Active energy ray-curable peelable adhesive composition

Abstract

To provide an active energy ray-curable peelable adhesive composition which has a high nonvolatile content and excellent storage stability in spite of using an aqueous acrylic resin.SOLUTION: The active energy ray-curable peelable adhesive composition contains an acrylic emulsion (A) and a radically polymerizable composition (B). The radically polymerizable composition (B) comprises the following (B1)-(B3): (B1) an active energy ray-curable compound; (B2) a surfactant having two or more reactive groups; and (B3) a surfactant other than (B2).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an active energy ray-curable peel-type pressure-sensitive adhesive composition, and more particularly to an active energy ray-curable peel-type pressure-sensitive adhesive composition having a high non-volatile content and excellent storage stability. [Background technology]

[0002] Conventionally, in processing steps such as the manufacture of integrated circuits and drilling holes using semiconductor wafers, adhesive sheets for surface protection have been used to temporarily protect the surface of the workpiece to prevent contamination and damage to the workpiece. In recent years, due to factors such as the miniaturization of processing technologies and the thinning of processed parts, there is a demand for an appropriate level of adhesive strength to be applied to the workpiece. However, since the adhesive sheet for surface protection must be peeled off after it has completed its role of protecting the surface, it is required that it can be peeled off with light force without leaving any glue behind.

[0003] In recent years, such surface protection pressure-sensitive adhesive sheets have come to be used not only for semiconductor wafers but also for processing various other materials. For such pressure-sensitive adhesive sheets, active energy ray-curable pressure-sensitive adhesive compositions that can be cured by irradiation with active energy rays and thereby reduce adhesive strength are widely used because they are less likely to damage the material to be protected. Such active energy ray curability can be exhibited, for example, by blending at least one of a monomer and an oligomer having an ethylenically unsaturated group with an acrylic resin, or by using an ethylenically unsaturated group-containing acrylic resin in which the acrylic resin itself contains an ethylenically unsaturated group.

[0004] The acrylic resin used to express the active energy ray curability has a very high viscosity, and is therefore usually synthesized in an organic solvent. Therefore, when using an active energy ray curable pressure-sensitive adhesive composition, it is common to dilute it with an organic solvent to adjust the viscosity, and then coat it on a member to be protected to form a coating film.

[0005] However, diluting with organic solvents at the time of use is problematic under VOC regulations regarding air pollution, working environment, fire hazards, etc. For this reason, in recent years, there has been an increasing demand for water-based acrylic resins, such as water-dispersible acrylic resins, which are used to exhibit active energy ray curability.

[0006] In response to such demands, for example, Patent Document 1 proposes a radiation-curable, removable, water-dispersible acrylic pressure-sensitive adhesive composition comprising an acrylic emulsion polymer and a radiation-curable, radically polymerizable polyfunctional monomer dispersed in water using a polymer dispersant containing a polymer having a weight-average molecular weight of 8,000 or more. Furthermore, Patent Document 2 proposes an emulsion-type pressure-sensitive adhesive composition comprising an acrylic emulsion obtained by a polymerization reaction in a non-emulsifier system, a self-emulsifying urethane (meth)acrylate compound, and a photopolymerization initiator. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2004-346296 A [Patent Document 2] JP 2012-001615 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, Patent Document 1 does not take into consideration the storage stability of the radiation-curable radically polymerizable polyfunctional monomer emulsified using a polymer dispersant containing a polymer with a weight-average molecular weight of 8,000 or more. When a high molecular weight emulsifier is used, the emulsion becomes large, which tends to cause precipitation and reduce storage stability. In addition, the composition of Patent Document 2 contains a UV-curable component that is a self-emulsifying urethane (meth)acrylate compound, and therefore it is difficult to achieve high non-volatile differentiation while maintaining a low viscosity. The drying properties when forming a coating film are not sufficient, and further improvement is required.

[0009] Under such circumstances, an object of the present invention is to provide an active energy ray-curable peel-type pressure-sensitive adhesive composition which has a high non-volatile content and excellent storage stability despite using a water-based acrylic resin. [Means for solving the problem]

[0010] However, the present inventors have conducted extensive research in light of the above circumstances and have found that an active energy ray-curable peel-type pressure-sensitive adhesive composition having a high non-volatile content and excellent storage stability can be obtained by comprising an acrylic emulsion (A) and a radically polymerizable composition (B), wherein the radically polymerizable composition (B) contains the following (B1) to (B3), thereby completing the present invention. (B1): Active energy ray-curable compound. (B2): A surfactant having two or more reactive groups. (B3): A surfactant other than (B2).

[0011] That is, the present invention has the following aspects. [1] An active energy ray-curable peel-type pressure-sensitive adhesive composition comprising an acrylic emulsion (A) and a radically polymerizable composition (B), wherein the glass transition temperature of a polymer contained in the acrylic emulsion (A) is 10°C or lower, and the radically polymerizable composition (B) comprises the following (B1) to (B3): (B1): Active energy ray-curable compound. (B2): A surfactant having two or more reactive groups. (B3): A surfactant other than (B2). [2] The active energy ray-curable peel-type pressure-sensitive adhesive composition according to [1], wherein the content of the surfactant (B2) having two or more reactive groups is 50 mass% or more of the total amount of surfactants contained in the radical polymerizable composition (B). [3] The active energy ray-curable peelable pressure-sensitive adhesive composition according to [1] or [2], wherein the surfactant (B2) having two or more reactive groups has a polyoxyalkylene chain in its structure. [4] The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the surfactant (B2) having two or more reactive groups is a urethane (meth)acrylate. [5] The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the active energy ray-curable compound (B1) has two or more (meth)acryloyl groups. [6] The active energy ray-curable peel-type pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the surfactant (B3) other than the (B2) is a surfactant represented by the following general formula (1): XO-(Y 1 O)m-(Y 2 O)n-SO 3 Z (1) (wherein X is a functional group having a double bond. Y 1 and Y 2 is an alkylene group, and Y 1 and Y 2 are different groups. Z is a counter ion. m is an integer of 1 or more, and n is an integer of 0 or more. Effect of the Invention

[0012] The present invention relates to an active energy ray-curable peel-type pressure-sensitive adhesive composition comprising an acrylic emulsion (A) and a radically polymerizable composition (B) comprising the following (B1) to (B3): (B1): Active energy ray-curable compound. (B2): A surfactant having two or more reactive groups. (B3): A surfactant other than (B2). Therefore, despite the use of a water-based acrylic resin, the non-volatile content is high and the storage stability is excellent, making it suitable for use as an adhesive in adhesive sheets for surface protection. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described below based on examples of the mode for carrying out the present invention. However, the present invention is not limited to the embodiment described below.

[0014] In the present invention, "Q and / or R (Q and R are optional configurations)" means at least one of Q and R, and means three possibilities: Q only, R only, and Q and R. When expressed as "q to r" (q and r are any numbers), unless otherwise specified, it includes the meaning of "greater than q and less than r", as well as "preferably greater than q" or "preferably smaller than r". When it is expressed as "q or more" (q is any number) or "r or less" (r is any number), it also includes the meaning that "it is preferably greater than q" or "it is preferably less than r".

[0015] In the present invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate. In addition, "acrylic resin" means a resin obtained by polymerizing a copolymerization component containing at least one (meth)acrylate monomer. In the present invention, the term "sheet" includes the meanings of "film" and "tape". In the present invention, the term "main component" means a component that has a significant effect on the properties of the target object, and the content of the component in the target object is usually 50 mass % or more, preferably 55 mass % or more, more preferably 60 mass % or more, and even more preferably 70 mass % or more, and may be 100 mass %.

[0016] An active energy ray-curable peel-type pressure-sensitive adhesive composition (hereinafter, sometimes referred to as "pressure-sensitive adhesive composition") according to one embodiment of the present invention comprises an acrylic emulsion (A) and a radically polymerizable composition (B) comprising the following (B1) to (B3): (B1): Active energy ray-curable compound. (B2): A surfactant having two or more reactive groups. (B3): A surfactant other than (B2). Each component is described below.

[0017] <<Acrylic emulsion (A)>> The acrylic emulsion (A) used in the present embodiment may be either an acrylic resin stabilized in water using an emulsifier (emulsifier-based acrylic emulsion) or an acrylic emulsion polymerized without using an emulsifier (non-emulsifier-based acrylic emulsion). The resin content of the acrylic emulsion (A) is preferably 30 to 70% by mass, and more preferably 40 to 65% by mass from the viewpoints of drying property and coatability. The "dispersion stabilized" state refers to a dispersion state in which the emulsion does not separate or precipitate and remains uniform even when left to stand for one month at 23° C. The emulsifier includes dispersants, and specifically refers to surfactants (anionic surfactants, cationic surfactants, and nonionic surfactants).

[0018] (Emulsifier-based acrylic emulsion) The emulsifier-based acrylic emulsion is produced by emulsion polymerization of radically polymerizable monomers.

[0019] The radical polymerizable monomer is a monomer mainly composed of a (meth)acrylic acid alkyl ester, and may contain a radical polymerizable functional monomer, a radical polymerizable polyfunctional monomer, or other radical polymerizable monomers, if desired.

[0020] As the (meth)acrylic acid alkyl ester, for example, a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 20 carbon atoms is preferable, and specifically, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyanyl ...butyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl Examples of the alkyl (meth)acrylate include aliphatic (meth)acrylic acid alkyl esters such as ethyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, and cyclohexyl (meth)acrylate, and aromatic (meth)acrylic acid alkyl esters such as benzyl (meth)acrylate. Among these, aliphatic (meth)acrylic acid alkyl esters are preferred, and furthermore, (meth)acrylic acid alkyl esters having an alkyl group with 1 to 8 carbon atoms are preferred, and (meth)acrylic acid alkyl esters having an alkyl group with 1 to 4 carbon atoms are more preferred. Most preferred is methyl methacrylate. These may be used alone or in combination of two or more.

