixture was continuously discharged from the autoclave, and when the residence time reached 3 times, 1 liter of the reaction mixture was sampled to terminate the polymerization reaction. After the polymerization was completed, a predetermined amount of NaOH aqueous solution was added to the sampled reaction mixture, and the catalyst residue was deashed. Furthermore, the obtained reaction mixture was washed 5 times with a large amount of water, and then the solvent and unreacted monomers were removed by reduced pressure distillation using an evaporator to obtain a copolymer of isopropenyltoluene and _C5 distillation components, namely, a (co)polymer (B4). The (co)polymer (B4) has a content of structural units derived from isopropenyltoluene of 93 mol%, a softening point of 100°C, a glass transition temperature (Tg) of 50°C, a number average molecular weight (Mn) of 700, a z average molecular weight (Mz) of 1500, a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., a dispersion (Mw/Mn) of 1.43, and a content of compounds with a molecular weight of less than 400 is 13%.

The (co)polymer (B4) was placed in a glass container mounted on the top of a thin film distillation apparatus (DN60 type, manufactured by Asahi Seisakusho Co., Ltd.), and then heated to 200°C. Thereafter, the liquid was passed through at 2 ml/min, and concentrated at a rotation speed of 180 rpm and a vacuum degree of 0.02 Pa, and the copolymer of isopropenyltoluene and _C5 distillation components, i.e., the (co)polymer (B1), was recovered in a glass eggplant bottle mounted on the bottom. The (co)polymer (B1) has a content of structural units derived from isopropenyltoluene of 93 mol %, a softening point of 110°C, a glass transition temperature (Tg) of 65°C, a number average molecular weight (Mn) of 850, a z average molecular weight (Mz) of 1600, a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., a dispersion (Mw/Mn) of 1.35, and a content of compounds with a molecular weight of 400 or less of 3%.

In addition, as a post-step of the thin film distillation device, a condenser was installed to condense the low boiling point component to recover the copolymer of isopropenyltoluene and _C5 distillation component, namely (co)polymer (B6). The content of structural units derived from isopropenyltoluene in (co)polymer (B6) was 93 mol%, the softening point was not determined, the glass transition temperature (Tg) was -5°C, the number average molecular weight (Mn) was 380, the z average molecular weight (Mz) was 400, the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), namely the dispersion (Mw/Mn), was 1.03, and the content of compounds with a molecular weight of 400 or less was 62%.

(Synthesis of (co)polymer (B2)) The same method as the synthesis of (co)polymer (B4) was used except that the polymerization temperature in the first and second stages of the autoclave was set to 20°C and the supply rate of the diluted catalyst was set to 50 ml/hour to obtain a copolymer of isopropenyltoluene and _C5 distillate component, i.e., (co)polymer (B2). The content of structural units derived from isopropenyltoluene in (co)polymer (B2) was 97 mol %, the softening point was 102°C, the glass transition temperature (Tg) was 65°C, the number average molecular weight (Mn) was 850, the z average molecular weight (Mz) was 1650, the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., the dispersion (Mw/Mn), was 1.41, and the content of compounds with a molecular weight of 400 or less was 6%.

(Synthesis of (co)polymer (B3)) A single polymer of isopropenyltoluene, i.e., (co)polymer (B3), was obtained by the same method as that for the synthesis of (co)polymer (B4), except that the _C5 distillate component obtained by thermal decomposition of petroleum naphtha was not supplied, the polymerization temperature in the first and second stages of the autoclave was set to 25°C, and the supply amount of the diluted catalyst was set to 30 ml/hour. The (co)polymer (B3) has a content of structural units derived from isopropenyltoluene of 100 mol %, a softening point of 102°C, a glass transition temperature (Tg) of 60°C, a number average molecular weight (Mn) of 770, a z average molecular weight (Mz) of 1400, a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., a dispersion (Mw/Mn) of 1.31, and a content of compounds with a molecular weight of 400 or less of 7%.

(Synthesis of (co)polymer (B5)) A copolymer of isopropenyltoluene and _C5 distillation component, i.e., (co)polymer (B5), was obtained by the same method as the synthesis of (co)polymer (B4), except that the supply amount of the diluted catalyst was set to 90 ml/hour. The content of structural units derived from isopropenyltoluene in (co)polymer (B5) was 93 mol %, the softening point was 110°C, the glass transition temperature (Tg) was 70°C, the number average molecular weight (Mn) was 900, the z average molecular weight (Mz) was 2400, the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., the dispersion (Mw/Mn), was 1.67, and the content of compounds with a molecular weight of 400 or less was 8%.

