Fluororesin sheet material and laminate containing the same

Abstract

To provide a fluororesin sheet-like material excellent in adhesive properties with a metal layer even in the case of adhesion at a temperature below a melting point of fluororesin.SOLUTION: A fluororesin sheet-like material satisfies at least one of the following (1) and (2) on at least one surface. (1) A maximum peak height (Rp) when a surface state is measured by an atomic force microscope is 30-150 nm. (2) A maximum valley depth (Rv) when the surface state is measured by the atomic force microscope is -30 to -120 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a fluororesin sheet material and a laminate containing the same. [Background technology]

[0002] To realize high-speed communication using next-generation information and communication (high-frequency 5G), printed circuit boards used in antennas and transmission lines are required to have low transmission loss characteristics. Against this backdrop, fluoropolymer materials (PTFE, PFA, etc.) with excellent electrical properties are attracting attention as insulating materials for printed circuit boards. On the other hand, fluoropolymer materials generally have poor adhesion to other materials, so surface modification technologies such as plasma treatment are used to improve adhesion (Patent Document 1, etc.).

[0003] Patent Document 1 describes a method for manufacturing a laminate in which both the inorganic layer surface and the fluororesin layer surface are surface-treated and then heat-compressed at a temperature above the melting point of the fluororesin, wherein the fluororesin layer is surface-treated by plasma treatment. It also describes a preferred range for the arithmetic mean roughness Ra of the surface-treated inorganic layer and the fluororesin layer, respectively.

[0004] Patent Document 2 describes a suitable range for the Ra of the resin layer on the side that adheres to the prepreg and the ten-point average roughness (Rz) of the metal layer in a resin-coated metal foil having a resin layer on the surface of the metal foil.

[0005] Patent Document 3 describes that by subjecting a fluororesin film to surface treatment and annealing treatment, and by setting the dimensional change rate and oxygen atom ratio of the fluororesin film within a specific range, defects during lamination between the fluororesin film and copper foil can be reduced, and a fluororesin film with excellent adhesion to copper foil can be obtained. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-181735 [Patent Document 2] International No. 2019 / 230569 [Patent Document 3] International No. 2022 / 158524 [Overview of the project] [Problems that the invention aims to solve]

[0007] This disclosure aims to provide a fluororesin sheet material that exhibits excellent adhesion to a metal layer even when bonded at a temperature below the melting point of the fluororesin. [Means for solving the problem]

[0008] This disclosure provides a fluororesin sheet material that satisfies at least one of the following conditions (1) and (2) on at least one of its surfaces. (1) The maximum peak height (Rp) when the surface condition is measured by atomic force microscopy is 30-150 nm. (2) The maximum peak depth (Rv) when the surface condition is measured by atomic force microscopy is -30 to -120 nm

[0009] It is preferable that the material is a fluororesin sheet that satisfies both of the above conditions (1) and (2). The fluororesin is preferably tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

[0010] The present disclosure also relates to a laminate comprising a fluororesin sheet-like material that satisfies at least one of the following conditions (3) and (4) on at least one of the surfaces in contact with the metal layer, and a metal layer. (3) The maximum peak height (Rp) when the surface condition is measured by atomic force microscopy is 30-150 nm. (4) The maximum peak depth (Rv) when the surface condition is measured by atomic force microscopy is -30 to -120 nm

[0011] In the above laminate, it is preferable that the Rz of the surface of the metal layer that contacts the fluororesin sheet-like material is 1.5 μm or less.

[0012] Also, in the above laminate, it is preferable that the fluororesin sheet-like material satisfies both of the above (3) and (4). In this laminate, it is preferable that the Rz of the surface of the metal layer that contacts the fluororesin sheet-like material is 1.5 μm or less.

[0013] In the above laminate, it is preferable that the oxygen element ratio measured by a scanning X-ray photoelectron spectrometer (XPS) on the measurement surface of the fluororesin sheet-like material is 1.35 atomic% or more.

[0014] In the above laminate, it is preferable that the amount of the functional group (C=O) measured by a scanning X-ray photoelectron spectrometer (XPS) on the measurement surface of the fluororesin sheet-like material is 2.0% or more.

