Adhesive composition, adhesive, and adhesive sheet

Abstract

To provide an adhesive composition which contains a vinyl polymer low in melt viscosity or solution viscosity even with high molecular weight and can obtain sufficient adhesive force and holding power after curing, and to provide an adhesive and an adhesive sheet.SOLUTION: An adhesive composition contains a vinyl polymer having a structure derived from a chain transfer agent (A) represented by the formula (1) (R' represents a hydrogen atom, a halogen atom, -OC(O)R", -CONH2, -CN, -COOR" or an aryl group; Y represents -SR", a halogen atom, -SO2R", -P(O)(OR")2, -SnR"3, -SiR"3 or -C(=O)OR"; and R" represents an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group). The adhesive and the adhesive sheet use the adhesive composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive composition, an adhesive, and an adhesive sheet.

Background Art

[0002] In the fields of adhesion such as dicing-related and adhesives, coating materials such as coating agents, inks, and paints, and electronic materials such as underfills, in order to meet various requirements such as improving the material performance that can withstand the use environment, simplifying the manufacturing process, and saving energy, materials, especially polymer materials, have been developed. When using a general polymer (linear polymer) material as an adhesive or a coating material, the polymer is often dissolved in a solvent to reduce its viscosity for use. On the other hand, a multi-branched polymer has a lower viscosity compared to a linear polymer of the same molecular weight, so that a solvent is not required or only a small amount is needed. In the applications of coating materials and adhesives, it is expected to be effective in reducing harmful volatile organic compounds (VOCs). As a method for synthesizing such a multi-branched polymer, for example, a method using an addition-fragmentation chain transfer (AFCT) agent (Non-Patent Document 1, Patent Documents 1 to 2) and a method using catalytic chain transfer with cobalt (Patent Document 3) are known.

[0003] In recent years, as an adhesive composition that can be applied onto a substrate and cured by irradiation with active energy rays, a composition containing a copolymer obtained by polymerizing an alkyl acrylate having an alkyl group with 1 to 4 carbon atoms, an unsaturated carboxylic acid such as acrylic acid, and a benzophenone derivative having a (meth)acryloyloxy group has been known (Patent Document 4).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] [Non-Patent Document 1] Seiya Kobatake, Bunichiro Yamada, “Radical polymerization of a trimer of methyl acrylate as polymerizable α-substituted acrylate”, molecular Chemistry and Physics, September 1997, Vol. 198, No. 9, pp. 2825-2837 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] Generally, when adjusting the adhesive performance, the glass transition temperature, molecular weight, and molecular weight distribution are changed. In particular, when used as a coating material that cures by irradiation with active energy rays or addition of a crosslinking agent, by increasing the molecular weight before curing, it can be cured more efficiently, so that the curing time can be reduced. On the other hand, when used as a coating agent to be cured, there has been a problem that when a high molecular weight polymer is used, the melt viscosity and solution viscosity at the same temperature become high, resulting in poor coatability.

[0007] An object of the present invention is to provide an adhesive composition, an adhesive, and an adhesive sheet that contain a vinyl polymer having a low melt viscosity or solution viscosity even at a high molecular weight and can obtain sufficient adhesive force and holding force after curing. [Means for Solving the Problems]

[0008] The present invention includes the following configurations. [1] An adhesive composition containing a vinyl polymer having a structure derived from a chain transfer agent (A) represented by the following formula (1). [Chemical Formula] (In formula (1), R’ is a hydrogen atom, a halogen atom, -OC(=O)R”, -C(=O)NH 2 , -CN, -C(=O)OR”, or an aryl group. Y is -SR”, a halogen atom, -SO 2 R”, -P(=O)(OR”) 2 , -SnR” 3 , -SiR” 3、 or -C(=O)OR”. Each R” is independently an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group.) [2] The pressure-sensitive adhesive composition according to [1], wherein the vinyl polymer contains a structural unit derived from a monomer (B) having a structure that generates active species upon photoexcitation. [3] The pressure-sensitive adhesive composition according to [2], wherein the mechanism for generating active species upon photoexcitation of the monomer (B) is a hydrogen abstraction type. [4] The pressure-sensitive adhesive composition according to [2] or [3], wherein the monomer (B) is a monomer having at least one selected from the group consisting of a benzophenone skeleton, a thioxanthone skeleton, an anthraquinone skeleton, and skeletons derived therefrom. [5] The pressure-sensitive adhesive composition according to [1], wherein the pressure-sensitive adhesive composition contains a crosslinking agent, and the vinyl polymer contains a structural unit derived from a monomer (C1) having a functional group that binds to the crosslinking agent. [6] The pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the weight average molecular weight of the vinyl polymer is 20,000 to 700,000. [7] The pressure-sensitive adhesive composition according to any one of [1] to [6], wherein the vinyl polymer has a branched structure. [8] A pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition according to any one of [1] to [7]. [9] A pressure-sensitive adhesive obtained by irradiating the pressure-sensitive adhesive composition according to any one of [1] to [7] with active energy rays.

[10] A pressure-sensitive adhesive obtained by crosslinking the crosslinking agent contained in the pressure-sensitive adhesive composition according to any one of [5] to [7].

[11] A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive according to any one of [8] to

[10] .

Advantages of the Invention

[0009] According to the present invention, there can be provided a pressure-sensitive adhesive composition, a pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet, which contain a vinyl polymer having a low melt viscosity or solution viscosity even if the molecular weight is high, and can obtain sufficient adhesive strength and holding power after curing.

Embodiments for Carrying Out the Invention

[0010] In the present invention, the numerical range represented by "~" means a numerical range including the numerical values before and after "~" as the lower limit value and the upper limit value, respectively. "(Meth)acryl" means acrylic or methacrylic. "(Meth)acrylate" means acrylate or methacrylate. "(Meth)acrylo" means acrylo or methacrylo. "Vinyl monomer" is a compound having a polymerizable double bond. As a preferred embodiment, the case where the pressure-sensitive adhesive composition is irradiated with an active energy ray described later to cure the pressure-sensitive adhesive composition is referred to as the "first embodiment" in the present invention. Further, the case where the pressure-sensitive adhesive composition contains a crosslinking agent described later and the crosslinking agent is reacted to cure the pressure-sensitive adhesive composition is referred to as the "second embodiment" in the present invention.

[0011] 〔Embodiment and First Embodiment〕 <Pressure-Sensitive Adhesive Composition> The pressure-sensitive adhesive composition according to the embodiment contains a vinyl polymer having a structure derived from a chain transfer agent (A) described later.

[0012] [Vinyl Polymer] The vinyl polymer according to the embodiment has a structure derived from a chain transfer agent (A). Further, the vinyl polymer in the first embodiment preferably has a constitutional unit derived from a monomer (B) (hereinafter, also simply referred to as "monomer (B)") that generates active species by photoexcitation and forms a crosslinked structure, and a constitutional unit derived from a vinyl monomer (C) other than the chain transfer agent (A) and the monomer (B).

