Resin sheet with surface treatment layer, primer composition, and method for manufacturing resin sheet with surface treatment layer.

Abstract

A resin sheet with a surface-treated layer is provided. This resin sheet contains a syndiotactic polystyrene resin. When a metal layer is laminated via an adhesive layer, it exhibits good adhesion to the adhesive layer, making the metal layer difficult to peel off, even under heat treatment conditions simulating a welding process. The surface-treated layer is present on one or both sides of the resin sheet. When elemental analysis is performed on at least one side of the surface-treated layer (the side not in contact with the resin sheet) using X-ray photoelectron spectroscopy (ESCA), Si, C, N, and O are observed, and their amounts satisfy a specific relationship.

Description

Technical Field

[0001] This invention relates to a resin sheet with a surface-treated layer, a primer composition, and a method for manufacturing the resin sheet with the surface-treated layer. More specifically, it relates to a resin sheet preferably used as a printed circuit board material, a primer composition, and a method for manufacturing the resin sheet. Background Technology

[0002] In recent years, the development of materials used in high-speed information communication equipment such as 5G has become increasingly active. To improve information transmission speed, researchers have developed plastic materials with low dielectric constants and low dielectric loss tangents at high frequencies above 10GHz. The same demand exists for printed circuit boards (PCBs) using plastic materials with excellent dielectric properties, including low dielectric constants and low dielectric loss tangents, requiring PCBs to have low transmission losses. These PCBs are typically exposed to high temperatures during manufacturing and use, therefore, they generally require high heat resistance and dimensional stability. For example, the soldering process in PCB manufacturing requires heat resistance capable of withstanding the heat treatment conditions in this process (e.g., 260°C for approximately 120 seconds).

[0003] To ensure heat resistance during the soldering process, fluoropolymers (e.g., polytetrafluoroethylene; PTFE) can be considered as materials for printed circuit boards. Patent Document 1 describes an example of a fluoropolymer substrate.

[0004] Syndiotactic polystyrene (hereinafter, sometimes simply referred to as SPS) is known as a material with low dielectric constant and dielectric loss tangent. Patent Document 2 describes a laminate for an electronic circuit board using a syndiotactic polystyrene-based resin. This laminate for an electronic circuit board 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 layers; and a second metal layer formed on the first metal layer. Examples of methods for forming the first metal layer include electroplating and vapor deposition.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-171480

[0008] Patent Document 2: Japanese Patent Application Publication No. 2015-2334 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] The PTFE and other fluoropolymer substrates described in Patent Document 1 exhibit low adhesion to metal foils, making it difficult to laminate them with metal foils of low surface roughness. Therefore, it is necessary to laminate metal foils with high surface roughness, which leads to a decrease in transmission loss of the fluoropolymer substrate in high-frequency regions. To improve adhesion, special treatments such as ultraviolet irradiation of the fluoropolymer substrate are required, which not only complicates the manufacturing process but also reduces productivity, thus increasing manufacturing costs.

[0011] In Patent Document 2, because the first metal layer is directly attached to the second resin layer containing syndiotactic polystyrene resin, stress is generated due to the difference in the coefficients of linear expansion between the second resin layer and the first metal layer. This sometimes causes 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 capable of withstanding the heat treatment conditions in welding processes.

[0012] The first objective of this invention is to provide a resin sheet with a surface-treated layer, the resin sheet containing a syndiotactic polystyrene resin, which exhibits good adhesion to the adhesive layer when a metal layer is laminated through an adhesive layer, making the metal layer difficult to peel off, and even under heat treatment conditions simulating a welding process, the metal layer is difficult to peel off. The second objective of this invention is to provide a primer composition. The third objective of this invention is to provide a method for manufacturing the resin sheet with a surface-treated layer.

[0013] Technical solutions to the problem

[0014] The present invention is described below.

[0015] [1] A resin sheet with a surface treatment layer, the resin sheet containing syndiotactic polystyrene resin, the surface treatment layer existing on one or both sides of the resin sheet, when elemental analysis is performed on at least one side of the surface treatment layer that is not in contact with the resin sheet by X-ray photoelectron spectroscopy (ESCA), Si, C, N, and O are observed, and the amounts of these atoms satisfy the following relationships (1) to (4).

[0016] Si / (C+N+O+Si)≥0.03···(1)

[0017] 1.0<O / Si≤3.0···(2)

[0018] C / Si≥1.0 ···(3)

[0019] 0.1≤N / Si≤2.5 ···(4).

[0020] [In equations (1) to (4), each atom symbol represents the content (atomic percentage) of each atom.]

[0021] [2] According to the resin sheet described in [1], the Si atomic content is 5 to 25 atomic%, and the N atomic content is 1 to 15 atomic%.

[0022] [3] 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, the surface treatment layer being a treatment layer formed by a primer composition containing a first silane compound (a) having an amino alkyl 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 primer composition contains 40 to 250 parts by mass of the second silane compound (b) relative to 100 parts by mass of the first silane compound (a).

[0023] [4] The resin sheet according to any one of [1] to [3], wherein an adhesive layer is laminated on the surface treatment layer.

[0024] [5] The resin sheet according to [4], wherein the adhesive layer contains a styrene-based elastomer.

[0025] [6] The resin sheet according to [4] or [5], wherein a metal layer is laminated on the adhesive layer.

[0026] [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 relative to 100 parts by mass of the first silane compound (a).

[0027] [8] The primer composition according to [7], wherein the primer composition further comprises at least one selected from the group consisting of a polyamine compound (c), water (e) and a dimethylsiloxane oligomer (f) having 6 or fewer silicon atoms, wherein all substituents except oxygen atoms bonded to silicon atoms are methyl.

[0028] [9] The primer composition according to [7] or [8], wherein, relative to 100 parts by weight of the first silane compound (a), the primer composition contains 100 to 250 parts by weight of a polyamine compound (c).

[0029]

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

[0030]

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

[10] , wherein, relative to 100 parts by mass of the first silane compound (a), the primer composition contains 10 to 500 parts by mass of a dimethylsiloxane oligomer (f) in which all substituents except oxygen atoms bonded to silicon atoms are methyl and the number of silicon atoms is 6 or less.

[0031]

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

[11] , wherein it contains two or more of the alcohols (d).

[0032]

[13] A method for manufacturing a resin sheet with a surface treatment layer, comprising: a substrate treatment step of performing a surface activation treatment on at least one surface of a resin sheet containing a syndiotactic polystyrene resin; a surface layer forming step of forming a base coating on the surface where the surface activation treatment has been performed; and a surface layer reaction step of heating the resin sheet on which the base coating has been formed.

[0033]

[14] According to the manufacturing method described in

[13] , 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.

[0034]

[15] The manufacturing method according to

[13] or

[14] , wherein the base coating is formed using a base coating composition containing a first silane compound (a) having an amino alkyl 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).

[0035]

[16] According to the manufacturing method described in

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

[0036]

[17] According to the manufacturing method described in

[15] or

[16] , the primer composition further comprises at least one 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 except oxygen atoms are methyl.

[0037] The effects of the invention

[0038] According to the present invention, a resin sheet with a surface-treated layer can be provided. 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 difficult to peel off, even under heat treatment conditions simulating a welding process. Furthermore, if the primer composition of the present invention is used, since the adhesion between the resin sheet and the adhesive layer is improved when a metal layer is laminated on the resin sheet via an adhesive layer, the metal layer is difficult to peel off, even under heat treatment conditions simulating a welding process. Additionally, according to the present invention, a method for manufacturing the resin sheet with a surface-treated layer can be provided. Detailed Implementation

[0039] The present invention will now be described in detail based on the embodiments, but the present invention is not limited to the embodiments described below, and can also be implemented by modifications within the scope of the foregoing and following spirit, all of which are included in the technical scope of the present invention.

[0040] In an embodiment of the resin sheet with a surface treatment layer of the present invention, the resin sheet contains a syndiotactic polystyrene resin, and the surface treatment layer exists on one or both sides of the resin sheet. When elemental analysis is performed on at least one side of the surface treatment layer, on the side not in contact with the resin sheet, by X-ray photoelectron spectroscopy (ESCA), Si, C, N, and O are observed, and the amounts of these atoms satisfy the following equations (1) to (4). X-ray photoelectron spectroscopy (ESCA) is sometimes also abbreviated as XPS (X-Ray Photoelectron Spectroscopy).

[0041] Si / (C+N+O+Si)≥0.03···(1)

[0042] 1.0<O / Si≤3.0···(2)

[0043] C / Si≥1.0 ···(3)

[0044] 0.1≤N / Si≤2.5 ···(4)

[0045] [In equations (1) to (4), each atom symbol represents the content (atomic percentage) of each atom.]

[0046] When the surface of the resin sheet with the surface treatment layer in the embodiment was analyzed by ESCA, Si, C, N and O were observed. By making the amount of these atoms satisfy the relationship of the above formulas (1) to (4), when the metal layer is stacked on the resin sheet through the adhesive layer, the adhesion between the resin sheet and the adhesive layer is good, the metal layer becomes difficult to peel off, and it becomes difficult to peel off even under the heat treatment conditions of the simulated welding process.

[0047] The value of Si / (C+N+O+Si) specified in formula (1) is 0.03 or more, preferably 0.08 or more, and 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.

[0048] The O / Si value specified in Formula (2) is greater than 1.0 and less than 3.0, preferably greater than 1.00, and more preferably less than 2.30. The O / Si value specified in Formula (2) is more preferably greater than 1.00, and more preferably less than 2.00. The closer the O / Si value specified in Formula (2) is to 1.50, the more preferred it is.

[0049] The C / Si value specified in formula (3) is 1.0 or more, 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.

[0050] The N / Si value specified in formula (4) is 0.1 to 2.5, and the N / Si value is preferably 0.2 or more, more preferably 0.3 or more. The N / Si value specified in 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.

[0051] When elemental analysis of the surface of the resin sheet with the surface treatment layer is performed by ESCA, the Si atomic content can be, for example, 5 to 25 atomic%. The Si atomic content is preferably 8 to 23 atomic%, more preferably 10 to 20 atomic%.