[0015] The present disclosure is a laminate including a fluororesin sheet-like material and a metal layer, where the surface on at least one surface that contacts the metal layer satisfies at least one of the following (5) and (6), and the oxygen element ratio measured by a scanning X-ray photoelectron spectrometer (XPS) on the measurement surface of the fluororesin sheet-like material is 1.35 atomic% or more. (5) When the surface state on at least one surface that contacts the metal layer is measured by an atomic force microscope in the state before laminating the fluororesin sheet-like material, the ratio (Rp(fluororesin sheet-like material) / Rp(metal foil)) of the maximum peak height (Rp) measured by the atomic force microscope on the surface of the metal foil on the surface that contacts the fluororesin sheet-like material in the state before laminating the metal foil is 50 to 250%. (6) The ratio (Rv(fluororesin sheet material) / Rp(metal foil)) between the absolute value of the maximum peak depth (Rv) measured by atomic force microscope on the surface state of at least one surface of the fluororesin sheet material in contact with the metal layer in the state before lamination of the metal foil and the maximum peak height (Rp) measured by atomic force microscope on the surface of the metal foil in contact with the fluororesin sheet material in the state before lamination of the metal foil is 50-200%.

[0016] The above laminate preferably satisfies both (5) and (6) above.

[0017] This disclosure relates to a laminate comprising a fluororesin sheet-like material and a metal layer, The laminate is also such that the surface of at least one of the surfaces in contact with the metal layer satisfies at least one of the following conditions (5) and (6), and the amount of functional groups (C=O) measured on the same surface of the fluororesin sheet material by scanning X-ray photoelectron spectroscopy (XPS) is 2.0% or more. (5) The ratio (Rp(fluororesin sheet material) / Rp(metal foil)) of the maximum peak height (Rp) measured by atomic force microscope on the surface state of at least one surface of the fluororesin sheet material in contact with the metal layer in the state before lamination of the metal foil, to the maximum peak height (Rp) measured by atomic force microscope on the surface of the metal foil in contact with the fluororesin sheet material in the state before lamination of the metal foil, is 50-250%. (6) The ratio (Rv(fluororesin sheet material) / Rp(metal foil)) between the absolute value of the maximum peak depth (Rv) measured by atomic force microscope on the surface state of at least one surface of the fluororesin sheet material in contact with the metal layer in the state before lamination of the metal foil and the maximum peak height (Rp) measured by atomic force microscope on the surface of the metal foil in contact with the fluororesin sheet material in the state before lamination of the metal foil is 50-200%.

[0018] The above laminate preferably satisfies both (5) and (6) above.

[0019] In the above laminate, it is preferable that the fluororesin is tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP). In the above laminate, it is preferable that the Rz of the surface of the metal layer that is in contact with the fluororesin sheet material is 1.5 μm or less.

[0020] In the above-described laminate, it is preferable that the adhesive strength between the measuring surface of the fluororesin sheet material and the metal layer is 0.5 N / cm or more. This disclosure also relates to a circuit board having the above-mentioned fluororesin sheet material or the above-mentioned laminate. [Effects of the Invention]

[0021] The fluororesin sheet material of this disclosure exhibits excellent adhesion to metal layers even when bonded at a temperature below the melting point of the fluororesin. [Modes for carrying out the invention]

[0022] The details of this disclosure are described below. Conventionally, in the surface modification of fluororesin sheets by plasma treatment, patents specifying the amount of oxygen element and the amount of specific functional groups as requirements for obtaining good adhesion are occasionally seen. However, for adhesion below the melting point, these requirements alone are insufficient to obtain satisfactory adhesion. Insufficient adhesion can lead to peeling and a decrease in the reliability of the substrate in subsequent processes.

[0023] This disclosure describes how, when surface-treating a fluororesin sheet material, improving the in-plane uniformity of the surface treatment results in good adhesion to a metal layer such as copper foil when bonded at a temperature below the melting point of the fluororesin. Conventionally, in order to improve adhesion, the Rz of the metal foil surface and the Ra and Rz of the fluororesin film surface have been evaluated. However, the present inventors focused on the maximum peak height (Rp) and maximum peak depth (Rv) of the fluororesin sheet-like material surface and revealed that when at least one of these is within a specific range, excellent adhesion to the metal layer can be achieved even when bonding is performed at a temperature below the melting point of the fluororesin. Furthermore, we found that when the relationship between the metal foil Rp and the Rp or Rv of the fluorine sheet material is specific, good adhesion is achieved, low transmission loss characteristics are maintained, and a laminate with excellent properties when used as a circuit board can be obtained.

[0024] (Fluororesin sheet material) The fluororesin sheet material of this disclosure is characterized in that the maximum peak height (Rp) of at least one surface state, when measured by atomic force microscopy, is 30 to 150 nm (1).

[0025] Because the maximum peak height (Rp) is between 30 and 150 nm, at bonding temperatures below the melting point of the fluororesin, the functional groups present on the surface of the metal foil and the fluororesin sheet material tend to be at an appropriate distance for bonding. As a result, adhesion to the metal foil is good, eliminating defects in appearance and peeling, and improving the reliability of the circuit board. By enabling bonding at temperatures below the melting point of fluororesin, warping of the metal foil is reduced, resulting in a better appearance. Furthermore, reduced peeling maintains surface smoothness, thus preserving low transmission loss characteristics. Lowering the bonding temperature also simplifies manufacturing and increases production efficiency.