[0013] (Chain transfer agent (A)) The chain transfer agent (A) is a compound represented by the following formula (1).

[0014] [Chemical formula]

[0015] In the formula (1), R’ is a hydrogen atom, a halogen atom, -OC(=O)R”, -C(=O)NH 2 , -CN, -C(=O)OR”, or an aryl group. Y is -SR”, a halogen atom, -SO 2 R”, -P(=O)(OR”) 2 , -SnR” 3 , -SiR” 3、 or -C(=O)OR”. R” is each independently an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group.)

[0016] Examples of the halogen atom in R’ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. As the halogen atom, a chlorine atom or a bromine atom is preferable. When R’ is a halogen atom, it shows an appropriate chain transfer constant value in the step (i) described later.

[0017] Examples of the aryl group in R’ include an aryl group having 6 to 18 carbon atoms. Examples of the aryl group having 6 to 18 carbon atoms include a phenyl group, a benzyl group, and a naphthyl group. The aryl group may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a carbamoyl group, a cyano group, a hydroxy group, an amino group, an amide group, a halogen atom, an allyl group, an epoxy group, an alkoxy group, and a group showing hydrophilicity or ionicity. Examples of the group exhibiting hydrophilicity or ionic property include, for example, an alkali salt of a carboxy group, an alkali salt of a sulfoxy group, a poly(alkylene oxide) group such as a polyethylene oxide group and a polypropylene oxide group, and a cationic substituent such as a quaternary ammonium base.

[0018] Examples of the halogen atom in Y include, for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. As the halogen atom, a chlorine atom or a bromine atom is preferable. When Y is a halogen atom, it exhibits an appropriate value of the chain transfer constant in the step (i) described later.

[0019] Examples of the alkyl group in R” include, for example, a linear or branched alkyl group having 1 to 20 carbon atoms. Specific examples of the linear or branched alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a t-butyl group, an i-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group.

[0020] Examples of the cycloalkyl group in R” include, for example, a cycloalkyl group having 3 to 20 carbon atoms. Specific examples of the cycloalkyl group having 3 to 20 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and an adamantyl group.

[0021] Examples of the aryl group in R” include, for example, an aryl group having 6 to 18 carbon atoms. Specific examples of the aryl group having 6 to 18 carbon atoms include a phenyl group, a benzyl group, and a naphthyl group.

[0022] Examples of the heterocyclic group in R” include heterocyclic groups having 5 to 18 carbon atoms containing an oxygen atom, a nitrogen atom or a sulfur atom as a hetero atom. Specific examples of the heterocyclic group include a γ-lactone group, an ε-caprolactone group and a morpholine group.

[0023] In addition, the alkyl group, cycloalkyl group, aryl group and heterocyclic group in R” may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a carbamoyl group, a cyano group, a hydroxy group, an amino group, an amide group, a halogen atom, an allyl group, an epoxy group, an alkoxy group, and a group showing hydrophilicity or ionic property. Examples of the group showing hydrophilicity or ionic property include an alkali salt of a carboxy group, an alkali salt of a sulfoxy group, a poly(alkylene oxide) group such as a polyethylene oxide group and a polypropylene oxide group, and a cationic substituent such as a quaternary ammonium base.

[0024] R” is preferably an alkyl group or a cycloalkyl group, more preferably an alkyl group, still more preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and particularly preferably a linear alkyl group having 1 to 6 carbon atoms.

[0025] Examples of the chain transfer agent (A) include 2-(halomethyl)acrylic acid esters in which R” in R’ is a linear alkyl group having 1 to 6 carbon atoms, such as methyl 2-(bromomethyl)acrylate, ethyl 2-(bromomethyl)acrylate, and propyl 2-(bromomethyl)acrylate; and 2-(arylsulfonylmethyl)acrylic acid esters in which R” in R’ is a linear alkyl group having 1 to 6 carbon atoms, such as methyl 2-(phenylsulfonylmethyl)acrylate, ethyl 2-(phenylsulfonylmethyl)acrylate, and propyl 2-(phenylsulfonylmethyl)acrylate. Among them, 2-(halomethyl)acrylic acid esters and 2-(arylsulfonylmethyl)acrylic acid esters in which R” in R’ is a linear alkyl group having 1 to 6 carbon atoms are preferred, 2-(bromomethyl)acrylic acid esters and 2-(phenylsulfonylmethyl)acrylic acid esters in which R” in R’ is a linear alkyl group having 1 to 6 carbon atoms are more preferred, methyl 2-(bromomethyl)acrylate, ethyl 2-(bromomethyl)acrylate, propyl 2-(bromomethyl)acrylate, methyl 2-(phenylsulfonylmethyl)acrylate, propyl 2-(phenylsulfonylmethyl)acrylate, ethyl 2-(phenylsulfonylmethyl)acrylate, and methyl 2-(phenylsulfonylmethyl)acrylate are even more preferred, and ethyl 2-(bromomethyl)acrylate and methyl 2-(phenylsulfonylmethyl)acrylate are particularly preferred. These chain transfer agents (A) can be used alone or in combination of two or more.

[0026] (Other chain transfer agents) In addition to the chain transfer agent (A), other chain transfer agents may be used in combination with the vinyl polymer. That is, the vinyl polymer according to the embodiment may further have a structure derived from other chain transfer agents other than the chain transfer agent (A). As the other chain transfer agent, a chain transfer agent in which the growing end radical of the polymer extracts a hydrogen atom in the chain transfer agent molecule to generate a radical is preferred, such as -OH, -SH, -C(=O)OH, -NH 2 , -NHR 1 , and -SO3 A chain transfer agent having at least one group selected from the group consisting of H is more preferable. However, the R 1 is an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group.

[0027] Other chain transfer agents include mercapto group-containing chain transfer agents such as n-dodecyl mercaptan; secondary hydroxyl group-containing chain transfer agents such as isopropyl alcohol and the like. Other chain transfer agents can be used alone or in combination of two or more.

[0028] (Monomer (B) that generates active species by photoexcitation and forms a crosslinked structure) Monomer (B) generates active species by photoexcitation of active energy rays such as ultraviolet rays and electron beams, and forms a crosslinked structure. Examples of the active species include radicals, cations, and anions, and radicals are preferable from the viewpoint of reactivity.

[0029] The mechanism for generating active species by photoexcitation of monomer (B) is preferably a hydrogen abstraction type. Examples of monomer (B) include monomers having at least one selected from the group consisting of a benzophenone skeleton, a thioxanthone skeleton, an anthraquinone skeleton, and skeletons derived therefrom. Since these skeletons include a benzophenone skeleton, an excited triplet state of the benzophenone skeleton is generated by photoexcitation, and a carbon radical A having a secondary hydroxyl group is formed by hydrogen abstraction from a hydrocarbon group. It is considered that this carbon radical A combines with a carbon radical B generated by hydrogen abstraction to form a crosslinked structure having a tertiary hydroxyl group and two phenyl groups at the crosslinking point. The crosslinked structure preferably contains, for example, a diphenylhydroxymethyl group. The phenyl group in the crosslinked structure may or may not have a substituent.

