TWI857104B - Method for manufacturing laminate and laminate - Google Patents

Abstract

The present invention provides a laminate having a polymer layer with excellent adhesion to a substrate layer and excellent electrical and mechanical properties, and a method for manufacturing the laminate. The method for manufacturing the laminate of the present invention is a method for manufacturing a laminate having a substrate layer and a polymer layer, wherein the polymer layer is formed on at least one surface of the substrate layer and comprises a thermoplastic polymer containing a unit based on tetrafluoroethylene and a unit based on perfluoro(alkyl vinyl ether). The manufacturing method comprises applying a liquid composition containing the powder of the thermoplastic polymer on the surface of the substrate layer and drying it to form a dry coating, heating the dry coating at a temperature above the melting temperature of the thermoplastic polymer for more than 15 seconds per 1 μm thickness of the polymer layer to form a molten coating, cooling the molten coating to a temperature below the glass transition point of the thermoplastic polymer within 120 seconds to obtain the laminate.

Description

Method for manufacturing laminate and laminate

The present invention relates to a method for manufacturing a laminate and the laminate.

Thermoplastic fluoropolymers such as polymers containing units based on tetrafluoroethylene and units based on ethylene, hexafluoropropylene or perfluoro(alkyl vinyl ether) have excellent physical properties such as chemical resistance, water and oil repellency, heat resistance, and electrical properties, and have hot melt processability, and are therefore used for various industrial purposes. If a liquid composition containing powders of these fluoropolymers is made into a coating agent and a polymer layer is formed on the surface of a substrate, it is easy to obtain a substrate with the physical properties of the fluoropolymer imparted to the surface (see Patent Document 1). Prior Art Documents Patent Documents

Patent document 1: International Publication No. 2018/016644

[The problem the invention is trying to solve]

The inventors of the present invention have conducted intensive research on the physical properties of a polymer layer formed from the above-mentioned liquid composition and containing a thermoplastic fluoropolymer. The inventors of the present invention have found that if a powder of a thermoplastic fluoropolymer containing units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether) is selected at this time, the physical properties of the polymer layer formed from the liquid composition containing it are easily affected by the formation conditions. It has also been found that if the heating conditions and cooling conditions in the above-mentioned formation conditions are adjusted, a polymer layer with higher surface smoothness is formed, and the adhesion with the substrate is improved. It has further been found that in a substrate having the above-mentioned polymer layer, the physical properties of the fluoropolymer constituting it (especially electrical properties such as dielectric loss tangent) are significantly manifested.

The purpose of the present invention is to provide a laminate having a polymer layer with excellent adhesion to a substrate layer, and a method for manufacturing the laminate. [Technical means for solving the problem]

The present invention has the following aspects. <1> A method for manufacturing a laminate, the laminate comprising a substrate layer and a polymer layer, the polymer layer being formed on at least one surface of the substrate layer and comprising a thermoplastic polymer comprising a tetrafluoroethylene-based unit and a perfluoro(alkyl vinyl ether)-based unit, the method for manufacturing the laminate comprising applying a liquid composition comprising a powder of the thermoplastic polymer on the surface of the substrate layer and drying the composition to form a dry coating, heating the dry coating at a temperature above the melting temperature of the thermoplastic polymer for a period of more than 15 seconds per 1 μm thickness of the polymer layer to form a molten coating, cooling the molten coating to a temperature below the glass transition point of the thermoplastic polymer within 120 seconds to obtain the laminate. <2> A manufacturing method as in <1>, wherein the thickness of the polymer layer is less than the thickness of the substrate layer. <3> A manufacturing method as in <1> or <2>, wherein the thickness of the polymer layer is 0.1 to 20 μm. <4> A manufacturing method as in any one of <1> to <3>, wherein the difference between the temperature when heating the dry coating and the temperature when cooling the molten coating is 75°C or more per 1 μm thickness of the polymer layer. <5> A manufacturing method as in any one of <1> to <4>, wherein the polymer layer comprises spherulites of the thermoplastic polymer, and the radius of the spherulites is 5 μm or less. <6> A manufacturing method as in any one of <1> to <5>, wherein the crystallinity of the polymer layer is 50% or more. <7> A manufacturing method as described in any one of <1> to <6>, wherein the thermoplastic polymer has a melting temperature of 260 to 320°C and a glass transition point of 75 to 125°C. <8> A manufacturing method as described in any one of <1> to <7>, wherein the thermoplastic polymer is: a thermoplastic polymer containing units based on tetrafluoroethylene, units based on perfluoro(propyl vinyl ether) and units based on monomers having polar functional groups; a thermoplastic polymer containing 2 to 4 mol% of units based on tetrafluoroethylene and units based on perfluoro(propyl vinyl ether); or a thermoplastic polymer containing units based on tetrafluoroethylene and units based on perfluoro(methyl vinyl ether). <9> A manufacturing method as described in any one of <1> to <8>, wherein the liquid composition contains an inorganic filler. <10> A manufacturing method as described in any one of <1> to <9>, wherein the substrate layer is a metal foil or a heat-resistant resin film. <11> A laminate having a substrate layer and a polymer layer, wherein the polymer layer is formed on at least one surface of the substrate layer and comprises a thermoplastic polymer containing units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), and the polymer layer comprises spherulites of the thermoplastic polymer, wherein the radius of the spherulites is 5 μm or less. <12> A laminate as described in <11>, wherein the crystallinity of the polymer layer is 50% or more. <13> A laminate as described in <11> or <12>, wherein the thermoplastic polymer has a melting temperature of 260 to 320°C and a glass transition point of 75 to 125°C. <14> A laminate as described in any one of <11> to <13>, wherein the substrate layer is a heat-resistant resin film, the polymer layer is formed on both sides of the substrate layer, and the absolute value of the linear expansion coefficient of the laminate is 50 ppm/°C or less. <15> A laminate as described in any one of <11> to <14>, which is used as a printed circuit board material. [Effect of the invention]

According to the present invention, a laminate useful as a printed circuit board material is obtained, wherein the substrate layer and the polymer layer have high adhesion, and have excellent electrical properties (especially low dielectric loss tangent) and mechanical properties (especially peel strength and low linear expansion).

