WO2019230568A1 - Method for producing resin-clad metal foil, and resin-clad metal foil - Google Patents

Abstract

Provided are: a method for efficiently producing a resin-clad metal foil that has electrical characteristics and mechanical strength, is useful for producing printed circuit boards, comprises a highly homogenous resin layer containing a fluoropolymer, and is less likely to warp; and a resin-clad metal foil obtained by the method. The method is for producing a resin-clad metal foil having a resin layer on the surface of a metal foil. In the method for producing a resin-clad metal foil: the surface of the metal foil is coated with a powder dispersion liquid containing a solvent and a powder of a tetrafluoroethylene polymer, the polymer having a melting point of greater than 260°C and the temperature range at which the polymer exhibits a storage modulus of 0.1-5.0 MPa being at 260°C or lower; the metal foil is held at a temperature in the aforementioned temperature range; and the tetrafluoroethylene polymer is fired at a temperature exceeding the aforementioned temperature range to form a resin layer containing the tetrafluoroethylene polymer on the surface of the metal foil.

Description

Manufacturing method of metal foil with resin and metal foil with resin

The present invention relates to a method for producing a metal foil with resin and a metal foil with resin.

A resin-attached metal foil having an insulating resin layer on the surface of the metal foil is used as a printed board by processing the metal foil by etching or the like.
A printed circuit board used for high-frequency signal transmission is required to have excellent transmission characteristics. In order to improve the transmission characteristics, it is necessary to use a resin having a low relative dielectric constant and dielectric loss tangent as the insulating resin layer of the printed board. Fluoropolymers such as polytetrafluoroethylene (PTFE) are known as resins having a small relative dielectric constant and dielectric loss tangent.
As a material for forming a resin-coated metal foil having a resin layer containing a fluoropolymer, a powder dispersion in which a fluoropolymer powder is dispersed in a solvent has been proposed (see Patent Documents 1 and 2).
This powder dispersion has an advantage that various physical properties of the resulting resin-coated metal foil can be arbitrarily adjusted by blending another insulating resin and its varnish. In addition, this powder dispersion has an advantage that a resin-coated metal foil can be formed simply by coating and drying on the surface of the metal foil.

International Publication No. 2017/222027 International Publication No. 2016/159102

As a printed circuit board production mode, another substrate (prepreg, etc.) is laminated on the surface of a resin layer (insulating resin layer) containing a fluoropolymer, and a metal foil with resin is multilayered, or on the surface of the resin layer. There is an aspect in which another substrate (coverlay film or the like) is stacked and packaged. In this case, it is necessary to laminate the resin layer and another substrate without warping the resin-coated metal foil from the viewpoint of electrical characteristics and productivity of the printed board.
A method is known in which a resin-coated metal foil having a resin layer containing a fluoropolymer is subjected to surface treatment (plasma treatment, corona treatment, electron beam treatment, etc.) and the warpage of the resin layer is controlled. Separately, it is necessary to subject the metal foil with resin to surface treatment. In addition, the surface treatment may induce temporal modification or shape change of the resin layer, and may impair the homogeneity of the resin layer.

The present inventors diligently studied to produce a metal foil with a resin which has a highly homogeneous resin layer containing a fluoropolymer and hardly warps from a powder dispersion containing a powder of a fluoropolymer. As a result, it has been found that the resin-coated metal foil can be efficiently produced by adjusting the physical properties of the fluoropolymer and the production conditions of the resin-coated metal foil.
The present invention provides a metal foil with a resin having a highly homogeneous resin layer containing a fluoropolymer, which has electrical characteristics and mechanical strength, and is useful for manufacturing a printed circuit board, and hardly warps. A simple manufacturing method is provided.

The present invention has the following aspects.
[1] A method for producing a resin-attached metal foil having a resin layer on the surface of the metal foil, having a temperature range showing a storage elastic modulus of 0.1 to 5.0 MPa at 260 ° C. or lower and a melting point of 260 ° C. A powder dispersion containing super tetrafluoroethylene polymer powder and solvent is applied to the surface of the metal foil, the metal foil is held at a temperature within the temperature range, and tetrafluoro at a temperature above the temperature range. A method for producing a resin-coated metal foil, comprising baking a ethylene-based polymer to form a resin layer containing a tetrafluoroethylene-based polymer on the surface of the metal foil.

[2] The manufacturing method according to [1], wherein a warp rate of the metal foil with resin is 7% or less.
[3] The production method according to [1] or [2], wherein the thickness of the metal foil is 2 to 40 μm.
[4] The production method according to any one of [1] to [3], wherein the resin layer has a thickness of 1 to 50 μm.
[5] The production method according to any one of [1] to [4], wherein the thickness of the metal foil is 2 to 20 μm and the thickness of the resin layer is 1 μm or more and less than 10 μm.
[6] The production method according to any one of [1] to [5], wherein the powder has a volume-based cumulative 50% diameter of 0.05 to 6.0 μm.
[7] The tetrafluoroethylene-based polymer is a polymer comprising units based on tetrafluoroethylene and units based on at least one monomer selected from the group consisting of perfluoro (alkyl vinyl ether), hexafluoropropylene and fluoroalkylethylene. The production method according to any one of [1] to [6].

[8] The tetrafluoroethylene-based polymer has at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group, an epoxy group, an amide group, an amino group, and an isocyanate group, [1] to [7 ] The manufacturing method in any one of.
[9] The production method according to any one of [1] to [8], wherein the powder dispersion contains a polymeric polyol.
[10] The production method according to any one of [1] to [9], wherein the time for holding the metal foil in the temperature region is 30 seconds to 5 minutes.
[11] The manufacturing method according to any one of [1] to [10], wherein the atmosphere when holding the metal foil in the temperature region is an atmosphere containing oxygen gas.
[12] The production method according to any one of [1] to [11], wherein the temperature at which the tetrafluoroethylene-based polymer is baked is over 320 ° C.

[13] having a resin layer having a thickness of 1 μm or more and less than 10 μm on the surface of a metal foil having a thickness of 2 to 20 μm, wherein the resin layer is composed of units based on tetrafluoroethylene, perfluoro (alkyl vinyl ether), hexafluoropropylene, and A resin-coated metal foil comprising a polymer containing a unit based on at least one monomer selected from the group consisting of fluoroalkylethylenes and having a warpage rate of 7% or less.
[14] The metal foil with resin according to [13], wherein a warpage rate is 5% or less.
[15] A method for producing a printed circuit board, wherein a resin-coated metal foil is produced by the production method according to any one of [1] to [12], and a patterned circuit is formed by etching the metal foil.

