Composition, sheet obtained using same, and production method therefor

Abstract

Provided is a composition from which a fluororesin-containing sheet having a low coefficient of linear expansion (CTE) can be obtained. The composition comprises a fluororesin and inorganic particles treated with two or more reactive silane coupling agents. In the composition set forth in claim 1, the inorganic particles treated with two or more reactive silane coupling agents are any of the following (1) to (3) or a combination of these. (1) A combination of inorganic particles treated with a reactive silane coupling agent and inorganic particles separately treated with a reactive silane coupling agent of a different kind. (2) Inorganic particles treated with a combination of two or more reactive silane coupling agents. (3) Inorganic particles treated with at least one reactive silane coupling agent and further treated with at least one other reactive silane coupling agent.

Description

Composition, sheet using same, and method for producing same

[0001] The present disclosure relates to a composition, a sheet using the same, and a method for producing the same.

[0002] High-frequency printed wiring boards with low transmission loss are in demand, and it is known to use fluororesin films in such high-frequency printed wiring boards (see, for example, Patent Document 1).

[0003] The use of a fluororesin composition containing a filler as a wiring board material is also described in Patent Documents 2 and 3. Furthermore, Patent Document 4 discloses the use of a fluororesin composition containing spherical silica particles in a fluororesin for a circuit board.

[0004] Japanese Patent Application Laid-Open No. 2015-8260 Japanese Patent Application Laid-Open No. 63-259907 Special Publication No. 2022-510017 International Publication No. 2020 / 145133

[0005] An object of the present disclosure is to provide a composition that can provide a sheet containing a fluororesin having a low coefficient of linear expansion (CTE).

[0006] The present disclosure is a composition comprising a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents.

[0007] The inorganic particles treated with two or more types of reactive silane coupling agents are preferably any one of the following (1) to (3), or a combination thereof: (1) A combination of inorganic particles each treated with a different type of reactive silane coupling agent, (2) Inorganic particles treated with two or more types of reactive silane coupling agents in combination, or (3) Inorganic particles treated with at least one type of reactive silane coupling agent and then further treated with at least another type of reactive silane coupling agent.

[0008] The inorganic particles are preferably inorganic particles containing silica as an essential component, the fluororesin is preferably a perfluororesin, and the perfluororesin is preferably polytetrafluoroethylene.

[0009] The content of the inorganic particles treated with two or more reactive silane coupling agents is preferably 40% by mass or more of the total composition, and more preferably 80% by mass or less of the total composition.

[0010] It is preferable that the inorganic particles treated with two or more types of reactive silane coupling agents are (1) above, and the amount of each reactive silane coupling agent treated is 0.050 to 3.0 mass% relative to the amount of each inorganic particle.

[0011] The combination of the two or more reactive silane coupling agents is preferably a combination in which the reactive groups of the reactive silane coupling agents react with each other to form at least one functional group selected from the group consisting of amide group, ester group, β-aminoester group, ureido group, urethane group, imide group, ether group, carbamide group, and thiourethane group.The reactive groups of the two or more reactive silane coupling agents are preferably selected from the group consisting of amino group, epoxy group, acrylic group, methacrylic group, isocyanate group, thiol group, carboxylic acid group, and acid anhydride group, and are a combination of reactive groups that react with each other. The combination of reactive groups of the two or more types of reactive silane coupling agents is preferably at least one selected from the group consisting of an amino group and an acid anhydride group, an amino group and an acrylic group, an amino group and a methacrylic group, an amino group and an isocyanate group, an acid anhydride group and an isocyanate group, an epoxy group and an acid anhydride group, an epoxy group and an acrylic group, an epoxy group and a methacrylic group, an epoxy group and an isocyanate group, an epoxy group and an amino group, and a thiol group and an isocyanate group.

[0012] The two or more reactive silane coupling agents are each selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-isocyanatepropyltriethoxysilane, and 3-trimethoxysilylpropylsuccinic anhydride, and preferably comprise a combination of reactive silane coupling agents having reactive groups that react with each other. The combination of reactive silane coupling agents is preferably at least one of 3-aminopropyltriethoxysilane and 3-isocyanatepropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride, or 3-isocyanatepropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride.

[0013] It is preferable that the fluororesin is polytetrafluoroethylene, the inorganic particles are silica, and the combination of the reactive silane coupling agents is at least one of 3-aminopropyltriethoxysilane and 3-isocyanatepropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride, or 3-isocyanatepropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride.

[0014] The present disclosure also relates to a sheet or film made from the above-described composition. The sheet or film preferably has at least one functional group selected from the group consisting of amide groups, ester groups, β-aminoester groups, ureido groups, urethane groups, imide groups, ether groups, carbamide groups, and thiourethane groups, formed from the reactive groups of the two or more reactive silane coupling agents. The sheet or film preferably has a linear thermal expansion (CTE) that is 10 to 40 ppm / K lower than the linear thermal expansion (CTE) of a sheet or film containing inorganic particles treated with only one of the two or more reactive silane coupling agents. The sheet or film preferably has a linear thermal expansion (CTE) of 200 ppm / K or less.

[0015] The present disclosure also provides a method for producing the above-mentioned sheet or film, characterized by molding and then processing a composition containing a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents.The present disclosure also provides a method for producing the above-mentioned sheet or film, characterized by molding and then processing a composition containing essentially a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents.

[0016] The present disclosure also provides a filler for a resin composition for electronic materials, which contains inorganic particles treated with two or more reactive silane coupling agents whose reactive groups react with each other. In the filler for a resin composition for electronic materials, the combination of the two or more reactive silane coupling agents is preferably a combination in which the reactive groups react with each other to form at least one functional group selected from the group consisting of an amide group, an ester group, a β-aminoester group, a ureido group, a urethane group, an imide group, an ether group, a carbamide group, and a thiourethane group.

[0017] The present disclosure also relates to a metal laminate having a metal layer and the above-mentioned sheet or film as essential layers. The metal layer is preferably copper foil. The present disclosure also relates to a circuit board having the above-mentioned metal laminate.

[0018] The composition of the present disclosure can be made into a sheet containing a fluororesin having a low coefficient of linear expansion (CTE).

[0019] The present disclosure will be described in detail below. High-frequency printed wiring boards require dielectric materials with low transmission loss. Among these, fluororesins are considered suitable for high-frequency applications due to their low dielectric constant, low dielectric dissipation factor, and excellent electrical properties. However, fluororesins have a very high coefficient of linear expansion (CTE), which poses a problem of separation from metal layers such as copper foil during circuit formation. Conventionally, a method of adding a filler to a fluororesin to lower the CTE has been common. For example, as described above, a fluororesin composition containing spherical silica particles blended with a fluororesin has been used in circuit boards.

[0020] The effect of adding a filler to reduce the CTE depends on the filler's inherent CTE and content, so the amount must be increased depending on the target CTE value. However, increasing the filler amount deteriorates processability, so fillers with a low CTE themselves are preferred, but there are limits.

[0021] The present disclosure is characterized by the use of inorganic particles treated with two or more types of reactive silane coupling agents as a filler to be added to a fluororesin. It has been known that fillers surface-treated with silane coupling agents are used as fillers to be added to fluororesins. It is generally believed that organic groups contained in silane coupling agents, etc., disappear at the temperatures used to process fluororesin sheets. Therefore, it has been thought that the effect of silane coupling agents is primarily to react with and bond with hydrophilic groups on the surface of inorganic materials to simply reduce the number of hydrophilic terminals, rather than to introduce organic groups.

[0022] However, as a result of the inventors' investigation of the above, it was found that the organic groups contained in the silane coupling agent do not disappear even when the fluororesin sheet is baked.Furthermore, it was found that by using two or more reactive silane coupling agents with reactive groups that react with each other, new functional groups that are thought to be generated by the reaction of both at the temperature at which the sheet is processed are generated, and the CTE of the resulting sheet can be reduced.

[0023] It was also confirmed that the CTE reduction effect is only observed when two or more reactive groups are combined, and that the CTE reduction effect cannot be obtained when a silane coupling agent that originally has a functional group that is generated when two or more reactive groups react with each other is used, rather than when two or more reactive groups are reacted during sheet processing to generate a functional group.

[0024] The reason why such a CTE reduction effect is obtained is not clear, but it is presumed to be due to the fact that new bonds are formed between inorganic particles as a result of the reactive groups of the reactive silane coupling agent reacting with each other.

[0025] The present disclosure relates to a composition comprising a fluororesin and inorganic particles treated with two or more reactive silane coupling agents. As described above, the composition comprises inorganic particles treated with two or more reactive silane coupling agents, each having a different reactive group that reacts to form a functional group. During processing after sheet formation, the two or more reactive groups react to generate new functional groups, thereby reducing the CTE of the sheet.

