KR20240034188A - Manufacturing method and composite sheet of composite sheet - Google Patents

Abstract

A method for producing a composite sheet, wherein a composite sheet is obtained by impregnating a woven or non-woven fabric of a liquid crystal polymer with a film containing a heat-meltable tetrafluoroethylene polymer having oxygen atoms, and the composite sheet.

Description

Manufacturing method and composite sheet of composite sheet

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

Recently, in the field of information and communications, there has been a demand for improved performance of materials used in printed wiring boards and the like due to the development of communications technologies such as high-frequency communications. Fluoropolymers, especially tetrafluoroethylene-based polymers, have excellent electrical properties and excellent heat resistance, and are therefore preferably used in printed wiring boards.

Patent Document 1 describes a composite sheet including a layer containing a liquid crystal polymer and a nonwoven fabric of the liquid crystal polymer on opposing surfaces of the layer containing the tetrafluoroethylene-based polymer.

Japanese Patent Publication No. 2017-119378

Tetrafluoroethylene-based polymers have excellent electrical properties and a high coefficient of linear expansion. Therefore, when the laminate of the composite sheet and the substrate described in Patent Document 1 is processed at 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 substrate was easy to peel off.

The present disclosure relates to providing a composite sheet excellent in 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> A method for producing a composite sheet, wherein a composite sheet is obtained by impregnating a woven or non-woven fabric of a liquid crystal polymer with a film containing a heat-meltable tetrafluoroethylene polymer having oxygen atoms.

<2> The production method according to <1>, wherein the melt flow rate of the tetrafluoroethylene-based polymer is 1 to 30 g/min under the condition of a load of 49 N.

<3> The production method according to <1> or <2>, wherein the melting temperature of the tetrafluoroethylene-based polymer is 260°C or higher.

<4> The production method according to any one of <1> to <3>, wherein the tetrafluoroethylene-based polymer has an oxygen-containing polar group, and the oxygen-containing polar group is a hydroxyl group-containing group or a carbonyl group-containing group.

<5> The tetrafluoroethylene-based polymer has an oxygen-containing polar group, and the number of oxygen-containing polar groups in the tetrafluoroethylene-based polymer is 10 to 5000 per 1×10 ⁶ carbon number in the main chain, <1 The manufacturing method according to any one of > to <4>.

<6> The tetrafluoroethylene-based polymer contains a unit based on perfluoroethylene, and the perfluoroethylene-based polymer accounts for the total units in the tetrafluoroethylene-based polymer. The production method according to any one of <1> to <5>, wherein the content of the unit based on is more than 2 mol%.

<7> The manufacturing method according to any one of <1> to <6>, wherein the liquid crystal polymer has a load deflection temperature of 240°C or higher.

<8> The production method according to any one of <1> to <7>, wherein the liquid crystal polymer contains a liquid crystalline aromatic polyester.

<9> The production method according to <8>, wherein the aromatic ring content of the aromatic polyester is 55% by mass or more.

<10> The manufacturing method according to any one of <1> to <9>, wherein the composite sheet has a thickness of 200 μm or less.

<11> The manufacturing method according to any one of <1> to <10>, wherein the film and the woven fabric or non-woven fabric are heat-compressed and the film is impregnated.

<12> The production method according to <11>, wherein the compression temperature in the thermocompression is within ±30°C of the melting temperature of the tetrafluoroethylene-based polymer.

<13> The manufacturing method according to <11> or <12>, wherein the compression pressure in the thermocompression is 1 MPa or more.

<14> The manufacturing method according to any one of <11> to <13>, wherein the thermocompression bonding is performed under reduced pressure.

<15> A composite sheet containing a woven or non-woven fabric of a liquid crystal polymer, and a heat-meltable tetrafluoroethylene-based polymer having an oxygen atom impregnated into the woven or non-woven fabric.

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

Hereinafter, modes for carrying out embodiments 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, etc.) are not essential, unless specifically stated. The same applies to the numerical values and their ranges, and do not limit the embodiments of the present disclosure.

In the present disclosure, the numerical range indicated using “~” includes the numerical values written before and after “~” as the minimum and maximum values, respectively.

In this disclosure, each component may contain multiple types of corresponding substances. When multiple types of substances corresponding to each component exist in the composition, the content rate or content of each component means the total content rate or content of the multiple types of substances present in the composition, unless otherwise specified.

In the present disclosure, plural types of particles corresponding to each component may be contained. When multiple types of particles corresponding to each component exist in the composition, the particle diameter of each component means the value for the mixture of the multiple types of particles present in the composition, unless otherwise specified.

In the present disclosure, a “composite sheet” is a sheet containing woven or non-woven fabric of a polymer and a liquid crystal polymer.

In the present disclosure, “film” and “sheet” are used interchangeably, and their thickness is not particularly limited.

In the present disclosure, the word “layer” includes cases where the layer or film is formed in the entire area when observing the area where the layer or film exists, as well as cases where the layer or film is formed only in a part of the area.

In the present disclosure, the word “lamination” refers to stacking layers, and two or more layers may be combined or two or more layers may be removable.

In the present disclosure, the “average particle diameter (D50)” is the volume-based cumulative 50% diameter of the particles determined by a laser diffraction/scattering method. That is, the particle size distribution is measured by a laser diffraction/scattering method, a cumulative curve is obtained with the total volume of the particle population being 100%, and the point on the cumulative curve at which the cumulative volume is 50% is the particle size.

The D50 of the particles is determined by dispersing the particles in water and analyzing them by a laser diffraction/scattering method using a laser diffraction/scattering type particle size distribution measuring device (LA-920 measuring instrument manufactured by Horiba Seisakusho Co., Ltd.).

In the present disclosure, the “specific surface area” is a value calculated by measuring particles by the gas adsorption (constant volume method) BET multipoint method, and is obtained using NOVA4200e (manufactured by Quantachrome Instruments).

In the present disclosure, “melting temperature” 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, “melt flow rate” means the polymer melt mass flow rate 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 using a dynamic viscoelasticity measurement (DMA) method.

In the present disclosure, “polymer” is a compound formed by polymerizing monomers. That is, “polymer” has a plurality of units based on monomers.

In the present disclosure, the “unit” in a polymer means an atomic group based on the monomer formed by polymerization of the monomer. The unit may be a unit formed directly through a polymerization reaction, or may be a unit in which a part of the unit is converted into a different structure by processing the polymer. Hereinafter, the unit based on monomer a is also simply referred to as “monomer a unit.”