According to the present invention, a metal foil with a resin having a high homogeneity resin layer containing a fluoropolymer, which has electrical characteristics and mechanical strength, and is useful for manufacturing a printed circuit board, is less likely to warp. Can be manufactured.

The following terms have the following meanings:
“D50 of powder” is a volume-based cumulative 50% diameter of powder determined by a laser diffraction / scattering method. That is, the particle size distribution of the powder is measured by the laser diffraction / scattering method, the cumulative curve is obtained with the total volume of the particle population as 100%, and the particle diameter is the point where the cumulative volume is 50% on the cumulative curve. .
“D90 of powder” is a volume-based cumulative 90% diameter of powder determined by a laser diffraction / scattering method. That is, the particle size distribution of the powder is measured by the laser diffraction / scattering method, the cumulative curve is obtained by setting the total volume of the particle population as 100%, and the particle diameter is the point where the cumulative volume is 90% on the cumulative curve. .
“Storage modulus of polymer” is a value measured based on ISO 6721-4: 1994 (JIS K7244-4: 1999).
“Polymer melting point” is a temperature corresponding to the maximum value of the melting peak measured by the differential scanning calorimetry (DSC) method.
“Wrapping ratio of metal foil with resin” is a measurement method defined in JIS C6471: 1995 (corresponding international standard IEC 249-1: 1982) for a test piece obtained by cutting a 180 mm square test piece from the metal foil with resin. Therefore, it is a measured value.
The “dimensional change rate of the metal foil with resin” is a value obtained as follows. A metal foil with resin is cut out at 150 mm square, holes are drilled at four corners using a 0.3 mm drill, and the positions of the holes are measured with a three-dimensional measuring instrument. The metal foil with resin is removed by etching and dried at 130 ° C. for 30 minutes. Measure the positions of the holes in the four corners with a three-dimensional measuring instrument. The dimensional change rate is calculated from the difference between the positions of the holes before and after etching.
“Arithmetic average roughness Ra” is an arithmetic average roughness measured based on JIS B0601: 2013 (ISO 4287: 1997, Amd. 1: 2009). The reference length lr (cut-off value λc) for the roughness curve when determining Ra was 0.8 mm.
“Heat resistant resin” means a polymer compound having a melting point of 280 ° C. or higher, or a polymer compound having a maximum continuous use temperature defined by JIS C4003: 2010 (IEC 60085: 2007) of 121 ° C. or higher.
“(Meth) acrylate” is a general term for acrylate and methacrylate.

In the production method of the present invention, a specific powder dispersion is applied to the surface of a metal foil, the metal foil is heated and held stepwise in a specific temperature atmosphere, and a specific tetrafluoroethylene polymer (hereinafter referred to as “TFE”). This is a method of forming a resin layer containing “based polymer” on the surface of the metal foil. The powder dispersion to be used is a dispersion in which TFE polymer powder is dispersed in the form of particles.

The reason why the metal foil with resin obtained by the present invention has a resin layer (hereinafter, also referred to as “F resin layer”) having excellent homogeneity and containing a TFE-based polymer is not necessarily clear. It is considered as follows.
The TFE-based polymer in the present invention has a predetermined meltability (having a melting point of more than 260 ° C.) and a predetermined elasticity (having a temperature range showing a storage elastic modulus of 0.1 to 5.0 MPa at 260 ° C. or less). And a certain elastic state is formed in the temperature range. When a dispersion containing such TFE polymer powder is applied to the surface of a metal foil and kept at a temperature within the above temperature range, the powder is not easily lost due to adhesiveness derived from elasticity, and is a densely packed film It is thought to form a state. In the present invention, after forming this coating state, the FFE layer is formed by firing the TFE polymer above the temperature range, so that a dense F resin layer with high homogeneity is formed as a result. It is considered that a metal foil with a resin which is difficult to warp was obtained.

The metal foil with resin in the present invention has an F resin layer on at least one surface of the metal foil. That is, the metal foil with resin may have an F resin layer only on one side of the metal foil, or may have an F resin layer on both sides of the metal foil.
The warp rate of the metal foil with resin is preferably 7% or less, and particularly preferably 5% or less. The lower limit of the warp rate is usually 0%. In this case, the handling property when processing the resin-coated metal foil into a printed board and the transmission characteristics of the obtained printed board are excellent.
The dimensional change rate of the resin-coated metal foil is preferably ± 1% or less, particularly preferably ± 0.2% or less. In this case, the printed board obtained from the resin-attached metal foil is easily multi-layered.

Examples of the material of the metal foil in the present invention include copper, copper alloy, stainless steel, nickel, nickel alloy (including 42 alloy), aluminum, aluminum alloy, titanium, titanium alloy and the like.
Examples of the metal foil include rolled copper foil and electrolytic copper foil. On the surface of the metal foil, a rust preventive layer (oxide film such as chromate), a heat-resistant layer or the like may be formed.

The ten-point average roughness of the surface of the metal foil is preferably 0.2 to 1.5 μm. In this case, the adhesiveness with the F resin layer becomes good, and a printed board having excellent transmission characteristics is easily obtained.
The thickness of metal foil should just be the thickness which can exhibit a function in the use of metal foil with a resin, 2 micrometers or more are preferable and 3 micrometers or more are especially preferable. Further, the thickness of the metal foil is preferably 40 μm or less, more preferably 20 μm or less, and particularly preferably 15 μm or less. Specific examples of the thickness of the metal foil include 2 to 40 μm, 2 to 20 μm, and 2 to 15 μm.
The surface of the metal foil may be treated with a silane coupling agent, the entire surface of the metal foil may be treated with a silane coupling agent, or a part of the surface of the metal foil is treated with a silane coupling agent. May be.

The F resin layer in the present invention is a resin layer containing a TFE polymer formed from the powder dispersion in the present invention by the production method of the present invention.

The water contact angle on the surface of the F resin layer is preferably 70 to 100 °, particularly preferably 70 to 90 °. If the said range is below an upper limit, the adhesiveness of F resin layer and another base material will be more excellent. If the said range is more than a minimum, the electrical property (low dielectric loss and low dielectric constant) of F resin layer will be more excellent.

