JP7207122B2 - Adhesive composition, adhesive, adhesive sheet, and laminate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition, and more particularly to a pressure-sensitive adhesive composition that has adhesiveness under normal conditions, and that cures by heating to firmly adhere to an adherend after being adhered to the adherend. The present invention also relates to a pressure-sensitive adhesive composition obtained by crosslinking the pressure-sensitive adhesive composition, which has good tackiness and excellent adhesiveness to members such as metals and plastic films. Furthermore, the present invention provides an adhesive sheet having an adhesive layer made of the above-mentioned adhesive, or an adhesive sheet in which the adhesive layer made of the above-mentioned adhesive is laminated with another member, and the adhesive sheet is laminated. The present invention relates to a laminate having excellent holding power of mating surfaces and excellent shear strength.

Conventionally, liquid adhesives using epoxy compounds have been used for bonding metals and plastics. Recently, there is also a demand for adhesives that have the properties of both pressure sensitive adhesives and adhesives, such as being sticky under normal conditions and hardening by heating after being applied to an adherend to form a strong bond. rising.
Examples of such adhesives include thermosetting adhesive compositions containing an acrylic copolymer having a specific composition, an epoxy resin, and an epoxy resin curing agent that is an organic acid dihydrazide having a specific particle size. proposed (see, for example, Patent Document 1).

JP 2013-253163 A

However, in the thermosetting adhesive composition disclosed in Patent Literature 1, the adhesive properties before heat curing are not considered at all, and the tackiness of the adhesive sheet is insufficient. rice field. Further, if softened to such an extent that it has tackiness before heat curing, problems such as insufficient cohesive force and poor holding power arise.

On the other hand, in order to improve the holding power, it is conceivable to use a cross-linking agent commonly used in acrylic pressure-sensitive adhesives. However, as in Patent Document 1, when a curing agent for epoxy resins having a small particle size is used in consideration of coatability, the curing agent and the cross-linking agent tend to react, and the degree of cross-linking of the acrylic resin is reduced. As a result, there arises a problem that the holding force is lowered.

Therefore, under such a background, the present invention forms a pressure-sensitive adhesive that is excellent in tackiness and holding power at room temperature (20±10° C.) before curing and also excellent in shear strength after curing. An object of the present invention is to provide a pressure-sensitive adhesive composition.

However, as a result of extensive research in view of such circumstances, the present inventors have found that acrylic resin (A), epoxy compound (B), acrylic resin cross-linking agent (C) (provided that epoxy compound (B) ) and a curing agent for epoxy compounds (D), by using a curing agent having a high melting point and an amino group as the curing agent for epoxy compounds (D), It is possible to suppress unintended reaction with the cross-linking agent for acrylic resin (C), and to obtain a pressure-sensitive adhesive that has excellent tackiness and holding power at room temperature before curing, and excellent shear strength after curing. We found that and completed the present invention.

That is, the present invention provides an acrylic resin (A), an epoxy compound (B), an acrylic resin crosslinking agent (C) (excluding the epoxy compound (B)), and an epoxy compound curing agent ( D) is a pressure-sensitive adhesive composition containing
A first aspect of the present invention is a pressure-sensitive adhesive composition in which the epoxy-based compound curing agent (D) is a curing agent having an amino group with a melting point of 185° C. or higher.

A second aspect of the present invention is a pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive composition of the first aspect.

Furthermore, the third aspect of the present invention is an adhesive sheet having an adhesive layer made of the adhesive of the second aspect. A fourth aspect is a laminate in which a pressure-sensitive adhesive layer and another member are laminated.

In the present invention, "curing" means curing of an epoxy-based compound by heating, and reaction between an acrylic resin and a cross-linking agent is simply referred to as "cross-linking".

The adhesive composition of the present invention comprises an acrylic resin (A), an epoxy compound (B), a cross-linking agent for acrylic resin (C) (excluding the epoxy compound (B)) and an epoxy A pressure-sensitive adhesive composition containing a curing agent for compounds (D), wherein the curing agent for epoxy compounds (D) is a curing agent having an amino group with a melting point of 185° C. or higher. Therefore, the pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive composition has excellent tackiness and holding power before curing, and exhibits high shear strength after curing. have. Therefore, the pressure-sensitive adhesive composition of the present invention can be used in various applications such as building materials, vehicle-mounted parts, electronic parts, semiconductor manufacturing processes, member sealing, aircraft parts, and sporting goods. It can be suitably used for adhesion purposes.

The present invention focuses on the reaction between a cross-linking agent for acrylic resins and a curing agent for epoxy-based compounds, which is usually considered unnecessary. That is, it is thought that the higher the melting point of the epoxy compound curing agent, the more stable it can be maintained in the composition, and the lower the reactivity with the functional group of the acrylic resin crosslinking agent. . As a result, the functional group of the acrylic resin reacts preferentially with the cross-linking agent, and it is thought that it is possible to suppress the deterioration of the holding power when used as a pressure-sensitive adhesive.

