JP2022034332A - Adhesive composition, adhesive sheet and laminate - Google Patents

Abstract

To provide an adhesive composition that can give an adhesive layer having superior room-temperature transferability and a good appearance of a coating layer before curing, and having high adhesion to an adherend after curing, and also having superior heat resistance.SOLUTION: An adhesive composition contains an acrylic resin (A), an epoxy compound (B), a curing agent (C) reactable with the epoxy compound (B), and a crosslinker (D). When an adhesive layer formed from the adhesive composition is heated at 160°C for 1 hour to be cured, the loss tangent (tanδ) at 23°C determined by dynamic viscoelasticity measurement is 1.5-5.SELECTED DRAWING: None

Description

The present invention relates to adhesive compositions, adhesive sheets and laminates. More specifically, the present invention relates to an adhesive composition for forming an adhesive layer which has adhesiveness under normal conditions, is adhered to an adherend, and then is cured by heating or the like to be firmly adhered. The present invention also relates to an adhesive sheet and a laminate having an adhesive layer having excellent room temperature transferability to an adherend and also excellent adhesiveness and heat resistance after curing.

Conventionally, a liquid adhesive using an epoxy compound has been used for adhering metals and plastics. Recently, there has been an increasing demand for adhesives that have both adhesive and adhesive properties, such as being adhesive under normal conditions and being cured by heating after being attached to the adherend to firmly adhere. As such a viscous adhesive, a heat-curable pressure-sensitive adhesive composition using an acrylic resin, an epoxy resin and an epoxy curing agent has been proposed (see, for example, Patent Document 1).

Further, in recent years, excellent adhesive strength is required in applications of flexible printed wiring boards (FPCs), especially in applications of adhering FPCs and reinforcing plates. For example, the terminal portion of a flexible printed wiring board made of a polyimide film is lined with a reinforcing base material such as a polyimide film, a glass epoxy plate, or a metal plate to increase its strength. In such an application, the adhesion between the polyimide film of the flexible printed wiring board and the reinforcing base material is performed by curing the thermosetting adhesive provided between them (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2013-203795 Japanese Unexamined Patent Publication No. 2017-17131

However, in the thermosetting pressure-sensitive adhesive composition disclosed in Patent Document 1, the adhesive strength after thermosetting is not considered at all, and when, for example, a pressure-sensitive adhesive sheet is produced using this composition. Has a problem that the elastic modulus after curing becomes too high and the adhesive strength is insufficient.

Further, Patent Document 2 describes an adhesive sheet obtained by containing an epoxy resin and an epoxy resin curing agent in an acrylic resin having a glass transition temperature of −5 to 15 ° C., and the adhesive sheet has an adhesive strength. Was excellent. However, this adhesive sheet needs to be attached to an adherend by heating (heat laminating), and is not excellent in transferability at room temperature. In the future, from the viewpoint of process optimization, room temperature transferability that can be attached to the adherend at room temperature will be required. Further, when used for electronic equipment applications, heat resistance is also required in which the adhesiveness does not easily change even when exposed to high temperatures.

Therefore, in the present invention, under such a background, the adhesiveness is excellent in room temperature transferability and the appearance of the coating film before curing, and after curing, it is excellent in adhesiveness to the adherend and also excellent in heat resistance. It is an object of the present invention to provide a pressure-sensitive adhesive composition from which a coating layer can be obtained.

However, as a result of diligent research in view of such circumstances, the present inventors have conducted an acrylic resin (A), an epoxy-based compound (B), a curing agent (C) and a cross-linking agent (C) that react with the epoxy-based compound (B). By defining the physical properties of the pressure-sensitive adhesive composition containing D) when the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is cured under predetermined conditions, before curing, We have found that a viscous adhesive layer having excellent room temperature transferability and appearance of a coating film, having an appropriate viscosity after curing, having excellent adhesiveness to an adherend, and having excellent heat resistance can be obtained, and the present invention has been developed. completed.

That is, the present invention is a pressure-sensitive adhesive composition containing an acrylic resin (A), an epoxy-based compound (B), a curing agent (C) that reacts with the epoxy-based compound (B), and a cross-linking agent (D). Therefore, when the adhesive layer formed from the adhesive composition is heated at 160 ° C. for 1 hour and cured, the loss positive contact (tan δ) at 23 ° C. obtained by dynamic adhesive elasticity measurement is obtained. The first gist is a viscous adhesive composition characterized by being 1.5 to 5.

The second gist of the present invention is an adhesive sheet having an adhesive layer formed from the adhesive composition, which is the first gist of the present invention.

The third gist of the present invention is a laminate in which an adhesive layer formed from the adhesive composition, which is the first gist, is laminated on an adherend.

According to the adhesive composition of the present invention, the adhesive film has excellent appearance and room temperature transferability before curing, has excellent adhesiveness to an adherend after curing, and has excellent heat resistance. An adhesive layer can be formed. Therefore, the adhesive layer formed from the adhesive composition of the present invention is used for various adhesive applications such as building materials, in-vehicle parts, electronic parts, semiconductor manufacturing processes, and member encapsulation. It can be suitably used for various adhesive bonding applications such as for aviation parts, sports equipment, etc., and is particularly useful for bonding an FPC and a reinforcing plate.

In the adhesive composition, it is usual to include an epoxy-based compound in an acrylic resin, and as an epoxy-based compound, bisphenol A type, bisphenol F type, etc. are used from the viewpoint of curability and handleability. Epoxy-based resins are used, and solid epoxy resins such as polyfunctional type, novolak phenol type, and biphenyl type are used from the viewpoint of creep characteristics. When these epoxy resins are blended with an acrylic resin, there is a concern that tack is easily lost and the transferability at room temperature is inferior, and a solution is required.
Therefore, in the present invention, attention is paid to the loss tangent (tan δ) at 23 ° C. obtained by dynamic viscoelasticity measurement after curing, the viscosity of the adhesive composition, the hardness and softness of the adhesive layer after curing. By examining the relationship between the effect of the present invention and the adhesive composition so that the loss tangent (tan δ) after curing is within a predetermined range, the adhesive composition has room temperature transferability before curing. It was found that excellent adhesiveness can be obtained after curing, and a viscous adhesive layer having surprisingly excellent heat resistance can be obtained.

Hereinafter, the present invention will be described in detail.
In the present invention, (meth) acrylic means acrylic or methacrylic, (meth) acryloyl means acryloyl or methacrylic, and (meth) acrylate means acrylate or methacrylate.