[0021] Examples of the radical polymerizable functional monomer include hydroxy group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; acetoacetyl group-containing monomers such as acetoacetoxymethyl (meth)acrylate and allyl acetoacetate; amide group-containing monomers such as acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N-methylmethacrylamide, N,N-dimethylmethacrylamide, N-methylol acrylamide, N-methylol methacrylamide, and diacetone acrylamide; amino group-containing monomers such as mono- or dimethylaminoethyl (meth)acrylate, mono- or diethylaminoethyl (meth)acrylate, mono- or dimethylaminopropyl (meth)acrylate, and mono- or diethylaminopropyl (meth)acrylate;γ-(meth)acryloxyethyl trimethoxysilane, γ-(meth)acryloxyethyl triethoxysilane, γ-(meth)acryloxypropyl trimethoxysilane, γ-(meth)acryloxypropyl triethoxysilane, γ-(meth)acryloxypropyl methyl dimethoxysilane, γ-(meth)acryloxypropyl dimethyl methoxysilane, γ-(meth)acryloxypropyl methyl diethoxysilane, γ-(meth)acryloxypropyl dimethyl ethoxysilane, γ-(meth)acryloxypropyl trichlorosilane, γ-(meth)acryloxypropyl methyl dichlorosilane, γ-(meth)acryloxypropyl dimethyl chlorosilane, γ-(meth)acryloxypropyl tripropyoxysilane, γ-(meth)acryloxypropyl methyl dipropionyl alkoxysilyl group-containing monomers such as oxysilane, γ-(meth)acryloxypropyl tributoxysilane, γ-(meth)acryloxybutyl trimethoxysilane, γ-(meth)acryloxypentyl trimethoxysilane, γ-(meth)acryloxyhexyl trimethoxysilane, γ-(meth)acryloxyhexyl triethoxysilane, γ-(meth)acryloxyoctyl trimethoxysilane, γ-(meth)acryloxydecyl trimethoxysilane, γ-(meth)acryloxydodecyl trimethoxysilane, γ-(meth)acryloxyoctadecyl trimethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tripropoxysilane, vinyl methyl dimethoxysilane, vinyl methyl diethoxysilane, and vinyl methyl dipropoxysilane;Examples of the monomer include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, it is particularly preferable to use a carboxyl group-containing monomer in terms of polymerization stability, storage stability, and the holding power and constant load holding power of the resulting pressure-sensitive adhesive composition. These radically polymerizable functional monomers may be used alone or in combination of two or more. The content of the carboxyl group-containing monomer is preferably 0.5 to 10 parts by mass per 100 parts by mass of the total amount of the radically polymerizable monomers. If the content is too high, the adhesive strength of the resulting pressure-sensitive adhesive composition tends to decrease. On the other hand, if the content is too low, the polymerization stability and storage stability tend to decrease.

[0022] Examples of the radical polymerizable polyfunctional monomer include alkylene glycol (meth)acrylates such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; dialkylene glycol (meth)acrylates such as diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate; and trialkylene glycol (meth)acrylates such as triethylene glycol di(meth)acrylate and tripropylene glycol di(meth)acrylate. polyalkylene glycol (meth)acrylates such as polyethylene glycol di(meth)acrylate and polypropylene glycol di(meth)acrylate; trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, glycerin methacrylate acrylate, glycerin di(meth)acrylate, tris(meth)acryloyloxyphosphate, diallyl terephthalate, tetraallyloxyethane, divinylbenzene, tri(meth)allyl isocyanurate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and the like. Examples of the other monomers include vinyl esters, vinylpyridine, vinyl acetate, vinyl propionate, styrene, acrylonitrile, methacrylonitrile, butadiene, and chloroprene.

[0023] The pH of such an acrylic emulsion measured at 25° C. is preferably 1.8 to 9.5, more preferably 2.0 to 9.5, and even more preferably 5.8 to 9.5. When the pH is within these ranges, the storage stability tends to be good.

[0024] The emulsifier-based acrylic emulsion is usually produced by emulsion polymerization using ion-exchanged water, and the surfactant is not particularly limited as long as it has the function of emulsifying each component in an aqueous medium, and anionic, cationic, nonionic, and amphoteric surfactants can be used.

[0025] Examples of the anionic surfactant include potassium oleate, sodium laurate, sodium dodecylbenzenesulfonate, sodium alkanesulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, sodium polyoxyethylene alkyl ether sulfate (e.g., LATEMURU E-118B manufactured by Kao Corporation), sodium polyoxyethylene alkyl allyl ether sulfate, polyoxyethylene alkyl phosphate, and polyoxyethylene alkyl allyl phosphate, as well as non-reactive surfactants such as alkyl allyl sulfosuccinate (e.g., ELEMINOL JS-20 manufactured by Sanyo Chemical Industries, Ltd., and LATEMURU S-180A and S-180 manufactured by Kao Corporation), and polyoxyethylene alkylpropenyl phenyl ether sulfate ammonium salt (e.g., AQUALON HS-10, HS-5, and B manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). C-10, BC-5, etc.), α-sulfo-ω-(1-(nonylphenoxy)methyl-2-(2-propenyloxy)ethoxy)-poly(oxy-1,2-ethanediyl) ammonium salt (for example, ADEKA REASOAP SE-10, SE-1025A, etc.), polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ester ammonium salt (for example, Aqualon KH, Daiichi Kogyo Seiyaku Co., Ltd. -10, etc.), α-sulfo-ω-(1-(alkoxy)methyl-2-(2-propenyloxy)ethoxy)-poly(oxy-1,2-ethanediyl)ammonium salts (e.g., ADEKA REASOAP SR-10, SR-1025, etc.), and polyoxyalkylene alkenyl ether ammonium sulfate salts (e.g., Kao Corporation: Latemul PD-104, etc.).

[0026] Examples of the cationic surfactant include non-reactive surfactants such as stearylamine hydrochloride, lauryltrimethylammonium chloride, and trimethyloctadecylammonium chloride.

[0027] Examples of the nonionic surfactant include non-reactive surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene oxypropyl block polymers, polyethylene glycol fatty acid esters, and polyoxyethylene sorbitan fatty acid esters, as well as reactive surfactants such as α-hydro-ω-(1-alkoxymethyl-2-(2-propenyloxy)ethoxy)-poly(oxy-1,2-ethanediyl)s (e.g., Adeka Reasoap ER-10, ER-20, ER-30, and ER-40, manufactured by ADEKA CORPORATION), polyoxyethylene alkyl propenyl phenyl ethers (e.g., Aqualon RN-20, RN-30, and RN-50, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and polyoxyalkyl alkenyl ethers (e.g., Latemul PD-420, PD-430, and PD-450, manufactured by Kao Corporation).

[0028] Furthermore, an amphoteric surfactant may be used as the amphoteric component. These surfactants may be used alone or in combination of two or more. From the viewpoints of polymerization stability and storage stability of the resulting pressure-sensitive adhesive composition, it is preferable that the composition contains an anionic surfactant.

[0029] In producing the acrylic emulsion, a polymerization initiator is preferably used. As the polymerization initiator, those generally used in radical polymerization can be used. Specifically, alkyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, p-methane hydroperoxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylhexanoyl peroxide, t-butyl ... Organic peroxides such as trimethylcyclohexane, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, diisobutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and t-butyl peroxyisobutyrate, 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), tolyl), potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, ammonium (amine) salt of 4,4'-azobis-4-cyanovaleric acid, 2,2'-azobis(2-methylamidoxime) dihydrochloride, 2,2'-azobis(2-methylbutanamidoxime) dihydrochloride tetrahydrate, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]-propionamide}, 2,2' -azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], various redox catalysts (in this case, ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, p-methane hydroperoxide, etc. are used as oxidizing agents, and sodium sulfite, acidic sodium sulfite, Rongalite, ascorbic acid, isoascorbic acid, etc. are used as reducing agents.Among these, potassium persulfate, ammonium persulfate, sodium persulfate, redox catalysts (oxidizing agents: potassium persulfate, ammonium persulfate, sodium persulfate; reducing agents: sodium sulfite, acidic sodium sulfite, Rongalit, ascorbic acid, isoascorbic acid), and the like are preferred in terms of excellent polymerization stability.

[0030] The acrylic emulsion is preferably produced by using ion-exchanged water and carrying out radical polymerization at a polymerization temperature of 50 to 100°C after replacing the polymerization system with an inert gas such as nitrogen gas.

[0031] The acrylic emulsion can be obtained by a known emulsion polymerization method such as a monomer dropping method, a pre-emulsion method, a pre-charge method, a seed emulsion polymerization method, or a power feed method. The polymer particle size of the obtained acrylic emulsion, as measured by a laser scattering method, is preferably from 40 to 250 nm, more preferably from 50 to 200 nm, and further preferably from 60 to 160 nm. In particular, when the particle size of the polymer is 40 to 250 nm, the viscosity, concentration, and thixotropy of the acrylic emulsion become appropriate, and there is a tendency for the wettability and adhesiveness to improve.

[0032] The glass transition temperature (Tg) of the polymer in the acrylic emulsion is 10°C or lower, more preferably from -70 to 10°C, and even more preferably from -60 to 5°C. If the glass transition temperature (Tg) of the polymer is too high, the elastic modulus of the pressure-sensitive adhesive increases, and there is a risk of the adhesive strength decreasing. Moreover, if the glass transition temperature (Tg) of the polymer is too low, the cohesive strength may decrease, resulting in a decrease in adhesive strength.

[0033] Here, the glass transition temperature (Tg) is calculated by the Fox formula shown below. (FOX formula) 1 / Tg=W 1 / Tg 1 +W 2 / Tg2 +···+W n / Tg n In the above formula, W 1 From W n indicates the mass fraction of each monomer used, and Tg 1 From Tg n means the glass transition temperature (unit: absolute temperature "K") of the homopolymer of each monomer. Additionally, absolute temperature is calculated as absolute temperature "K" = Celsius temperature "℃" + 273.15.

[0034] The glass transition temperature (Tg) is the temperature at which the polymer particles in an emulsion undergo a phase change from a hard and brittle glass state to a soft rubber state, and the presence of this inflection point can be easily confirmed by measuring it with an analyzer such as a differential scanning calorimeter (DSC).

[0035] (Non-emulsifier acrylic emulsion) The non-emulsifier-based acrylic emulsion is preferably a synthetic resin emulsion containing polymer particles having a core-shell structure, and specifically, a synthetic resin emulsion containing polymer particles having a core-shell structure, in which the shell is made of a polymer obtained by polymerizing a carboxyl group-containing monomer and a hydrophilic comonomer in an aqueous medium, and the core is made of a polymer of a monomer mixture obtained by polymerizing a monomer mixture of a radically polymerizable main monomer and a radically polymerizable functional monomer in an aqueous polymer solution of the carboxyl group-containing monomer and the hydrophilic comonomer that is not neutralized, is preferred.

[0036] That is, a polymer particle having a core-shell structure is a polymer particle consisting of a central core and a shell that covers the core. In the present invention, the polymer particle having a core-shell structure includes not only the case where the shell completely covers the core, but also the case where the shell covers only a part of the core.

