JP2022121248A - Adhesive composition, laminate film, and printed wiring board - Google Patents

Abstract

To provide an adhesive composition that has low dielectric constants and high storage stability, a laminate film having a cured layer of the adhesive composition, and a printed wiring board including the laminate film.SOLUTION: An adhesive composition contains a modified thermoplastic elastomer and a curing agent and has a dielectric constant of 2.0-3.0. Relative to 100 pts.wt. of the modified thermoplastic elastomer, it contains an oxetane resin of 5 pts.wt. or more and less than 200 pts.wt.SELECTED DRAWING: None

Description

The present invention relates to adhesive compositions, laminated films, and printed wiring boards.

2. Description of the Related Art In recent years, electronic devices such as portable personal computers and mobile phones are becoming more sophisticated, smaller, and more multifunctional. Along with this, there is a strong demand for higher density, smaller size, and thinner thickness for electronic components that constitute electronic devices.

Furthermore, with the progress of information technology (IT) or information communication technology (ICT), it is required to process large amounts of information at high speed. Along with this, transmission signals are becoming higher in frequency, and materials constituting printed wiring boards are required to have a low dielectric constant (ε) and a low dielectric loss tangent (tan δ).

Patent Document 1 describes an adhesive composition containing a modified polyolefin resin, an epoxy resin, and a curing accelerator as low dielectric constant materials.

Japanese Patent No. 6718148

Adhesive compositions used in the manufacture of electronic devices are desired to facilitate handling in the manufacturing process of electronic devices. Therefore, for example, a laminated film having an adhesive layer formed by coating an adhesive composition in the form of a film is required to have excellent storage stability and a long shelf life. .

However, adhesive compositions containing epoxy resins tend to have a fast curing rate but a short shelf life. Although the adhesive composition described in Patent Document 1 has been improved in storage stability, it is insufficient, and further improvement is required.

The present invention provides an adhesive composition having a low dielectric constant and excellent storage stability, a laminated film having a cured layer obtained by curing the adhesive composition, and a printed wiring board provided with the laminated film. With the goal.

The present inventors have found that the use of an oxetane resin in a low dielectric constant adhesive composition containing a modified thermoplastic elastomer and a curing agent improves the storage stability of the adhesive composition. He found this and completed the present invention.

A first aspect of the present invention is an adhesive composition containing a modified thermoplastic elastomer and a curing agent and having a dielectric constant of 2.0 to 3.0, comprising 100 parts by weight of the modified thermoplastic elastomer The adhesive composition is characterized by containing 5 parts by weight or more and less than 200 parts by weight of an oxetane resin.

A second aspect is the adhesive composition of the first aspect, wherein the modified thermoplastic elastomer has at least one functional group selected from carboxyl groups and acid anhydride groups.

A third aspect is characterized in that the adhesive composition of the first or second aspect contains 5 to 100 parts by weight of an oxetane resin with respect to 100 parts by weight of the modified thermoplastic elastomer.

A fourth aspect is the adhesive composition of any one of the first to third aspects, wherein the modified thermoplastic elastomer is at least one selected from modified styrene thermoplastic elastomers and modified polyolefin resins. characterized by

A fifth aspect is the adhesive composition of any one of the first to fourth aspects, wherein the modified thermoplastic elastomer is modified styrene-ethylene-butylene-styrene, modified styrene-ethylene-propylene-styrene, or modified polypropylene. , or modified styrene-isoprene-styrene.

A sixth aspect is characterized in that in the adhesive composition of any one of the first to fifth aspects, the oxetane resin is at least one compound represented by the following structural formula (1).

In the structural formula (1) above, A is 1,4-phenylene or 4,4'-biphenylylene, and n is an integer of 1-3.

A seventh aspect is a laminated film comprising, on at least one surface of a substrate film, a cured layer obtained by curing the adhesive composition according to any one of the first to sixth aspects.

An eighth aspect is a printed wiring board comprising the laminated film of the seventh aspect.

The adhesive composition of the present invention has a low dielectric constant and excellent storage stability. Therefore, it is suitable as a laminated film having a cured layer in which the adhesive is cured, and as an adhesive for a printed wiring board provided with the laminated film.

The present invention will be described below based on preferred embodiments.

The adhesive composition of the embodiment contains a modified thermoplastic elastomer and a curing agent, and has a dielectric constant of 2.0 to 3.0. The adhesive composition of the embodiment contains 5 parts by weight or more and less than 200 parts by weight of the oxetane resin with respect to 100 parts by weight of the modified thermoplastic elastomer.