[0030] From the viewpoint of reactivity, a benzophenone derivative represented by the following formula (4) is preferable as monomer (B).

[0031] [Chemical formula]

[0032] In formula (4), R A and R B each independently represent an alkyl group, an alkoxy group, a hydroxyl group, a carboxy group, or a halogen atom. n is an integer from 0 to 5. m is an integer from 0 to 4. X represents a (meth)acryloyloxy group or a (meth)acryloyloxyalkyleneoxy group.

[0033] R A and R B As the alkyl group of R and R , a linear or branched alkyl group having 1 to 10 carbon atoms is preferred, and a linear or branched alkyl group having 1 to 5 carbon atoms is more preferred. As the alkoxy group, a linear or branched alkoxy group having 1 to 10 carbon atoms is preferred, and a linear or branched alkoxy group having 1 to 5 carbon atoms is more preferred. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. n is preferably an integer from 0 to 3, more preferably 0. m is preferably an integer from 0 to 3, more preferably 0.

[0034] As the alkylene group in the (meth)acryloyloxyalkyleneoxy group of X, an alkylene group having 2 to 10 carbon atoms is preferred, and an alkylene group having 2 to 6 carbon atoms is more preferred. Examples of the (meth)acryloyloxyalkyleneoxy group include a 2-(meth)acryloyloxyethoxy group, a 2-(meth)acryloyloxypropoxy group, and the like.

[0035] Examples of the monomer represented by the formula (4) include 4-acryloyloxybenzophenone, 4-methacryloyloxybenzophenone, 4-[2-(acryloyloxy)ethoxy]benzophenone, 4-[2-(methacryloyloxy)ethoxy]benzophenone, 2-hydroxy-4-acryloyloxybenzophenone, 2-hydroxy-4-methacryloyloxybenzophenone, 2-hydroxy-4-(2-acryloyloxy)ethoxybenzophenone, 2-hydroxy-4-(2-methyl-2-acryloyloxy)ethoxybenzophenone, 2-hydroxy-4-acryloyloxy-5-tert-butylbenzophenone, and 2-hydroxy-4-acryloyloxy-2',4'-dichlorobenzophenone. Among them, 4-acryloyloxybenzophenone, 4-methacryloyloxybenzophenone, and 4-[2-(methacryloyloxy)ethoxy]benzophenone are preferred. As the monomer (B), one kind may be used alone, or two or more kinds may be used in combination.

[0036] (Vinyl monomer (C)) The vinyl monomer (C) is not particularly limited as long as it is a monomer other than the chain transfer agent (A) and the monomer (B), and (meth)acrylic acid and (meth)acrylate compounds are preferred. Examples of the (meth)acrylate compound include alkyl (meth)acrylate having an alkyl group with 1 to 30 carbon atoms, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, polyethylene glycol (meth)acrylate and its alkyl ether, benzyl (meth)acrylate, phenyl (meth)acrylate, 3-(triethoxysilyl)propyl (meth)acrylate, and 2-(dimethylamino)ethyl (meth)acrylate and its quaternary alkylammonium salt.

[0037] As the alkyl (meth)acrylate having an alkyl group with 1 to 30 carbon atoms, an alkyl (meth)acrylate having a linear or branched alkyl group with 1 to 10 carbon atoms is preferable, an alkyl acrylate having a linear or branched alkyl group with 1 to 10 carbon atoms is more preferable, an alkyl acrylate having a linear alkyl group with 1 to 6 carbon atoms and an alkyl acrylate having a branched alkyl group with 3 to 10 carbon atoms are particularly preferable, and n-butyl acrylate and 2-ethylhexyl acrylate are most preferable. These vinyl monomers (C) can be used alone or in combination of two or more.

[0038] In addition, the vinyl polymer may contain a small amount of other structural units other than the structural units derived from the (meth)acrylate-based compound as long as the effects of the present invention are not impaired. The other structural units are not particularly limited as long as they are structural units derived from a vinyl monomer capable of radical polymerization. Examples of the vinyl monomer capable of radical polymerization include styrene-based monomers such as α-methylstyrene, vinyltoluene, and styrene; vinyl ether-based monomers such as methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether; fumaric acid, monoalkyl esters and dialkyl esters of fumaric acid; maleic acid, monoalkyl esters and dialkyl esters of maleic acid; itaconic acid, monoalkyl esters and dialkyl esters of itaconic acid; (meth)acrylonitrile, (meth)acrylamide, butadiene, isoprene, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ketone, vinyl pyridine, and vinyl carbazole. These vinyl monomers capable of radical polymerization can be used alone or in combination of two or more.

[0039] The vinyl monomer (C) is preferably used such that the ratio (mol%) of the total number of moles of (meth)acrylic acid and (meth)acrylate compounds to the total number of moles of the vinyl monomer (C) is 50 mol% or more. Thereby, a vinyl polymer in which x described later is 50 mol% or more can be obtained. The ratio (mol%) of the total number of moles of (meth)acrylic acid and (meth)acrylate compounds to the total number of moles of the vinyl monomer (C) is more preferably 60 mol% or more, and even more preferably 70 mol% or more.

[0040] The vinyl polymer according to the embodiment preferably has a structure represented by the following formula (2).

[0041]

Chemical formula

[0042] The meanings of the symbols in formula (2) are as follows. R and R 1 ~R n are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group. Z is a group derived from a radical polymerization initiator, a group derived from the chain transfer agent (A), or a group derived from another chain transfer agent. X 1 ~X n are each independently a hydrogen atom, a methyl group, or a structure represented by formula (3), and at least one of X 1 ~X n is a structure represented by formula (3). R n and X n in, n is a natural number from 2 to 10,000.

[0043]

Chemical formula

[0044] The meanings of the symbols in formula (3) are as follows. R and R 1 ~Rn is independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group, Z is a group derived from a radical polymerization initiator, a group derived from a chain transfer agent (A), or a group derived from another chain transfer agent, and X 1 ~X n is independently a hydrogen atom, a methyl group, or a structure represented by formula (3). R n and X n in which n is a natural number from 2 to 10,000.

[0045] R and R in formula (2) 1 ~R n and R in formula (3) 1 ~R n are independent of each other, and X in formula (2) 1 ~X n and X in formula (3) 1 ~X n are independent of each other.

[0046] Since at least one of X in formula (2) 1 ~X n is a structure represented by formula (3), the vinyl polymer has a branched structure.

