JP2024093529A - Adhesive composition, laminate with adhesive layer, flexible copper-clad laminate, and flexible flat cable - Google Patents

Abstract

To provide an adhesive composition which can improve adhesive strength to a fluorine-based base material without adversely affecting dielectric characteristics of a cured product of the adhesive composition, a laminate with an adhesive layer using the same, and a flexible copper-clad laminate and a flexible flat cable using the same.SOLUTION: An adhesive composition contains a modified-polyolefin-based resin (A) having a reactive functional group reacting with an epoxy group, an epoxy resin (B) and an unmodified polyolefin-based resin (C) including an ethylene-propylene copolymer unit or an ethylene-butene copolymer unit, and is used for a fluorine-based base material. A laminate with an adhesive layer includes a fluorine-based base material film on at least one surface of an adhesive layer composed of the adhesive composition. The flexible copper-clad laminate or the flexible flat cable has a fluorine-based base material film on one surface of the adhesive layer in the laminate with the adhesive layer, and a copper foil or a copper wire on the other surface of the adhesive layer.SELECTED DRAWING: None

Description

The present invention 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 invention 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 applications 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, and polyimide resin is widely used as the material for the base film. Then, for example, a flexible printed wiring board is manufactured by attaching the coverlay film via the adhesive layer to the surface having the wiring portion 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.

A known type of printed wiring board is a build-up type multilayer printed wiring board 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 widely epoxy-based adhesive compositions that contain an epoxy resin and a thermoplastic resin that is reactive with this epoxy resin.

For example, Patent Document 1 discloses an adhesive composition containing as essential components an acid-modified polyolefin resin (A) and an epoxy resin-based compound (B) having two or more epoxy groups in one molecule and ten or more hydroxyl groups in one molecule.

JP 2013-91702 A

In recent years, the demand for mobile communication devices such as mobile phones and information device terminals has been expanding rapidly, and signals are becoming increasingly higher in frequency due to the need to process large amounts of data at high speed. 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.

In addition, in the past, polyimide film base films have been widely used in the above-mentioned FPC-related products, but as the frequencies of the above-mentioned signals become higher, fluorine-based base films such as polytetrafluoroethylene base films, which have good dielectric properties, are increasingly being used.

However, even if the cured product of conventional adhesive compositions exhibits good dielectric properties in the high frequency range, it is difficult to improve the adhesive strength to fluorine-based substrates, for which demand is expected to increase in the future.

The present invention was made in consideration of these problems, and aims to provide an adhesive composition that can improve the adhesive strength to fluorine-based substrates without adversely affecting the dielectric properties of the cured product of the adhesive composition, a laminate with an adhesive layer using the same, and a flexible copper-clad laminate or flexible flat cable using the same.

The adhesive composition, the laminate with an adhesive layer, the flexible copper-clad laminate, and the flexible flat cable according to the present invention are as follows:

[1]
A modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group;
An epoxy resin (B);
and (C) an unmodified polyolefin resin containing ethylene-propylene copolymer units or ethylene-butene copolymer units,
An adhesive composition for use with fluorine-based substrates.
[2]
The content of the unmodified polyolefin resin (C) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A);
The adhesive composition according to the above [1].
[3]
The weight average molecular weight Mw of the unmodified polyolefin resin (C) is 5,000 or more and 200,000 or less.
The adhesive composition according to the above [1] or [2].
[4]
The unmodified polyolefin resin (C) contains 40% by mass or more and 60% by mass or less of ethylene units and 1% by mass or more and 15% by mass or less of diene units.
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 the above item [1] [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]
When a polytetrafluoroethylene substrate and a copper foil are bonded using the adhesive composition, the T-peel adhesion strength between the polytetrafluoroethylene substrate and the copper foil measured in accordance with JIS K6854-3 at a tensile speed of 50 mm/min and a test temperature of 23°C is 1.3 N/cm or more.
The adhesive composition according to any one of the above [1] to [9].
[11]
A laminate with an adhesive layer, comprising an adhesive layer made of the adhesive composition according to any one of [1] to [10] above, and a fluorine-based substrate film in contact with at least one surface of the adhesive layer.
[12]
A flexible copper-clad laminate comprising the fluorine-based substrate film on one side of the adhesive layer in the laminate with an adhesive layer according to [11] above, and a copper foil on the other side of the adhesive layer.
[13]
A flexible flat cable comprising the fluorine-based substrate film on one side of the adhesive layer in the laminate with an adhesive layer according to [11] 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 adhesive strength to a fluorine-based substrate film 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, the laminate with the adhesive layer can improve the adhesive strength to the fluorine-based substrate film without adversely affecting the dielectric properties of the adhesive layer after the adhesive composition is cured.