The following terms have the following meanings. "Thermoplastic polymer" means a polymer that exhibits melt fluidity, and refers to a polymer that has a melt flow rate of 0.1 to 1000 g/10 minutes at a temperature 20°C higher than the melting temperature of the polymer under a load of 49 N. Furthermore, "melt flow rate (MFR)" means the melt mass flow rate of a polymer as specified in JIS K 7210:1999 (ISO 1133:1997). "Melting temperature (melting point) of a polymer" is the temperature corresponding to the maximum value of the melting peak of a polymer measured by differential scanning calorimetry (DSC). "Glass transition point of a polymer" is a value obtained by analyzing and measuring a polymer by dynamic viscoelasticity measurement (DMA). "Average particle size of powder (D50)" is the volume-based cumulative 50% particle size of powder obtained by laser diffraction and scattering method. That is, the particle size distribution of powder is measured by laser diffraction and scattering method, and the total volume of the particle cluster of powder is set as 100% to obtain the cumulative curve. The average particle size of powder (D50) is the particle size at the point where the cumulative volume is 50% on the cumulative curve. "D100 of powder" is the volume-based cumulative 100% particle size of powder measured in the same way. The D50 and D100 of powder are obtained by dispersing the powder in water and using a laser diffraction and scattering particle size distribution measuring device (LA-920 measuring device manufactured by Horiba, Ltd.). "Layer crystallinity" is obtained by performing X-ray diffraction on the isolated layer. That is, in the obtained X-ray diffraction pattern, a straight line connecting the diffraction intensity at a diffraction angle of 10° and the diffraction intensity at a diffraction angle of 2θ of 25° is used as a reference line, and the area enclosed by the reference line and the diffraction intensity curve is separated into two symmetrical peaks by contour fitting, and the one with a larger diffraction angle 2θ is taken as the crystallinity peak, and the ratio of the above crystallinity peak in the above area is obtained. "Ten-point average roughness of the surface of the substrate layer (Rzjis)" is the value specified in Annex JA of JIS B 0601:2013. "Heat-resistant resin" means a polymer compound with a melting point of 280°C or above, or a polymer compound with a maximum continuous use temperature of 121°C or above as specified in JIS C 4003:2010 (IEC 60085:2007). "Unit" in a polymer can be an atomic group directly formed from a monomer by polymerization reaction, or an atomic group formed by treating a polymer obtained by polymerization reaction by a specific method and converting a part of the structure. Units based on monomer A contained in a polymer are also simply referred to as "monomer A units". "Weight average molecular weight (Mw)" is the standard polystyrene conversion value of the polymer measured by gel permeation chromatography (GPC). "(Meth) acrylic polymer" is a general term for polymers of methacrylate and polymers of acrylate. "(Meth)acrylate" is a general term for acrylate and methacrylate.

The manufacturing method of the present invention (this method) is to apply a liquid composition on at least one surface of a substrate layer and dry it to form a dry coating, heat the dry coating to form a molten coating, and cool the molten coating. The liquid composition contains a powder of a thermoplastic polymer (hereinafter also referred to as "PFA-based polymer"), and the thermoplastic polymer contains a unit based on tetrafluoroethylene (TFE) (TFE unit) and a unit based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE unit). By this method, a laminate having a substrate layer and a polymer layer formed on at least one surface of the substrate layer and containing a PFA-based polymer is manufactured. The heating of the dry coating in this method is performed for a time of more than 15 seconds per 1 μm thickness of the polymer layer and at a temperature above the melting temperature of the PFA-based polymer. In this method, the cooling of the molten coating is performed within 120 seconds to a temperature below the glass transition point of the PFA-based polymer.

The inventors of the present invention have discovered that if the heating conditions in the formation of a molten coating (a coating comprising a PFA-based polymer in a molten state) and the cooling conditions in the formation of a polymer layer (a coating comprising a PFA-based polymer formed by cooling the molten coating) are respectively set to the above conditions, the adhesion between the polymer layer and the substrate layer in the laminate is excellent, and the electrical properties (especially low dielectric loss tangent) and mechanical properties (especially peel strength and low linear expansion) of the polymer layer are remarkably excellent.

The reason is not necessarily clear, and it is considered as follows. It is believed that if the dry coating is heated under the above conditions, the powder of the PFA-based polymer is fully melted as a whole, forming a molten coating in which the PFA-based polymer is highly fluid. It is believed that if the molten coating in the above state is cooled under the above conditions, at least part of the PFA-based polymer, which is a crystalline polymer, is densely crystallized (solidified), and its spherulites become sufficiently small. In other words, it is also believed that the polymer layer contains microscopic spherulites of the PFA-based polymer, and the size of the microscopic steps (concavities and convexities) on its surface becomes sufficiently small. As a result, it is believed that the adhesion between the base material layer and the polymer layer in the laminate is improved, and its characteristics are significantly improved.

Specifically, the inventors of the present invention have found that the peel strength is significantly improved in a laminate whose substrate layer is a metal foil (metal foil with a polymer layer attached) or a printed circuit board obtained therefrom. The reason for this is believed to be that the adhesion between the polymer layer and the substrate layer is improved due to the above reasons, and the amount of air or voids present therein becomes sufficiently small. In addition, the inventors of the present invention have found that the dielectric loss tangent (Df) is significantly reduced in the polymer layer of the laminate or printed circuit board. The reason for this is believed to be that the PFA-based polymer is densely crystallized and the characteristics of the PFA-based polymer are highly expressed. The dielectric loss tangent of the polymer layer in the laminate at a frequency of 10 GHz is preferably 0.0020 or less, more preferably 0.0015 or less. The dielectric loss tangent is preferably 0.0001 or more. The transmission loss of the printed circuit board manufactured by the laminate is sufficiently reduced.

Furthermore, the inventors have found that the linear expansion of a laminate in which the substrate layer is a heat-resistant resin film and polymer layers are formed on both sides of the substrate layer is significantly reduced, and warping is not easy to occur. The reason is believed to be that the adhesion between the polymer layer and the substrate layer is improved due to the above reasons. The linear expansion coefficient (absolute value) of the polymer layer in the above laminate is preferably less than 50 ppm/℃, and more preferably 25 ppm/℃. The above linear expansion coefficient (absolute value) is preferably greater than 1 ppm/℃.

The polymer layer of the present invention is preferably a spherulite containing a PFA-based polymer. The radius of the spherulite is preferably less than 5 μm, more preferably less than 3 μm, and further preferably less than 1 μm. The radius is preferably greater than 0.01 μm, more preferably greater than 0.1 μm. The PFA-based polymer of the present invention contains a TFE unit and a PAVE unit. Furthermore, an etheric oxygen atom may be inserted between carbon atoms of the perfluoroalkyl group of the side chain of the PAVE unit.

The crystallinity of the polymer layer of the present invention is preferably the crystallinity of the PFA-based polymer in the polymer layer. The crystallinity of the polymer layer is preferably 50% or more, more preferably 60% or more, further preferably 65% or more, and particularly preferably 70% or more. The crystallinity of the polymer layer is preferably 99% or less. According to this method, the molten PFA-based polymer is rapidly cooled to a specific temperature to form a polymer layer, so it is easy to form a polymer layer with the above crystallinity. As a result, it is easy to form a polymer layer with excellent adhesion or electrical properties to the above-mentioned substrate layer, a low linear expansion coefficient, and excellent thermal conductivity.

The fluorine content of the PFA-based polymer is preferably 70-76% by mass, more preferably 72-76% by mass. The PFA-based polymer preferably contains 90-99 mol% of TFE units relative to all units constituting the polymer. The PFA-based polymer preferably contains 1-10 mol% of PAVE units relative to all units constituting the polymer. Examples of PAVE include perfluoro(methyl vinyl ether) ( _CF2 = _CFOCF3 : PMVE), perfluoro(ethyl vinyl ether) (CF2=CFOCF2CF3), perfluoro( _propyl vinyl ether _{) ( CF2} = _CFOCF2CF2CF3 : _PPVE ), _{CF2 = CFOCF2CF2CF2CF3 ,} and perfluoro(propoxypropyl vinyl ether) ( _CF2 = _{CFOCF2CF ( CF3 ) OCF2CF2CF3} : _PPOVE ) _.