The thickness of the F resin layer is preferably 1 μm or more, more preferably 2 μm or more, and particularly preferably 5 μm or more. The thickness of the F resin layer is preferably 50 μm or less, more preferably 15 μm or less, and particularly preferably less than 10 μm. In this range, it is easy to balance the transmission characteristics of the printed circuit board and the warpage suppression of the metal foil with resin. When the metal foil with resin has F resin layers on both surfaces of the metal foil, the composition and thickness of each F resin layer are preferably the same from the viewpoint of suppressing warpage of the metal foil with resin.
Specific examples of the thickness of the F resin layer include 1 to 50 μm, and examples include 1 to 15 μm, 1 to less than 10 μm, and 5 to 15 μm.
A preferred embodiment of the thickness of the metal foil and the thickness of the F resin layer in the present invention includes an embodiment in which the former is 2 to 20 μm and the latter is 1 μm or more and less than 10 μm. In the production method of the present invention, as described above, a dense F resin layer having high homogeneity is formed, and thus warpage can be suppressed even with such a thin metal foil with resin.

The relative dielectric constant of the F resin layer is preferably 2.0 to 3.5, more preferably 2.0 to 3.0. In this case, the resin-coated metal foil can be suitably used for a printed circuit board or the like that is excellent in both the electrical characteristics and adhesiveness of the F resin layer and requires a low dielectric constant.
Ra of the surface of the F resin layer is less than the thickness of the F resin layer, and is preferably 2.2 to 8 μm. In this range, it is easy to balance the adhesion and workability of other substrates.

The powder containing the TFE polymer in the present invention (hereinafter also referred to as “F powder”) may contain components other than the TFE polymer as long as the effects of the present invention are not impaired. The main component is preferable. 80 mass% or more is preferable and, as for content of TFE type polymer in F powder, 100 mass% is especially preferable.
The D50 of the F powder is preferably 0.05 to 6.0 μm, more preferably 0.1 to 3.0 μm, and particularly preferably 0.2 to 3.0 μm. In this range, the fluidity and dispersibility of the F powder are improved, and the electrical characteristics (low dielectric constant, etc.) and heat resistance of the TFE polymer in the resin-coated metal foil are most easily developed.
D90 of the F powder is preferably 8 μm or less, more preferably 6 μm or less, and particularly preferably 5 μm or less. The D90 of the powder is preferably 0.3 μm or more, particularly preferably 0.8 μm or more. In this range, the fluidity and dispersibility of the F powder are good, and the electric characteristics (low dielectric constant, etc.) and heat resistance of the F resin layer are most easily developed.
The bulk density of the F powder is preferably 0.05 g / mL or more, particularly preferably 0.08 to 0.5 g / mL.
The densely packed bulk density of the F powder is preferably 0.05 g / mL or more, particularly preferably 0.1 to 0.8 g / mL.

The method for producing F powder is not particularly limited, and the methods described in [0065] to [0069] of International Publication No. 2016/017801 can be employed. In addition, as long as desired powder is marketed, you may use F powder.
The TFE polymer in the present invention has a melting point of more than 260 ° C., preferably 260 to 320 ° C., particularly preferably 275 to 320 ° C., and most preferably 295 to 310 ° C. In this case, the TFE-based polymer is baked while maintaining the adhesiveness based on its elasticity, and it is easier to form a dense F resin layer.

The TFE polymer in the present invention has a temperature range showing a storage elastic modulus of 0.1 to 5.0 MPa at 260 ° C. or less. For example, the TFE polymer has a storage elastic modulus at 260 ° C. of 0.1 to 5.0 MPa.
The storage elastic modulus of the TFE polymer is preferably 0.2 to 4.4 MPa, and particularly preferably 0.5 to 3.0 MPa. Further, the temperature range in which the TFE polymer exhibits such storage elastic modulus is preferably in the range of 180 to 260 ° C., particularly preferably in the range of 200 to 260 ° C. In this case, in the temperature range, the F powder tends to effectively exhibit elasticity based on elasticity.

The TFE-based polymer is a polymer including units (TFE units) based on tetrafluoroethylene (TFE). The TFE-based polymer may be a TFE homopolymer or a copolymer of TFE and another monomer copolymerizable with TFE (hereinafter also referred to as a comonomer). The TFE-based polymer preferably contains 75 to 100 mol% of TFE units and 0 to 25 mol% of units based on a comonomer with respect to all units contained in the polymer.
TFE polymers include polytetrafluoroethylene (PTFE), copolymers of TFE and ethylene, copolymers of TFE and propylene, copolymers of TFE and perfluoro (alkyl vinyl ether) (PAVE), PFE, and TFE and hexafluoropropylene (HFP). Copolymer of HFE, copolymer of TFE and fluoroalkylethylene (FAE), copolymer of TFE and chlorotrifluoroethylene.

The _{PAVE, CF 2 = CFOCF 3,} 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 is mentioned.
The _{FAE, CH 2 = CH (CF} 2) 2 F, CH 2 = CH (CF 2) 3 F, CH 2 = CH (CF 2) 4 F, CH 2 = CF (CF 2) 3 H, CH 2 = CF (CF ₂ ) ₄ H.
As a preferable embodiment of the TFE-based polymer, a polymer including a TFE unit and a unit based on at least one monomer selected from the group consisting of PAVE, HFP, and FAE (hereinafter also referred to as “comonomer unit F”) is also included. It is done.

The polymer preferably contains 90 to 99 mol% of TFE units and 1 to 10 mol% of comonomer units F with respect to all units contained in the polymer. The polymer may be composed of only TFE units and comonomer units F, and may further contain other units.

As a preferred embodiment of the TFE polymer, at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group, an epoxy group, an amide group, an amino group and an isocyanate group (hereinafter also referred to as “functional group”). And a polymer containing TFE units (hereinafter also referred to as “polymer F1”).
The functional group may be contained in a unit in the TFE polymer, or may be contained in a terminal group of the main chain of the polymer F1. Examples of the latter polymer include polymers having a functional group as a terminal group derived from a polymerization initiator, a chain transfer agent, or the like.
As the polymer F1, a polymer including a unit having a functional group and a TFE unit is preferable. Further, the polymer F1 in this case preferably further includes other units, and particularly preferably includes the comonomer unit F.
As the functional group, a carbonyl group-containing group is preferable from the viewpoint of adhesion between the F resin layer and the metal foil. Examples of the carbonyl group-containing group include a carbonate group, a carboxy group, a haloformyl group, an alkoxycarbonyl group, an acid anhydride residue (—C (O) OC (O) —), a fatty acid residue, and the like. An anhydride residue is preferred.

