Laminate and method for forming laminate

Abstract

The present invention provides a laminate having excellent adhesiveness between a copper-containing base material and a perfluoropolymer film. The present invention also provides a method for forming said laminate having excellent adhesiveness. Provided is a laminate characterized by comprising a copper-containing base material and a perfluoropolymer-containing film, wherein the adhesive strength between the base material and the film is not less than 0.2 N / mm, and the film has a surface roughness of less than 15 μm.

Description

Laminate and method for forming laminate

[0001] FIELD The present disclosure relates to laminates and methods of forming laminates.

[0002] In general, perfluoropolymers, in particular, are widely used as coating materials for metal substrates, taking advantage of the excellent insulating properties, heat resistance, chemical resistance, flame retardancy, and the like that fluororesins possess.

[0003] For example, Patent Document 1 describes an insulated wire used for a motor coil, in which an insulating layer made of fluororesin is provided on a copper conductor by extrusion coating.

[0004] Also known is a bus bar in which an insulating layer is formed on a copper conductor by electrostatically applying a powder coating made of a thermosetting resin such as an epoxy resin (Patent Document 2, etc.).

[0005] JP 2009-245857 A JP 2020-35575 A

[0006] An object of the present disclosure is to provide a laminate having excellent adhesion between a copper-containing substrate and a perfluoropolymer coating, and a method for forming such a laminate having excellent adhesion.

[0007] The present disclosure provides a laminate comprising a substrate containing copper and a coating containing a perfluoropolymer, wherein the adhesive strength between the substrate and the coating is 0.2 N / mm or more, and the surface roughness of the coating is less than 15 μm.

[0008] The perfluoropolymer is preferably a copolymer containing tetrafluoroethylene (TFE) units and at least one selected from the group consisting of perfluoroalkyl vinyl ether (PAVE) units and hexafluoropropylene (HFP) units. The perfluoropolymer is preferably a TFE / HFP copolymer. The adhesive strength between the substrate and the coating is preferably 0.2 N / mm or more and 1.2 N / mm or less, and the surface roughness of the coating is preferably 0.1 μm or more and less than 1.5 μm.

[0009] The present disclosure also relates to a method for forming a laminate, which comprises applying a primer composition to a copper-containing substrate, then electrostatically applying a powder composition containing a perfluoropolymer, and heating the resulting mixture to a temperature equal to or higher than the melting point of the perfluoropolymer to form a film. In the laminate-forming method, it is preferable to heat the resulting mixture to a temperature equal to or higher than the melting point of the perfluoropolymer in an oxygen-free environment to form a film. Furthermore, it is preferable to apply a powder composition containing a perfluoropolymer having a melting point lower than 310°C by electrostatically applying the composition, and then heating the resulting mixture to a temperature equal to or higher than the melting point of the perfluoropolymer but lower than 320°C in an oxygen-free environment to form a film.

[0010] The present disclosure also provides a method for forming a laminate, comprising electrostatically applying a powder composition containing a perfluoropolymer having a melting point of less than 310°C onto a copper-containing substrate, and heating the resulting mixture to a temperature equal to or higher than the melting point of the perfluoropolymer and lower than 320°C to form a film. In the above-described method for forming a laminate, it is preferable to heat the resulting mixture to a temperature equal to or higher than the melting point of the perfluoropolymer and lower than 320°C in the absence of oxygen to form a film.

[0011] The present disclosure also provides a method for forming a laminate, which comprises applying a powder composition containing a perfluoropolymer onto a copper-containing substrate by electrostatic coating, and heating the powder composition to a temperature equal to or higher than the melting point of the perfluoropolymer in an oxygen-free environment to form a film.

[0012] As mentioned above, it is preferable to use two or more of the above-described methods for forming a laminate in combination.

[0013] In the above-mentioned method for forming a laminate, the perfluoropolymer is preferably a copolymer containing tetrafluoroethylene (TFE) units and at least one unit selected from the group consisting of perfluoroalkyl vinyl ether (PAVE) units and hexafluoropropylene (HFP) units.

[0014] In the above-mentioned method for forming a laminate, it is preferable that the primer composition essentially contains a perfluoropolymer and further contains one or more resins selected from the group consisting of polyamideimide, polyethersulfone, and polyarylene sulfide.

[0015] The present disclosure also relates to a laminate formed by any of the above-described laminate forming methods. In the laminate formed by any of the above-described laminate forming methods, the perfluoropolymer is preferably a TFE / HFP copolymer. The present disclosure also relates to an article having the above-described laminate. The present disclosure also relates to a magnet wire having the above-described laminate. The present disclosure also relates to a bus bar having the above-described laminate. The present disclosure also relates to a high-frequency substrate having the above-described laminate.

[0016] The laminate of the present disclosure has excellent adhesion between the copper-containing substrate and the perfluoropolymer coating, and the method for forming the laminate of the present disclosure can provide a laminate having excellent adhesion between the copper-containing substrate and the perfluoropolymer coating.

[0017] FIG. 2 is an explanatory diagram showing the state of the coating when measuring the adhesive strength between the coating and the substrate in the examples.

[0018] The present disclosure will be described in detail below. A laminate in which a perfluoropolymer coating having excellent insulating properties is formed on a substrate such as copper or a copper alloy is expected to be used in magnet wires, bus bars, high-frequency substrates, etc.

[0019] A known method for forming the laminate involves forming a coating made of an extrusion composition containing a perfluoropolymer on a long copper substrate. However, such a laminate has problems such as insufficient adhesion between the substrate and the coating, which can cause peeling or cracking of the coating when bent, or uneven thickness of the coating.