[0026] In the present disclosure, it is necessary to use inorganic particles treated with two or more types of reactive silane coupling agents. "Inorganic particles treated with two or more types of reactive silane coupling agents" refers to any of the following (1) to (3), or (4) a combination thereof. (1) A combination of inorganic particles each treated with a different type of reactive silane coupling agent. (2) Inorganic particles treated with two or more types of reactive silane coupling agents. (3) Inorganic particles treated with at least one type of reactive silane coupling agent and then further treated with at least another type of reactive silane coupling agent.

[0027] Among the above, (1) is preferable in that when treating with a reactive silane coupling agent, the entire inorganic particle surface can be uniformly treated with the reactive silane coupling agent. Therefore, in the case of (1), each reactive silane coupling agent is uniformly applied to the entire treated inorganic particle surface, and the reaction between reactive groups is easily caused.

[0028] (Inorganic Particles) Inorganic particles that can be used in the present disclosure are not particularly limited, and examples thereof include inorganic particles that are one or more types selected from ceramics, talc, mica, alumina, zinc oxide, tin oxide, titanium oxide, silicon oxide, calcium carbonate, calcium oxide, magnesium oxide, potassium titanate, forsterite, glass fiber, glass chips, glass beads, silica, calcium fluoride, boron nitride, barium sulfate, molybdenum disulfide, and potassium carbonate whiskers. Two or more types of these may be used in combination. Among these, at least one type selected from the group consisting of silica, titanium oxide, magnesium oxide, alumina, and forsterite is particularly preferred. In particular, it is preferred that the inorganic particles contain silica as an essential component. It is preferred that the inorganic particles are partially or entirely silica.

[0029] The shape of the inorganic particles is not particularly limited, and examples thereof include spherical and crushed shapes. Among these, spherical shapes are preferred. Spherical shapes are preferred because they are easy to process uniformly during drilling and have a small specific surface area and low transmission loss. In the present disclosure, it is most preferred to use spherical silica.

[0030] The spherical inorganic particles mentioned above mean particles whose particle shape is close to a perfect sphere, and specifically, the sphericity is preferably 0.80 or more, more preferably 0.85 or more, even more preferably 0.90 or more, and most preferably 0.95 or more. The sphericity is calculated by taking a photograph with an SEM and calculating the value from the area and perimeter of the observed particle using the formula (sphericity) = {4π × (area) ÷ (perimeter)2}. The closer to 1, the closer to a perfect sphere. Specifically, the average value measured for 100 particles using an image processing device (Spectris Inc.: FPIA-3000) is used.

[0031] In the present disclosure, the inorganic particles preferably have an average particle size of 0.1 to 10 μm. The average particle size here is the D50 value measured using a laser diffraction particle size distribution analyzer. If the average particle size is less than 0.1 μm, aggregation of the inorganic particles occurs, and a sufficient effect tends to be insufficient. Furthermore, if the average particle size exceeds 10 μm, the sheet tends to be difficult to form into a thin film. The lower limit of the average particle size is more preferably 0.2 μm. The upper limit of the average particle size is more preferably 5 μm.

[0032] The silica particles used in the present disclosure preferably have an average particle size of 0.2 to 10 μm. If the average particle size is less than 0.2 μm, the silica particles tend to absorb a large amount of water. If the average particle size exceeds 10 μm, the sheet tends to be difficult to form into a thin film. The lower limit of the average particle size is more preferably 0.3 μm, and even more preferably 0.4 μm. The upper limit of the average particle size is more preferably 5 μm, and even more preferably 3 μm.

[0033] The inorganic particles may be of two or more types having different average particle sizes. For example, when silica particles having average particle sizes of 2.1 μm and 0.5 μm, each having a different reactive functional group, are used, the contact surface area between particles is larger than when particles of a single average particle size are used, and the reaction between the reactive functional groups may be more likely to occur.

[0034] Furthermore, the spherical silica particles used in the present disclosure preferably have a D90 / D10 of 2 or more (preferably 2.3 or more, 2.5 or more) and a D50 of 10 μm or less when integrating the volume from the smallest particle diameter. Furthermore, it is preferable that the D90 / D50 is 1.5 or more (more preferably 1.6 or more). It is also preferable that the D50 / D10 is 1.5 or more (more preferably 1.6 or more). Since small spherical silica particles can enter the gaps between large spherical silica particles, it is possible to achieve excellent filling properties and high fluidity. In particular, it is preferable that the particle size distribution has a higher frequency on the small particle diameter side compared to a Gaussian curve. The particle size can be measured using a laser diffraction / scattering particle size distribution analyzer. It is also preferable that coarse particles having a particle size above a certain size have been removed using a filter or the like.

[0035] The water absorption of the spherical silica is preferably 1.0% or less, and more preferably 0.5% or less. The water absorption is based on the mass of the spherical silica when dry. The water absorption is measured by leaving a dry sample at 40°C and 80% RH for 1 hour, and measuring the water content generated by heating at 200°C using a Karl Fischer moisture content analyzer.

[0036] The spherical silica can also be obtained by heating the dielectric sheet at 600°C for 30 minutes in an air atmosphere to burn off the fluororesin, extracting the spherical silica particles, and then measuring the above-mentioned parameters using the above-mentioned method.

[0037] The spherical silica may be commercially available silica particles that satisfy the above-mentioned properties. Examples of commercially available silica particles include Denka fused silica FB grade (manufactured by Denka Company Ltd.), Denka fused silica SFP grade (manufactured by Denka Company Ltd.), Excelica (manufactured by Tokuyama Corporation), high-purity synthetic spherical silica particles Admafine (manufactured by Admatechs Co., Ltd.), Admanano (manufactured by Admatechs Co., Ltd.), and Admafuse (manufactured by Admatechs Co., Ltd.).

[0038] (Silane Coupling Agent) In the present disclosure, two or more types of reactive silane coupling agents are used. The two or more types of reactive silane coupling agents used preferably include a combination of reactive silane coupling agents each having a different reactive group that reacts to form a functional group. That is, the reactive silane coupling agents used include at least one type of reactive silane coupling agent each having a different reactive group, and include a combination of reactive silane coupling agents in which the reactive groups react to form a functional group. The combination of reactive silane coupling agents used is preferably a combination in which the reactive groups react to form at least one functional group selected from the group consisting of an amide group, an ester group, a β-aminoester group, a ureido group, a urethane group, an imide group, an ether group, a carbamide group, and a thiourethane group. In particular, a combination in which at least one functional group selected from the group consisting of an amide group, an imide group, a ureido group, a urethane group, and a β-aminoester group is more preferred.

[0039] The reactive group forming the functional group as described above is preferably selected from the group consisting of an amino group, an epoxy group, an acrylic group, a methacrylic group, an isocyanate group, a thiol group, a carboxylic acid group, and an acid anhydride group. In particular, it is more preferable that it is selected from the group consisting of an amino group, an acrylic group, a methacrylic group, an isocyanate group, and an acid anhydride group. Furthermore, it is preferable that the reactive groups of two or more reactive silane coupling agents are each selected from the group consisting of an amino group, an epoxy group, an acrylic group, a methacrylic group, an isocyanate group, a thiol group, a carboxylic acid group, and an acid anhydride group, and that they include a combination of reactive groups that react with each other.

[0040] In addition, the combination of reactive groups of the reactive silane coupling agent may include an amino group and an acid anhydride group, an amino group and an acrylic group, an amino group and a methacrylic group, an amino group and an isocyanate group, an acid anhydride group and an isocyanate group, an epoxy group and an acid anhydride group, an epoxy group and an acrylic group, an epoxy group and a methacrylic group, an epoxy group and an isocyanate group, an epoxy group and an amino group, a thiol group and an isocyanate group, etc. Among these, the combinations of an amino group and an acid anhydride group, an amino group and an acrylic group, an amino group and a methacrylic group, an amino group and an isocyanate group, and an acid anhydride group and an isocyanate group are preferred. These combinations are preferred because they have sufficient reactivity at sheet processing temperatures. In addition, the reactive silane coupling agent used may contain two or more of these combinations.

[0041] Examples of the reactive silane coupling agent having the reactive group include aminosilane, epoxysilane, acrylsilane, methacrylsilane, isocyanatesilane, mercaptosilane, and acid anhydride silane.

