CN113508036B

CN113508036B - Laminate and method for producing laminate

Info

Publication number: CN113508036B
Application number: CN202080015896.4A
Authority: CN
Inventors: 山边敦美; 细田朋也; 笠井涉; 寺田达也
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2019-02-21
Filing date: 2020-02-17
Publication date: 2023-06-13
Anticipated expiration: 2040-02-17
Also published as: TW202041379A; WO2020171024A1; CN113508036A; JPWO2020171024A1; KR20210128376A

Abstract

The invention provides a laminate having a thick polymer layer of TFE polymer and having a low warp rate, and a method for producing the laminate. In the laminate 1, a polymer layer 3 including a plurality of unit polymer layers 31 containing a tetrafluoroethylene polymer is laminated on a long base layer 2, and the absolute value of the linear expansion coefficient of the polymer layer 3 is 50 ppm/DEG C or less. Each unit polymer layer 31 of the laminate 1 is formed of a powder dispersion liquid containing tetrafluoroethylene polymer powder, a dispersant or binder, and a liquid dispersion medium.

Description

Laminate and method for producing laminate

Technical Field

The present invention relates to a laminate in which a polymer layer including a plurality of unit polymer layers containing a tetrafluoroethylene polymer is laminated on a long base layer, and a method for producing the laminate.

Background

Tetrafluoroethylene polymers (TFE polymers) such as Polytetrafluoroethylene (PTFE) are excellent in chemical resistance, water and oil repellency, heat resistance, electrical characteristics, and other physical properties. Therefore, when a polymer layer or film of TFE-based polymer is laminated on a base material layer, a laminate having the above characteristics can be obtained. The laminate is suitable for use as a material for a printed wiring board.

However, since TFE-based polymers lack adhesion, heat treatment is required to form a polymer layer on the surface of a base material layer, regardless of whether a dispersion or a film is used. In this case, the TFE polymer has a high linear expansion coefficient, and thus the laminate is likely to warp. Therefore, it is necessary to take measures to limit the thickness of the polymer layer or to combine the polymer layer with another layer having a different linear expansion coefficient (see patent documents 1 and 2).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2011-0110157

Patent document 2: japanese patent laid-open publication 2016-046433

Disclosure of Invention

However, the laminate of

patent documents

1 and 2 has limited embodiments because the structure (thickness, layer structure) of the polymer layer and the usable base material layer are limited. A thin base material layer having a large area cannot be obtained, and in particular, a laminate having a thick polymer layer composed mainly of a TFE polymer formed only on the surface of a long metal foil, which has a low warp rate and which is firmly bonded to the thin base material layer cannot be obtained.

The present inventors have found, after intensive studies, that when using a TFE-based polymer, when constituting the polymer layers such that a plurality of unit polymer layers are stacked, and setting the conditions (thickness, molding conditions, etc.) of each unit polymer layer, a laminate having a thick polymer layer and a low warp rate can be obtained.

Technical proposal adopted for solving the technical problems

The present invention has the following technical matters.

[1] A laminate comprising a long base layer and a polymer layer comprising a plurality of unit polymer layers containing a tetrafluoroethylene polymer, wherein the absolute value of the linear expansion coefficient of the polymer layer is 50 ppm/DEG C or less.

[2] The laminate of [1], wherein the thickness of the polymer layer is greater than the thickness of the base material layer.

[3] The laminate according to [1] or [2], wherein the thickness of the polymer layer is 20 μm or more.

[4] The laminate according to any one of [1] to [3], wherein the thickness of each of the unit polymer layers is 10 μm or less.

[5] The laminate according to any one of [1] to [4], wherein the thickness of the base material layer is less than 20 μm.

[6] The laminate of any one of [1] to [5], wherein the polymer layer comprises a combination of unit polymer layers of: in the adjacent 2 unit polymer layers, the thickness of the unit polymer layer on the side closer to the base material layer is greater than the thickness of the unit polymer layer on the side farther from the base material layer.

[7] The laminate of any one of [1] to [6], wherein the polymer layer comprises a combination of unit polymer layers of: and adjacent 2 unit polymer layers each containing a different component from the tetrafluoroethylene polymer, wherein the distribution density of the different component contained in the unit polymer layer on the side closer to the base material layer is lower than the distribution density of the different component contained in the unit polymer layer on the side farther from the base material layer in the adjacent 2 unit polymer layers.

[8] The laminate according to any one of [1] to [7], wherein the polymer layers have minute spaces between adjacent 2 of the unit polymer layers.

[9] The laminate according to any one of [1] to [8], wherein the base material layer is a metal foil.

[10] The laminate according to any one of [1] to [9], wherein the tetrafluoroethylene polymer is a polymer having an oxygen-containing polar group.

[11] A method for producing a laminate, wherein a polymer layer comprising a plurality of unit polymer layers containing a tetrafluoroethylene polymer, each of the unit polymer layers being formed from a powder dispersion comprising a tetrafluoroethylene polymer powder, a dispersant or a binder, and a liquid dispersion medium, is laminated on a long base layer, and the absolute value of the linear expansion coefficient of the polymer layer is 50 ppm/DEG C or less.

[12] The method according to [11], wherein the dispersant is a dispersant composed of a thermally decomposable fluoropolymer.

[13] The production method according to [11] or [12], wherein the adhesive is polyamideimide or polyimide.

[14] The method of producing a polymer film according to any one of [11] to [13], wherein each of the unit polymer layers is formed to have a thickness of 10 μm or less.

Effects of the invention

According to the present invention, since the plurality of unit polymer layers containing the tetrafluoroethylene polymer are laminated, a laminate having a low warp curvature and a thick polymer layer can be obtained.

Drawings

Fig. 1 is a schematic cross-sectional view of one embodiment of a laminate of the present invention.

Fig. 2 is a schematic structural view of an example of a laminate manufacturing apparatus used in the present invention.

Detailed Description

The "D50 of the powder" means a particle diameter at which 50% of the volume of the powder is accumulated, and means a particle diameter at which 50% of the volume is accumulated, by measuring the particle size distribution of the powder by a laser diffraction/scattering method, and obtaining an accumulation curve by taking the total volume of the clusters of the powder particles as 100%.

"D90 of powder" is the particle diameter of 90% of the volume basis cumulative of the powder obtained in the same manner.

"melt viscosity of a polymer" means a value measured by keeping a polymer sample (2 g) heated to a measurement temperature for 5 minutes in advance at a measurement temperature under a load of 0.7MPa using a flow tester and a 2. Phi. -8L die, based on ASTM D1238.

"melting temperature (melting point) of a polymer" means a temperature corresponding to the maximum value of the melting peak of the polymer measured by a Differential Scanning Calorimeter (DSC) method.

The "viscosity of the powder dispersion" means the viscosity of the powder dispersion measured by an E-type viscometer at 25.+ -. 2 ℃ and with a rotation speed of a rotor of 50 rpm.

The "viscosity ratio of the powder dispersion" is a value obtained by measuring the viscosity of the powder dispersion with an E-type viscometer under an environment of 25.+ -. 2 ℃ while changing the rotation speed of the rotor, and dividing the viscosity at a rotation speed of 5rpm by the viscosity at a rotation speed of 50 rpm.

"ten-point average roughness (Rzjis)" is JIS B0601: 2013 is specified in the annex JA.

"arithmetic average roughness (Ra)" means an arithmetic average roughness measured in accordance with JIS B0601:2013 (ISO 4287:1997, amd.1:2009). The reference length lr (cutoff value λc) for determining the roughness curve at the time of Ra was set to 0.8mm.

"warpage of laminate" means that a square test piece of 180mm square is cut out from the laminate according to JIS C6471: 1995 (corresponding to the measurement method defined in International Standard IEC 249-1:1982).

The "linear expansion coefficient of the polymer layer" means a value (ppm/. Degree. C.) obtained from the dimensional change rate of a single sheet of the polymer layer (length: 20cm, width: 4 cm) obtained by preparing the single sheet of the polymer layer from the laminate, subjecting the single sheet to an annealing treatment at 150℃for 30 minutes, and then heating the single sheet from 30℃to 200℃at 2℃per minute under a nitrogen atmosphere with a tension of 6mN applied thereto.

The laminate and the method for producing the same according to the present invention will be described below based on preferred embodiments shown in the drawings.

Fig. 1 is a schematic cross-sectional view of an embodiment of a laminate according to the present invention, and fig. 2 is a schematic structural view of an example of a laminate manufacturing apparatus used in the present invention.

For convenience of explanation, the upper side in fig. 1 and 2 will be referred to as "upper" or "upper" and the lower side will be referred to as "lower" or "lower". In addition, for convenience of explanation, the dimensional ratio of fig. 1 and 2 is different from that of actual ones.

The laminate 1 shown in fig. 1 has a long base layer 2 and a polymer layer 3 laminated on the base layer 2. The polymer layer 3 includes a plurality of (in this embodiment, 3) unit polymer layers 31 containing tetrafluoroethylene polymer (TFE polymer), and minute spaces 32 between adjacent 2 unit polymer layers 31.

In differentiating the 3 unit polymer layers 31, the

unit polymer layers

311, 312, 313 are sequentially written from bottom to top. When dividing 2 minute spaces 32, minute spaces 321 and minute spaces 322 are sequentially indicated from bottom to top.

In addition, according to the cross-sectional analysis of the laminate, the interface between each unit polymer layer may be distinguished by the difference in composition between the unit polymer layers or the minute space between the layers, or may not be distinguished by the integration of each unit polymer layer in the height direction.

The laminate 1 can be manufactured by a manufacturing apparatus shown in fig. 2, for example.

