WO2023002998A1

WO2023002998A1 - Composite sheet and method for producing composite sheet

Info

Publication number: WO2023002998A1
Application number: PCT/JP2022/028124
Authority: WO
Inventors: 敦美光永; 渉笠井; 陽美中満
Original assignee: Ａｇｃ株式会社
Priority date: 2021-07-20
Filing date: 2022-07-19
Publication date: 2023-01-26
Also published as: TW202313346A; JPWO2023002998A1

Abstract

A composite sheet comprising woven or nonwoven fabric of a liquid-crystal polymer and, infiltrated into the woven or nonwoven fabric of a liquid-crystal polymer, a heat-fusible tetrafluoroethylene-based polymer having an oxygen-containing polar group.

Description

Composite sheet and method for producing composite sheet

The present disclosure relates to a composite sheet and a method for manufacturing the composite sheet.

2. Description of the Related Art In recent years, in the field of information communication, there has been a demand for improved performance of materials used for printed wiring boards and the like due to the development of communication technology such as high-frequency communication. Fluorine polymers, particularly tetrafluoroethylene-based polymers, are excellent in electrical properties and heat resistance, and are therefore suitably used for printed wiring boards.
Patent Literature 1 describes a composite sheet comprising a liquid crystal polymer-containing nonwoven fabric on the facing surfaces of a layer containing a liquid crystal polymer and a layer containing a tetrafluoroethylene-based polymer.

JP 2017-119378 A

A tetrafluoroethylene-based polymer has excellent electrical properties and a high coefficient of linear expansion. Therefore, when the laminate of the composite sheet and the base material described in Patent Document 1 is processed at a high temperature, for example, when subjected to a reflow process in the production of a wiring board, the composite sheet thermally expands and the composite sheet and the base material are separated from each other. It was easy to peel off the material.
The present disclosure relates to providing a composite sheet having excellent electrical properties and low linear expansion and a method for manufacturing the composite sheet.

Means for solving the above problems include the following aspects.
<1> Composite containing a heat-melting liquid crystal polymer woven fabric or non-woven fabric and a heat-melting tetrafluoroethylene-based polymer having an oxygen-containing polar group impregnated in the liquid crystal polymer fabric or non-woven fabric sheet.
<2> The composite sheet according to <1>, wherein the oxygen-containing polar group is a hydroxyl group-containing group or a carbonyl group-containing group.
<3> The composite sheet according to <1> or <2>, wherein the liquid crystal polymer contains a liquid crystalline aromatic polyester.
<4> The composite sheet according to any one of <1> to <3>, wherein the tetrafluoroethylene-based polymer has a melting point of 260 to 320°C.
<5> The composite sheet according to any one of <1> to <4>, wherein the liquid crystal polymer has a melting point of 230 to 350°C.
<6> The composite sheet according to any one of <1> to <5>, wherein the absolute value of the difference between the melting point of the tetrafluoroethylene-based polymer and the melting point of the liquid crystal polymer is 30° C. or less.
<7> The composite sheet according to any one of <1> to <6>, further comprising a polymer different from the tetrafluoroethylene-based polymer.
<8> The composite sheet according to any one of <1> to <7>, further containing inorganic particles.
<9> A group comprising at least one selected from the group consisting of a polymer different from the tetrafluoroethylene-based polymer and inorganic particles, and a polymer different from the tetrafluoroethylene-based polymer and the inorganic particles The composite sheet according to any one of <1> to <8>, wherein the total content of at least one selected from the above is more than 5% by mass with respect to the total mass of the composite sheet.
<10> Contains at least one selected from the group consisting of a polymer different from the tetrafluoroethylene-based polymer and inorganic particles, and is different from the tetrafluoroethylene-based polymer with respect to the mass of the tetrafluoroethylene-based polymer The composite sheet according to any one of <1> to <9>, wherein the total mass ratio of at least one selected from the group consisting of the polymer and the inorganic particles is 0.1 or more.
<11> The composite sheet according to any one of <1> to <10>, which has a thickness of less than 50 μm.
<12> A method for producing a composite sheet, comprising thermocompression bonding a sheet containing a heat-meltable tetrafluoroethylene-based polymer having an oxygen-containing polar group and a woven or nonwoven fabric of a liquid crystal polymer to obtain a composite sheet.
<13> The manufacturing method according to <12>, wherein the sheet is formed from a dispersion containing particles of the tetrafluoroethylene-based polymer.
<14> A method for producing a composite sheet, comprising impregnating a liquid crystal polymer woven or nonwoven fabric with a dispersion containing particles of a heat-melting tetrafluoroethylene polymer having an oxygen-containing polar group to obtain a composite sheet.
<15> The production method according to <14>, wherein the dispersion further contains at least one selected from the group consisting of a polymer different from the tetrafluoroethylene-based polymer and inorganic particles.

According to the present disclosure, a composite sheet having excellent electrical properties and low linear expansion and a method for manufacturing the composite sheet are provided.

Hereinafter, the form for implementing the embodiment of the present disclosure will be described in detail. However, the embodiments of the present disclosure are not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the embodiments of the present disclosure.

In the present disclosure, the numerical range indicated using "-" includes the numerical values before and after "-" as the minimum and maximum values, respectively.
In the present disclosure, each component may contain multiple types of applicable substances. When there are multiple types of substances corresponding to each component in the composition, the content rate or content of each component is the total content rate or content of the multiple types of substances present in the composition unless otherwise specified. means quantity.
Plural types of particles corresponding to each component in the present disclosure may be included. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means a value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.
In the present disclosure, the term "layer" includes the case where the layer or film is formed in the entire region when the region where the layer or film is present is formed only in a part of the region. case is also included.
In the present disclosure, the term "laminate" indicates stacking layers, and two or more layers may be bonded, or two or more layers may be detachable.
In the present disclosure, a "composite sheet" is a sheet comprising a polymer and a woven or non-woven fabric of liquid crystal polymer.
In the present disclosure, the “volume average particle diameter (D50)” is the volume-based cumulative 50% diameter of particles determined by a laser diffraction/scattering method. That is, the particle size distribution is measured by a laser diffraction/scattering method, and the cumulative curve is obtained with the total volume of the group of particles being 100%.
The D50 of the particles is determined by dispersing the particles in water and using a laser diffraction/scattering particle size distribution analyzer (
It can be determined by analysis by a laser diffraction/scattering method using an LA-920 measuring instrument (manufactured by Horiba, Ltd.).
In the present disclosure, the “specific surface area” is a value calculated by measuring particles by gas adsorption (constant volume method) BET multipoint method, and is determined using NOVA4200e (manufactured by Quantachrome Instruments).
In the present disclosure, the "melting point of the tetrafluoroethylene-based polymer" is the temperature corresponding to the maximum value of the melting peak of the polymer measured by differential scanning calorimetry (DSC).
In the present disclosure, the "melting point of the liquid crystal polymer" is obtained by heating the liquid crystal polymer film at a rate of 20°C/min using a differential scanning calorimeter to completely melt it, and then heating the melt to 50°C/min. It is the temperature showing the endothermic peak when the material is rapidly cooled to 50°C at a high speed and then heated again at a speed of 20°C/min.
In the present disclosure, "melt flow rate" means the melt mass flow rate of a polymer as defined in JIS K 7210-1:2014 (ISO1133-1:2011).
In the present disclosure, "glass transition point (Tg)" is a value measured by analyzing a polymer by dynamic viscoelasticity measurement (DMA).
In the present disclosure, the “viscosity” is determined by measuring the dispersion using a Brookfield viscometer under conditions of 25° C. and 30 rpm. The measurement is repeated 3 times, and the average value of the 3 measurements is taken.
In the present disclosure, the “thixotropic ratio” is a value calculated by dividing the viscosity η ₁ of the dispersion measured at a rotation speed of 30 rpm by the viscosity η ₂ measured at a rotation speed of 60 rpm. is. Each viscosity measurement is repeated three times, and the average value of the three measurements is taken.
In the present disclosure, a "polymer" is a compound formed by polymerizing monomers. That is, a "polymer" has multiple monomer-based units.
In the present disclosure, a "unit" in a polymer means an atomic group based on the monomer formed by polymerization of the monomer. The units may be units directly formed by a polymerization reaction, or may be units in which some of said units have been converted to another structure by treatment of the polymer. Hereinafter, units based on monomer a are also simply referred to as "monomer a units".