PFA-based polymers may be polymers containing only TFE units and PAVE units, or may be polymers containing other units. PFA-based polymers may be polymers having polar functional groups. Examples of polymers having polar functional groups include: PFA-based polymers having polar functional groups at the terminal groups of the main chains of the polymers; PFA-based polymers into which polar functional groups are introduced by plasma treatment, ionizing radiation treatment, or corona treatment; PFA-based polymers containing TFE units, PAVE units, and units based on monomers having polar functional groups (hereinafter also referred to as "polar monomers") (hereinafter also referred to as "polar units").

The polar functional group is preferably a hydroxyl group, a carbonyl group, an acetal group or a phosphonic acid group (-OP(O)OH ₂ ), and is more preferably a carbonyl group from the viewpoint of further improving the adhesion to the substrate layer. The hydroxyl group is preferably a group containing an alcoholic hydroxyl group, and is more preferably -CF ₂ CH ₂ OH, -C(CF ₃ ) ₂ OH or a 1,2-diol group (-CH(OH)CH ₂ OH). The carbonyl-containing group is a group containing a carbonyl group (＞C(O)), preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH ₂ ), an anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.) or a carbonate group (-OC(O)O-). Specific examples of polar monomers include itaconic anhydride, cisconic anhydride, 5-northene-2,3-dicarboxylic anhydride (also known as bicycloheptene dicarboxylic anhydride; hereinafter also referred to as "NAH") or maleic anhydride.

The PFA-based polymer is preferably: (i) a polymer containing TFE units, PAVE units and polar units; (ii) a polymer containing TFE units and 2-4 mol% of PPVE units; or (iii) a polymer containing TFE units and PMVE units. When the polymer of the above (i) is crystallized, the polar functional groups interact with each other, thereby easily promoting the formation of a layered structure, generating micro-spherulites, and easily further improving the adhesion with the substrate layer. Furthermore, the adhesion between the substrate layer and the polymer layer is easily further improved by the polar functional groups. Among all the units constituting the polymer of the above (i), the ratio of TFE units, the ratio of PAVE units, and the ratio of polar units are preferably 90-99 mol%, 0.5-9.97 mol%, and 0.01-3 mol%, respectively.

The PAVE unit of the polymer of (ii) above is a PPVE unit, and among all the units constituting the polymer, a moderate amount (2 to 4 mol%) of the PPVE unit is contained, so that during crystallization, the formation of a layered structure is easily promoted to generate micro-spherulites, and the adhesion with the substrate layer is easily further improved. The polymer preferably contains a TFE unit and a PPVE unit, and contains 96 to 98 mol% of the TFE unit and 2 to 4 mol% of the PPVE unit.

The PAVE unit of the polymer of (iii) above is a PMVE unit with a short side chain, which can easily promote the formation of a layered structure during crystallization, generate microspherulites, and easily further improve the adhesion with the substrate layer. The polymer preferably contains 10-20 mol% of PMVE units. The polymer preferably contains TFE units and PMVE units, and contains 80-90 mol% of TFE units and 10-20 mol% of PMVE units.

The PFA polymers in the present invention may be used alone or in combination of two or more. As the latter aspect, there may be exemplified an aspect in which a PFA polymer is used together with the polymer of (i) above, the polymer of (iii) above, or a thermoplastic polymer containing TFE units and PPOVE units. The former PFA polymer is a PFA polymer different from the latter polymer, and preferably contains TFE units and PPVE units, and contains more than 98 mol% and less than 100% TFE units, and more than 0 mol% and less than 2 mol% PPVE units. In the above aspect, the latter polymer functions as a crystal nucleus, and the crystallization of the former PFA polymer is easily promoted with the crystal nucleus as the center, generating microspherulites, and easily improving the adhesion with the substrate layer. The mass ratio of the former PFA-based polymer to the latter polymer is preferably 2 to 50, more preferably 5 to 35. In this case, it is easier to adjust the radius of the generated spherulites.

The melt viscosity of the PFA polymer at 380°C is preferably 1×10 ² to 1×10 ⁶ Pa·s, more preferably 1×10 ³ to 1×10 ⁶ Pa·s. The melting temperature of the PFA polymer is preferably 260 to 320°C, more preferably 280 to 320°C. The glass transition point of the PFA polymer is preferably 75 to 125°C, more preferably 80 to 100°C. If the above PFA polymer is used, a dense polymer layer with excellent adhesion can be easily formed.

The D50 of the powder in this method is preferably less than the thickness of the polymer layer. The powder is preferably 0.05 to 6 μm, more preferably 0.1 to 3 μm. In addition, its D100 is preferably 10 μm or less, more preferably 5 μm or less. Under this range of D50 and D100, the powder has good fluidity and dispersibility, and it is easy to form a dense and excellent polymer layer. The powder may contain components other than PFA polymers, and is preferably composed of PFA polymers. The content of PFA polymers in the powder is preferably 80% by mass or more, and more preferably 100% by mass. As components other than PFA polymers, there can be listed: aromatic polyesters, polyamide imides, thermoplastic polyimides, polyphenylene ethers, and polyphenylene oxides.

The liquid composition in this method preferably contains a liquid medium. The liquid medium is a dispersion medium for the powder and is a liquid compound that is inert at 25°C. The liquid medium is preferably a volatile compound having a boiling point lower than the components other than the liquid medium contained in the liquid composition. The liquid medium may be used alone or two or more may be mixed. The liquid medium is preferably polar and non-aqueous. The boiling point of the liquid medium is preferably 80 to 275°C, more preferably 125 to 250°C. In this case, when forming a dry film, the powder flows effectively as the liquid medium evaporates, and the powder is easily and densely filled.

Specific examples of liquid media include: water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, N,N-dimethylformamide, N,N-dimethylacetamide, methyl ethyl ketone, N-methyl-2-pyrrolidone, γ-butyrolactone, cyclohexanone, cyclopentanone, dimethyl sulfoxide, diethyl ether, dioxane, ethyl lactate, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isopropyl ketone, cyclopentanone, cyclohexanone, ethylene glycol monoisopropyl ether, and solvents (methyl solvent, ethyl solvent, etc.). From the viewpoint of adjusting the liquid properties (viscosity, thixotropic ratio, etc.) of the liquid composition, the liquid medium is preferably an organic liquid medium (organic compound), more preferably a ketone or an amide, and further preferably methyl ethyl ketone, cyclohexanone, or N-methyl-2-pyrrolidone.

The liquid composition in the present method preferably further includes a polymer binder. Furthermore, the polymer constituting the agents is a polymer different from the PFA-based polymer, preferably butylene diimide resin, urethane resin, polyimide, polyamide, polyamide imide, polyphenylene ether, polyphenylene oxide, liquid crystal polyester and (meth) acrylic polymer, more preferably butylene diimide resin, polyimide and polyamide. When the binder is butylene diimide resin, polyimide and polyamide, the polymer layer is easy to be flexible and has excellent adhesion. As binders, preferred are butylene imide resins, polyimide and polyamide, all of which are aromatic. Polyimide is preferably thermoplastic.

If the liquid composition contains a polymer binder, the powder falling in the coating is suppressed, and the surface smoothness of the polymer layer is further improved. If the liquid composition contains a polymer dispersant, the liquid properties and dispersion stability of the liquid composition are further improved, and the coating is formed more densely.