The adhesive composition of the present invention is a curing agent (C) that reacts with an acrylic resin (A), an epoxy compound (B), and an epoxy compound (B) (hereinafter, a curing agent for an epoxy compound (C). ) Or simply abbreviated as a curing agent (C)) and a cross-linking agent (D) (hereinafter, may be referred to as a cross-linking agent (D) for an acrylic resin). In the following, the adhesive composition of the present invention may be referred to as "adhesive composition [I]".

[Adhesive composition [I]]
As described above, the adhesive composition [I] of the present invention comprises an acrylic resin (A), an epoxy compound (B), a curing agent for an epoxy compound (C), and a cross-linking agent for an acrylic resin (D). ) Is contained. Each component constituting the adhesive adhesive composition [I] will be described.

<Acrylic resin (A)>
The acrylic resin (A) is a resin obtained by polymerizing a polymerization component containing at least one (meth) acrylic monomer, and for example, the (meth) acrylic monomer is used as a main component, and in some cases, another Examples thereof include an acrylic resin obtained by polymerizing a polymerization component containing various polymerizable monomers.

The term "main component" of the (meth) acrylic monomer means that the (meth) acrylic monomer is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight, based on the entire polymerization component. It means that it contains the above.

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

Examples of the derivative of the (meth) acrylic acid include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and 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 Examples thereof include alkyl group-containing (meth) acrylates such as -2-propylpentyl (meth) acrylate and n-octadecyl (meth) acrylate.

Further, as another example of the above-mentioned (meth) acrylic acid derivative, for example, cycloalkyl (meth) acrylate such as cyclohexyl (meth) acrylate and cyclopentyl (meth) acrylate; aralkyl (meth) acrylate such as benzyl (meth) acrylate. Biphenyloxy structure-containing (meth) acrylates such as biphenyloxyethyl (meth) acrylates; 2-isobornyl (meth) acrylates, 2-norbornylmethyl (meth) acrylates, 5-norbornen-2-yl-methyl (meth) Acrylate, 3-methyl-2-norbornylmethyl (meth) acrylate, dicyclopentenyl (meth) acrylicate, dicyclopentenyloxyethyl (meth) acrylicate, dicyclopentanyl (meth) acrylicate, etc. Polycyclic (meth) acrylate; 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, methoxydiethylene glycol (meth) ) Acrylate, ethoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethylcarbitol (meth) acrylate, phenoxyethyl (meth) acrylate, alkylphenoxypolyethylene glycol (meth) acrylate and other alkoxy groups or phenoxy groups ( Meta) 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) acrylates, 8-hydroxyoctyl (meth) acrylates, 10-hydroxydecyl (meth) acrylates, 12-hydroxylauryl (meth) acrylates, and [4- (hydroxymethyl) Cyclohexyl] Methyl acrylate, cyclohexanedimethanol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate and other hydroxyl group-containing (meth) acrylates; glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl Epoxy group-containing (meth) acrylates such as ether; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,2-trifluoroethylethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, hexafluoro Halogen-containing (meth) acrylates such as propyl (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate; dimethylaminoethyl (meth) Alkylaminoalkyl (meth) acrylates such as acrylates; 3-oxetanylmethyl (meth) acrylates, 3-methyl-oxetanylmethyl (meth) acrylates, 3-ethyl-oxetanylmethyl (meth) acrylates, 3-butyl-oxetanylmethyl (meth) acrylates. ) Oxetane group-containing (meth) acrylates such as acrylates and 3-hexyl-oxetanylmethyl (meth) acrylates; and the like.

Examples of the (meth) acrylamide derivative include N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N-isopropyl. N-alkyl group-containing (meth) acrylamide derivatives such as butyl (meth) acrylamide and N-hexyl (meth) acrylamide; N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-methylol-N-propane N-hydroxyalkyl group-containing (meth) acrylamide derivatives such as (meth) acrylamide; N-aminoalkyl group-containing (meth) acrylamide derivatives such as aminomethyl (meth) acrylamide and aminoethyl (meth) acrylamide; N-methoxymethyl ( N-alkoxy group-containing (meth) acrylamide derivatives such as meta) acrylamide and N-ethoxymethyl (meth) acrylamide; N-mercaptoalkyl group-containing (meth) acrylamide such as mercaptomethyl (meth) acrylamide and mercaptoethyl (meth) acrylamide. Derivatives; examples thereof include heterocyclic-containing (meth) acrylamide derivatives such as N-acrylamide morpholine, N-acryloylpiperidin, N-methacryloylpiperidin, and N-acrylloylpyrrolidine.

These (meth) acrylic monomers may be used alone or in combination of two or more. Among these (meth) acrylic monomers, an alkyl group-containing (meth) acrylate is preferably used. The number of carbon atoms of the alkyl group in the alkyl group-containing (meth) acrylate is usually 1 to 20, preferably 1 to 12, more preferably 1 to 8, and further preferably 1 to 4. It is preferable that the alkyl group has a small number of carbon atoms because it has excellent compatibility with the epoxy compound (B) described later.

Further, among these (meth) acrylic monomers, the monomer having an acryloyl group is preferably contained in an amount of 25% by weight or more, and 35% by weight or more, based on the total polymerization component of the acrylic resin (A). Is more preferable. The upper limit of the content of the monomer having an acryloyl group with respect to the entire polymerization component of the acrylic resin (A) is 100% by weight. By increasing the content ratio of the monomer having an acryloyl group, the transferability after forming the adhesive layer is excellent without impairing the adhesiveness before curing, and the handleability is improved.

As the monomer having such an acryloyl group, acrylic acid or a derivative thereof, acrylamide or a derivative thereof can be selected and used from the various (meth) acrylic monomers described above.

When an acrylic acid derivative is used as the monomer having an acryloyl group, for example, the glass transition temperature is high and the molecular weight of the acrylic resin (A) can be easily increased. Therefore, the glass transition temperature when the homopolymer is prepared is 0 ° C. The above acrylic acid derivatives are preferable. In particular, methyl acrylate is preferable in terms of polymerizability.

Further, considering the reactivity with the cross-linking agent (D) for an acrylic resin described later, an acrylate containing a hydroxyl group is suitable, for example, a hydroxyalkyl acrylate such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. Is preferable. Further, it is also preferable to use acrylic acid for the same reason that the acrylate containing the hydroxyl group is suitable.

