KR20240020269A - Sheet - Google Patents

Abstract

(Problem) Provision of a sheet containing uncooked polytetrafluoroethylene and inorganic particles, which makes it difficult for the inorganic particles to peel off, and which has excellent electrical properties, low linear expansion, physical strength, and adhesion to other materials.
(Solution) Comprising uncooked polytetrafluoroethylene, inorganic particles, and a resin having at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group-containing group, an epoxy group, and an amino group, and the poly A sheet wherein the total content of tetrafluoroethylene, the inorganic particles, and the resin is 90% by mass or more.

Description

Sheet

The present invention relates to a predetermined sheet containing unfired polytetrafluoroethylene, a method of manufacturing the sheet, and a method of manufacturing a laminate comprising the sheet.

Polytetrafluoroethylene is attracting attention as a material for the dielectric layer of printed circuit boards because it has excellent electrical properties such as low dielectric constant and low dielectric loss tangent. Patent Document 1 describes forming a dielectric layer from a sheet made of polytetrafluoroethylene and inorganic particles. Patent Document 2 describes a dielectric layer reinforced with a reinforced woven fabric containing polytetrafluoroethylene, inorganic particles, and a reinforced woven fabric.

Japanese Patent Publication No. 2021-061406 Japanese Patent Publication No. 2020-507888

When a layered molded product having a layer containing polytetrafluoroethylene and inorganic particles is formed from a sheet containing uncooked polytetrafluoroethylene and inorganic particles, in the sheet, the inorganic particles tend to aggregate, and its physical properties There is a problem that it is difficult to fully manifest this. In addition, when processing the sheet, there is a problem that the inorganic particles are prone to peeling off and that the physical strength such as toughness is insufficient, so it is easy to break. In addition, these sheets require adhesion to other base layers such as metal foil, but the adhesion is not yet sufficient.

The present inventors have found that a sheet containing uncooked polytetrafluoroethylene, inorganic particles, and a resin having a predetermined functional group in a predetermined ratio is unlikely to cause the inorganic particles to peel off, and has excellent electrical properties, low linear expansion, physical strength, and It was discovered that it had excellent adhesion to other materials, leading to the present invention.

The present invention has the following aspects.

[1] It contains uncooked polytetrafluoroethylene, inorganic particles, and a resin having at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group-containing group, an epoxy group, and an amino group, and the polytetra A sheet wherein the total content of fluoroethylene, the inorganic particles, and the resin is 90% by mass or more.

[2] The sheet of [1] above, wherein the inorganic particles are particles containing at least one inorganic substance selected from the group consisting of silica, boron nitride, and titanium dioxide.

[3] The sheet of [1] or [2] above, wherein the resin contains at least one of a heat-meltable tetrafluoroethylene polymer, an aromatic polymer, or a precursor thereof.

[4] The sheet of any one of [1] to [3] above, wherein the resin contains a heat-meltable tetrafluoroethylene polymer and an aromatic polymer or a precursor thereof.

[5] The sheet according to [3] or [4], wherein the heat-meltable tetrafluoroethylene polymer has a melting temperature of 260 to 320°C.

[6] The sheet of [3] or [4] above, wherein the aromatic polymer or its precursor is polyimide, polyamidoimide, a polyimide precursor, or a polyamidoimide precursor.

[7] The sheet of any one of [1] to [6] above, wherein the polytetrafluoroethylene content is 10% by mass or more.

[8] Any sheet of [1] to [7] above, wherein the resin content is 5% by mass or more.

[9] The sheet of any one of the above [1] to [8], wherein the ratio of the content of the inorganic particles to the total content of the polytetrafluoroethylene and the content of the resin is 0.1 or more.

[10] The sheet of any one of the above [1] to [9] having a thickness of 50 ㎛ or more.

[11] A sheet manufacturing method to obtain a sheet according to any one of the above [1] to [10] by bending a liquid composition containing the polytetrafluoroethylene particles, the inorganic particles, and the resin.

[12] The production method of [11] above, wherein the average particle diameter of the polytetrafluoroethylene particles is 0.1 to 10 μm.

[13] The production method of [11] or [12] above, in which the flexible materials obtained by softening the liquid composition are layered and bonded to each other.

[14] A method for producing a fired sheet in which the polytetrafluoroethylene is fired by heating any one of the sheets of [1] to [10] above.

[15] A method for producing a laminate by thermocompressing any one of the sheets of [1] to [10] above and a base material to obtain a laminate having a base layer and a polymer layer.

According to the present invention, it contains uncooked polytetrafluoroethylene, inorganic particles, and a resin having a predetermined functional group, and the inorganic particles are difficult to peel, and have excellent electrical properties, low linear expansion, physical strength, and adhesion to other materials. An excellent sheet is obtained.

The following terms have the following meanings.

“Tetrafluoroethylene-based polymer” is a polymer containing a unit based on tetrafluoroethylene (hereinafter also referred to as “TFE”).

“Heat-meltable tetrafluoroethylene-based polymer” means a tetrafluoroethylene-based polymer at a temperature where the melt flow rate is 1 to 1000 g/10 min under the condition of a load of 49 N.

“Polymer melting temperature (melting point)” is the temperature corresponding to the maximum value of the melting peak measured for the polymer by differential scanning calorimetry (DSC).

“The glass transition point (Tg) of the polymer” is a value measured by analyzing the polymer using the dynamic viscoelasticity measurement (DMA) method.

“D50 of particles” is the average particle diameter of the particles, and is the cumulative 50% diameter based on the volume of the particles determined by the laser diffraction/scattering method. That is, the particle size distribution of the particles 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 becomes 50% is the particle diameter.

“D90 of particles” is the cumulative volume particle diameter of the particles, and is the volume-based cumulative 90% diameter of the particles, obtained in the same manner as “D50”.

“Viscosity of the liquid composition” is a value measured for the liquid composition using a B-type viscometer under room temperature (25°C) and a rotation speed of 30 rpm. The measurement is repeated three times, and the average value of the three measurements is taken.

“Monomer-based unit” 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 described as “monomer a unit.”

