Resin sheet having surface treatment layer, primer composition, and production method for resin sheet having surface treatment layer

Abstract

Provided is a resin sheet that has a surface treatment layer, the resin sheet including a syndiotactic polystyrene resin and, when layered onto a metal layer via an adhesive layer, having favorable adhesion to the adhesive layer and not readily releasing the metal layer, even when subjected to heat treatment conditions that simulate a soldering process.　A resin sheet that has a surface treatment layer according to the present invention includes a syndiotactic polystyrene resin. The surface treatment layer is on one or both surfaces of the resin sheet, and, at at least one surface, when the surface of the surface treatment layer that is not in contact with the resin sheet is subjected to elemental analysis by x-ray photoelectron spectroscopy (ESCA), Si, C, N, and O are observed, and the amounts thereof satisfy a prescribed relationship.

Description

Resin sheet with surface-treated layer, primer composition, and method for manufacturing resin sheet with surface-treated layer

[0001] The present invention relates to a resin sheet with a surface-treated layer, a primer composition, and a method for producing a resin sheet with a surface-treated layer. More specifically, the present invention relates to a resin sheet, a primer composition, and a method for producing a resin sheet that can be suitably used as a material for printed wiring boards.

[0002] In recent years, there has been active development of materials for use in devices used in high-speed information communications such as 5G. Plastic materials have been developed that have a low dielectric constant at high frequencies above 10 GHz to improve information transmission speeds and a low dielectric loss tangent to reduce communication loss. There is a similar need for printed wiring boards made of plastic materials with low dielectric constants and dielectric loss tangents and excellent dielectric properties, and printed wiring boards with low transmission loss are in demand. Such printed wiring boards are often exposed to high-temperature environments during the manufacturing process and use, and generally require high heat resistance and dimensional stability. For example, soldering is a manufacturing process for printed wiring boards, and heat resistance that can withstand the heat treatment conditions (e.g., 260°C, approximately 120 seconds) used in this process is required.

[0003] In order to ensure heat resistance sufficient to withstand the soldering process, it is conceivable to use a fluororesin (e.g., polytetrafluoroethylene; PTFE) as a material for the printed wiring board. An example of a fluororesin substrate is described in Patent Document 1.

[0004] Syndiotactic polystyrene (hereinafter sometimes referred to as SPS) is known as a material with a low dielectric constant and dielectric loss tangent, and Patent Document 2 describes a laminate for electronic circuit boards using a syndiotactic polystyrene-based resin. This laminate for electronic circuit boards includes a first resin layer containing a thermoplastic resin, a second resin layer containing a syndiotactic polystyrene-based resin laminated on the first resin layer, a first metal layer laminated on the second resin layer without any other layer therebetween, and a second metal layer formed on the first metal layer. Plating and vapor deposition are exemplified as methods for forming the first metal layer.

[0005] JP 2003-171480 A JP 2015-2334 A

[0006] The fluororesin substrates such as PTFE described in Patent Document 1 have poor adhesion to metal foils, making it difficult to laminate them with metal foils having low surface roughness. Therefore, it is necessary to laminate metal foils with high surface roughness, which reduces the transmission loss of the fluororesin substrate in the high-frequency range. To improve adhesion, special treatments such as ultraviolet irradiation of the fluororesin substrate are required, which not only complicates the manufacturing process but also leads to reduced productivity and increases manufacturing costs.

[0007] In Patent Document 2, since the first metal layer is directly bonded onto the second resin layer containing a syndiotactic polystyrene resin, stress occurs due to the difference in linear expansion coefficient between the second resin layer and the first metal layer, which can cause the first metal layer to peel off from the second resin layer, making it impractical. Furthermore, while syndiotactic polystyrene has excellent dielectric properties, it has low heat resistance and is not a material that can withstand the heat treatment conditions in the soldering process.

[0008] A first object of the present invention is to provide a resin sheet with a surface-treated layer, the resin sheet containing a syndiotactic polystyrene resin, which, when a metal layer is laminated thereon via an adhesive layer, has good adhesion to the adhesive layer, making the metal layer less likely to peel, and which also makes the metal layer less likely to peel even when subjected to heat treatment conditions simulating a soldering process. A second object of the present invention is to provide a primer composition. A third object of the present invention is to provide a method for producing a resin sheet with a surface-treated layer.

[0009] The present invention is as follows: [1] A resin sheet with a surface treatment layer, the resin sheet containing a syndiotactic polystyrene resin, the surface treatment layer being present on one or both sides of the resin sheet, and when at least one of the surfaces of the surface treatment layer, the side not in contact with the resin sheet, is subjected to elemental analysis by X-ray photoelectron spectroscopy (ESCA), Si, C, N, and O are observed, and the amounts of these elements satisfy the relationships of the following formulas (1) to (4): Si / (C+N+O+Si)≧0.03 (1) 1.0<O / Si≦3.0 (2) C / Si≧1.0 (3) 0.1≦N / Si≦2.5 (4) [In formulas (1) to (4), each atomic symbol indicates the content (atomic %) of the corresponding atom.] [2] The resin sheet according to [1], wherein the Si atom content is 5 to 25 atomic % and the N atom content is 1 to 15 atomic %. [3] A resin sheet with a surface treatment layer, wherein the resin sheet contains a syndiotactic polystyrene resin, and the surface treatment layer is present on one or both sides of the resin sheet, and the surface treatment layer is a treatment layer made of a primer composition containing a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups, a second silane compound (b) having an alkenyl group and two or more alkoxy groups, and an alcohol (d), and the primer composition contains 40 to 250 parts by mass of the second silane compound (b) per 100 parts by mass of the first silane compound (a). [4] The resin sheet according to any one of [1] to [3], wherein an adhesive layer is laminated on the surface treatment layer. [5] The resin sheet according to [4], wherein the adhesive layer contains a styrene-based elastomer. [6] The resin sheet according to [4] or [5], wherein a metal layer is laminated on the adhesive layer. [7] A primer composition comprising: a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups; a second silane compound (b) having an alkenyl group and two or more alkoxy groups; and an alcohol (d), wherein the amount of the second silane compound (b) is 40 to 250 parts by mass per 100 parts by mass of the first silane compound (a).[8] The primer composition according to [7], further comprising at least one member selected from the group consisting of a polyamine compound (c), water (e), and a dimethylsiloxane oligomer (f) having 6 or fewer silicon atoms, in which all substituents other than the silicon-bonded oxygen atom are methyl groups. [9] The primer composition according to [7] or [8], wherein the primer composition contains 100 to 250 parts by mass of the polyamine compound (c) per 100 parts by mass of the first silane compound (a).

[10] The primer composition according to any one of [7] to [9], wherein the primer composition contains 2,000 parts by mass or less of water (e) per 100 parts by mass of the first silane compound (a).

[11] The primer composition according to any one of [7] to

[10] , wherein the primer composition contains 10 to 500 parts by mass of a dimethylsiloxane oligomer (f) having 6 or fewer silicon atoms, in which all substituents other than the oxygen atom bonded to the silicon atom are methyl groups, per 100 parts by mass of the first silane compound (a).

[12] The primer composition according to any one of [7] to

[11] , wherein the alcohol (d) contains two or more types.

[13] A method for producing a resin sheet with a surface-treated layer, comprising: a pretreatment step of performing a surface activation treatment on at least one surface of a resin sheet containing a syndiotactic polystyrene resin; a surface layer formation step of forming a primer layer on the surface-activated surface; and a surface layer reaction step of heating the resin sheet with the primer layer formed thereon.

[14] The production method according to

[13] , wherein the surface activation treatment is one or a combination of two or more of corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, radiation treatment, and flame treatment.

[15] The method according to

[13] or

[14] , wherein the primer layer is formed using a primer composition containing a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups, a second silane compound (b) having an alkenyl group and two or more alkoxy groups, and an alcohol (d).

[16] The method according to

[15] , wherein the amount of the second silane compound (b) in the primer composition is 40 to 250 parts by mass per 100 parts by mass of the first silane compound (a).

[17] The method according to

[15] or

[16] , wherein the primer composition further contains at least one member selected from the group consisting of a polyamine compound (c), water (e), and a dimethylsiloxane oligomer (f) having six or fewer silicon atoms, in which all of the substituents other than the oxygen atom bonded to the silicon atom are methyl groups.

[0010] According to the present invention, a resin sheet with a surface-treated layer can be provided in which, when a metal layer is laminated on a resin sheet via an adhesive layer, the adhesion between the resin sheet and the adhesive layer is good, making the metal layer less likely to peel, and even when subjected to heat treatment conditions simulating a soldering process. Furthermore, by using the primer composition according to the present invention, when a metal layer is laminated on a resin sheet via an adhesive layer, the adhesion between the resin sheet and the adhesive layer is good, making it possible to make the metal layer less likely to peel, and even when subjected to heat treatment conditions simulating a soldering process. Furthermore, according to the present invention, a method for producing a resin sheet with a surface-treated layer can be provided.

[0011] The present invention will be specifically described below based on the embodiments, but the present invention is not limited to the following embodiments, and can be implemented with modifications within the scope of the above and below-described intent, and all of these modifications are included in the technical scope of the present invention.

[0012] In an embodiment of the resin sheet with a surface treatment layer according to the present invention, the resin sheet contains a syndiotactic polystyrene resin, the surface treatment layer is present on one or both sides of the resin sheet, and when the surface of at least one of the surface treatment layers that is not in contact with the resin sheet is subjected to elemental analysis by X-ray photoelectron spectroscopy (ESCA; Electron Spectroscopy for Chemical Analysis), Si, C, N, and O are observed, and the amounts of these elements satisfy the relationships of the following formulas (1) to (4). X-ray photoelectron spectroscopy (ESCA) is also sometimes abbreviated as XPS (X-ray Photoelectron Spectroscopy). Si / (C+N+O+Si)≧0.03 (1) 1.0<O / Si≦3.0 (2) C / Si≧1.0 (3) 0.1≦N / Si≦2.5 (4) [In formulas (1) to (4), each atomic symbol indicates the content (atomic %) of each atom.]

[0013] When the surface of the resin sheet with the surface treatment layer in the embodiment is subjected to elemental analysis by ESCA, Si, C, N, and O are observed, and the amounts of these elements satisfy the relationships of the above formulas (1) to (4). When a metal layer is laminated on the resin sheet via an adhesive layer, the adhesion between the resin sheet and the adhesive layer is good, and the metal layer is less likely to peel off, and further, the metal layer is less likely to peel off even when subjected to heat treatment conditions simulating a soldering process.

[0014] The value of Si / (C+N+O+Si) defined by formula (1) is 0.03 or more, and the value of Si / (C+N+O+Si) is preferably 0.08 or more, more preferably 0.1 or more. There is no particular upper limit to the value of Si / (C+N+O+Si), but, for example, it is preferably 0.22 or less, more preferably 0.2 or less, and even more preferably 0.19 or less. That is, the value of Si / (C+N+O+Si) is preferably 0.08 to 0.22, more preferably 0.1 to 0.2, and even more preferably 0.1 to 0.19.

[0015] The O / Si value defined by formula (2) is greater than 1.0 and equal to or less than 3.0, preferably greater than 1.00 and equal to or less than 2.30. The O / Si value defined by formula (2) is more preferably greater than 1.00 and equal to or less than 2.00. The O / Si value defined by formula (2) is particularly preferably close to 1.50.

