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

Abstract

To provide an adhesive composition capable of improving dispersibility of a silica filler without adversely affecting dielectric characteristics of a cured product of the adhesive composition, a laminate with an adhesive layer using the same, a flexible copper-clad laminate using the same, and a flexible flat cable.SOLUTION: The adhesive composition contains modified polyolefin resins (A) having reactive functional groups that react with epoxy groups, epoxy resins (B), and silica fillers (C), wherein the silica fillers (C) have a silanol group concentration of 0. 5mmol / g or less. The laminate with the adhesive layer has a substrate film on at least one surface of the adhesive layer composed of the adhesive composition. The flexible copper-clad laminate or the flexible flat cable includes a substrate film on one surface of the adhesive layer in the laminate having an adhesive layer, and includes copper foil or copper wiring on the other surface of the adhesive layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] 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 producing 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. [Background technology]

[0002] Flexible printed circuit boards (hereinafter referred to as "FPCs") are capable of three-dimensional, high-density mounting even in limited spaces, and their applications are expanding. In recent years, as electronic devices have become smaller and lighter, FPC-related products have become more diverse and demand for them has increased.

[0003] Examples of such FPC-related products include 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 in the production of these products.

[0004] Furthermore, 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 to the surface having the wiring portion via the adhesive layer using a heat press or the like. In this case, the adhesive layer of the coverlay film needs to have strong adhesion to both the wiring portion and the base film.

[0005] Also known as printed wiring boards are multilayer printed wiring boards that use a build-up method, in which conductor layers and organic insulating layers are alternately laminated on the surface of a substrate. When manufacturing such multilayer printed wiring boards, an insulating adhesive layer-forming material called a "bonding sheet" is used to bond the conductor layers and organic insulating layers. The insulating adhesive layer must be able to be embedded in the wiring portion and must have strong adhesion to both the constituent materials of the conductor portion (e.g., copper) that form the circuit and the organic insulating layer (e.g., polyimide resin).

[0006] As adhesive compositions used in such FPC-related products, epoxy-based adhesive compositions containing an epoxy resin and a thermoplastic resin reactive with this epoxy resin are widely used.

[0007] For example, Patent Document 1 discloses an adhesive composition containing an olefin resin having at least one reactive functional group, an epoxy resin, and an inorganic filler such as silica for controlling thixotropy. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2018-513891 Summary of the Invention [Problem to be solved by the invention]

[0009] In recent years, demand for mobile communication devices such as mobile phones and information terminals has been expanding rapidly, and the need to process large amounts of data at high speed has led to an increase in signal frequencies. 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 dissipation factor) in the high-frequency range for the cured product after the adhesive composition has hardened.

[0010] However, when a silica filler is added to adjust the physical properties of an adhesive composition, the dielectric properties of the cured product may be impaired. Furthermore, 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 uniform adhesive layer thin film due to the silica filler aggregates.

[0011] The present invention has been made in view of the above problems, and aims to provide an adhesive composition that can improve the dispersibility of silica filler without adversely affecting the dielectric properties of a cured product of the adhesive composition, a laminate with an adhesive layer that uses the same, and a flexible copper-clad laminate or a flexible flat cable that uses the same. [Means for solving the problem]

[0012] 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.

[0013] [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% by mass or less. The adhesive composition according to [1] above. [3] The BET specific surface area of ​​the silica filler (C) is 1m 2 / g or more 10m 2 / g or less, The adhesive composition according to [1] or [2] above. [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 [1] to [3] above. [5] The modified polyolefin resin (A) is an acid-modified polyolefin resin. The adhesive composition according to any one of [1] to [4] above. [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 [1] to [5] above. [7] The epoxy resin (B) is a polyfunctional epoxy resin having an alicyclic skeleton. The adhesive composition according to any one of [1] to [6] above. [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 [1] to [7] above. [9] a cured product of the adhesive composition has a relative dielectric constant of 2.5 or less and a dielectric loss tangent of 0.01 or less, measured at a frequency of 10 GHz; The adhesive composition according to any one of [1] to [8] above.

[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 substrate film in contact with at least one side of the adhesive layer.

