Liquid composition, method for producing substrate with polymer layer, and substrate with polymer layer

Abstract

Provided are a liquid composition that contains a tetrafluoroethylene-based polymer and that can form a thick polymer layer in which the occurrence of cracks and voids is suppressed, and a polymer-layered substrate that includes the polymer layer. [Solution] A liquid composition comprising particles of a tetrafluoroethylene-based polymer, a dispersant polymer, and a liquid dispersion medium, wherein the dispersant polymer is a non-dissociative polymerizable (meth)acrylate-based polymer having a weight-average molecular weight of 30,000 to 90,000 and having at least one structural unit derived from a (meth)acrylate having a group selected from a perfluoroalkyl group, a perfluoroalkenyl group, a siloxane group, or an alkyl group, and a structural unit derived from a (meth)acrylate having an oxyalkylene group.

Description

[Technical Field]

[0001] The present invention relates to a liquid composition containing a tetrafluoroethylene-based polymer, a method for producing a substrate with a polymer layer using the liquid composition, and the substrate with a polymer layer. [Background technology]

[0002] Tetrafluoroethylene-based polymers such as polytetrafluoroethylene (PTFE) have excellent physical properties such as electrical properties, water and oil repellency, chemical resistance, and heat resistance, and are used in a variety of applications. In recent years, to accommodate the increasing speed and frequency of mobile communication devices such as mobile phones, insulating materials for printed circuit boards of communication devices are required to have high thermal conductivity, a low coefficient of linear expansion, a low dielectric constant, and a low dielectric loss tangent, and tetrafluoroethylene-based polymers with low dielectric constant and low dielectric loss tangent have attracted attention. Patent Document 1 proposes a composition containing fine particles of a tetrafluoroethylene-based polymer and a fluorine-based dispersant polymer that exhibits a specific weight loss rate. Patent Document 2 proposes a composition containing a specific fluorine-based dispersant polymer having methyl methacrylate, a depolymerizable monomer, as an essential structural unit, and fine particles of a tetrafluoroethylene-based polymer. Patent Document 3 proposes a composition containing a specific fluorine-containing oligomer and fine particles of PTFE. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-078102 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-110697 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-074129 Summary of the Invention [Problem to be solved by the invention]

[0004] The compositions disclosed in Patent Documents 1 to 3 are said to have excellent dispersibility of fine particle tetrafluoroethylene polymers. However, the surfaces of coating films formed from these compositions are prone to cracking, and this tendency becomes more pronounced when attempting to form thick coating films. Furthermore, printed circuit board materials must have a high level of balance between their electrical properties, heat resistance, mechanical properties, and adhesiveness (adhesion) between the conductive layer and the insulating layer, and therefore the affinity and uniform dispersibility of the components that make up the composition must be taken into consideration. The present inventors have discovered that a liquid composition containing tetrafluoroethylene-based polymer particles and containing a specific dispersant can form a dense, thick polymer layer (film) that is excellent in mechanical properties, heat resistance, electrical properties (low linear expansion coefficient, low dielectric constant, low dielectric tangent, etc.), adhesion, etc., and that is suppressed from generating cracks, and have arrived at the present invention. An object of the present invention is to provide a liquid composition that contains a tetrafluoroethylene-based polymer and that can form a thick polymer layer that is suppressed from generating cracks and voids, and a polymer layer-attached substrate that includes the polymer layer. [Means for solving the problem]

[0005] The present invention has the following aspects. [1] A liquid composition comprising particles of a tetrafluoroethylene-based polymer, a dispersant polymer, and a liquid dispersion medium, wherein the dispersant polymer is a non-dissociative polymerizable (meth)acrylate-based polymer having a weight-average molecular weight of 30,000 to 90,000 and having at least one structural unit derived from a (meth)acrylate having a group selected from a perfluoroalkyl group, a perfluoroalkenyl group, a siloxane group, or an alkyl group, and a structural unit derived from a (meth)acrylate having an oxyalkylene group. [2] The liquid composition according to [1], wherein the tetrafluoroethylene-based polymer comprises a heat-fusible tetrafluoroethylene-based polymer having an oxygen-containing polar group. [3] The liquid composition according to [1] or [2], wherein the content of the tetrafluoroethylene-based polymer particles is 30% by mass or more. [4] The liquid composition according to any one of [1] to [3], wherein the average particle size (D50) of the particles of the tetrafluoroethylene polymer is 1 μm or more and less than 10 μm. [5] The specific surface area of ​​the particles of the tetrafluoroethylene-based polymer is 25 m 2 The liquid composition of any one of [1] to [4], wherein the solubility is 0.01% or less. [6] The liquid composition according to any one of [1] to [5], wherein the perfluoroalkyl group and the perfluoroalkenyl group each independently have 6 to 12 carbon atoms. [7] The liquid composition according to any one of [1] to [6], wherein the alkyl group has 12 or more and 40 or less carbon atoms. [8] The siloxane group is a dimethylpolysiloxane unit (-(CH3)2SiO 2 / 2 The liquid composition of any one of [1] to [7], wherein the aryl group is a group having -). [9] The liquid composition according to any one of [1] to [8], wherein the oxyalkylene group is a group having an oxyethylene unit.

[10] The liquid composition according to any one of [1] to [9], wherein the liquid dispersion medium is a non-aqueous polar solvent.

[11] The liquid composition according to any one of [1] to

[10] , wherein the liquid dispersion medium is at least one non-aqueous polar solvent selected from the group consisting of amides, ketones, and esters.

