JP2884423B2 - Active energy ray-curable pressure-sensitive adhesive composition for hot melt - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an active energy ray-curable pressure-sensitive adhesive composition for hot melt, and more particularly to an acrylic copolymer having a specific molecular weight. A specific amount of at least one compound selected from compounds having a specific molecular weight range having two or more ethylenically unsaturated bonds in one molecule, and a specific amount of an antioxidant. The present invention relates to an active energy ray-curable pressure-sensitive adhesive composition for hot melt.

[Conventional technology and its problems]

Conventionally, many adhesives have been known for active energy ray-curable pressure-sensitive adhesives. However, these adhesives still have many problems that need to be solved.

For example, Japanese Patent Application Laid-Open No. Sho 50-136328 discloses that "alkyl acrylate (alkyl group having 3 to 10 carbon atoms) 50 to 100".
Parts by weight, 20-100 parts by weight of vinyl acetate, COOH, CN, CON on the side chain
H ₂ and is coated or impregnated with a copolymer composed mainly of vinyl monomer 3-15 parts by weight on a support sheet having a selected polar group from the group of derivatives thereof, which retain pressure sensitive adhesive properties Pressure-sensitive adhesive tape characterized by irradiating ionizing radiation within a range of from 3 to 35 Mrad to form an appropriate crosslink.

However, in order to impart sufficient cohesive force to the pressure-sensitive adhesive layer of the “pressure-sensitive adhesive tape” in the above proposal, it is generally necessary to irradiate a relatively high dose of ionizing radiation. In many cases, the pressure-sensitive adhesiveness of the agent layer is extremely reduced, and it is easy for the pressure-sensitive adhesive tape to maintain various properties such as heat resistance, pressure-sensitive adhesiveness, adhesive strength, and cohesive force in a well-balanced manner. is not. Further, if the irradiation dose of the ionizing radiation is too large, the “support sheet” may be deteriorated, and there is a problem that the material of the support sheet is limited by itself.

Furthermore, in order to use the above-mentioned copolymer as a hot-melt pressure-sensitive adhesive, the coating must be heated to a considerably high temperature in order to secure the coating viscosity.
Problems such as thermal deterioration are likely to occur. Further, when an organic solvent is used to avoid thermal coloring and thermal deterioration, the organic solvent volatilizes into the air during coating, deteriorating the working environment and easily causing problems such as air pollution.

Next, JP-A-59-176370 discloses that "radical cross-linking to 100 parts by weight of a copolymer having a molecular weight of 100,000 to 600,000 and containing an alkyl ester of acrylic acid or methacrylic acid as a main component is carried out by ultraviolet rays or electron beams. One unsaturated bond that can cause
A pressure-sensitive adhesive composition comprising 1 to 50 parts by weight of an oligomer having a molecular weight of 1,000 to 20,000 having two or more in the molecule and 0 to 10 parts by weight of a photosensitizer and capable of being radically crosslinked by ultraviolet rays or electron beams. . "Has been proposed.

However, the oligomer used in the second proposal has a molecular weight larger than the molecular weight range of the compound having “two or more ethylenically unsaturated bonds in one molecule” of the present invention. Viscosity tends to be high, lowering the viscosity at the time of coating requires higher temperature heating, thermal polymerization of the oligomer, easy to cause thermal degradation, etc., the resulting pressure-sensitive adhesive layer is colored, It tends to be difficult to maintain the balance among the various properties such as heat resistance, pressure-sensitive adhesiveness, adhesive strength, and cohesive strength. There is also a problem that it is difficult to reuse the composition once melted by heating.

The present inventors have conducted research to solve the problems of these conventional active energy ray-curable pressure-sensitive adhesives. As a result, an acrylic copolymer having a specific molecular weight has a molecular weight of 2 per molecule. Solving the above-mentioned problems by providing a specific amount of at least one compound selected from a compound having a specific molecular weight range having at least two ethylenically unsaturated bonds and an antioxidant, thereby achieving excellent active energy ray curing. It has been found that a pressure-sensitive adhesive composition for hot-melt molding can be obtained, and the present invention has been completed.