The flexible copper-clad laminate has the above-mentioned configuration. Therefore, the flexible copper-clad laminate can improve the adhesive strength to the fluorine-based substrate film without adversely affecting the dielectric properties of the adhesive layer after the adhesive composition in the laminate with the adhesive layer is cured.

The flexible flat cable has the above-mentioned configuration. Therefore, the flexible flat cable can improve the adhesive strength to the fluorine-based substrate film without adversely affecting the dielectric properties of the adhesive layer after the adhesive composition in the laminate with the adhesive layer is cured.

One embodiment of the present invention will be described below, but the present invention is not limited to this.

1. Adhesive composition 1.1 Use of adhesive composition The adhesive composition of this embodiment is used for a fluorine-based substrate. That is, the adhesive composition of this embodiment is an adhesive composition for a fluorine-based substrate. Examples of the fluorine-based substrate include a fluorine resin substrate made of a fluorine resin, and a substrate made of a resin other than a fluorine resin and coated with a fluorine resin on the surface thereof. Specific examples of the shape of the substrate include a film, a sheet, and a plate. The shape of the substrate is not particularly limited and can be appropriately selected as desired.

Fluorine resin is a resin containing fluorine atoms. Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), and fluorine-containing polyimide. As the fluorine-based substrate, a polytetrafluoroethylene substrate and a tetrafluoroethylene-perfluoroalkylvinylether copolymer substrate are preferred from the viewpoint of dielectric properties, etc. The fluorine-based substrate may contain inorganic fillers, etc.

Examples of resins that are not fluororesins and can be used as the substrate include polyimide, polyether ether ketone, polyphenylene sulfide, aramid, polyethylene naphthalate, liquid crystal polymer, etc. As resins that are not fluororesins, polyimide, polyethylene naphthalate, and liquid crystal polymer are preferred from the viewpoints of adhesion and electrical properties, etc.

1.2 Composition of the 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 an unmodified polyolefin resin (C) containing ethylene-propylene copolymer units or ethylene-butene copolymer units. The composition of the adhesive composition will be specifically described below.

1.2.1 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 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 an epoxy resin (B). The unmodified polyolefin resin described in the description of the modified polyolefin resin (A) may be different from or the same as the unmodified polyolefin resin (C) described in detail later.

Examples of 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 carboxyl 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 carboxyl groups and amino groups, and more preferably carboxyl 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 using 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 modification assistant for improving the graft efficiency by a modifying agent such as α,β-unsaturated carboxylic acid, a stabilizer for adjusting the resin stability, and the like can 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, 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 in 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 an ethylene-propylene-butene copolymer. From the viewpoint of obtaining particularly excellent adhesiveness, it is preferable to use an unmodified polypropylene resin having a propylene unit content of 50% by mass or more and 98% by mass or less. When the propylene unit content 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 preferable, and itaconic anhydride and maleic anhydride are particularly preferable 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 the solubility in the solvent, and further improve the adhesiveness. 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 and 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, more preferably 0.2% by mass or more and 18% by mass or less, based on 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 or the like. When the graft mass is 20% by mass or less, sufficient adhesiveness to adherends made of resins or 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-based resin (A) can be determined by Fourier transform infrared spectroscopy.

The radical initiator used in the production of the 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 the content of modified polyolefin resin (A) of 50 parts by mass or more, it is possible to easily develop good adhesive properties. In addition, 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.

1.2.2 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 carboxyl groups in the modified polyolefin resin (A) to impart adhesion to adherends and heat resistance to the cured product of the adhesive.