The unit having a functional group is preferably a unit based on a monomer having a functional group, a unit based on a monomer having a carbonyl group-containing group, a unit based on a monomer having a hydroxy group, a unit based on a monomer having an epoxy group, and an isocyanate group A unit based on a monomer having a carbonyl group is more preferred, and a unit based on a monomer having a carbonyl group-containing group is particularly preferred.
As the monomer having a carbonyl group-containing group, a cyclic monomer having an acid anhydride residue, a monomer having a carboxy group, a vinyl ester or (meth) acrylate is preferable, and a cyclic monomer having an acid anhydride residue is particularly preferable.
As the cyclic monomer, itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride (also referred to as hymic anhydride, hereinafter also referred to as “NAH”) or maleic anhydride is preferable.
As the polymer F1, a polymer containing a functional group-containing unit, a TFE unit, and a PAVE unit or an HFP unit is preferable. Specific examples of the polymer F1 include the polymer (X) described in International Publication No. 2018/16644.

The proportion of TFE units in the polymer F1 is preferably 90 to 99 mol% of all units contained in the polymer F1.
The proportion of PAVE units in the polymer F1 is preferably 0.5 to 9.97 mol% of all units contained in the polymer F1.
The proportion of the units having a functional group in the polymer F1 is preferably 0.01 to 3 mol% of all units contained in the polymer F1.

The solvent in the present invention is a dispersion medium, a solvent compound that is liquid at 25 ° C. and does not react with F powder, has a lower boiling point than components other than the solvent contained in the powder dispersion, and is heated or the like. Solvent compounds that can be volatilized and removed are preferred.
Solvent compounds include water, alcohol (methanol, ethanol, isopropanol, etc.), nitrogen-containing compounds (N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, etc.), sulfur-containing compounds (dimethyl). Sulfoxide etc.), ether (diethyl ether, dioxane etc.), ester (ethyl lactate, ethyl acetate etc.), ketone (methyl ethyl ketone, methyl isopropyl ketone, cyclopentanone, cyclohexanone etc.), glycol ether (ethylene glycol monoisopropyl ether etc.), Examples include cellosolve (methyl cellosolve, ethyl cellosolve, etc.). A solvent compound may be used individually by 1 type, and may use 2 or more types together.
As the solvent compound, a solvent which does not volatilize instantaneously is preferable, a solvent compound having a boiling point of 80 to 275 ° C. is preferable, and a solvent compound having a boiling point of 125 to 250 ° C. is particularly preferable. In this range, the stability of the wet film (film containing a solvent) formed from the powder dispersion applied to the surface of the metal foil is high.
The solvent in the wet film is removed by the end of the baking of the TFE polymer. Dissipation of the solvent from the wet film may occur before reaching the temperature range showing the specific storage elastic modulus, or may occur while being held in the temperature range showing the specific storage elastic modulus. Good. In some cases, it may occur during firing of the TFE polymer. Preferably, the solvent in the above boiling range is used to diffuse at least a part of the solvent in the wet film in a state where the TFE-based polymer is held in the temperature region showing the specific storage elastic modulus.
The solvent compound is preferably an organic compound, such as cyclohexane (boiling point: 81 ° C.), 2-propanol (boiling point: 82 ° C.), 1-propanol (boiling point: 97 ° C.), 1-butanol (boiling point: 117 ° C.), 1- Methoxy-2-propanol (boiling point: 119 ° C), N-methylpyrrolidone (boiling point: 202 ° C), γ-butyrolactone (boiling point: 204 ° C), cyclohexanone (boiling point: 156 ° C) and cyclopentanone (boiling point: 131 ° C) N-methylpyrrolidone, γ-butyrolactone, cyclohexanone and cyclopentanone are particularly preferable.

The proportion of F powder in the powder dispersion is preferably 5 to 60% by mass, particularly preferably 35 to 50% by mass. In this range, it is easy to control the relative dielectric constant and dielectric loss tangent of the F resin layer low. Moreover, the uniform dispersion of the powder dispersion is high, and the mechanical strength of the F resin layer is excellent.
The proportion of the solvent in the powder dispersion is preferably 15 to 65% by mass, particularly preferably 25 to 50 parts by mass. In this range, the applicability of the powder dispersion is excellent, and poor appearance of the resin layer hardly occurs.

The powder dispersion in the present invention may contain other materials as long as the effects of the present invention are not impaired. Other materials may or may not dissolve in the powder dispersion.
The powder dispersant preferably contains a dispersant from the viewpoint of improving the dispersion stability of the powder dispersion. As the dispersant, a compound having a hydrophobic site and a hydrophilic site (surfactant) is particularly preferable from the viewpoint of imparting adhesiveness to the surface properties of the F resin layer.
When the powder dispersion contains a dispersant, the proportion of the dispersant in the powder dispersion is preferably from 0.1 to 30% by mass, particularly preferably from 5 to 10 parts by mass. In this range, it is easy to balance the uniform dispersibility of the F powder with the hydrophilicity and electrical characteristics of the surface of the F resin layer.

As the dispersant in the present invention, a polyol, polyoxyalkylene glycol, polycaprolactam and a polymer polyol are preferable, and a polymer polyol is more preferable.
The polymeric polyol refers to a polymer having a unit based on a monomer having a carbon-carbon unsaturated double bond and two or more hydroxyl groups. As the polymer polyol, polyvinyl alcohol, polyvinyl butyral and fluoropolyol are particularly preferable, and fluoropolyol is most preferable. However, the fluoropolyol is not a TFE-based polymer but a polymer having a hydroxyl group and a fluorine atom. The fluoropolyol may be modified by chemically modifying a part of the hydroxyl group.

The fluoropolyol is a (meth) acrylate having a polyfluoroalkyl group or a polyfluoroalkenyl group (hereinafter also referred to as “(meth) acrylate F”) and a (meth) acrylate having a polyoxyalkylene monool group (hereinafter, “ A copolymer (hereinafter also referred to as “dispersion polymer F”) with (meth) acrylate AO ”is particularly preferred.
(Meth) acrylate F is preferably a compound represented by the formula CH ₂ ═CR ¹ C (O) O—X ¹ —R ^F.
R ¹ represents a hydrogen atom or a methyl group.
X ¹ is — (CH ₂ ) ₂ —, — (CH ₂ ) ₃ —, — (CH ₂ ) ₄ —, — (CH ₂ ) ₂ NHC (O) —, — (CH ₂ ) ₃ NHC (O) — Or —CH ₂ CH (CH ₃ ) NHC (O) — is shown.
R ^F represents —OCF (CF ₃ ) (C (CF (CF ₃ ) ₂ ) (═C (CF ₃ ) ₂ ), —OC (CF ₃ ) (═C (CF (CF ₃ ) ₂ ) (CF ( CF ₃ ) ₂ ), —OCH (CH ₂ OCH ₂ CH ₂ (CF ₂ ) ₄ F) _2, —OCH (CH ₂ OCH ₂ CH ₂ (CF ₂ ) ₆ F) ₂ , — (CF ₂ ) ₄ F or -(CF ₂ ) ₆ F is shown.
(Meth) acrylate AO is preferably a compound represented by the formula CH ₂ ═CR ² C (O) O—Q ² —OH.
R ² represents a hydrogen atom or a methyl group.
Q ² represents — (CH ₂ ) _m (OCH ₂ CH ₂ ) _n —, — (CH ₂ ) _m (OCH ₂ CH (CH ₃ )) _n — or — (CH ₂ ) _m (OCH ₂ CH ₂ CH ₂ CH ₂ ) _n — (m represents an integer of 1 to 4, n represents an integer of 2 to 100, and n is preferably an integer of 2 to 20).

