Composition, paste-like composition, sheet, metal-clad laminate, circuit board, and method for producing sheet

Abstract

Provided are: a composition having improved molding extrudability; and a sheet obtained from said composition. The composition contains a polytetrafluoroethylene resin and a filler. The surface of the filler is treated with a silane coupling agent having a functional group that includes a nitrogen atom. The treatment amount thereof is not less than 0.1 mass% and less than 1.0 mass% relative to the weight of the filler following the surface treatment. When paste extrusion molding is carried out under condition 1 below, the extrusion pressure is 10 N·mm-2 or less. <Condition 1> Paste extrusion molding is carried out using a method comprising placing 70.0 g of a powder, which has been left for 2 hours at room temperature and comprises a composition containing a polytetrafluoroethylene resin and a filler, and 13.3 g of a hydrocarbon oil as a processing aid in a plastic container having a capacity of 250 mL, mixing for 3 minutes, leaving for 2 hours in a constant temperature tank at 25ºC, and carrying out paste extrusion by passing the mixture through a die having a cylinder diameter of 30 mm, an outlet port diameter of 5 mm, a reduction ratio of 36, a land length of 27.5 mm and an introduction angle of 48° at an extrusion speed of 50 mm / min and a temperature of 40ºC, thereby obtaining a bead extrusion molded product.

Description

Composition, paste-like composition, sheet, metal-clad laminate, circuit board, and method for producing sheet

[0001] The present disclosure relates to a composition, a paste-like composition, a sheet, a metal clad laminate, a circuit board, and a method for producing the sheet.

[0002] There is a demand for high-frequency printed wiring boards with low transmission loss. The use of fluororesin films in such high-frequency printed wiring boards is known (see, for example, Patent Document 1). Patent Documents 2 and 3 also describe the use of fluororesins containing fillers as wiring board materials.

[0003] Furthermore, Patent Document 4 discloses that a fluororesin composition in which spherical silica particles are blended with a fluororesin is used for a circuit board.

[0004] JP 2015-8260 JP 63-259907 A JP 2022-510017 WO 2020 / 145133

[0005] An object of the present disclosure is to provide a composition having improved molding extrudability and a sheet obtained therefrom.

[0006] The present disclosure relates to a composition comprising a polytetrafluoroethylene resin and a filler, wherein the surface of the filler is treated with a silane coupling agent having a functional group containing a nitrogen atom, and the amount of the treatment is 0.1 mass % or more and less than 1.0 mass % based on the weight of the filler after the surface treatment, and the composition is paste extrusion molded under the following condition 1 at an extrusion pressure of 10 N mm －２ The composition is characterized by the following: <Condition 1> Paste extrusion molding is performed by placing 70.0 g of powder made of a composition containing polytetrafluoroethylene resin and a filler, which had been left at room temperature for 2 hours, and 13.3 g of hydrocarbon oil as a processing aid in a 250 mL plastic container, mixing them for 3 minutes, leaving them in a constant temperature bath at 25°C for 2 hours, and then extruding the paste at an extrusion rate of 50 mm / min at 40°C through a die with a cylinder diameter of 30 mm, an outlet diameter of 5 mm, a reduction ratio of 36, a land length of 27.5 mm, and an introduction angle of 48° to obtain a bead extrusion molded product.

[0007] The filler is preferably an inorganic filler. The inorganic filler is preferably silica. The composition preferably contains 10 to 70 mass % of the silica. The silica is preferably a filler having a dielectric loss tangent (measured at 10 GHz) / (surface area of ​​the silica (m ２ / g)) is preferably 0.00001 to 0.00035.

[0008] The silane coupling agent is preferably a surface treatment agent having an isocyanate group or an amino group, and is preferably 3-isocyanatepropyltriethoxysilane or 3-aminopropyltriethoxysilane.

[0009] The composition preferably contains 10 to 80% by mass of filler and 20 to 90% by mass of polytetrafluoroethylene resin. A sheet obtained by rolling the composition preferably has a dielectric loss tangent of 0.01 or less at 25°C and 10 GHz. The composition preferably contains 30 to 50% by mass of polytetrafluoroethylene resin and 50 to 70% by mass of filler, and the amount of silane coupling agent used is 0.1% to 0.9% by mass of the filler weight after surface treatment. The filler is preferably silica, and the silane coupling agent preferably has an isocyanate group or an amino group.

[0010] The present disclosure relates to a composition containing a polytetrafluoroethylene resin and a filler, wherein the composition is paste extruded under the following condition 1 at an extrusion pressure of 10.0 N mm －２The composition is also a composition having a peel strength of 3 N / cm or more when subjected to a peel strength test under Condition 2 below. <Condition 1> Paste extrusion molding is performed by placing 70.0 g of a powder composed of a composition containing polytetrafluoroethylene resin and a filler, which has been left at room temperature for 2 hours, and 13.3 g of a hydrocarbon oil as a processing aid into a 250 mL plastic container, mixing for 3 minutes, and leaving the mixture in a constant temperature bath at 25°C for 2 hours. The paste is then extruded at an extrusion rate of 50 mm / min and a temperature of 40°C through a die with a cylinder diameter of 30 mm, an outlet diameter of 5 mm, a reduction ratio of 36, a land length of 27.5 mm, and an introduction angle of 48° to obtain a bead extrusion molded product. <Condition 2> A 90-degree peel test, which is a peel strength test, is performed using a method in accordance with JIS C 6481-1996.

[0011] The present disclosure also provides a paste-like composition comprising the above-described composition and a processing aid. The processing aid is preferably a petroleum-based solvent. The present disclosure also provides a paste-like composition comprising the above-described composition and a processing aid that is a petroleum-based solvent. The paste-like composition of the present disclosure preferably contains 15 to 25 parts by mass of the processing aid relative to the total amount of the polytetrafluoroethylene resin and the filler.

[0012] The present disclosure also provides a sheet made from the above-described composition and having a thickness of 0.1 to 2 mm. The sheet is preferably made of an insulating material.