[12] The liquid composition according to any one of [1] to

[11] , wherein the non-dissociatively polymerizable (meth)acrylate polymer does not have any structural unit derived from a thermally decomposable (meth)acrylate, or any structural unit having an acetal, hemiacetal, ketal, or hemiketal.

[13] The liquid composition according to any one of [1] to

[12] , which has a viscosity of 1000 mPa or less.

[14] A method for producing a substrate with a polymer layer, comprising: applying any one of the liquid compositions of [1] to

[13] to a surface of a substrate to form a coating layer made of the liquid composition on the surface of the substrate; and heating the substrate having the coating layer thereon to form a polymer layer containing the tetrafluoroethylene-based polymer and having a thickness of 20 μm or more on the surface of the substrate.

[15] A substrate with a polymer layer, which has a polymer layer having a thickness of 20 μm or more and which is formed from the liquid composition of any one of [1] to

[13] and contains the tetrafluoroethylene-based polymer. [Effects of the Invention]

[0006] According to the present invention, there is provided a liquid composition that can form a thick polymer layer containing a tetrafluoroethylene-based polymer and that is free from cracks and voids. A polymer-layered substrate (laminate) having the polymer layer can be effectively used, for example, as a printed wiring board material. DETAILED DESCRIPTION OF THE INVENTION

[0007] The following terms have the following meanings: "Average particle size (D50)" is the volume-based cumulative 50% diameter of particles determined by laser diffraction / scattering. In other words, particle size distribution is measured by laser diffraction / scattering, and a cumulative curve is calculated with the total volume of the particle group as 100%. The average particle size (D50) is the particle size at the point on the cumulative curve where the cumulative volume is 50%. The D50 of particles is determined by dispersing the particles in water and analyzing them by the laser diffraction / scattering method using a laser diffraction / scattering particle size distribution measuring device (LA-920 measuring device, manufactured by Horiba, Ltd.). The "average particle size (D90)" is the volume-based cumulative 90% diameter of particles, which is determined in the same manner as D50. The specific surface area of ​​the particles is a value calculated by measuring the particles by the gas adsorption (constant volume method) BET multipoint method, and is determined using NOVA4200e (manufactured by Quantachrome Instruments). The "melting temperature" is the temperature corresponding to the maximum value of the melting peak of a polymer as measured by differential scanning calorimetry (DSC). The "glass transition temperature (Tg)" is a value measured by analyzing a polymer using the dynamic mechanical analysis (DMA) method. The "viscosity" is determined by measuring the composition using a Brookfield viscometer at 25°C and 30 rpm. The measurement is repeated three times, and the average value of the three measurements is used. The "thixotropy ratio" is a value calculated by dividing the viscosity η1 of a composition measured at a rotation speed of 30 rpm by the viscosity η2 measured at a rotation speed of 60 rpm. Each viscosity measurement is repeated three times, and the average value of the three measurements is used. The term "unit" in a polymer refers to an atomic group based on a monomer formed by polymerization of the monomer. The unit may be a unit formed directly by a polymerization reaction, or may be a unit in which a portion of the unit is converted into a different structure by processing the polymer. Hereinafter, a unit based on monomer a will also be referred to simply as a "monomer a unit."

[0008] The present invention provides a liquid composition (hereinafter also referred to as "the composition") comprising particles (hereinafter also referred to as "F particles") of a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer"), a dispersant polymer, and a liquid dispersion medium, wherein the dispersant polymer is a non-dissociative polymerizable (meth)acrylate-based polymer having a weight-average molecular weight of 30,000 to 90,000, and having at least one structural unit derived from a (meth)acrylate having a group selected from a perfluoroalkyl group, a perfluoroalkenyl group, a siloxane group, or an alkyl group, and a structural unit derived from a (meth)acrylate having an oxyalkylene group.

[0009] This composition can be used to form a thick polymer layer that is free of cracks and voids. Such a polymer layer has excellent physical properties, such as heat resistance, mechanical properties, and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent) based on the F polymer, and a substrate with such a polymer layer can be effectively used in a variety of applications that take advantage of these properties. The reason why a thick polymer layer (for example, 20 μm or more) in which the occurrence of cracks and voids is suppressed can be obtained from this composition is not entirely clear, but is thought to be as follows.

[0010] If the dispersant polymer in a liquid composition containing F particles has a thermally decomposable group or contains a depolymerizable monomer such as methyl methacrylate as a constituent component, when the liquid composition is heated to form a molded product such as a layer, the dispersant polymer decomposes and becomes low in molecular weight, which not only causes a rapid decrease in its functionality but also induces localized foaming due to the decomposition products, making it likely that the physical properties of the molded product will decrease. In contrast, the present composition contains a dispersant polymer that contains structural units with low thermal decomposition properties and has a weight-average molecular weight (Mw) within a specific range, which is thought to suppress the foaming tendency of the composition itself and facilitate improvement of its rheological properties (viscosity, thixotropy ratio, etc.), as well as to mitigate functional degradation of the dispersant polymer and localized foaming when the composition is heated to form a molded product. Furthermore, it is presumed that a relatively high Mw of the dispersant polymer not only suppresses the bleed-out of the dispersant polymer when heated, but also enhances the interaction between the dispersant polymer and the F polymer; in other words, it makes it easier for the dispersant polymer to function as a binder component for the F particles. As a result, it is believed that the occurrence of cracks is suppressed and molded articles such as dense, thick polymer layers with few voids can be obtained from this composition, and that the molded articles are endowed with high levels of properties based on the F polymer.