The method for producing a composite sheet of the present disclosure includes impregnating a woven or non-woven fabric of a liquid crystal polymer with a film containing a heat-meltable tetrafluoroethylene-based polymer having an oxygen atom (hereinafter also referred to as “F polymer”), This is how to obtain a composite sheet. The composite sheet manufactured by the manufacturing method of the present disclosure has excellent electrical properties and low linear expansion properties.

In general, tetrafluoroethylene-based polymers have excellent electrical properties such as low dielectric constant and low dielectric loss tangent, and have a large coefficient of linear expansion. In conventional composite sheets using tetrafluoroethylene-based polymers, low linear expansion properties are not sufficient. In addition, in the composite sheet of Patent Document 1, the tetrafluoroethylene-based polymer was impregnated into the nonwoven fabric of the liquid crystal polymer, and the two were merely entangled and bonded to each other, and the adhesiveness of the interface was insufficient. As a result, the laminate of the composite sheet and the base material had problems such as thermal expansion and separation from the base material when processed at high temperatures.

The inventors carefully studied and found that a composite sheet obtained by impregnating a woven or non-woven fabric of a liquid crystal polymer with a film of a heat-meltable tetrafluoroethylene polymer having oxygen atoms has excellent electrical properties and low linear expansion, and when laminated with a base material, It was found that the peel strength was also excellent. The reason for this is not necessarily clear, but it is thought to be as follows.

In the above impregnation, the oxygen atoms contained in the tetrafluoroethylene-based polymer affect the conformation of the tetrafluoroethylene-based polymer, thereby improving the adhesion at the interface between the tetrafluoroethylene-based polymer and the woven or non-woven fabric of the liquid crystal polymer. do. As a result, it is believed that the linear expansion of the tetrafluoroethylene-based polymer is buffered by the woven or non-woven fabric of the liquid crystal polymer, and both polymer properties are expressed in a highly balanced manner.

Additionally, the oxygen atoms in the tetrafluoroethylene polymer are thought to improve adhesion to the substrate, and these properties are thought to provide a material useful as a low transmission loss material, for example.

In the manufacturing method of the composite sheet of the present disclosure, woven or non-woven fabric of liquid crystal polymer is used. As the liquid crystal polymer, a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state 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 the liquid crystal polymer may be a woven fabric or non-woven fabric containing the liquid crystal polymer, and may contain other materials. The content of the liquid crystal polymer relative to the total mass of the woven or non-woven fabric of the liquid crystal polymer is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 100% by mass.

As the liquid crystal polymer, liquid crystal polyester is preferable. Liquid crystalline polyester may be liquid crystalline polyesteramide, liquid crystalline polyester ether, liquid crystalline polyester carbonate, or liquid crystalline polyesterimide.

Liquid crystalline polyester is preferably a liquid crystalline aromatic polyester, and specifically, a polycondensate of an aromatic dicarboxylic acid, an aromatic diol or an aromatic hydroxycarboxylic acid, an aromatic dicarboxylic acid, an aromatic diol, and an aromatic hydroxycarboxylic acid. Polycondensates of boxylic acids, etc. can be mentioned.

Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid.

Aromatic diols include 4,4'-dihydroxybiphenyl and bisphenol A.

Examples of aromatic hydroxycarboxylic acids include parahydroxybenzoic acid and 2-hydroxy-6-naphthoic acid.

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 together as long as liquid crystallinity is exhibited. Examples of aliphatic diol include ethylene glycol.

Among them, the liquid crystal polymer is preferably a liquid crystalline aromatic polyester with an aromatic ring content of 55% by mass or more from the viewpoint of excellent heat resistance. The aromatic ring content of the liquid crystalline aromatic polyester is more preferably 60 mass% or more. The aromatic ring content is preferably 80% by mass or less, more preferably 75% by mass or less, and still more preferably 70% by mass or less. While these liquid crystal polymers have a small degree of freedom of conformation and have excellent heat resistance, they have difficulty interacting with other polymers. However, in the present disclosure, the F polymer has an oxygen atom, has a relatively high degree of freedom of conformation, and has a high affinity with the liquid crystal polymer, so it easily adheres well to the liquid crystal polymer with a high aromatic ring content.

In the present disclosure, the aromatic ring content is obtained from the following formula. In addition, the carbon atom contained in the substituent bonded to the aromatic ring is not included in the carbon atom forming the aromatic ring.

Aromatic ring content (mass%) = 100

For example, the aromatic ring content in typical units contained in liquid crystalline aromatic polyester is as follows, and the aromatic ring content in liquid crystalline aromatic polyester can be calculated based on the copolymerization ratio (molar ratio) of each unit.

2-Hydroxy-6-naphthoic acid: 71%

4,4'-dihydroxybiphenyl: 78%

Terephthalic acid: 54%

2,6-naphthalenedicarboxylic acid: 66%

Examples of the liquid crystalline polyesteramide include aromatic polyesteramide in which aminophenol is copolymerized with the liquid crystalline aromatic polyester.

Specifically, the liquid crystal polymer includes the liquid crystal polymer described in paragraphs 0032 to 0039 of Japanese Patent Application Laid-Open No. 2017-119378.

The load deflection temperature 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 load deflection temperature is preferably 400°C or lower. In this case, a composite sheet is preferable because it has excellent heat resistance. In addition, since the F polymer has oxygen atoms and a relatively high degree of freedom of conformation, it easily adheres well to liquid crystal polymers that have a high load deflection temperature, that is, have a small degree of freedom of conformation and are difficult to interact with other polymers.

Additionally, it is preferable that the load deflection temperature of the liquid crystal polymer exceeds the melting temperature of the F polymer. In this case, under high temperature exposure, a highly advanced matrix structure of the liquid crystal polymer and F polymer is likely to be formed, and the electrical properties and low linear expansion properties of the composite sheet are likely to be further improved.

In addition, the load deflection temperature is a value measured with a load of 0.46 MPa according to ASTMD648.

The average fiber diameter of the nonwoven fabric of the liquid crystal polymer is preferably 0.01 to 20 μm, more preferably 0.05 to 10 μm, and most preferably 0.1 to 4 μm. The average fiber diameter is obtained by measuring the fiber diameters of 200 fibers by electron microscopy and calculating the average value excluding data from the 10 thinnest and 10 thickest fibers.

The volume basis weight of the nonwoven fabric of the liquid crystal polymer is preferably 3 to 100 cm ³ /m ² , more preferably 5 to 60 cm ³ /m ² , and still more preferably 10 to 40 cm ³ /m ² .

In addition, the volume basis weight of the liquid crystal polymer nonwoven fabric is obtained by dividing the weight per unit area of the liquid crystal polymer nonwoven fabric by the specific gravity of the liquid crystal polymer nonwoven fabric.