[Means for solving the problem]

The present invention relates to the following A to C, A. Acrylic copolymer having at least one functional group selected from carboxyl group, amide group, substituted amide group, amino group, substituted amino group and mercapto group. ,That
Copolymer 100 having a weight average molecular weight of 50,000 to 500,000 by GPC
Parts by weight, B. having two or more ethylenically unsaturated bonds in one molecule,
And 1 to 10 parts by weight of one or more compounds selected from compounds having a molecular weight of less than 1000, and C. 0.1 to 1 part by weight of an antioxidant (however, Compounds having one ethylenically unsaturated bond are excluded) and their adhesive strength (JIS Z-0237
Active energy ray-curable pressure-sensitive adhesive composition for hot melt, wherein the pressure-sensitive adhesive composition is 600 g / 25 mm or more.

 Hereinafter, the present invention will be described in detail.

The active energy ray-curable pressure-sensitive adhesive composition for hot melt of the present invention is an acrylic copolymer, and its GP
It comprises a copolymer (A) having a polymerization average molecular weight of 50 to 500,000 by C as a main component.

As the acrylic copolymer (A), an acrylic copolymer obtained by copolymerizing the following (a) and (b) and, if necessary, further adding a monomer of (c) is used. It is preferable to use it from the viewpoint of a good balance of the adhesive strength, cohesive strength and pressure-sensitive adhesiveness of the obtained pressure-sensitive adhesive layer.

(A) An acrylate monomer represented by the general formula CH ₂ CHCHCOOR ⁵ (where R ⁵ represents a C ₂ -C ₁₈ linear or branched alkyl group), and a homopolymer thereof (B) a monomer having at least one functional group in addition to the radically polymerizable unsaturated group, (c) a monomer having at least one functional group,
Monomers other than (a) and (b), which can be copolymerized with

The acrylate monomer of the above (a) is represented by the general formula CH
₂ = CHCOOR ⁵ , the homopolymer has a glass transition point of −20 ° C. or less, and R ⁵ of the acrylate monomer (a) is C _{2 to} C ₁₈ , preferably C ₂ to C _{12 represents} a linear or branched alkyl group. Examples of such groups R ^5, ethyl group, n- propyl group, n- butyl group, i- butyl, n- hexyl, n- octyl group, i- octyl, 2-ethylhexyl, i -Nonyl group and the like. Specific examples thereof include ethyl acrylate, n-propyl acrylate, n-butyl acrylate, i-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, i-octyl acrylate, and 2 -Ethylhexyl acrylate, i-nonyl acrylate, and the like.

The amount of the acrylate monomer (a) used is, for example, 5% in the total 100% by weight of the monomers (a) to (c).
0% or more, preferably 63 to 99.8% by weight, particularly preferably 8%
Amounts of the order of 0 to 96.5% by weight are preferred. By appropriately selecting and using the acrylate monomer (a) in the above-mentioned usage amount range, it is possible to achieve a good balance of adhesive strength, pressure-sensitive adhesive property and cohesive strength.

Examples of the monomer having at least one functional group in addition to the radically polymerizable unsaturated group (b) include a functional group such as a carboxyl group, an amide group or a substituted amide group, and an amino group. Alternatively, a monomer having a substituted amino group, a mercapto group, or the like can be mentioned. In the present invention, one or more of these monomers can be appropriately selected and used. Specific examples of these monomers include, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride,
Carboxyl group-containing monomers such as fumaric acid, crotonic acid and citraconic acid (preferably acrylic acid, methacrylic acid and itaconic acid); for example, acrylamide, methacrylamide, N, N-dimethylacrylamide, N-methylacrylamide (preferably Is an amide group or substituted amide group-containing monomer such as acrylamide or methacrylamide); for example, aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl Amino group- or substituted amino group-containing monomers such as methacrylate, N, N-diethylaminoethyl methacrylate, (preferably, N, N-dimethylaminoethyl methacrylate and N, N-diethylaminoethyl methacrylate);
Examples thereof include mercapto group-containing monomers such as vinyl mercaptan and allyl mercaptan; and the like. Among these monomers (b), it is preferable to use at least one or more monomers selected from the group consisting of a carboxy group-containing monomer, an amide group-containing monomer and a substituted amino group-containing monomer. Particularly preferred.