[0013] The present disclosure also relates to a metal clad laminate having a metal layer and the above-described sheet as essential layers. The metal layer is preferably copper foil. The present disclosure also relates to a circuit board characterized by having a sheet made from the above-described composition and a metal layer. The metal constituting the metal layer is preferably copper. The copper is preferably rolled copper or electrolytic copper. The circuit board is preferably a printed circuit board, a laminated circuit board, or a high-frequency board.

[0014] The present disclosure also provides a method for producing a sheet, comprising a step of rolling the composition.

[0015] The composition of the present disclosure has excellent extrusion moldability and can give a sheet with good performance.

[0016] The present disclosure will be described in detail below. In this disclosure, "room temperature" means "25°C." Many studies have been conducted on compositions containing fluororesins and fillers. Meanwhile, in the field of high-frequency printed wiring boards, increasingly high levels of performance, such as low dielectric constant, low loss, and low expansion, have been required in recent years. Therefore, it is necessary to improve these sheet properties by increasing the filler content.

[0017] However, in paste extrusion molding, when the amount of filler added is large, there is a problem that moldability deteriorates, and the sheet is prone to waviness, tearing, voids, etc. The present disclosure provides a composition that can solve these problems and can be used to mold a sheet with good performance.

[0018] This disclosure relates to a composition containing a polytetrafluoroethylene resin and a filler, wherein the surface of the filler is treated with a silane coupling agent having a functional group containing a nitrogen atom, and the amount of the treatment is 0.1% or more and less than 1.0% by mass based on the weight of the filler after the surface treatment, and the extrusion pressure when paste extrusion molding is performed according to the above condition 1 is 10 N mm －２ The composition is as follows:

[0019] (Filler) The filler used in the present disclosure is a filler treated with a silane coupling agent having a functional group containing a nitrogen atom. The present disclosure was completed by finding that a composition containing such a filler has excellent paste extrusion moldability.

[0020] Examples of the functional group containing a nitrogen atom include an amino group and an isocyanate group. These functional groups have polarity, and it is believed that the interaction between the filler and the fluororesin provides excellent effects.

[0021] Examples of silane coupling agents having an amino group include 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride. Examples of silane coupling agents having an isocyanate group include 3-isocyanatepropyltriethoxysilane and 3-isocyanatepropyltrimethoxysilane. Of these, 3-isocyanatepropyltriethoxysilane and 3-aminopropyltriethoxysilane are particularly preferred.

[0022] The filler of the present disclosure is treated with the above-mentioned specific silane coupling agent in an amount of 0.1 mass % or more and less than 1.0 mass % based on the weight of the filler after surface treatment. A treatment amount within this range is preferable in that the filler and the fluororesin interact with each other, resulting in good extrusion moldability.

[0023] The upper limit of the treatment amount is more preferably 0.9% by mass, and even more preferably 0.6% by mass.

[0024] In the present disclosure, the filler may be entirely treated with a silane coupling agent having a functional group containing a nitrogen atom, or may be partially combined with other treated fillers or untreated fillers. In this case, it is preferable that 0.05% by mass or more of the filler is treated with a silane coupling agent having a functional group containing a nitrogen atom. The content is more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more.

[0025] The filler that can be used in the present disclosure is not particularly limited, and examples thereof include organic fillers that are one or more selected from aramid fibers, polyphenyl esters, polyphenylene sulfide, polyimides, polyether ether ketones, polyphenylenes, polyamides, and wholly aromatic polyester resins, and inorganic fillers that are one or more selected from ceramics, talc, mica, aluminum oxide, zinc oxide, tin oxide, titanium oxide, silicon oxide, calcium carbonate, calcium oxide, magnesium oxide, potassium titanate, glass fibers, glass chips, glass beads, silicon carbide, calcium fluoride, boron nitride, barium sulfate, molybdenum disulfide, and potassium carbonate whiskers. Two or more of these may also be used in combination.

[0026] The filler is not particularly limited in shape, but is preferably a spherical filler, which is preferable because it is easy to process uniformly during drilling and has a small specific surface area and therefore low transmission loss.

[0027] Among these, inorganic fillers are preferred, silica is particularly preferred, and spherical silica particles are most preferred. Inorganic fillers are preferred because they have good extrusion moldability and provide a sheet with a low dielectric constant, low loss, and low expansion, and silica is particularly preferred.

[0028] The spherical filler means a particle whose 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.

[0029] The spherical filler used in the present disclosure preferably has 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 the volume is calculated from the smallest particle size. Furthermore, it is preferable that the D90 / D50 is 1.5 or more (even more preferably 1.6 or more). It is preferable that the D50 / D10 is 1.5 or more (even more preferably 1.6 or more). Furthermore, it is more preferable that the D50 is 5 μm or less. Since small-sized spherical silica particles can enter the gaps between large-sized spherical silica particles, excellent filling properties and high fluidity can be achieved. In particular, it is preferable that the particle size distribution has a higher frequency on the small particle size side compared to a Gaussian curve. The particle size can be measured using a laser diffraction / scattering particle size distribution analyzer. Furthermore, since coarse particles make it difficult to form a thin sheet, it is preferable that coarse particles having a particle size above a certain size have been removed using a filter or the like.

[0030] The spherical silica particles preferably have a water absorption of 1.0% or less, more preferably 0.5% or less. The water absorption is based on the mass of the silica particles 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.

[0031] Alternatively, the spherical silica particles can be measured using the above-mentioned methods after the fluororesin sheet is heated at 600°C for 30 minutes in an air atmosphere to burn off the fluororesin and the spherical silica particles are removed.

[0032] The spherical silica particles 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.).

[0033] The spherical filler has a dielectric loss tangent of (the filler measured at 10 GHz) / (the surface area of ​​the filler (m ２ / g)) is preferably 0.00001 to 0.00035.

