JP7582182B2 - Low Dielectric Laminate - Google Patents

Description

The present invention relates to a laminate having low dielectric properties. More specifically, the present invention relates to a laminate that can be used for flexible printed wiring boards, coverlay films, and bonding sheets.

Flexible printed circuit boards (FPCs) have excellent flexibility and can accommodate the multi-functionality and miniaturization of personal computers and smartphones, and are therefore widely used to incorporate electronic circuit boards into narrow and complex interiors. In recent years, electronic devices have become smaller, lighter, more dense, and more powerful, and these trends have led to increasingly higher requirements for the performance of wiring boards (electronic circuit boards). In particular, as the transmission signal speed in FPCs increases, the frequency of the signal increases, and as a result, there is an increasing demand for low dielectric properties (low dielectric constant, low dielectric tangent) in the high-frequency range for FPCs. Patent Document 1 discloses a coverlay film (laminate) having a thermosetting adhesive layer made of a thermosetting adhesive composition containing a polyolefin resin, a carbodiimide resin, a multifunctional epoxy resin, and a filler.

JP 2019-127501 A

However, the coverlay film (laminate) described in Patent Document 1 contains a filler, but does not take into consideration the dispersibility of the filler in the adhesive layer, so the linear expansion properties of the laminate are insufficient. The present invention has been made in response to the above problems, and its purpose is to provide a laminate with excellent adhesive properties, dielectric properties, and linear expansion properties of the adhesive layer.

A laminate in which a metal substrate, an adhesive layer, and a resin substrate are laminated in this order,
The adhesive layer contains a filler (A) and a cured product of an acid-modified polyolefin (B) and an epoxy resin (C),
A laminate in which, in a cross section of the adhesive layer in a direction perpendicular to the surface of the laminate, the number a1 of the filler (A) contained in a region from the midpoint to the surface of the metal substrate is greater than the number b1 of the filler (A) contained in a region from the midpoint to the surface of the resin substrate.

It is preferable that the ratio of a1 to b1 is a1/b1 = less than 100/more than 0 to more than 50/less than 50.

The filler (A) is preferably one or more selected from the group consisting of phosphorus-containing flame-retardant fillers, aluminum hydroxide, silica, titanium oxide, and carbon black. Furthermore, it is preferable that the cured product component of the adhesive layer contains an oligophenylene ether (D) and/or a polycarbodiimide (E) having a number average molecular weight of 3000 or less.

It is preferable that the adhesive layer has a relative dielectric constant (ε _c ) of 3.0 or less and a dielectric loss tangent (tan δ) of 0.02 or less at 1 GHz.

A printed wiring board containing the laminate as a component.

The laminate of the present invention has an appropriately set dispersibility of the filler in the adhesive layer, and therefore has excellent adhesion and dielectric properties in the adhesive layer, as well as excellent linear expansion properties, making it possible to provide a laminate with good dimensional stability.

FIG. 1 is a cross-sectional view of a laminate in a direction perpendicular to the surface.

The present invention will be described in more detail below based on the following embodiments. However, the present invention is not limited to the following embodiments, and it is of course possible to make appropriate modifications within the scope of the above and below described intent, and all of these are included in the technical scope of the present invention.

<Laminate>
The laminate of the present invention is formed by laminating a metal substrate, an adhesive layer, and a resin substrate in this order. The metal substrate and the adhesive layer may be directly laminated, or another substrate (layer) may be laminated therebetween. It is preferable that the metal substrate and the adhesive layer are directly laminated. Also, the adhesive layer and the resin substrate may be directly laminated, or another substrate (layer) may be laminated therebetween. It is preferable that the adhesive layer and the resin substrate are directly laminated. That is, it is preferable that the metal substrate, the adhesive layer, and the resin substrate are directly laminated (three layers of metal substrate/adhesive layer/resin substrate).

In addition, another substrate may be laminated on the laminate via an adhesive layer. For example, there may be four layers of adhesive layer/metal substrate/adhesive layer/resin substrate, four layers of metal substrate/adhesive layer/resin substrate/adhesive layer, or five layers of adhesive layer/metal substrate/adhesive layer/resin substrate/adhesive layer.

An example of a laminate is shown in Figure 1. The laminate 10 in Figure 1 is formed by laminating a metal substrate 1, an adhesive layer 3, and a resin substrate 2 in this order, and the adhesive layer 3 includes a region 3a (hereinafter also referred to as adhesive layer 3a) closer to the surface of the metal substrate and a region 3b (hereinafter also referred to as adhesive layer 3b) closer to the surface of the resin substrate.

The method for producing the laminate is not particularly limited, but can be performed, for example, by the following method. First, an adhesive composition a containing a filler (A), an acid-modified polyolefin (B) and an epoxy resin (C) is applied to the surface of the metal substrate 1 and dried to produce an adhesive layer 3a. Next, an adhesive composition b containing less filler (A) than the adhesive composition a is applied to the surface and dried to produce an adhesive layer 3b. Next, the resin substrate 2 is laminated and heat-treated (cured) to obtain a laminate. Conversely, the adhesive composition b is applied to the surface of the resin substrate 2 and dried to produce an adhesive layer 3b, and then the adhesive composition a is applied and dried to produce an adhesive layer 3a, and then the metal substrate 1 is laminated and heat-treated (cured).

When the laminate is used as a component of a printed wiring board, it is preferable to form a conductor circuit.

<Adhesive Layer>
The adhesive layer of the present invention contains a filler (A) and a cured product of an acid-modified polyolefin (B) and an epoxy resin (C), and the number a1 of the filler (A) in the adhesive layer 3a is greater than the number b1 of the filler (A) in the adhesive layer 3b.