[0016] The C / Si value defined by formula (3) is 1.0 or more, and the C / Si value is preferably 1.5 or more, and more preferably 2 or more. There is no particular upper limit to the C / Si value, but, for example, it is preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. That is, the C / Si value is preferably 1.5 to 10, more preferably 2 to 8, and even more preferably 2 to 7.

[0017] The N / Si value defined by formula (4) is 0.1 to 2.5, and is preferably 0.2 or more, more preferably 0.3 or more. The N / Si value defined by formula (4) is preferably 2 or less, more preferably 1 or less. That is, the N / Si value is preferably 0.2 to 2, more preferably 0.3 to 1.

[0018] The resin sheet with a surface treatment layer may have a Si atom content of, for example, 5 to 25 atomic % when the surface is subjected to elemental analysis by ESCA, preferably 8 to 23 atomic %, and more preferably 10 to 20 atomic %.

[0019] When the surface of the resin sheet with a surface treatment layer is subjected to elemental analysis by ESCA, the N atom content may be, for example, 1 to 15 atomic %, preferably 3 to 13 atomic %, and more preferably 5 to 10 atomic %.

[0020] The resin sheet with the surface treatment layer preferably has an Si atom content of 5 to 25 atomic % and an N atom content of 1 to 15 atomic % when the surface is subjected to elemental analysis by ESCA.

[0021] In an embodiment of the resin sheet with a surface treatment layer according to the present invention, the resin sheet contains a syndiotactic polystyrene resin, and the surface treatment layer is present on one or both sides of the resin sheet. The surface treatment layer is a treatment layer made of a primer composition containing a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups, a second silane compound (b) having an alkenyl group and two or more alkoxy groups, and an alcohol (d), and the primer composition contains 40 to 250 parts by mass of the second silane compound (b) per 100 parts by mass of the first silane compound (a).

[0022] The surface treatment layer of the resin sheet is a treatment layer made of a primer composition containing the above-mentioned first silane compound (a), second silane compound (b), and alcohol (d), and by containing a predetermined amount of the second silane compound (b) in the primer composition, when a metal layer is laminated on the surface of the resin sheet via an adhesive layer, the adhesion between the surface treatment layer of the resin sheet and the adhesive layer is good, making the metal layer less likely to peel. Furthermore, even when such a laminate is subjected to heat treatment conditions similar to those in a soldering process, the metal layer is less likely to peel.

[0023] In an embodiment of the primer composition according to the present invention, the primer composition comprises a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups, a second silane compound (b) having an alkenyl group and two or more alkoxy groups, and an alcohol (d), and the amount of the second silane compound (b) is 40 to 250 parts by mass per 100 parts by mass of the first silane compound (a).

[0024] (a) First Silane Compound The first silane compound has an aminoalkyl group and two or more alkoxy groups.

[0025] The aminoalkyl group may be linear or branched. The aminoalkyl group preferably has 3 to 15 carbon atoms. The linear aminoalkyl group preferably has 3 to 10 carbon atoms, more preferably 3 to 8, and even more preferably 3 to 5 carbon atoms. The branched aminoalkyl group preferably has 3 to 15 carbon atoms, more preferably 3 to 13, and even more preferably 3 to 10 carbon atoms. The aminoalkyl group may have multiple amino groups via two or more carbon atoms. The number of aminoalkyl groups bonded to a silicon atom is generally 1. Examples of the aminoalkyl group include a γ-aminopropyl group and an N-(β-aminoethyl)-γ-aminopropyl group.

[0026] The number of carbon atoms in the alkoxy group may be, for example, 1 or 2 or more, preferably 6 or less, more preferably 1 to 3, and even more preferably 1 to 2. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a normal propoxy group. The number of alkoxy groups may be 2 or 3.

[0027] Examples of the first silane compound include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and N-(β-aminoethyl)-γ-aminopropylmethyldiethoxysilane. Of these, only one type may be used alone, or two or more types may be mixed and used. Among these, it is preferable to use γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and more preferably N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. It is preferable not to use a silane compound in which a Si atom, a C atom, and an N atom are bonded in this order, or a silane compound in which a Si atom, a C atom, a C atom, and an N atom are bonded in this order.

[0028] (b) Second Silane Compound The second silane compound has an alkenyl group and two or more alkoxy groups.

[0029] There are no limitations on the structure of the alkenyl group, but it is preferably linear. The number of carbon atoms in the alkenyl group is preferably 6 or less, more preferably 2 or 3. Examples of alkenyl groups include vinyl groups, 1-propenyl groups, allyl groups (2-propenyl groups), 1-hexenyl groups, and 5-hexenyl groups. The number of alkenyl groups may be, for example, one or two. The alkenyl group is preferably located at the terminal of the carbon chain.

[0030] The number of carbon atoms in the alkoxy group may be, for example, 1 or 2 or more, preferably 6 or less, more preferably 1 to 3, and even more preferably 1 to 2. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a normal propoxy group. The number of alkoxy groups may be 2 or 3.

[0031] Examples of the second silane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, 5-hexenyltrimethoxysilane, and 5-hexenyltriethoxysilane. Of these, one type may be used alone, or two or more types may be mixed and used. Among these, it is preferable to use vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, allyltrimethoxysilane, or 5-hexenyltrimethoxysilane, and more preferably vinyltrimethoxysilane.

[0032] In the primer composition, the amount of the second silane compound (b) is 40 to 250 parts by mass per 100 parts by mass of the first silane compound (a). If the amount of the second silane compound (b) is less than 40 parts by mass, the adhesion between the surface-treated layer (treated with the primer composition) and the adhesive layer cannot be improved. Therefore, the content of the second silane compound (b) is set to 40 parts by mass or more. The content of the second silane compound (b) is preferably 80 parts by mass or more, more preferably 110 parts by mass or more, and even more preferably 120 parts by mass or more per 100 parts by mass of the first silane compound (a). If the amount of the second silane compound (b) exceeds 250 parts by mass, the types of adhesive layers that exhibit good adhesion to the surface-treated layer (treated with the primer composition) are limited, resulting in reduced versatility. Furthermore, the storage stability of the primer composition is reduced. Therefore, the content of the second silane compound (b) is set to 250 parts by mass or less. The content of the second silane compound (b) is preferably 210 parts by mass or less, more preferably 180 parts by mass or less, per 100 parts by mass of the first silane compound (a). That is, the amount of the second silane compound (b) in the primer composition is preferably 80 to 210 parts by mass, more preferably 110 to 180 parts by mass, and even more preferably 120 to 180 parts by mass, per 100 parts by mass of the first silane compound (a).

[0033] It should be noted that a silane compound having an aminoalkyl group, an alkenyl group, and two or more alkoxy groups in the molecule is not classified as either the first silane compound (a) or the second silane compound (b).

[0034] (d) Alcohol By including alcohol (d) in the primer composition, the drying rate after application of the primer composition to a substrate can be adjusted, the rate at which adhesiveness develops after drying can be controlled, and the storage stability of the primer composition can be improved.

[0035] The alcohol (d) may be linear or branched. The number of carbon atoms in the alcohol may be, for example, 1 or 2 or more. The number of carbon atoms in the alcohol is, for example, preferably 4 or less, more preferably 3 or less. Examples of the alcohol (d) include methyl alcohol, ethyl alcohol, normal propyl alcohol, and isopropyl alcohol. Of these, only one type may be used alone, or two or more types may be used in combination.

[0036] The primer composition preferably contains two or more types of alcohol (d). When the primer composition contains two or more types of alcohol (d), it preferably contains two or more types of alcohol having 1 to 3 carbon atoms. Preferred combinations of alcohols (d) include, for example, a combination of methyl alcohol and normal propyl alcohol, and a combination of methyl alcohol, ethyl alcohol, and normal propyl alcohol.

[0037] The amount of alcohol (d) contained in the primer composition is not particularly limited, but may be, for example, 1,000 to 2,000 parts by mass per 100 parts by mass of the first silane compound (a). The amount of alcohol (d) is preferably 1,100 parts by mass or more, more preferably 1,200 parts by mass or more, per 100 parts by mass of the first silane compound (a). The amount of alcohol (d) is preferably 1,900 parts by mass or less, more preferably 1,800 parts by mass or less, per 100 parts by mass of the first silane compound (a). When two or more types of alcohol (d) are contained, the amount of alcohol (d) is the total amount. That is, the amount of alcohol (d) in the primer composition is preferably 1,100 to 1,900 parts by mass, more preferably 1,200 to 1,800 parts by mass, per 100 parts by mass of the first silane compound (a).

[0038] The primer composition may further contain at least one member selected from the group consisting of polyamine compounds (c), water (e), and dimethylsiloxane oligomers (f) having 6 or less silicon atoms, in which all of the substituents other than oxygen atoms bonded to silicon atoms are methyl groups.

[0039] (c) Polyamine Compound The polyamine compound (c) is an organic compound having two or more amino groups. By including the polyamine compound (c) in the primer composition, the storage stability of the primer composition is improved.

[0040] Examples of the polyvalent amine compound (c) include hydrocarbon polyvalent amine compounds such as 1,2-ethanediamine (ethylenediamine), 1,3-propanediamine, 2-methyl-2-propyl-1,3-propanediamine, 1,2-propanediamine, 2-methyl-1,3-propanediamine, 1,4-butanediamine (putrescine), 2,3-dimethyl-1,4-butanediamine, 1,3-butanediamine, 1,2-butanediamine, 2-ethyl-1,4-butanediamine, and 2-methyl-1,4-butanediamine. Of these, only one type may be used alone, or two or more types may be mixed and used. Of these, the use of ethylenediamine is preferred.

[0041] When the primer composition contains the polyamine compound (c), the amount of the polyamine compound (c) in the primer composition may be, for example, 100 to 250 parts by mass relative to 100 parts by mass of the first silane compound (a). The amount of the polyamine compound (c) in the primer composition is preferably 90 to 230 parts by mass, more preferably 80 to 210 parts by mass.

[0042] (e) Water By including water (e) in the primer composition, the thickness of the surface treatment layer, which is the treatment layer of the primer composition, can be adjusted. As the water (e), for example, ion-exchanged water may be used.

[0043] When the primer composition contains water (e), the amount of water (e) is not particularly limited, but may be, for example, 2000 parts by mass or less relative to 100 parts by mass of the first silane compound (a). The amount of water (e) is preferably 1500 parts by mass or less, more preferably 1000 parts by mass or less, relative to 100 parts by mass of the first silane compound (a).

[0044] (f) Dimethylsiloxane Oligomer Dimethylsiloxane oligomer (f) is an oligomer in which all substituents other than the oxygen atom bonded to the silicon atom are methyl groups and the number of silicon atoms is 6 or less. Dimethylsiloxane oligomer (f) serves as a solvent for the primer composition and also functions as a compatibilizer for the first silane compound (a), the second silane compound (b), and the alcohol (d). The number of silicon atoms in dimethylsiloxane oligomer (f) may be 6 or less, and may be 5 or less, or 4 or less.

[0045] Examples of the dimethylsiloxane oligomer (f) include hexamethyldisiloxane, octamethyltrisiloxane, and octamethylcyclotetrasiloxane. These may be used singly or in combination of two or more. Among these, hexamethyldisiloxane is preferred.