[0037] A method for producing a synthetic resin emulsion in the case where the acrylic emulsion (A) is a synthetic resin emulsion containing polymer particles having a core-shell structure will be described below. First, a carboxyl group-containing monomer and a hydrophilic comonomer are prepared and polymerized in an aqueous medium to obtain an aqueous solution of the polymer that will become the shell. Next, without neutralizing this aqueous polymer solution, a monomer mixture for forming the core polymer and a pH adjuster are added, and a polymerization reaction is carried out to obtain a synthetic resin emulsion. That is, in the method for producing the synthetic resin emulsion, the polymer (water-soluble polymer) that will become the shell is formed in the early stage of polymerization and exists in the polymerization system as a water-soluble polymer. Then, in the presence of the aqueous solution of the water-soluble polymer, a monomer mixture is added to proceed with polymerization. At this time, the water-soluble polymer that will become the shell also functions as an emulsifier in the polymerization system, and the polymerization proceeds, and finally, particles having a so-called core-shell structure are formed in which the water-soluble polymer that will become the shell covers the core polymer.

[0038] The monomer mixture is preferably composed of monomers selected so that the glass transition temperature (Tg) of the polymer obtained after polymerization is 10° C. or lower. The glass transition temperature (Tg) of the core polymer obtained by the polymerization is preferably 10° C. or lower, more preferably −70° C. to 10° C., and most preferably −60° C. to 5° C. In this manner, when the core polymer obtained by the polymerization has a Tg of 10° C. or lower, the pressure-sensitive adhesive composition containing the synthetic resin emulsion exhibits good tack, which is preferable.

[0039] The shell of the polymer particles having the core-shell structure may be, for example, a polymer of a carboxyl group-containing monomer and a hydrophilic comonomer. That is, the polymer that becomes the shell (hereinafter, sometimes referred to as a "shell polymer") can be obtained by polymerizing the carboxyl group-containing monomer and the hydrophilic comonomer in an aqueous medium in the presence of a polymerization initiator.

[0040] Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, etc. These can be used alone or in combination of two or more. Among these, acrylic acid or methacrylic acid is preferred, and acrylic acid is particularly preferred in terms of reactivity with other monomers, stability during polymerization, and balancing between solubility in water and adhesive properties.

[0041] The amount of the carboxyl group-containing monomer used is preferably 1 to 50% by mass, more preferably 2 to 40% by mass, based on the total amount of monomers in the shell. In this manner, when the amount of the carboxyl group-containing monomer used is within the above range, the sensitivity to moisture is reduced, and therefore, changes in adhesive properties during daily use are reduced, which is preferable.

[0042] The hydrophilic comonomer is preferably one other than the carboxy group-containing monomer and has a solubility in water of 2 g / 100 g or more, and specific examples thereof include (meth)acrylic acid hydroxy ester, (meth)acrylic acid ester having n oxyethylene structures in the side chain, vinyl pyrrolidone, vinyl acetate, N-methylolacrylamide, alkoxymethylacrylamide, dimethylaminoethyl methacrylate, diacetone acrylamide, N-butylacrylamide, acrylamide, methacrylamide, phosphate group-containing monomer, etc. These may be used alone or in combination of two or more kinds. Among these, from the viewpoints of copolymerizability with the carboxy group-containing monomer and ease of swelling in water, (meth)acrylic acid hydroxy esters are preferred, and among these, hydroxyethyl (meth)acrylate is particularly preferably used.

[0043] The amount of the hydrophilic comonomer used is preferably 50 to 99% by mass, more preferably 60 to 98% by mass, based on the total monomers in the shell. In this way, when the amount of the hydrophilic comonomer used is within the above range, the stability during polymerization is good, and it is possible to prevent the viscosity during polymerization from increasing significantly, so that a product with good stability can be obtained, and stable adhesive performance can be obtained, which is preferable.

[0044] The polymerization initiator used for polymerizing the carboxyl group-containing monomer and the hydrophilic comonomer in an aqueous medium is, for example, a radical decomposition by heat or a reducing substance to proceed with the addition polymerization of the monomer, and includes water-soluble or oil-soluble persulfates, peroxides, azobis compounds, etc. Specific examples include potassium persulfate, ammonium persulfate, t-butyl hydroperoxide, hydrogen peroxide, azobisisobutylnitrile (AIBN), etc. These can be used alone or in combination of two or more kinds.

[0045] The polymerization initiator may be used in combination with a transition metal ion, such as ferric sulfate, cupric chloride, or ferric chloride.

[0046] The polymerization process of the polymer that becomes the shell will be specifically described as follows. First, the polymerization for obtaining the polymer that will become the shell is carried out by charging an aqueous medium into a reaction vessel, heating it, then adding a carboxyl group-containing monomer and a hydrophilic monomer, further heating it, and adding a polymerization initiator as appropriate to proceed with the polymerization reaction. This results in an aqueous solution (aqueous polymer solution) in which a transparent water-soluble polymer is dissolved or dispersed in water. Examples of aqueous media that can be used here include water and mixtures of water and alcohols such as ethanol. The aqueous polymer solution obtained is used in the next step of polymerizing the polymer that will become the core without neutralization.

[0047] The core of the polymer particle having a core-shell structure is preferably made of a polymer of a monomer mixture consisting of a radically polymerizable main monomer and a radically polymerizable functional monomer, the polymer having a glass transition temperature (Tg) of 10° C. or less. For this reason, the monomer of the monomer mixture is preferably selected so that the polymer obtained after polymerization has a Tg of 10° C. or less. That is, the core polymer (hereinafter sometimes referred to as "core polymer") is formed by polymerizing the shell polymer as described above, and then adding the monomer mixture and a pH adjuster to an aqueous solution of this polymer without neutralizing the aqueous solution (i.e., without neutralizing the aqueous solution), and then emulsion polymerizing the resulting solution.

[0048] In the method for producing the synthetic resin emulsion, the polymerization of the core polymer is started in the presence of an aqueous solution of the polymer (water-soluble polymer) that forms the shell, while the aqueous solution is still in an unneutralized state. The reason why the aqueous solution of the polymer is used in the subsequent core formation step without going through a neutralization process is that the pH of the aqueous solution of the polymer (water-soluble polymer) can be kept in the acidic range, preferably at pH 7 or less, by not carrying out the neutralization process, and thus the polymerization reaction can proceed stably. As a result, only a part of the polymer component is neutralized by the pH adjuster added during emulsion polymerization during polymerization, and it is considered that only the polymerization stability (or storage stability) can be improved without impairing the reactivity of the polymerization system.

[0049] It is also preferable to carry out the emulsion polymerization for forming the core polymer immediately after the formation of the shell polymer, since the water-soluble polymer formed in the first polymerization does not exist alone but is partially copolymerized with the core polymer component, thereby improving the stain resistance.

[0050] The monomer used to form the core polymer is preferably a monomer mixture consisting of a radically polymerizable main monomer and a radically polymerizable functional monomer. The radically polymerizable main monomer is a monomer that is the main component of the core polymer and has radical polymerizability. The radically polymerizable functional monomer is a functional monomer that can modify the core polymer to further impart functions and has radical polymerizability.

[0051] Examples of the radically polymerizable main monomer include (meth)acrylic acid alkyl esters, olefins, vinyl esters, aromatic vinyl compounds, etc. These may be used alone or in combination of two or more kinds.

[0052] More specifically, examples of the (meth)acrylic acid alkyl ester include (meth)acrylic acid alkyl esters having an alkyl group with 1 to 12 carbon atoms, such as methyl, ethyl, n-butyl, t-butyl, propyl, 2-ethylhexyl, octyl, etc., cyclohexyl acrylate, cyclohexyl methacrylate, etc. Examples of the olefin include ethylene, propylene, etc. Examples of the vinyl ester include vinyl acetate, vinyl ester of a branched carboxylic acid, vinyl laurate, etc. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, etc.

[0053] Among these, the radical polymerizable main monomer is preferably the (meth)acrylic acid alkyl ester, styrene, or vinyl ester of branched carboxylic acid, and more preferably used in combination of two or more. Specific examples include a combination of two or more (meth)acrylic acid alkyl esters, a combination of two or more (meth)acrylic acid alkyl esters and styrene, and a combination of a vinyl ester of branched carboxylic acid and an alkyl methacrylate ester, which are preferred from the viewpoint of polymerization stability and the like. Among these, the radical polymerizable main monomer is most preferably used in combination of two or more (meth)acrylic acid alkyl esters. Specifically, a combination of 2-ethylhexyl (meth)acrylate / butyl (meth)acrylate / methyl (meth)acrylate, or a combination of 2-ethylhexyl (meth)acrylate / methyl (meth)acrylate is preferred. Such a combination is preferred because it is easy to adjust the glass transition temperature (Tg) of the core polymer to 0° C. or less, and is advantageous from the viewpoint of improving various adhesive properties.

[0054] The amount of the radically polymerizable main monomer used is preferably 50 to 99% by mass, more preferably 70 to 98% by mass, based on the total monomers in the core. If the amount used is too small, sufficient adhesiveness as a pressure-sensitive adhesive composition may not be obtained, whereas if the amount used is too large, the hydrophobicity becomes too high, and polymerization tends to become unstable.

[0055] Examples of the radical polymerizable functional monomer include functional monomers having a carboxy group, an alkoxysilyl group, a hydroxyl group, an amide group, a nitrile group, a glycidyl group, a methylol group, a carbonyl group, a quaternary ammonium salt, an ethylene oxide chain, and chlorine in the side chain, etc. These may be used alone or in combination of two or more kinds.

[0056] Examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, crotonic acid, and maleic acid.

[0057] Other functional monomers include monomers having an alkoxysilyl group, such as vinyltriethoxysilane and 3-methacryloxypropyltriethoxysilane. Also, monomers having a hydroxyl group include, for example, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl methacrylate, and hydroxybutyl acrylate. Monomers having an amide group include, for example, acrylamide and methacrylamide. Monomers having a nitrile group include, for example, acrylonitrile. Also, monomers having the glycidyl group include, for example, glycidyl methacrylate and glycidyl acrylate. Monomers having a methylol group include, for example, N-methylol acrylamide. Monomers having a carbonyl group include, for example, acetoacetoxyethyl methacrylate. Monomers having chlorine in the side chain include, for example, vinyl chloride and vinylidene chloride.

[0058] When a monomer having a carboxy group is used as the radical polymerizable functional monomer, the amount used is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total monomers in the core. That is, if the amount used is too small, the polymerization stability may be insufficient, whereas if the amount used is too large, the resulting emulsion may have too high a viscosity or insufficient adhesive strength.

