Prepreg for printed wiring board, metal-clad laminate for printed wiring board, and printed wiring board

Abstract

One aspect of the present invention provides a prepreg for a printed wiring board, the prepreg comprising: a thermosetting composition or a semi-cured product of the thermosetting composition, wherein the thermosetting composition contains 65 parts by mass or more of an inorganic filler relative to 100 parts by mass of a thermosetting compound, the inorganic filler containing, as a material, at least one substance that is selected from the group consisting of silica, quartz glass, and magnesium oxide, and the thermosetting compound containing at least one compound that is selected from the group consisting of a polyphenylene ether compound that has a carbon-carbon unsaturated double bond in each molecule, a hydrocarbon compound that has a carbon-carbon unsaturated double bond in each molecule, and a thermosetting compound that has a fluorine atom in each molecule; and a fibrous base material that contains liquid crystal polymer fibers which have a dielectric loss tangent of 0.0015 or less at 5 GHz and 25°C. The respective abundance ratios of groups in the surface of the fibrous base material as determined by X-ray photoelectron spectroscopy are in a specific relationship.

Description

Prepreg for printed wiring board, metal-clad laminate for printed wiring board, and printed wiring board

[0001] The present invention relates to a prepreg for a printed wiring board, a metal-clad laminate for a printed wiring board, and a printed wiring board.

[0002] As the amount of information processed increases, integration technologies for various electronic devices are advancing, such as the high integration of semiconductor devices, high-density wiring, and multi-layering. Furthermore, printed wiring boards used in various electronic devices are required to be high-frequency compatible, such as server boards for communication infrastructure equipment applications such as network equipment, servers, and AI (artificial intelligence) processors, and millimeter-wave radar boards for automotive applications. Substrate materials for forming the insulating layers of printed wiring boards used in various electronic devices are required to have excellent low-dielectric properties, such as low relative permittivity and dielectric loss tangent, in order to increase signal transmission speed and reduce signal transmission loss. Such substrate materials may contain resin components with low relative permittivity and dielectric loss tangent, and may also contain a fibrous substrate such as glass cloth in addition to the resin component. While glass cloth is often used as the fibrous substrate, the use of substrates containing fibers other than glass cloth has also been considered. Examples of materials using substrates containing fibers other than glass cloth as the fibrous substrate include the fiber-reinforced resin composite material described in Patent Document 1. Furthermore, examples of the fibrous base material contained in the substrate material include surface-modified wholly aromatic polyester fibers described in Patent Document 2.

[0003] Patent Document 1 describes a fiber-reinforced resin composite material comprising aromatic polyester fibers contained in a heat-resistant resin, the surfaces of which are plasma-etched and aminopolyamide-treated. Patent Document 1 discloses that the resulting composite material has excellent heat resistance and excellent interfacial adhesion, and is therefore able to withstand drilling, and can be effectively used as a printed wiring board material, etc.

[0004] Patent Document 2 describes a surface-modified wholly aromatic polyester fiber that contains a wholly aromatic polyester polymer and has a ratio of the number of oxygen atoms to the number of carbon atoms on the fiber surface of 30 to 60%. Patent Document 2 discloses that a surface-modified wholly aromatic polyester fiber can be obtained that has excellent fiber strength and excellent interfacial adhesion with a matrix resin and is suitable for use in circuit boards and the like.

[0005] Substrate materials for forming insulating layers of printed wiring boards are required to not only have excellent low dielectric properties but also to provide cured products that are excellent in heat resistance and processability.

[0006] Japanese Patent Application Laid-Open No. 2-6538 International Publication No. 2019 / 131219

[0007] The present invention has been made in view of the above circumstances, and aims to provide a prepreg for printed wiring boards that can give a cured product having low dielectric properties, excellent heat resistance, and excellent processability. Another aim of the present invention is to provide a metal-clad laminate for printed wiring boards and a printed wiring board obtained using the prepreg.

[0008] One aspect of the present invention is a fiber substrate comprising a thermosetting composition or a semi-cured product of the thermosetting composition containing a thermosetting compound and an inorganic filler, and a liquid crystal polymer fiber, wherein the thermosetting compound contains at least one selected from the group consisting of a polyphenylene ether compound having a carbon-carbon unsaturated double bond in its molecule, a hydrocarbon compound having a carbon-carbon unsaturated double bond in its molecule, and a thermosetting compound having a fluorine atom in its molecule, and the inorganic filler is at least one selected from the group consisting of silica, quartz glass, and magnesium oxide. The liquid crystal polymer fiber has a dielectric loss tangent of 0.0015 or less at 25°C and 5 GHz, and the ratio of the total amount of groups represented by the following formula (3), groups represented by the following formula (4), and groups represented by the following formula (5) to the total amount of groups represented by the following formula (1) and groups represented by the following formula (2), as measured by X-ray photoelectron spectroscopy, on the surface of the fibrous substrate is 0.3 or more and less than 0.55:

[0009]

[0010]

[0011]

[0012]

[0013]

[0014] These and other objects, features, and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0015] Fig. 1 is a schematic cross-sectional view showing an example of a prepreg according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate according to an embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing an example of a printed wiring board according to an embodiment of the present invention.

[0016] Electronic devices, particularly small portable devices such as mobile communication terminals and laptops, are rapidly becoming more diverse, powerful, thin, and compact. Accordingly, the printed wiring boards used in these products are also required to have even higher performance, such as finer conductor wiring, more multi-layered conductor wiring layers, thinner designs, and improved mechanical properties. For this reason, the insulating layers of printed wiring boards used in various electronic devices are required to have minimal defects even when drilled with a drill or laser to form through holes and via holes. Specifically, the substrate material for forming the insulating layer of a printed wiring board is required to have an insulating layer that is, for example, less likely to cause delamination between the wiring and the insulating layer even when cut, and that is also less likely to cause delamination between the resin component contained in the insulating layer and the fibrous base material. Therefore, the insulating layer of a printed wiring board is required to have excellent processability that can sufficiently suppress defects that may occur during processing such as drilling.

[0017] Printed wiring boards used in various electronic devices are also required to be resistant to changes in the external environment, etc. For example, they are also required to have excellent heat resistance so that they can be used even in relatively high-temperature environments. Therefore, substrate materials for constituting the insulating layer of printed wiring boards are required to produce cured products with excellent heat resistance.

[0018] When a conventional substrate containing fibers other than glass cloth is used as the fibrous substrate, for example, when the fiber-reinforced resin composite material described in Patent Document 1 is used, or when a substrate containing the surface-modified wholly aromatic polyester fiber described in Patent Document 2 is used, there is a concern that the heat resistance and processability may be insufficient. Specifically, when the fiber-reinforced resin composite material described in Patent Document 1 is used, the heat resistance is insufficient. Patent Document 1 also examines the interfacial adhesion when polyimide resin and epoxy resin are used as the heat-resistant resin containing the aromatic polyester fiber, but does not particularly examine when other resins are used. Therefore, there is a concern that the fiber-reinforced resin composite material described in Patent Document 1 may have insufficient interfacial adhesion and insufficient processability. Patent Document 2 also does not particularly examine heat resistance, and there is a concern that a material containing the surface-modified wholly aromatic polyester fiber described in Patent Document 2 and a resin may have insufficient heat resistance. Patent Document 2 also examines the interfacial shear stress when an epoxy resin is contained, but does not particularly examine when other resins are used. Therefore, in the material in which a resin is contained in the surface-modified wholly aromatic polyester fiber described in Patent Document 2, there is a concern that the interfacial adhesion may be insufficient, and the processability may be insufficient.

[0019] For these reasons, substrate materials for forming insulating layers of printed wiring boards are required to provide cured products with low dielectric properties, heat resistance, and excellent processability.

[0020] As a result of extensive investigations, the present inventors have found that the above-mentioned object of providing a prepreg for printed wiring boards which gives a cured product having low dielectric properties, excellent heat resistance and processability can be achieved by the present invention described below.

[0021] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0022] [Printed Wiring Board Prepreg] A prepreg according to one embodiment of the present invention is a printed wiring board prepreg comprising a thermosetting composition (resin composition) or a semi-cured product of the thermoplastic composition, and a fibrous substrate. Examples of this prepreg 1 include, as shown in FIG. 1 , a thermosetting composition or a semi-cured product of the thermosetting composition 2, and a fibrous substrate 3 present in the thermosetting composition or the semi-cured product of the thermosetting composition 2. In this embodiment, the semi-cured product refers to a thermosetting composition (resin composition) that has been partially cured to the extent that it can be further cured. In other words, the semi-cured product refers to a thermosetting composition that has been semi-cured (B-staged). For example, when a thermosetting composition is heated, its viscosity initially gradually decreases as it melts, and then curing begins, and the viscosity gradually increases. In such a case, the semi-cured state can be described as the state between when the viscosity begins to gradually decrease and before it is completely cured.

[0023] The prepreg according to this embodiment may be a prepreg comprising a semi-cured product of the thermosetting composition as described above, or may be a prepreg comprising the uncured thermosetting composition itself. That is, the prepreg according to this embodiment may be a prepreg comprising a semi-cured product of the thermosetting composition (the thermosetting composition in B stage) and a fibrous base material, or a prepreg comprising the thermosetting composition before curing (the thermosetting composition in A stage) and a fibrous base material.

[0024] The thermosetting composition in the prepreg according to this embodiment contains a thermosetting compound and an inorganic filler. The thermosetting compound contains at least one selected from the group consisting of a polyphenylene ether compound having a carbon-carbon unsaturated double bond in its molecule, a hydrocarbon-based compound having a carbon-carbon unsaturated double bond in its molecule, and a thermosetting compound having a fluorine atom in its molecule (fluorine-containing thermosetting compound). The inorganic filler contains at least one material selected from the group consisting of silica, quartz glass, and magnesium oxide. The content of the inorganic filler is 65 parts by mass or more per 100 parts by mass of the thermosetting compound. That is, the thermosetting composition is a thermosetting composition containing 65 parts by mass or more of an inorganic filler containing at least one material selected from the group consisting of silica, quartz glass, and magnesium oxide per 100 parts by mass of a thermosetting compound containing at least one material selected from the group consisting of the polyphenylene ether compound, the hydrocarbon-based compound, and the fluorine-containing thermosetting compound. The fibrous base material in the prepreg according to this embodiment includes liquid crystal polymer fibers having a dielectric loss tangent of 0.0015 or less at 25°C and 5 GHz, and the ratio (b / a) of the total amount (b) of groups represented by the following formula (3), groups represented by the following formula (4), and groups represented by the following formula (5) to the total amount (a) of groups represented by the following formula (1) and groups represented by the following formula (2) measured on the surface of the fibrous base material by X-ray photoelectron spectroscopy (XPS) is 0.3 or more and less than 0.55.

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] The prepreg provides a cured product with low dielectric properties, excellent heat resistance, and excellent processability. This is believed to be due to the following reasons.

[0031] First, when the prepreg is cured, the cured product of the prepreg contains the cured product of the thermosetting composition together with the fibrous base material. The thermosetting composition (or semi-cured thermosetting composition) contained in the prepreg contains the thermosetting compound containing at least one selected from the group consisting of the polyphenylene ether compound, the hydrocarbon compound, and the fluorine-containing thermosetting compound. Furthermore, the thermosetting composition (or semi-cured thermosetting composition) constituting the prepreg contains a relatively large amount of the inorganic filler, with the inorganic filler being 65 parts by mass or more per 100 parts by mass of the thermosetting compound. From these facts, it is believed that the cured product of the thermosetting composition will have excellent heat resistance while maintaining the excellent low dielectric properties of the thermosetting compound. Furthermore, since the fibrous base material provided in the prepreg contains liquid crystal polymer fibers having a dielectric dissipation factor of 0.0015 or less at 5 GHz at 25°C, it is believed that when the prepreg is cured, it will produce a cured product with low dielectric properties and excellent heat resistance. Furthermore, since the thermosetting composition (or semi-cured thermosetting composition) constituting the prepreg is highly filled with the inorganic filler as described above, it is believed that the cured product of the thermosetting composition will be relatively hard (for example, will have a relatively high storage modulus or a small dimensional change rate due to heating). Furthermore, the fibrous base material has a surface where the abundance ratio of each group measured by X-ray photoelectron spectroscopy satisfies the above relationship. Specifically, the group represented by formula (3), the group represented by formula (4), and the group represented by formula (5) are more polar than the group represented by formula (1) and the group represented by formula (2). The fibrous substrate has, on its surface, a certain amount or more of groups with relatively high polarity (higher than the groups represented by formula (1) and formula (2)), such as the group represented by formula (3), the group represented by formula (4), and the group represented by formula (5), such that the abundance ratio of each group satisfies the above relationship. From this, it is considered that the fibrous substrate has relatively high adhesion between the cured product of the thermosetting composition and the fibrous substrate in the cured product of the prepreg.That is, the relatively highly polar groups present on the surface of the fibrous substrate such that the abundance ratio of each group satisfies the above relationship are believed to favorably contribute to improving the adhesion between the cured product of the thermosetting composition and the fibrous substrate. Therefore, the cured product of the prepreg is believed to be a cured product with excellent processability that can sufficiently suppress defects that may occur during processing such as drilling. Specifically, even when the cured product of the prepreg is cut, it is believed that peeling is unlikely to occur between the cured product of the thermosetting composition and the fibrous substrate. Furthermore, if a metal layer or wiring is present on the surface of the cured product of the prepreg (such as a metal-clad laminate or printed wiring board having an insulating layer containing the cured product of the prepreg), it is believed that defects that may occur due to the suppression of peeling between the cured product of the thermosetting composition and the fibrous substrate in the cured product of the prepreg, such as peeling between the metal layer or the wiring and the cured product (the insulating layer), are also suppressed. For this reason, it is believed that peeling is unlikely to occur between the metal layer or the wiring and the cured product (the insulating layer). Furthermore, the insulating layer provided on the printed wiring board is also required to have excellent low dielectric properties, such as a low relative dielectric constant and a low dielectric loss tangent, in order to suppress losses due to increased resistance accompanying miniaturization of wiring. The cured product of the prepreg not only has excellent heat resistance and processability, but also has excellent low dielectric properties, such as a low relative dielectric constant and a low dielectric loss tangent. For these reasons, the prepreg is suitable as a prepreg used in producing a printed wiring board, i.e., a prepreg for a printed wiring board. It is also suitable as a prepreg used in producing a metal-clad laminate for a printed wiring board.

