WO2024143121A1

WO2024143121A1 - Adhesive composition, laminate with adhesive layer, flexible copper clad laminate, and flexible flat cable

Info

Publication number: WO2024143121A1
Application number: PCT/JP2023/045751
Authority: WO
Inventors: 健人大村; 晋次北; 真平川
Original assignee: 東亞合成株式会社
Priority date: 2022-12-27
Filing date: 2023-12-20
Publication date: 2024-07-04

Abstract

This adhesive composition comprises: a modified polyolefin resin (A) having a reactive functional group which reacts with an epoxy group; an epoxy resin (B); and a silica filler (C). The silanol group concentration of the silica filler (C) is 0.5 mmol/g or less. This laminate with an adhesive layer is provided with a base film on at least one surface of the adhesive layer, the adhesive layer being made of the adhesive composition. This flexible copper clad laminate or flexible flat cable is provided with a base film on one surface of the adhesive layer of the laminate with the adhesive layer, and is also provided with a copper foil or a copper wiring on the other surface of the adhesive layer.

Description

Adhesive composition, laminate with adhesive layer, flexible copper-clad laminate, and flexible flat cable

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Application No. 2022-209966, filed on December 27, 2022, the contents of which are incorporated herein by reference.

The present disclosure relates to an adhesive composition, a laminate with an adhesive layer, a flexible copper-clad laminate, and a flexible flat cable. More specifically, the present disclosure relates to an adhesive composition suitable for bonding electronic components and the like, particularly for the manufacture of products related to flexible printed wiring boards, a laminate with an adhesive layer using the same, and a flexible copper-clad laminate and a flexible flat cable using the same.

Flexible printed circuit boards (hereafter referred to as "FPCs") are capable of three-dimensional, high-density mounting even in limited spaces, and so their uses are expanding. In recent years, as electronic devices have become smaller and lighter, FPC-related products have become more diverse and demand is increasing.

　Products related to such FPCs include, for example, flexible copper-clad laminates made by bonding polyimide film and copper foil together, flexible printed wiring boards in which electronic circuits are formed on flexible copper-clad laminates, flexible printed wiring boards with reinforcement plates made by bonding flexible printed wiring boards and reinforcement plates together, multilayer boards made by stacking and bonding flexible copper-clad laminates or flexible printed wiring boards, and flexible flat cables (hereinafter also referred to as "FFCs") in which copper wiring is bonded to a base film, and adhesives are usually used when manufacturing these.

When manufacturing the FPC, a laminate with an adhesive layer, called a "coverlay film," is usually used to protect the wiring portion. This coverlay film comprises an insulating base film and an adhesive layer formed on its surface, with polyimide resin being widely used as the material for the base film. A flexible printed wiring board is then manufactured by attaching the coverlay film via the adhesive layer to the surface having the wiring portion, for example, using a heat press or the like. At this time, the adhesive layer of the coverlay film needs to have strong adhesion to both the wiring portion and the base film.

Furthermore, as a type of printed wiring board, a build-up type multilayer printed wiring board is known in which conductor layers and organic insulating layers are alternately laminated on the surface of a substrate. When manufacturing such a multilayer printed wiring board, an insulating adhesive layer forming material called a "bonding sheet" is used to bond the conductor layers and the organic insulating layers. The insulating adhesive layer must be embeddable in the wiring portion and have strong adhesion to both the constituent material of the conductor part that forms the circuit (copper, etc.) and the organic insulating layer (polyimide resin, etc.).

The adhesive compositions used in such FPC-related products are generally epoxy-based adhesive compositions that contain an epoxy resin and a thermoplastic resin that is reactive with the epoxy resin.

For example, Patent Document 1 discloses an adhesive composition that contains an olefin resin having at least one reactive functional group, an epoxy resin, and an inorganic filler such as silica to control thixotropy.

JP 2018-513891 A

　In recent years, the demand for mobile communication devices such as mobile phones and information device terminals has been expanding rapidly, and the need to process large amounts of data at high speed has led to signals becoming increasingly higher in frequency. As signal speeds and frequencies increase, adhesives used in FPC-related products are required to have good dielectric properties (low dielectric constant and low dielectric tangent) in the high frequency range for the cured product after the adhesive composition has hardened.

However, when silica filler is added to adjust the physical properties of the adhesive composition, the dielectric properties of the cured product may be impaired. In addition, the silica filler aggregates in the adhesive composition, reducing the dispersibility of the silica filler. When the dispersibility of the silica filler decreases, it becomes difficult to obtain a smooth and homogeneous thin adhesive layer due to the silica filler aggregates.

The present disclosure has been made in consideration of such problems, and aims to provide an adhesive composition that can improve the dispersibility of silica filler without adversely affecting the dielectric properties of the cured product of the adhesive composition, as well as a laminate with an adhesive layer that uses the same, and a flexible copper-clad laminate or flexible flat cable that uses the same.

The adhesive composition, adhesive layer-attached laminate, flexible copper-clad laminate, and flexible flat cable disclosed herein are as follows:

[1]
The composition contains a modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group, an epoxy resin (B), and a silica filler (C),
The silanol group concentration of the silica filler (C) is 0.5 mmol/g or less.
Adhesive composition.
[2]
The water content of the silica filler (C) is 0.1 mass% or less.
The adhesive composition according to the above [1].
[3]
The BET specific surface area of the silica filler (C) is 1 m ² /g or more and 10 m ² /g or less.
The adhesive composition according to the above [1] or [2].
[4]
The content of the silica filler (C) is 10 parts by mass or more and 90 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A).
The adhesive composition according to any one of the above [1] to [3].
[5]
The modified polyolefin resin (A) is an acid-modified polyolefin resin.
The adhesive composition according to any one of the above [1] to [4].
[6]
The modified polyolefin resin (A) is a resin obtained by graft-modifying an unmodified polyolefin resin with a modifying agent containing an α,β-unsaturated carboxylic acid or a derivative thereof.
The adhesive composition according to any one of the above [1] to [5].
[7]
The epoxy resin (B) is a polyfunctional epoxy resin having an alicyclic skeleton.
The adhesive composition according to any one of the above [1] to [6].
[8]
the content of the modified polyolefin resin (A) is 50 parts by mass or more per 100 parts by mass of the solid content of the adhesive composition;
The content of the epoxy resin (B) is 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A).
The adhesive composition according to any one of the above [1] to [7].
[9]
a cured product of the adhesive composition has a relative dielectric constant of 2.5 or less and a dielectric dissipation factor of 0.01 or less, measured at a frequency of 10 GHz;
The adhesive composition according to any one of the above [1] to [8].
[10]
A laminate with an adhesive layer, comprising an adhesive layer made of the adhesive composition according to any one of [1] to [9] above, and a base film in contact with at least one surface of the adhesive layer.
[11]
A flexible copper-clad laminate comprising the adhesive layer-attached laminate according to the above-mentioned [10], the base film being provided on one side of the adhesive layer, and a copper foil being provided on the other side of the adhesive layer.
[12]
A flexible flat cable comprising the base film on one side of the adhesive layer in the laminate with an adhesive layer according to [10] above, and a copper wiring on the other side of the adhesive layer.