[0059] The monomers forming the core polymer may include a radical polymerizable polyfunctional monomer. Examples of the radical polymerizable polyfunctional monomer include divinyl compounds, di(meth)acrylate compounds, tri(meth)acrylate compounds, tetra(meth)acrylate compounds, diallyl compounds, triallyl compounds, and tetraallyl compounds. More specifically, divinylbenzene, divinyl adipate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,3-butyl di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, diallyl phthalate, triallyl dicyanurate, and tetraallyloxyethane.

[0060] The method of adding the monomer that forms the core polymer includes a batch polymerization method in which the entire amount is added to a reaction vessel at once, and a dropping method in which the monomer is added dropwise, but the dropping method is preferably used.

[0061] In the production of the synthetic resin emulsion, it is preferable to add a pH adjuster together with the monomer for forming the core polymer when dropping it. The reason why the pH adjuster is added together with the monomer for forming the core is that the pH adjuster is added during polymerization of the core polymer, so that the particles are uniformly partially neutralized from the inside, and as a result, the polymerization reaction proceeds more stably than when the film after film formation is not neutralized or neutralized afterwards. In addition, compared to when the aqueous solution of the polymer (water-soluble polymer) forming the shell is neutralized and polymerized, the copolymerization between the shell polymer and the core polymer is not impaired, and the shell polymer is also partially copolymerized with the core polymer, so that the contamination resistance is further improved.

[0062] Examples of the pH adjuster include alkali metal salts, ammonia, and amines. The amount of the pH adjuster used is preferably 1 to 75% by mass, more preferably 3 to 50% by mass, based on the total unsaturated carboxylic acid including the core and shell. That is, if the amount used is too small, the neutralization of the unsaturated carboxylic acid may be insufficient, and the polymerization may become unstable. Conversely, if the amount used is too large, the viscosity after neutralization may be significantly high, the workability may decrease, and the sensitivity to moisture in the air may increase, and the physical properties during use may become unstable.

[0063] The polymerization carried out to form the core polymer is carried out by subjecting the monomer mixture and It is also possible to carry out the polymerization in an aqueous medium containing other components in addition to the pH adjuster. Examples of the other components include a polymerization initiator, a protective colloid, a chain transfer agent, an ultraviolet absorber, and a photo-oxidation inhibitor. These can be used alone or in combination of two or more kinds.

[0064] Examples of the polymerization initiator include water-soluble or oil-soluble persulfates, peroxides, and azobis compounds. Specific examples include potassium persulfate, ammonium persulfate, t-butyl hydroperoxide, hydrogen peroxide, and azobisisobutylnitrile (AIBN). These can be used alone or in combination of two or more. The polymerization initiator may be used in combination with a transition metal ion as necessary. Examples of the transition metal ion include ferric sulfate, cupric chloride, and ferric chloride.

[0065] Examples of the protective colloid include polyvinyl alcohol and its derivatives, cellulose ether and its derivatives, and starch derivatives, which are used in the form of an aqueous solution.

[0066] Examples of the chain transfer agent include alcohols such as methanol, ethanol, propanol, and butanol, carboxylic acids having 2 to 8 carbon atoms such as acetone, methyl ethyl ketone, cyclohexane, acetophenone, acetaldehyde, propionaldehyde, n-butylaldehyde, furfural, and benzaldehyde, and mercaptans such as dodecyl mercaptan, lauryl mercaptan, normal mercaptan, thioglycolic acid, octyl thioglycolate, and thioglycerol. These may be used alone or in combination of two or more.

[0067] As the ultraviolet absorbing agent, benzophenone derivatives and benzotriazole derivatives are preferably used. Some of these have a radical polymerizable unsaturated bond, and such derivatives are preferred because they can be copolymerized with the synthetic resin component.

[0068] As the photo-oxidation inhibitor, a hindered phenol-based or hindered piperidine-based agent can be suitably used. Some of these have a radically polymerizable unsaturated bond, and such agents are preferred because they can be copolymerized with the synthetic resin component.

[0069] Thus, an acrylic emulsion (A) having polymer particles with a core-shell structure is obtained, and in the present invention, the gel fraction of the acrylic emulsion (A) is preferably 40 to 90% by mass, more preferably 45 to 85% by mass, and particularly preferably 50 to 80% by mass. If the gel fraction is too low, the cohesive strength of the coating film tends to decrease, and if it is too high, the adhesive strength before UV irradiation tends to decrease.

[0070] Examples of methods for adjusting the gel fraction of the acrylic emulsion (A) to 40 to 90% by mass include blending a chain transfer agent, copolymerizing a polyfunctional unsaturated monomer (a monomer having at least two unsaturated groups in the molecule) or an unsaturated monomer having a self-crosslinking functional group (such as a hydrolyzable silyl group-containing monomer or a methylol group-containing monomer) as a copolymerization component, and copolymerizing unsaturated monomers having functional groups that can react with each other.

[0071] The gel fraction of the acrylic emulsion (A) refers to the proportion of the solvent-insoluble portion of the resin composition, and is calculated as the ratio (%) of the remaining coating mass after immersion in toluene at 23°C for 24 hours and drying of a 25 μm coating film of the acrylic emulsion (A) dried at 100°C for 3 minutes to the coating mass before immersion.

[0072] From the viewpoint of improving storage stability, it is preferable that the average particle size of the polymer contained in the obtained acrylic emulsion (A) is 2 μm or less, and particularly preferably 1 μm or less. The average particle size was measured by dropping 0.1 g of emulsion into 500 g of water, stirring and dispersing the emulsion to prepare an evaluation sample, and measuring the average particle size at 23° C. in Volume-Wt NICOMP DISTRIBUTION mode using a NICOMP380 manufactured by Particle Sizing Systems.

[0073] <<Radically polymerizable composition (B)>> In the present embodiment, the radical polymerizable composition (B) used together with the acrylic emulsion (A) comprises an active energy ray-curable compound (B1), a surfactant (B2) having two or more reactive groups, and a surfactant (B3) other than (B2).

[0074] <Active energy ray-curable compound (B1)> The active energy ray-curable compound (B1) refers to any compound that undergoes a chemical reaction and solidifies when irradiated with active energy rays such as ultraviolet rays or electron beams. In the present embodiment, it is preferable to use a compound such as a (meth)acrylate monomer or a urethane acrylate, and in particular, one having two or more (meth)acryloyl groups. Specific examples of the active energy ray-curable compound (B1) used in the present embodiment are shown below, and these can be used alone or in combination of two or more kinds.

[0075] Examples of the (meth)acrylate monomer include monofunctional (meth)acrylate monomers, difunctional (meth)acrylate monomers, and trifunctional or higher functional (meth)acrylate monomers. Examples of monofunctional (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-phenoxy-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, glycerin mono(meth)acrylate, glycidyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, Acrylate, dicyclopentanyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)-methyl (meth)acrylate, cyclohexanespiro-2-(1,3-dioxolan-4-yl)-methyl (meth)acrylate, cyclic trimethylolpropane formal acrylate, 3-ethyl-3-oxetanyl methyl (meth)acrylate, γ-butyrolactone (meth)acrylate, n-butyl (meth)acrylate, heptyl acrylate, Xyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, n-stearyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, nonylphenol propylene oxide modified (n=2.5) (Meth)acrylate, half (meth)acrylate of phthalic acid derivative such as 2-(meth)acryloyloxyethyl acid phosphate, 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, furfuryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, carbitol (meth)acrylate, butoxyethyl (meth)acrylate, (meth)acryloylmorpholine, allyl (meth)acrylate, polyoxyethylene secondary alkyl ether acrylate.

[0076] Examples of bifunctional (meth)acrylate monomers include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and ethylene oxide. Examples of the di(meth)acrylate include modified bisphenol A di(meth)acrylate, propylene oxide modified bisphenol A di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,6-hexanediol ethylene oxide modified di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid modified neopentyl glycol di(meth)acrylate, and 2-(meth)acryloyloxyethyl acid phosphate diester.

[0077] Examples of trifunctional or higher (meth)acrylate monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, isocyanuric acid ethylene oxide modified triacrylate, ethylene oxide modified dipentaerythritol hexa(meth)acrylate, ethylene oxide modified pentaerythritol tetra(meth)acrylate, caprolactone modified dipentaerythritol hexa(meth)acrylate, and caprolactone modified pentaerythritol tetra(meth)acrylate. The (meth)acrylate monomers can be used alone or in combination of two or more kinds.

[0078] As the (meth)acrylate monomer, one having two or more (meth)acryloyl groups, i.e., a bifunctional or higher (meth)acrylate monomer is preferred, a trifunctional or higher (meth)acrylate monomer is more preferred, a tetrafunctional or higher (meth)acrylate monomer is even more preferred, and a pentafunctional or higher (meth)acrylate monomer is even more preferred, in that the adhesive strength of the paste after UV irradiation is easily reduced. In particular, dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate are preferred. The hydroxyl value of the (meth)acrylate monomer is usually 0 to 300 mgKOH / g, preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, even more preferably 20 mgKOH / g or more, particularly preferably 30 mgKOH / g or more, and most preferably 35 mgKOH / g or more. If the hydroxyl value is equal to or more than the lower limit, hydrophilicity is increased and water resistance is improved. The hydroxyl value of the (meth)acrylate monomer is preferably 150 mgKOH / g or less, more preferably 130 mgKOH / g or less, even more preferably 125 mgKOH / g or less, particularly preferably 100 mgKOH / g or less, and most preferably 60 mgKOH / g or less. If the hydroxyl value is equal to or less than the upper limit, the storage stability is improved. The lower limit and the upper limit of the hydroxyl value of the active energy ray curable compound (B1) can be arbitrarily combined, and for example, 5 to 150 mgKOH / g are preferable, 10 to 130 mgKOH / g are more preferable, 20 to 125 mgKOH / g are more preferable, 30 to 100 mgKOH / g are particularly preferable, and 35 to 60 mgKOH / g are most preferable.

[0079] The active energy ray curable compound (B1) may be a urethane (meth)acrylate (excluding the surfactant (B2)). The urethane (meth)acrylate is water-insoluble and water-dispersible. "Water-insoluble and water-dispersible" means that it does not fall into either of the above definitions of "water-soluble" and "water-dispersible".

[0080] Examples of urethane (meth)acrylates include reaction products of polyisocyanates, polyols, and hydroxyl-containing (meth)acrylates, and reaction products of polyisocyanates and hydroxyl-containing (meth)acrylates. Among these, reaction products of polyisocyanates (b1) and hydroxyl-containing (meth)acrylates (b2) are preferred because they tend to reduce the adhesive strength of the paste after UV irradiation.