(Synthesis of (co)polymer (B7)) A single polymer of isopropenyltoluene, i.e., (co)polymer (B7), was obtained by the same method as that for the synthesis of (co)polymer (B4), except that α-methylstyrene and styrene were supplied in a mass ratio (α-methylstyrene/styrene) of 60/40 instead of isopropenyltoluene and the _C5 distillate component obtained by thermal decomposition of petroleum naphtha, the polymerization temperature in the first and second stages of the autoclave was set to 7°C, and the supply amount of the diluted catalyst was set to 120 ml/hour. The (co)polymer (B7) had a content of structural units derived from α-methylstyrene of 55 mol%, a softening point of 97°C, a glass transition temperature (Tg) of 55°C, a number average molecular weight (Mn) of 840, a z average molecular weight (Mz) of 3000, a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., a dispersion (Mw/Mn) of 1.98, and a content of compounds with a molecular weight of less than 400 was 14%.

The compositions, softening points, glass transition temperatures (Tg), number average molecular weights (Mn), z average molecular weights (Mz), the ratio of weight average molecular weights (Mw) to number average molecular weights (Mn), i.e., the dispersion (Mw/Mn), and the content of compounds having a molecular weight of 400 or less of (co)polymers (B1) to (B7) are shown in Table 1. In Table 1, "IPT" represents isopropenyltoluene.

[Table 1] (Co)polymer B1 B2 B3 B4 B5 B6 B7 Composition IPT/C ₅ Distillation Composition IPT/C ₅ Distillation Composition IPT IPT/C ₅ Distillation Composition IPT/C ₅ Distillation Composition IPT/C ₅ Distillation Composition α-Methylstyrene/Styrene IPT:93mol% IPT:97mol% IPT:100mol% IPT:93mol% IPT:93mol% IPT:93mol% α-Methylstyrene: 55 mol% Softening point ℃ 110 102 102 100 110 - 97 Tg ℃ 65 65 60 50 70 -5 55 Mn - 850 850 770 700 900 380 840 Mz - 1600 1650 1400 1500 2400 400 3000 Mw/Mn - 1.35 1.41 1.31 1.43 1.67 1.03 1.98 The proportion of compounds with a molecular weight of 400 or less % 3 6 7 13 8 62 14

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

[Preparation and evaluation of adhesive processed products] The ethyl acetate/toluene solution containing the (meth)acrylic resin (A1), any one of the (co)polymers (B1) to (co)polymers (B3), and the crosslinking agent (C) are mixed at room temperature so that the ratio of the (meth)acrylic resin (A1), any one of the (co)polymers (B1) to (co)polymers (B7), and the crosslinking agent (C) contained in the solution becomes the mass ratio shown in Table 2, thereby obtaining an ethyl acetate/toluene solution of an adhesive composition.

The obtained adhesive composition was coated on release paper in an ethyl acetate/toluene solution so that the film thickness after drying was 10 to 50 μm, and dried at 100°C for 10 minutes, and then a 25 μm PET film was pressed onto the coated surface to prepare an adhesive sheet. The adhesive sheet was left at 50°C for 3 days to allow the adhesive composition to fully crosslink.

<Measurement of total light transmittance> The peeling paper of the adhesive sheet having a film thickness of 50 μm was peeled off to expose the adhesive layer, and a PET film having a thickness of 25 μm was pressed onto the exposed adhesive layer to obtain a test piece. The structure of the test piece was PET film/adhesive layer/PET film = 25/50/25 μm. Thereafter, the total light transmittance of the test piece was measured in accordance with JIS K7361.

<Measurement of Adhesive Strength> The adhesive sheet having an adhesive layer thickness of 15μm or 30μm was cut into pieces with a width of 25mm and a length of 150mm to prepare a test piece. The peeling paper of the test piece was peeled off to expose the adhesive layer, and the exposed adhesive layer was brought into contact with a stainless steel plate (SUS) in an environment of 23°C, and a 2kg rubber roller was moved back and forth twice to press the test piece. After leaving it for 20 minutes, the 180° peel strength was measured at a speed of 300mm/min in accordance with JIS Z0237.

Tables 2 and 3 show the formulation of the adhesive composition constituting the produced adhesive processed products, and the total light transmittance and adhesive force of the adhesive processed products.

[Table 2] Project Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 formula (Meth) acrylic resin A1 67 67 67 78 78 (Co)polymer B1 32 - - 20 - B2 - 32 - - 20 B3 - - 32 - - Crosslinking agent C1 1 1 1 2 2 Reviews Total light transmittance [%] 87.5 87.5 87.5 87.5 87.5 Adhesion (adhesive layer thickness 15μm, adherend: SUS) [N/25mm] 10.8 11.0 9.7 9.3 9.5 Adhesion (adhesive layer thickness 30μm, adherend: SUS) [N/25mm] 13.0 13.0 11.7 11.3 11.0

[Table 3] Project Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Comparison Example 6 Comparison Example 7 Comparative Example 8 Comparative Example 9 formula (Meth) acrylic resin A1 98 67 67 67 67 67 78 78 78 (Co)polymer B4 - 32 - - - 16 20 - - B5 - - 32 - - - - 20 - B6 - - - 32 - 16 - - - B7 - - - - 32 - - - 20 Crosslinking agent C1 2 1 1 1 1 1 2 2 2 Reviews Total light transmittance [%] 87.5 87.5 86.8 87.5 85.7 87.5 87.5 86.9 86.8 Adhesion (adhesive layer thickness 15μm, adherend: SUS) [N/25mm] 4.9 8.5 9.8 4.8 8.2 6.7 7.0 7.8 6.2 Adhesion (adhesive layer thickness 30μm, adherend: SUS) [N/25mm] 5.5 10.9 12.3 5.4 10.0 8.2 9.0 10.2 8.0

FIG. 1 shows the relationship between the total light transmittance of Examples 1 to 5 and Comparative Examples 1 to 9 and the adhesive force when the film thickness of the adhesive layer is 15 μm.