The nonwoven fabric of liquid crystal polymer may be manufactured or ready-made.

The liquid crystal polymer nonwoven fabric may be formed using either a dry method or a wet method.

In the case of molding into a nonwoven fabric by a dry method, especially by melting, it is generally molded in a temperature region higher than the glass transition temperature, and in a temperature region where the liquid crystal structure collapses and orients randomly at a temperature even higher than the temperature region where the liquid crystal structure is in a non-flowing state. You can. Although it varies depending on the chemical structure of the liquid crystal polymer, for example, melt molding is possible at a molding temperature of 200 to 400°C. Melt molding methods for nonwoven fabrics of liquid crystal polymers include the spun bond method and the melt blow method, for example, the molding method described in International Publication No. 2010/098400.

In the wet method, a nonwoven fabric is formed by using pre-spun liquid crystal polymer fibers as a raw material, cutting them to a certain length, and forming single fibers into a sheet by a papermaking method as exemplified in Japanese Patent Application Laid-Open No. 2012-36538. can do.

The nonwoven fabric of the liquid crystal polymer may be formed by electrolytically spinning a solution containing the liquid crystal polymer, or may be formed by the method exemplified in Japanese Patent Application Publication No. 2010-196228, that is, a method of stretching the filament of the liquid crystal polymer while heating it with a laser. . In this case, a nonwoven fabric containing liquid crystal polymer fibers with a narrow average fiber diameter can be obtained.

The liquid crystal polymer woven fabric can also be regarded as a liquid crystal polymer fiber fabric, and specifically includes a plain fabric.

The warp density of the plain fabric of the liquid crystal polymer is preferably 2 to 80 pieces/cm, and more preferably 4 to 60 pieces/cm.

The weft density of the plain fabric of the liquid crystal polymer is preferably 2 to 80 pieces/cm, and more preferably 4 to 60 pieces/cm.

The liquid crystal polymer fiber is preferably a fiber obtained by melt spinning the liquid crystal polymer. The liquid crystal polymer fiber obtained by melt spinning may be further heat treated to improve strength.

The fiber of the liquid crystal polymer may be made of one type of liquid crystal polymer, or may be made of two or more types of liquid crystal polymer.

The liquid crystal polymer fiber 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 a core component and a sheath component.

The woven or non-woven fabric of the liquid crystal polymer is preferably surface treated. In this case, the affinity between the woven or non-woven fabric of the liquid crystal polymer and the F polymer is improved, and the adhesion between the woven or non-woven fabric of the liquid crystal polymer and the F polymer is likely to improve. In addition, the F polymer easily impregnates even the fine pores of the woven or non-woven fabric of the liquid crystal polymer, so the mechanical properties of the resulting composite sheet are likely to be improved.

Surface treatments include corona treatment and plasma treatment. Plasma treatment includes vacuum plasma treatment and atmospheric pressure plasma treatment, and vacuum plasma treatment is preferable.

The vacuum plasma treatment is preferably performed in an atmosphere containing argon gas, an atmosphere containing oxygen gas, or an atmosphere containing hydrogen gas and nitrogen gas.

In the production method of the present disclosure, a film containing F polymer (hereinafter also referred to as F film) is used. One type of F polymer may be used, or two or more types may be used.

A tetrafluoroethylene-based polymer is a polymer containing a unit (hereinafter also referred to as a “TFE unit”) based on tetrafluoroethylene (hereinafter also referred to as “TFE”). The content of the TFE unit in the tetrafluoroethylene-based polymer is preferably 50 mol% or more, and 90 mol% or more relative to all units in the tetrafluoroethylene-based polymer, from the viewpoint of appropriately expressing the characteristics of the TFE unit. This is more preferable. The content rate may be 99 mol% or less, and may be 98 mol% or less.

F polymer has oxygen atoms. According to the manufacturing method of the present disclosure using F polymer, a composite sheet excellent in electrical properties and low linear expansion is obtained. Additionally, composite sheets produced using F polymer tend to have excellent adhesion to the substrate.

In the present disclosure, a polymer “having an oxygen atom” means a polymer having an oxygen atom that is also a constituent atom of the polymer, and even if oxygen atoms are inevitably mixed during the manufacturing process, such oxygen atoms are mixed. Polymers with oxygen atoms are not included in the polymers “having oxygen atoms.”

In one aspect, the F polymer includes a heat-meltable tetrafluoroethylene-based polymer having an oxygen-containing polar group. In this case, the oxygen-containing polar group in the F polymer interacts with the liquid crystal polymer or the substrate, so the composite sheet tends to have low linear expansion and excellent adhesion to the substrate, which is preferable.

Examples of the oxygen-containing polar group include a hydroxyl group-containing group, a carbonyl group-containing group, an epoxy group-containing group, and a phosphono group-containing group. A hydroxyl group-containing group or a carbonyl group-containing group is preferable, and a carbonyl group-containing group is more preferable. The number of oxygen-containing polar groups in the F polymer may be one or two or more.

The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, and -CF ₂ CH ₂ OH and -C(CF ₃ ) ₂ OH are more preferable.

Carbonyl group-containing groups include carboxyl group, alkoxycarbonyl group, amide group, isocyanate group, carbamate group (-OC(O)NH ₂ ), acid anhydride residue (-C(O)OC(O)-), and imide residue (- 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 the F polymer is preferably 10 to 5,000, more preferably 100 to 3,000 per 1×10 ⁶ carbon atoms in the main chain. In addition, the number of oxygen-containing polar groups can be quantified by the composition of the polymer or the method described in International Publication No. 2020/145133.

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, with the former being preferred. Examples of the latter include tetrafluoroethylene-based polymers having oxygen-containing polar groups as terminal groups derived from polymerization initiators, chain transfer agents, etc., polymers obtained by plasma treatment or ionizing radiation treatment of tetrafluoroethylene-based polymers, etc. . On the other hand, the F polymer or its film may not have been subjected to surface treatment such as plasma treatment or ionizing line treatment.

Monomers having a carbonyl group-containing group are preferably itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as “NAH”), and the resulting composite sheet From the viewpoint of excellent adhesiveness, NAH is more preferable.

F polymers having oxygen-containing polar groups include polytetrafluoroethylene (PTFE), a polymer containing TFE units and ethylene-based units (ETFE), and TFE units and propylene-based units. A polymer containing TFE units and units based on perfluoro(alkylvinylether) (PAVE) (PAVE units), or a polymer containing TFE units and units based on hexafluoropropylene (HFP units). A polymer containing (FEP) is preferred, PFA and FEP having an oxygen-containing polar group are more preferred, and PFA having an oxygen-containing polar group is further preferred. These polymers may further contain units based on other comonomers.