The present invention will be described in detail below.
In the present invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate. .
Further, "acrylic resin" is a resin obtained by polymerizing a polymerizable component containing at least one (meth)acrylic monomer.

In the present invention, the "glass transition temperature" is a value measured using a differential scanning calorimeter (DSC Q2000, manufactured by TA Instruments). The measurement temperature range is -85 to 200°C, and the temperature rise rate is 5°C/min.

The adhesive composition of the present invention contains an acrylic resin (A), an epoxy compound (B), a cross-linking agent for acrylic resins (C) and a curing agent for epoxy compounds (D). The above (A), (B), (C) and (D) will be described in order below.

<Acrylic resin (A)>
Examples of the acrylic resin (A) include acrylic resins obtained by polymerizing a polymerization component containing a (meth)acrylic monomer as a main component and optionally other various polymerizable monomers.
The term "contained as a main component" means that the content is usually 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more based on the total polymerization components.

Examples of the (meth)acrylic monomer include (meth)acrylic acid or derivatives thereof, (meth)acrylamide or derivatives thereof, and the like.

Derivatives of the above (meth)acrylic acid include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth) Acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3- Pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl -Alkyl group-containing (meth)acrylates such as 2-propylpentyl (meth)acrylate and n-octadecyl (meth)acrylate.

Other examples of derivatives of (meth)acrylic acid include cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate. ;biphenyloxy structure-containing (meth)acrylates such as biphenyloxyethyl (meth)acrylate; 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth) acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate and other Cyclic (meth)acrylate; 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate , ethoxydiethyleneglycol (meth)acrylate, methoxypolyethyleneglycol (meth)acrylate, ethylcarbitol (meth)acrylate, phenoxyethyl (meth)acrylate, alkylphenoxypolyethyleneglycol (meth)acrylate and other alkoxy or phenoxy group-containing (meth)acrylates acrylate; and the like.

Furthermore, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxy Hydroxyalkyl (meth)acrylates such as hexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, [4-(hydroxymethyl)cyclohexyl ] Hydroxyl group-containing (meth) acrylates such as methyl acrylate, cyclohexanedimethanol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate; glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl ether Epoxy group-containing (meth)acrylates such as; 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl Halogen-containing (meth)acrylates such as (meth)acrylates, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate; dimethylaminoethyl (meth)acrylate Alkylaminoalkyl (meth)acrylates such as; 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate, 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate oxetane group-containing (meth)acrylates such as acrylates and 3-hexyl-oxetanylmethyl (meth)acrylate;

Examples of (meth)acrylamide derivatives include N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-alkyl group-containing (meth)acrylamide derivatives such as N-butyl (meth)acrylamide and N-hexyl (meth)acrylamide; N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-methylol-N - N-hydroxyalkyl group-containing (meth)acrylamide derivatives such as propane (meth)acrylamide; N-aminoalkyl group-containing (meth)acrylamide derivatives such as aminomethyl (meth)acrylamide and aminoethyl (meth)acrylamide; N-methoxy N-alkoxy group-containing (meth)acrylamide derivatives such as methyl (meth)acrylamide and N-ethoxymethyl (meth)acrylamide; ) acrylamide derivatives; heterocycle-containing (meth)acrylamide derivatives such as N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine and N-acryloylpyrrolidine;

These (meth)acrylic monomers may be used alone or in combination of two or more. Among them, monomers that are alkyl esters of (meth)acrylic acid are preferably used, and alkyl (meth)acrylates having 1 to 20 carbon atoms are particularly preferable. Furthermore, those having 1 to 12 carbon atoms are preferred, those having 1 to 8 carbon atoms are more preferred, and those having 1 to 4 carbon atoms are particularly preferred. This is because the smaller the number of carbon atoms, the better the compatibility with the epoxy-based compound (B), which will be described later.

In addition, among these (meth)acrylic monomers, the monomer having an acryloyl group is preferably contained in an amount of 25% by weight or more, more preferably 35% by weight or more, based on the total polymerization components of the acrylic resin (A). is. By increasing the content of the acryloyl group-containing monomer, excellent transferability after formation of the adhesive layer can be obtained without impairing the adhesive property before curing, resulting in good handleability.
In addition, "transferability" means that after forming an adhesive layer on a release film, it is attached to the surface of a member to be adhered, and after sticking, when peeling off the release film, the adhesive It refers to the ability to transfer the layer to the member neatly without failing to transfer or tearing apart. Moreover, the above-mentioned "crying apart" refers to a phenomenon in which peeling cannot be performed at a desired interface and peeling occurs at an interface other than the desired interface.

As such a monomer having an acryloyl group, among the various (meth)acrylic monomers described above, a monomer containing an acryloyl group such as acrylic acid or its derivatives, acrylamide or its derivatives may be selected and used. can be done.