As is clear from Table 2, Table 3 and Figure 1, the adhesive composition containing the (co)polymer has higher adhesive force than the adhesive composition not containing the (co)polymer containing the structural unit derived from isopropenyltoluene. In addition, the adhesive composition containing the (co)polymer satisfying all the requirements (B-1) to (B-5) has higher adhesive force and transparency than the adhesive composition containing the (co)polymer not satisfying any one of the requirements (B-1) to (B-5).

This application claims priority based on Japanese application No. 2019-117570 filed on June 25, 2019, and the contents described in the patent scope, specification, and drawings of the application are incorporated into this application. [Industrial Applicability]

According to the present invention, an adhesive composition having high transparency and high adhesiveness is provided. The present invention can be suitably implemented in various applications that require transparency of the adhesive composition.

without

FIG. 1 is a graph showing the relationship between the total light transmittance of Example 1 and Comparative Examples 1 to 3 and the adhesive force when the film thickness of the adhesive layer is 10 μm.

Claims (6)

An adhesive composition comprising 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), and 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 set to 100 parts by mass), wherein the (meth)acrylic resin (A) satisfies the following (A-1) and (A-2), and the ( The copolymer (B) satisfies all of the following (B-1) to (B-5); (A-1) contains structural units derived from (meth)acrylates having an alkyl group with a carbon number of 1 or more and 12 or less, and structural units derived from (meth)acrylates containing hydroxyl groups; (A-2) has a glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) in the range of -80°C or more and 0°C or less; (B-1) contains structural units derived from isopropenyltoluene in an amount of 20 mol% or more relative to the total amount of its structural units; (B-2) has a hydroxyl group-containing (meth)acrylate; (A-3) has a glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) in the range of -80°C or more and 0°C or less; (B-1) contains structural units derived from isopropenyltoluene in an amount of 20 mol% or more relative to the total amount of its structural units; (B-2) has a hydroxyl group-containing (meth)acrylate; (A-4) has a hydroxyl group-containing (meth)acrylate; (A-5) has a hydroxyl group-containing (meth)acrylate; (A-6) has a hydroxyl group-containing (meth)acrylate; (A-7) has a hydroxyl group-containing (meth)acrylate; (A-8) has a hydroxyl group-containing (meth)acrylate; (A-9) has a hydroxyl group-containing (meth)acrylate; (A-11) has a hydroxyl group-containing (meth)acrylate; (A-12) has a hydroxyl group-containing (meth)acrylate; (A-13) has a hydroxyl group-containing (meth)acrylate; (A-14) has a hydroxyl group-containing (meth)acrylate; (A-15) has a hydroxyl group-containing (meth)acrylate; (A-16) has a hydroxyl group-containing (meth)acrylate; (A-17 (B-3) The glass transition temperature (Tg) measured by differential scanning calorimeter (DSC) is within the range of 40°C to 80°C; (B-4) The content of compounds with a molecular weight of 400 or less in terms of polystyrene measured by gel permeation chromatography (GPC) is 10% by mass or less; (B-5) The number average molecular weight (Mn) in terms of polystyrene measured by gel permeation chromatography (GPC) is within the range of 750 to 1000, the z-average molecular weight (Mz) is within the range of 1200 to 2000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), i.e., the dispersion (Mw/Mn), is 1.5 or less. The adhesive composition as described in claim 1, wherein the (co)polymer (B) satisfies the following (B-6); (B-6) contains 1 mol% or more and 80 mol% or less of structural units derived from monomers selected from the group consisting of styrene, α-methylstyrene, indene, vinyltoluene and unsaturated aliphatic hydrocarbon compounds having 4 or 5 carbon atoms, relative to the total amount of its structural units. An adhesive processed product is a tape, a label, a sheet or a double-sided tape, and is obtained by processing the adhesive composition described in claim 1 or claim 2. The adhesive processed product as described in claim 3 has an adhesive layer with a thickness of 5 μm or more and 50 μm or less. The adhesive processed product as described in claim 3 or claim 4, wherein the total light transmittance measured in accordance with JIS K7361 is 87% or more. An adhesive processed product as described in claim 3 or claim 4, wherein the adhesive layer is brought into contact with a stainless steel plate (SUS) in an environment of 23°C, and is pressed by moving a 2kg rubber roller back and forth twice. After being left for 20 minutes, the 180° peel strength measured at a speed of 300mm/minute in accordance with JIS Z0237 is greater than 9N/25mm.

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