[0011] The F polymer in the present invention is a polymer containing units (hereinafter also referred to as "TFE units") based on tetrafluoroethylene (hereinafter also referred to as "TFE"). The polymer F is preferably heat-fusible. Here, a heat-fusible polymer means a polymer that has a temperature at which the melt flow rate is 1 to 1000 g / 10 min under a load of 49 N. The melting temperature of the F polymer is preferably 200°C or higher, more preferably 260°C or higher. The melting temperature of the F polymer is preferably 325°C or lower, more preferably 320°C or lower. The melting temperature of the F polymer is preferably 200 to 320°C. In this case, the composition is likely to have excellent processability, and the polymer layer formed from the composition is likely to have excellent heat resistance.

[0012] The glass transition point of the F polymer is preferably 50° C. or higher, more preferably 75° C. or higher. The glass transition point of the F polymer is preferably 150° C. or lower, more preferably 125° C. or lower. The fluorine content of the F polymer is preferably 70% by mass or more, more preferably 72 to 76% by mass. The surface tension of the F polymer is preferably 16 to 26 mN / m. The surface tension of the F polymer can be measured by placing a droplet of a mixture for wetting tension testing (manufactured by Wako Pure Chemical Industries, Ltd.) specified in JIS K 6768 on a flat plate made of the F polymer.

[0013] The F polymer is preferably a polymer containing TFE units and units based on ethylene (ETFE), a polymer containing TFE units and units based on propylene, a polymer containing TFE units and units based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE units) (PFA), or a polymer containing TFE units and units based on hexafluoropropylene (FEP), with PFA and FEP being more preferred, and PFA being even more preferred. These polymers may further contain units based on other comonomers. PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3, or CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), and PPVE is more preferred.

[0014] The F polymer preferably has an oxygen-containing polar group, more preferably has a hydroxyl-containing group or a carbonyl-containing group, and even more preferably has a carbonyl-containing group. In this case, the composition is likely to have excellent dispersion stability and ease of handling, and the polymer layer formed from the composition is likely to have excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent). The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF2CH2OH and -C(CF3)2OH. The carbonyl group-containing group is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH), an acid anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.), a formyl group, a halogenoformyl group, a urethane group (-NHC(O)O-), a carbamoyl group (-C(O)-NH), a ureido group (-NH-C(O)-NH), an oxamoyl group (-NH-C(O)-C(O)-NH), or a carbonate group (-OC(O)O-), and more preferably an acid anhydride residue. When the F polymer has an oxygen-containing polar group, the number of oxygen-containing polar groups in the F polymer is 1×10 6 The number per unit is preferably 10 to 5000, more preferably 100 to 3000. The number of oxygen-containing polar groups in the F polymer can be quantified based on the polymer composition or the method described in WO 2020 / 145133.

[0015] The oxygen-containing polar group may be contained in a unit derived from 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 include an F polymer having an oxygen-containing polar group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and an F polymer obtained by subjecting an F polymer to plasma treatment or ionizing radiation treatment.

[0016] The F polymer is preferably a polymer having a carbonyl group-containing group containing TFE units and PAVE units, more preferably a polymer containing TFE units, PAVE units, and units based on a monomer having a carbonyl group-containing group, in which the total units contain 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol%, respectively, in that order. Specific examples of such F polymers include the polymers described in WO 2018 / 16644. The monomer having a carbonyl group-containing group is preferably itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and more preferably NAH.

[0017] The F particles contained in the present composition are particles containing an F polymer, and preferably consist of an F polymer. The D50 of the F particles is preferably 1 μm or more and less than 10 μm. The F particles may be solid particles or non-hollow particles. The F particles may be secondary particles formed from nanometer-order fine particles. The D50 of the F particles is preferably 1.0 μm or more, more preferably 1.5 μm or more. The D50 of the F particles is preferably 6 μm or less, more preferably 5 μm or less. Furthermore, the D90 of the F particles is preferably 8 μm or less, and more preferably 6 μm or less. When the D50 and D90 of the F particles are within the above ranges, the above-mentioned mechanism of action is more easily manifested, and it is easier to obtain the present composition that can form a thick polymer layer in which the occurrence of cracks and voids is suppressed. One type of F particle may be used, or two or more types may be used.

[0018] The specific surface area of ​​F particles is 25m 2 / g or less, and 1 to 25m 2 / g, and 6 to 15m 2 When the specific surface area of ​​the F particles is within the above range, in other words, even when the F particles have a relatively large average particle diameter (D50) and a small specific surface area, the above-described mechanism of action makes it easy to obtain the present composition, which is capable of forming a thick polymer layer in which the occurrence of cracks and voids is suppressed.

[0019] The dispersant polymer contained in the present composition is a non-dissociative polymerizable (meth)acrylate polymer having a weight average molecular weight (Mw) of 30,000 to 90,000, which has at least one structural unit derived from a (meth)acrylate having a group selected from a perfluoroalkyl group, a perfluoroalkenyl group, a siloxane group, or an alkyl group (hereinafter also referred to as "(meth)acrylate A"), and a structural unit derived from a (meth)acrylate having an oxyalkylene group (hereinafter also referred to as "(meth)acrylate B"). In other words, the dispersant polymer is a non-dissociative polymerizable (meth)acrylate polymer having, at its side chains, a group selected from a perfluoroalkyl group, a perfluoroalkenyl group, a siloxane group, or an alkyl group based on a structural unit derived from (meth)acrylate A, and an oxyalkylene group based on a structural unit derived from (meth)acrylate B, and having an Mw of 30,000 to 90,000. In this specification, "(meth)acrylate" is a term that collectively refers to acrylate, methacrylate, and both. The Mw of the dispersant polymer is more preferably 35,000 to 60,000. When the Mw of the dispersant polymer is within the above range, the foaming tendency of the composition is suppressed, the rheological properties (viscosity, thixotropy ratio, etc.) are improved, and handling properties such as film-forming properties tend to be improved. Furthermore, due to the above-mentioned mechanism of action, the occurrence of cracks is suppressed, and a dense, thick polymer layer with few voids is likely to be obtained.