[0081] [Polyisocyanate (b1)] Examples of the polyisocyanate (b1) include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, trimer compounds or higher polymer compounds of these polyisocyanates, allophanate polyisocyanates, biuret polyisocyanates, adduct polyisocyanates, and water-dispersible polyisocyanates. Examples of aromatic polyisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate. Examples of aliphatic polyisocyanates include pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, and lysine triisocyanate. Examples of alicyclic polyisocyanates include hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate. These polyisocyanates (b1) may be used alone or in combination of two or more.

[0082] Among these, aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and lysine diisocyanate, and alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate and norbornene diisocyanate are preferred in terms of little yellowing, and isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate and hydrogenated xylylene diisocyanate are more preferred, and isophorone diisocyanate and hydrogenated xylylene diisocyanate are even more preferred in terms of excellent low crystallinity.

[0083] [Hydroxyl group-containing (meth)acrylate (b2)] The hydroxyl group-containing (meth)acrylate (b2) has one ethylenically unsaturated group. The number of the first and second terminals may be one, two, or three or more. Examples of the hydroxyl group-containing (meth)acrylate having one ethylenically unsaturated group include: 2-Hydroxyethyl (meth)acrylate, 2-Hydroxypropyl (meth)acrylate acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate Examples of the hydroxyl group-containing (meth)acrylates having two ethylenically unsaturated groups include glycerin di(meth)acrylate and 2-hydroxy-3-acryloyloxypropyl methacrylate. Examples of the hydroxyl group-containing (meth)acrylates having two ethylenically unsaturated groups include glycerin di(meth)acrylate and 2-hydroxy-3-acryloyloxypropyl methacrylate. Examples of the hydroxyl group-containing (meth)acrylates having two ethylenically unsaturated groups include glycerin di(meth)acrylate and 2-hydroxy-3-acryloyloxypropyl methacrylate. Examples of hydroxyl group-containing (meth)acrylates having three or more ethylenically unsaturated groups include pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, and ethylene oxide-modified dipentaerythritol penta(meth)acrylate. These hydroxyl group-containing (meth)acrylates (b2) may be used alone or in combination of two or more.

[0084] Among these, hydroxyl-containing (meth)acrylates containing two or more ethylenically unsaturated groups are preferred because the adhesive strength of the glue is likely to decrease after UV irradiation, more preferably hydroxyl-containing (meth)acrylates containing three or more ethylenically unsaturated groups, and even more preferably pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate.

[0085] The weight average molecular weight of the urethane (meth)acrylate is preferably 500 or more, more preferably 1,000 or more, even more preferably 1,300 or more, and particularly preferably 1,500 or more. If the weight average molecular weight of the urethane (meth)acrylate is the lower limit or more, the cohesive force is improved and the initial adhesive strength of the paste is high. The weight average molecular weight of the urethane (meth)acrylate is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 20,000 or less. If the weight average molecular weight of the urethane (meth)acrylate is the upper limit or less, the emulsification property and emulsion stability are excellent. The lower limit and the upper limit of the weight average molecular weight of the urethane (meth)acrylate can be arbitrarily combined, and for example, 1,000 to 100,000 are preferable, 1,300 to 50,000 are more preferable, and 1,500 to 20,000 are more preferable.

[0086] The method for producing the urethane (meth)acrylate is not particularly limited, and for example, a method can be used in which polyisocyanate (b1) and hydroxyl group-containing (meth)acrylate (b2) are charged into a reactor all at once or dropwise and reacted. The reaction is terminated when the residual isocyanate group content in the reaction system reaches 0.5 mass % or less, thereby obtaining a urethane (meth)acrylate.

[0087] In the above-mentioned production method, it is preferable to use a catalyst for the purpose of promoting the reaction. Examples of such catalysts include organometallic compounds, metal salts, amine catalysts, bismuth catalysts, zirconium catalysts, zinc 2-ethylhexanoate / zirconium tetraacetylacetonate. Examples of organometallic compounds include dibutyltin dilaurate, trimethyltin hydroxide, tetra-n-butyltin, and tin octoate. Examples of metal salts include zinc octenoate, tin octenoate, cobalt naphthenate, stannous chloride, and stannic chloride. Examples of amine catalysts include triethylamine, benzyldiethylamine, 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]undecene, N,N,N',N'-tetramethyl-1,3-butanediamine, and N-ethylmorpholine. Examples of bismuth catalysts include bismuth nitrate, bismuth bromide, bismuth iodide, bismuth sulfide, and other organic bismuth compounds such as dibutyl bismuth dilaurate and dioctyl bismuth dilaurate, and organic acid bismuth salts such as bismuth 2-ethylhexanoate, bismuth naphthenate, bismuth isodecanoate, bismuth neodecanoate, bismuth laurate, bismuth maleate, bismuth stearate, bismuth oleate, bismuth linoleate, bismuth acetate, bismuth rebisneodecanoate, bismuth disalicylate, and bismuth digallate. Examples of zirconium catalysts include inorganic zirconium, organic zirconium, and zirconium alone. Among these, dibutyltin dilaurate and 1,8-diazabicyclo[5,4,0]undecene are preferred. Note that these catalysts may be used alone or in combination of two or more.

[0088] In the above-mentioned production method, it is possible to use an organic solvent that does not have a functional group that reacts with an isocyanate group, for example, an organic solvent such as an ester such as ethyl acetate or butyl acetate, a ketone such as methyl ethyl ketone or methyl isobutyl ketone, or an aromatic such as toluene or xylene. From the viewpoint of reducing the environmental load, it is preferable to carry out the reaction without a solvent.

[0089] The reaction temperature can be from 30 to 90° C., and preferably from 40 to 80° C. The reaction time can be from 2 to 10 hours, and preferably from 3 to 8 hours.

[0090] When urethane (meth)acrylate is used, the ratio of urethane (meth)acrylate in 100% by mass of the active energy ray curable compound (B1) is preferably 5% by mass or more, more preferably 20% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more. The ratio of the urethane (meth)acrylate is preferably 100% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less. If the ratio of the urethane (meth)acrylate is within the above range, the emulsion stability is excellent. The lower limit and the upper limit of the ratio of the urethane (meth)acrylate can be arbitrarily combined, and for example, 5 to 100% by mass is preferable, 20 to 100% by mass is more preferable, 50 to 95% by mass is more preferable, and 70 to 90% by mass is particularly preferable.

[0091] The viscosity of the active energy ray curable compound (B1) at 60°C can be 1 mPa·s or more, preferably 10 mPa·s or more, more preferably 100 mPa·s or more, even more preferably 200 mPa·s or more, and particularly preferably 500 mPa·s or more. If the viscosity of the active energy ray curable compound (B1) is equal to or more than the lower limit of the above range, the need to reduce the viscosity by forced emulsification increases. The viscosity of the active energy ray curable compound (B1) at 60°C can be 100,000 mPa·s or less, preferably 500,000 mPa·s or less, more preferably 200,000 mPa·s or less, even more preferably 100,000 mPa·s or less, and particularly preferably 50,000 mPa·s or less. If the viscosity of the active energy ray curable compound (B1) is equal to or less than the upper limit of the above range, it becomes easy to apply shear force, and the emulsification property and emulsion stability are improved. The lower limit and the upper limit of the viscosity of the active energy ray-curable compound (B1) can be arbitrarily combined and can be, for example, 1 to 100,000 mPa·s, preferably 10 to 500,000 mPa·s, more preferably 100 to 200,000 mPa·s, still more preferably 200 to 100,000 mPa·s, and particularly preferably 500 to 50,000 mPa·s. The viscosity was measured using an E-type viscometer.

[0092] The content of the active energy ray curable compound (B1) in the pressure-sensitive adhesive composition of the present invention is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on the total of 100% by mass of the active energy ray curable compound (B1) and the surfactant. If the content of the active energy ray curable compound (B1) is equal to or more than the lower limit, the physical properties derived from the active energy ray curable compound (B1) are easily exhibited, and the adhesive strength of the paste after UV irradiation is easily reduced. The content of the active energy ray curable compound (B1) is preferably 99% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, particularly preferably 85% by mass or less, and particularly preferably 80% by mass or less. If the content of the active energy ray curable compound (B1) is equal to or less than the upper limit of the above range, the relative amount of the surfactant required to emulsify the active energy ray curable compound (B1) is less likely to be insufficient, and the emulsification property and emulsion stability are improved. The lower limit and the upper limit of the content of the active energy ray-curable compound (B1) can be arbitrarily combined, and is, for example, preferably 40 to 99 mass%, more preferably 50 to 95 mass%, further preferably 60 to 90 mass%, and particularly preferably 70 to 80 mass%.

[0093] <Surfactant (B2) Having Two or More Reactive Groups> As the surfactant having two or more reactive groups (hereinafter, sometimes referred to as surfactant (B2)), a surfactant that is water-soluble or water-dispersible is preferably used. In this embodiment, "water-soluble" means that the material can maintain a uniform appearance when it is dissolved in a 10% by mass aqueous solution. Also, "water-dispersible" means that the material is dispersed in a 10% by mass aqueous dispersion with a particle size (median diameter) of less than 100 nm. The particle size (median diameter) can be measured using a laser scattering / diffraction device (LA950V2, manufactured by Horiba, Ltd.). The surfactants (B2) shown below can be used alone or in combination of two or more kinds.

[0094] The reactive group of the surfactant (B2) can be exemplified by a functional group having a double bond, preferably a (meth)acryloyl group or an allyl group. The main chain structure of the surfactant (B2) is not limited as long as it has two or more reactive groups. In addition, the surfactant (B2) preferably has a hydrophilic group in the molecule. The hydrophilic group is preferably a nonionic group, more preferably a polyoxyalkylene chain, and even more preferably a polyoxyethylene chain. Specific examples include polyvinyl alcohol, acrylic (meth)acrylate, urethane (meth)acrylate, polyester (meth)acrylate, and polyether (meth)acrylate, each of which has two or more functional groups having a double bond.

[0095] Among these, urethane (meth)acrylates which are water-soluble or water-dispersible and have two or more functional groups with double bonds are preferred because the urethane bonds are more hydrophilic and the molecular design can be easily controlled. Examples of urethane (meth)acrylates that satisfy these conditions include the reaction product of the above-mentioned polyisocyanate (b1), hydroxyl group-containing (meth)acrylate (b2), and polyoxyethylene group-containing compound (b3). Also usable are reaction products of polyisocyanate (b1), hydroxyl group-containing (meth)acrylate (b2), polyoxyethylene group-containing compound (b3), and carboxyl group-containing polyol (b4), in which some or all of the carboxyl groups have been neutralized with a base.