[0032] From the above, it is believed that the prepreg described above can provide a prepreg for printed wiring boards that has low dielectric properties, heat resistance, and excellent processability as a cured product.

[0033] <Fibrous Substrate> The fibrous substrate in the prepreg according to this embodiment includes a liquid crystal polymer fiber having a dielectric loss tangent of 0.0015 or less at 5 GHz at 25°C. That is, the liquid crystal polymer fiber is a fiber composed of a liquid crystal polymer having a dielectric loss tangent of 0.0015 or less at 5 GHz at 25°C. Specific examples of the polymer fiber include a woven fabric made of a liquid crystal polymer fiber having a dielectric loss tangent of 0.0015 or less at 5 GHz at 25°C. The fibrous substrate is also a fibrous substrate in which the ratio of the total amount of the groups represented by formula (3), the groups represented by formula (4), and the groups represented by formula (5) to the total amount of the groups represented by formula (1) and the groups represented by formula (2) on the surface of the fibrous substrate, as measured by X-ray photoelectron spectroscopy, is 0.3 or more and less than 0.55.

[0034] As described above, the dielectric dissipation factor of the liquid crystal polymer fiber at 5 GHz at 25°C may be 0.0015 or less, but is preferably 0.001 or less. Furthermore, the lower the dielectric dissipation factor of the liquid crystal polymer fiber, the more preferable it is. In practice, however, it is generally 0.0003 or more. Therefore, the dielectric dissipation factor of the liquid crystal polymer fiber at 5 GHz at 25°C is preferably 0.0003 to 0.0015, and more preferably 0.0003 to 0.001. When the dielectric dissipation factor of the liquid crystal polymer fiber is within the above range, a prepreg for printed wiring boards having sufficiently excellent low dielectric properties as a cured product can be obtained. Furthermore, the dielectric constant of the liquid crystal polymer fiber at 5 GHz at 25°C is preferably 2.3 to 3.7, and more preferably 2.5 to 3.5. When the dielectric constant of the liquid crystal polymer fiber is within the above range, a prepreg for printed wiring boards having sufficiently excellent low dielectric properties as a cured product can be obtained. The dielectric constant and dielectric loss tangent here refer to the dielectric constant and dielectric loss tangent at 25°C and 5 GHz, and specifically include the dielectric constant and dielectric loss tangent of a cured product of a prepreg at 25°C and 5 GHz, measured by a cavity resonator perturbation method.

[0035] The liquid crystal polymer fiber is not particularly limited as long as it has a dielectric loss tangent of 0.0015 or less, and examples thereof include fibers containing a wholly aromatic polyester polymer and having a dielectric loss tangent of 0.0015 or less. Examples of the liquid crystal polymer fiber (e.g., fibers containing the wholly aromatic polyester polymer) include fibers obtained by melt-spinning a liquid crystal polyester. The liquid crystal polyester contains structural units (e.g., repeating units) derived from acids such as aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids. The structural units derived from acids such as aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids are not particularly limited as long as they do not impair the effects of the present invention. Furthermore, the liquid crystal polyester may further contain other structural units derived from aromatic diamines, aromatic hydroxyamines, aromatic aminocarboxylic acids, etc., as long as they do not impair the effects of the present invention. The structural units are preferably structural units represented by the following formulas (6) to (9).

[0036]

[0037]

[0038]

[0039]

[0040] In formulas (6) to (9), X represents at least one selected from the groups represented by formulas (10) to (17).

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] In formulas (10), (13), and (16), m represents 0 to 2. In formulas (10) to (12), (16), and (17), Y represents a hydrogen atom or a substituent of an aromatic ring. When Y represents a substituent, the number of Y's (number of substituents) is in the range of 1 or more and the maximum number of substituents that can be introduced into the aromatic ring. Examples of the substituent include a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, an aryloxy group, or an aralkyloxy group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include an alkyl group having 1 to 4 carbon atoms, more specifically, a methyl group, an ethyl group, an isopropyl group, and a t-butyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, and an n-butoxy group. Examples of the aryl group include a phenyl group and a naphthyl group. Examples of the aralkyl group include a benzyl group (phenylmethyl group) and a phenethyl group (phenylethyl group). Examples of the aryloxy group include a phenoxy group. Examples of the aralkyloxy group include a benzyloxy group. Furthermore, examples of the structural unit represented by formula (6) include structural units derived from aromatic hydroxycarboxylic acids such as 6-hydroxy-2-naphthoic acid. Examples of the structural unit represented by formula (7) include structural units derived from aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid. Examples of the structural unit represented by formula (8) include structural units derived from aromatic diols such as 4,4'-dihydroxybiphenyl.

[0050] Examples of the combination of structural units in the liquid crystalline polyester include combinations of structural units represented by the following formulas (18) to (35). When a structural unit represented by one formula can have multiple structures, multiple structural units represented by one formula may be used in combination.

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] In the formulas (19), (21) to (25), (28) to (30), and (32) to (35), n represents 1 or 2, and multiple constitutional units represented by the same formula but with different n numbers may be used in combination.

[0070] In formula (31), Y １ and Y ２ Each of Y independently represents a hydrogen atom or a substituent. Examples of the substituent include the same groups as those listed for Y. １ and Y ２ Preferred examples of include a hydrogen atom, a chlorine atom, a bromine atom, and a methyl group.

[0071] In formula (31), Z represents a group represented by the following formulas (36) to (40). That is, Z is at least one selected from the group consisting of groups represented by the following formulas (36) to (40).

[0072]

[0073]

[0074]

[0075]

[0076]

[0077] The liquid crystalline polyester preferably contains a naphthalene skeleton as the structural unit, and more preferably contains a structural unit (A) derived from hydroxynaphthoic acid.

[0078] Examples of liquid crystalline polyesters containing the structural unit (A) include those containing a structural unit (A) derived from hydroxynaphthoic acid and further containing a structural unit (B) derived from hydroxybenzoic acid. Examples of the structural unit (A) include a structural unit represented by the following formula (41) (a structural unit derived from 6-hydroxy-2-naphthoic acid). Examples of the structural unit (B) include a structural unit represented by the following formula (42) (a structural unit derived from p-hydroxybenzoic acid). From the viewpoint of improving melt moldability, the molar ratio of the structural unit (A) to the structural unit (B) in the liquid crystalline polyester is preferably 1:1 to 1:9, more preferably 1:1 to 1:7, and even more preferably 1:1 to 1:5. The total amount of the structural unit (A) and the structural unit (B) in the liquid crystalline polyester is preferably 65 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 80 to 100 mol%. It is also preferable that the content of the structural unit (A) in the liquid crystalline polyester is 4 to 45 mol %, and the content of the structural unit (B) is 50 to 70 mol %.

[0079]

[0080]

[0081] Examples of liquid crystalline polyesters containing the structural unit (A) include those containing a structural unit (A) derived from hydroxynaphthoic acid, and further containing a structural unit (C) derived from an aromatic dicarboxylic acid, and a structural unit (D) derived from a dihydroxy aromatic compound. Examples of the structural unit (A) include a structural unit represented by the above formula (41) (a structural unit derived from 6-hydroxy-2-naphthoic acid). Examples of the structural unit (C) include a structural unit represented by the following formula (43) (a structural unit derived from 2,6-naphthalenedicarboxylic acid). Examples of the structural unit (D) include a structural unit derived from hydroquinone and a structural unit derived from dihydroxybiphenyl, and specific examples include a structural unit represented by the following formula (44) (a structural unit derived from hydroquinone) and a structural unit represented by the following formula (45) (a structural unit derived from 4,4'-dihydroxybiphenyl). As described above, the liquid crystalline polyester may contain the structural unit (A), the structural unit (C), and the structural unit (D). For example, a liquid crystalline polyester consisting of the structural unit (A), the structural unit (C), and the structural unit (D) is preferred. The liquid crystalline polyester preferably contains, as the structural unit (D), both a structural unit represented by the following formula (44) and a structural unit represented by the following formula (45). The content of the structural unit (A) in the liquid crystalline polyester is preferably 50 to 70 mol%, more preferably 55 to 65 mol%, based on the total of the structural unit (A), the structural unit (C), and the structural unit (D). The content of the structural unit (C) is preferably 10 to 30 mol%, more preferably 15 to 25 mol%, based on the total of the structural unit (A), the structural unit (C), and the structural unit (D). The content of the structural unit (D) is preferably 10 to 30 mol %, and more preferably 15 to 25 mol %, based on the total content of the structural unit (A), the structural unit (C), and the structural unit (D).When the contents of the structural units (A), (C), and (D) are within the above ranges, a liquid crystal polymer fiber having a dielectric loss tangent of 0.0015 or less at 5 GHz at 25°C can be suitably obtained, and thus a prepreg for printed wiring boards can be obtained as a cured product having sufficiently excellent low dielectric properties. The total amount of the structural units (A), (C), and (D) in the liquid crystal polyester is preferably 65 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 80 to 100 mol%.

[0082]

[0083]

[0084]

[0085] The melting point of the liquid crystalline polyester is not particularly limited, and is preferably 250 to 360°C, and more preferably 260 to 320°C. The melting point referred to here is the main endothermic peak temperature observed when measured using a differential scanning calorimeter (DSC; Mettler "TA3000") in accordance with JIS K7121. In this method, the DSC apparatus is used, and 10 to 20 mg of sample is placed in an aluminum pan. Nitrogen is flowed as a carrier gas at 100 cc / min, and the endothermic peak is measured when the temperature is increased at a heating rate of 20°C / min. Depending on the type of polymer, a clear peak may not appear during the first heating run (1st run) in the DSC measurement. In this case, the sample is first heated at a heating rate of 50°C / min to a temperature 50°C higher than the expected flow temperature, and then held at that temperature for 3 minutes until it is completely melted. Thereafter, the sample is cooled to 50°C at a heating rate of -80°C / min, and then the endothermic peak is measured at a heating rate of 20°C / min.

[0086] The liquid crystalline polyester may contain other thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyether ether ketone, and fluororesin, as long as the effects of the present invention are not impaired. The liquid crystalline polyester may contain various additives such as inorganic substances, colorants such as carbon black, dyes and pigments, antioxidants, ultraviolet absorbers, and light stabilizers. Examples of inorganic substances include titanium oxide, kaolin, silica, and barium oxide.

[0087] As described above, the fibrous substrate has a surface, as measured by X-ray photoelectron spectroscopy, in which the ratio (b / a) of the total amount (b) of the groups represented by formula (3), the groups represented by formula (4), and the groups represented by formula (5) to the total amount (a) of the groups represented by formula (1) and the groups represented by formula (2) is 0.3 or more and less than 0.55. The ratio (b / a) is 0.3 or more and less than 0.55, preferably 0.35 to 0.53, and more preferably 0.45 to 0.5. The groups represented by formula (3), the groups represented by formula (4), and the groups represented by formula (5) are more polar than the groups represented by formula (1) and the groups represented by formula (2). Therefore, the ratio (b / a) represents the ratio of groups with relatively high polarity to groups with relatively low polarity on the surface of the fibrous substrate. When the ratio (b / a) is within the above range, the fibrous substrate has excellent adhesion to the cured product of the thermosetting composition. That is, on the surface of the fibrous substrate, the relatively highly polar group, so that the ratio (b / a) is within the above range, is considered to favorably contribute to improving the adhesion between the cured product of the thermosetting composition and the fibrous substrate. Therefore, even when the obtained cured prepreg is cut, it is considered that peeling is unlikely to occur between the cured product of the thermosetting composition and the fibrous substrate. In addition, when a metal layer or wiring is present on the surface of the cured prepreg (in a metal-clad laminate or wiring board having an insulating layer containing the cured prepreg), in the cured prepreg, problems that may occur due to the suppression of peeling between the cured product of the thermosetting composition and the fibrous substrate, such as peeling between the metal layer or the wiring and the cured product (the insulating layer), are also considered to be suppressed. From this, it is also considered that peeling is unlikely to occur between the metal layer or the wiring and the cured product (the insulating layer). Therefore, it is believed that a prepreg can be obtained that has excellent processability as a cured product.

[0088] The X-ray photoelectron spectroscopy can be measured using a general X-ray photoelectron spectroscopy. The ratio (b / a) can be measured, for example, as follows. The surface of the fibrous substrate is subjected to surface X-ray analysis using an X-ray photoelectron spectroscopy analyzer. The spectrum resulting from the carbon peak obtained by this surface X-ray analysis is then subjected to peak separation analysis using predetermined analysis software, and the peak area derived from each bond is calculated by analyzing the spectrum using a relative sensitivity coefficient. The ratio (b / a) is then calculated using the calculated peak areas derived from each bond. Here, when calculating the ratio (b / a), a is used as the sum of the peak area derived from the group represented by formula (1) with a bond energy of 284 eV (i.e., the —C—C— bond) and the peak area derived from the group represented by formula (2) with a bond energy of 285 eV (i.e., the —C—H bond). Furthermore, when calculating the ratio (b / a), b is the sum of the peak area derived from the group represented by formula (3) with a binding energy of 288 eV (i.e., a —C═O bond), the peak area derived from the group represented by formula (4) with a binding energy of 289 eV (i.e., a —COO bond), and the group represented by formula (5) with a binding energy of 286 eV (i.e., a —C—O— bond). Based on these values, the ratio (b / a) measured by XPS can be calculated. The X-ray photoelectron spectrometer is not particularly limited as long as it can perform measurements by X-ray photoelectron spectroscopy, and examples thereof include a scanning X-ray photoelectron spectrometer (PHI 5000 VersaProbe manufactured by ULVAC-PHI, Inc.). X-ray photoelectron spectroscopy can be performed by irradiating a sample with X-rays under vacuum using a scanning X-ray photoelectron spectrometer such as the PHI 5000 Versaprobe manufactured by ULVAC-PHI, Inc. The measurement conditions for the surface X-ray analysis are not particularly limited as long as they allow the ratio (b / a) to be measured. For example, the measurement conditions include a condition in which monochromatic Al-Kα rays are used as X-rays and the X-ray beam diameter is about 100 μmφ (25 W, 15 kV).