The sheet of the present invention (hereinafter also referred to as “this sheet”) is made of uncalcined polytetrafluoroethylene (hereinafter, polytetrafluoroethylene is referred to as “PTFE” and uncalcined polytetrafluoroethylene is referred to as “uncalcined PTFE”). 」, and a resin having at least one functional group selected from the group consisting of an inorganic particle, a carbonyl group-containing group, a hydroxy group-containing group, an epoxy group, and an amino group (hereinafter also referred to as “this resin”). ), and the total content of unfired PTFE, inorganic particles, and this resin is 90% by mass or more. In other words, this sheet is a self-supporting film-like sheet containing unfired PTFE, inorganic particles, and this resin as main components.

In the present sheet, the present resin having the above-described functional group not only suppresses aggregation of the inorganic particles by interacting with the inorganic particles and promotes uniform dispersion of the inorganic particles in the sheet, but also acts as a binder component, including uncalcined PTFE and inorganic particles. It is also thought that the particles are held firmly. In other words, it is thought that the present sheet has a structure in which the present resin is used as a matrix, and unsintered PTFE and inorganic particles are firmly held and uniformly dispersed. As a result, it is believed that in this sheet, peeling of the inorganic particles was suppressed, the physical properties of both PTFE and the inorganic particles were expressed to a high degree, and the physical strength was improved. In addition, it is believed that by containing this resin having this functional group, this sheet has excellent affinity with other substrates such as metal foil, and its adhesiveness has improved.

PTFE in the present invention may be a homopolymer of TFE, and may be a trace amount of perfluoro(alkylvinyl ether) (hereinafter also referred to as “PAVE”) or hexafluoropropylene (hereinafter also referred to as “HFP”). .), so-called modified PTFE, which is a copolymer of TFE and a comonomer such as fluoroalkyl ethylene, may be used. The proportion of TFE units in PTFE is preferably 99.5 mol% or more, and more preferably 99.9 mol% or more, of all units.

PTFE is preferably PTFE with a number average molecular weight, Mn, calculated based on the following formula (1) of 200,000 or more.

In formula (1), Mn represents the number average molecular weight of PTFE, and ΔHc represents the crystallization heat quantity (cal/g) of PTFE measured by differential scanning calorimetry.

Uncalcined PTFE in the present invention means PTFE that has not been exposed to a temperature higher than the melting temperature of PTFE after being produced by polymerization. Additionally, calcined PTFE refers to PTFE that has been produced by polymerization and then exposed to a temperature equal to or higher than the melting temperature of PTFE. In addition, in this specification, the melting temperature of PTFE is set to 327°C.

The uncalcined PTFE may be in a fibril form or a non-fibril form, and is preferably in a fibril form. If the unsintered PTFE is in a fibril form, the unsintered PTFE easily supports inorganic particles in this sheet, and the inorganic particles are unlikely to be peeled off from this sheet. In addition, the unfired PTFE becomes easily entangled with the inorganic particles and the resin, and the toughness of the sheet tends to improve. In other words, fibril-shaped uncalcined PTFE can be considered to be easy to adhere to inorganic particles or the present resin.

The unfired PTFE in this sheet preferably exists in particle form. In this case, the unsintered PTFE particles are preferably the same as the unsintered PTFE particles contained in the liquid composition described later.

The uncalcined PTFE may be PTFE obtained by an emulsion polymerization method or PTFE obtained by a suspension polymerization method. PTFE obtained by emulsion polymerization is preferable from the viewpoint of low crystallinity and ease of increasing sheet toughness.

The shape of the inorganic particles in the present invention is preferably spherical, needle-like, or plate-shaped, more preferably spherical, flaky, or layered, and even more preferably spherical or flaky.

It is preferable that the spherical inorganic particles are substantially spherical. A roughly spherical shape means that the ratio of the minor axis to the major axis is 0.7 or more when the inorganic particle is observed with a scanning electron microscope (SEM). The proportion of approximately spherical inorganic particles is preferably 95% or more.

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

The inorganic particles may be hollow. In this case, this sheet is likely to have excellent electrical properties.

Inorganic particles are particles containing at least one type of inorganic substance, and particles containing carbon, inorganic nitride, or inorganic oxide are preferable.

Specific examples of inorganic substances include carbon, boron nitride, aluminum nitride, beryllia, silica, wollastonite, talc, cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, and titanium dioxide.

From the viewpoint of improving the electrical properties and low linear expansion of the sheet, the inorganic particles are preferably particles containing at least one inorganic substance selected from the group consisting of silica, boron nitride, and titanium dioxide. The silica is preferably amorphous silica. Boron nitride is preferably hexagonal boron nitride. Titanium dioxide is preferably rutile titanium dioxide.

The D50 of the inorganic particles 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 particles is preferably 1 to 20 m2/g.

The surface of the inorganic particle may be surface treated with a silane coupling agent. In this case, the affinity between the inorganic particles and the unfired PTFE and the present resin is improved, making it difficult for the inorganic particles to peel off from the present sheet. Additionally, this sheet tends to have excellent electrical properties and low linear expansion properties.

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

Specific examples of particles containing silica include the “Admapain” series (manufactured by Admatex), the “SFP” series (manufactured by Denka Corporation), and the “E-SPHERES” series (manufactured by Pacific Cement Corporation). there is.

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

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

One type of inorganic particle may be used, and two or more types may be used. For example, as the inorganic particles, silica particles, boron nitride particles, and titanium dioxide particles may be used in combination. In this case, the respective contents of silica particles, boron nitride particles, and titanium dioxide particles in the total amount of inorganic particles are preferably 10 to 60% by mass, 10 to 60% by mass, and 5 to 40% by mass in this order. .

This resin is a resin having at least one functional group (hereinafter also referred to as “this functional group”) selected from the group consisting of a carbonyl group-containing group, a hydroxy group-containing group, an epoxy group, and an amino group, and is a fluororesin and a liquid crystalline aromatic group. At least one type of pattern selected from the group consisting of polyester resins such as polyester, imide resin, epoxy resin, maleimide resin, urethane resin, polyphenylene ether resin, polyphenylene oxide resin, and polyphenylene sulfide resin. It is preferable that it is a resin having a functional group.