[0046] When the primer composition contains dimethylsiloxane oligomer (f), the amount of dimethylsiloxane oligomer (f) is not particularly limited, but may be, for example, 10 to 500 parts by mass per 100 parts by mass of the first silane compound (a). The amount of dimethylsiloxane oligomer (f) is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, per 100 parts by mass of the first silane compound (a). The amount of dimethylsiloxane oligomer (f) is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, per 100 parts by mass of the first silane compound (a). That is, the amount of dimethylsiloxane oligomer (f) is preferably 30 to 300 parts by mass, more preferably 50 to 200 parts by mass, per 100 parts by mass of the first silane compound (a). When two or more types of dimethylsiloxane oligomer (f) are contained, the amount of the dimethylsiloxane oligomer (f) is the total amount.

[0047] The resin sheet contains a syndiotactic polystyrene resin (A) as a constituent resin. Hereinafter, the syndiotactic polystyrene resin may be referred to as "SPS," "syndiotactic polystyrene," or "component (A)." The resin sheet is preferably an unstretched sheet containing the syndiotactic polystyrene resin (A) or a film obtained by biaxially stretching an unstretched sheet containing the syndiotactic polystyrene resin (A). That is, the resin sheet is preferably an unstretched sheet or a biaxially stretched film having a surface treatment layer formed thereon, which is a treatment layer made of a primer composition. Hereinafter, of the resin sheets that are precursors before the surface treatment layer is formed, an unstretched sheet will be simply referred to as a "sheet," and a biaxially stretched film will be simply referred to as a "film," and these will collectively be referred to as a "raw resin sheet."

[0048] (A) Syndiotactic Polystyrene Resin The syndiotactic structure in the syndiotactic polystyrene resin (A) is a stereochemical structure in which phenyl groups, which are side chains, are alternately positioned in opposite directions relative to the main chain formed from carbon-carbon bonds, and the tacticity is quantified by nuclear magnetic resonance (C-NMR) using a carbon isotope. Tacticity measured by C-NMR can be expressed by the proportion of multiple consecutive structural units present, for example, dyads when there are two, triads when there are three, and pentads when there are five. In the present invention, the styrene polymer having a syndiotactic structure generally refers to polystyrene, poly(alkylstyrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), poly(vinyl benzoate ester), hydrogenated polymers thereof, mixtures thereof, or copolymers containing these as the main component, having a syndiotacticity of preferably 75 mol % or more, more preferably 85 mol % or more in the form of racemic dyads, or preferably 30 mol % or more, more preferably 50 mol % or more in the form of racemic pentads.

[0049] Examples of poly(alkylstyrenes) include poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tert-butylstyrene), poly(phenylstyrene), poly(vinylnaphthalene), and poly(vinylstyrene). Examples of poly(halogenated styrenes) include poly(chlorostyrene), poly(bromostyrene), and poly(fluorostyrene). Examples of poly(halogenated alkylstyrenes) include poly(chloromethylstyrene). Examples of poly(alkoxystyrenes) include poly(methoxystyrene) and poly(ethoxystyrene). Among these, more preferred styrene-based polymers include polystyrene, poly(alkylstyrene), poly(halogenated styrene), hydrogenated polystyrene, and copolymers containing these structural units, and particularly preferred styrene-based polymers include polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tert-butylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), hydrogenated polystyrene, and copolymers containing these structural units.

[0050] The syndiotactic polystyrene resin (A) may be a copolymer of styrene having a syndiotactic structure and another monomer. In this case, the content of styrene having a syndiotactic structure in the syndiotactic polystyrene resin (A) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 100% by mass, relative to 100% by mass of the syndiotactic polystyrene resin (A). A content of styrene having a syndiotactic structure of 50% by mass or more results in excellent dielectric properties, solder heat resistance, dimensional change rate, and linear expansion coefficient. Note that, since there is a possibility of a deterioration in these performances, it is preferable to keep the content of the unsaturated nitrile group-containing monomer low. The content of the unsaturated nitrile group-containing monomer in the syndiotactic polystyrene resin (A) is preferably 2% by mass or less, more preferably less than 2% by mass, even more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0051] The syndiotactic polystyrene resin (A) may be a single styrene polymer or a mixture of two or more styrene polymers.

[0052] Although there are no particular limitations on the composition ratio of the styrene polymer, it is preferable that the content of the substituted styrene unit is in the range of 3 to 50 mol %. If the content of the substituted styrene unit is 3 mol % or more, modification is easy. If the content of the substituted styrene unit is 50 mol % or less, compatibility with other components can be maintained.

[0053] The molecular weight of the syndiotactic polystyrene resin (A) is not particularly limited, but the weight-average molecular weight is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. By setting the weight-average molecular weight to 10,000 or more, the thermal and mechanical properties of the resulting composition or molded article are not reduced and are excellent. The upper limit of the weight-average molecular weight of the syndiotactic polystyrene resin (A) is not particularly limited, but is preferably 500,000 or less, more preferably 400,000 or less. The molecular weight distribution of the syndiotactic polystyrene resin (A) is not limited to a particular range, and various types can be used. That is, the weight-average molecular weight of the syndiotactic polystyrene resin (A) is preferably 10,000 to 500,000, more preferably 50,000 to 400,000, and even more preferably 100,000 to 400,000.

[0054] The syndiotactic polystyrene resin (A) preferably has a melt flow rate (MFR) of 1 to 60 g / 10 min, more preferably 2 to 40 g / 10 min, even more preferably 3 to 30 g / 10 min, and most preferably 4 to 20 g / 10 min, as measured at 300° C. under a load of 1.2 kg. By setting the melt flow rate of the syndiotactic polystyrene resin (A) within the above range, a raw material resin sheet, which is a precursor of a resin sheet having good physical properties, can be obtained, and the raw material resin sheet can have a uniform thickness.

[0055] The melting point of the syndiotactic polystyrene resin (A) is preferably 250° C. or higher, more preferably 260° C. or higher, and is preferably 300° C. or lower, more preferably 290° C. or lower. That is, the melting point of the syndiotactic polystyrene resin (A) is preferably 250 to 300° C., more preferably 260 to 290° C.

[0056] The glass transition temperature of the syndiotactic polystyrene resin (A) is preferably 80°C or higher, more preferably 90°C or higher, and is preferably 120°C or lower, more preferably 110°C or lower. By setting the melting point and glass transition temperature of the syndiotactic polystyrene resin (A) within the above ranges, the resin sheet will have a low linear expansion coefficient and good dimensional stability. That is, the glass transition temperature of the syndiotactic polystyrene resin (A) is preferably 80 to 120°C, more preferably 90 to 110°C.

[0057] Representative commercially available syndiotactic polystyrene resins (A) include, for example, XAREC (registered trademark) 142ZE, XAREC (registered trademark) 300ZC, XAREC (registered trademark) 130ZC, and XAREC (registered trademark) 90ZC manufactured by Idemitsu Kosan Co., Ltd. Among these, only one type may be used alone, or two or more types may be used in combination.

[0058] The content of the syndiotactic polystyrene resin (A) in the resin sheet is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, because this improves the dielectric properties. The upper limit of the content of the syndiotactic polystyrene resin (A) is not particularly limited, but is preferably less than 100% by mass, more preferably 99% by mass or less, and even more preferably 95% by mass or less, because this improves the linear expansion coefficient and dimensional stability. That is, the content of the syndiotactic polystyrene resin (A) in the resin sheet is preferably 40% by mass or more but less than 100% by mass, more preferably 50 to 99% by mass, even more preferably 60 to 95% by mass, even more preferably 70 to 95% by mass, even more preferably 80 to 95% by mass, and particularly preferably 90 to 95% by mass.

[0059] Such syndiotactic polystyrene resin (A) can be produced, for example, by polymerizing a styrene monomer (a monomer corresponding to the above-mentioned styrene polymer) in an inert hydrocarbon solvent or in the absence of a solvent using a condensation product of a titanium compound, water, and trialkylaluminum as a catalyst (JP-A-62-187708). Poly(halogenated alkylstyrene) can be obtained by the method described in JP-A-1-46912, and hydrogenated polymers thereof can be obtained by the method described in JP-A-1-178505.

[0060] The resin sheet may contain, in addition to the syndiotactic polystyrene-based resin (A), at least one selected from the group consisting of a rubber-like elastomer (B), a fibrous filler (C), a non-fibrous filler (D), and an antioxidant (E).

[0061] (B) Rubber-like elastomer The resin sheet may contain a rubber-like elastomer (B) (hereinafter also referred to as component (B)). The rubber-like elastomer (B) is preferably added because it imparts appropriate flexibility and improves mechanical properties when the raw resin sheet is wound up, thereby suppressing cracking of the raw resin sheet.

[0062] Examples of the rubber-like elastomer (B) include a single polymer made of polyolefin, polystyrene, or polyacrylate, or a composition made of a copolymer containing these components. Specific examples of the rubber-like elastomer (B) include natural rubber, polybutadiene, polyisoprene, polyisobutylene, neoprene, polysulfide rubber, thiokol rubber, acrylic rubber, urethane rubber, silicone rubber, epichlorohydrin rubber, ethylene-propylene copolymer rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM), ethylene-α-olefin copolymer rubber, styrene-butadiene block copolymer (SBR), hydrogenated styrene-butadiene block copolymer (SEB, SEBC), styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), styrene-isoprene block copolymer (SIR), hydrogenated styrene-isoprene block copolymer (SEP), styrene-isoprene block copolymer (SBR), hydrogenated styrene-isoprene block copolymer (SEB ... Examples of suitable core-shell particulate elastomers include isoprene-styrene block copolymers (SIS), hydrogenated styrene-isoprene-styrene block copolymers (SEPS), butadiene-acrylonitrile-styrene-core-shell rubber (ABS), methyl methacrylate-butadiene-styrene-core-shell rubber (MBS), methyl methacrylate-butyl acrylate-styrene-core-shell rubber (MAS), octyl acrylate-butadiene-styrene-core-shell rubber (MABS), alkyl acrylate-butadiene-acrylonitrile-styrene-core-shell rubber (AABS), butadiene-styrene-core-shell rubber (SBR), and siloxane-containing core-shell rubbers such as methyl methacrylate-butyl acrylate-siloxane, as well as modified rubbers thereof. One of these may be used alone, or two or more may be mixed and used. Of these, it is preferable to use ethylene-α-olefin copolymer rubber, SEBS, SIR, SEP, SIS, SEPS, or modified rubbers thereof.

[0063] As the rubber-like elastomer (B), it is preferable to use one having high heat resistance from the viewpoint of the processing temperature when mixed with the syndiotactic polystyrene-based resin (A). For example, by mixing a rubber-like elastomer (B) in which unsaturated bonds are selectively or completely hydrogenated, the amount of gas generated during heat pressing can be suppressed.

[0064] The rubber-like elastomer (B) preferably has a melt flow rate (MFR) of 0.1 to 40 g / 10 min, more preferably 1.0 to 20 g / 10 min, and even more preferably 1.5 to 14 g / 10 min, measured at 230° C. under a load of 2.16 kg. By setting the melt flow rate of the rubber-like elastomer (B) within the above range, compatibility with the syndiotactic polystyrene-based resin (A) is improved, and the thickness of the raw material resin sheet can be made uniform.