[0020] The perfluoroalkyl group and the perfluoroalkenyl group in the (meth)acrylate A preferably each independently have 6 to 12 carbon atoms. Examples of perfluoroalkyl groups include a perfluorohexyl group (-(CF2)6F), a perfluorooctyl group, and a perfluorodecyl group. Examples of perfluoroalkenyl groups include groups containing a structure derived from a trimer of hexafluoropropene (such as -CF(CF3)C(=C(CF3)2)(CF(CF3)2), -C(CF3)=C(CCF(CF3)2)2, etc.). The siloxane group of (meth)acrylate A is a dimethylpolysiloxane unit (-(CH3)2SiO 2 / 2 The number of repeating dimethylsiloxane units is preferably 2 or more and 100 or less, and more preferably 2 or more and 50 or less. The number of carbon atoms in the alkyl group of the (meth)acrylate A is preferably 12 or more and 40 or less, and more preferably 18 or more and 36 or less. The alkyl group may be linear or branched, or may have a cyclic structure.

[0021] As the (meth)acrylate A, CH2=C(R 1 )-COO-R 2 -O-Rf (A1) CH2=C(R 1 )-COO-R 3 -OH (A2) CH2=C(R 1 )-COO-R 4 (A3) (In formulas (A1) to (A3), R 1 represents a hydrogen atom or a methyl group, and R 2 represents a divalent saturated aliphatic hydrocarbon group having 1 to 50 carbon atoms, Rf represents a perfluoroalkyl group or a perfluoroalkenyl group, and R 3 represents a siloxane group, and R 4 represents an alkyl group having 12 to 40 carbon atoms.) Among these, (meth)acrylate A is preferably a (meth)acrylate having a perfluoroalkyl group or a perfluoroalkenyl group, from the viewpoint that the dispersant polymer is likely to exhibit the above-mentioned mechanism of action of the present invention.

[0022] The oxyalkylene group contained in (meth)acrylate B is preferably an oxypropylene group or a group having an oxyethylene unit, more preferably a group having an oxyethylene unit. The number of repeating units of the oxyalkylene group is preferably in the range of 1 to 100, more preferably in the range of 6 to 70. Examples of (meth)acrylate B include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, poly(ethylene glycol·propylene glycol)-monomethacrylate, polyethylene glycol·polypropylene glycol-monomethacrylate, poly(ethylene glycol·tetramethylene glycol)-monomethacrylate, poly(propylene glycol·tetramethylene glycol)-monomethacrylate, and propylene glycol·polybutylene glycol-monomethacrylate.

[0023] In the non-dissociatively polymerizable (meth)acrylate polymer, the content of the structural units derived from (meth)acrylate A relative to the total of the structural units derived from (meth)acrylate A and the structural units derived from (meth)acrylate B is preferably in the range of 40 to 70% by molar ratio, which makes it easier for the above-mentioned mechanism of action to be realized.

[0024] In addition, in the present composition, the non-dissociative polymerizable (meth)acrylate polymer serving as the dispersant polymer preferably does not have any structural units derived from thermally decomposable (meth)acrylates or structural units having acetal, hemiacetal, ketal, or hemiketal, in other words, it preferably does not have any structural units derived from the above-mentioned monomers that dissociate upon heating. In this specification, the thermally decomposable (meth)acrylate means an alkyl (meth)acrylate having 1 to 4 carbon atoms in the alkyl ester moiety, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. The dispersant polymer may be used alone or in combination of two or more.

[0025] The liquid dispersion medium contained in the present composition is a compound that is liquid at 25°C under atmospheric pressure, and preferably has a boiling point of 50 to 240°C. One type of liquid dispersion medium may be used, or two or more types may be used. When two or more types of liquid dispersion medium are used, the two or more types of liquid dispersion medium are preferably mutually miscible. Examples of the liquid dispersion medium include non-polar solvents such as aliphatic hydrocarbons and aromatic hydrocarbons, and polar solvents such as water, alcohols, ethers, amides, ketones, esters, etc. Among these, the liquid dispersion medium is preferably a non-aqueous polar solvent, and more preferably at least one non-aqueous polar solvent selected from the group consisting of amides, ketones, and esters. Examples of amides include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropanamide, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-diethylformamide, hexamethylphosphoric triamide, and 1,3-dimethyl-2-imidazolidinone. Examples of ketones include acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl isopentyl ketone, 2-heptanone, cyclopentanone, cyclohexanone, and cycloheptanone. Examples of esters include methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, ethyl 3-ethoxypropionate, γ-butyrolactone, and γ-valerolactone. Of these, N-methyl-2-pyrrolidone is more preferred.