<Modified thermoplastic elastomer>
The adhesive composition of embodiments contains a modified thermoplastic elastomer. Modified thermoplastic elastomers are elastic polymers (elastomers) having thermoplasticity, and are materials in which the polymers are modified with specific functional groups. The thermoplastic elastomer mainly contributes to low dielectric properties, heat resistance, improved adhesiveness of the adhesive composition, and improved flexibility when the adhesive composition is formed into a film.

In order to impart elasticity as an elastomer to a thermoplastic resin, for example, a soft segment and a hard segment may be provided in the molecular structure. Alternatively, a physical cross-linked structure may be provided that cross-links the molecular structure at room temperature (eg, 5 to 35° C.) and reduces cross-linkability and increases fluidity at higher temperatures. Alternatively, it may be a polymer blend in which a rubber component is dispersed in a resin component.

In order to contribute to low dielectric properties of the adhesive composition, it is preferably a modified thermoplastic elastomer obtained by modifying a low polar thermoplastic elastomer. The modified thermoplastic elastomer is preferably at least one selected from modified styrenic thermoplastic elastomers and modified polyolefin resins.

A modified styrenic thermoplastic elastomer is a material obtained by modifying a styrenic thermoplastic elastomer with a specific functional group. Styrenic thermoplastic elastomers include copolymers having polyolefin blocks and polystyrene blocks. At least one selected from ethylene, propylene, butene, isobutene, butadiene, isoprene and the like can be used as the olefin used as the monomer of the polyolefin block. Units derived from dienes such as butadiene and isoprene may be converted into units such as ethylene, propylene and butylene (butene) by hydrogenation (hydrogenation).

Specific examples of the modified styrene thermoplastic elastomer include at least one selected from modified styrene-ethylene-butylene-styrene, modified styrene-ethylene-propylene-styrene, modified styrene-butylene-styrene, and modified styrene-isoprene-styrene. is mentioned. The weight ratio of styrene units in the modified styrenic thermoplastic elastomer is preferably 10 to 40% by weight, more preferably 10 to 30% by weight, and 10 to 25% by weight, relative to the total weight of the modified styrenic thermoplastic elastomer. More preferred.

A modified polyolefin resin is a material obtained by modifying a polyolefin resin to be a thermoplastic elastomer with a specific functional group. The polyolefin resin may be an olefinic thermoplastic elastomer. At least one selected from ethylene, propylene, butene, isobutene, butadiene, isoprene and the like can be used as the olefin used as the monomer of the modified polyolefin resin. The polyolefin resin may be a homopolymer containing one olefin or a copolymer containing two or more olefins.

Specific examples of modified polyolefin resins include modified polypropylene and modified polyethylene. The modified polypropylene may be a propylene homopolymer or a copolymer of propylene and ethylene, butene, isobutene, butadiene, isoprene, or the like. The weight ratio of propylene units in the modified polypropylene is preferably 50 to 98% by weight with respect to the total weight of the modified polypropylene.

The modified thermoplastic elastomer is preferably at least one selected from modified styrene-ethylene-butylene-styrene, modified styrene-ethylene-propylene-styrene, modified polypropylene, and modified styrene-isoprene-styrene.

Functional groups used for modification of the modified thermoplastic elastomer include carboxyl groups, acid anhydride groups, amino groups, hydroxyl groups (hydroxyl groups), and the like. From the viewpoint of lowering the dielectric constant of the adhesive composition, the functional group used for modifying the modified thermoplastic elastomer is preferably a carboxyl group or an acid anhydride group. When the modified thermoplastic elastomer has at least one functional group selected from a carboxyl group or an acid anhydride group, the carboxyl group or the acid anhydride group reacts with the oxetane ring of the oxetane resin to form an adhesive composition. It can improve the adhesiveness and heat resistance of objects.

Modifying monomers used to modify thermoplastic elastomers with carboxyl groups or acid anhydride groups include α,β-unsaturated carboxylic acids or acid anhydrides thereof. Specific examples of α,β-unsaturated carboxylic acids include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, tetrahydrophthalic acid, norbornene Unsaturated dicarboxylic acids such as dicarboxylic acids; aconitic acid; Specific examples of α,β-unsaturated carboxylic acid anhydrides include maleic anhydride, citraconic anhydride, itaconic anhydride, tetrahydrophthalic anhydride, norbornene dicarboxylic anhydride, and aconitic anhydride.