When an acrylamide derivative is used as the monomer having an acryloyl group, for example, dialkylacrylamide and N-acryloylmorpholine are suitable because the glass transition temperature is high and the compatibility with the epoxy compound (B) is excellent. .. In particular, by using an acrylamide derivative having a glass transition temperature of 0 ° C. or higher when the homopolymer is prepared, the glass transition temperature of the obtained acrylic resin (A) can be maintained high and the adhesion to the adherend can be improved. It is preferable in that it can be enhanced.

The polymerization component constituting the acrylic resin (A) may contain a polymerizable monomer other than the (meth) acrylic monomer (hereinafter referred to as “other polymerizable monomer”).
Examples of the other polymerizable monomer include unsaturated carboxylic acids such as crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide-N-glycolic acid, and silicic acid; Carboxylic acid vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl stearate, vinyl benzoate; monomers containing aromatic rings such as styrene and α-methylstyrene; acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, alkyl Examples thereof include vinyl ether, vinyl toluene, vinyl pyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, allyltrimethylammonium chloride, dimethylallylvinyl ketone and the like. These may be used alone or in combination of two or more.

The polymerization component constituting the acrylic resin (A) preferably contains a functional group-containing monomer. As the functional group-containing monomer, it is preferable to contain at least one functional group-containing monomer selected from the hydroxyl group-containing monomer such as the above-mentioned hydroxyl group-containing (meth) acrylate and the carboxy group-containing monomer such as acrylic acid. Of these, a functional group-containing monomer containing a (meth) acryloyl group is preferable, and a functional group-containing monomer containing an acryloyl group is more preferable. Among these, 2-hydroxyethyl acrylate and acrylic acid are particularly preferable, and 2-hydroxyethyl acrylate is more preferable.

The content of the functional group-containing monomer is preferably 0.1 to 30% by weight, more preferably 1 to 25% by weight, based on the entire polymerization component constituting the acrylic resin (A). It is more preferably 3 to 20% by weight. If the amount of the functional group-containing monomer is too small, the cohesive force tends to decrease, and the adhesive strength after curing tends to decrease. On the contrary, if the amount is too large, the storage stability of the adhesive layer tends to decrease and the pot life tends to be shortened.

As a polymerization method of the acrylic resin (A), conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization and emulsion polymerization can be used. For example, a method of mixing or dropping a polymerization component and a polymerization initiator which are appropriately selected in an organic solvent and polymerizing under predetermined polymerization conditions can be mentioned. Of these, 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. Such as aliphatic alcohols; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; and the like. These organic solvents may be used alone or in combination of two or more.

Among these organic solvents, esters of ethyl acetate, butyl acetate, etc. from the viewpoints of ease of polymerization reaction, effect of chain transfer, ease of drying when coating the adhesive composition, and safety. Kind: Ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone are preferable, and ethyl acetate is particularly preferable.

Examples of the polymerization initiator used for such solution radical polymerization include 2,2'-azobisisobutyronitrile and 2,2'-azobis-2-methylbutyronitrile, which are ordinary radical polymerization initiators. , 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (methylpropionic acid) and other azo-based initiators; benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, cumene. Organic peroxides such as hydroperoxide; and the like; can be appropriately selected and used according to the monomer to be used. These polymerization initiators may be used alone or in combination of two or more.

In this way, the acrylic resin (A) used in the present invention can be obtained.

The weight average molecular weight (Mw) of the acrylic resin (A) is preferably 100,000 or more, more preferably 150,000 to 1,500,000, particularly preferably 200,000 to 1,000,000, and even more preferably 250,000 to 800,000. Is. If the weight average molecular weight is too small, the toughness and cohesive force of the obtained adhesive layer tend to decrease. Further, if the weight average molecular weight is too large, the viscosity tends to be too high and the scaling tends to increase during polymerization, and the compatibility with the epoxy compound (B) and the handleability tend to decrease.

The dispersity [weight average molecular weight (Mw) / number average molecular weight (Mn)] of the acrylic resin (A) is preferably 10 or less, more preferably 7 or less, still more preferably 5.5 or less. be. If the degree of dispersion is too high, the cohesive force 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 converted to the standard polystyrene molecular weight, and is a high-speed liquid chromatograph (manufactured by Japan Waters, "Waters 2695 (main body)" and "Waters 2414 (detector)"). Column: Chromatography GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical number of stages: 10000 stages / piece, filler material: styrene-divinylbenzene copolymer, filling The agent particle size (10 μm) can be measured by connecting three in series, and the number average molecular weight can also be measured by the same method. 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 −50 ° C. or higher, more preferably −20 to 100 ° C., still more preferably 0 to 75 ° C., and particularly preferably 10 to 50 ° C. Particularly preferably, it is 15 to 40 ° C. When the glass transition temperature deviates from a predetermined range, the value of tan δ at 23 ° C. after curing tends to decrease, and the adhesive strength tends to decrease.

The glass transition temperature is calculated from the following Fox formula.

Tg: Glass transition temperature of polymer (K)
Tga: Monomer A homopolymer glass transition temperature (K) Wa: Monomer A weight fraction Tgb: Monomer B homopolymer glass transition temperature (K) Wb: Monomer B weight fraction Tgn: Monomer N homo Polymer glass transition temperature (K) Wn: Weight fraction of monomer N (Wa + Wb + ... + Wn = 1)

That is, the glass transition temperature of the acrylic resin is a value calculated by applying the glass transition temperature and the weight fraction when a homopolymer is prepared from each monomer constituting the acrylic resin to the Fox formula.
The glass transition temperature when a homopolymer is prepared from the monomers constituting the acrylic resin is usually determined by the Polymer Handbook [Polymer HandBook, J. Mol. Brandrup, Interscience, 1989], this value can be used for determination. Further, the glass transition temperature when a homopolymer is prepared from the monomers constituting the acrylic resin can be measured by a differential scanning calorimeter (DSC) by a method compliant with JIS K7121-1987 or JIS K6240.

The refractive index of the acrylic resin (A) is usually 1.440 to 1.600. It is preferable to reduce the difference in the refractive index from the members to be laminated because the light loss at the interface of the members is small.

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

<Epoxy compound (B)>
The epoxy compound (B) used in the present invention includes an epoxy compound having one or more epoxy groups in one molecule, preferably an epoxy compound having one or two epoxy groups, and more preferably two epoxy groups. Examples thereof include epoxy compounds having one. These compounds may be used alone or in combination of two or more. If the number of epoxy groups in one molecule is too large, it becomes too hard after curing, and the adhesive strength tends to decrease.