The F polymer is preferably a polymer having a carbonyl group-containing group that contains a TFE unit and a PAVE unit, and more preferably contains a TFE unit, a PAVE unit, and a unit based on a monomer having a carbonyl group-containing group, and the TFE unit and the PAVE It is a polymer containing units based on monomers having a unit and a carbonyl group-containing group, and containing 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol% of these units in this order, relative to all units, or 87 It is more preferable that it is a polymer containing - 96 mol%, 0.99 - 9.97 mol%, and 3 - 6 mol%. The former case is preferable because it is easy to obtain a composite sheet with excellent heat resistance. In the latter case, it is preferable because it is easy to obtain a composite sheet with excellent adhesion between the woven or non-woven fabric of the F polymer and the liquid crystal polymer. Specific examples of such F polymer include the polymer described in International Publication No. 2018/016644.

In a new aspect, the F polymer includes a heat-meltable tetrafluoroethylene-based polymer containing a PAVE unit. In this case, by having a PAVE unit, the freedom of conformation of the F polymer can be improved while maintaining the excellent electrical properties of the tetrafluoroethylene-based polymer, so that the composite sheet has electrical properties, low linear expansion, and adhesion to the substrate. It is desirable because it is easy to excel. The heat-meltable tetrafluoroethylene-based polymer containing a PAVE unit may not have a carbonyl group-containing group or may not contain a unit based on a monomer having a carbonyl group-containing group.

PAVE is preferably CF ₂ =CFOCF ₃ , CF ₂ =CFOCF ₂ CF ₃ and CF ₂ =CFOCF ₂ CF ₂ CF ₃ (hereinafter also referred to as PPVE), and more preferably PPVE.

In the F polymer containing a PAVE unit, the content of the PAVE unit in all units in the F polymer is preferably 1.0 mol% or more, more preferably 2.0 mol% or more, and still more preferably 2.3 mol% or more. It is thought that when the content of PAVE units is more than the above lower limit, the melt fluidity of the F polymer increases and microspherulites are easily formed, and the adhesive strength improves. From the viewpoint of heat resistance, the content of PAVE units in all units in the F polymer is preferably 10.0 mol% or less, and more preferably 5.0 mol% or less.

The F polymer, which contains a PAVE unit and has a PAVE unit content of 2.0 mol% or more in all units in the F polymer, is preferably terminal fluorinated, and the number of oxygen-containing polar groups in the F polymer is the number of carbon atoms in the main chain. The number per 1×10 ⁶ is preferably 500 or less, more preferably 100 or less, and even more preferably 0.

In this case, the formation of a lamellar structure is promoted during crystallization of the F polymer, and microspherulites are likely to be generated, so that the adhesion of the liquid crystal polymer to the woven or non-woven fabric or the substrate is likely to increase. This polymer consists of a TFE unit and a PPVE unit, and the TFE unit content is preferably 95.0 to 98.0 mol%, and the PPVE unit content is preferably 2.0 to 5.0 mol%.

F polymer is heat meltable.

A heat-meltable polymer refers to a polymer at which a melt flow rate is 1 to 1000 g/10 min under the condition of a load of 49 N.

The melt flow rate of the F polymer is preferably 1 to 30 g/min, and more preferably 5 to 30 g/min, under the condition of a load of 49 N, from the viewpoint of satisfactorily impregnating the F polymer into the woven or nonwoven fabric of the liquid crystal polymer. .

From the viewpoint of improving the heat resistance of the composite sheet, the melting temperature of the F polymer is preferably 200°C or higher, and more preferably 260°C or higher. The melting temperature of the F polymer is preferably 325°C or lower, and more preferably 320°C or lower, from the viewpoint of satisfactorily impregnating the F polymer into the woven or non-woven fabric of the liquid crystal 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, and more preferably 75°C or higher. The glass transition point of the F polymer is preferably 150°C or lower, and more preferably 125°C or lower, from the viewpoint of satisfactory impregnation into woven or non-woven fabrics of the liquid crystal polymer.

From the viewpoint of improving the electrical properties and heat resistance of the composite sheet, the fluorine content of the F polymer is preferably 70% by mass or more, and more preferably 72 to 76% by mass. Additionally, the fluorine content is determined from the polymer composition.

The surface tension of F polymer is preferably 16 to 26 mN/m. The surface tension can be measured by placing a droplet of the wetness index reagent (manufactured by Fujifilm 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 tends to have excellent adhesion to the woven or non-woven fabric of the liquid crystal polymer because it has oxygen atoms.

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 or non-woven fabric and the base material.

The F film may be composed of only the F polymer, or may additionally contain components other than the F polymer. The content of F polymer in the F film is preferably 50% by mass or more, and more preferably 80% by mass or more. The content of F polymer is preferably 100% by mass or less.

The F film may contain a polymer different from the F polymer (hereinafter also referred to as “different polymer”). Different polymers include tetrafluoroethylene-based polymers that do not have oxygen atoms, non-heat-meltable tetrafluoroethylene-based polymers, epoxy resins, polyimide resins, polyamic acids that are polyimide precursors, polyamideimide resins, and polyamideimide resins. Precursor of, acrylic resin, phenol resin, liquid crystalline polyester resin, polyolefin resin, modified polyphenylene ether resin, polyfunctional cyanate ester resin, polyfunctional maleimide-cyanate ester resin, polyfunctional maleimide resin, vinyl ester. Resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, melamine-urea cocondensation resin, styrene resin, polycarbonate resin, polyarylate resin, polysulfone, polyallyl sulfone, polyamide resin, polyetheramide , polyphenylene sulfide, polyallyl ether ketone, polyphenylene ether, and polytetrafluoroethylene. As different polymers, non-heat meltable tetrafluoroethylene polymers and aromatic polymers are preferable. One type of different polymer may be used, or two or more types may be used.

Tetrafluoroethylene-based polymers that do not have oxygen atoms include PTFE, ETFE, polymers containing TFE units and propylene-based units, and FEP. These polymers may or may not further contain units based on other comonomers. However, the polymers exemplified above do not have oxygen atoms.

Examples of non-heat meltable tetrafluoroethylene polymers include non-heat meltable PTFE.

As the aromatic polymer, aromatic polyimide, aromatic polyamic acid, aromatic polyamidoimide, and aromatic polyamidoimide precursors are more preferable.