[0096] An example of the polyoxyethylene group-containing compound (b3) is polyethylene glycol. The carboxyl group-containing polyol (b4) is preferably an aliphatic polyhydroxycarboxylic acid, more preferably a diol monocarboxylic acid having a molecular weight of 100 to 200 or a neutralized salt thereof, particularly preferably dimethylolbutanoic acid or dimethylolpropionic acid, and further preferably dimethylolbutanoic acid. The carboxyl groups derived from the carboxyl group-containing polyol (b4) are partially or completely neutralized with a base to become neutralized salts, thereby becoming hydrophilic.

[0097] The mass average molecular weight of the surfactant (B2) is preferably 500 or more, more preferably 1,000 or more. If the mass average molecular weight of the surfactant (B2) is the lower limit or more, the cohesive force is improved and the initial adhesive strength of the paste is high. The mass average molecular weight of the surfactant (B2) is preferably 50,000 or less, more preferably 20,000 or less. If the mass average molecular weight of the surfactant (B2) is the upper limit or less, the viscosity tends to be moderate and easy to handle. The lower limit and the upper limit of the mass average molecular weight of the surfactant (B2) can be arbitrarily combined, and for example, 500 to 50,000 are preferable, and 1,000 to 20,000 are more preferable.

[0098] When the surfactant (B2) is a urethane (meth)acrylate, the mass average molecular weight of the urethane (meth)acrylate is preferably 500 or more, more preferably 1,000 or more, and particularly preferably 2,000 or more. If the mass average molecular weight of the urethane (meth)acrylate is the lower limit or more, the cohesive force is improved and the initial adhesive strength of the paste is high. The mass average molecular weight of the urethane (meth)acrylate is preferably 50,000 or less, more preferably 20,000 or less, and particularly preferably 10,000 or less. If the mass average molecular weight of the urethane (meth)acrylate is the upper limit or less, the viscosity tends to be moderate and easy to handle. The lower limit and the upper limit of the mass average molecular weight of the surfactant (B2) can be arbitrarily combined, and for example, 500 to 50,000 are preferable, 1,000 to 20,000 are more preferable, and 2,000 to 10,000 are particularly preferable.

[0099] When the surfactant (B2) is a urethane (meth)acrylate, the viscosity of the urethane (meth)acrylate at 60°C is preferably 500 mPa·s or more, more preferably 1,000 mPa·s or more, and even more preferably 2,000 mPa·s or more. If the viscosity of the urethane (meth)acrylate is within the above range, there is a tendency for the urethane (meth)acrylate to have excellent handleability. The lower and upper limits of the viscosity of the urethane (meth)acrylate can be arbitrarily combined, and for example, 500 to 1,000,000 mPa·s is preferable, 1,000 to 500,000 mPa·s is more preferable, and 2,000 to 100,000 mPa·s is even more preferable. The viscosity can be measured by an E-type viscometer.

[0100] The method for producing the urethane (meth)acrylate is not particularly limited, and may be, for example, a method in which polyisocyanate (b1), hydroxyl group-containing (meth)acrylate (b2), polyoxyethylene group-containing compound (b3), and carboxyl group-containing polyol (b4) are charged in a reactor all at once or dropwise and reacted. The reaction is terminated when the residual isocyanate group content in the reaction system becomes 0.5 mass% or less, thereby obtaining the urethane (meth)acrylate.

[0101] In the above-mentioned production method, it is preferable to use a catalyst for the purpose of promoting the reaction. Examples of such catalysts include organometallic compounds, metal salts, amine catalysts, bismuth catalysts, zirconium catalysts, zinc 2-ethylhexanoate / zirconium tetraacetylacetonate. Examples of organometallic compounds include dibutyltin dilaurate, trimethyltin hydroxide, tetra-n-butyltin, and tin octoate. Examples of metal salts include zinc octenoate, tin octenoate, cobalt naphthenate, stannous chloride, and stannic chloride. Examples of amine catalysts include triethylamine, benzyldiethylamine, 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]undecene, N,N,N',N'-tetramethyl-1,3-butanediamine, and N-ethylmorpholine. Examples of bismuth catalysts include bismuth nitrate, bismuth bromide, bismuth iodide, bismuth sulfide, and other organic bismuth compounds such as dibutyl bismuth dilaurate and dioctyl bismuth dilaurate, and organic acid bismuth salts such as bismuth 2-ethylhexanoate, bismuth naphthenate, bismuth isodecanoate, bismuth neodecanoate, bismuth laurate, bismuth maleate, bismuth stearate, bismuth oleate, bismuth linoleate, bismuth acetate, bismuth rebisneodecanoate, bismuth disalicylate, and bismuth digallate. Examples of zirconium catalysts include inorganic zirconium, organic zirconium, and zirconium alone. Among these, dibutyltin dilaurate and 1,8-diazabicyclo[5,4,0]undecene are preferred. These catalysts can be used alone or in combination of two or more.

[0102] In the method for producing the urethane (meth)acrylate, an organic solvent having no functional group reactive with an isocyanate group, for example, an organic solvent such as esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatics such as toluene and xylene, can be used. From the viewpoint of reducing the environmental load, it is preferable to carry out the reaction without a solvent. The temperature (reaction temperature) when reacting the polyisocyanate (b1), the hydroxyl group-containing (meth)acrylate (b2), the polyoxyethylene group-containing compound (b3), and the carboxyl group-containing polyol (b4) can be 30 to 90°C, and preferably 40 to 80°C. The reaction time can be 2 to 10 hours, and preferably 3 to 8 hours.

[0103] The content of the surfactant (B2) in the pressure-sensitive adhesive composition of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 76% by mass or more, based on the total mass of the surfactant. If the content of the surfactant (B2) is equal to or more than the lower limit, the emulsion has a small particle size and a sharp particle size distribution, and the storage stability, particularly the freeze-thaw stability, is improved. The content of the surfactant (B2) is preferably 99.5% by mass or less, more preferably 99% by mass or less, even more preferably 95% by mass or less, and particularly preferably 90% by mass or less, based on the total mass of the surfactant. If the content of the surfactant (B2) is equal to or less than the upper limit, the physical properties derived from the active energy ray-curable compound (B1) are easily exhibited, and the adhesive strength of the paste after UV irradiation is easily reduced. The lower limit and upper limit of the content of the surfactant (B2) relative to the total mass of the surfactants can be combined in any combination, and is, for example, preferably 50 to 99.5 mass%, more preferably 60 to 99 mass%, even more preferably 70 to 95 mass%, and particularly preferably 76 to 90 mass%.

[0104] The content of the surfactant (B2) in the pressure-sensitive adhesive composition of the present invention is preferably 0.9% by mass or more, more preferably 4.0% by mass or more, even more preferably 8.5% by mass or more, and particularly preferably 18% by mass or more, based on the total 100% by mass of the active energy ray curable compound (B1) and the surfactant. If the content of the surfactant (B2) is above the lower limit, the emulsion has a small particle size and a sharp particle size distribution, and the storage stability is improved. The content of the surfactant (B2) is preferably 59.9% by mass or less, more preferably 49% by mass or less, even more preferably 38.5% by mass or less, and particularly preferably 25% by mass or less, based on the total 100% by mass of the active energy ray curable compound (B1) and the surfactant. If the content of the surfactant (B2) is below the upper limit, the physical properties derived from the active energy ray curable compound (B1) are easily exhibited, and the adhesive strength of the paste after UV irradiation is easily reduced. The lower limit and upper limit of the content of the surfactant (B2) relative to the total of 100 mass% of the active energy ray-curable compound (B1) and the surfactant can be arbitrarily combined, and is, for example, preferably 0.9 to 59.9 mass%, more preferably 4.0 to 49 mass%, even more preferably 8.5 to 38.5 mass%, and particularly preferably 18 to 25 mass%.

[0105] <Surfactant (B3) other than (B2)> The surfactant other than surfactant (B2) (hereinafter sometimes referred to as surfactant (B3)) is usually a surfactant having one reactive group. By further including surfactant (B3) in addition to surfactant (B2), a small particle size and uniform emulsion tends to be obtained.

[0106] The surfactant (B3) is preferably a surfactant having one functional group having a double bond. Such a functional group is preferably a (meth)acryloyl group or an allyl group. The surfactant (B3) shown below can be used alone or in combination of two or more kinds.

[0107] The surfactant (B3) preferably has a linear structure, and more preferably has a linear polyoxyalkylene structure. The alkylene group of the linear polyoxyalkylene chain is preferably an alkylene group having 2 to 4 carbon atoms. The surfactant (B3) preferably has such a linear polyoxyalkylene structure such that one of its two terminals is a functional group having a double bond, and the other terminal has a hydrophilic group. The hydrophilic group is preferably an ionic group (cationic, anionic or amphoteric), particularly preferably an anionic group, and particularly preferably a sulfonate group.

[0108] As the surfactant (B3), a surfactant represented by the following general formula (1) is more preferably used since it allows obtaining an aqueous emulsion composition with smaller particle size and greater uniformity. XO-(Y 1 O) m -(Y 2 O) n -SO 3 Z···(1) (wherein X is a functional group having a double bond. Y 1 and Y 2 are each independently an alkylene group, and Y 1 and Y 2 are different groups. Z is a counter ion. m is an integer of 1 or more, and n is an integer of 0 or more.

[0109] The functional group having a double bond of X is preferably a (meth)acryloyl group or an allyl group. Y 1 and Y 2 is preferably an alkylene group having 2 to 4 carbon atoms. m is preferably 2 or more, and more preferably 3 or more. The upper limit of m is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. n is preferably 1 or more, and more preferably 2 or more. The upper limit of n is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. Z is preferably NH4 + , Na + and particularly preferably NH 4 + It is.

[0110] Examples of such surfactants (B3) include (meth)acrylate-based, allyl-based, maleic acid-based, and itaconic acid-based surfactants. Specific examples include sulfoethyl methacrylate sodium salt, sulfoethyl methacrylate ammonium salt, allyl group-containing polyoxyethylene nonylphenyl ether sulfonate, polyoxyethylene lauryl ether maleate, polyoxyethylene lauryl ether methacrylate, polyoxyethylene nonylphenyl ether acrylate, and allyl group-containing polyoxyethylene nonylphenyl ether. These may be used alone or in combination of two or more.