[0047] The fact that the vinyl polymer has the structures represented by formulas (2) and (3) means that in the 1 1H-NMR measurement of the vinyl polymer, there are peaks with chemical shift values of 5.5 to 5.6 ppm and 6.1 to 6.2 ppm, and 13 in the 13C-NMR measurement, it can be confirmed from the presence of a peak with a chemical shift value of 38 to 41 ppm. Here, 1 The peaks with chemical shift values of 5.5 to 5.6 ppm and 6.1 to 6.2 ppm in the 1H-NMR measurement mean the presence of terminal double bonds in the vinyl polymer in formula (2). Also, 13 the peak with a chemical shift value of 38 to 41 ppm in the 13C-NMR measurement means that the vinyl polymer has a branched structure represented by formula (3).

[0048] In the vinyl polymer, it is preferable that a terminal double bond is introduced as shown in the formula (2). This terminal double bond has polymerizability and is useful because a graft copolymer can be easily synthesized by copolymerizing it with a vinyl monomer.

[0049] As a first embodiment of the present invention, the vinyl polymer preferably has a structural unit derived from the monomer (B) and also has a structural unit derived from a (meth) acrylic acid or (meth) acrylate compound as shown in the formulas (2) and (3).

[0050] In the vinyl polymer, in the formulas (2) and (3), when the ratio of the number of moles of hydrogen atoms to the total number of moles of hydrogen atoms and methyl groups contained in X 1 ~X n is defined as x, x is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more. When x is 50 mol% or more, the vinyl polymer has a high degree of branching. Note that x is a value determined by the charging ratio of (meth) acrylic acid and (meth) acrylate compounds in the monomer (B) and the vinyl monomer (C) as raw materials.

[0051] The weight average molecular weight (Mw) of the vinyl polymer is not particularly limited, but is preferably 20,000 to 700,000, more preferably 50,000 to 600,000, even more preferably 70,000 to 500,000, particularly preferably 100,000 to 400,000, and most preferably 150,000 to 350,000. By using such a vinyl polymer as a raw material, a molded article and a coating film excellent in elastic modulus and mechanical strength can be obtained. The weight average molecular weight is a value calculated by converting the value measured by gel permeation chromatography (GPC) to standard polymethyl methacrylate (PMMA).

[0052] The melt viscosity at 130°C (130°C melt viscosity), which is the melt viscosity of the vinyl polymer at 130°C before curing, is preferably 10 to 300 Pa·s, more preferably 15 to 200 Pa·s, and even more preferably 20 to 150 Pa·s. When the solution viscosity of the vinyl polymer is below the upper limit value, low viscosity can be achieved, resulting in excellent handleability. When the solution viscosity of the vinyl polymer is above the lower limit value, the process suitability for processes such as coating film formation is enhanced. Note that the melt viscosity at 130 °C when uncured can be measured by the method described in the examples.

[0053] (Method for producing vinyl polymer) Examples of the method for producing a vinyl polymer include a method including the following step (i). Step (i): A step of subjecting a polymerizable composition containing a chain transfer agent (A), a vinyl monomer (C), and a polymerization initiator (D) to polymerization. The polymerizable composition may contain, if necessary, any one of the monomer (B), a solvent, and other additives, or two or more thereof.

[0054] The polymerization initiator (D) is not particularly limited, and conventionally known compounds can be used, but a radical polymerization initiator is preferred. Examples of the radical polymerization initiator include azo-based radical polymerization initiators and peroxide-based radical polymerization initiators.

[0055] Specific examples of the azo-based radical polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile). Specific examples of the peroxide-based radical polymerization initiator include 2,4-dichlorobenzoyl peroxide, t-butyl peroxypivalate, o-methylbenzoyl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t-butyl peroxy-2-ethylhexanoate, cyclohexanone peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, lauroyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, and di-t-butyl peroxide. The radical polymerization initiator may be used alone or in combination of two or more.

[0056] The solvent is not particularly limited. Examples thereof include alcohol solvents (such as methanol and ethanol), aromatic hydrocarbon solvents (such as toluene, ethylbenzene, xylene, and anisole), ketone solvents (such as acetone, methyl isobutyl ketone, and methyl ethyl ketone), and ester solvents (such as butyl acetate and ethyl acetate). The solvent can be used alone or in combination of two or more.

[0057] The content of the chain transfer agent (A) in the polymerizable composition is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the vinyl monomer (C). When the content of the chain transfer agent (A) is at least the lower limit value, a branched structure can be appropriately introduced into the resulting vinyl polymer. When the content of the chain transfer agent (A) is at most the upper limit value, properties such as the elastic modulus, mechanical strength, and durability of the vinyl polymer can be sufficiently obtained.

[0058] The content of the monomer (B) in the polymerizable composition is preferably 0.001 to 30 parts by mass, more preferably 0.005 to 20 parts by mass, and even more preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the vinyl monomer (C).

[0059] The content of the polymerization initiator (D) in the polymerizable composition is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the vinyl monomer (C). When the content of the polymerization initiator (D) is within the above range, an appropriate polymerization rate can be obtained in the step (i) described later.

[0060] The content of the solvent in the polymerizable composition is preferably 0 to 300 parts by mass, more preferably 10 to 200 parts by mass, and even more preferably 20 to 150 parts by mass with respect to 100 parts by mass of the vinyl monomer (C). When the content of the solvent is within the above range, an appropriate polymerization rate can be obtained in the step (i) described later, and the solution viscosity after the formation of the vinyl polymer is reduced, resulting in excellent handleability.

[0061] Examples of other additives include pigments, ultraviolet absorbers, mold release agents, defoaming agents, plasticizers, viscosity modifiers, and the like. Known compounds can be used as these additives.

[0062] In step (i), a polymerizable composition containing a chain transfer agent (A), a monomer (B), a vinyl monomer (C), and a polymerization initiator (D) is subjected to polymerization. The polymerizable composition may contain a solvent and other additives as necessary. According to the method for producing a vinyl polymer according to the embodiment, a vinyl polymer having a branched chain or a graft copolymer which is a vinyl polymer having a graft chain can be produced by the step (i).

[0063] As used herein, a "graft copolymer" is a polymer having one or more blocks connected as a side chain polymer structure to a main chain polymer structure. In a polymer having a branched chain, the structures of the main chain polymer and the side chain polymer may be different or the same. On the other hand, in a graft copolymer, the structures of the main chain polymer and the side chain polymer are different in the type (structure) of monomer units or different in composition or sequence distribution even if they are the same monomer units.

[0064] Conventional methods for producing graft copolymers include, for example, a method in which a macromonomer having a radically polymerizable double bond at its end is produced as a side-chain polymer structure and then radically polymerized with a monomer that becomes a constituent unit of the main-chain polymer; a method in which a main-chain polymer having a reaction point and a macromonomer having a reaction point are produced in advance and then reacted; a method in which, after producing the main-chain polymer, a radical is generated on the main-chain polymer using an initiator having a hydrogen abstraction ability, and a monomer that becomes a constituent unit of the side-chain polymer is reacted to produce a side-chain polymer structure. Here, the "macromonomer" means a polymer having a radically polymerizable group or an addition-reactive functional group. All of these methods require two or more polymerization steps. In contrast, according to the method for producing a vinyl polymer according to the embodiment, a vinyl polymer having a branched chain or a graft chain can be produced by only one polymerization step, that is, only the above step (i). Note that the method for producing a vinyl polymer according to the embodiment may further include a polymerization step in the second and subsequent steps.