[0065] It is also preferable that the rubber-like elastomer (B) contains a styrene-based thermoplastic elastomer. When the rubber-like elastomer (B) contains a styrene-based thermoplastic elastomer, the amount of the styrene-based thermoplastic elastomer (hereinafter sometimes referred to as the styrene ratio) is preferably 5 to 60% by mass, more preferably 8 to 50% by mass, even more preferably 10 to 40% by mass, and particularly preferably 15 to 32% by mass. By setting the amount of the styrene-based thermoplastic elastomer to 5% by mass or more, the compatibility between the (A) and (B) components is improved, resulting in good mechanical properties. By setting the amount of the styrene-based thermoplastic elastomer to 60% by mass or less, the elastic modulus of the (B) component is not too high, thereby enhancing the stress relaxation effect, improving the flexibility of the raw resin sheet, suppressing the polarity of the resin sheet, and suppressing an increase in the dielectric constant.

[0066] When the rubber-like elastomer (B) is contained, the amount thereof is preferably 1 to 40 parts by mass, more preferably 3 to 30 parts by mass, and even more preferably 5 to 25 parts by mass, per 100 parts by mass of the syndiotactic polystyrene-based resin (A). By setting the amount of the rubber-like elastomer (B) to 1 part by mass or more, the flexibility of the raw material resin sheet is improved, and the winding property on a roll is improved. In addition, the drilling processability in the subsequent process is improved. By setting the amount of the rubber-like elastomer (B) to 40 parts by mass or less, the raw material resin sheet is prevented from becoming too soft, sticking to the roll is prevented, and the heat resistance required for a high-frequency circuit board can be maintained.

[0067] Representative commercially available products of the rubber-like elastic material (B) include, for example, Tuftec (registered trademark) H1062, Tuftec (registered trademark) H1041, Tuftec (registered trademark) H1517, Tuftec (registered trademark) H1521, and Tuftec (registered trademark) H1062, all manufactured by Asahi Kasei Corp. Of these, only one type may be used alone, or two or more types may be used in combination.

[0068] (C) Fibrous Filler The resin sheet may contain a fibrous filler (C) (hereinafter also referred to as component (C)). The fibrous filler (C) is a fibrous filler that can improve the linear expansion coefficient and dimensional change suppression effect in the direction parallel to the extrusion direction (MD) of the raw resin sheet, which is the precursor of the resin sheet. It is a filler that is preferably contained in a resin sheet that may still have some residual strain even if it is unstretched. In addition, by blending the fibrous filler (C), the solder heat resistance of the resin sheet and the laminate can be improved.

[0069] The fibrous filler (C) can be inorganic or organic fibers. Examples of inorganic fibers include wollastonite (or whiskers) and glass fibers, with glass fibers being preferred due to their dielectric properties. Examples of organic fibers include resin fibers.

[0070] The shape of the fibrous filler (C) is not particularly limited, and may be any shape such as roving, surfacing mat, chopped strand mat, satin weave, lattice weave, plain weave, open plain weave, twill weave, or net.

[0071] The type of fibrous filler (C) is not particularly limited, and may be, for example, glass containing a large amount of alkali (C glass), alkali-free glass (E glass), glass containing a large amount of boric acid (D glass), or glass with an adjusted balance of silicic acid and boric acid (NE glass). Among these, it is preferable to use glass containing a large amount of boric acid (D glass) or glass with an adjusted balance of silicic acid and boric acid (NE glass), and more preferably D glass. In D glass, SiO ２ The preferred range of the content is 65.0 to 80.0 mass %, and in this case, B ２ O ３ The preferred range of the content is 15.0 to 30.0 mass %. ２ The preferred range of the content is 45.0 to 65.0 mass %, and in this case, B ２ O ３ The preferred range of the content is 10.0 to 25.0 mass %.

[0072] The cross-sectional shape of the fibrous filler (C) may be either circular or non-circular.

[0073] The glass fiber having a circular cross section preferably has a fiber diameter of 1 to 50 μm, more preferably 2 to 20 μm, and even more preferably 3 to 15 μm.

[0074] Glass fibers with a non-circular cross section include those in which the cross section perpendicular to the longitudinal direction of the glass fiber has a substantially elliptical, substantially oval, or substantially cocoon-shaped shape, and in such cases, the flatness of the cross section is preferably 1.5 to 8. The flatness is the ratio of the major axis to the minor axis when a rectangle of the minimum area circumscribing the cross section perpendicular to the longitudinal direction of the glass fiber is assumed, and the length of the long side of this rectangle is the major axis and the length of the short side is the minor axis.

[0075] The thickness of the glass fiber is not particularly limited, but the minor axis is about 1 to 20 μm and the major axis is about 2 to 100 μm.

[0076] The D50 average fiber length of the fibrous filler (C) is preferably 40 to 4000 μm, more preferably 40 to 3200 μm, even more preferably 45 to 2000 μm, and most preferably 50 to 500 μm. When the D50 average fiber length of the fibrous filler (C) is 40 μm or more, the surface area of ​​the fibrous filler (C) is sufficiently large, improving the adhesion at the interface between the matrix resin components (A) and (C), and improving the physical properties of the raw resin sheet. By setting the D50 average fiber length of the fibrous filler (C) to 4000 μm or less, the rigidity of the raw resin sheet can be prevented from becoming too high, and the occurrence of cracks observed during winding of the raw resin sheet can be suppressed. Furthermore, the occurrence of aggregates in the raw resin sheet can be suppressed.

[0077] The fibrous filler (C) may be surface-treated or may not be surface-treated. When the fibrous filler (C) is surface-treated, examples of the coupling agent used for the surface treatment include a silane coupling agent and a titanium coupling agent. Among these, it is particularly preferable to use a silane coupling agent for the surface treatment in view of compatibility with the (A) component.

[0078] Specific examples of silane coupling agents include triethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(1,1-epoxycyclohexyl)ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ- Examples of suitable silanes include aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltris(2-methoxyethoxy)silane, N-methyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-4,5-dihydroimidazolepropyltriethoxysilane, hexamethyldisilazane, N,N-bis(trimethylsilyl)urea, and 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine. Among these, preferred are aminosilanes and epoxysilanes such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-aminopropyltrimethoxysilane.

[0079] Specific examples of titanium-based coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, tetra(1,1-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate, and bis(dioctyl pyrophosphate)oxyacetate. titanate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctyl phosphate)titanate, isopropyl tricumyl phenyl titanate, isopropyl tri(N-amidoethyl, aminoethyl)titanate, dicumyl phenyloxyacetate titanate, diisostearoyl ethylene titanate, etc. Among these, isopropyl tri(N-amidoethyl, aminoethyl)titanate is preferred.

[0080] The method for surface treating the fibrous filler (C) with a coupling agent is not particularly limited, and examples thereof include a sizing treatment in which an organic solvent solution or suspension containing the coupling agent is applied to the fibrous filler (C) as a sizing agent, a dry mixing treatment using a Henschel mixer, super mixer, Loedige mixer, V-type blender, or the like, a spray method, an integral blend method, a dry concentrate method, etc., and the surface treatment can be carried out by a method appropriate for the shape of the fibrous filler (C). Among these, surface treatment by sizing treatment, dry mixing treatment, or spray method is preferred.

[0081] In the surface treatment, a glass film-forming substance may be used together with the coupling agent. The film-forming substance is not particularly limited, and examples thereof include polyester-based, urethane-based, epoxy-based, acrylic-based, vinyl acetate-based, and polyether-based polymers.

[0082] In the surface treatment, a compatibilizer may be used together with the coupling agent. The use of the compatibilizer can improve the interfacial strength between the syndiotactic polystyrene resin (A) and the fibrous filler (C) and non-fibrous filler (D). As the compatibilizer, for example, a modified polymer may be used.

[0083] Specific examples of the compatibilizer include modified polyphenylene ether polymers such as styrene-maleic anhydride copolymer (SMA), styrene-glycidyl methacrylate copolymer, terminal carboxylic acid-modified polystyrene, terminal epoxy-modified polystyrene, terminal oxazoline-modified polystyrene, terminal amine-modified polystyrene, sulfonated polystyrene, styrene-based ionomers, styrene-methyl methacrylate-graft polymer, (styrene-glycidyl methacrylate)-methyl methacrylate-graft copolymer, acid-modified acrylic-styrene-graft polymer, (styrene-glycidyl methacrylate)-styrene-graft polymer, polybutylene terephthalate-polystyrene-graft polymer, polyphenylene ether, (styrene-maleic anhydride)-polyphenylene ether-graft polymer, maleic anhydride-modified polyphenylene ether, fumaric acid-modified polyphenylene ether, glycidyl methacrylate-modified polyphenylene ether, and amine-modified polyphenylene ether. Among these, unmodified or modified polyphenylene ether is preferred, and maleic anhydride-modified polyphenylene ether and fumaric acid-modified polyphenylene ether are more preferred.

[0084] When the fibrous filler (C) is contained, the amount thereof is preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, and even more preferably 5 to 30 parts by mass, per 100 parts by mass of the syndiotactic polystyrene-based resin (A), in order to balance the target linear expansion coefficient with the dimensional stability and impact resistance / mechanical properties.

[0085] Representative commercially available products of the fibrous filler (C) include, for example, HDT09100T manufactured by Tochu Co., Ltd., EPH80M-01N manufactured by Nippon Electric Glass Co., Ltd., ChopVantageHP-3610 manufactured by Nippon Electric Glass Co., Ltd., EFH30-01 manufactured by Central Glass Fiber Co., Ltd., and ECS301HP-3-H manufactured by Chongqing International Composite Materials Co., Ltd. Among these, only one type may be used alone, or two or more types may be used in combination.

[0086] (D) Non-fibrous Filler The resin sheet may contain a non-fibrous filler (D) (hereinafter also referred to as component (D)). The non-fibrous filler (D) is a non-fibrous filler that is expected to have an effect of suppressing the linear expansion coefficient and dimensional change in the direction parallel to the extrusion direction (MD) and the direction perpendicular to the extrusion direction (TD) of the sheet, which is a precursor of the resin sheet.

[0087] The shape of the non-fibrous filler (D) is not particularly limited, and may be, for example, spherical, granular, or plate-like, with granular being preferred.

[0088] As the non-fibrous filler (D), an organic filler or an inorganic filler may be used, and it is preferable to use an inorganic filler.

[0089] As the organic filler, for example, an organic spherical, granular or plate-like filler may be used. The type of polymer used as the organic filler is not particularly limited, but considering the processing temperature of the syndiotactic polystyrene resin (A), when the polymer is a crystalline resin, it is preferable that the melting point is above 280 ° C, more preferably above 300 ° C. When the polymer is an amorphous resin, it is preferable that the glass transition temperature is above 150 ° C, more preferably above 180 ° C. By setting the melting point and glass transition temperature within the above ranges, the shape of the filler can be maintained when processed into a raw resin sheet, and the effect of suppressing the linear expansion coefficient of the resin sheet can be exhibited.

[0090] Examples of inorganic fillers include inorganic spherical, granular, or plate-shaped fillers. Examples of inorganic fillers include talc, carbon black, graphite, titanium dioxide, silica, mica, calcium carbonate, calcium sulfate, barium carbonate, magnesium carbonate, magnesium sulfate, barium sulfate, oxysulfate, tin oxide, alumina, kaolin, silicon carbide, metal powder, glass powder, glass flakes, and glass beads. Among these, silica is particularly preferred from the viewpoints of productivity, cost, and the dielectric properties of the filler itself, and amorphous silica or fused silica is more preferred. Amorphous silica has lower hardness than crystalline silica, so its use can reduce wear on machines and screws. Fused silica is sphericalized by surface tension through surface tension by melting the raw material in a flame and rapidly solidifying the vaporized gas, resulting in fewer sharp edges and a stable shape without the filler itself collapsing.