[0026] Furthermore, the fluororesin sheet material of this disclosure is characterized in that the maximum peak depth (Rv) when the surface state of at least one surface is measured by atomic force microscopy is -30 to -120 nm (2).

[0027] Because the maximum peak depth (Rv) is between -30 and -120 nm and the maximum peak height (Rp), at bonding temperatures below the melting point of the fluororesin, the functional groups present on the surface of the metal foil and the fluororesin sheet material are at an appropriate distance for bonding. As a result, adhesion to the metal foil is good, eliminating defects in appearance and peeling, and improving the reliability of the circuit board. By enabling bonding at temperatures below the melting point of fluororesin, warping of the metal foil is reduced, resulting in a better appearance. Furthermore, reduced peeling maintains surface smoothness, thus preserving low transmission loss characteristics. Lowering the bonding temperature also simplifies manufacturing and increases production efficiency.

[0028] Here, the maximum mountain height (Rp) and maximum mountain depth (Rv) are determined by the following method. Using a scanning atomic force microscope (AFM5000, manufactured by Hitachi High-Tech Corporation), the surface Rp and surface Rv of a 10 μm square area on the surface of a fluororesin sheet material and a metal foil were measured under the conditions described below. Cantilever: SI-DF20 (tip radius < 10 nm, spring constant 15 N / m) Measurement mode: AC mode Scanning frequency: 1Hz Pixel count: 256 x 256

[0029] The fluororesin sheet material of this disclosure preferably has a maximum peak height (Rp) of 30 to 150 nm and a maximum peak depth (Rv) of -30 to -120 nm when the surface state of at least one surface is measured by atomic force microscopy (1) (2). Thus, by satisfying both conditions, the functional groups present on the surface of the metal foil and the fluororesin sheet material become even more suitable for bonding at bonding temperatures below the melting point of the fluororesin.

[0030] The maximum peak height (Rp) is preferably 40 to 120 nm, and more preferably 50 to 100 nm. Furthermore, the maximum peak depth (Rv) is preferably -40 to -100 nm, and more preferably -50 to -90 nm.

[0031] The fluororesin sheet material of this disclosure, which satisfies the physical properties described above, can be surface-treated by corona discharge, for example, by using nitrogen gas, argon, and carbon dioxide as inert gases, and by imparting functional groups with carbon dioxide, thereby improving the in-plane uniformity of the surface treatment. Details of the surface treatment method will be described later.

[0032] (Fluororesin) The fluororesin contained in the fluororesin sheet material of this disclosure is not particularly limited as long as it is a fluorine-containing resin, and known fluororesins can be used. In particular, tetrafluoroethylene (TFE)-(per)fluoro(alkyl vinyl ether) copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene (HFP) copolymer (FEP) is preferred.

[0033] (Per)fluoro(alkyl vinyl ether) (PAVE) may be a fluoroalkyl vinyl ether or a perfluoro(alkyl vinyl ether). In this disclosure, "perfluoro(alkyl vinyl ether)" means an alkyl vinyl ether that does not contain a CH bond. The PAVE that constitutes the above PAVE unit is given by the general formula (1): CF2 = CFO(CF2CFY 1 O) p -(CF2CF2CF2O) q -R f (1) (In the formula, Y 1 represents F or CF3, and R f represents a perfluoroalkyl group having 1 to 5 carbon atoms. p represents an integer from 0 to 5, and q represents an integer from 0 to 5. ) Monomers represented by general formula (2): CFX=CXOCF2OR 1 (2) (wherein X is the same or different and represents H, F or CF3, and R 1 represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms which may contain 1 to 2 atoms selected from the group consisting of H, Cl, Br and I, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms which may contain 1 to 2 atoms selected from the group consisting of H, Cl, Br and I). At least one selected from the group consisting of monomers represented by the formula can be mentioned.

[0034] Among them, as the above PAVE, a monomer represented by the general formula (1) is preferable, and at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether) (PPVE) is more preferable, and PPVE is even more preferable.

[0035] The content of the PAVE unit in the above TFE / PAVE copolymer is preferably 1.0 to 10% by mass, more preferably 2.0% by mass or more, further preferably 3.5% by mass or more, particularly preferably 4.0% by mass or more, most preferably 5.0% by mass or more, more preferably 8.0% by mass or less, further preferably 7.0% by mass or less, particularly preferably 6.5% by mass or less, and most preferably 6.0% by mass or less with respect to all monomer units. The amount of the above PAVE unit is 19 measured by the F-NMR method. The above TFE / PAVE copolymer may be a copolymer consisting only of TFE units and PAVE units.