In the present invention, polymerizable monomers other than (meth)acrylic monomers (hereinafter referred to as "other polymerizable monomers") that can be used in the acrylic resin (A) include, for example, crotonic acid and malein. Unsaturated carboxylic acids such as acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide-N-glycolic acid, cinnamic acid; vinyl acetate, vinyl propionate, vinyl stearate, vinyl benzoate, etc. Carboxylic acid vinyl ester monomers; monomers containing aromatic rings such as styrene and α-methylstyrene; , dialkyl fumarate, allyl alcohol, acryl chloride, methyl vinyl ketone, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone, and the like. These may be used independently and may use 2 or more types together.

In addition, the acrylic resin (A) used in the present invention preferably contains a functional group-containing monomer as a polymerizable component from the viewpoint of excellent tackiness and holding power before curing, and such a functional group-containing monomer is a hydroxyl group. It is preferably a functional group-containing monomer containing at least one monomer selected from containing monomers and carboxy group-containing monomers. Among them, a functional group-containing monomer having a (meth)acryloyl group is preferable, and a functional group-containing monomer having an acryloyl group is more preferable. Among these, 2-hydroxyethyl acrylate and acrylic acid are particularly preferred.

The content of such a functional group-containing monomer is preferably 0.1 to 30% by weight, more preferably 1 to 25% by weight, based on the total polymerization components of the acrylic resin (A). 3 to 20% by weight is particularly preferred. If the amount of the above functional group-containing monomer is too small, the cohesive force of the adhesive tends to decrease. tend to become

As the method for polymerizing the acrylic resin (A), conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization and emulsion polymerization can be used. Among them, solution radical polymerization and bulk polymerization are preferable, and solution radical polymerization is particularly preferable in that the acrylic resin (A) can be stably obtained.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, n-propyl alcohol, and isopropyl alcohol. and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. These organic solvents can be used alone or in combination of two or more.

Among these organic solvents, esters such as ethyl acetate and butyl acetate are preferred from the viewpoints of easiness of polymerization reaction, effect of chain transfer, easiness of drying during coating of the pressure-sensitive adhesive composition, and safety. , acetone, methyl ethyl ketone, and methyl isobutyl ketone are preferred, and ethyl acetate is particularly preferred.

Further, as the polymerization initiator used for such solution radical polymerization, a usual radical polymerization initiator can be used, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2- Azo initiators such as methylbutyronitrile, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(methylpropionic acid), benzoyl peroxide, lauroyl peroxide, di-t-butyl Examples include organic peroxides such as peroxides and cumene hydroperoxide, which can be appropriately selected and used in accordance with the monomers to be used. These polymerization initiators can be used alone or in combination of two or more.

Thus, the acrylic resin (A) used in the present invention is obtained.

The weight average molecular weight (Mw) of the acrylic resin (A) is preferably 150,000 or more, particularly preferably 150,000 to 1,500,000, more preferably 200,000 to 1,000,000, and particularly preferably 250,000 to 1,500,000. 800,000. If the weight-average molecular weight is too small, the toughness and cohesive strength of the pressure-sensitive adhesive to be obtained tend to decrease, and tack and holding power before curing and shear strength after curing tend to decrease. On the other hand, if the weight-average molecular weight is too large, the viscosity tends to be too high, resulting in increased scaling during polymerization, reduced compatibility with the epoxy compound (B), and reduced handleability. .

Further, the degree of dispersion [weight average molecular weight (Mw)/number average molecular weight (Mn)] of the acrylic resin (A) is preferably 15 or less, particularly preferably 10 or less, further preferably 5.5 or less. be. If the degree of dispersion is too high, the cohesion tends to decrease. The lower limit of the degree of dispersion is usually 1.

The weight-average molecular weight of the acrylic resin (A) is the weight-average molecular weight in terms of standard polystyrene molecular weight. ”), column: Shodex GPC KF-806L (exclusion limit molecular weight: 2×10 ⁷ , separation range: 100 to 2×10 ⁷ , theoretical plate number: 10,000 plates/line, packing material: styrene-divinylbenzene co- Polymer, filler particle size: 10 μm) are connected in series and used, and the number average molecular weight can also be measured by the same method. Further, the degree of dispersion can be obtained from the measured values of the weight average molecular weight and the number average molecular weight.

The glass transition temperature (Tg) of the acrylic resin (A) is preferably 15°C or higher. It is more preferably 15 to 200°C, particularly preferably 20 to 180°C. If the glass transition temperature is too low, the shear strength after curing tends to decrease. If it is too high, the tackiness before curing tends to be low.

The acrylic resin (A) generally has a refractive index of 1.440 to 1.600. It is preferable to reduce the difference in refractive index between the laminated member and the member to reduce the optical loss at the member interface.

The above refractive index is a value obtained by measuring the acrylic resin (A) made into a thin film at 23° C. with a NaD line using a refractive index measuring device (“Abbe refractometer 1T” manufactured by Atago Co., Ltd.).

<Epoxy compound (B)>
Examples of the epoxy compound (B) used in the present invention include monofunctional epoxy compounds having one epoxy group and polyfunctional epoxy compounds having two or more epoxy groups. These compounds may be used alone or in combination of two or more. Also, it preferably contains a polyfunctional epoxy compound having two or more epoxy groups, since the shear strength after curing tends to be high.