[0091] The silica preferably has a granular or spherical shape, and more preferably a granular shape. The granular or spherical shape of the silica facilitates mixing when added to a molten resin. Furthermore, since the silica is stable regardless of the direction of force, it is less likely to be broken and less likely to be detached during the production of a raw resin sheet. Furthermore, the deterioration of the mechanical properties of the resin sheet is reduced. The silica may also be hollow.

[0092] The D50 average particle size of the non-fibrous filler (D) is preferably 0.1 to 45 μm, more preferably 0.2 to 30 μm, even more preferably 0.3 to 20 μm, and even more preferably 0.5 to 10 μm. When the D50 average particle size of the non-fibrous filler (D) is 0.1 μm or more, aggregation of the (D) components is suppressed, they do not become foreign matter within the resin sheet, and mechanical properties are less likely to deteriorate. When the D50 average particle size of the non-fibrous filler (D) is 45 μm or less, the spacing between the (D) components does not become too narrow, and the propagation of cracks at the interface when stress is generated can be suppressed. In addition, heat resistance can be maintained during the soldering process.

[0093] When the non-fibrous filler (D) is contained, the amount thereof is preferably 1 to 60 parts by mass, more preferably 3 to 50 parts by mass, and even more preferably 5 to 40 parts by mass, per 100 parts by mass of the syndiotactic polystyrene resin (A). By setting the amount of the non-fibrous filler (D) to 1 part by mass or more, the compounding effect of the (D) component can be exerted. By setting the amount of the non-fibrous filler (D) to 60 parts by mass or less, the smoothness of the raw resin sheet is improved, making it easier to control the thickness, and it is possible to suppress aggregation of the (D) components within the resin sheet and suppress deterioration of mechanical properties.

[0094] When hollow amorphous silica or hollow fused silica is contained as the non-fibrous filler (D), the amount does not depend on the above range. The use of hollow silica is expected to further reduce the dielectric constant. The thickness of the hollow silica film is preferably 0.5 to 2.0 μm, more preferably 0.5 to 1.5 μm, and even more preferably 0.5 to 1.2 μm. If the film thickness is too thin, the silica may crack during screw mixing in a twin-screw kneader, making it impossible to maintain its hollow shape. If the film thickness is too thick, the volume fraction of the hollow portions decreases, and the effect of reducing the dielectric constant may not be achieved.

[0095] The hollow silica preferably has a D50 average particle size of 3 to 45 μm. A D50 average particle size of 3 μm or more is expected to have the effect of lowering the dielectric constant. A D50 average particle size of 45 μm or less will result in a decrease in the mechanical properties of the raw resin sheet.

[0096] The non-fibrous filler (D) may or may not be surface-treated. When the non-fibrous filler (D) is surface-treated, a known surface treatment agent may be used for the surface treatment. For example, by performing a hydrophobic treatment using a silane coupling agent or a titanate coupling agent, the dispersion state in the syndiotactic polystyrene resin (A) can be improved and the generation of aggregates in the resin sheet can be suppressed.

[0097] Representative commercially available products of the non-fibrous filler (D) include, for example, silica particles FB-3SDC manufactured by Denka Company Limited, silica particles FB-7SDC manufactured by Denka Company Limited, silica particles SFP-130MC manufactured by Denka Company Limited, hollow glass beads iM-30k manufactured by 3M Japan Ltd., calcium carbonate "Whiten P-30" manufactured by Shiraishi Calcium Industry Co., Ltd., and "Magnesia RF-98" manufactured by Ube Material Industries, Ltd. Among these, only one type may be used alone, or two or more types may be used in combination.

[0098] (E) Antioxidant The resin sheet may contain an antioxidant (E) (hereinafter also referred to as component (E)) from the viewpoint of processability. The antioxidant (E) may be either a primary antioxidant that prevents oxidation by capturing generated radicals, or a secondary antioxidant that prevents oxidation by decomposing generated peroxides. Examples of primary antioxidants include phenolic antioxidants and amine-based antioxidants. Examples of secondary antioxidants include phosphorus-based antioxidants and sulfur-based antioxidants. The incorporation of these antioxidants alone or in combination can suppress the decrease in molecular weight of component (A) or (B) during the production of the SPS resin composition and can suppress the generation of gas from component (A) or (B) during the hot-pressing process during the production of the resin sheet.

[0099] Examples of phenolic antioxidants include monophenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,6-di-t-butyl-4-[4,6-bis(octylthio)-1,3,5-triazin-2-ylamino]phenol, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Antioxidants: 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine, N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl- bisphenol-based antioxidants such as 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzyl, ... and polymeric phenolic antioxidants such as benzene, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-sec-triazine-2,4,6-(1H,3H,5H)trione, and d-α-tocophenol. Among these, it is preferable to use a polymeric phenolic antioxidant, and more preferably pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate].

[0100] Examples of the amine-based antioxidant include alkyl-substituted diphenylamines.

[0101] Examples of phosphorus-based antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyldiisodecyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenylditridecyl)phosphite, octadecyl phosphite, tris(nonylphenyl)phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)- ... 0-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, tris(2,4-di-t-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,4-di-t-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,6-di-t-butyl-4-methylphenyl)phosphite, 2,2'-methylenebis(4,6-di-t-butylphenyl)octylphosphite, 3,9-bis(2,6-di-t-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane), and the like.

[0102] Examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythritol tetrakis(3-laurylthiopropionate), and 2-mercaptobenzimidazole.

[0103] The antioxidant (E) may be used alone or in a mixture of two or more. When two or more types are used in combination, two or more primary antioxidants may be used, two or more secondary antioxidants may be used, or one or more primary antioxidants and one or more secondary antioxidants may be used in combination. For example, by using a primary antioxidant and a secondary antioxidant in combination, it is expected that both primary and secondary oxidations can be prevented. Among these, the use of a primary antioxidant alone or two or more primary antioxidants is preferred because it can suppress thermal degradation during processing of the resin sheet. The use of a phenolic antioxidant (particularly a polymeric phenolic antioxidant) alone or two or more phenolic antioxidants (particularly a polymeric phenolic antioxidant) is more preferred.

[0104] The thermal decomposition temperature of the antioxidant (E) is preferably 250°C or higher. By using an antioxidant (E) with a thermal decomposition temperature of 250°C or higher, the antioxidant (E) itself can be prevented from thermally decomposing during melt extrusion, thereby reducing the occurrence of problems such as contamination of the melt extruder and yellow discoloration of the polymer. The thermal decomposition temperature of the antioxidant (E) is more preferably 280°C or higher, even more preferably 300°C or higher, and particularly preferably 320°C or higher. A higher thermal decomposition temperature of the antioxidant (E) is preferable, as a higher thermal decomposition temperature enhances the effect of improving the breakdown voltage at high temperatures. The upper limit of the thermal decomposition temperature of the antioxidant (E) is, for example, about 500°C or lower. That is, the thermal decomposition temperature is preferably 250 to 500°C, more preferably 280 to 500°C, even more preferably 300 to 500°C, and particularly preferably 320 to 500°C. In this specification, the temperature at which the mass of the antioxidant (E) decreases by 5 mass % is defined as the thermal decomposition temperature.

[0105] The melting point of the antioxidant (E) is preferably 90°C or higher. By using an antioxidant (E) with a melting point of 90°C or higher, the antioxidant (E) melts faster than the polymer during melt extrusion, preventing the polymer from slipping at the screw feed section of the extruder. As a result, problems such as unstable polymer feed and uneven thickness of the raw resin sheet are less likely to occur. The melting point of the antioxidant (E) is more preferably 120°C or higher, even more preferably 150°C or higher, and particularly preferably 170°C or higher. However, if the melting point of the antioxidant (E) is too high, the antioxidant (E) tends to be difficult to melt even during melt extrusion, resulting in poor dispersion within the polymer. This can lead to problems such as the antioxidant (E) only exerting its effects locally. Therefore, the melting point of the antioxidant (E) is preferably 300°C or lower, more preferably 250°C or lower, even more preferably 220°C or lower, and particularly preferably 200°C or lower. That is, the melting point is preferably 90 to 300°C, more preferably 120 to 250°C, even more preferably 150 to 220°C, and particularly preferably 170 to 200°C.

[0106] The amount of antioxidant (E) is preferably 0.1 to 8 mass% based on the mass of the resin sheet. By including 0.1 mass% or more of antioxidant (E), the heat resistance and heat degradation resistance of the raw resin sheet can be improved. If the amount of antioxidant (E) is too small, the effect of adding antioxidant (E) is insufficient, and the effect of improving the breakdown voltage tends to be reduced. The amount of antioxidant (E) is more preferably 0.2 mass% or more, even more preferably 0.3 mass% or more, and particularly preferably 0.5 mass% or more. However, if the content of antioxidant (E) is too high, the antioxidant (E) tends to aggregate easily in the resin sheet, which tends to increase defects caused by the antioxidant (E), and such defects deteriorate the mechanical properties of the resin sheet. From this perspective, the amount of antioxidant (E) is more preferably 6 mass% or less, even more preferably 4 mass% or less, and particularly preferably 2 mass% or less. That is, the amount of the antioxidant (E) is more preferably 0.2 to 6 mass %, further preferably 0.3 to 4 mass %, and particularly preferably 0.5 to 2 mass %, based on the mass of the resin sheet.

[0107] As the antioxidant (E), commercially available products may be used as they are. Examples of commercially available products include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] available under the trade name IRGANOX 1010 manufactured by Ciba Specialty Chemicals or ANOX 20 manufactured by BASF Japan Ltd., and N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine available under the trade name IRGANOX 1024 manufactured by Ciba Specialty Chemicals. For N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide], a product under the trade name IRGANOX 1098 manufactured by Ciba Specialty Chemicals can be used, and for 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane), a product under the trade name PEP-36 manufactured by ADEKA Corporation can be used.

[0108] The resin sheet may further contain a flame retardant, a release agent, a lubricant, a viscosity reducer, a curing agent, etc. The type of flame retardant is not particularly limited, but for example, a halogen-based flame retardant containing bromine, or an organic or inorganic phosphate, phosphoric acid ester, or phosphorus copolymer can be suitably used. The flame retardant may be in the form of a liquid or a solid, but from the viewpoint of long-term stability, it is preferable to use one that is solid at room temperature.

[0109] <Raw Material Resin Sheet> The raw material resin sheet is an unstretched sheet containing component (A) or a film obtained by biaxially stretching the unstretched sheet. The unstretched sheet may not only be completely unstretched, but may also have some residual strain. Specifically, the stretching ratio is preferably 1.3 or less in both the direction parallel to the extrusion direction of the sheet (longitudinal direction, MD) and the direction perpendicular to the extrusion direction of the sheet (transverse direction, TD).

[0110] The roll temperature during production of the raw resin sheet is preferably 30°C to 100°C, more preferably 40°C to 98°C, and even more preferably 60°C to 95°C. By setting the roll temperature within the above range, the roll winding properties can be made uniform and small. If the roll temperature is below 30°C, condensation may occur on the roll surface, and water droplets may adhere to the sheet and be transferred as surface unevenness. If the roll temperature exceeds 100°C, the molten resin may stick to the roll, making it difficult to stretch and wind the sheet.