[0089] Examples of the fibrous substrate include a fibrous substrate containing the liquid crystal polymer fiber, the surface of which is subjected to a surface treatment such that the ratio (b / a) is 0.3 or more and less than 0.55. The surface treatment is not particularly limited as long as the ratio (b / a) is 0.3 or more and less than 0.55, and examples thereof include plasma treatment. Examples of the plasma treatment include oxygen gas plasma treatment (surface treatment using plasma generated using oxygen gas as raw material gas), oxygen and carbon tetrafluoride mixed gas plasma treatment (surface treatment using plasma generated using oxygen and carbon tetrafluoride mixed gas as raw material gas), and argon, hydrogen, and nitrogen mixed gas plasma treatment (surface treatment using plasma generated using argon, hydrogen, and nitrogen mixed gas as raw material gas). That is, the fibrous substrate may be, for example, a fibrous substrate whose surface has been subjected to plasma treatment. More specifically, examples include fibrous substrates whose surface has been subjected to at least one plasma treatment selected from the group consisting of oxygen gas plasma treatment, oxygen and carbon tetrafluoride mixed gas plasma treatment, and argon, hydrogen, and nitrogen mixed gas plasma treatment. By subjecting the surface of the fibrous substrate to plasma treatment, a fibrous substrate having the ratio (b / a) of 0.3 or more and less than 0.55 can be obtained. Therefore, by using such a fibrous substrate, a prepreg can be obtained that is a cured product with low dielectric properties, heat resistance, and excellent processability. Specifically, by subjecting the fibrous substrate to plasma treatment, the affinity of the fibrous substrate with the resin composition contained (impregnated) in the prepreg is improved, thereby improving adhesion to the resin composition. Therefore, a prepreg can be obtained that is a cured product with low dielectric properties, heat resistance, and excellent processability. Among the plasma treatments, the oxygen and carbon tetrafluoride mixed gas plasma treatment is preferred because it can produce a chemical surface modification effect in a shorter time than the oxygen gas plasma treatment. Of the plasma treatments, the oxygen gas plasma treatment is preferred because it mainly produces a chemical surface modification rather than a physical etching effect and is environmentally friendly.The oxygen and carbon tetrafluoride mixed gas plasma treatment raises concerns about environmental regulations due to the carbon tetrafluoride's extremely high global warming potential. The argon, hydrogen, and nitrogen mixed gas plasma treatment has a stronger physical etching effect than chemical surface modification. These plasma treatments may be used alone or in combination of two or more.

[0090] The conditions for the plasma treatment are not particularly limited as long as the ratio (b / a) is 0.3 or more and less than 0.55. The plasma irradiation amount in the plasma treatment is 0.35 to 0.65 W / cm in watt density. ２ is preferably 0.45 to 0.55 W / cm ２ The time for which the plasma treatment is carried out varies depending on the amount of raw material gas, plasma density, etc., but is preferably 10 to 40 minutes, and more preferably 20 to 30 minutes, for example.

[0091] The plasma treatment may be a treatment using microwave plasma (plasma excited by microwaves) or RF (Radio Frequency) plasma (plasma excited by RF). These plasmas may be pulse-excited or DC-excited. The microwaves may be, for example, microwaves with a frequency of 1 GHz or higher, which is an industrially usable frequency band and capable of generating high-density non-equilibrium plasma. Microwaves with a frequency of 2.45 GHz are preferred. In the case of microwave plasma, the microwave power used to generate the plasma atmosphere may be, for example, 300 W or higher. RF plasma is widely used in industry, and the excitation frequency used to generate RF plasma is generally 13.56 MHz in Japan due to legal regulations.

[0092] <Thermosetting Composition> As described above, the thermosetting composition in the prepreg according to this embodiment includes a thermosetting compound and an inorganic filler. Examples of the thermosetting composition include a thermosetting resin composition containing a thermosetting compound and an inorganic filler, which is used together with a fibrous base material in the prepreg.

[0093] (Thermosetting Compound) As described above, examples of the thermosetting compound include polyphenylene ether compounds having a carbon-carbon unsaturated double bond in the molecule, hydrocarbon compounds having a carbon-carbon unsaturated double bond in the molecule, and thermosetting compounds having a fluorine atom in the molecule (fluorine-containing thermosetting compounds). These thermosetting compounds may be used alone or in combination of two or more.

[0094] (Thermosetting Compound: Polyphenylene Ether Compound) The polyphenylene ether compound is not particularly limited as long as it is a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule. Examples of the polyphenylene ether compound include polyphenylene ether compounds having a carbon-carbon unsaturated double bond at a terminal, and more specifically, polyphenylene ether compounds having a substituent having a carbon-carbon unsaturated double bond at a molecular terminal, such as modified polyphenylene ether compounds whose terminals are modified with a substituent having a carbon-carbon unsaturated double bond.

[0095] Examples of the substituent having a carbon-carbon unsaturated double bond include a group represented by the following formula (42) and a group represented by the following formula (47). That is, examples of the polyphenylene ether compound include a polyphenylene ether compound having at least one selected from the group represented by the following formula (42) and the group represented by the following formula (47) in the molecule.

[0096]

[0097] In formula (46), p represents 0 to 10. Ar represents an arylene group. １ ~R ３ are independent of each other. That is, R１ ~R ３ may be the same group or different groups. １ ~R ３ represents a hydrogen atom or an alkyl group. In the formula (46), when p is 0, this indicates that Ar is directly bonded to the polyphenylene ether.

[0098] The arylene group is not particularly limited. Examples of the arylene group include monocyclic aromatic groups such as a phenylene group and polycyclic aromatic groups such as a naphthalene ring. The arylene group also includes derivatives in which a hydrogen atom bonded to the aromatic ring is substituted with a functional group such as an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

[0099] The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0100] In formula (47), R ４ represents a hydrogen atom or an alkyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0101] Examples of the group represented by the formula (46) include a vinylbenzyl group (ethenylbenzyl group) represented by the following formula (48): Furthermore, examples of the group represented by the formula (47) include an acryloyl group and a methacryloyl group.

[0102]

[0103] More specifically, examples of the substituent include vinylbenzyl groups (ethenylbenzyl groups) such as o-ethenylbenzyl groups, m-ethenylbenzyl groups, and p-ethenylbenzyl groups, vinylphenyl groups, acryloyl groups, and methacryloyl groups. The polyphenylene ether compound may have one type of substituent, or two or more types. The polyphenylene ether compound may have, for example, any one of an o-ethenylbenzyl group, an m-ethenylbenzyl group, and a p-ethenylbenzyl group, or may have two or three types of these.

[0104] The polyphenylene ether compound has a polyphenylene ether chain in the molecule, and preferably has, for example, a repeating unit represented by the following formula (49) in the molecule.

[0105]

[0106] In formula (49), t represents 1 to 50. ５ ~R ８ are independent of each other. That is, R ５ ~R ８ may be the same group or different groups. ５ ~R ８ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0107] R ５ ~R ８ Specific examples of the functional groups mentioned in the above include the following:

[0108] The alkyl group is not particularly limited, but is preferably an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0109] The alkenyl group is not particularly limited, but is preferably an alkenyl group having 2 to 18 carbon atoms, and more preferably an alkenyl group having 2 to 10 carbon atoms. Specific examples include a vinyl group, an allyl group, and a 3-butenyl group.

[0110] The alkynyl group is not particularly limited, but is preferably an alkynyl group having 2 to 18 carbon atoms, and more preferably an alkynyl group having 2 to 10 carbon atoms. Specific examples include an ethynyl group and a prop-2-yn-1-yl group (propargyl group).

[0111] The alkylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkyl group, but for example, an alkylcarbonyl group having 2 to 18 carbon atoms is preferred, and an alkylcarbonyl group having 2 to 10 carbon atoms is more preferred. Specific examples include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, and a cyclohexylcarbonyl group.

[0112] The alkenylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkenyl group, but for example, an alkenylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkenylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include an acryloyl group, a methacryloyl group, and a crotonoyl group.

[0113] The alkynylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkynyl group, but for example, an alkynylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkynylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include a propioloyl group.

[0114] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polyphenylene ether compound are not particularly limited, and specifically, are preferably 500 to 5,000, more preferably 800 to 4,000, and even more preferably 1,000 to 3,000. The weight-average molecular weight and number-average molecular weight may be measured by a general molecular weight measurement method, specifically, values ​​measured using gel permeation chromatography (GPC) may be used. Furthermore, when the polyphenylene ether compound has a repeating unit represented by formula (49) in the molecule, t is preferably a value such that the weight-average molecular weight and number-average molecular weight of the polyphenylene ether compound fall within the above ranges. Specifically, t is preferably 1 to 50.

[0115] When the weight-average molecular weight and number-average molecular weight of the polyphenylene ether compound are within the above ranges, the compound has the excellent low dielectric properties of polyphenylene ether, and the cured product not only has excellent heat resistance but also has excellent moldability. This is believed to be due to the following reasons. When the weight-average molecular weight and number-average molecular weight of a typical polyphenylene ether are within the above ranges, the compound has a relatively low molecular weight, which tends to reduce heat resistance. In contrast, the polyphenylene ether compound has one or more unsaturated double bonds at its terminals, and therefore, as the curing reaction progresses, a cured product with sufficiently high heat resistance is believed to be obtained. Furthermore, when the weight-average molecular weight and number-average molecular weight of the polyphenylene ether compound are within the above ranges, the compound has a relatively low molecular weight, which is believed to result in excellent moldability. Therefore, it is believed that such a polyphenylene ether compound not only has excellent heat resistance but also provides a cured product with excellent moldability.

[0116] The average number of the substituents (number of terminal functional groups) at the molecular terminals per molecule of the polyphenylene ether compound is not particularly limited. Specifically, it is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1.5 to 3. If the number of terminal functional groups is too small, it tends to be difficult to obtain a cured product with sufficient heat resistance. On the other hand, if the number of terminal functional groups is too large, the reactivity becomes too high, which may cause problems such as reduced shelf life and reduced flowability of the thermosetting composition. In other words, when such a polyphenylene ether compound is used, insufficient flowability may cause molding defects such as the generation of voids during multilayer molding, making it difficult to obtain a highly reliable printed wiring board.

[0117] The number of terminal functional groups of a polyphenylene ether compound can be exemplified by a numerical value representing the average number of the substituents per molecule of all polyphenylene ether compounds present in 1 mole of the polyphenylene ether compound. The number of terminal functional groups can be measured, for example, by measuring the number of hydroxyl groups remaining in the obtained polyphenylene ether compound and calculating the difference from the number of hydroxyl groups in the polyphenylene ether before it has the substituents (before modification). This difference from the number of hydroxyl groups in the polyphenylene ether before modification is the number of terminal functional groups. The number of hydroxyl groups remaining in the polyphenylene ether compound can be measured by adding a quaternary ammonium salt (tetraethylammonium hydroxide) that associates with hydroxyl groups to a solution of the polyphenylene ether compound and measuring the UV absorbance of the resulting mixed solution.

[0118] The intrinsic viscosity of the polyphenylene ether compound is not particularly limited. Specifically, it may be 0.03 to 0.12 dl / g, preferably 0.04 to 0.11 dl / g, and more preferably 0.06 to 0.095 dl / g. If the intrinsic viscosity is too low, the molecular weight tends to be low, and it tends to be difficult to achieve low dielectric properties such as a low dielectric constant and a low dielectric loss tangent. On the other hand, if the intrinsic viscosity is too high, the viscosity tends to be high, sufficient fluidity cannot be achieved, and the moldability of the cured product tends to be reduced. Therefore, if the intrinsic viscosity of the polyphenylene ether compound is within the above range, excellent heat resistance and moldability of the cured product can be achieved.

[0119] The intrinsic viscosity here is the intrinsic viscosity measured in methylene chloride at 25° C., and more specifically, it is the value measured, for example, with a viscometer using a 0.18 g / 45 ml methylene chloride solution (liquid temperature: 25° C.). Examples of such viscometers include the AVS500 Visco System manufactured by Schott.

[0120] Examples of the polyphenylene ether compound include a polyphenylene ether compound represented by the following formula (50) and a polyphenylene ether compound represented by the following formula (51). As the polyphenylene ether compound, these polyphenylene ether compounds may be used alone, or these two types of polyphenylene ether compounds may be used in combination.

[0121]

[0122]

[0123] In formula (50) and formula (51), R ９ ~R １６ and R １７ ~R ２４ are independent of each other. That is, R ９ ~R １６ and R １７ ~R ２４ may be the same group or different groups. ９ ~R １６ and R １７ ~R ２４represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. １ and X ２ are independent of each other. １ and X ２ and may be the same group or different groups. １ and X ２ represents a substituent having a carbon-carbon unsaturated double bond. A and B represent repeating units represented by the following formulas (52) and (53), respectively. In addition, in formula (51), Y Ａ represents a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms.

[0124]

[0125]

[0126] In the formulas (52) and (53), t1 and t2 each represent an integer of 0 to 20. ２５ ~R ２８ and R ２９ ~R ３２ are independent of each other. That is, R ２５ ~R ２８ and R ２９ ~R ３２ may be the same group or different groups. ２５ ~R ２８ and R ２９ ~R ３２ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

[0127] The polyphenylene ether compound represented by the formula (50) and the polyphenylene ether compound represented by the formula (51) are not particularly limited as long as they satisfy the above-mentioned constitution. Specifically, in the formula (50) and the formula (51), R ９ ~R １６ and R １７ ~R ２４As described above, each of R is independent. ９ ~R １６ and R １７ ~R ２４ may be the same group or different groups. ９ ~R １６ and R １７ ~R ２４ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0128] In formula (52) and formula (53), t1 and t2 preferably represent 0 to 20, as described above. Furthermore, t1 and t2 preferably represent a numerical value such that the sum of t1 and t2 is 1 to 30. Therefore, it is more preferable that t1 represents 0 to 20, t2 represents 0 to 20, and the sum of t1 and t2 represents 1 to 30. Furthermore, R ２５ ~R ２８ and R ２９ ~R ３２ are independent of each other. That is, R ２５ ~R ２８ and R ２９ ~R ３２ may be the same group or different groups. ２５ ~R ２８ and R ２９ ~R ３２ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0129] R ９ ~R ３２ is R in the above formula (49). ５ ~R ８ is the same as

[0130] In the formula (51), Y Ａ As described above, Y is a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms. ＡExamples of the group include a group represented by the following formula (54).