Examples of the monofunctional epoxy compounds include alkyl glycidyl ether, alkoxyglycidyl ether, phenol glycidyl ether, EO (ethylene oxide)-modified phenol glycidyl ether, and allyl glycidyl ether.

Among the polyfunctional epoxy compounds described above, bifunctional epoxy compounds having two epoxy groups include, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, Diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, diglycidyl terephthalate, diglycidyl-o-phthalate, diglycidyl resorcinol ether, bisphenol A diglycidyl compounds and their hydrogenates, bisphenol F diglycidyl compounds and Hydrogenated products thereof, biphenyl-type diglycidyl compounds and derivatives thereof, and the like are included.

Furthermore, polyfunctional epoxy compounds having three or more epoxy groups include, for example, trifunctional epoxy compounds such as glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, triglycidyl isocyanurate and derivatives thereof, and pentaerythritol triglycidyl ether. tetrafunctional epoxy compounds such as pentaerythritol tetraglycidyl ether, diglycerol tetraglycidyl ether, and ditrimethylolpropane tetraglycidyl ether; Functional epoxy compounds; Hexafunctional epoxy compounds such as sorbitol hexaglycidyl ether and dipentaerythritol hexaglycidyl ether; system compound; and the like.
Among these, epoxy compounds having a functionality of 2 or more are particularly preferable, and epoxy compounds having a functionality of 3 or more are more preferable.

The epoxy-based compound (B) is preferably an epoxy-based compound that is liquid at 25° C. from the viewpoint that the adhesive strength, holding power, tackiness, etc. of the pressure-sensitive adhesive before curing are well balanced.

The viscosity of the epoxy compound that is liquid at 25°C is preferably 100 to 30,000 mPa·s/25°C, more preferably 120 to 15,000 mPa·s/25°C. 125 to 2,500 mPa·s/25°C is particularly preferred. If the viscosity is too high, the tackiness of the pressure-sensitive adhesive tends to decrease, and if it is too low, the cohesive strength of the pressure-sensitive adhesive tends to decrease.

The weight average molecular weight (Mw) of the epoxy compound (B) is preferably 150 to 50,000, more preferably 250 to 30,000, particularly preferably 300 to 10,000. If the molecular weight is too low, it tends to evaporate at high temperatures or emit white smoke. If it is too high, compatibility with the acrylic resin (A) tends to decrease.

The weight-average molecular weight of the epoxy-based compound (B) is the weight-average molecular weight in terms of standard polystyrene molecular weight. It is measured by using a total of four lines, one line, one ACQUITY APC XT 200 line, and two ACQUITY APC XT 45 lines in series.

Furthermore, the content of the epoxy compound (B) is preferably 25 to 300 parts by weight, more preferably 40 to 250 parts by weight, relative to 100 parts by weight of the acrylic resin (A). In particular, it is preferably 50 to 200 parts by weight, more preferably 60 to 160 parts by weight. If the content of the epoxy-based compound (B) relative to the acrylic resin (A) is too low, the tackiness of the pressure-sensitive adhesive decreases, resulting in a decrease in handling properties, or when the members are bonded together and cured, adhesion is impaired. If it is too large, the holding power of the pressure-sensitive adhesive tends to decrease.

<Crosslinking agent for acrylic resin (C)>
The pressure-sensitive adhesive composition of the present invention contains a cross-linking agent (C) for acrylic resins, and by containing the cross-linking agent (C) for acrylic resins, the pressure-sensitive adhesive composition is crosslinked. It is suitable in terms of increasing the cohesive strength of the pressure-sensitive adhesive, improving the holding power, and improving the releasability after curing. The acrylic resin crosslinking agent (C) excludes those used as the epoxy compound (B).

As such a cross-linking agent for acrylic resins (C), known cross-linking agents can be used. A cross-linking agent may be mentioned.

Examples of the isocyanate-based cross-linking agent include tolylene diisocyanate-based compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate; xylylene diisocyanate compounds such as methyl xylylene diisocyanate; aromatic isocyanate compounds such as 1,5-naphthalene diisocyanate and triphenylmethane triisocyanate; hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, and isocyanate compounds thereof Examples include adducts with polyol compounds such as trimethylolpropane, burettes and isocyanurates of these polyisocyanate compounds, and the like.

Examples of the aziridine-based cross-linking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4 ,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide) and the like.

Furthermore, examples of the melamine-based cross-linking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins. be done.

Examples of the aldehyde cross-linking agent include glyoxal, malondialdehyde, succindialdehyde, maleinedialdehyde, glutaredialdehyde, formaldehyde, acetaldehyde, and benzaldehyde.

Examples of the metal chelate-based cross-linking agents include acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, panadium, chromium, and zirconium. etc.