[0036] When the above fluororesin sheet-like material is made of a TFE / PAVE copolymer, the melting point is preferably 280 to 322 ° C, more preferably 290 ° C or higher, and more preferably 315 ° C or lower.

[0037] When the above-mentioned fluororesin sheet material is made of a TFE / PAVE copolymer, the glass transition temperature (Tg) is preferably 70 to 110°C, more preferably 80°C or higher, and more preferably 100°C or lower. The above-mentioned glass transition temperature is a value obtained by dynamic viscoelasticity measurement.

[0038] The above TFE / HFP copolymer contains TFE units and HFP units. The TFE unit content in the above TFE / HFP copolymer is preferably 70% by mass or more, more preferably 85% by mass or more, preferably 99.8% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less, based on the total monomer units.

[0039] The above TFE / HFP copolymer preferably has a mass ratio (TFE / HFP) of 70-99 / 1-30 (mass%) of TFE units to HFP units. More preferably, the above mass ratio (TFE / HFP) is 85-95 / 5-15 (mass%).

[0040] The above TFE / HFP copolymer may further contain (per)fluoro(alkyl vinyl ether) (PAVE) units. Examples of PAVE units included in the above TFE / HFP copolymer are the same as those described above. The above TFE / PAVE copolymer does not contain HFP units, and therefore differs from the TFE / HFP / PAVE copolymer in this respect.

[0041] When the above TFE / HFP copolymer is a copolymer containing TFE units, HFP units, and PAVE units (hereinafter also referred to as "TFE / HFP / PAVE copolymer"), it is preferable that the mass ratio (TFE / HFP / PAVE) is 70-99.8 / 0.1-25 / 0.1-25 (mass%). It is more preferable that the above mass ratio (TFE / HFP / PAVE) is 75-98 / 1.0-15 / 1.0-10 (mass%). It is preferable that the above TFE / HFP / PAVE copolymer contains 1% by mass or more of HFP units and PAVE units in total with respect to the total monomer units.

[0042] The above TFE / HFP / PAVE copolymer preferably contains 25% by mass or less of HFP units relative to the total monomer units. More preferably, the HFP unit content is 20% by mass or less, even more preferably 18% by mass or less, and particularly preferably 15% by mass or less. Furthermore, the HFP unit content is preferably 0.1% by mass or more, more preferably 1% by mass or more, and particularly preferably 2% by mass or more. Note that the HFP unit content is... 19 It can be measured by the 1F-NMR method.

[0043] The PAVE unit content is more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 3% by mass or less. Furthermore, the PAVE unit content is preferably 0.1% by mass or more, and more preferably 1% by mass or more. Note that the PAVE unit content is 19 It can be measured by the 1F-NMR method.

[0044] The above TFE / PAVE copolymer and the above TFE / HFP copolymer may further contain other ethylenically active monomer (α) units. The other ethylenically active monomer (α) units are not particularly limited as long as they are monomer units copolymerizable with TFE, HFP, and PAVE, and include, for example, fluorinated ethylenically active monomers such as vinyl fluoride (VF), vinylidene fluoride (VdF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE), and non-fluorinated ethylenically active monomers such as ethylene, propylene, and alkyl vinyl ethers. The content of the other ethylenically active monomer (α) units is preferably 0 to 25% by mass, and more preferably 0.1 to 25% by mass.

[0045] When the above copolymer is a TFE / HFP / PAVE / other ethylenically active monomer (α) copolymer, the mass ratio (TFE / HFP / PAVE / other ethylenically active monomer (α)) is preferably 70-98 / 0.1-25 / 0.1-25 / 0.1-25 (mass%). The above TFE / HFP / PAVE / other ethylenically active monomer (α) copolymer preferably contains a total of 1% by mass or more of monomer units other than TFE units.

[0046] The melting point of the above TFE / HFP copolymer is preferably 200 to 322°C, more preferably above 200°C, even more preferably above 220°C, even more preferably below 300°C, and even more preferably below 280°C.

[0047] The glass transition temperature (Tg) of the above TFE / HFP copolymer is preferably 60 to 110°C, more preferably 65°C or higher, and more preferably 100°C or lower. The above glass transition temperature is a value obtained by dynamic viscoelasticity measurement.

[0048] The above-mentioned fluororesin can be produced by conventionally known methods, such as emulsion polymerization or suspension polymerization, by appropriately mixing monomers that form its constituent units and additives such as polymerization initiators. Among these, it is more preferable that it is obtained by emulsion polymerization.

[0049] The above-mentioned fluororesin preferably has a melt flow velocity of 1 to 50 g / 10 min at 372°C and a load of 49 N.