The hydroxy group-containing group is a group containing a hydroxyl group, and a group containing an alcoholic hydroxyl group is preferable.

The carbonyl group-containing group is a group containing a carbonyl group, and includes a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH ₂ ), and an acid anhydride residue (-C(O)OC(O)- ), imide residues (-C(O)NHC(O)-, etc.), and carbonate groups (-OC(O)O-), and carboxyl groups, amide groups, imide residues, or acid anhydride residues are preferred. .

This resin is a heat-meltable tetrafluoroethylene-based polymer having this functional group (hereinafter also referred to as “F polymer”), an aromatic polymer having this functional group, or a precursor of the aromatic polymer (hereinafter referred to as “aromatic polymer”). Alternatively, the precursor is also referred to as “AR polymer.”) It is preferable that it contains at least one of the following, and it is more preferable that it contains F polymer and AR polymer.

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. In this case, this sheet is likely to be excellent in heat resistance, low linear expansion, and processability.

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.

The fluorine content of the F polymer is preferably 70% by mass or more, and is more preferably 72 to 76% by mass. In this case, the F polymer and green PTFE are more likely to interact.

The surface tension of the F polymer is preferably 16 to 26 mN/m. In addition, the surface tension of the F polymer can be measured by placing a droplet of the wett index reagent (manufactured by Wako Pure Chemical Industries, Ltd.) on a flat plate made of the F polymer.

F polymers include polymers containing TFE units and ethylene-based units, polymers containing TFE units and propylene-based units, polymers containing TFE units and PAVE-based units (PAVE units), polymers (PFA), Polymers comprising TFE units and units based on HFP (FEP) are preferred, PFA and FEP are more preferred, and PFA is still more preferred. These polymers may contain units based on another comonomer.

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.

As the functional group of the F polymer, a hydroxy group-containing group or a carbonyl group-containing group is preferable, and a carbonyl group-containing group is more preferable. In this case, not only does the interaction of the F polymer with unfired PTFE and inorganic particles increase, but the adhesion of the sheet is also likely to improve.

The hydroxy group-containing groups of the F polymer are preferably -CF ₂ CH ₂ OH and C(CF ₃ ) ₂ OH.

The carbonyl group-containing group of the F polymer is preferably a carboxyl group, alkoxycarbonyl group, amide group, isocyanate group, carbamate group, acid anhydride residue, imide residue or carbonate group, and more preferably an acid anhydride residue.

When the F polymer has a hydroxy group-containing group or a carbonyl group-containing group, the number of hydroxy group-containing groups or carbonyl group-containing groups in the F polymer is preferably 10 to 5,000 per 1 × 10 ⁶ carbon atoms in the main chain, and 100 to 100. 3000 is more preferable. In addition, the number of hydroxy group-containing groups or carbonyl group-containing groups in the F polymer can be quantified by the composition of the polymer or the method described in International Publication No. 2020/145133.

This functional group of the F polymer 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. Examples of the latter embodiment include F polymers having oxygen-containing polar groups as terminal groups derived from polymerization initiators, chain transfer agents, etc., and F polymers obtained by plasma treatment or ionizing radiation treatment of F polymers.

The monomer having a carbonyl group-containing group is preferably itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as “NAH”), and more preferably NAH. do.

The F polymer is preferably a polymer having a carbonyl group-containing group, including TFE units and PAVE units, and includes TFE units, PAVE units, and units based on monomers having a carbonyl group-containing group, and for all units, these units are In this order, it is more preferable that the polymer contains 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol%. Specific examples of such F polymer include the polymer described in International Publication No. 2018/16644.

The shape of the F polymer in this sheet may be particulate or non-particulate. The F polymer may be bonded with uncalcined PTFE or inorganic particles. When the F polymer is in particulate form, the F polymer particles are preferably the same as the F polymer particles that may be included in the liquid composition, which will be described later.

AR polymer may be thermosetting or thermoplastic.

The functional group that the AR polymer has is preferably an amino group or a carbonyl group-containing group, and more preferably at least one selected from the group consisting of an amino group, an amide group, a carboxyl group, and an imide residue. In this case, not only does the interaction of the AR polymer with unfired PTFE and inorganic particles increase, but the adhesion of the sheet is also likely to improve.

Examples of the AR polymer include aromatic polyimide, polyamic acid or an aromatic polyimide precursor that is a salt thereof, aromatic polyamidoimide, aromatic polyamideimide precursor, aromatic polyetherimide, and aromatic polyetherimide precursor, and include aromatic polyimide and polyamic acid. An aromatic polyimide precursor that is a mixed acid or a salt thereof, aromatic polyamidoimide, or an aromatic polyamidoimide precursor is more preferable.

The AR polymer may be water-soluble. Examples of the water-soluble AR polymer include water-soluble aromatic polyimide precursors, water-soluble polyamidoimide, and their precursors.

Examples of water-soluble aromatic polyimide precursors include polyamic acid and salts thereof obtained by polymerizing tetracarboxylic dianhydride and diamine.

Examples of the water-soluble aromatic polyamidoimide or its precursor include polyamidoimide or its precursor obtained by reacting at least one of diisocyanate or diamine with a tribasic acid anhydride.

Examples of tetracarboxylic dianhydride include pyromellitic acid anhydride and biphenyltetracarboxylic acid anhydride.

Examples of the diamine include phenylenediamine, 3,3'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenyl ether.

Examples of diisocyanate include 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, and 3,3'-diphenylmethane diisocyanate. You can.

The number average molecular weight (Mn) of the AR polymer is preferably 5000 to 50000.

The acid value of the AR polymer is preferably 20 to 100 mg/KOH.

Additionally, the acid value of the AR polymer is 0.5 g of the AR polymer, 0.15 g of 1,4-diazabicyclo[2.2.2]octane, 60 g of N-methyl-2-pyrrolidone, and 1 mL of ion-exchanged water. It is obtained by titrating the mixed solution with a potentiometric titrator using a 0.05 mol/L ethanolic potassium hydroxide solution. In addition, when the AR polymer has an acid anhydride group, the acid value when the acid anhydride group is ring-opened is taken as the acid value of the AR polymer.

Specific examples of AR polymer 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 Research Institute), “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 Electric Materials Co., Ltd.).