[0131]

[0132] In the formula (54), R ３３ and R ３４ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include a methyl group. Examples of the group represented by formula (54) include a methylene group, a methylmethylene group, and a dimethylmethylene group, and among these, a dimethylmethylene group is preferred.

[0133] In the formula (50) and the formula (51), X １ and X ２ are each independently a substituent having a carbon-carbon double bond. In the polyphenylene ether compound represented by the formula (50) and the polyphenylene ether compound represented by the formula (51), X １ and X ２ may be the same group or different groups.

[0134] More specific examples of the polyphenylene ether compound represented by the formula (50) include polyphenylene ether compounds represented by the following formula (55).

[0135]

[0136] More specific examples of the polyphenylene ether compound represented by the formula (50) include a polyphenylene ether compound represented by the following formula (56) and a polyphenylene ether compound represented by the following formula (57).

[0137]

[0138]

[0139] In the above formulas (55) to (57), t1 and t2 are the same as t1 and t2 in the above formulas (52) and (53). １ ~R ３, p and Ar are R in the above formula (46). １ ~R ３ , p and Ar. In addition, in the above formula (56) and the above formula (57), Y Ａ is Y in the above formula (50). Ａ In addition, in the above formula (57), R ４ is R in the above formula (47). ４ is the same as

[0140] The method for synthesizing the polyphenylene ether compound used in the present embodiment is not particularly limited as long as it is possible to synthesize a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule. Specific examples of this method include a method of reacting polyphenylene ether with a compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded.

[0141] Examples of the compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded include compounds in which a halogen atom is bonded to a substituent represented by formulas (46) to (48). Specific examples of the halogen atom include a chlorine atom, a bromine atom, an iodine atom, and a fluorine atom, with a chlorine atom being preferred. More specific examples of the compound in which a halogen atom is bonded to a substituent having a carbon-carbon unsaturated double bond include o-chloromethylstyrene, p-chloromethylstyrene, and m-chloromethylstyrene. The compound in which a halogen atom is bonded to a substituent having a carbon-carbon unsaturated double bond may be used alone or in combination of two or more. For example, o-chloromethylstyrene, p-chloromethylstyrene, and m-chloromethylstyrene may be used alone or in combination of two or more.

[0142] The polyphenylene ether used as a raw material is not particularly limited as long as it can ultimately synthesize a predetermined polyphenylene ether compound. Specific examples include polyphenylene ethers composed of 2,6-dimethylphenol and at least one of a bifunctional phenol and a trifunctional phenol, and compounds containing polyphenylene ether as a main component, such as poly(2,6-dimethyl-1,4-phenylene oxide). A bifunctional phenol is a phenolic compound having two phenolic hydroxyl groups per molecule, such as tetramethylbisphenol A. A trifunctional phenol is a phenolic compound having three phenolic hydroxyl groups per molecule.

[0143] The polyphenylene ether compound can be synthesized by the method described above. Specifically, the polyphenylene ether and the compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded to each other are dissolved in a solvent and stirred. By doing so, the polyphenylene ether reacts with the compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded to each other, thereby obtaining the polyphenylene ether compound used in this embodiment.

[0144] The reaction is preferably carried out in the presence of an alkali metal hydroxide. It is believed that this allows the reaction to proceed smoothly. This is believed to be because the alkali metal hydroxide functions as a dehydrohalogenating agent, specifically, a dehydrochlorinating agent. That is, it is believed that the alkali metal hydroxide eliminates hydrogen halide from the phenol group of the polyphenylene ether and the compound in which the substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded, and as a result, the substituent having a carbon-carbon unsaturated double bond is bonded to the oxygen atom of the phenol group in place of the hydrogen atom of the phenol group of the polyphenylene ether.

[0145] The alkali metal hydroxide is not particularly limited as long as it can act as a dehalogenating agent, and examples thereof include sodium hydroxide, etc. The alkali metal hydroxide is usually used in the form of an aqueous solution, specifically, an aqueous sodium hydroxide solution.

[0146] The reaction conditions, such as the reaction time and reaction temperature, vary depending on the compound in which the substituent having a carbon-carbon unsaturated double bond is bonded to a halogen atom, and are not particularly limited as long as the conditions are such that the reaction proceeds favorably. Specifically, the reaction temperature is preferably room temperature to 100°C, and more preferably 30 to 100°C. The reaction time is preferably 0.5 to 20 hours, and more preferably 0.5 to 10 hours.

[0147] The solvent used in the reaction is not particularly limited as long as it can dissolve the polyphenylene ether and the compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded, and does not inhibit the reaction between the polyphenylene ether and the compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded. Specific examples include toluene.

[0148] The above reaction is preferably carried out in the presence of not only an alkali metal hydroxide but also a phase transfer catalyst. That is, the above reaction is preferably carried out in the presence of an alkali metal hydroxide and a phase transfer catalyst. Doing so is believed to allow the reaction to proceed more smoothly. This is believed to be due to the following: A phase transfer catalyst has the function of incorporating an alkali metal hydroxide, is soluble in both a polar solvent phase such as water and a nonpolar solvent phase such as an organic solvent, and is capable of transferring between these phases. Specifically, when an aqueous solution of sodium hydroxide is used as the alkali metal hydroxide and an organic solvent such as toluene, which is incompatible with water, is used as the solvent, even if the aqueous solution of sodium hydroxide is added dropwise to the solvent being used for the reaction, the solvent and the aqueous solution of sodium hydroxide separate, and it is believed that the sodium hydroxide is unlikely to migrate to the solvent. In this case, it is believed that the aqueous solution of sodium hydroxide added as the alkali metal hydroxide is unlikely to contribute to promoting the reaction. On the other hand, when the reaction is carried out in the presence of an alkali metal hydroxide and a phase transfer catalyst, the alkali metal hydroxide is transferred to the solvent while being incorporated into the phase transfer catalyst, and the aqueous sodium hydroxide solution is thought to contribute more to promoting the reaction. Therefore, when the reaction is carried out in the presence of an alkali metal hydroxide and a phase transfer catalyst, the reaction is thought to proceed more smoothly.

[0149] The phase transfer catalyst is not particularly limited, but examples thereof include quaternary ammonium salts such as tetra-n-butylammonium bromide.

[0150] The thermosetting composition used in this embodiment preferably contains, as the polyphenylene ether compound, the polyphenylene ether compound obtained as described above.

[0151] (Thermosetting Compound: Hydrocarbon Compound) The hydrocarbon compound is not particularly limited as long as it is a hydrocarbon compound having a carbon-carbon unsaturated double bond in the molecule, and examples thereof include polyfunctional vinyl aromatic compounds. The polyfunctional vinyl aromatic compound, for example, contains a repeating unit (c) derived from a divinyl aromatic compound and a repeating unit (d) derived from a monovinyl aromatic compound, and contains a structural unit (c1) represented by the following formula (58) as part of the repeating unit (c) derived from the divinyl aromatic compound:

[0152]

[0153] In formula (58), R ３５ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.

[0154] In the polyfunctional vinyl aromatic copolymer, when the sum of the repeating units (c) and (d) is taken as 100 mol %, it is preferable that the repeating unit (c) is contained in an amount of 2 mol % or more and less than 95 mol % and the repeating unit (d) is contained in an amount of 5 mol % or more and less than 98 mol %. When the sum of the repeating units (c) and (d) is taken as 100 mol %, it is preferable that the repeating unit (c1) is contained in an amount of 2 to 80 mol %.

[0155] The polyfunctional vinyl aromatic copolymer preferably has a number average molecular weight Mn of 300 to 100,000 and a molecular weight distribution (Mw / Mn) expressed as the ratio of the weight average molecular weight Mw to the number average molecular weight of 100.0 or less. The polyfunctional vinyl aromatic copolymer is also preferably soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform.

[0156] The polyfunctional vinyl aromatic copolymer is not particularly limited, but examples thereof include a copolymer containing a repeating unit (c) derived from a divinyl aromatic compound and a repeating unit (d) derived from a monovinyl aromatic compound, as represented by the following formula (59): These repeating units may be arranged regularly or randomly.

[0157]

[0158] In formula (59), R ３６ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from a monovinyl aromatic compound, and R ３７ and R ３８ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from a divinyl aromatic compound. h, i, j, and k each independently represent an integer of 0 to 200, provided that the total of these is 2 to 20,000.

[0159] The polyfunctional vinyl aromatic copolymer is a copolymer represented by the formula (59), ３６ ~R ３８ are each independently an aromatic hydrocarbon group selected from the group consisting of a phenyl group which may have a substituent, a biphenyl group which may have a substituent, a naphthalene group which may have a substituent, and a terphenyl group which may have a substituent.

[0160] The polyfunctional vinyl aromatic copolymer is preferably solvent-soluble. In addition, the repeating unit referred to in this specification is derived from a monomer and includes a unit that is present in the main chain of the copolymer and appears repeatedly, and a unit or terminal group that is present at the end or side chain. The repeating unit is also referred to as a structural unit.

[0161] The structural unit (c) derived from the divinylaromatic compound is preferably contained in an amount of 2 mol% or more and less than 95 mol% of the total of the structural unit (c) derived from the divinylaromatic compound and the structural unit (d) derived from the monovinyl aromatic compound. The structural unit (c) derived from the divinylaromatic compound can have a variety of structures, such as one in which only one of two vinyl groups has reacted or two in which two have reacted. Among these, the repeating unit in which only one vinyl group has reacted, represented by formula (58), is preferably contained in an amount of 2 to 80 mol%, more preferably 5 to 70 mol%, even more preferably 10 to 60%, and particularly preferably 15 to 50%, relative to the total. By keeping the repeating unit in which only one vinyl group has reacted, represented by formula (58), within the above range (e.g., 2 to 80 mol%), it is believed that the dielectric loss tangent is low, heat resistance is excellent, and compatibility with other resins is excellent. If the repeating unit in which only one vinyl group represented by the formula (58) has reacted is too small (for example, less than 2 mol%), the heat resistance tends to decrease, whereas if the repeating unit in which only one vinyl group represented by the formula (58) has reacted is too large (for example, more than 80 mol%), the adhesion strength tends to decrease.

[0162] The vinyl group present in the formula (58) acts as a cross-linking component and is thought to contribute to the development of heat resistance of the polyfunctional vinyl aromatic copolymer.On the other hand, the structural unit (d) derived from the monovinyl aromatic compound does not have a vinyl group, since it is thought that polymerization usually proceeds through a 1,2-addition reaction of the vinyl group.In other words, the structural unit (d) derived from the monovinyl aromatic compound does not act as a cross-linking component, but is thought to contribute to the development of moldability.

[0163] Styrene is a preferred example of the monovinyl aromatic compound. Furthermore, as the monovinyl aromatic compound, a monovinyl aromatic compound other than styrene can also be used together with styrene. When the structural unit (d) derived from the monovinyl aromatic compound contains a structural unit (d1) derived from styrene and a structural unit (d2) derived from a monovinyl aromatic compound other than styrene, the content of the structural unit (d1) derived from styrene is preferably 99 to 20 mol%, and more preferably 98 to 30 mol%, when the total content of the structural unit (d1) derived from styrene and the structural unit (d2) derived from the monovinyl aromatic compound other than styrene is taken as 100 mol%. A content of the structural unit (d1) derived from styrene within the above range is preferable because it combines thermal oxidative degradation resistance and moldability. If the structural unit (d1) derived from styrene is too high (e.g., greater than 99 mol%), heat resistance tends to decrease. Furthermore, if the structural unit (d2) derived from the monovinyl aromatic compound other than styrene is too high (e.g., greater than 80 mol%), moldability tends to decrease.

[0164] The number average molecular weight of the polyfunctional vinyl aromatic copolymer (number average molecular weight measured using GPC in terms of standard polystyrene) is preferably 300 to 100,000, more preferably 400 to 50,000, and even more preferably 500 to 10,000. If the molecular weight of the polyfunctional vinyl aromatic copolymer is too low (for example, Mn is less than 300), the amount of monofunctional copolymer component contained in the polyfunctional vinyl aromatic copolymer increases, which tends to reduce the heat resistance of the cured product. On the other hand, if the molecular weight of the polyfunctional vinyl aromatic copolymer is too high (for example, Mn is more than 100,000), gel tends to be easily formed and the viscosity increases, which tends to reduce moldability. The molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (weight average molecular weight measured using GPC in terms of standard polystyrene) to Mn of the polyfunctional vinyl aromatic copolymer, is preferably 100.0 or less, more preferably 50.0 or less, even more preferably 1.5 to 30.0, and particularly preferably 2.0 to 20.0. If the molecular weight distribution (Mw / Mn) is too large (for example, if Mw / Mn exceeds 100.0), the processing characteristics of the polyfunctional vinyl aromatic copolymer (B) tend to deteriorate, and gel tends to form.

[0165] The divinylaromatic compound is thought to play a role in forming a branched structure to impart multifunctionality, and also to function as a cross-linking component to impart heat resistance when the resulting multifunctional vinyl aromatic copolymer is thermally cured. Examples of the divinylaromatic compound are not limited as long as they are aromatic compounds having two vinyl groups, but preferred examples include divinylbenzene (including positional isomers or mixtures thereof), divinylnaphthalene (including positional isomers or mixtures thereof), and divinylbiphenyl (including positional isomers or mixtures thereof). These compounds may be used alone or in combination of two or more. From the viewpoint of moldability, the divinylaromatic compound is more preferably divinylbenzene (m-isomer, p-isomer, or a mixture of positional isomers thereof).

[0166] Examples of the monovinyl aromatic compound include styrene and monovinyl aromatic compounds other than styrene. As the monovinyl aromatic compound, for example, it is desirable to use styrene as an essential component and a monovinyl aromatic compound other than styrene in combination.