[0050] The above-mentioned fluororesin is preferable to have fewer functional groups, and in particular, a lower number of unstable end groups. Such fluororesins can be produced by adjusting the conditions during manufacturing (polymerization reaction), or by reducing the number of unstable end groups by performing fluorine gas treatment, heat treatment, or supercritical gas extraction treatment on the polymerized fluororesin. Fluorine gas treatment is preferred due to its excellent processing efficiency and the fact that some or all of the unstable end groups are converted to -CF3, which becomes a stable end group. Using a fluororesin with a reduced number of unstable end groups in this way is preferable because it lowers the electrostatic loss tangent and reduces the loss of electrical signals.

[0051] The number of unstable end groups mentioned above is not particularly limited, but for fluororesins with a main chain of 10 carbon atoms... 6 The value per unit is preferably 450 or less, more preferably 250 or less, even more preferably 100 or less, and most preferably 50 or less. Considering the effect of reducing dielectric loss tangent, it is preferably less than 10, and even more preferably 5 or less.

[0052] Examples of unstable end groups include functional groups such as -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), hydroxyl groups (-CH2OH, etc.), -CONH2, -COOR (R=CH3, etc.), -CF2H, and -OCOO-R (n-propyl carbonate, etc.).

[0053] The number of unstable end groups is measured specifically by the following method. First, the above-mentioned fluororesin is melted and compressed to produce a film with a thickness of 0.25 to 0.3 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the above-mentioned fluororesin, and a difference spectrum is obtained from the base spectrum, which is completely fluorinated and does not contain any functional groups. From the absorption peak of a specific functional group that appears in this difference spectrum, the number of carbon atoms in the above-mentioned fluororesin is calculated according to the following formula (A): 1 × 10 6 Calculate the number of unstable terminals per unit. N = I × K / t (A) I: Absorbance K: Correction coefficient t: Film thickness (mm)

[0054] For reference, Table 1 shows the absorption frequency, molar extinction coefficient, and correction factor for the unstable end groups used in this specification. The molar extinction coefficient was determined from FT-IR measurement data of a small molecule model compound.

[0055] [Table 1]

[0056] The above fluorination treatment can be carried out by bringing an unfluorinated fluororesin into contact with a fluorine-containing compound.

[0057] The fluorine-containing compounds mentioned above are not particularly limited, but include fluorine radical sources that generate fluorine radicals under fluorination treatment conditions. Examples of fluorine radical sources include F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and halogenated fluorides (e.g., IF5, ClF3).

[0058] The fluorine radical source, such as F2 gas, may be at 100% concentration, but it is preferable to mix it with an active gas and dilute it to 5-50% by mass before use, and more preferably to 15-30% by mass before use. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, but nitrogen gas is preferred from an economic standpoint.

[0059] The conditions for the above fluorination treatment are not particularly limited, and the fluororesin may be brought into contact with a fluorine-containing compound in a molten state. However, it is usually carried out at a temperature below the melting point of the fluororesin, preferably 20 to 220°C, and more preferably 100 to 200°C. The above fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 25 hours. The above fluorination treatment preferably involves bringing an unfluorinated fluororesin into contact with fluorine gas (F2 gas).

[0060] In this specification, the content of each monomer unit constituting the fluororesin can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer.

[0061] The fluororesin sheet material of this disclosure may contain components other than fluororesin. The components that can be contained are not particularly limited, but include silica particles, fillers such as glass short fibers, and thermosetting resins and thermoplastic resins that do not contain fluorine. The content of components other than fluororesin is not particularly limited, but is more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0062] Preferably, the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS) on at least one surface of the fluororesin sheet material of this disclosure is 1.35 atomic% or more. Furthermore, the oxygen element ratio is more preferably 1.5 atomic% or higher, even more preferably 1.8 atomic% or higher, and most preferably 2.0 atomic% or higher. Furthermore, the upper limit of the oxygen element ratio is not particularly limited, but is preferably 25 atomic% or less, more preferably 20 atomic% or less, and even more preferably 15 atomic% or less. If the oxygen element ratio is within the above range, it is advantageous in that the amount of functional groups contributing to adhesion is suitable.

[0063] Here, the oxygen element ratio is determined by the following method. (Method for measuring the oxygen element ratio) The oxygen element ratio on the surface of a fluororesin sheet material was measured using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.) under the conditions described below. Carbon, oxygen, fluorine, nitrogen, and silicon were detected, and the oxygen element ratio was determined from the composition ratio of C1s, O1s, F1s, N1s, and Si2p. Radiation source: Monochromatized AlKα Beam diameter: 100 μm X-ray output: 25W Measurement area: 1000μm x 300μm Pass energy: 23.5 eV Detection angle: 45°

[0064] Furthermore, it is preferable that the amount of functional groups (C=O) measured by scanning X-ray photoelectron spectroscopy (XPS) on at least one surface of the fluororesin sheet material of this disclosure is 2.0% or more. Furthermore, the amount of functional groups (C=O) is more preferably 3% or more. It is more preferable that the amount be 4% or more, and most preferable that it be 5% or more. Furthermore, the upper limit of the amount of the above-mentioned functional group (C=O) is not specifically limited, but is preferably 35% or less, more preferably 30% or less, and even more preferably 20% or less. If the amount of functional groups (C=O) falls within the above range, the amount of functional groups that contribute to adhesion will be optimal, which is advantageous in that it improves adhesion and durability.