[0065] The polymerization method of the polymerizable composition is not particularly limited, and for example, conventionally known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be used. The polymerization reaction may be carried out in the presence of air, but from the viewpoint of the efficiency of radical polymerization, it is preferably carried out in an inert gas atmosphere such as nitrogen or argon. Known methods are used as the method of carrying out in an inert gas atmosphere. For example, a method of blowing an inert gas into the polymerizable composition, a method of repeating freezing, degassing, and melting can be used.

[0066] The polymerization temperature is not particularly limited, but from the viewpoint of the polymerization rate, it is preferably 0 to 150°C, more preferably 20 to 120°C. The polymerization time is not particularly limited, but it is preferably 0.5 to 48 hours, more preferably 4 to 48 hours.

[0067] From the viewpoint of improving the molecular weight and degree of branching of the resulting vinyl polymer, the conversion rate of the vinyl monomer (C) in step (i) is preferably 85% or more, more preferably 90% or more, still more preferably 95% or more, and particularly preferably 98% or more. Here, the conversion rate (%) of the vinyl monomer (C) can be determined from the measurement values of 1H-NMR measurement using a nuclear magnetic resonance apparatus (manufactured by JEOL Ltd., ECZ400S, 400 MHz) with CDCl 3 used 1 as the measurement solvent. Specifically, the conversion rate (%) of the vinyl monomer (C) can be calculated as the ratio of the integrated value of the peaks derived from the remaining vinyl monomer (C) to the integrated value of the peaks derived from the constituent units derived from the vinyl monomer (C) in the produced vinyl polymer, using the integrated value of the peaks derived from the remaining vinyl monomer (C) and the integrated value of the peaks derived from the constituent units derived from the vinyl monomer (C) in the produced vinyl polymer, with respect to the sum of the amount of the remaining vinyl monomer (C) and the amount of the constituent units derived from the vinyl monomer (C) in the produced vinyl polymer.

[0068] [Other components] The pressure-sensitive adhesive composition according to the embodiment may further contain other components other than the vinyl polymer according to the above-described embodiment. Other components that can be contained in the pressure-sensitive adhesive composition are not particularly limited, and examples thereof include solvents, fillers, crosslinking agents, tackifier resins, antioxidants, light stabilizers, metal deactivators, anti-aging agents, moisture absorbers, rust preventives, hydrolysis inhibitors, and reaction catalysts.

[0069] The pressure-sensitive adhesive composition according to the embodiment may be in the form of a liquid pressure-sensitive adhesive composition containing a solvent or in the form of a hot-melt type pressure-sensitive adhesive composition not containing a solvent.

[0070] 〔Second Embodiment〕 <Pressure-Sensitive Adhesive Composition> The pressure-sensitive adhesive composition in the second embodiment of the present invention contains a vinyl polymer and a crosslinking agent described below. Further, the pressure-sensitive adhesive composition in the second embodiment may further contain other components other than the vinyl polymer and the crosslinking agent according to the second embodiment described below. Other components that can be contained in the adhesive composition are not particularly limited, and examples thereof include solvents, fillers, tackifying resins, antioxidants, light stabilizers, metal deactivators, anti-aging agents, moisture absorbers, rust preventives, hydrolysis inhibitors, and reaction catalysts.

[0071] [Vinyl polymer] The vinyl polymer in the second embodiment preferably has structural units derived from a chain transfer agent (A) and a monomer that binds to a crosslinking agent (hereinafter, also simply referred to as "monomer (C1)"). The vinyl polymer in the second embodiment may or may not have structural units derived from a vinyl monomer (C) other than the vinyl monomer (C1). Further, the vinyl polymer in the second embodiment may or may not have structural units derived from the monomer (B). Since the chain transfer agent (A), the monomer (B), and the vinyl monomer (C) are in the same form as in the above-described first embodiment, the description thereof is omitted. The monomer (C1) is a (meth)acrylate compound having a hydroxy group. Examples of the monomer (C1) include hydroxyalkyl acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, N-methylol (meth)acrylamide, and hydroxyethyl acrylamide; secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; and hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate. These can be used alone or in combination of two or more.

[0072] Among the above-mentioned hydroxyl group-containing monomers, primary hydroxyl group-containing monomers are preferred in terms of excellent reactivity with crosslinking agents, 2-hydroxyethyl (meth)acrylate is preferred in terms of stability during polymerization, and it is preferable to use 4-hydroxybutyl (meth)acrylate in terms of fast reactivity with crosslinking agents and short aging time. Furthermore, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred in that they have few impurities such as di(meth)acrylate during monomer preparation, and high-purity products can be obtained, making them easy to manufacture.

[0073] As shown in the above formulas (2) and (3), the vinyl polymer in the second embodiment has a structural unit derived from (meth)acrylic acid or a (meth)acrylate-based compound, and at least a part of the structural unit is preferably a structural unit derived from monomer (C1).

[0074] (Method for producing vinyl polymer) Examples of the method for producing the vinyl polymer in the second embodiment include methods including the above step (i). Since the polymerization initiator (D), solvent, and other additives used in step (i) are in the same manner as in the above-described first embodiment, the description thereof is omitted. In the second embodiment, the content of monomer (C1) in the polymerizable composition is preferably 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass, and even more preferably 0.03 to 3 parts by mass with respect to 100 parts by mass of vinyl monomer (C).

[0075] The solution viscosity, which is the viscosity of a butyl acetate solution at a solid content concentration of 50 to 60% by mass of the vinyl polymer of the present invention, is preferably 500 to 25,000 mPa·s, more preferably 800 to 23,000 mPa·s, and even more preferably 1,000 to 20,000 mPa·s. When the solution viscosity of the vinyl polymer of the present invention is below the above upper limit value, low viscosity can be achieved, so the handleability is excellent. When the solution viscosity of the vinyl polymer of the present invention is above the above lower limit value, the process suitability such as film formation becomes high. The solution viscosity can be measured by the method described in the examples.

[0076] [Crosslinking agent] In the present invention, it is also preferable to use a crosslinking agent in terms of improving the adhesion to the substrate or improving the durability of the adhesive. The crosslinking agent is a compound that reacts with the functional groups in the vinyl polymer used in the present invention to form a crosslinked structure. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and aziridine-based crosslinking agents. By containing the crosslinking agent, the crosslinking speed of the adhesive composition is increased, and the aging period during film production is shortened, so that the adhesive can be obtained economically and efficiently.