The ratio (a1/b1) of the number a1 of adhesive layers 3a to the number b1 of adhesive layers 3b is preferably less than 100/more than 0 to more than 50/less than 50. Since this results in good linear expansion properties, it is more preferably 99/1 to 51/49, even more preferably 98/2 to 52/48, even more preferably 97/3 to 53/47, particularly preferably 96/4 to 54/46, and most preferably 95/5 to 55/45.

The adhesive layer 3a and adhesive layer 3b are located on the metal substrate 1 side from the midpoint of the length (film thickness of adhesive layer 3) perpendicular to the surface of the laminate, and the resin substrate 2 side is located on the adhesive layer 3a and 3b, respectively. The midpoint here refers to the intermediate position between the surface of the adhesive layer that contacts the metal substrate 1 and the surface of the adhesive layer that contacts the resin substrate 2, and refers to the position that is 50% from the metal substrate 1 and 50% from the resin substrate 2 when the film thickness of the adhesive layer is 100%. In other words, the adhesive layer 3a is located within 50% of the adhesive layer 3 from the metal substrate 1. The adhesive layer 3b is located within 50% of the adhesive layer 3 from the resin substrate 2. The boundary between the adhesive layer 3a and the adhesive layer 3b may be clear, or may be indistinct and integrated.

The thickness of the adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and particularly preferably 20 μm or more, since this provides good adhesive strength. In addition, the thickness is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm, since this provides flexibility to the adhesive layer.

The number of fillers (A) can be measured using an electron microscope. Specifically, the laminate is cut in a direction perpendicular to its surface, and the number of fillers (A) contained in the adhesive layer 3a and adhesive layer 3b on the cut surface is visually counted. The number of fillers (A) contained in the adhesive layer is proportional to the content of filler (A) contained in the adhesive composition applied to the resin substrate or metal substrate. Note that fillers (A) with a major axis of less than 15 nm are not counted because their linear expansion effect is weak.

<Filler (A)>
The filler (A) used in the present invention (hereinafter also simply referred to as component (A)) is not particularly limited as long as it has the effect of low linear expansion when its dispersibility in the adhesive layer is appropriately set. Among them, it is preferably one or more selected from the group consisting of phosphorus-containing flame-retardant fillers, aluminum hydroxide, silica, titanium oxide, and carbon black.

The phosphorus-containing flame-retardant filler is not particularly limited as long as it is a filler that contains a phosphorus atom in its structure. Examples include phosphinic acid derivatives and phosphazene compounds, with phosphinic acid derivatives being preferred and phenanthrene-type phosphinic acid derivatives being more preferred. Examples of phenanthrene-type phosphinic acid derivatives include 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (Sanko Co., Ltd., trade name: HCA), 10-benzyl-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide (Sanko Co., Ltd., trade name: BCA), 10-(2,5-dihydroxyphenyl)-10-H-9-oxa-10-phosphaphenanthrene-10-oxide (Sanko Co., Ltd., trade name: HCA-HQ), and finely ground 10-(2,5-dihydroxyphenyl)-10-H-9-oxa-10-phosphaphenanthrene-10-oxide (Sanko Co., Ltd., trade name: HCA-HQ-HS). These can be used alone or in combination of two or more. Among them, HCA-HQ-HS is preferred.

Commercially available aluminum hydroxide products include Hidilite (registered trademark) H42M, Hidilite H43M, and Hidilite H42STV manufactured by Showa Denko K.K., and B1403 and B1403T manufactured by Nippon Light Metal Co., Ltd. These may be used alone or in combination of two or more. Among these, Hidilite H42M manufactured by Showa Denko K.K. is preferred.

Commercially available silica products include S0-C1, S0-C2, S0-C3, S0-C4, S0-C5, and S0-C6 manufactured by Admattex Co., Ltd., and FB-3SDC manufactured by Denka Co., Ltd. These may be used alone or in combination of two or more types. Of these, FB-3SDC manufactured by Denka Co., Ltd. is preferred.

Commercially available titanium oxide products include TIPAQUE (registered trademark) CR-60 manufactured by Ishihara Sangyo Kaisha, Ltd. and JR-403 manufactured by Teika Co., Ltd. These can be used alone or in combination of two or more types. Of these, JR-403 manufactured by Teika Co., Ltd. is preferred.

Commercially available carbon black products include Mitsubishi Chemical's Good Flowability #MA100 and General Purpose Color #44. These can be used alone or in combination of two or more. Among these, Good Flowability #MA100 is preferred.

The content of the filler (A) is preferably 0.1 parts by mass or more per 100 parts by mass of the acid-modified polyolefin (B). Since the linear expansion properties are good, the content is more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more. Also, since the adhesive properties are good, the content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

The shape of the filler (A) is not particularly limited, but at least one selected from the group consisting of spherical fillers, needle-like fillers, rod-like fillers, fibrous fillers, flat fillers, scale-like fillers, and plate-like fillers is preferred. Among these, the use of spherical fillers can reduce uneven distribution of stress concentration, and also makes it easier to reduce distortion during thermal expansion. In addition, as long as it is selected from the group consisting of spherical fillers, needle-like fillers, rod-like fillers, fibrous fillers, flat fillers, scale-like fillers, and plate-like fillers, one type may be used or multiple types may be used in combination.

It is preferable that the filler (A) has a major axis of 15 nm or more. By having a major axis of 15 nm or more, the linear expansion property is easily improved. Therefore, the major axis of the filler (A) is more preferably 20 nm or more, even more preferably 50 nm or more, and even more preferably 0.1 μm or more. On the other hand, the upper limit of the major axis of the filler (A) is not particularly limited, but may be, for example, 50 μm or less, 30 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less.