Specific examples of polymer binders include (meth)acrylic polymers such as the "ADVANCELL" series (manufactured by Sekisui Chemical Co., Ltd.), the "ARON" series (manufactured by Toagosei Co., Ltd.), the "Oricox" series (manufactured by Kyoeisha Chemical Co., Ltd.), the "PHORET" series (manufactured by Soken Chemical Co., Ltd.), and the "Dicfine" series (manufactured by DIC Corporation); polyamide imides such as the "HPC" series (manufactured by Hitachi Chemical Co., Ltd.); "Neopulim" series (manufactured by Mitsubishi Gas Chemical Co., Ltd.), "SPIXAREA" series (manufactured by Somar Co., Ltd.), "Q-PILON" series (manufactured by PI Technical Laboratory), "WINGO" series (manufactured by WINGO TECHNOLOGY Co., Ltd.), and "TOHMIDE" series (manufactured by T&K Chemical Co., Ltd.). TOKA Co., Ltd.), "KPI-MX" series (manufactured by Kawamura Industrial Co., Ltd.), "UPIA-AT" series (manufactured by Ube Industries, Ltd.), and other polyimides.

The liquid composition in the present method preferably further comprises a polymer dispersant. The polymer dispersant preferably comprises a polymer having a hydrophilic part and a hydrophobic part. The above polymer preferably has these parts in the side chain of the polymer. The hydrophilic part is preferably a molecular chain containing a non-ionic functional group, and more preferably a group containing an alcoholic hydroxyl group or a polyoxyalkylene group. The polyoxyalkylene group may contain one type of polyoxyalkylene group, or may contain two or more types of polyoxyalkylene groups. In the latter case, different types of polyoxyalkylene groups may be arranged randomly or in blocks. The polyoxyalkylene group is preferably a polyoxyethylene group or a polyoxypropylene group, and more preferably a polyoxyethylene group.

The hydrophobic part is preferably an alkyl group, an ethynyl group, a polysiloxane group, a perfluoroalkyl group or a perfluoroalkenyl group, and more preferably a perfluoroalkyl group or a perfluoroalkenyl group. The carbon number of the perfluoroalkyl group or the perfluoroalkenyl group is preferably 4 to 16. In addition, an etheric oxygen atom may be inserted between carbon atoms of the perfluoroalkyl group or the perfluoroalkenyl group.

The polymer is preferably non-ionic. The weight average molecular weight of the polymer is preferably 2000 to 80000. The fluorine content of the polymer is more preferably 20 to 50% by mass. The content of the oxyalkylene group of the polymer is more preferably 20 to 50% by mass. The hydroxyl value of the polymer is preferably 10 to 300 mgKOH/g.

As a suitable embodiment of the above polymer, there can be cited a polymer having a perfluoroalkyl group or a perfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group as the side chain. As a more suitable embodiment of the above polymer, there can be cited a copolymer of a (meth)acrylate having a perfluoroalkyl group or a perfluoroalkenyl group and a (meth)acrylate having a polyoxyalkylene group or an alcoholic hydroxyl group. As specific examples of polymer dispersants, there can be cited: "FTERGENT" series (manufactured by NEOS), "Surflon" series (manufactured by AGC Seimei Chemical Co., Ltd.), "MEGAFAC" series (manufactured by DIC Corporation), and "Unidyne" series (manufactured by Daikin Industries, Ltd.).

The liquid composition in this method may further include fluorine-containing polymers other than PFA-based polymers. As a suitable embodiment of the above-mentioned fluorine-containing polymer, a powder of polytetrafluoroethylene (PTFE) can be cited. In this case, the physical properties based on PTFE (electrical properties such as low dielectric loss tangent) are easily and significantly expressed in the polymer layer (molded product). PTFE is preferably PTFE (low molecular weight PTFE) having a number average molecular weight (Mn) of 200,000 or less calculated based on the following formula (1). Mn＝2.1×1010×ΔHc－5.16・・・(1) In formula (1), ΔHc represents the crystallization heat (cal/g) of PTFE measured by differential scanning calorimetry. The Mn of low molecular weight PTFE is preferably 10 or less, and more preferably 50,000 or less. The Mn of low molecular weight PTFE is preferably 10,000 or more.

It is believed that when the liquid composition in the present method contains these components, when the polymer layer is formed by melt coating, these components function as crystal nuclei, promote the crystallization of the PFA-based polymer around the crystal nuclei, and easily form micro spherulites of the PFA-based polymer. As a result, the adhesion between the substrate layer and the polymer layer in the laminate is likely to be further improved, and its electrical characteristics and mechanical properties are likely to be further improved.

The liquid composition in this method preferably further contains an inorganic filler. In the above case, the polymer layer is easy to have excellent electrical properties and low linear expansion. In addition, the dry coating, melt coating and polymer layer are easy to have excellent thermal conductivity. When forming the polymer layer, the above film and layer are easy to be quickly and evenly heated and cooled, so the polymer layer is easy to have excellent surface smoothness and uniformity.

The inorganic filler is preferably a nitride filler or an inorganic oxide filler, more preferably a boron nitride filler, a curium oxide filler (a filler of a curium oxide), a silicate filler (a silica filler, a wollastonite filler, a talc filler, or a metal oxide filler (aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, etc.), and more preferably a silica filler, a boron nitride filler, and a talc filler. Boron nitride, silica, and talc tend to interact more strongly with PFA-based polymers, and inorganic fillers containing them tend to further improve the dispersion stability of the liquid composition. In addition, in the polymer layer, the physical properties of boron nitride, silica, or talc tend to be significantly manifested.

The inorganic filler may be a sintered inorganic filler. In other words, the inorganic filler may be ceramic. The absolute value of the linear expansion coefficient of the inorganic filler is preferably 8 ppm/°C or less, and more preferably 5 ppm/°C or less. The absolute value of the linear expansion coefficient is preferably 1 ppm/°C or more. In the above case, it is easy to control the size of the polymer layer when forming the polymer layer, and the polymer layer is easy to have excellent low linear expansion.

The inorganic filler is preferably surface treated with a silane coupling agent on at least a portion of its surface. The silane coupling agent is preferably 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-butylpropyltrimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, 3-methacryloyloxypropyltriethoxysilane or 3-isocyanatopropyltriethoxysilane.

The average particle size of the inorganic filler is preferably 20 μm or less, more preferably 10 μm or less. The average particle size is preferably 0.1 μm or more, more preferably 1 μm or more. The shape of the inorganic filler can be any of granular, needle-shaped (fibrous), and plate-shaped, preferably plate-shaped. When the shape of the inorganic filler is plate-shaped, the inorganic filler is easy to align, and the thermal conductivity of the dry coating, melt coating, and polymer layer in the plane direction is easy to improve. As a result, when forming the polymer layer, the above-mentioned film and layer are easy to heat and cool quickly and evenly, and the polymer layer is easy to have excellent surface smoothness and uniformity. Specific shapes of the inorganic filler include: spherical, scale-like, layer-like, leaf-like, almond-like, columnar, cockscomb-like, isometric, leaf-like, mica-like, block-like, flat-plate-like, wedge-like, rose-like, net-like, and angular column-like. The inorganic filler may be hollow, and may include hollow fillers and non-hollow fillers.