Specific examples of aromatic polymers include the “Upia AT” series (manufactured by Ube Kosan Corporation), the “Neoprim (registered trademark)” series (manufactured by Mitsubishi Gas Chemical Corporation), and the “Speakeria (registered trademark)” series (manufactured by Somal Corporation). , “Q-PILON (registered trademark)” series (manufactured by PI Technology Laboratories), “WINGO” series (manufactured by Wingo Technologies), “Tomide (registered trademark)” series (manufactured by T&K TOKA), “KPI-MX” series (manufactured by Kawamura Sangyo Co., Ltd.), “HPC-1000”, and “HPC-2100D” (all manufactured by Showa Denko Materials Co., Ltd.).

When the F film contains different polymers, the content of the different polymers relative to the total mass of the F film is preferably 0.1 to 60 mass%, and more preferably 1 to 40 mass%.

When the different polymer is a non-heat-meltable tetrafluoroethylene-based polymer, the content rate of the non-heat-meltable tetrafluoroethylene-based polymer relative to the total mass of the F film is preferably 10 to 60 mass%, and is 20 to 50 mass%. is more preferable.

When the different polymer is an aromatic polymer, the content of the aromatic polymer relative to the total mass of the F film is preferably 0.1 to 30 mass%, and more preferably 1 to 10 mass%.

The F film may contain an inorganic filler. The inorganic filler is preferably a carbon filler, an inorganic nitride filler, or an inorganic oxide filler, and includes carbon fiber filler, glass fiber filler, boron nitride filler, aluminum nitride filler, beryllia filler, silica filler, wollastonite filler, talc filler, and cerium oxide. The filler, aluminum oxide filler, magnesium oxide filler, zinc oxide filler or titanium oxide filler is more preferable, and boron nitride filler or silica filler is more preferable. One type of inorganic filler may be used, or two or more types may be used.

The D50 of the inorganic filler is preferably 20 μm or less, and more preferably 10 μm or less. D50 is preferably 0.01 μm or more, and more preferably 0.1 μm or more.

The specific surface area of the inorganic filler is preferably 1 to 20 m ² /g.

The surface of the inorganic filler may be surface treated with a silane coupling agent.

Silane coupling agents include 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane. A silane coupling agent having a functional group, such as oxysilane and 3-isocyanate propyltriethoxysilane, is preferable.

The shape of the inorganic filler is preferably spherical, needle-like, fibrous or plate-like, preferably spherical, scaly or lamellar, and more preferably spherical or scaly.

It is preferable that the spherical inorganic filler is approximately spherical. A roughly spherical shape means that when the inorganic filler is observed with a scanning electron microscope (SEM), the proportion occupied by the inorganic filler having a ratio of the minor axis to the major axis of 0.7 or more is 95% or more.

The aspect ratio of the non-spherical inorganic filler is preferably 2 or more, and more preferably 5 or more. The aspect ratio is preferably 10000 or less.

Specific examples of silica fillers include the “Adma Fine” series (manufactured by Admatex), the “SFP” series (manufactured by Denka Corporation), the “E-SPHERES” series (manufactured by Taiheiyo Cement Corporation), and “Q” 」series (manufactured by Ginet).

Specific examples of zinc oxide fillers include the “FINEX” series (manufactured by Sakai Chemical Industry Co., Ltd.).

Specific examples of titanium oxide fillers include the “Taifake (registered trademark)” series (manufactured by Ishihara Sangyo Co., Ltd.) and the “JMT” series (manufactured by Teika Co., Ltd.).

Specific examples of talc fillers include the “SG” series (manufactured by Nippon Talc Co., Ltd.).

Specific examples of steatite fillers include the “BST” series (manufactured by Nippon Talc Co., Ltd.).

Specific examples of boron nitride fillers include the “UHP” series (manufactured by Showa Denko), and the “GP” and “HGP” grades of the “Dencarboron Nitride” series (manufactured by Denka).

When the F film contains an inorganic filler, the content of the inorganic filler relative to the total mass of the F film is preferably 1 to 50 mass%, and more preferably 5 to 20 mass%.

In addition to the ingredients described above, F film contains an organic filler, thixotropic imparting agent, antifoaming agent, silane coupling agent, dehydrating agent, plasticizer, weathering agent, antioxidant, heat stabilizer, lubricant, antistatic agent, brightener, colorant, and conductive material. , it may contain other ingredients such as mold release agents, surface treatment agents, viscosity regulators, and flame retardants. The content of components excluding the F polymer, a polymer different from the F polymer, and inorganic filler in the total mass of the F film is preferably 0 to 10 mass%.

The thickness of the F film is preferably 1 to 200 μm.

The F film may be surface treated with a silane coupling agent. The silane coupling agent includes the same silane coupling agent that may be used for surface treatment of the inorganic filler described above. In this case, the adhesion of the interface between the F polymer and the woven or non-woven fabric of the liquid crystal polymer and the adhesion to the base material of the composite sheet are easily increased, which is preferable.

The F film may be formed by melt-extruding F polymer. In this case, a sheet that additionally contains a different polymer, inorganic filler or other component can be formed by melt-kneading the F polymer and the different polymer, inorganic filler or other component and extrusion molding.

The F film may be formed from a dispersion containing F polymer particles and a liquid dispersion medium. For example, the F film is laminated with a layer containing the temporary substrate and the F polymer by applying a dispersion containing particles of the F polymer to the surface of a temporary substrate and heating the temporary substrate to which the dispersion has been applied. It may be formed by obtaining a sieve and removing the temporary substrate from the laminate.

Heating of the temporary substrate to which the dispersion has been applied is preferably carried out in two steps: heating to remove the liquid dispersion medium and heating to bake the F polymer.

Examples of the temporary substrate include metal foil and resin film, and methods for removing the temporary substrate include peeling and etching.

In this case, a sheet further containing a different polymer, inorganic filler or other component can be formed by using F polymer particles and a liquid dispersion medium and a dispersion liquid further containing a different polymer, inorganic filler or other component.

The ratio of the volume concentration of the F polymer in the composite sheet to the volume concentration of the woven or non-woven fabric of the liquid crystal polymer is preferably 0.6 or more, and more preferably 1 or more, assuming that the volume concentration of the woven or non-woven fabric of the liquid crystal polymer is 1. . This ratio is preferably 4 or less, and more preferably 3 or less.

The relative dielectric constant of the composite sheet is preferably 3.0 or less, and more preferably 2.5 or less. The relative dielectric constant is preferably 1.5 or more.

The dielectric loss tangent of the composite sheet is preferably 0.0100 or less, and more preferably 0.0010 or less. The dielectric loss tangent is preferably 0.0001 or more.

The 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, and more preferably 10 μm or more. The thickness of the composite sheet is preferably 200 μm or less, more preferably 100 μm or less, and may be less than 50 μm.

The composite sheet may be in roll form or in sheet form.