In the present invention, among the epoxy compounds (B), those which are liquid at 25 ° C. are preferable, and those having a low viscosity and a high epoxy equivalent are preferably contained.
As such an epoxy compound, an epoxy compound (b1) having a viscosity at 25 ° C. of 2000 mPa · s or less and an epoxy equivalent of 300 g / eq or more is particularly preferable. The viscosity of the epoxy compound (b1) at 25 ° C. is preferably 2000 mPa · s or less in that tack is easily applied to the adhesive layer before curing, more preferably 1 to 1500 mPa · s, and particularly preferably. Is 1 to 1200 mPa · s, more preferably 50 to 1000 mPa · s. If the viscosity is too high, the room temperature transferability tends to decrease. If the viscosity is too low, it volatilizes during heat curing and tends to generate bubbles.
The above viscosity is a value measured using a B-type viscometer in accordance with JIS K 7233.

Further, the epoxy equivalent of the epoxy compound (b1) is preferably 300 g / eq or more in terms of adhesive strength after curing, more preferably 310 to 10000 g / eq, and particularly preferably 320 to 5000 g / eq. It is more preferably 350 to 2500 g / eq, and particularly preferably 400 to 2000 g / eq. If the epoxy equivalent is too low, the adhesive strength after curing tends to decrease. If the epoxy equivalent is too high, the compatibility with the acrylic resin (A) tends to decrease.
The epoxy equivalent is a value measured according to JIS K 7236 using a potentiometric titrator.

The weight average molecular weight of the epoxy compound (b1) is preferably 300 to 5000, more preferably 350 to 4000, and particularly preferably 400 to 2000. If the molecular weight is too small, it volatilizes during heat curing, and bubbles tend to be generated in the coating film to deteriorate the appearance of the coating film. If it is too large, the viscosity tends to increase and the room temperature transferability tends to decrease.
The weight average molecular weight of the epoxy compound (b1) is measured by the same method as the weight average molecular weight of the acrylic resin (A).

Specific examples of the epoxy compound (b1) include "jER (registered trademark) 871" and "jER (registered trademark) YX7400" manufactured by Mitsubishi Chemical Corporation, and "EP-4005" and "ED" manufactured by ADEKA Corporation. -502 "," ED-502S "," ED-506 "," EPICLON (registered trademark) 1650-75MPX "manufactured by DIC," EPICLON (registered trademark) 1051-75M "and the like can be mentioned.

In the present invention, the epoxy compound (B) is preferably contained as the epoxy compound (b1), but is generally other than the epoxy compound (b1) as long as the transferability before curing is not impaired. A known epoxy compound used for adhesive applications and the like can also be used in combination.

Examples of such known epoxy compounds include monofunctional epoxy compounds having one epoxy group in the molecule and polyfunctional epoxy compounds having two or three or more epoxy groups. These compounds may be used alone or in combination of two or more.

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

Among the above polyfunctional epoxy compounds, bifunctional epoxy compounds having two epoxy groups include, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, and diethylene glycol di. Diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, diglycidyl terephthalate, diglycidyl-o-phthalate, diglycidyl resorcinol ether, bisphenol A type diglycidyl compound and its hydroxide, bisphenol F type diglycidyl compound and its Examples thereof include hydrogenated products, biphenyl-type diglycidyl compounds and derivatives thereof.

Examples of the polyfunctional epoxy compound having three or more epoxy groups include 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, ditrimethylolpropane tetraglycidyl ether; polyglycerol pentaglycidyl ether, pentaeristol pentaglycidyl ether, dipentaeristol pentaglycidyl ether and the like. Epoxide compounds; sorbitol hexaglycidyl ethers: hexafunctional epoxy compounds such as dipentaeristol hexaglycidyl ethers; polyglycidyl ethers, phenol novolac type epoxy compounds, cresol novolac type epoxy compounds; and the like.

In the present invention, the content ratio of the epoxy compound (b1) to the entire epoxy compound (B) is preferably 30% by weight or more in terms of room temperature transferability before curing and adhesive strength after curing. It is preferably 50% by weight or more, and particularly preferably 60% by weight or more. If the content of the epoxy compound (b1) is too small, the room temperature transferability before curing tends to decrease, and the value of tan δ after curing tends to decrease. The upper limit of the content ratio is 100% by weight.

The viscosity of the epoxy compound (B) including the epoxy compound (b1) as a whole is preferably 1 to 10000 mPa · s, more preferably 10 to 5000 mPa · s from the viewpoint of room temperature transferability before curing. Particularly preferably, it is 50 to 2500 mPa · s. If the viscosity is too low, the cohesive force before curing tends to decrease, and if it is too high, the room temperature transferability before curing tends to decrease.
The viscosity is a value measured using a B-type viscometer in accordance with JIS K 7233.

The content of the epoxy compound (B) is preferably 1 to 150 parts by weight, more preferably 3 to 120 parts by weight, and particularly preferably 5 to 5 to 100 parts by weight with respect to 100 parts by weight of the acrylic resin (A). It is 100 parts by weight, more preferably 10 to 75 parts by weight. If the content of the epoxy compound (B) with respect to the acrylic resin (A) is too small, the room temperature transferability before curing tends to decrease, and if it is too large, the cohesive force before curing decreases or after curing. It tends to cause a decrease in the adhesive strength of the.

<Curing agent for epoxy compounds (C)>
The curing agent (C) for an epoxy-based compound is a compound that is used as a curing agent for the epoxy-based compound (B) and has a functional group that can react with the epoxy group of the epoxy-based compound (B).
Examples of the curing agent (C) include amines, polyamides, imidazoles, polypeptide hardeners, acid anhydrides, and the like. These may be used alone or in combination of two or more. Among the above-mentioned curing agents (C), it is particularly preferable to use an amine compound because it is excellent in storage stability and curability when a viscous adhesive is formed, and among them, dicyandiamide and organic acid hydrazide are preferable. Among the organic acid hydrazides, adipic acid dihydrazide and sebacic acid dihydrazide are particularly preferable because they have an excellent curing rate.

The curing agent (C) may be liquid or solid, but in terms of storage stability when a viscous adhesive is formed and in terms of pot life of the viscous adhesive composition. It is preferably solid, and further, it is dispersed and contained in the state of powder in that the coating film becomes smooth and the adhesive area with the member increases when the coating film is cured and the adhesive strength after curing is increased. Is preferable. When powder is used as the curing agent (C), the particle size of the powder should be set to 1.2 times or less of the film thickness at the time of forming the adhesive layer. It is preferable, and it is more preferable that it is 1 times or less.