Specific examples of inorganic fillers include: silica fillers (Admafine manufactured by Admatechs, E-SPHERES series manufactured by Pacific Cement, SiliNax series manufactured by Nippon Steel Mining, Ecco sphere series manufactured by Emerson & Cuming, SFP series manufactured by DENKA, etc.), zinc oxide surface-treated with esters such as propylene glycol dicaprate (FINEX series manufactured by Sakai Chemical Industry Co., Ltd., etc.), titanium oxide fillers coated with polyols and inorganic substances (Tipaque series manufactured by Ishihara Sangyo Co., Ltd., etc.), rutile titanium dioxide surface-treated with alkyl silane (JMT series manufactured by Teikoku Chemical Co., Ltd., etc.), talc fillers (NIPPON TALC's "SG" series, etc.), block talc filler (NIPPON TALC's "BST" series, etc.), magnesium oxide filler (UBE MATERIALS's "Magnesia" series, etc.), boron nitride filler (Akidenko's "UHP", "HGP" series, etc.).

Within the scope that does not impair the effect of the present invention, the liquid composition in this method may contain a thixotropic agent, a defoaming agent, a silane coupling agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a coloring agent, a conductive agent, a mold release agent, a surface treatment agent, a viscosity regulator, and a flame retardant. The viscosity of the liquid composition at 25°C is preferably less than 10000 mPa·s, and more preferably 10 to 1000 mPa·s. The thixotropic ratio of the liquid composition is preferably 1 to 2.5, and more preferably 1.2 to 2.

The ratio of the PFA-based polymer in the liquid composition is preferably 5 to 60% by mass, more preferably 15 to 50% by mass. Within this range, it is easy to form a polymer layer with excellent electrical properties and adhesion to the substrate layer. When the liquid composition contains a liquid medium, the ratio of the liquid medium in the liquid composition is preferably 40 to 95% by mass, more preferably 50 to 85% by mass. When the liquid composition contains a polymer binder, the ratio of the polymer binder in the liquid composition is preferably 0.01 to 1% by mass. When the liquid composition contains a polymer dispersant, the ratio of the dispersant in the liquid composition is preferably 1 to 15% by mass. In this case, it is easy to further improve the original physical properties of the PFA-based polymer in the polymer layer. When the liquid composition contains an inorganic filler, the ratio of the inorganic filler in the liquid composition is preferably 1 to 50% by mass, more preferably 5 to 30% by mass. In this case, a polymer layer having excellent electrical properties and low linear expansion properties can be easily formed.

In the present method, the liquid composition is applied to the surface of the substrate layer by any method that forms a stable liquid coating on the surface of the substrate layer, and examples thereof include: spraying method, roller coating method, rotary coating method, gravure coating method, micro-gravure coating method, gravure offset coating method, doctor coating method, contact coating method, rod coating method, die nozzle coating method, injection merrer rod method, slot die nozzle coating method, and notch wheel coating method.

The formation of the dry coating in this method is carried out by drying the liquid composition (liquid coating) on the surface of the substrate layer. As drying methods for the liquid coating, there can be listed: heating drying, drying by blowing air (gas), natural drying, etc. Among them, as a drying method, heating drying is preferred because it can stably maintain the shape of the liquid coating and dry the liquid coating in a short time. In addition, a part of the liquid medium that can be contained in the liquid composition may also remain in the dry coating. The heating temperature (temperature of the atmosphere) at this time can be set according to the boiling point of the liquid medium that can be contained in the liquid composition, etc., so as not to reach the melting temperature of the PFA-based polymer. It is preferably 90 to 250°C, and more preferably 100 to 200°C. In addition, the heating time is preferably 0.1 to 10 minutes, and more preferably 0.5 to 5 minutes. Furthermore, the heating in the heat drying can be implemented in one stage, or in two or more stages at different temperatures.

The formation of the melt coating in this method is carried out by heating the dry coating to melt the PFA polymer in the dry coating. The heating temperature (atmosphere temperature) at this time is higher than the melting temperature of the PFA polymer and can be set according to the type of the PFA polymer. It is preferably 300-400°C, more preferably 320-390°C, and further preferably 340-380°C. In addition, the heating at this time can be implemented in one stage or in two or more stages at different temperatures.

The dry coating is heated for more than 15 seconds per 1 μm thickness of the formed polymer layer. In this way, the powder of the PFA-based polymer is fully heated as a whole, and the PFA-based polymer is highly fluid in the molten coating. The heating time of the dry coating for each 1 μm thickness of the formed polymer layer is preferably more than 30 seconds, and more preferably more than 45 seconds. From the perspective of productivity of the laminate, the above heating time is preferably less than 100 seconds. For example, when forming a polymer layer with a thickness of 4 μm, the above heating time is more than 60 seconds, preferably more than 120 seconds, and more preferably more than 180 seconds.

As heating methods for forming dry coatings and melt coatings, there are: methods using a ventilation drying furnace, methods using a heat irradiation furnace such as infrared rays. The state of the atmosphere during heating at this time can be either normal pressure or reduced pressure. The atmosphere at this time can be any of an oxidizing gas (oxygen, etc.) atmosphere, a reducing gas (hydrogen, etc.) atmosphere, and an inert gas (helium, neon, argon, nitrogen, etc.) atmosphere. From the perspective of suppressing the deterioration and degradation of the polymer component contained in the liquid composition, an atmosphere containing 80 to 100% by volume of an inert gas is preferred. From the viewpoint of promoting the decomposition of the dispersant and other components contained in the liquid composition and reducing the dielectric loss tangent of the polymer layer, an atmosphere containing 1 to 20 volume % of oxygen is preferred.

The formation of the polymer layer in this method is carried out by cooling the molten film to solidify the PFA-based polymer in the molten film. The cooling at this time is carried out by rapidly cooling the molten film to a specific temperature below the glass transition point of the PFA-based polymer within 120 seconds. By this rapid cooling, the PFA-based polymer is densely crystallized and solidified, thereby promoting the formation of micro-spherulites. In addition, when the liquid composition contains an inorganic filler, by this rapid cooling, the inorganic filler in the molten film is easily oriented, and the polymer layer is easy to have excellent low linear expansion. The time for the cooling temperature to reach the above-mentioned specific temperature is preferably within 100 seconds, and more preferably within 60 seconds. Furthermore, from the perspective of improving the productivity of the laminate, the lower limit of the above-mentioned time is usually 10 seconds. The cooling rate of the melt coating is preferably 0.25°C/sec or more per 1 μm thickness of the formed polymer layer, more preferably 2.5°C/sec or more. The upper limit of the cooling rate is usually 30°C/sec.

The above cooling can be adjusted not only by adjusting the cooling temperature (temperature of the atmosphere), but also by selecting a substrate layer having a thermal conductivity sufficiently higher than that of the PFA-based polymer, or a polymer layer sufficiently thinner than the substrate layer. Specifically, the thermal conductivity of the substrate layer relative to the thermal conductivity of the PFA-based polymer is preferably 1000 or more, more preferably 1250 to 3000. The specific value of the thermal conductivity of the substrate layer is preferably 200 W/m・K or more, more preferably 250 to 600 W/m・K. As the above substrate layer, a metal substrate can be listed, and a metal foil can be listed preferably.

The above cooling temperature can be set according to the glass transition point of the PFA polymer, preferably 0 to 70°C, more preferably 10 to 40°C. In addition, the time for maintaining the above cooling temperature is preferably 1 to 30 minutes, more preferably 3 to 15 minutes. Furthermore, the difference between the heating temperature when forming the molten coating and the cooling temperature when forming the polymer layer is preferably 75°C or more per 1 μm thickness of the formed polymer layer, more preferably 100°C or more. In this case, the crystallization of the PFA polymer proceeds rapidly, which easily promotes the formation of microspherulites, and the physical properties of the polymer layer are easily further improved.