The acrylic resin crosslinking agent (C) may be used alone, or two or more of them may be used in combination. Among the above acrylic resin crosslinking agents (C), isocyanate crosslinking agents are particularly preferably used in terms of improving adhesion to members and reactivity with the acrylic resin (A). Among them, particularly preferred are tolylene diisocyanate-based compounds, and particularly preferred are adducts of tolylene diisocyanate and trimethylolpropane, in terms of excellent holding power and adhesive physical properties.

The content of the acrylic resin crosslinking agent (C) is preferably 0.1 to 30 parts by weight, more preferably 1 to 25 parts by weight, with respect to 100 parts by weight of the acrylic resin (A). It is preferably 2.5 to 20 parts by weight. When the content ratio of the acrylic resin crosslinking agent (C) to the acrylic resin (A) is within the above range, there is a tendency that particularly excellent holding power and transferability are obtained.

<Curing agent for epoxy compound (D)>
The epoxy compound curing agent (D) used as the curing agent for the epoxy compound (B) has an amino group capable of reacting with an epoxy group, and has a melting point of 185° C. or higher. It is.

The curing agent for epoxy compound (D) needs to have a melting point of 185° C. or higher from the standpoint of holding power before curing. It is preferably 186° C. or higher, particularly preferably 190° C. or higher. If the melting point is too low, it will easily react with the acrylic resin cross-linking agent (C), and the holding power of the tacky-adhesive will decrease. The upper limit is usually 300°C. Moreover, when the melting point of the curing agent can be obtained as a range, the upper limit of the melting point should be equal to or higher than the above melting point. The melting point of the epoxy resin curing agent (D) is measured by differential scanning calorimetry (DSC).

Examples of the curing agent (D) for epoxy compounds having a melting point of 185° C. or higher and an amino group include dicyandiamide (209° C.); sebacic acid dihydrazide (186-188° C.); ° C.), isophthalic acid dihydrazide (215 to 225° C.) and other organic acid hydrazide compounds; N,N-dialkylurea derivatives, N,N-dialkylthiourea derivatives, urea compounds such as dimethylureas; Amine compounds such as polyamines; melamines; guanamines such as acetoguanamine (213 to 273° C.) and benzoguanamine (228° C.); guanidines; ketimine compounds; These may be used alone or in combination of two or more. In addition, the numerical value in the above ( ) indicates the melting point.

Among these epoxy-based compound curing agents (D), dicyandiamide and organic acid hydrazide compounds are preferable in terms of excellent tackiness and holding power before curing of the composition and excellent shear strength after curing. Organic acid hydrazide compounds are preferred, and sebacic acid dihydrazide and dodecane dihydrazide are particularly preferred.

In addition, it is preferable that the epoxy-based compound curing agent (D) is powder from the standpoint of storage stability of the adhesive sheet and reactivity with the epoxy-based compound (B).
In the present invention, the term “powder” refers to a powder that is solid at 25° C. and has an average particle size of 0.01 to 500 μm as measured by a laser diffraction/scattering method. Among them, those having an average particle diameter of 0.1 to 350 μm are preferable, and those having an average particle diameter of 1 to 100 μm are more preferable. If the average particle size is too small, the storage stability of the pressure-sensitive adhesive composition tends to decrease.

When the epoxy-based compound curing agent (D) is powder, the average particle diameter thereof is determined in consideration of the film thickness when forming the adhesive layer comprising the adhesive of the present invention. It is preferable to select one having an average particle diameter of 1.2 times or less, more preferably 1 time or less, of the film thickness of the pressure-sensitive adhesive layer. If the particle size is too large for the film thickness, the unevenness of the pressure-sensitive adhesive layer becomes large, and voids are likely to occur during lamination, or the contact area decreases, resulting in a tendency for the adhesive strength to decrease. There is

The content of the epoxy compound curing agent (D) is preferably 10 to 200 parts by weight, more preferably 15 to 100 parts by weight, and particularly preferably 100 parts by weight of the acrylic resin (A). 20 to 60 parts by weight. When the content of the epoxy compound curing agent (D) is within the above range, the adhesive strength before curing, the storage stability over time, and the shear strength after curing when used as a pressure-sensitive adhesive. They tend to be particularly good.

In addition, the content of the epoxy compound curing agent (D) is preferably 10 to 100 parts by weight, more preferably 15 to 80 parts by weight, with respect to 100 parts by weight of the epoxy compound (B). It is preferably 20 to 60 parts by weight. When the content of the epoxy-based compound curing agent (D) is within the above range, the storage stability over time and the shear strength after curing tend to be particularly excellent.

Further, the curing agent (D) is 10% with respect to the total of the acrylic resin (A), the epoxy compound (B), the acrylic resin cross-linking agent (C), and the epoxy compound curing agent (D). It is preferably contained in an amount of up to 30% by weight. Within the above range, the adhesive strength and tackiness before curing are excellent, and the shear strength after curing is also excellent.

Various optional components can be added to the pressure-sensitive adhesive composition used in the present invention as long as the effects of the present invention are not impaired. These optional components are described below.