The modifying monomer may be copolymerized on the main chain of the thermoplastic elastomer or may be grafted on the side chains of the thermoplastic elastomer. In grafting, for example, an unmodified thermoplastic elastomer and a modified monomer may be reacted in the presence of a radical initiator. Radical initiators include aromatic peroxides such as benzoyl peroxide and dicumyl peroxide; aliphatic peroxides such as dilauroyl peroxide and di-t-butyl peroxide; and hydroperoxides such as cumene hydroperoxide.

The weight ratio of the modified monomer units in the modified thermoplastic elastomer is preferably 0.1 to 20% by weight with respect to the total weight of the modified thermoplastic elastomer. The weight average molecular weight (Mw) of the modified thermoplastic elastomer is not particularly limited, but is, for example, 10,000 to 500,000, more preferably 30,000 to 250,000.

<Oxetane resin>
The adhesive composition of the embodiment contains an oxetane resin. An oxetane resin is a compound having an oxetane ring, which is a four-membered ring having an ether bond. The oxetane ring is cationic polymerizable and exhibits curability similar to the oxirane ring, which is a three-membered ring having an ether bond contained in epoxy resins. By containing an oxetane resin in the adhesive composition of the embodiment, the adhesiveness and heat resistance of the adhesive composition can be improved.

The oxetane resin may be a monofunctional oxetane resin having one oxetane ring per molecule, or a polyfunctional oxetane resin having two or more oxetane rings per molecule. A bifunctional oxetane resin having two oxetane rings in one molecule is preferred because it polymerizes linearly and hardly inhibits the flexibility of the modified thermoplastic elastomer.

The oxetane resin may be an aromatic oxetane resin having an aromatic ring such as a benzene ring or a naphthalene ring, or may be an aliphatic oxetane resin having no aromatic ring. An aromatic oxetane resin has a rigid molecular skeleton derived from an aromatic ring, and has higher thermal stability than an aliphatic chain. Therefore, by including an aromatic oxetane resin in the adhesive composition of the embodiment, the heat resistance of the adhesive composition can be further improved.

The oxetane resin may be a compound having a functional group such as a hydroxyl group (hydroxyl group), a carbonyl group, an ester group, or a compound in which the oxygen atoms in the molecule form only ether bonds. From the viewpoint of low dielectric properties of the adhesive composition, an oxetane resin that does not contain a highly polar functional group such as a hydroxyl group is preferred. The oxetane resin may contain ether bonds other than the oxetane ring.

The ether bond includes an acyclic ether bond, a 5-membered cyclic ether bond (tetrahydrofuran ring), and a 6-membered cyclic ether bond (tetrahydropyran ring). The oxetane resin preferably does not have a three-membered cyclic ether bond (epoxy group or oxirane ring) and vinyl ether group as a curable functional group different from the oxetane ring.

The oxetane resin preferably contains at least one compound represented by the following structural formula (1).

In the above structural formula (1), A is a divalent organic group, more preferably a divalent hydrocarbon group or a divalent polyether group, still more preferably a divalent aromatic hydrocarbon group is. The divalent aromatic hydrocarbon group includes a phenylene group, a biphenylylene group, a naphthylene group, an anthrylene group, a phenanthrylene group and the like. A divalent aromatic hydrocarbon group may have one or more substituents such as an alkyl group and a phenyl group.

When A is 1,4-phenylene, the compound represented by the above structural formula (1) is represented by the following structural formula (2).

When A is 4,4'-biphenylylene, the compound represented by the above structural formula (1) is represented by the following structural formula (3).

When A is 1,4-phenylene or 4,4'-biphenylylene, the group represented by A has a linear structure, and two groups shown on the left and right of the above structural formula (2) or (3) It is preferable because it serves as an appropriate spacer for the oxirane ring.

In the structural formulas (1) to (3) above, n is an integer of 1 or more, preferably an integer of 1 to 3. The compounds represented by the above structural formulas (1) to (3) can contain at least one of a compound where n = 1, a compound where n = 2, or a compound where n = 3, where n is It may contain two or more different compounds.

The adhesive composition of the embodiment preferably contains 5 parts by weight or more and less than 200 parts by weight of the oxetane resin with respect to 100 parts by weight of the modified thermoplastic elastomer. Thereby, both heat resistance and storage stability of the adhesive composition can be achieved. If the proportion of the oxetane resin is less than 5 parts by weight, the heat resistance is lowered, which is not preferable. If the proportion of the oxetane resin is 200 parts by weight or more, the adhesion or storage stability is lowered, which is not preferable.

More preferably, the adhesive composition contains 5 to 100 parts by weight of the oxetane resin, more preferably 10 to 100 parts by weight of the oxetane resin, based on 100 parts by weight of the modified thermoplastic elastomer. It is particularly preferred to contain 50 to 100 parts by weight.