[0167] It is believed that the styrene, as a monomer component, serves to impart excellent low dielectric properties and thermal oxidative degradation resistance to the polyfunctional vinyl aromatic copolymer, and also serves as a chain transfer agent to control the molecular weight of the polyfunctional vinyl aromatic copolymer. In addition, the monovinyl aromatic compound other than styrene is believed to improve the solvent solubility and processability of the polyfunctional vinyl aromatic copolymer.

[0168] Examples of the monovinyl aromatic compound other than styrene are not limited as long as they are aromatic compounds other than styrene having one vinyl group, but include vinyl aromatic compounds such as vinylnaphthalene and vinylbiphenyl; and nuclear alkyl-substituted vinyl aromatic compounds such as o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylvinylbenzene, m-ethylvinylbenzene, and p-ethylvinylbenzene. The monovinyl aromatic compound other than styrene is preferably ethylvinylbenzene (including each positional isomer or a mixture thereof), ethylvinylbiphenyl (including each positional isomer or a mixture thereof), or ethylvinylnaphthalene (including each positional isomer or a mixture thereof) because they prevent gelation of the polyfunctional vinyl aromatic copolymer, are highly effective in improving solvent solubility and processability, are low cost, and are easily available. Furthermore, the monovinyl aromatic compound other than styrene is preferably ethylvinylbenzene (m-isomer, p-isomer, or a mixture of these positional isomers) from the viewpoints of low dielectric properties and cost.

[0169] In addition to the divinyl aromatic compound and the monovinyl aromatic compound, one or more other monomer components such as a trivinyl aromatic compound, a trivinyl aliphatic compound, a divinyl aliphatic compound, or a monovinyl aliphatic compound may be used in the polyfunctional vinyl aromatic copolymer, and structural units (e) derived therefrom may be introduced within a range that does not impair the effects of the present invention.

[0170] Examples of the other monomer components include 1,3,5-trivinylbenzene, 1,3,5-trivinylnaphthalene, 1,2,4-trivinylcyclohexane, ethylene glycol diacrylate, butadiene, 1,4-butanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether, and triallyl isocyanurate. These can be used alone or in combination of two or more.

[0171] The molar fraction of the other monomer component relative to the sum of all monomer components is preferably less than 30 mol %. That is, the molar fraction of the structural unit (e) derived from the other monomer component relative to the sum of all monomer components constituting the copolymer [the sum of the structural unit (c) derived from the divinyl aromatic compound, the structural unit (d) derived from the monovinyl aromatic compound, and the structural unit (e) derived from the other monomer components] is preferably less than 30 mol %.

[0172] (Thermosetting compound: fluorine-containing thermosetting compound) The fluorine-containing thermosetting compound is not particularly limited as long as it is a thermosetting compound having a fluorine atom in the molecule, and examples thereof include thermosetting resins having a fluorine atom in the molecule. Examples of the fluorine-containing thermosetting compound include polymers having a unit based on a fluoroolefin and a unit containing a crosslinkable reactive group in the molecule. Examples of the fluoroolefin include olefins in which one or more hydrogen atoms are substituted with fluorine atoms. Examples of the fluoroolefin-based units include units obtained by polymerizing the fluoroolefin. Examples of the crosslinkable reactive groups include groups that can be cured by heating, with the crosslinkable reactive groups reacting with each other.

[0173] Examples of the fluorine-containing thermosetting compound include fluororesins having a structure represented by the following formula (60).

[0174]

[0175] In formula (60), q represents 1 to 100, L represents a cycloalkylidene group having 5 to 12 carbon atoms which may have a substituent, and R ３９ and R ４０ each independently represents at least one selected from the group consisting of hydrogen, fluorine, saturated or unsaturated hydrocarbon groups having 1 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen, and aryl groups having 6 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen, and Q represents a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond.

[0176] In formula (60), q is preferably 1 to 100, more preferably 3 to 50, and even more preferably 5 to 30. By setting q within the above-mentioned range, sufficient heat resistance, an appropriate glass transition temperature (Tg), and sufficient solvent solubility can be simultaneously achieved. Furthermore, by setting q within the above-mentioned range, the number of substituents Q contained in the resin per unit weight can be adjusted to achieve appropriate crosslinkability and excellent electrical properties (such as dielectric constant and dielectric dissipation factor). Furthermore, when a varnish is formed using a fluororesin having the structure of formula (60), setting q within the above-mentioned range can impart an appropriate viscosity to the varnish.

[0177] In formula (60), Q is a cycloalkylidene group having 5 to 12 carbon atoms which may have a substituent. Among these, Q is preferably one selected from the group consisting of a cyclopentylidene group which may have a substituent, a cyclohexylidene group which may have a substituent, and a cyclododecylidene group which may have a substituent. Without wishing to be bound by any theory, it is believed that the cycloalkylidene group contributes to increased solvent solubility and a reduced dielectric constant due to increased bulkiness.

[0178] The substituent present on the cycloalkylidene group may be a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms, or an aryl group having 6 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms. Examples of saturated or unsaturated hydrocarbon groups having 1 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms include methyl, ethyl, propyl, 2-methylpropyl (isobutyl), butyl, pentyl, trifluoromethyl, pentafluoroethyl, perfluoropropyl, vinyl, allyl, 1-methylvinyl, 2-butenyl, and 3-butenyl. Examples of aryl groups having 6 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms include phenyl, naphthyl (including 1-isomer and 2-isomer), and perfluorophenyl.

[0179] In formula (60), R３９ and R ４０ are each independently hydrogen, fluorine, a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen, or an aryl group having 6 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen. Examples of saturated or unsaturated hydrocarbon groups having 1 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen include methyl, ethyl, propyl, 2-methylpropyl (isobutyl), butyl, pentyl, trifluoromethyl, pentafluoroethyl, perfluoropropyl, vinyl, allyl, 1-methylvinyl, 2-butenyl, and 3-butenyl. Examples of aryl groups having 6 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen include phenyl, naphthyl (including the 1-isomer and the 2-isomer), and perfluorophenyl.

[0180] In formula (60), Q is a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond. In some embodiments, Q is a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond and at least one fluorine atom. In other embodiments, Q is a group containing an olefinic carbon-carbon double bond or a carbon-carbon triple bond but no fluorine atoms.

[0181] (Inorganic Filler) The inorganic filler is not particularly limited as long as it contains at least one material selected from the group consisting of silica, quartz glass, and magnesium oxide. Examples of the inorganic filler include fillers that can be used as fillers in thermosetting compositions such as thermosetting resin compositions and contain at least one material selected from the group consisting of silica, quartz glass, and magnesium oxide. The filler containing silica as a material is not particularly limited, and examples include crushed silica, spherical silica, and silica particles, with spherical silica being preferred. Furthermore, the inorganic filler may be a filler containing at least one material selected from the group consisting of silica, quartz glass, and magnesium oxide, and may also contain other inorganic fillers (other inorganic fillers). Examples of the other inorganic filler include metal oxides other than silica and magnesium oxide, metal hydroxides, molybdates, talc, aluminum borate, barium sulfate, aluminum nitride, boron nitride, barium titanate, strontium titanate, calcium titanate, magnesium carbonates such as anhydrous magnesium carbonate, and calcium carbonate. Examples of the metal oxides other than silica and magnesium oxide include alumina, titanium oxide, magnesium oxide, and mica. Examples of the metal hydroxides include magnesium hydroxide and aluminum hydroxide. Examples of the molybdates include zinc molybdate, calcium molybdate, and magnesium molybdate. The inorganic fillers may be used alone or in combination of two or more.

[0182] The inorganic filler may be a surface-treated or untreated inorganic filler. Examples of the surface treatment include treatment with a silane coupling agent.

[0183] The silane coupling agent is not particularly limited, and examples thereof include silane coupling agents having at least one functional group selected from the group consisting of vinyl group, styryl group, methacryloyl group, acryloyl group, phenylamino group, isocyanurate group, ureido group, mercapto group, isocyanate group, epoxy group, and acid anhydride group. That is, the silane coupling agent has at least one reactive functional group selected from vinyl group, styryl group, methacryloyl group, acryloyl group, phenylamino group, isocyanurate group, ureido group, mercapto group, isocyanate group, epoxy group, and acid anhydride group, and further includes compounds having a hydrolyzable group such as a methoxy group or an ethoxy group.

[0184] Examples of the silane coupling agent include those having a vinyl group, such as vinyltriethoxysilane and vinyltrimethoxysilane. Examples of the silane coupling agent include those having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane. Examples of the silane coupling agent include those having a methacryloyl group, such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylethyldiethoxysilane. Examples of the silane coupling agent include those having an acryloyl group, such as 3-acryloxypropyltrimethoxysilane and 3-acryloxypropyltriethoxysilane. Examples of the silane coupling agent include those having a phenylamino group, such as N-phenyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltriethoxysilane.

[0185] The average particle size of the inorganic filler is not particularly limited, and is preferably 0.05 to 10 μm, and more preferably 0.1 to 8 μm. Here, the average particle size refers to the volume average particle size. The volume average particle size can be measured, for example, by a laser diffraction method.

[0186] (Content) The content of the inorganic filler is 65 parts by mass or more, preferably 70 to 150 parts by mass, and more preferably 80 to 130 parts by mass, per 100 parts by mass of the thermosetting compound. Furthermore, the content of the inorganic filler is 45 parts by mass or more, preferably 50 to 107 parts by mass, and more preferably 57 to 93 parts by mass, per 100 parts by mass of the thermosetting composition. The content of the thermosetting compound is 36 to 96 parts by mass, preferably 50 to 82 parts by mass, and more preferably 57 to 75 parts by mass, per 100 parts by mass of the thermosetting composition. When the content of the inorganic filler is within the above range, a prepreg can be obtained that has excellent low dielectric properties, heat resistance, and processability as a cured product. This is believed to be due to the following: Because the thermosetting composition contains a relatively large amount of the inorganic filler, the cured product of the thermosetting composition is believed to have excellent heat resistance. Furthermore, since the thermosetting composition constituting the prepreg (or the thermosetting composition resulting in a semi-cured product) is highly filled with the inorganic filler as described above, it is believed that the cured product of the thermosetting composition will be relatively hard (for example, the storage modulus will be relatively high, the dimensional change rate due to heating will be small, etc.). For this reason, it is believed that the cured product of the prepreg will be a cured product with excellent processability that can sufficiently suppress defects that may occur during processing such as drilling. Specifically, it is believed that even when the cured product of the prepreg is cut, peeling is unlikely to occur between the cured product of the thermosetting composition and the fibrous substrate. Furthermore, if a metal layer or wiring is present on the surface of the cured product of the prepreg (such as a metal-clad laminate or printed wiring board having an insulating layer containing the cured product of the prepreg), it is believed that defects that may occur due to suppression of peeling between the cured product of the thermosetting composition and the fibrous substrate in the cured product of the prepreg, such as peeling between the metal layer or wiring and the cured product (the insulating layer), are also suppressed. This also suggests that peeling is unlikely to occur between the metal layer or wiring and the cured product (the insulating layer), and therefore a prepreg can be obtained that has low dielectric properties, heat resistance, and excellent processability as a cured product.

[0187] (Other Components) The thermosetting composition according to this embodiment may contain, as necessary, components other than the thermosetting compound and the inorganic filler (other components) within a range that does not impair the effects of the present invention. Examples of other components contained in the thermosetting composition according to this embodiment may further include additives such as a reactive compound capable of reacting with the thermosetting compound, a thermoplastic resin (elastomer), a reaction initiator, a curing accelerator, a catalyst, a polymerization retarder, a polymerization inhibitor, a dispersant, a leveling agent, a silane coupling agent, an antifoaming agent, an antioxidant, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a dye or pigment, and a lubricant.

[0188] The thermosetting composition according to this embodiment may contain the reactive compound. The reactive compound is a compound different from the thermosetting compound, and examples thereof include compounds that react with the thermosetting compound. Examples of the reactive compound include, but are not limited to, styrene, styrene derivatives, acrylate compounds having an acryloyl group in the molecule, methacrylate compounds having a methacryloyl group in the molecule, vinyl compounds having a vinyl group in the molecule, maleimide compounds having a maleimide group in the molecule, modified maleimide compounds, alkenyl isocyanurate compounds, acenaphthylene compounds, cyanate ester compounds, and active ester compounds. The other reactive compounds may be used alone or in combination of two or more.

[0189] Examples of the styrene derivatives include bromostyrene and dibromostyrene.

[0190] Examples of the acrylate compound include polyfunctional acrylate compounds having two or more acryloyl groups in the molecule, such as tricyclodecane dimethanol diacrylate.

[0191] Examples of the methacrylate compound include polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule, such as tricyclodecane dimethanol diacrylate.

[0192] Examples of the vinyl compound include polyfunctional vinyl compounds having two or more vinyl groups in the molecule, such as divinylbenzene and polybutadiene.

[0193] Examples of the maleimide compound include a monofunctional maleimide compound having one maleimide group in the molecule and a polyfunctional maleimide compound having two or more maleimide groups in the molecule. Examples of the modified maleimide compound include a modified maleimide compound in which a portion of the molecule is modified with an amine, a modified maleimide compound in which a portion of the molecule is modified with a silicone, and a modified maleimide compound in which a portion of the molecule is modified with both an amine and a silicone.

[0194] The alkenyl isocyanurate compound may be any compound having an isocyanurate structure and an alkenyl group in the molecule, and examples thereof include trialkenyl isocyanurate compounds such as triallyl isocyanurate (TAIC).

[0195] The acenaphthylene compound is a compound having an acenaphthylene structure in the molecule. Examples of the acenaphthylene compound include acenaphthylene, alkylacenaphthylenes, halogenated acenaphthylenes, and phenylacenaphthylenes. Examples of the alkylacenaphthylenes include 1-methylacenaphthylene, 3-methylacenaphthylene, 4-methylacenaphthylene, 5-methylacenaphthylene, 1-ethylacenaphthylene, 3-ethylacenaphthylene, 4-ethylacenaphthylene, and 5-ethylacenaphthylene. Examples of the halogenated acenaphthylenes include 1-chloroacenaphthylene, 3-chloroacenaphthylene, 4-chloroacenaphthylene, 5-chloroacenaphthylene, 1-bromoacenaphthylene, 3-bromoacenaphthylene, 4-bromoacenaphthylene, and 5-bromoacenaphthylene. Examples of the phenylacenaphthylenes include 1-phenylacenaphthylene, 3-phenylacenaphthylene, 4-phenylacenaphthylene, and 5-phenylacenaphthylene. The acenaphthylene compound may be a monofunctional acenaphthylene compound having one acenaphthylene structure in the molecule, as described above, or a polyfunctional acenaphthylene compound having two or more acenaphthylene structures in the molecule.