<Other optional ingredients>
Other optional components include, for example, conductive agents such as carbon and metal; inorganic fillers such as metal particles and glass particles; Tackifiers such as cyclic petroleum resins and styrene resins; fillers; antioxidants; UV absorbers; silane coupling agents; ionic compounds, peroxides, crosslinking accelerators such as urethanization catalysts; cross-linking retarder; and various other additives. These may be used alone or in combination of two or more.

In addition to the above additives, a small amount of impurities contained in raw materials for manufacturing constituent components of the pressure-sensitive adhesive composition may be contained.

The adhesive composition used in the present invention comprises the acrylic resin (A), the epoxy compound (B), the acrylic resin cross-linking agent (C), and the epoxy compound curing agent (D), and further It can be obtained by mixing other optional components as necessary.

The method of mixing these components is not particularly limited, and there are various methods such as a method of mixing each component at once, a method of mixing an arbitrary component and then mixing the remaining components all at once or sequentially. can be adopted.

The pressure-sensitive adhesive composition of the present invention can be made into a pressure-sensitive adhesive by reacting and crosslinking the acrylic resin (A) and the crosslinking agent for acrylic resin (C). A tacky-adhesive sheet can be obtained by laminating a tacky-adhesive layer made of an agent on a substrate such as a plastic film.
In the present invention, the term "sheet" is not particularly distinguished from "film" and "tape", but is used to include these.

The adhesive sheet is preferably a double-faced sheet without a substrate in which a separator (release sheet) is laminated on both sides of an adhesive layer, because it is easy to handle.

As a method for producing the adhesive sheet, for example, the adhesive composition is coated on a separator or a base material, dried, and then a separator (a separator having a different release force when coated on a separator) is applied. The method of laminating, etc. are mentioned.

When applying the adhesive composition, it is preferable to dilute the adhesive composition with a solvent before coating. Especially preferred is 20 to 60% by weight. Further, the solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive composition. For example, ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, aromatic solvents such as toluene and xylene, methanol, ethanol, and propyl alcohol. alcohol-based solvents such as Among these, ethyl acetate is preferably used in terms of solubility, drying property, price, and the like.

The viscosity of the diluted adhesive composition is preferably 500 to 15,000 mPa·s/25°C, more preferably 1,000 to 10,000 mPa·s/25°C. If the viscosity is too low and a component with a large specific gravity is used, the component tends to settle.

Examples of the method of applying the pressure-sensitive adhesive composition include roll coating, die coating, gravure coating, comma coating, and screen printing.

The thickness of the adhesive layer in the obtained adhesive sheet is preferably 5 to 250 μm, particularly preferably 25 to 200 μm, further preferably 50 to 175 μm. If the pressure-sensitive adhesive layer is too thin, the thickness accuracy tends to decrease and the pressure-sensitive adhesive strength tends to decrease. tend to

Further, the adhesive sheet may be subjected to aging treatment at least one of room temperature (23° C.) and heating. The aging treatment is performed as a reaction time for chemical cross-linking between the acrylic resin (A) and the cross-linking agent for acrylic resin (C) in order to balance the adhesive physical properties of the adhesive agent. As the conditions, the temperature is usually room temperature to 40° C., and the time is usually 1 to 30 days. good.

The gel fraction of the pressure-sensitive adhesive is preferably 10 to 90% by weight, particularly preferably 15 to 70% by weight, more preferably 15 to 70% by weight, from the viewpoint of adhesion to members, reworkability, and holding power. is 20 to 60% by weight. If the gel fraction of the pressure-sensitive adhesive is too low, the cohesive force will be low and the members will tend to shift when the pressure-sensitive adhesive layer is cured. Sufficient adhesion between the adhesive layer and the interface of the member cannot be obtained, and the shear strength after curing tends to decrease.

The gel fraction is a measure of the degree of cross-linking (degree of curing), and is calculated, for example, by the following method. That is, the adhesive is collected by picking from an adhesive sheet having an adhesive layer formed on the surface of a substrate or the like. The collected adhesive agent was wrapped in a 200-mesh SUS wire mesh and immersed in ethyl acetate adjusted to 23° C. for 24 hours. The weight percentage of the undissolved pressure-sensitive adhesive component is defined as the gel fraction.

In the present invention, the tacky-adhesive layer made of the tacky-adhesive is cured by heating to increase the adhesive force. As for the heating conditions, the heating temperature is preferably 100 to 250°C, more preferably 120 to 200°C, and particularly preferably 130 to 185°C. If the temperature is too low, the curing time tends to be long and the workability tends to decrease. If the temperature is too high, the epoxy compound (B) tends to volatilize or ignite. The heating time is preferably 5 to 180 minutes, more preferably 30 to 120 minutes, particularly preferably 45 to 90 minutes. If the time is too short, the shear strength tends to decrease, and if it is too long, the workability tends to decrease.

Then, the ratio of the shear strength (MPa) after heating at 140 ° C. for 60 minutes and the shear strength (MPa) after curing to the shear strength (MPa) before curing is 10 or more. The balance of durability is preferable, more preferably 20 or more, particularly preferably 100 or more. The upper limit of the ratio of shear strength after curing to shear strength before curing is usually 10,000.