The manufacturing apparatus 100 shown in fig. 2 includes: the roll 10 around which the base material layer 2 is wound, the die coater 12 which coats the powder dispersion 300 on the surface of the base material layer 2 to form a wet film, the drying furnace D which removes the liquid dispersion medium from the wet film to form a dry film, the firing furnace F which fires the dry film to form the unit polymer layer 31, and the roll 16 which winds up the base material layer 2 on which the unit polymer layer 31 is formed.

The manufacturing apparatus 100 further includes: the guide roller 18 for guiding the substrate layer 2 unwound from the roller 10 to the die coater 12, the back roller 20 for guiding the substrate layer 2 on which the wet film is formed to the drying furnace D while being disposed opposite to the die coater 12 via the substrate layer 2, the guide roller 22 and the guide roller 24 for guiding the substrate layer 2 on which the unit polymer layer 31 is formed to the roller 16 while passing through the drying furnace D and the baking furnace F.

The manufacturing apparatus 100 further includes: the powder coating apparatus includes a tank 26 storing a powder dispersion 300, a stirring device 30 having stirring blades 28 for stirring the powder dispersion 300 in the tank 26, an ultrasonic device 32 for irradiating the powder dispersion 300 in the tank 26 with ultrasonic waves, a liquid feed line 34 for feeding the powder dispersion 300 in the tank 26 to the die coater 12, a pump 36 provided midway in the liquid feed line 34, and a filter 38 provided midway in the liquid feed line 34.

The substrate layer 2 of the present invention is preferably a metal foil. When the metal foil is processed, the laminate 1 can be suitably used as a printed wiring board. The metal constituting the metal foil may be: copper, copper alloys, stainless steel, nickel alloys (including 42 alloys as well), aluminum alloys, titanium alloys.

The metal foil is preferably a copper foil, more preferably a rolled copper foil having no distinction between the front and back surfaces or an electrolytic copper foil having distinction between the front and back surfaces, and still more preferably a rolled copper foil. Since the surface roughness of the rolled copper foil is small, transmission loss can be reduced even when the laminate 1 is processed into a printed wiring board. The rolled copper foil is preferably used after being immersed in a hydrocarbon organic solvent to remove the rolling oil.

The ten-point average roughness (Rzjis) of the surface of the base material layer 2 is preferably 0.01 μm or more, more preferably 0.2 μm or more, and still more preferably 0.7 μm or more. The ten-point average roughness is preferably 4 μm or less, more preferably 1.5 μm or less, and still more preferably less than 1.0 μm. In this case, the adhesion to the polymer layer 3 is good, and a printed wiring board excellent in transfer characteristics can be easily obtained.

The thickness of the base material layer 2 may be any thickness that can sufficiently function in the application of the laminate 1. The thickness of the base material layer 2 is preferably less than 20 μm, more preferably 2 to 15 μm.

In addition, a part or the whole of the surface of the base material layer 2 may be treated with a silane coupling agent.

The ten-point average roughness of the surface of the base material layer 2 may be appropriately adjusted by etching the surface or by roughening the formation of the treated layer.

The powder dispersion 300 of the present invention comprises TFE-based polymer powder, a dispersant or binder, and a liquid dispersion medium.

The D50 of the powder of the invention is preferably 0.05 to 6. Mu.m, more preferably 0.2 to 3. Mu.m. Within this range, the fluidity and dispersibility of the powder are good, and the electrical characteristics (low dielectric constant, etc.) and heat resistance of the polymer layer 3 are most likely to be exhibited. The D90 of the powder is preferably 8 μm or less, more preferably 5 μm or less. Within this range, the fluidity and dispersibility of the powder are good, and the electrical characteristics (low dielectric constant, etc.) and heat resistance of the polymer layer 3 are most likely to be exhibited.

The powder of the present invention is preferably a powder containing a TFE-based polymer as a main component. The content of the TFE-based polymer in the powder is preferably 80 mass% or more, more preferably 100 mass%.

The powder may contain a heat-resistant nonfluoropolymer such as aromatic polyester, polyamide imide, thermoplastic polyimide, polyphenylene ether, and polyphenylene ether.

The loose packing density of the powder is preferably 0.08 to 0.5g/mL. The dense packing density of the powder is more preferably 0.1 to 0.8g/mL.

The TFE-based polymer of the present invention is a polymer containing a Tetrafluoroethylene (TFE) -based unit (hereinafter also referred to as "TFE unit").

The melt viscosity of TFE-based polymers at 380℃is preferably 1X 10 ² ～1×10 ⁸ Pa.s, more preferably 1X 10 ³ ～1×10 ⁶ Pa·s。

The TFE-based polymer is preferably a homopolymer (PTFE) composed of TFE units, a copolymer (hereinafter also referred to as "PFA") containing TFE units and units based on perfluoro (alkyl vinyl ether) (hereinafter also referred to as "PAVE units"), a copolymer containing TFE units and units based on hexafluoropropylene (hereinafter also referred to as "HFP units"), or a copolymer containing TFE units and units based on fluoroalkyl ethylene (hereinafter also referred to as "FAE units").

Homopolymers composed of TFE units also include polymers containing very small amounts of units other than TFE units (i.e., modified PTFE). The polymer containing an extremely small amount of other units preferably contains 99.5 mol% or more, more preferably 99.9 mol% or more of TFE units relative to the total units contained in the polymer.

In addition, PTFE also includes low molecular weight PTFE.

As the PTFE of low molecular weight, there may be mentioned: for high molecular weight PTFE (melt viscosity of about 1X 10) ⁹ ～1×10 ¹⁰ Pa·s), a polymer obtained by irradiation with radiation (see, for example, international publication No. 2018/026012), a polymer obtained by using a chain transfer agent at the time of TFE polymerization (see, for example, international publication No. 2010/114033), a polymer having a core-shell structure composed of a core portion and a shell portion and having the above melt viscosity only in the shell portion (see, for example, international publication No. 2016/170918), and the like.

The standard specific gravity (specific gravity measured by ASTM D4895-04) of the low-molecular-weight PTFE is preferably 2.14 to 2.22, more preferably 2.16 to 2.20.

The TFE-based polymer also includes a copolymer containing a unit other than TFE unit as described above. The copolymer containing other units preferably contains more than 0.5 mole% of other units relative to the total units of the polymer. The other units are preferably units having a functional group described below, in addition to the PAVE unit, HFP unit, and FAE unit.

The TFE-based polymer preferably has an oxygen-containing polar group. It is considered that the oxygen-containing polar group strongly interacts with an oxide or a metal atom present on the surface of the metal foil as the base material layer 2, and thus the polymer layer 3 exhibits high adhesion with the base material layer 2.

The oxygen-containing polar group may be contained in a unit based on a monomer having an oxygen-containing polar group, may be contained at a terminal portion of a polymer main chain, or may be introduced into a polymer by surface treatment (radiation treatment, electron beam treatment, corona treatment, plasma treatment, or the like). The oxygen-containing polar group may be a group obtained by modifying a polymer having a group capable of forming an oxygen-containing polar group. The type of the oxygen-containing polar group contained in the terminal part of the polymer main chain can be obtained by adjusting the components (polymerization initiator, chain transfer agent, etc.) used in the polymerization of the polymer.

As the TFE-based polymer having an oxygen-containing polar group, a copolymer having a unit based on a monomer having an oxygen-containing polar group is preferable.

The oxygen-containing polar group is a polar atomic group containing an oxygen atom. However, the oxygen-containing polar group includes not an ester bond itself and an ether bond itself, but an atomic group including these bonds as characteristic groups.

As the oxygen-containing polar group, a hydroxyl group, a carbonyl group, an acetal group and an oxycycloalkyl group are preferable, and-CF is more preferable ₂ CH ₂ OH、-C(CF ₃ ) ₂ OH, 1, 2-diol (-CH (OH) CH) ₂ OH), acetal, > C (O), -CF ₂ C (O) OH, > CFC (O) OH, carboxamide (-C (O) NH) ₂ Etc.), acid anhydride residues (-C (O) OC (O) -), imide residues (-C (O) NHC (O) -, etc.), dicarboxylic acid residues (-CH (C (O) OH) CH ₂ C (O) OH, etc.), a carbonate group (-OC (O) O-), an epoxy group and an oxetanyl group, and an acid anhydride residue is more preferable.

The TFE-based polymer is preferably a polymer containing TFE units, HFP units, PAVE units or FAE units (hereinafter, these will be collectively referred to as "PAE units"), and units based on monomers having an oxygen-containing polar group (hereinafter, also referred to as "polar units").

The ratio of TFE units to the total units constituting the TFE-based polymer is preferably 50 to 99 mol%, particularly preferably 90 to 99 mol%.

As the PAE unit, a PAVE unit and an HFP unit are preferable, and a PAVE unit is particularly preferable. The TFE-based polymer may contain more than 2 PAE units.

The proportion of the PAE unit relative to the total units constituting the TFE-based polymer is preferably 0 to 10 mol%, particularly preferably 0.5 to 9.97 mol%.

Examples of the monomer constituting PAVE include: CF (compact flash) ₂ ＝CFOCF ₃ (PMVE)、CF ₂ ＝CFOCF ₂ CF ₃ 、CF ₂ ＝CFOCF ₂ CF ₂ CF ₃ (PPVE)、CF ₂ ＝CFOCF ₂ CF ₂ CF ₂ CF ₃ 、CF ₂ ＝CFO(CF ₂ ) ₈ F, preferably PMVE and PPVE.