<Acid-modified polyolefin (B)>
The acid-modified polyolefin (B) (hereinafter also simply referred to as component (B)) used in the present invention is not limited, but is preferably one obtained by grafting at least one of α,β-unsaturated carboxylic acid and its acid anhydride to a polyolefin resin. The polyolefin resin refers to a polymer mainly composed of a hydrocarbon skeleton, such as a homopolymer of an olefin monomer exemplified by ethylene, propylene, butene, butadiene, isoprene, etc., or a copolymer with other monomers, and a hydrogenated or halogenated product of the obtained polymer. In other words, the acid-modified polyolefin is preferably one obtained by grafting at least one of α,β-unsaturated carboxylic acid and its acid anhydride to at least one of polyethylene, polypropylene, and propylene-α-olefin copolymer.

Propylene-α-olefin copolymers are copolymers of propylene as the main component with an α-olefin. As the α-olefin, for example, one or more of ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, etc. can be used. Of these α-olefins, ethylene and 1-butene are preferred. There are no limitations on the ratio of the propylene component to the α-olefin component in the propylene-α-olefin copolymer, but it is preferable that the propylene component be 50 mol% or more, and more preferably 70 mol% or more.

Examples of at least one of the α,β-unsaturated carboxylic acids and their acid anhydrides include maleic acid, itaconic acid, citraconic acid, and their acid anhydrides. Among these, acid anhydrides are preferred, and maleic anhydride is more preferred. Specific examples include maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, maleic anhydride-modified propylene-ethylene-butene copolymer, etc., and these acid-modified polyolefins can be used alone or in combination of two or more.

From the viewpoint of heat resistance and adhesion to resin substrates and metal substrates, the acid value of the acid-modified polyolefin (B) is preferably 5 mgKOH/g or more, more preferably 6 mgKOH/g or more, and even more preferably 7 mgKOH/g or more. By making it equal to or greater than the lower limit, compatibility with the epoxy resin (C) is improved, and excellent adhesive strength can be achieved. In addition, the crosslinking density is high, and solder heat resistance is good. The upper limit is preferably 40 mgKOH/g or less, more preferably 30 mgKOH/g or less, and even more preferably 20 mgKOH/g or less. By making it equal to or less than the upper limit, adhesion is good.

The number average molecular weight (Mn) of the acid-modified polyolefin (B) is preferably in the range of 10,000 to 50,000. More preferably, it is in the range of 15,000 to 45,000, even more preferably in the range of 20,000 to 40,000, and particularly preferably in the range of 22,000 to 38,000. By making it equal to or greater than the lower limit, the cohesive force is good and excellent adhesion can be achieved. Furthermore, by making it equal to or less than the upper limit, excellent flowability and operability can be achieved.

The acid-modified polyolefin (B) is preferably a crystalline acid-modified polyolefin. In the present invention, the term "crystalline" refers to a polyolefin that shows a clear melting peak during the heating process when heated from -100°C to 250°C at a rate of 20°C/min using a differential scanning calorimeter (DSC).

The melting point (Tm) of the acid-modified polyolefin (B) is preferably in the range of 50°C to 120°C. More preferably, it is in the range of 60°C to 100°C, and most preferably in the range of 70°C to 90°C. By making it equal to or greater than the lower limit, the cohesive force derived from the crystals is improved, and excellent adhesion and solder heat resistance can be achieved. Furthermore, by making it equal to or less than the upper limit, excellent solution stability and fluidity are achieved, and operability during adhesion is improved.

The heat of fusion (ΔH) of the acid-modified polyolefin (B) is preferably in the range of 5 J/g to 60 J/g. More preferably, it is in the range of 10 J/g to 50 J/g, and most preferably in the range of 20 J/g to 40 J/g. By making it equal to or greater than the lower limit, the cohesive force derived from the crystals becomes good, and excellent adhesion and solder heat resistance can be achieved. Furthermore, by making it equal to or less than the upper limit, excellent solution stability and flowability are achieved, and operability during adhesion is good.

The method for producing the acid-modified polyolefin (B) is not particularly limited, and examples thereof include a radical graft reaction (i.e., a reaction in which radical species are generated in the main chain polymer and the radical species is used as the polymerization initiation point to graft polymerize an unsaturated carboxylic acid and an acid anhydride).

As the radical generator, although there is no particular limitation, it is preferable to use an organic peroxide. As the organic peroxide, although there is no particular limitation, peroxides such as di-tert-butyl peroxyphthalate, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, lauroyl peroxide, etc.; azonitriles such as azobisisobutyronitrile, azobisisopropionitrile, etc., can be mentioned.

<Epoxy resin (C)>
The epoxy resin (C) used in the present invention (hereinafter, also simply referred to as component (C)) is not particularly limited as long as it has a glycidyl group in the molecule, but preferably has two or more glycidyl groups in the molecule. Specifically, although not particularly limited, at least one selected from the group consisting of biphenyl type epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, alicyclic epoxy resin, dicyclopentadiene type epoxy resin, tetraglycidyl diaminodiphenylmethane, triglycidyl paraaminophenol, tetraglycidyl bisaminomethylcyclohexanone, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and epoxy-modified polybutadiene can be used. Preferably, it is a biphenyl type epoxy resin, a novolac type epoxy resin, a dicyclopentadiene type epoxy resin, or an epoxy-modified polybutadiene. More preferably, it is a dicyclopentadiene type epoxy resin or a novolac type epoxy resin.

The content of epoxy resin (C) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of acid-modified polyolefin (B). By making it equal to or more than the lower limit, a sufficient curing effect can be obtained, and excellent adhesion and solder heat resistance can be exhibited. In addition, it is preferable that it is 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less. By making it equal to or less than the upper limit, low dielectric properties are improved. In other words, by making it within the above range, an adhesive layer having excellent adhesion, solder heat resistance, and low dielectric properties can be obtained.