[0026] The content of F particles in the composition is preferably 25% by mass or more, more preferably 30% by mass or more, and is preferably 55% by mass or less, more preferably 50% by mass or less. The content of the dispersant polymer in the composition is preferably in the range of 1 to 15% by mass relative to the total mass of the composition, and more preferably 1 to 20% by mass, and more preferably 1 to 10% by mass, relative to the content of the F particles. The content of the liquid dispersion medium in the composition is preferably 25% by mass or more, more preferably 40% by mass or more. The content of the liquid dispersion medium is preferably less than 70% by mass, more preferably 65% ​​by mass or less. Furthermore, the content of the liquid dispersion medium in the composition is preferably 60 to 180% by mass relative to the content of the F particles.

[0027] The present composition may further contain other nonionic surfactants, such as glycol-based surfactants and acetylene-based surfactants, different from the dispersant polymer described above, within the range that does not impair the effects of the present invention.

[0028] The composition may further contain inorganic particles, in which case the polymer layer formed from the composition is likely to have excellent electrical properties and low linear expansion. Examples of inorganic particles include silicon compounds such as quartz powder, silica, wollastonite, talc, silicon nitride, silicon carbide, and mica; nitrogen compounds such as boron nitride and aluminum nitride; metal oxides such as aluminum oxide, zinc oxide, titanium oxide, cerium oxide, beryllium oxide, magnesium oxide, nickel oxide, vanadium oxide, copper oxide, iron oxide, and silver oxide; carbon fibers; carbon allotropes such as graphite, graphene, and carbon nanotubes; and metals such as silver and copper. One type of inorganic particle may be used, or two or more types may be used in combination. The inorganic particles preferably have a D50 of 0.1 to 50 μm. The surfaces of the inorganic particles may be surface-treated with a silane coupling agent. When the present composition further contains inorganic particles, the content of the inorganic particles in the present composition is preferably 1 to 25% by mass.

[0029] The present composition may further contain another resin different from the F polymer. Such another resin may be contained in the present composition as non-hollow particles, or may be dissolved or dispersed in the liquid dispersion medium that constitutes the present composition. Examples of other resins include polyester resins such as liquid crystalline aromatic polyesters, polyimide resins, polyamideimide resins, epoxy resins, maleimide resins, urethane resins, polyphenylene ether resins, polyphenylene oxide resins, and polyphenylene sulfide resins. When the present composition further contains another resin, the content of the other resin relative to the F particles is preferably 1 to 25% by weight.

[0030] The present composition may further contain additives such as a thixotropic agent, a viscosity modifier, an antifoaming agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a colorant, a conductive agent, a mold release agent, and a flame retardant.

[0031] The composition can be obtained by mixing F particles, a dispersant polymer, a liquid dispersion medium, and, if necessary, other nonionic surfactants, inorganic particles, other resins, additives, etc. The composition can be obtained by mixing the F particles, dispersant polymer, and liquid dispersion medium all at once, or by mixing them in multiple batches. Furthermore, when the other nonionic surfactants, inorganic particles, other resins, additives, etc. are further mixed as needed, there are no particular limitations on the order of mixing. For example, they can be mixed with the F particles in advance, or they can be added to the liquid dispersion medium in advance and then mixed with the F particles and dispersant polymer, or they can be mixed when the F particles, dispersant polymer, and liquid dispersion medium are mixed.

[0032] Examples of mixing devices for obtaining the present composition include agitators equipped with blades, such as a Henschel mixer, pressure kneader, Banbury mixer, and planetary mixer; grinding devices equipped with media, such as a ball mill, attritor, basket mill, sand mill, sand grinder, Dyno Mill, Dispermat, SC Mill, spike mill, and agitator mill; and dispersing devices equipped with other mechanisms, such as a microfluidizer, nanomizer, ultimizer, ultrasonic homogenizer, dissolver, disper, high-speed impeller, thin film swirling high-speed mixer, planetary mixer, and V-type mixer.

[0033] The viscosity of the composition is preferably 10 mPa·s or higher, more preferably 50 mPa·s or higher. The viscosity of the composition is preferably 3000 mPa·s or lower, more preferably 1000 mPa·s or lower. In this case, the composition exhibits low foaming and excellent coatability, and is likely to form a dense, thick polymer layer with reduced cracking and voids. Furthermore, the composition having a viscosity within this range is likely to exhibit the physical properties of the F polymer to a high degree in the polymer layer formed therefrom. The thixotropy ratio of the present composition is preferably 1.0 to 3.0, in which case the present composition is likely to form a dense, thick polymer layer that has excellent coatability and uniformity and is free from cracks and voids.

[0034] The present invention also relates to a method for producing a substrate with a polymer layer, which comprises applying the composition to a surface of a substrate to form a coating layer comprising the composition on the surface of the substrate, and heating the substrate having the coating layer thereon to form a polymer layer containing the tetrafluoroethylene-based polymer and having a thickness of 20 μm or more on the surface of the substrate (hereinafter also referred to as "the method"). In this method, the method for applying the present composition to the surface of the substrate may be any method that forms a stable liquid coating (wet film) of the present composition on the surface of the substrate, and examples of such methods include coating methods, droplet ejection methods, and immersion methods, with roll coating, knife coating, bar coating, die coating, and spraying methods being preferred.

[0035] The substrate is preferably a heat-resistant substrate, and examples of the heat-resistant substrate include metal substrates such as metal foils of copper, nickel, aluminum, titanium, alloys thereof, and the like; heat-resistant resin films such as liquid crystal polymers such as polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyaryl ether ketone, polyamideimide, liquid crystal polyester, and tetrafluoroethylene-based polymers other than F polymers, such as polytetrafluoroethylene; prepreg substrates (precursors of fiber-reinforced resin substrates), ceramic substrates such as silicon carbide, aluminum nitride, and silicon nitride; and glass substrates. Among these, the heat-resistant substrate is preferably a film of a heat-resistant resin selected from polyimide, liquid crystal polymer, and polytetrafluoroethylene, and more preferably a polyimide film.