The adhesive composition has the above-mentioned configuration. Therefore, the adhesive composition can improve the dispersibility of the silica filler without adversely affecting the dielectric properties of the cured product of the adhesive composition.

The laminate with the adhesive layer has the above-mentioned configuration. Therefore, even if the adhesive composition constituting the adhesive layer of the laminate with the adhesive layer contains silica filler, the dielectric properties of the adhesive layer after the adhesive composition is cured are not adversely affected. Furthermore, in the laminate with the adhesive layer, the silica filler has good dispersibility in the adhesive composition constituting the adhesive layer, so that agglomerations of the silica filler are suppressed, and the adhesive layer can be made into a smooth and homogeneous thin film.

The flexible copper-clad laminate has the above-mentioned configuration. Therefore, even if the adhesive composition constituting the adhesive layer in the laminate with the adhesive layer contains silica filler, the flexible copper-clad laminate does not adversely affect the dielectric properties of the adhesive layer after the adhesive composition is cured. Furthermore, since the dispersion of the silica filler in the adhesive composition constituting the adhesive layer in the laminate with the adhesive layer is good, the flexible copper-clad laminate suppresses the formation of silica filler aggregates, and the adhesive layer can be made into a smooth and homogeneous thin film.

The flexible flat cable has the above-mentioned configuration. Therefore, even if the adhesive composition constituting the adhesive layer in the laminate with the adhesive layer contains silica filler, the flexible flat cable does not adversely affect the dielectric properties of the adhesive layer after the adhesive composition is cured. Furthermore, since the silica filler in the adhesive composition constituting the adhesive layer in the laminate with the adhesive layer has good dispersibility, the flexible flat cable suppresses agglomerations of the silica filler, and the adhesive layer can be made into a smooth and homogeneous thin film.

Below, one embodiment of the present disclosure is described, but the present disclosure is not limited to this embodiment.

1. Adhesive composition 1.1 Composition of adhesive composition The adhesive composition of this embodiment contains a modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group, an epoxy resin (B), and a silica filler (C), and the silanol group concentration of the silica filler (C) is 0.5 mmol/g or less. The composition of the adhesive composition will be specifically described below.

1.1.1 Modified polyolefin resin (A)
The modified polyolefin resin (A) has a reactive functional group that reacts with an epoxy group. That is, the modified polyolefin resin (A) can be said to be an unmodified polyolefin resin to which a reactive functional group that reacts with an epoxy group has been introduced, or it can be said to be a resin modified by an unmodified polyolefin resin with a modifier having a reactive functional group that reacts with an epoxy group, or it can be said to be a resin modified so that the unmodified polyolefin resin has reactivity with the epoxy resin (B).

Reactive functional groups that react with epoxy groups include groups having active hydrogen, active ester groups, etc., and examples of groups having active hydrogen include carboxy groups, amino groups, hydroxyl groups, acid anhydride groups, and thiol groups. These can be used alone or in combination of two or more. From the standpoint of reactivity, etc., the reactive functional groups that react with epoxy groups are preferably carboxy groups and amino groups, and more preferably carboxy groups.

The modified polyolefin resin (A) is preferably an acid-modified polyolefin resin, specifically a resin having a portion derived from an unmodified polyolefin resin and a graft portion derived from a modifying agent, and preferably an unmodified polyolefin resin graft-modified with a modifying agent containing an α,β-unsaturated carboxylic acid or a derivative thereof.

The modified polyolefin resin (A) can be produced by a known method through graft modification (graft polymerization), and a radical initiator may be used during production. Examples of methods for producing the modified polyolefin resin (A) include a solution method in which an unmodified polyolefin resin is heated and dissolved in a solvent such as toluene, and the modifying agent and radical initiator are added, and a melting method in which the unmodified polyolefin resin, the modifying agent, and the radical initiator are melt-kneaded using a Banbury mixer, kneader, extruder, or the like. The method for using the unmodified polyolefin resin, the modifying agent, and the radical initiator is not particularly limited, and they may be added to the reaction system all at once or successively. In addition, when producing the modified polyolefin resin (A), a modifying auxiliary for improving the grafting efficiency by a modifying agent such as α,β-unsaturated carboxylic acid, a stabilizer for adjusting the resin stability, and the like may be further used.

The unmodified polyolefin resin used in the production of modified polyolefin resin (A) is not particularly limited as long as it has a structural unit derived from an olefin, but homopolymers or copolymers having 2 to 20 carbon atoms, such as ethylene, propylene, butene, pentene, hexene, heptene, octene, and 4-methyl-1-pentene, are preferably used. The unmodified polyolefin resin is more preferably a homopolymer or copolymer of an olefin having 2 to 6 carbon atoms.

As the unmodified polyolefin resin used in the production of the modified polyolefin resin (A), specifically, an unmodified polypropylene resin is suitable. In this case, the modified polyolefin resin (A) can be specifically a resin having a portion derived from an unmodified polypropylene resin and a graft portion derived from a modifying agent, and preferably is a resin in which the unmodified polypropylene resin is graft-modified with a modifying agent containing an α,β-unsaturated carboxylic acid or a derivative thereof. The unmodified polypropylene resin is not particularly limited as long as it has a structural unit derived from propylene and is not modified with a modifying agent such as an α,β-unsaturated carboxylic acid or a derivative thereof, but a copolymer of propylene and an olefin having 2 to 20 carbon atoms, such as ethylene, butene, pentene, hexene, heptene, octene, or 4-methyl-1-pentene, is preferably used. The unmodified polypropylene resin is more preferably a copolymer of propylene and an olefin having 2 to 6 carbon atoms.