[0020] On the other hand, a method of forming a perfluoropolymer coating on the surface of a copper substrate by electrostatic coating using a powder composition containing a perfluoropolymer has been considered. This powder coating method has the advantage of being able to form a good coating even on substrates with complex shapes compared to extrusion coating. However, it has been difficult to ensure sufficient adhesion between the copper substrate and the perfluoropolymer coating.

[0021] In particular, the present disclosure provides a laminate having excellent adhesion by forming a laminate having a perfluoropolymer coating on a copper-containing substrate by at least one of the following methods (1) to (3). Furthermore, the laminate of the present disclosure also has excellent surface smoothness. (1) A primer composition is applied to a copper-containing substrate, and then a powder composition containing a perfluoropolymer is applied by electrostatic coating, and the resulting mixture is heated to a temperature equal to or higher than the melting point of the perfluoropolymer to form a film. (2) A powder composition containing a perfluoropolymer having a melting point less than 310°C is applied to a copper-containing substrate by electrostatic coating, and the resulting mixture is heated to a temperature equal to or higher than the melting point of the perfluoropolymer but lower than 320°C to form a film. (3) A powder composition containing a perfluoropolymer is applied to a copper-containing substrate by electrostatic coating, and the resulting mixture is heated in the absence of oxygen to a temperature equal to or higher than the melting point of the perfluoropolymer to form a film.

[0022] The above-described method for forming a laminate can provide a laminate having an adhesion strength between the copper-containing substrate and the coating of 0.2 N / mm or more and a surface roughness of the coating of less than 15 μm. Such a laminate exhibits particularly excellent performance when applied to magnet wires, bus bars, high-frequency substrates, and the like, which have copper-containing conductors as their substrates.

[0023] (Laminate) The laminate of the present disclosure includes a substrate containing copper and a coating containing a perfluoropolymer, wherein the adhesive strength between the substrate and the coating is 0.2 N / mm or more, and the surface roughness of the coating is less than 15 μm.

[0024] In the laminate of the present disclosure, the adhesion strength between the substrate and the coating is 0.2 N / mm or more. Having an adhesion strength of 0.2 N / mm or more prevents peeling or cracking of the coating when folded, and prevents problems such as uneven film thickness. The adhesion strength between the substrate and the coating is preferably 0.3 N / mm or more, and more preferably 0.4 N / mm or more. There is no particular upper limit to the adhesion strength, but a value of 1.2 N / mm or less is sufficient, and even if the adhesion strength is 1.0 N / mm or less, the effects required in the present disclosure are sufficiently achieved. In this specification, the adhesion strength is a value obtained by the adhesion strength measurement method in the examples below.

[0025] The above-mentioned adhesion strength means the adhesion strength between the substrate and the primer coating when a primer coating is applied to the surface of the substrate in advance and then a coating made of a powder composition containing a perfluoropolymer is provided, as in the method for forming a laminate according to (1) above.

[0026] The surface roughness of the coating is preferably less than 1.5 μm. A surface roughness of less than 1.5 μm is advantageous in that good electrical properties can be exhibited. The surface roughness of the coating is preferably 1.0 μm or less, more preferably 0.7 μm or less. The lower limit of the surface roughness is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.1 μm or more. In this specification, the surface roughness is a value obtained by the surface roughness measurement method in the examples below. The surface roughness of the coating can be reduced to less than 1.5 μm, for example, by heating at a temperature 20° C. or more higher than the melting point of the perfluoropolymer for 20 minutes or more.

[0027] (Substrate) The substrate used in the laminate of the present disclosure contains copper, and examples thereof include simple copper metal and copper alloys. For example, simple copper metal includes tough pitch copper and oxygen-free copper. Other examples include composite copper containing trace components such as aluminum, nickel, and silver, and copper-aluminum clad materials. The substrate used in the laminate of the present disclosure is preferably simple copper metal.

[0028] The substrate may be subjected to a surface treatment such as cleaning or sandblasting, as required. Roughening the surface of the substrate by surface treatment increases the anchoring effect with the powder composition used in forming the coating, further improving adhesion to the coating.

[0029] (Perfluoropolymer) The perfluoropolymer contained in the coating of the laminate of the present disclosure is not particularly limited, and any known perfluoropolymer can be used. Examples of the perfluoropolymer include those obtained by polymerizing one or more perfluoromonomers such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and perfluoro(alkyl vinyl ether) (PAVE) as monomer components.

[0030] The PAVE is not particularly limited, and may be one or more of perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), perfluoropropyl vinyl ether (PPVE), etc., with perfluoropropyl vinyl ether (PPVE) being particularly preferred.

[0031] The perfluoropolymer is preferably a copolymer essentially containing tetrafluoroethylene units and at least one unit selected from the group consisting of perfluoroalkyl vinyl ether units and hexafluoropropylene units. Two or more of these copolymers may also be used in combination.

[0032] Specifically, TFE / PAVE copolymer (PFA), TFE / HFP copolymer (FEP), TFE / PAVE / HFP copolymer, etc. are preferred. In particular, TFE / HFP copolymer and TFE / PAVE / HFP copolymer are suitable because they can be formed into a film at a relatively low temperature.

[0033] The melting point of the perfluoropolymer is preferably less than 310°C. The melting point is more preferably 200°C or more and less than 310°C, and even more preferably 220°C or more and 270°C or less. If the melting point is within the above range, a smooth surface can be obtained without reducing heat resistance. In this specification, the melting point is the temperature corresponding to the maximum value in the heat of fusion curve when heated at a rate of 10°C / min using a differential scanning calorimeter (DSC).