<Curing agent>
The adhesive composition of the embodiment contains a curing agent. The curing agent may be any substance that accelerates or participates in curing of the modified thermoplastic elastomer, curing of the oxetane resin, or curing by reaction between the modified thermoplastic elastomer and the oxetane resin.

Curing agents for curing modified thermoplastic elastomers include, for example, polyisocyanates such as diisocyanates and triisocyanates. Curing agents for curing oxetane resins include dicarboxylic acids, acid anhydrides, bisphenol compounds and the like. Curing catalysts for oxetane resins include aliphatic sulfonium salts such as trialkylsulfonium salts, aromatic sulfonium salts such as triarylsulfonium salts, and aromatic iodonium salts such as diaryliodonium salts.

The content of the curing agent in the adhesive composition is not particularly limited, but may be, for example, 0.01 to 10 parts by weight of the curing agent per 100 parts by weight of the modified thermoplastic elastomer.

<Adhesive composition>
The adhesive composition of the embodiment contains a modified thermoplastic elastomer, an oxetane resin, and a curing agent as essential components. Optional components of the adhesive composition include fillers, flame retardants, reaction accelerators, cross-linking agents, polymerization inhibitors, coupling agents, thermosetting resins, thermoplastic resins, dyes, pigments, thickeners, lubricants, Antifoaming agents, ultraviolet absorbers, and the like are included.

The adhesive composition of the embodiment preferably has a low epoxy resin content, and more preferably contains no epoxy resin. The proportion of the epoxy resin in the adhesive composition is preferably less than 0.5 parts by weight, more preferably 0.2 parts by weight or less, and 0.05 parts by weight with respect to 100 parts by weight of the modified thermoplastic elastomer. It is more preferably 0.01 part by weight or less, and particularly preferably 0 part by weight.

The adhesive compositions of embodiments have low dielectric properties. The dielectric constant (ε) of the adhesive composition is preferably 2.0 to 3.0, more preferably 2.0 to 2.5. Furthermore, the dielectric loss tangent (tan δ) of the adhesive composition is preferably 0.005 or less. The dielectric properties of the adhesive composition may be measured on the adhesive composition in a dry state or on a cured layer after curing the adhesive composition. The adhesive composition before curing may be in an uncured state such as A-stage or in a semi-cured state such as B-stage.

The adhesive composition of the embodiment may be formed into a film form by coating, drying, etc. from a liquid adhesive liquid in which each component is dissolved or dispersed in a solvent. The adhesive liquid may be a solution or a dispersion liquid, but preferably dissolves at least the modified thermoplastic elastomer and the oxetane resin.

The solvent for the adhesive liquid is not particularly limited, but hydrocarbon solvents such as benzene, toluene and xylene; glycol solvents such as ethylene glycol ethyl ether, propylene glycol dimethyl ether and ethylene glycol monomethyl ether acetate; Ether-based solvents; Ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclopentanone; Ester-based solvents such as ethyl acetate, butyl acetate, and γ-butyrolactone; N,N-dimethylformamide, N,N-dimethyl Amide solvents such as acetamide and N-methyl-2-pyrrolidone; sulfur-containing solvents such as dimethylsulfoxide; chlorine solvents such as dichloromethane, chloroform and 1,2-dichloroethane; .

Examples of the method for preparing the adhesive liquid include a method in which each component of the adhesive composition and a solvent are added to a container equipped with a stirring device and stirred. If you want to shorten the dissolution time, you may heat it. The solid content of the adhesive liquid is not particularly limited, but is, for example, 10 to 50% by weight, preferably 15 to 40% by weight.

In order to prepare an adhesive film in which an adhesive composition is formed from an adhesive liquid, a method of applying the adhesive liquid to a coating substrate and drying the solvent from the adhesive liquid on the coating substrate can be mentioned. . The coating substrate is not particularly limited as long as it is a material having a surface capable of receiving the applied adhesive liquid, but plastic film, metal foil, paper, woven fabric, non-woven fabric, or a laminate containing these is mentioned. The dried adhesive film may be laminated and integrated with the coating substrate. The coated surface of the coating substrate may be subjected to a release treatment to form the adhesive film releasable from the coating substrate.

The method of applying the adhesive liquid is not particularly limited, but air doctor coating, bar coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, Coating methods such as calender coating, dam coating, dip coating and die coating, and printing methods such as gravure printing, intaglio printing, screen printing and stencil printing can be used.