[0052] When elemental analysis of the surface of a resin sheet with a surface-treated layer is performed using ESCA, the nitrogen atom content can be, for example, 1 to 15 atomic percent. The nitrogen atom content is preferably 3 to 13 atomic percent, more preferably 5 to 10 atomic percent.

[0053] When elemental analysis of the surface of the resin sheet with the surface treatment layer is performed by ESCA, the Si atomic content is preferably 5-25% and the N atomic content is preferably 1-15%.

[0054] In an embodiment of the resin sheet with a surface treatment layer of the present invention, the resin sheet contains a syndiotactic polystyrene resin, and the surface treatment layer exists on one or both sides of the resin sheet. The surface treatment layer is a treatment layer formed by a primer composition containing a first silane compound (a) having an amino alkyl 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 the primer composition, relative to 100 parts by mass of the first silane compound (a), the second silane compound (b) is contained in 40 to 250 parts by mass.

[0055] The surface treatment layer of the resin sheet is formed from a primer composition containing the aforementioned first silane compound (a), second silane compound (b), and alcohol (d). By including a predetermined amount of the second silane compound (b) in the primer composition, when a metal layer is laminated onto the surface of the resin sheet via an adhesive layer, the adhesion between the surface treatment layer and the adhesive layer of the resin sheet improves, and the metal layer becomes difficult to peel off. Furthermore, even when this laminate is subjected to heat treatment conditions similar to those used in welding processes, the metal layer remains difficult to peel off.

[0056] In embodiments of the primer composition of the present invention, 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) are contained, wherein the amount of the second silane compound (b) is 40 to 250 parts by mass relative to 100 parts by mass of the first silane compound (a).

[0057] (a) First silane compound

[0058] The first silane compound has an aminoalkyl group and two or more alkoxy groups.

[0059] The aminoalkyl group can be linear or branched. The aminoalkyl group preferably has 3 to 15 carbon atoms. For example, the linear aminoalkyl group preferably has 3 to 10 carbon atoms, more preferably 3 to 8, and even more preferably 3 to 5. For example, the branched aminoalkyl group preferably has 3 to 15 carbon atoms, more preferably 3 to 13, and even more preferably 3 to 10. The aminoalkyl group may also have multiple amino groups linked by two or more carbon atoms. The number of aminoalkyl groups bonded to silicon atoms is usually 1. Examples of aminoalkyl groups include γ-aminopropyl and N-(β-aminoethyl)-γ-aminopropyl.

[0060] The number of carbon atoms in the alkoxy group can be, for example, 1, 2 or more, preferably 6 or less, more preferably 1 to 3, and even more preferably 1 to 2. Examples of alkoxy groups include methoxy, ethoxy, and n-propoxy. The number of alkoxy groups can be 2 or 3.

[0061] Examples of the first silane compound include, for example, 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. One compound may be used alone, or two or more may be used in combination. Among these compounds, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane are preferred, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is more preferred. It should be noted that silane compounds that do not use Si, C, and N atoms in this order are preferred.

[0062] (b) Second silane compounds

[0063] The second silane compound has an alkenyl group and two or more alkoxy groups.

[0064] There are no restrictions on the structure of the alkenyl group, but it is preferably linear. The alkenyl group preferably has 6 or fewer carbon atoms, more preferably 2 or 3. Examples of alkenyl groups include vinyl, 1-propenyl, allyl (2-propenyl), 1-hexenyl, 5-hexenyl, etc. The number of alkenyl groups can be, for example, one or two. The alkenyl group is preferably located at the end of the carbon chain.

[0065] The number of carbon atoms in the alkoxy group can be, for example, 1, 2 or more, preferably 6 or less, more preferably 1 to 3, and even more preferably 1 to 2. Examples of alkoxy groups include methoxy, ethoxy, and n-propoxy. The number of alkoxy groups can be 2 or 3.

[0066] Examples of second silane compounds include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, 5-hexenyltrimethoxysilane, and 5-hexenyltriethoxysilane. One of these compounds can be used alone, or two or more can be used in combination. Among these compounds, vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, allyltrimethoxysilane, or 5-hexenyltrimethoxysilane are preferred, and vinyltrimethoxysilane is more preferably used.

[0067] In the primer composition, the amount of the second silane compound (b) is 40 to 250 parts by mass relative to 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 treatment layer and the adhesive layer, which is the treatment layer formed by the primer composition, cannot be improved. Therefore, the content of the second silane compound (b) should be 40 parts by mass or more. The content of the second silane compound (b) relative to 100 parts by mass of the first silane compound (a) 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. If the amount of the second silane compound (b) exceeds 250 parts by mass, the types of adhesive layers that can produce good adhesion to the surface treatment layer, which is the treatment layer formed by the primer composition, will be limited, resulting in reduced versatility. In addition, the storage stability of the primer composition will also decrease. Therefore, the content of the second silane compound (b) should be 250 parts by mass or less. The content of the second silane compound (b) relative to 100 parts by mass of the first silane compound (a) is preferably 210 parts by mass or less, more preferably 180 parts by mass or less. That is, in the primer composition, the amount of the second silane compound (b) relative to 100 parts by mass of the first silane compound (a) 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.

[0068] It should be noted that silane compounds with an aminoalkyl group, an alkenyl group, or two or more alkoxy groups in their molecule are neither classified as primary silane compounds (a) nor as secondary silane compounds (b).

[0069] (d) alcohol

[0070] By including alcohol (d) in the primer composition, the drying speed of the primer composition after application to the substrate can be adjusted, thereby regulating the speed at which the adhesive properties emerge after drying. Furthermore, the storage stability of the primer composition can be improved.

[0071] The alcohol (d) can be linear or branched. The number of carbon atoms in the alcohol can be, for example, 1 or 2 or more. Preferably, the number of carbon atoms in the alcohol is 4 or less, more preferably 3 or less. Examples of alcohols (d) include methanol, ethanol, n-propanol, and isopropanol. One type can be used alone, or two or more types can be used in combination.

[0072] The primer composition preferably contains two or more alcohols (d). When the primer composition contains two or more alcohols (d), it is preferable to contain two or more alcohols having 1 to 3 carbon atoms. Preferred combinations of alcohols (d) include, for example, a combination of methanol and n-propanol, or a combination of methanol, ethanol, and n-propanol.

[0073] The amount of alcohol (d) contained in the primer composition is not particularly limited, but may be, for example, 1000 to 2000 parts by mass relative to 100 parts by mass of the first silane compound (a). The amount of alcohol (d) relative to 100 parts by mass of the first silane compound (a) is preferably 1100 parts by mass or more, more preferably 1200 parts by mass or more. The amount of alcohol (d) relative to 100 parts by mass of the first silane compound (a) is preferably 1900 parts by mass or less, more preferably 1800 parts by mass or less. When two or more alcohols (d) are contained, the amount of alcohol (d) refers to their total amount. That is, in the primer composition, the amount of alcohol (d) relative to 100 parts by mass of the first silane compound (a) is preferably 1100 to 1900 parts by mass, more preferably 1200 to 1800 parts by mass.

[0074] The primer composition may also contain at least one of the following groups: a polyamine compound (c), water (e), and a dimethylsiloxane oligomer (f) having 6 or fewer silicon atoms, in which all substituents except oxygen atoms are methyl.

[0075] (c) Polyamine compounds

[0076] Polyamine compound (c) refers to an organic compound having two or more amino groups. By including polyamine compound (c) in the primer composition, the storage stability of the primer composition is improved.

[0077] Examples of polyamine compounds (c) include, for instance, 1,2-ethylenediamine (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, etc., which are hydrocarbon-based polyamine compounds. One type can be used alone, or two or more can be used in combination. Among these compounds, ethylenediamine is preferred.

[0078] When the primer composition contains a polyamine compound (c), the amount of polyamine compound (c) in the primer composition relative to 100 parts by mass of the first silane compound (a) can be, for example, 100 to 250 parts by mass. The amount of polyamine compound (c) in the primer composition is preferably 90 to 230 parts by mass, more preferably 80 to 210 parts by mass.

[0079] (e) water

[0080] By including water (e) in the primer composition, the thickness of the surface treatment layer, which is a treatment layer formed from the primer composition, can be adjusted. For example, ion-exchanged water can be used as the water (e).

[0081] When the primer composition contains water (e), the amount of water (e) is not particularly limited, but it may be contained in the range of up to 2000 parts by mass 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).

[0082] (f) Dimethylsiloxane oligomers

[0083] Dimethylsiloxane oligomer (f) refers to an oligomer in which all substituents except oxygen atoms bonded to silicon atoms are methyl groups and the number of silicon atoms is 6 or less. Dimethylsiloxane oligomer (f) serves as a solvent in primer compositions and 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) only needs to be 6 or less; it can be 5 or less, or 4 or less.

[0084] Examples of dimethylsiloxane oligomers (f) include hexamethyldisiloxane, octamethyltrisiloxane, and octamethylcyclotetrasiloxane. One or more of these compounds can be used alone or in combination. Hexamethyldisiloxane is preferred among these compounds.

[0085] When the primer composition contains dimethylsiloxane oligomer (f), the amount of dimethylsiloxane oligomer (f) is not particularly limited, but it may contain, for example, 10 to 500 parts by mass relative to 100 parts by mass of the first silane compound (a). The amount of dimethylsiloxane oligomer (f) relative to 100 parts by mass of the first silane compound (a) is preferably 30 parts by mass or more, more preferably 50 parts by mass or more. The amount of dimethylsiloxane oligomer (f) relative to 100 parts by mass of the first silane compound (a) is preferably 300 parts by mass or less, more preferably 200 parts by mass or less. That is, the amount of dimethylsiloxane oligomer (f) relative to 100 parts by mass of the first silane compound (a) is preferably 30 to 300 parts by mass, more preferably 50 to 200 parts by mass. When two or more types of dimethylsiloxane oligomers (f) are contained, the amount of dimethylsiloxane oligomer (f) refers to their total amount.

[0086] The resin sheet uses syndiotactic polystyrene resin (A) as its constituent resin. Syndiotactic polystyrene resin is sometimes referred to as "SPS," "syndiotactic polystyrene," or "(A) component" below. The resin sheet is preferably an unstretched sheet containing syndiotactic polystyrene resin (A), or a film obtained by biaxially stretching an unstretched sheet containing syndiotactic polystyrene resin (A). That is, the resin sheet preferably has a surface treatment layer formed as a treatment layer from a primer composition on the unstretched sheet or the biaxially stretched film. Hereinafter, the unstretched sheet will be simply referred to as "sheet," and the biaxially stretched film will be simply referred to as "film," and both will be collectively referred to as "raw material resin sheet."