The composite sheet of the present disclosure includes a woven fabric or nonwoven fabric of a heat-melting liquid crystal polymer (hereinafter also simply referred to as "liquid crystal polymer") and oxygen-containing polar groups impregnated in the woven fabric or nonwoven fabric of the liquid crystal polymer. and a heat-meltable tetrafluoroethylene-based polymer (hereinafter also referred to as “F polymer”). The composite sheet of the present disclosure is excellent in electrical properties and low linear expansion.

In general, tetrafluoroethylene-based polymers have excellent electrical properties such as low dielectric and low dielectric loss tangent, but also have a large coefficient of linear expansion. Conventional composite sheets using tetrafluoroethylene-based polymers do not have sufficient low linear expansion properties. Further, in conventional composite sheets, the tetrafluoroethylene-based polymer is impregnated into the liquid crystal polymer woven fabric or non-woven fabric, and the two are entangled and adhered, and the adhesion at the interface is insufficient. As a result, the laminate of the composite sheet and the base material has problems such as thermal expansion during processing at high temperature and separation from the base material.
The present inventors conducted extensive studies and found that a composite sheet obtained by impregnating a liquid crystal polymer woven or non-woven fabric with F polymer has excellent electrical properties and low linear expansion properties.

In the composite sheet of the present disclosure, the oxygen-containing polar groups in the F polymer interact well with the liquid crystal polymer, thereby improving the adhesion between the F polymer and the liquid crystal polymer, and the linear expansion of the F polymer is greater than that of the liquid crystal polymer. It is considered that the physical properties of both polymers are highly balanced while being well cushioned by the woven fabric or non-woven fabric.
It is also believed that the oxygen-containing polar groups in the tetrafluoroethylene-based polymer also improve adhesion to substrates, and these properties are believed to provide a material that is useful, for example, as a low transmission loss material.
The composite sheet may contain, in addition to the liquid crystal polymer woven fabric or nonwoven fabric and the F polymer, a polymer different from the F polymer, inorganic particles, various additives, and the like. Each component of the composite sheet will be described below.

The composite sheet of the present disclosure contains F polymer, which is a hot-melt tetrafluoroethylene-based polymer having oxygen-containing polar groups. One type of F polymer may be used, or two or more types may be used.
The F polymer may be particulate or non-particulate in the composite sheet, the latter being preferred. The F polymer in the composite sheet is preferably calcined. From the viewpoint of excellent adhesion between the F polymer and the woven fabric or non-woven fabric of the liquid crystal polymer, the F polymer in the composite sheet is preferably a baked product of particles of the F polymer.

A tetrafluoroethylene-based polymer is a polymer containing units (hereinafter also referred to as "TFE units") based on tetrafluoroethylene (hereinafter also referred to as "TFE"). The content of the TFE units in the tetrafluoroethylene-based polymer is preferably 50 mol % or more, more preferably 90 mol % or more, based on the total units in the polymer, from the viewpoint of suitably exhibiting the properties of the TFE units. The above content may be 99 mol % or less, or 98 mol % or less.

The F polymer has oxygen-containing polar groups. The oxygen-containing polar group includes a hydroxyl group-containing group, a carbonyl group-containing group, a phosphono group-containing group, and the like, preferably a hydroxyl group-containing group or a carbonyl group-containing group, more preferably a carbonyl group-containing group. The F polymer may have one or more oxygen-containing polar groups.
The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF ₂ CH ₂ OH and -C(CF ₃ ) ₂ OH.
A carbonyl group-containing group includes a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH ₂ ), an acid anhydride residue (-C(O)OC(O)-), an imide Residues (--C(O)NHC(O)--, etc.) and carbonate groups (--OC(O)O--) are preferred, and acid anhydride residues are more preferred.

The number of oxygen-containing polar groups in F polymer is preferably 10 to 5,000, more preferably 100 to 3,000 per 1×10 ⁶ carbon atoms in the main chain. The number of oxygen-containing polar groups can be quantified by the composition of the polymer or the method described in WO2020/145133.
The oxygen-containing polar group may be contained in a unit based on a monomer in the F polymer, or may be contained in a terminal group of the main chain of the F polymer, the former being preferred. As the latter aspect, a tetrafluoroethylene polymer having an oxygen-containing polar group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., a polymer obtained by plasma treatment or ionizing radiation treatment of a tetrafluoroethylene polymer, etc. is mentioned.

As the monomer having a carbonyl group-containing group, itaconic anhydride, citraconic anhydride and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH") are preferable, and adhesiveness to the liquid crystal polymer is improved. From the standpoint of superiority, NAH is more preferable.

F polymers are polymers with oxygen-containing polar groups, polytetrafluoroethylene (PTFE), a polymer containing TFE units and ethylene-based units (ETFE), a polymer containing TFE units and propylene-based units, TFE It is preferably a polymer (PFA) containing units and units based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE units), a polymer containing TFE units and units based on hexafluoropropylene (FEP), oxygen-containing polar PFA and FEP having a group are more preferred, and PFA having an oxygen-containing polar group is even more preferred. As the PAVE unit, CF2 ₌ _CFOCF3 _, CF2 ₌ _CFOCF2CF3 and CF2 ₌ _CFOCF2CF2CF3 ₍ hereinafter also referred to as PPVE) _are preferable, and PPVE is more preferable. These polymers may also contain units based on other comonomers.

The F polymer is preferably a polymer having carbonyl group-containing groups comprising TFE units and PAVE units, more preferably comprising units based on monomers having TFE units, PAVE units and carbonyl group-containing groups, TFE units , PAVE units and units based on monomers having a carbonyl group-containing group, with respect to all units, these units in this order 90 to 99 mol%, 0.99 to 9.97 mol%, 0.01 to More preferably, the polymer contains 3 mol %. Specific examples of such F polymers include the polymers described in WO2018/016644.

F polymers are hot meltable.
A hot-melt polymer means a polymer for which there exists a temperature at which the melt flow rate is between 1 and 1000 g/10 minutes under the condition of a load of 49N.
The melt flow rate of the F polymer is preferably 1 to 30 g/min, more preferably 5 to 30 g/min under a load of 49 N from the viewpoint of impregnating the woven or nonwoven fabric of the liquid crystal polymer with the F polymer satisfactorily.

From the viewpoint of improving the heat resistance of the composite sheet, the melting point of the F polymer is preferably 200° C. or higher, more preferably 260° C. or higher. The melting point of the F polymer is preferably 325° C. or lower, more preferably 320° C. or lower, from the viewpoint of satisfactorily impregnating the liquid crystal polymer woven fabric or non-woven fabric with the F polymer.
From the viewpoint of improving the heat resistance of the composite sheet, the glass transition point of the F polymer is preferably 50° C. or higher, more preferably 75° C. or higher. The glass transition point of the F polymer is preferably 150° C. or lower, more preferably 125° C. or lower, from the viewpoint of good impregnation into the liquid crystal polymer woven fabric or non-woven fabric.
The fluorine content of the F polymer is preferably 70% by mass or more, more preferably 72 to 76% by mass, from the viewpoint of improving the electrical properties and heat resistance of the composite sheet. In addition, fluorine content is calculated|required from a polymer composition.