[11] A flexible copper-clad laminate comprising the adhesive layer-attached laminate according to

[10] above, 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 substrate film on one side of the adhesive layer in the laminate with adhesive layer described in

[10] above, and copper wiring on the other side of the adhesive layer. [Effects of the Invention]

[0014] The adhesive composition has the above-described configuration, and therefore can improve the dispersibility of the silica filler without adversely affecting the dielectric properties of a cured product of the adhesive composition.

[0015] The laminate with an adhesive layer has the above-mentioned configuration. Therefore, even if the adhesive composition constituting the adhesive layer of the laminate with an adhesive layer contains a silica filler, the dielectric properties of the adhesive layer after the adhesive composition is cured are not adversely affected. Furthermore, in the laminate with an 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 uniform thin film.

[0016] The flexible copper-clad laminate has the above-mentioned configuration. Therefore, even if the adhesive composition constituting the adhesive layer in the adhesive layer-attached laminate contains a 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 silica filler in the adhesive composition constituting the adhesive layer in the adhesive layer-attached laminate has good dispersibility, silica filler agglomerates are suppressed, and the adhesive layer can be made into a smooth, uniform thin film.

[0017] The flexible flat cable has the above-described configuration. Therefore, even if the adhesive composition constituting the adhesive layer in the adhesive layer-attached laminate contains a 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 adhesive layer-attached laminate is well dispersed, the flexible flat cable suppresses the formation of silica filler aggregates, allowing the adhesive layer to be a smooth, uniform thin film. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will be described below, but the present invention is not limited to this embodiment.

[0019] 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 silica filler (C) has a silanol group concentration of 0.5 mmol / g or less. The composition of the adhesive composition will be specifically described below.

[0020] 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 into which a reactive functional group that reacts with an epoxy group has been introduced, or it can be said to be a resin obtained by modifying 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 obtained by modifying an unmodified polyolefin resin so as to have reactivity with the epoxy resin (B).

[0021] Examples of reactive functional groups that react with epoxy groups include groups having active hydrogen and active ester groups, 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 viewpoint of reactivity, the reactive functional group that reacts with epoxy groups is preferably a carboxyl group or an amino group, and more preferably a carboxyl group.

[0022] The modified polyolefin resin (A) is preferably an acid-modified polyolefin resin, and specifically, it can be a resin having a portion derived from an unmodified polyolefin resin and a graft portion derived from a modifying agent, and is preferably a resin in which an unmodified polyolefin resin has been graft-modified with a modifying agent containing an α,β-unsaturated carboxylic acid or a derivative thereof.

[0023] The modified polyolefin resin (A) can be produced by graft modification (graft polymerization) using known methods, 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 modifier and radical initiator are added, and a melt method in which the unmodified polyolefin resin, modifier, and radical initiator are melt-kneaded using a Banbury mixer, kneader, extruder, or the like. The unmodified polyolefin resin, modifier, and radical initiator may be added to the reaction system either all at once or sequentially. When producing the modified polyolefin resin (A), a modification aid for improving the grafting efficiency of the modifier, such as an α,β-unsaturated carboxylic acid, or a stabilizer for adjusting the resin stability may also be used.

[0024] The unmodified polyolefin resin used in producing the 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.

[0025] The unmodified polyolefin resin used in producing the modified polyolefin resin (A) is preferably an unmodified polypropylene resin. In this case, the modified polyolefin resin (A) may be a resin having a portion derived from the unmodified polypropylene resin and a graft portion derived from a modifier. Preferably, the unmodified polypropylene resin is graft-modified with a modifier containing an α,β-unsaturated carboxylic acid or its derivative. The unmodified polypropylene resin is not particularly limited as long as it has structural units derived from propylene and is not modified with a modifier such as an α,β-unsaturated carboxylic acid or its derivative. Preferred examples of the unmodified polypropylene resin include copolymers of propylene and an olefin having 2 to 20 carbon atoms, such as ethylene, butene, pentene, hexene, heptene, octene, and 4-methyl-1-pentene. The unmodified polypropylene resin is more preferably a copolymer of propylene and an olefin having 2 to 6 carbon atoms.

[0026] The content ratios of structural units in the unmodified polyolefin resin and the unmodified polypropylene resin can be selected arbitrarily. From the viewpoint of advantageous adhesion to poorly adhesive substrates, the modified polyolefin resin (A) is preferably a modified resin of at least one unmodified polypropylene resin selected from the group consisting of ethylene-propylene, propylene-butene, and an ethylene-propylene-butene copolymer. From the viewpoint of obtaining particularly excellent adhesive properties, 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 bonded joint after bonding two members. The molecular weights of the unmodified polyolefin resin and the unmodified polypropylene resin are not particularly limited.