The amount of the monomer (b) to be used depends on the amount of the monomer (a) to
For example, 15% by weight or less, preferably 0.2 to 10% by weight, and particularly preferably 1 to 6% by weight in the total 100% by weight of (c).
A small amount can be exemplified. When the amount of the monomer (b) is not more than the upper limit, the viscosity of the resulting active energy ray-curable pressure-sensitive adhesive composition for hot melt during application is not excessively high, and It is preferable that the pressure-sensitive adhesive property of the pressure-sensitive adhesive layer to be used does not become too low. On the other hand, by setting the amount to be used to be 0.5% by weight or more, a good balance between the adhesive force and the cohesive force can be obtained. It is preferable because it can be achieved.

Further, the comonomer (c) other than (a) and (b) copolymerizable with the monomers (a) and (b) includes, for example, methyl acrylate, t-butyl acrylate, and cyclohexyl. Acrylic acid monomers other than the above (a) such as acrylate and stearyl acrylate; for example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate; n-octyl methacrylate, i-octyl methacrylate, 2
-Methacrylic acid ester monomers such as -ethylhexyl methacrylate, i-nonyl methacrylate, n-dodecyl methacrylate, i-dodecyl methacrylate and stearyl methacrylate; for example, saturated fatty acid vinyls such as vinyl formate, vinyl acetate, vinyl propionate and vinyl versatate Ester monomers; for example, dibutyl malate, dibutyl fumarate, dibutyl itaconate,
C ₁ to α, β-unsaturated dicarboxylic acids such as dioctyl malate, dioctyl fumarate and dioctyl itaconate
_C18 linear or branched alkyl esters; for example, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and ethylvinylbenzene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile And the like.

The amount of the comonomer (c) used is from the above-mentioned monomers (a) to
The total amount of (c) is generally 50% by weight or less, preferably 36.8% by weight or less, and particularly preferably about 2 to 15% by weight, based on 100% by weight. Since the use of the comonomer (c) can vary depending on the type of the comonomer, the amount of the comonomer cannot be uniquely determined. It is useful to adjust the balance and the like as desired, so that the above range can be appropriately selected so as to meet such purpose. When the amount of the comonomer (c) is equal to or less than the upper limit of the above range, the pressure-sensitive adhesiveness does not become too low, and an appropriate balance between the adhesive force and the pressure-sensitive adhesiveness is maintained. Therefore, when the comonomer (c) is used, it is preferable to select and use an appropriate amount within the above range.

The glass transition point (hereinafter, sometimes abbreviated as Tg) of the acrylic copolymer as a main component of the active energy ray-curable hot melt pressure-sensitive adhesive composition of the present invention is preferably -20 ° C or lower. -30 ° C or lower. Temperatures below the upper limit are preferred because they have excellent pressure sensitive adhesive properties.

In addition, the weight average molecular weight of the acrylic copolymer according to the GPC method (hereinafter may be abbreviated as ▲).
Is from 500,000 to 500,000, preferably from 100,000 to 400,000. Below the lower limit, the adhesive strength and cohesive strength of the obtained pressure-sensitive adhesive layer may be insufficient, while above the upper limit, a higher melting temperature may be required to obtain a suitable coating viscosity. Since it is necessary, thermal degradation of the acrylic copolymer and thermal polymerization of a compound having “two or more ethylenically unsaturated bonds in one molecule” described later may occur, which is not preferable.

In the present invention, the glass transition point (Tg) of the acrylic copolymer is a value measured and determined as follows.

Glass transition point: In a cylindrical cell of about 5 mm in inner diameter and about 5 mm in depth made of aluminum foil about 0.05 mm thick, about 50 of acrylic copolymer
About 10 mg of a sample of the organic solvent solution by weight is weighed and dried at 100 ° C. for 2 hours to be used as a measurement sample. Seiko Denshi Kogyo Co., Ltd. SSC-5000 type differential scanning calorimeter (Differential Sc
anning Calormeter), heating rate from -150 ℃ to 10 ℃
Determine the measurement at / min.