The composite sheet may be surface treated. Surface treatments include discharge treatments such as corona discharge treatment and plasma treatment, plasma graft polymerization treatment, light irradiation treatment such as electron beam irradiation and excimer UV light irradiation, etching treatment using flame, and wet etching treatment using metallic sodium. You can. Through these surface treatments, polar functional groups such as hydroxy groups, carbonyl groups, and carboxyl groups can be introduced into the surface of the composite sheet.

The linear expansion coefficient of the composite sheet is preferably 80 ppm/°C or lower, more preferably 50 ppm/°C or lower, further preferably 30 ppm/°C or lower, and especially preferably 20 ppm/°C or lower. The lower limit of the linear expansion coefficient is, for example, 5 ppm/°C. The linear expansion coefficient is measured by the method specified in JIS C 6471:1995. Specifically, it is measured by the method described in the Examples.

In the method for producing a composite sheet of the present disclosure, a woven or non-woven fabric of a liquid crystal polymer is impregnated with a film containing F polymer. The impregnation may be carried out by impregnating one surface of the liquid crystal polymer woven or non-woven fabric with the F film, or by impregnating both surfaces of the liquid crystal polymer woven or non-woven fabric with the F film.

Impregnation is preferably carried out by thermocompression bonding a film containing F polymer and a woven or non-woven fabric of the liquid crystal polymer. In this case, the F polymer is likely to be impregnated between the fibers of the woven or non-woven fabric of the liquid crystal polymer. As a result, the adhesion between the woven or non-woven fabric of the liquid crystal polymer and the F polymer tends to increase, which is preferable.

Thermocompression is, for example, a method of overlapping the film with a woven or non-woven fabric of liquid crystal polymer and passing it between a pair of heated rolls, a method of applying pressure by sandwiching it between a pair of opposing heat plates, or a method of applying pressure with a heat plate and This can be done by placing it between rolls and applying pressure. The compression temperature in thermocompression is preferably equal to or higher than the melting temperature of the F polymer -30°C, and more preferably equal to or higher than the melting temperature of the F polymer from the viewpoint of easy impregnation of the liquid crystal polymer into the woven or non-woven fabric. . The pressing temperature is preferably below the melting temperature of the F polymer +30°C. The temperature of thermocompression is preferably 280 to 380°C, and more preferably 300 to 330°C.

The compression pressure in thermal compression is preferably 0.2 MPa or more, more preferably 1 MPa or more, and more preferably 10 MPa or more. The compression pressure is preferably 1000 MPa or less, and more preferably 300 MPa or less.

From the viewpoint of obtaining a composite sheet with reduced air bubbles, heat compression is preferably performed under reduced pressure. When thermal compression is performed under reduced pressure, the atmospheric pressure is preferably 10 KPa or less, and more preferably 1 KPa or less.

The composite sheet may be laminated with a base material to form a laminate. The composite sheet of the present disclosure tends to have excellent adhesion to a substrate. In addition, since the composite sheet of the present disclosure is excellent in low linear expansion, it is difficult to peel off from the base material even if the laminate is processed at high temperature.

As a base material, a metal substrate (metal foil of copper, nickel, aluminum, titanium, their alloys, etc.), heat-resistant resin film (polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyallyl ether ketone, polyamideimide) , heat-resistant resin films such as liquid crystalline polyester and tetrafluoroethylene polymers), prepreg substrates (precursors of fiber-reinforced resin substrates), ceramic substrates (ceramic substrates such as silicon carbide, aluminum nitride, and silicon nitride), and glass substrates. can be mentioned.

The shape of the base material includes planar shape, curved shape, and uneven shape. Additionally, the shape of the base material may be any of thin, plate, film, and fibrous shapes.

The 10-point average roughness of the surface of the substrate is preferably 0.01 to 0.05 μm.

The surface of the substrate may be surface treated with a silane coupling agent or may be plasma treated.

A method of laminating a composite sheet and a base material includes heat compression bonding. Examples of the method of thermocompression include the same method as the thermocompression in the production of the composite sheet described above.

In the method for producing a composite sheet of the present disclosure, a woven or non-woven fabric of a liquid crystal polymer may be impregnated with an F film to form a composite sheet and simultaneously laminated with a base material to obtain a laminate of the composite sheet and the base material. For example, if the woven or non-woven fabric of liquid crystal polymer, the F film, and the base material are overlapped in this order and heat-compressed, a laminate of the composite sheet and the base material is obtained. Examples of the method of thermocompression include the same method as the thermocompression in the production of the composite sheet described above.

In the method for producing a composite sheet of the present disclosure, a woven or non-woven fabric of a liquid crystal polymer is impregnated with an F film to form a composite sheet, and at the same time, the composite sheet is laminated with copper foil, and the composite sheet and the copper foil are bonded together to form a copper-clad lamination. You can get a sieve. For example, if a woven or non-woven fabric of liquid crystal polymer, an F film, and copper foil are overlapped in this order and heat-compressed, a copper-clad laminate in which a composite sheet and copper foil are bonded is obtained. Examples of the method of thermocompression include the same method as the thermocompression in the production of the composite sheet described above.

The substrate may be removed from the laminate to obtain a separate composite sheet.

The peeling strength of the composite sheet and the base material in the laminate is preferably 10 to 100 N/cm, and more preferably 12 to 100 N/cm.

The use of the composite sheet is not particularly limited. Composite sheets are useful as antenna parts, printed boards, aircraft parts, automobile parts, sports equipment, food industry products, heat dissipation parts, etc.

Specifically, electric wire covering materials (aircraft wires, etc.), enamel wire covering materials used in motors such as electric vehicles, electrical insulating tape, insulating tape for oil drilling, oil transport hoses, hydrogen tanks, materials for printed boards, separators (precision Filtration membrane, ultrafiltration membrane, reverse osmosis membrane, ion exchange membrane, dialysis membrane, gas separation membrane, etc.), electrode binder (for lithium secondary battery, fuel cell, etc.), copy roll, cover for furniture, car dashboard, home appliance, etc., sliding member (load) bearings, yaw bearings, sliding shafts, valves, bearings, bushes, seals, thrust washers, wear rings, pistons, slide switches, gears, cams, belt conveyors, food transport belts, etc.), tension ropes, wear pads, wear strips, Tube lamps, test sockets, wafer guides, wear parts of centrifugal pumps, chemical and water supply pumps, tools (shovels, files, awls, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, gutts of rackets, Dies, toilets, container coverings, power devices, transistors, thyristors, rectifiers, transformers, power MOS FETs, CPUs, heat dissipation fins, metal heat sinks, blades of windmills, wind power generation facilities, aircraft, etc., housings of personal computers and displays, electronic devices. Materials, interior and exterior of automobiles, sealing materials for processing machines, vacuum ovens, and plasma processing devices that heat-process under low oxygen, heat dissipation components in processing units such as sputtering and various dry etching devices, electromagnetic shields, process films for semiconductor sintering processes, It is useful as a release film for high-temperature encapsulation of power semiconductors, etc.