[0087] (A) Syndiotactic polystyrene resin

[0088] The syndiotactic structure in syndiotactic polystyrene resin (A) refers to a stereochemical structure that is isotactic, i.e., a stereostructure in which phenyl groups, as side chains, alternate in opposite directions relative to the main chain formed by carbon-carbon bonds. Its stereoregularity is quantified by carbon-isotope nuclear magnetic resonance (C-NMR). The stereoregularity determined by C-NMR can be expressed as the proportion of consecutive structural units present; for example, 2 units constitute a binatorial group, 3 units a triatorial group, and 5 units a pentatorial group. In this invention, styrene polymers having a syndiotactic structure refer to polystyrene, poly(alkylstyrene), poly(halostyrene), poly(haloalkylstyrene), poly(alkoxystyrene), poly(vinylbenzoate), their hydrogenated polymers, and mixtures thereof, or copolymers in which they are the main components, typically having a stereoregularity of 75 mol% or more (preferably 85 mol% or more) of syndiotactic binatorial group or 30 mol% or more (preferably 50 mol% or more) of syndiotactic pentatorial group.

[0089] Examples of poly(alkylstyrene) include, for example, poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tert-butylstyrene), poly(phenylstyrene), poly(vinylnaphthalene), and poly(vinylstyrene). Examples of poly(halostyrene) include, for example, poly(chlorostyrene), poly(bromostyrene), and poly(fluorostyrene). Examples of poly(haloalkylstyrene) include, for example, poly(chloromethylstyrene). Examples of poly(alkoxystyrene) include, for example, poly(methoxystyrene) and poly(ethoxystyrene). Among these, more preferred styrene-based polymers include polystyrene, poly(alkylstyrene), poly(halostyrene), hydrogenated polystyrene, and copolymers containing their structural units. 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 their structural units.

[0090] The syndiotactic polystyrene resin (A) can also be a copolymer of styrene with a syndiotactic structure and other monomers. In this case, the content of syndiotactic styrene in the syndiotactic polystyrene resin (A) relative to 100% by mass is preferably 50% by mass or more, more preferably 60% by mass or more, further 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. Since the content of syndiotactic styrene is 50% by mass or more, the dielectric properties, weld heat resistance, dimensional change rate, and coefficient of linear expansion are excellent. It should be noted that, since there is a possibility that these properties may decrease, the content of unsaturated nitrile monomers is preferably as low as possible. The content of unsaturated nitrile monomers in the syndiotactic polystyrene resin (A) is preferably 2% by mass or less, more preferably less than 2% by mass, further preferably 1% by mass or less, and particularly preferably 0% by mass.

[0091] Syndiotactic polystyrene resin (A) can use only one type of styrene polymer or a mixture of two or more types.

[0092] There are no particular restrictions on the composition ratio of styrene-based polymers, but it is preferred that the content of substituted styrene units be in the range of 3 to 50 mol%. If the content of substituted styrene units is above 3 mol%, modification becomes easier. If the content of substituted styrene units is below 50 mol%, compatibility with other components can be maintained.

[0093] 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 maintaining a weight-average molecular weight of 10,000 or more, the thermal and mechanical properties of the resulting composition or molded article are maintained well without degradation. The upper limit of the weight-average molecular weight of the syndiotactic polystyrene resin (A) is not particularly limited, but for example, it is preferably 500,000 or less, more preferably 400,000 or less. There is also no limitation on the width of the molecular weight distribution of the syndiotactic polystyrene resin (A), and various distributions are applicable. 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.

[0094] The melt flow rate (MFR) of the syndiotactic polystyrene resin (A), measured at 300°C and under a load of 1.2 kg, is preferably 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. By keeping the melt flow rate of the syndiotactic polystyrene resin (A) within the above range, it is possible to obtain a raw material resin sheet with good physical properties as a precursor for resin sheets, and to make the thickness of the raw material resin sheet uniform.

[0095] The melting point of the syndiotactic polystyrene resin (A) is preferably 250°C or higher, more preferably 260°C or higher, and more 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.

[0096] The glass transition temperature of the syndiotactic polystyrene resin (A) is preferably 80°C or higher, more preferably 90°C or higher, and preferably 120°C or lower, more preferably 110°C or lower. By keeping the melting point and glass transition temperature of the syndiotactic polystyrene resin (A) within the above ranges, the resin sheet exhibits a low coefficient of linear expansion and good dimensional stability. That is, the glass transition temperature of the syndiotactic polystyrene resin (A) is preferably 80–120°C, more preferably 90–110°C.

[0097] Representative commercially available products of syndiotactic polystyrene resins (A) include XAREC (registered trademark) 142ZE, XAREC (registered trademark) 300ZC, XAREC (registered trademark) 130ZC, and XAREC (registered trademark) 90ZC manufactured by Idemitsu Kosan Co., Ltd. These resins can be used individually or in combination.

[0098] Because it improves dielectric properties, the content of syndiotactic polystyrene resin (A) in the resin sheet is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, even more preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more. There is no particular upper limit to the content of syndiotactic polystyrene resin (A), but because it improves the coefficient of linear expansion and dimensional stability, it is preferably less than 100% by mass, more preferably 99% by mass or less, and even more preferably 95% by mass or less. That is, the content of syndiotactic polystyrene resin (A) in the resin sheet is preferably 40% by mass or more and less than 100% by mass, more preferably 50 to 99% by mass, more preferably 60 to 95% by mass, even more preferably 70 to 95% by mass, more preferably 80 to 95% by mass, and particularly preferably 90 to 95% by mass.

[0099] Such syndiotactic polystyrene resins (A) can be manufactured, for example, in an inert hydrocarbon solvent or in the absence of solvent, by polymerizing styrene monomers (monomers corresponding to the aforementioned styrene polymers) using a condensation product of a titanium compound, water, and trialkylaluminum as a catalyst (Japanese Patent Application Publication No. 62-187708). Furthermore, poly(haloalkylstyrene) can be obtained by the method described in Japanese Patent Application Publication No. 1-46912, and their hydrogenated polymers can be obtained by the method described in Japanese Patent Application Publication No. 1-178505, etc.

[0100] In addition to syndiotactic polystyrene resin (A), the resin sheet may also contain at least one selected from the group consisting of rubber-like elastomer (B), fibrous filler (C), non-fibrous filler (D), and antioxidant (E).

[0101] (B) Rubber-like elastomer

[0102] The resin sheet may also contain a rubber-like elastomer (B) (hereinafter also referred to as component (B)). Since the rubber-like elastomer (B) can impart moderate softness to the raw resin sheet while improving its mechanical properties, it is preferred to be compounded.

[0103] Examples of rubber-like elastomers (B) include single polymers composed of polyolefins, polystyrene, or polyacrylates, or compositions composed of multiple copolymers containing these components. Specific examples of rubber-like elastomers (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), and styrene-isoprene-styrene block copolymer (SI). S), 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), siloxane-containing core-shell rubbers including methyl methacrylate-butyl acrylate-siloxane, and other core-shell type particulate elastomers, or rubbers modified from these. One type can be used alone, or two or more types can be mixed. Among these, ethylene-α-olefin copolymer rubber, SEBS, SIR, SEP, SIS, SEPS, or rubbers modified from these are preferred.

[0104] From the viewpoint of the processing temperature when mixing with syndiotactic polystyrene resin (A), it is preferable to use a rubber-like elastomer with high heat resistance. For example, by mixing a rubber-like elastomer (B) whose unsaturated bond portion has been selectively hydrogenated or fully hydrogenated, the amount of gas generated during hot pressing can be suppressed.

[0105] The melt flow rate (MFR) of the rubber-like elastomer (B), measured at 230°C and under a load of 2.16 kg, is preferably 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. By keeping the melt flow rate of the rubber-like elastomer (B) within the above range, its compatibility with the syndiotactic polystyrene resin (A) is improved, and the thickness of the raw material resin sheet can be made more uniform.

[0106] The rubber-like elastomer (B) preferably 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 making the amount of the styrene-based thermoplastic elastomer 5% by mass or more, the compatibility between component (A) and component (B) is improved, and the mechanical properties become better. By making the amount of the styrene-based thermoplastic elastomer 60% by mass or less, since the elastic modulus of component (B) does not become too high, the stress relief effect is improved, thereby improving the softness of the raw material resin sheet and suppressing the polarity of the resin sheet, thus suppressing the increase of the dielectric constant.

[0107] When the rubber-like elastomer (B) is present, its amount relative to 100 parts by weight of syndiotactic polystyrene resin (A) is preferably 1 to 40 parts by weight, more preferably 3 to 30 parts by weight, and even more preferably 5 to 25 parts by weight. By making the amount of rubber-like elastomer (B) 1 part by weight or more, the softness of the raw resin sheet is improved, and the winding performance on the roller becomes better. In addition, the processability for drilling with a drill bit in subsequent processes is also improved. By making the amount of rubber-like elastomer (B) 40 parts by weight or less, it is possible to prevent the raw resin sheet from becoming too soft, prevent it from sticking to the roller, and maintain the heat resistance required for the high-frequency circuit board.

[0108] Representative commercially available products of rubber-like elastomers (B) include Tuftec (registered trademark) H1062, Tuftec (registered trademark) H1041, Tuftec (registered trademark) H1517, Tuftec (registered trademark) H1521, and Tuftec (registered trademark) H1062 manufactured by Asahi Kasei Corporation. These can be used individually or in combination.

[0109] (C) Fibrous packing

[0110] Resin sheets may also contain fibrous filler (C) (hereinafter also referred to as component (C)). Fiberous filler (C) is a type of filler that can improve the coefficient of linear expansion and dimensional changes in the direction parallel to the extrusion direction (MD) of the raw resin sheet, which is the precursor of the resin sheet. It is preferably added to resin sheets that inevitably retain residual strain even when not stretched. Furthermore, by compounding fibrous filler (C), the weld heat resistance of the resin sheet and the laminate can be improved.