The content of the curing agent (C) is preferably 1 to 100 parts by weight, more preferably 3 to 80 parts by weight, and particularly preferably 5 to 5 to 100 parts by weight with respect to 100 parts by weight of the epoxy compound (B). It is 70 parts by weight, more preferably 7 to 50 parts by weight. If the content ratio of the curing agent (C) to the epoxy compound (B) is too small, the curing rate tends to be slow or the curing temperature tends to be high, and if it is too large, streaks are generated during coating. Also, the pot life of the adhesive composition tends to be shortened.

<Crosslinking agent (D)>
In the adhesive composition [I] of the present invention, in addition to the above-mentioned acrylic resin (A), epoxy-based compound (B) and curing agent (C) for epoxy-based compound, acrylic resin (A) is further added. It contains a cross-linking agent (D) (cross-linking agent for acrylic resin (D)). By containing the cross-linking agent (D), the adhesive adhesive composition [I] can be cross-linked, and the cohesive force of the adhesive adhesive can be improved. Since the acrylic resin (A) is also crosslinked by the epoxy compound (B), the crosslinking agent (D) in the present invention excludes the epoxy compound (B).

As the cross-linking agent (D), a known cross-linking agent can be used, and examples thereof include an isocyanate-based cross-linking agent, an aziridine-based cross-linking agent, a melamine-based cross-linking agent, an aldehyde-based cross-linking agent, and a metal chelate-based cross-linking agent.
These cross-linking agents (D) may be used alone or in combination of two or more.

Examples of the isocyanate-based cross-linking agent include tolylene diisocyanate compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate; 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and tetra. Xylylene diisocyanate compounds such as methyl xylylene diisocyanate; aromatic isocyanate compounds such as 1,5-naphthalenedi isocyanate and triphenylmethane triisocyanate; hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, and these isocyanate-based compounds. Examples thereof include an adduct form with a polyol compound such as trimethylolpropane, a buretto form and an isocyanurate form of these polyisocyanate compounds.

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

Examples of the melamine-based cross-linking agent include hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexabutoxymethyl melamine, hexapentyloxymethyl melamine, hexahexyl oxymethyl melamine, and melamine resin.

Examples of the aldehyde-based cross-linking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardaldehyde, formaldehyde, acetaldehyde, and benzaldehyde.

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

In the present invention, the content of the cross-linking agent (D) is preferably 0.01 to 15 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the acrylic resin (A). , Particularly preferably 0.5 to 5 parts by weight, still more preferably 1 to 3 parts by weight. If the content of the cross-linking agent (D) is too small, the adhesion to the substrate after curing tends to be poor and the adhesive strength tends to decrease, and if it is too large, the tack before curing tends to decrease and the room temperature transferability tends to decrease. There is.

<Arbitrary ingredient>
In the adhesive composition [I] of the present invention, in addition to the above components, as optional components, for example, a conductive agent such as carbon or metal; an inorganic filler such as metal particles or glass particles; a urethane resin or rosin. , Rossin ester, hydrogenated rosin ester, phenol resin, aliphatic petroleum resin, alicyclic petroleum resin, styrene resin and other tackifiers; fillers; antioxidants; UV absorbers; silane coupling agents; It can also contain various additives such as a cross-linking accelerator such as an ionic compound, a peroxide and an esterification catalyst; a cross-linking retarder such as acetylacetone; These may be used alone or in combination of two or more.

In addition to the above-mentioned optional components, the adhesive composition [I] of the present invention has the effect of the present invention such as impurities contained in the raw materials for producing the constituent components of the adhesive composition [I]. May be contained within a range that does not impair.

The adhesive composition [I] of the present invention includes an acrylic resin (A), an epoxy compound (B), a curing agent for an epoxy compound (C), a cross-linking agent for an acrylic resin (D), and the like. It can be obtained by mixing arbitrary components.
The method for mixing these components is not particularly limited, and various methods such as a method of mixing each component in a batch, a method of mixing an arbitrary component, and then a method of mixing the remaining components in a batch or sequentially. Can be adopted.
Thus, the adhesive composition [I] according to the present invention is obtained.

The adhesive composition [I] of the present invention has a function of being cured by heating at 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 storage stability tends to decrease, and if the temperature is too high, the adherends that can be used are limited, so that the versatility tends to be poor.

In the present invention, when the adhesive layer formed from the adhesive composition [I] is heated at 160 ° C. for 1 hour and cured, the loss tangent at 23 ° C. obtained by dynamic viscoelasticity measurement ( It is characterized in that tan δ) is 1.5 to 5.
The preferred range of such loss tangent (tan δ) is 1.55 to 4.8, more preferably 1.6 to 4.5, particularly preferably 1.7 to 4.2, still more preferably 1.8 to 4. , Particularly preferably 1.9 to 3. If the loss tangent (tan δ) is too small, the viscosity at 23 ° C. is insufficient and the adhesive strength is lowered, and if it is too large, the viscosity becomes too high and the cohesive force is lowered.

Here, the loss tangent (tan δ) at 23 ° C. obtained by dynamic viscoelasticity measurement means an index of the strength of the viscous tendency of the adhesive layer at that temperature, and the measuring method is as follows. It is as follows.

First, the adhesive layer formed to have a thickness of 100 μm or more is heated at 160 ° C. for 1 hour to be cured. Next, using a humidity control viscoelastic device, an adhesive jig: diameter 20 mm parallel plate, strain: 0.1%, frequency: 1 Hz, temperature rise rate: 3 ° C / min, measurement temperature: -100 to 150 ° C. Dynamic viscoelasticity measurement is performed under the conditions, and the measurement is performed by reading the numerical value of tan δ at 23 ° C. from the obtained viscoelasticity curve.

In the present invention, in order to adjust the loss tangent (tan δ) to the above range, for example, (1) a method of adjusting the glass transition temperature of the acrylic resin (A), and (2) the epoxy compound (B). Examples thereof include a method of adjusting by an epoxy equivalent, and (3) a method of adjusting by a combination of the above (1) and (2). Of these, the method (3) is preferable because it is easy to align the peak top temperatures of the loss tangents (tan δ) of the acrylic resin (A) and the epoxy compound (B), that is, it is easy to sharpen the peaks.