[0036] The shape of the substrate may be flat, curved, or uneven, and may be any of foil, plate, film, and fiber. In this method, the substrate may be a long substrate. In this case, a roll-to-roll process can be applied, and the polymer layer-bearing substrate of the present invention described below can be produced as a roll-shaped product in a long form, which is preferable from the viewpoint of improving productivity. The ten-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.

[0037] Next, the substrate having the coating layer is heated to remove the liquid dispersion medium and melt and bake the F polymer, thereby forming a polymer layer containing the F polymer and having a thickness of 20 μm or more on the surface of the substrate. When the coating layer is dried to remove the liquid dispersion medium, the coating layer is heated to a temperature at which the liquid dispersion medium volatilizes, forming a dry coating on the surface of the substrate. The heating for removing the liquid dispersion medium is preferably carried out at a temperature equal to or higher than the boiling point of the liquid dispersion medium, for example, 80 to 200°C. During this heating, a dry coating is formed by packing of the F particles. During heating, air may be blown onto the surface to promote removal of the liquid dispersion medium by air drying. During drying, the liquid dispersion medium does not necessarily have to be completely evaporated, but it is sufficient to evaporate it to an extent that the layer shape after holding is stable and a free-standing film can be maintained. The dried coating is further heated at a temperature above the melting point of the F polymer to form a polymer layer (hereinafter also referred to as "F layer") having a thickness of 20 μm or more and containing a fused and sintered body of F particles on the surface of the substrate, thereby producing a substrate with a polymer layer. In other words, a laminate having an F layer and a substrate layer in this order is obtained. The heating is preferably carried out at 340 to 400°C.

[0038] The above-mentioned heating methods include a method using an oven, a method using a ventilation drying furnace, and a method using heat rays such as infrared rays. The heat source in the device may be a contact type heat source (hot air, hot plate, etc.) or a non-contact type heat source (infrared rays, etc.). Heating may be carried out under normal pressure (atmospheric pressure) or reduced pressure, and the heating atmosphere may be either air or an inert gas (helium gas, neon gas, argon gas, nitrogen gas, etc.). The heating time is preferably from 0.1 to 30 minutes, more preferably from 0.5 to 20 minutes.

[0039] In this method, the F layer is formed through the steps of coating the present composition on a substrate and heating. These steps may be performed once each, or may be repeated two or more times. For example, the present composition may be coated on the surface of a substrate to obtain a coating layer, and an F layer may be formed by heating, and the present composition may be further coated on the surface of the F layer to form a coating layer, and a second F layer may be formed by heating. Alternatively, the present composition may be coated on the surface of a substrate to obtain a coating layer, and after the liquid dispersion medium is removed by heating, the present composition may be further coated on the surface, and an F layer may be formed by the above-mentioned heating.

[0040] The composition may be disposed on only one surface of a substrate, or on both surfaces of a substrate. In the former case, a substrate with a polymer layer having an F layer on one surface of the substrate is obtained, while in the latter case, a substrate with a polymer layer having an F layer on both surfaces of the substrate is obtained. By separating the substrate from the polymer layer-attached substrate, a film or sheet containing the F polymer, which is a fused and sintered product of the F particles, can be obtained.

[0041] Suitable specific examples of the polymer layer-attached substrate include a metal clad laminate having a metal foil and an F layer on at least one surface of the metal foil, and a multilayer film having a polyimide film and an F layer on both surfaces of the polyimide film.

[0042] The thickness of the F layer is preferably 20 μm or more, more preferably 25 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more. The thickness of the F layer is preferably 1000 μm or less. The dielectric constant of the F layer is preferably 2.4 or less, more preferably 2.0 or less. The dielectric constant is preferably greater than 1.0. The dielectric dissipation factor of the F layer is preferably 0.0022 or less, more preferably 0.0020 or less. The dielectric dissipation factor is preferably greater than 0.0010. The thermal conductivity of the F layer is preferably 1 W / m·K or more, more preferably 3 W / m·K or more. The thermal conductivity of the F layer refers to the thermal conductivity in the in-plane direction of the F layer.

[0043] The linear expansion coefficient of the F layer is preferably 100 ppm / °C or less, more preferably 80 ppm / °C or less. The lower limit of the linear expansion coefficient of the F layer is 30 ppm / °C. The linear expansion coefficient refers to the value measured for a test piece in the range of 25°C or more and 260°C or less according to the measurement method specified in JIS C 6471:1995. The peel strength between the F layer and the substrate is preferably 10 N / cm or more, more preferably 15 N / cm or more, and is preferably 100 N / cm or less.

[0044] The present invention also relates to a substrate with a polymer layer, which has a polymer layer (F layer) having a thickness of 20 μm or more and which contains an F polymer and is formed from the composition. In such a substrate with a polymer layer, the substrate is preferably a heat-resistant substrate, and more preferably a metal foil or a heat-resistant resin film. Details of the heat-resistant substrate, metal foil, or heat-resistant resin film are the same as those described above in the explanation of this method. Furthermore, such a polymer layer-attached substrate may have an F layer on one surface of the substrate, or may have F layers on both surfaces of the substrate. The preferred ranges of the thickness, dielectric constant, dielectric loss tangent, thermal conductivity, linear expansion coefficient, and peel strength between the polymer layer and the substrate layer of such a polymer layer-attached substrate are the same as the preferred ranges of the thickness, dielectric constant, dielectric loss tangent, thermal conductivity, linear expansion coefficient, and peel strength between the F layer and the substrate in the polymer layer-attached substrate formed from the composition described above.