[0111] As the fibrous filler (C), inorganic or organic fibers can be used. For example, wollastonite (or whiskers) or glass fiber can be used as inorganic fibers, with glass fiber being more preferred from the perspective of dielectric properties. For example, resin-based fibers can be used as organic fibers.

[0112] The shape of the fibrous filler (C) is not particularly limited. For example, it can be any shape such as untwisted roving, surfacing mat, chopped strand mat, satin weave, checkered weave, plain weave, open-weave plainweave, twill weave, mesh, etc.

[0113] The type of fibrous filler (C) is not particularly limited; for example, any of the following can be used: alkali-rich glass (C glass), alkali-free glass (E glass), boric acid-rich glass (D glass), or glass with a balanced silica-to-boric acid ratio (NE glass). Among these, boric acid-rich glass (D glass) or glass with a balanced silica-to-boric acid ratio (NE glass) is preferred, and D glass is more preferred. In D glass, the preferred range for SiO2 content is 65.0–80.0% by mass, and the preferred range for B2O3 content is 15.0–30.0% by mass. In NE glass, the preferred range for SiO2 content is 45.0–65.0% by mass, and the preferred range for B2O3 content is 10.0–25.0% by mass.

[0114] The cross-sectional shape of the fibrous packing (C) can be circular or non-circular.

[0115] The fiber diameter of the circular cross-section glass fiber is preferably 1 to 50 μm, more preferably 2 to 20 μm, and even more preferably 3 to 15 μm.

[0116] Glass fibers with non-circular cross-sections include those with a cross-sectional shape that is approximately elliptical, approximately oblong, or approximately cocoon-shaped perpendicular to the length of the glass fiber. In this case, the flatness of the cross-sectional shape is preferably 1.5 to 8. Flatness refers to the ratio of the major axis to the minor axis when assuming there exists a rectangle with the smallest area circumscribed in the cross-section perpendicular to the length of the glass fiber, with the length of the long side of the rectangle defined as the major axis and the length of the short side defined as the minor axis.

[0117] There is no particular limitation on the thickness of glass fibers, with a short diameter of 1 to 20 μm and a long diameter of about 2 to 100 μm.

[0118] The average D50 fiber length of the fibrous filler (C) is preferably 40–4000 μm, more preferably 40–3200 μm, even more preferably 45–2000 μm, and most preferably 50–500 μm. As long as the average D50 fiber length of the fibrous filler (C) is above 40 μm, the surface area of ​​the fibrous filler (C) is sufficiently large, improving the interfacial adhesion between component (A) and component (C) of the matrix resin, thereby improving the physical properties of the raw resin sheet. By keeping the average D50 fiber length of the fibrous filler (C) below 4000 μm, excessive rigidity of the raw resin sheet can be suppressed, and visible cracking during the winding of the raw resin sheet can be prevented. Furthermore, the formation of agglomerates in the raw resin sheet can also be suppressed.

[0119] The fibrous filler (C) may be untreated or surface-treated. When the fibrous filler (C) is surface-treated, coupling agents used in the surface treatment include, for example, silane coupling agents or titanium-based coupling agents. Among these, from the viewpoint of compatibility with component (A), the use of a silane coupling agent for surface treatment is particularly preferred.

[0120] Specific examples of silane coupling agents include triethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, γ-epoxypropoxypropyltrimethoxysilane, 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, and γ-aminopropyltriethoxysilane. Silanes, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyl-tri(2-methoxy-ethoxy)silane, N-methyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane, 3-ureopropyltrimethoxysilane, 3-4,5-dihydroimidazoliumpropyltriethoxysilane, hexamethyldisilazane, N,N-bis(trimethylsilyl)urea, 3-triethoxysilyl-N-(1,3-dimethyl-butene)propylamine, etc. Among these, aminosilanes and epoxysilanes such as γ-epoxypropoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-aminopropyltrimethoxysilane are preferred.

[0121] Specific examples of titanium-based coupling agents include isopropyl triisostearoyl titanate, isopropyl tri-dodecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphoryloxy) titanate, tetraisopropyl bis(dioctyl phosphite oxy) titanate, tetraoctyl bis(di-tetrazyl phosphite oxy) titanate, tetra(1,1-diallyloxymethyl-1-butyl)bis(di-tetrazyl phosphite oxy) titanate, and bis(dioctyl pyrophosphoryloxy) titanate. Examples of titanium dioxide esters include bis(dioctylpyrophosphonoyloxy)ethylene titanate, isopropyl trioctyl titanate, isopropyl dimethacryloyl isostearyl titanate, isopropyl isostearyl diacryloyl titanate, isopropyl tris(dioctylphosphonoyloxy) titanate, isopropyl tricumylphenyl titanate, isopropyl tris(N-amidoethyl, aminoethyl) titanate, dicumylphenyloxyethylene titanate, and diisostearoyl ethylene titanate. Among these, isopropyl tris(N-amidoethyl, aminoethyl) titanate is preferred.

[0122] There are no particular limitations on the method of surface treatment of fibrous filler (C) using coupling agents. Examples include: sizing treatment by applying an organic solvent solution or suspension containing the aforementioned coupling agent to the fibrous filler (C); dry mixing treatment using a Henschel mixer, super mixer, Lödige mixer, V-type mixer, etc.; and treatment by spraying, integral blending, or dry concentration. The appropriate method can be adopted according to the shape of the fibrous filler (C). Among these, surface treatment by sizing, dry mixing, or spraying is preferred.

[0123] When performing surface treatment, coupling agents can be used in conjunction with film-forming substances for glass. There are no particular limitations on the film-forming substances; examples include polyester-based, polyurethane-based, epoxy-based, acrylic-based, vinyl acetate-based, and polyether-based polymers.

[0124] During surface treatment, coupling agents and compatibilizers can be used together. By using compatibilizers, the interfacial strength between syndiotactic polystyrene resin (A) and fibrous fillers (C) and non-fibrous fillers (D) can be improved. Modified polymers can be used as compatibilizers, for example.

[0125] Specific examples of compatibilizers include: styrene-maleic anhydride copolymer (SMA), styrene-glycidyl methacrylate copolymer, terminal carboxylic acid modified polystyrene, terminal epoxy modified polystyrene, terminal oxazoline modified polystyrene, terminal amino modified polystyrene, sulfonated polystyrene, styrene-based ionomers, styrene-methyl methacrylate graft polymers, (styrene-glycidyl methacrylate)-methyl methacrylate graft copolymers, acid-modified acrylic acid-styrene graft polymers, (styrene-glycidyl methacrylate)-styrene graft polymers, polybutylene terephthalate-polystyrene graft polymers, polyphenylene ether, (styrene-maleic anhydride)-polyphenylene ether graft polymers, maleic anhydride modified polyphenylene ether, fumaric acid modified polyphenylene ether, glycidyl methacrylate modified polyphenylene ether, amino modified polyphenylene ether, and other modified polyphenylene ether polymers. Among these, unmodified or modified polyphenylene ether is preferred, and maleic anhydride-modified polyphenylene ether and fumaric acid-modified polyphenylene ether are more preferred.

[0126] When fibrous filler (C) is present, in order to balance the target coefficient of linear expansion, dimensional stability, impact resistance, and mechanical properties, its amount relative to 100 parts by weight of syndiotactic polystyrene resin (A) is preferably 1 to 50 parts by weight, more preferably 3 to 40 parts by weight, and even more preferably 5 to 30 parts by weight.

[0127] Representative commercially available products as fibrous fillers (C) include, for example, HDT09100T manufactured by Touchu 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. These can be used individually or in combination with two or more types.

[0128] (D) Non-fibrous packing

[0129] Resin sheets may also contain non-fibrous fillers (D) (hereinafter also referred to as (D) components). Non-fibrous fillers (D) are non-fibrous fillers that are expected to suppress the coefficient of linear expansion and dimensional changes in both the direction parallel (MD) and the direction perpendicular (TD) to the extrusion direction of the sheet, which is the precursor of the resin sheet.

[0130] The shape of the non-fibrous filler (D) is not particularly limited. For example, it can be any shape such as spherical, granular, or plate-shaped, but granular is preferred.

[0131] As a non-fibrous packing material (D), organic or inorganic packing materials can be used, with inorganic packing materials being preferred.

[0132] As organic fillers, organic spherical, granular, or plate-shaped fillers can be used, for example. The type of polymer used as an organic filler is not particularly limited. Considering the processing temperature of the syndiotactic polystyrene resin (A), when the polymer is a crystalline resin, its melting point is preferably above 280°C, more preferably above 300°C. When the polymer is an amorphous resin, its glass transition temperature is preferably above 150°C, more preferably above 180°C. By keeping the melting point and glass transition temperature within the above ranges, the filler shape can be maintained during processing into raw resin sheets, thereby suppressing the coefficient of linear expansion of the resin sheet.

[0133] As inorganic fillers, inorganic spherical, granular, or plate-shaped fillers can be used, for example. 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 microspheres. Among these, silica is particularly preferred from the viewpoint of productivity, cost, and the dielectric properties of the filler itself, and amorphous silica or fused silica is more preferred. Compared to crystalline silica, amorphous silica has lower hardness, thus its use can suppress wear on machinery and screws. Fused silica, being formed by melting raw materials in a flame and rapidly cooling and solidifying the volatile gases, becomes spherical due to surface tension, resulting in fewer sharp parts, no splintering, and easy formation of a stable shape.

[0134] The shape of silica is preferably granular or spherical, more preferably granular. Because silica is granular or spherical, it is easier to mix when added to molten resin. Furthermore, since it is stable under stress from any direction, silica is not easily broken down and does not easily detach during the manufacture of raw resin sheets. In addition, it reduces the degradation of the mechanical properties of the resin sheets. Silica can also be hollow.

[0135] The average D50 particle size of the non-fibrous filler (D) is preferably 0.1–45 μm, more preferably 0.2–30 μm, even more preferably 0.3–20 μm, and still more preferably 0.5–10 μm. Since the average D50 particle size of the non-fibrous filler (D) is 0.1 μm or more, it can suppress the aggregation of the (D) components, preventing them from becoming foreign matter within the resin sheet and thus minimizing the decrease in mechanical properties. Since the average D50 particle size of the non-fibrous filler (D) is 45 μm or less, the spacing between the (D) components will not become too narrow, thus suppressing the propagation of cracks at the interface when stress is generated. Furthermore, it can maintain heat resistance during the welding process.