[0034] The dielectric loss tangent of a filler is significantly affected by the polar functional groups on the surface. For example, in the case of silica, the amount of Si-OH groups on the surface affects the dielectric loss tangent. More specifically, the greater the amount of Si-OH groups on the surface, the greater the dielectric loss tangent of the filler. For this reason, in the present disclosure, it is preferable to reduce the amount of Si-OH on the surface.

[0035] From this viewpoint, (dielectric tangent of the filler measured at 10 GHz) / (surface area of ​​the filler (m ２ The ratio of (R / g) is an index showing the amount of surface polar functional groups per unit surface area of ​​the filler. The present inventors have found that when the amount of such surface polar functional groups is reduced to within the above-mentioned predetermined range, a fluororesin sheet having particularly excellent low dielectric constant, low loss, and low expansion can be obtained, and have completed the present disclosure.

[0036] (Dielectric loss tangent of the filler measured at 10 GHz) / (surface area of ​​the filler (m ２ In order to obtain a filler having a ratio of (R / g) within the above-mentioned range, it is necessary to select the filler and then perform a surface treatment. That is, the polar functional groups present on the filler surface are reacted by the surface treatment to reduce the amount of polar functional groups, thereby making it possible to obtain a filler having a ratio within the above-mentioned range. Such surface treatments are described in detail below.

[0037] (Dielectric tangent of the filler measured at 10 GHz) / (surface area of ​​the filler (m ２ The upper limit of the saturation coefficient (μm / g) is more preferably 0.00030, and even more preferably 0.00025.

[0038] In this disclosure, the dielectric loss tangent of the filler measured at 10 GHz was measured using a cylindrical cavity resonator and a network analyzer. A filler powder sample was filled into a quartz tube and loaded into the resonator. The characteristics of the resonator (resonance frequency and Q value) were obtained before and after inserting the sample, and the dielectric loss tangent was calculated from the results. This measurement method complies with the Japanese Industrial Standard JIS 2565 Microwave Ferrite Core Test Method, and measurements were performed in an environment of room temperature of 25°C and humidity of 40%.

[0039] In the present disclosure, the surface area (m ２ / g) is not particularly limited, but is preferably 1 to 10. Setting it within the above range is preferable in that the fluororesin sheet has a good balance between low loss and low linear expansion. The lower limit is more preferably 1.2, and even more preferably 1.5. The upper limit is more preferably 9, and even more preferably 7.

[0040] In the present disclosure, the surface area (m ２ / g) means the specific surface area, and is a value based on the BET method, and can be measured using a specific surface area measuring device such as a "Macsorb HM model-1208" (manufactured by MACSORB Corporation). When the fluororesin sheet of the present disclosure contains two or more types of fillers, the surface area measured for all of the blended fillers falls within the above-mentioned range.

[0041] (Filler Content) The filler content is preferably 10 to 80% by mass relative to the total amount of the composition. Setting the content within this range is preferable in that it is possible to obtain performance such as a low dielectric constant, low loss, and low expansion. The lower limit is more preferably 40% by mass, and even more preferably 50% by mass. The upper limit is more preferably 75% by mass, and even more preferably 70% by mass.

[0042] (Polytetrafluoroethylene Resin) The composition of the present disclosure contains polytetrafluoroethylene resin (hereinafter, sometimes referred to as PTFE). PTFE has low dielectric properties and can be suitably used for the purposes of the present disclosure. PTFE preferably has fibrillar properties. Fibrillar PTFE means PTFE that can be paste-extruded as unsintered polymer powder.

[0043] PTFE can be modified polytetrafluoroethylene (hereinafter referred to as modified PTFE), can be homopolytetrafluoroethylene (hereinafter referred to as homoPTFE), or can be a mixture of modified PTFE and homoPTFE.In addition, from the viewpoint of maintaining good moldability of polytetrafluoroethylene, the content ratio of modified PTFE in polymeric PTFE is preferably 10% by weight or more and 98% by weight or less, more preferably 50% by weight or more and 95% by weight or less. 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.

[0044] 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. 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.

[0045] 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% by weight, more preferably 0.01 to 0.30% by weight, of the total monomer units. The total monomer units are the parts derived from all monomers in the molecular structure of the modified PTFE.

[0046] 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.

[0047] 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)

[0048] In the formula, Rf represents a perfluoroorganic group.

[0049] 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.

[0050] 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).

[0051] The perfluoroalkylethylene (PFAE) is not particularly limited, and examples thereof include perfluorobutylethylene (PFBE) and perfluorohexylethylene (PFHE).

[0052] The modifying monomer in the modified PTFE is preferably at least one (for example, 1 to 6) selected from the group consisting of HFP, CTFE, VDF, PAVE, PFAE, and ethylene.

[0053] The fluororesin is preferably non-melt-moldable. "Non-melt-moldable" 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.

[0054] In the present disclosure, it is preferable to use such a fluororesin that cannot be melt-molded and to form the fluororesin sheet by a molding method that fibrillates the fluororesin. The molding method will be described later.

[0055] The PTFE preferably has an 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.

[0056] 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.

[0057] 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.

[0058] In this embodiment, the molecular weight (number average molecular weight) of the PTFE constituting the PTFE powder 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.

[0059] Methods for measuring the number average molecular weight of PTFE include a method determining it from standard specific gravity and a measurement method based on dynamic viscoelasticity in the melt. The method for determining it from standard specific gravity can be carried out by using a sample molded in accordance with ASTM D-4895 98 and a water displacement method based on ASTM D-792. The measurement method based on 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.

[0060] 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. The refractive index is a value measured using a refractometer (Abbemat 300).

[0061] The PTFE preferably has a maximum endothermic peak temperature (crystalline melting point) of 340±7°C.

[0062] 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.

[0063] The low-melting-point PTFE is a powder produced by emulsion polymerization, has the maximum endothermic peak temperature (crystalline melting point), a dielectric constant (ε) of 2.08 to 2.2, and a dielectric dissipation factor (tan δ) of 1.9 × 10 to 4.0 × 10. 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.