The monomers constituting FAE include: CH (CH) ₂ ＝CH(CF ₂ ) ₂ F(PFEE)、CH ₂ ＝CH(CF ₂ ) ₃ F、CH ₂ ＝CH(CF ₂ ) ₄ F(PFBE)、CH ₂ ＝CF(CF ₂ ) ₃ H、CH ₂ ＝CF(CF ₂ ) ₄ H, preferably PFEE and PFBE.

The proportion of the PAE unit relative to the total units constituting the TFE-based polymer is preferably 0.5 to 9.97 mol%.

As the polar unit, a monomer unit having a cyclic acid anhydride residue is preferable. The polar units contained in the TFE-based polymer may be 2 or more.

As monomers having cyclic anhydride residues, itaconic anhydride, citraconic anhydride, 5-norbornene-2, 3-dicarboxylic anhydride (alias: nadic anhydride also referred to as "NAH" hereinafter) and maleic anhydride are preferred, and NAH is particularly preferred.

The proportion of the polar unit is preferably 0.01 to 3 mol% based on the total units constituting the TFE-based polymer.

The TFE-based polymer in this case may further include units other than TFE units, PAE units, and polar units (hereinafter also referred to as "4 th units"). There may be more than 2 units 4.

The monomer forming the 4 th unit may be: ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride (VDF), chlorotrifluoroethylene (CTFE). Ethylene, VDF and CTFE are preferable as the monomer forming the 4 th unit, and ethylene is particularly preferable.

The proportion of the 4 th unit in the TFE unit is preferably 0 to 50 mol%, particularly preferably 0 to 40 mol%, based on the total units constituting the TFE polymer.

The melting temperature of the TFE-based polymer is preferably 140 to 320 ℃, more preferably 200 to 320 ℃, particularly preferably 260 to 320 ℃. In this case, the adhesion of the polymer layer 3 to the base material layer 2 is easily further improved.

The TFE-based polymer is preferably PFA containing PAVE units in an amount of 2 mol% or more based on the total units.

As PFA, more preferable are PFA (1) having a polar functional group comprising TFE units, PAVE units and units based on a monomer having a polar functional group, and PFA (2) having no polar functional group comprising TFE units and PAVE units and having a PAVE unit content of 2.0 to 5.0 mol% with respect to the whole units.

The PFA (1) preferably contains 90 to 99 mol% of TFE unit, 1.5 to 9.97 mol% of PAVE unit, and 0.01 to 1.5 mol% of unit based on the monomer having a polar functional group, respectively, with respect to the total units.

In addition, as the monomer having a polar functional group, itaconic anhydride, citric anhydride, and NAH are preferable.

As a specific example of PFA (1), there is mentioned a polymer described in International publication No. 2018/16644.

The PFA (2) is composed of only TFE units and PAVE units, and preferably contains 95.0 to 98.0 mol% of TFE units and 2.0 to 5.0 mol% of PAVE units relative to the total units.

The PAVE unit content in PFA (2) is preferably 2.1 mol% or more, more preferably 2.2 mol% or more, based on the total units.

Further, the absence of the polar functional group in the PFA (2) means that the number of carbon atoms relative to the main chain constituting the polymer is 10 ⁶ The polymer has less than 500 polar functional groups. The number of the polar functional groups is preferably 100 or less, more preferably less than 50. The lower limit of the number of polar functional groups is usually 0.

The PFA (2) can be produced using a polymerization initiator, a chain transfer agent, or the like that does not generate a polar functional group as a terminal group of the polymer main chain, or can be produced by subjecting PFA having a polar functional group (PFA having a polar functional group derived from a polymerization initiator in a terminal group of the polymer main chain, or the like) to a fluorination treatment. As a method of the fluorination treatment, a method using fluorine gas is exemplified (refer to japanese patent application laid-open No. 2019-194314, etc.).

The liquid dispersion medium of the present invention is a dispersion medium in which powder is dispersed, and is a liquid compound at 25 ℃, and may be an aqueous liquid dispersion medium or a nonaqueous liquid dispersion medium.

As the liquid dispersion medium, water, amide, alcohol, sulfoxide, ester, ketone, and glycol ether are preferable, water, ketone, and amide are more preferable, and ketone and amide are further preferable. Since the interaction between the dispersant (particularly EO polymer described later) and these liquid dispersion media is high, the film forming property (thixotropic ratio, adhesiveness, transparency, etc.) of the powder dispersion 300 is easily improved. The liquid dispersion medium may be used in combination of 2 or more.

Specific examples of the liquid dispersion medium include: water, methanol, ethanol, isopropanol, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, diethyl ether, dioxane, ethyl lactate, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isopropyl ketone, cyclopentanone, cyclohexanone, ethylene glycol monoisopropyl ether, cellosolve (methyl cellosolve, ethyl cellosolve, etc.).

The liquid dispersion medium is preferably a compound which does not instantaneously volatilize, more preferably a compound having a boiling point of 80 to 275 ℃, and still more preferably a compound having a boiling point of 125 to 250 ℃. Within this range, when the liquid dispersion medium is distilled off from the powder dispersion 300 by heating, volatilization of the liquid dispersion medium and decomposition and flow of the dispersant effectively proceed.

As the above-mentioned liquid dispersion medium, methyl ethyl ketone, cyclohexane, 2-propanol, 1-butanol, 1-methoxy-2-propanol, N-methyl-2-pyrrolidone, gamma-butyrolactone, cyclohexanone and cyclopentanone are preferable, and methyl ethyl ketone, cyclohexanone and N-methyl-2-pyrrolidone are more preferable.

The dispersant of the present invention is preferably a thermally decomposable fluoropolymer different from the TFE-based polymer, more preferably a fluoropolymer having a thermal decomposition start temperature of 50 to 150 ℃ and a mass reduction rate of 50 mass%/min or more at 150 ℃. As will be described later, within this range, the components from the dispersant are concentrated in the polymer layer, and the warp rate of the laminate is more easily controlled.

The thermal decomposition start temperature is a temperature at which the dispersant starts to decrease in mass in analysis of the dispersant using a thermogravimetric analyzer.

The mass reduction rate means a mass reduction rate (%) of the dispersant when the dispersant is exposed at 150 ℃ for 30 minutes in analysis of the dispersant using a thermogravimetric analyzer.

The weight average molecular weight of the thermally decomposable fluoropolymer is preferably 2000 to 80000, more preferably 6000 to 20000. The weight-average molecular weight of the thermally decomposable fluoropolymer is excellent not only in the function as a dispersant, but also the amount of the component (e.g., decomposed product) derived from the thermally decomposable fluoropolymer remaining in the polymer layer 3 can be easily controlled.

Further, from the viewpoint of exhibiting good thermal decomposition behavior, the above-mentioned thermally decomposable fluorine-containing polymer is preferably an oxyethylene-based polymer (hereinafter also referred to as "EO polymer") having an oxyethylene group (hereinafter also referred to as "EO group") and a polyfluoroalkoxycarbonyl group (hereinafter also referred to as "F group").

In this case, the EO group content of the EO polymer is preferably 20 to 50% by mass, more preferably 25 to 40% by mass. In the case of the EO polymer having the EO group in the above content, the EO group content and the F group content are more balanced, and therefore, the EO polymer functions as a dispersant in a temperature range for converting a wet film into a dry film. In addition, if the above EO polymer is used, the amount of the component derived from the EO polymer in the polymer layer 3 can be more easily controlled. Therefore, the polymer layer 3 not only exhibits high adhesion and excellent electrical characteristics, but also is easily formed with a low warp rate.

As the EO group-containing group, preferred is a group of the formula contained in the side chain of the EO polymer: -C (O) O- (CH) ₂ CH ₂ O) _n -R ^H The radicals represented.

The symbols in the formula represent the following meanings:

n is 12 to 200, preferably 20 to 120.

R ^H Is a hydrogen atom, an alkyl group or a phenyl group, preferably a hydrogen atom or a methyl group.

The side chain containing EO group of the above structure is used for converting wet film Decomposition starts in the temperature range of the dry film, and is therefore preferable. In addition, if the number of n or R ^H The choice may be made to adjust the affinity of the EO polymer for the powder and liquid dispersion medium accordingly.

Specific examples of the group represented by the above formula include: -C (O) O- (CH) ₂ CH ₂ O) ₉₀ -H、-C(O)O-(CH ₂ CH ₂ O) ₁₂₀ -H、-C(O)O-(CH ₂ CH ₂ O) ₂₃ -CH ₃ 、-C(O)O-(CH ₂ CH ₂ O) ₆₆ -CH ₃ 、-C(O)O-(CH ₂ CH ₂ O) ₉₀ -CH ₃ 、-C(O)O-(CH ₂ CH ₂ O) ₁₂₀ -CH ₃ 、-C(O)O-(CH ₂ CH ₂ O) ₃₀ -(CH ₂ ) ₁₂ H、-C(O)O-(CH ₂ CH ₂ O) ₃₀ -(CH ₂ ) ₁₈ H、-C(O)O-(CH ₂ CH ₂ O) ₄ -(CH ₂ ) ₁₂ H、-C(O)O-(CH ₂ CH ₂ O) ₆ ·(CH ₂ CH(CH ₃ )O) ₅ -Ph. In the above formula, ph represents a phenyl group.

On the other hand, the fluorine content of the EO polymer is preferably 20 to 40 mass%, more preferably 25 to 40 mass%. In the case of the EO polymer having the above fluorine content, the F group content and the EO group content are more well balanced, and therefore the EO polymer functions as a dispersant in a temperature range where a wet film is converted into a dry film. In addition, if the above EO polymer is used, the amount of the component derived from the EO polymer in the polymer layer 3 can be more easily controlled. Therefore, the polymer layer 3 not only exhibits high adhesion and excellent electrical characteristics, but also is easily formed with a low warp rate.