[0111] The content of the surfactant (B3) in the pressure-sensitive adhesive composition of the present invention is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, and particularly preferably 2.0% by mass or more, based on the total of 100% by mass of the active energy ray curable compound (B1) and the surfactant. If the content of the surfactant (B3) is equal to or more than the lower limit, the emulsion tends to have a small particle size and a sharp particle size distribution, and storage stability is improved. The content of the surfactant (B3) is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 7.0% by mass or less, and particularly preferably 5.0% by mass or less. If the content of the surfactant (B3) is equal to or less than the upper limit, the physical properties derived from the active energy ray curable compound (B1) are easily exhibited, and the adhesive strength of the paste after UV irradiation is easily reduced. The lower and upper limits of the content of the surfactant (B3) can be arbitrarily combined and are, for example, preferably 0.1 to 20 mass%, more preferably 1.0 to 10 mass%, further preferably 1.5 to 7.0 mass%, and particularly preferably 2.0 to 5.0 mass%.

[0112] The compounding ratio of the active energy ray-curable compound (B1), the surfactant having two or more reactive groups (B2), and the surfactant (B3) other than (B2) is not particularly limited. However, from the standpoint of storage stability, the ratio of (B2) to (B1), (B2 / B1), is preferably in the range of 0.01 to 1.5, and more preferably in the range of 0.1 to 1.0. From the standpoint of storage stability, the ratio of (B3) to (B1), (B3 / B1), is preferably in the range of 0.01 to 0.1, and more preferably in the range of 0.03 to 0.08. Furthermore, from the standpoint of storage stability, the ratio of (B3) to (B2), (B3 / B2), is preferably in the range of 0.01 to 1.0, and more preferably in the range of 0.1 to 0.5.

[0113] The radically polymerizable composition (B) used in the present embodiment can be prepared in the form of an emulsion by, for example, mixing and stirring the active energy ray-curable compound (B1), the surfactant (B2), and, if used, the photopolymerization initiator (C) all at once, adding the surfactant (B3), adding purified water while heating and stirring in a dispersing device, and adding an antifoaming agent and a preservative, if used.

[0114] <Photopolymerization initiator (C)> In the present embodiment, it is preferable to contain a photopolymerization initiator (C) in addition to the acrylic emulsion (A) and the radical polymerizable composition (B). The photopolymerization initiator (C) may be used alone or in combination of two or more kinds.

[0115] As the photopolymerization initiator (C), for example, from the viewpoint of promoting curing when irradiated with active energy rays, it is preferable to further contain a photopolymerization initiator (C). In addition, the photopolymerization initiator (C) can be used alone or in combination of two or more kinds.

[0116] The photopolymerization initiator (C) is not particularly limited as long as it generates radicals by the action of light, and examples thereof include 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylenephenyl)-2-hydroxy-2-methylpropan-1-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyldimethyl ether, and the like. Examples of the benzoxanthane include tirketal, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3'-dimethyl-4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, camphorquinone, dibenzosuberone, 2-ethylanthraquinone, 4',4''-diethylisophthalophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, α-acyloxime ester, acylphosphine oxide, methylphenyl glyoxylate, benzil, 9,10-phenanthrenequinone, and 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone. Among these, benzil dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoin isopropyl ether, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl) ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, amides are preferred, and 1-hydroxycyclohexyl phenyl ketone (Omnirad 184; manufactured by IGMResins), 2-hydroxy-2-methyl-1-phenylpropan-1-one (Omnirad 1173; manufactured by IGMResins), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907; manufactured by IGMResins), and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Omnirad TPO; manufactured by IGMResins) are particularly preferred.

[0117] As the photopolymerization initiator (C), it is preferable to use a photopolymerization initiator that is water-soluble or water-dispersible, in order to further enhance the functionality of the aqueous dispersion as a pressure-sensitive adhesive composition. Examples of such photopolymerization initiator (C) include 2-(3-dimethylamino-2-hydroxypropoxy)-3,4-dimethyl-9H-thioxanthone-9-one methchloride (Quantacure QTX; manufactured by Octel Chemicals) and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (Omnirad 2959; manufactured by IGM Resins), which can be used alone or in combination of two or more kinds. Among these, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (Omnirad 2959; manufactured by IGM Resins) is more preferred.

[0118] The timing of adding the photopolymerization initiator (C) is not particularly limited, and the photopolymerization initiator (C) may be forcibly emulsified together with the acrylic emulsion (A), the radically polymerizable composition (B), etc., or may be added to the emulsion composition after the forcible emulsification. However, in the case of a water-insoluble and solid photopolymerization initiator (C), forcibly emulsifying them together tends to result in better coating appearance.

[0119] In addition to the components (A) and (B) and the optional photopolymerization initiator (C), the pressure-sensitive adhesive composition of the present invention may contain, if necessary, for example, an antifoaming agent, a preservative, a wetting agent, a plasticizer (liquid polybutene, mineral oil, lanolin, liquid polyisoprene, liquid polyacrylate, etc.), an antifungal agent, an antirust agent, an antifreeze agent, a high-boiling point solvent, a pigment, a colorant, a filler (zinc oxide, titanium white, calcium carbonate, clay, etc.), a metal powder, a thickener, an adhesion control agent, an ultraviolet absorber, an antioxidant, etc.

[0120] The adhesive composition according to the present embodiment can be produced by mixing such materials by, for example, a known method. The components (A) and (B) and other optional components may be mixed at once, but they may also be mixed in several batches, for example, by first mixing the components A and B and then mixing the other components into the mixture of the components A and B.

[0121] The adhesive composition thus obtained can be applied to a substrate, dried, and used as an adhesive sheet containing an adhesive layer. This adhesive sheet is usually used by being attached to an adherend. For example, it can be widely used as a protective sheet for the surface of a metal plate, a glass plate, a plastic plate, etc., or as a temporary fixing sheet, and is particularly useful for temporary adhesion in the back grinding process and dicing process of semiconductor wafers.

[0122] The substrate to which the pressure-sensitive adhesive composition is applied is preferably a film that transmits active energy rays. Examples of such films include transparent films such as polyvinyl chloride, polybutene, polybutadiene, polyurethane, ethylene-vinyl acetate polymer, polyethylene terephthalate, polyethylene, polypropylene, ethylene-propylene polymer, polymethylpentene, and polybutylene terephthalate.

[0123] The pressure-sensitive adhesive composition can be applied to a substrate by a conventional method such as roll coating, die coating, gravure coating, comma coating, screen printing, etc. The thickness of the pressure-sensitive adhesive layer after coating and drying is usually 10 to 50 μm, and preferably 15 to 40 μm.

[0124] When the pressure-sensitive adhesive sheet is attached to an adherend, it is also preferable to carry out an aging treatment. Such an aging treatment is carried out in order to balance the adhesive properties, and the aging conditions are usually room temperature to 70°C and the aging time is usually 1 to 30 days, and specifically, for example, 23°C for 1 to 20 days, or 40°C for 1 to 7 days.

[0125] The pressure-sensitive adhesive sheet can be easily peeled off from the adherend because the pressure-sensitive adhesive layer is cured by irradiation with active energy rays.

[0126] For the irradiation of active energy rays, light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, electromagnetic waves such as X-rays and gamma rays, as well as electron beams, proton beams, neutron beams, etc. can be used. Curing by ultraviolet irradiation is advantageous in terms of curing speed, ease of availability of irradiation equipment, cost, etc.

[0127] As a light source for the ultraviolet irradiation, for example, a high pressure mercury lamp, an electrodeless lamp, an ultra-high pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, etc. can be used. In the case of the high pressure mercury lamp, for example, 5 to 3,000 mJ / cm 2, preferably 10 to 2,000 mJ / cm 2 In the case of the electrodeless lamp, for example, the irradiation condition is 2 to 1,500 mJ / cm. 2 , preferably 5 to 500 mJ / cm 2 This is carried out under the following conditions. The irradiation time varies depending on the type of light source, the distance between the light source and the coated surface, the coating thickness, and other conditions, but is usually several seconds to several tens of seconds, and in some cases may be a fraction of a second. On the other hand, in the case of the electron beam irradiation, it is preferable to use an electron beam having an energy in the range of, for example, 50 to 1,000 Kev, and to set the irradiation dose at 2 to 50 Mrad. EXAMPLES

[0128] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are based on mass.

[0129] First, the following materials were prepared for use in the examples and comparative examples.

[0130] <Acrylic emulsion (A)> (A-1): Acrylic emulsion (VDM7410; Japan Coating Resin Co., Ltd.; Tg=0℃) (A-2): Acrylic emulsion (M461; Japan Coating Resin Co., Ltd.; Tg = -46°C) (A'-1): Acrylic emulsion (M6969D; Japan Coating Resin Co., Ltd.; Tg = 37°C)

[0131] <Active energy ray-curable compound (B1)> (B1-1): Dipentaerythritol acrylic acid adduct (KAYARAD DPHA; manufactured by Nippon Kayaku Co., Ltd.) (B1-2) and (B1-3) were synthesized as follows: [Synthesis of (B1-2)] Into a flask equipped with an internal thermometer, a stirrer, and a cooling tube, 66.18 g (0.298 mol) of isophorone diisocyanate, 933.82 g (0.799 mol) of an acrylic acid adduct of dipentaerythritol [hydroxyl value: 48.0 mg KOH / g], 0.80 g of 2,6-di-tert-butylcresol as a polymerization inhibitor, and 0.04 g of dibutyltin dilaurate as a reaction catalyst were added and reacted at 70°C. The reaction was terminated when the remaining isocyanate groups reached 0.1% or less, and a composition containing a urethane acrylate compound was obtained (resin concentration: 100%). [Synthesis of (B1-3)] Into a flask equipped with an internal thermometer, a stirrer, and a cooling tube, 181.69 g (0.817 mol) of isophorone diisocyanate, 818.31 g (1.676 mol) of an acrylic acid adduct of pentaerythritol [hydroxyl value: 114.9 mg KOH / g], 0.80 g of 2,6-di-tert-butylcresol as a polymerization inhibitor, and 0.04 g of dibutyltin dilaurate as a reaction catalyst were added and reacted at 70°C. The reaction was terminated when the remaining isocyanate groups reached 0.1% or less, and a composition containing a urethane acrylate compound was obtained (resin concentration: 100%).

[0132] <Surfactant (B2) Having Two or More Reactive Groups> A urethane acrylate (B2-1), which is a surfactant having two or more reactive groups, was used, which was prepared as described below. [Synthesis of (B2-1)] Into a flask equipped with an internal thermometer, a stirrer, and a condenser, 96.1 g (0.432 mol) of isophorone diisocyanate, 606 g (0.519 mol) of an acrylic acid adduct of dipentaerythritol [hydroxyl value: 48.0 mg KOH / g], 1.65 g of 2,6-di-tert-butylcresol as a polymerization inhibitor, and 0.1 g of dibutyltin dilaurate as a reaction catalyst were added and reacted at 70°C. Then, when the residual isocyanate groups reached 2.1% or less, the mixture was cooled to 60°C, and 298 g (0.302 mol) of polyethylene glycol (hydroxyl value: 114.0 mg KOH / g, mass average molecular weight calculated from the hydroxyl value: 984) was added and reacted at 60°C. The reaction was terminated when the residual isocyanate groups reached 0.1% or less, yielding a composition containing a urethane acrylate compound (resin concentration: 100%).