[0111] The pressure of the touch roll when producing the raw resin sheet is preferably a linear pressure of 50 to 2000 N / cm. By setting the pressure within this range, the sheet thickness can be made uniform. If the pressure is less than 50 N / cm, unevenness in the sheet thickness may occur. If the pressure exceeds 2000 N / cm, the sheet thickness may become non-uniform and residual stress may remain, which may reduce the sheet's winding ability.

[0112] The thickness of the sheet when producing the raw resin sheet is preferably 50 to 2000 μm. If the thickness of the sheet is less than 50 μm, it is difficult to apply pressure uniformly, and mechanical properties may deteriorate. If the thickness of the sheet is more than 2000 μm, it is difficult to apply sufficient pressure, and the sheet thickness tends to become non-uniform.

[0113] The material of the two rolls used in producing the raw resin sheet is not particularly limited and may be rubber, metal, resin, or the like, but metal is preferred from the viewpoint of applying pressure evenly.

[0114] When performing biaxial stretching, the stretching ratio, stretching temperature, and stretching speed are not particularly limited as long as the object of the present invention can be achieved, but are preferably within the following ranges. Stretching improves the heat-resistant dimensional stability of the raw resin sheet and the resin sheet. Stretching methods include uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching, but sequential biaxial stretching or simultaneous biaxial stretching is preferred, and simultaneous biaxial stretching is more preferred. When uniaxial stretching is performed, the linear expansion coefficient in the non-stretched direction does not decrease, and heat-resistant dimensional stability may decrease. When sequential biaxial stretching is performed, the decrease in the thermal expansion coefficient in the first stretched direction becomes smaller, and heat-resistant dimensional stability may decrease, and this tendency becomes stronger unless the stretching speed is reduced.

[0115] The stretching ratio in both the MD and TD directions is within a range where breakage does not occur beyond 2.0 times, preferably 2.0 to 5.0 times, and more preferably 2.3 to 4.0 times. It is preferable that the stretching ratios in the MD and TD directions are similar. Specifically, when the stretching ratio in the MD direction is PMD and the stretching ratio in the TD direction is PTD, "PTD - PMD" is preferably -0.6 to +0.6, more preferably -0.3 to +0.3. The stretching ratio in the MD direction is based on the MD length immediately before stretching. The stretching ratio in the TD direction is based on the TD length immediately before stretching. By adjusting the stretching ratio within the above range, the difference in the linear expansion coefficients between the MD and TD directions is reduced, allowing the reduction in the linear expansion coefficient to be controlled. For example, increasing the stretching ratio in a given direction increases the reduction in the linear expansion coefficient in that direction.

[0116] When TgP (°C) is defined as the glass transition temperature of the syndiotactic polystyrene resin (A) constituting the raw resin sheet, the stretching temperature is preferably TgP or higher and TgP + 30°C or lower. From the viewpoint of further improving heat-resistant dimensional stability, tensile strength, and tensile elongation, the stretching temperature is more preferably TgP°C or higher and TgP + 25°C or lower. By adjusting the stretching temperature within the above range, the decrease in the linear expansion coefficient can be controlled. For example, lowering the stretching temperature increases the decrease in the linear expansion coefficient. However, if the stretching temperature is too low, stress concentration is likely to occur, making the sheet more likely to break. On the other hand, if the stretching temperature is too high, the sheet will not crystallize sufficiently, the decrease in the thermal expansion coefficient will be small, and dimensional stability during heat resistance may be reduced. The stretching temperature is the temperature of the raw resin sheet when stretched. When the syndiotactic polystyrene resin (A) is composed of two or more polymers, the TgP of the syndiotactic polystyrene resin (A) can be confirmed from an endothermic peak (relaxation of the amorphous part) observed by differential scanning calorimetry (DSC).

[0117] The stretching speed is 50 to 10,000% / min in both the MD and TD directions, preferably 100 to 5,000% / min, and more preferably 100 to 3,000% / min. The stretching speed is a value calculated by {(dimension after stretching / dimension before stretching)-1} x 100 (%) / stretching time. By adjusting the stretching speed within the above range, the decrease in the linear expansion coefficient can be controlled. For example, increasing the stretching speed increases the decrease in the linear expansion coefficient.

[0118] The thickness of the resin sheet is preferably 10 to 2000 μm, more preferably 15 to 1000 μm, even more preferably 20 to 500 μm, and most preferably 25 to 300 μm. When the thickness of the resin sheet is 10 μm or more, the resin sheet is less likely to crack. When the thickness of the resin sheet is 2000 μm or less, the occurrence of partial shrinkage (sink marks) is suppressed, and thickness unevenness does not occur.

[0119] In order to set the thickness of the resin sheet within the above range, the thickness of the raw resin sheet is preferably 10 to 2000 μm, more preferably 15 to 1000 μm, even more preferably 20 to 500 μm, and most preferably 25 to 300 μm.

[0120] An adhesive layer may be laminated on the surface of the surface treatment layer. The form of the adhesive layer is not limited, and may be, for example, a coating of adhesive or a laminate of an adhesive sheet. The composition of the adhesive layer is not particularly limited, and for example, polyolefin, maleimide, polyphenylene ether, polyphenylene sulfide, styrene-based elastomer, etc. may be used as the base material. Among these, it is preferable that the adhesive layer contains a styrene-based elastomer.

[0121] The adhesive layer may further contain a curing agent. Examples of curing agents include aliphatic epoxy, alicyclic epoxy, benzoxazine, carbodiimide, isocyanate, etc. The adhesive layer may also contain additives such as fillers such as silica and mica, and flame retardants.

[0122] (Adhesive Sheet) The adhesive layer may be formed using an adhesive sheet that is a precursor. For example, the adhesive sheet may be a sheet obtained by applying an adhesive composition to a release substrate, drying it to partially harden it, and then laminating a release substrate on top of that. A specific configuration may be release substrate / adhesive layer / release substrate. Laminating a release substrate functions as a protective layer for the substrate or adhesive layer. Furthermore, by using a release substrate, the release substrate can be released from the adhesive sheet and the adhesive layer can be transferred to another substrate.

[0123] The thickness of the adhesive sheet is, for example, preferably 5 to 200 μm, more preferably 8 to 150 μm, even more preferably 10 to 100 μm, and most preferably 12 to 80 μm. By making the thickness of the adhesive sheet 5 μm or more, the occurrence of pinholes can be prevented. In addition, the adhesive strength can be increased. By making the thickness of the adhesive sheet 200 μm or less, thickness unevenness can be reduced. In addition, residual solvent can be reduced, and blisters can be prevented from occurring during pressing in the production of printed wiring boards.

[0124] The release substrate is not particularly limited, but examples include paper such as fine paper, kraft paper, roll paper, and glassine paper, with coating layers of clay, polyethylene, polypropylene, or other filler on both sides, and then a silicone-based, fluorine-based, or alkyd-based release agent coated on each of these coating layers. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer alone, and films such as polyethylene terephthalate coated with the above-mentioned release agent. Due to factors such as the release force between the release substrate and the adhesive layer and the adverse effect of silicone on electrical properties, it is preferable to use polypropylene-sealed fine paper on both sides and then apply an alkyd-based release agent thereon, or polyethylene terephthalate coated with an alkyd-based release agent.

[0125] A metal layer may be laminated on the surface of the adhesive layer. The material constituting the metal layer may be any conventionally known conductive material that can be used for printed wiring boards. Examples of materials constituting the metal layer include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as alloys thereof, plated products, and metals treated with other metals such as zinc or chromium compounds. The metal layer is preferably a metal foil, more preferably a copper foil. Copper foils include electrolytic foils and rolled foils, and either type of copper foil may be used.

[0126] The thickness of the metal layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 10 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less. By making the metal layer thickness 1 μm or more, sufficient electrical performance of the printed wiring board can be obtained. By making the metal layer thickness 50 μm or less, processing efficiency during the production of the printed wiring board can be improved. That is, the thickness of the metal layer is preferably 1 to 50 μm, more preferably 3 to 30 μm, and even more preferably 10 to 25 μm.

[0127] Representative commercially available metal foils include, for example, low-roughness copper foil "CF-T4X-SV18" and low-roughness copper foil "CF-T9DA-SV-18" manufactured by Fukuda Metal Foil and Powder Co., Ltd., and copper foil "DGTSEU2" and copper foil "GTS-MP" manufactured by Furukawa Electric Co., Ltd.

[0128] The printed wiring board may be a laminate in which an adhesive layer and a metal layer are laminated in this order on a surface-treated layer of a resin sheet containing a syndiotactic polystyrene resin as a constituent resin.

[0129] The peel strength at the interface between the surface treatment layer and the adhesive layer of the resin sheet must be 0.3 N / mm or more. The peel strength is preferably 0.4 N / mm or more, more preferably 0.5 N / mm or more, since this improves the durability of the laminate. There are no particular restrictions on the upper limit of the peel strength, but for printed wiring board applications, 2 N / mm or less is sufficient, and 1.5 N / mm or less is acceptable. That is, the peel strength is preferably 0.3 to 2 N / mm, more preferably 0.4 to 1.5 N / mm, and even more preferably 0.5 to 1.5 N / mm.

[0130] The laminate may comprise a resin sheet having a surface treatment layer, an adhesive layer, and a metal layer laminated in this order, and although other layers may be laminated between the adhesive layer and the metal layer, it is preferable that the resin sheet having a surface treatment layer, the adhesive layer, and the metal layer are laminated directly to each other.

[0131] The laminate may have an adhesive layer and a metal layer laminated in this order on both sides of a resin sheet having a surface treatment layer. For example, it may be a laminate of metal layer / adhesive layer / resin sheet / adhesive layer / metal layer. When an adhesive layer and a metal layer are laminated on both sides of a resin sheet, it is preferable that the resin sheet is the innermost layer. In the case of such a laminate on both sides, another layer may be laminated between the adhesive layer and the metal layer, but it may also be a laminate in which the resin sheet, adhesive layer, and metal layer are directly laminated.

[0132] Next, an embodiment of a method for producing a resin sheet with a surface treatment layer according to the present invention will be described. The resin sheet with a surface treatment layer can be produced by a method including a pretreatment step of performing a surface activation treatment on at least one surface of a resin sheet containing a syndiotactic polystyrene-based resin (i.e., a raw resin sheet), a surface layer formation step of forming a primer layer on the surface that has been subjected to the surface activation treatment, and a surface layer reaction step of heating the resin sheet on which the primer layer has been formed.

[0133] [Preparation Step] In the preparation step, a surface activation treatment is performed on at least one surface of a resin sheet (raw resin sheet) containing a syndiotactic polystyrene resin. By performing the surface activation treatment on the surface of the raw resin sheet, functional groups can be added to the surface of the raw resin sheet, and effects such as changing the contact angle, improving adhesion, and removing surface contamination can be expected. In addition, the subsequent application of a primer composition can be performed effectively. Examples of surface activation treatments include corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, radiation treatment, and flame treatment. These treatments may be performed alone or in combination of two or more. The surface activation treatment may be performed on at least one surface of the raw resin sheet, or may be performed on both surfaces of the raw resin sheet.

[0134] The conditions for the corona discharge treatment in the surface activation treatment may be, for example, an output of 80 to 150 W and a conveying speed of 0.5 to 1.5 m / min.