The cured product of the acid-modified polyolefin (B) and the epoxy resin (C) (hereinafter simply referred to as the cured product) refers to a cured product formed by the reaction of the (B) and (C) components. When the adhesive layer as a whole is taken as 100% by mass, it is preferable that the cured product contains 40% by mass or more. Since the strength of the adhesive layer is improved, it is more preferable that the cured product contains 50% by mass or more, even more preferable that the cured product contains 60% by mass or more, even more preferable that the cured product contains 70% by mass or more, and particularly preferable that the cured product contains 75% by mass or more.

The curing conditions for components (B) and (C) are not particularly limited, but are preferably 100 to 200°C, more preferably 110 to 180°C, and even more preferably 120 to 150°C. The time can be set appropriately, and is preferably about 1 to 10 hours, more preferably 2 to 8 hours, and even more preferably 3 to 5 hours.

It is preferable that the curing components of the adhesive layer further contain an oligophenylene ether (D) and a polycarbodiimide (E) having a number average molecular weight of 3,000 or less.

<Oligophenylene ether (D)>
The oligophenylene ether (D) (hereinafter also simply referred to as component (D)) used in the present invention has a number average molecular weight (Mn) of 3000 or less, and preferably a compound having a structural unit represented by the following general formula (1) and/or a structural unit represented by the following general formula (2) can be used. By containing component (D), the solder heat resistance of the adhesive layer is improved.

一般式（１）中、Ｒ_１，Ｒ_２，Ｒ_３，Ｒ_４は、それぞれ独立に、水素原子、置換されていてもよいアルキル基、置換されていてもよいアルケニル基、置換されていてもよいアルキニル基、置換されていてもよいアリール基、置換されていてもよいアラルキル基または置換されていてもよいアルコキシ基であることが好ましい。置換されていてもよいアルキル基の「アルキル基」は、例えば、炭素数が１以上６以下、好ましくは炭素数が１以上３以下の、直鎖状又は分岐鎖状のアルキル基である。より具体的には、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ペンチル基、ヘキシル基等が挙げられ、メチル基またはエチル基であることがより好ましい。置換されていてもよいアルケニル基の「アルケニル基」としては、例えば、エテニル基、１－プロペニル基、２－プロペニル基、３－ブテニル基、ペンテニル基、ヘキセニル基等が挙げられ、エテニル基または１－プロペニル基であることがより好ましい。置換されていてもよいアルキニル基の「アルキニル基」としては、例えば、エチニル基、１－プロピニル基、２－プロピニル（プロパルギル）基、３－ブチニル基、ペンチニル基、ヘキシニル基等が挙げられ、エチニル基、１－プロピニル基または２－プロピニル（プロパルギル）基であることがより好ましい。置換されていてもよいアリール基の「アリール基」としては、例えば、フェニル基、ナフチル基等が挙げられ、フェニル基であることがより好ましい。置換されていてもよいアラルキル基の「アラルキル基」としては、例えば、ベンジル基、フェネチル基、２－メチルベンジル基、４－メチルベンジル基、α－メチルベンジル基、２－ビニルフェネチル基、４－ビニルフェネチル基等が挙げられ、ベンジル基であることがより好ましい。置換されていてもよいアルコキシ基の「アルコキシ基」は、例えば炭素数が１以上６以下、好ましくは炭素数が１以上３以下の、直鎖状又は分岐鎖状のアルコキシ基である。例えば、メトキシ基、エトキシ基、プロポキシ基、イソプロポキシ基、ブトキシ基、ｓｅｃ－ブトキシ基、ｔｅｒｔ－ブトキシ基、ペンチルオキシ基、ヘキシルオキシ基等が挙げられ、メトキシ基またはエトキシ基であることがより好ましい。上記のアルキル基、アリール基、アルケニル基、アルキニル基、アラルキル基、及びアルコキシ基が置換されている場合、置換基を１または２以上有していてよい。このような置換基としては、例えば、ハロゲン原子（例えば、フッ素原子、塩素原子、臭素原子）、炭素数１～６のアルキル基（例えば、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ペンチル基、ヘキシル基）、アリール基（例えば、フェニル基、ナフチル基）、アルケニル基（例えば、エテニル基、１－プロペニル基、２－プロペニル基）、アルキニル基（例えば、エチニル基、１－プロピニル基、２－プロピニル基）、アラルキル基（例えば、ベンジル基、フェネチル基）、アルコキシ基（例えば、メトキシ基、エトキシ基）等が挙げられる。なかでもＲ_１およびＲ_４がメチル基であり、Ｒ_２およびＲ_３が水素であることが好ましい。