[0027] The modifier may include an α,β-unsaturated carboxylic acid and its derivative. Examples of the α,β-unsaturated carboxylic acid include maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, aconitic acid, and norbornene dicarboxylic acid. Derivatives of unsaturated carboxylic acids include acid anhydrides, acid halides, amides, imides, and esters. Preferred modifiers include itaconic anhydride, maleic anhydride, aconitic anhydride, and citraconic anhydride, with itaconic anhydride and maleic anhydride being particularly preferred in terms of adhesiveness. When a modifier is used, it may be one or more selected from α,β-unsaturated carboxylic acids and their derivatives. Examples of the modifier include 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.

[0028] The modifying agent may contain other compounds (other modifying agents) in addition to the α,β-unsaturated carboxylic acid, etc., depending on the purpose. Examples of the other compounds (other modifying agents) 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=CR 1 COOR 2 (1) (In formula (1), R 1 is a hydrogen atom or a methyl group, and R 2 is a hydrocarbon group.)

[0029] In the formula (1) representing the (meth)acrylic acid ester, R 1 is a hydrogen atom or a methyl group, preferably a methyl group. 2is a hydrocarbon group, preferably an alkyl group having 8 to 18 carbon atoms. Examples of the compound represented by 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, it is preferable to use a modifier further containing a (meth)acrylate ester having an alkyl group having 8 to 18 carbon atoms, as this improves heat-resistant adhesion. In particular, it is preferable to use a modifier containing octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, or stearyl (meth)acrylate.

[0030] 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. The combined use of an α,β-unsaturated carboxylic acid or its derivative with another modifier as the modifier can improve the grafting rate of the modifier, improve solubility in solvents, and further improve adhesiveness. When a modifier other than the (meth)acrylic acid ester represented by formula (1) is used, it is desirable that the amount used does not exceed the total amount of the α,β-unsaturated carboxylic acid and its derivative and the (meth)acrylic acid ester.

[0031] As described above, the modified polyolefin resin (A) may have at least a graft moiety derived from a modifier. Hereinafter, the content of the graft moiety contained in the modified polyolefin resin (hereinafter also referred to as "graft mass") will be described.

[0032] The modified polyolefin resin (A) may have a graft moiety derived from an α,β-unsaturated carboxylic acid or a derivative thereof. In the modified polyolefin resin (A), the graft mass of the graft moiety 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. A graft mass of 0.1% by mass or more provides excellent solubility in solvents and particularly excellent adhesiveness to adherends made of metals and the like. Furthermore, a graft mass of 20% by mass or less provides sufficient adhesiveness to adherends made of resins and the like.

[0033] The graft mass derived from an α,β-unsaturated carboxylic acid or its derivative in the modified polyolefin resin (A) can be determined by alkali titration. However, when the derivative of the 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.

[0034] When the modified polyolefin resin (A) contains a graft moiety derived from a (meth)acrylic acid ester represented by the above formula (1), the graft mass is preferably from 0.1 to 30% by mass, more preferably from 0.3 to 25% by mass, relative to 100% by mass of the modified polyolefin resin (A). When the graft mass is from 0.1 to 30% by mass, the resin has excellent solubility in solvents and excellent compatibility with other resins or elastomers, as described below, when these are contained, thereby further improving adhesion to adherends.

[0035] 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.

[0036] 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 an organic peroxide such as benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, or cumene hydroperoxide.

[0037] Examples of the modifying aid that can be used in producing the modified polyolefin resin (A) include divinylbenzene, hexadiene, dicyclopentadiene, etc. Examples of the stabilizer that can be used include hydroquinone, benzoquinone, nitrosophenylhydroxy compounds, etc.

[0038] The weight-average molecular weight Mw of the modified polyolefin resin (A) is preferably from 30,000 to 250,000, more preferably from 50,000 to 200,000. 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 adherends, and also has excellent solvent resistance at the bonded joint after bonding.

[0039] 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.

[0040] The content of the 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 the modified polyolefin resin (A) be 50 parts by mass or more, it is possible to easily exhibit good adhesive properties. The content of the 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.