The thickness of the polymer layer is preferably less than the thickness of the substrate layer. The ratio of the thickness of the substrate layer to the thickness of the polymer layer is preferably 1.5 or more, more preferably 2 or more. The above ratio is preferably 100 or less, more preferably 10 or less. The thickness of the polymer layer is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm, and further preferably 1 to 5 μm. As suitable aspects of the thickness of the polymer layer and the thickness of the substrate layer in this method, the former is 1 to 5 μm and the latter is 6 to 25 μm.

The substrate layer in this method is preferably a metal foil or a heat-resistant resin film. The ten-point average roughness of the surface of the metal foil is preferably less than 0.5 μm, and more preferably less than 0.1 μm. The ten-point average roughness of the surface of the metal foil is preferably more than 0.01 μm. In this case, the polymer layer with higher surface smoothness and the metal foil are further highly bonded. Therefore, in the laminate (metal foil with polymer layer) or the printed circuit board processed therefrom, the dielectric loss tangent (Df) is more significantly reduced. Specifically, in the case where the substrate layer in this method is a metal foil, the dielectric loss tangent of the laminate at a frequency of 10 GHz is preferably less than 0.0020, and more preferably less than 0.0015. The dielectric loss tangent is preferably greater than 0.0001. The material of the metal foil includes: copper, copper alloy, stainless steel, nickel, nickel alloy (including 42 alloy), aluminum, aluminum alloy, titanium, titanium alloy, etc. The metal foil is preferably a rolled copper foil or an electrolytic copper foil.

The surface of the metal foil can be treated with an anti-rust treatment (forming an oxide film such as chromate). In addition, the surface of the metal foil can also be treated with a silane coupling agent. The treatment range at this time can be a part of the surface of the metal foil or the entire surface. The thickness of the metal foil is preferably 0.1 to 20 μm, and more preferably 0.5 to 10 μm.

In addition, a carrier metal foil including two or more layers of metal foil can also be used as the metal foil. As the carrier metal foil, there can be cited a carrier copper foil including a carrier copper foil (thickness: 10-35 μm) and an extremely thin copper foil (thickness: 2-5 μm) laminated on the carrier copper foil with an intermediate release layer. If the above-mentioned carrier copper foil is used, a fine pattern can be formed by the MSAP (Modified Semi-Additive) process. As the above-mentioned release layer, it is preferably a metal layer including nickel or chromium, or a multi-layer metal layer formed by laminating the metal layer. As a specific example of the carrier metal foil, the product name "FUTF-5DAF-2" manufactured by Futian Metal Foil Powder Industry Co., Ltd. can be cited.

The heat-resistant resin film is a film containing one or more heat-resistant resins, and may be a single-layer film or a multi-layer film. Glass fibers or carbon fibers may be embedded in the heat-resistant resin film. Examples of heat-resistant resins include polyimide, polyarylate, polysulfone, polyarylsulfone, aromatic polyamide, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamide imide, liquid crystalline polyester, and liquid crystalline polyesteramide, preferably polyimide. In the case where the substrate layer is a heat-resistant resin film, it is preferred to form polymer layers on both sides of the substrate layer. In this case, since the polymer layers with high surface smoothness are formed on both sides of the heat-resistant resin film, the linear expansion coefficient of the laminate is likely to be significantly reduced. In addition, the laminate is not prone to warping, so its workability during processing is excellent.

In this method, if the composition is applied (coated) on both sides of a substrate layer, a laminate having a substrate layer and polymer layers formed on both surfaces of the substrate layer is obtained. As specific examples of the above-mentioned laminate, a polyimide film and a multilayer film having polymer layers on both surfaces of the polyimide film can be cited. The above-mentioned laminate has excellent electrical properties, heat resistance such as reflow resistance, chemical resistance, surface smoothness and other physical properties, and is suitable as a printed circuit board material, etc. The absolute value of the linear expansion coefficient of the above-mentioned laminate is preferably 50 ppm/℃ or less, and more preferably 25 ppm/℃ or less. The absolute value of the linear expansion coefficient is preferably 1 ppm/℃ or less.

As the laminate of the present invention, there can be cited a laminate having a polymer layer formed on at least one surface of a substrate layer and comprising a PFA-based polymer, wherein the polymer layer comprises spherulites of the PFA-based polymer, and the radius of the spherulites is 5 μm or less. The laminate of the present invention can be manufactured by this method. The various structures of the laminate of the present invention, including their appropriate forms, are the same as the structures in this method.

In order to further improve the low linear expansion or adhesion of the polymer layer of the laminate of the present invention, the outermost surface can also be further surface treated. As the surface treatment method, it can be listed: annealing treatment, corona treatment, plasma treatment, ozone treatment, excimer treatment, silane coupling treatment. The conditions for annealing treatment are preferably set to 120-180°C, the pressure to 0.005-0.015 MPa, and the time to 30-120 minutes. As the gas used in the plasma treatment, it can be listed: oxygen, nitrogen, rare gas (argon, etc.), hydrogen, ammonia, vinyl acetate. These gases can be used alone or in combination to make a mixed gas.

Other substrates may be further laminated on the outermost surface of the polymer layer of the laminate of the present invention. As other substrates, heat-resistant resin films, prepregs as precursors of fiber-reinforced resin sheets, laminates having heat-resistant resin film layers, and laminates having prepreg layers may be cited. Furthermore, the prepreg is a sheet-like substrate in which a thermosetting resin or a thermoplastic resin is impregnated in a reinforcing fiber (glass fiber, carbon fiber, etc.) base material (tow, woven fabric, etc.). As heat-resistant resin films, the above-mentioned heat-resistant resin films may be cited.

As a lamination method, a method of hot pressing the laminate and other substrates can be cited. When the other substrate is a prepreg, the hot pressing conditions are preferably set to a temperature of 120 to 300°C, a pressure of the atmosphere of 20 kPa or less under reduced pressure (vacuum), and a pressurized pressure of 0.2 to 10 MPa. When the other substrate is a heat-resistant resin film, the hot pressing conditions are preferably set to a temperature of 310 to 400°C. The laminate of the present invention has a polymer layer with excellent electrical properties, and is therefore suitable as a printed substrate material. Specifically, the laminate of the present invention can be used as a flexible metal foil laminate or a rigid metal foil laminate for the manufacture of printed circuit boards, and can be particularly suitably used as a flexible metal foil laminate for the manufacture of flexible printed circuit boards.

A printed circuit board is obtained by etching a metal foil whose base layer is a laminate of metal foil (metal foil with a polymer layer) to form a transmission circuit. Specifically, a printed circuit board can be manufactured by a method of etching a metal foil to form a specific transmission circuit. A printed circuit board manufactured from a metal foil with a polymer layer has a transmission circuit and a polymer layer formed of metal foil in this order. Specific examples of the structure of the printed circuit board include transmission circuit/polymer layer/prepreg layer, transmission circuit/polymer layer/prepreg layer/polymer layer/transmission circuit, transmission circuit/polymer layer/polyimide layer, and transmission circuit/polymer layer/polyimide layer/polymer layer/transmission circuit. In the manufacture of the printed circuit board, an interlayer insulating film may be formed on the transmission circuit, a solder resist may be laminated on the transmission circuit, or a cover film may be laminated on the transmission circuit. As the material of the interlayer insulating film, the solder resist, and the cover film, the liquid composition may be used.