[0064] The high melting point PTFE powder is also a powder 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 (tan δ) of 1.6 × 10 to 2.2 × 10. －４ Examples of 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.

[0065] 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.

[0066] Powdered PTFE 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.

[0067] The PTFE content is preferably 20 to 90% by mass relative to the total amount of the composition. By using such a content, good moldability can be obtained. The lower limit is more preferably 25% by mass, and even more preferably 30% by mass. The upper limit is more preferably 80% by mass, and even more preferably 70% by mass, and even more preferably 50% by mass.

[0068] (Extrusion Pressure) The composition of the present disclosure was paste extruded under the following condition 1 at an extrusion pressure of 10 N mm－２ <Condition 1> Paste extrusion molding was performed by placing 70.0 g of powder made of a composition containing polytetrafluoroethylene resin and a filler, which had been left at room temperature for 2 hours, and 13.3 g of a hydrocarbon oil (trade name: IP2028, manufactured by Idemitsu Kosan Co., Ltd.) serving as a processing aid, into a 250 mL plastic container, mixing them for 3 minutes, and leaving them in a constant temperature bath at 25°C for 2 hours.The paste was then extruded through a die (cylinder diameter: 30 mm, exit diameter: 5 mm, reduction ratio: 36, land length: 27.5 mm, introduction angle: 48°) at an extrusion rate of 50 mm / min and 40°C to obtain a bead (extrusion molded product).

[0069] The hydrocarbon oil used in the paste extrusion molding under condition 1 was an isoparaffinic hydrocarbon oil (density at 15°C: 0.789 g / cm ３ , flash point: 86 ° C, aniline point: 89 ° C, distillation range: 213 ° C to 262 ° C, kinematic viscosity at 37.8 ° C: 2.64 mm ２ / s), and as such an isoparaffin hydrocarbon oil, "IP Solvent 2028" manufactured by Idemitsu Kosan Co., Ltd. can be used.

[0070] A composition having such properties is preferable in that it can be extruded well and problems such as waviness of the sheet can be improved. －２ Preferably, it is 9 N mm or less. －２ More preferably, it is 8 N mm or less. －２ The lower limit is not particularly limited, but it is, for example, 0.1 N mm －２ It can be more than that.

[0071] The dielectric loss tangent of a sheet obtained by rolling the composition of the present disclosure is preferably 0.01 or less at 25°C and 10 GHz. Having such a dielectric loss tangent is preferable because it allows for a low-loss sheet. Here, the sheet for measuring the dielectric loss tangent was obtained by rolling the composition of the present disclosure with two metal rolls to obtain a sample with a film thickness of 125 μm, drying it at 200°C for 2 hours, and baking it at 360°C for 15 minutes.

[0072] The composition of the present disclosure preferably has a 10 GHz dielectric loss tangent of 0.01 or less, as measured by the method described above. A dielectric loss tangent within this range is preferable in that it results in low loss. The dielectric loss tangent here is measured by the method described in the examples.

[0073] The present disclosure relates to a composition containing a polytetrafluoroethylene resin and a filler, and when paste extrusion molding is performed under the above condition 1, the extrusion pressure is 10.0 N mm －２ The composition also has a peel strength of 3 N / cm or more when subjected to a peel strength test under Condition 2 below. The higher the peel strength, the more preferable it is, and there is no particular upper limit, but it may be, for example, 50 N / cm or less. <Condition 2> A peel strength test (90-degree peel test) was conducted using a method in accordance with JIS C 6481-1996. If the sheet of the present disclosure satisfies the above range, it can be bonded to the metal layer with sufficient strength. Sheets containing a large amount of filler may have reduced adhesiveness, but the present disclosure can provide the good adhesiveness described above.

[0074] (Regarding Composition) The sheet of the present disclosure contains the above-described filler and fluororesin. If necessary, it may contain components other than the filler and fluororesin, or may consist solely of the filler and fluororesin. The content of components other than the filler and fluororesin is preferably 10% by weight or less (0% by weight, i.e., not contained, or greater than 0% by weight and 10% by weight or less). In other words, the total content of the fluororesin and filler is preferably, for example, 90% by weight or more and 100% by weight or less relative to the sheet weight. The ratio Wf / Wr of the mass of the filler Wf to the mass Wr of the fluororesin may be, for example, 0.6 to 1.5.

[0075] (Sheet molding) The composition of the present disclosure can be subjected to paste extrusion molding. A sheet obtained using the composition of the present disclosure also constitutes the present disclosure. Such molding is described in detail below.

[0076] (Processing aid) The composition of the present disclosure is a composition for paste extrusion molding. Therefore, during molding, a processing aid is added to the composition and used in a paste form. Such a paste composition is also part of the present disclosure.

[0077] The processing aid is not particularly limited, and examples thereof include commonly used hydrocarbon oils. Examples of organic liquid aids that can be used include petroleum solvents such as solvent naphtha, white oil, and petroleum ether, and alcohol solvents such as methanol, ethanol, isopropyl alcohol, ethylene glycol, and glycerin. In addition to the organic liquid aid, an aqueous aid such as water may be used. In this case, the organic liquid aid is used as the main component. That is, in a mixed aid of the organic liquid aid and the aqueous aid, the proportion of the organic liquid aid in the total solvent is 80% by weight or more, preferably 90% by weight or more, and more preferably 98% by weight or more.

[0078] The processing aid is preferably contained in a proportion of 15 to 25% by mass relative to the total amount of the composition. By using such a proportion, good moldability can be obtained. The lower limit is more preferably 16% by mass, and even more preferably 17% by mass. The upper limit is more preferably 23% by mass, and even more preferably 21% by mass.