The polymerization method of the acrylic copolymer of the present invention is not particularly limited, and known methods such as solution polymerization and emulsion polymerization can be employed, but the active energy ray-curable type is obtained from the copolymer mixture obtained by polymerization. In producing the pressure-sensitive adhesive composition for hot melt, it is preferable to employ solution polymerization in which a processing step is relatively simple and can be performed in a short time.

In the solution polymerization, generally, a predetermined organic solvent, a monomer mixture, a polymerization initiator, and a chain transfer agent used as needed are charged into a polymerization tank, and the mixture is stirred in a nitrogen stream or at the reflux temperature of the organic solvent. The reaction is carried out by heating for several hours. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator and / or the chain transfer agent may be sequentially added.

As the organic solvent, for example, benzene, toluene, xylene, aromatic hydrocarbons such as aromatic naphtha; n-
Aliphatic or alicyclic hydrocarbons such as hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, turpentine oil; ethyl acetate, n-butyl acetate; n-
Esters such as amyl acetate, 3-methoxybutyl acetate, methyl benzoate, cellosolve acetate, butyl cellosolve acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, methyl cyclohexanone; methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc. Ethers; for example, alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol and t-butyl alcohol; it can. These organic solvents can be used alone or in combination of two or more.

Since the active energy ray-curable pressure-sensitive adhesive composition for hot melt of the present invention needs to be substantially solvent-free, of the organic solvents described above, the organic solvent obtained from the obtained copolymer solution is used. It is preferable to use an organic solvent having a boiling point of from 50 to 150 ° C., particularly from 60 to 100 ° C., which is easy to volatilize and isolate the copolymer, among which n-hexane, ethyl acetate, acetone and methyl ethyl ketone It is particularly preferable to use an organic solvent such as methyl alcohol, n-propyl alcohol and the like.

Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, t-butylperoxyvivalate, and the like. Organic peroxides of, for example, 2,2'-azobis-i-butyronitrile,
2,2'-azobis-2,4-dimethylvaleronitrile, 2,
An azo compound such as 2'-azobis-4-methoxy-2,4-dimethylvaleronitrile; and the like can be used alone or in combination. The amount of the polymerization initiator used is
Generally, about 0.01 to 0.3 parts per 100 parts by weight of the total monomers
Parts by weight, preferably about 0.01 to 0.15 parts by weight.

Further, as the chain transfer agent, for example, cyanoacetic acid; alkyl cyanoacetate esters alkyl group C ₁ -C _8; bromoacetic acid esters alkyl group C ₁ -C _8;; bromoacetate anthracene, phenanthrene, fluorene, 9
Aromatic compounds such as -phenylfluorene; aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, p-nitrotoluene; benzoquinone, 2,3,5,
Benzoquinone derivatives such as 6-tetramethyl-p-benzoquinone; borane derivatives such as tributylborane; carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloro methane, tribromo methane, 3-chloro-1-halogenated hydrocarbons such as propene, chloral, aldehydes such as furaldehyde, alkyl mercaptans C ₁ -C _18; thiophenol, aromatic mercaptans such as toluene mercaptan Mercaptoacetic acid; mercaptoacetic acid
C ₁ -C ₁₀ alkyl esters; C ₁ hydroxamate Le alkyl mercaptans -C _12; Binen, terpenes such Tapinoren; can be exemplified.

When the above-mentioned chain transfer agent is used, its use amount is preferably about 0.005 to 3.0 parts by weight per 100 parts by weight of the total of the monomers.

The polymerization temperature is generally in the range of about 30 to 180 ° C, preferably about 60 to 150 ° C.

The copolymer solution suitably used in the present invention thus obtained usually contains the acrylic copolymer in an amount of 20 to 90% by weight.
In order to obtain the hot-melt pressure-sensitive adhesive composition of the present invention, the acrylic copolymer is isolated by removing an organic solvent from the copolymer solution by a known method such as distillation. Let it.

The active energy ray-curable pressure-sensitive adhesive composition for hot melt of the present invention has two or more ethylenically unsaturated bonds in one molecule together with the acrylic copolymer (A), and Compounds having a molecular weight of less than 1000 (hereinafter referred to as
Or a compound having one ethylenically unsaturated bond in one molecule (B). Things.