In this sheet, the AR polymer may be particulate or non-particulate, and is preferably non-particulate. The AR polymer may be bonded to unfired PTFE and inorganic particles.

The resin in this sheet is an F polymer and an aromatic polymer having this functional group, a precursor of F polymer and an aromatic polymer having this functional group, or a F polymer, an aromatic polymer having this functional group, and a precursor of an aromatic polymer having this functional group. It is preferable to include any of the following. In this case, a strong matrix of the present resin is formed in the present sheet, and the unfired PTFE and inorganic particles are easily supported firmly and uniformly on it, and the physical properties and adhesive properties of the present sheet are likely to be further improved. In particular, when this resin contains both F polymer and AR polymer, this tendency is likely to become noticeable because the F polymer, which has high affinity for PTFE, supports the uncalcined PTFE to a high degree, while the AR polymer enhances the binder effect between components. . Additionally, when the present resin contains both F polymer and AR polymer, in this sheet, the F polymer and AR polymer may form a crosslinked product.

The total content of unfired PTFE, inorganic particles, and this resin in this sheet is 90% by mass or more, and is preferably 95% by mass or more. The upper limit of total content is 100% by mass. In other words, in this sheet, the content of unfired PTFE, inorganic particles, and components different from the present resin is less than 10% by mass, and is preferably 5% by mass or less. Different components include, for example, reinforcing fibers. The lower limit of the content of the above different components is 0 mass%. Due to the above-described action mechanism, even at this component content ratio, this sheet has excellent physical properties such as flexibility and toughness, and can express the respective physical properties of PTFE and inorganic particles in a highly balanced manner.

The content of unfired PTFE in this sheet is preferably 10 mass% or more, and more preferably 15 mass% or more. The content of unfired PTFE is preferably 60% by mass or less, and more preferably 40% by mass or less.

The content of inorganic particles in this sheet is preferably 20% by mass or more, and more preferably 40% by mass or more. The content of the inorganic particles is preferably 80% by mass or less, and more preferably 70% by mass or less.

The ratio of the content of inorganic particles to the total content of unfired PTFE and the content of inorganic particles in this sheet is preferably 0.1 or more, more preferably 0.2 or more, and still more preferably 0.3 or more. This ratio is preferably less than 1, more preferably 0.8 or less, and even more preferably 0.6 or less. Due to the action mechanism described above, even if the ratio is such a high value, the physical properties of the inorganic particles in the sheet are likely to be expressed to a high degree.

The content of this resin in this sheet is preferably 0.1% by mass or more, and more preferably 5% by mass or more. The content of this resin is preferably 60% by mass or less, and more preferably 30% by mass or less.

The ratio of the content of this resin to the total content of unfired PTFE and this resin in this sheet is preferably 0.05 or more, more preferably 0.2 or more, and still more preferably 0.5 or more. This ratio is preferably less than 1, and more preferably 0.5 or less.

When this resin is an F polymer, the content of F polymer in this sheet is preferably 10% by mass or more, and more preferably 15% by mass or more. The content of F polymer is preferably 60% by mass or less, and more preferably 30% by mass or less.

The AR polymer content in this sheet is preferably 0.1% by mass or more, and more preferably 1% by mass or more. The AR polymer content is preferably 10% by mass or less, and more preferably 5% by mass or less.

When this resin contains both F polymer and AR polymer, the ratio of the F polymer content to the total content of F polymer and AR polymer in this resin is preferably 0.6 or more, and 0.9 or more. It is more desirable. This ratio is preferably less than 1, and more preferably 0.99 or less.

When the content of unfired PTFE, inorganic particles, and this resin in this sheet is within this range, the above-described action mechanism is more likely to be expressed.

This sheet also contains liquid lubricants, liquid dispersion media, coagulants, nonionic surfactants, pH adjusters and pH buffering agents, organic particles, organic pigments, metallic soaps, lubricants, and organic monomers, described later, in amounts not exceeding 10% by mass. , organic substances such as organic oligomers with a degree of polymerization of 50 or less, thixotropic agents, viscosity regulators, antifoaming agents, silane coupling agents, dehydrating agents, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, colorants, conductive agents. , other components such as release agents, surface treatment agents, and flame retardants may be included.

The thickness of this sheet is preferably 50 μm or more, and more preferably 100 μm or more. The thickness of this sheet is preferably 1000 μm or less, and more preferably 500 μm or less. Due to the action mechanism described above, even at this thickness, this sheet is excellent in physical strength such as toughness.

The tensile strength of this sheet is preferably 200 MPa or more, and more preferably 300 MPa or more. The tensile strength of this sheet is preferably 800 MPa or less. In addition, the tensile strength can be measured using TENSILON (manufactured by TOYO BALDWIN CO., LTD., model: UTM-5T) under the conditions of a load cell rating of 5000 kg, a distance between chucks of 110 mm, and a speed of 10 mm/min. You can.

This sheet is preferably obtained by softening a liquid composition (hereinafter also referred to as “this composition”) containing unfired PTFE particles, inorganic particles, and this resin. In addition, casting means pressing and spreading a fluid composition, and casting can be performed by a method as described later.

The D50 of the unfired PTFE particles in this composition is preferably 10 μm or less, and more preferably 1 μm or less. The D50 of the unfired PTFE particles is preferably 0.1 μm or more. Additionally, the D90 of the unfired PTFE particles is preferably 20 μm or less. In this case, the unfired PTFE, the inorganic particles, and the main resin easily interact, and it is easy to obtain a main sheet with excellent uniformity of component distribution.

As the inorganic particles in this composition, the same inorganic particles as the inorganic particles contained in this sheet described above are preferable.

This resin in this composition may be in particulate form, may be in non-particulate form, and may be dissolved in this composition.

When the present resin contains F polymer, it is preferable that the F polymer in the present composition is in particulate form. The D50 of the F polymer particles (hereinafter also referred to as “F particles”) in this composition is preferably 0.1 μm or more, and more preferably 1 μm or more. The D50 of the F particles is preferably 8 μm or less.

The specific surface area of the F particles is preferably 1 to 25 m2/g.