The content ratio of the structural units in the unmodified polyolefin resin and the unmodified polypropylene resin can be selected arbitrarily. From the viewpoint of being advantageous for adhesion to poorly adhesive adherends, the modified polyolefin resin (A) is preferably a modified resin of an unmodified polypropylene resin which is at least one selected from the group consisting of ethylene-propylene, propylene-butene, and ethylene-propylene-butene copolymers. From the viewpoint of obtaining particularly excellent adhesiveness, it is preferable to use an unmodified polypropylene resin in which the content ratio of propylene units is 50% by mass or more and 98% by mass or less. If the content ratio of propylene units is within the above-mentioned range, flexibility can be imparted to the adhesive part after the two members are bonded. The molecular weight of the unmodified polyolefin resin and the unmodified polypropylene resin is not particularly limited.

The modifier may include α,β-unsaturated carboxylic acids and their derivatives. Examples of α,β-unsaturated carboxylic acids include maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, aconitic acid, and norbornene dicarboxylic acid. Examples of derivatives of unsaturated carboxylic acids include acid anhydrides, acid halides, amides, imides, and esters. As the modifier, itaconic anhydride, maleic anhydride, aconitic anhydride, and citraconic anhydride are preferred, and itaconic anhydride and maleic anhydride are particularly preferred in terms of adhesiveness. When a modifier is used, it is sufficient to use one or more selected from α,β-unsaturated carboxylic acids and their derivatives, and it may be a combination of one or more α,β-unsaturated carboxylic acids and one or more derivatives thereof, a combination of two or more α,β-unsaturated carboxylic acids, or a combination of two or more derivatives of α,β-unsaturated carboxylic acids.

The modifier may contain other compounds (other modifiers) in addition to the α,β-unsaturated carboxylic acid, etc., depending on the purpose. Examples of the other compounds (other modifiers) include (meth)acrylic acid esters represented by the following formula (1), (meth)acrylic acid, other (meth)acrylic acid derivatives, aromatic vinyl compounds, cyclohexyl vinyl ether, etc. These other compounds may be used alone or in combination of two or more.
_CH2 = ^CR1COOR2 ( ¹ )
(In formula (1), R ¹ is a hydrogen atom or a methyl group, and R ² is a hydrocarbon group.)

In the formula (1) representing the (meth)acrylic acid ester, R ¹ is a hydrogen atom or a methyl group, preferably a methyl group. R ² is a hydrocarbon group, preferably an alkyl group having 8 to 18 carbon atoms. Examples of the compound represented by the formula (1) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl (meth)acrylate. These compounds may be used alone or in combination of two or more. In this embodiment, since the heat-resistant adhesiveness is improved, it is preferable to use a modifier that further contains a (meth)acrylic acid ester having an alkyl group having 8 to 18 carbon atoms, and it is particularly preferable that the modifier contains octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, or stearyl (meth)acrylate.

Examples of (meth)acrylic acid derivatives other than (meth)acrylic acid esters include hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, and isocyanate-containing (meth)acrylic acid. Examples of aromatic vinyl compounds include styrene, o-methylstyrene, p-methylstyrene, and α-methylstyrene. By using an α,β-unsaturated carboxylic acid or its derivative in combination with another modifier as the above modifier, it is possible to improve the graft rate by the modifier, improve solubility in solvents, and further improve adhesion. When using a modifier other than the (meth)acrylic acid ester represented by the above formula (1), it is desirable that the amount used does not exceed the total amount used of the α,β-unsaturated carboxylic acid or its derivative, and the (meth)acrylic acid ester.

As described above, the modified polyolefin resin (A) can have at least a graft portion derived from the modifier. The content of the graft portion contained in the modified polyolefin resin (hereinafter also referred to as "graft mass") will be explained below.

The modified polyolefin resin (A) may have a graft portion derived from an α,β-unsaturated carboxylic acid or a derivative thereof. In the modified polyolefin resin (A), the graft mass of the graft portion derived from an α,β-unsaturated carboxylic acid or a derivative thereof is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 0.2% by mass or more and 18% by mass or less, relative to 100% by mass of the modified polyolefin resin (A) from the viewpoint of adhesiveness. When the graft mass is 0.1% by mass or more, the resin has excellent solubility in solvents and is particularly excellent in adhesiveness to adherends made of metals and the like. When the graft mass is 20% by mass or less, sufficient adhesiveness to adherends made of resins and the like can be obtained.

The graft mass derived from α,β-unsaturated carboxylic acid or its derivative in modified polyolefin resin (A) can be determined by alkali titration, but if the derivative of α,β-unsaturated carboxylic acid is an imide or the like that does not have an acid group, the graft mass can be determined by Fourier transform infrared spectroscopy.

When the modified polyolefin resin (A) contains a graft portion derived from the (meth)acrylic acid ester represented by the above formula (1), the graft mass is preferably 0.1% by mass or more and 30% by mass or less, and more preferably 0.3% by mass or more and 25% by mass or less, relative to 100% by mass of the modified polyolefin resin (A). When the graft mass is 0.1% by mass or more and 30% by mass or less, the resin has excellent solubility in solvents and excellent compatibility with other resins or elastomers described below when they are contained, and the adhesion to the adherend can be further improved.

When the above-mentioned modifying agent contains a (meth)acrylic acid ester represented by the above-mentioned formula (1), the graft mass in the obtained modified polyolefin resin (A) can be determined by Fourier transform infrared spectroscopy.

The radical initiator used in the production of modified polyolefin resin (A) can be appropriately selected from known ones, but it is preferable to use organic peroxides such as benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and cumene hydroperoxide.

Examples of modification aids that can be used in the production of modified polyolefin resin (A) include divinylbenzene, hexadiene, dicyclopentadiene, etc. Examples of stabilizers include hydroquinone, benzoquinone, nitrosophenyl hydroxy compounds, etc.

The weight average molecular weight Mw of the modified polyolefin resin (A) is preferably 30,000 or more and 250,000 or less, and more preferably 50,000 or more and 200,000 or less. When the weight average molecular weight Mw of the modified polyolefin resin (A) is within the above range, an adhesive composition can be obtained that has excellent solubility in solvents and initial adhesion to the adherend, and further has excellent solvent resistance at the bonded joint after bonding.

The acid value of the modified polyolefin resin (A) is preferably 0.1 mgKOH/g or more and 50 mgKOH/g or less, more preferably 0.5 mgKOH/g or more and 40 mgKOH/g or less, and even more preferably 1.0 mgKOH/g or more and 30 mgKOH/g or less. When the acid value of the modified polyolefin resin (A) is within the above range, the adhesive composition is sufficiently cured, and good adhesion, heat resistance, and resin flow properties are obtained.

The content of modified polyolefin resin (A) is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 65 parts by mass or more, per 100 parts by mass of the solid content of the adhesive composition. By having a content of modified polyolefin resin (A) of 50 parts by mass or more, it is possible to easily develop good adhesive properties. The content of modified polyolefin resin (A) is preferably 99 parts by mass or less per 100 parts by mass of the solid content of the adhesive composition. In this disclosure, "solid content" means components excluding the solvent.