The drying method of the adhesive liquid is not particularly limited, but can be appropriately set according to the type of solvent, the thickness of the adhesive liquid, the area, and the like. The drying temperature is, for example, 60 to 150°C. The drying time is, for example, 1 to 60 minutes, more preferably 1 to 30 minutes, still more preferably 1 to 10 minutes. The shorter the drying time, the higher the productivity, which is preferable. The coating substrate may be a sheet having a flat surface or a roll that can be wound up.

When the adhesive liquid is applied to the roll-shaped coating substrate, the adhesive liquid is continuously applied on the flat part of the coating substrate while pulling out the coating substrate from the roll and conveying it in the length direction. You can apply it. The adhesive liquid applied to the coating substrate may be sequentially dried at a predetermined drying temperature for a predetermined drying time, and then wound into a roll again. A release treatment may be applied to the surface of the coating substrate opposite to the surface to which the adhesive liquid is applied. A release paper or a release film that has been subjected to a release treatment may be superimposed on the dried adhesive film to protect the adhesive film.

A laminate in which the adhesive composition of the embodiment is laminated on a release sheet can be used as a bonding sheet. The release sheet may be a release film mainly composed of a plastic film or a release paper mainly composed of paper. Although the thickness of the release sheet is not particularly limited, it is preferably a release film with a thickness of 10 to 100 μm or a release paper with a thickness of 50 to 200 μm.

The material of the release film is not particularly limited, but examples include polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyethylene terephthalate, polyethylene naphthalate, and the like. The material of the release paper is not particularly limited, but examples thereof include polyethylene-coated paper and polypropylene-coated paper. The release sheet may be subjected to release treatment using a release agent such as silicone. Although the thickness of the adhesive film used for the bonding sheet can be set arbitrarily, it is preferably 5 to 50 μm, more preferably 5 to 25 μm in dry state.

A release sheet may be laminated on at least one side of the adhesive film. By superimposing the adhesive film from which the release sheet has been removed on the adherend and curing the adhesive film, the adherend can be adhered. An adhesive film with a substrate may be produced by laminating a substrate such as copper foil on one side of the adhesive film. The base material and the adherend can be bonded by laying the adherend on the opposite side of the base material of the adhesive film with the base material and curing the adhesive film.

Among adhesive films with a substrate, those using a copper foil as a substrate can be used as an adhesive film with a copper foil (FRCC: Flexible Resin Coated Copper). The thickness of the copper foil is preferably 5-50 μm, more preferably 9-25 μm. Although the thickness of the adhesive film used for FRCC can be set arbitrarily, it is preferably 1 to 50 μm, more preferably 1 to 25 μm in dry state.

Among adhesive films with a substrate, those using an electrically insulating film as a substrate can be used as a coverlay film. It is preferable that the electrically insulating film have heat resistance capable of coping with heat curing of the adhesive film. The material of the electrically insulating film is not particularly limited, but polyimide, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyparabanic acid, polyether ether ketone, polyphenylene sulfide, liquid crystal polymer (LCP), syndiotactic polystyrene, polycarbonate. etc.

Although the thickness of the electrically insulating film can be set arbitrarily, it is, for example, 1 to 50 μm, preferably 3 to 38 μm, particularly preferably 5 to 25 μm. For the purpose of increasing the strength of adhesion with the adhesive composition, the surface of the electrically insulating film may be subjected to surface treatment such as chemical solution treatment, plasma treatment, corona discharge treatment, sandblast treatment, and the like. Although the thickness of the adhesive film used for the coverlay film can be set arbitrarily, it is preferably 5 to 50 μm, more preferably 5 to 38 μm, even more preferably 5 to 25 μm in a dry state.

Among adhesive films with a substrate, those using a copper clad laminate (CCL) as a substrate can be used as a copper clad laminate with an adhesive. For example, a copper foil may be laminated on one surface of the electrically insulating film, and an adhesive film may be laminated on the other surface of the electrically insulating film. If the copper-clad laminate has flexibility, it can be used to produce a flexible printed wiring board.

From the viewpoint of obtaining an adhesive composition having excellent storage stability and a long shelf life, the adhesive film of the embodiment preferably has a large resin flow after storage of the adhesive film at 40° C. for 7 days. When the resin flow is large, the shelf life is excellent, and the embedding of irregularities such as wiring is excellent. However, if the resin flow is too large, the adhesive may overflow from the edge of the substrate, etc., and the thickness of the adhesive required for adhesive strength and solder heat resistance may not be ensured. A suitable range of resin flow is preferably 0.15 to 1.0 mm, more preferably 0.2 to 0.7 mm.