In this case, the F polymer, uncalcined PTFE, and inorganic particles easily interact, and it is easy to obtain a sheet with excellent uniformity of component distribution.

When the present resin contains an AR polymer, the AR polymer in the present composition is preferably in a liquid state or dissolved in a liquid dispersion medium described later. In this case, the AR polymer easily functions as a binder for the uncalcined PTFE and the inorganic particles, and the uncalcined PTFE and the inorganic particles are easily supported firmly on this sheet.

Unfired PTFE, inorganic particles, and this resin may be included in the present composition as composite particles bonded together. The composite particles form a core-shell structure in which a core is made of unsintered PTFE, inorganic particles, or this resin, and a component not contained in the core among unsintered PTFE, inorganic particles, or this resin is used as a shell. You can stay.

This composition is preferably obtained by mixing unsintered PTFE particles, inorganic particles, this resin, and a liquid lubricant, and is more preferably obtained by mixing aggregates of unsintered PTFE particles, inorganic particles, this resin, and a liquid lubricant. desirable. In this case, each component is likely to be uniformly dispersed in this sheet.

The composition may be obtained by distilling off the liquid dispersion medium from a state containing unsintered PTFE particles, inorganic particles, and the present resin, and a liquid dispersion medium or a liquid lubricant, or may include unsintered PTFE particles, inorganic particles, and the present resin. , it may be obtained by adding a trace amount of the above liquid component to a mixed powder that does not contain liquid components such as a liquid dispersion medium or liquid lubricant.

As a liquid lubricant, liquid compounds that can be removed by heating, distillation, extraction, etc. are preferable, and liquid compounds that can be removed by heating and have a boiling point of 300°C or lower are more preferable.

Liquid lubricants include naphtha, white oil, liquid paraffin, toluene, xylene, hexane, n-decane, tetradecane, dodecane, and polyethylene glycol, with tetradecane or dodecane being preferred.

One type of liquid lubricant may be used, or two or more types may be used.

The content of the liquid lubricant in this composition is preferably 10 to 60% by mass, more preferably 20 to 40% by mass.

Mixing devices for obtaining the present composition include stirring devices with blades such as Henschel mixers, pressure kneaders, Banbury mixers and planetary mixers, ball mills, attritors, basket mills, sand mills, sand grinders, dyno mills, and desiccant machines. Grinding equipment with media such as fur mat, SC mill, spike mill and agitator mill, microfluidizer, nanomizer, altimer, ultrasonic homogenizer, dissolver, disper, high-speed impeller, thin film gyratory high-speed Dispersing devices equipped with other mechanisms such as mixers, revolution and revolution stirrers, and V-type mixers can be cited, and V-type mixers are preferable.

The aggregate of unsintered PTFE particles, inorganic particles, and the present resin is obtained, for example, by removing the liquid dispersion medium from a dispersion containing the unsintered PTFE particles, inorganic particles, this resin, and the liquid dispersion medium.

A liquid dispersion medium is a compound that is liquid at 25°C under atmospheric pressure. One type of liquid dispersion medium may be used, or two or more types may be used. When using two types of liquid dispersion media, it is preferable that the two types of liquid dispersion media are compatible with each other.

The liquid dispersion medium is preferably a compound selected from the group consisting of water, amides, ketones, esters, and glycols. Specifically, water, N-methyl-2-pyrrolidone, γ-butyrolactone, methyl ethyl ketone, cyclohexanone, cyclopentanone, ethylene glycol, and propylene glycol are mentioned, and water is more preferable. In this case, it is easy to obtain a sheet in which the unfired PTFE particles, inorganic particles, and resin are uniformly dispersed.

The content of the liquid dispersion medium in the dispersion is preferably 40% by mass or more, and more preferably 60% by mass or more. The content of the liquid dispersion medium is preferably 90% by mass or less, and more preferably 80% by mass or less.

The dispersion may further contain a nonionic surfactant for the purpose of improving dispersion stability.

Nonionic surfactants are preferably glycol-based surfactants, acetylene-based surfactants, silicone-based surfactants, or fluorine-based surfactants, and silicone-based surfactants are more preferable. One type of nonionic surfactant may be used, or two or more types may be used. When using two types of nonionic surfactants, it is preferable that the nonionic surfactants are a silicone-based surfactant and a glycol-based surfactant.

Specific examples of nonionic surfactants include “Ptergent” series (manufactured by Neos), “Supron” series (manufactured by AGC Semichemicals), “Megapac” series (manufactured by DIC), and “Unidyne” ” series (manufactured by Daikin Industries), “BYK-347”, “BYK-349”, “BYK-378”, “BYK-3450”, “BYK-3451”, “BYK-3455”, “BYK-3456” (manufactured by Big Chemical Japan Co., Ltd.), “KF-6011”, “KF-6043” (manufactured by Shin-Etsu Chemical Co., Ltd.), “Tergitol” series (manufactured by Dow Chemical Co., Ltd., “Tergitol TMN-100X”, etc.). .

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

When the liquid dispersion medium is water, the dispersion may contain a pH adjuster or pH buffer. In this case, it is easy to improve the stability of the dispersion. Examples of pH adjusters include amines, ammonia, and citric acid. Examples of the pH buffer include tris(hydroxymethyl)aminomethane, ethylenediamine 4 acetic acid, ammonium bicarbonate, ammonium carbonate, and ammonium acetate.

The dispersion may further contain other components described above that may be included in the present sheet.

The dispersion can be obtained by mixing unfired PTFE, inorganic particles, this resin, and a liquid dispersion medium.

When the present resin contains F polymer, the dispersion is preferably obtained by mixing a mixture containing unfired PTFE and a liquid dispersion medium with a mixture containing inorganic particles, particles of F polymer, and a liquid dispersion medium.

When the present resin contains AR polymer, the dispersion is preferably obtained by mixing inorganic particles with a mixture containing uncalcined PTFE, AR polymer, and a liquid dispersion medium.

The mixing device for obtaining the dispersion liquid may be the same as the mixing device described above that can be used to obtain the present composition, and a planetary mixer is preferable.

Removal of the liquid dispersion medium from the dispersion liquid containing uncalcined PTFE, inorganic particles, this resin, and the liquid dispersion medium can be carried out by filtration, heating, distillation, etc., and is preferably carried out by heating.