[0041] 1.1.2 Epoxy resin (B) Next, we will explain the epoxy resin (B). 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 adhesive.

[0042] Examples of the epoxy resin (B) include bisphenol A type epoxy resins, bisphenol F type epoxy resins, and hydrogenated versions thereof; 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-butanediol 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 diol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether; glycidylamine-based epoxy resins such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane; and linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil. Additionally, 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.

[0043] Examples of the epoxy resin (B) include brominated bisphenol A epoxy resins, phosphorus-containing epoxy resins, dicyclopentadiene skeleton-containing epoxy resins, naphthalene skeleton-containing epoxy resins, anthracene-type epoxy resins, tertiary butylcatechol-type epoxy resins, triphenylmethane-type epoxy resins, tetraphenylethane-type epoxy resins, biphenyl-type epoxy resins, and bisphenol S-type epoxy resins. These epoxy resins (B) may be used alone or in combination of two or more. Among the epoxy resins (B), epoxy resins without a glycidylamino group are preferred because they improve the storage stability of the laminate with the adhesive layer. Furthermore, as the epoxy resin (B), polyfunctional epoxy resins with an alicyclic skeleton are preferred, and epoxy resins with a dicyclopentadiene skeleton are more preferred, since they provide an adhesive composition with excellent dielectric properties.

[0044] The epoxy resin (B) preferably has two or more epoxy groups in one molecule. This is because a crosslinked structure is formed by reaction with the modified polyolefin resin (A), which allows high heat resistance to be achieved. 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, resulting in sufficient heat resistance.

[0045] The content of the 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 the modified polyolefin resin (A). When the content of the epoxy resin (B) is 1 part by mass or more, sufficient adhesiveness is obtained. When the content of the epoxy resin (B) is 20 parts by mass or less, peel strength and dielectric properties are improved.

[0046] 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.

[0047] Silica fillers are useful for adjusting the mechanical properties of adhesive compositions. Specifically, adding silica fillers to adhesive compositions can reduce the flow (resin flow) of the adhesive layer. When dispersing such silica fillers in resin compositions, the interaction between the resin composition and the functional groups on the silica filler surface is usually utilized. When the silica filler has few functional groups on its surface and therefore 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 thinking, the higher the silanol group concentration of the silica filler, the better. However, in reality, the opposite is true. The present inventors have found that when a silica filler is used together with a modified polyolefin resin (A) and an epoxy resin (B), the dispersibility of the silica filler can be improved by controlling the silanol group concentration to a low concentration range of 0.5 mmol / g or less.

[0048] If the silanol group concentration of the silica filler (C) exceeds 0.5 mmol / g, aggregates of the silica filler (C) will form in the adhesive composition within a short period of time, resulting in poor dispersibility of the silica filler (C). This will also make it difficult to obtain a uniform coating film of the adhesive composition, adversely affecting 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 viewpoint of ensuring the dispersibility-improving effect of the silica filler (C), the silanol group concentration of the silica filler (C) is preferably greater 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.

[0049] Specifically, the silica filler (C) can be composed of an aggregate of silica particles having silanol groups on their surfaces (silica powder having silanol groups on their surfaces). The silica filler (C) can be obtained, for example, by surface-treating silica powder with a surface-treating agent capable of introducing silanol groups. Examples of the surface-treating agent include alkoxysilanes such as methyltrimethoxysilane and organosilazanes such as hexamethyldisilazane (HMDS). These can be used alone or in combination of two or more. Furthermore, commercially available silica fillers can be used as the silica filler (C).

[0050] 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 sphere.

[0051] The water 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 setting the water content of the silica filler (C) to 0.1% by mass or less, the dispersibility of the silica filler (C) can be reliably improved without adversely affecting the dielectric properties of the cured product of the adhesive composition and the adhesive layer after curing the adhesive composition. In particular, setting the water content of the silica filler (C) to less than 0.08% by mass makes it easier to further improve the dispersibility of the silica filler. Note that the lower the water content of the silica filler (C), the better the parameter, so the lower limit is not particularly limited. The method for measuring the water content of the silica filler (C) will be described in detail in the Examples below.

[0052] The BET specific surface area of ​​the silica filler (C) is 1m 2 / g or more 10m 2 / g or less, and 2 / g or more 8m 2 / g or less is more preferable, and 2 / g or more 7m 2 / g or less is more preferable. 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.