More preferably, the group F has the formula contained in the side chain of the EO polymer: -C (O) O-Q ^H -R ^F The radicals represented.

The symbols in the formula represent the following meanings:

Q ^H is methylene (-CH) ₂ (-) or ethylene (-CH) ₂ CH ₂ (-), preferably ethylene.

R ^F Is a plurality of carbon numbers of 1 to 6Fluoroalkyl groups, preferably- (CF) ₂ ) ₄ F or- (CF) ₂ ) ₆ F。

The side chain containing the F group is due to Q ^H Is less in carbon number and is therefore composed of R ^F The influence of the fluorine atom on the electron withdrawing property is further improved, and the cleavage of the ester bond is more likely to occur. Therefore, the amount of decomposition products of the EO polymer in the polymer layer 3 can be more easily controlled. In addition, if R is ^F The type of (c) is selected, and the affinity of the EO polymer for the powder and the liquid dispersion medium can be adjusted in accordance with the type.

Specific examples of the F group include: -C (O) OCH ₂ (CF ₂ ) ₆ F、-C(O)OCH ₂ (CF ₂ ) ₄ F、-C(O)OCH ₂ CH ₂ (CF ₂ ) ₆ F、-C(O)OCH ₂ CH ₂ (CF ₂ ) ₄ F。

As EO polymers of the invention, it is preferable to include those based on the formula: CH (CH) ₂ ＝CX ^H C(O)O-(CH ₂ CH ₂ O) _n -R ^H The units of the compounds represented (hereinafter also denoted as "units EO") and based on the formula: CH (CH) ₂ ＝CX ^F C(O)O-Q ^H -R ^F A polymer of a unit of the compound represented (hereinafter also referred to as "unit F").

The symbols in the formula represent the following meanings:

X ^H is a hydrogen atom or a methyl group.

R ^H The same meaning as described above.

X ^F The hydrogen atom, chlorine atom or methyl group is preferable.

Q ^H And R is ^F Respectively as defined above.

The amount of unit EO and the amount of unit F are preferably 10 to 40 mol% and 60 to 90 mol% in this order with respect to the total units contained in the EO polymer.

If the amount of each unit relative to the total units contained in the EO polymer is within the above-described range, the dispersibility of the powder dispersion 300 is further improved, and the amount of the component derived from the EO polymer in the polymer layer 3 can be appropriately controlled. Therefore, the polymer layer 3 exhibits various physical properties including adhesiveness and electrical characteristics with good balance, and is easily formed with a low warpage.

The EO polymer may be composed of only units EO and units F, or may further contain additional units other than units EO and units F within a range that does not impair the effects of the present invention.

The mass reduction rate of the EO polymer at 150℃is preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more. If the mass reduction rate at 150 ℃ is within the above range, it is considered that decomposition of EO group occurs preferentially in the temperature range for converting the wet film into dry film, and also decomposition of F group occurs. Therefore, the EO polymer sufficiently plays a role as a dispersant for the powder in the process of drying the wet film, and a dry film excellent in shape stability can be obtained.

Further, the mass reduction rate of the EO polymer at 350℃is preferably 80% or more, more preferably 90% or more. If the mass reduction ratio at 150 ℃ and 350 ℃ satisfies the above-described relationship, it is considered that the component derived from the residual EO polymer gradually decomposes in the temperature range at which the dry film is converted into the polymer layer 3 (fired film). Therefore, the amount of gas generated by decomposition of the component derived from the EO polymer is small, and excessive reduction in the surface smoothness of the obtained polymer layer 3 is easily suppressed.

The thermal decomposition behavior of such EO polymers can be adjusted by the choice of the EO and F group species and the setting of the EO and F group content.

The adhesive of the present invention is a reagent different from the polymer constituting the TFE-based polymer and the dispersant, and is preferably polyamide imide or polyimide.

When the powder dispersion contains the binder, powder falling is suppressed, uniformity and surface smoothness of the polymer layer 3 are further improved, and linear expansibility is easily flattened. Further, the dispersion stability and physical properties (viscosity, thixotropic ratio, etc.) of the powder dispersion are further improved, and the formation of the polymer layer 3 is easily and more densely performed. As a result, the adhesive not only suppresses an increase in the warp curvature of the laminate 1, but also makes it easier to improve the adhesion between the base material layer 2 and the polymer layer 3.

The 5% weight reduction temperature of the adhesive is preferably 260℃or higher, more preferably 320℃or higher. The 5% weight reduction temperature of the adhesive is preferably 600 ℃ or less. In this case, the adhesion between the base material layer 2 and the polymer layer 3 and the adjacent 2 polymer layers 31 is more easily improved.

The binder is soluble in the liquid dispersion medium of the powder dispersion, and the solubility of the powder dispersion in the liquid dispersion medium at 25 ℃ (g/100 g of the liquid dispersion medium) is preferably 5 to 30. In this case, the original physical properties of the TFE-based polymer such as electric characteristics are maintained, and the adhesion is easily improved. In particular, when the proportion of the binder in the powder dispersion is low, the above effect is more easily enhanced.

The polymer constituting the adhesive may be a non-reactive polymer or a reactive polymer.

The non-reactive polymer is a polymer having no reactive group that reacts under the conditions of use of the powder dispersion. For example, the non-reactive polyimide is a polyimide that has been imidized, that is, a polyimide that will not undergo imidization any more.

The reactive polymer is a polymer having the reactive group and reacting (condensation reaction, addition reaction, etc.) under the conditions of use of the powder dispersion. For example, the reactive polyimide is a precursor of polyimide (polyimide obtained by partially imidizing a polyamide acid or the like), that is, polyimide obtained by further imidizing a powder dispersion under the conditions (such as heating).

The polymer constituting the adhesive may be thermoplastic or thermosetting.

If the polymer is thermoplastic, the fluidity of the adhesive resin increases in the heating history when forming a layer (coating film) from the powder dispersion, and a dense and uniform polymer layer is formed, so that the adhesion is easily improved. As the thermoplastic polymer, a non-reactive thermoplastic polymer is preferable.

The glass transition temperature of the thermoplastic polymer is preferably 500 ℃ or less. The glass transition temperature is more preferably 200℃or higher. In this case, during the formation of the polymer layer 3, dense deposition is more easily promoted.

If the polymer constituting the adhesive is thermosetting, the linear expansibility of the polymer layer is more likely to be reduced by containing the cured product. As the thermosetting polymer, a reactive thermosetting polymer is preferable.

Specific examples of the adhesive include: polyamide imide such as "HPC" (manufactured by hitachi chemical corporation), "neobulim" (manufactured by mitsubishi gas chemical corporation), the "SPIXAREA" (manufactured by Somar chemical corporation), the "Q-PILON" (manufactured by PI technology institute (manufactured by tikoku corporation), the "WINGO" (manufactured by WINGO technology corporation), the "tohmideo" (manufactured by tohmn corporation), the "KPI-MX" (manufactured by kappa corporation), the "upi-MX" (manufactured by kappa corporation), and the "UPIA-Att" (manufactured by kappa corporation).

The proportion of the powder in the powder dispersion 300 of the present invention is preferably 20 to 60% by mass, more preferably 30 to 50% by mass. Within this range, the polymer layer 3 excellent in electric characteristics and heat resistance is easily formed.

The proportion of the dispersant in the powder dispersion 300 of the present invention is preferably 1 to 15% by mass, more preferably 3 to 10% by mass. Within this range, the dispersibility of the powder dispersion 300 is further improved, and the physical properties (electrical characteristics, adhesiveness, etc.) of the polymer layer 3 are more easily improved.

The proportion of the liquid dispersion medium in the powder dispersion 300 of the present invention is preferably 30 to 70% by mass, more preferably 40 to 60% by mass. Within this range, the powder dispersion 300 is excellent in coatability, and the layer (coating film) formability is easily improved.

The powder dispersion 300 of the present invention may contain other materials within a range that does not impair the effects of the present invention. Other materials may or may not be dissolved in the powder dispersion 300.

The other materials include non-curable resins.

The non-curable resin may be: non-melting resin and hot melting resin.

The non-melt resin may be a cured product of a curable resin.

Examples of the hot-melt resin include: thermoplastic resins such as thermoplastic polyimide, and heat-fusible cured products of curable resins.

Examples of the thermoplastic resin include polyester resins, polyolefin resins, styrene resins, polycarbonates, thermoplastic polyimides, polyarylates, polysulfones, polyarylsulfones, aromatic polyamides, aromatic polyether amides, polyphenylene sulfides, polyaryletherketones, polyamideimides, liquid crystalline polyesters, polyphenylene oxides, preferably thermoplastic polyimides, liquid crystalline polyesters, and polyphenylene oxides.

Further, as other materials, there may be mentioned: thixotropic imparting agents, defoamers, inorganic fillers, reactive alkoxysilanes, dehydrating agents, plasticizers, weather-proofing agents, antioxidants, heat stabilizers, lubricants, antistatic agents, brighteners, colorants, conductive agents, mold release agents, surface treatment agents, viscosity modifiers, flame retardants.

The viscosity of the powder dispersion 300 of the present invention is preferably 10 to 10000 mPas, more preferably 15 to 1000 mPas, and even more preferably 25 to 500 mPas. In this case, not only the dispersibility of the powder dispersion 300 but also the coatability and the miscibility with varnishes of different polymers are excellent.