[0034] The MFR of the perfluoropolymer is preferably 1 to 40 g / 10 min. A melt flow rate within the above range results in good interlayer adhesion. Furthermore, the flow during application is good, resulting in high surface smoothness. Furthermore, prolonged heating is not required to achieve the desired film smoothness, and degradation of the perfluoropolymer does not pose a problem. A more preferred lower limit is 5 g / 10 min, and a more preferred upper limit is 30 g / 10 min.

[0035] In this specification, the MFR is a value measured at a temperature of 372°C under a load of 5 kg in accordance with ASTM D2116. The perfluoropolymer can be made to have an MFR within the above range by adjusting the molecular weight, etc.

[0036] The method for producing the perfluoropolymer is not particularly limited, and it can be obtained, for example, by copolymerization using a conventionally known polymerization method such as emulsion polymerization or suspension polymerization.

[0037] In addition to the perfluoropolymer, the coating may contain a heat stabilizer, a color pigment additive, etc., which will be described later. The coating preferably contains 70 to 100% by mass of perfluoropolymer. A perfluoropolymer content within the above range is advantageous in that good electrical properties can be exhibited. A more preferred lower limit is 90% by mass, and an even more preferred lower limit is 95% by mass.

[0038] In the laminate of the present disclosure, the thickness of the coating is preferably 10 to 200 μm, more preferably 20 μm or more, even more preferably 30 μm or more, more preferably 150 μm or less, and even more preferably 100 μm or less. If the thickness is too thick, it may be difficult to miniaturize devices such as motors when used in such devices. On the other hand, if the thickness is too thin, sufficient insulation may not be obtained.

[0039] The dielectric constant of the coating is preferably 2.1 to 2.8, and more preferably 2.6 μm or less. Having a dielectric constant within this range is advantageous in that it can exhibit good insulating properties. In this specification, the dielectric constant is a value obtained by the dielectric constant measurement method described in the Examples below.

[0040] (Method of Forming Laminate) The laminate of the present disclosure is preferably formed by applying a powder composition containing the perfluoropolymer onto a substrate by electrostatic coating, and then heating to form a film.

[0041] (Powder Composition) In the present disclosure, the powder composition used for film formation contains the perfluoropolymer powder.

[0042] The powder composition preferably has an average particle size of 1 to 100 μm. If the particle size is less than 1 μm, electrostatic repulsion tends to occur when the composition is applied, making it difficult to form a film. If the particle size exceeds 100 μm, the smoothness of the resulting film may deteriorate. A more preferred lower limit is 10 μm, and a more preferred upper limit is 80 μm.

[0043] The average particle size of the powder composition can be adjusted to fall within the above range by adjusting the conditions for pulverization and classification in the method for producing the powder composition described below. In this specification, the average particle size is a value measured by a laser diffraction method. Specifically, it is a volume-based median diameter measured using an MT-3300II manufactured by Microtrac.

[0044] The powder composition preferably has an apparent density of 0.5 to 1.1 g / ml. If the apparent density is less than 0.5 g / ml, foaming may occur during application or the number of applications may increase, making electrostatic application difficult. If the apparent density is more than 1.1 g / ml, industrial production of such a powder composition may become difficult. A preferred lower limit of the apparent density is 0.7 g / ml, and a more preferred upper limit is 1.0 g / ml. In this specification, the apparent density (g / ml) is a value obtained by measurement in accordance with JIS K 6891.

[0045] The powder composition may contain a heat stabilizer. When the powder composition contains the heat stabilizer, it can prevent the perfluoropolymer from becoming unstable when heated at a temperature near the melting point or higher, thereby preventing coloration and foaming of the coating film, which may occur. In order to prevent oxidation of the perfluoropolymer, the heat stabilizer is preferably at least one selected from the group consisting of amine-based antioxidants, organic sulfur-containing compounds, and metal powders.

[0046] Examples of the amine antioxidant include aromatic amines having an aromatic hydrocarbon group such as a phenyl group or a naphthyl group in the molecule, such as phenylenediamine compounds such as N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and reaction products of diphenylamine and diisobutylene; and other aromatic secondary amine compounds such as dinaphthylamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine, phenylcyclohexyl-p-phenylenediamine, and styrenated diphenylamine.

[0047] Examples of the organic sulfur-containing compound include mercaptobenzimidazole compounds such as 2-mercaptobenzimidazole and 2-mercaptomethylbenzimidazole; 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, dibenzothiazyl disulfide, 2-(4'-morpholinodithio)benzothiazole, N-cyclohexyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolyl Examples of suitable mercaptobenzothiazole compounds include thiazolylsulfenamide and other mercaptoimidazoline compounds, such as 2-mercaptoimidazoline; and dithiocarbamic acids, such as pentamethylenedithiocarbamic acid, pipecolyldithiocarbamic acid, dimethyldithiocarbamic acid, diethyldithiocarbamic acid, dibutyldithiocarbamic acid, and N-ethyl-N-phenyldithiocarbamic acid. These may also be in the form of metal salts with, for example, Zn, Sn, Cd, Cu, or Fe; or organic salts, such as piperidine salts or pipecolyl salts.

[0048] Examples of the organic sulfur-containing compound include thiuram compounds, such as thiuram monosulfides such as tetramethylthiuram monosulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetrabutylthiuram disulfide; and other thiuram compounds such as dipentamethylenethiuram tetrasulfide. The organic sulfur-containing compound may also be a thiourea derivative such as N,N'-diethylthiourea, dibutylthiourea, or dilaurylthiourea.

[0049] The metal powder may be one or more of cobalt powder, iron powder, zinc powder, tin powder, and copper powder. The metal powder is preferably used in combination with the organic sulfur-containing compound and / or the amine-based antioxidant rather than used alone.