Examples of epoxy resins (B) include 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, and 1,4-butanediol diglycidyl ether. Examples of epoxy resins that can be used include, but are not limited to, glycidyl ether-based epoxy resins such as diol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenyl glycidyl ether ethane, triphenyl glycidyl 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, for example, 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. In addition, as the epoxy resin (B), a polyfunctional epoxy resin having an alicyclic skeleton is preferred, and an epoxy resin having a dicyclopentadiene skeleton is more preferred, since an adhesive composition with excellent dielectric properties can be obtained.

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. In addition, when an epoxy resin having 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.

1.2.3 Unmodified polyolefin resin (C)
The unmodified polyolefin resin (C) is an important component for realizing the effect of improving the adhesive strength to a fluorine-based substrate by using it together with the modified polyolefin resin (A) and the epoxy resin (B). The adhesive composition of the present embodiment can realize the adhesive strength to a fluorine-based substrate, which has been difficult to improve by other methods, by the simple method of adding the unmodified polyolefin resin (C).

The unmodified polyolefin resin (C) contains ethylene-propylene copolymer units or ethylene-butene copolymer units. In other words, the unmodified polyolefin resin (C) can be said to be an unmodified polyolefin resin that contains ethylene-propylene copolymer units or ethylene-butene copolymer units.

The unmodified polyolefin resin (C) may contain both ethylene-propylene copolymer units and ethylene-butene copolymer units. The unmodified polyolefin resin (C) may further contain diene units, styrene units, etc., in addition to the ethylene-propylene copolymer units or ethylene-butene copolymer units. Specific examples of diene units include 5-ethylidene-2-norbornene, vinylidene norbornene, dicyclopentadiene, and 1,4-hexadiene.

Specific examples of the unmodified polyolefin resin (C) include ethylene-α-olefin copolymers such as ethylene-propylene terpolymers (EPDM, EPT), ethylene-propylene copolymers (EPM), ethylene-butene copolymers, ethylene-propylene-butene copolymers, ethylene-1-hexene copolymers, and ethylene-1-octene copolymers; and styrene elastomers such as styrene-ethylene-butylene-styrene block copolymers (SEBS), styrene-ethylene-propylene-styrene block copolymers (SEPS), styrene-ethylene-butene-styrene-styrene block copolymers (SEBSS), styrene-isobutylene-styrene block copolymers (SIBS), and styrene-isoprene-styrene block copolymers (SIS). These unmodified polyolefin resins (C) may be used alone or in combination of two or more. Of these, ethylene-propylene terpolymers are preferred from the viewpoints of their large effect of improving the adhesive strength to fluorine-based substrates and their high solubility in solvents.

The unmodified polyolefin resin (C) preferably contains 40% by mass or more and 60% by mass or less of ethylene units and 1% by mass or more and 15% by mass or less of diene units. The ethylene unit content is more preferably 45% by mass or more and 55% by mass or less. The diene unit content is more preferably 1.5% by mass or more and 12% by mass or less. The ethylene unit and diene unit contents in the unmodified polyolefin resin (C) can be measured by nuclear magnetic resonance spectroscopy (NMR).

If the content of ethylene units and diene units in the unmodified polyolefin resin (C) is within the above range, the solubility in the solvent is good due to the moderate content of ethylene units and diene units, and the adhesive composition can be easily prepared. In addition, if the content of ethylene units in the unmodified polyolefin resin (C) is within the above range, the mechanical strength of the cured product of the adhesive composition is easily ensured. If the content of ethylene units in the unmodified polyolefin resin (C) is high or the content of diene units is low, the solubility in the solvent tends to decrease. In addition, if the content of ethylene units in the unmodified polyolefin resin (C) is low, the mechanical strength of the cured product of the adhesive composition tends to decrease.

The weight average molecular weight Mw of the unmodified polyolefin resin (C) is preferably 5,000 or more and 200,000 or less, more preferably 5,000 or more and 180,000 or less, and even more preferably 5,000 or more and 150,000 or less. The weight average molecular weight Mw is the value calculated by converting the molecular weight measured by gel permeation chromatography (hereinafter also referred to as "GPC") into polystyrene.