[0053] 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, relative to 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, the flow (resin flow) of the adhesive layer is easily reduced. When the content of the silica filler (C) is 90 parts by mass or less, the deterioration of the adhesive properties of the adhesive composition is easily suppressed.

[0054] 1.1.4 Other ingredients In addition to the above-described modified polyolefin resin (A), epoxy resin (B), and silica filler (C), the adhesive composition of the present embodiment may contain other thermoplastic resins, tackifiers, flame retardants, curing agents, curing accelerators, coupling agents, heat aging inhibitors, inorganic fillers other than silica fillers, leveling agents, antifoaming agents, pigments, ultraviolet absorbers, and solvents, etc., to the extent that the functionality of the adhesive composition is not affected.

[0055] (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 resins, polypropylene resins, polyvinyl resins, etc. These thermoplastic resins may be used alone or in combination of two or more.

[0056] (tackifier) Examples of the tackifier include coumarone-indene resins, terpene resins, terpene-phenol resins, rosin resins, pt-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, petroleum-based hydrocarbon resins, hydrogenated hydrocarbon resins, turpentine-based resins, etc. These tackifiers may be used alone or in combination of two or more.

[0057] (Flame retardant) 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.

[0058] (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.

[0059] 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, relative to 100 parts by mass of the epoxy resin (B).

[0060] (curing 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 may be a tertiary amine curing accelerator, a tertiary amine salt curing accelerator, or an imidazole curing accelerator.

[0061] Examples of tertiary amine curing accelerators include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, and 1,8-diazabicyclo[5.4.0]undecene.

[0062] Examples of tertiary amine salt curing accelerators include formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, and phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene; and formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, and phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

[0063] 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' 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(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.

[0064] When the adhesive composition of this embodiment contains a curing accelerator, the content of the curing accelerator is preferably 1 part by mass to 15 parts by mass, more preferably 1 part by mass to 10 parts by mass, and even more preferably 2 parts by mass to 5 parts by mass, relative to 100 parts by mass of the epoxy resin (B). When the content of the curing accelerator is within the above range, excellent adhesiveness and heat resistance can be exhibited.

[0065] (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 imidazolesilane; 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.

[0066] (thermal antioxidant) 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 phenolic 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 antioxidants may be used alone or in combination of two or more.

[0067] (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.

[0068] (solvent) The adhesive composition of this embodiment can be produced by mixing a modified polyolefin resin (A), an epoxy resin (B), a silica filler (C), and, if necessary, other components. The mixing method is not particularly limited as long as the adhesive composition is homogeneous. Since the adhesive composition is preferably used in the form of a solution or dispersion, a solvent such as an organic solvent is usually also used.

[0069] 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. When the adhesive composition contains a solvent and is a solution or dispersion (resin varnish) in which the modified polyolefin resin (A), the epoxy resin (B), and the silica filler (C) are dissolved or dispersed in the solvent, coating onto the substrate film and formation of an adhesive layer can be carried out smoothly, and an adhesive layer of the desired thickness can be easily obtained.

[0070] Among the solvents exemplified above, 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.

[0071] Furthermore, 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 ensuring that the content of the alicyclic hydrocarbon and / or the alcohol-based solvent is within the above range, an adhesive composition with excellent storage stability at low temperatures can be obtained.

[0072] Furthermore, among the solvents exemplified above, 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 keeping the toluene content within the above range, the solubility of the epoxy resin (B) and the like in the solvent can be improved.

[0073] When the adhesive composition contains a solvent such as an organic solvent, the solid content is preferably in the range of 5 to 50% by mass, more preferably 10 to 40% by mass, from the viewpoint of workability including the formation of the adhesive layer. When the solid content is 80% by mass or less, the viscosity of the solution is appropriate, making it easy to apply uniformly.

[0074] 1.2 Dielectric properties of the cured adhesive composition The adhesive composition of this embodiment preferably has a dielectric constant (Dk, εr) of 2.5 or less and a dielectric loss tangent (Df, tanδ) of 0.01 or less, measured at a frequency of 10 GHz. The 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.

[0075] 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, which have strict requirements for dielectric properties in response to the increasing speed and frequency of signals in recent years. The dielectric constant and dielectric loss tangent can be adjusted by the type and content of each component in the adhesive composition.