[0136] When non-fibrous filler (D) is present, its amount relative to 100 parts by weight of syndiotactic polystyrene resin (A) is preferably 1 to 60 parts by weight, more preferably 3 to 50 parts by weight, and even more preferably 5 to 40 parts by weight. By making the amount of non-fibrous filler (D) 1 part by weight or more, the blending effect brought by component (D) can be utilized. By making the amount of non-fibrous filler (D) 60 parts by weight or less, the smoothness of the raw resin sheet becomes good, which not only makes it easier to control the thickness, but also inhibits the aggregation of component (D) within the resin sheet and inhibits the decrease in mechanical properties.

[0137] When amorphous silica hollow material or molten silica hollow material is contained as a non-fibrous filler (D), its amount does not depend on the above range. By using hollow silica, it is expected that the dielectric constant can be further reduced. The film thickness of the hollow silica 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 becomes too thin, the silica may crack during screw mixing in a twin-screw mixer, and the hollow shape may not be maintained. If the film thickness becomes too thick, the volume fraction of the hollow portion will decrease, and therefore the effect of reducing the dielectric constant may not be achieved.

[0138] The D50 average particle size of hollow silica is preferably 3–45 μm. Since the D50 average particle size is 3 μm or larger, it is expected to reduce the dielectric constant. However, if the D50 average particle size is below 45 μm, the mechanical properties of the raw material resin sheet will decrease.

[0139] The non-fibrous filler (D) may or may not have undergone surface treatment. When the non-fibrous filler (D) is surface treated, a known surface treatment agent may be used as the surface treatment agent. For example, hydrophobic treatment can be performed by using a silane-based coupling agent or a titanate-based coupling agent, which can improve its dispersion in the syndiotactic polystyrene resin (A) and suppress the formation of aggregates in the resin sheet.

[0140] Representative commercially available non-fibrous fillers (D) include, for example, silica particles FB-3SDC, FB-7SDC, and SFP-130MC manufactured by Denka Corporation; hollow glass microspheres iM-30k manufactured by 3M Japan; calcium carbonate "Whiton P-30" manufactured by Shiraishi Calcium Industries, Ltd.; and "Magnesia RF-98" manufactured by Ube Materials Co., Ltd. These can be used individually or in combination with two or more types.

[0141] (E) Antioxidants

[0142] From a processability perspective, resin sheets can also contain antioxidants (E) (hereinafter also referred to as component (E)). Antioxidants (E) can be either primary antioxidants that capture generated free radicals to prevent oxidation, or secondary antioxidants that decompose generated peroxides to prevent oxidation. Examples of primary antioxidants include phenolic antioxidants and amine antioxidants. Examples of secondary antioxidants include phosphorus-based antioxidants and sulfur-based antioxidants. By compounding these antioxidants, either alone or in combination, it is possible to suppress the decrease in molecular weight of component (A) or component (B) during the manufacture of the SPS resin composition, and to suppress the generation of gases originating from component (A) or component (B) during the hot-pressing process in the manufacture of the resin sheet.

[0143] Examples of phenolic antioxidants include, for example, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2-tert-butyl-4-methoxyphenol, 3-tert-butyl-4-methoxyphenol, 2,6-di-tert-butyl-4-[4,6-bis(octylthio)-1,3,5-triazin-2-ylamino]phenol, and n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. Phenolic antioxidants; 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, N,N'-1,6-hexylidenebis[3 Bisphenolic antioxidants such as 3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, 3,9-bis[1,1-dimethyl-2-[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane; 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3, 5-Di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3,3'-bis-(4'-hydroxy-3'-tert-butylphenyl)butyrate] glycol ester, 1,3,5-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)-triazine-2,4,6-(1H,3H,5H)trione, d-α-tocopherol, and other high molecular weight phenolic antioxidants. Among these, high molecular weight phenolic antioxidants are preferred, and pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is more preferred.

[0144] Examples of amine-based antioxidants include, for example, alkyl-substituted diphenylamines.

[0145] Examples of phosphorus-based antioxidants include: triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylene-bis(3-methyl-6-tert-butylphenyl di(tetrazyl)) phosphite, octadecyl phosphite, tri(nonylphenyl) phosphite, pentaerythritol diisodecyl diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 10-(3,5-di-tert-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. -Oxides, 10-decoxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, tris(2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetramethylbis(2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetramethylbis(2,6-di-tert-butyl-4-methylphenyl) phosphite, 2,2'-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, etc.

[0146] Examples of sulfur-based antioxidants include: dilaurate 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearate 3,3'-thiodipropionate, pentaerythritol tetra(3-lauryl thiopropionate), and 2-mercaptobenzimidazole.

[0147] Antioxidants (E) can be used alone or in combination of two or more. When using two or more in combination, it is possible to use two or more primary antioxidants, two or more secondary antioxidants, or one or more primary antioxidants combined with one or more secondary antioxidants. For example, by using primary and secondary antioxidants in combination, it is expected to prevent both primary and secondary oxidation simultaneously. Among these methods, using a primary antioxidant alone or using two or more primary antioxidants is preferred as it can suppress thermal degradation during resin sheet processing. Using a phenolic antioxidant alone (especially a high molecular weight phenolic antioxidant) or using two or more phenolic antioxidants (especially high molecular weight phenolic antioxidants) is even more preferred.

[0148] 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, thermal decomposition of the antioxidant (E) itself during melt extrusion can be prevented, thus reducing the likelihood of problems such as contamination of the melt extruder or yellowing of the polymer. The thermal decomposition temperature of the antioxidant (E) is more preferably 280°C or higher, further preferably 300°C or higher, and particularly preferably 320°C or higher. A higher thermal decomposition temperature of the antioxidant (E) is better, as it results in a greater increase in the insulation 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 250–500°C, more preferably 280–500°C, further preferably 300–500°C, and particularly preferably 320–500°C. It should be noted that, in this specification, the temperature at which the mass of the antioxidant (E) decreases by 5% by mass is defined as the thermal decomposition temperature.

[0149] 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, it is possible to prevent the antioxidant (E) from melting before the polymer during melt extrusion, thus preventing the polymer from slipping in the screw feed section of the extruder. As a result, problems such as unstable polymer supply or severe unevenness in the thickness of the raw material resin sheet are less likely to occur. The melting point of the antioxidant (E) is more preferably 120°C or higher, further 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) is difficult to melt even during melt extrusion, often resulting in poor dispersion within the polymer. This can lead to problems such as the effect of the added antioxidant (E) only being locally apparent. Therefore, the melting point of the antioxidant (E) is preferably 300°C or lower, more preferably 250°C or lower, further preferably 220°C or lower, and particularly preferably 200°C or lower. That is, the melting point is preferably 90-300℃, more preferably 120-250℃, even more preferably 150-220℃, and particularly preferably 170-200℃.

[0150] Based on the mass of the resin sheet, the amount of antioxidant (E) is preferably 0.1% to 8% by mass. Containing 0.1% or more of antioxidant (E) can improve the heat resistance and heat degradation resistance of the raw resin sheet. If the amount of antioxidant (E) is too low, the effect of adding antioxidant (E) is insufficient, often resulting in a lower improvement in the insulation breakdown voltage. The amount of antioxidant (E) is more preferably 0.2% or more by mass, further preferably 0.3% or more by mass, and particularly preferably 0.5% or more by mass. However, if the content of antioxidant (E) is too high, antioxidant (E) is prone to agglomeration in the resin sheet, often leading to an increase in defects originating from antioxidant (E), and consequently, a decrease in the mechanical properties of the resin sheet. From the above perspective, the amount of antioxidant (E) is more preferably 6% or less by mass, further preferably 4% or less by mass, and particularly preferably 2% or less by mass. That is, based on the mass of the resin sheet, the amount of antioxidant (E) is more preferably 0.2 to 6% by mass, more preferably 0.3 to 4% by mass, and particularly preferably 0.5 to 2% by mass.

[0151] As an antioxidant (E), commercially available products can be used directly. For example, regarding pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], products under the trade name IRGANOX 1010 manufactured by Ciba Specialty Chemicals or ANOX 20 manufactured by BASF Japan can be used; regarding N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, products under the trade name IRGANOX 1024 manufactured by Ciba Specialty Chemicals can be used; regarding N,N'-1,6-hexylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], products under the trade name IRGANOX manufactured by Ciba Specialty Chemicals can be used. 1098 etc.; Regarding 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, PEP-36 etc. manufactured by ADEKA Co., Ltd. can be used.

[0152] Resin sheets may further contain flame retardants, release agents, lubricants, tack reducers, curing agents, etc. The type of flame retardant is not particularly limited, but preferred options include halogenated flame retardants containing bromine, organic or inorganic phosphates, phosphate esters, phosphorus copolymers, etc. The flame retardant can be in liquid or solid form, but from the viewpoint of long-term stability, substances that are solid at room temperature are preferred.

[0153] <Raw Material Resin Sheets>

[0154] 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 can be completely unstretched, and the presence of a small amount of residual strain is acceptable. Specifically, the stretch ratio is preferably 1.3 or less in both the direction parallel to the extrusion direction of the sheet (longitudinal, MD) and the direction perpendicular to it (transverse, TD).

[0155] When manufacturing the raw resin sheet, the roller temperature 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 roller temperature within the above range, the winding properties on the roller can be made more uniform and less uneven. If the roller temperature is below 30°C, condensation will form on the roller surface, and water droplets may adhere to the sheet, causing unevenness in the transfer. If the roller temperature exceeds 100°C, molten resin will adhere to the roller, making it difficult to stretch and wind the sheet.

[0156] When manufacturing raw resin sheets, the pressure of the clamping rollers 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 below 50 N / cm, the sheet thickness may become uneven. If the pressure exceeds 2000 N / cm, the sheet thickness will become uneven, and residual stress is likely to remain, leading to a decrease in the sheet's rollability.

[0157] When manufacturing raw material resin sheets, the sheet thickness is preferably 50–2000 μm. If the sheet thickness is less than 50 μm, it is difficult to apply pressure evenly, and the mechanical properties may decrease. If the sheet thickness exceeds 2000 μm, sufficient pressure cannot be applied, and the sheet thickness is prone to becoming uneven.