[0065] Here, the amount of functional group (C=O) is determined by the following method. (Method for measuring the amount of functional groups (C=O)) The C1s narrow spectrum obtained by XPS was separated into five peaks using MultiPak software (ULVAC-PHI) under the conditions described below, and the ratio of these peaks was used to determine the peak width at half maximum (FMAX). The FMAX of peaks 1 to 4 were standardized to 1.83, and the FMAX of peak 5 was adjusted to match the shape of the original spectrum.

[0066] [Table 2]

[0067] The fluororesin sheet material of this disclosure preferably has a thickness of 1 to 100 μm. The upper limit is more preferably 50 μm or less, and even more preferably 30 μm or less. The lower limit is more preferably 3 μm or more, and even more preferably 5 μm or more.

[0068] The thickness of the above-mentioned fluororesin sheet material was measured using the reflection spectroscopy method of the film thickness measurement system F20 (manufactured by Filmetrics).

[0069] The arithmetic mean roughness (Ra) of the fluororesin sheet material of this disclosure at a 10 μm square is preferably 20 nm or less, more preferably 15 nm or less, and even more preferably 10 nm or less. The lower limit is not particularly limited, but is preferably 5 nm or more. If Ra is within the above range, it is preferable because the raw material itself has high smoothness, and the surface treatment can be applied more uniformly within the plane.

[0070] Furthermore, it is preferable that the difference between the oxygen element ratio of the fluororesin sheet material of this disclosure measured by scanning X-ray photoelectron spectroscopy (XPS / ESCA) on its surface and the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS / ESCA) after etching the fluororesin sheet material with an argon gas cluster ion beam at an incident angle of 45° in the depth direction for 15 minutes is 1.0 atomic% or more. Increasing the difference in the oxygen element ratio from the surface to the depth direction is preferable because it allows for obtaining a predetermined transmission loss while maintaining adhesion.

[0071] The oxygen element ratio after etching, as described above, represents the oxygen element ratio on the surface of the fluororesin sheet material before surface treatment. Therefore, the difference in the oxygen element ratio above represents the increase in the oxygen element ratio due to the surface treatment.

[0072] The above-mentioned fluororesin sheet material preferably has an adhesive strength greater than 30 N / m when two sheets of the same surface are bonded together at 200°C, either on one side or both sides. Having such an adhesive strength ensures that the fluororesin sheet material maintains excellent adhesion when used in combination with various other substrates, even after heat treatment. The above adhesive strength is more preferably greater than 50 N / m, and even more preferably greater than 100 N / m.

[0073] More specifically, the above adhesive strength was determined by overlapping the surface-treated surfaces of two fluororesin sheet materials and preparing a sample using heat pressing (200°C, 0.1 MPa, 60 s). This sample was then cut into 10 mm wide strips, and the peel strength was measured using a precision universal testing machine, Autograph AGS-X 100N (manufactured by Shimadzu Corporation). The unbonded portion of the strip sample was grasped by the upper and lower chucks of the Autograph and pulled at a speed of 100 mm per minute. The resulting value was defined as the adhesive strength.

[0074] The resin sheet material of this disclosure preferably has a dielectric loss tangent of less than 0.0015 at 10 GHz. This is preferable because it can keep the loss of electrical signals in the circuit low. The dielectric loss tangent is more preferably less than 0.0013, even more preferably less than 0.0010, and most preferably 0.00050 or less. Furthermore, assuming that signals are transmitted at higher frequencies and antennas are transmitted and received, the dielectric loss tangent at 40 GHz is preferably less than 0.0015, more preferably less than 0.0013, even more preferably less than 0.0010, and most preferably 0.00050 or less. In order to keep the dielectric loss tangent within the above range, it is preferable to use a resin with few unstable end groups, and more preferably to use a fluororesin that has undergone end fluorination treatment.

[0075] (Method for manufacturing fluororesin sheet material) The following details an example of a method for manufacturing the fluororesin sheet material of the present disclosure described above. However, the fluororesin sheet material of the present disclosure is not limited to those manufactured by the following methods. The fluororesin sheet material of this disclosure is not limited in terms of the molding method used to form the sheet material, but examples include a melt molding method such as extrusion molding, and a casting method in which a solution or dispersion containing fluororesin is prepared, applied to a substrate, and dried. Furthermore, the sheet may be stretched by a uniaxial stretching or biaxial stretching method, or it may be an unstretched sheet. Furthermore, the fluororesin sheet material may have a laminated structure that includes a fluororesin layer in part.