Removal of the liquid dispersion medium is preferably performed by adding a coagulant to the dispersion and then removing the liquid dispersion medium and, if necessary, the coagulant. When removing by heating, the heating temperature is preferably higher than the boiling point of the liquid dispersion medium and the coagulant.

As a coagulant, primary alcohol is preferable, and methanol, ethanol, isopropanol, and butanol are more preferable.

It is preferable to add the primary alcohol in an amount that is 0.2 to 1 in mass ratio with respect to the content of the liquid dispersion medium in the dispersion.

This sheet is preferably obtained by softening the composition. In this case, it is easy to obtain a sheet in which the unfired PTFE is easily fibrillated and the inorganic particles are unlikely to peel off. Additionally, it is easy to obtain this sheet with excellent electrical properties and toughness.

Casting of the composition is preferably carried out by press molding, extrusion molding, or calendar molding, and more preferably by calender molding. In addition, calender molding refers to a method of rolling a composition by passing it between a plurality of rolls.

Casting of this composition may be performed using one type of molding method, or may be performed by combining two or more types of molding methods. In addition, casting may be performed by repeating one type of molding method multiple times. For example, the wool sheet obtained by extrusion molding the present composition may be further softened by calender molding, or the wool sheet obtained by calender molding the present composition may be further softened by calender molding. In this case, it is easy to obtain a sheet of arbitrary thickness that is excellent in toughness and uniformity.

A plurality of rolls in calender molding may be used, and it is preferable to use a combination of four. Arrangement methods of the four rolls include I-type, S-type, inverted L-type, Z-type, and inclined Z-type.

Casting of the composition may be carried out while heating at a temperature below the melting temperature of unfired PTFE, or may be carried out without heating.

This sheet may be obtained by layering and bonding the flexible materials obtained by softening the present composition. In this case, the toughness of this sheet is likely to be improved.

The method includes laminating a plurality of sheets of flexible materials of the present composition and rolling them. This lamination and rolling may be repeated to adjust the thickness and physical properties of the resulting sheet.

When repeating lamination and rolling, it is desirable to change the casting direction of the flexible material. Specifically, a method of casting a composition by overlapping it on the surface of one flexible material so that the casting directions intersect perpendicularly to each other is included.

The number of plies of flexible substances is preferably 10 to 1000. The softening ratio of the flexible material is preferably 100 to 20,000 times.

Flexibility at this time can be determined by the same method as the molding method used to soften the composition, and is preferably performed by calender molding.

When the composition contains a liquid lubricant, the sheet is preferably obtained by softening the composition and removing the liquid lubricant. Methods for removing the liquid lubricant include heating, distillation, and extraction, with heating being preferred. The liquid lubricant does not need to be completely removed, and the total content of unfired PTFE, inorganic particles, and this resin in this sheet is 90% by mass or more, so that this sheet can form a sheet as a self-supporting film. It can be removed to that extent. The heating temperature is preferably 100 to 200°C.

Heating devices include ovens and ventilation drying furnaces. The heat source in the device may be a contact type heat source such as hot air or a hot plate, or may be a non-contact type heat source such as infrared rays.

In addition, each heating may be performed under normal pressure or under reduced pressure.

Additionally, the atmosphere for each heating may be any of an air atmosphere, an inert gas atmosphere such as helium gas, neon gas, argon gas, or nitrogen gas.

When this sheet is heated above the melting temperature of PTFE, a sheet containing fired PTFE (hereinafter also referred to as a “fired sheet”) is obtained. The fired sheet, like the present sheet, is difficult to peel off inorganic particles and is excellent in electrical properties, low linear expansion, physical strength, and adhesion to other materials.

The heating temperature is higher than the melting temperature of PTFE, and is preferably 360 to 400°C. The heating time is preferably 0.1 to 30 minutes. The heating method and conditions include the same methods and conditions as the heating for removing the liquid lubricant described above.

The thickness of the fired sheet is preferably 50 μm or more, and more preferably 100 μm or more. The thickness of the fired sheet is preferably 500 μm or less, and more preferably 300 μm or less. In this case, it is easy to balance physical properties such as mechanical strength, low linear expansion, and electrical properties of the fired sheet.

When this sheet is thermocompressed with a base material, a laminate having a base layer and a polymer layer containing PTFE and inorganic particles is obtained.

As a base material, metal substrates such as metal foils such as copper, nickel, aluminum, titanium, and alloys thereof, polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyallyl ether ketone, polyamideimide, and liquid crystalline polyester. and heat-resistant resin films such as tetrafluoroethylene-based polymers, prepreg substrates that are precursors of fiber-reinforced resin substrates, ceramic substrates such as silicon carbide, aluminum nitride, or silicon nitride, and glass substrates.

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.

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

Methods of thermocompression include a method of applying pressure between the base material and the main sheet with a pair of opposing hot plates, a method of passing the base material and the main sheet between a pair of opposing rolls, and a method of pressing the base material and the main sheet with a roll on a hot plate. One method is to apply pressure to this sheet.

The thermocompression temperature is preferably 200°C or higher, more preferably higher than the melting temperature of PTFE, and even more preferably 350°C or higher. The temperature for thermocompression is preferably 400°C or lower. It is preferable to bake PTFE by heating during thermocompression bonding.

Heat compression may be performed under reduced pressure. In this case, from the viewpoint of suppressing deterioration of the base material and the main sheet due to oxidation, it is preferable to carry out the vacuum degree of 20 kPa or less. Heat compression is preferably performed using a vacuum press.

During heat compression, from the viewpoint of suppressing adhesion of the sheet to the hot plate or roll, a release film is placed between the surface of the sheet and the hot plate or roll, or the surface of the hot plate or roll is surface treated with a release agent. It is desirable to do so.

The thickness of the release film is preferably 50 to 150 μm.

Release films include polyimide films, and specific examples include "Apical NPI" (manufactured by Kaneka Corporation), "Kafton EN" (Toray Dupont Corporation), and "Upirex S" (Ube Industries). can be mentioned.