[0077] Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate-based compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate; xylylene diisocyanate-based compounds such as 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and tetramethylxylylene diisocyanate; aromatic isocyanate-based compounds such as 1,5-naphthalene diisocyanate and triphenylmethane triisocyanate; hexamethylene diisocyanate, isophorone diisocyanate, and adducts of these isocyanate-based compounds with polyol compounds such as trimethylolpropane, biuret bodies, and isocyanurate bodies of these polyisocyanate compounds. One selected from these can be used alone or in combination of two or more. Among them, tolylene diisocyanate-based crosslinking agents are preferable in terms of pot life and durability, xylylene diisocyanate-based crosslinking agents or isocyanate-based crosslinking agents containing an isocyanurate skeleton are preferable in terms of shortening the aging time, and aromatic ring-free isocyanate-based crosslinking agents are preferable in terms of yellowing resistance. Specifically, among these, tolylene diisocyanate, xylylene diisocyanate, an adduct of hexamethylene diisocyanate and trimethylolpropane, and a nurate body are preferable in terms of excellent balance of durability, pot life, and crosslinking speed.

[0078] Examples of the epoxy crosslinking agent include bisphenol A-epichlorohydrin type epoxy resins, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, and the like. One of these can be used alone, or two or more of them can be used in combination.

[0079] Examples of the metal chelate crosslinking agent include acetylacetone or acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, palladium, chromium, zirconium, etc. One of these can be used alone, or two or more of them can be used in combination.

[0080] Examples of the aziridine crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), and the like. One can be used alone, or two or more can be used in combination.

[0081] It is preferable to use at least one crosslinking agent selected from the group consisting of isocyanate crosslinking agents, epoxy crosslinking agents, metal chelate crosslinking agents, and aziridine crosslinking agents, and particularly preferably to use an isocyanate crosslinking agent.

[0082] The content of the crosslinking agent is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and particularly preferably 1 to 10 parts by mass with respect to 100 parts by mass of the vinyl polymer. If the content of the crosslinking agent is the above lower limit value, the cohesive force of the pressure-sensitive adhesive composed of the pressure-sensitive adhesive composition in the second embodiment is sufficient, and the stain resistance tends to improve. If the content of the crosslinking agent is below the above upper limit value, the crosslinking agent reacts sufficiently, and the contamination of the adherend can be suppressed.

[0083] In the pressure-sensitive adhesive composition of the present invention, a crosslinking agent other than an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a metal chelate-based crosslinking agent, and an aziridine-based crosslinking agent may be contained within a range not losing the effects of the present invention. For example, a melamine-based crosslinking agent, an aldehyde-based crosslinking agent, an amine-based crosslinking agent, etc. may be contained.

[0084] Examples of the above melamine-based crosslinking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, melamine resin, etc.

[0085] Examples of the above aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutaraldehyde, formaldehyde, acetaldehyde, benzaldehyde, etc.

[0086] Examples of the above amine-based crosslinking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethylenetetraamine, isophoronediamine, amino resin, polyamide, etc.

[0087] The vinyl polymer contained in the pressure-sensitive adhesive composition according to the above-described embodiment has a branched structure by using a chain transfer agent (A). Even if it has a high molecular weight, its melt viscosity and solution viscosity are low, and due to the increase in molecular weight, it can be crosslinked more efficiently. Further, the pressure-sensitive adhesive composition according to the embodiment can obtain sufficient adhesive strength and holding power after curing. This is presumably because since the vinyl polymer has a branched structure, the reaction points are densely present compared to a linear polymer having the same composition and the same molecular weight, and thus it can be cured more efficiently.

[0088] <Pressure-sensitive adhesive, pressure-sensitive adhesive sheet> The pressure-sensitive adhesive according to the embodiment is a pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition according to the embodiment. The pressure-sensitive adhesive according to the first embodiment may use the pressure-sensitive adhesive composition according to the first embodiment in an uncured state, or may be one cured by irradiating active energy rays. From the viewpoint of versatility, ultraviolet rays are preferable as the active energy rays. The pressure-sensitive adhesive according to the second embodiment may use the pressure-sensitive adhesive composition according to the second embodiment in an uncured state, or may be one cured by reacting a crosslinking agent.

[0089] The pressure-sensitive adhesive sheet according to the embodiment is a pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive according to the embodiment, and has a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition according to the embodiment. The pressure-sensitive adhesive layer may be composed of the pressure-sensitive adhesive composition, may be composed of a cured product obtained by irradiating ultraviolet rays to the pressure-sensitive adhesive composition according to the first embodiment, or may be a cured product obtained by reacting a crosslinking agent in the pressure-sensitive adhesive composition according to the second embodiment. From the viewpoint of the handleability of the pressure-sensitive adhesive sheet, a pressure-sensitive adhesive layer composed of a cured product obtained by curing the pressure-sensitive adhesive composition according to the first embodiment with ultraviolet rays or a cured product obtained by reacting a crosslinking agent in the pressure-sensitive adhesive composition according to the second embodiment is preferable. The irradiation amount of ultraviolet rays is preferably 1 to 150 mJ / cm 2 and more preferably 5 to 100 mJ / cm 2 and even more preferably 10 to 50 mJ / cm 2 is even more preferable.

[0090] The pressure-sensitive adhesive sheet according to the embodiment may be composed only of a pressure-sensitive adhesive layer formed by shaping the pressure-sensitive adhesive composition according to the embodiment into a sheet form, or may be in the form of a laminate in which a release base material is laminated on one or both sides of a pressure-sensitive adhesive layer formed by shaping the pressure-sensitive adhesive composition according to the embodiment into a sheet form.

[0091] The thickness of the pressure-sensitive adhesive layer according to the embodiment can be appropriately set according to the application, preferably 10 to 500 μm, more preferably 20 to 100 μm.

[0092] The application of the pressure-sensitive adhesive sheet according to the embodiment is not particularly limited. For example, it can be used for bonding window stickers for vehicles, buildings, etc., bonding labels in label displays, bonding various panels in display displays such as liquid crystal panels, and bonding transparent plate materials such as glass.

Examples

[0093] Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to the examples described below, and various modifications are possible without departing from the gist of the present invention.

[0094] [Raw materials] The abbreviations of the raw materials used in the examples and comparative examples are shown below.

[0095] (Chain transfer agent (A)) EBMA: Ethyl 2-(bromomethyl)acrylate (manufactured by Chemicure Co., Ltd.) ASME: Methyl 2-(benzenesulfonylmethyl)acrylate (manufactured in Production Example 1)

[0096] (Monomer (B)) 4-ABP: 4-Acryloyloxybenzophenone (manufactured by Sino-biochemical Laboratory Co., Ltd.)