[0158] When manufacturing raw material resin sheets, the material of the two rollers is not particularly limited; they can be rubber, metal, resin, etc. However, from the viewpoint of applying pressure evenly, metal is preferred.

[0159] When performing biaxial stretching, the stretching ratio, stretching temperature, and stretching speed are not particularly limited as long as the objective of this invention is achieved, but are preferably set within the following ranges. Stretching improves the heat resistance and dimensional stability of the raw resin sheet. Among the stretching methods are uniaxial stretching, step-by-step biaxial stretching, and simultaneous biaxial stretching; step-by-step biaxial stretching or simultaneous biaxial stretching is preferred, and simultaneous biaxial stretching is more preferred. If uniaxial stretching is performed, the coefficient of linear expansion in the unstretched direction will not decrease, and the heat resistance and dimensional stability may decrease. If step-by-step biaxial stretching is performed, the decrease in the coefficient of thermal expansion in the initially stretched direction will be smaller, and the heat resistance and dimensional stability may decrease; therefore, this tendency will be stronger if the stretching speed is not reduced.

[0160] The stretching ratio is within the range where cracking does not occur when it is 2.0 times or more in both the MD and TD directions, particularly preferably 2.0 to 5.0 times, and more preferably 2.3 to 4.0 times. The stretching ratios in the MD and TD directions are preferably 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, and more preferably -0.3 to +0.3. It should be noted that the stretching ratio in the MD direction is based on the length in the MD direction before stretching begins. The stretching ratio in the TD direction is based on the length in the TD direction before stretching begins. By adjusting the stretching ratio within the above range, the difference in the coefficients of linear expansion in the MD and TD directions will decrease, and the rate of decrease in the coefficient of linear expansion can be controlled. For example, if the stretching ratio in a specified direction is increased, the rate of decrease in the coefficient of linear expansion in that direction will increase.

[0161] Regarding the stretching temperature, when the glass transition temperature of the syndiotactic polystyrene resin (A) constituting the raw material resin sheet is defined as TgP (°C), it is preferably above TgP and below TgP+30°C. From the viewpoint of further improving heat resistance dimensional stability, tensile strength, and tensile elongation, it is more preferably above TgP and below TgP+25°C. By adjusting the stretching temperature within the above range, the decrease in the coefficient of linear expansion can be controlled. For example, if the stretching temperature is lowered, the decrease in the coefficient of linear expansion will be greater. However, if the stretching temperature is too low, stress concentration is likely to occur, which may lead to easy breakage of the sheet. On the other hand, if the stretching temperature is too high, the crystallization of the sheet will become insufficient, resulting in a smaller decrease in the coefficient of thermal expansion, and the dimensional stability under heat may decrease. It should be noted that the stretching temperature is the temperature of the raw material resin sheet during stretching. When the syndiotactic polystyrene resin (A) is composed of two or more polymers, the TgP of the syndiotactic polystyrene resin (A) can be confirmed by the endothermic peak (relaxation of the amorphous region) observed by differential scanning calorimetry (DSC).

[0162] The stretching speed is 50–10000% / min in both the MD and TD directions, preferably 100–5000% / min, and more preferably 100–3000% / min. The stretching speed is a value calculated using {(stretched dimension / unstretched dimension) - 1} × 100 (%) / stretching time. By adjusting the stretching speed within the above range, the decrease in the coefficient of linear expansion can be controlled. For example, increasing the stretching speed will result in a greater decrease in the coefficient of linear expansion.

[0163] The thickness of the resin sheet is preferably 10–2000 μm, more preferably 15–1000 μm, even more preferably 20–500 μm, and most preferably 25–300 μm. Because the resin sheet is 10 μm or thicker, it becomes less prone to breakage. Because the resin sheet is 2000 μm or less thick, localized shrinkage (shrinkage marks) can be suppressed, thus preventing uneven thickness.

[0164] In order to make the thickness of the resin sheet within the above range, the thickness of the raw material 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.

[0165] An adhesive layer may also be laminated on the surface of the surface-treated layer. The form of the adhesive layer is not limited; for example, it can be a coating of adhesive or a laminate of adhesive sheet. The composition of the adhesive layer is not particularly limited; for example, polyolefins, maleimide, polyphenylene ether, polyphenylene sulfide, styrene-based elastomers, etc., can be used as the main agent. Among these, the adhesive layer preferably contains a styrene-based elastomer.

[0166] The adhesive layer may further contain a curing agent. Examples of curing agents include aliphatic epoxy resins, cycloaliphatic epoxy resins, benzoxazine, carbodiimide, and isocyanates. Additionally, the adhesive layer may contain fillers such as silica or mica, as well as flame retardants, as additives.

[0167] (Adhesive sheet)

[0168] The adhesive layer can also be formed using an adhesive sheet as a precursor. For example, an adhesive sheet can be formed by coating an adhesive composition onto a release substrate, drying it to allow it to semi-cure, and then laminating the release substrate on top. A specific configuration could be: release substrate / adhesive layer / release substrate. By laminating the release substrate, it functions as a protective layer for either the substrate or the adhesive layer. Furthermore, by using the release substrate, it can be peeled off from the adhesive sheet, and the adhesive layer can be transferred to other substrates.

[0169] The thickness of the adhesive sheet is preferably 5–200 μm, more preferably 8–150 μm, even more preferably 10–100 μm, and most preferably 12–80 μm. By making the thickness of the adhesive sheet 5 μm or more, pinholes can be prevented. Furthermore, the adhesive strength can be improved. By making the thickness of the adhesive sheet 200 μm or less, thickness unevenness can be reduced. In addition, residual solvent can be reduced, preventing blistering during the pressing and manufacturing of printed circuit boards.

[0170] The release substrate is not particularly limited, but examples include materials made by applying a coating layer of clay, polyethylene, polypropylene, or other sealant to both sides of high-grade paper, kraft paper, roll paper, glassine paper, etc., and then further coating each coating layer with a silicone-based, fluorine-based, or alkyd-based release agent. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer, as well as materials made by coating the aforementioned release agent onto films such as polyethylene terephthalate. Due to reasons such as the release force between the release substrate and the adhesive layer, and the adverse effects of silicone on electrical properties, materials made by applying an alkyd-based release agent to both sides of high-grade paper after polypropylene sealant treatment, or materials made by applying an alkyd-based release agent to polyethylene terephthalate, are preferred.

[0171] A metal layer may also be laminated on the surface of the adhesive layer. Any conventionally known conductive material suitable for printed circuit boards can be used as the material constituting the metal layer. Examples of materials constituting the metal layer include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their respective alloys, electroplated products, and metals treated with zinc or chromium compounds. The metal layer is preferably a metal foil, more preferably a copper foil. Copper foil can be electrolytic foil or rolled foil; either type of copper foil can be used.

[0172] The thickness of the metal layer is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 10 μm or more, and 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 circuit board can be obtained. By making the metal layer thickness 50 μm or less, processing efficiency during the fabrication of the printed circuit board is 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.

[0173] Representative commercially available metal foil products include, for example, low-roughness copper foil “CF-T4X-SV18” and low-roughness copper foil “CF-T9DA-SV-18” manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., and copper foil “DGTSEU2” and copper foil “GTS-MP” manufactured by Furukawa Electric Industry Co., Ltd.

[0174] As a printed circuit board, it can be used on a surface-treated layer of a resin sheet with an adhesive layer and a metal layer stacked in this order.

[0175] The peel strength at the interface between the surface treatment layer and the adhesive layer of the resin sheet needs to be 0.3 N / mm or higher. Since this improves the durability of the laminate, a peel strength of 0.4 N / mm or higher is preferred, and more preferably 0.5 N / mm or higher. There is no particular upper limit to the peel strength, but for printed circuit boards, 2 N / mm or less is sufficient, and even 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.

[0176] For laminates, it is sufficient to stack a resin sheet with a surface treatment layer, an adhesive layer, and a metal layer in sequence. Other layers may also be stacked between the adhesive layer and the metal layer, but it is preferable to stack the resin sheet with a surface treatment layer, the adhesive layer, and the metal layer directly, respectively.

[0177] The laminate can also consist of an adhesive layer and a metal layer stacked on both sides of a resin sheet with a surface-treated layer, in this order. For example, it could be a laminate of metal layer / adhesive layer / resin sheet / adhesive layer / metal layer. When adhesive layers and metal layers are stacked on both sides of a resin sheet, the resin sheet is preferably the innermost layer. In such a two-sided laminate, other layers can also be stacked between the adhesive layer and the metal layer, or it can be a laminate in which the resin sheet, adhesive layer, and metal layer are directly stacked.

[0178] Next, an embodiment of the method for manufacturing the 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 manufactured by a method comprising: a substrate treatment step, wherein a surface activation treatment is performed on at least one surface of a resin sheet containing a syndiotactic polystyrene resin (i.e., a raw material resin sheet); a surface layer forming step, wherein a base coating is formed on the surface having undergone the surface activation treatment; and a surface layer reaction step, wherein the resin sheet on which the base coating is formed is heated.

[0179] [Substrate Treatment Process]

[0180] In the substrate treatment process, a surface activation treatment is performed on at least one surface of a resin sheet (raw material resin sheet) containing syndiotactic polystyrene resin. By performing a surface activation treatment on the surface of the raw material resin sheet, functional groups can be added to the surface of the raw material resin sheet, and effects such as changes in contact angle, improved adhesion, and removal of surface contaminants are expected to be obtained. In addition, the subsequent coating of the primer composition can be carried out more effectively. Examples of surface activation treatments include corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, radiation treatment, and flame treatment. These treatments can be performed individually or in combination of two or more. The surface activation treatment can be performed on at least one surface of the raw material resin sheet or on both surfaces of the raw material resin sheet.

[0181] The conditions for corona discharge treatment in surface activation can be, for example, an output power of 80–150W and a conveying speed of 0.5–1.5 m / min.