[0196] The cyanate ester compound is a compound having a cyanate group in the molecule, and examples thereof include 2,2-bis(4-cyanatephenyl)propane, bis(3,5-dimethyl-4-cyanatephenyl)methane, and 2,2-bis(4-cyanatephenyl)ethane.

[0197] The active ester compound is a compound having an ester group with high reactivity in the molecule, and examples thereof include benzenecarboxylic acid active ester, benzenedicarboxylic acid active ester, benzenetricarboxylic acid active ester, benzenetetracarboxylic acid active ester, naphthalenecarboxylic acid active ester, naphthalenedicarboxylic acid active ester, naphthalenetricarboxylic acid active ester, naphthalenetetracarboxylic acid active ester, fluorenecarboxylic acid active ester, fluorenedicarboxylic acid active ester, fluorenetricarboxylic acid active ester, and fluorenetetracarboxylic acid active ester.

[0198] As described above, the thermosetting composition according to this embodiment may contain a reaction initiator. The curing reaction can proceed even if the thermosetting composition does not contain a reaction initiator. However, depending on the process conditions, it may be difficult to raise the temperature high enough for curing to proceed, so a reaction initiator may be added. The reaction initiator is not particularly limited as long as it can accelerate the curing reaction of the thermosetting composition, and examples thereof include peroxides and organic azo compounds. Examples of peroxides include dicumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, and benzoyl peroxide. Examples of organic azo compounds include azobisisobutyronitrile. Furthermore, if necessary, a metal carboxylate or the like can be used in combination. This can further accelerate the curing reaction. Among these, α,α'-bis(t-butylperoxy-m-isopropyl)benzene is preferably used. Because α,α'-bis(t-butylperoxy-m-isopropyl)benzene has a relatively high reaction initiation temperature, it can suppress the acceleration of the curing reaction when curing is not necessary, such as during prepreg drying, and can suppress a decrease in the shelf life of the thermosetting composition. Furthermore, because α,α'-bis(t-butylperoxy-m-isopropyl)benzene has low volatility, it does not volatilize during prepreg drying or storage, and therefore has good stability. Furthermore, the reaction initiators may be used alone or in combination of two or more.

[0199] As described above, the resin composition according to this embodiment may contain an elastomer. Examples of the elastomer include styrene-based copolymers. Examples of the styrene-based copolymer include methylstyrene (ethylene / butylene) methylstyrene copolymer, methylstyrene (ethylene-ethylene / propylene) methylstyrene copolymer, styrene-isoprene copolymer, styrene-isoprene styrene copolymer, styrene (ethylene / butylene) styrene copolymer, styrene (ethylene-ethylene / propylene) styrene copolymer, styrene-butadiene styrene copolymer, styrene (butadiene / butylene) styrene copolymer, styrene-isobutylene styrene copolymer, and hydrogenated versions thereof. The elastomers listed above may be used alone or in combination of two or more.

[0200] As described above, the thermosetting composition according to this embodiment may contain a curing accelerator. The curing accelerator is not particularly limited as long as it can accelerate the curing reaction of the thermosetting composition. Specific examples of the curing accelerator include imidazoles and their derivatives, organophosphorus compounds, amines such as secondary amines and tertiary amines, quaternary ammonium salts, organoboron compounds, and metal soaps. Examples of the imidazoles include 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-phenyl-4-methylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole. Examples of the organophosphorus compounds include triphenylphosphine, diphenylphosphine, phenylphosphine, tributylphosphine, and trimethylphosphine. Examples of the amines include dimethylbenzylamine, triethylenediamine, triethanolamine, and 1,8-diaza-bicyclo(5,4,0)undecene-7 (DBU). Examples of the quaternary ammonium salts include tetrabutylammonium bromide. Examples of the organoboron compounds include tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate, and tetra-substituted phosphonium tetra-substituted borates such as tetraphenylphosphonium ethyltriphenylborate. The metal soap refers to a fatty acid metal salt, and may be either a linear fatty acid metal salt or a cyclic fatty acid metal salt. Specific examples of the metal soap include linear fatty acid metal salts and cyclic fatty acid metal salts having 6 to 10 carbon atoms. More specifically, examples of the curing accelerator include aliphatic metal salts composed of linear fatty acids such as stearic acid, lauric acid, ricinoleic acid, and octylic acid, or cyclic fatty acids such as naphthenic acid, and metals such as lithium, magnesium, calcium, barium, copper, and zinc. For example, zinc octylate is included. The curing accelerators may be used alone or in combination of two or more.

[0201] As described above, the thermosetting composition according to this embodiment may contain a silane coupling agent. The silane coupling agent may be contained in the thermosetting composition, or may be contained as a silane coupling agent that has been surface-treated in advance on an inorganic filler contained in the thermosetting composition. Among these, the silane coupling agent is preferably contained as a silane coupling agent that has been surface-treated in advance on an inorganic filler. It is more preferable to contain the silane coupling agent in advance on an inorganic filler in this way, and further to contain the silane coupling agent in the thermosetting composition. In addition, in the case of a prepreg, the prepreg may contain the silane coupling agent that has been surface-treated in advance on a fibrous substrate. Examples of the silane coupling agent include the same silane coupling agents as those used when surface-treating the inorganic filler described above.

[0202] As described above, the thermosetting composition according to this embodiment may contain a flame retardant. The inclusion of a flame retardant can enhance the flame retardancy of the cured product of the thermosetting composition. The flame retardant is not particularly limited. Specifically, in fields where halogen-based flame retardants such as bromine-based flame retardants are used, for example, ethylene dipentabromobenzene, ethylene bistetrabromoimide, decabromodiphenyl oxide, tetradecabromodiphenoxybenzene, and bromostyrene-based compounds that react with the polymerizable compounds, which have melting points of 300°C or higher, are preferred. The use of a halogen-based flame retardant is believed to suppress halogen elimination at high temperatures and prevent a decrease in heat resistance. Furthermore, in fields where halogen-free materials are required, phosphorus-containing flame retardants (phosphorus-based flame retardants) are sometimes used. Examples of the phosphorus-based flame retardant include, but are not limited to, phosphate ester-based flame retardants, phosphazene-based flame retardants, bisdiphenylphosphine oxide-based flame retardants, and phosphinate-based flame retardants. A specific example of a phosphate ester-based flame retardant is a condensed phosphate ester of dixylenyl phosphate. A specific example of a phosphazene-based flame retardant is phenoxyphosphazene. A specific example of a bisdiphenylphosphine oxide-based flame retardant is xylylenebisdiphenylphosphine oxide. A specific example of a phosphinate-based flame retardant is, for example, a metal phosphinate salt of an aluminum dialkylphosphinate. As the flame retardant, each of the exemplified flame retardants may be used alone or in combination of two or more.

[0203] The prepreg may contain a silane coupling agent. The type of silane coupling agent is not particularly limited. As long as the silane coupling agent is contained in the prepreg, the method of adding the silane coupling agent is not limited. As a method of adding the silane coupling agent, for example, as described above, when producing the thermosetting composition, the silane coupling agent may be added by adding an inorganic filler that has been surface-treated in advance with the silane coupling agent, or the inorganic filler and the silane coupling agent may be added by an integral blending method. Furthermore, when producing the prepreg, the silane coupling agent may be added to the prepreg by using a fibrous base material that has been surface-treated in advance with the silane coupling agent.

[0204] (Varnish) The thermosetting composition used in this embodiment may be prepared in the form of a varnish. For example, when producing a prepreg, the thermosetting composition may be prepared in the form of a varnish for the purpose of impregnating the fibrous substrate. That is, the thermosetting composition may be used as a varnish (varnish). In the thermosetting composition used in this embodiment, the thermosetting compound is dissolved in the varnish. Such a varnish-like composition (varnish) is prepared, for example, as follows.

[0205] First, each component that is soluble in an organic solvent is added to the organic solvent and dissolved. Heating may be performed as necessary. Then, components that are insoluble in the organic solvent are added as needed, and the mixture is dispersed using a ball mill, bead mill, planetary mixer, roll mill, or the like until a predetermined dispersion state is achieved, thereby preparing a varnish-like composition. The organic solvent used here is not particularly limited as long as it dissolves the polymer and the curing agent and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

[0206] (Dielectric Properties of Prepreg) In order to suppress losses due to increased resistance associated with miniaturization of wiring, insulating layers provided on printed wiring boards are also required to have excellent low-dielectric properties, such as low dielectric constant and dielectric dissipation factor. The prepreg not only has excellent heat resistance and processability, but also provides a cured product with excellent low-dielectric properties, such as low dielectric constant and dielectric dissipation factor. Specifically, the prepreg has a cured product with a dielectric constant of preferably 2.3 to 3.5, more preferably 2.5 to 3.3. The prepreg also has a cured product with a dielectric dissipation factor of preferably 0.0025 or less, more preferably 0.002 or less. The lower the dielectric dissipation factor of the cured prepreg, the better. The lower the dielectric dissipation factor, the better. The lower limit of the dielectric dissipation factor is not particularly limited, but may be, for example, 0.0005 or more. When the cured prepreg has a dielectric constant and dielectric dissipation factor within the above ranges, the prepreg has excellent low-dielectric properties. It is preferable to adjust the composition of the thermosetting composition, for example, the content of inorganic fillers, etc., so that the dielectric constant and dielectric dissipation factor of the cured prepreg are within the above ranges. The dielectric constant and dielectric dissipation factor here include the dielectric constant and dielectric dissipation factor of the cured prepreg at 25°C and 10 GHz, and more specifically, the dielectric constant and dielectric dissipation factor of the cured prepreg at 25°C and 10 GHz, measured by a cavity resonator perturbation method.

[0207] (Resin Content in Prepreg) The resin content in the prepreg is not particularly limited, but is preferably 40 to 90 mass %, more preferably 45 to 90 mass %, and even more preferably 50 to 80 mass %. If the resin content is too low, it tends to be difficult to obtain low dielectric properties. If the resin content is too high, the coefficient of thermal expansion (CTE) tends to increase and the plate thickness accuracy tends to decrease. The resin content here is the ratio of the mass of the prepreg minus the mass of the fibrous base material to the mass of the prepreg [= (mass of prepreg - mass of fibrous base material) / mass of prepreg x 100].

[0208] (Prepreg Thickness) The thickness of the prepreg is not particularly limited, but is preferably 0.015 to 0.2 mm, more preferably 0.02 to 0.15 mm, and even more preferably 0.03 to 0.13 mm. If the prepreg is too thin, a large number of prepregs are required to obtain the desired substrate thickness. On the other hand, if the prepreg is too thick, the resin content tends to be low, making it difficult to obtain the desired low dielectric properties.

[0209] (Manufacturing Method) Next, a manufacturing method of the prepreg according to this embodiment will be described.

[0210] The method for producing the prepreg is not particularly limited as long as it can produce the prepreg. Specifically, when producing the prepreg, the thermosetting composition used in the present embodiment is often prepared in the form of a varnish as described above and used as a varnish.

[0211] Examples of a method for producing the prepreg 1 include a method in which the thermosetting composition 2, for example, the thermosetting composition 2 prepared in the form of a varnish, is impregnated into the fibrous base material 3, and then the fibrous base material 3 is dried.

[0212] The thermosetting composition 2 is impregnated into the fibrous substrate 3 by immersion, coating, or the like. Impregnation can be repeated multiple times as necessary. In this case, by repeating the impregnation using multiple thermosetting compositions with different compositions and concentrations, it is possible to adjust the final composition and impregnation amount to the desired one.

[0213] The fibrous substrate 3 impregnated with the thermosetting composition (varnish) 2 is heated under desired conditions, for example, at 80°C to 180°C for 1 minute to 10 minutes. This heating process yields a prepreg 1 in an uncured (A-stage) or semi-cured (B-stage) state. The heating process also volatilizes the organic solvent from the varnish, reducing or eliminating the organic solvent.

[0214] [Metal-clad laminate and printed wiring board] By using the prepreg according to this embodiment, a metal-clad laminate and a printed wiring board can be obtained as follows.

[0215] (Metal-Clad Laminate) The metal-clad laminate 11 according to this embodiment is a metal-clad laminate for printed wiring boards. As shown in FIG. 2, the metal-clad laminate 11 includes an insulating layer 12 containing a cured product of the prepreg 1 shown in FIG. 1, and a metal foil 13 disposed on the insulating layer 12. Examples of the metal-clad laminate 11 include a metal-clad laminate composed of an insulating layer 12 obtained by curing the prepreg 1 shown in FIG. 1 and a metal foil 13 laminated together with the insulating layer 12. The insulating layer 12 may also be composed of a cured product of the prepreg 1. The thickness of the metal foil 13 varies depending on the performance required of the final printed wiring board, and is not particularly limited. The thickness of the metal foil 13 can be appropriately set depending on the desired purpose, and is preferably, for example, 0.2 to 70 μm. Examples of the metal foil 13 include copper foil and aluminum foil. When the metal foil is thin, it may be a carrier-attached copper foil having a release layer and a carrier to improve handling. FIG. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate 11 according to an embodiment of the present invention.

[0216] The method for producing the metal-clad laminate 11 is not particularly limited as long as the metal-clad laminate 11 can be produced using the prepreg 1. Specific examples of methods for producing the metal-clad laminate 11 using the prepreg 1 include a method in which one or more prepregs 1 are stacked, and then a metal foil 13 such as copper foil is stacked on both sides or one side of the prepreg 1, and the metal foil 13 and the prepreg 1 are heated and pressurized to form an integrated laminate, thereby producing a double-sided or single-sided metal foil-clad laminate 11. That is, the metal-clad laminate 11 is obtained by stacking the metal foil 13 on the prepreg 1 and then heating and pressurizing the laminate. The heating and pressurizing conditions can be appropriately set depending on the thickness of the metal-clad laminate 11, the type of thermosetting composition contained in the prepreg 1, and the like. For example, the temperature can be 170 to 230°C, the pressure can be 0.5 to 5 MPa, and the time can be 60 to 150 minutes.