[0050] Among these, the heat stabilizer is preferably an aromatic ring-containing compound, and more preferably an aromatic amine, a mercaptobenzothiazole-based compound, or a mercaptobenzimidazole-based compound, because stability is required at temperatures near the melting point of the perfluoropolymer contained in the powder composition or higher, for example, at high temperatures of about 250° C. or higher. When the powder composition is used in applications such as semiconductor manufacturing equipment, the heat stabilizer is preferably a non-metallic compound that does not leave behind metal residues.

[0051] The heat stabilizer can be produced by a conventionally known method, but commercially available products can usually be used.

[0052] The amount of the heat stabilizer is preferably 0.001 to 5 parts by mass per 100 parts by mass of the perfluoropolymer. If it is less than 0.001 part by mass, the thermal stability of the perfluoropolymer may deteriorate, and if it exceeds 5 parts by mass, discoloration of the resulting coating or foaming due to decomposition of the heat stabilizer occurs, which is undesirable. More preferably, it is 0.003 to 2 parts by mass.

[0053] The powder composition may contain a coloring pigment. Examples of coloring pigments include titanium oxide, cobalt oxide, carbon, chromium oxide, iron oxide, and mica. The amount of the coloring pigment is preferably 0.001 to 5 parts by mass per 100 parts by mass of the TFE copolymer. If the amount is less than 0.001 part by mass, the desired coloring may not be obtained, and if the amount is more than 5 parts by mass, foaming may occur in the resulting coating. More preferably, the amount is 0.003 to 2 parts by mass.

[0054] The powder composition may contain additives, etc., as needed, in combination with the perfluoropolymer and the optional stabilizer and / or coloring pigment. The additives are not particularly limited, and examples include those used in general powder compositions. Examples of the additives include other pigments such as anti-rust pigments and calcined pigments for the purpose of rust prevention, etc.; coating film reinforcing materials such as carbon fiber, glass fiber, glass flakes, and mica for the purpose of preventing coating film shrinkage; and conductivity-imparting materials such as conductive carbon for the purpose of imparting conductivity, and may also be leveling agents, antistatic agents, etc.

[0055] The content of the additive is preferably 0 to 10.0% by mass, more preferably 0 to 5.0% by mass, based on the powder composition.

[0056] The average particle size of the heat stabilizer, color pigment, and additives is preferably 0.1 to 70 μm, and more preferably 0.1 to 50 μm. If these particle sizes fall within this range, they will be uniformly dispersed in the composition and stable coating will be possible. These average particle sizes are values ​​measured by laser diffraction. Specifically, they are volume-based median diameters measured using an MT-3300II manufactured by Microtrac.

[0057] The powder composition used in the present disclosure can be produced by mixing the above-mentioned components. Appropriate crushing can be achieved by using various crushers such as a jet mill, a hammer mill, a pin mill, etc., and combining these as needed, and adjusting the crushing conditions, the crushing time, and the blending of the resin components used in combination.

[0058] The method for forming a laminate according to the present disclosure is particularly suitable for forming a laminate comprising a copper substrate and a perfluoropolymer coating by at least one of the following methods (1) to (3). Forming a laminate by such a method can improve adhesion and surface smoothness. (1) A primer composition is applied to a copper-containing substrate, and then the powder composition is applied by electrostatic coating and heated to a temperature equal to or higher than the melting point of the perfluoropolymer to form a film. (2) The powder composition comprising a perfluoropolymer having a melting point less than 310°C is applied to a copper-containing substrate by electrostatic coating and heated to a temperature equal to or higher than the melting point of the perfluoropolymer but lower than 320°C to form a film. (3) The powder composition is applied to a copper-containing substrate by electrostatic coating and heated to a temperature equal to or higher than the melting point of the perfluoropolymer in an oxygen-free environment to form a film.

[0059] The above method (1) involves forming a primer coating on a substrate in advance, and is advantageous in that the adhesion between the perfluoropolymer layer and the substrate can be further improved by providing a primer layer before forming a perfluoropolymer film on a copper-containing substrate.

[0060] (Primer composition) The primer composition used in the method (1) above is preferably the same as the above-mentioned perfluoropolymer that forms film.That is, it is preferably the copolymer that comprises tetrafluoroethylene unit and at least one selected from the group consisting of perfluoroalkyl vinyl ether unit and hexafluoropropylene unit.Specifically, TFE / PAVE copolymer (PFA), TFE / HFP copolymer (FEP), TFE / PAVE / HFP copolymer etc. are preferred.

[0061] The primer composition preferably further contains one or more heat-resistant resins selected from the group consisting of polyamideimide (PAI), polyethersulfone (PES), and polyarylene sulfide (PAS).

[0062] (Polyamide-imide) PAI is a resin made of a polymer having an amide bond and an imide bond in its molecular structure. The PAI is not particularly limited, and examples thereof include a resin made of a high molecular weight polymer obtained by a reaction between an aromatic diamine having an amide bond in the molecule and an aromatic tetracarboxylic acid such as pyromellitic acid; a reaction between an aromatic tricarboxylic acid such as trimellitic anhydride and a diamine such as 4,4-diaminophenyl ether or a diisocyanate such as diphenylmethane diisocyanate; or a reaction between a dibasic acid having an aromatic imide ring in the molecule and a diamine. The PAI is preferably made of a polymer having an aromatic ring in the main chain, due to its excellent heat resistance.

[0063] The glass transition temperature of the PAI is preferably 200°C or higher, more preferably 250°C or higher. A glass transition temperature within the above range can improve the heat resistance of the primer composition. The glass transition temperature of the PAS is preferably 320°C or lower, more preferably 300°C or lower, and even more preferably 280°C or lower. The glass transition temperature is measured using a differential scanning calorimetry (DSC) device.