[0182] Resin sheets containing syndiotactic polystyrene resins (raw resin sheets) can be unstretched sheets or films obtained by biaxially stretching unstretched sheets. Resin sheets containing syndiotactic polystyrene resins (raw resin sheets) can also undergo heat treatment and annealing. Heat treatment and annealing can improve the crystallinity of the syndiotactic polystyrene resin in the raw resin sheet, thereby improving the weldability and heat resistance of the resin sheet. Furthermore, it can improve the dimensional accuracy of the resin sheet.

[0183] The heating temperature during heat treatment is not particularly limited, and can be, for example, 180°C to 220°C. Heat treatment can be carried out, for example, under vacuum or under pressure, preferably under both vacuum and pressure. The pressure during pressurization can be, for example, 1 to 3 MPa. Heat treatment can be carried out, for example, using a vacuum press.

[0184] There is no particular limitation on the heating temperature during annealing; for example, it can be 160℃ to 200℃. Annealing can be performed, for example, using a constant temperature bath. The heating temperature during annealing can be set relatively lower than the heating temperature during heat treatment.

[0185] [Surface layer formation process]

[0186] In the surface layer formation process, a primer coating is formed on the surface that has undergone surface activation treatment using a primer composition. Hereinafter, the primer coating will sometimes be referred to as the surface layer.

[0187] In the formation of the primer coating, 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) is used, wherein the amount of the second silane compound (b) is 100 to 250 parts by mass relative to 100 parts by mass of the first silane compound (a).

[0188] There are no particular limitations on the method for forming the primer layer; examples include methods such as coating the surface of a resin sheet with the primer composition or immersing the resin sheet in the primer composition. The primer composition can be diluted with water (e).

[0189] [Surface layer reaction process]

[0190] In the surface layer reaction process, a resin sheet with a base coating is heated to cause a surface layer reaction, thereby producing a resin sheet with a surface-treated layer. The heating temperature is not particularly limited, and can be, for example, 80°C to 120°C. The heating time is not particularly limited, and can be, for example, 3 to 15 minutes. Heating can be carried out under normal or reduced pressure, or a constant temperature bath can be used.

[0191] Heating can also be used for curing. There is no particular limitation on the curing temperature; for example, it can be 80℃ to 120℃. Curing can be carried out, for example, using a constant temperature bath. The curing temperature can be set relatively lower than the heating temperature.

[0192] This application claims priority based on Japanese Patent Application No. 2024-006321, filed on January 18, 2024. The entire contents of the description of the aforementioned Japanese Patent Application No. 2024-006321 are incorporated herein by reference.

[0193] Example

[0194] The present invention will be described in more detail below with examples, but the present invention is not limited to the following examples. Of course, modifications can be made to implement the invention within the scope of the foregoing and following spirit, and these modifications are all included within the technical scope of the present invention. In addition, in the following examples, unless otherwise stated, "parts" and "%" are expressed on a mass basis.

[0195] (1) Raw materials and their characteristics

[0196] The following describes the raw materials used in the embodiments, categorized by each component of the laminate, based on their characteristics. It should be noted that the melting point of the raw materials is the value measured using a differential scanning calorimeter (hereinafter referred to as DSC, TA Instruments Japan's "Q-2000"), obtained by melting at a rate of 20°C / min, cooling to resinify, and then re-melting. The glass transition temperature of the raw materials is the temperature at the starting point (rising point, inflection point) of the endothermic peak during the heating process. Other characteristics are listed as nominal values ​​from the raw material manufacturer's product catalog.

[0197] [Resin Sheets]

[0198] (A) Syndiotactic polystyrene resin

[0199] XAREC (registered trademark) 90ZC manufactured by Idemitsu Kosan Co., Ltd. (syndiotactic polystyrene, 100% by mass, weight average molecular weight 200,000, MFR of 9 g / 10 min measured at 300°C and under a load of 1.2 kg, melting point 271°C, glass transition temperature 96°C).

[0200] (B) Rubber-like elastomer

[0201] Tuftec (registered trademark) H1062 manufactured by Asahi Kasei Corporation (8% by mass, styrene ratio of 18% by mass, MFR of 4.5 g / 10 min measured at 230°C and under a load of 2.16 kg)

[0202] (C) Fibrous packing

[0203] HDT09100T (12% mass, D glass, fiber diameter 9μm, D50 average fiber length 100μm) manufactured by Touchu Co., Ltd.

[0204] (D) Non-fibrous packing

[0205] FB-3SDC silica particles (10% by mass, D50 average particle size 3.1 μm) manufactured by Denka Corporation.

[0206] (E) Antioxidants

[0207] ANOX 20 (0.2% by mass, pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], melting point 118°C), manufactured by BASF Japan Co., Ltd. ANOX 20 decreases 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 ANOX 20 is 350°C.

[0208] [Primer Composition]

[0209] (a) First silane compound: N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane

[0210] (b) Second silane compound: vinyltrimethoxysilane

[0211] (c) Polyamine compounds: ethylenediamine

[0212] (d) Alcohols: ethanol, methanol, n-propanol

[0213] (e) water

[0214] (f) Dimethylsiloxane oligomers: hexamethyldisiloxane

[0215] [Adhesive layer]

[0216] Aron Mighty AF-711 (flame retardant grade, 25μm thickness), a low-dielectric adhesive film manufactured by Toa Sekkei Co., Ltd.

[0217] [Metallic layer]

[0218] Fukuda Metal Foil & Powder Industry Co., Ltd. manufactures low-roughness copper foil "CF-T4X-SV18" (18μm thickness, Rz1.1μm).

[0219] (2) Experimental Example

[0220] (Experiments 1 and 5)

[0221] The components of raw materials (a) to (e) are blended and compounded to produce unstretched sheets. Specifically, using a φ36mm co-rotating twin-screw extruder, components (a) to (e) are fed into the main feeder or side feeder respectively, and blended at a resin temperature of 300°C. After extruding four strips from a φ4mm circular die, the strips are cooled and solidified in a water-cooling tank, and then pelletized to obtain cylindrical resin granules. The obtained cylindrical resin granules are fed into the hopper of a φ20mm single-screw extruder, and remelted at a resin temperature of 300°C. They are then extruded into sheets from a T-die, compressed and cooled between two metal compression rollers and a take-up roller (all rollers are at a temperature of 90°C), and then wound onto a φ80mm paper tube at a speed of 1m / min, thereby producing an unstretched sheet (raw material resin sheet) with a thickness of 300μm. The pressure of the clamping roller is set to a linear pressure of 100 N / cm. It should be noted that in this specification, the direction parallel to the sheet extrusion direction is defined as MD, and the direction perpendicular to it is defined as TD.

[0222] Next, the obtained unstretched sheet (raw resin sheet) is subjected to heat treatment and annealing to manufacture resin sheets. For heat treatment, unstretched sheets cut to the appropriate size according to the panel dimensions of a vacuum press (MHPC-V-450-450, manufactured by Nippon Steel) are prepared. A release film PEEK (Shin-Etsu Sepia Film, 50μm thick), an SUS board (#400, 1.5mm thick, SUS304), and a cushioning material (Yamauchi Original Mat, YOM model) are sequentially laminated on both sides of this sheet, and the laminate is then placed into the vacuum press. In the vacuum press, the temperature is increased from room temperature to 200°C at a rate of 7°C / min, and then pressed under vacuum (below 4mmHg) and a pressure of 2MPa for 30 minutes. Afterward, it is slowly cooled to approximately 50°C, and the vacuum is released to obtain the heat-treated sheet. Next, the heat-treated sheet is annealed. Annealing is performed by placing the heat-treated sheet in a constant temperature bath set at 180°C for 30 minutes. After that, the sheet is removed from the constant temperature bath and left to stand until it cools to room temperature. The stacked release film, SUS board and cushioning material are then removed to obtain the resin sheet.

[0223] The crystallization of the annealed resin sheet was confirmed using a differential scanning calorimeter (Hitachi High Science & Technology Co., Ltd., DSC7020) according to JISK7121 (2012). Specifically, 5 mg of resin sheet was placed in an aluminum sample pan and heated from room temperature at a rate of 20°C / min. If no exothermic peak was observed within the temperature range of 100°C to 220°C, it was determined that the crystallization of the syndiotactic polystyrene resin had been completed through heat treatment during vacuum pressing. The results confirmed that the resin sheet used in this embodiment had been crystallized.

[0224] The resin sheet obtained after annealing was subjected to corona discharge treatment as a surface activation treatment. The corona discharge treatment was performed twice on both sides of the resin sheet using a corona discharge treatment device (manufactured by Kasuga Electric Co., Ltd., high frequency power supply, AGI-023S, wire electrode 1φ2.4m), with an output power of 130W and a conveying speed of 1m / min.

[0225] The resin sheet obtained by corona discharge treatment 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: In a 200ml glass bottle, 40g ethanol, 10g methanol, 25g n-propanol, and 8g ethylenediamine were added and stirred to form a homogeneous solution. Next, 5g hexamethyldisiloxane, 5g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and 7g vinyltrimethoxysilane were added and stirred to obtain a homogeneous primer composition 1. Then, 15g of deionized water was added to the obtained primer composition 1 for dilution to prepare solution 1 containing water-soluble adhesive-promoting primer composition 1.

[0226] After air-drying until the solution containing primer composition 1 no longer drips from the surface of the resin sheet, it is suspended in a constant temperature bath set at 90°C for 10 minutes to dry. After drying, the resin sheet is removed from the constant temperature bath and left to stand until it cools to room temperature, thus producing resin sheet 1 with a surface treatment layer.

[0227] (Experiment 2)

[0228] In Experiment 1, resin sheets 2 with a surface-treated layer were manufactured under the same conditions, 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 as follows: 40g of ethanol, 10g of methanol, and 25g of n-propanol were added to a 200ml glass bottle and stirred to form a homogeneous solution. Next, 5g of hexamethyldisiloxane, 5g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and 7g of vinyltrimethoxysilane were added and stirred to obtain a homogeneous primer composition 2. Then, 15g of deionized water was added to the obtained primer composition 2 for dilution to prepare solution 2 containing water-soluble adhesive-promoting primer composition 2.

[0229] (Experiment 3, Experiment 4)

[0230] In Experiment 1, resin sheets 3 and 4 were manufactured under the same conditions as in Experiment 1, except that corona discharge treatment was not applied to the annealed resin sheet and a surface treatment layer was not formed as a treatment layer composed of primer composition 1.