Since composite sheets are excellent in electrical properties and low linear expansion, they are preferably used in applications where these properties are desired. For example, composite sheets are preferably used for materials such as copper-clad laminates for printed wiring boards.

The composite sheet in one aspect of the present disclosure is a composite sheet containing a woven or non-woven fabric of a liquid crystal polymer and an F polymer impregnated with the woven or non-woven fabric of the liquid crystal polymer.

As for the characteristics of the composite sheet, the above-described information can be applied. The composite sheet is preferably manufactured by the manufacturing method of the present disclosure described above.

Example

Hereinafter, embodiments of the present disclosure will be described in detail through examples, but the embodiments of the present disclosure are not limited to these.

1. Preparation of each ingredient

[film]

Film 1: Polymer 1 (polymer 1) containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units in this order, and having 1000 acid anhydride groups, which are carbonyl group-containing groups, per 1×10 ⁶ carbon atoms in the main chain. Melt temperature: 300 ℃, melt flow rate: 20 g/10 min) film (thickness: 12 ㎛)

Film 2: Polymer 2 (polymer 2) containing 94.9 mol%, 0.1 mol%, and 5.0 mol% of TFE units, NAH units, and PPVE units in this order, and having 1000 acid anhydride groups, which are carbonyl group-containing groups, per 1×10 ⁶ carbon atoms in the main chain. Melt temperature: 260 ℃, melt flow rate: 20 g/10 min) film (thickness: 12 ㎛)

Film 3: Contains 97.5 mol% and 2.5 mol% of TFE units and PPVE units in this order, and is substantially free of terminal fluorinated functional groups (i.e., substantially free of functional groups intended as constituent parts of the polymer). Film (thickness: 12 μm) of polymer 3 (melt temperature: 305 °C, melt flow rate: 25 g/10 min)

Film 4: Polymer 4 (molten) containing 75 mol% and 25 mol% of TFE units and HFP units in this order, and substantially not containing oxygen atoms (i.e., not having oxygen atoms that are intended as constituent atoms of the polymer) Temperature: 260 ℃, melt flow rate: 24 g/10 min) film (thickness: 12 ㎛)

Film 5: Polymer 1 (polymer 1) containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units in this order, and having 1000 acid anhydride groups, which are carbonyl group-containing groups, per 1 × 10 ⁶ carbon atoms in the main chain. Melt temperature: 300 ℃, melt flow rate: 20 g/10 min) film (thickness: 50 ㎛)

[Nonwoven fabric of liquid crystal polymer]

Nonwoven fabric 1: Film-like nonwoven fabric of liquid crystalline aromatic polyester with an aromatic ring content of 60% by mass or more (load bending temperature: 300°C, specific gravity: 1.42 g/cm ³ , fiber diameter: 7 ㎛, volume basis weight: 9.9 cm ³ /m ² )

Nonwoven fabric 2: Film-like nonwoven fabric of liquid crystalline aromatic polyester with an aromatic ring content of 60% by mass or more (load bending temperature: 300°C, specific gravity: 1.42 g/cm ³ , fiber diameter: 7 ㎛, volumetric basis weight: 28.2 cm ³ /m ² )

Nonwoven fabric 3: Film-like nonwoven fabric of liquid crystalline aromatic polyester with an aromatic ring content of 60% by mass or more (load bending temperature: 300°C, specific gravity: 1.42 g/cm ³ , fiber diameter: 3 ㎛, volume basis weight: 4.2 cm ³ /m ² )

Nonwoven fabric 4: Film-like nonwoven fabric of liquid crystalline aromatic polyester with an aromatic ring content of 60% by mass or more (load bending temperature: 300°C, specific gravity: 1.42 g/cm ³ , fiber diameter: 3 ㎛, volume basis weight: 16.9 cm ³ /m ² )

[Woven fabric of liquid crystal polymer]

Woven fabric 1: Plain fabric of liquid crystalline aromatic polyester with an aromatic ring content of 60% by mass or more (load bending temperature: 300°C, specific gravity: 1.42 g/cm ³ , fiber diameter: 7 ㎛, thickness: 123 ㎛, volume basis weight: 32 cm ³ /m ² , warp density: 20 pieces/cm, weft density: 20 pieces/cm)

Woven fabric 2: Plain fabric of liquid crystalline aromatic polyester (load bending temperature: 350°C, weight per unit area: 45 g/m ² , “Vectran (registered trademark)” manufactured by Kuraray Co., Ltd.)

[Copper foil]

Copper foil 1: Copper foil (thickness: 18 ㎛, average roughness of 10 points on the surface: 0.8 ㎛)

2. Preparation of copper clad laminate

[Example 1]

Two sheets of film 1 are overlapped on both sides of nonwoven fabric 1, and copper foil 1 is additionally overlapped on both sides, resulting in a lamination with copper foil 1/film 1/film 1/nonwoven fabric 1/film 1/film 1/copper foil 1 in this order. Get 1 water. Laminate 1 is thermocompressed under reduced pressure under thermocompression conditions of temperature 320°C, pressure 10 MPa, and time 10 minutes, and film 1 is impregnated from both surfaces of nonwoven fabric 1, resulting in nonwoven fabric 1 and the polymer impregnated in nonwoven fabric 1. A copper-clad laminate 1 (thickness: 94 μm) containing 1 and copper foil 1 laminated on both outer sides is obtained.

[Example 2]

One sheet of film 1 is overlapped on both sides of the nonwoven fabric 2, and copper foil 1 is additionally overlapped on the outside of both sides to obtain a laminate 2 having copper foil 1/film 1/nonwoven fabric 2/film 1/copper foil 1 in this order. . Laminate 2 is thermocompressed under reduced pressure under thermocompression conditions of temperature 320°C, pressure 10 MPa, and time 10 minutes, and film 1 is impregnated from both surfaces of nonwoven fabric 2, resulting in nonwoven fabric 2 and the polymer impregnated in nonwoven fabric 2. 1 and copper clad laminate 2 (thickness: 88 μm) containing copper foil laminated on both outer sides are obtained.

[Example 3]

Copper-clad laminate 3 (thickness: 89 μm) was obtained in the same manner as in Example 1, except that non-woven fabric 1 was changed to non-woven fabric 3.