If the weight average molecular weight Mw of the unmodified polyolefin resin (C) is within the above range, the adhesive composition has a suitable fluidity, resulting in good dimensional stability during thermocompression bonding, and has good compatibility with the modified polyolefin resin (A), making it easier to suppress liquid separation of the adhesive composition. If the weight average molecular weight Mw is small, the adhesive composition has an increased fluidity and a tendency for dimensional stability during thermocompression bonding to decrease. If the weight average molecular weight Mw is large, the compatibility with the modified polyolefin resin (A) decreases, resulting in a tendency for liquid separation of the adhesive composition to occur.

The Mooney viscosity of the unmodified polyolefin resin (C), measured at 100°C in accordance with JIS K6300-1:2000, is preferably 35 or less, and more preferably 20 or less, from the viewpoint of solubility in solvents, etc.

The content of unmodified polyolefin resin (C) is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 30 parts by mass or less, and even more preferably 5 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of modified polyolefin resin (A).

If the content of unmodified polyolefin resin (C) is within the above range, the compatibility with modified polyolefin resin (A) is good, and liquid separation of the adhesive composition is easily suppressed. If the content of unmodified polyolefin resin (C) is high, the compatibility with modified polyolefin resin (A) decreases, and liquid separation of the adhesive composition tends to occur.

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

(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, and hydrated glass. 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 curing 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' -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). When 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, silica, 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 unmodified polyolefin resin (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 the solvent 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 unmodified polyolefin resin (C) are dissolved or dispersed in the solvent, application to the fluorine-based 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.

Among the above-mentioned solvents, the solvent used in the adhesive composition of this embodiment preferably contains an alicyclic hydrocarbon solvent, such as methylcyclohexane and/or cyclohexane, and an alcohol solvent. In this embodiment, the content of the alicyclic hydrocarbon per 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.

The solvent used in the adhesive composition of this embodiment preferably contains toluene among the above-mentioned solvents. 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 solid content is preferably in the range of 5% to 50% by mass, more preferably 10% to 40% by mass. When the solid content is 80% by mass or less, the viscosity of the solution is appropriate and it is easy to apply uniformly.

1.3 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 suitably used 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.

The dielectric constant (Dk, εr) and dielectric loss tangent (Df, tan δ) of the cured product of the adhesive composition measured at a frequency of 10 GHz are parameters that are better the lower, so there are no particular limitations on the lower limit values. The method for measuring the dielectric constant and dielectric loss tangent will be described in detail in the examples below.

1.4 T-peel adhesion strength of adhesive composition When the adhesive composition of the present embodiment is used to bond a polytetrafluoroethylene substrate and a copper foil, the T-peel adhesion strength between the polytetrafluoroethylene substrate and the copper foil, measured in accordance with JIS K6854-3 at a tensile speed of 50 mm/min and a test temperature of 23° C., is preferably 1.3 N/cm or more. The T-peel adhesion strength is preferably 1.5 N/cm or more, more preferably 1.8 N/cm or more, and even more preferably 2.0 N/cm or more.

When the adhesive composition of this embodiment is used to bond a polytetrafluoroethylene substrate to a copper foil, the T-peel adhesive strength between the polytetrafluoroethylene substrate and the copper foil, measured in accordance with JIS K6854-3 at a tensile speed of 50 mm/min and a test temperature of 23°C, is preferably 30 N/cm or less. The method for measuring the T-peel adhesive strength of the adhesive composition will be described in detail in the Examples below. In the above, a polytetrafluoroethylene substrate is used as the fluorine-based substrate to be bonded to the copper foil. However, in the field of adhesive compositions, a polytetrafluoroethylene substrate, which is usually considered difficult to bond due to peeling, is selected as a representative fluorine-based substrate and used as a standard. The fluorine-based substrate for which the adhesive composition of this embodiment is used is not limited to a polytetrafluoroethylene substrate.

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.

A fluorine-based substrate film is used as the substrate film of the laminate with an adhesive layer. The fluorine-based substrate that constitutes the fluorine-based substrate film is as described above in "1. Adhesive composition," so a detailed explanation is omitted here.