In the general formula (1), R ₁ , R ₂ , R ₃ , and R ₄ are each preferably independently a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, or an optionally substituted alkoxy group. The "alkyl group" of the optionally substituted alkyl group is, for example, a linear or branched alkyl group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. More specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group, and more preferably a methyl group or an ethyl group. Examples of the "alkenyl group" of the optionally substituted alkenyl group include, for example, an ethenyl group, a 1-propenyl group, a 2-propenyl group, a 3-butenyl group, a pentenyl group, a hexenyl group, and the like, with an ethenyl group or a 1-propenyl group being more preferred. Examples of the "alkynyl group" of the optionally substituted alkynyl group include, for example, an ethynyl group, a 1-propynyl group, a 2-propynyl (propargyl) group, a 3-butynyl group, a pentynyl group, a hexynyl group, and the like, with an ethynyl group, a 1-propynyl group, or a 2-propynyl (propargyl) group being more preferred. Examples of the "aryl group" of the optionally substituted aryl group include, for example, a phenyl group, a naphthyl group, and the like, with a phenyl group being more preferred. Examples of the "aralkyl group" of the aralkyl group which may be substituted include a benzyl group, a phenethyl group, a 2-methylbenzyl group, a 4-methylbenzyl group, an α-methylbenzyl group, a 2-vinylphenethyl group, a 4-vinylphenethyl group, and the like, with a benzyl group being more preferred. The "alkoxy group" of the alkoxy group which may be substituted is, for example, a linear or branched alkoxy group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. Examples include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and the like, with a methoxy group or an ethoxy group being more preferred. When the above alkyl group, aryl group, alkenyl group, alkynyl group, aralkyl group, and alkoxy group are substituted, they may have one or more substituents. Examples of such a substituent include halogen atoms (e.g., fluorine, chlorine, and bromine atoms), alkyl groups having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl), aryl groups (e.g., phenyl and naphthyl), alkenyl groups (e.g., ethenyl, 1-propenyl, and 2-propenyl), alkynyl groups (e.g., ethynyl, 1-propynyl, and 2-propynyl), aralkyl groups (e.g., benzyl and phenethyl), and alkoxy groups (e.g., methoxy and ethoxy). Of these, it is preferable that R ₁ and R ₄ are methyl groups and R ₂ and R ₃ are hydrogen.

一般式（２）中、Ｒ_１１，Ｒ_１２，Ｒ_１３，Ｒ_１４，Ｒ_１５，Ｒ_１６，Ｒ_１７，Ｒ_１８は、それぞれ独立に、水素原子、置換されていてもよいアルキル基、置換されていてもよいアルケニル基、置換されていてもよいアルキニル基、置換されていてもよいアリール基、置換されていてもよいアラルキル基または置換されていてもよいアルコキシ基であることが好ましい。なお、各置換基の定義は、前記のとおりである。アルキル基としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ペンチル基、ヘキシル基等が挙げられ、メチル基であることが好ましい。なかでもＲ_１３、Ｒ_１４、Ｒ_１７およびＲ_１８がメチル基であり、Ｒ_１１、Ｒ_１２、Ｒ_１５およびＲ_１６が水素であることが好ましい。また、－Ａ－は、炭素数２０以下の直鎖状、分岐状もしくは環状の２価の炭化水素基、または酸素であることが好ましい。Ａの炭素数は１以上１５以下であることがより好ましく、さらに好ましくは２以上１０以下である。また、Ａの２価の炭化水素基としては、メチレン基、エチレン基、ｎ－プロピレン基、ｎ－ブチレン基、シクロヘキシレン基、フェニレン基等が挙げられ、なかでもフェニレン基であることが好ましい。特に好ましくは酸素である。

In the general formula (2), R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ , R ₁₇ , and R ₁₈ are each preferably independently a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, or an optionally substituted alkoxy group. The definition of each substituent is as described above. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group, and a methyl group is preferable. Among them, it is preferable that R ₁₃ , R ₁₄ , R ₁₇ , and R ₁₈ are a methyl group, and R ₁₁ , R ₁₂ , R ₁₅ , and R ₁₆ are hydrogen. In addition, -A- is preferably a linear, branched or cyclic divalent hydrocarbon group having 20 or less carbon atoms, or oxygen. The number of carbon atoms in A is more preferably 1 to 15, and even more preferably 2 to 10. In addition, examples of the divalent hydrocarbon group in A include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a cyclohexylene group, and a phenylene group, and among these, a phenylene group is preferable. Oxygen is particularly preferable.

The (D) component may be a modified polyphenylene ether functionalized in part or in whole with an ethylenically unsaturated group such as a vinylbenzyl group, an epoxy group, an amino group, a hydroxy group, a mercapto group, a carboxyl group, or a silyl group. Furthermore, it is preferable that both ends have a hydroxy group, an epoxy group, or an ethylenically unsaturated group. Examples of the ethylenically unsaturated group include alkenyl groups such as ethenyl groups, allyl groups, methacrylic groups, propenyl groups, butenyl groups, hexenyl groups, and octenyl groups, cycloalkenyl groups such as cyclopentenyl groups and cyclohexenyl groups, and alkenylaryl groups such as vinylbenzyl groups and vinylnaphthyl groups. In addition, both ends may be the same functional group or different functional groups. From the viewpoint of highly controlling the balance between low dielectric tangent and reduction of resin residue, it is preferable that both ends are hydroxy groups or vinylbenzyl groups, and it is more preferable that both ends are hydroxy groups or vinylbenzyl groups.

一般式（３）において、ｎは３以上であることが好ましく、より好ましくは５以上であり、２３以下であることが好ましく、より好ましくは２１以下であり、さらに好ましくは１９以下である。 As the compound having a structural unit represented by general formula (1), a compound represented by general formula (3) is particularly preferred.

In formula (3), n is preferably 3 or more, more preferably 5 or more, and is preferably 23 or less, more preferably 21 or less, and further preferably 19 or less.

一般式（４）において、ｎは２以上であることが好ましく、より好ましくは４以上であり、２３以下であることが好ましく、より好ましくは２０以下であり、さらに好ましくは１８以下である。 Moreover, as the compound having a structural unit represented by the general formula (2), a compound represented by the general formula (4) is particularly preferable.

In formula (4), n is preferably 2 or more, more preferably 4 or more, and is preferably 23 or less, more preferably 20 or less, and further preferably 18 or less.

The number average molecular weight of component (D) must be 3000 or less, more preferably 2700 or less, and even more preferably 2500 or less. The number average molecular weight of component (D) is preferably 500 or more, and more preferably 700 or more. By setting the number average molecular weight of component (D) to the lower limit or more, the flexibility of the adhesive layer can be improved. On the other hand, by setting the number average molecular weight of component (D) to the upper limit or less, the solubility in organic solvents can be improved.