[0079] (Paste extrusion molding) The method for producing the sheet may include the steps of: mixing the PTFE powder obtained using a hydrocarbon surfactant with an extrusion aid (1a), paste extrusion molding the resulting mixture (1b), rolling the extrudate obtained by extrusion molding (1c), drying the rolled sheet (1d), and firing the dried sheet to obtain a molded body (1e). The paste extrusion molding can also be carried out by adding conventionally known additives such as pigments and fillers to the PTFE powder.

[0080] (Sheet) The sheet of the present disclosure obtained by the above-described molding will be described in detail below. The sheet of the present disclosure preferably has a specific gravity of 1.95 to 2.19. If the specific gravity is less than 1.95, the problem of a low rate of change in dielectric tangent upon water absorption, as described above, cannot be fully achieved. Furthermore, if the specific gravity exceeds 2.19, the relative dielectric constant becomes high, which is undesirable.

[0081] The lower limit of the specific gravity is more preferably 1.97, and even more preferably 1.98. The upper limit of the specific gravity is more preferably 2.18, and even more preferably 2.17. The specific gravity is a value measured by the density and specific gravity measurement method by the submerged weighing method in accordance with JIS Z 8807 (Methods for measuring density and specific gravity of solids) 8.

[0082] The sheet of the present disclosure preferably has a water absorption rate of 0.10% or less. By setting the specific gravity within the above range, the sheet of the present disclosure has a low porosity. It is preferable to reduce the porosity and achieve the above-mentioned water absorption rate. A water absorption rate of the above-mentioned value is preferable in that it can suitably achieve the objective of reducing the rate of change of the dielectric loss tangent upon water absorption.

[0083] In the present disclosure, the water absorption rate is a value measured by the density and specific gravity measurement method according to JIS Z 8807 (Methods for measuring density and specific gravity of solids) 8, submerged weighing method.

[0084] The water absorption is more preferably 0.8% or less, and even more preferably 0.6% or less. Since a low water absorption does not cause any particular problems, the lower limit is not particularly limited and may be 0%. The lower limit is preferably 0.0001%.

[0085] The sheet of the present disclosure preferably has a linear expansion coefficient of 120 ppm / K or less. By using such a linear expansion coefficient, it is possible to obtain a dielectric sheet with excellent dimensional stability against shrinkage. The linear expansion coefficient is more preferably 70 ppm / K or less, and even more preferably 50 ppm / K or less.

[0086] The lower limit of the linear expansion coefficient is not particularly limited, but is more preferably 5 ppm / K, and even more preferably 10 ppm / K.

[0087] The linear expansion coefficient in this specification was determined by performing TMA measurement in a tensile mode using a TMA-7100 (manufactured by Hitachi High-Tech Science Corporation), using a sheet cut out to a length of 20 mm, a width of 5 mm, and a thickness of 150 μm 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 -10 to 160°C.

[0088] The sheet of the present disclosure preferably has a film thickness of 0.03 to 2 mm. By achieving a film thickness within this range, the sheet becomes suitable for applications described in detail below in this disclosure. The lower limit is more preferably 0.05 mm, and even more preferably 0.1 mm. The upper limit is more preferably 1 mm, and even more preferably 0.5 mm.

[0089] The film thickness in this disclosure is a value measured with a film thickness meter.

[0090] The sheet of the present disclosure preferably has a rate of change in relative dielectric constant of 0.025 or less, more preferably 0.023 or less, and even more preferably 0.021 or less in the temperature range of −50 to 150° C. A value within this range is preferred in that changes in electrical properties due to temperature are minimal, and stable performance can be obtained when used in high-frequency printed circuit boards.

[0091] The sheet of the present disclosure preferably has a dielectric loss tangent of 0.01 or less at 25°C and 10 GHz. More preferably, it is 0.05 or less, even more preferably 0.0015 or less, and most preferably 0.0010 or less. By having such a dielectric loss tangent, it is possible to obtain a low-loss sheet, which is preferable. The lower limit of the dielectric loss tangent of the sheet of the present disclosure at 25°C and 10 GHz is not particularly limited, and may be 0.0001%.

[0092] The sheet of the present disclosure can be used as an insulating material for a circuit board. When used as a circuit board, it is preferable to laminate it with a conductive layer. The conductive layer is preferably a metal layer.

[0093] (Metal-clad laminate) The sheet-shaped resin composition of the present disclosure can be used by laminating it with other substrates as a sheet for printed wiring boards. That is, it can be suitably used as an insulating material for circuit boards.

[0094] The present disclosure also relates to a metal clad laminate having a metal layer and the above-mentioned sheet as essential layers. The metal clad laminate of the present disclosure is, for example, a metal clad laminate characterized in that a metal layer is bonded to one or both sides of the above-mentioned sheet (e.g., a fluororesin film). As described above, the fluororesin-containing film of the present disclosure is particularly suitable for use in printed wiring board applications, and therefore can be suitably used as such a metal clad laminate.

[0095] In the present disclosure, examples of metal species constituting the metal layer include copper (e.g., rolled copper, electrolytic copper, etc.), aluminum, SUS, nickel, gold, ruthenium, etc. Alloys of these can also be used. From the viewpoint of conductivity and circuit processability, it is preferable to use copper. A heat-resistant layer (nickel plating, titanium plating, etc.) or a rust-preventive layer (chromate treatment layer, etc.) may be formed on the copper surface. Furthermore, the surface may be chemically treated with a silane coupling agent. Among these, it is preferable to use copper foil as the metal layer.

[0096] The copper foil preferably has an Rz of 1.6 μm or less. That is, the fluororesin composition of the present disclosure also has excellent adhesion to copper foil, which has a high smoothness of Rz of 1.6 μm or less. Furthermore, the copper foil only needs to have an Rz of 1.6 μm or less on at least the surface that adheres to the fluororesin film described above, and the Rz value of the other surface is not particularly limited. The Rz is the sum of the values ​​of the highest point (maximum peak height: Rp) and the deepest point (maximum valley depth: Rv). The surface roughness 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.