[0042] Specific examples of the reactive silane coupling agent include aminosilanes such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane; epoxysilanes such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; acrylicsilanes such as 3-acryloxypropyltrimethoxysilane; methacrylsilanes such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; isocyanatesilanes such as 3-isocyanatepropyltriethoxysilane; Examples include mercaptosilanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane, and acid anhydride silanes such as 3-trimethoxysilylpropylsuccinic anhydride. Two or more types may be appropriately selected from these and used in combination so that the reactive groups react with each other to form the above-described functional group.

[0043] Among these, it is preferable to use two or more reactive silane coupling agents selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-isocyanatepropyltriethoxysilane, and 3-trimethoxysilylpropylsuccinic anhydride, in which reactive groups react with each other.

[0044] Specific combinations of reactive silane coupling agents include 3-aminopropyltriethoxysilane and 3-isocyanatepropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride, and 3-isocyanatepropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride. These combinations are suitable because they have sufficient reactivity at sheet processing temperatures.

[0045] The method of treating inorganic particles with a reactive silane coupling agent is not particularly limited, and may be suitably carried out by a known method.For example, it can be obtained by a dry method in which a solution containing a reactive silane coupling agent or the like is sprayed onto the inorganic particles under stirring, and then mixed and dried to treat, or a wet method in which a reactive silane coupling agent is directly added to a slurry containing inorganic particles or the like, and then mixed, aged, and dried to treat.

[0046] The treatment with the reactive silane coupling agent may involve treating the inorganic particles with each reactive silane coupling agent separately, or may involve treating the inorganic particles with two or more reactive silane coupling agents in combination. Furthermore, after treatment with one or more reactive silane coupling agents, the inorganic particles may be further treated with one or more other reactive silane coupling agents. These treatment methods can yield inorganic particles treated with two or more reactive silane coupling agents selected from the group consisting of (1) to (4) above.

[0047] When treating with one type of reactive silane coupling agent, the amount of reactive silane coupling agent to be treated is preferably 0.050 to 3.0 mass% relative to the amount of inorganic particles to be treated. It is more preferably 0.070 mass% or more, and even more preferably 0.10 mass% or more. It is more preferably 2.5 mass% or less, and even more preferably 2.0 mass% or less. A treatment amount of reactive silane coupling agent within this range is advantageous in terms of improving the electrical properties of the inorganic particles, reducing the CTE of the sheet, improving the electrical properties of the sheet, and improving the moldability of the sheet. Furthermore, the reaction between reactive groups during sheet processing is also favorable.

[0048] In addition, when two or more kinds of reactive silane coupling agents are used together to treat inorganic particles, the total amount of reactive silane coupling agents used is preferably 0.1 to 3 mass% relative to the amount of inorganic particles to be treated. In addition, the ratio of the reactive silane coupling agents used in the treatment is preferably 1:2 to 2:1 by mass, or 1:2 to 2:1 by molar ratio, more preferably 1:1 by molar ratio, for the ratio of two kinds of silane coupling agents having reactive groups that react with each other.

[0049] (Filler for resin compositions for electronic materials) By using inorganic particles treated by the above-mentioned treatment method together with a fluororesin or the like, the CTE of the resulting sheet can be reduced. For this reason, inorganic particles treated with two or more types of reactive silane coupling agents are suitable for use as a filler in resin compositions for electronic materials used in circuit boards and the like. The present disclosure also relates to a filler for resin compositions for electronic materials containing inorganic particles treated with two or more types of reactive silane coupling agents whose reactive groups react with each other.

[0050] In the filler for a resin composition for electronic materials, the combination of two or more reactive silane coupling agents is preferably a combination in which reactive groups react with each other to form at least one functional group selected from the group consisting of an amide group, an ester group, a β-aminoester group, a ureido group, a urethane group, an imide group, an ether group, a carbamide group, and a thiourethane group. Furthermore, the inorganic particles treated with two or more reactive silane coupling agents contained in the filler for a resin composition for electronic materials are preferably the same as the inorganic particles treated with two or more reactive silane coupling agents contained in the composition.

[0051] (Fluororesin) Fluororesin has low dielectric properties and can therefore be suitably used in the present disclosure.

[0052] The fluororesin that can be used in the present disclosure is not particularly limited, and examples thereof include polytetrafluoroethylene (PTFE), tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] copolymer [FEP], TFE / alkyl vinyl ether copolymer [PFA], TFE / HFP / alkyl vinyl ether copolymer [EPA], TFE / chlorotrifluoroethylene [CTFE] copolymer, TFE / ethylene copolymer [ETFE], polyvinylidene fluoride [PVdF], tetrafluoroethylene having a molecular weight of 300,000 or less [LMW-PTFE], etc. These fluororesins may be used alone or in combination of two or more.

[0053] Among them, the fluororesin is preferably a perfluoro-based fluororesin. In particular, polytetrafluoroethylene (PTFE) is preferred from the viewpoints of low dielectric constant and low linear expansion coefficient. PTFE having fibrillar properties is preferred. Fibrillar PTFE means PTFE that can be extruded into a paste as unsintered polymer powder.

[0054] PTFE may be modified polytetrafluoroethylene (hereinafter referred to as modified PTFE), may be homopolytetrafluoroethylene (hereinafter referred to as homoPTFE), or may be a mixture of modified PTFE and homoPTFE. Note that, from the viewpoint of maintaining good moldability of polytetrafluoroethylene, the content ratio of modified PTFE in polymeric PTFE is preferably 10% by mass or more and 98% by mass or less, more preferably 50% by mass or more and 95% by mass or less.

[0055] The homo-PTFE is not particularly limited, and homo-PTFE disclosed in JP-A-53-60979, JP-A-57-135, JP-A-61-16907, JP-A-62-104816, JP-A-62-190206, JP-A-63-137906, JP-A-2000-143727, JP-A-2002-201217, WO 2007 / 046345 pamphlet, WO 2007 / 119829 pamphlet, WO 2009 / 001894 pamphlet, WO 2010 / 113950 pamphlet, WO 2013 / 027850 pamphlet, etc. can be suitably used. Among these, homo-PTFE having high stretchability and disclosed in JP-A-57-135, JP-A-63-137906, JP-A-2000-143727, JP-A-2002-201217, WO 2007 / 046345, WO 2007 / 119829, WO 2010 / 113950, etc. is preferred.

[0056] Modified PTFE is made up of TFE and monomer other than TFE (hereinafter referred to as modified monomer).Modified PTFE can include, but is not limited to, the one that is uniformly modified by modified monomer, the one that is modified at the beginning of polymerization reaction, or the one that is modified at the end of polymerization reaction.Modified PTFE is preferably the TFE copolymer obtained by subjecting TFE and a small amount of monomer other than TFE to polymerization within the range that does not significantly impair the properties of TFE homopolymer.

[0057] The modified PTFE can be suitably used, for example, those disclosed in JP-A-60-42446, JP-A-61-16907, JP-A-62-104816, JP-A-62-190206, JP-A-64-1711, JP-A-2-261810, JP-A-11-240917, JP-A-11-240918, WO 2003 / 033555 pamphlet, WO 2005 / 061567 pamphlet, WO 2007 / 005361 pamphlet, WO 2011 / 055824 pamphlet, WO 2013 / 027850 pamphlet, etc. Among these, modified PTFE having high stretchability and disclosed in JP-A-61-16907, JP-A-62-104816, JP-A-64-1711, JP-A-11-240917, WO 2003 / 033555, WO 2005 / 061567, WO 2007 / 005361, WO 2011 / 055824, etc. are preferred.

[0058] The modified PTFE contains TFE units based on TFE and modified monomer units based on a modified monomer. The modified monomer units are a part of the molecular structure of the modified PTFE that is derived from the modified monomer. The modified PTFE preferably contains modified monomer units in an amount of 0.001 to 0.500 mass% of the total monomer units, and more preferably 0.01 to 0.30 mass%. The total monomer units are the parts derived from all monomers in the molecular structure of the modified PTFE.

[0059] The modified monomer is not particularly limited as long as it can be copolymerized with TFE, and examples thereof include perfluoroolefins such as hexafluoropropylene (HFP); chlorofluoroolefins such as chlorotrifluoroethylene (CTFE); hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF); perfluorovinyl ether; perfluoroalkylethylene (PFAE), ethylene, etc. The modified monomer used may be one kind or multiple kinds.

[0060] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorounsaturated compounds represented by the following general formula (1): CF ２ =CF-ORf (1) (wherein Rf represents a perfluoroorganic group.)

[0061] In this specification, a perfluoroorganic group is an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0062] An example of a perfluorovinyl ether is perfluoro(alkyl vinyl ether) (PAVE), which is represented by the above general formula (1) and in which Rf is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5. Examples of the perfluoroalkyl group in PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group. Preferred PAVEs are perfluoropropyl vinyl ether (PPVE) and perfluoromethyl vinyl ether (PMVE).