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 fluorine-based substrate film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer to produce a laminate with an adhesive layer having a B-stage adhesive layer.

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 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 fluorine-based substrate film, but the fluorine-based substrate film functions as a release film. The bonding sheet may also have an adhesive layer between two release films. In this case, at least one of the release films needs to be a fluorine-based substrate film. The release film is peeled off when the bonding sheet is used.

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 fluorine-based substrate film that functions as a release film, and then dry it in the same manner as in the case of the coverlay film.

In order to fully exert adhesive strength, the thickness of the adhesive layer can be preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less, and even more preferably 10 μm or more and 50 μm or less. In addition, from the viewpoint of thinning the laminate with the adhesive layer, the thickness of the fluorine-based substrate film can be preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and even more preferably 5 μm or more and 30 μm or less.

3. Flexible copper-clad laminate The flexible copper-clad laminate according to this embodiment has a fluorine-based substrate 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 fluorine-based substrate 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 fluorine-based substrate 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 fluorine-based substrate 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.

For example, a method for manufacturing a flexible copper-clad laminate includes bringing the adhesive layer of the above-mentioned adhesive layer-attached 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 fluorine-based substrate 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 a fluorine-based substrate film and a copper wiring using the laminate with the adhesive layer. That is, the flexible flat cable can be configured by laminating a fluorine-based substrate film, an adhesive layer, and a copper wiring in this order. The adhesive layer and the copper wiring may be formed on both sides of the fluorine-based substrate film. The above-mentioned adhesive composition has excellent adhesion to an article containing copper, and therefore the flexible flat cable has excellent stability as an integrated product.

One method for manufacturing a flexible flat cable is, for example, to bring the adhesive layer of the laminate with the adhesive layer into contact with copper wiring, perform thermal lamination at a temperature of, for example, 80°C to 150°C, and then harden 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 desired.

The present invention will be described in more detail with reference to examples, but the present invention 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
GPC measurement was carried out under the following conditions to determine the weight average molecular weight Mw of the modified polyolefin resin (A) and the unmodified polyolefin resin (C).
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) 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. Next, the adhesive layer was 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 using a network analyzer 85071E-300 (manufactured by Agilent) by a split post dielectric resonator method (SPDR method) at a temperature of 23° C. and a frequency of 10 GHz. Of the relative dielectric constant and the dielectric loss tangent, a dielectric loss tangent of 0.01 or less, which tends to be considered important as a low dielectric property, is used as the criterion for "not adversely affecting the dielectric properties."

(4) Peel Adhesion Strength A release PET film with 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, a rolled copper foil with a thickness of 12 μm was superimposed 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. and a pressure of 0.5 MPa. Next, the release PET film was peeled off from the adhesive layer, and a fluorine-based substrate was superimposed 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. and a pressure of 0.5 MPa. Note that two types of fluorine-based substrates were used: a polytetrafluoroethylene (PTFE) substrate and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).

The laminated test piece was heated and pressed at a temperature of 180°C and a pressure of 3 MPa for 60 minutes to obtain an adhesive test piece. This adhesive test piece was cut to a predetermined size to obtain a sample for a tensile test. Using this sample for a tensile test, a tensile test was performed in accordance with JIS K6854-3 at a tensile speed of 50 mm/min and a test temperature of 23°C by T-peel, and the T-peel adhesive strength was calculated. The sample for a tensile test, which has a layering order of polytetrafluoroethylene substrate/adhesive layer of adhesive composition/copper foil, is indicated as "PTFE/Ad/Cu" in Table 1. Similarly, the sample for a tensile test, which has a layering order of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer substrate/adhesive layer of adhesive composition/copper foil, is indicated as "PFA/Ad/Cu" in Table 1.