[0076] By performing surface treatment on one or both sides of the fluororesin sheet material obtained by this method under appropriate conditions, a fluororesin sheet material having the above-mentioned specific maximum peak height (Rp) and maximum peak depth (Rv) can be obtained.

[0077] The specific methods for surface modification described above are not limited, but some specific examples are detailed below. Surface modification of fluororesin sheet materials can be performed using conventional discharge treatments such as corona discharge treatment, glow discharge treatment, plasma discharge treatment, and sputtering treatment. Corona discharge treatment is particularly preferred. For example, surface free energy can be controlled by introducing oxygen gas, nitrogen gas, hydrogen gas, carbon dioxide gas, methane gas, ethylene gas, etc., into the discharge atmosphere. Alternatively, surface modification can be performed by exposing the surface to be modified to an atmosphere of an inert gas containing organic compounds, applying a high-frequency voltage between electrodes to induce a discharge, thereby generating active species on the surface, and then introducing functional groups of organic compounds or graft polymerization of polymerizable organic compounds. Examples of the above-mentioned inert gases include nitrogen gas, helium gas, and argon gas.

[0078] In particular, it is preferable to use nitrogen gas and argon gas in combination. Furthermore, it is preferable to use carbon dioxide gas. The ratio (volume) of nitrogen gas to argon gas is preferably 90 / 10 to 40 / 60, and more preferably 80 / 20 to 50 / 50. Although not certain, it is thought that adjusting the Ar ratio to a suitable range stabilizes the discharge and allows for more uniform surface modification. Furthermore, the amount of carbon dioxide is preferably 0.05 to 5% by volume, and more preferably 0.1 to 2% by volume, relative to the nitrogen gas / argon gas. Although not certain, it is thought that mixing an appropriate amount of carbon dioxide brings the functional groups on the surface of the fluororesin sheet material that contribute to adhesion into a suitable range.

[0079] Examples of organic compounds in the inert gas containing the organic compound include polymerizable or nonpolymerizable organic compounds containing oxygen atoms, such as vinyl esters like vinyl acetate and vinyl formate; acrylic acid esters like glycidyl methacrylate; ethers like vinyl ethyl ether, vinyl methyl ether, and glycidyl methyl ether; carboxylic acids like acetic acid and formic acid; alcohols like methyl alcohol, ethyl alcohol, phenol, and ethylene glycol; ketones like acetone and methyl ethyl ketone; carboxylic acid esters like ethyl acetate and ethyl formate; and acrylic acids like acrylic acid and methacrylic acid. Of these, vinyl esters, acrylic acid esters, and ketones are preferred because the modified surface is less likely to deactivate, i.e., has a long lifespan and is easy to handle, and vinyl acetate and glycidyl methacrylate are particularly preferred.

[0080] The concentration of the organic compound in the inert gas containing the organic compound varies depending on its type, the type of fluororesin to be surface-modified, etc., but is usually 0.1 to 3.0% by volume, preferably 0.1 to 1.0% by volume, more preferably 0.15 to 1.0% by volume, and even more preferably 0.30 to 1.0% by volume. The discharge conditions should be appropriately selected depending on the desired degree of surface modification, the type of fluororesin, and the type and concentration of organic compounds. Typically, the discharge rate is 50-1500 W·min / m². 2 Preferably 70 W·min / m 2 More than 1400W min / m 2 Discharge treatment will be performed within the following range. The processing temperature can be any temperature within the range of 0°C to 100°C. However, it is preferable to keep the temperature below 80°C due to concerns about stretching and wrinkling of the fluororesin sheet material. The degree of surface modification of the fluororesin sheet material is such that, considering the deactivation of oxygen elements on the surface due to heat during lamination with metal foil, etc., and the resulting decrease in adhesive strength, the oxygen element abundance observed by ESCA is preferably 1.5% or more, more preferably 1.75% or more, more preferably 2.0% or more, and even more preferably 2.5% or more. There is no specific upper limit, but considering the impact on productivity and other physical properties, it is preferable that it be 25.0% or less. While there are no specific requirements regarding the relative abundance of nitrogen, it is preferable that it be 0.1% or higher.