The surface tension of the F polymer is preferably 16-26 mN/m. The surface tension can be measured by placing a droplet of a wetting index reagent (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) on a flat plate made of F polymer. Even if the F polymer has a low surface tension, the F polymer has an oxygen-containing polar group, so it tends to have excellent adhesiveness to the woven fabric or non-woven fabric of the liquid crystal polymer.
The spherulite radius of the F polymer in the composite sheet is preferably 0.2 to 10 μm, more preferably 0.5 to 5 μm, from the viewpoint of adhesion of the liquid crystal polymer to the woven fabric or nonwoven fabric and substrate.

From the viewpoint of electrical properties, the content of the F polymer relative to the total mass of the composite sheet is preferably 10% by mass or more, more preferably 30% by mass or more. From the viewpoint of low linear expansion, the content is preferably 80% by mass or less, more preferably 60% by mass or less.
In the composite sheet, the content of the F polymer with respect to the total mass excluding the liquid crystal polymer woven fabric or non-woven fabric is preferably 30% by mass or more, more preferably 50% by mass or more, from the viewpoint of electrical properties. The content is preferably 100% by mass or less, more preferably 80% by mass or less.

The composite sheets of the present disclosure contain woven or nonwoven fabrics of liquid crystal polymers. As the liquid crystal polymer, a thermotropic liquid crystal polymer is preferable. One type of liquid crystal polymer may be used, or two or more types may be used.
The woven fabric or non-woven fabric of liquid crystal polymer may be a woven fabric or non-woven fabric containing liquid crystal polymer, and may contain other materials. The content of the liquid crystal polymer is preferably 50% by mass or more, more preferably 80% by mass or more, based on the total mass of the liquid crystal polymer woven fabric or nonwoven fabric.

Liquid crystalline polyester is preferred as the liquid crystalline polymer. The liquid crystalline polyester may be a liquid crystalline polyester amide, a liquid crystalline polyester ether, a liquid crystalline polyester carbonate, or a liquid crystalline polyester imide.
The liquid crystalline polyester is preferably a liquid crystalline aromatic polyester, and specifically, a polycondensate of an aromatic dicarboxylic acid and an aromatic diol or an aromatic hydroxycarboxylic acid, an aromatic dicarboxylic acid, an aromatic diol and an aromatic A polycondensate with hydroxycarboxylic acid and the like can be mentioned.

Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid.
Aromatic diols include 4,4'-dihydroxybiphenyl, bisphenol A and the like.
Aromatic hydroxycarboxylic acids include parahydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 6-hydroxy-2-naphthoic acid and the like.
In addition to these aromatic dicarboxylic acids, aromatic diols, and aromatic hydroxycarboxylic acids, components such as aliphatic dicarboxylic acids, aliphatic diols, and aliphatic hydroxycarboxylic acids may be used in combination as long as liquid crystallinity is exhibited. . Aliphatic diols include ethylene glycol.

Among them, as the liquid crystal polymer, a liquid crystal aromatic polyester having an aromatic ring content of 55% by mass or more is preferable from the viewpoint of excellent heat resistance. The aromatic ring content of the liquid crystalline aromatic polyester is more preferably 65% by mass or more. The aromatic ring content is preferably 80% by mass or less. Such a liquid crystal polymer has a small degree of conformational freedom and excellent heat resistance, but it is difficult to interact with other polymers. However, in the present disclosure, since the F polymer has a high affinity with the liquid crystal polymer, it easily adheres well to such a liquid crystal polymer having a high aromatic ring content.

In the present disclosure, the aromatic ring content is obtained from the following formula. The carbon atoms contained in the substituents bonded to the aromatic ring are not included in the carbon atoms forming the aromatic ring.
Aromatic ring content (% by mass) = 100 x [mass of carbon atoms forming aromatic rings in polymer skeleton (g)/total mass of polymer (g)]
For example, the aromatic ring content in a typical unit contained in a liquid crystalline aromatic polyester is as follows, based on the copolymerization ratio (molar ratio) of each unit, the aromatic ring content of the liquid crystalline aromatic polyester Amount can be calculated.
2-hydroxy-6-naphthoic acid: 71%
4,4'-dihydroxybiphenyl: 78%
Terephthalic acid: 54%
2,6-naphthalenedicarboxylic acid: 66%

The liquid crystalline polyester amide includes an aromatic polyester amide obtained by copolymerizing the liquid crystalline aromatic polyester with aminophenol.
Specific examples of liquid crystal polymers include liquid crystal polymers described in paragraphs 0032 to 0039 of JP-A-2017-119378.

The deflection temperature under load of the liquid crystal polymer is preferably 240° C. or higher, more preferably 270° C. or higher, and even more preferably 300° C. or higher. The deflection temperature under load is preferably 400° C. or less. In this case, the composite sheet is preferable because it tends to be excellent in heat resistance. In addition, since the F polymer has an oxygen-containing polar group, it easily adheres well to a liquid crystal polymer which has a high deflection temperature under load, that is, has a small degree of conformational freedom and hardly interacts with other polymers.
The deflection temperature under load is a value measured according to ASTM D648 with a load of 0.46 MPa.

The melting point of the liquid crystal polymer is preferably 230° C. or higher, more preferably 280° C. or higher. The melting point of the liquid crystal polymer is preferably 350° C. or lower, more preferably 330° C. or lower. The melting point of the liquid crystal polymer may be adjusted by heat-treating the liquid crystal polymer.
A liquid crystal polymer having such a melting point not only has excellent heat resistance on its own, but also tends to increase interaction with the F polymer when exposed to high temperatures, and tends to further improve the low linear expansion property of the composite sheet.

In particular, when the absolute value of the difference between the melting point of the F polymer and the melting point of the liquid crystal polymer is 30°C or less, the interaction between the polar groups of the polymer softened by exposure to high temperatures increases, so this tendency tends to become noticeable. The difference (absolute value) is preferably 25° C. or less, more preferably 20° C. or less. The difference (absolute value) is preferably 0° C. or more.

The specific gravity of the liquid crystal polymer nonwoven fabric is preferably 1.0 to 3.0, more preferably 1.5 to 2.0.
The average fiber diameter of the liquid crystal polymer nonwoven fabric is preferably 0.01 to 20 μm, more preferably 3 to 10 μm. The average fiber diameter is obtained by measuring the fiber diameters of 200 fibers by electron microscope observation, and excluding the data of the 10 thinnest and 10 thickest fibers, and obtaining the average value.
The basis weight (mass per unit) of the liquid crystal polymer nonwoven fabric is preferably 1 to 300 g/m ² , more preferably 3 to 30 g/m ² .

The nonwoven fabric of the liquid crystal polymer may be a manufactured one or a ready-made one.
The non-woven fabric of liquid crystal polymer can be molded, for example, at a molding temperature of 300-400.degree.
Examples of the method for molding the nonwoven fabric of liquid crystal polymer include a spunbond method and a melt blow method, and examples thereof include the molding method described in International Publication No. 2010/098400.
Specific examples of liquid crystal polymers include "Vecrus" series (manufactured by Kuraray Kuraflex), "Vectran" series (manufactured by Kuraray), and "UENO LCP" series (manufactured by Ueno Pharmaceutical Co., Ltd.).

The woven fabric of liquid crystal polymer can also be regarded as a woven fabric of liquid crystal polymer fibers, and specifically includes a plain weave fabric.
The warp density of the liquid crystal polymer plain weave is preferably 2 to 80/cm, more preferably 4 to 60/cm.
The weft density of the liquid crystal polymer plain weave is preferably 2 to 80 wefts/cm, more preferably 4 to 60 wefts/cm.
The liquid crystal polymer fiber is preferably a fiber obtained by melt-spinning a liquid crystal polymer. The liquid crystal polymer fibers obtained by melt spinning may be further heat-treated in order to improve the strength.
The liquid crystal polymer fibers may consist of one kind of liquid crystal polymer or two or more kinds of liquid crystal polymers.
The fiber of the liquid crystal polymer may be a core-sheath composite fiber having a core-sheath structure. In this case, the liquid crystal polymer may be contained as a core component, may be contained as a sheath component, or may be contained as both a core component and a sheath component.