[0045] Substrates with a polymer layer formed from the present composition are useful as antenna parts, printed circuit boards, aircraft parts, automobile parts, sporting goods, food industry products, heat dissipation parts, etc. Specifically, these include electric wire coating materials (aircraft electric wires, rectangular wires, FFC (Flexible Flat Cable), etc.), enameled wire coating materials used in motors for electric vehicles, etc., power generation coating materials, electrical insulating tape, insulating tape for oil drilling, oil transport hoses, hydrogen tanks, materials for printed circuit boards, separation membranes (microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, gas separation membranes, etc.), electrode binders (for lithium secondary batteries, fuel cells, etc.), carrier films for fuel cells, tape base films for semiconductor manufacturing processes (dicing tape, pick-up tape, etc.), release films for semiconductor molding, liquid crystal antennas, reflectors, transmission lines, COF (Chip on Fibre), base films for electrostatic chucks used in semiconductor manufacturing processes, electrostatic chucks used in display manufacturing processes, copy rolls, furniture, automobile dashboards, covers for home appliances, etc., sliding parts (load bearings, yaw bearings, sliding shafts, valves, bearings, bushings, 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 for centrifugal pumps, chemical and water supply pumps, tools (shovels, files, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, racket strings, dies, toilets, container coating materials, heat dissipation substrates for mounting power devices, heat dissipation materials for wireless communication devices, transistors, thyristors, rectifiers, transformers, power MOS It is useful for FETs, CPUs, heat dissipation fins, metal heat sinks, blades for wind turbines, wind power generation equipment, aircraft, etc., housings for personal computers and displays, electronic device materials, interior and exterior parts of automobiles, sealing materials for processing machines and vacuum ovens that perform heat treatment under low oxygen conditions, plasma processing equipment, etc., heat dissipation parts in processing units for sputtering and various dry etching equipment, etc., and electromagnetic wave shielding. Substrates with a polymer layer formed from the present composition are particularly useful as electronic substrate materials such as flexible printed wiring boards and rigid printed wiring boards, protective films and heat dissipating substrates, particularly heat dissipating substrates for automobiles. [Example]

[0046] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. 1. Preparation of each ingredient [F Polymer] F particle 1: Contains 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units, in that order, and has a carbonyl group-containing group with a main chain carbon number of 1×10 6 Tetrafluoroethylene polymer (F polymer 1, melting point: 300°C) particles (D50: 2.0 μm, specific surface area: 7 m) with 1000 particles per particle 2 / g) F particle 2: F polymer 1 particle (D50: less than 1.0 μm, specific surface area: 7 m 2 / g) F particle 3: A polymer containing 97.5 mol% TFE units and 2.5 mol% PPVE units, in that order, and having a carbonyl group-containing group number of 1×10 main chain carbon atoms. 6 Particles (D50: 2.5 μm, specific surface area: 10 m) made of tetrafluoroethylene polymer (melting temperature: 300°C) with less than 50 particles per particle 2 / g) [Dispersant polymer] Dispersant polymer 1: Mw 40000 Dispersant polymer 2: Mw 20000 Dispersant polymer 3: Mw 100,000 The above dispersant polymers 1 to 3 are all non-dissociative polymerizable (meth)acrylate polymers having a structural unit derived from a (meth)acrylate having a perfluoroalkenyl group and a structural unit derived from a (meth)acrylate having an oxyethylene group. The Mw of the dispersant polymers 1 to 3 was measured using GPC ("HLC-8120GPC" manufactured by Tosoh Corporation) under the following measurement conditions, and expressed as a standard polystyrene equivalent value. column: Sample column: TSK guard column SuperHZ-H (1 column) + TSKgel SuperHZM-H (2 columns) Reference column: TSKgel SuperH-RC (1 column) Eluent: tetrahydrofuran (THF) Flow rate: 0.6ml / min Measurement temperature: 40℃ Sample concentration: 0.2% by mass (THF solution) Sample injection volume: 10 μl Detector: Differential refractometer (RI) [Liquid dispersion medium] NMP: N-methylpyrrolidone

[0047] 2. Example of production of liquid composition [Example 1] F particles 1, dispersant polymer 1, and NMP were placed in a pot, and zirconia balls were then placed in. The pot was then rolled at 150 rpm for 1 hour to obtain a liquid composition 1 containing F particles 1 (40 parts by mass), dispersant polymer 1 (4 parts by mass), and NMP (56 parts by mass). [Example 2] Liquid composition 2 containing F particles 2 (40 parts by mass), dispersant polymer 1 (4 parts by mass), and NMP (56 parts by mass) was obtained in the same manner as in Example 1, except that F particles 2 were used instead of F particles 1. [Example 3] Liquid composition 3 containing F particles 3 (40 parts by mass), dispersant polymer 1 (4 parts by mass), and NMP (56 parts by mass) was obtained in the same manner as in Example 1, except that F particles 3 were used instead of F particles 1. [Example 4] Liquid composition 4 containing F particles 1 (40 parts by mass), dispersant polymer 2 (4 parts by mass), and NMP (56 parts by mass) was obtained in the same manner as in Example 1, except that dispersant polymer 2 was used instead of dispersant polymer 1. [Example 5] Liquid composition 5 containing F particles 1 (40 parts by mass), dispersant polymer 3 (4 parts by mass), and NMP (56 parts by mass) was obtained in the same manner as in Example 1, except that dispersant polymer 3 was used instead of dispersant polymer 1.