[0217] (Printed Wiring Board) As shown in FIG. 3, the printed wiring board 21 according to this embodiment has an insulating layer 12 containing a cured product of the prepreg 1 shown in FIG. 1 and wiring 14 provided on the insulating layer 12. Examples of the printed wiring board 21 include a wiring board composed of an insulating layer 12 formed by curing the prepreg 1 shown in FIG. 1 and wiring 14 laminated together with the insulating layer 12 and formed by partially removing the metal foil 13. That is, the printed wiring board 21 has an insulating layer 12 containing a cured product of the prepreg 1 and wiring 14 bonded to the insulating layer 12. The insulating layer 12 may also be made of a cured product of the prepreg 1. FIG. 3 is a schematic cross-sectional view showing an example of a printed wiring board 21 according to an embodiment of the present invention.

[0218] The method for manufacturing the printed wiring board 21 is not particularly limited as long as the printed wiring board 21 can be manufactured using the prepreg 1. Examples of methods for manufacturing the printed wiring board 21 using the prepreg 1 include a method for manufacturing the printed wiring board 21 in which wiring is provided as a circuit on the surface of the insulating layer 12 by etching the metal foil 13 on the surface of the metal-clad laminate 11 manufactured as described above. That is, the printed wiring board 21 is obtained by forming a circuit by partially removing the metal foil 13 on the surface of the metal-clad laminate 11. In addition to the above methods, examples of methods for forming a circuit include circuit formation by a semi-additive process (SAP) or a modified semi-additive process (MSAP).

[0219] When the prepreg according to the present embodiment is cured, it becomes a cured product having low dielectric properties, excellent heat resistance, and excellent processability. Therefore, the metal-clad laminate and the printed wiring board obtained using this prepreg are respectively provided with an insulating layer having low dielectric properties, excellent heat resistance, and excellent processability. Furthermore, the printed wiring board can be manufactured using the metal-clad laminate.

[0220] As described above, this specification discloses various aspects of the technology, the main technologies of which are summarized below.

[0221] A prepreg for printed wiring boards according to a first aspect of the present invention comprises a thermosetting composition containing a thermosetting compound and an inorganic filler, or a semi-cured product of the thermosetting composition, and a fibrous substrate containing liquid crystal polymer fibers, wherein the thermosetting compound contains at least one selected from the group consisting of polyphenylene ether compounds having a carbon-carbon unsaturated double bond in the molecule, hydrocarbon compounds having a carbon-carbon unsaturated double bond in the molecule, and thermosetting compounds having a fluorine atom in the molecule, and the inorganic filler is selected from the group consisting of silica, quartz glass, and magnesium oxide. The prepreg for printed wiring boards contains at least one inorganic filler as a material, the content of the inorganic filler being 65 parts by mass or more relative to 100 parts by mass of the thermosetting compound, the liquid crystal polymer fiber having a dielectric loss tangent of 0.0015 or less at 25°C and 5 GHz, and the ratio of the total amount of the groups represented by formula (3), the groups represented by formula (4), and the groups represented by formula (5) to the total amount of the groups represented by formula (1) and the groups represented by formula (2) on the surface of the fibrous substrate, as measured by X-ray photoelectron spectroscopy, is 0.3 or more and less than 0.55.

[0222] A prepreg for a printed wiring board according to a second aspect of the present invention is a prepreg for a printed wiring board according to the first aspect of the present invention, wherein the fibrous base material includes a fibrous base material whose surface has been subjected to plasma treatment.

[0223] A prepreg for printed wiring boards according to a third aspect of the present invention is a prepreg for printed wiring boards according to the first or second aspect of the present invention, wherein the fibrous base material has been subjected to a surface treatment with at least one plasma treatment selected from the group consisting of oxygen gas plasma treatment, oxygen and carbon tetrafluoride mixed gas plasma treatment, and argon, hydrogen, and nitrogen mixed gas plasma treatment.

[0224] A metal-clad laminate for printed wiring boards according to a fourth aspect of the present invention is a metal-clad laminate for printed wiring boards comprising an insulating layer containing a cured product of the prepreg for printed wiring boards according to any one of the first to third aspects of the present invention, and a metal foil.

[0225] A printed wiring board according to a fifth aspect of the present invention is a printed wiring board comprising an insulating layer containing a cured product of the printed wiring board prepreg according to any one of the first to third aspects of the present invention, and wiring.

[0226] According to the present invention, there is provided a prepreg for a printed wiring board, which can give a cured product having low dielectric properties, excellent heat resistance, and excellent processability. Furthermore, according to the present invention, there are provided a metal-clad laminate for a printed wiring board, and a printed wiring board, which are obtained using the prepreg.

[0227] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0228] Examples 1 to 8 and Comparative Examples 1 to 4 In these examples, each component used in preparing the prepreg will be described.

[0229] (Thermosetting Compound) Hydrocarbon-based compound: A polyfunctional vinyl aromatic copolymer obtained by the following reaction.

[0230] 3.0 mol (390.6 g) of divinylbenzene, 1.8 mol (229.4 g) of ethylvinylbenzene, 10.2 mol (1066.3 g) of styrene, and 15.0 mol (1532.0 g) of n-propyl acetate were charged into a 5.0 L reactor, and 600 mmol of a boron trifluoride diethyl ether complex was added at 70 ° C., followed by a reaction for 4 hours. Thereafter, to terminate the reaction, an aqueous sodium bicarbonate solution was added to the resulting reaction solution, and the oil layer was washed three times with pure water. The mixture was then subjected to vacuum degassing at 60 ° C., and a solid (polymer) was recovered. The resulting solid was weighed, confirming that 896.7 g was obtained.

[0231] The structure of the solid (polymer) obtained above was analyzed using a nuclear magnetic resonance spectrometer, JNM-LA600, manufactured by JEOL Ltd. １３ C-NMR and １ The measurement was carried out by H-NMR analysis. １ was used, and the resonance line of tetramethylsilane was used as an internal standard. １３ C-NMR and １In addition to the H-NMR measurement results, the amount of a specific structural unit introduced was calculated from data on the total amount of each structural unit introduced into the copolymer obtained by gas chromatography (GC) analysis, and the amount of pendant vinyl group units contained in the polyfunctional vinyl aromatic copolymer was calculated from the amount of the specific structural unit introduced at the terminal and the number average molecular weight obtained by the GPC measurement.

[0232] The resulting solid was subjected to the above-mentioned １３ C-NMR and １ By performing H-NMR analysis, resonance lines derived from each monomer unit were observed. Furthermore, based on the results of NMR measurement and GC analysis, it was found that this solid was the polyfunctional vinyl aromatic copolymer. Based on the results of NMR measurement and GC analysis, the constituent units of this polyfunctional vinyl aromatic copolymer were calculated as follows: structural units derived from divinylbenzene: 30.4 mol% (33.1 mass%), structural units derived from styrene: 57.4 mol% (52.7 mass%), structural units derived from ethylvinylbenzene: 12.2 mol% (14.2 mass%), and structural units with residual vinyl groups derived from divinylbenzene: 23.9 mol% (25.9 mass%).

[0233] The molecular weight and molecular weight distribution of the obtained solid (polyfunctional vinyl aromatic copolymer) were measured using GPC (HLC-8120GPC manufactured by Tosoh Corporation) with tetrahydrofuran as the solvent, a flow rate of 1.0 ml / min, a column temperature of 38°C, and a calibration curve based on monodisperse polystyrene. As a result, the number average molecular weight Mn of the obtained solid was 2980, the weight average molecular weight Mw was 41300, and Mw / Mn was 13.9.

[0234] Polyphenylene ether compound: A polyphenylene ether compound having a vinylbenzyl group (ethenylbenzyl group) at the end (a modified polyphenylene ether compound obtained by reacting polyphenylene ether with chloromethylstyrene).

[0235] Specifically, it is a modified polyphenylene ether compound obtained by the following reaction.

[0236] First, 200 g of polyphenylene ether (SA90 manufactured by SABIC Innovative Plastics, 2 terminal hydroxyl groups, weight average molecular weight Mw 1700), 30 g of a 50:50 mass ratio mixture of p-chloromethylstyrene and m-chloromethylstyrene (chloromethylstyrene: CMS manufactured by Tokyo Chemical Industry Co., Ltd.), 1.227 g of tetra-n-butylammonium bromide as a phase transfer catalyst, and 400 g of toluene were charged into a 1-liter three-neck flask equipped with a temperature controller, a stirrer, a cooling device, and a dropping funnel, and the mixture was stirred. The polyphenylene ether, chloromethylstyrene, and tetra-n-butylammonium bromide were stirred until they were dissolved in toluene. The mixture was gradually heated, and finally heated until the liquid temperature reached 75 ° C. Then, an aqueous sodium hydroxide solution (20 g sodium hydroxide / 20 g water) was added dropwise to the solution as an alkali metal hydroxide over 20 minutes. The mixture was then stirred at 75°C for an additional 4 hours. Next, the contents of the flask were neutralized with 10% by mass hydrochloric acid, and a large amount of methanol was added. This caused a precipitate to form in the liquid in the flask. That is, the product contained in the reaction solution in the flask was reprecipitated. The precipitate was then filtered, washed three times with a mixture of methanol and water in a mass ratio of 80:20, and then dried under reduced pressure at 80°C for 3 hours.

[0237] The obtained solid is １ H-NMR (400MHz, CDCl ３ , TMS). As a result of NMR measurement, a peak derived from a vinylbenzyl group (ethenylbenzyl group) was confirmed at 5 to 7 ppm. This confirmed that the obtained solid was a modified polyphenylene ether compound having a vinylbenzyl group (ethenylbenzyl group) as the substituent at the molecular end in the molecule. Specifically, it was confirmed that it was an ethenylbenzylated polyphenylene ether. This modified polyphenylene ether compound obtained was represented by the above formula (56), in which Y in formula (56) is a dimethylmethylene group (represented by formula (54), and R in formula (54) is a ３３ and R ３４ is a methyl group), Ar is a phenylene group, and R１ ~R ３ was a hydrogen atom and p was 1.

[0238] The number of terminal functional groups of the modified polyphenylene ether was measured as follows.

[0239] First, the modified polyphenylene ether was accurately weighed. The weight at that time was designated X (mg). Then, this weighed modified polyphenylene ether was dissolved in 25 mL of methylene chloride, and 100 μL of a 10 mass% ethanol solution of tetraethylammonium hydroxide (TEAH) (TEAH:ethanol (volume ratio) = 15:85) was added to the solution, and the absorbance (Abs) at 318 nm was measured using a UV spectrophotometer (UV-1600 manufactured by Shimadzu Corporation). Then, from the measurement results, the number of terminal hydroxyl groups of the modified polyphenylene ether was calculated using the following formula.

[0240] Residual OH amount (μmol / g) = [(25×Abs) / (ε×OPL×X)]×10 ６ Here, ε is the extinction coefficient and is 4700 L / mol·cm, and OPL is the cell optical path length and is 1 cm.

[0241] The calculated residual OH amount (number of terminal hydroxyl groups) of the modified polyphenylene ether was almost zero, which indicated that the hydroxyl groups of the polyphenylene ether before modification were almost entirely modified. This indicated that the decrease from the number of terminal hydroxyl groups of the polyphenylene ether before modification was the number of terminal hydroxyl groups of the polyphenylene ether before modification. In other words, it was found that the number of terminal hydroxyl groups of the polyphenylene ether before modification was the number of terminal functional groups of the modified polyphenylene ether. In other words, the number of terminal functional groups was two.

[0242] The intrinsic viscosity (IV) of the modified polyphenylene ether was measured in methylene chloride at 25° C. Specifically, the intrinsic viscosity (IV) of the modified polyphenylene ether was measured by using a viscometer (AVS500 Visco System manufactured by Schott) to measure a 0.18 g / 45 ml methylene chloride solution (liquid temperature 25° C.) of the modified polyphenylene ether. As a result, the intrinsic viscosity (IV) of the modified polyphenylene ether was 0.086 dl / g.

[0243] The molecular weight distribution of the modified polyphenylene ether was measured using GPC. The weight average molecular weight (Mw) was calculated from the molecular weight distribution. The Mw was found to be 1,900.

[0244] Fluorine-containing thermosetting compound: represented by formula (60), q is 1, L is a cyclohexyl group, and R ３９ , is a fluorine atom, and R ４０ is a fluorine atom.

[0245] Specifically, it is a fluororesin obtained by the following reaction.

[0246] A glass reaction vessel was charged with 0.805 g (3.0 mmol) of 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z) and 0.912 g (6.6 mmol) of potassium carbonate. The pressure inside the glass reaction vessel was reduced to vacuum and then replaced with nitrogen. 10 mL of dimethylacetamide (DMAc) was then added to the glass reaction vessel. The reaction mixture was heated to 150°C with stirring and stirred for 3 hours. After heating was stopped, the reaction mixture was cooled to room temperature. 0.802 g (2.4 mmol) of decafluorobiphenyl was then added to the reaction mixture. The reaction mixture was heated to 70°C with stirring and stirred for 4 hours. The reaction mixture was then shielded from light, and 0.17 mL (0.233 g, 1.2 mmol) of 2,3,4,5,6-pentafluorostyrene was added. Stirring was continued at 70°C for 15 hours. After stirring was stopped, the reaction mixture was cooled to room temperature. The reaction mixture was then poured into 0.5 L of pure water. The reaction mixture was filtered under suction, and the resulting solid was washed with pure water and methanol. The washed solid was dried under reduced pressure to obtain approximately 1.14 g of a fluororesin.

[0247] (Inorganic filler) Silica: silica filler (EQ-2410-SBG manufactured by Zhejiang Sanshi New Materials Technology Co., Ltd.) Quartz glass: quartz glass filler (PQSF manufactured by Jiangsu Pacific Quartz Co., Ltd.) Magnesium oxide: magnesium oxide filler (RF-10CS manufactured by Ube Material Industries, Ltd.)