Further, the glass transition temperature of the cured product obtained by curing the adhesive layer formed from the adhesive composition [I] at 160 ° C. × 1 hour is preferably −20 to 100 ° C., more preferably. Is 0 to 75 ° C, particularly preferably 10 to 50 ° C, and even more preferably 15 to 35 ° C. If it deviates from such a range, the value of the loss tangent (tan δ) becomes low and the adhesive strength tends to decrease.
The glass transition temperature of the cured product can be measured using a dynamic viscoelastic device in the same manner as in the method for measuring the loss tangent, and the tanδ peak top temperature in the obtained viscoelastic curve is defined as the glass transition temperature.

[Adhesive sheet and laminate]
The adhesive composition [I] of the present invention can be made into an adhesive by cross-linking the acrylic resin (A). Further, by laminating and forming the adhesive layer containing the adhesive on a substrate such as a plastic film, it is possible to obtain an adhesive sheet having a laminated structure of the substrate / adhesive layer. can. Further, by laminating this adhesive layer on the adherend, it is possible to obtain a laminated body having a laminated structure of the adherend / adhesive layer. In the following, the base material and the adherend are collectively referred to as "members".

The adhesive sheet includes a substrate-less double-sided adhesive in which a separator (release sheet) is laminated on both sides of the adhesive layer in addition to the adhesive sheet in which the adhesive layer is laminated on the substrate. There is an adhesive sheet, and a double-sided adhesive sheet is preferable in terms of ease of handling.

As a method for producing the adhesive sheet, for example, the adhesive composition [I] is applied onto a substrate, dried, a separator is attached, and the adhesive is kept at room temperature (without heating). A method of performing an aging treatment by at least one of aging and aging in a heated state can be mentioned. The adhesive composition [I] is applied to the separator, dried, and then the separator and another separator having a different peeling power are bonded to each other and subjected to an aging treatment to obtain both sides without a base material. Adhesive sheets can be manufactured.

The aging treatment is a treatment performed in order to chemically crosslink the acrylic resin (A) and the cross-linking agent (D) to develop an appropriate adhesiveness to the adhesive adhesive. As the aging conditions, for example, the temperature is usually room temperature (20 ± 10 ° C.) to 40 ° C., and the time is usually 1 to 30 days. Specifically, for example, 23 ° C. for 1 to 20 days, 40. Conditions such as 1 to 7 days at ° C can be mentioned.

When applying the adhesive composition [I], it is preferable to dilute the adhesive composition [I] with a solvent and apply the adhesive composition [I], and the solid content concentration is preferably 5 to 65 weight by weight. %, More preferably 20 to 60% by weight, and particularly preferably 30 to 55% by weight.

The solvent is not particularly limited as long as it dissolves the adhesive composition. For example, ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, 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. Etc. Alcohol-based solvent; etc. can be used. Among these, ethyl acetate is preferably used in terms of solubility, dryness, price and the like.

The viscosity of the diluted adhesive composition [I] is preferably 500 to 15000 mPa · s / 25 ° C, more preferably 1000 to 10000 mPa · s / 25 ° C. If the viscosity is too low, when a component having a heavy specific gravity is used, the component tends to settle easily, and the concentration of the component in the adhesive composition [I] tends to be non-uniform.

Examples of the coating method of the adhesive composition [I] include roll coating, die coating, gravure coating, comma coating, screen printing and the like.

The thickness of the adhesive layer in the adhesive sheet is preferably 5 to 250 μm, more preferably 25 to 200 μm, and even more preferably 50 to 175 μm. If the adhesive layer is too thin, the thickness accuracy tends to decrease or the adhesive strength tends to be low. If the adhesive layer is too thick, the adhesive sheet is rolled. The adhesive layer tends to stick out from the edges.

The gel fraction of the adhesive layer is preferably 1 to 99% by weight, more preferably 5 to 95% by weight, still more preferably, from the viewpoint of adhesion to the substrate and the adherend and adhesiveness before curing. Is 10 to 90% by weight. If the gel content of the adhesive layer is too low, the adhesion to the substrate after curing tends to be poor and the adhesive strength tends to decrease, and if it is too high, the adhesive sheet is attached to the adherend. Sufficient adhesion between the adhesive layer and the interface of the member cannot be obtained, and the adhesive strength after curing tends to decrease.

The gel fraction is a measure of the degree of cross-linking (curing degree), and is calculated by, for example, the following method. First, the adhesive is collected by picking from the adhesive sheet in which the adhesive layer is laminated on the surface of the base material, and the adhesive is wrapped in a 200 mesh SUS wire mesh and heated to 23 ° C. Immerse in prepared ethyl acetate for 24 hours. The weights of the adhesive layer before and after the immersion in ethyl acetate are measured, and the difference between the two weights is taken as the weight of the insoluble adhesive component remaining in the wire mesh. The weight percentage of the insoluble adhesive component remaining in the wire mesh with respect to the weight of the adhesive layer before the immersion in ethyl acetate is defined as the gel fraction.

In the present invention, since the adhesive composition [I] has a function of being cured by heating at a predetermined temperature, the adhesive force of the adhesive layer in the adhesive sheet is increased, and the adhesive sheet is increased. Sticks to the adherend.
The heating temperature for curing the adhesive is preferably 100 to 250 ° C, more preferably 120 to 200 ° C, and even more preferably 130 to 185 ° C. If the temperature is too low, the curing time tends to be long and the workability tends to decrease, and 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, and even more preferably 45 to 90 minutes. If the time is too short, the curing tends to be insufficient and the adhesive strength tends to decrease, and if it is too long, the workability tends to decrease.

The adhesive sheet having the adhesive layer laminated on the surface of the separator can be easily adhered by simply peeling off the separator and adhering the adhesive layer to the target adherend surface. Since the adhesive layer can be transferred, the work efficiency is very good.

Further, a laminated body in which other members are laminated via the above-mentioned adhesive layer, that is, a laminated body having a laminated structure of an adherend / adhesive layer / other members, is adhesively bonded. Since the agent layer has high adhesiveness before curing and exhibits high adhesive strength after curing, it is difficult for other members to easily shift or peel off from the adherend. Therefore, by using the adhesive composition [I] of the present invention, a laminate having high adhesive reliability and excellent appearance can be obtained.