[0063] The perfluoroalkylethylene (PFAE) is not particularly limited, and examples thereof include perfluorobutylethylene (PFBE) and perfluorohexylethylene (PFHE).

[0064] The modifying monomer in the modified PTFE is preferably at least one selected from the group consisting of HFP, CTFE, VDF, PAVE, PFAE, and ethylene.

[0065] The fluororesin is preferably non-melt-processable. "Non-melt-processable" means that the resin does not have sufficient fluidity even when heated above its melting point, and cannot be molded by melt molding techniques commonly used for resins. PTFE falls into this category.

[0066] In the present disclosure, it is preferable to use particles of such non-melt-processable fluororesin and form them into a fluororesin sheet by a molding method that fibrillates the particles. The molding method will be described later.

[0067] The PTFE preferably has a standard specific gravity (SSG) of 2.0 to 2.3. The use of such PTFE facilitates the production of PTFE membranes with high strength (cohesion and puncture strength per unit thickness). PTFE with a large molecular weight has long molecular chains, making it difficult to form a structure in which the molecular chains are regularly arranged. In this case, the length of the amorphous portion increases, and the degree of entanglement between molecules increases. It is believed that when the degree of entanglement between molecules is high, the PTFE membrane is less likely to deform under an applied load and exhibits excellent mechanical strength. Furthermore, the use of PTFE with a large molecular weight facilitates the production of PTFE membranes with small average pore sizes.

[0068] The lower limit of the SSG is more preferably 2.05, and even more preferably 2.1. The upper limit of the SSG is more preferably 2.25, and even more preferably 2.2.

[0069] The standard specific gravity [SSG] was measured by preparing a sample in accordance with ASTM D-4895-89 and measuring the specific gravity of the obtained sample by the water displacement method.

[0070] In this embodiment, the molecular weight (number average molecular weight) of the PTFE constituting the PTFE particles is, for example, in the range of 2 million to 12 million. The lower limit of the molecular weight of PTFE may be 3 million or 4 million. The upper limit of the molecular weight of PTFE may be 10 million.

[0071] Methods for measuring the number average molecular weight of PTFE include a method determining it from standard specific gravity and a method measuring dynamic viscoelasticity in the melt. The method for determining it from standard specific gravity can be carried out by the water displacement method in accordance with ASTM D-792 using a sample molded in accordance with ASTM D-4895 98. The measurement method using dynamic viscoelasticity is explained, for example, by S. Wu in Polymer Engineering & Science, 1988, Vol. 28, 538 and the same document, 1989, Vol. 29, 273.

[0072] The refractive index of the PTFE is preferably in the range of 1.2 to 1.6. Having such a refractive index is preferable in terms of low dielectric constant. The refractive index can be adjusted to within the above range by adjusting the polarizability or the flexibility of the main chain. The lower limit of the refractive index is more preferably 1.25, more preferably 1.30, and most preferably 1.32. The upper limit of the refractive index is more preferably 1.55, more preferably 1.50, and most preferably 1.45.

[0073] The refractive index is a value measured using a refractometer (Abbemat 300).

[0074] The PTFE preferably has a maximum endothermic peak temperature (crystalline melting point) of 340±7°C.

[0075] The PTFE may be a low-melting-point PTFE having a maximum peak temperature of 338°C or lower on the endothermic curve on the crystalline melting curve measured by a differential scanning calorimeter, or a high-melting-point PTFE having a maximum peak temperature of 342°C or higher on the endothermic curve on the crystalline melting curve measured by a differential scanning calorimeter.

[0076] The low-melting-point PTFE powder is a powder particle produced by emulsion polymerization, has the maximum endothermic peak temperature (crystalline melting point) described above, a dielectric constant (ε) of 2.08 to 2.2, and a dielectric loss tangent (tan δ) of 1.9 × 10 －４ ~4.0 x 10 －４Examples of commercially available products include Polyflon fine powders F201, F203, F205, F301, and F302 manufactured by Daikin Industries, Ltd., CD090 and CD076 manufactured by Asahi Glass Co., Ltd., and TF6C, TF62, and TF40 manufactured by DuPont.

[0077] The high melting point PTFE powder is also a powder particle produced by emulsion polymerization, and has the above-mentioned maximum endothermic peak temperature (crystalline melting point), a dielectric constant (ε) of 2.0 to 2.1, and a dielectric loss tangent (tanδ) of 1.6×10 －４ ~2.2 × 10 －４ Commercially available products include Polyflon fine powders F104 and F106 manufactured by Daikin Industries, Ltd., CD1, CD141, and CD123 manufactured by Asahi Glass Co., Ltd., and TF6 and TF65 manufactured by DuPont.

[0078] The powder formed by secondary aggregation of both PTFE polymer particles usually preferably has an average particle size of 250 to 2000 μm. In particular, granulated powder obtained by granulation using a solvent is preferred from the viewpoint of improving the flowability when filling a mold during preforming.

[0079] Powdered PTFE particles satisfying the above-described parameters can be obtained by conventional manufacturing methods, such as those described in International Publication Nos. 2015-080291 and 2012-086710.

[0080] (Composition) The composition of the present disclosure contains the above-described fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents (hereinafter, sometimes referred to as treated inorganic particles).

[0081] As described above, the fluororesin used in the present disclosure is preferably a non-melt-processable fluororesin. When using such a fluororesin, it is preferable to form it into a sheet by fibrillating powdered PTFE as a raw material.

[0082] The powdered PTFE preferably has a primary particle size of 0.05 to 10 μm. The use of such a powder offers the advantages of excellent moldability and dispersibility. The primary particle size here is a value measured in accordance with ASTM D 4895.

[0083] The powdered PTFE preferably contains 50% by mass or more, more preferably 80% by mass or more, of polytetrafluoroethylene resin having a secondary particle diameter of 500 μm or more.The PTFE having a secondary particle diameter of 500 μm or more within this range has the advantage of being able to produce a sheet with high strength.By using PTFE having a secondary particle diameter of 500 μm or more, a sheet with lower resistance and excellent toughness can be obtained.

[0084] The lower limit of the secondary particle diameter is more preferably 300 μm, and even more preferably 350 μm. The upper limit of the secondary particle diameter is more preferably 700 μm or less, and even more preferably 600 μm or less. The secondary particle diameter can be determined, for example, by a sieving method.

[0085] The powdered PTFE preferably has an average primary particle diameter of 50 nm or more, since a sheet with higher strength and excellent homogeneity can be obtained. It is more preferably 100 nm or more, even more preferably 150 nm or more, and particularly preferably 200 nm or more. The larger the average primary particle diameter of PTFE, the more effectively the increase in paste extrusion pressure can be suppressed when the powder is used for paste extrusion molding, resulting in excellent moldability. The upper limit is not particularly limited, but may be 500 nm. From the viewpoint of productivity in the polymerization process, it is preferably 350 nm.

[0086] The average primary particle diameter can be determined by preparing a calibration curve of the transmittance of 550 nm projected light per unit length of an aqueous dispersion of PTFE obtained by polymerization, the polymer concentration of which is adjusted to 0.22% by mass, and the average primary particle diameter determined by measuring the unidirectional diameter in a transmission electron microscope photograph, and measuring the transmittance of the aqueous dispersion to be measured, and then using the calibration curve.

[0087] The PTFE particles used in the present disclosure may have a core-shell structure. Examples of PTFE particles having a core-shell structure include modified polytetrafluoroethylene, which contains a core of high molecular weight polytetrafluoroethylene and a shell of lower molecular weight polytetrafluoroethylene or modified polytetrafluoroethylene. Examples of such modified polytetrafluoroethylene include the polytetrafluoroethylene described in JP-A-2005-527652.

[0088] The inorganic particles treated with two or more reactive silane coupling agents are preferably present in an amount of 40% by mass or more relative to the total amount of the composition. This amount is preferable in that it can maintain a low dielectric constant, a low dielectric tangent, and a low transmission loss while reducing the linear expansion coefficient, and also provides good sheet processability. The amount is more preferably 45% by mass or more, and even more preferably 50% by mass or more. The upper limit of the amount of inorganic particles is not particularly limited, but is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less.