This sheet may be heat-compressed only on one surface of the substrate, or may be heat-compressed on both sides of the substrate. In the former case, a laminate having a base material layer and a polymer layer on one surface of the base layer is obtained, and in the latter case, a laminate having a base layer and a polymer layer on both surfaces of the base layer is obtained.

Preferred specific examples of the laminate include a metal foil and a metal-clad laminate having a polymer layer on at least one surface of the metal foil, a polyimide film, and a multilayer film having a polymer layer on both surfaces of the polyimide film. I can hear it.

The peeling strength of the polymer layer and the base material layer is preferably 10 to 100 N/cm.

Additionally, the base material layer may be removed from the laminate to obtain a sheet containing PTFE, inorganic particles, and this resin.

This sheet, fired sheet, and laminate having a base layer and a polymer layer are useful as antenna parts, printed boards, aircraft parts, automobile parts, sports equipment, food industry products, heat dissipation parts, paints, cosmetics, etc.

Specifically, electric wire covering materials such as aircraft wires, enamel wire covering materials used in motors such as electric vehicles, electrical insulating tape, insulating tape for oil drilling, petroleum transport hoses, hydrogen tanks, materials for printed circuit boards, microfiltration membranes, ultraviolet rays. Separation membranes such as filtration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, and gas separation membranes, electrodes and electrolyte binders for lithium secondary batteries and fuel cells, copy rolls, covers for furniture, automobile dashboards, home appliances, sliding members, tension, etc. Ropes, wear pads, wear strips, tube lamps, test sockets, wafer guides, wear parts of centrifugal pumps, chemical and water supply pumps, tools such as shovels, files, awls, and saws, boilers, hoppers, pipes, ovens, furnaces, etc. Two days, suits, racket guts, dice, toilets, container covering materials, 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., personal As casings for computers and displays, electronic device materials, interior and exterior of automobiles, sealing materials for processing machines, vacuum ovens, and plasma processing devices that perform heat processing under low oxygen, heat dissipation components within processing units such as sputtering and various dry etching devices, and electromagnetic wave shields. useful. Sliding members include load bearings, yaw bearings, sliding shafts, valves, bearings, bushes, seals, thrust washers, wear rings, pistons, slide switches, gears, cams, belt conveyors, and food transport belts.

Although the present sheet, the manufacturing method of the present sheet, and the manufacturing method of the laminate containing the present sheet have been described above, the present invention is not limited to the configuration of the above-described embodiment.

For example, this sheet may have any other configuration added to the configuration of the above-described embodiment, or may be replaced with any configuration that performs the same function. In addition, the method of manufacturing the present sheet and the method of manufacturing the laminate containing the present sheet may further include any other process in the configuration of the above embodiment, or may be substituted with an arbitrary process that produces the same effect. .

Example

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these.

1. Preparation of each ingredient and each member

[Dispersion]

Dispersion 1: Aqueous dispersion containing 60% by mass of particles (D50: 0.3 μm) made of uncooked PTFE (PTFE1. Melting temperature: 327°C) (“AD-911E” manufactured by AGC)

[Inorganic particles]

Inorganic particle 1: spherical silica (D50: 1 ㎛)

[Resin particles]

Resin particle 1: Tetrafluoroethylene system containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE unit, NAH unit, and PPVE unit in this order, and having 1000 carbonyl group-containing groups per 1 × 10 ⁶ main chain carbon number. Particles (D50: 2.1 ㎛) made of polymer (F resin 1. Melting temperature: 300 ℃)

Resin particle 2: Tetrafluoroethylene-based polymer containing 98.7 mol% and 1.3 mol% of TFE units and PPVE units in this order, and having no carbonyl group-containing group, hydroxy group, epoxy group, or amino group (F Resin 2. Melt Temperature: 305 ℃) particles (D50: 1.8 ㎛)

Resin particle 3: Particles made of powdery uncalcined PTFE obtained by removing water from dispersion 1

[Resin Varnish]

Varnish 1: Water varnish containing a precursor of aromatic polyamidoimide (PAI 1. Has a carboxyl group and an amide group. Acid value: 50 mgKOH/g)

[Surfactants]

Surfactant 1: Polyoxyalkylene-modified polydimethylsiloxane having a dimethylsiloxane unit in the main chain and an oxyethylene group in the side chain.

[Glass Cloth]

Glass cloth 1: Glass cloth (“1078” manufactured by Arisa and Fiberglass Co., Ltd.)

2. Sheet manufacturing example

(Example 1)

The dry blend of inorganic particles 1 and resin particles 1, water, and surfactant 1 were added to the planetary mixer and mixed. Subsequently, the mixture of dispersion liquid 1 and varnish 1 and water were added in multiple portions and stirred to obtain mixture 1. Methanol was added while stirring the mixture 1, 20 parts by mass of PTFE 1, 60 parts by mass of inorganic particles 1, 18.5 parts by mass of resin particles 1, 1.5 parts by mass of PAI 1, 1 part by mass of surfactant 1, 100 parts by mass of water, and 70 parts by mass. Agglomerate 1 containing PTFE particles 1, inorganic particles 1, resin particles 1, and PAI 1, formed from composition 1 of a mass part of methanol, was recovered.

The aggregate 1 and dodecane heated under vacuum at 60°C for 24 hours were placed in a V-type mixer and mixed at 24°C for 5 minutes at a rotation speed of 10 rpm to obtain paste-like liquid composition 1.

Liquid composition 1 was passed between a pair of rolling rolls to obtain a flexible mother sheet 1 with a thickness of 3 mm. Mother sheet 1 was softened using an inverted L-shaped calender and further heated at 150°C for 30 minutes to remove dodecane, thereby obtaining Sheet 1 with a thickness of 200 μm. In sheet 1, the total content of PTFE 1, inorganic particles 1, F resin 1, and PAI 1 or polyamideimide, which is a reaction product of PAI 1, is 98% by mass or more, and the content of PTFE 1 is 15% by mass. As above, the total content of F resin 1 and PAI 1 or polyamideimide, which is a reaction product of PAI 1, was 15% by mass or more, and the content of inorganic particles was 50% by mass or more.