1.1.2 Epoxy resin (B)
Next, the epoxy resin (B) will be described. The epoxy resin (B) is a component that reacts with reactive functional groups such as carboxy groups in the modified polyolefin resin (A) to impart adhesion to adherends and heat resistance to the cured product of the adhesive.

Epoxy resins (B) include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and hydrogenated versions of these; glycidyl ester-based epoxy resins such as orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-hydroxybenzoic acid glycidyl ester, tetrahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, and trimellitic acid triglycidyl ester; ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butadiene glycol diglycidyl ether, and the like. Examples of epoxy resins that can be used include, but are not limited to, glycidyl ether-based epoxy resins such as hexanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, polyglycidyl ether of sorbitol, and polyglycidyl ether of polyglycerol; glycidyl amine-based epoxy resins such as triglycidyl isocyanurate and tetraglycidyl diaminodiphenylmethane; and linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil. Novolac-type epoxy resins such as phenol novolac epoxy resin, o-cresol novolac epoxy resin, and bisphenol A novolac epoxy resin can also be used.

Furthermore, examples of the epoxy resin (B) include brominated bisphenol A type epoxy resin, phosphorus-containing epoxy resin, dicyclopentadiene skeleton-containing epoxy resin, naphthalene skeleton-containing epoxy resin, anthracene type epoxy resin, tertiary butyl catechol type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, biphenyl type epoxy resin, bisphenol S type epoxy resin, etc. These epoxy resins (B) may be used alone or in combination of two or more. Among the epoxy resins (B), epoxy resins without glycidylamino groups are preferred. This is because the storage stability of the laminate with the adhesive layer is improved. Furthermore, as the epoxy resin (B), polyfunctional epoxy resins with alicyclic skeletons are preferred, and epoxy resins with dicyclopentadiene skeletons are more preferred, since they provide an adhesive composition with excellent dielectric properties.

The epoxy resin (B) is preferably one having two or more epoxy groups in one molecule. This is because it forms a crosslinked structure by reaction with the modified polyolefin resin (A), and can exhibit high heat resistance. Furthermore, when an epoxy resin with two or more epoxy groups is used, the degree of crosslinking with the modified polyolefin resin (A) is sufficient, and sufficient heat resistance can be obtained.

The content of epoxy resin (B) is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of modified polyolefin resin (A). When the content of epoxy resin (B) is 1 part by mass or more, sufficient adhesion is obtained. When the content of epoxy resin (B) is 20 parts by mass or less, peel adhesion strength and dielectric properties are good.

1.1.3 Silica filler (C)
The silica filler (C) has a silanol group concentration on its surface of 0.5 mmol/g or less.

Silica filler is useful for adjusting the mechanical properties of the adhesive composition. Specifically, by adding silica filler to the adhesive composition, the flow (resin flow) of the adhesive layer can be reduced. When dispersing such silica filler in a resin composition, the interaction between the resin composition and the functional groups on the surface of the silica filler is usually utilized. When the silica filler surface has few functional groups and has little interaction with the resin composition, it is necessary to add a silane coupling agent or the like to enhance the interaction with the silica filler. Based on this conventional idea, the higher the silanol group concentration of the silica filler, the better. However, in reality, the opposite is true, and the present inventors have found that when the silica filler is used together with the modified polyolefin resin (A) and the epoxy resin (B), the dispersibility of the silica filler can be improved by suppressing the silanol group concentration to a low concentration range of 0.5 mmol/g or less.

If the silanol group concentration of the silica filler (C) exceeds 0.5 mmol/g, aggregates of the silica filler (C) are generated in the adhesive composition in a short period of time, and the dispersibility of the silica filler (C) deteriorates. This also makes it difficult to obtain a homogeneous coating film of the adhesive composition, which adversely affects the dielectric properties of the cured product of the adhesive composition. From the viewpoints of improving the dispersibility of the silica filler (C) and reducing the dielectric properties of the cured product of the adhesive composition, the silanol group concentration of the silica filler (C) is preferably 0.2 mmol/g or less, more preferably less than 0.2 mmol/g, and even more preferably 0.15 mmol/g or less. From the viewpoints of ensuring the dispersibility improvement effect of the silica filler (C), the silanol group concentration of the silica filler (C) is preferably more than 0 mmol/g, more preferably 0.005 mmol/g or more, and even more preferably 0.01 mmol/g or more. The method for measuring the silanol group concentration of the silica filler (C) will be described in detail in the examples below.

The silica filler (C) can be specifically composed of an aggregate of silica particles having silanol groups on the surface (silica powder having silanol groups on the surface). The silica filler (C) can be obtained, for example, by surface treating silica powder with a surface treatment agent capable of introducing silanol groups. Examples of the surface treatment agent include alkoxysilanes such as methyltrimethoxysilane, and organosilazanes such as hexamethyldisilazane (HMDS). These can be used alone or in combination of two or more. In addition, commercially available silica fillers can be used as the silica filler (C).

The shape of each silica particle constituting the silica filler (C) is not particularly limited. From the viewpoint of improving the dispersibility of the silica filler (C), the shape of the silica particles is preferably spherical, and more preferably true spherical.

The moisture content of the silica filler (C) is preferably 0.1% by mass or less, more preferably less than 0.08% by mass, even more preferably 0.06% by mass or less, even more preferably 0.03% by mass or less, and most preferably 0.02% by mass or less. By making the moisture content of the silica filler (C) 0.1% by mass or less, it is possible to reliably improve the dispersibility of the silica filler (C) without adversely affecting the dielectric properties of the cured product of the adhesive composition and the adhesive layer after the adhesive composition is cured. In particular, by making the moisture content of the silica filler (C) less than 0.08% by mass, it is easier to improve the dispersibility of the silica filler. Note that the lower the moisture content of the silica filler (C), the better the parameter, so the lower limit is not particularly limited. In addition, the method for measuring the moisture content of the silica filler (C) will be described in detail in the examples below.

The BET specific surface area of the silica filler (C) is preferably ¹ m2/g or more and ¹⁰ m2/g or less, more preferably ² m2/g or more and ⁸ m2/g or less, and even more preferably ³ m2/g or more and 7 ^m2 /g or less. By setting the BET specific surface area of the silica filler (C) within the above range, it becomes easier to suppress the generation of aggregates of the silica filler (C). The method for measuring the BET specific surface area of the silica filler (C) will be described in detail in the examples below.