[0097] (Other chain transfer agents) IPA: Isopropyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0098] (Vinyl monomer (C)) nBA: n-butyl acrylate (manufactured by Mitsubishi Chemical Corporation) AAc: acrylic acid (manufactured by Mitsubishi Chemical Corporation)

[0099] (Monomer (C1)) HEMA: 2-hydroxyethyl acrylate (manufactured by Mitsubishi Chemical Corporation)

[0100] (Polymerization initiator (D)) AIBN: 2,2’-azobis(isobutyronitrile) (manufactured by Fujifilm Wako Pure Chemical Corporation)

[0101] (Crosslinking agent) D-101E: tolylene diisocyanate (manufactured by Mitsui Chemicals, Inc., Takenate (registered trademark) D-101E)

[0102] [Measurement method and evaluation method] <Weight-average molecular weight of vinyl polymer> The weight-average molecular weight of the vinyl polymer was measured using gel permeation chromatography (GPC) (HLC-8320 manufactured by Tosoh Corporation). After preparing a 0.2 mass% tetrahydrofuran solution of the vinyl polymer, 10 μL of the solution was injected into an apparatus equipped with columns manufactured by Tosoh Corporation (TSKgel SuperHZM-M (inner diameter 4.6 mm, length 15 cm), HZM-M (inner diameter 4.6 mm, length 15 cm), HZ-2000 (inner diameter 4.6 mm, length 15 cm), TSKguardcolumn SuperHZ-L (inner diameter 4.6 mm, length 3.5 cm)). Measurement was carried out under the conditions of a flow rate of 0.35 mL / min, an eluent of tetrahydrofuran (stabilizer BHT), and a column temperature of 40°C, and the weight-average molecular weight (Mw) was calculated in terms of standard polymethyl methacrylate (PMMA).

[0103] <Conversion rate of vinyl monomer (C)> The conversion rate (%) of vinyl monomer (C) was measured using a nuclear magnetic resonance apparatus (ECZ400S, 400 MHz, manufactured by JEOL Ltd.), with CDCl 3 used as 1It was determined from the measurement values of 1H-NMR measurement. Specifically, using the integrated value of the peak derived from the remaining vinyl monomer (C) and the integrated value of the peak derived from the structural unit derived from the vinyl monomer (C) in the produced vinyl polymer, it was calculated as the ratio of the amount of the structural unit derived from the produced vinyl monomer (C) to the total of the amount of the remaining vinyl monomer (C) and the amount of the structural unit derived from the produced vinyl monomer (C).

[0104] <Melt viscosity at 130 °C> The vinyl polymer composition obtained in each example was diluted with ethyl acetate so that the solid content became 33.3% by mass, and it was visually confirmed that there was no undissolved polymer, and a resin composition in a liquid state at normal temperature (23 °C) was obtained. The resin composition was coated on a PET film subjected to a peeling treatment with an applicator and dried at 90 °C for 1 hour to form an adhesive layer having a thickness of 50 μm. The melt viscosity of the adhesive layer was measured using a viscoelasticity measuring device HAAKE MARS. The viscosity (η * ) value when measured at 130 °C and a frequency of 0.02 Hz using a cone plate with a diameter of 35 mm was taken as the value of the melt viscosity at 130 °C before irradiation.

[0105] <Solid content concentration of vinyl polymer composition> The solid content concentration in the vinyl polymer solution obtained in each example was measured. A part of the solution was aliquoted into an aluminum dish, weighed, vacuum dried at 60 °C overnight, and then weighed. The solid content ratio in the polymer solution was calculated from the weight change before and after drying.

[0106] <Solution viscosity of vinyl polymer composition> The viscosity of the vinyl polymer composition obtained in each example was measured at 25.0 °C using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., TV-25). The obtained value was taken as the solution viscosity of the vinyl polymer.

[0107] <Adhesive force> In each case, the release PET of the adhesion test piece obtained was peeled off to expose the adhesive layer, and it was bonded to a 30 mm × 110 mm stainless steel (SUS) plate using a 3 kg hand roller so that the bonding surface became 25 mm × 70 mm. The peel strength (N / 25 mm) with respect to the SUS plate was measured at a peel angle of 180° and a tensile speed of 300 mm / min, and this was taken as the adhesive strength. When measuring the adhesive strength, if the adhesive layer could be peeled at the interface between the two adhesive surfaces and the peeled surface was not rough, it was defined as "interface peeling". If the interface between the two adhesives became unclear, the adhesive layer was destroyed, irregularities occurred on the peeled surface, and it became a fish-scale shape, it was defined as "cohesive failure".

[0108] <Retention force> At one end of the adhesion test piece obtained in each case, the release PET was peeled off to expose the adhesive layer, and it was horizontally bonded to a 30 mm × 110 mm SUS plate using a 3 kg hand roller so that the bonding surface became 25 mm × 25 mm. It was left in a thermostatic and humidity-controlled chamber tester at a temperature of 80°C for 15 minutes. Immediately after that, the SUS plate was installed so that a force was applied in the shear direction to the bonding surface, a 1.0 kg load was applied with the other end of the test piece facing downwards, and the holding time was measured and taken as the retention force. Note that the holding time was measured with a maximum of 24 hours. In the table, the cases where the holding time reached the upper limit are described as "24<".

[0109] [Production Example 1: ASME synthesis] Methyl methacrylate (48.06 g, 480.0 mmol) and methanol (252.8 g) were placed in a 2.0 L separable flask, cooled to 0°C, and then iodine (144.2 g, 568.0 mmol) and sodium benzenesulfinate dihydrate (201.8 g, 1008 mmol) were added little by little and stirred at room temperature for 5 hours. Next, dichloromethane (800.0 mL) was added for dilution, a saturated aqueous sodium carbonate solution (160.0 mL) and a 5% aqueous sodium bisulfite solution (160.0 mL) were added. After liquid separation, 30.00 g of magnesium sulfate was added to the organic layer for drying, and then the solvent was distilled off. Next, dichloromethane (280.0 mL) was added, and triethylamine (97.14 g, 960.0 mmol) was added dropwise over 30 minutes, followed by stirring at room temperature for 2 hours. Next, after distilling off the solvent, column chromatography was performed using silica gel (3.000 kg) to obtain 61.00 g of a white solid ASME.

[0110] [Production Example 2] (Preparation of vinyl polymer) To a 250 mL separable flask, 2.50 parts by mass of EBMA as a chain transfer agent (A), 0.13 parts by mass of 4-ABP as a monomer (B), 94.8 parts by mass of nBA as a vinyl monomer (C), 5.0 parts by mass of AAc, 0.31 parts by mass of AIBN as a polymerization initiator (D), and 102.5 parts by mass of ethyl acetate as a solvent were added. The temperature was raised to 65 °C and stirred for 2 hours. Then the temperature was raised to 70 °C and stirred for 4 hours. Then, after cooling to room temperature, the obtained resin composition was recovered from the flask to obtain a vinyl polymer composition (P-1). The conversion rate of the vinyl monomer (C) and the evaluation results of the obtained vinyl polymer composition (P-1) are shown in Table 1.