The content of component (D) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of component (B). It is also preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less. By keeping it within the above range, an adhesive layer with excellent adhesion and solder heat resistance can be obtained.

<Polycarbodiimide (E)>
The polycarbodiimide (E) (hereinafter also simply referred to as component (E)) used in the present invention is not particularly limited as long as it has a carbodiimide group in the molecule. A polycarbodiimide having two or more carbodiimide groups in the molecule is preferred. By using a polycarbodiimide, the carboxyl group of the acid-modified polyolefin (B) reacts with the carbodiimide group, enhancing the interaction between the adhesive layer and the substrate, and improving the adhesiveness. In addition, the solder heat resistance of the adhesive layer is improved.

The content of the (E) component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the (B) component. By making it equal to or more than the lower limit, an interaction with the substrate is exhibited, and the adhesion is improved. In addition, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. By making it equal to or less than the upper limit, excellent dielectric properties can be exhibited. In other words, by making it within the above range, an adhesive layer having excellent low dielectric properties in addition to adhesion and solder heat resistance can be obtained.

The adhesive layer of the present invention preferably has a relative dielectric constant (εc) of 3.0 or less at a frequency of 1 GHz. More preferably, it is 2.6 or less, and even more preferably, it is 2.3 or less. There is no particular lower limit, but in practical use, it is 2.0. Furthermore, the dielectric constant (εc) over the entire frequency range from 1 GHz to 30 GHz is preferably 3.0 or less, more preferably 2.6 or less, and even more preferably 2.3 or less.

The adhesive layer of the present invention preferably has a dielectric loss tangent (tan δ) of 0.02 or less at a frequency of 1 GHz. More preferably, it is 0.01 or less, and even more preferably, it is 0.008 or less. There is no particular lower limit, but in practical use, it is 0.0001. Furthermore, the dielectric loss tangent (tan δ) over the entire frequency range of 1 GHz to 30 GHz is preferably 0.02 or less, more preferably 0.01 or less, and even more preferably 0.05 or less.

In the present invention, the dielectric constant (εc) and the dielectric loss tangent (tan δ) can be measured as follows. For example, a metal layer is formed on both sides of the adhesive layer by a thin film method such as vapor deposition or sputtering, or by applying a conductive paste to form a capacitor, and the capacitance is measured to calculate the dielectric constant (εc) and the dielectric loss tangent (tan δ) from the thickness and area. In addition, when measuring the dielectric constant and the dielectric loss tangent of the adhesive layer from the laminate, the metal substrate and/or the resin substrate may be removed before the measurement, or the laminate, the adhesive layer/metal substrate, or the adhesive layer/resin substrate may be measured as is, and then the dielectric constant and the dielectric loss tangent of the metal substrate and/or the resin substrate may be subtracted.

<Resin substrate>
The resin substrate is not particularly limited as long as it is a substrate made of a resin material that can be coated with the adhesive composition, dried, and used to produce a laminate. Examples of the resin substrate include polyester resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine resin. Film-like resin is preferred.

The thickness of the resin substrate is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, because this improves the strength of the laminate. Also, the thickness is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less, because this improves the processing efficiency during circuit fabrication.

<Metal substrate>
The metal substrate may be any conventionally known conductive material that can be used for a circuit board. Examples of the material include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their alloys, plated products, and metals treated with other metals such as zinc and chromium compounds. Metal foil is preferred, and copper foil is more preferred.

The thickness of the metal substrate is not particularly limited, but is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 10 μm or more, in order to obtain sufficient electrical performance of the circuit. Also, in order to improve the processing efficiency during circuit fabrication, the thickness is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

The metal substrate is usually provided in a rolled form. There is no particular limitation on the form of the metal substrate used when manufacturing the printed wiring board of the present invention. When a ribbon-shaped metal substrate (metal foil) is used, there is no particular limitation on its length. There is also no particular limitation on its width, but it is preferably about 250 to 500 cm.

The metal substrate may be subjected to a surface treatment. Examples of the surface treatment include ITO treatment, plasma treatment, blast treatment, primer treatment, anchor agent treatment, etc.

<Printed Wiring Board>
The printed wiring board in the present invention includes the laminate of the present invention as a component. The printed wiring board is manufactured by a conventionally known method such as a subtractive method using a metal-clad laminate. If necessary, the printed wiring board is a general term for so-called flexible circuit boards (FPC), flat cables, circuit boards for tape automated bonding (TAB), etc., in which a conductor circuit formed by a metal foil is partially or entirely covered with a cover film, screen printing ink, etc.

The printed wiring board of the present invention can have any laminated structure that can be used as a printed wiring board. For example, it can be a printed wiring board composed of a laminate (resin substrate/adhesive layer/metal substrate)/adhesive layer/cover film layer.

<Example>
The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the examples. In the examples and comparative examples, parts simply indicate parts by mass.

(Physical property evaluation method)

Acid value: acid-modified polyolefin (B)
The acid value (mg KOH/g) in the present invention was measured by dissolving the acid-modified polyolefin (B) in toluene and titrating it with a methanol solution of sodium methoxide using phenolphthalein as an indicator.

Number average molecular weight (Mn)
The number average molecular weight in the present invention is measured by gel permeation chromatography (hereinafter, GPC, standard substance: polystyrene resin, mobile phase: tetrahydrofuran, column: Shodex KF-802 + KF-804L + KF-806L, column The values were measured using a temperature of 30° C., a flow rate of 1.0 ml/min, and a detector: an RI detector.