The content of the silica filler (C) is preferably 10 parts by mass or more and 90 parts by mass or less, more preferably 15 parts by mass or more and 80 parts by mass or less, and even more preferably 20 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of the modified polyolefin resin (A). When the content of the silica filler (C) is 10 parts by mass or more, it is easier to reduce the flow (resin flow) of the adhesive layer. When the content of the silica filler (C) is 90 parts by mass or less, it is easier to suppress a decrease in the adhesive properties of the adhesive composition.

1.1.4 Other Components The adhesive composition of the present embodiment may contain, in addition to the above-mentioned modified polyolefin resin (A), epoxy resin (B), and silica filler (C), other thermoplastic resins, tackifiers, flame retardants, curing agents, curing accelerators, coupling agents, heat aging inhibitors, inorganic fillers other than silica fillers, leveling agents, defoamers, pigments, UV absorbers, solvents, and the like, to the extent that the functions of the adhesive composition are not adversely affected.

(Thermoplastic resin)
Examples of the other thermoplastic resins include phenoxy resins, polyamide resins, polyester resins, polycarbonate resins, polyphenylene oxide resins, polyurethane resins, polyacetal resins, polyethylene-based resins, polypropylene-based resins, and polyvinyl-based resins, etc. These thermoplastic resins may be used alone or in combination of two or more kinds.

(Tackifier)
Examples of the tackifier include coumarone-indene resin, terpene resin, terpene-phenol resin, rosin resin, p-t-butylphenol-acetylene resin, phenol-formaldehyde resin, xylene-formaldehyde resin, petroleum-based hydrocarbon resin, hydrogenated hydrocarbon resin, turpentine-based resin, etc. These tackifiers may be used alone or in combination of two or more kinds.

(Flame retardants)
The flame retardant may be either an organic flame retardant or an inorganic flame retardant. Examples of organic flame retardants include phosphorus-based flame retardants such as melamine phosphate, melamine polyphosphate, guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, ammonium amido phosphate, ammonium amido polyphosphate, carbamate phosphate, carbamate polyphosphate, aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanium tetrakisdiethylphosphinate, titanyl bismethylethylphosphinate, titanium tetrakismethylethylphosphinate, titanyl bisdiphenylphosphinate, and titanium tetrakisdiphenylphosphinate; nitrogen-based flame retardants such as triazine-based compounds such as melamine, melam, and melamine cyanurate, cyanuric acid compounds, isocyanuric acid compounds, triazole-based compounds, tetrazole compounds, diazo compounds, and urea; and silicon-based flame retardants such as silicone compounds and silane compounds. Examples of inorganic flame retardants include metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, barium hydroxide, and calcium hydroxide, metal oxides such as tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, molybdenum oxide, and nickel oxide, zinc carbonate, magnesium carbonate, barium carbonate, zinc borate, hydrated glass, etc. These flame retardants may be used alone or in combination of two or more.

(Hardening agent)
Examples of the curing agent include, but are not limited to, amine-based curing agents and acid anhydride-based curing agents. Examples of the amine-based curing agent include melamine resins such as methylated melamine resin, butylated melamine resin, and benzoguanamine resin, dicyandiamide, and 4,4'-diphenyldiaminosulfone. Examples of the acid anhydride include aromatic acid anhydrides and aliphatic acid anhydrides. These curing agents may be used alone or in combination of two or more.

The content of the curing agent is preferably 1 part by mass or more and 100 parts by mass or less, and more preferably 5 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of the epoxy resin (B).

(Cure Accelerator)
The curing accelerator is used for the purpose of accelerating the reaction between the modified polyolefin resin (A) and the epoxy resin (B), and examples of the curing accelerator that can be used include tertiary amine curing accelerators, tertiary amine salt curing accelerators, and imidazole curing accelerators.

Tertiary amine curing accelerators include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, 1,8-diazabicyclo[5.4.0]undecene, etc.

Tertiary amine salt curing accelerators include the formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene, and the formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

Imidazole-based hardening accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, '-undecylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, etc. These curing accelerators may be used alone or in combination of two or more.

When the adhesive composition of this embodiment contains a curing accelerator, the content of the curing accelerator is preferably 1 part by mass or more and 15 parts by mass or less, more preferably 1 part by mass or more and 10 parts by mass or less, and even more preferably 2 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the epoxy resin (B). If the content of the curing accelerator is within the above range, excellent adhesion and heat resistance can be exhibited.

(Coupling Agent)
Examples of the coupling agent include silane-based coupling agents such as vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatepropyltriethoxysilane, and imidazole silane; titanate-based coupling agents; aluminate-based coupling agents; and zirconium-based coupling agents. These may be used alone or in combination of two or more.

(Heat aging inhibitor)
Examples of the heat aging inhibitor include antioxidants, and specific examples thereof include 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenol, triethylene Examples of antioxidants include phenol-based antioxidants such as ethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate; sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate and dimyristyl-3,3'-dithiopropionate; and phosphorus-based antioxidants such as trisnonylphenyl phosphite and tris(2,4-di-tert-butylphenyl)phosphite. These may be used alone or in combination of two or more.

(Inorganic filler)
Examples of the inorganic filler include powders of titanium oxide, aluminum oxide, zinc oxide, carbon black, talc, copper, silver, etc. These may be used alone or in combination of two or more.

(solvent)
The adhesive composition of the present embodiment can be produced by mixing the modified polyolefin resin (A), the epoxy resin (B), the silica filler (C), and other components as necessary. The mixing method is not particularly limited as long as the adhesive composition is homogeneous. Since the adhesive composition is preferably used in the state of a solution or dispersion, a solvent such as an organic solvent is usually also used.

Examples of solvents include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone; aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and mesitylene; esters such as methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; and aliphatic hydrocarbons such as hexane, heptane, cyclohexane, and methylcyclohexane. These solvents may be used alone or in combination of two or more. If the adhesive composition contains a solvent and is a solution or dispersion (resin varnish) in which the modified polyolefin resin (A), epoxy resin (B), and silica filler (C) are dissolved or dispersed in the solvent, application to the substrate film and formation of the adhesive layer can be carried out smoothly, and an adhesive layer of the desired thickness can be easily obtained.

The solvent used in the adhesive composition of this embodiment preferably contains, among the above-mentioned examples, an alicyclic hydrocarbon solvent such as methylcyclohexane and/or cyclohexane, and an alcohol-based solvent. In this embodiment, the content of the alicyclic hydrocarbon relative to 100 parts by mass of the solvent is preferably 20 parts by mass or more and 90 parts by mass or less, and more preferably 40 parts by mass or more and 80 parts by mass or less.