[0089] When the inorganic particles treated with the reactive silane coupling agent of above-mentioned two or more kinds are the above-mentioned (1), the ratio of the two kinds of inorganic particles treated with the silane coupling agent having reactive groups that react with each other can be appropriately set, taking into consideration the treatment amount of each reactive silane coupling agent.For example, when the treatment amount of the reactive silane coupling agent is about the same, the ratio of the two kinds of inorganic particles treated with the silane coupling agent having reactive groups that react with each other is preferably 1:2 to 2:1 in mass ratio, or 1:2 to 2:1 in molar ratio, more preferably 1:1 in molar ratio.

[0090] In the composition of the present disclosure, when the inorganic particles treated with the two or more reactive silane coupling agents are (1) above, it is preferable that the amount of each reactive silane coupling agent treated is 0.050 to 3.0 mass% relative to the amount of each inorganic particle.

[0091] Furthermore, the ratio of the two or more reactive silane coupling agents in the composition, in terms of the ratio of two types of silane coupling agents having reactive groups that react with each other, is preferably a mass ratio of 1:2 to 2:1 or a molar ratio of 1:2 to 2:1, and more preferably a molar ratio of 1:1.

[0092] The composition of the present disclosure may contain components other than the fluororesin and treated inorganic particles, or may consist only of the fluororesin and treated inorganic particles. The content of components other than the fluororesin and treated inorganic particles is preferably 10 mass% or less based on the total amount of the composition. In particular, it is preferable for the composition to consist essentially of the fluororesin and treated inorganic particles. Note that "consisting essentially of the fluororesin and treated inorganic particles" means that the content of components other than the treated inorganic particles and the fluororesin is 3 mass% or less based on the total amount of the composition.

[0093] The components contained are not particularly limited, and examples thereof include fluorine-free thermosetting resins and thermoplastic resins. The composition of the present disclosure preferably does not contain glass fibers. The absence of glass fibers or glass fiber cloth has the advantages of making it possible to reduce the thickness of the sheet, making the sheet more flexible, and making it easier to use in applications where it is used in a bent state.

[0094] In the present disclosure, fillers other than the inorganic particles may be used as long as they do not impair the object of the present disclosure. The filler to be used is not particularly limited, and examples thereof include organic fillers selected from one or more of polyphenyl ester, polyphenylene sulfide, polyimide, polyether ether ketone, polyphenylene, polyamide, and wholly aromatic polyester resin. Two or more of these may also be used in combination.

[0095] The method for producing the composition of the present disclosure is not particularly limited and may be performed by a known method. For example, it can be obtained by mixing a fluororesin, treated inorganic particles, and other components as necessary. When the treated inorganic particles (1) or (4) are used, a pre-mixed mixture may be mixed with the fluororesin, or multiple treated inorganic particles may be mixed with the fluororesin when mixing with the fluororesin.

[0096] (Sheet) The composition of the present disclosure is preferably used to form a sheet. The present disclosure also relates to a sheet made of the composition. In addition, the sheet of the present disclosure preferably has at least one functional group selected from the group consisting of an amide group, an ester group, a β-aminoester group, a ureido group, a urethane group, an imide group, an ether group, a carbamide group, and a thiourethane group, which is formed from reactive groups of two or more reactive silane coupling agents.

[0097] The sheet of the present disclosure preferably has a coefficient of linear expansion (CTE) of 200 ppm / °C or less. A CTE within this range is preferred because it results in a sheet with low shrinkage and excellent dimensional stability. The upper limit is more preferably 150 ppm / °C, even more preferably 100 ppm / °C, and even more preferably 80 ppm / °C. The lower limit is preferably 10 ppm / °C, and more preferably 18 ppm / °C.

[0098] In this specification, the CTE is determined by performing TMA measurement using a TMA-7100 (manufactured by Hitachi High-Tech Science Corporation) in a tensile mode, using a fluororesin sheet cut into a length of 20 mm and a width of 5 mm as a sample piece, setting the distance between chucks at 10 mm, and applying a load of 49 mN at a heating rate of 2°C / min from 0 to 150°C, from the amount of displacement of the sample.

[0099] Furthermore, it is preferable that the CTE of the sheet of the present disclosure is 10 to 40 ppm / K lower than the CTE of a sheet containing inorganic particles treated with only one of the two or more reactive silane coupling agents used to treat the inorganic particles. The "CTE of a sheet containing inorganic particles treated with only one reactive silane coupling agent" refers to the largest CTE value among the CTEs of sheets obtained using inorganic particles treated with only one reactive silane coupling agent.

[0100] The sheet of the present disclosure preferably has a dielectric loss tangent of 0.0015 or less at 10 GHz. By setting the dielectric loss tangent within this range, it is possible to reduce the loss of electrical signals in the circuit. The dielectric loss tangent is more preferably 0.0012 or less, and even more preferably 0.0011 or less. On the other hand, the lower limit of the dielectric loss tangent is preferably 0.00001.

[0101] The sheet of the present disclosure preferably has a relative dielectric constant of 3.5 or less at 10 GHz. A dielectric constant within this range is preferable in that it has low dielectric loss. The upper limit of the relative dielectric constant is more preferably 3.2, and even more preferably 3.1. Meanwhile, the lower limit of the relative dielectric constant is preferably 2.0, and more preferably 2.5.

[0102] In this specification, the relative permittivity (Dk) and dielectric loss tangent (Df) at 10 GHz are values ​​determined by measuring Dk and Df at 25°C and 10 GHz using a split cylinder type permittivity / dielectric loss tangent measuring device (manufactured by EM Lab).

[0103] The sheet of the present disclosure preferably has a thickness of 5 to 250 μm. The lower limit of the thickness is more preferably 15 μm or more, and even more preferably 30 μm or more. The upper limit of the thickness is more preferably 230 μm or less, and even more preferably 200 μm or less. The thickness can be selected taking into consideration the balance between the electrical properties and linear expansion coefficient of the laminate.

[0104] (Method for manufacturing a sheet) The sheet of the present disclosure can be obtained, for example, by forming a film of a composition obtained by mixing the above-mentioned fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents, followed by firing. The present disclosure also provides a method for manufacturing a sheet, characterized by forming a film of a composition obtained by mixing a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents, followed by firing. The method for forming the film is not particularly limited, and can be performed by paste extrusion molding, powder rolling molding, etc.

[0105] The specific methods for the paste extrusion molding and powder rolling molding are not particularly limited, but the following describes general methods.

[0106] (Paste extrusion molding) The method for producing the sheet may include, for example, a step (1a) of mixing a powdered fluororesin obtained using a hydrocarbon surfactant, inorganic particles, and an extrusion aid, a step (1b) of paste extrusion molding the resulting mixture, a step (1c) of rolling the extrudate obtained by extrusion molding, a step (1d) of drying the rolled sheet, and a step (1e) of firing the dried sheet to obtain a molded product. The paste extrusion molding can also be performed by adding conventional additives such as pigments and fillers to the fluororesin and treated inorganic particles.

[0107] The extrusion aid is not particularly limited, and any commonly known extrusion aid can be used, such as hydrocarbon oil.

[0108] In the above step (1e), the baking temperature is preferably 200 to 400°C, and the baking time is preferably 1 to 60 minutes. As described above, when the sheet is baked, the reactive groups of two or more types of reactive silane coupling agents react with each other, and new functional groups are generated. Alternatively, the reaction between the reactive groups of two or more types of reactive silane coupling agents may be carried out not only during baking of the sheet, but also by subjecting the sheet to thermal processing, etc. In the case of other processing, the temperature is preferably 200 to 400°C.

[0109] (Powder Rolling Molding) The sheet can also be formed by powder rolling molding. Powder rolling molding is a method in which a powdered fluororesin is fibrillated by applying shear force, thereby forming it into a sheet. It is preferable to then include a step of calcining the mixture to obtain a molded product. More specifically, the sheet can be obtained by a production method including, for example, the following steps: (1) applying shear force while mixing a raw material composition containing a fluororesin and treated inorganic particles; (2) forming the mixture obtained by step (1) into a bulk shape; (3) rolling the bulk mixture obtained by step (2) into a sheet shape; and (4) calcining the sheet-like product obtained above at 200 to 400°C for 1 to 60 minutes. Note that step (2) may be omitted.

[0110] In powder rolling molding, when the sheet is fired, the reactive groups of two or more types of reactive silane coupling agents react with each other, and new functional groups are generated. Alternatively, the reaction between the reactive groups of two or more types of reactive silane coupling agents may be carried out not only during firing, but also by other processes such as thermal processing of the sheet. In other processes, the temperature is preferably 200 to 400°C.

[0111] When producing a sheet by the above-mentioned powder rolling molding method, it is preferable to form a film of a composition that does not contain any liquid components and is essentially composed of a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents, and then bake the film. Note that "essentially composed of a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents" means that the content of components other than the fluororesin and the inorganic particles is 3 mass% or less based on the total amount of the composition. In particular, it is preferable to mix only the fluororesin and the treated inorganic particles and then mold the mixture.