[0064] The melting point of the PAI is preferably 250°C or higher, more preferably 260°C or higher. A melting point within the above range can improve the heat resistance of the resin composition. The melting point of the PAI is preferably 320°C or lower, more preferably 300°C or lower. The melting point is measured using a differential scanning calorimetry (DSC) device.

[0065] (Polyethersulfone) The PES has excellent adhesion to the object to be coated, and has sufficient heat resistance even at the temperature during baking when forming the coating film, and the resulting coating film has excellent corrosion resistance and water vapor resistance.

[0066] PES is, for example, a compound represented by the following general formula:

[0067] The resin is a polymer having a repeating unit represented by the formula:

[0068] There are no particular limitations on the PES, and examples thereof include resins made of polymers obtained by polycondensation of dichlorodiphenyl sulfone and bisphenol.

[0069] The glass transition temperature of PES is preferably 200°C or higher, more preferably 205°C or higher, and even more preferably 210°C or higher. A glass transition temperature within the above range can improve the heat resistance of the primer composition. Furthermore, the glass transition temperature of PES is preferably 250°C or lower, and more preferably 240°C or lower. The glass transition temperature is measured using a differential scanning calorimetry (DSC) device.

[0070] (Polyarylene Sulfide) Examples of PAS include those having a repeating unit represented by the following general formula: -(Ar-S)- (where Ar represents an arylene group and S represents sulfur), and the content of the repeating unit in the resin is preferably 70 mol% or more. Examples of arylene groups include p-phenylene, m-phenylene, o-phenylene, alkyl-substituted phenylene, phenyl-substituted phenylene, halogen-substituted phenylene, amino-substituted phenylene, amido-substituted phenylene, p,p'-diphenylene sulfone, p,p'-biphenylene, and p,p'-biphenylene ether. PAS can be broadly classified into resins having a crosslinked or branched structure (crosslinked type) and resins having substantially no crosslinked or branched structure (linear type). However, either the crosslinked type or the linear type can be used without any problems in the present disclosure. A preferred example of PAS is polyphenylene sulfide.

[0071] The PAS preferably has a glass transition temperature of 70°C or higher, more preferably 80°C or higher, and even more preferably 85°C or higher. A glass transition temperature within the above range can improve the heat resistance of the resin composition. The glass transition temperature of the PAS is preferably 300°C or lower, and more preferably 250°C or lower. The glass transition temperature is measured using a differential scanning calorimetry (DSC) device.

[0072] The melting point of the PAS is preferably 180°C or higher, more preferably 190°C or higher. A melting point within the above range can improve the heat resistance of the resin composition. The melting point of the PAS is preferably 380°C or lower, more preferably 350°C or lower. The melting point is measured using a differential scanning calorimetry (DSC) device.

[0073] The resin is preferably PES or PAS, and more preferably PAS, because it can form a coating film that has excellent adhesion to the substrate and excellent non-stick properties. Each of PES and PAS may consist of one type or two or more types.

[0074] The resin is preferably a mixture of PES or PAS and PAI. That is, the resin may be a mixture of PAS and PAI, or a mixture of PES and PAI. When the resin contains PAI in addition to PAS or PES, a coating film with excellent secondary adhesion (adhesion to the substrate after repeated heating and cooling of the coating film) can be obtained. The resin is more preferably a mixture of PAS and PAI, that is, a mixture of PAS and PAI. Each of PAS, PES, and PAI may consist of one type or two or more types.

[0075] When the resin is a mixture of PAS or PES and PAI, the amount of the PAS or PES is preferably 20 to 80 mass %, more preferably 30 to 70 mass %, of the total amount of the PAS or PES and the PAI.

[0076] In the composition, the mass ratio of the perfluoropolymer to the resin (perfluoropolymer / resin) is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 to 90 / 10, and even more preferably 50 / 50 to 85 / 15. When the mass ratio of the fluororesin to the heat-resistant resin is within the above range, the adhesive strength between the perfluoropolymer layer and the primer layer and the adhesive strength between the primer layer and the substrate can be increased.

[0077] The primer composition may contain other additives as appropriate. The primer composition is preferably a powder composition, and the primer layer is preferably formed by electrostatic coating, followed by heating to form a film, similar to the formation of a perfluoropolymer film. The primer layer is also preferably formed by the above method (2) and / or (3).

[0078] The thickness of the primer film is preferably 10 to 100 μm, more preferably 20 to 80 μm. A primer film thickness within the above range is advantageous in that good adhesive strength can be exhibited between the perfluoropolymer layer and the substrate.

[0079] The powder composition is applied onto the primer coating by electrostatic coating, followed by heating and baking to form a coating. The electrostatic coating is not particularly limited and may be performed by a conventional method.

[0080] The heating temperature is preferably a temperature equal to or higher than the melting point of the perfluoropolymer. Specifically, it is preferably the melting point + 20°C or higher. The upper limit of the heating temperature may be less than 320°C from the viewpoint of suppressing oxidation of the substrate and deterioration of the coating. The heating time is preferably 5 minutes or more, more preferably 10 minutes or more. The upper limit of the heating time may be 60 minutes or less from the viewpoint of suppressing oxidation of the substrate and deterioration of the coating.

[0081] As described above, method (2) involves electrostatically applying the powder composition containing a perfluoropolymer having a melting point of less than 310°C onto a substrate, and then heating the resulting substrate to a temperature equal to or higher than the melting point of the perfluoropolymer and less than 320°C to form a film.