<Laminated film>
By curing the adhesive composition of the embodiment on a substrate, a laminated film having a cured layer of the adhesive composition can be produced. A method for curing the adhesive composition is not particularly limited, but includes, for example, a method of heating to a temperature of 150 to 180°C. The heating time is, for example, 20 minutes to 5 hours, and may be 30 minutes to 2 hours. Heating methods include, for example, hot air circulation ovens, presses, and autoclaves.

The base material of the laminated film is not particularly limited, but includes plastic films, metal foils, papers, woven fabrics, non-woven fabrics, and laminates containing these. The plastic film may be the electrically insulating film described above. The metal foil may be the copper foil described above. The substrate of the laminated film may be a plastic film or a composite film mainly composed of plastic. A laminated film substrate may be used as the coating substrate described above. When laminating the cured layer on a substrate different from the coating substrate, for example, an adhesive film formed from the adhesive composition before curing is transferred from the coating substrate onto the substrate, and the adhesive film is formed on the substrate. It may be cured.

<Printed wiring board>
The printed wiring board of the embodiment can be produced by including the cured layer of the adhesive composition or the laminated film. The printed wiring board may be a printed circuit board in which circuits are connected by circuit parts such as printed parts and mounting parts. It may be a printed wiring board having wiring before circuit components are formed. The wiring may be formed by patterning the copper foil of the laminated film by etching or the like. Copper foil may be used to form parts or functions such as antennas integrally with the wiring.

The printed wiring board may be a rigid printed wiring board having a rigid insulating substrate. The printed wiring board may be a flexible printed wiring board having a flexible insulating substrate. The insulating substrate may be a flex-rigid printed wiring board having a rigid portion and a flexible portion. The flexible insulating substrate may be the electrically insulating film described above. An insulating substrate having a rigid portion and a flexible portion may be formed by laminating a rigid insulating material on a partial region of the electrically insulating film.

Since the adhesive composition of the embodiment has a low dielectric constant, it is suitable as a material for high frequency printed wiring boards. Since the adhesive composition of the embodiment has excellent storage stability, it can be used as an adhesive used for producing a laminated film having a cured layer in which the adhesive is cured, and a printed wiring board provided with the laminated film. preferred.

Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

EXAMPLES The present invention will be specifically described below with reference to examples.

(Preparation of adhesive solution)
Each component having the composition shown in Table 1 below was charged into a container, and all components were dissolved using a solvent. The resulting liquid was filtered through a nylon mesh (wire diameter: 30 μm, 255 mesh) to obtain an adhesive solution. During preparation of the adhesive solution, the temperature of the solution was controlled so as not to exceed 30°C.

"Modified polyolefin" shown in Table 1 is a thermoplastic elastomer composed of modified polypropylene (weight average molecular weight: 100,000) modified with carboxyl groups or acid anhydride groups.
"Modified TPS" shown in Table 1 is a styrenic thermoplastic elastomer (TPS) composed of modified styrene-ethylene-butylene-styrene (weight average molecular weight: 150,000) modified with a carboxyl group or an acid anhydride group.
"Oxetane resin a" shown in Table 1 is a compound (n=1 to 3) represented by the above structural formula (2).
“Oxetane resin b” shown in Table 1 is a compound (n=1 to 3) represented by the above structural formula (3).
The "epoxy resin" shown in Table 1 is a biphenyl aralkyl epoxy resin (epoxy value 280-300 g/eq).
The "curing agent" shown in Table 1 is a sulfonium salt catalyst curing agent.

(Preparation of adhesive film)
An applicator was used to apply the adhesive solution to a release-treated polyethylene terephthalate film (silicone treatment, thickness 38 μm) so that the thickness after drying was 25 μm. Then, it was dried in a ventilation oven set at 100° C. for 5 minutes to obtain an adhesive film having a thickness of 25 μm.

(Measurement of adhesive strength to LCP)
Using a roll laminator, the adhesive film was laminated on a 25 μm-thick LCP film (trade name: Vecstar (registered trademark) CT-Z, manufactured by Kuraray Co., Ltd.). Working conditions were a roll temperature of 120° C., a pressure of 30 N/cm, and a speed of 0.5 m/min. Next, the same LCP films as above were laminated to obtain a laminate in which two LCP films were bonded together via an adhesive film. The laminate was heat-pressed under the conditions of 160°C x 0.5 MPa x 2 minutes, then heat-cured in a ventilation oven at 180°C x 1 hour, and then cut into 10 mm x 100 mm pieces to measure adhesive strength to LCP. A sample for Using a universal tensile tester (manufactured by Orientec Co., Ltd.), the LCP film of the measurement sample was peeled off in the direction of 90° at a tensile speed of 50 mm/min to measure the adhesive strength.