Specific examples of (meth) acrylate F include CH ₂ ═CHCOO (CH ₂ ) ₄ OCF (CF ₃ ) (C (CF (CF ₃ ) ₂ ) (= C (CF ₃ ) ₂ ), CH ₂ ═CHCOO ( _{CH 2) 4 OC (CF 3} ) (= C (CF (CF 3) 2) (CF (CF 3) 2), CH 2 = C (CH 3) COO (CH 2) 2 NHCOOCH (CH 2 OCH 2 CH _{2 (CF 2) 6 F)} 2, CH 2 = C (CH 3) COO (CH 2) 2 NHCOOCH (CH 2 OCH 2 CH 2 (CF 2) 4 F) 2, CH 2 = C (CH 3) COO _{(CH 2) 2 NHCOOCH (CH} 2 OCH 2 (CF 2) 6 F) 2, CH 2 = C (CH 3) COO (CH 2) 2 NHCOOCH (CH 2 OCH 2 (CF 2) 4 F) 2, CH _{2 = C (CH 3) COO (} CH 2) 3 NHCOOCH (CH 2 OCH 2 (CF 2) 6 F) 2, CH 2 = C (CH 3) COO (CH 2) 3 NHCOOCH (CH 2 OCH 2 (CF 2 ) ₄ F) ₂
As specific examples of (meth) acrylate AO, CH ₂ ═CHCOO (CH ₂ CH ₂ O) ₈ OH, CH ₂ ═CHCOO (CH ₂ CH ₂ O) ₁₀ OH, CH ₂ ═CHCOO (CH ₂ CH ₂ O) ₁₂ OH, CH ₂ = C (CH ₃ ) COO (CH ₂ CH (CH ₃ ) O) ₈ OH, CH ₂ = C (CH ₃ ) COO (CH ₂ CH (CH ₃ ) O) ₁₂ OH, CH ₂ = _{C (CH 3) COO (CH} 2 CH (CH 3) O) 16 OH and the like.

The ratio of units based on (meth) acrylate F to the total units contained in dispersion polymer F is preferably 20 to 60 mol%, particularly preferably 20 to 40 mol%.
The ratio of units based on (meth) acrylate AO to the total units contained in the dispersion polymer F is preferably 40 to 80 mol%, particularly preferably 60 to 80 mol%.
The dispersion polymer F may consist of only a unit based on (meth) acrylate AO and a unit based on (meth) acrylate AO, and may further include other units.
The fluorine content of the dispersion polymer F is preferably 10 to 45% by mass, particularly preferably 15 to 40% by mass.
The dispersion polymer F is preferably nonionic.
The weight average molecular weight of the dispersion polymer F is preferably 2000 to 80000, particularly preferably 6000 to 20000.

The powder dispersion in the present invention may further contain other materials other than the dispersant. Such other material may be a non-curable resin or a curable resin.
Examples of the non-curable resin include a heat-meltable resin and a non-meltable resin. Examples of the heat-meltable resin include thermoplastic polyimide. Examples of the non-meltable resin include a cured product of a curable resin.
Examples of the curable resin include a polymer having a reactive group, an oligomer having a reactive group, a low molecular compound, and a low molecular compound having a reactive group. Examples of the reactive group include a carbonyl group-containing group, a hydroxy group, an amino group, and an epoxy group.

Examples of the curable resin include epoxy resin, thermosetting polyimide, polyamic acid which is a polyimide precursor, thermosetting acrylic resin, phenol resin, thermosetting polyester resin, thermosetting polyolefin resin, thermosetting modified polyphenylene ether resin. And polyfunctional cyanate resin, polyfunctional maleimide-cyanate resin, polyfunctional maleimide resin, vinyl ester resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, and melamine-urea cocondensation resin. Among these, from the point useful for printed circuit board applications, the thermosetting resin is preferably a thermosetting polyimide, a polyimide precursor, an epoxy resin, a thermosetting acrylic resin, a bismaleimide resin, and a thermosetting polyphenylene ether resin. Epoxy resins and thermosetting polyphenylene ether resins are particularly preferred.

Specific examples of the epoxy resin include naphthalene type epoxy resin, cresol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, Cresol novolac epoxy resin, phenol novolac epoxy resin, alkylphenol novolac epoxy resin, aralkyl epoxy resin, biphenol epoxy resin, dicyclopentadiene epoxy resin, trishydroxyphenylmethane epoxy compound, phenol and phenolic hydroxyl group Epoxides of condensates with aromatic aldehydes, diglycidyl ethers of bisphenol, diglycidyl ethers of naphthalenediol, phenols Glycidyl etherified product, diglycidyl ethers of alcohols, triglycidyl isocyanurate.
As the bismaleimide resin, a resin composition (BT resin) using a bisphenol A type cyanate ester resin and a bismaleimide compound described in JP-A-7-70315, described in International Publication No. 2013/008667. And those described in the background art thereof.
The polyamic acid usually has a reactive group that can react with the functional group of the polymer F1.
Examples of the diamine and polycarboxylic dianhydride forming the polyamic acid include, for example, [0020] of Japanese Patent No. 5766125, [0019] of Japanese Patent No. 5766125, and [0055] of Japanese Patent Application Laid-Open No. 2012-145676. , [0057] and the like. Among them, aromatic diamines such as 4,4′-diaminodiphenyl ether and 2,2-bis [4- (4-aminophenoxy) phenyl] propane, pyromellitic dianhydride, 3,3 ′, 4,4 A polyamic acid comprising a combination with an aromatic polyvalent carboxylic dianhydride such as '-biphenyltetracarboxylic dianhydride and 3,3', 4,4'-benzophenonetetracarboxylic dianhydride is preferred.