When a polyunsaturated compound (B) having a molecular weight of 1,000 or more is used, the melt viscosity of the obtained hot-melt pressure-sensitive adhesive composition becomes high, so that a higher coating temperature is required to obtain a suitable coating viscosity. However, in such a case, thermal degradation of the acrylic copolymer and thermal polymerization of the polyunsaturated compound or the like may occur, which is not preferable.

Examples of such a polyunsaturated compound (B) include ethylene glycol diglycidyl ether diacrylate, diethylene glycol diglycidyl ether dimethacrylate, triethylene glycol diglycidyl ether dimethacrylate, propylene glycol diglycidyl ether diacrylate, and sorbitol tetraglycidyl. Poly (meth) acrylates of polyepoxy compounds such as ether tetramethacrylate, glycerol triglycidyl ether triacrylate, bisphenol A-diglycidyl ether diacrylate; for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, triethylene Propylene glycol diacrylate, 1,4-butanegio Rudiacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate hydroxyvivalate, trimethylolethane trimethacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol Poly (meth) acrylates of polyols such as triacrylate, pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate; for example, (meth) allyl (meth) acrylates such as allyl acrylate and allyl methacrylate; for example, diallyl maleate and diallyl fuma (Meth) allyl ester of a radically polymerizable dicarboxylic acid such as acrylate, diallyl itaconate; Rirufutareto, triallyl cyanurate, (meth) allyl ester of a polycarboxylic acid other than the above, such as triallyl isocyanurate; and the like, etc. kill.

Of these polyunsaturated compounds (B), the use of polyol polymeth) acrylate is preferred from the viewpoints of easy availability and good balance of various physical properties of the obtained pressure-sensitive adhesive composition. These can be used alone or in combination of two or more.

The component (B) acts as a diluent for the acrylic copolymer (A) before irradiation with active energy rays so as to keep the viscosity at the time of application at an appropriate low level, and polymerizes itself by irradiation with active energy rays. And / or a resin which is converted into a solid resin by a crosslinking reaction with the acrylic copolymer (A) is preferably used. Therefore, as the component (B), those having a melting point of room temperature (about 20 ° C.) or lower and a boiling point of 160 ° C. or higher, preferably 200 ° C. or higher are preferable.

The amount of the polyunsaturated compound (B) used is 1 to 10 parts by weight based on 100 parts by weight of the acrylic copolymer (A).
Preferably it is 2 to 8 parts by weight. If the pressure-sensitive adhesive layer is used in excess of the upper limit, the pressure-sensitive adhesive property of the resulting pressure-sensitive adhesive layer may be reduced. Is insufficient, and the cohesive strength and adhesive strength of the pressure-sensitive adhesive layer may be insufficient, which is not preferable.

The active energy ray-curable pressure-sensitive adhesive composition for hot melt according to the present invention comprises, together with the acrylic copolymer (A) and the polyunsaturated compound (B), an antioxidant (C).
Is contained in an amount of 0.1 to 1 part by weight based on 100 parts by weight of the copolymer (A). If the amount of the antioxidant (C) exceeds the upper limit, the curing reaction by active energy ray irradiation may not proceed sufficiently, and the cohesive strength and adhesive strength of the obtained pressure-sensitive adhesive layer may be insufficient. It is not preferred,
If it is less than the lower limit, the effect of adding the component (C) is unlikely to appear, and the acrylic copolymer is thermally degraded at the time of heating coating, or the polyunsaturated compound is thermally polymerized, resulting in excellent pressure sensitivity. It is not preferable because the adhesive layer may not be obtained and the reuse of the heated pressure-sensitive adhesive composition for hot melt may become impossible.

As the above antioxidant, generally, phenolic,
There are aromatic amines, sulfides, phosphites and the like. Of these, for example, 2,6-di-t-butyl-
4-methylphenol, n-octadecyl-3-
(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate, pentaerythritol-tetrakis [3- (3', 5-di-t-butyl-4'-hydroxyphenyl) propionate], 2 Phenolic antioxidants such as 2,2'-methylenebis (6-t-butyl-4-methylphenol) monoacrylate are preferable because they have excellent heat stability, oxidation stability, heat discoloration resistance, and evaporation resistance. 2,2'-Methylenebis (6-t-butyl-4-methylphenol) monoacrylate is most preferred from the viewpoint of the less coloring of the pressure-sensitive adhesive layer from which the resulting pressure-sensitive adhesive layer is obtained.