Melting point and heat of fusion The melting point and heat of fusion in the present invention are values measured using a differential scanning calorimeter (hereinafter, abbreviated as DSC, manufactured by TA Instruments Japan, Q-2000) from the top temperature and area of the melting peak when the material is heated and melted at a rate of 20° C./min, cooled to form a resin, and then heated and melted again.

Peel strength (adhesion)
The adhesive composition b described below was applied to a 12.5 μm thick polyimide film (Apical (registered trademark), manufactured by Kaneka Corporation) so that the thickness after drying would be 12.5 μm, and dried at 130° C. for 3 minutes. Next, the adhesive composition a was applied to the adhesive composition b surface so that the thickness after drying would be 12.5 μm, and dried at 130° C. for 3 minutes. The adhesive film (B stage product) obtained in this manner was laminated to a rolled copper foil (BHY series, manufactured by JX Metals Corporation) having a thickness of 18 μm. The laminate was pressed for 30 seconds at 160° C. under a pressure of 40 kgf/cm ² so that the shiny surface of the rolled copper foil was in contact with the adhesive layer, and the adhesive was bonded. The laminate was then heat-treated at 140° C. for 4 hours to harden the film, and a sample for peel strength evaluation was obtained. The sample for peel strength evaluation was subjected to a 90° peel test at 25° C. and a tensile speed of 50 mm/min to measure the peel strength. This test indicates the adhesive strength at room temperature.
<Evaluation criteria>
◎: 1.0 N/mm or more ○: 0.8 N/mm or more and less than 1.0 N/mm △: 0.5 N/mm or more and less than 0.8 N/mm ×: Less than 0.5 N/mm

Solder Heat Resistance Samples were prepared in the same manner as in the above peel strength test, and a 2.0 cm x 2.0 cm sample piece was aged at 23°C for 2 days and then floated in a molten solder bath at 280°C for 10 seconds to check for any changes in appearance such as blistering.
<Evaluation criteria>
◎: No blistering ○: Some blistering △: Many blistering ×: Blistering and discoloration

Dielectric constant (εc) and dielectric tangent (tan δ)
The adhesive composition b described below was applied to a 100 μm thick Teflon (registered trademark) sheet so that the thickness after drying and curing was 12.5 μm, and dried at 130 ° C for 3 minutes. Next, the adhesive composition a was applied to the adhesive composition b surface so that the thickness after drying was 12.5 μm, and dried at 130 ° C for 3 minutes. Then, after curing by heat treatment at 140 ° C for 4 hours, the Teflon (registered trademark) sheet was peeled off to obtain a test adhesive layer sheet. The obtained test adhesive layer sheet was cut into strips of 8 cm × 3 mm to obtain a test sample. The dielectric constant (εc) and dielectric loss tangent (tan δ) were measured using a network analyzer (manufactured by Anritsu Corporation) by a cavity resonator perturbation method under conditions of a temperature of 23 ° C and a frequency of 1 GHz. The obtained relative dielectric constant and dielectric loss tangent were evaluated as follows.
<Evaluation criteria for dielectric constant>
◎: 2.3 or less ○: More than 2.3 and less than 2.6 △: More than 2.6 and less than 3.0 ×: More than 3.0 <Evaluation criteria for dielectric loss tangent>
◎: 0.008 or less ○: More than 0.008 and 0.01 or less △: More than 0.01 and 0.02 or less ×: More than 0.02

Number of fillers (A) The laminate was cut in a direction perpendicular to the surface, and the cut surface was photographed with an electron microscope. The number of fillers contained in the adhesive layer 3a and the adhesive layer 3b on the cut surface was counted visually. Note that fillers (A) with a major axis of less than 15 nm were not counted because their linear expansion effect was weak.

Linear Expansion Using a thermomechanical analyzer (Hitachi High-Tech Science Corporation, "TMA-7100"), the test sample with a total film thickness of 25 μm used in the above-mentioned relative dielectric constant measurement was cut into a length of 1.5 cm and introduced into the device. The temperature was raised from 20° C. to 250° C. under conditions of a load of 5 g and a heating rate of 10° C./min. Based on the obtained data on temperature and dimensional change, the average linear expansion coefficient at 30° C. was calculated and used to evaluate the low expansion property of the test sample.
<Evaluation criteria for linear expansion coefficient>
The evaluation criteria are values at 30°C.
◎: 500 ppm or less ○: More than 500 ppm and less than 550 ppm △: More than 550 ppm and less than 600 ppm ×: More than 600 ppm

Production Example of Resin Composition (F-1) 30 parts by mass of filler (A-1), 100 parts by mass of acid-modified polyolefin (B-1), 20 parts by mass of epoxy resin (C-1), 382 parts by mass of methylcyclohexane, 39 parts by mass of methyl ethyl ketone, and 11 parts by mass of toluene were blended and stirred uniformly to obtain a resin composition (F-1).

Production Examples of Resin Compositions (F-2) to (F-23) Resin compositions (F-2) to (F-23) were produced in the same manner as for resin composition (F-1). The blending amounts are shown in Table 1.

Example 1
A resin composition (F-12) was applied to a polyimide (PI) film (manufactured by DuPont Toray under the trade name Kapton EN50) so that the thickness after drying was 12.5 μm, and dried at 130 ° C. for 3 minutes. Next, a resin composition (F-11) was applied to a thickness after drying of 12.5 μm, and dried at 130 ° C. for 3 minutes. Next, the glossy surface of a copper foil (manufactured by JX Nippon Oil & Gas Exploration BHY, thickness 18 μm) was bonded to the resin composition (F-11) layer so that it was in contact with the resin composition (F-11) layer, and pressed and bonded at 160 ° C. under a pressure of 40 kgf / cm ² for 30 seconds. Then, the laminate was cured by heat treatment at 140 ° C. for 4 hours to obtain a laminate. The ratio of the number of fillers (A) contained in the adhesive layer 3a and the adhesive layer 3b was a1 / a2 = 52 / 48 (30 / 28). The results are shown in Table 2.