Examples of the heat-meltable resin include thermoplastic resins such as thermoplastic polyimide, and heat-meltable cured products of curable resins.
As thermoplastic resins, polyester resin, polyolefin resin, styrene resin, polycarbonate, thermoplastic polyimide, polyarylate, polysulfone, polyarylsulfone, aromatic polyamide, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamide Examples include imide, liquid crystalline polyester, polyphenylene ether, and the like, and thermoplastic polyimide, liquid crystalline polyester, and polyphenylene ether are preferable.

Furthermore, as other materials that can be included in the powder dispersion in the present invention, binders, thixotropic agents, antifoaming agents, inorganic fillers, reactive alkoxysilanes, dehydrating agents, plasticizers, weathering agents, antioxidants , Heat stabilizers, lubricants, antistatic agents, brighteners, colorants, conductive agents, mold release agents, surface treatment agents, viscosity modifiers, flame retardants, and the like.
If the powder dispersion liquid in the present invention includes a binder, it is possible to suppress the omission (powder omission) of the F powder from the metal foil when forming the F resin layer. Examples of the binder include thermoplastic organic binders and thermosetting organic binders. The binder is preferably a compound that decomposes and volatilizes in the temperature range where the TFE polymer is fired. Examples of such a binder include an acrylic resin binder, a cellulose resin binder, a vinyl alcohol resin binder, a wax resin binder, and gelatin. A binder may be used individually by 1 type and may use 2 or more types together.

In the present invention, the powder dispersion is applied to the surface of the metal foil.
The coating method may be any method as long as it is a method for forming a stable wet film made of a powder dispersion on the surface of the metal foil after coating, spray method, roll coating method, spin coating method, gravure coating method, micro gravure coating method, Examples include a gravure offset method, a knife coat method, a kiss coat method, a bar coat method, a die coat method, a fountain Mayer bar method, and a slot die coat method.
In addition, before providing the metal foil to a temperature range where the TFE polymer exhibits a storage elastic modulus of 0.1 to 5.0 MPa, the state of the wet film is adjusted by heating the metal foil at a temperature lower than the temperature range. May be. In addition, preparation is performed to such an extent that a solvent does not volatilize completely, and it is usually performed to the extent that a 50 mass% or less solvent is volatilized.

In the present invention, after the powder dispersion is applied to the surface of the metal foil, the temperature within the temperature range where the TFE polymer exhibits a storage elastic modulus of 0.1 to 5.0 MPa (hereinafter also referred to as “holding temperature”). ) Hold the metal foil. The holding temperature indicates the temperature of the atmosphere.
Holding may be performed in one stage or in two or more stages at different temperatures.
Examples of the holding method include a method using an oven, a method using a ventilation drying furnace, and a method of irradiating heat rays such as infrared rays.
The atmosphere in holding may be in a state of normal pressure or reduced pressure. The holding atmosphere may be any of an oxidizing gas (oxygen gas, etc.) atmosphere, a reducing gas (hydrogen gas, etc.) atmosphere, and an inert gas (helium gas, neon gas, argon gas, nitrogen gas, etc.) atmosphere. It may be.
The atmosphere in the holding is preferably an atmosphere containing oxygen gas from the viewpoint of improving the adhesiveness of the F resin layer.
The oxygen gas concentration (volume basis) in the atmosphere containing oxygen gas is preferably 1 × 10 ² to 3 × 10 ⁵ ppm, particularly preferably 0.5 × 10 ³ to 1 × 10 ⁴ ppm. In this range, it is easy to balance the adhesion of the F resin layer and the suppression of oxidation of the metal foil.
The holding temperature is preferably 150 to 260 ° C, particularly preferably 200 to 260 ° C.
The holding time at the holding temperature is preferably 0.1 to 10 minutes, and particularly preferably 0.5 to 5 minutes.

In the present invention, the FFE layer is formed on the surface of the metal foil by firing the TFE polymer at a temperature exceeding the above temperature range (hereinafter also referred to as “calcination temperature”). The firing temperature indicates the temperature of the atmosphere. In the present invention, since the fusion of the TFE polymer proceeds in a state where the F powder is densely packed, an F resin layer having excellent homogeneity is formed, and the resin-coated metal foil is less likely to warp. If the powder dispersion contains a thermomeltable resin, an F resin layer made of a mixture of a TFE polymer and a soluble resin is formed. If the powder dispersion contains a thermosetting resin, the TFE polymer and a thermosetting resin are formed. An F resin layer made of a cured resin is formed.
Examples of the heating method include a method using an oven, a method using a ventilation drying furnace, and a method of irradiating heat rays such as infrared rays. In order to improve the smoothness of the surface of the F resin layer, pressurization may be performed with a heating plate, a heating roll, or the like. As a heating method, a method of irradiating far infrared rays is preferable because firing can be performed in a short time and the far infrared furnace is relatively compact. The heating method may be a combination of infrared heating and hot air heating.
The effective wavelength band of far infrared rays is preferably 2 to 20 μm, more preferably 3 to 7 μm from the viewpoint of promoting uniform fusion of the TFE polymer.

The atmosphere in firing may be any state under normal pressure or reduced pressure. The atmosphere in the firing is any of an oxidizing gas (oxygen gas, etc.) atmosphere, a reducing gas (hydrogen gas, etc.) atmosphere, and an inert gas (helium gas, neon gas, argon gas, nitrogen gas, etc.) atmosphere. From the viewpoint of suppressing oxidative deterioration of the metal foil and the F resin layer to be formed, a reducing gas atmosphere or an inert gas atmosphere is preferable.
The atmosphere in the firing is preferably a gas atmosphere composed of an inert gas and having a low oxygen gas concentration, and a gas atmosphere composed of nitrogen gas and having an oxygen gas concentration (volume basis) of less than 500 ppm is preferred. The oxygen gas concentration (volume basis) is particularly preferably 300 ppm or less. The oxygen gas concentration (volume basis) is usually 1 ppm or more.

The firing temperature is preferably more than 320 ° C., particularly preferably 330 to 380 ° C. In this case, the TFE polymer can more easily form a dense F resin layer.
The time for maintaining the firing temperature is preferably 30 seconds to 5 minutes, and more preferably 1 to 2 minutes.
When the resin layer in the metal foil with resin is a conventional insulating material (cured product of thermosetting resin such as polyimide), heating for a long time is required to cure the thermosetting resin. On the other hand, in the present invention, the resin layer can be formed by heating in a short time by fusing the TFE polymer. Moreover, when a powder dispersion liquid contains a thermosetting resin, a calcination temperature can be made low. Thus, the manufacturing method of this invention is a method with a small heat load to the metal foil at the time of forming a resin layer in metal foil with resin, and is a method with little damage to metal foil.