[0097] The thickness of the copper foil is not particularly limited, but is preferably in the range of 1 to 100 μm, more preferably in the range of 5 to 50 μm, and even more preferably in the range of 9 to 35 μm.

[0098] The copper foil is not particularly limited, and specific examples include rolled copper foil and electrolytic copper foil.

[0099] The copper foil having an Rz of 1.6 μm or less is not particularly limited, and commercially available products can be used. Examples of commercially available copper foils having an Rz of 1.6 μm or less include electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.).

[0100] The copper foil may be surface-treated to enhance the adhesive strength with the fluororesin film of the present disclosure.

[0101] The surface treatment is not particularly limited, but includes silane coupling treatment, plasma treatment, corona treatment, UV treatment, electron beam treatment, etc. The reactive functional group of the silane coupling agent is not particularly limited, but from the viewpoint of adhesion to the resin substrate, it is preferable that the reactive functional group has at least one (e.g., 1 to 4) 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 includes 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 (e.g., an oxide film such as chromate), a heat-resistant layer, etc. formed thereon.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] The copper-clad laminate of the present disclosure may further include a layer other than the copper foil and the fluororesin film. The layer other than the copper foil and the fluororesin film is preferably at least one (e.g., 1 to 12) 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.

[0106] The layers other than the copper foil and the fluororesin film are not particularly limited as long as they are made of the above-mentioned resins, and the thickness of the layers other than the copper foil and the fluororesin film is preferably within the range of 12.5 to 260 μm.

[0107] In the metal-clad laminate of the present disclosure, the metal layer may be formed on one or both sides of the roll film. Methods for forming the metal layer include laminating (adhering) metal foil to the surface of the roll film, vapor deposition, plating, and the like. Methods for laminating metal foil include a heat press method. The heat press temperature may be from the melting point of the dielectric film −150°C to the melting point of the dielectric film +40°C. The heat press time is, for example, 1 to 30 minutes. The laminate can be produced using a heat press pressure of 0.1 to 10 MPa.

[0108] The present disclosure also relates to a circuit board comprising the above-described sheet and a metal layer. The above-described metal-clad laminate is not particularly limited in its application and is used as a circuit board. Examples of circuit boards include printed circuit boards, laminated circuit boards, and high-frequency boards. A printed 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 printed circuit board formed from the metal-clad laminate of the present disclosure is not particularly limited. The printed circuit board may be a rigid board, a flexible board, or a rigid-flexible board. The printed circuit board may be a single-sided board, a board, a double-sided board, or a multilayer board (such as a built-up board). It is particularly suitable for use as a flexible board or a rigid board. It is particularly suitable for use as a high-frequency printed circuit board of 10 GHz or more.

[0109] The circuit board is not particularly limited, and can be produced by a general method using the above-mentioned metal-clad laminate.

[0110] The laminate for a circuit board is also a laminate characterized by having a metal layer, the above-mentioned fluororesin film, and a substrate layer. The substrate layer is not particularly limited, but preferably has a fabric layer made of glass fiber and a resin film layer.

[0111] The glass fiber fabric layer is a layer made of glass cloth, glass nonwoven fabric, or the like. Commercially available glass cloth can be used, and glass cloth treated with a silane coupling agent is preferred to enhance affinity with the fluororesin. Examples of glass cloth materials include E-glass, C-glass, A-glass, S-glass, D-glass, NE-glass, and low-dielectric-constant glass, with E-glass, S-glass, and NE-glass being preferred due to their ease of availability. The fiber weave may be plain weave or twill weave. The thickness of the glass cloth is typically 5 to 90 μm, preferably 10 to 75 μm, but it is preferable to use glass cloth that is thinner than the fluororesin film used.

[0112] The laminate may use a glass nonwoven fabric as a fabric layer made of glass fibers. Glass nonwoven fabric is a fabric in which short glass fibers are fixed with a small amount of a binder compound (resin or inorganic substance), or a fabric in which the shape is maintained by entanglement of the short glass fibers without the use of a binder compound. Commercially available glass nonwoven fabrics can be used. The diameter of the short glass fibers is preferably 0.5 to 30 μm, and the fiber length is preferably 5 to 30 mm. Specific examples of binder compounds include resins such as epoxy resins, acrylic resins, cellulose, polyvinyl alcohol, and fluororesins, as well as inorganic substances such as silica compounds. The amount of binder compound used is typically 3 to 15 mass% relative to the short glass fibers. Examples of materials for the short glass fibers include E-glass, C-glass, A-glass, S-glass, D-glass, NE-glass, and low-dielectric-constant glass. The thickness of the glass nonwoven fabric is typically 50 to 1000 μm, preferably 100 to 900 μm. The thickness of the glass nonwoven fabric in this application refers to a value measured in accordance with JIS P8118:1998 using a digital gauge DG-925 (load 110 grams, face diameter 10 mm) manufactured by Ono Sokki Co., Ltd. In order to increase the affinity with the fluororesin, the glass nonwoven fabric may be treated with a silane coupling agent.

[0113] Since most glass nonwoven fabrics have a very high porosity of 80% or more, it is preferable to use a sheet that is thicker than a sheet made of fluororesin and compress it under pressure.

[0114] The glass fiber fabric layer may be a layer formed by laminating a glass cloth and a glass nonwoven fabric. This allows the properties of both layers to be combined to obtain suitable properties. The glass fiber fabric layer may be in the form of a prepreg impregnated with a resin.

[0115] The laminate may have a glass fiber fabric layer and a fluororesin film bonded at the interface, or the glass fiber fabric layer may be partially or entirely impregnated with the fluororesin film. Furthermore, the laminate may be one in which a glass fiber fabric is impregnated with a fluororesin composition to produce a prepreg. The prepreg thus obtained may further be laminated with the fluororesin film of the present disclosure. In this case, the fluororesin composition used to produce the prepreg is not particularly limited, and the fluororesin film of the present disclosure may also be used.