The composite sheet may further contain inorganic particles. One type of inorganic particles may be used, or two or more types may be used. In the composite sheet, inorganic particles are preferably dispersed in the F polymer.
The shape of the inorganic particles is preferably spherical, needle-like, fibrous or plate-like, preferably spherical, scale-like or layer-like, more preferably spherical or scale-like. The inorganic particles may be hollow.
The spherical inorganic particles are preferably substantially spherical. The term “substantially spherical” means that, when the inorganic particles are observed with a scanning electron microscope (SEM), inorganic particles having a minor axis to major axis ratio of 0.7 or more account for 95% or more by number. do.
The aspect ratio of non-spherical inorganic particles is preferably 2 or more, more preferably 5 or more. The aspect ratio is preferably 10,000 or less.

The material of the inorganic particles is preferably carbon, inorganic nitride or inorganic oxide, and carbon, boron nitride, aluminum nitride, beryllia, silica, wollastonite, talc, cerium oxide, aluminum oxide, magnesium oxide, zinc oxide or oxide. Titanium is more preferred, and boron nitride or silica are even more preferred.

D50 of the inorganic particles is preferably 20 μm or less, more preferably 10 μm or less. D50 is preferably 0.01 μm or more, more preferably 0.1 μm or more.
The specific surface area of the inorganic particles is preferably 1-20 m ² /g.

The surfaces of the inorganic particles may be surface-treated with a silane coupling agent.
Silane coupling agents include 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3- Silane coupling agents with functional groups such as isocyanatopropyltriethoxysilane are preferred.

Specific examples of silica particles include the "ADMAFINE" series (manufactured by Admatechs), the "SFP" series (manufactured by Denka), the "E-SPHERES" series (manufactured by Taiheiyo Cement Co., Ltd.), and the "Q" series (Ginet company).
Specific examples of zinc oxide particles include the "FINEX" series (manufactured by Sakai Chemical Industry Co., Ltd.).
Specific examples of titanium oxide particles include the "Tipake (registered trademark)" series (manufactured by Ishihara Sangyo Co., Ltd.) and the "JMT" series (manufactured by Tayca Corporation).
Specific examples of talc particles include "SG" series (manufactured by Nippon Talc Co., Ltd.).
Specific examples of steatite particles include the "BST" series (manufactured by Nippon Talc Co., Ltd.).
Specific examples of boron nitride particles include "UHP" series (manufactured by Showa Denko KK), and "GP" and "HGP" grades of the "DENKA BORON NITRIDE" series (manufactured by DENKA CORPORATION).

When the composite sheet contains inorganic particles, the content of the inorganic particles with respect to the total weight of the composite sheet is preferably 5% by mass or more, and 10% by mass or more, from the viewpoint of the strength and low linear expansion of the composite sheet. good too. The content is preferably 40% by mass or less, more preferably 20% by mass or less, from the viewpoint of suitably expressing the properties of polymers including F polymer.
In the composite sheet, the ratio of the mass of the inorganic particles to the mass of the F polymer is preferably 0.1 or more, more preferably 0.2 or more, from the viewpoint of strength and low linear expansion of the composite sheet. The ratio is preferably 1 or less, more preferably 0.6 or less.

The composite sheet of the present disclosure may further contain a polymer different from the F polymer (hereinafter also referred to as "different polymer").
Different polymers may be thermosets or thermoplastics. One type of different polymer may be used, or two or more types may be used.
The different polymers may be included in the woven or non-woven fabric of the liquid crystal polymer or dispersed in the F polymer, the latter being preferred.

Examples of different polymers include tetrafluoroethylene-based polymers other than F polymer, polyester resins (liquid crystalline aromatic polyesters, etc.), imide resins, epoxy resins, maleimide resins, urethane resins, polyphenylene ether resins, polyphenylene oxide resins, and polyphenylene sulfide resins. etc.

Tetrafluoroethylene-based polymers other than the F polymer include heat-melting PTFE, ETFE, PFA, FEP, and non-heat-melting PTFE that do not have oxygen-containing polar groups. is preferred. The non-heat-fusible PTFE may be contained in the composite sheet as particles or may be non-particulate.

The different polymer is preferably an aromatic polymer and a tetrafluoroethylene-based polymer other than the F polymer, and at least selected from the group consisting of aromatic polyimides, aromatic polyamic acids, aromatic polyamideimides, and precursors of aromatic polyamideimides. More preferred are one aromatic imide polymer, as well as non-heat-melting PTFE.

Specific examples of aromatic polyimides include "Upia-AT" series (manufactured by Ube Industries, Ltd.), "Neoprim (registered trademark)" series (manufactured by Mitsubishi Gas Chemical Company, Inc.), "Spixeria (registered trademark)" series (manufactured by Somar ), "Q-PILON (registered trademark)" series (manufactured by PI Technical Research Institute), "WINGO" series (manufactured by Wingo Technology), "Tomide (registered trademark)" series (manufactured by T&K TOKA), "KPI- MX" series (manufactured by Kawamura Sangyo Co., Ltd.), and "HPC-1000" and "HPC-2100D" (both manufactured by Showa Denko Materials).

The content of different polymers can be adjusted depending on the desired properties to be obtained.
When the composite sheet contains different polymers, the content of the different polymers with respect to the total weight of the composite sheet is preferably 0.1% by mass or more, more preferably 3% by mass or more. The content is preferably 60% by mass or less, more preferably 40% by mass or less.
The ratio of the mass of the different polymers to the mass of the F polymer in the composite sheet is preferably 0.005 or more, more preferably 0.05 or more. The ratio is preferably 5 or less, more preferably 4 or less.

When the composite sheet contains non-thermally fusible PTFE as a different polymer, the non-thermally fusible PTFE content is preferably 10 to 60% by mass, more preferably 20 to 40% by mass, relative to the total mass of the composite sheet.
The ratio of the mass of the non-thermally fusible PTFE to the mass of the F polymer in the composite sheet is preferably 0.5-5, more preferably 1-4.
When the content of non-thermally fusible PTFE is within such a range, the composite sheet tends to have excellent electrical properties.

When the composite sheet contains an aromatic polymer as a different polymer, the content of the aromatic polymer with respect to the total weight of the composite sheet is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass.
The ratio of the mass of the aromatic polymer to the mass of the F polymer in the composite sheet is preferably 0.01-0.2, more preferably 0.05-0.1.
When the content of the aromatic polymer is in such a range, the composite sheet tends to be excellent in low linear expansion and adhesiveness.

When the composite sheet contains at least one selected from the group consisting of different polymers and inorganic particles, the total content of at least one selected from the group consisting of different polymers and inorganic particles is more than 5% by mass, more preferably 15% by mass or more. The content is preferably 50% by mass or less, more preferably 30% by mass or less.

When the composite sheet contains at least one selected from the group consisting of different polymers and inorganic particles, the ratio of the total weight of at least one selected from the group consisting of different polymers and inorganic particles to the weight of the F polymer is 0.1 or more is preferable, and 0.3 or more is more preferable. The ratio is preferably 0.7 or less, more preferably 0.5 or less.

In addition to the above components, the composite sheet contains organic particles, a thixotropic agent, an antifoaming agent, a silane coupling agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, Other ingredients such as whitening agents, coloring agents, conductive agents, release agents, surface treatment agents, viscosity modifiers, and flame retardants may also be contained. Moreover, the composite sheet may contain a component derived from the dispersion described below.

The dielectric constant of the composite sheet is preferably 3.0 or less, more preferably 2.5 or less. A dielectric constant of 1.5 or more is preferable.
The dielectric loss tangent of the composite sheet is preferably 0.0100 or less, more preferably 0.0010 or less. The dielectric loss tangent is preferably 0.0001 or more.
Relative permittivity and dielectric loss tangent are measured at a frequency of 10 GHz by the SPDR (split post dielectric resonance) method.