When the active energy ray-curable hot melt pressure-sensitive adhesive composition of the present invention uses ultraviolet rays or the like as an active energy ray as described later, the acrylic copolymer (A) and the polyunsaturated compound (B) are used. ) And antioxidant (C)
In addition to the above, a photopolymerization initiator can be used in combination.

Examples of the photopolymerization initiator include diacetyl, benzyl, benzophenone, benzoin, ω-bromoacetophenone, chloroacetone, benzoquinone, anthraquinone, 2-ethylanthraquinone, benzoin isopropyl ether, and benzoin ethyl ether. Can be 0.1 to 15 parts by weight based on 100 parts by weight of the total of (A) and (B).

Further, the pressure-sensitive adhesive composition of the present invention has a boiling point of water and an organic solvent used for solution polymerization of the acrylic copolymer, which is normal, within a range not impairing the excellent effects of the present invention. May contain volatile solvents having a temperature of 250 ° C. or less, but the content of these solvents is 10 parts by weight based on 100 parts by weight of the total of the acrylic copolymer (A) and the polyunsaturated compound (B). Parts by weight, preferably 5 parts by weight or less, particularly preferably 1 part by weight or less.

The pressure-sensitive adhesive composition of the present invention further optionally,
For example, cumarone indene resin, terpene phenol resin, pt-butylphenol acetylene resin,
Phenol / formaldehyde resin, terpene resin, xylene / formaldehyde resin, petroleum hydrocarbon resin,
Tackifying resins such as hydrogenated hydrocarbon resins, rosin derivatives, and turpentine resins; for example, ethylene-vinyl acetate copolymer resins, ethylene-acrylic copolymer resins, ethylene-vinyl acetate-acrylic copolymer resins And other modifying resins; and the like. The addition amount of these resins is, based on 100 parts by weight of the total of the components (A) and (B), a tackifying resin, for example, 0 to 60 parts by weight,
In particular, 0 to 40 parts by weight;
50 parts by weight, especially 0 to 20 parts by weight;

In addition to these, the pressure-sensitive adhesive composition of the present invention may be optionally used, for example, a phthalic acid ester such as dioctyl phthalate, a phosphate ester such as tricresyl phosphate, a plasticizer such as polybutene or process oil. Organic or inorganic coloring agents such as titanium oxide, carbon black, phthalocyanine blue, etc .;
Known additives such as inorganic fillers such as talc, calcium carbonate, silica, aluminum hydroxide, and glass powder; photopolymerization initiation aids; ultraviolet absorbers;

As described above, the pressure-sensitive adhesive composition of the present invention is preferably used, for example, in an acrylic copolymer solution obtained by solution polymerization in an organic solvent having a boiling point of 60 to 100 ° C such as ethyl acetate, for example, trimethylolpropane. Polyunsaturated compounds (B) such as triacrylate and ethoxylated trimethylolpropane triacrylate, for example, 2,2'-methylenebis (6-t-butyl-4-methylphenol)
An antioxidant (C) such as monoacrylate [trade name: Sumilizer GM, manufactured by Sumitomo Chemical Co., Ltd.] and, if necessary, a photopolymerization initiator such as, for example, benzoin ethyl ether, were added, and thoroughly stirred and mixed. Thereafter, the organic solvent used during the solution polymerization is distilled off by heating, and the organic solvent is further removed using, for example, drying under reduced pressure, and, if necessary, a tackifying resin, a modifying resin, a plasticizer, and a pigment. Can be produced by adding and mixing.

The active energy ray-curable pressure-sensitive adhesive composition for hot melt of the present invention is heat-melted according to a generally known method, applied to various substrates at an appropriate thickness, and then formed. By irradiating active energy rays to such an extent that the pressure-sensitive adhesive property of the layer is not lost, the layer can be cured to form a pressure-sensitive adhesive layer on the base material. Examples of the melting temperature include a temperature of about 100 to 180 ° C.