The metal foil with resin in the present invention may be subjected to a surface treatment on the surface of the F resin layer in order to control the linear expansion coefficient of the F resin layer or to further improve the adhesion of the F resin layer. .
Surface treatment methods for the surface of the F resin layer include annealing treatment, corona discharge treatment, atmospheric pressure plasma treatment, vacuum plasma treatment, UV ozone treatment, excimer treatment, chemical etching, silane coupling treatment, fine surface roughening treatment, etc. Is mentioned.
The temperature in the annealing treatment is preferably from 80 to 190 ° C, particularly preferably from 120 to 180 ° C.
The pressure in the annealing treatment is preferably 0.001 to 0.030 MPa, and particularly preferably 0.005 to 0.015 MPa.
The annealing treatment time is preferably 10 to 300 minutes, particularly preferably 30 to 120 minutes.
Examples of the plasma irradiation apparatus in the plasma treatment include a high frequency induction method, a capacitively coupled electrode method, a corona discharge electrode-plasma jet method, a parallel plate type, a remote plasma type, an atmospheric pressure plasma type, an ICP type high density plasma type, and the like. .
Examples of the gas used for the plasma treatment include oxygen gas, nitrogen gas, rare gas (such as argon), hydrogen gas, ammonia gas, and the like, and rare gas or nitrogen gas is preferable. Specific examples of the gas used for the plasma treatment include argon gas, a mixed gas of hydrogen gas and nitrogen gas, and a mixed gas of hydrogen gas, nitrogen gas and argon gas.
As an atmosphere in the plasma treatment, an atmosphere having a volume fraction of a rare gas or nitrogen gas of 70% by volume or more is preferable, and an atmosphere of 100% by volume is particularly preferable. Within this range, Ra on the surface of the F resin layer is adjusted to 2.0 μm or less, and fine irregularities are easily formed on the surface of the F resin layer.

The metal foil with resin obtained in the present invention can be easily laminated with another substrate because the surface of the F resin layer is excellent in homogeneity and hardly warps.
Examples of the other substrate include a heat resistant resin film, a prepreg as a precursor of a fiber reinforced resin plate, a laminate having a heat resistant resin film layer, and a laminate having a prepreg layer.
A prepreg is a sheet-like substrate obtained by impregnating a base material (tow, woven fabric, etc.) of a reinforcing fiber (glass fiber, carbon fiber, etc.) with a thermosetting resin or a thermoplastic resin.
The heat resistant resin film is a film including one or more kinds of heat resistant resins, and may be a single layer film or a multilayer film.
Examples of the heat resistant resin include polyimide, polyarylate, polysulfone, polyarylsulfone, aromatic polyamide, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, and liquid crystalline polyester.

Examples of the method of laminating another base material on the surface of the F resin layer of the resin-coated metal foil in the present invention include a method of hot pressing the resin-coated metal foil and another substrate.
When the other substrate is a prepreg, the press temperature is preferably not higher than the melting point of the TFE polymer, more preferably 120 to 300 ° C, and particularly preferably 160 to 220 ° C. In this range, the F resin layer and the prepreg can be firmly bonded while suppressing thermal degradation of the prepreg.
When the substrate is a heat resistant resin film, the pressing temperature is preferably 310 to 400 ° C. In this range, the F resin layer and the heat resistant resin film can be firmly bonded while suppressing the thermal deterioration of the heat resistant resin film.

The hot pressing is preferably performed under a reduced pressure atmosphere, and particularly preferably performed at a vacuum degree of 20 kPa or less. In this range, air bubbles can be prevented from entering the interfaces of the F resin layer, the substrate, and the metal foil in the laminate, and deterioration due to oxidation can be suppressed.
Moreover, it is preferable to raise the temperature after reaching the vacuum degree during hot pressing. If the temperature is raised before reaching the degree of vacuum, the F resin layer is compressed in a softened state, that is, in a state with a certain degree of fluidity and adhesion, which causes bubbles.
The pressure in the hot press is preferably 0.2 MPa or more. The upper limit of the pressure is preferably 10 MPa or less. In this range, the F resin layer and the substrate can be firmly adhered while suppressing breakage of the substrate.

The metal foil with resin and the laminate thereof in the present invention can be used as a flexible copper-clad laminate or a rigid copper-clad laminate for the production of printed boards.
For example, a method for processing a metal foil of a resin-coated metal foil in the present invention into a conductor circuit (pattern circuit) having a predetermined pattern by etching or the like, or an electroplating method (semi-additive method (SAP method) for resin-coated metal foil in the present invention. ), A modified semi-additive method (MSAP method, etc.)), a printed circuit board can be produced from the resin-coated metal foil in the present invention.
In manufacturing a printed circuit board, after forming a pattern circuit, an interlayer insulating film may be formed on the pattern circuit, and a pattern circuit may be further formed on the interlayer insulating film. The interlayer insulating film can be formed by, for example, the powder dispersion in the present invention.
In the production of a printed circuit board, a solder resist may be laminated on the pattern circuit. A solder resist can be formed with the powder dispersion liquid in this invention, for example.
In manufacturing a printed circuit board, a coverlay film may be laminated on the pattern circuit. The coverlay film can be formed by, for example, the powder dispersion in the present invention.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
Various measurement methods are shown below.

<Melting point of polymer>
Using a differential scanning calorimeter (Seiko Instruments, DSC-7020), the TFE polymer was heated at a rate of 10 ° C./min and measured.
<Storage modulus of polymer>
Based on ISO 6721-4: 1994 (JIS K7244-4: 1999), using a dynamic viscoelasticity measuring device (DMS6100, manufactured by SII Nanotechnology), frequency 10 Hz, static force 0.98 N, dynamic displacement 0 The temperature was increased from 20 ° C. at a rate of 2 ° C./min under the condition of 0.035%, and the storage elastic modulus at 260 ° C. was measured.
<D50 and D90 of powder>
Using a laser diffraction / scattering particle size distribution measuring device (LA-920 measuring instrument, manufactured by Horiba, Ltd.), the powder was dispersed in water and measured.