The thickness of the composite sheet is preferably 5 μm or more, more preferably 10 μm or more. The thickness of the composite sheet is preferably 200 μm or less, more preferably 100 μm or less.
The composite sheet may be roll-shaped or sheet-shaped.

The composite sheet may be surface-treated. Surface treatment includes corona discharge treatment, discharge treatment such as plasma treatment, plasma graft polymerization treatment, electron beam irradiation, light irradiation treatment such as excimer UV light irradiation, Itro treatment using flame, and wet etching treatment using sodium metal. is mentioned. These surface treatments can introduce polar functional groups such as hydroxyl groups, carbonyl groups, and carboxy groups onto the surface of the composite sheet.

The coefficient of linear expansion of the composite sheet is preferably 80 ppm/°C or less, more preferably 30 ppm/°C or less. The lower limit of the coefficient of linear expansion is 5 ppm/°C. The coefficient of linear expansion is measured by the method specified in JIS C 6471:1995. Specifically, it is measured by the method described in Examples.

The manufacturing method of the composite sheet is not particularly limited as long as the composite sheet of the present disclosure is obtained. The composite sheet may be produced using a sheet or dispersion liquid containing each component described above, or may be produced by a production method described below.

A method for producing a composite sheet in one aspect of the present disclosure is a method for obtaining a composite sheet by thermocompression bonding a sheet containing an F polymer and the sheet and a woven or nonwoven fabric of a liquid crystal polymer. Hereinafter, this manufacturing method is also referred to as "thermocompression bonding method".

When the thermocompression bonding method is used, the sheet containing the F polymer may be a ready-made one or a new one.
The thickness of the sheet containing the F polymer is preferably 1-200 μm.
A sheet containing F polymer may be formed from a dispersion containing particles of F polymer. For example, a sheet containing an F polymer can be produced by applying a dispersion containing particles of the F polymer to the surface of a temporary substrate, heating the temporary substrate to which the dispersion has been applied, and It may be formed by a method comprising obtaining a laminate having a material and a layer containing an F polymer, and removing the temporary substrate from the laminate.

As a method for heating the temporary base material to which the dispersion liquid has been applied, the same heating method as in the dispersion liquid impregnation method, which will be described later, can be mentioned, and the preferred mode thereof is also the same.
Examples of the temporary base material include metal foils and resin films, and methods for removing the temporary base material include peeling, etching, and the like.

The sheet containing the F polymer may be formed by melt extruding the F polymer. A sheet further containing a different polymer or inorganic particles can be formed by melt-kneading the F polymer with a different polymer or inorganic particles and extruding.

Thermocompression bonding is performed by superimposing a sheet containing the F polymer on a liquid crystal polymer woven or nonwoven fabric and passing it between a pair of heated rolls, sandwiching it between a pair of opposing hot plates and applying pressure, or heat It can be performed by crimping by a method of sandwiching between a plate and a roll and applying pressure. The temperature for thermocompression bonding is preferably the melting point of the F polymer or higher, more preferably the melting point +20° C. or higher, from the viewpoint that the liquid crystal polymer woven fabric or non-woven fabric can be easily impregnated with the F polymer. The temperature for thermocompression bonding is preferably 300 to 380.degree.
The pressure for thermocompression bonding is preferably 0.2 to 10 MPa.
From the viewpoint of obtaining a composite sheet with reduced air bubbles, the thermocompression bonding is preferably performed under reduced pressure. When thermocompression bonding is performed under reduced pressure, the atmospheric pressure is preferably 10 KPa or less, more preferably 1 KPa or less.

In a further aspect of the present disclosure, a method of making a composite sheet includes impregnating a liquid crystal polymer woven or nonwoven fabric with a dispersion containing particles of F polymer. Hereinafter, this production method is also referred to as "dispersion liquid impregnation method". In one embodiment, a method for producing a composite sheet by a dispersion impregnation method comprises: impregnating a liquid crystal polymer woven or nonwoven fabric with a dispersion containing F polymer particles; heating the woven or nonwoven fabric of to obtain a composite sheet.
When the composite sheet is produced by the dispersion impregnation method, the F polymer tends to be impregnated between the fibers of the liquid crystal polymer woven or nonwoven fabric. As a result, the adhesion between the woven fabric or non-woven fabric of the liquid crystal polymer and the F polymer tends to increase, which is preferable.

Impregnation can be performed by disposing the dispersion liquid on the surface of the liquid crystal polymer woven or non-woven fabric. Examples of the impregnation method include a coating method, a droplet discharge method, and an immersion method, preferably a roll coating method, a knife coating method, a bar coating method, a die coating method, a roller immersion method, or a spray method, and more preferably a roller immersion method. .

The liquid crystal polymer woven fabric or nonwoven fabric impregnated with the dispersion is preferably heated to remove the dispersion medium, and further heated to calcine the F polymer. In this case, a composite sheet is obtained in which the woven fabric or non-woven fabric of the liquid crystal polymer is impregnated with the fired F polymer.
Heating for removing the dispersion medium is preferably carried out at 100 to 200° C. for 0.1 to 30 minutes. Also, during the heating, air may be blown to facilitate the removal of the liquid dispersion medium by air-drying.
Heating for sintering the F polymer is preferably performed at a temperature equal to or higher than the melting point of the F polymer, more preferably at 300 to 400° C. for 0.1 to 30 minutes.
Heating devices for each heating include an oven and a ventilation drying oven. The heat source in the device may be a contact heat source (hot air, hot plate, etc.) or a non-contact heat source (infrared radiation, etc.).
Further, each heating may be performed under normal pressure or under reduced pressure.
Moreover, the atmosphere in each heating may be either an air atmosphere or an inert gas (helium gas, neon gas, argon gas, nitrogen gas, etc.) atmosphere.

The impregnation and heating of the dispersion may be repeated two or more times. For example, the liquid dispersion is placed on the surface of a liquid crystal polymer woven fabric or nonwoven fabric and heated to remove the liquid dispersion medium and to bake the F polymer to obtain a composite sheet impregnated with the F polymer. Subsequently, the dispersion liquid is placed on the surface of the sheet and heated to remove the liquid dispersion medium and calcine the F polymer to obtain a composite sheet impregnated with the F polymer. When the impregnation and heating of the dispersion liquid are repeated, it is preferable to repeat the impregnation and heating of the dispersion liquid 2 to 8 times.
When the impregnation and heating of the dispersion liquid are repeated, the same kind of dispersion liquid may be used, or a different kind of dispersion liquid may be used. When the impregnation and heating of the dispersion liquid are repeated, the dispersion liquid containing F polymer particles (hereinafter also referred to as "F particles") may be used at least once.

When the impregnation and heating of the dispersion liquid are repeated, the dispersion liquid used in the first impregnation is preferably a dispersion liquid containing F particles. In this case, components such as F particles contained in the subsequent dispersion liquid are likely to be retained by the liquid crystal polymer woven fabric or non-woven fabric. Further, the dispersion liquid used in the first impregnation is more preferably a dispersion liquid containing F particles and non-heat-fusible PTFE particles (hereinafter also referred to as "PTFE particles"). In this case, components such as F particles contained in the subsequent dispersion are more likely to be retained in the woven fabric or non-woven fabric of the liquid crystal polymer.
The dispersion used in the final impregnation is preferably a dispersion containing F particles. In this case, the surface of the composite sheet tends to be excellent in smoothness and adhesiveness. Further, the dispersion used in the final impregnation is more preferably a dispersion containing F particles and PTFE particles. In this case, the surface of the composite sheet not only has excellent smoothness and adhesiveness, but also tends to have higher physical properties of PTFE.
The dispersions used in impregnations other than the first and last are preferably dispersions containing PTFE particles. In this case, the composite sheet tends to have high PTFE physical properties such as electrical properties.