The above active energy rays are ultraviolet rays or electron beams,
α-rays, β-rays, ionizing radiations such as γ-rays or X-rays, such as problems with equipment, ease of handling, and the use of pressure-sensitive adhesive compositions that have better storage stability, etc. From the viewpoint, the use of an electron beam is preferred.

The term "to the extent that the pressure-sensitive adhesive property is not lost" means that the value of the pressure-sensitive adhesive property is 100 g / in accordance with the method of JIS Z-0237 as described later.
It means that it is 25mm or more.

For example, when the active energy ray is ultraviolet light, the irradiation dose of the active energy ray can be adjusted by adjusting the intensity of the lamp, the distance to the surface to be irradiated, and the irradiation time. Assuming 10 using illuminometer
10001000 mJ / cm ² , preferably 50 to 500 mJ / cm ² .

In the case of an electron beam, for example, the irradiation dose can be adjusted by adjusting the voltage, current, and irradiation time, and the dose is measured using a CTA dosimeter on the irradiation surface, and is 0.5 to 10 Mrad, preferably 2 to 8 Mrad. It is better to

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

The method for measuring the viscosity at the time of heating and the method for evaluating the thermal stability of the composition of the present invention, the method for preparing a pressure-sensitive adhesive sheet for the physical property test of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesiveness, the adhesive force and the cohesive force The measuring method is as follows.

(1) Measurement of viscosity during heating Using a Contrabass viscometer Rheomat 30 (trade name), cone plate PK1, measurement temperature 150 ° C, shear rate 50se
Measure under the condition of c- ¹ . The hot viscosity of the composition of the present invention is preferably 10,000 cps or less.

(2) Thermal stability of composition The pressure-sensitive adhesive composition for hot melt is put in a glass bottle, sealed, and left in a thermostat at 150 ° C to measure the time until the fluidity is lost. The thermal stability is preferably at least one day, particularly preferably at least three days.

(3) Method of preparing pressure-sensitive adhesive sheet for test A composition prepared by melting a pressure-sensitive adhesive composition for electron beam-curable hot melt at 150 ° C. on a 50 μm polyethylene terephthalate film so as to have a thickness of about 25 μm. Coating, irradiating the surface of the obtained layer of the composition with an electron beam of 4 Mrad,
The composition was cured to obtain a test pressure-sensitive adhesive sheet.

(4) Measurement of pressure-sensitive adhesiveness Brushed with # 280 water-resistant abrasive paper specified in JIS R-6253
Using the pressure-sensitive adhesive sheet for test prepared in the previous section (3) on a SUS 304 stainless steel plate, press-bond it according to the method of JIS Z-0237, and after 20 minutes, at 20 ° C, 65% RH, and peeling speed of 300 mm / min. The peel strength (g / 25 mm) is measured under the conditions. The value of the pressure-sensitive adhesiveness is preferably 400 g / 25 mm or more, and particularly preferably 600 g / 25 mm or more.

(5) Measurement of adhesive strength Using the same pressure-sensitive adhesive sheet for test created in the previous section (3) on the same stainless steel plate as used in the previous section (4),
Crimping according to the method of Z-0237, 24 hours later, 20 ° C, 65% R
H, its peel strength (g / 25m
m). The adhesive strength is preferably at least 600 g / 25 mm, particularly preferably at least 1000 g / 25 mm.

(6) Measurement of cohesive force The pressure-sensitive adhesive sheet for test prepared in the previous section (3) is attached to the same stainless steel plate as used in the previous section (4) so that the adhesion area becomes 25 × 25 mm ^2. Then, a 2 kg roller was pressed back and forth once.

A 1 kg static load is applied to the sample in an atmosphere of 40 ° C. × 30% RH, and the time until the load drops is measured. The cohesive force is preferably at least 100 minutes, particularly preferably at least 500 minutes.

Reference Example 1 In a separable flask equipped with a reflux condenser, a thermometer, a stirrer, and a sequential dropping apparatus, an organic solvent for initial addition and 80 parts by weight of ethyl acetate (EAc) and azobisisobutyronitrile as a polymerization initiator were added. (AIBN) 0.0125 parts by weight, and then add 25 parts by weight of a monomer mixture consisting of 94 parts by weight of butyl acrylate (BA) and 6 parts by weight of acrylic acid (AA), and heat the mixture. The polymerization was carried out for 40 minutes while adjusting the temperature.