[0082] When forming a coating made of a powder composition containing a perfluoropolymer on the surface of a copper-containing substrate, heating the powder composition at a temperature range of 320°C or higher tends to promote oxidation of copper, which may result in a loss of adhesion between the copper substrate and the perfluoropolymer coating. Therefore, in method (2), heating at a temperature below 320°C suppresses oxidation of copper and improves adhesion between the copper substrate and the perfluoropolymer coating. The heating temperature is preferably below 300°C.

[0083] In the above method (3), the powder composition is applied by electrostatic coating and heated to a temperature equal to or higher than the melting point of the perfluoropolymer in an oxygen-free environment. By heating in an oxygen-free environment, oxidation of the substrate can be suppressed, and the formation of a brittle oxide layer can be suppressed, resulting in good adhesion to the substrate.

[0084] Heating in the absence of oxygen can be carried out in an inert gas containing at most 1% by mass of oxygen, such as nitrogen gas.

[0085] In the above method (3), the heating temperature and heating time are preferably the same as those in the above method (1).

[0086] Among the above methods (1) to (3), it is particularly preferable to use methods (1), (2), and (3) in combination. It is also preferable to use methods (1) and (3) in combination, or methods (2) and (3) in combination. The combination of these two methods can also suppress the formation of an oxide film, and by applying the primer composition, good adhesion to copper substrates can be achieved.

[0087] The method for forming a laminate as described above can provide a laminate having excellent adhesion and surface smoothness. The present disclosure also provides a method for forming a laminate, which comprises applying a primer composition to a copper-containing substrate, then applying the powder composition by electrostatic coating, and heating the resulting coating to a temperature equal to or higher than the melting point of the perfluoropolymer to form a film.

[0088] The present disclosure also provides a method for forming a laminate, which comprises electrostatically applying the powder composition containing a perfluoropolymer having a melting point of less than 310°C onto a substrate containing copper, and heating the resulting substrate to a temperature equal to or higher than the melting point of the perfluoropolymer and less than 320°C to form a film.

[0089] The present disclosure also provides a method for forming a laminate, which comprises applying the powder composition to a copper-containing substrate by electrostatic coating, and heating the resulting coating to a temperature equal to or higher than the melting point of the perfluoropolymer in an oxygen-free environment to form a film.

[0090] These methods (1) to (3) can be used alone or in combination to obtain a laminate with excellent adhesiveness and surface smoothness. It is also preferable to use two or more of the methods (1) to (3) in combination. Specifically, as described above, it is preferable to use methods (1) and (3) in combination, or methods (2) and (3), and it is particularly preferable to use methods (1), (2), and (3) in combination.

[0091] The present disclosure also relates to an article having the laminate. Specifically, the laminate of the present disclosure is suitable for use in articles such as magnet wire, bus bar, and high-frequency substrate. Copper or copper alloys are usually used as conductors for these articles, and the laminate of the present disclosure is suitable for use.

[0092] The present disclosure also relates to a magnet wire having the laminate of the present disclosure. The magnet wire is used for coils of motors, transformers, etc. Examples of motors include motors for electric vehicles, compressor motors for air conditioners and refrigerators, and sealed motors.

[0093] The present disclosure also relates to a busbar having a laminate of the present disclosure. Busbars are used as wiring members for transmitting current in electric vehicles and power conversion devices such as inverters and converters. Busbars are also used in distribution boards (cubicles), control panels, batteries, and the like, and conduct large amounts of current. Busbars have the characteristic of being able to efficiently supply large amounts of current to each component due to their low electrical resistance. Furthermore, since wiring work can be completed simply by fastening the busbar with screws, it is possible to relatively easily branch large-capacity power sources throughout the entire panel, even in large distribution boards and control panels. Taking advantage of these characteristics, busbars are widely used in place of cables or conductors. For example, in a battery module having multiple batteries, the terminals of one battery are electrically connected to the terminals of another battery via a busbar.

[0094] The laminate of the present disclosure is preferably used as a circuit board. A circuit board is a plate-shaped component that electrically connects electronic components such as semiconductors and capacitor chips while simultaneously arranging and fixing them in a limited space. The configuration of a circuit board formed from the laminate of the present disclosure is not particularly limited. The circuit board may be any of a rigid board, a flexible board, and a rigid-flexible board. The circuit board may be any of a single-sided board, a board, a double-sided board, and a multilayer board (such as a pulled-up board). In particular, it can be preferably used for flexible boards and rigid boards. In particular, it can be preferably used as a high-frequency board of 10 GHz or more. The present disclosure also relates to a high-frequency board having the laminate of the present disclosure.

[0095] In this disclosure, a high-frequency circuit does not simply refer to a circuit that transmits only high-frequency signals, but also includes circuits that also have transmission lines on the same plane that transmit signals other than high-frequency signals, such as a transmission line that converts high-frequency signals into low-frequency signals and outputs the generated low-frequency signals to the outside, or a transmission line that supplies power to drive high-frequency compatible components.The high-frequency substrate of this disclosure can be suitably used for mobile communication terminals such as mobile phones, smartphones, and tablet devices, communication devices such as Wi-Fi devices, surface acoustic wave (SAW) devices, and radar components.It can also be used as a circuit board for antennas, filters, etc.

[0096] A circuit board can be manufactured by a general method using the above-mentioned laminate.

[0097] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the tables, "%" and "parts" represent "% by mass" and "parts by mass", respectively. The properties shown in the examples were measured by the following methods.

[0098] Film Thickness The film thickness was measured using a film thickness meter LZ-373 manufactured by Kett Electric Laboratory.