(Measurement of adhesive strength to Cu)
An adhesive film was laminated on a copper foil (trade name: FQ-VLP, manufactured by Mitsui Mining & Smelting Co., Ltd.) with a thickness of 18 μm using a roll laminator. Working conditions were a roll temperature of 120° C., a pressure of 30 N/cm, and a speed of 0.5 m/min. Next, the same copper foils as above were laminated to obtain a laminate in which the shiny surfaces of the two copper foils were bonded together via an adhesive film. The laminate was heat-pressed under the conditions of 160°C x 0.5 MPa x 2 minutes, then heat-cured in a ventilation oven at 180°C x 1 hour, and then cut into 10 mm x 100 mm pieces to measure the adhesion strength to Cu. A sample for Using a universal tensile tester (manufactured by Orientec Co., Ltd.), the copper foil of the measurement sample was peeled off in the direction of 90° at a tensile speed of 50 mm/min to measure the adhesive strength.

(Measurement of solder heat resistance)
A sample for measurement of solder heat resistance temperature using LCP was prepared in the same manner as the sample for measurement of adhesive strength to LCP, except that the cut size of the sample for measurement was 25 mm × 25 mm. In addition, a sample for measurement of solder heat resistance temperature using Cu was produced in the same manner as the sample for measurement of adhesive strength to Cu, except that the cut size of the sample for measurement was 25 mm × 25 mm. Each sample for measurement was subjected to humidity conditioning treatment under conditions of 20° C.×65% RH×96 hours, and then floated in a solder bath at a predetermined temperature for 60 seconds. Both the measurement sample using LCP and the measurement sample using Cu were evaluated to have solder heat resistance at the relevant temperature when abnormalities such as swelling, tearing, and turning up did not occur during the 60-second float. . If any abnormality occurred in the measurement sample using LCP or Cu, it was evaluated as having no solder heat resistance at that temperature. The temperature of the solder bath was set at 220° C. or 260° C., and the highest temperature with solder heat resistance was measured.

(Measurement of dielectric properties)
Adhesive films with a thickness of 25 μm were successively laminated using a roll laminator to obtain an adhesive laminate with a thickness of 200 μm. With the release-treated polyethylene terephthalate film superimposed on both sides of the adhesive laminate, it was cured by heating in a ventilation oven at 180° C. for 1 hour, then cut into 2 mm×50 mm pieces and measured for dielectric properties. A sample for The release-treated polyethylene terephthalate film was removed immediately before the measurement, and the dielectric constant (ε) and dielectric loss tangent (tan δ) at 10 GHz were measured for the adhesive laminate by the cavity resonator perturbation method.

(Measurement of resin flow)
The laminate obtained by laminating the adhesive film on the release-treated polyethylene terephthalate film was stored in an environment of 40° C. for 7 days. After being stored at 40° C. for 7 days, the laminate was punched with a punch having a punch hole diameter of 6 mmφ, and a roll laminator was used to apply a 25 μm-thick LCP film (trade name: Vecstar (registered trademark) CT). -Z. manufactured by Kuraray Co., Ltd.). The operating conditions of the roll laminator were a roll temperature of 120° C., a pressure of 30 N/cm, and a speed of 0.5 m/min. Next, a copper foil (trade name: FQ-VLP, manufactured by Mitsui Mining & Smelting Co., Ltd.) having a thickness of 18 μm is laminated using a roll laminator on the side of the adhesive film from which the release-treated polyethylene terephthalate film has been peeled off. Then, a sample for measurement of resin flow was obtained, which consisted of a laminate in which an LCP film and a copper foil were bonded together via an adhesive film having punched holes. The center of the punched hole portion of the measurement sample was marked, a cross was drawn, and the diameter of the punched hole (diameter before hot pressing: d0) was measured with a microscope. After the measurement sample was heat-pressed under the conditions of 160° C.×0.5 MPa×2 minutes, the diameter of the punch hole of the measurement sample (diameter after hot-pressing: d1) was measured with a microscope. Half of the value obtained by subtracting the diameter (d1) after hot pressing from the diameter (d0) before hot pressing, {(d0−d1)/2} was defined as the resin flow (mm).

(Measurement result)
Table 1 shows the measurement results for each of the above items.