[0076] The adhesive composition of this embodiment preferably has a relative dielectric constant (Dk, εr) of 2.0 or more and a dielectric loss tangent (Df, tanδ) of 0 or more, measured at a frequency of 10 GHz. Methods for measuring the relative dielectric constant and dielectric loss tangent will be described in detail in the examples below.

[0077] 2.Laminate with adhesive layer The laminate with an adhesive layer according to this embodiment includes an adhesive layer made of the adhesive composition described above and a substrate 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 part of the adhesive composition has begun to harden, and refers to a state in which the hardening of the adhesive composition progresses further by heating or the like.

[0078] One embodiment of the adhesive layer-attached laminate is a coverlay film, which is typically a laminate in which an adhesive layer is formed on at least one surface of a substrate film, making it difficult to peel the substrate film and the adhesive layer from each other.

[0079] Examples of the substrate film included in the laminate with an adhesive layer include a polyimide film, a polyether ether ketone film, a polyphenylene sulfide film, an aramid film, a polyethylene naphthalate film, a liquid crystal polymer film, etc. Among these, from the viewpoints of adhesiveness and electrical properties, a polyimide film, a polyethylene naphthalate film, and a liquid crystal polymer film are preferred.

[0080] 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, thereby producing a laminate with an adhesive layer having a B-stage adhesive layer formed thereon.

[0081] The drying temperature when removing the solvent is preferably 40 to 250° C., more preferably 70 to 170° C. Drying can be carried out by passing the laminate coated with the adhesive composition through a furnace that performs hot air drying, far-infrared heating, high-frequency induction heating, or the like.

[0082] If necessary, a release film may be laminated on the surface of the adhesive layer for storage, etc. As the release film, 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 can be used.

[0083] 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 may be the same as those described above.

[0084] A bonding sheet can be produced, for example, by applying a resin varnish containing the adhesive composition and a solvent to the surface of a release film and drying it in the same manner as in the case of the coverlay film.

[0085] The thickness of the adhesive layer can be 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 fully exert adhesive strength. The thickness of the base film can be 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.

[0086] 3. Flexible copper clad laminate The flexible copper-clad laminate according to this embodiment includes a substrate film on one side of the adhesive layer of the above-mentioned adhesive layer-attached laminate, and a copper foil on the other side of the adhesive layer. Specifically, the flexible copper-clad laminate can be configured by bonding a substrate film and a copper foil together using the above-mentioned adhesive layer-attached laminate. That is, the flexible copper-clad laminate can be configured by laminating a 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 substrate film. Since the above-mentioned adhesive composition has excellent adhesion to copper-containing articles, the flexible copper-clad laminate has excellent stability as an integrated product.

[0087] A method for producing a flexible copper-clad laminate includes, for example, bringing the adhesive layer of the above-mentioned adhesive layer-attached laminate into surface contact with a copper foil, performing thermal lamination at a temperature of, for example, 80°C to 150°C, and then curing 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.

[0088] 4. Flexible flat cable The flexible flat cable according to this embodiment includes a substrate film on one side of the adhesive layer of the above-mentioned adhesive layer-attached laminate, and a copper wiring on the other side of the adhesive layer. Specifically, the flexible flat cable can be configured by bonding a substrate film and a copper wiring together using the above-mentioned adhesive layer-attached laminate. That is, the flexible flat cable can be configured by laminating the substrate film, adhesive layer, and copper wiring in this order. The adhesive layer and copper wiring may be formed on both sides of the substrate film. Because the above-mentioned adhesive composition has excellent adhesion to copper-containing articles, the flexible flat cable has excellent stability as an integrated product.

[0089] A method for producing a flexible flat cable includes, for example, contacting the adhesive layer of the adhesive layer-attached laminate 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 appropriately selected as desired. [Example]

[0090] 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 mass unless otherwise specified.

[0091] 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). 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 (2 columns), Two TSKgel SuperHZ2500 (manufactured by Tosoh Corporation) Column temperature: 40℃ Eluent: tetrahydrofuran 0.35 ml / min Detector: RI (differential refractive index detector)

[0092] (2) Acid value 1 g of modified polyolefin resin (A) was dissolved in 30 ml of toluene, and an automatic titrator "AT-510" manufactured by Kyoto Electronics Manufacturing Co., Ltd., connected to the "APB-510-20B" buret, was used. Potentiometric titration was performed using a 0.01 mol / L benzyl alcohol KOH solution as the titration reagent, and the mg of KOH per 1 g of resin was calculated.