Examples 2 to 13, Comparative Examples 1 to 3
Examples 2 to 13 and Comparative Examples 1 to 3 were carried out in the same manner as in Example 1. The results are shown in Table 2.

The filler (A), acid-modified polyolefin (B), epoxy resin (C), oligophenylene ether (D) and polycarbodiimide (E) used in Table 1 are as follows.
<Filler (A)>
Filler (A-1): Phosphorus-based flame-retardant filler (HCA-HQ-HS, manufactured by Sanko Co., Ltd., spherical, particle size: 1.5 μm)
Filler (A-2): Aluminum hydroxide (Hijilite H42M manufactured by Showa Denko K.K., particle size: 1.0 μm)
Filler (A-3): Silica (FB-3SDC manufactured by Denka Co., Ltd., spherical, particle size: 3 μm)
Filler (A-4): Titanium oxide (TIPAQUE CR-50, manufactured by Ishihara Sangyo Kaisha, Ltd., particle size: 0.25 μm)
Filler (A-5): Carbon black (Carbon black with good flowability #MA100, manufactured by Mitsubishi Chemical Corporation, spherical, particle size: 24 nm)
<Epoxy resin (C)>
Epoxy resin (C-1): Dicyclopentadiene type epoxy resin: HP-7200 (manufactured by DIC Corporation, epoxy equivalent: 259 g/eq)
Epoxy resin (C-2): Epoxy modified polybutadiene resin: JP-100 (manufactured by Nippon Soda Co., Ltd.)
<Oligophenylene ether (D)>
Oligophenylene ether (D-1): Oligophenylene ether styrene modified product: OPE-2St 1200 (manufactured by Mitsubishi Gas Chemical Company, Inc., Mn1000, compound having the structure of general formula (4))
Oligophenylene ether (D-2): Oligophenylene ether: SA90 (manufactured by SABIC Corporation, Mn1800, compound having the structure of general formula (3))
<Polycarbodiimide (E)>
Polycarbodiimide resin (E-1): V-09GB (manufactured by Nisshinbo Chemical Inc., carbodiimide equivalent: 216 g/eq)

<Acid-modified polyolefin (B)>
Production Example 1
In a 1L autoclave, 100 parts by mass of propylene-butene copolymer (Mitsui Chemicals "Tafmer (registered trademark) XM7080"), 150 parts by mass of toluene, 19 parts by mass of maleic anhydride, and 6 parts by mass of di-tert-butyl peroxide were added, and the temperature was raised to 140 ° C., and then the mixture was stirred for another 3 hours. Thereafter, the resulting reaction liquid was cooled and poured into a container containing a large amount of methyl ethyl ketone to precipitate a resin. Thereafter, the liquid containing the resin was centrifuged to separate and purify the acid-modified propylene-butene copolymer in which maleic anhydride was graft-polymerized, (poly)maleic anhydride, and low molecular weight substances. Thereafter, the mixture was dried under reduced pressure at 70 ° C. for 5 hours to obtain a maleic anhydride-modified propylene-butene copolymer (B-1, acid value 19 mg KOH / g, number average molecular weight 25,000, Tm 80 ° C., ΔH 35 J / g).

Production Example 2
A maleic anhydride-modified propylene-butene copolymer (B-2, acid value 7 mgKOH/g, number average molecular weight 35,000, Tm 82°C, ΔH 25 J/g) was obtained in the same manner as in Production Example 1, except that the amount of maleic anhydride added was changed to 6 parts by mass.

The laminate of the present invention has good adhesive and dielectric properties as well as good linear expansion properties, making it useful for flexible printed wiring board applications, particularly FPC applications where low dielectric properties (low dielectric constant, low dielectric tangent) in the high frequency range are required.

1 Metal base material 2 Resin base material 3 Adhesive layer 3a Adhesive layer 3a
3b Adhesive layer 3b
10 Laminate

Claims (7)

A laminate in which a metal substrate, an adhesive layer, and a resin substrate are laminated in this order,
The adhesive layer contains a filler (A) and a cured product of an acid-modified polyolefin (B) and an epoxy resin (C),
The content of the filler (A) is 0.1 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the acid-modified polyolefin (B),
The major axis of the filler (A) is 15 nm or more and 5 μm or less,
A laminate in which, in a cross section of the adhesive layer in a direction perpendicular to the surface of the laminate, the number a1 of the filler (A) contained in a region from the midpoint to the surface of the metal substrate is greater than the number b1 of the filler (A) contained in a region from the midpoint to the surface of the resin substrate. The laminate according to claim 1, wherein the ratio of a1 to b1 is a1/b1 = less than 100/more than 0 to more than 50/less than 50. The laminate according to claim 1 or 2, wherein the filler (A) is one or more selected from the group consisting of phosphorus-containing flame-retardant fillers, aluminum hydroxide, silica, titanium oxide, and carbon black. The laminate according to any one of claims 1 to 3 further contains an oligophenylene ether (D) having a number average molecular weight of 3,000 or less in the cured product component of the adhesive layer. The laminate according to any one of claims 1 to 4 further contains polycarbodiimide (E) in the cured component of the adhesive layer. The laminate according to any one of claims 1 to 5, wherein the adhesive layer has a relative dielectric constant (εc) of 3.0 or less and a dielectric tangent (tan δ) of 0.02 or less at 1 GHz. A printed wiring board comprising the laminate according to any one of claims 1 to 6 as a component.

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