[0099] Surface Roughness of Coating The surface roughness Ra of the coating was measured using a surface roughness measuring instrument, Surtronic DUO II, manufactured by Taylor Hobson.

[0100] Adhesion Strength Between Coating and Substrate: The adhesion strength between the coating and substrate was measured using a Shimadzu AGS-J Autograph (50N). As shown in Figure 1, two 50 mm parallel incisions were made in the coating of the laminate along the long axis, with both ends perpendicular to the coating along the short axis. One end was peeled off 10 mm and clamped in an upper chuck (not shown). The substrate was fixed to the bottom so that the long side was horizontal. When the device was moved in the pulling direction, a jig was used that moved horizontally in conjunction with the vertical movement distance, and the angle was adjusted so that the peeled coating was always perpendicular to the long side of the substrate. The tensile stress was measured when the device was pulled at 100 mm / min until 30 mm of peeling was achieved, and the maximum stress was taken as the adhesion strength.

[0101] The dielectric constant of the film was calculated from the capacitance measured using a Hioki LCR HiTester 3522-50 by using the following formula: C = Ca + Cb (where C is the capacitance per unit length of the film (pf / m) and is the sum of the capacitance Ca of the flat portion and the capacitance Cb of each curved portion.) Ca = (ε / ε ０ ) x 2 x (L １ +L ２ ) / TCb=(ε / ε ０ ) × 2πε ０ / Log{(r+T) / r} / r (where ε ０ is the dielectric constant of a vacuum, and the long side of the copper plate L １ , short side L ２ , T is the thickness of the coating.)

[0102] Comparative Example 1: Perfluoropolymer powder A (TFE / PPVE copolymer, melting point 301°C) was electrostatically coated on a copper plate (thickness 1 mm), and the coated plate was heated in an oxygen atmosphere in a drying furnace at 350°C for 30 minutes to obtain a coating. The properties of this coating were evaluated.

[0103] Example 1: Electrostatic coating was carried out on a copper plate using PFA primer A (PFA / polyamideimide / polyarylene sulfide = 80 / 10 / 10 (mass%)), which was then heated in a drying furnace under an oxygen atmosphere at 350 ° C for 30 minutes to obtain a coating. Furthermore, electrostatic coating was carried out using perfluoropolymer powder A, which was then heated in a drying furnace under an oxygen atmosphere at 350 ° C for 30 minutes to obtain a coating. The properties of this coating were evaluated.

[0104] Example 2 A copper plate was electrostatically coated with perfluoropolymer powder A, and the coated plate was heated at 350°C for 30 minutes in a drying oven in an oxygen-free atmosphere substituted with nitrogen to obtain a coating. The properties of the coating were evaluated.

[0105] Example 3: A copper plate was electrostatically coated using PFA primer A, and heated in a drying oven under a nitrogen-substituted oxygen-free atmosphere at 350°C for 30 minutes to obtain a coating. Further, perfluoropolymer powder A was electrostatically coated, and heated in a drying oven under an oxygen-free atmosphere at 350°C for 30 minutes to obtain a coating. The properties of this coating were evaluated.

[0106] Comparative Example 2: Perfluoropolymer powder B (TFE / HFP copolymer, melting point 269°C) was electrostatically coated on a copper plate, and the plate was heated in an oxygen atmosphere in a drying furnace at 320°C for 30 minutes to obtain a coating. The properties of this coating were evaluated.

[0107] Example 4: A copper plate was electrostatically coated using FEP primer B (FEP / polyethersulfone = 80 / 20 (mass%)), and heated in a drying oven under an oxygen atmosphere at 320 ° C for 30 minutes to obtain a coating. Further, perfluoropolymer powder B was electrostatically coated, and heated in a drying oven under an oxygen atmosphere at 320 ° C for 30 minutes to obtain a coating. The properties of this coating were evaluated.

[0108] Example 5 Perfluoropolymer powder B was electrostatically coated on a copper plate, and the plate was heated in an oxygen atmosphere in a drying furnace at 290°C for 30 minutes to obtain a coating. The properties of this coating were evaluated.

[0109] Example 6 A copper plate was electrostatically coated with perfluoropolymer powder B, and the coated plate was heated in a drying oven in an oxygen-free atmosphere substituted with nitrogen at 320°C for 30 minutes to obtain a coating. The properties of the coating were evaluated.

[0110] Example 7: Electrostatic coating was carried out on a copper plate using FEP primer B, and the resultant was heated in a drying oven under an oxygen atmosphere at 290°C for 30 minutes to obtain a coating. Further, electrostatic coating was carried out using perfluoropolymer powder B, and the resultant was heated in a drying oven under an oxygen atmosphere at 290°C for 30 minutes to obtain a coating. The properties of this coating were evaluated.

[0111] Example 8: Electrostatic coating is carried out on a copper plate using FEP primer B, and this is heated in a drying oven under an oxygen-free atmosphere substituted with nitrogen at 320 ° C for 30 minutes to obtain a coating.Furthermore, electrostatic coating is carried out using perfluoropolymer powder B, and this is heated in a drying oven under an oxygen-free atmosphere at 320 ° C for 30 minutes to obtain a coating.The properties of this coating are evaluated.

[0112] Example 9 A copper plate was electrostatically coated with perfluoropolymer powder B, and the coated plate was heated at 290°C for 30 minutes in a drying oven in an oxygen-free atmosphere substituted with nitrogen to obtain a coating. The properties of this coating were evaluated.

[0113] Example 10: Copper plate is electrostatically coated with FEP primer B, and then heated in a drying oven under an oxygen-free atmosphere substituted with nitrogen at 290 ° C for 30 minutes to obtain a coating.Furthermore, perfluoropolymer powder B is electrostatically coated, and then heated in a drying oven under an oxygen-free atmosphere at 290 ° C for 30 minutes to obtain a coating.The properties of this coating are evaluated.