[0093] (3) Physical properties of silica filler (C) (3-1) Method for measuring silanol group concentration and moisture 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 5mm, and approximately 0.6mL of carbon tetrachloride was added. After thoroughly stirring the resulting sample, near-infrared measurement was performed under the following conditions. 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: 8000~4000cm -1

[0094] (3-2) Method for measuring the specific surface area of ​​silica filler The specific surface area of ​​the silica filler was measured by the BET adsorption method using nitrogen gas (N2) as the adsorption gas.

[0095] (4) Dielectric properties (relative permittivity and dielectric loss tangent) A 38 μm-thick release PET film was prepared, and one surface was coated with the adhesive composition listed in Table 1. The coated film was then placed in an oven and dried at 90°C for 3 minutes to form a 50 μm-thick coating (adhesive layer), yielding an adhesive layer. 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 x 80 mm) made of the cured adhesive composition. The relative permittivity (Dk, εr) and dielectric dissipation factor (Df, tanδ) were measured using a network analyzer 85071E-300 (Agilent) by the split post dielectric resonator (SPDR) method at a temperature of 23°C and a frequency of 10 GHz. Note that for sample 2C in Table 1, a uniform 50 μm coating was not obtained due to aggregates of the silica filler (c5), so dielectric properties were not measured. Furthermore, the criterion for determining whether a material "does not adversely affect the dielectric properties" is whether the dielectric loss tangent, which tends to be considered important as a low dielectric property among the relative permittivity and the dielectric loss tangent, does not exceed the dielectric loss tangent of sample 1C (composition not including silica filler).

[0096] (5) Dispersibility of silica filler (C) The adhesive composition with the dispersed silica filler was left to stand at room temperature (25°C), and after a specified number of days, the presence or absence of silica filler aggregates was visually confirmed. Even if sedimentation of the silica filler was observed, if the silica filler returned to a uniformly dispersed state by light shaking, it was determined that no silica filler aggregates had occurred.

[0097] The numbers in Table 1 indicate the number of days until silica filler aggregates were observed. For example, a sample marked "2" indicates that silica filler aggregates were observed on the second day. The silica filler dispersibility evaluation test was conducted for a maximum of 7 days, and if no silica filler aggregates were observed during this period, a ">7" was recorded. A "0" indicates that silica filler aggregates were observed immediately after dispersion using the disperser. In Table 1, samples that took 7 days or more until silica filler aggregates appeared were marked "A," indicating excellent silica filler dispersibility. Samples that took 1 day or more but less than 7 days until silica filler aggregates appeared were marked "B," indicating good silica filler dispersibility. Samples that took less than 1 day until silica filler aggregates appeared were marked "C," indicating poor silica filler 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.

[0098] (6) Resin flow A 38 μm-thick release PET film was prepared, and one surface thereof was coated with the adhesive composition listed in Table 1. The coated film was then placed in an oven and dried at 90°C for 3 minutes to obtain a B-stage adhesive layer (25 μm thick). A 12 μm-thick electrolytic copper foil was then placed on the adhesive layer so that it was in surface contact with the surface, and lamination was performed for 30 seconds at a temperature of 120°C, a pressure of 0.5 MPa, and a vacuum. A φ3 mm hole was then drilled in the resulting laminate, and the release PET film was peeled from the adhesive layer. A resin substrate was then placed on top of the foil so that it was in surface contact with the foil, and lamination was performed for 30 seconds at a temperature of 120°C, a pressure of 0.5 MPa, and a vacuum. The laminated test piece was then heated and pressed at a temperature of 180°C and a pressure of 3 MPa for 3 minutes, and the extent of adhesive seepage into the φ3 mm hole was observed under a microscope. This observation was performed three times, and the average of the measured maximum adhesive flow lengths was recorded as the resin flow.

[0099] 2. Raw materials for adhesive compositions 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.

[0100] 100 parts by mass of a propylene-butene random copolymer composed 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 cylinder temperature set to 170°C. The extruder was then degassed under reduced pressure to remove any 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.