As a specific aspect of the printed circuit board, a multilayer printed circuit board formed by multi-layering the printed circuit board can be cited. As a suitable aspect of the multilayer printed circuit board, an aspect having one or more of the following structures can be cited: the outermost layer of the multilayer printed circuit board is a polymer layer, and a metal foil or a transmission circuit, a polymer layer and a prepreg layer or a polyimide layer are stacked in sequence. Furthermore, the number of the above structures is preferably plural (two or more). Moreover, a transmission circuit can be further arranged between the polymer layer and the prepreg layer or the polyimide layer. The multilayer printed circuit board of the above aspect has particularly excellent heat resistance and processability due to the outermost polymer layer. Specifically, even at 288°C, the interface between the polymer layer and the prepreg layer or the polyimide layer is not easily bulged, or the interface between the metal foil (transmission circuit) and the polymer layer is not easily peeled off. In particular, even when the metal foil forms the transmission circuit, the polymer layer and the metal foil (transmission circuit) are firmly bonded, so it is not easy to warp, and the heat-resistant processability is excellent.

As a suitable embodiment of a multi-layer printed circuit substrate, an embodiment having one or more of the following structures can also be cited: the outermost layer of the multi-layer printed circuit substrate is a prepreg layer, and a metal foil or a transmission circuit, a polymer layer, and a prepreg layer are stacked in sequence. Furthermore, the number of the above structures is preferably plural (two or more). In addition, a transmission circuit can be further arranged between the polymer layer and the prepreg layer. The multi-layer printed circuit substrate of the above embodiment has excellent heat resistance and processability even if the outermost layer has a prepreg layer. Specifically, even at 300°C, it is not easy to produce bulging at the interface between the polymer layer and the prepreg layer or peeling at the interface between the metal foil (transmission circuit) and the polymer layer. In particular, even when the metal foil forms a transmission circuit, the polymer layer and the metal foil (transmission circuit) are firmly bonded, so warping is not easy to occur, and heat-resistant processing is excellent. That is, according to the present invention, it is easy to obtain a printed circuit board with various structures, and even if the printed circuit board is not subjected to various surface treatments, each interface is firmly bonded, and interface bulging or interface peeling under heating, especially bulging or peeling of the outermost layer, is suppressed.

The above describes the manufacturing method of the laminate and the laminate of the present invention, but the present invention is not limited to the above-mentioned embodiment. For example, the laminate of the present invention can have any other structure by adding to the above-mentioned embodiment, and can also be replaced with any structure that produces the same effect. Furthermore, the manufacturing method of the laminate of the present invention can have any other steps by adding to the above-mentioned embodiment, and can also be replaced with any steps that produce the same effect. Embodiment

The present invention is specifically described below by way of examples, but the present invention is not limited thereto. 1. Preparation of each component [PFA-based polymer] Polymer 1: A polymer containing 98.0 mol% of TFE units, 0.1 mol% of NAH units, and 1.9 mol% of PPVE units, and having polar functional groups (melting temperature: 300°C, glass transition point: 95°C) Polymer 2: A polymer containing 97.5 mol% of TFE units and 2.5 mol% of PPVE units, and having no polar functional groups (melting temperature: 305℃, glass transition point: 85℃) Polymer 3: A polymer containing 98.7 mol% TFE units and 1.3 mol% PPVE units, and no polar functional groups (melting temperature: 305℃, glass transition point: 90℃) Polymer 4: A polymer containing 85.0 mol% TFE units and 15.0 mol% PMVE units, and no polar functional groups (melting temperature: 285℃, glass transition point: 85℃)

[Powder] Powder 1: Powder containing polymer 1 (D50: 1.7 μm) Powder 2: Powder containing polymer 2 (D50: 3.2 μm) Powder 3: Powder containing 80 parts by mass of polymer 3 and 20 parts by mass of polymer 4 (D50: 2.7 μm) Powder 4: Powder containing polymer 3 (D50: 2.4 μm) [Filler] Filler 1: Plate-shaped boron nitride filler (D50: 7.0 μm)

[Solvent] NMP: N-methyl-2-pyrrolidone [Dispersant] Dispersant 1: Non-ionic (meth)acrylate polymer having perfluoroolefin and polyoxyethylene groups and alcoholic hydroxyl groups in the side chains ("FTERGENT 710FL" manufactured by NEOS) [Metal foil] Copper foil 1: Low-roughening electrolytic copper foil (thickness: 12 μm, ten-point average roughness of the surface: 0.08 μm) [Heat-resistant resin film] Film 1: Aromatic polyimide film (thickness: 25 μm, "Kapton EN" manufactured by DuPont Toray)

1. Preparation of liquid composition (Liquid composition 1) After NMP (67 parts by mass) and dispersant 1 (3 parts by mass) were placed in a container to prepare a solution, powder 1 (30 parts by mass) was placed. Thereafter, a zirconia ball was added, and the container was rolled at 150 rpm for 1 hour to prepare liquid composition 1 in which powder 1 was dispersed. In addition, the viscosity of liquid composition 1 at 25°C was 25 mPa・s, and no obvious precipitate was produced even when left at 25°C, indicating excellent dispersibility. (Liquid compositions 2-4) Liquid composition 2 was prepared by replacing powder 1 in liquid composition 1 with powder 2, liquid composition 3 was prepared by replacing powder 1 in liquid composition 1 with powder 3, and liquid composition 4 was prepared by replacing powder 1 in liquid composition 1 with powder 4.

(Liquid composition 5) First, powder 3 (30 parts by mass), dispersant 1 (2 parts by mass), and NMP (45 parts by mass) were added to a container, and zirconia balls were added. Then, the container was rolled at 150 rpm for 1 hour to prepare a composition. Filler 1 (10 parts by mass), dispersant 1 (1 part by mass), and NMP (12 parts by mass) were added to another container, and zirconia balls were added. Then, the container was rolled at 150 rpm for 1 hour to prepare a composition. The combination of the two was added to another container, and zirconia balls were added. Then, the container was rolled at 150 rpm for 1 hour to prepare a liquid composition 5 in which powder 2 and filler 1 were dispersed. Furthermore, the viscosity of the liquid composition 5 at 25°C was 25 mPa·s. Even when left at 25°C, no obvious precipitate was generated, indicating excellent dispersibility.

2. Production of copper foil with polymer layer The liquid composition 1 is applied to the surface of the copper foil 1 by roller-to-roll method using a small-diameter reverse gravure method to form a liquid coating. Next, the copper foil is passed through a drying furnace and heated at 150°C for 300 seconds to form a dry coating. Thereafter, the dry coating is heated at 380°C for 600 seconds in a far-infrared oven under a nitrogen atmosphere to melt it. Next, the molten coating is cooled at 20°C to produce a copper foil 1 with a polymer layer (thickness: 4 μm) formed on the surface of the copper foil 1. The heating time of the dry coating is 150 seconds per 1 μm thickness of the polymer layer, and the molten coating is cooled to 95°C (glass transition point of polymer 1) within 25 seconds. The cooling rate is 2.9°C/sec per 1 μm thickness of the polymer layer.