<Homogeneity of resin layer>
The resin layer irradiated with light was visually observed from above and evaluated according to the following criteria.
○: The pattern is not confirmed.
Δ: Yuzu skin pattern is confirmed.
X: The pattern of a yuzu skin is confirmed and resin omission is confirmed centering on an edge part.
<Curved ratio of metal foil with resin>
A 180 mm square test piece was cut out from the metal foil with resin, and the test piece was measured according to the measurement method defined in JIS C6471: 1995.
(Circle): The curvature rate of metal foil with resin is 5% or less.
(Triangle | delta): The curvature rate of metal foil with resin is more than 5% and 7% or less.
X: The curvature rate of the resin-attached metal foil is more than 7%.

[TFE polymer]
Polymer 1: a copolymer containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of units based on TFE, NAH, and PPVE in this order, and has a melting point of 300 ° C. A polymer having a storage elastic modulus at 260 ° C. of 1.1 MPa.
Polymer 2: A polymer containing 98 mol% and 2 mol% of units based on TFE and PPVE in this order, a melting point of 310 ° C, and a storage modulus at 260 ° C of 4.8 MPa.
Polymer 3: A copolymer having 82 mol% and 18 mol% of units based on TFE and HFP in this order, a melting point of 265 ° C., and a storage elastic modulus at 260 ° C. of 0.5 MPa.
Polymer 4: A polymer containing 99.5 mol% or more of units based on TFE, a melting point of over 320 ° C., and a storage elastic modulus at 260 ° C. of over 5.0 MPa.

[Dispersant]
Dispersant 1: A copolymer of an acrylate having a perfluoroalkenyl group, an acrylate having a polyoxyethylene group and an alcoholic hydroxyl group (nonionic surfactant).
[Metal foil]
Copper foil 1: Low-roughened copper foil having a thickness of 12 μm (10-point average roughness of the surface is 0.6 μm).

[powder]
Powder 1: Powder of polymer 1 having D50 of 1.7 μm and D90 of 3.8 μm (sparsely packed bulk density 0.269 g / mL, densely packed bulk density 0.315 g / mL).
Powder 2: Powder of polymer 2 having D50 of 2.4 μm and D90 of 5.5 μm.
Powder 3: Powder of polymer 3 having D50 of 3.1 μm and D90 of 5.9 μm.
Powder 4: Powder of polymer 4 having D50 of 0.3 μm and D90 of 0.6 μm.

[Example 1]
Dispersion 1 was prepared by mixing 50 parts by mass of powder 1, 5 parts by mass of dispersant 1, and 45 parts by mass of N-methylpyrrolidone.
Dispersion 1 is applied to the surface of copper foil 1 using a die coater, and the copper foil 1 is passed through a ventilation drying oven (atmosphere temperature: 260 ° C., atmosphere gas: nitrogen gas having an oxygen gas concentration of 8000 ppm) and held for 1 minute. Then, it is further passed through a far-infrared furnace (temperature: 340 ° C., gas: nitrogen gas having an oxygen gas concentration of less than 100 ppm) and held for 1 minute, and has a resin layer (thickness 5 μm) of polymer 1 on the surface of copper foil A copper foil with resin was obtained. The evaluation results regarding the homogeneity of the resin layer and the warpage rate of the metal foil with resin are shown in Table 1 below.

[Examples 2 to 5]
Except changing the atmosphere temperature of a powder and a ventilation drying furnace, it carried out similarly to Example 1, obtained the copper foil with resin, and evaluated each. The results are summarized in Table 1 below.

The production method of the present invention is a method suitable for production of a metal foil with resin having a highly homogeneous resin layer containing a fluoropolymer and hardly warping, and is useful for production of a printed circuit board or the like.
The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2018-104010 filed on May 30, 2018 are incorporated herein by reference as the disclosure of the specification of the present invention. It is.

Claims (15)

1. A process for producing a resin-coated metal foil having a resin layer on the surface of the metal foil, having a temperature region showing a storage elastic modulus of 0.1 to 5.0 MPa at 260 ° C. or less and having a melting point of more than 260 ° C. A powder dispersion containing a powder of fluoroethylene polymer and a solvent is applied to the surface of the metal foil, the metal foil is held at a temperature within the temperature range, and the tetrafluoroethylene polymer is further maintained at a temperature above the temperature range. A method for producing a metal foil with a resin, in which a resin layer containing a tetrafluoroethylene-based polymer is formed on the surface of the metal foil by baking the resin.
2. The manufacturing method according to claim 1, wherein the warp rate of the resin-attached metal foil is 7% or less.
3. The manufacturing method according to claim 1 or 2, wherein the thickness of the metal foil is 2 to 40 µm.
4. 4. The production method according to claim 1, wherein the resin layer has a thickness of 1 to 50 μm.
5. The manufacturing method according to any one of claims 1 to 4, wherein the thickness of the metal foil is 2 to 20 µm, and the thickness of the resin layer is 1 µm or more and less than 10 µm.
6. 6. The production method according to claim 1, wherein the powder has a volume-based cumulative 50% diameter of 0.05 to 6.0 μm.
7. The tetrafluoroethylene-based polymer is a polymer comprising units based on tetrafluoroethylene and units based on at least one monomer selected from the group consisting of perfluoro (alkyl vinyl ether), hexafluoropropylene and fluoroalkylethylene. Item 7. The production method according to any one of Items 1 to 6.
8. The tetrafluoroethylene-based polymer has at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group, an epoxy group, an amide group, an amino group, and an isocyanate group. The production method according to item.
9. The production method according to any one of claims 1 to 8, wherein the powder dispersion contains a polymeric polyol.
10. The production method according to any one of claims 1 to 9, wherein a time for holding the metal foil in the temperature region is 30 seconds to 5 minutes.
11. The manufacturing method according to any one of claims 1 to 10, wherein the atmosphere when holding the metal foil in the temperature region is an atmosphere containing oxygen gas.
12. The production method according to any one of claims 1 to 11, wherein a temperature at which the tetrafluoroethylene-based polymer is calcined is more than 320 ° C.
13. A metal foil having a thickness of 2 to 20 μm has a resin layer with a thickness of 1 μm or more and less than 10 μm, and the resin layer is composed of units based on tetrafluoroethylene, perfluoro (alkyl vinyl ether), hexafluoropropylene and fluoroalkylethylene. A resin-attached metal foil comprising a polymer containing a unit based on at least one monomer selected from the group consisting of: and a warpage rate of 7% or less.
14. The metal foil with a resin according to claim 13, wherein the warpage rate is 5% or less.
15. A method for producing a printed circuit board, wherein a metal foil with resin is produced by the production method according to any one of claims 1 to 12, and the metal foil is etched to form a pattern circuit.