(Example 2)

Mixture 2 was obtained in the same manner as in Example 1, except that Resin Particle 1 was changed to Resin Particle 2. Sheet 2 was obtained in the same manner as in Example 1, using mixture 2 instead of mixture 1.

(Example 3)

Sheet 3 was obtained in the same manner as in Example 1, except that Resin Particle 1 was changed to Resin Particle 2 and Varnish 1 was not used.

(Example 4)

After immersing the glass cloth 1 in the mixture 2, it was heated at 100°C and dried to obtain a parent sheet in which the glass cloth 1 was impregnated with the PTFE particles 1. The mother sheet was casted using an inverted L-shaped calender to obtain Sheet 4, which had a thickness of 200 μm and a glass cloth 1 content of more than 10% by mass.

(Example 5)

To the Henschel mixer, 15 parts by mass of resin particles 3, 13 parts by mass of resin particles 1, 60 parts by mass of inorganic particles 1, 2 parts by mass of PAI 1, and 10 parts by mass of tetradecane were added, and stirred at 1000 rpm for 2 minutes. And aggregate 5 was obtained. Sheet 5 was obtained in the same manner as in Example 1, except that aggregate 5 was changed to aggregate 1.

3. Sheet evaluation example

3-1. Evaluation of bending resistance

From each of sheets 1 to 5, a 50 mm × 100 mm square test piece was cut. The test piece was bent at an angle of 180° along a 2 mm mandrel according to the method specified in JIS K 5600-5-1. The bent test piece was visually inspected and its bending resistance was evaluated according to the following standards.

[Evaluation standard]

○: No cracks were observed in the test piece.

×: Cracks were confirmed in the test piece.

3-2. Evaluation of powder dropout

After performing evaluation 3-1, each sheet was removed from the mandrel. The adhesion of the powder to the mandrel was visually confirmed, and the ease of powder removal was evaluated according to the following criteria.

[Evaluation standard]

○: Adhesion of powder to the mandrel was not confirmed.

×: Adhesion of powder to the mandrel was confirmed.

3-3. Evaluation of adhesiveness

Each of sheets 1 to 5 is overlapped with a long piece of copper foil (thickness: 18 μm, average roughness of 10 points on the surface: 0.8 μm), vacuum pressed at 380°C and thermocompressed, and PTFE particles 1 are fired on the copper foil and its surface. Laminates 1 to 5 having a polymer layer containing water were obtained.

Rectangular test pieces with a length of 100 mm and a width of 10 mm were cut from each of laminates 1 to 5. The position 50 mm from one end in the longitudinal direction of the test piece was fixed, and the copper foil and the polymer layer were peeled from one end in the longitudinal direction at an angle of 90° to the test piece at a tensile speed of 50 mm/min. The maximum load upon peeling was taken as the peeling strength (N/cm), and the adhesiveness of the sheet was evaluated according to the following standards.

[Evaluation standard]

○: Peeling strength was 12 N/cm or more.

Δ: Peel strength was 10 N/cm or more and less than 12 N/cm.

×: Peel strength was less than 10 N/cm.

3-4. Evaluation of electrical properties

For each of the laminates 1 to 4, the copper foil was removed by etching with an aqueous ferric chloride solution, and fired sheets 1 to 4 consisting of a single polymer layer were obtained. The dielectric constant and dielectric loss tangent (measurement frequency: 10 GHz) of the fired sheet were measured using the SPDR (split post dielectric resonance) method.

The results of each evaluation are summarized and shown in Table 1 below.

As can be seen from the above results, the sheet of the present invention had excellent bending resistance and adhesiveness, and the powder was difficult to fall off. Additionally, the fired sheet obtained from the sheet of the present invention was excellent in low dielectric constant and low dielectric loss tangent. Therefore, it is believed that the sheet of the present invention has excellent uniformity of component distribution and exhibits the properties of unfired PTFE, inorganic particles, and the present resin to a high degree. The sheet of the present invention, or the fired sheet and laminate obtained from the sheet of the present invention, are resistant to peeling of inorganic particles, are excellent in electrical properties, low linear expansion, physical strength, and adhesion to other materials, and are used as printed circuit board materials. useful.

Claims (15)

It contains uncooked polytetrafluoroethylene, inorganic particles, and a resin having at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group-containing group, an epoxy group, and an amino group, and the polytetrafluoroethylene A sheet wherein the total content of the inorganic particles and the resin is 90% by mass or more. According to claim 1,
A sheet wherein the inorganic particles are particles containing at least one inorganic substance selected from the group consisting of silica, boron nitride, and titanium dioxide. According to claim 1,
A sheet wherein the resin contains at least one of a heat-meltable tetrafluoroethylene polymer, an aromatic polymer, or a precursor thereof. According to claim 1,
A sheet wherein the resin contains a heat-meltable tetrafluoroethylene-based polymer and an aromatic polymer or a precursor thereof. According to claim 3,
A sheet wherein the heat-meltable tetrafluoroethylene polymer has a melting temperature of 260 to 320°C. According to claim 3,
A sheet wherein the aromatic polymer or its precursor is polyimide, polyamidoimide, a polyimide precursor, or a polyamideimide precursor. According to claim 1,
A sheet containing 10% by mass or more of the polytetrafluoroethylene. According to claim 1,
A sheet having a content of the above resin of 5% by mass or more. According to claim 1,
A sheet wherein the ratio of the content of the inorganic particles to the total content of the polytetrafluoroethylene and the content of the resin is 0.1 or more. According to claim 1,
Sheets with a thickness of 50 ㎛ or more. A method for producing a sheet, wherein the sheet according to claim 1 is obtained by flowing a liquid composition containing the polytetrafluoroethylene particles, the inorganic particles, and the resin. According to claim 11,
A production method wherein the average particle diameter of the polytetrafluoroethylene particles is 0.1 to 10 μm. The method of claim 11 or 12,
A manufacturing method in which flexible materials obtained by softening the liquid composition are layered and bonded to each other. A method for producing a fired sheet, comprising heating the sheet according to any one of claims 1 to 10 to bake the polytetrafluoroethylene. A method for producing a laminate, wherein the sheet according to any one of claims 1 to 10 and a substrate are thermocompressed to obtain a laminate having a substrate layer and a polymer layer.