Thixotropic ratio (. Eta.) of powder dispersion 300 of the present invention ₁ /η ₂ ) Preferably 0.8 to 1.4. In this case, not only the dispersibility of the powder dispersion 300 but also the coatability of the powder dispersion 300 is good, and the uniformity of the unit polymer layer 31 is easily improved. Furthermore, the miscibility of the powder dispersion 300 with varnishes of different polymers is further improved. In addition, thixotropic ratio (. Eta. ₁ /η ₂ ) By measuring the viscosity eta of the powder dispersion 300 at a rotation speed of 30rpm ₁ Divided by the viscosity eta of the powder dispersion 300 measured at a rotational speed of 60rpm ₂ To calculate。

The laminate 1 shown in fig. 1 can be manufactured as follows using the manufacturing apparatus 100 shown in fig. 2.

First, the powder dispersion 300 is applied to the surface of the substrate layer 2 unwound from the roll 10 by the die coater 12, and the powder dispersion is sequentially passed through the drying furnace D and the baking furnace F to form the unit polymer layer 311, and the substrate layer 2 is wound around the roll 16.

Thereafter, the base material layer 2 on which the unit polymer layer 311 is formed is unwound from the roll 16, the unit polymer layer 312 is formed on the surface of the unit polymer layer 311 in the same manner as described above, and the base material layer 2 is wound up on the roll 10.

Thereafter, the base material layer 2 formed with the unit polymer layers 311 and 312 is unwound from the roll 10, the unit polymer layer 313 is formed on the surface of the unit polymer layer 312 in the same manner as described above, and the base material layer 2 is wound up on the roll 16.

The powder dispersion 300 is preferably subjected to a dispersing process by the stirring device 30 and the ultrasonic device 32 immediately before being transferred to the die coater 12. Thus, the powder contained in the powder dispersion 300 can be sufficiently dispersed, and aggregation can be suppressed.

The temperature at the time of the dispersion treatment is preferably 25 to 75 ℃, particularly preferably 35 to 60 ℃, from the viewpoint of promoting the dispersion of the powder.

The stirring speed during the stirring treatment is preferably 100 to 5000rpm, and particularly preferably 300 to 1000rpm. Within this range, the powder can be uniformly dispersed in the powder dispersion 300, and simultaneously, deterioration (aggregation, fibrillation, etc.) of the TFE-based polymer can be easily suppressed.

The flow pattern of the powder dispersion 300 during the stirring process is preferably an upward flow or an upward and downward circulation flow from the viewpoint of promoting redispersion of the sedimentation component of the powder dispersion 300.

When the dispersion-treated powder dispersion 300 is fed to the die coater 12 through the feed line 34, it is preferable to reduce the shear stress applied to the powder dispersion 300 and suppress the deterioration of the TFE-based polymer.

For example, the pressure (absolute value) applied to the powder dispersion 300 is preferably greater than 0MPa and not more than 0.1 MPa.

In addition, foreign matter should be removed from the feed liquid, and the pressure applied to the powder dispersion 300 when the powder dispersion 300 is passed through the filter 38 is also included in the shear stress.

The pore diameter of the filter 38 is preferably 50 to 250. Mu.m.

The fed powder dispersion 300 is discharged from the die coater 12 and applied to the surface of the fed base material layer 2 or the unit polymer layer 31 to form a wet film (liquid film).

As in the present embodiment, when the powder dispersion 300 is applied while the long substrate layer 2 is transported in a roll-to-roll manner, the productivity of the laminate 1 is improved.

In addition, the powder dispersion 300 may be applied by a die coating method using the die coater 12, and the following methods may be used: spray coating, roll coating, spin coating, gravure coating, micro gravure coating, gravure offset coating, doctor blading, touch coating, bar coating, jet meyer wire bar coating, slot die coating.

In the drying furnace D, the wet film is dried by removing the liquid dispersion medium from the wet film while maintaining the wet film at the volatilization temperature of the liquid dispersion medium.

The "drying temperature (volatilization temperature of the liquid dispersion medium)" is preferably a temperature of not less than the boiling point of the liquid dispersion medium, more preferably a temperature of +50℃. The drying temperature refers to the temperature of the atmosphere in the drying oven D. In this case, it is preferable to volatilize 50 mass% or more of the liquid dispersion medium contained in the powder dispersion 300.

Drying may be performed in a manner of 2 stages or more at different temperatures.

The drying may be performed under either normal pressure or reduced pressure.

The drying atmosphere may be any of an oxidizing gas atmosphere (oxygen, etc.), a reducing gas atmosphere (hydrogen, etc.), and an inert gas atmosphere (helium, neon, argon, nitrogen, etc.).

The drying temperature is preferably 50 to 280℃and more preferably 120 to 260 ℃. The drying time is preferably 0.1 to 30 minutes, more preferably 0.5 to 20 minutes.

If the wet film is dried under the above conditions, the laminate 1 can be suitably manufactured while maintaining high productivity.

The drying oven D may be an oven, a ventilation drying oven, or a device for radiating heat rays such as infrared rays.

In the firing furnace F, the TFE-based polymer is fired at a firing temperature exceeding the drying temperature to form the unit polymer layer 31. Since the dry film obtained by removing the liquid dispersion medium from the wet film is baked, the TFE polymer is fused in a state where the powders are closely packed, and a uniform unit polymer layer 31 is formed.

In addition, if the powder dispersion 300 contains a heat-fusible resin, the unit polymer layer 31 composed of a mixture of the TFE-based polymer and the heat-fusible resin is formed, and if the powder dispersion 300 contains a thermosetting resin, the unit polymer layer 31 composed of a cured product of the TFE-based polymer and the thermosetting resin is formed.

The firing temperature is preferably 300℃or higher, more preferably 330 to 380℃and still more preferably 350 to 370 ℃. Within this range, the fusion of the TFE-based polymer and the inhibition of the generation of hydrofluoric acid due to the decomposition of the TFE-based polymer are easily balanced. The firing temperature refers to the temperature of the atmosphere in the firing furnace D.

The firing time is preferably 30 seconds to 30 minutes, more preferably 1 minute to 30 seconds. Within this range, the melt-bonding of the TFE-based polymer and the productivity of the laminate 1 are easily balanced.

The firing may be performed under either normal pressure or reduced pressure.

The firing atmosphere may be any of an oxidizing gas atmosphere (oxygen, etc.), a reducing gas atmosphere (hydrogen, etc.), and an inert gas atmosphere (helium, neon, argon, nitrogen, etc.). However, from the viewpoint of suppressing the oxidative degradation of each of the base material layer 2 and the unit polymer layer 31 formed, a reducing gas atmosphere and an inert gas atmosphere are preferable as the firing atmosphere.

The oxygen concentration in the inert gas atmosphere is controlled to a low level, and the concentration thereof is preferably 100 to 500ppm, more preferably 200 to 300ppm.

The reducing gas atmosphere is preferably a mixed gas composed of an inert gas and a reducing gas, the oxygen concentration of which is suppressed to a low level, and more preferably a mixed gas composed of nitrogen and 0.1% by volume or more but less than 4% by volume of hydrogen, the oxygen concentration of which is suppressed to 100 to 500 ppm. The oxygen concentration in the gas mixture is more preferably 200 to 300ppm.

In addition, in the firing, in order to improve the smoothness of the surface of the unit polymer layer 31, the pressure may be applied with a heating plate, a heating roller, or the like.

The firing furnace F may be an oven, a ventilating drying furnace, a device for radiating heat rays such as infrared rays, or the like. In addition, the baking furnace F is preferably a device for radiating far infrared rays (far infrared ray furnace) from the viewpoint of being capable of baking in a short time and being relatively compact.

The heat source of the firing furnace F may be a combination of an infrared radiation source and a hot air supply source.

The effective wavelength band of far infrared rays is preferably 2 to 20. Mu.m, more preferably 3 to 7. Mu.m, from the viewpoint of promoting homogeneous fusion of TFE-based polymers.

In the drying furnace D and the firing furnace F, the heat source is preferably disposed above the inside of the furnace, so that the wet film and the dry film are directly heated. With the above configuration, preferential heat conduction on the base material layer 2 can be prevented. As a result, the wet film and the dry film are easily heated uniformly, and the obtained unit polymer layer 31 is less likely to cause defective firing.

When a plurality of unit polymer layers 31 are laminated in the above manner, a polymer layer 3 can be formed to obtain a laminate 1.

The absolute value of the linear expansion coefficient of the polymer layer of the laminate 1 is 50 ppm/DEG C or less, preferably 30 ppm/DEG C or less, and more preferably 25 ppm/DEG C or less. The absolute value of the linear expansion coefficient of the polymer layer of the laminate 1 is preferably 0.1 ppm/DEG C or more, more preferably 1 ppm/DEG C or more. In the case of the laminate 1 having the polymer layer having the linear expansion coefficient, warpage can be further suppressed, and thus a printed wiring board excellent in characteristics can be manufactured.

Such a laminate 1 can be obtained by appropriately setting the conditions of each unit polymer layer 31.

The unit polymer layers 31 preferably contain a TFE-based polymer as a main component. The TFE polymer content in each unit polymer layer 31 is preferably 80 mass% or more, and more preferably 90 mass% or more. The upper limit thereof is 100 mass%. By stacking a plurality of the unit polymer layers 31, a laminate which is not easily warped and in which only the polymer layer 3 composed mainly of a TFE-based polymer is formed on a large-area thin base material layer can be obtained.