The composite sheet is preferably a composite sheet obtained by impregnating a woven fabric or non-woven fabric of a liquid crystal polymer with F polymer, non-heat-melting PTFE and F polymer in this order. In this case, the composite sheet tends to be excellent in low linear expansion, adhesiveness with other substrates, and electrical properties.
As a method for producing such a composite sheet, a liquid crystal polymer woven or nonwoven fabric is first impregnated with a dispersion containing F particles and heated, then impregnated with a dispersion containing PTFE particles and heated, and finally F particles. A method of impregnating and heating a dispersion containing The first and last dispersions are preferably independently dispersions containing F particles and PTFE particles. Moreover, it is preferable that the impregnation and heating of the dispersion liquid containing the PTFE particles are carried out a plurality of times.

In the thermocompression bonding method or the dispersion liquid impregnation method described above, the melting point of the F polymer, the melting point of the liquid crystal polymer, and the absolute value of the difference between the melting point of the F polymer and the melting point of the liquid crystal polymer are preferably within the ranges described above. In this case, during heating in both methods, the interaction between the polar groups of the softened polymer tends to increase, a dense matrix structure of the F polymer and the liquid crystal polymer is formed, and the electrical properties and low linear expansion of the composite sheet are improved. Easier to improve. In addition, when the composite sheet contains inorganic particles, the supportability of the inorganic particles is likely to be improved.
A dispersion liquid containing F particles, which may be used for the thermocompression bonding method or the dispersion liquid impregnation method, will be described below.

The dispersion liquid is obtained by dispersing the F particles in a liquid dispersion medium. The dispersion may contain inorganic particles, polymers different from the F polymer, and other ingredients described as components of the composite sheet. When the dispersion contains different polymers, the different polymers may be dispersed in particles in the dispersion or dissolved in the liquid dispersion medium. Moreover, the dispersion liquid may contain a surfactant or a silane coupling agent.

From the viewpoint of dispersion stability, D50 of the F particles is preferably 0.1 μm or more, more preferably more than 0.3 μm, and even more preferably 1 μm or more. From the viewpoint of dispersion stability, the D50 of the F particles is preferably 25 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less.
The specific surface area of the F particles is preferably 1 to 25 m ² /g.
One type of F particles may be used, or two or more types may be used.

An F particle is a particle comprising an F polymer and may consist of an F polymer.
The F particles may contain a polymer other than the F polymer, an inorganic compound, or the like, and may form a core-shell structure in which the F polymer is the core and the shell is the polymer other than the F polymer or the inorganic compound, and the F A core-shell structure may be formed with a polymer as the shell and a polymer different from the F polymer or an inorganic compound as the core.
Polymers other than F polymers include aromatic polyesters, polyamideimides, polyimides, and maleimides.
Inorganic compounds include silica and boron nitride.

The content of F particles relative to the total amount of the dispersion is preferably 10% by mass or more, more preferably 20% by mass or more, from the viewpoint of impregnating a sufficient amount of F polymer into the liquid crystal polymer woven or nonwoven fabric. From the viewpoint of the dispersion stability of the dispersion medium, the content of the F particles relative to the total amount of the dispersion liquid is preferably 60% by mass or less, more preferably 40% by mass or less.

The liquid dispersion medium is a compound that is liquid at 25°C under atmospheric pressure, and preferably has a boiling point of 50 to 240°C. One liquid dispersion medium may be used, or two or more liquid dispersion mediums may be used. When two or more liquid dispersion media are used, the two or more liquid dispersion media are preferably compatible with each other.

The liquid dispersion medium is preferably a compound selected from the group consisting of water, amides, ketones and esters, more preferably water.
Amides include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropanamide, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy- N,N-dimethylpropanamide, N,N-diethylformamide, hexamethylphosphoric triamide, and 1,3-dimethyl-2-imidazolidinone.
Ketones include acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl isopentyl ketone, 2-heptanone, cyclopentanone, cyclohexanone, and cycloheptanone.
Esters include methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, ethyl 3-ethoxypropionate, γ-butyrolactone, and γ - Valerolactone.

The content of the liquid dispersion medium with respect to the total amount of the dispersion is preferably 40% by mass or more, more preferably 50% by mass or more. The content of the liquid dispersion medium with respect to the total amount of the dispersion liquid is preferably 90% by mass or less, more preferably 80% by mass or less.

The dispersion may contain inorganic particles. Details of the inorganic particles are as described above.
When the dispersion contains inorganic particles, the content of the inorganic particles is preferably 10 to 40% by mass, more preferably 10 to 30% by mass, relative to the total amount of the dispersion.

The dispersion may contain different polymers. Details of the polymers different from the F polymer are given above. The different polymers may be contained as particles in the dispersion or dissolved in the liquid dispersion medium.
When the dispersion contains different polymers, the content of the different polymers with respect to the total amount of the dispersion is preferably 0.1% by mass or more, more preferably 0.3% by mass or more. The content is preferably 60% by mass or less, more preferably 40% by mass or less.

If the different polymer is non-heat-fusible PTFE, the non-heat-fusible PTFE is preferably included in the dispersion as particles. D50 of the non-heat-fusible PTFE particles is preferably 0.1 to 1 μm.
The content of non-thermally fusible PTFE particles with respect to the total amount of the dispersion is preferably 20 to 60% by mass.
The ratio of the mass of the non-thermally fusible PTFE particles to the mass of the F particles in the dispersion is preferably 0.5-5, more preferably 1-3. In this case, it is easy to obtain a composite sheet having excellent electrical properties.

When the different polymer is an aromatic polymer, the aromatic polymer is preferably dissolved in the liquid dispersion medium and included in the dispersion.
The content of the aromatic polymer with respect to the total amount of the dispersion is preferably 0.1 to 30% by mass, preferably 0.3 to 10% by mass.
In this case, it is easy to obtain a composite sheet with low linear expansion and excellent adhesion to the substrate.

The dispersion preferably contains a surfactant. The surfactant is preferably a nonionic surfactant.
The nonionic surfactant is preferably a glycol-based surfactant, an acetylene-based surfactant, a silicone-based surfactant or a fluorine-based surfactant, and more preferably a silicone-based surfactant. One type of nonionic surfactant may be used, or two or more types may be used. When using two types of nonionic surfactants, the nonionic surfactants are preferably a silicone-based surfactant and a glycol-based surfactant.

Specific examples of nonionic surfactants include "Futhergent (registered trademark)" series (manufactured by Neos), "Surflon (registered trademark)" series (manufactured by AGC Seimi Chemical Co., Ltd.), and "Megafac (registered trademark)". series (manufactured by DIC), "Unidyne (registered trademark)" series (manufactured by Daikin Industries, Ltd.), "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451 ”, “BYK-3455”, “BYK-3456” (manufactured by BYK-Chemie Japan), “KF-6011”, “KF-6043” (manufactured by Shin-Etsu Chemical Co., Ltd.), and “Tergitol” series (manufactured by Dow Chemical , "Tergitol TMN-100X", etc.).

When the dispersion contains a nonionic surfactant, the content of the nonionic surfactant in the dispersion is preferably 1 to 15% by mass.

The dispersion may further contain a silane coupling agent. In this case, the silane coupling agent acts as a binder for the F particles, and the F polymer easily impregnates the woven fabric or non-woven fabric of the liquid crystal polymer satisfactorily.
Examples of the silane coupling agent include those similar to the silane coupling agent that may be used for the surface treatment of the inorganic particles described above.
When the dispersion contains a silane coupling agent, the content of the silane coupling agent in the dispersion is preferably 1 to 10% by mass.

The dispersion may further contain a pH adjuster or pH buffer to adjust the pH. pH adjusters include amines, ammonia, and citric acid. pH buffers include tris(hydroxymethyl)aminomethane, ethylenediaminetetraacetic acid, ammonium bicarbonate, ammonium carbonate, and ammonium acetate.
The dispersion may further contain other components described above as components of the composite sheet.