The pressure-sensitive adhesive of the present invention has excellent characteristics such as excellent tackiness and holding power before curing, and high shear strength after curing. Therefore, it can be suitably used for various purposes such as building materials, on-vehicle parts, electronic parts, semiconductor manufacturing processes, member sealing, aviation parts, sporting goods and the like.

Then, the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer made of this pressure-sensitive adhesive is peeled off the separator covering the surface of the pressure-sensitive adhesive layer, and the surface of the pressure-sensitive adhesive layer is applied to the target member surface. The adhesive layer can be easily transferred just by sticking it, which makes the work very convenient.

A laminate obtained by laminating other members via the adhesive layer has a high holding power before curing and exhibits a high shear strength after curing. , not easily displaced or peeled off, and of excellent quality.

EXAMPLES 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 the gist thereof is not exceeded. In the examples, "parts" and "%" mean weight standards.
First, the following components were prepared prior to the examples.

<Acrylic resin (A)>
[Preparation of acrylic resin (A-1)]
80 parts of ethyl acetate, 21 parts of methyl ethyl ketone, and 0 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator were added to a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer. After charging .036 parts and heating the internal temperature to reach the boiling point, 49.5 parts of methyl acrylate (MA), 45 parts of methyl methacrylate (MMA), 5 parts of 2-hydroxyethyl acrylate (2HEA), acrylic acid (AAc) ), 4 parts of ethyl acetate, and 0.036 parts of a polymerization initiator (AIBN) was added dropwise over 2 hours while maintaining the boiling state. After that, while continuing the reaction, 0.036 parts of the polymerization initiator (AIBN) was added twice, reacted for 7 hours, and then diluted to give an acrylic resin (A-1) solution (solid content concentration of 36.0 %, viscosity 6,040 mPa s/25° C., acrylic resin (A-1): weight average molecular weight (Mw) 260,000, degree of dispersion (Mw/Mn) 2.1, glass transition temperature (Tg) 39.8 °C) was obtained.

<Epoxy compound (B)>
The following were prepared as the epoxy compound (B).
(B-1): Trimethylolpropane polyglycidyl ether (manufactured by Nagase Chemtex, "Denacol EX-321", liquid, viscosity 130 mPa s/25°C, epoxy equivalent 140 g/mol, number of epoxy groups 2 to 3)

<Crosslinking agent for acrylic resin (C)>
The followings were used as the cross-linking agent (C) for acrylic resins.
(C-1): Adduct of tolylene diisocyanate and trimethylolpropane (manufactured by Tosoh Corporation, "Coronate L55E")

<Curing agent for epoxy compound (D)>
As the curing agent (D) for epoxy-based compounds, the following was used and pulverized under the following conditions using a bead mill before compounding.
(D-1): Sebacic acid dihydrazide (manufactured by Otsuka Chemical Co., Ltd., melting point 186-188°C)
(D-2): dodecane dihydrazide (manufactured by Otsuka Chemical Co., Ltd., melting point 188-192° C.)
(D-3): Dicyandiamide (manufactured by Mitsubishi Chemical Corporation, melting point 209-213°C)
(D'-1): Salicylic acid dihydrazide (manufactured by Otsuka Chemical Co., Ltd., melting point 147-150°C)
(D'-2): Organic acid hydrazidozide curing agent (manufactured by Otsuka Chemical Co., melting point 164 to 169°C)
(D'-3): Adipic acid hydrazide (manufactured by Otsuka Chemical Co., Ltd., melting point 177-183°C)

[Pulverization conditions]
The epoxy compound curing agent (D) and glass beads having a particle size of 1 mm were placed in a 250 mL container and pulverized for 5 minutes at a frequency of 600 rpm using a rocking shaker (manufactured by Seiwa Giken Co., Ltd.).

<Examples 1 to 3, Comparative Examples 1 to 3>
A pressure-sensitive adhesive composition was obtained by blending the above components according to Table 1 below and adjusting the solid content concentration to a range of 30 to 60% using ethyl acetate.

A pressure-sensitive adhesive sheet [I] was produced from the obtained pressure-sensitive adhesive composition according to the procedure shown below. Thereafter, using this adhesive sheet [I], the gel fraction, ball tack, holding power, and shear strength after curing were evaluated as follows.
The evaluation method and evaluation criteria for each item are as follows. These results are also shown in Table 1 below.

<Preparation of adhesive sheet [I]>
The pressure-sensitive adhesive composition was applied to a 38 μm-thick heavy release silicon separator (manufactured by Mitsui Tocello Co., Ltd., “SPPET03 38BU”) using a comma coater so that the thickness after drying was 50 μm. dried for a minute. Then, a 38 μm-thick light release silicone separator (manufactured by Mitsui Tocello Co., Ltd., “SPPET01 38BU”) was attached to the surface of the dried adhesive layer to prepare an adhesive sheet [I] (light release silicon separator/adhesive layer/heavy release silicone separator).