[0112] The sheet obtained by the above method may be subjected to a surface treatment on one or both sides. Fluororesin is generally a material that is difficult to adhere to copper foil. Therefore, the sheet may be subjected to a surface treatment to improve lamination properties. Such surface treatments are generally known to involve increasing the amount of oxygen atoms on the resin surface.

[0113] The specific method of the surface treatment is not particularly limited, and any known method can be used. Conventional discharge treatments such as plasma discharge treatment, corona discharge treatment, glow discharge treatment, and sputtering treatment can be used as the surface treatment of the sheet. Among these, plasma treatment is preferred.

[0114] The sheet of the present disclosure obtained as described above can be suitably used as a sheet for a circuit board by laminating it with other substrates. The present disclosure also provides a metal laminate having a metal layer and the above sheet as essential layers. For example, a laminate may be obtained by adhering a metal foil to one or both sides of the above sheet.

[0115] The metal layer is preferably copper foil. The copper foil preferably has a surface roughness (Rz) of 2.0 μm or less. When the surface roughness (Rz) is 2.0 μm or less, the interface between the copper foil and the fluororesin sheet becomes smooth, the metal interface conductivity is high, and transmission loss is low, which is preferable. The copper foil only needs to have an Rz of 2.0 μm or less on at least the surface that adheres to the above-mentioned sheet, and the Rz of the other surface is not particularly limited.

[0116] The Rz is the sum of the highest point (maximum peak height: Rp) and the deepest point (maximum valley depth: Rv). The Rz is the ten-point average roughness defined in JIS-B0601. In this specification, the Rz is a value measured using a surface roughness meter (product name: Surfcom 470A, manufactured by Tokyo Seiki Co., Ltd.) with a measurement length of 4 mm.

[0117] The copper foil preferably has a surface roughness (Rq) of 0.01 to 0.15 μm. An Rq within the above range is preferable because it can increase the metal interface conductivity and effectively reduce transmission loss. The copper foil may have an Rq of 0.01 to 0.15 μm on at least the surface that adheres to the sheet, and the Rq of the other surface is not particularly limited. The Rq of the surface that adheres to the sheet is more preferably 0.015 to 0.1 μm, and even more preferably 0.03 to 0.08 μm. The Rq is the root-mean-square height. In this specification, the Rq is a value measured using a stylus-type surface roughness tester (product name: SE600A, manufactured by Kosaka Laboratory Co., Ltd.) with a measurement length of 4 mm.

[0118] The thickness of the copper foil is not particularly limited, but is preferably 1 to 100 μm, more preferably 5 to 50 μm, and even more preferably 9 to 35 μm.

[0119] The copper foil is not particularly limited, and specific examples include rolled copper foil and electrolytic copper foil.

[0120] The copper foil having an Rz of 2.0 μm or less and / or an Rq of 0.01 to 0.15 μm is not particularly limited, and commercially available foils can be used, such as electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm / Rq 0.05 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.).

[0121] The copper foil may be surface-treated to increase the peel strength with the sheet of the present disclosure.

[0122] The surface treatment is not particularly limited, but may be a silane coupling treatment, a plasma treatment, a corona treatment, a UV treatment, an electron beam treatment, or the like. The reactive functional group of the silane coupling agent is not particularly limited, but from the viewpoint of adhesion to a resin substrate such as the fluororesin sheet of the present disclosure, it is preferable that the reactive functional group has at least one selected from an amino group, a (meth)acrylic group, a mercapto group, and an epoxy group at the terminal. Furthermore, the hydrolyzable group is not particularly limited, but may include alkoxy groups such as a methoxy group and an ethoxy group. The copper foil used in the present disclosure may have a rust-preventive layer (such as an oxide film such as chromate), a heat-resistant layer, or the like formed thereon.

[0123] The surface-treated copper foil having a surface treatment layer of the above-mentioned silane compound on the copper foil surface can be produced by preparing a solution containing the silane compound and then surface treating the copper foil with this solution.

[0124] The copper foil may have a roughened layer on its surface from the viewpoint of improving adhesion to a resin substrate, etc. If the roughened layer may deteriorate the performance required in the present disclosure, the amount of roughening particles electrodeposited on the copper foil surface may be reduced as needed, or the copper foil may not be roughened at all.

[0125] In order to improve various properties, one or more layers selected from the group consisting of a heat-resistant layer, a rust-proofing layer, and a chromate-treated layer may be provided between the copper foil and the surface-treated layer. These layers may be a single layer or multiple layers.

[0126] The metal laminate of the present disclosure may further include a layer other than the metal layer and the sheet of the present disclosure. The layer other than the metal layer and the sheet of the present disclosure is preferably a layer made of at least one resin selected from the group consisting of polyimide, modified polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, modified polyphenylene ether, polyphenylene ether, and polybutadiene.

[0127] The resin layer, which is a layer other than the metal layer and the sheet of the present disclosure, may contain reinforcing fibers. The reinforcing fibers are not particularly limited, but for example, glass cloth, particularly low dielectric type, is preferred.

[0128] The metal layer and layers other than the sheet of the present disclosure preferably have a thickness of 12.5 to 260 μm.

[0129] In the metal laminate of the present disclosure, the metal layer may be formed on one or both sides of the rolled sheet. Examples of methods for forming the metal layer include laminating (adhering) copper foil to the surface of the rolled sheet, vapor deposition, and plating. For example, a method for laminating the copper foil includes a heat press method. The heat press temperature may be between the melting point of the sheet minus 150°C and the melting point of the sheet plus 40°C. The heat press time is, for example, 1 to 30 minutes.

[0130] For example, a suitable method for producing a copper clad laminate is to laminate the sheet of the present disclosure and copper foil, heat the laminate at 180 to 390°C, and press-form the laminate under a pressure of 0.5 to 5 MPa in a vacuum or in an inert gas atmosphere. By press-forming under such conditions, the sheet of the present disclosure does not deteriorate and can be bonded to the copper foil.

[0131] (Film) In the present disclosure, a film may be formed using the composition of the present disclosure. The present disclosure also relates to a film made of a composition containing a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents. The film of the present disclosure can be obtained by applying a dispersion of a powder containing a fluororesin and the treated inorganic particles in a liquid medium onto a substrate, drying the dispersion, and then heating the applied dispersion.

[0132] The metal laminate of the present disclosure is not particularly limited in its application and is used as a circuit board. The present disclosure also relates to a circuit board having the above-mentioned metal laminate. A circuit board is a plate-shaped component that electrically connects electronic components such as semiconductors and capacitor chips while simultaneously arranging and fixing them in a limited space. The configuration of a circuit board formed from the derivative or copper-clad laminate of the present disclosure is not particularly limited. The circuit board may be any of a rigid board, a flexible board, and a rigid-flexible board. The circuit board may be any of a single-sided board, a double-sided board, and a multilayer board (such as a build-up board). It is particularly suitable for use in flexible boards and rigid boards. When the sheet of the present disclosure does not contain glass fiber or a cloth made of glass fiber, it is suitable for use in flexible boards. It is particularly suitable for use as a printed circuit board for high frequencies of 10 GHz or more.

[0133] In this disclosure, a high-frequency circuit does not simply refer to a circuit that transmits only high-frequency signals, but also includes circuits that also have transmission lines on the same plane that transmit signals other than high-frequency signals, such as a transmission line that converts a high-frequency signal into a low-frequency signal and outputs the generated low-frequency signal to the outside, or a transmission line that supplies power to drive high-frequency compatible components. The circuit board can also be used as a circuit board for antennas, filters, etc. The present disclosure also relates to antennas formed from the circuit board. It is particularly suitable for use as a millimeter-wave antenna for mobility applications such as automobiles and aircraft.

[0134] The circuit board is not particularly limited, and can be produced by a general method using the above-mentioned metal laminate.

[0135] The sheet and metal laminate of the present disclosure are used as electrical and electronic components, such as antennas used in electronic devices and communication devices, such as ETC, GPS, wireless LAN, and mobile phones, high-speed transmission connectors, CPU sockets, millimeter-wave and quasi-millimeter-wave radars, such as collision prevention radars, RFID tags, capacitors, inverter parts, cable coating materials, insulating materials for secondary batteries, such as lithium-ion batteries, and speaker diaphragms.