The viscosity of the dispersion liquid is preferably 10 mPa·s or more, more preferably 100 mPa·s or more. The viscosity of the dispersion liquid is preferably 10,000 mPa·s or less, more preferably 3000 mPa·s or less.
The viscosity of the dispersion is a value measured using a Brookfield viscometer under the conditions of 25° C. and 30 rpm. The measurement is repeated 3 times, and the average value of the 3 measurements is taken.
The thixotropic ratio of the dispersion is preferably 1.0 to 3.0.
The pH of the dispersion is preferably 5-10, more preferably 8-10.

The dispersion can be produced by mixing F particles and a liquid dispersion medium.
When the dispersion liquid further contains other components such as inorganic particles and particles of a different polymer, the dispersion liquid can be obtained by adding F particles and other components to the liquid dispersion medium at once and mixing them, or adding F particles to the liquid dispersion medium. A method of sequentially adding and mixing the particles and other components, a method of premixing the F particles and the liquid dispersion medium and the other components and the liquid dispersion medium and then mixing them, or a method of mixing the F particles and the other components. It is preferable to manufacture by a method of mixing with a liquid dispersion medium. Mixing of these may be performed in a batch system or in a continuous system.

Mixing equipment includes stirring equipment with blades (Henschel mixer, pressure kneader, Banbury mixer, planetary mixer, etc.), grinding equipment with media (ball mill, attritor, basket mill, sand mill, sand grinder, dyno mill, dispermat, SC mill, spike mill or agitator mill, etc.), dispersing equipment with other mechanisms (microfluidizer, nanomizer, ultimizer, ultrasonic homogenizer, dissolver, disper, high-speed impeller, rotation or revolution stirrer and thin film swirl) type high-speed mixer, etc.).

As a suitable method for producing the dispersion liquid, the F particles and part of the liquid dispersion medium are kneaded in advance to obtain a kneaded material, and the kneaded material is further added to the remaining liquid dispersion medium to obtain the dispersion liquid. method. The liquid dispersion medium used for kneading and addition may be the same type of liquid dispersion medium or different types of liquid dispersion mediums. When the dispersion further contains other components such as inorganic particles and particles of a polymer different from the F polymer, the other components may be mixed during kneading or added.

The kneaded product obtained by kneading may be in the form of a paste (such as a paste having a viscosity of 1000 to 100,000 mPa·s) or wet powder (a viscosity of 10,000 to 100,000 Pa·s as measured by a capillograph). s, wet powder, etc.).

The viscosity measured by a capillary graph is defined by using a capillary with a capillary length of 10 mm and a capillary radius of 1 mm, a furnace body diameter of 9.55 mm, a load cell capacity of 2 t, a temperature of 25 ° C., and a shear rate of 1 s ⁻ It is a value measured as ¹ .

Mixing in kneading is preferably performed with a planetary mixer. A planetary mixer is a stirring device having two stirring blades that rotate and revolve with each other.

Mixing in the addition is preferably performed with a thin-film swirling high-speed mixer. A thin-film swirling high-speed mixer is a stirring device that spreads F particles and a liquid dispersion medium in the form of a thin film on the inner wall surface of a cylindrical stirring tank, swirls them, and mixes them while exerting centrifugal force.

The composite sheet may be a laminate laminated with a substrate. Since the composite sheet of the present disclosure has an excellent coefficient of linear expansion, even if the laminate is subjected to high-temperature processing, it is difficult to separate from the substrate.
As the base material, metal substrates (copper, nickel, aluminum, titanium, metal foils of their alloys, etc.), heat-resistant resin films (polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, Liquid crystalline polyester, heat-resistant resin film such as tetrafluoroethylene polymer), prepreg substrate (precursor of fiber reinforced resin substrate), ceramic substrate (ceramic substrate such as silicon carbide, aluminum nitride, silicon nitride), and glass substrate mentioned.

Examples of the shape of the substrate include planar, curved, and uneven shapes. Moreover, the shape of the substrate may be any of foil, plate, film, and fibrous.
The ten-point average roughness of the substrate surface is preferably 0.01 to 0.05 μm.
The surface of the substrate may be surface-treated with a silane coupling agent or plasma-treated.
As a method of laminating the composite sheet and the substrate, a method of thermocompression bonding can be mentioned. As a method of thermocompression bonding, the same method as the thermocompression bonding in the above-described thermocompression bonding method can be used.
The peel strength between the composite sheet and the substrate in the laminate is preferably 10 to 100 N/cm.

Applications of the composite sheet of the present disclosure are not particularly limited. The composite sheet of the present disclosure is useful as antenna parts, printed circuit boards, aircraft parts, automobile parts, sporting goods, food industrial goods, heat dissipation parts, and the like.
Specifically, electric wire coating materials (wires for aircraft, etc.), enameled wire coating materials used for motors such as electric vehicles, electrical insulating tapes, insulating tapes for oil drilling, oil transportation hoses, hydrogen tanks, printed circuit boards materials, separation membranes (microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, gas separation membranes, etc.), electrode binders (for lithium secondary batteries, fuel cells, etc.), copy rolls, Furniture, automobile dashboards, home appliance covers, sliding parts (load bearings, yaw bearings, slide shafts, valves, bearings, bushes, seals, thrust washers, wear rings, pistons, slide switches, gears, cams, belt conveyors , food conveyor belts, etc.), tension ropes, wear pads, wear strips, tube ramps, test sockets, wafer guides, wear parts for centrifugal pumps, chemical and water supply pumps, tools (shovels, files, awls, saws, etc.), Boilers, hoppers, pipes, ovens, baking molds, chutes, racket guts, dies, toilet bowls, container coverings, power devices, transistors, thyristors, rectifiers, transformers, power MOS FETs, CPUs, heat radiating fins, metal heat radiating plates, wind turbines , blades for wind power generation equipment and aircraft, housings for personal computers and displays, electronic device materials, interior and exterior materials for automobiles, processing machines and vacuum ovens that perform heat treatment under low oxygen conditions, sealing materials for plasma processing equipment, etc. Spatter and various other materials It is useful as a heat radiation component in a processing unit such as a dry etching device, an electromagnetic wave shield, and the like.

The composite sheet of the present disclosure is excellent in electrical properties and low linear expansion properties, and is therefore suitable for applications where such properties are desired. For example, the composite sheet is suitably used as a material such as a copper-clad laminate for printed wiring boards.

The embodiments of the present disclosure will be described in detail below by way of examples, but the embodiments of the present disclosure are not limited to these.

1. Preparation of each component of the dispersion liquid [F particles]
F particle 1: 97.9 mol%, 0.1 mol% and 2.0 mol% of TFE units, NAH units and PPVE units in this order, and 1000 carbonyl groups per 1×10 ⁶ main chain carbon atoms Particles (D50: 2.1 μm) of hot-melt polymer 1 (melting point: 300 ° C., melt flow rate: 25 g / 10 minutes)
F Particle 2: A hot-melt polymer 2 containing 98.5 mol% and 1.5 mol% of TFE units and PPVE units in this order and having no oxygen-containing polar group (melting point: 300°C, melt flow rate: 22 g/10 min) particles (D50: 2.4 μm)
[Inorganic particles]
Inorganic particles 1: spherical silica (D50: 1 μm)
[Woven fabric or non-woven fabric of liquid crystal polymer]
Nonwoven fabric 1: “Vecrus” manufactured by Kuraray Kuraflex Co., Ltd. (basis weight: 9 g/m ² )
Woven fabric 1: A liquid crystalline aromatic polyester plain fabric having an aromatic ring content of 60% by mass or more (load deflection temperature: 300°C, specific gravity: 1.42 g/cm ³ , fiber diameter: 7 µm, thickness: 123 µm , volume basis weight: 32 cm ³ /m ² , warp density: 20/cm, weft density: 20/cm)
Fabric 2: Fabric of liquid crystalline aromatic polyester (melting point: 320°C) (deflection temperature under load: 350°C, basis weight: 45 g/cm ² )
Fabric 3: Fabric of liquid crystalline aromatic polyester (melting point: 230°C) (basis weight: 41 g/cm ² )