The adhesive adhesive composition [I] of the present invention has adhesiveness under normal conditions, and the adhesive adhesive layer made of this adhesive adhesive composition [I] has excellent room temperature transferability before curing. Further, when this adhesive layer is attached to the adherend and then cured by heating or the like, it adheres firmly and has excellent adhesiveness to the adherend. Therefore, the adhesive composition [I] of the present invention is used for various adhesive applications such as building materials, in-vehicle parts, electronic parts, semiconductor manufacturing processes, member encapsulation, and aviation parts. It can be suitably used for various adhesive bonding applications such as those for sports equipment.
In the present invention, it is particularly useful for applications of flexible printed wiring boards (FPCs), for example, for bonding FPCs and reinforcing plates, and for bonding FPCs and reinforcing plates, sticking to an adherend. It is not necessary to use heat sticking (heat laminating) for sticking, and it is possible to stick to the adherend at room temperature, and even after curing, not only adhesiveness but also heat resistance and moisture heat resistance are good. , It is highly expected in the future.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. In the example, "part" and "%" mean the weight standard.
In addition, the weight average molecular weight, dispersity, glass transition temperature, and other physical properties of the acrylic resin in the following examples were measured according to the above-mentioned methods.
First, the following ingredients were prepared prior to the examples.

<Acrylic resin (A)>
[Preparation of acrylic resin (A-1)]
80 parts of ethyl acetate, 6 parts of methyl ethyl ketone, and 0 azobisisobutyronitrile (AIBN) as a polymerization initiator in a 4-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer. .036 parts charged and heated to reach the boiling point, then 40 parts of methyl acrylate (MA), 10 parts of methyl methacrylate (MMA), 45 parts of n-butyl methacrylate, 5 parts of 2-hydroxyethyl acrylate (2HEA). , 4 parts of ethyl acetate and 0.036 part of the polymerization initiator (AIBN) were added dropwise over 2 hours while maintaining the boiling state. Then, while continuing the reaction, 0.05 part of the polymerization initiator (AIBN) was added twice, the reaction was carried out for 7 hours, and then the mixture was diluted to obtain an acrylic resin (A-1) solution (solid content concentration 45. 1%, viscosity 12,400 mPa · s / 25 ° C., acrylic resin (A-1): weight average molecular weight (Mw) 288,000, dispersibility (Mw / Mn) 2.2, glass transition temperature (Tg) 19.7 ° C.) was obtained.

[Preparation of acrylic resin (A-2)]
80 parts of ethyl acetate, 6 parts of methyl ethyl ketone, and 0 azobisisobutyronitrile (AIBN) as a polymerization initiator in a 4-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer. .036 parts charged and heated to reach the boiling point, then 40 parts of methyl acrylate (MA), 20 parts of methyl methacrylate (MMA), 35 parts of n-butyl methacrylate, 5 parts of 2-hydroxyethyl acrylate (2HEA). , 4 parts of ethyl acetate and 0.036 part of the polymerization initiator (AIBN) were added dropwise over 2 hours while maintaining the boiling state. Then, while continuing the reaction, 0.05 part of the polymerization initiator (AIBN) was added twice, the reaction was carried out for 7 hours, and then the mixture was diluted to obtain an acrylic resin (A-2) solution (solid content concentration 43. 6%, viscosity 10,800 mPa · s / 25 ° C., acrylic resin (A-2): weight average molecular weight (Mw) 267,000, dispersibility (Mw / Mn) 1.98, glass transition temperature (Tg) 26.3 ° C.) was obtained.

<Epoxy compound (B)>
The following epoxy compounds (B) were prepared.
(B-1): jER® YX7400 (manufactured by Mitsubishi Chemical Corporation) Viscosity 200 mPa · s at 25 ° C., epoxy equivalent 440 g / eq, number of functional groups 2
(B-2): jER® YX7105 (manufactured by Mitsubishi Chemical Corporation) Viscosity at 25 ° C. 53,000 mPa · s, epoxy equivalent 480 g / eq, number of functional groups 2
(B-3): Denacol EX-321 (manufactured by Nagase ChemteX Corporation), viscosity at 25 ° C., 140 mPa · s, epoxy equivalent 140 g / eq, number of functional groups 2-3
(B-4): jER 828 (manufactured by Mitsubishi Chemical Corporation) Viscosity at 25 ° C. 13,500 mPa · s, epoxy equivalent 189 g / eq, number of functional groups 2
(B-5): jER 1032H80 (manufactured by Mitsubishi Chemical Corporation) solid at 25 ° C., epoxy equivalent 160 g / eq, number of functional groups 3

<Curing agent for epoxy compounds (C)>
The following were prepared as the curing agent (C) for the epoxy compound.
(C-1): Adipic acid dihydrazide (ADH-S: manufactured by Otsuka Chemical Co., Ltd.)

<Crosslinking agent (D)>
The following were prepared as the cross-linking agent (D).
(D-1): Coronate L55E (manufactured by Tosoh Corporation: trimethylolpropane and tolylene diisocyanate adduct)

<Examples 1 to 3 and Comparative Examples 1 to 5>
The above components were blended according to Table 1 below, and the solid content concentration was adjusted to the range of 30 to 60% using ethyl acetate to obtain a viscous adhesive composition.

Using the obtained adhesive composition, an adhesive sheet having an adhesive layer was prepared according to the procedure shown below. Then, using this adhesive sheet, as shown below, the gel fraction of the adhesive sheet before curing, room temperature transferability, loss tangent after curing (tanδ), glass transition temperature (Tg) of the cured product, The adhesive strength after curing and after the heat resistance test was evaluated.
The evaluation methods and evaluation criteria for each item are as follows. In addition, these results are also shown in Table 1 below.

<Making an adhesive sheet>
The adhesive composition is applied to a heavy-release silicon separator (manufactured by Mitsui Chemicals Tohcello Co., Ltd., "SPPET03 38BU") having a thickness of 38 μm using a comma coater so that the thickness after drying is 50 μm, and the temperature is 100 ° C. It was dried for 3 minutes to form a viscous adhesive layer. A lightly peelable silicon separator (manufactured by Mitsui Chemicals Tohcello Co., Ltd., "SPPET01 38BU") having a thickness of 38 μm was attached to the surface of the adhesive layer, and then aged at 40 ° C. for 3 days to prepare an adhesive sheet (adhesive sheet). Light peeling silicon separator / adhesive layer / heavy peeling silicon separator laminate).

[Gel fraction]
The adhesive layer was collected from the obtained adhesive sheet by picking, the adhesive was wrapped in a 200 mesh SUS wire mesh, and immersed in ethyl acetate adjusted to 23 ° C. for 24 hours to obtain acetate. The weight percentage of the insoluble adhesive component remaining in the wire mesh with respect to the weight of the adhesive layer before the ethyl immersion was defined as the gel fraction.