The content of the alcohol-based solvent relative to 100 parts by mass of the solvent is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 10 parts by mass or less. By having the content of the alicyclic hydrocarbon and/or the alcohol-based solvent within the above range, an adhesive composition with excellent storage stability at low temperatures can be obtained.

In addition, among the above-mentioned solvents, the solvent used in the adhesive composition of this embodiment preferably contains toluene. In this embodiment, the toluene content per 100 parts by mass of the adhesive composition is preferably 10 parts by mass or more and 60 parts by mass or less, and more preferably 20 parts by mass or more and 40 parts by mass or less. By having the toluene content within the above range, the solubility of the epoxy resin (B) and the like in the solvent can be improved.

When the adhesive composition contains a solvent such as an organic solvent, from the viewpoint of workability including the formation of the adhesive layer, the solids concentration is preferably in the range of 5% to 50% by mass, more preferably 10% to 40% by mass. If the solids concentration is 80% by mass or less, the viscosity of the solution is appropriate and it is easy to apply uniformly.

1.2 Dielectric properties of the cured product of the adhesive composition The adhesive composition of this embodiment preferably has a relative dielectric constant (Dk, εr) of 2.5 or less and a dielectric loss tangent (Df, tan δ) of 0.01 or less, measured at a frequency of 10 GHz. The relative dielectric constant is preferably less than 2.5, more preferably less than 2.4, and even more preferably less than 2.4. The dielectric loss tangent is preferably less than 0.01, more preferably less than 0.005, and even more preferably less than 0.002.

If the dielectric constant is 2.5 or less and the dielectric loss tangent is 0.01 or less, the adhesive composition can be used favorably in FPC-related products that have stringent requirements for dielectric properties in response to the increasing signal speeds and higher signal frequencies of recent years. The dielectric constant and dielectric loss tangent can be adjusted by adjusting the type and content of each component in the adhesive composition.

In addition, it is preferable that the adhesive composition of this embodiment has a relative dielectric constant (Dk, εr) of 2.0 or more and a dielectric loss tangent (Df, tan δ) of 0 or more when the adhesive composition is cured, measured at a frequency of 10 GHz. The method for measuring the relative dielectric constant and dielectric loss tangent will be described in detail in the examples below.

2. Laminate with Adhesive Layer The laminate with adhesive layer according to this embodiment includes an adhesive layer made of the above-mentioned adhesive composition and a base film in contact with at least one surface of the adhesive layer. The adhesive layer may be in a B-stage state. The B-stage state of the adhesive layer refers to a semi-cured state in which a part of the adhesive composition has begun to cure, and refers to a state in which the curing of the adhesive composition progresses further by heating or the like.

One example of a laminate with an adhesive layer is a coverlay film. A coverlay film is usually a laminate in which an adhesive layer is formed on at least one surface of a base film, and it is difficult to peel the base film from the adhesive layer.

Examples of the substrate film that may be included in the laminate with an adhesive layer include polyimide film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polyethylene naphthalate film, and liquid crystal polymer film. Among these, polyimide film, polyethylene naphthalate film, and liquid crystal polymer film are preferred from the viewpoints of adhesion and electrical properties.

As a method for producing a laminate with an adhesive layer, for example, a resin varnish containing the above-mentioned adhesive composition and a solvent is applied to the surface of a substrate film such as a polyimide film to form a resin varnish layer, and then the solvent is removed from this resin varnish layer to produce a laminate with an adhesive layer having a B-stage adhesive layer formed.

The drying temperature when removing the solvent is preferably 40 to 250°C, and more preferably 70 to 170°C. Drying can be performed by passing the laminate coated with the adhesive composition through a furnace where hot air drying, far-infrared heating, high-frequency induction heating, etc. are performed.

If necessary, a release film may be laminated on the surface of the adhesive layer for storage, etc. Examples of the release film that can be used include known films such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release-treated paper, polyolefin resin-coated paper, polymethylpentene (TPX) film, and fluororesin film.

Another embodiment of the laminate with an adhesive layer is a bonding sheet. The bonding sheet also has the above-mentioned adhesive layer formed on the surface of a base film, but the base film functions as a release film. The bonding sheet may also have an adhesive layer between two release films. The release films are peeled off when the bonding sheet is used. The release films that can be used are similar to those described above.

One method for producing a bonding sheet is, for example, to apply a resin varnish containing the adhesive composition and a solvent to the surface of a release film, and then dry it in the same manner as for the coverlay film.

The thickness of the adhesive layer is preferably 5 μm to 100 μm, more preferably 10 μm to 70 μm, and even more preferably 10 μm to 50 μm, in order to provide sufficient adhesive strength. The thickness of the base film is preferably 5 μm to 100 μm, more preferably 5 μm to 50 μm, and even more preferably 5 μm to 30 μm, in order to reduce the thickness of the laminate with the adhesive layer.

3. Flexible copper-clad laminate The flexible copper-clad laminate according to this embodiment has a base film on one side of the adhesive layer in the laminate with the adhesive layer, and a copper foil on the other side of the adhesive layer. Specifically, the flexible copper-clad laminate can be configured by laminating a base film and a copper foil using the laminate with the adhesive layer. That is, the flexible copper-clad laminate can be configured by laminating a base film, an adhesive layer, and a copper foil in this order. The adhesive layer and the copper foil may be formed on both sides of the base film. The above-mentioned adhesive composition has excellent adhesion to an article containing copper, so that the flexible copper-clad laminate has excellent stability as an integrated product.

A method for manufacturing a flexible copper-clad laminate includes, for example, bringing the adhesive layer of the above-mentioned adhesive-layered laminate into surface contact with copper foil, performing thermal lamination at a temperature of, for example, 80°C to 150°C, and then hardening the adhesive layer by after-curing. The after-curing conditions can be, for example, 100°C to 200°C and 30 minutes to 4 hours. The copper foil is not particularly limited, and electrolytic copper foil, rolled copper foil, etc. can be used.

4. Flexible Flat Cable The flexible flat cable according to the present embodiment includes a base film on one side of the adhesive layer in the laminate with the adhesive layer, and a copper wiring on the other side of the adhesive layer. Specifically, the flexible flat cable can be configured by bonding the base film and the copper wiring together using the laminate with the adhesive layer. That is, the flexible flat cable can be configured by laminating the base film, the adhesive layer, and the copper wiring in this order. The adhesive layer and the copper wiring may be formed on both sides of the base film. The adhesive composition described above has excellent adhesion to copper-containing articles, and therefore the flexible flat cable has excellent stability as an integrated product.