[0114] Comparative Example 3 and Examples 11 to 17 The properties of the coating were evaluated in the same manner as in Comparative Example 2 and Examples 4 to 10, except that perfluoropolymer powder C (TFE / HFP / PPVE copolymer, melting point 257°C) was used instead of perfluoropolymer powder B. The results are shown in Tables 1 and 2.

[0115]

[0116]

[0117] From the results in Table 1, it can be seen that the laminates of the examples had excellent adhesion between the substrate and the coating, and the surface roughness of the coating was low.

[0118] Example 18: The outer periphery of a copper rectangular electric wire substrate was electrostatically coated using FEP primer B, and heated in a drying furnace in a nitrogen-substituted, oxygen-free atmosphere at 320°C for 30 minutes to obtain a coating. Furthermore, perfluoropolymer powder C was electrostatically coated, and heated in a drying furnace in an oxygen-free atmosphere at 320°C for 30 minutes to obtain a coating. The primer layer of this coating had a thickness of 50 μm, and the perfluoropolymer layer had a thickness of 50 μm. The surface roughness was 0.7 μm, and the relative dielectric constant was 2.3. Furthermore, the adhesion strength to the substrate was evaluated using the following procedure. Two rectangular electric wire substrates, each 50 mm long and approximately parallel to the longitudinal axis, were cut into the coating at right angles along the minor axis at both ends, and the ends were peeled off by 10 cm and clamped in the upper chuck of an AGS-J autograph (50N) (manufactured by Shimadzu Corporation). The conductor was fixed to the bottom so that the longitudinal direction was horizontal. When the device was moved in the tensile direction, a jig that moved horizontally in conjunction with the vertical movement distance was used to adjust the angle so that the peeled coating was always perpendicular to the conductor in the longitudinal direction. The tensile stress when pulled at 100 mm / min until 30 mm was peeled off was measured, and the adhesion strength corresponding to the maximum stress was 0.4 (N / mm).

[0119] The laminate of the present disclosure can be suitably used for magnet wires, bus bars, high-frequency substrates, and the like, which have a copper base material.

Claims

1. A laminate comprising a substrate containing copper and a coating containing a perfluoropolymer, wherein the adhesive strength between the substrate and the coating is 0.2 N / mm or more, and the surface roughness of the coating is less than 15 μm.

2. The laminate according to claim 1, wherein the perfluoropolymer is a copolymer containing tetrafluoroethylene (TFE) units and at least one unit selected from the group consisting of perfluoroalkyl vinyl ether (PAVE) units and hexafluoropropylene (HFP) units.

3. The laminate according to claim 1 or 2, wherein the perfluoropolymer is a TFE / HFP copolymer.

4. The laminate according to claim 2, wherein the adhesive strength between the substrate and the coating is 0.2 N / mm or more and 1.2 N / mm or less, and the surface roughness of the coating is 0.1 μm or more and less than 1.5 μm.

5. A method for forming a laminate, comprising applying a primer composition onto a copper-containing substrate, applying a powder composition containing a perfluoropolymer by electrostatic coating, and heating the resulting mixture to a temperature equal to or higher than the melting point of the perfluoropolymer to form a film.

6. A method for forming a laminate, comprising electrostatically applying a powder composition containing a perfluoropolymer having a melting point of less than 310°C onto a copper-containing substrate, and heating the substrate to a temperature equal to or higher than the melting point of the perfluoropolymer and less than 320°C to form a film.

7. A method for forming a laminate, comprising electrostatically applying a powder composition containing a perfluoropolymer onto a copper-containing substrate, and heating the resulting substrate in the absence of oxygen to a temperature equal to or higher than the melting point of the perfluoropolymer to form a film.

8. A method for forming a laminate, comprising the combined use of two or more of the methods for forming a laminate according to claims 5 to 7.

9. The method for forming a laminate according to claim 5, characterized in that the film is formed by heating to a temperature equal to or higher than the melting point of said perfluoropolymer in an oxygen-free environment.

10. A method for forming a laminate according to claim 5, characterized in that a powder composition containing a perfluoropolymer having a melting point of less than 310°C is applied by electrostatic coating, and a film is formed by heating in an oxygen-free environment to a temperature equal to or higher than the melting point of the perfluoropolymer and less than 320°C.

11. The method for forming a laminate according to claim 6, characterized in that the film is formed by heating in the absence of oxygen to a temperature equal to or higher than the melting point of the perfluoropolymer and lower than 320°C.

12. The method for forming a laminate according to any one of claims 5 to 11, wherein the perfluoropolymer is a copolymer containing a tetrafluoroethylene (TFE) unit and at least one unit selected from the group consisting of a perfluoroalkyl vinyl ether (PAVE) unit and a hexafluoropropylene (HFP) unit.

13. The method for forming a laminate according to any one of claims 5, 9, 10 and 12, characterized in that the primer composition essentially contains a perfluoropolymer and further contains one or more resins selected from the group consisting of polyamideimide, polyethersulfone and polyarylene sulfide.

14. A laminate formed by the method for forming a laminate according to any one of claims 5 to 13.

15. The laminate of claim 14, wherein said perfluoropolymer is a TFE / HFP copolymer.

16. An article having a laminate according to any one of claims 1 to 4.

17. A magnet wire comprising a laminate according to any one of claims 1 to 4.

18. A busbar comprising a laminate according to any one of claims 1 to 4.

19. A high frequency substrate having the laminate according to any one of claims 1 to 4.

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