[0101] (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")

[0102] (3) Silica filler (C) Silica filler (c1) (Sakai Chemical Industry Co., Ltd., "Sciqas-LT", average particle size 0.7 μm, spherical, organosilazane-treated) Silica filler (c2) (Sakai Chemical Industry Co., Ltd., "Sciqas," average particle size 0.7 μm, spherical, organosilazane-treated) Silica filler (c3) (Sakai Chemical Industry Co., Ltd., "Sciqas", average particle size 0.7 μm, spherical, untreated) Silica filler (c4) (Tokuyama Corporation, "Excelica SE-1", average particle size 0.5 μm, spherical) Silica filler (c5) (Nippon Aerosil Co., Ltd., "Aerosil RY-200", spherical) 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 of the present invention. However, for the sake of convenience in creating Table 1, it is listed in the column for silica filler (C).

[0103] (4) Other Curing accelerator (imidazole-based curing accelerator) (Shikoku Chemicals Corporation, "Curesol C11Z") Solvent (a mixed solvent of toluene and methylcyclohexane (mass ratio = 20:80) The amount of solvent was adjusted appropriately so that the solid content of the adhesive composition would be 15 to 30% by mass.

[0104] 3. Preparation and Evaluation of Adhesive Compositions The above raw materials except for the silica filler (C) were added to a 1000 ml flask equipped with a stirrer in the proportions 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 an adhesive composition that did not contain the silica filler (C). For Samples 1 to 8 and Sample 2C, the specified amount of silica filler (C) shown in Table 1 was then added, and the mixture was stirred at 2000 rpm for 10 minutes using a disperser to disperse the silica filler (C), thereby preparing an adhesive composition that contained the silica filler (C). Each adhesive composition was prepared in this manner and evaluated. The results are shown in Table 1.

[0105] 4. Production and evaluation of laminates with adhesive layers Using the above adhesive composition, a laminate with an adhesive layer was produced and evaluated as described in the explanation for each evaluation method above. The results are shown in Table 1.

[0106] [Table 1]

[0107] Table 1 reveals the following: Sample 1C had a relatively high resin flow because the adhesive composition did not contain silica filler (C). Furthermore, Sample 1C was an adhesive composition that did not contain silica filler (C), and the cured product had a dielectric constant of 2.3 (Dk) and a dielectric dissipation factor of 0.0017 (Df).

[0108] Furthermore, although the adhesive composition of Sample 2C contained a silica filler, the silanol group concentration of the silica filler exceeded 0.5 mmol / g. As a result, silica filler aggregates formed in the adhesive composition within a short period of time, resulting in poor dispersion of the silica filler. This also prevented the formation of a uniform coating film, making it impossible to measure the dielectric properties of the cured adhesive composition.

[0109] In contrast, Samples 1 to 8 contain adhesive compositions containing 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. Therefore, 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 curing the adhesive composition. Furthermore, the addition of the silica filler also reduced range flow.

[0110] Furthermore, Samples 1 to 8 show that by using a silica filler with a water content of 0.1% by mass or less, the dispersibility of the silica filler can be reliably improved 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, a comparison of Samples 1 to 7 with Sample 8 confirms that the dispersibility of the silica filler can be more easily improved by using a silica filler with a water content of less than 0.08% by mass.

[0111] The present invention is not limited to the above-described embodiments and examples, and various modifications are possible without departing from the spirit of the present invention. Furthermore, the configurations shown in the above-described embodiments and examples can be combined in any manner.

Claims

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 silica filler (C) has a silanol group concentration of 0.5 mmol / g or less. Adhesive composition.

2. The water content of the silica filler (C) is 0.1% by mass or less. The adhesive composition of claim 1.

3. The silica filler (C) has a BET specific surface area of ​​1 m ２ / g or more 10m ２ / g or less, The adhesive composition of claim 1.

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 of claim 1.

5. The modified polyolefin resin (A) is an acid-modified polyolefin resin. The adhesive composition of claim 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 of claim 1.

7. The epoxy resin (B) is a polyfunctional epoxy resin having an alicyclic skeleton. The adhesive composition of claim 1.

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 of claim 1.

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 of claim 1.

10. 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.

11. A flexible copper-clad laminate comprising the adhesive layer-attached laminate according to claim 10, the substrate 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 of the laminate with an adhesive layer according to claim 10 and a copper wiring on the other side of the adhesive layer.

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