2. Manufacture of composite sheet (Example 1)
In a pot, 30 parts by mass of F particles 1, 15 parts by mass of inorganic particles 1, 1 part by mass of a silicone-based surfactant, and 64 parts by mass of water are added, and zirconia balls are added. Then, the pot is rolled at 150 rpm for 1 hour to obtain Dispersion Liquid 1 (viscosity: 200 mPa·s). After disposing the obtained dispersion liquid 1 on the nonwoven fabric 1 by a roller dipping method, it is passed through a drying oven at 120° C. for 5 minutes to be heated and dried. After that, the composite sheet 1 (thickness: 40 μm) in which the nonwoven fabric 1 is impregnated with the baked F particles 1 is obtained by heating and baking in a far-infrared furnace at 340° C. for 10 minutes. In the composite sheet 1, the content of the inorganic particles 1 is 16% by mass, and the mass ratio of the content of the inorganic particles 1 to the content of the polymer 1 is 0.5.
(Example 2)
A composite sheet 2 (thickness: 140 μm) in which the woven fabric 1 is impregnated with the baked F particles 1 is obtained in the same manner as in Example 1 except that the nonwoven fabric 1 is changed to the woven fabric 1 . In the composite sheet 2, the content of the inorganic particles 1 is 7% by mass, and the mass ratio of the content of the inorganic particles 1 to the content of the polymer 1 is 0.5.
(Example 3)
A composite sheet 3 (thickness: 140 μm) in which the woven fabric 2 is impregnated with the baked F particles 1 is obtained in the same manner as in Example 1 except that the nonwoven fabric 1 is changed to the woven fabric 2 . In the composite sheet 3, the content of the inorganic particles 1 is 7% by mass, and the mass ratio of the content of the inorganic particles 1 to the content of the polymer 1 is 0.5.
(Example 4)
A composite sheet 4 in which the woven fabric 2 was impregnated with the baked product of the F particles 1 in the same manner as in Example 1 except that the inorganic particles 1 were not used in the preparation of the dispersion 1 and the nonwoven fabric 1 was changed to the woven fabric 2. (thickness: 140 μm).
(Example 5)
A composite sheet 5 in which the woven fabric 3 is impregnated with the fired product of the F particles 1 in the same manner as in Example 1 except that the inorganic particles 1 are not used in the preparation of the dispersion 1 and the nonwoven fabric 1 is changed to the woven fabric 3. (thickness: 140 μm).
(Example 6: Comparative example)
A composite sheet 6 (thickness: 140 μm) in which the woven fabric 1 is impregnated with the baked product of the F particles 2 is obtained in the same manner as in Example 1 except that the F particles 1 are changed to the F particles 2 . Inorganic particles 1 are peeled off during drying and firing in the production of composite sheet 6 .

3. Composite sheet evaluation
3-1. Peel strength Each of the obtained composite sheets and a copper foil are thermally compressed and laminated to prepare a copper-clad laminate, and a rectangular test piece having a length of 100 mm and a width of 10 mm is obtained from the copper-clad laminate. cut out. A position 50 mm from one end in the length direction of the test piece is fixed, and the copper foil and the composite sheet are peeled off from one end in the length direction at a pulling speed of 50 mm/min at 90° to the test piece. The maximum load at the time of peeling is taken as the peel strength (N/cm), and evaluation is made according to the following evaluation criteria.
[Evaluation criteria]
A: 12 N/cm or more.
B: Less than 12 N/cm.
3-2. Linear expansion coefficient For each of the obtained composite sheets, a 180 mm square square test piece was cut out, and the linear expansion of the test piece was measured in the range of 25 ° C. or higher and 260 ° C. or lower according to the measurement method specified in JIS C 6471: 1995. The modulus is measured and evaluated according to the following criteria.
AA: 20 ppm/°C or less A: More than 20 ppm/°C and less than 30 ppm/°C B: More than 30 ppm/°C and less than 40 ppm/°C C: More than 40 ppm/°C

3-3. Electrical properties For each of the obtained composite sheets, a sample with a length of 10 cm and a width of 5 cm was cut, and the relative permittivity and dielectric loss tangent (measurement frequency: 10 GHz) were measured by the SPDR (split post dielectric resonance) method, Evaluation is made according to the following evaluation criteria.
[Evaluation criteria]
A: The dielectric constant is 2.2 or less and the dielectric loss tangent is less than 0.0010.
B: Relative permittivity is 2.2 or less and dielectric loss tangent is 0.0010 or more and less than 0.0020, or relative permittivity is more than 2.2 and 2.4 or less and dielectric loss tangent is less than 0.0010 is.
C: Relative permittivity is more than 2.2 and 2.4 or less, and dielectric loss tangent is 0.0010 or more and less than 0.0020.
Table 1 below summarizes the evaluation results for each composite sheet. As shown in the table below, Composite Sheets 1 to 5 are excellent in electrical properties and low linear expansion properties. In addition, composite sheets 1 to 5 were also evaluated as good in terms of peel strength.

The disclosures of Japanese Patent Application Nos. 2021-119739 and 2021-172596 are incorporated herein by reference in their entireties.
All publications, patent applications and technical standards mentioned herein are to the same extent as if each individual publication, patent application and technical standard were specifically and individually noted to be incorporated by reference. incorporated herein by reference.

Claims

A composite sheet containing a heat-melting liquid crystal polymer woven or non-woven fabric and a heat-melting tetrafluoroethylene-based polymer having an oxygen-containing polar group impregnated in the liquid crystal polymer woven or non-woven fabric.
The composite sheet according to claim 1, wherein the oxygen-containing polar group is a hydroxyl group-containing group or a carbonyl group-containing group.
The composite sheet according to claim 1 or 2, wherein the liquid crystal polymer contains a liquid crystalline aromatic polyester.
The composite sheet according to claim 1 or 2, wherein the tetrafluoroethylene-based polymer has a melting point of 260 to 320°C.
The composite sheet according to claim 1 or 2, wherein the liquid crystal polymer has a melting point of 230 to 350°C.
The composite sheet according to claim 1 or 2, wherein the absolute value of the difference between the melting point of the tetrafluoroethylene-based polymer and the melting point of the liquid crystal polymer is 30°C or less.
The composite sheet according to claim 1 or 2, further comprising a polymer different from the tetrafluoroethylene-based polymer.
The composite sheet according to claim 1 or 2, further containing inorganic particles.
At least one selected from the group consisting of a polymer different from the tetrafluoroethylene-based polymer and inorganic particles, and is selected from the group consisting of a polymer different from the tetrafluoroethylene-based polymer and the inorganic particles 3. The composite sheet according to claim 1 or 2, wherein the total content of at least one of said composite sheets is greater than 5% by weight relative to the total weight of said composite sheet.
a polymer different from the tetrafluoroethylene-based polymer, and at least one selected from the group consisting of inorganic particles, a polymer different from the tetrafluoroethylene-based polymer relative to the mass of the tetrafluoroethylene-based polymer, 3. The composite sheet according to claim 1, wherein the total mass ratio of at least one selected from the group consisting of inorganic particles is 0.1 or more.
The composite sheet according to claim 1 or 2, having a thickness of less than 50 µm.
A method for producing a composite sheet, in which a sheet containing a heat-melting tetrafluoroethylene polymer having an oxygen-containing polar group is thermocompressed with a woven or nonwoven fabric of a liquid crystal polymer to obtain a composite sheet.
The manufacturing method according to claim 12, wherein the sheet is formed from a dispersion containing particles of the tetrafluoroethylene-based polymer.
A method for producing a composite sheet, comprising impregnating a woven or nonwoven fabric of a liquid crystal polymer with a dispersion containing particles of a heat-melting tetrafluoroethylene-based polymer having an oxygen-containing polar group to obtain a composite sheet.
The production method according to claim 14, wherein the dispersion further contains at least one selected from the group consisting of a polymer different from the tetrafluoroethylene-based polymer and inorganic particles.