[0136] Examples of high-speed communication compatible substrates include base station antenna substrates, antenna distribution substrates, substrates for RRH (Remote Radio Head), which is the radio part of a wireless base station, substrates for the control unit or baseband unit (BBU: Base Band Unit) of a wireless base station, transceiver substrates for high-speed communication, substrates for RNC (Radio Network Controller), substrates for high-speed transmitters, substrates for high-speed receivers, substrates for high-speed signal multiplexing circuits, substrates for Wi-Fi using the 60 GHz band, and substrates for data transfer used in data center servers. Examples of high-speed communication compatible substrates include antenna substrates, such as substrates for massive MIMO (massive multiple-input multiple-output) antennas aimed at high-capacity communication required by standards from 5G onwards. Further examples include receiving antennas for microwave spatial transmission wireless power supply. The sheet of the present disclosure has good adhesion to unroughened copper foil, which has low transmission loss. Therefore, when an antenna is obtained by processing a copper clad laminate containing the sheet of the present disclosure and unroughened copper foil, the gain is improved, making it particularly suitable for antennas.

[0137] The sheet of the present disclosure can be used not only as an insulator for a substrate but also as an insulator for a signal line coating material, for example, as an insulating coating material (e.g., insulating tube) for a waveguide for transmitting high-speed signals, a QSFP cable for a high-speed LAN, a coaxial cable for high-speed communication (e.g., an SFP+ cable, a QSFP+ cable, etc.), a coaxial cable for low loss, etc.

[0138] When using such high frequencies, materials used in electrical components such as connectors and communication devices such as casings are required to have stable electrical properties such as a low relative permittivity (εr) and a low dielectric loss tangent (tanδ). The sheet of the present disclosure can also be used as an insulating material for such materials.

[0139] The sheet of the present disclosure can also be used as an insulating material for connector printed wiring boards that require soldering. Because the sheet of the present disclosure has excellent heat resistance, problems are unlikely to occur even at high temperatures during soldering.

[0140] In dielectric waveguides, materials with low dielectric loss are required to transmit high-frequency millimeter waves or submillimeter waves with low loss. The sheet of the present disclosure can also be used as an insulating material for dielectric waveguides that transmit millimeter waves, submillimeter waves, etc. Examples of dielectric waveguides include cylindrical dielectric waveguides, rectangular dielectric waveguides, elliptical dielectric waveguides, tubular dielectric waveguides, image waveguides, insulator image waveguides, trapped image waveguides, rib guides, strip dielectric waveguides, inverted strip waveguides, H guides, and nonradiative dielectric waveguides (NRD guides).

[0141] In this disclosure, mobility refers to all means and methods related to movement and transportation, including automobiles in general, such as private cars, buses, taxis, and trucks, as well as two-wheeled vehicles such as motorcycles, bicycles, and mopeds, trains, senior cars, and compact one-seater personal mobility vehicles. Furthermore, mobility is not necessarily limited to vehicles that move on land, but may also be vehicles that move in the air or underwater.

[0142] The laminate for a circuit board may be formed by laminating a metal layer, the above-mentioned sheet, and a substrate layer. The substrate layer is not particularly limited, but examples thereof include a fabric layer made of glass fiber and a resin film layer.

[0143] The resin film used as the substrate layer is preferably a heat-resistant resin film or a thermosetting resin film. Examples of heat-resistant resin films include polyimide, modified polyimide, liquid crystal polymer, and polyphenylene sulfide. Examples of thermosetting resins include those containing epoxy resin, bismaleimide, polyphenylene oxide, modified polyphenylene ether, polyphenylene ether, and polybutadiene. The heat-resistant resin film and the thermosetting resin film may contain reinforcing fibers. While the reinforcing fibers are not particularly limited, glass cloth, particularly low-dielectric type fibers, are preferred.

[0144] The dielectric properties, linear expansion coefficient, water absorption coefficient, and other properties of the heat-resistant resin film and the thermosetting resin film are not particularly limited, but for example, the dielectric constant at 20 GHz is preferably 3.8 or less, more preferably 3.4 or less, and even more preferably 3.2 or less. The dielectric loss tangent at 20 GHz is preferably 0.0030 or less, more preferably 0.0025 or less, and even more preferably 0.0020 or less. The linear expansion coefficient is preferably 100 ppm / °C or less, more preferably 70 ppm / °C or less, and even more preferably 40 ppm / °C or less. The water absorption coefficient is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less.

[0145] When the sheet and metal laminate of the present disclosure are laminated with a substrate layer such as a resin film layer, the metal laminate can be laminated by adhering the sheet layer side of the present disclosure of the metal laminate to the substrate layer. In this case, the sheet layer side of the metal laminate of the present disclosure may be surface-treated before lamination to improve adhesion performance. The surface treatment here is not particularly limited, and examples include the above-mentioned plasma treatment.

[0146] In the laminate, the stacking order and manufacturing method of the metal layer, substrate, and sheet of the present disclosure described above are not particularly limited, and a layer configuration according to the purpose can be used. Specific examples of the stacking order include a substrate layer / sheet / metal layer, a metal layer / sheet / substrate layer / sheet / metal layer, and a metal layer / substrate layer / sheet / substrate layer / metal layer. Furthermore, other layers can be included as needed.

[0147] The present disclosure will be specifically described below based on examples. However, the present invention is not limited to the following examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0148] (Example 1) (Powder Rolling Molding) PTFE powder (average particle size: 500 μm, apparent density: 460 g / L, standard specific gravity: 2.17) and two types of silica particles treated with reactive silane coupling agents having different reactive groups were weighed in the proportions shown in Table 1, and stirred twice for 30 seconds at room temperature with a Wonder Crusher at a setting of 6. The resulting mixture was rolled with two rolls (roll gap: set to 100 μm, roll temperature: 100° C.) to obtain a sample with a film thickness of 150 μm, and then baked at 360° C. for 15 minutes to obtain a sheet. The silica particles treated with a reactive silane coupling agent used were silica particles treated with 3-aminopropyltriethoxysilane (treatment amount 1% by mass) (manufactured by Admatechs: SC6500-SQ, average particle size: 2.1 μm) and silica particles treated with 3-isocyanatepropyltriethoxysilane (treatment amount 1% by mass) (manufactured by Admatechs: SC6500-SQ, average particle size: 2.1 μm). The obtained sheets were evaluated based on the following criteria.

[0149] (Comparative Examples 1a to 1c) Sheets were obtained in the same manner as in Example 1, except that one type of silica particles treated with a silane coupling agent shown in Table 1 was used. Each of the obtained sheets was evaluated based on the following criteria.

[0150] (Examples 2 to 6) Sheets were obtained in the same manner as in Example 1, except that two types of silica particles treated with a reactive silane coupling agent shown in Table 1 were used. In addition, for Example 6, a sheet was obtained in the same manner as in Example 1, except that silica particles treated with a reactive silane coupling agent in the treatment amount shown in Table 1 were used. Each of the obtained sheets was evaluated based on the following criteria.

[0151] (Comparative Examples 2a, 3a, 4a, 6a, 6b) Sheets were obtained in the same manner as in Example 1, except that silica particles treated with the silane coupling agents shown in Table 1 were used. For Comparative Examples 6a and 6b, sheets were obtained in the same manner as in Example 1, except that two types of silica particles treated with the reactive silane coupling agents in the treatment amounts shown in Table 1 were used. Each of the obtained sheets was evaluated based on the following criteria.

[0152] (Comparative Examples 5a and 5b) Sheets were obtained in the same manner as in Example 1, except that silica particles treated with the silane coupling agents shown in Table 1 were used. In Comparative Example 5a, two types of silica particles treated with reactive silane coupling agents each having different reactive groups were used. Each obtained sheet was evaluated based on the following criteria.

[0153] Example 7 (Paste Extrusion Molding) PTFE powder (average particle size: 500 μm, apparent density: 460 g / L, standard specific gravity: 2.17) and two types of silica particles treated with the reactive silane coupling agent used in Example 1 were weighed out in predetermined amounts and mixed in a mixer in the presence of dry ice. The temperature during mixing was -10°C or below. 21% oil (Isopar H) was added to the resulting mixed powder, mixed, and aged for approximately 5 hours. The aged composition was preformed under a pressure of 3 MPa, and the preformed compact was extruded at 40°C and 50 mm / min to obtain an extruded sample. The extruded sample was rolled using two rolls (roll gap: set to 500-80 μm) to obtain a sample with a film thickness of 125 μm. This sample was dried at 200°C for 2 hours and then baked at 360°C for 15 minutes to obtain a sheet. The resulting sheet was evaluated based on the following criteria.