[Example 4]

Copper-clad laminate 4 (thickness: 77 μm) was obtained in the same manner as in Example 2, except that non-woven fabric 1 was changed to non-woven fabric 4.

[Example 5]

Film 1 was changed to Film 2, and copper-clad laminate 5 (thickness: 94 μm) was obtained in the same manner as in Example 1 except that the thermocompression temperature was 290°C.

[Example 6]

Copper-clad laminate 6 (thickness: 94 μm) was obtained in the same manner as in Example 1 except that Film 1 was changed to Film 3.

[Example 7]

Copper-clad laminate 7 (thickness: 94 μm) was obtained in the same manner as in Example 1 except that Film 1 was changed to Film 4.

[Example 8]

Copper-clad laminate 8 (thickness: 130 μm) was obtained in the same manner as in Example 1, except that Film 1 was changed to Film 5 and non-woven fabric 1 was changed to Woven Fabric 1.

[Example 9]

Copper-clad laminate 9 (thickness: 130 μm) was obtained in the same manner as in Example 1, except that Film 1 was changed to Film 5 and non-woven fabric 1 was changed to Woven Fabric 2.

3. Manufacturing of composite sheets

For the copper-clad laminate 1, the copper foil was removed by etching with an aqueous ferric chloride solution and then dried by heating in an oven at 100°C for 1 hour to obtain composite sheet 1.

Composite sheets 2 to 9 are obtained in the same manner as composite sheet 1 except that copper clad laminate 1 is changed to copper clad laminate 2 to 9.

4. Evaluation

4-1. peel strength

A rectangular test piece with a length of 100 mm and a width of 10 mm was cut from each copper-clad laminate. A position 50 mm from one end in the longitudinal direction of the test piece is fixed, and the copper foil and the composite sheet are peeled at a tensile speed of 50 mm/min at an angle of 90° to the test piece from one end in the longitudinal direction. The maximum load when peeling is taken as the peeling strength (N/cm). As a result, the peeling strength of the copper-clad laminate was as follows.

[Evaluation standard]

A: It is more than 12 N/cm.

B: 10 N/cm or more, less than 12 N/cm.

C: Less than 10 N/cm.

4-2. linear expansion coefficient

For each composite sheet, a square test piece measuring 180 mm in length is cut out, and the linear expansion coefficient of the test piece is measured in the range of 25°C to 260°C according to the measurement method specified in JIS C 6471:1995. . As a result, the linear expansion coefficient of the composite sheet is as follows.

[Evaluation standard]

AA: 20 ppm/℃ or less.

A: It is more than 20 ppm/℃ and less than 30 ppm/℃.

B: More than 30 ppm/℃ and less than 50 ppm/℃.

C: greater than 50 ppm/°C.

4-3. electrical properties

For each composite sheet, 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 using the SPDR (split post dielectric resonance) method. As a result, the electrical properties of the composite sheet are as follows. In addition, since the composite sheet 7 had a high linear expansion coefficient and the adhesion to the copper foil in the copper-clad laminate 7 was also low, the measurement was not performed.

[Evaluation standard]

AA: The relative dielectric constant is 2.2 or less, and the dielectric loss tangent is less than 0.0010.

A: The relative dielectric constant is 2.2 or less, and the dielectric loss tangent is 0.0010 to 0.0020, or the relative dielectric constant is 2.2 to 2.4, and the dielectric loss tangent is less than 0.0010.

B: The relative dielectric constant is between 2.2 and 2.4, and the dielectric loss tangent is between 0.0010 and 0.0020.

Table 1 below shows the materials used in the production of each copper-clad laminate and composite sheet, the thickness of the copper-clad laminate, and the evaluation results.

As shown in the table, composite sheets 1 to 6, 8, and 9 are excellent in electrical properties and low linear expansion properties, and composite sheet 9 in particular is excellent in low linear expansion properties. Additionally, composite sheets 1 to 6, 8, and 9 are also excellent in peeling strength from copper foil.

The disclosures of Japanese Patent Application Nos. 2021-119740 and 2021-172597 are incorporated herein by reference in their entirety.

All documents, patent applications, and technical standards described in this specification are herein incorporated by reference to the same extent as if each individual document, patent application, or technical standard were specifically and individually indicated to be incorporated by reference. .

Claims (15)

A method for producing a composite sheet, wherein a composite sheet is obtained by impregnating a woven or non-woven fabric of a liquid crystal polymer with a film containing a heat-meltable tetrafluoroethylene polymer having oxygen atoms. According to claim 1,
A production method wherein the melt flow rate of the tetrafluoroethylene-based polymer is 1 to 30 g/min under the condition of a load of 49 N. The method of claim 1 or 2,
A production method wherein the melting temperature of the tetrafluoroethylene-based polymer is 260°C or higher. The method of claim 1 or 2,
A production method wherein the tetrafluoroethylene-based polymer has an oxygen-containing polar group, and the oxygen-containing polar group is a hydroxyl group-containing group or a carbonyl group-containing group. The method of claim 1 or 2,
A production method wherein the tetrafluoroethylene-based polymer has an oxygen-containing polar group, and the number of the oxygen-containing polar groups in the tetrafluoroethylene-based polymer is 10 to 5000 per 1×10 ⁶ carbon number in the main chain. The method of claim 1 or 2,
The tetrafluoroethylene-based polymer contains units based on perfluoro(alkylvinyl ether), and accounts for the total units in the tetrafluoroethylene-based polymer. A production method wherein the unit content is greater than 2 mol%. The method of claim 1 or 2,
A manufacturing method wherein the liquid crystal polymer has a load deflection temperature of 240° C. or higher. The method of claim 1 or 2,
A production method wherein the liquid crystal polymer contains a liquid crystalline aromatic polyester. According to claim 8,
A production method wherein the aromatic ring content of the aromatic polyester is 55% by mass or more. The method of claim 1 or 2,
A manufacturing method, wherein the composite sheet has a thickness of 200 μm or less. The method of claim 1 or 2,
A manufacturing method of heat-compressing the film and the woven fabric or non-woven fabric to impregnate the film. According to claim 11,
A production method wherein the compression temperature in the thermocompression is within ±30°C of the melting temperature of the tetrafluoroethylene-based polymer. According to claim 11,
A manufacturing method wherein the compression pressure in the thermal compression is 1 MPa or more. According to claim 11,
A manufacturing method in which the thermal compression is carried out under reduced pressure. A composite sheet containing a woven or non-woven fabric of a liquid crystal polymer and a heat-meltable tetrafluoroethylene-based polymer having an oxygen atom impregnated into the woven fabric or non-woven fabric.