[0111] [Production Examples 3 to 8] A polymerizable composition was prepared in the same manner as in Production Example 2 except that the amounts of the chain transfer agent (A), other chain transfer agents, monomer (B), and vinyl monomer (C) were changed as shown in Table 1, and this was subjected to polymerization to obtain vinyl polymer compositions (P-2) to (P-7). The conversion rate of the vinyl monomer (C) and the evaluation results of the obtained vinyl polymer compositions (P-2) to (P-7) are shown in Table 1.

[0112]

Table 1

[0113] [Example 1-1] The vinyl polymer composition (P-1) was diluted with ethyl acetate so that the solid content was 33.3% by mass, and it was visually confirmed that there was no undissolved polymer, and a resin composition in a liquid state at room temperature (23 °C) was obtained. Next, the resin composition was coated on a PET film with a thickness of 38 μm using an applicator and dried at 90°C for 1 hour to form an adhesive layer. Using a high-pressure mercury lamp of 85 mW, the PET film (PET) on which the adhesive layer was formed was irradiated with ultraviolet rays (UV-C) in the air to cure the adhesive layer. The UV-C irradiation dose was 35 mJ / cm 2 (actual measurement value by an integrated light quantity meter UV POWER PUCK II (S / N 13685) (manufactured by EIT, USA)). A PET film (release PET) subjected to a release treatment was overlaid on the upper surface thereof to obtain a laminate having a structure of release PET - adhesive layer - PET. The thickness of the adhesive layer was 50 μm. The cured laminate was cut into strips having a width of 25 mm and a length of 250 mm to obtain an adhesive test piece. The evaluation results of the obtained adhesive test pieces are shown in Table 2.

[0114] [Examples 1-2 to 1-5, Comparative Examples 1-1 to 1-3] Adhesive test pieces were obtained in the same manner as in Example 1-1 except that the vinyl polymer composition used was changed as described in Table 2. The evaluation results of the obtained adhesive test pieces are shown in Table 2.

[0115] [Table 2]

[0116] All of the adhesive test pieces obtained in Examples 1-1 to 1-5 had a low melt viscosity before curing and achieved both good adhesive strength and high holding power after curing. On the other hand, the adhesive test pieces obtained in Comparative Examples 1-1 to 1-3 had a high melt viscosity even though they had the same composition ratio and molecular weight as the vinyl copolymers of Examples 1-1 to 1-5 because a chain transfer agent with a different structure was added instead of the chain transfer agent (A) during the production of the vinyl polymer. If the melt viscosity is too high, the handleability is poor, which is not industrially preferable. In particular, in Comparative Example 1-3, adhesive residue due to cohesive failure occurs and the holding power is inferior to that of Example 1-5 having the same composition, so it is not suitable for use as an adhesive.

[0117] [Production Examples 9 to 11] A polymerizable composition was prepared in the same manner as in Production Example 2, except that the amounts of the chain transfer agent (A), other chain transfer agents, and the vinyl monomer (C) were changed as shown in Table 3, and this was subjected to polymerization to obtain vinyl polymer compositions (P-8) to (P-10). Table 3 shows the conversion rate of the vinyl monomer (C) and the evaluation results of the obtained vinyl polymer compositions (P-8) to (P-10).

[0118] [Table 3]

[0119] [Example 2-1] To 100 parts by mass of the solid content of the vinyl polymer composition (P-8), 5.0 parts by mass of D-101E as a crosslinking agent in terms of solid content was added, and after stirring at room temperature (23°C), it was visually confirmed that there was no residue, and a resin composition in a liquid state at room temperature (23°C) was obtained. Next, the resin composition was coated on a PET film with a thickness of 25 μm using an applicator, dried at 80°C for 5 minutes, and then aged at 40°C for 1 week or more to form an adhesive layer. Then, a peeled PET film (peeled PET) was overlaid on the upper surface of the adhesive layer to obtain a laminate having a structure of peeled PET - adhesive layer - PET. The thickness of the adhesive layer was 25 μm. The laminate was cut into strips with a width of 25 mm and a length of 250 mm to obtain adhesive test pieces. Table 4 shows the evaluation results of the obtained adhesive test pieces.

[0120] [Examples 2-2, 2-3, Comparative Example 2-1] Adhesive test pieces were obtained in the same manner as in Example 6, except that the vinyl polymer composition and the amount of the crosslinking agent used were changed as shown in Table 4. Table 4 shows the evaluation results of the obtained adhesive test pieces.

[0121] [Table 4]

[0122] The vinyl polymer compositions P-8 or P-9 used in Examples 2-1 to 2-3 had a low solution viscosity. Further, the adhesive test pieces obtained in Examples 2-1 to 2-3 had both good adhesive strength and high holding power. On the other hand, the vinyl polymer composition P-10 used in Comparative Example 2-1 had a high solution viscosity even though it had the same composition ratio, molecular weight, and solid content concentration as the vinyl copolymer used in Examples 2-1 to 2-3, because a chain transfer agent having a different structure was added instead of the chain transfer agent (A) during production. If the solution viscosity is too high, it is inferior in handleability and thus not industrially preferable.

Claims

1. A pressure-sensitive adhesive composition comprising a vinyl polymer having a structure derived from a chain transfer agent (A) represented by the following formula (1): 【Chemistry 1】 In formula (1), R' is a hydrogen atom, a halogen atom, -OC(=O)R", -C(=O)NH ２ , -CN, -C(=O)OR", or an aryl group. Y is -SR", a halogen atom, -SO ２ R”, ​​-P (=O) (OR”) ２ , -SnR" ３ , -SiR ３、 or -C(=O)OR", where each R" is independently an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group.

2. The pressure-sensitive adhesive composition according to claim 1 , wherein the vinyl polymer contains a structural unit derived from a monomer (B) having a structure that generates an active species upon photoexcitation.

3. The pressure-sensitive adhesive composition according to claim 2 , wherein a mechanism for generating active species by photoexcitation of the monomer (B) is a hydrogen abstraction mechanism.

4. The pressure-sensitive adhesive composition according to claim 2 or 3, wherein the monomer (B) is a monomer having at least one skeleton selected from the group consisting of a benzophenone skeleton, a thioxanthone skeleton, an anthraquinone skeleton, and skeletons derived therefrom.

5. The pressure-sensitive adhesive composition contains a crosslinking agent, The pressure-sensitive adhesive composition according to claim 1 , wherein the vinyl polymer contains a structural unit derived from a monomer (C1) having a structure capable of bonding with the crosslinking agent.

6. The pressure-sensitive adhesive composition according to claim 2 or 5, wherein the weight average molecular weight of the vinyl polymer is 20,000 to 700,000.

7. The pressure-sensitive adhesive composition according to claim 1 , wherein the vinyl polymer has a branched structure.

8. A pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition according to claim 1.

9. A pressure-sensitive adhesive obtained by irradiating the pressure-sensitive adhesive composition according to claim 2 with active energy rays.

10. A pressure-sensitive adhesive obtained by crosslinking the crosslinking agent contained in the pressure-sensitive adhesive composition according to claim 5 .

11. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive according to any one of claims 8 to 10.

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