[0135] The resin sheet (raw material resin sheet) containing a syndiotactic polystyrene resin may be an unstretched sheet or a film obtained by biaxially stretching an unstretched sheet. The resin sheet (raw material resin sheet) containing a syndiotactic polystyrene resin may be subjected to heat treatment and annealing treatment. By performing heat treatment and annealing treatment, the crystallinity of the syndiotactic polystyrene resin contained in the raw material resin sheet can be increased, thereby improving the solder heat resistance of the resin sheet. In addition, the thermal dimensional accuracy of the resin sheet can be improved.

[0136] The heating temperature in the heat treatment is not particularly limited and may be, for example, 180°C to 220°C. The heat treatment may be carried out, for example, in a vacuum or under pressure, and is preferably carried out both in a vacuum and under pressure. The pressure during pressure application may be, for example, 1 to 3 MPa. The heat treatment may be carried out using, for example, a vacuum press.

[0137] The heating temperature in the annealing treatment is not particularly limited and may be, for example, 160° C. to 200° C. The annealing treatment may be performed using, for example, a thermostatic bath. The heating temperature in the annealing treatment may be relatively lower than the heating temperature in the heat treatment.

[0138] [Surface Layer Forming Step] In the surface layer forming step, a primer layer is formed on the surface that has been subjected to the surface activation treatment using a primer composition. Hereinafter, the primer layer may be referred to as the surface layer.

[0139] The primer layer is formed using a primer composition containing a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups, a second silane compound (b) having an alkenyl group and two or more alkoxy groups, and an alcohol (d), in which the amount of the second silane compound (b) is 100 to 250 parts by mass per 100 parts by mass of the first silane compound (a).

[0140] The method for forming the primer layer is not particularly limited, and examples thereof include a method of applying a primer composition to the surface of a resin sheet, a method of immersing a resin sheet in the primer composition, etc. The primer composition may be diluted with water (e).

[0141] [Surface Layer Reaction Step] In the surface layer reaction step, a resin sheet with a surface treatment layer can be produced by heating the resin sheet on which the primer layer has been formed to cause a reaction in the surface layer. The heating temperature is not particularly limited and may be, for example, 80°C to 120°C. The heating time is not particularly limited and may be, for example, 3 to 15 minutes. Heating may be performed at normal pressure or reduced pressure, and a thermostatic bath may be used.

[0142] After heating, curing (hardening treatment) may be performed. The curing temperature is not particularly limited and may be, for example, 80°C to 120°C. Curing may be performed using, for example, a thermostatic bath. The curing temperature may be relatively lower than the heating temperature.

[0143] This application claims the benefit of priority based on Japanese Patent Application No. 2024-006321, filed on January 18, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-006321 are incorporated herein by reference.

[0144] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples, and modifications can of course be made within the scope of the above and below-described aims, and all such modifications are included within the technical scope of the present invention. In the following examples, parts and percentages are expressed by mass unless otherwise specified.

[0145] (1) Raw Materials and Raw Material Characteristics The raw materials used in the examples are listed below along with the raw material characteristics for each component of the laminate. The melting points of the raw materials were measured using a differential scanning calorimeter (hereinafter referred to as DSC, "Q-2000" manufactured by TA Instruments Japan) at a rate of 20 ° C. / min to melt, then cooled to form a resin, and then heated again to melt. The glass transition temperature of the raw materials was taken as the temperature at the start (rise) of the endothermic peak during the heating process. For other characteristics, the nominal values ​​listed in the catalog values ​​of the raw material manufacturers were listed.

[0146] [Resin sheet] (A) Syndiotactic polystyrene resin: XAREC (registered trademark) 90ZC manufactured by Idemitsu Kosan Co., Ltd. (syndiotactic polystyrene not modified with a compound having a polar group, 100% by mass, weight average molecular weight 200,000, MFR measured at 300°C under a load of 1.2 kg was 9 g / 10 min, melting point 271°C, glass transition temperature 96°C). (B) Rubber-like elastomer: Tuftec (registered trademark) H1062 manufactured by Asahi Kasei Corporation (8% by mass, styrene ratio 18% by mass, MFR measured at 230°C under a load of 2.16 kg was 4.5 g / 10 min). (C) Fibrous filler: HDT09100T manufactured by Tochu Co., Ltd. (12% by mass, D glass, fiber diameter (diameter) 9 μm, D50 average fiber length 100 μm). (D) Non-fibrous filler Silica particles FB-3SDC (10% by mass, D50 average particle size 3.1 μm) manufactured by Denka Co., Ltd. (E) Antioxidant ANOX20 (0.2% by mass, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], melting point 118°C) manufactured by BASF Japan Ltd. ANOX20 decreased by 1% by mass at 166°C, 3% by mass at 335°C, 5% by mass at 350°C, and 10% by mass at 369°C. The thermal decomposition temperature of ANOX20 was 350°C.

[0147] [Primer composition] (a) First silane compound: N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (b) Second silane compound: vinyltrimethoxysilane (c) Polyamine compound: ethylenediamine (d) Alcohol: ethyl alcohol, methyl alcohol, normal propyl alcohol (e) Water (f) Dimethylsiloxane oligomer: hexamethyldisiloxane

[0148] [Adhesive layer] Low dielectric adhesive film "Aron Mighty AF-711" (flame retardant grade, thickness 25 μm) manufactured by Toagosei Co., Ltd.

[0149] [Metal layer] Low roughness copper foil “CF-T4X-SV18” manufactured by Fukuda Metal Foil and Powder Industry Co., Ltd. (thickness 18 μm, Rz 1.1 μm)

[0150] (2) Experimental Examples (Experiments 1 and 5) Raw materials (A) to (E) were blended and kneaded to produce an unstretched sheet. Specifically, a φ36 mm twin-screw extruder was used, and each of the components (A) to (E) was fed into the main feeder or side feeder, respectively, and compounded at a resin temperature of 300°C. Four strands were extruded from a φ4 mm round die, and the strands were cooled and solidified in a water-cooled bath and cut to obtain cylindrical resin pellets. The obtained cylindrical resin pellets were placed in the hopper of a φ20 mm single-screw extruder, remelted at a resin temperature of 300 ° C, extruded into a sheet from a T-die, compressed and cooled to solidification by sandwiching between two rolls, a metal touch roll and a take-up roll (both roll temperatures were 90 ° C), and then taken up at a speed of 1 m / min onto a φ80 mm paper tube to produce a 300 μm thick unstretched sheet (raw resin sheet). The pressure of the touch roll was a linear pressure of 100 N / cm. In this specification, the direction parallel to the extrusion direction of the sheet is defined as MD, and the direction perpendicular to the extrusion direction is defined as TD.

[0151] Next, the obtained unstretched sheet (raw resin sheet) was subjected to heat treatment and annealing treatment to produce a resin sheet. For the heat treatment, an unstretched sheet appropriately cut according to the face plate size of a vacuum press (MHPC-V-450-450, manufactured by Japan Steel Works) was prepared, and a release film PEEK (Shin-Etsu Sepia Film, thickness 50 μm), a SUS plate (#400, thickness 1.5 mm, SUS304), and a cushion material (Yamauchi Original Mat, YOM type) were laminated on both sides of this sheet in this order, and the laminate was placed in a vacuum press. In the vacuum press, the sheet was heated from room temperature to 200 ° C. at a heating rate of 7 ° C. / min, pressed under vacuum (less than 4 mmHg) at a pressure of 2 MPa for 30 minutes, and then slowly cooled to about 50 ° C., after which the vacuum state was released to obtain a heat-treated sheet. The heat-treated sheet was then subjected to an annealing treatment by leaving the heat-treated sheet in a thermostatic chamber set at 180°C for 30 minutes, and then removing the sheet from the thermostatic chamber and leaving it to cool to room temperature. The laminated release film, SUS plate, and cushioning material were then removed to obtain a resin sheet.

[0152] Whether the resin sheet obtained by annealing has crystallized was confirmed in accordance with JIS K7121 (2012) using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, DSC7020). Specifically, when 5 mg of the resin sheet was placed in an aluminum pan and heated from room temperature at a temperature increase rate of 20 ° C. / min, if no exothermic peak was observed in the temperature range of 100 ° C. to 220 ° C., it was determined that crystallization of the syndiotactic polystyrene resin was completed by heat treatment during vacuum pressing. As a result, it was confirmed that the resin sheet used in this example had crystallized.

[0153] The resin sheet obtained after the annealing treatment was subjected to a corona discharge treatment as a surface activation treatment. The corona discharge treatment was performed twice on both surfaces of the resin sheet using a corona discharge treatment device (manufactured by Kasuga Electric Co., Ltd., high-frequency power supply, special AGI-023S, wire electrode 1φ2.4 m) at an output of 130 W and a conveying speed of 1 m / min.

[0154] The corona discharge-treated resin sheet was immersed in Solution 1 containing Primer Composition 1 for 2 minutes, then removed from the solution and hung vertically to air-dry. Solution 1 containing Primer Composition 1 was prepared as follows: 40 g of ethyl alcohol, 10 g of methyl alcohol, 25 g of normal propyl alcohol, and 8 g of ethylenediamine were added to a 200 ml glass bottle and stirred to form a homogeneous solution. Next, 5 g of hexamethyldisiloxane, 5 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and 7 g of vinyltrimethoxysilane were added and stirred to obtain a homogeneous Primer Composition 1. Next, 15 g of ion-exchanged water was added to the resulting Primer Composition 1 to dilute it, thereby preparing Solution 1 containing Water-Soluble Adhesion-Promoting Primer Composition 1.

[0155] After air-drying until the solution containing primer composition 1 stopped dripping from the sheet surface, the resin sheet was hung in a thermostatic chamber set to 90° C. for 10 minutes to dry. After drying, the resin sheet was removed from the thermostatic chamber and allowed to stand until it cooled to room temperature, thereby producing a resin sheet 1 with a surface treatment layer.

[0156] (Experiment 2) A resin sheet 2 with a surface treatment layer was produced under the same conditions as in Experiment 1, except that Solution 2 containing Primer Composition 2 was used instead of Solution 1 containing Primer Composition 1. Solution 2 containing Primer Composition 2 was prepared using the following procedure. 40 g of ethyl alcohol, 10 g of methyl alcohol, and 25 g of normal propyl alcohol were added to a 200 ml glass bottle and stirred to form a homogeneous solution. Next, 5 g of hexamethyldisiloxane, 5 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and 7 g of vinyltrimethoxysilane were added and stirred to obtain a homogeneous primer composition 2. Next, 15 g of ion-exchanged water was added to the obtained primer composition 2 to dilute it, thereby preparing Solution 2 containing a water-soluble adhesion-promoting primer composition 2.

[0157] (Experiment 3, Experiment 4) Resin sheets 3 and 4 were produced under the same conditions as in Experiment 1, except that the resin sheet obtained by annealing in Experiment 1 was not subjected to corona discharge treatment and that a surface treatment layer, which was a treatment layer using primer composition 1, was not formed.

[0158] (Experiment 6) Resin sheet 6 was produced under the same conditions as in Experiment 1, except that the surface treatment layer, which was a treatment layer using primer composition 1, was not formed.

[0159] Cases where corona discharge treatment was performed are indicated by ○ in Table 1, and cases where corona discharge treatment was not performed are indicated by - in Table 1. Table 1 shows the types of solutions (Solution 1, Solution 2) used when forming a surface treatment layer on the surface of the resin sheet. In Table 1, - indicates that a surface treatment layer was not formed.