[0231] (Experiment 6)

[0232] In Experiment 1, resin sheet 6 was manufactured under the same conditions as in Experiment 1, except that a surface treatment layer consisting of a primer composition 1 was not formed.

[0233] When corona discharge treatment is performed, it is marked with "○" in Table 1; when corona discharge treatment is not performed, it is marked with "-". Table 1 shows the types of solutions (solution 1, solution 2) used to form a surface treatment layer on the surface of the resin sheet. In Table 1, "-" indicates that no surface treatment layer is formed.

[0234] [Table 1]

[0235]

[0236] Elemental analysis of the surface of the resin sheets obtained in Experiments 1, 3-6 was performed using an ESCA (Ext. Sci. C. X-ray photoelectron spectroscopy analyzer). The ESCA used was a K-Alpha+ analyzer manufactured by Thermo Fisher Scientific. The results of the elemental analysis are shown in Table 1 above. Furthermore, based on the results of the elemental analysis, the values ​​of Si / (C+N+O+Si) specified in Equation (1), O / Si specified in Equation (2), C / Si specified in Equation (3), and N / Si specified in Equation (4) were calculated. The calculated values ​​are shown in Table 1 above.

[0237] Next, adhesive layers were laminated on both sides of the resin sheets obtained in Experiments 1-6. For laminating the adhesive layers, two adhesive sheets (Aron Mighty AF-711) with release films laminated on both sides were prepared. One side of the release film was peeled off, and the exposed side of the adhesive layer was aligned and overlapped with the resin sheet. The sheets were then passed through a roller laminator (MCK manufacturing, MRS-600 type) set to 120℃, 0.5m / min, and 0.3MPa to laminate the resin sheet and adhesive layer, resulting in a laminate. The laminate structure 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 obtained in Experiments 3, 4, and 6 was: release film / adhesive layer / resin sheet / adhesive layer / release film.

[0238] Next, regarding the laminate of the resin sheet and adhesive layer, the release film on both sides was peeled off, and the metal layer (CF-T4X-SV) was overlapped on the exposed side of the adhesive layer to obtain the 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.

[0239] Next, the resulting laminate was subjected to heat treatment. In addition, for experiments 4 and 5, curing (solidification) was further performed after heat treatment.

[0240] Heat treatment involved sequentially layering an SUS plate (#400, 1.5 mm thick, SUS304) and a cushioning material (Yamauchi Original Mat, YOM model) onto both sides of the resulting laminate, and then placing the laminate into a vacuum press. Vacuum pressing was performed in the vacuum press under either condition 1 or condition 2 described below. Table 1 shows the vacuum pressing conditions (condition 1, condition 2) for each experiment.

[0241] Condition 1: Heat from room temperature to 180°C at a rate of 6°C / min, and press under vacuum and pressure of 2MPa for 60 minutes.

[0242] Condition 2: Heat from room temperature to 120°C at a rate of 6°C / min, and press under vacuum and pressure of 2MPa for 15 minutes.

[0243] After vacuum pressing, the material is slowly cooled to about 50°C, the vacuum is released, and the heat-treated laminate is removed.

[0244] Next, for experiments 4 and 5, the heat-treated laminates were placed in a constant temperature bath set to 100°C and left to stand for 24 hours under a nitrogen atmosphere (approximately 20 L / min) for curing. Curing was indicated by “○” in Table 1 for products that underwent curing, and by “-” for products that did not. After curing, the laminates were removed from the constant temperature bath and left to stand until cooled to room temperature, resulting in a resin sheet with a metal layer laminated between the adhesive layer and the laminate.

[0245] The heat-treated or cured laminates were used as resin sheets, and the peel strength and heat resistance of the resulting resin sheets were evaluated.

[0246] (Peel strength)

[0247] A 5mm slit was cut into the metal layer on one side of a resin sheet with a metal layer laminated between the adhesive layer and the metal layer to prepare a specimen for peel strength testing. The peel strength at the interface between the resin sheet and the adhesive layer was measured using a tensile compression testing machine (TG-2kN manufactured by Minebea Mitsukoshi Co., Ltd.) at a tensile speed of 50mm / min and a 90° peel. The measurement results are shown in Table 1.

[0248] (Heat resistance)

[0249] The heat resistance of the resin sheet with a metal layer laminated by an adhesive layer was evaluated using a floating soldering test. The resin sheet was cut into 25×25mm pieces to prepare test samples. A solder bath (POT-103C, manufactured by Taiyo Electric Industry Co., Ltd.) containing lead-free solder (lead-free rod solder, M705-BAR, manufactured by Taiyo Electric Industry Co., Ltd.) was set to 260°C, and the test samples were floated on the molten solder. After standing for 1 minute, the test samples were removed from the solder bath and allowed to stand until cooled to room temperature. The appearance of the test samples was visually inspected to check for blistering caused by air bubbles and foreign matter on the metal layer, and to check for any peeling of the metal layer. Tests without blistering caused by air bubbles and foreign matter on the metal layer, and without peeling of the metal layer, were considered acceptable and evaluated as having good heat resistance. The evaluation result was marked "○" in Table 1. Bubbling caused by air bubbles, bubbling caused by foreign matter, or peeling on the metal layer are considered unqualified and evaluated as having poor heat resistance. The evaluation result is marked as "×" in Table 1.

[0250] From Table 1, the following findings can be obtained. Elemental analysis of the surface of the resin sheets obtained in Experiments 1 and 5 using ESCA revealed the presence of Si, C, N, and O, with the amounts of these atoms satisfying the relationships between equations (1) to (4). As a result, when a metal layer is laminated onto the resin sheet via an adhesive layer, the peel strength at the interface between the resin sheet and the adhesive layer is high, the adhesion between the resin sheet and the adhesive layer becomes good, and the metal layer becomes difficult to peel off. Furthermore, the resin sheet with a metal layer laminated via an adhesive layer exhibits excellent heat resistance. Since the resin sheets obtained in Experiments 1, 2, and 5 have a surface treatment layer that meets the requirements specified in this invention, when a metal layer is laminated via an adhesive layer, the peel strength at the interface between the resin sheet and the adhesive layer is high, the adhesion between the resin sheet and the adhesive layer is good, and the metal layer is difficult to peel off. Furthermore, the resin sheet with a metal layer laminated via an adhesive layer exhibits excellent heat resistance.

[0251] On the other hand, when the surface of the resin sheets obtained in Experiments 3, 4, and 6 was analyzed by ESCA, although Si, C, N, and O were observed, the amounts of these atoms did not satisfy the relationship of any of the terms in Equations (1) to (4). As a result, even when a metal layer was laminated on the resin sheet through an adhesive layer, the peel strength at the interface between the resin sheet and the adhesive layer was very low, the adhesion between the resin sheet and the adhesive layer was poor, and the metal layer was easily peeled off. In addition, the resin sheet with a metal layer laminated through an adhesive layer had poor heat resistance. Since the resin sheets obtained in Experiments 3, 4, and 6 did not form a surface treatment layer, when a metal layer was laminated through 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. In addition, the resin sheet with a metal layer laminated through an adhesive layer had poor heat resistance.

Claims

1. A resin sheet with a surface-treated layer, wherein, The resin sheet contains syndiotactic polystyrene resin, and the surface treatment layer exists on one or both sides of the resin sheet. When elemental analysis is performed on the side of the surface treatment layer that is not in contact with the resin sheet by X-ray photoelectron spectroscopy (ESCA), Si, C, N, and O are observed, and the amounts of these atoms satisfy the following relationships (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 equations (1) to (4), each atom symbol represents the content of each atom, and the unit is % (atoms).

2. The resin sheet according to claim 1, wherein, The Si atom content is 5–25 atoms, and the N atom content is 1–15 atoms.

3. A resin sheet with a surface-treated layer, wherein, The resin sheet contains a syndiotactic polystyrene resin, and the surface treatment layer exists on one or both sides of the resin sheet. The surface treatment layer is a treatment layer formed by a primer composition containing a first silane compound a having an amino alkyl 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 the primer composition, relative to 100 parts by mass of the first silane compound a, there are 40 to 250 parts by mass of the second silane compound b.

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 stacked on the adhesive layer.

7. A primer composition, wherein, The compound 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. The amount of the second silane compound b is 40 to 250 parts by mass relative to 100 parts by mass of the first silane compound a.

8. The primer composition according to claim 7, wherein, The primer composition further comprises at least one selected from the group consisting of a polyamine compound c, water e, and a dimethylsiloxane oligomer f whose substituents other than oxygen atoms are all methyl and have 6 or fewer silicon atoms.

9. The primer composition according to claim 7, wherein, The primer composition contains 100 to 250 parts by weight of a polyamine compound c, relative to 100 parts by weight of the first silane compound a.

10. The primer composition according to claim 7, wherein, The primer composition contains less than 2,000 parts by mass of water e relative to 100 parts by mass of the first silane compound a.

11. The primer composition according to claim 7, wherein, Relative to 100 parts by mass of the first silane compound a, the primer composition contains 10 to 500 parts by mass of a dimethylsiloxane oligomer f, in which all substituents except oxygen atoms bonded to silicon atoms are methyl and the number of silicon atoms is 6 or less.

12. The primer composition according to claim 7, wherein, It contains two or more of the alcohols d.

13. A method for manufacturing a resin sheet with a surface treatment layer, comprising: a substrate treatment step of performing a surface activation treatment on at least one surface of a resin sheet containing a syndiotactic polystyrene resin; A surface layer forming process in which a base coating is formed on the surface that has undergone the aforementioned surface activation treatment; And a surface layer reaction process involving heating the resin sheet to which the base coating 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 the following: corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, radiation treatment, and flame treatment.

15. The manufacturing method according to claim 13, wherein, The base coat is formed using a base coat composition containing a first silane compound a having an amino alkyl 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, The amount of the second silane compound b in the primer composition is 40 to 250 parts by mass relative to 100 parts by mass of the first silane compound a.

17. The manufacturing method according to claim 15, wherein, The primer composition further comprises at least one selected from the group consisting of a polyamine compound c, water e, and a dimethylsiloxane oligomer f whose substituents other than oxygen atoms are all methyl and have 6 or fewer silicon atoms.

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