[Gel fraction]
The adhesive was collected by picking from the adhesive layer formed on the separator using the adhesive sheet [I]. The collected adhesive agent was wrapped in a 200-mesh SUS wire mesh and immersed in ethyl acetate adjusted to 23° C. for 24 hours. The weight percentage of the undissolved pressure-sensitive adhesive component was calculated from the following formula to determine the gel fraction.
Gel fraction (%) = [weight of adhesive after immersion]/[weight of adhesive before immersion] x 100

[Ball tack]
After peeling off the light release silicone separator of the adhesive sheet [I] and transferring it to a 38 μm PET film, the heavy release silicone separator was peeled off and the adhesive layer was subjected to a ball tack test. The ball tack test was carried out in accordance with JIS Z 0237 with an inclined plate angle of 30° at 23° C. and an atmosphere of 50% RH. Evaluation criteria are as follows.
(Evaluation criteria)
◎・・・Ball number over 5 ○・・・Ball number 3 or more and 5 or less ×・・・Ball number less than 3

[Holding power]
After peeling off the light release silicon separator of the adhesive sheet [I] and transferring it to a 38 μm PET film, peel off the heavy release silicon separator so that the adhesion area is 25 mm × 25 mm. was attached to a polished SUS plate, left to stand for 30 minutes under the conditions of 23 ° C. x 50% RH, and then under the conditions of 40 ° C., a load of 1 kg was applied, and the holding force measurement method of JIS Z 0237 was applied. The deviation was evaluated according to the Evaluation criteria are as follows.
(Evaluation criteria)
○・・・No deviation after 24 hours △・・・There is deviation after 24 hours ×・・・Drop after 24 hours

[Shear strength after curing]
The pressure-sensitive adhesive sheet [I] was cut into a size of 25 mm×12.5 mm and transferred to a SUS plate. A SUS plate of the same size was pasted on the opposite side of the transferred SUS plate, the pasted part was fixed with a clip, and after curing at 140°C for 1 hour or 180°C for 1 hour, it was placed under the conditions of 23°C and 50% RH. Using AUTO Graph AG-X Plus (manufactured by Shimadzu), shear strength (MPa) was measured at a speed of 5 mm/min. Evaluation criteria are as follows.
(Evaluation criteria)
◎: 15 MPa or more ◯: 10 MPa or more and less than 15 MPa △: 5 MPa or more and less than 10 MPa ×: less than 5 MPa

Examples 1 to 3 using a curing agent for epoxy compounds with a high melting point did not inhibit the reaction between the crosslinking agent for acrylic resin and the acrylic resin, and the holding power before heat curing and the shear strength after heat curing were improved. I know you're good.
On the other hand, Comparative Examples 1 to 3 using a curing agent for epoxy compounds with a low melting point have good shear strength after curing, but the cross-linking agent for acrylic resin is consumed, and the gel fraction decreases. It was low and the holding power before curing was poor.
Further, in Examples 1 to 3, even if a powdery epoxy compound curing agent with a fine particle size was used, the reaction between the acrylic resin and the acrylic resin crosslinking agent was inhibited by the epoxy compound curing agent. It was excellent in holding power before curing and shear strength after curing.
Further, since the adhesive sheet of the present invention has a high holding power before curing, it is not necessary to fix the member by curing, and it is very useful because it can be transported and stored.

The pressure-sensitive adhesive composition of the present invention is excellent in tackiness and holding power before curing, and exhibits high shear strength after curing. Suitable for electronic parts, semiconductor manufacturing processes, member sealing, aviation parts, and adhesive/adhesive applications for sporting goods.

Claims (10)

Acrylic resin (A), epoxy compound (B), acrylic resin cross-linking agent (C) (excluding epoxy compound (B)) and epoxy compound curing agent (D) An adhesive composition comprising:
The epoxy compound curing agent (D) is a curing agent having an amino group with a melting point of 185° C. or higher, and the epoxy compound curing agent (D) is an organic acid hydrazide compound. An adhesive composition characterized by: 2. The polymer according to claim 1, wherein the acrylic resin (A) is a polymer of polymerization components containing a functional group-containing monomer containing at least one monomer selected from hydroxyl group-containing monomers and carboxy group-containing monomers. Adhesive composition. 3. The adhesive composition according to claim 1, wherein said epoxy compound (B) is liquid at 25[deg.]C. 4. The adhesive composition according to any one of claims 1 to 3, wherein the epoxy compound curing agent (D) is powder. The content of the epoxy compound curing agent (D) is 10 to 200 parts by weight with respect to 100 parts by weight of the acrylic resin ( A). The adhesive composition described. A pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 5 , which is crosslinked. The adhesive according to claim 6 , which is cured by heating at 100 to 250°C. 8. The pressure-sensitive adhesive according to claim 6 or 7 , wherein the ratio of shear strength (MPa) after curing to shear strength (MPa) before curing is 10 or more. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive according to any one of claims 6 to 8 . A laminate comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive according to any one of claims 6 to 8 and another member.