A method for manufacturing a flexible flat cable includes, for example, contacting the adhesive layer of the laminate with the adhesive layer with copper wiring, performing thermal lamination at a temperature of, for example, 80°C to 150°C, and then hardening the adhesive layer by after-curing. The after-curing conditions can be, for example, 100°C to 200°C and 30 minutes to 4 hours. The shape of the copper wiring is not particularly limited and can be selected as appropriate as desired.

The present disclosure will be explained in more detail with reference to examples, but the present disclosure is not limited thereto. In the following, parts and percentages are by weight unless otherwise specified.

1. Evaluation Method (1) Weight Average Molecular Weight Mw
The weight average molecular weight Mw of the modified polyolefin resin (A) was determined by GPC measurement under the following conditions.
The weight average molecular weight Mw was calculated by converting the retention time measured by GPC based on the retention time of standard polystyrene.
Apparatus: Alliance 2695 (Waters)
Column: TSKgel SuperMultiporeHZ-H x 2,
2 bottles of TSKgel Super HZ2500 (manufactured by Tosoh Corporation)
Column temperature: 40°C
Eluent: Tetrahydrofuran 0.35 ml/min Detector: RI (differential refractive index detector)

(2) Acid value 1 g of modified polyolefin resin (A) was dissolved in 30 ml of toluene, and an automatic titration device "AT-510" manufactured by Kyoto Electronics Manufacturing Co., Ltd. was used, which was connected to an "APB-510-20B" manufactured by the same company as a buret. Potentiometric titration was performed using a 0.01 mol/L benzyl alcohol-based KOH solution as the titration reagent, and the number of mg of KOH per 1 g of resin was calculated.

(3) Physical properties of silica filler (C) (3-1) Method for measuring silanol group concentration and water content of silica filler 0.05g to 0.5g of a given silica filler was weighed into a glass cell with an optical path length of 5 mm, and about 0.6mL of carbon tetrachloride was added to it. After thoroughly stirring the obtained sample, near-infrared measurement was performed under the following conditions. Then, the silanol group concentration and water content of the silica filler were calculated from the peak integral ratio of the obtained spectrum.
Equipment: Nicolet iS50
Detector: MCT
Measurement method: Transmission measurement Measurement range: 8000 to ⁴⁰⁰⁰ cm

(3-2) Method for Measuring Specific Surface Area of Silica Filler The specific surface area of the silica filler was measured by the BET adsorption method using nitrogen gas (N ₂ ) as the adsorption gas.

(4) Dielectric properties (dielectric constant and dielectric tangent)
A release PET film having a thickness of 38 μm was prepared, and the adhesive composition described in Table 1 was applied to one surface of the film. The coated film was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) having a thickness of 50 μm, and an adhesive layer was obtained. The adhesive layer was then placed in an oven and heat-treated at 180° C. for 60 minutes. The release film was then peeled off to obtain a test piece (150 mm×80 mm) made of a cured product of the adhesive composition. The relative dielectric constant (Dk, εr) and dielectric loss tangent (Df, tan δ) were measured at a temperature of 23° C. and a frequency of 10 GHz using a network analyzer 85071E-300 (manufactured by Agilent) by the split post dielectric resonator method (SPDR method). Note that in sample 2C in Table 1, a homogeneous coating film of 50 μm could not be obtained due to the aggregates of the silica filler (c5), so the dielectric properties were not measured. Furthermore, the criterion for "not adversely affecting the dielectric properties" is that the dielectric tangent, which tends to be considered important as a low dielectric property among the relative dielectric constant and the dielectric tangent, does not exceed the dielectric tangent of sample 1C (composition not including silica filler).

(5) Dispersibility of Silica Filler (C) The adhesive composition in which the silica filler was dispersed was left to stand at room temperature (25°C), and after a specified number of days, the occurrence of silica filler aggregates was visually confirmed. Even if the silica filler was found to have settled, if it returned to a uniformly dispersed state by light shaking, it was determined that no silica filler aggregates had occurred.

The numbers in Table 1 indicate the number of days until the occurrence of silica filler agglomerates. For example, a sample marked "2" indicates that the occurrence of silica filler agglomerates was observed on the second day. The silica filler dispersibility evaluation test was performed for a maximum of 7 days, and if no occurrence of silica filler agglomerates was observed during this period, it was marked ">7". Also, "0" indicates that the occurrence of silica filler agglomerates was observed immediately after dispersion using a disperser. In Table 1, when the number of days until the occurrence of silica filler agglomerates was 7 days or more, it was marked "A" as the silica filler had excellent dispersibility. When the number of days until the occurrence of silica filler agglomerates was 1 day or more but less than 7 days, it was marked "B" as the silica filler had good dispersibility. When the number of days until the occurrence of silica filler agglomerates was less than 1 day, it was marked "C" as the silica filler had poor dispersibility. In addition, when the above rating was A or B, it was determined that the dispersibility of the silica filler had been improved, and when the above rating was C, it was determined that the dispersibility of the silica filler had not been improved.

(6) Resin flow A release PET film having a thickness of 38 μm was prepared, and the adhesive composition described in Table 1 was applied to one surface of the film. The coated film was then placed in an oven and dried at 90 ° C for 3 minutes to obtain a B-stage adhesive layer (thickness 25 μm). Then, an electrolytic copper foil having a thickness of 12 μm was superposed on the surface of the adhesive layer so as to be in surface contact, and lamination was performed for 30 seconds under vacuum conditions at a temperature of 120 ° C, a pressure of 0.5 MPa, and a temperature of 120 ° C, a pressure of 0.5 MPa, and a temperature of 120 ° C, a pressure of 0.5 MPa, and a temperature of 120 ° C, a pressure of 0.5 MPa, and a pressure of 120 ° C, and a pressure of 0.5 MPa, and a temperature of 120 ° C, a pressure of 0.5 MPa, and ...

2. Raw Materials for the Adhesive Composition The following raw materials for the adhesive composition were prepared.
(1) Modified polyolefin resin (A)
As the modified polyolefin resin (A), an acid-modified polypropylene resin (a1) was prepared by the method described below.

100 parts by mass of a propylene-butene random copolymer consisting of 65% by mass of propylene units and 35% by mass of 1-butene units, produced using a metallocene catalyst as a polymerization catalyst, 1 part by mass of maleic anhydride, 0.3 parts by mass of lauryl methacrylate, and 0.4 parts by mass of di-t-butyl peroxide were kneaded and reacted using a twin-screw extruder with the maximum temperature of the cylinder set to 170°C. After that, degassing was performed under reduced pressure in the extruder to remove the remaining unreacted material, producing an acid-modified polypropylene resin (a1). The acid-modified polypropylene resin (a1) had a weight average molecular weight Mw of 70,000, an acid value of 10 mgKOH/g, and a propylene/butene mass ratio of 65/35.