Next, while maintaining the internal temperature at 80 to 85 ° C., a residual addition mixture consisting of 75 parts by weight of the monomer mixture, 20 parts by weight of EAc and 0.125 parts by weight of AIBN was successively dropped over about 90 minutes,
The internal temperature was kept at 80 to 85 ° C. for further 90 minutes to obtain an acrylic copolymer solution having a solid content of about 50% by weight. Mw of this copolymer is 20
The Tg was -44 ° C.

Reference Examples 2 to 5 Using the same apparatus as in Reference Example 1 and using the monomer composition, the initial addition mixture and the sequential addition mixture shown in Table 1, polymerization was carried out in the same manner as in Reference Example 1 to obtain an acrylic resin. A copolymer solution was obtained. Table 1 shows the Mw and Tg of this copolymer.

Example 1 To 100 parts by weight of the acrylic copolymer solution obtained in Reference Example 1, Sumilizer GM [trade name: Sumitomo Chemical Co., Ltd .: 2,2'-methylenebis (6-t-) was used as an antioxidant. Butyl-4-methylphenol) monoacrylate (MBPM
A)], add and mix 0.25 parts by weight, concentrate by vacuum drying to a solid content of 99% by weight, and then trimethylolpropane triacrylate (TMPTA) as a polyunsaturated compound.
1.5 parts by weight were mixed to obtain an electron beam-curable pressure-sensitive adhesive composition for hot melt. Table 2 shows the measurement results of various physical properties of the obtained composition.

Example 2 and Comparative Examples 1 and 2 An electron beam-curable pressure-sensitive adhesive composition for a hot melt was obtained in the same manner as in Example 1 except that the amount of TMPTA was changed. Table 2 shows the measurement results of the composition and various physical properties of the obtained composition.

Example 3 In Example 1, instead of using 1.5 parts by weight of TMPTA,
TMPTA 0.5 parts by weight and Photomer 4149-SN [trade name; manufactured by San Nopco Co., Ltd .: ethoxylated trimethylolpropane triacrylate (TMPTEA)] 1.5 parts by weight in the same manner except that pressure-sensitive adhesive for electron beam-curable hot melt is used. Agent composition was obtained. Table 2 shows the measurement results of various physical properties of the obtained composition.

Comparative Examples 3 and 4 In Example 1, an electron beam-curable hot melt was prepared in the same manner as in Example 1 except that the acrylic copolymer solution of Reference Example 2 or 3 was used instead of the acrylic copolymer dense liquid of Reference Example 1. A pressure-sensitive adhesive composition was obtained. Table 2 shows the measurement results of the composition and various physical properties of the obtained composition.

Comparative Example 5 An electron beam-curable pressure-sensitive adhesive composition for hot melt was obtained in the same manner as in Example 1 except that no antioxidant was used. Table 2 shows the measurement results of the composition and various physical properties of the obtained composition.

Examples 4 and 5 In the same manner as in Example 1, except that the acrylic copolymer solution of Reference Example 4 or 5 was used instead of the acrylic copolymer solution of Reference Example 1, the sensitivity for an electron beam-curable hot melt was used. A pressure-sensitive adhesive composition was obtained. Table 2 shows the measurement results of the composition and various physical properties of the obtained composition.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C09J 4/06

Claims (1)

(57) [Claims] An acrylic copolymer having at least one functional group selected from the group consisting of A to C, A. carboxyl group, amide group, substituted amide group, amino group, substituted amino group and mercapto group. And that
Copolymer 100 having a weight average molecular weight of 50,000 to 500,000 by GPC
Parts by weight, B. having two or more ethylenically unsaturated bonds in one molecule,
And 1 to 10 parts by weight of one or more compounds selected from compounds having a molecular weight of less than 1000, and C. 0.1 to 1 part by weight of an antioxidant (however, Compounds having one ethylenically unsaturated bond are excluded) and their adhesive strength (JIS Z-0237
Active energy ray-curable pressure-sensitive adhesive composition for hot melt, wherein the pressure-sensitive adhesive composition is 600 g / 25 mm or more.