[0154] Example 8 A sheet was obtained in the same manner as in Example 5, except that silica particles treated with 3-aminopropyltriethoxysilane (treatment amount 1% by mass) (manufactured by Admatechs: SC2500-SQ, average particle size: 0.5 μm) were used instead of silica particles treated with 3-aminopropyltriethoxysilane (treatment amount 1% by mass) (manufactured by Admatechs: SC6500-SQ, average particle size: 2.1 μm). The obtained sheet was evaluated based on the following criteria.

[0155] [Sheet Thickness] Measured using a micrometer.

[0156] [Dielectric Constant (Dk) and Dielectric Loss Tangent (Df) of Sheet] The dielectric constant and dielectric loss tangent at 25° C. and 10 GHz were measured using a split cylinder type dielectric constant / dielectric loss tangent measuring device (manufactured by EM Lab).

[0157] [Coefficient of Linear Expansion (CTE)] TMA measurement was carried out in a tensile mode using a TMA-7100 (manufactured by Hitachi High-Tech Science Corporation). A fluororesin sheet cut into a length of 20 mm and a width of 5 mm was used as a sample piece, and the distance between chucks was set to 10 mm. The coefficient of linear expansion was determined from the displacement of the sample at a heating rate of 2°C / min from 0 to 150°C while applying a load of 49 mN.

[0158] [Evaluation Criteria for the Effect of Reducing the Coefficient of Linear Expansion (CTE)] The CTE of the sheet of each Example was compared with the CTE of the sheet using silica particles treated with only one of the two reactive silane coupling agents used in each Example, which showed the highest value, and the difference was calculated. Furthermore, in Comparative Examples 5a, 1a, and 5b, the CTE of Comparative Example 5a was compared with the CTE of Comparative Example 1a and Comparative Example 5b, which showed the highest value, and the difference was calculated. Furthermore, in Example 7, the CTE of Example 7 was compared with the CTE of Comparative Example 1a and Comparative Example 1b, which showed the highest value, and the difference was calculated. Furthermore, in Example 8, the CTE of Example 8 was compared with the CTE of Comparative Example 4a and the CTE of a sheet using only one type of silica particles (manufactured by Admatechs Co., Ltd.: SC2500-SQ, average particle size: 0.5 μm) treated with 3-aminopropyltriethoxysilane (treatment amount 1% by mass), which showed the highest value, and the difference was calculated.

[0159] [Confirmation of bonding] The sheets of Comparative Example 1a, Comparative Example 4a, and Example 5 were each analyzed by IR (transmission method) and compared. Comparative Example 1a: No imide group peak Comparative Example 4a: No imide group peak Example 5: Imide group peak present (1784, 1710 cm-1) As described above, it was found that in the sheet of Example 5, two types of silane coupling agents reacted to form imide groups.

[0160] The results are shown in Tables 1 and 2.

[0161]

[0162]

[0163] From the above results, it can be seen that the sheets of the examples have low CTE, low Dk and Df, and can be suitably used as circuit board materials. Furthermore, when inorganic particles treated with two types of silane coupling agents are used, as in the sheets of the examples, it is clear that the CTE is significantly reduced compared to when only one type is treated, or when a silane coupling agent having a functional group is used. Furthermore, from the results of Comparative Example 5a, Comparative Example 1a, and Comparative Example 5b, it was found that the effect of reducing the CTE of the sheet cannot be obtained unless the combination of reactive groups that react with each other is used.

[0164] The sheet of the present disclosure can be suitably used in metal laminates for circuit boards.

Claims

1. A composition comprising a fluororesin and inorganic particles treated with two or more reactive silane coupling agents.

2. The composition according to claim 1, wherein the inorganic particles treated with two or more types of reactive silane coupling agents are any one of the following (1) to (3), or a combination thereof: (1) A combination of inorganic particles each treated separately with a different type of reactive silane coupling agent, (2) Inorganic particles treated in combination with two or more types of reactive silane coupling agents, or (3) Inorganic particles treated with at least one type of reactive silane coupling agent and then further treated with at least another type of reactive silane coupling agent.

3. The composition according to claim 1 or 2, wherein the inorganic particles are inorganic particles containing silica as an essential component.

4. The composition according to any one of claims 1 to 3, wherein the fluororesin is a perfluororesin.

5. The composition according to claim 4, wherein said perfluororesin is polytetrafluoroethylene.

6. The composition according to any one of claims 1 to 5, wherein the content of the inorganic particles treated with two or more types of reactive silane coupling agents is 40 mass % or more of the total composition.

7. The composition according to any one of claims 1 to 5, wherein the content of the inorganic particles treated with two or more types of reactive silane coupling agents is 80 mass % or less of the total composition.

8. The composition according to claim 2, wherein the inorganic particles treated with two or more types of reactive silane coupling agents are (1), and the amount of each reactive silane coupling agent used is 0.050 to 3.0 mass % relative to the amount of the inorganic particles to be treated.

9. The composition according to any one of claims 1 to 8, wherein the combination of two or more reactive silane coupling agents is a combination in which reactive groups of the reactive silane coupling agents react with each other to form at least one functional group selected from the group consisting of an amide group, an ester group, a β-aminoester group, a ureido group, a urethane group, an imide group, an ether group, a carbamide group, and a thiourethane group.

10. The composition according to any one of claims 1 to 8, wherein the reactive groups of the two or more reactive silane coupling agents are each selected from the group consisting of amino groups, epoxy groups, acrylic groups, methacrylic groups, isocyanate groups, thiol groups, carboxylic acid groups, and acid anhydride groups, and the composition contains a combination of reactive groups that react with each other.

11. The composition according to any one of claims 1 to 8, wherein the combination of reactive groups of the two or more reactive silane coupling agents is at least one selected from the group consisting of an amino group and an acid anhydride group, an amino group and an acrylic group, an amino group and a methacrylic group, an amino group and an isocyanate group, an acid anhydride group and an isocyanate group, an epoxy group and an acid anhydride group, an epoxy group and an acrylic group, an epoxy group and a methacrylic group, an epoxy group and an isocyanate group, an epoxy group and an amino group, and a thiol group and an isocyanate group.

12. The composition according to any one of claims 1 to 8, wherein the two or more reactive silane coupling agents are each selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-isocyanatepropyltriethoxysilane, and 3-trimethoxysilylpropylsuccinic anhydride, and the composition comprises a combination of reactive silane coupling agents having reactive groups that react with each other.

13. The composition according to any one of claims 1 to 8, wherein the combination of reactive silane coupling agents is at least one of 3-aminopropyltriethoxysilane and 3-isocyanatepropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride, or 3-isocyanatepropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride.

14. The composition according to claim 1 or 2, wherein the fluororesin is polytetrafluoroethylene, the inorganic particles are silica, and the combination of the reactive silane coupling agents is at least one of 3-aminopropyltriethoxysilane and 3-isocyanatepropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride, or 3-isocyanatepropyltriethoxysilane and 3-trimethoxysilylpropylsuccinic anhydride.

15. A sheet or film comprising the composition according to any one of claims 1 to 14.

16. The sheet or film according to claim 15, which has at least one functional group selected from the group consisting of an amide group, an ester group, a β-aminoester group, a ureido group, a urethane group, an imide group, an ether group, a carbamide group, and a thiourethane group, formed from reactive groups of the two or more reactive silane coupling agents.

17. The sheet or film according to claim 15 or 16, which has a coefficient of linear thermal expansion (CTE) that is 10 to 40 ppm / K lower than the coefficient of linear thermal expansion (CTE) of a sheet or film containing inorganic particles treated with only one of the two or more reactive silane coupling agents.

18. The sheet or film according to any one of claims 15 to 17, which has a coefficient of linear expansion (CTE) of 200 ppm / K or less.

19. A method for producing a sheet or film according to any one of claims 15 to 18, characterized in that a composition containing a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents is molded and then processed.

20. A method for producing a sheet or film according to any one of claims 15 to 18, characterized in that a composition consisting essentially of a fluororesin and inorganic particles treated with two or more types of reactive silane coupling agents is molded and then processed.

21. A filler for a resin composition for electronic materials, containing inorganic particles treated with two or more types of reactive silane coupling agents whose reactive groups react with each other.

22. A filler for a resin composition for electronic materials according to claim 21, wherein the combination of two or more reactive silane coupling agents is a combination in which reactive groups react with each other to form at least one functional group selected from the group consisting of an amide group, an ester group, a ureido group, a urethane group, an imide group, an ether group, a carbamide group, and a thiourethane group.

23. A metal laminate comprising a metal layer and the sheet or film according to any one of claims 15 to 18 as essential layers.

24. The metal laminate of claim 23, wherein the metal layer is copper foil.

25. A circuit board comprising the metal laminate according to claim 23 or 24.