[0048] 3. Example of manufacturing substrate with polymer layer and evaluation of polymer layer Substrates with polymer layers were produced using each of Liquid Compositions 1 to 5, and the formed polymer layers were evaluated. Specifically, each liquid composition was applied to one side of a polyimide film (substrate 1: 25 μm thick) using a roll-to-roll process using a small-diameter gravure reverse method to form a coating layer. The polyimide film with this coating layer was heated by passing it through a ventilated drying oven at 150°C for 5 minutes, and then passed through a far-infrared oven at 350°C for 5 minutes to melt and sinter the F particles, resulting in polymer-layered substrates 1 to 5, each of which had a polymer layer (50 μm thick) containing the molten and sintered F particles on one side of substrate 1. The presence or absence of cracks was observed at any 10 points on the surface of the polymer layer of each of the polymer layer-attached substrates 1 to 5 using an optical microscope (30x magnification), and evaluated according to the following criteria. <Crack evaluation> ◯: No cracks observed in the polymer layer △: Trace cracks are observed on the surface of the polymer layer ×: Deep cracks reaching deep into the polymer layer are observed Furthermore, the cross section of each polymer layer of the polymer layer-attached substrates 1 to 5 was observed with a transmission electron microscope (SEM), and the voids in the polymer layer were evaluated according to the following criteria. <Evaluation of voids> ○: Dense layer with no voids observed △: Partial voids observed ×: Pores are observed to an extent that affects the surface properties The results are shown in Table 1.

[0049] [Table 1]

[0050] Furthermore, electrolytic copper foil (Fukuda Metal Foil & Powder Co., Ltd., "CF-T49A-DS-HD2", thickness: 12 μm) was placed on the surface of the polymer layer of each of the polymer layer-attached substrates 1 to 5, and pressed under vacuum at 340°C for 20 minutes to obtain copper clad laminates 1 to 5. The interlayer adhesion between the copper foil and the polymer layer of the obtained copper clad laminate 1 was significantly higher than that of each of the copper clad laminates 2 to 5. [Industrial Applicability]

[0051] The liquid composition of the present invention can form a thick polymer layer that is free of cracks and voids. A polymer-layered substrate (laminate) having the polymer layer exhibits the physical properties of the F polymer to a high degree, and the polymer layer also has excellent interlayer adhesion with the substrate and metal foil, making it effective for applications such as printed wiring boards.

Claims

1. A liquid composition comprising particles of a tetrafluoroethylene-based polymer, a dispersant polymer, and a liquid dispersion medium, wherein the dispersant polymer is a non-dissociative polymerizable (meth)acrylate-based polymer having a weight average molecular weight of 30,000 to 90,000 and having at least one structural unit derived from a (meth)acrylate having a group selected from a perfluoroalkyl group, a perfluoroalkenyl group, a siloxane group, or an alkyl group, and a structural unit derived from a (meth)acrylate having an oxyalkylene group.

2. The liquid composition according to claim 1 , wherein the tetrafluoroethylene-based polymer comprises a heat-fusible tetrafluoroethylene-based polymer having an oxygen-containing polar group.

3. The liquid composition according to claim 1 , wherein the content of the tetrafluoroethylene-based polymer particles is 30% by mass or more.

4. The liquid composition according to claim 1, wherein the average particle size (D50) of the particles of the tetrafluoroethylene-based polymer is 1 μm or more and less than 10 μm.

5. The specific surface area of ​​the tetrafluoroethylene-based polymer particles is 25 m ２ The liquid composition according to claim 1, wherein the viscosity is 1 / g or less.

6. The liquid composition according to claim 1, wherein the perfluoroalkyl group and the perfluoroalkenyl group each independently have 6 to 12 carbon atoms.

7. The liquid composition according to claim 1 , wherein the alkyl group has 12 or more and 40 or less carbon atoms.

8. The siloxane group is a dimethylpolysiloxane unit (-(CH ３ ) ２ SiO ２／２ The liquid composition according to claim 1, wherein the aryl group is a group having aryl groups.

9. The liquid composition according to claim 1 , wherein the oxyalkylene group is a group having an oxyethylene unit.

10. The liquid composition according to claim 1 , wherein the liquid dispersion medium is a non-aqueous polar solvent.

11. 2. The liquid composition according to claim 1, wherein the liquid dispersion medium is at least one non-aqueous polar solvent selected from the group consisting of amides, ketones, and esters.

12. The liquid composition according to claim 1, wherein the non-dissociatively polymerizable (meth)acrylate polymer does not have any structural units derived from a thermally decomposable (meth)acrylate, or structural units having an acetal, hemiacetal, ketal, or hemiketal.

13. The liquid composition according to claim 1, having a viscosity of 1000 mPa or less.

14. A method for producing a substrate with a polymer layer, comprising: applying the liquid composition according to any one of claims 1 to 13 to a surface of a substrate to form a coating layer comprising the liquid composition on the surface of the substrate; and heating the substrate having the coating layer thereon to form a polymer layer containing the tetrafluoroethylene-based polymer and having a thickness of 20 µm or more on the surface of the substrate.

15. A substrate with a polymer layer, which has a polymer layer having a thickness of 20 μm or more and which contains the tetrafluoroethylene-based polymer and is formed from the liquid composition according to any one of claims 1 to 13.

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