[0133] <Surfactant (B3) other than (B2)> (B3-1): Polyoxyalkylene alkenyl ether ammonium sulfate (Latemul PD-104; manufactured by Kao Corporation; solid content concentration 20%): corresponds to the above general formula (1).

[0134] <Photopolymerization initiator (C)> (C-1): 1-hydroxycyclohexyl phenyl ketone (Omnirad 184; IGM Resins) (C-2): 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (Omnirad TPO-H; IGM Resins) (C-3): 1-(9,9-dibutyl-9H-fluoren-2-yl)-2-methyl-2-morpholin-4-yl-propan-1-one

[0135] Next, emulsions having radically polymerizable compositions (B) were prepared using the prepared components as follows: The compositions of the emulsions are shown in Table 1 below. The values ​​of each component shown in Table 1 are all expressed in terms of solid content (the same applies to Tables 2 and 3 described below).

[0136] [Preparation of emulsion I] 200 g of (B1-1), 60 g of (B2-1), 6 g of (C-1), 2 g of (C-2), and 1 g of (C-3) were added to a cylindrical container and stirred, after which 50 g of (B3-1) was added. Purified water was then added while heating and stirring in a dispersing device to prepare an emulsion composition (non-volatile content 51.7%).

[0137] [Preparation of emulsion II] An emulsion composition (non-volatile content 53.4%) was prepared in the same manner as in Emulsion I, except that (B1-1) was replaced with (B1-2).

[0138] [Preparation of emulsion III] An emulsion composition (non-volatile content 53.5%) was prepared in the same manner as in Emulsion I, except that (B1-1) was replaced with (B1-3).

[0139] [Preparation of Emulsion IV] An emulsion composition (non-volatile content 50.0%) was prepared in the same manner as for emulsion I, except that (B3-1) was not used.

[0140] [Preparation of emulsion V] An emulsion composition (non-volatile content 50.0%) was prepared in the same manner as for emulsion I, except that (B2-1) was not used.

[0141] [Preparation of emulsion VI] 200 g of (B1-1), 6 g of (C-1), 2 g of (C-2), and 1 g of (C-3) were added to a cylindrical container and stirred, and then 50 g of an aqueous polyvinyl alcohol solution (PVOH: saponification degree 88%, molecular weight 37,000, non-volatile content 20%) was added as an emulsifier. Purified water was then added while heating and stirring in a dispersing device to prepare an emulsion composition (non-volatile content 55.3%).

[0142] [Preparation of emulsion ※VII] Into a flask equipped with an internal thermometer, a stirrer, and a condenser, 65.4 g (0.40 mol) of hexamethylene diisocyanate trimer (isocyanate group content 21.1%), 265.8 g (0.519 mol) of an acrylic acid adduct of dipentaerythritol [hydroxyl value: 46.0 mg KOH / g], 0.30 g of 2,6-di-tert-butylcresol as a polymerization inhibitor, and 0.05 g of dibutyltin dilaurate as a reaction catalyst were added and reacted at 50°C. When the residual isocyanate group was 1.4% or less, 168.8g (0.302 moles) of methoxy-polyethylene glycol-allyl ether [hydroxyl value: 37.3mgKOH / g, mass average molecular weight calculated from hydroxyl value: 1504] was added in 4 portions and reacted at 60℃. When the residual isocyanate group was 0.1% or less, ion-exchanged water preheated to 60℃ was added dropwise. When the resin concentration reached 20%, the addition was stopped, and the mixture was stirred for 5 minutes to produce a water dispersion of a self-emulsifying urethane (meth)acrylate compound. Note that this is not an emulsion but a dispersion, so it is annotated as "emulsion※VII" and omitted from Table 1.

[0143] [Table 1]

[0144] <Examples 1 to 7 and Comparative Examples 1 to 6> Each of the components (or compositions) prepared above was weighed into a polypropylene container in the amounts shown in Tables 2 and 3 below, and stirred at 2,000 rpm for 60 seconds in a planetary centrifugal mixer (ARE-310; manufactured by THINKY Corporation) to obtain the desired adhesive composition.

[0145] Next, pressure-sensitive adhesive sheets were produced using each of the Examples and Comparative Examples as pressure-sensitive adhesive layers as described below. That is, the obtained pressure-sensitive adhesive composition was applied to the surface of a polyolefin film that had been subjected to a corona discharge treatment so that the thickness after drying would be 25 μm, and after drying at 100° C. for 3 minutes, the composition was attached to a 38 μm polyester-based release sheet with a light peeling property (Lumirror (registered trademark) SP01-38BU; manufactured by Mitsui Chemicals Tocello Co., Ltd.) and aged for 7 days in an environment of 23° C. to obtain a pressure-sensitive adhesive sheet.

[0146] The pressure-sensitive adhesive compositions of the Examples and Comparative Examples were evaluated for room temperature storage stability as described below, and the pressure-sensitive adhesive sheets obtained above were evaluated for the following items (initial adhesive strength, adhesive strength after UV irradiation, adhesive residue). The results are shown in Tables 2 and 3 below.

[0147] [Adhesive strength before exposure to active energy rays (initial adhesive strength)] A test piece of 25 mm x 100 mm was cut out from the obtained adhesive sheet, and the light release 38 μm polyester-based release sheet was peeled off to expose the adhesive layer. The adhesive layer surface was then placed against alkali-free glass (Eagle XG; Corning Incorporated, thickness 1.1 mm) and a 2 kg rubber roller was rolled back and forth twice in an atmosphere of 23°C and 50% RH to pressurize and attach the test piece to the alkali-free glass, and the test piece was then left to stand in the same atmosphere for 30 minutes. Then, the 180 degree peel strength (N / 25 mm) was measured at a peel speed of 300 mm / min, and the initial adhesive strength was evaluated based on the following evaluation criteria. (Evaluation Criteria) ◎ Peel strength is 10.0 (N / 25 mm) or more. ○ Peel strength is 5.0 (N / 25mm) or more and less than 10.0 (N / 25mm). × Peel strength is less than 5.0 (N / 25 mm).

[0148] [Adhesive strength after exposure to active energy rays (post-UV adhesive strength)] A test piece similar to that used in the evaluation of initial adhesive strength was prepared, and this test piece was attached under pressure to non-alkali glass in the same manner as in the evaluation of initial adhesive strength, and left to stand for 30 minutes in the same atmosphere. Then, an 80W high-pressure mercury lamp was used to irradiate the non-alkali glass with ultraviolet light (cumulative irradiation amount 180mJ / cm 2 ) and allowed to stand for 30 minutes in an atmosphere of 23°C and 50% RH, after which the 180° peel strength (N / 25 mm) was measured at a peel speed of 300 mm / min and evaluated according to the following criteria. (Evaluation Criteria) ◎ Peel strength is less than 0.1 (N / 25 mm). ○ Peel strength is 0.1 (N / 25mm) or more and less than 0.2 (N / 25mm). × Peel strength is 0.2 (N / 25 mm) or more.

[0149] [Glue residue] After measuring the post-UV adhesive strength, the alkali-free glass surface was visually observed and evaluated based on the following evaluation criteria. (Evaluation Criteria) 〇 No glue residue at all. △···Slight traces of sticker are visible. × The sticker marks are noticeable.

[0150] [Room temperature storage stability] The pressure-sensitive adhesive compositions obtained in Examples 1 to 7 and Comparative Examples 1 to 6 were placed in a container with a lid and allowed to stand at room temperature of 23° C. Then, the state of the pressure-sensitive adhesive composition over time was visually observed and evaluated based on the following evaluation criteria. (Evaluation criteria). ○ No separation or precipitation occurred for more than one week. △: Separation and precipitation occurred in more than 2 days but less than 1 week. ×: Separation and precipitation occurred within 2 days.

[0151] [Table 2]

[0152] [Table 3]

[0153] As shown in Tables 2 and 3, Examples 1 to 7 used acrylic emulsions (A-1 and / or A-2) and, as component B, active energy ray-curable compound (B1), surfactant (B2) having two or more reactive groups, and surfactant (B3) other than (B2), and therefore all of the physical properties, including resin content, room temperature storage stability, initial adhesive strength, post-UV adhesive strength (easy peeling after UV), and adhesive residue (non-adherend contamination), were good. In contrast, Comparative Examples 1 and 2 were inferior in initial adhesive strength since they contained an acrylic emulsion (A'-1) whose glass transition temperature (Tg) was outside the range specified by the present invention. In addition, the products (Comparative Examples 3 and 4) that did not contain at least one of (B1), (B2), and (B3) as the B component had poor storage stability at room temperature. In addition, since precipitation occurred immediately after the liquid preparation, other physical properties could not be evaluated. Comparative Example 6, in which a water dispersion of a self-emulsifying urethane (meth)acrylate compound was used as the component B, had a low resin content. Moreover, the composition using PVOH as component B (Comparative Example 5) had poor room temperature storage stability. [Industrial Applicability]

[0154] The active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention has a high non-volatile content and excellent storage stability, and therefore can be suitably used as a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet for surface protection.

Claims

1. An active energy ray-curable peel-type pressure-sensitive adhesive composition comprising an acrylic emulsion (A) and a radically polymerizable composition (B), the glass transition temperature of the polymer contained in the acrylic emulsion (A) is 10° C. or lower, The radical polymerizable composition (B) has the following (B1) to (B3): (B1): An active energy ray-curable compound. (B2): A surfactant having two or more reactive groups. (B3): A surfactant other than (B2).

2. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the content of the surfactant (B2) having two or more reactive groups is 50 mass% or more of the total amount of surfactants contained in the radical polymerizable composition (B).

3. 3. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the surfactant (B2) having two or more reactive groups has a polyoxyalkylene chain in its structure.

4. 3. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the surfactant (B2) having two or more reactive groups is a urethane (meth)acrylate.

5. 3. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the active energy ray-curable compound (B1) has two or more (meth)acryloyl groups.

6. 3. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the surfactant (B3) other than the surfactant (B2) is a surfactant represented by the following general formula (1): XO-(Y 1 O)m-(Y 2 O)n-SO 3 Z ・・・(1) (wherein X is a functional group having a double bond. Y 1 and Y 2 is an alkylene group, and Y 1 and Y 2 are different groups; Z is a counter ion; m is an integer of 1 or more, and n is an integer of 0 or more.

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