The adhesive films of Examples 1 to 7 have a resistance of 7 N/cm or more to both the LCP film suitably used as an electrical insulating film for printed wiring boards and the copper foil suitably used as a wiring material. It exhibited high adhesive strength of , had solder heat resistance of 260°C, and had low dielectric properties. Regarding the storage stability of the adhesive composition, the adhesive films of Examples 1 to 7 had a resin flow of 0.15 to 1.0 mm even after storage at 40°C for 7 days, which is an appropriate range. and has been shown to have a long shelf life.

The resin flow when punch holes are punched in the adhesive film, laminated with a base material or the like, and hot-pressed indicates the fluidity of the adhesive composition in the manufacturing process of printed wiring boards and the like. A large value of resin flow at the time of hot pressing indicates that it is excellent in embedding in irregularities such as wiring. However, if the resin flow is too large, the adhesive may overflow from the edge of the substrate, etc., and the thickness of the adhesive required for adhesive strength and solder heat resistance may not be ensured. From the viewpoint of workability in hot press, the resin flow is required to be within an appropriate range.

The resin flow value measured after the adhesive film is stored at 40°C for a long period of time indicates that even if the adhesive composition before curing is stored at room temperature (5 to 35°C), curing does not progress easily, and the storage life is sufficient. (shelf life). A thermosetting adhesive may undergo a gradual curing reaction even at a lower temperature than processing conditions such as hot press, resulting in a decrease in the resin flow value. Therefore, even after the adhesive composition is stored at 40° C. for a long period of time, it is shown that if the resin flow is within the appropriate range, the storage stability is excellent.

Regarding the adhesive film of Example 4, the resin flow after storage at 40°C for 14 days was measured. , the resin flow was in the appropriate range.

The adhesive film of Comparative Example 1 had low adhesive strength to the LCP film and the copper foil, and the resin flow was too large, resulting in low adhesiveness and workability. This is probably because the proportion of the oxetane resin was too high.
The adhesive film of Comparative Example 2 did not have solder heat resistance at 260° C. and had low heat resistance. This is probably because the ratio of the oxetane resin was too small.

It was found that the adhesive film of Comparative Example 3 had a short shelf life because the resin flow was small after storage at 40° C. for 7 days. When the resin flow was measured by changing the elapsed time of storage at 40 ° C. in the range of 0 days to 14 days, the adhesive film of Comparative Example 3 had an initial resin flow of about 0.43 mm and a resin flow of about 2 days after 2 days. The resin flow was about 0.08 mm after 4 days and about 0.04 mm after 14 days.

It was found that the adhesive film of Comparative Example 4 had a slightly short shelf life because the resin flow was slightly small after storage at 40° C. for 7 days. The adhesive film of Comparative Example 4 had an initial resin flow of about 0.54 mm and a resin flow of about 0.54 mm after 2 days. 0.38 mm, the resin flow after 4 days was about 0.24 mm, which was an appropriate range, but the resin flow after 7 days was about 0.13 mm (see Table 1), and the resin flow after 14 days was about 0.13 mm. 0.10 mm, which is lower than the appropriate range.

Claims (8)

An adhesive composition containing a modified thermoplastic elastomer and a curing agent and having a dielectric constant of 2.0 to 3.0,
An adhesive composition characterized by containing 5 parts by weight or more and less than 200 parts by weight of an oxetane resin with respect to 100 parts by weight of the modified thermoplastic elastomer. 2. The adhesive composition according to claim 1, wherein said modified thermoplastic elastomer has at least one functional group selected from carboxyl groups and acid anhydride groups. 3. The adhesive composition according to claim 1, wherein the adhesive composition contains 5 to 100 parts by weight of the oxetane resin per 100 parts by weight of the modified thermoplastic elastomer. The adhesive composition according to any one of claims 1 to 3, wherein the modified thermoplastic elastomer is at least one selected from modified styrenic thermoplastic elastomers and modified polyolefin resins. The modified thermoplastic elastomer is at least one selected from modified styrene-ethylene-butylene-styrene, modified styrene-ethylene-propylene-styrene, modified polypropylene, and modified styrene-isoprene-styrene. The adhesive composition according to any one of Items 1 to 4. The oxetane resin is at least one compound represented by the following structural formula (1),

6. In any one of claims 1 to 5, wherein A is 1,4-phenylene or 4,4'-biphenylylene, and n is an integer of 1 to 3 in the structural formula (1). The adhesive composition described. A laminated film comprising a cured layer obtained by curing the adhesive composition according to any one of claims 1 to 6 on at least one surface of a base film. A printed wiring board comprising the laminated film according to claim 7 .