[0116] 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 epoxy resin, bismaleimide, polyphenylene oxide, modified polyphenylene ether, polyphenylene ether, and polybutadiene. The heat-resistant resin film and thermosetting resin film may contain reinforcing fibers. While the reinforcing fibers are not particularly limited, glass cloth, particularly low-dielectric fibers, are preferred. The dielectric properties, linear expansion coefficient, water absorption, and other characteristics of the heat-resistant resin film and thermosetting resin film are not particularly limited. For example, the dielectric constant at 20 GHz is preferably 3.8 or less, more preferably 3.4 or less, and even more preferably 3.0 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 is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less.

[0117] The present disclosure will be specifically described below based on examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass", respectively.

[0118] (Composition) A composition was obtained by mixing the raw materials shown in Table 1. The raw materials are as follows: (PTFE) PTFE having the following properties was used: Particle size: 500 μm Apparent density: 460 g / L Standard specific gravity: 2.17 Melting point: 327° C.

[0119] (Silica 1 to 5) For silica 1, 2, and 4, SC-6500SQ (particle size 2.1 μm, spherical) manufactured by Admatechs was used. For silica 3, SC-2500SQ (particle size 0.5 μm, spherical) manufactured by Admatechs was used. For silica 5, AS-1 (particle size 3.0 μm, crushed) manufactured by Tatsumori Co., Ltd. was used. The silicas were subjected to the following surface treatments. Silica 1: NCO, treatment amount 0.2 mass% Silica 2: aminopropyl, treatment amount 0.2 mass% Silica 4: aminopropyl, treatment amount 1.0 mass%

[0120] The treating agents used in the surface treatment are as follows: NCO: 3-isocyanatepropyltriethoxysilane Aminopropyl: 3-aminopropyltriethoxysilane

[0121]

[0122] (Preparation of Peel Strength Test Sheet) (Examples 1-2, Comparative Examples 2-4) 28 g of the above PTFE and 42 g of silica were weighed and mixed in a mixer in the presence of dry ice. The temperature during mixing was -10°C or lower. The obtained powder was left at room temperature for 2 hours, then placed in a plastic container, and 13.3 g of a processing aid, hydrocarbon oil (product name: IP2028, manufactured by Idemitsu Kosan Co., Ltd.), was added. The mixture was mixed for 3 minutes, left in a thermostatic oven at 25°C for 2 hours, and then heated to 40°C using a mold with a flat outlet to extrude the mixture into a paste. The obtained sheet was rolled with two metal rolls to obtain a sample with a film thickness of 125 μm. The sample was dried at 200°C for 2 hours and then baked at 360°C for 15 minutes. The obtained sheet was laminated with Cu foil (electrolytic copper, thickness: 18 μm, surface roughness Rz of the side to be bonded to the sheet: 1.4 μm) and pressed for 5 minutes at a heating temperature of 320°C and a pressure of 15 kN to obtain a sheet for peel strength testing. For Comparative Examples 2 to 4, the paste extrusion could not be performed, and no sheets could be produced. (Comparative Example 1) Sheet production was attempted using the same method as in Examples 1 and 2 and Comparative Examples 2 to 4, except that 14 g of PTFE and 56 g of silica were weighed, but the paste extrusion could not be performed and no sheets could be produced.

[0123] (Peel Strength Test) A peel strength test (90-degree peel test) was carried out according to JIS C 6481-1996. Approximately 1 cm of the resin at the end of the bonded assembly in which a sheet was bonded to one side of the copper foil obtained above was peeled off, and the assembly was clamped in the chuck of a testing machine and the peel strength (unit: N / cm) was measured at a pulling speed (moving speed) of 50 mm / min.

[0124] (Bead Extrusion Pressure) (Examples 1-2, Comparative Examples 2-4) 28 g of the above PTFE and 42 g of silica were weighed and mixed in a mixer in the presence of dry ice. The temperature during mixing was −10° C. or lower. The obtained powder was left at room temperature for 2 hours, then placed in a 250 mL plastic container, and 13.3 g of a processing aid, hydrocarbon oil (product name: IP2028, manufactured by Idemitsu Kosan Co., Ltd.), was added. The mixture was mixed for 3 minutes and left in a constant temperature bath at 25° C. for 2 hours. After that, paste extrusion was performed through a die (cylinder diameter 30 mm, outlet diameter 5 mm, reduction ratio 36, land length 27.5 mm, introduction angle 48°) at an extrusion rate of 50 mm / min and 40° C. to obtain beads (extrusion molded products). This method was used to check whether paste extrusion was possible, and, if so, the extrusion pressure. Comparative Example 1 The same methods as in Examples 1 and 2 and Comparative Examples 2 to 4 were used except that 14 g of PTFE and 56 g of silica were weighed out, respectively, to check whether the paste could be extruded and, if so, the extrusion pressure.

[0125] (T-die extrudability) (Examples 1-2, Comparative Examples 2-4) 28 g of the above PTFE and 42 g of silica were weighed and mixed in a mixer in the presence of dry ice. The temperature during mixing was −10°C or below. The resulting powder was left at room temperature for 2 hours, then placed in a plastic container, and 13.3 g of a processing aid, hydrocarbon oil (product name: IP2028, manufactured by Idemitsu Kosan Co., Ltd.), was added. The mixture was mixed for 3 minutes, and then left in a thermostatic oven at 25°C for 2 hours. After that, the mixture was heated to 40°C using a mold with a flat outlet and paste-extruded. A sheet (extrusion molded product) with a width of 100 mm and a thickness of 1 mm was obtained. Using this method, the feasibility of paste extrusion was confirmed. (Comparative Example 1) The feasibility of paste extrusion was confirmed using the same method as in Examples 1-2 and Comparative Examples 2-4, except that 14 g of the above PTFE and 56 g of silica were weighed.

[0126] (Dielectric Loss Tangent (Sheet)) The dielectric loss tangent (Df) was measured at 25° C. and 10 GHz using a split cylinder type dielectric constant / dielectric loss tangent measuring device (manufactured by EM Lab).