The thickness of each unit polymer layer 31 is preferably 10 μm or less, more preferably 8 μm or less, and still more preferably 5 μm or less. The lower limit of the thickness of each unit polymer layer 31 is usually 0.5 μm. When the thickness of each unit polymer layer 31 is made small, the linear expansion coefficient of each unit polymer layer 31 itself becomes small. Therefore, it is considered that even if the multi-layer unit polymer 31 is laminated, the linear expansion coefficient of the entire polymer layer 3 can be suppressed to a low level.

In addition, the polymer layer 3 may be formed on only one surface of the base material layer 2, or may be formed on both surfaces of the base material layer 2.

Further, when the thickness of the unit polymer layer is 10 μm or less, the physical properties such as chemical resistance of the laminate are also easily improved. For example, in the laminate having the same thickness of the polymer layer 3, the laminate having the thickness of each unit polymer layer 31 of 10 μm or less is more excellent in etching resistance. Specifically, when the base material (copper foil or the like) of the laminate is removed with an etching solution, swelling of the polymer layer 3 is easily suppressed.

As described above, each unit polymer layer 31 is formed by fusing TFE-based polymers in a state where powders are closely packed. Therefore, each unit polymer layer 31 is considered to be in a compact state. When the next unit polymer layer 31 is formed on the surface of the unit polymer layer 31 in such a state, as shown in fig. 1, it is considered that minute spaces 32 between 2 unit polymer layers 31 are easily formed. The minute space 32 is considered to contain an atmosphere gas and a gaseous decomposition product of the dispersing agent at the time of coating the powder dispersion 300.

The existence of the minute space 32 is thought to alleviate the stress difference between the adjacent 2 unit polymer layers 31 caused by expansion and contraction of the TFE-based polymer, and the effect of reducing the linear expansion coefficient of the entire polymer layer 3 is more remarkable. That is, the minute space 32 serves to alleviate a stress difference generated between the adjacent 2 unit polymer layers 31, that is, to function as a buffer. Therefore, such minute spaces 32 are preferably present between the unit polymer layers.

The thickness of each unit polymer layer 31 may be the same or different. In different cases, it is preferable that the thickness of the unit polymer layer on the side closer to the substrate is larger than that on the side farther from the substrate. In the case where the polymer layer 31 is composed of 3 or more unit polymer layers, it is preferable that the polymer layer includes a combination of the following unit polymer layers: of the adjacent 2 unit polymer layers, the thickness of the unit polymer layer on the side closer to the base material layer is larger than that on the side farther from the base material layer. The polymer layers comprising the above combinations of unit polymer layers may also comprise combinations of adjacent 2 unit polymer layers having the same thickness.

Specifically, in the polymer layer 3 shown in fig. 1, among the adjacent 2 unit polymer layers 31, the thickness of the unit polymer layer 31 on the lower side (the side closer to the base material layer 2) is larger than the thickness of the unit polymer layer 31 on the upper side (the side farther from the base material layer 2). In other words, the thickness becomes smaller in the order of the unit polymer layer 311, the unit polymer layer 312, and the unit polymer layer 313. Thereby, since the warp rate per polymer layer 31 becomes smaller as it gets farther from the base material layer 2, the linear expansion coefficient of the polymer layer 3 as a whole can be suppressed at a lower level.

In this case, the thickness of the unit polymer layer 311 is preferably 7 to 9 μm, the thickness of the unit polymer layer 312 is preferably 5 to 7 μm, and the thickness of the unit polymer layer 313 is preferably 3 to 5 μm.

In addition, in the polymer layer 3 shown in fig. 1, the thickness of the unit polymer layer 312 may be the same as the thickness of the unit polymer layer 313.

The thickness of the polymer layer 3 is preferably greater than the thickness of the substrate layer 2. According to the manufacturing method of the present invention, such a laminate 1 having a thick polymer layer 3 can be easily obtained. The specific thickness of the polymer layer 3 is preferably 20 μm or more, more preferably 25 μm or more, and still more preferably 30 μm or more. The upper limit of the thickness of the polymer layer 3 is usually 100 μm.

The polymer layer 3 preferably contains a component different from the TFE-based polymer. When the unit polymer layer contains the above-mentioned component, the distribution density of the above-mentioned component contained in the unit polymer layer on the side closer to the base material is preferably lower than the distribution density of the above-mentioned component contained in the unit polymer layer on the side farther from the base material. The unit polymer layer on the side closer to the substrate may be free of the above components.

In the case where the polymer layer 3 is composed of 3 or more unit polymer layers, it is preferable that the polymer layer includes a combination of the following unit polymer layers: in the adjacent 2 unit polymer layers, the distribution density of the above-mentioned components contained in the unit polymer layer on the side closer to the base material layer is lower than the distribution density of the above-mentioned components contained in the unit polymer layer on the side farther from the base material layer. The polymer layers including the above combinations of unit polymer layers may further include combinations in which the distribution densities of the above components contained in adjacent 2 unit polymer layers are equal, or combinations in which none of the unit polymer layers contains the above components.

Specifically, in the polymer layer 3 shown in fig. 1, it is preferable that the upper unit polymer layer 31 (the side far from the base material layer 2) of the adjacent 2 unit polymer layers 31 contains a component different from that of the TFE-based polymer layer.

As a suitable embodiment in the case where the polymer layer 3 contains the above-described components, the following embodiments can be exemplified: the component is contained in each unit polymer layer 31, and the distribution density of the component contained in the unit polymer layer 31 on the side closer to the base material layer is lower than the distribution density of the component contained in the unit polymer layer 31 on the side farther from the base material in the adjacent 2 unit polymer layers.

Further, as a suitable embodiment, an embodiment in which an inorganic filler is contained as a different component can be exemplified. Examples of the inorganic filler include: boron nitride filler, beryllium oxide filler, silica filler, wollastonite filler, talc filler, cerium oxide filler, aluminum oxide filler, magnesium oxide filler, zinc oxide filler, titanium oxide filler, and the like. In the above embodiment, the inorganic filler contained in each unit polymer layer may be the same inorganic filler or may be different inorganic fillers. The shape and the content of the inorganic filler contained in each unit polymer layer may be the same or different.

For example, in the case where the polymer layer 3 of the laminate 1 shown in fig. 1 contains at least 2 types of irregularly shaped silica fillers selected from the group consisting of spherical silica fillers, scaly silica fillers and fibrous silica fillers, the shapes of the silica fillers contained in the unit polymer layers 311, 312 and 313 as the respective unit polymer layers may be scaly, spherical and fibrous, respectively, the fibers, scales, and spheres may be formed, or the spheres, scales, or fibers may be formed, or the scales, spheres, or scales may be formed, or the spheres, scales, or spheres may be formed, or the fibers, spheres, or fibers may be formed, or the spheres, fibers, or spheres may be formed.

In these preferred embodiments, the physical properties such as the linear expansion coefficient of the polymer layer of the laminate 1 can be more easily adjusted based on the physical properties of the components.

As a suitable component different from the TFE-based polymer, a component derived from a dispersant is exemplified.

The above components are preferably the dispersant itself or a decomposition product (decomposition residue) of the dispersant.

As a suitable component different from the TFE-based polymer, a component derived from an adhesive is exemplified.

The above-mentioned components are preferably the adhesive itself or a reactant of the adhesive (in the case where the adhesive is composed of a curable polymer, a cured product of the curable polymer, or the like).

The component different from the TFE-based polymer may be contained in the polymer layer 3 as particles, or may be contained in the polymer layer 3 by being compatible with the TFE-based polymer. In the former case, it is preferable that the particles be contained in a layer based on a TFE-based polymer.

For example, in the polymer layer 3 shown in fig. 1, each unit polymer layer 31 uses a TFE polymer as a matrix 31a, and particles 31b having a different composition from the TFE polymer are dispersed in the matrix 31 a.

The particles 31b are particles of a component different from the TFE-based polymer, and may be thermoplastic resin particles added to the powder dispersion 300 in addition to the dispersing agent (fluoropolymer) or decomposed particles thereof. Since the linear expansion coefficient of the particles 31b is higher than that of the TFE-based polymer, if the unit polymer layer 31 contains the particles 31b, the linear expansion coefficient thereof can be further reduced.

Further, as shown in fig. 1, in the adjacent 2 unit polymer layers 31, the amount of the particles 31b contained in the unit polymer layer 31 on the lower side (the side closer to the base material layer 2) is smaller than the amount of the particles 31b contained in the unit polymer layer 31 on the upper side (the side farther from the base material layer 2). In other words, the amount of the particles 31b contained in the unit polymer layer 31 sequentially increases in the order of the unit polymer layer 311, the unit polymer layer 312, and the unit polymer layer 313. Thereby, since the linear expansion coefficient of the unit polymer layer 31 becomes smaller as it gets farther from the base material layer 2, the linear expansion coefficient of the polymer layer 3 as a whole can be suppressed to a lower level.

In the case where the particles 31b are decomposed particles of the dispersant, the above-described structure may be formed when the unit polymer layers 31 are laminated. That is, when the polymer layer 3 is formed, the lower unit polymer layer 311 undergoes a heat history of 3 times of drying and firing, the middle unit polymer layer 312 undergoes a heat history of 2 times of drying and firing, and the upper unit polymer layer 313 undergoes a heat history of 1 time of drying and firing. The difference in the degree of decomposition of the dispersant occurs in the unit polymer layers 311 to 313 due to the difference in the heat history. This is considered to be an important cause of the formation of the above structure. Therefore, the above-described structure can be easily obtained by lamination of the unit polymer layers 31 as in the present invention.

For the same reason, when the

minute spaces

321 and 322 are formed in the laminate 3, the thickness (volume) of the minute space 321 tends to be larger than the thickness (volume) of the minute space 322 according to the difference in the amount of the gaseous decomposition product of the dispersant.