[0160]

[0161] The surfaces of the resin sheets obtained in Experiments 1, 3 to 6 were subjected to elemental analysis using ESCA (X-ray photoelectron spectroscopy). A Thermo Fisher Scientific K-Alpha+ ESCA was used. The results of the elemental analysis are also shown in Table 1 above. Based on the results of the elemental analysis, the value of Si / (C + N + O + Si) defined by formula (1), the value of O / Si defined by formula (2), the value of C / Si defined by formula (3), and the value of N / Si defined by formula (4) were each calculated. The calculated values ​​are also shown in Table 1 above.

[0162] Next, adhesive layers were laminated on both sides of the resin sheets obtained in Experiments 1 to 6. To laminate the adhesive layers, two adhesive sheets (Aron Mighty AF-711) with release films laminated on both sides were prepared, the release film on one side was peeled off, and the exposed adhesive layer was placed facing the resin sheet. The resin sheet and adhesive layer were laminated by passing through a roll laminator (MCK, MRS-600 model) set at 120 ° C, 0.5 m / min, and 0.3 MPa to obtain a laminate. The laminate structure of the laminates obtained in Experiments 1, 2, and 5 was release film / adhesive layer / resin sheet with surface treatment layer / adhesive layer / release film. The laminate structure of the laminates obtained in Experiments 3, 4, and 6 was release film / adhesive layer / resin sheet / adhesive layer / release film.

[0163] Next, the release films on both sides of the laminate of the resin sheet and adhesive layer were peeled off, and a metal layer (CF-T4X-SV) was overlaid on the exposed adhesive layer to obtain a laminate. The laminate structure obtained in Experiments 1, 2, and 5 was metal layer / adhesive layer / resin sheet with surface treatment layer / adhesive layer / metal layer. The laminate structure obtained in Experiments 3, 4, and 6 was metal layer / adhesive layer / resin sheet / adhesive layer / metal layer.

[0164] Next, the resulting laminate was subjected to a heat treatment. In Experiments 4 and 5, the laminate was further subjected to a curing (hardening) treatment after the heat treatment.

[0165] The heat treatment was performed by stacking SUS plates (#400, 1.5 mm thick, SUS304) and cushioning material (Yamauchi Original Mat, YOM type) on both sides of the obtained laminate in this order, and then placing the obtained laminate in a vacuum press. Vacuum pressing was performed in the vacuum press under the following condition 1 or condition 2. Table 1 shows the vacuum pressing conditions (condition 1, condition 2) used in each experiment. Condition 1: The temperature was increased from room temperature to 180°C at a rate of 6°C / min, and the laminate was pressed under vacuum at a pressure of 2 MPa for 60 minutes. Condition 2: The temperature was increased from room temperature to 120°C at a rate of 6°C / min, and the laminate was pressed under vacuum at a pressure of 2 MPa for 15 minutes.

[0166] After vacuum pressing, the laminate was gradually cooled to about 50° C., the vacuum was released, and the heat-treated laminate was taken out.

[0167] Next, for Experiments 4 and 5, the heat-treated laminate was placed in a thermostatic chamber set at 100°C and left to stand for 24 hours in a nitrogen atmosphere (approximately 20 L / min) to be cured. Cases where curing was performed are indicated by ○ in Table 1, and cases where curing was not performed are indicated by - in Table 1. After curing, the laminate was removed from the thermostatic chamber and left to stand until it cooled to room temperature, thereby obtaining a resin sheet in which a metal layer was laminated via an adhesive layer.

[0168] The laminate obtained by the heat treatment or the laminate after curing was made into a resin sheet, and the peel strength and heat resistance of the obtained resin sheet were evaluated.

[0169] (Peel Strength) A 5 mm wide cut was made in the metal layer on one side of a resin sheet having a metal layer laminated thereon via an adhesive layer to prepare a test piece for measuring peel strength. Using a tension-compression testing machine (TG-2kN manufactured by MinebeaMitsumi Inc.), the resin sheet was peeled at a 90° angle at a tensile speed of 50 mm / min, and the peel strength at the interface between the resin sheet and the adhesive layer was measured. The measurement results are shown in Table 1.

[0170] (Heat Resistance) The heat resistance of the resin sheet on which the metal layer was laminated via the adhesive layer was evaluated by a solder float test. The resin sheet was cut into a size of 25 x 25 mm to prepare a test piece. A solder bath (POT-103C manufactured by Taiyo Electric Industrial Co., Ltd.) containing lead-free solder (lead-free solder bar, M705-BAR manufactured by Taiyo Electric Industrial Co., Ltd.) was set to 260 ° C, and the test piece was floated on the molten solder. After leaving it for 1 minute, the test piece was removed from the solder bath and left to cool to room temperature. The appearance of the test piece was visually observed to check for the presence of bubbles and foreign matter in the metal layer and for peeling on the metal layer. A test piece without bubbles and foreign matter in the metal layer and without peeling on the metal layer was deemed to pass, and the heat resistance was evaluated as good, and the evaluation result was indicated as ○ in Table 1. If the metal layer had blistering due to air bubbles, blistering due to foreign matter, or peeling, the sample was deemed unacceptable and evaluated as having poor heat resistance, and the evaluation result was recorded as x in Table 1.

[0171] The following can be inferred from Table 1. When the surfaces of the resin sheets obtained in Experiments 1 and 5 were subjected to elemental analysis by ESCA, Si, C, N, and O were observed, and the amounts of these elements satisfied the relationships of Equations (1) to (4). As a result, when a metal layer was laminated onto the resin sheet via an adhesive layer, the peel strength at the interface between the resin sheet and the adhesive layer was high, the adhesion between the resin sheet and the adhesive layer was good, and the metal layer was less likely to peel off. Furthermore, the resin sheets on which the metal layer was laminated via the adhesive layer had excellent heat resistance. Since the resin sheets obtained in Experiments 1, 2, and 5 had a surface treatment layer that satisfied the requirements specified in the present invention, when a metal layer was laminated onto the resin sheet via an adhesive layer, the peel strength at the interface between the resin sheet and the adhesive layer was high, the adhesion between the resin sheet and the adhesive layer was good, and the metal layer was less likely to peel off. Furthermore, the resin sheets on which the metal layer was laminated via the adhesive layer had excellent heat resistance.

[0172] On the other hand, when the resin sheets obtained in Experiments 3, 4, and 6 were subjected to elemental analysis by ESCA, Si, C, N, and O were observed on the surface, but the amounts of these elements did not satisfy any of the relationships in Equations (1) to (4). As a result, even when a metal layer was laminated onto the resin sheet via an adhesive layer, the peel strength at the interface between the resin sheet and the adhesive layer was low, the adhesion between the resin sheet and the adhesive layer was poor, and the metal layer was easily peeled off. Furthermore, the resin sheets on which the metal layer was laminated via an adhesive layer also had poor heat resistance. Since the resin sheets obtained in Experiments 3, 4, and 6 did not have a surface treatment layer formed, when a metal layer was laminated onto the resin sheet via an adhesive layer, the peel strength at the interface between the resin sheet and the adhesive layer was low, the adhesion between the resin sheet and the adhesive layer was poor, and the metal layer was easily peeled off. Furthermore, the resin sheets on which the metal layer was laminated via an adhesive layer also had poor heat resistance.

Claims

1. A resin sheet with a surface treatment layer, wherein the resin sheet contains a syndiotactic polystyrene-based resin, the surface treatment layer is present on one or both sides of the resin sheet, and when the surface of at least one side of the surface treatment layer that does not contact the resin sheet is subjected to elemental analysis by X-ray photoelectron spectroscopy (ESCA), Si, C, N, and O are observed, and the amounts of these satisfy the relationships of the following formulas (1) to (4). A resin sheet with a surface treatment layer. Si / (C + N + O + Si) ≥ 0.03 ··· (1) 1.0 < O / Si ≤ 3.0 ··· (2) C / Si ≥ 1.0 ··· (3) 0.1 ≤ N / Si ≤ 2.5 ··· (4) [In formulas (1) to (4), each atomic symbol indicates the content (atomic%) of each atom.] 2. The resin sheet according to claim 1, wherein the Si atom content is 5 to 25 atomic% and the N atom content is 1 to 15 atomic%.

3. A resin sheet with a surface treatment layer, wherein the resin sheet contains a syndiotactic polystyrene-based resin, the surface treatment layer is present on one or both sides of the resin sheet, and the surface treatment layer is a treatment layer formed by a primer composition containing a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups, a second silane compound (b) having an alkenyl group and two or more alkoxy groups, and an alcohol (d), and in the primer composition, the second silane compound (b) is contained in an amount of 40 to 250 parts by mass with respect to 100 parts by mass of the first silane compound (a). A resin sheet with a surface treatment layer.

4. The resin sheet according to claim 1 or 3, wherein an adhesive layer is laminated on the surface treatment layer.

5. The resin sheet according to claim 4, wherein the adhesive layer contains a styrene-based elastomer.

6. The resin sheet according to claim 4, wherein a metal layer is laminated on the adhesive layer.

7. A primer composition containing a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups, a second silane compound (b) having an alkenyl group and two or more alkoxy groups, and an alcohol (d), and the amount of the second silane compound (b) is 40 to 250 parts by mass with respect to 100 parts by mass of the first silane compound (a).

8. The primer composition according to claim 7, further containing at least one selected from the group consisting of a polyvalent amine compound (c), water (e), and a dimethylsiloxane oligomer (f) having 6 or less silicon atoms in which all substituents other than oxygen atoms bonded to silicon atoms are methyl groups.

9. The primer composition according to claim 7, wherein the primer composition contains 100 to 250 parts by mass of the polyvalent amine compound (c) with respect to 100 parts by mass of the first silane compound (a).

10. The primer composition according to claim 7, wherein the primer composition contains 2000 parts by mass or less of water (e) with respect to 100 parts by mass of the first silane compound (a).

11. The primer composition according to claim 7, wherein the primer composition contains 10 to 500 parts by mass of a dimethylsiloxane oligomer (f) having 6 or less silicon atoms in which all substituents other than oxygen atoms bonded to silicon atoms are methyl groups with respect to 100 parts by mass of the first silane compound (a).

12. The primer composition according to claim 7, containing two or more kinds of the alcohol (d).

13. A method for manufacturing a resin sheet with a surface treatment layer, comprising: a pre-treatment step of performing a surface activation treatment on at least one surface of a resin sheet containing a syndiotactic polystyrene-based resin; a surface layer forming step of forming a primer layer on the surface subjected to the surface activation treatment; and a surface layer reaction step of heating the resin sheet on which the primer layer is formed.

14. The manufacturing method according to claim 13, wherein the surface activation treatment is any one or a combination of two or more of corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, radiation treatment, and flame treatment.

15. The manufacturing method according to claim 13, wherein the primer layer is formed using a primer composition containing a first silane compound (a) having an aminoalkyl group and two or more alkoxy groups, a second silane compound (b) having an alkenyl group and two or more alkoxy groups, and an alcohol (d).

16. The manufacturing method according to claim 15, wherein in the primer composition, the amount of the second silane compound (b) is 40 to 250 parts by mass with respect to 100 parts by mass of the first silane compound (a).

17. The production method according to claim 15, wherein the primer composition further contains at least one selected from the group consisting of a polyvalent amine compound (c), water (e), and a dimethylsiloxane oligomer (f) having 6 or less silicon atoms, in which all substituents other than oxygen atoms bonded to silicon atoms are methyl groups.

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