Copper foils with polymer layer 2 to 5 were manufactured in the same manner as copper foil with polymer layer 1 except that liquid compositions 2 to 5 were used instead of liquid composition 1. In the manufacture of any copper foil with polymer layer, the heating time of the dry coating was 150 seconds per 1 μm thickness of the polymer layer, and the time for cooling the molten coating to the glass transition point of the PFA-based polymer was 25 to 60 seconds. (Copper foil with polymer layer 6 (comparative example)) Copper foil with polymer layer 6 was manufactured in the same manner as copper foil with polymer layer 4 except that the heating time of the dry coating was set to 40 seconds and the heating time of the dry coating was set to 10 seconds per 1 μm thickness of the polymer layer. (Copper foil with polymer layer 7 (comparative example)) Copper foil with polymer layer 7 was manufactured in the same manner as copper foil with polymer layer 4 except that the molten film was cooled in an atmosphere of 200°C and an atmosphere of 20°C, and the time for cooling the molten film to 90°C (glass transition point of polymer 3) was more than 120 seconds.

3. Measurement and evaluation of copper foil with polymer layer <Measurement of spherulite radius> In each copper foil with polymer layer, the copper foil was dissolved with an acid aqueous solution to obtain the polymer layer. The spherulite radius was measured by using a polymer phase structure analysis system using small-angle light scattering ("PP-1000" manufactured by Otsuka Chemical Co., Ltd.) to obtain the correlation between the scattering vector q (μm ^-1 ) and the scattering intensity (Is) on the copper foil side of the obtained polymer layer. If the scattering vector with the highest scattering intensity is set to qmax, it is expressed as qmax = (4πn/λ ₀ ) × sin(θmax/2) [here, λ ₀ is the wavelength of light in a vacuum, n is the refractive index of the medium, and θmax is the scattering angle at the peak position of the scattering intensity], and the spherulite radius R (μm) = 4.09/qmax is derived.

<Adhesion> The cross-section of each copper foil with a polymer layer was observed using a SEM (Scanning electron microscope), and the state of the interface between the copper foil and the polymer layer was evaluated based on the following criteria. A: The entire interface is tightly bonded. B: The entire interface is tightly bonded, but there are gaps. C: There are gaps on the entire interface.

<Peel strength> A rectangular specimen (length: 100 mm, width: 10 mm) was cut from each copper foil with a polymer layer. Then, the specimen was fixed at a position 50 mm away from one end in the longitudinal direction, and the copper foil and polymer layer were peeled off from one end in the longitudinal direction at a tensile speed of 50 mm/min at 90°. The maximum load at this time was measured as the peel strength (N/cm), and evaluated according to the following criteria. A: The peel strength is 12 N/cm or more. B: The peel strength is 8 N/cm or more and less than 12 N/cm. C: The peel strength is less than 8 N/cm.

<Dielectric loss tangent> A square specimen with a length of 100 mm and a width of 50 mm was cut from the polymer layer. The dielectric loss tangent of the polymer layer was measured by the cavity resonator perturbation method using a network analyzer as a measuring instrument and evaluated according to the following criteria. The measurement frequency was set to 10 GHz. A: The dielectric loss tangent was less than 0.0015. B: The dielectric loss tangent was between 0.0015 and 0.0030. C: The dielectric loss tangent exceeded 0.0030.

<Linear expansion coefficient> A square specimen with a width of 3 mm and a length of 10 mm was cut from the polymer layer and measured using a thermomechanical analyzer ("TMA/SS6100" manufactured by SII Nano Technology) when the temperature was raised from 0°C to 400°C at 10°C/min, cooled to 10°C at 40°C/min, and then raised from 10°C to 200°C at 10°C/min. The measurement load was set to 29.4 mN and the measurement atmosphere was set to air. A: The absolute value of the linear expansion coefficient is less than 30 ppm/°C. B: The absolute value of the linear expansion coefficient exceeds 30 ppm/°C and is less than 50 ppm/°C. C: The absolute value of the linear expansion coefficient exceeds 50 ppm/°C. The results are shown in Table 1 below.

[Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Liquid composition number 1 2 3 4 5 4 4 Powder Type 1 2 3 4 3 4 4 Type of filler - - - - 1 - - Spherulite radius [μm] 0.5 0.8 0.9 5 0.7 10 12 Adhesion A B B B A C C Peel strength A B B B A C C Dielectric loss tangent A A A B A C C Linear expansion coefficient A A B B A C C

Furthermore, the crystallinity of the polymer layer of the copper foils 1, 2 and 5 with polymer layers is above 60%, and the thermal conductivity of the copper foils 1, 2 and 5 with polymer layers is also superior to that of other copper foils with polymer layers.

4. Production of laminated film The liquid composition 1 is applied to the surface of the film 1 by roller-to-roller method by a small-diameter reverse gravure method to form a liquid coating, which is passed through a drying furnace and heated at 150°C for 180 seconds to form a dry coating. Furthermore, a dry coating is formed on the other surface of the film 1 in the same manner. Thereafter, the dry coating is heated at 380°C for 1200 seconds in a far-infrared oven to melt it, and then cooled to obtain a laminated film 1 with a polymer layer (thickness: 25 μm) formed on both sides of the film 1. The heating time of the dry coating is 48 seconds for every 1 μm thickness of the polymer layer, and the molten coating is cooled to 95°C (glass transition point of polymer 1) within 45 seconds.

The linear expansion coefficient of the obtained laminated film 1 was measured in the same manner as the linear expansion coefficient of the polymer layer. As a result, the absolute value of the linear expansion coefficient of the laminated film 1 was 22 ppm/℃. Industrial Availability

The laminate of the present invention can be suitably used as a printed circuit board material for transmitting high-frequency signals. In addition, according to the manufacturing method of the present invention, the laminate can be efficiently manufactured.

Claims (7)

A method for manufacturing a laminate, wherein the laminate comprises a substrate layer and a polymer layer, wherein the substrate layer is a metal foil or a heat-resistant resin film, and the polymer layer is formed on at least one surface of the substrate layer and comprises a thermoplastic polymer having a tetrafluoroethylene-based unit and a perfluoro(alkyl vinyl ether)-based unit and having a polar functional group, and the thickness of the polymer layer is 0.1-20 μm. The liquid composition of the thermoplastic polymer powder is applied to the surface of the substrate layer and dried to form a dry coating. The dry coating is heated at a temperature above the melting temperature of the thermoplastic polymer for more than 15 seconds per 1 μm thickness of the polymer layer to form a molten coating. The molten coating is cooled to a temperature below the glass transition point of the thermoplastic polymer within 120 seconds to obtain the laminate. The manufacturing method of claim 1, wherein the thickness of the polymer layer is less than the thickness of the substrate layer. The manufacturing method of claim 1 or 2, wherein the difference between the temperature when heating the dry coating and the temperature when cooling the molten coating is greater than 75°C per 1μm thickness of the polymer layer. The manufacturing method of claim 1 or 2, wherein the polymer layer comprises spherulites of the thermoplastic polymer, and the radius of the spherulites is less than 5 μm. As in the manufacturing method of claim 1 or 2, wherein the crystallinity of the above-mentioned polymer layer is above 50%. The manufacturing method of claim 1 or 2, wherein the thermoplastic polymer has a melting temperature of 260-320°C and a glass transition point of 75-125°C. The manufacturing method of claim 1 or 2, wherein the liquid composition contains an inorganic filler.