(2) Epoxy resin (B)
Dicyclopentadiene skeleton-containing epoxy resin (b1) (hereinafter also referred to as DCPD type epoxy resin (b1)) (manufactured by DIC Corporation, "EPICLON HP-7200")

(3) Silica filler (C)
Silica filler (c1) (manufactured by Sakai Chemical Industry Co., Ltd., "Sciqas-LT", average particle size 0.7 μm, spherical, organosilazane-treated product)
Silica filler (c2) (manufactured by Sakai Chemical Industry Co., Ltd., "Sciqas", average particle size 0.7 μm, spherical, organosilazane-treated product)
Silica filler (c3) (manufactured by Sakai Chemical Industry Co., Ltd., "Sciqas", average particle size 0.7 μm, spherical, untreated product)
Silica filler (c4) (Tokuyama Corporation, "Exelica SE-1", average particle size 0.5 μm, spherical)
Silica filler (c5) (manufactured by Nippon Aerosil Co., Ltd., "Aerosil RY-200", spherical)
In addition, since the silica filler (c5) has a silanol group concentration exceeding 0.5 mmol/g, it does not correspond to the silica filler (C) referred to in the adhesive composition according to the present disclosure, but for the convenience of creating Table 1, it is listed in the column for silica filler (C).

(4) Others - Curing accelerator (imidazole-based curing accelerator) (manufactured by Shikoku Kasei Corporation, "Curesol C11Z")
Solvent (a mixed solvent of toluene and methylcyclohexane (mass ratio = 20:80)
The amount of the solvent was appropriately adjusted so that the solid content of the adhesive composition was 15 to 30% by mass.

3. Production and evaluation of adhesive composition The above-mentioned raw materials other than the silica filler (C) were added to a 1000 ml flask equipped with a stirrer in the prescribed ratio shown in Table 1, and a solvent was added and stirred at room temperature (25°C) for 6 hours to dissolve, thereby preparing an adhesive composition not containing the silica filler (C). Thereafter, for samples 1 to 8 and sample 2C, the prescribed amount of silica filler (C) shown in Table 1 was added, and the silica filler (C) was dispersed by stirring using a disperser at 2000 rpm for 10 minutes, thereby preparing an adhesive composition containing the silica filler (C). In this way, each adhesive composition was prepared and evaluated. The results are shown in Table 1.

4. Production and evaluation of laminates with adhesive layer Using the above adhesive composition, laminates with adhesive layers were produced and evaluated as described in the explanation of each evaluation method above. The results are shown in Table 1.

From Table 1, the following can be seen. That is, sample 1C had a relatively high resin flow because the adhesive composition did not contain silica filler (C). In addition, sample 1C was an adhesive composition that did not contain silica filler (C) and had a cured product with a relative dielectric constant of 2.3 (Dk) and a dielectric dissipation factor of 0.0017 (Df).

In addition, although the adhesive composition of sample 2C contains silica filler, the silanol group concentration of the silica filler exceeds 0.5 mmol/g. As a result, silica filler aggregates were generated in the adhesive composition of sample 2C within a short period of time, and the dispersibility of the silica filler was poor. This also prevented a homogeneous coating from being obtained, and the dielectric properties of the cured product of the adhesive composition could not be measured.

In contrast to these, in samples 1 to 8, the adhesive composition contains a modified polyolefin resin (A), an epoxy resin (B), and a silica filler (C) with a silanol group concentration of 0.5 mmol/g or less. As a result, samples 1 to 8 were able to improve the dispersibility of the silica filler without adversely affecting the dielectric properties of the cured product of the adhesive composition or the adhesive layer after the adhesive composition has been cured. Furthermore, the addition of the silica filler was able to reduce range flow.

Furthermore, Samples 1 to 8 show that by using a silica filler with a moisture content of 0.1% by mass or less, it is possible to reliably improve the dispersibility of the silica filler without adversely affecting the dielectric properties of the cured product of the adhesive composition and the adhesive layer after the adhesive composition has been cured. In particular, when comparing Samples 1 to 7 with Sample 8, it was confirmed that by using a silica filler with a moisture content of less than 0.08% by mass, it is easier to improve the dispersibility of the silica filler.

This disclosure is not limited to the above-described embodiments and examples, and various modifications are possible without departing from the spirit of the disclosure. Furthermore, the configurations shown in the above-described embodiments and examples can be combined in any manner.

Claims

The composition contains a modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group, an epoxy resin (B), and a silica filler (C),
The silanol group concentration of the silica filler (C) is 0.5 mmol/g or less.
Adhesive composition.
The water content of the silica filler (C) is 0.1 mass% or less.
The adhesive composition of claim 1.
The BET specific surface area of the silica filler (C) is 1 m 2 /g or more and 10 m 2 /g or less.
The adhesive composition of claim 1.
The content of the silica filler (C) is 10 parts by mass or more and 90 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A).
The adhesive composition of claim 1.
The modified polyolefin resin (A) is an acid-modified polyolefin resin.
The adhesive composition of claim 1.
The modified polyolefin resin (A) is a resin obtained by graft-modifying an unmodified polyolefin resin with a modifying agent containing an α,β-unsaturated carboxylic acid or a derivative thereof.
The adhesive composition of claim 1.
The epoxy resin (B) is a polyfunctional epoxy resin having an alicyclic skeleton.
The adhesive composition of claim 1.
the content of the modified polyolefin resin (A) is 50 parts by mass or more per 100 parts by mass of the solid content of the adhesive composition;
The content of the epoxy resin (B) is 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A).
The adhesive composition of claim 1.
a cured product of the adhesive composition has a relative dielectric constant of 2.5 or less and a dielectric dissipation factor of 0.01 or less, measured at a frequency of 10 GHz;
The adhesive composition of claim 1.
A laminate with an adhesive layer comprising an adhesive layer made of the adhesive composition according to any one of claims 1 to 9 and a substrate film in contact with at least one surface of the adhesive layer.
A flexible copper-clad laminate comprising the adhesive layer of the laminate according to claim 10, the base film being provided on one side of the adhesive layer, and copper foil being provided on the other side of the adhesive layer.
A flexible flat cable comprising the base film on one side of the adhesive layer in the laminate with adhesive layer described in claim 10, and copper wiring on the other side of the adhesive layer.