On the other hand, in the case where the particles 31b are thermoplastic resin particles, the above-described structure can be easily formed by adjusting the amount of the thermoplastic resin contained in the powder dispersion 300 used for each unit polymer layer 31.

The above-described structure may be actively obtained if the unit polymer layers 31 are formed under at least 1 different condition among the heating temperature (drying temperature or firing temperature), the heating time (drying time or firing time), and the heating atmosphere (drying atmosphere or firing atmosphere).

Since the laminate 1 is required to have a warp rate within the above range, the unit polymer layers 31 do not need to contain the particles 31b entirely, but only 1 layer (for example, only the unit polymer layers 313) or 2 layers (for example, the unit polymer layers 313 and 312) of the multilayered unit polymer layers 31 may contain the particles 31b, or the unit polymer layers 31 may not contain the particles 31b entirely. The polymer layer 3 having the above-described structure can be obtained by adjusting the molding conditions of each unit polymer layer 31.

In addition, when the manufacturing apparatus 100 shown in fig. 2 is used, the rotation direction of the roll 16 for winding up the base material layer 2 in which the unit polymer layer 311 is formed is clockwise, while the rotation direction of the roll 10 for winding up the base material layer 2 in which the unit polymer layer 312 is formed is counterclockwise. Further, the rotation direction of the roller 16 for winding up the base material layer 2 on which the unit polymer layer 313 is formed is clockwise. In this way, the rotation direction of the roll for winding up the base material layer 2 is reversed every time the unit polymer layer 31 is formed. Therefore, each time the unit polymer layer 31 is formed, the direction of the tensile force applied to the unit polymer layer 31 is reversed. This is also considered to contribute to the effect of reducing the warp curvature of the laminate 1.

The surface of the polymer layer 3 of the laminate 1 may be subjected to a surface treatment in order to reduce the linear expansion coefficient of the polymer layer 3 and to adjust the adhesiveness of the polymer layer 3.

The surface treatment may be: annealing treatment, corona discharge treatment, atmospheric pressure plasma treatment, vacuum plasma treatment, UV ozone treatment, excimer treatment, chemical etching, silane coupling treatment, and surface micro-roughening treatment.

The temperature, pressure and time of annealing treatment are preferably 120-180 ℃ and 0.005-0.015 MPa for 30-120 minutes in sequence.

Examples of the plasma irradiation device in the plasma treatment include: high-frequency induction type, capacitive coupling type electrode type, corona discharge electrode-plasma jet type, parallel plate type, remote plasma type, atmospheric pressure plasma type, ICP type high-density plasma type, and the like.

The gases used for plasma treatment include: oxygen, nitrogen, rare gas (argon, etc.), hydrogen, ammonia, etc., preferably rare gas and nitrogen.

Specific examples of the gas used for the plasma treatment include: argon gas; a mixture of hydrogen and nitrogen, and a mixture of hydrogen, nitrogen and argon.

The atmosphere in the plasma treatment is preferably an atmosphere in which the volume fraction of rare gas or nitrogen is 70% by volume or more, and more preferably an atmosphere in which the volume fraction of these gases is 100% by volume. Within this range, the arithmetic average roughness (Ra) of the surface of the polymer layer 3 is adjusted to 2.0 μm or less, and fine irregularities are easily formed on the surface of the polymer layer 3.

The laminate 1 of the present invention may be a multilayer laminate obtained by laminating 2 or more sheets of the polymer layer 3 as a bonding layer, or may be a multilayer laminate obtained by laminating other sheets or films. Examples of the other plate or film include: resin films, fiber-reinforced resin sheets, substrates such as prepregs as precursors thereof, and metal foils. The metal foil here is preferably the same metal foil (e.g., copper foil) as the base material layer 2.

The laminate 1 of the present invention is preferably a copper-clad laminate used for manufacturing a printed wiring board, particularly a flexible printed wiring board. When the copper foil portion of the copper-clad laminate is processed by etching or the like, a printed wiring board can be obtained.

The layer structure of the multilayer laminate may be: substrate/polymer layer 3/substrate layer 2, metal foil/polymer layer 3/substrate layer 2/polymer layer 3/metal foil. The term "metal foil/polymer layer 3/base material layer 2" means a layer structure in which the metal foil, polymer layer 3 and base material layer 2 are sequentially arranged in this order, and other layer structures are the same. For example, a multilayer laminate having a layer structure of metal foil/polymer layer 3/base material layer 2 can be produced by laminating a metal foil on the surface of polymer layer 3 of laminate 1 of the present invention.

As the base material, there may be mentioned: a heat-resistant resin film, a fiber-reinforced resin sheet, a laminate having a heat-resistant resin film layer, and a laminate having a fiber-reinforced resin layer. When a multilayer laminate for producing a flexible printed wiring board is produced using the laminate 1 of the present invention, a heat-resistant resin film is preferable as the substrate. The heat-resistant resin is a polymer compound having a melting temperature of 280 ℃ or higher or JIS C4003:2010 A polymer compound having a maximum continuous use temperature of 121 ℃ or higher, which is defined in (IEC 60085:2007).

The heat-resistant resin film is a film containing 1 or more heat-resistant resins, and may be a single-layer film or a multilayer film.

Examples of the heat-resistant resin include: polyimide (aromatic polyimide, etc.), polyarylate, polysulfone, polyarylsulfone (polyethersulfone, etc.), aromatic polyamide, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystal polyester.

The thickness of the heat-resistant resin film is preferably 0.5 to 100. Mu.m, more preferably 3 to 25. Mu.m, from the viewpoints of flaking and mechanical strength of the printed wiring board.

The prepreg is a sheet-like substrate obtained by impregnating a base material (short chips, woven fabric, etc.) of reinforcing fibers (glass fibers, carbon fibers, etc.) with a thermosetting resin or a thermoplastic resin.

As a method of lamination, a method of hot-pressing the laminate 1 of the present invention and a substrate is exemplified.

The pressing temperature when the substrate is a prepreg is preferably not higher than the melting temperature of the TFE-based polymer, and particularly preferably 160 to 220 ℃. Within this range, thermal degradation of the prepreg can be suppressed, and the polymer layer 3 can be firmly bonded to the prepreg.

The pressurizing temperature is preferably 310 to 400 ℃ when the substrate is a heat-resistant resin film. Within this range, thermal degradation of the heat-resistant resin film can be suppressed, and the polymer layer 3 and the heat-resistant resin film can be firmly bonded.

The hot pressing is preferably performed under a reduced pressure atmosphere, and particularly preferably performed under a vacuum of 20kPa or less. Within this range, air bubbles can be suppressed from being mixed in the interface between the polymer layer 3 and the substrate or the metal foil, and deterioration due to oxidation of the multilayer laminate can be suppressed.

In the hot pressing, it is preferable to raise the temperature after the vacuum degree is reached. Accordingly, the pressure bonding can be performed in a state before the polymer layer 3 is softened, that is, in a state before the polymer layer exhibits a certain level of fluidity and adhesion, and thus the generation of bubbles can be prevented.

The pressure during hot pressing is preferably 0.2MPa or more. The upper limit of the pressure is preferably 10MPa or less. Within this range, breakage of the substrate can be suppressed, and the polymer layer 3 can be firmly bonded to the substrate.

The multilayer laminate produced by using the laminate 1 of the present invention can be used for producing printed wiring boards as a flexible copper-clad laminate or a rigid copper-clad laminate.

For example, a printed wiring board can be manufactured by using a method of forming a conductor circuit having a predetermined pattern by etching or the like on the base material layer 2 of the laminate 1 of the present invention, or a method of forming a conductor circuit by plating (semi-additive method (SAP method), modified semi-additive method (MSAP method), or the like) on the laminate 1 of the present invention.

In the production of the printed wiring board, after the conductor circuit is formed, an interlayer insulating film may be formed on the conductor circuit, and the conductor circuit may be further formed on the interlayer insulating film. In addition, a solder resist or a cover film may be laminated on the conductor circuit. The interlayer insulating film, the solder resist, and the cover film may be formed of the powder dispersion 300, for example.

The laminate and the method for producing the laminate of the present invention have been described above, but the present invention is not limited to the configuration of the above embodiment.

For example, the laminate of the present invention may be added to the structure of the above embodiment, or may be replaced with any structure that performs the same function.

In the method for producing a laminate according to the present invention, any other process may be added to the structure of the above embodiment, or any process that performs the same function may be substituted.

The number of unit polymer layers 31 is not limited to 3, but may be 2 or 4 or more.

Further, at least one of the

minute spaces

321 and 322 may be omitted. For example, in the case where the minute space 321 is omitted, the unit polymer layer 312 may be formed under reduced pressure.

The powder dispersion 300 may be applied in a state where the base material layer 2 is fixed to the base material without being transported in a roll-to-roll manner.

Examples

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

1. Preparation of the ingredients

[ TFE-based Polymer ]

TFE-based polymer 1: a copolymer comprising TFE-based units, NAH-based units and PPVE-based units in this order of 97.9 mol%, 0.1 mol% and 2.0 mol% (melt temperature: 300 ℃ C., melt viscosity: 3X 10 at 380 ℃ C.) ⁵ Pa·s)

TFE-based polymer 2: a copolymer comprising TFE units and PPVE units in this order of 98.7 mol% and 1.3 mol% (melt viscosity at a melt temperature of 305℃and 380 ℃ C.: 3X 10) ⁵ Pa·s)

[ powder ]

Powder 1: powder of TFE-based polymer 1 having D50 of 2.6 μm and D90 of 7.1. Mu.m.