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, the mixture was degassed 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) Unmodified polyolefin resin (C)
Ethylene-propylene terpolymer (c1) (Mitsui Chemicals, Inc., "EPT X-4010M") [weight average molecular weight Mw = 113,000, ethylene unit: 54 mass%, diene unit: 7.6 mass%, Mooney viscosity (1+4@100°C) = 8]
Ethylene-propylene terpolymer (c2) (Mitsui Chemicals, Inc., "EPT PX-009M") [weight average molecular weight Mw = 122,000, ethylene unit: 60 mass%, diene unit: 1.5 mass%, Mooney viscosity (1+4@100°C) = 10]
Ethylene-propylene terpolymer (c3) (manufactured by LION ELASTOMERS, "TRILENE T65") [weight average molecular weight Mw = 7,000, ethylene unit: 45 mass%, diene unit: 10.5 mass%]
SEBS (c4) (manufactured by Asahi Kasei Chemicals Corporation, "Tuftec H1043") [weight average molecular weight Mw = 141,000, ethylene unit: 29% by mass]
SEBS (c5) (Kraton Polymer Japan, "MD1623") [weight average molecular weight Mw = 22,000, ethylene unit: 36% by mass]

(4) Others - Curing accelerator (imidazole-based curing accelerator) (manufactured by Shikoku Kasei Corporation, "Curesol C11Z")
Solvent (mixture 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 compositions The above-mentioned raw materials were added to a 1000 ml flask equipped with a stirrer in the prescribed ratios shown in Table 1, and a solvent was added and the mixture was stirred at room temperature (25° C.) for 6 hours to dissolve, thereby preparing and evaluating each adhesive composition. The results are shown in Table 1.

4. Production and evaluation of laminates with adhesive layers Using the above adhesive compositions, laminates with adhesive layers were produced and evaluated as described in the explanations for each of the above evaluation methods. The results are shown in Table 1.

From Table 1, the following can be seen. In other words, the adhesive composition of sample 1C contains modified polyolefin resin (A) and epoxy resin (B), but does not contain unmodified polyolefin resin (C) containing ethylene-propylene copolymer units or ethylene-butene copolymer units. Therefore, sample 1C was unable to improve the adhesive strength to the fluorine-based substrate film.

In contrast, in Samples 1 to 13, the adhesive composition contains a modified polyolefin resin (A) and an epoxy resin (B), and further contains an unmodified polyolefin resin (C) containing ethylene-propylene copolymer units or ethylene-butene copolymer units. Therefore, Samples 1 to 13 were able to improve the adhesive strength to the fluorine-based substrate film without adversely affecting the dielectric properties of the cured product of the adhesive composition or the adhesive layer after the adhesive composition is cured.

In addition, when comparing samples 1 to 13, samples 1 to 11, which used ethylene-propylene terpolymer as the unmodified polyolefin resin (C), were able to improve the adhesive strength to the fluorine-based substrate film more than samples 12 and 13, which used SEBS, a styrene-based elastomer, as the unmodified polyolefin resin (C). This is thought to be because the styrene-based elastomer contains hard styrene units in the hard segment, which reduces the adhesiveness to the fluorine-based substrate film.

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

Claims (13)

A modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group;
An epoxy resin (B);
and (C) an unmodified polyolefin resin containing ethylene-propylene copolymer units or ethylene-butene copolymer units,
An adhesive composition for use with fluorine-based substrates. The content of the unmodified polyolefin resin (C) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A);
The adhesive composition of claim 1. The weight average molecular weight Mw of the unmodified polyolefin resin (C) is 5,000 or more and 200,000 or less.
The adhesive composition of claim 1. The unmodified polyolefin resin (C) contains 40% by mass or more and 60% by mass or less of ethylene units and 1% by mass or more and 15% by mass or less of diene units.
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. When a polytetrafluoroethylene substrate and a copper foil are bonded using the adhesive composition, the T-peel adhesion strength between the polytetrafluoroethylene substrate and the copper foil measured in accordance with JIS K6854-3 at a tensile speed of 50 mm/min and a test temperature of 23°C is 1.3 N/cm or more.
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 10 and a fluorine-based substrate film in contact with at least one surface of the adhesive layer. A flexible copper-clad laminate comprising the fluorine-based substrate film on one side of the adhesive layer in the laminate with adhesive layer according to claim 11, and copper foil on the other side of the adhesive layer. A flexible flat cable comprising the fluorine-based substrate film on one side of the adhesive layer in the laminate with adhesive layer according to claim 11, and copper wiring on the other side of the adhesive layer.