[0248] (Fibrous substrate) Fibrous substrate A: A liquid crystal polymer fiber [a liquid crystal polymer fiber consisting of 60 mol% of the structural unit represented by the formula (41) (structural unit derived from 6-hydroxy-2-naphthoic acid), 20 mol% of the structural unit represented by the formula (43) (structural unit derived from 2,6-naphthalenedicarboxylic acid), 15 mol% of the structural unit represented by the formula (44) (structural unit derived from hydroquinone), and 5 mol% of the structural unit represented by the formula (45) (structural unit derived from 4,4'-dihydroxybiphenyl)] was treated with plasma under the conditions shown in Table 1 (oxygen gas was used as the raw material gas, and the plasma irradiation dose was 0.5 W / cm in watt density). ２The fibrous substrate A was subjected to an oxygen gas plasma treatment for 10 minutes. The ratio (b / a) of this fibrous substrate A was measured by the method described below, and was found to be 0.32, as shown in Table 1.

[0249] The ratio (b / a) of the fibrous substrate was measured as follows. First, a surface X-ray analysis was performed on the surface of the fibrous substrate using an X-ray photoelectron spectrometer (XPS, PHI 5000 Versaprobe manufactured by ULVAC-PHI, Inc.). This surface X-ray analysis was performed by irradiating the surface of the fibrous substrate with X-rays under the following conditions from a direction perpendicular to the surface under vacuum, adjusting the irradiation height, and performing the analysis at a position where photoelectrons emitted due to ionization of the sample could be detected with the strongest intensity.

[0250] X-ray used: Monochrome Al-Kα ray X-ray beam diameter: Approximately 100 μmφ (25 W, 15 kV) Analysis area: Approximately 100 μmφ The spectrum obtained by the surface X-ray analysis was analyzed using analysis software provided with the apparatus (quantitative conversion using a relative sensitivity coefficient incorporated in the analysis software, etc.), to measure the ratio (b / a).

[0251] The dielectric loss tangent (Df) of the fibrous substrate made of liquid crystal polymer fiber was measured at 5 GHz using a network analyzer (N5230A manufactured by Keysight Technologies, Inc.) in an environment of 25 ° C. As a result, the dielectric loss tangent Df of the fibrous substrate A made of liquid crystal polymer fiber at 10 GHz at 25 ° C. was the value (0.0004) shown in Table 1. That is, it can be seen that the dielectric loss tangent Df of the liquid crystal polymer fiber constituting the fibrous substrate A at 10 GHz at 25 ° C. was also the value (0.0004) shown in Table 1.

[0252] Fibrous substrate B: The same fibrous substrate as used in fibrous substrate A (before plasma treatment) was subjected to the plasma treatment conditions shown in Table 1 (oxygen gas was used as the raw material gas, and the plasma irradiation amount was 0.5 W / cm in watt density). ２The fibrous substrate was subjected to oxygen gas plasma treatment under the conditions of (a) 0.0004 (the treatment time for the plasma treatment was 20 minutes). That is, fibrous substrate B was the same as fibrous substrate A except that the plasma treatment conditions were changed to the above conditions. When the ratio (b / a) of this fibrous substrate B was measured by the above method, it was 0.44 as shown in Table 1. The dielectric loss tangent Df at 10 GHz at 25°C of fibrous substrate B made of liquid crystal polymer fibers was the same as that of fibrous substrate A, being the value shown in Table 1 (0.0004). That is, it can be seen that the dielectric loss tangent Df at 10 GHz at 25°C of the liquid crystal polymer fibers constituting the fibrous substrate B was also the value shown in Table 1 (0.0004).

[0253] Fibrous substrate C: The same fibrous substrate as used in fibrous substrate A (before plasma treatment) was subjected to the plasma treatment conditions shown in Table 1 (oxygen gas was used as the raw material gas, and the plasma irradiation amount was 0.5 W / cm in watt density). ２ The fibrous substrate was subjected to oxygen gas plasma treatment under the conditions of (a) 0.0004 (the treatment time for the plasma treatment was 20 minutes). That is, fibrous substrate C was the same as fibrous substrate A except that the plasma treatment conditions were changed to the above conditions. When the ratio (b / a) of this fibrous substrate C was measured by the above method, it was 0.21 as shown in Table 1. The dielectric loss tangent Df at 10 GHz at 25°C of the fibrous substrate C made of liquid crystal polymer fibers was the same as that of the fibrous substrate A, being the value shown in Table 1 (0.0004). That is, it can be seen that the dielectric loss tangent Df at 10 GHz at 25°C of the liquid crystal polymer fibers constituting the fibrous substrate C was also the value shown in Table 1 (0.0004).

[0254] Fibre substrate D: A fibrous substrate containing liquid crystal polymer fibers (HT series manufactured by Kuraray Co., Ltd.) was subjected to plasma treatment under the conditions shown in Table 1 (oxygen gas was used as the raw material gas, and the plasma irradiation dose was 0.5 W / cm in watt density). ２The fibrous substrate D was subjected to an oxygen gas plasma treatment for 5 minutes. The ratio (b / a) of this fibrous substrate D was measured by the above-mentioned method and was 0.21 as shown in Table 1. The dielectric loss tangent Df of fibrous substrate D at 25°C and 10 GHz was also measured by the above-mentioned method and was the value (0.0020) shown in Table 1.

[0255] Fibre substrate E: A fibrous substrate containing liquid crystal polymer fibers (HT series manufactured by Kuraray Co., Ltd.) was subjected to plasma treatment under the conditions shown in Table 1 (oxygen gas was used as the raw material gas, and the plasma irradiation dose was 0.5 W / cm in watt density). ２ The fibrous substrate E was subjected to an oxygen gas plasma treatment for 20 minutes. The ratio (b / a) of this fibrous substrate E was measured by the above-mentioned method and was found to be 0.44, as shown in Table 1. The dielectric loss tangent Df of fibrous substrate E at 10 GHz and 25°C was the same as that of fibrous substrate D, being the value (0.0020) shown in Table 1.

[0256] [Preparation Method] First, all components other than the inorganic filler (thermosetting compound) were added to toluene to a solids concentration of 30% by mass and mixed. The mixture was stirred for 60 minutes. The inorganic filler was then added to the resulting liquid to obtain the composition (parts by mass) shown in Table 1, and the inorganic filler was dispersed using a bead mill. This resulted in a varnish-like composition (varnish).

[0257] Next, the resulting varnish was impregnated into a fibrous substrate shown in Table 1, and then heated and dried at 100 to 160°C for about 2 to 8 minutes to obtain a prepreg. The thickness of the prepreg after curing was adjusted to about 125 µm (the thermosetting compound content was about 74% by mass).

[0258] (Evaluation Board) Then, 18 μm thick copper foil (ultra-low roughness electrolytic copper foil CF-T4X-SV manufactured by Fukuda Metal Foil & Powder Co., Ltd.) was placed on both sides of each obtained prepreg to form a pressure body, and heated and pressed at a temperature of 220° C. for 2 hours at a pressure of 2 MPa to obtain a copper foil-clad laminate (metal-clad laminate) with a thickness of approximately 0.16 mm, with copper foil bonded to both sides. This obtained copper foil-clad laminate was used as an evaluation board.

[0259] The evaluation substrate prepared as described above was evaluated by the following method.

[0260] [Dielectric Properties (Dielectric Loss Tangent Df)] The copper foil was removed from the evaluation substrate by etching. The substrate thus obtained was used as a test specimen, and the relative permittivity and dielectric loss tangent at 25°C and 10 GHz were measured using a cavity resonator perturbation method. Specifically, the dielectric loss tangent (Df) of the test specimen at 10 GHz was measured using a network analyzer (N5230A manufactured by Keysight Technologies, Inc.) in an environment of 25°C.

[0261] [Heat Resistance (Oven Heat Resistance)] The evaluation substrate was left in a dryer set to a predetermined temperature for 1 hour, and the evaluation substrate was visually inspected for the presence or absence of blistering after leaving it. The lowest temperature at which blistering was confirmed was used as the evaluation standard for heat resistance. In Table 1, this lowest temperature is referred to as the blistering temperature. If no blistering was confirmed at 260°C, the evaluation was "pass", and if blistering was confirmed at 260°C, the evaluation was "fail". If blistering was confirmed at 260°C, the blistering temperature was indicated as "-".

[0262] [Storage Modulus] The evaluation substrate was cut into a size of 10 mm x 40 mm and attached to a dynamic viscoelasticity measuring device (DMS6100 manufactured by Seiko Instruments Inc.) A test was performed at a strain amplitude of 10 μm, a frequency of 10 Hz (sine wave), and a temperature rise rate of 5° C. / min, and the storage modulus (MPa) at 40° C. was measured.

[0263] [Thermal Expansion] The copper foil was removed from the evaluation substrate by etching to obtain an unclad plate having a length of 25 mm and a width of 5 mm. The cut unclad plate was used as a test piece, and the test piece was heated at 50 ° C for 2 hours. Then, the test piece was heated at 260 ° C for 2 hours. At this time, the distance between two predetermined points on the test piece in the warp direction of the fibrous substrate was measured after heating at 50 ° C and after heating at 260 ° C. The length after heating at 260 ° C (260 ° C. length) minus the length after heating at 50 ° C (50 ° C. length) was calculated as a ratio (%) [(260 ° C. length - 50 ° C. length) / 50 ° C. length × 100] to the 50 ° C. length. This ratio (dimensional change rate) (%) was used as an evaluation criterion for thermal expansibility.

[0264] [Processability] The evaluation substrate was cut, and the end surface obtained by the cutting was observed using a scanning electron microscope (S-3000N manufactured by Hitachi High-Tech Fielding Corporation). As a result, if no peeling of the copper foil was confirmed, it was evaluated as "passable", and if peeling of the copper foil was confirmed, it was evaluated as "poor". Processability was evaluated based on the presence or absence of peeling of the copper foil on the end surface after cutting.

[0265] The results of the above evaluations are shown in Tables 1 and 2.

[0266]

[0267]

[0268] Tables 1 and 2 show that prepregs (Examples 1 to 8) comprising a thermosetting composition or a semi-cured product of the thermosetting composition containing 65 parts by mass or more of the inorganic filler per 100 parts by mass of the thermosetting compound, and a fibrous substrate containing liquid crystal polymer fibers having a dielectric dissipation factor of 0.0015 or less, and the ratio (b / a) being 0.3 or more and less than 0.55, exhibited excellent low dielectric properties, heat resistance, and processability. Specifically, Examples 1 to 8 exhibited excellent heat resistance compared to Comparative Examples 1 and 3, where a fibrous substrate containing a ratio (b / a) of less than 0.3 was used. Furthermore, Examples 1 to 8 exhibited excellent heat resistance and processability compared to Comparative Example 2, where the inorganic filler content was less than 65 parts by mass. Compared to Comparative Examples 3 and 4, where a fibrous substrate containing liquid crystal polymer fibers having a dielectric dissipation factor of more than 0.0015 was used, Examples 1 to 8 exhibited low dielectric properties due to their lower dielectric dissipation factor. Furthermore, it can be inferred that the processability is excellent when the storage modulus is high and the thermal expansion (rate of dimensional change due to thermal expansion) is low, based on the storage modulus and thermal expansion shown in Table 1. This also shows that Examples 1 to 8 have excellent processability.

[0269] From the above, it can be seen that Examples 1 to 8 have excellent low dielectric properties, heat resistance, and processability. Therefore, it was found that a prepreg can be obtained that provides a cured product with excellent low dielectric properties, heat resistance, and processability when it is provided with a thermosetting composition or a semi-cured product of the thermosetting composition containing 65 parts by mass or more of the inorganic filler per 100 parts by mass of the thermosetting compound, and a fibrous substrate containing liquid crystal polymer fibers having a dielectric dissipation factor of 0.0015 or less, and the abundance ratio (b / a) of each group on the surface of the fibrous substrate measured by X-ray photoelectron spectroscopy is 0.3 or more and less than 0.55.

[0270] This application is based on Japanese Patent Application No. 2024-080586 filed on May 17, 2024, the contents of which are incorporated herein by reference.

[0271] In order to express the present invention, the present invention has been properly and sufficiently described through the embodiments in the above, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims.

[0272] The present invention provides a prepreg for printed wiring boards that can give cured products with low dielectric properties, excellent heat resistance, and excellent processability. The present invention also provides a metal-clad laminate for printed wiring boards and a printed wiring board obtained using the prepreg.

Claims

1. A fiber substrate comprising a thermosetting composition containing a thermosetting compound and an inorganic filler or a semi-cured product of the thermosetting composition, and a liquid crystal polymer fiber, wherein the thermosetting compound contains at least one selected from the group consisting of polyphenylene ether compounds having a carbon-carbon unsaturated double bond in the molecule, hydrocarbon compounds having a carbon-carbon unsaturated double bond in the molecule, and thermosetting compounds having a fluorine atom in the molecule, and the inorganic filler contains at least one material selected from the group consisting of silica, quartz glass, and magnesium oxide, and the content of the inorganic filler is 65 parts by mass or more relative to 100 parts by mass of the thermosetting compound, and the liquid crystal polymer fiber has a dielectric loss tangent of 0.0015 or less at 5 GHz at 25°C, A prepreg for printed wiring boards, in which the ratio of the total amount of groups represented by the following formula (3), groups represented by the following formula (4), and groups represented by the following formula (5) to the total amount of groups represented by the following formula (1) and groups represented by the following formula (2) on the surface of the fibrous substrate, as measured by X-ray photoelectron spectroscopy, is 0.3 or more and less than 0.

55.

2. The prepreg for printed wiring boards according to claim 1, wherein the fibrous base material includes a fibrous base material whose surface has been subjected to plasma treatment.

3. The prepreg for printed wiring boards according to claim 1, wherein the fibrous substrate comprises a fibrous substrate whose surface has been subjected to at least one plasma treatment selected from the group consisting of oxygen gas plasma treatment, oxygen and carbon tetrafluoride mixed gas plasma treatment, and argon, hydrogen, and nitrogen mixed gas plasma treatment.

4. A metal-clad laminate for printed wiring boards, comprising an insulating layer containing a cured product of the prepreg for printed wiring boards according to any one of claims 1 to 3, and a metal foil.

5. A printed wiring board comprising an insulating layer containing a cured product of the printed wiring board prepreg according to any one of claims 1 to 3, and wiring.

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