[0127] (Dielectric loss tangent (filler)) The dielectric loss tangent of the filler was measured at 10 GHz using a cylindrical cavity resonator and a network analyzer. A filler powder sample was filled into a quartz tube and loaded into the resonator. The characteristics of the resonator (resonance frequency and Q value) were obtained before and after inserting the sample, and the dielectric loss tangent was calculated from the results. This measurement method complies with Japanese Industrial Standard JIS 2565, Test Method for Ferrite Cores for Microwaves.

[0128] [Specific Surface Area of ​​Filler] This is a value based on the BET method, and was measured using a specific surface area measuring device "Macsorb HM model-1208" (manufactured by MACSORB).

[0129]

[0130] It is clear from Table 2 that the compositions of the present disclosure provide good sheets.

[0131] The sheet of the present disclosure can be suitably used in particular for high-frequency printed circuit boards.

Claims

1. A composition containing polytetrafluoroethylene resin and a filler, wherein the surface of the filler is treated with a silane coupling agent having a functional group containing a nitrogen atom, and the amount of the treatment is 0.1% by mass or more and less than 1.0% by mass of the filler after the surface treatment, and the composition is paste extruded under the following condition 1 at an extrusion pressure of 10 N mm －２ A composition characterized by the following: <Condition 1> Paste extrusion molding is performed by placing 70.0 g of powder made of a composition containing polytetrafluoroethylene resin and a filler, which has been left at room temperature for 2 hours, and 13.3 g of hydrocarbon oil as a processing aid into a 250 mL plastic container, mixing them for 3 minutes, leaving them in a constant temperature bath at 25°C for 2 hours, and then extruding the paste at an extrusion rate of 50 mm / min at 40°C through a die with a cylinder diameter of 30 mm, an outlet diameter of 5 mm, a reduction ratio of 36, a land length of 27.5 mm, and an introduction angle of 48° to obtain a bead extrusion molded product.

2. The composition according to claim 1, wherein the filler is an inorganic filler.

3. The composition of claim 2, wherein said inorganic filler is silica.

4. The composition according to claim 3, wherein the silica is contained in an amount of 10 to 70% by mass.

5. The silica is (dielectric tangent of silica measured at 10 GHz) / (surface area of ​​silica (m ２ 5. The composition according to claim 3, wherein the ratio of (a) to (b) is from 0.00001 to 0.00035.

6. The composition according to any one of claims 1 to 5, wherein the silane coupling agent is a surface treatment agent having an isocyanate group or an amino group.

7. The composition according to any one of claims 1 to 6, wherein the silane coupling agent is 3-isocyanatepropyltriethoxysilane or 3-aminopropyltriethoxysilane.

8. The composition according to any one of claims 1 to 7, wherein the filler content is 10 to 80% by mass and the polytetrafluoroethylene resin content is 20 to 90% by mass.

9. The composition according to any one of claims 1 to 8, wherein the sheet obtained by rolling the composition has a dielectric loss tangent of 0.01 or less at 25°C and 10 GHz.

10. The composition according to any one of claims 1 to 9, wherein the polytetrafluoroethylene resin content is 30 to 50% by mass, the filler content is 50 to 70% by mass, the amount of silane coupling agent used is 0.1% to 0.9% by mass based on the weight of the filler after surface treatment, the filler is silica, and the silane coupling agent has an isocyanate group or an amino group.

11. A composition containing polytetrafluoroethylene resin and a filler, which is paste extruded under the following condition 1 with an extrusion pressure of 10.0 N mm －２ A composition having a peel strength of 3 N / cm or more when subjected to a peel strength test under Condition 2 below. <Condition 1> Paste extrusion molding is performed by placing 70.0 g of a powder composed of a composition containing polytetrafluoroethylene resin and a filler, which has been left at room temperature for 2 hours, and 13.3 g of a hydrocarbon oil as a processing aid in a 250 mL plastic container, mixing for 3 minutes, and leaving the mixture in a constant temperature bath at 25°C for 2 hours. The paste is then extruded at an extrusion rate of 50 mm / min and 40°C through a die with a cylinder diameter of 30 mm, an outlet diameter of 5 mm, a reduction ratio of 36, a land length of 27.5 mm, and an introduction angle of 48° to obtain a bead extrusion molded product. <Condition 2> A 90-degree peel test, which is a peel strength test, is performed using a method in accordance with JIS C 6481-1996.

12. A paste-like composition comprising the composition according to any one of claims 1 to 11 and a processing aid.

13. The paste-like composition according to claim 12, wherein the processing aid is a petroleum-based solvent.

14. The paste-like composition according to claim 12 or 13, which contains 15 to 25 parts by mass of a processing aid relative to the total amount of the polytetrafluoroethylene resin and the filler.

15. A paste-like composition comprising the composition according to claim 8 and a processing aid which is a petroleum-based solvent, the processing aid being contained in an amount of 15 to 25 parts by mass relative to the total amount of the polytetrafluoroethylene resin and filler.

16. A sheet made from the composition according to any one of claims 1 to 11 and having a thickness of 0.1 to 2 mm.

17. The sheet of claim 16, which is an insulating material.

18. A metal clad laminate comprising a metal layer and a sheet made from the composition according to any one of claims 1 to 11 as essential layers.

19. The metal clad laminate according to claim 18, wherein the metal layer is copper foil.

20. A circuit board comprising a sheet made from the composition according to any one of claims 1 to 11 and a metal layer.

21. The circuit board according to claim 20, wherein the metal constituting the metal layer is copper.

22. The circuit board according to claim 21, wherein the copper is rolled copper or electrolytic copper.

23. The circuit board according to any one of claims 20 to 22, which is a printed circuit board, a laminated circuit board, or a high-frequency board.

24. A method for producing a sheet, comprising a step of rolling the composition according to any one of claims 1 to 11.