Powder 2: powder of TFE-based polymer 2 having D50 of 2.3 μm and D90 of 6.9. Mu.m

D50 and D90 were measured by dispersing the powder in water using a laser diffraction/scattering particle size distribution measuring apparatus (LA-920 measuring apparatus manufactured by horiba corporation).

[ dispersant ]

Fluoropolymer 1: sequentially comprising in order of 81 mol% and 19 mol% based on CH ₂ ＝C(CH ₃ )C(O)OCH ₂ CH ₂ (CF ₂ ) ₆ Units of F and based on CH ₂ ＝C(CH ₃ )C(O)O(CH ₂ CH ₂ O) ₂₃ Copolymers of H units (mass reduction at 150 ℃ C.: 70% and mass reduction at 350 ℃ C.: 90%)

[ adhesive ]

Polyimide 1: non-reactive thermoplastic polyimide (5% weight loss temperature: 300 ℃ C. Or higher, glass transition temperature: 260 ℃ C.)

2. Preparation of the Dispersion

(Dispersion 1)

47 parts by mass of N-methyl-2-pyrrolidone (NMP), 2.5 parts by mass of fluoropolymer 1, and 50 parts by mass of powder 1 were put into a pot, and then zirconia balls were put into the pot. Thereafter, the pot was rolled at 150rpm for 1 hour to disperse the powder 1 in NMP, thereby preparing a dispersion 1.

(Dispersion 2)

46.5 parts by mass of N-methyl-2-pyrrolidone (NMP), 2.5 parts by mass of fluoropolymer 1, 0.5 part by mass of polyimide 1, and 50 parts by mass of powder 1 were put into a pot, and then zirconia balls were put into the pot. Thereafter, the pot was rolled at 150rpm for 1 hour to disperse the powder 1 in NMP to prepare dispersion 2.

(Dispersion 3)

A dispersion 3 was produced in the same manner as in the dispersion 1, except that the powder 2 was used instead of the powder 1.

EXAMPLE 1 evaluation example of laminate production (one)

Examples 1 to 1

First, the dispersion 1 was applied by a bar coating method to the surface of a long copper foil (thickness: 18 μm) to form a wet film. Thereafter, the copper foil on which the wet film was formed was passed through a drying oven, and dried by heating at 120 ℃ for 5 minutes, to obtain a dry film. Thereafter, the dry film was heated at 380℃for 3 minutes in a nitrogen oven. Thereby, a 1 st unit polymer layer (thickness 5 μm) was formed on the surface of the copper foil. In addition, the heat sources of the drying furnace and the firing furnace are arranged above the inside of the furnace, so that the wet film and the dry film are directly heated.

Thereafter, in the same manner as described above, the operation of forming the unit polymer layer (thickness 5 μm) on the surface of the 1 st unit polymer layer was repeated 5 times, to produce the laminate 11 having the polymer layer (total thickness 30 μm).

Further, as a result of confirming the cross section of the laminate 11 by a Scanning Electron Microscope (SEM), it was confirmed that a minute space was present between 2 adjacent unit polymer layers. Further, it was confirmed that the particulate component different from the fluoropolymer 1 was present in each of the unit polymer layers, and the distribution density of the component contained in the unit polymer layer on the side closer to the copper foil was lower than the distribution density of the component contained in the unit polymer layer on the side farther from the base material.

Examples 1 to 2

Laminate 12 was produced in the same manner as in example 1-1, except that the thicknesses of the 1 st and 2 nd unit polymer layers in example 1-1 were set to 8 μm, the thicknesses of the 3 rd and 4 th unit polymer layers were set to 4 μm, and the thicknesses of the 5 th and 6 th unit polymer layers were set to 3 μm.

Examples 1 to 3

Laminate 13 was produced in the same manner as in example 1-1, except that dispersion 2 was used instead of dispersion 1 in forming the 1 st unit polymer layer in example 1-1.

Examples 1 to 4

Laminate 14 was produced in the same manner as in example 1-1, except that dispersion 3 was used instead of dispersion 1 in example 1-1.

Examples 1 to 5 (comparative examples)

Laminate 15 was produced in the same manner as in example 1-1, except that the polymer layer (thickness 30 μm) was formed in 1 operation.

Each laminate was evaluated.

< coefficient of linear expansion of laminate >)

Rectangular polymer layer test pieces 20mm long by 4mm wide were cut from the laminate. The test piece was annealed at 150℃for 30 minutes with a tension of 6mN applied in the longitudinal direction. Thereafter, the dimensional change rate of the test piece when the test piece was exposed to an atmosphere in which the temperature was raised from 30℃to 200℃at 2℃per minute was measured as the linear expansion coefficient (ppm/. Degree.C) of the laminate.

< peel Strength of laminate >

Rectangular (length 100mm, width 10 mm) test pieces were cut from the laminate. The position 50mm from one end of the test piece in the longitudinal direction was fixed, the copper foil and the polymer layer were peeled off from the one end of the test piece in the longitudinal direction at 90 ° from the one end of the test piece at a stretching speed of 50 mm/min, and the maximum load at this time was measured as the peel strength (N/cm) of the laminate.

The results are summarized in Table 1.

TABLE 1

EXAMPLE 2 evaluation example of laminate production (second example)

[ example 2-1]

A laminate 21 having a polymer layer (total thickness 24 μm) composed of 3 unit polymer layers was produced in the same manner as in example 1-1, except that the thickness of the unit polymer layer was set to 8 μm and the operation of forming the unit polymer layer was performed 3 times.

[ examples 2-2]

A laminate 22 having a polymer layer (total thickness 24 μm) composed of 2 unit polymer layers was produced in the same manner as in example 1-1, except that the thickness of the unit polymer layer was set to 12 μm and the operation of forming the unit polymer layer was performed 2 times.

The absolute value of the linear expansion coefficient of each laminate is 25 ppm/DEG C or less.

The copper foil of each laminate was removed by etching treatment with an acidic aqueous solution, and the thickness of the polymer layer after the etching treatment was measured. The thickness of the polymer film of the laminate 21 after the etching treatment was 26. Mu.m, and the thickness of the polymer film of the laminate 22 was 30. Mu.m.

Industrial applicability

The laminate of the present invention has excellent electrical characteristics and adhesion, and has a polymer layer firmly fixed to a base layer, and therefore can be used for processing into antenna parts, printed wiring boards, insulating layers for power semiconductors, parts for aircraft, parts for automobiles, and the like.

Further, the entire contents of the specification, claims, abstract and drawings of japanese patent application No. 2019-029014, japanese patent application No. 2019-075502, and japanese patent application No. 2019-144667, which are filed on even 21 in 2019 02 and 04 and on even 06, are cited as disclosure of the present specification.

Symbol description

1 … laminate, 2 … base layer, 3 … polymer layer, 31 (311 to 312) … unit polymer layer, 31a … matrix, 31b … particles, 32 (321 to 322) … mini space, 100 … manufacturing apparatus, 10 … roll, 12 … die coater, 16 … roll, 18 … guide roll, 20 … die backing roll, 22 … guide roll, 24 … guide roll, 26 … groove, 28 … stirring blade, 30 … stirring apparatus, 32 … ultrasonic apparatus, 34 … liquid feed line, 36 … pump, 38 … filter, D … drying oven, F … firing oven, 300 … powder dispersion.

Claims

1. A laminate comprising a long base layer and a polymer layer comprising a plurality of unit polymer layers containing a tetrafluoroethylene polymer, wherein the absolute value of the linear expansion coefficient of the polymer layer is 50 ppm/DEG C or less,

wherein the polymer layer comprises a combination of unit polymer layers of: of the adjacent 2 unit polymer layers, the thickness of the unit polymer layer on the side closer to the base material layer is larger than the thickness of the unit polymer layer on the side farther from the base material layer,

Wherein the polymer layers have minute spaces between 2 adjacent ones of the unit polymer layers.

2. The laminate of claim 1, wherein the thickness of the polymer layer is greater than the thickness of the substrate layer.

3. The laminate according to claim 1 or 2, wherein the thickness of the polymer layer is 20 μm or more.

4. The laminate according to claim 1, wherein each of the unit polymer layers has a thickness of 10 μm or less.

5. The laminate of claim 1, wherein the substrate layer has a thickness of less than 20 μm.

6. The laminate of claim 1, wherein the polymer layer comprises a combination of unit polymer layers of: and adjacent 2 unit polymer layers each containing a different component from the tetrafluoroethylene polymer, wherein the distribution density of the different component contained in the unit polymer layer on the side closer to the base material layer is lower than the distribution density of the different component contained in the unit polymer layer on the side farther from the base material layer in the adjacent 2 unit polymer layers.

7. The laminate of claim 1, wherein the substrate layer is a metal foil.

8. The laminate according to claim 1, wherein the tetrafluoroethylene polymer is a polymer having an oxygen-containing polar group.

9. The method for producing a laminate according to claim 1, wherein a polymer layer comprising a plurality of unit polymer layers containing a tetrafluoroethylene polymer, each of which is formed of a powder dispersion containing a tetrafluoroethylene polymer powder, a dispersant or an adhesive, and a liquid dispersion medium, and an absolute value of a linear expansion coefficient of the polymer layer is 50ppm/°c or less are laminated on a long substrate layer.

10. The method according to claim 9, wherein the dispersant is a dispersant composed of a thermally decomposable fluoropolymer.

11. The production method according to claim 9 or 10, wherein the adhesive is polyamideimide or polyimide.

12. The manufacturing method according to claim 9, wherein each of the unit polymer layers is formed to a thickness of 10 μm or less.