[Appearance of coating film]
The appearance of the obtained adhesive sheet was visually confirmed and evaluated as follows.
○ ・ ・ ・ No bubbles or unevenness △ ・ ・ ・ There are a few bubbles × ・ ・ ・ There are many bubbles and unevenness

[Room temperature transferability]
The light peeling silicon separator of the adhesive sheet produced above is peeled off, and the adhesive layer side is bonded to a polyimide film (Kapton 200H: manufactured by Toray DuPont) at room temperature, and the adhesive sheet with a film substrate is attached. Got It was visually confirmed whether or not the adhesive layer was transferred to the polyimide film when the heavy-release silicon separator was peeled off from the obtained adhesive sheet with a film substrate, and evaluated according to the following criteria.
○ ・ ・ ・ Transferred × ・ ・ ・ Not transferred

[Loss tangent (tanδ)]
The lightly peeled silicone separator was peeled off from the prepared adhesive sheet, laminated so that the adhesive layer had a thickness of 150 to 200 μm, and further heat-cured at 160 ° C. for 1 hour to obtain a test piece. After that, the test piece cut into 5 mm × 30 mm was subjected to a humidity control viscoelastic device (DVA-225) at a frequency of 1 Hz and a measurement temperature of -100 to 150 ° C. under the condition of 3 ° C./min temperature rise at 23 ° C. The value of the loss tangent (tan δ) was measured.

[Glass transition temperature (Tg) of cured product]
The tanδ peak top temperature in the viscoelastic curve obtained in the measurement of the loss tangent (tanδ) was defined as the glass transition temperature.

[Adhesive strength after curing]
The light peeling silicon separator of the adhesive sheet produced above is peeled off, and the adhesive layer side is bonded to a polyimide film (Kapton 200H: manufactured by Toray DuPont) at room temperature, and the adhesive sheet with a film substrate is attached. Got After cutting out the obtained adhesive sheet with a film substrate to a width of 25 mm, the heavy-release silicon separator is peeled off, and the adhesive layer side is attached to a SUS-BA plate by reciprocating a 1 kg roller twice at room temperature. After being attached, it was heat-cured at 160 ° C. for 1 hour. After that, after adjusting the temperature in a 23 ° C. × 50% RH environment, the adhesive strength of 180 ° peeling at a speed of 300 mm / min using AUTO Graph AG-X Plus (manufactured by Shimadzu Corporation) (unit: N / cm). Was measured and evaluated according to the following criteria.
◎ ・ ・ ・ Higher than 15N / cm ○ ・ ・ ・ 10 ～ 15N / cm
× ・ ・ ・ Less than 10 N / cm

[Adhesive strength after heat resistance test]
The light peeling silicon separator of the adhesive sheet produced above is peeled off, and the adhesive layer side is bonded to a polyimide film (Kapton 200H: manufactured by Toray DuPont) at room temperature, and the adhesive sheet with a film substrate is attached. Got After cutting out the obtained adhesive sheet with a film substrate to a width of 25 mm, the heavy-release silicon separator is peeled off, and the adhesive layer side is attached to a SUS-BA plate by reciprocating a 1 kg roller twice at room temperature. After being attached, it was heat-cured at 160 ° C. for 1 hour. After further standing at 150 ° C. for 250 hours and then adjusting the temperature in a 23 ° C. × 50% RH environment, 180 ° peeling was performed at a speed of 300 mm / min using AUTO Graph AG-X Plus (manufactured by Shimadzu Corporation). Adhesive strength (unit: N / cm) was measured and evaluated according to the following criteria.
◎ ・ ・ ・ Higher than 15N / cm ○ ・ ・ ・ 10 ～ 15N / cm
× ・ ・ ・ Less than 10 N / cm

From the above results, in the examples in which the predetermined loss tangent (tan δ) at the time of curing was in a specific range, the coating film appearance and room temperature transferability were excellent, and the adhesiveness and heat resistance after curing were excellent. .. On the other hand, in the comparative examples that did not satisfy the loss tangent (tan δ), some of them were inferior in adhesiveness and heat resistance, and some were inferior in the appearance of the coating film and the transferability at room temperature.

According to the adhesive composition [I] of the present invention, the adhesive property at room temperature and the appearance of the coating film are excellent before curing, the adhesiveness to the adherend is excellent after curing, and the heat resistance is also improved. An excellent adhesive layer can be formed. Therefore, the adhesive layer formed from the adhesive composition [I] of the present invention is used for various adhesive applications such as building materials, in-vehicle parts, electronic parts, and semiconductor manufacturing processes. It can be suitably used for various adhesive bonding applications such as member sealing, aviation parts, and sports equipment, and is particularly useful for bonding an FPC and a reinforcing plate.

Claims (10)

An adhesive composition containing an acrylic resin (A), an epoxy compound (B), a curing agent (C) that reacts with an epoxy compound (B), and a cross-linking agent (D).
When the adhesive layer formed from the adhesive composition was heated at 160 ° C. for 1 hour and cured, the loss tangent (tan δ) at 23 ° C. obtained by dynamic viscoelasticity measurement was 1.5. A viscoelastic adhesive composition characterized by being ~ 5. The adhesive composition according to claim 1, wherein the acrylic resin (A) has a weight average molecular weight of 100,000 or more. The epoxy compound (B) according to claim 1 or 2, wherein the epoxy compound (B) contains an epoxy compound (b1) having a viscosity at 25 ° C. of 2000 mPa · s or less and an epoxy equivalent of 300 g / eq or more. Epoxy composition. The viscosity according to any one of claims 1 to 3, wherein the content of the epoxy compound (B) is 1 to 150 parts by weight with respect to 100 parts by weight of the acrylic resin (A). Adhesive composition. The adhesive composition according to any one of claims 1 to 4, wherein the curing agent (C) is an amine compound. The adhesive according to any one of claims 1 to 5, wherein the content of the curing agent (C) is 1 to 100 parts by weight with respect to 100 parts by weight of the epoxy compound (B). Epoxy composition. The invention according to any one of claims 1 to 6, wherein the content of the cross-linking agent (D) is 0.01 to 15 parts by weight with respect to 100 parts by weight of the acrylic resin (A). Adhesive composition. The adhesive composition according to any one of claims 1 to 7, which has a function of being cured by heating at 100 to 250 ° C. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 8. A laminated body, wherein the adhesive layer formed from the adhesive composition according to any one of claims 1 to 8 is laminated on an adherend.