[0081] In the above surface modification process, the discharge rate, which indicates the output per unit area, should be 1.0 to 10 W / cm². 2 It is preferable to perform the discharge treatment within the specified range and adjust the gas concentration / line velocity ratio to a range of 0.005 to 0.05 L / m. The gas concentration / line velocity ratio referred to here is the ratio obtained by dividing the concentration of the organic compound in the organic compound-containing inert gas by the line velocity. If the flow rate is lower than 0.005 L / m, the space will not be sufficiently filled with gas relative to the transport speed, making it difficult for the activated gas to come into contact with the surface of the fluororesin sheet material, and the uniformity within the surface tends to decrease. If the flow rate is higher than 0.05 L / m, the surface will be overtreated and damaged, causing low molecular weight compounds to form on the surface, which will create a brittle layer and conversely lead to a decrease in adhesive strength. Therefore, it is presumed that the surface of the fluororesin sheet material will be treated more uniformly and the desired adhesive strength will be obtained, so treatment within this range is particularly preferable.

[0082] Furthermore, in the above method, it is preferable to perform a surface treatment on the fluororesin sheet material such that the difference between the oxygen element ratio measured on one or both sides of the surface state using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) and the oxygen element ratio measured after etching the fluororesin-containing layer with an argon gas cluster ion beam at an incident angle of 45° in the depth direction for 15 minutes, and then measuring it using a scanning X-ray photoelectron spectroscopy (XPS / ESCA), is 1.0 atomic% or more.

[0083] In the above method, surface treatment with a gas containing an organic compound is preferable because it can create localized irregularities on the resin surface, thereby reducing the coefficient of dynamic friction between the metal foil surface and the fluororesin sheet-like material surface to 0.4 or less. In other words, in addition to good adhesive strength, a low coefficient of dynamic friction can be achieved. This is preferable because it prevents winding defects when a long laminate is formed.

[0084] The fluororesin sheet material surface-treated by the above method may be annealed to remove residual stress beforehand. This reduces dimensional changes in the fluororesin sheet material due to heat from the pressure roll during the lamination process with metal foil to manufacture a laminate, allowing for bonding without wrinkles and thus suppressing defects in the appearance of the laminate. Since these heat treatments reduce the amount of oxygen on the surface of the fluororesin sheet material, it is preferable to perform surface modification under conditions that ensure a sufficient amount of surface oxygen is obtained when the fluororesin sheet material and metal foil are bonded together.

[0085] Annealing can be carried out by heat treatment. This heat treatment can be performed, for example, by passing the material through a heating furnace in a roll-to-roll manner. Heat treatment may also be performed in a batch-type drying oven.

[0086] The annealing temperature is preferably above the glass transition temperature of the fluororesin - 20°C and below the melting point, more preferably above the glass transition temperature of the fluororesin and below the melting point - 20°C, and even more preferably above the glass transition temperature of the fluororesin and below the melting point - 60°C. The annealing time is not particularly limited, but can be appropriately adjusted, for example, between 0.5 and 60 minutes.

[0087] When heating using the roll-to-roll method described above, the tension can be adjusted appropriately depending on the thickness of the fluororesin sheet material and the set temperature, but it is preferable to keep it at 20 N / m or less. Heating under these conditions is preferable because it allows for sufficient relaxation of internal stress and prevents dimensional changes.

[0088] The above surface treatment and annealing treatments are not limited to any particular order, nor are they limited to being performed only once; they may be performed two or more times.

[0089] (Laminated structure) The fluororesin sheet material of this disclosure is suitably used to form laminates with metals, resin substrates, and the like. The present disclosure also relates to a laminate comprising a fluororesin sheet-like material and a metal layer, wherein the maximum peak height (Rp) of at least one surface in contact with the metal layer is 30 to 150 nm when measured by atomic force microscopy. Furthermore, this disclosure also relates to a laminate comprising a metal layer and a fluororesin sheet-like material (4) having a maximum peak depth (Rv) of -30 to -120 nm when the surface state of at least one of the surfaces in contact with the metal layer is measured by atomic force microscopy.

[0090] In the case of such a laminate, the functional groups present on the surface of the metal foil and the fluororesin sheet material tend to be at an appropriate distance for bonding in the micro-region, resulting in improved adhesion and durability.

[0091] The laminate of the present disclosure is preferably configured such that a surface of the fluororesin sheet material having the above-mentioned properties is in contact with a metal layer. Furthermore, if the fluororesin sheet material is a laminate in which one surface is in contact with a metal layer, it is sufficient that the surface condition of that surface satisfies the above characteristics. Also, if the fluororesin sheet material is a laminate in which both surfaces are in contact with a metal layer, it is sufficient that the surface condition of at least one surface satisfies the above characteristics, and it is particularly preferable that the surface conditions of both surfaces satisfy the above characteristics.

[0092] Furthermore, it is preferable that the laminate includes a fluororesin sheet-like material and a metal layer, wherein the maximum peak height (Rp) of at least one surface in contact with the metal layer, measured by atomic force microscopy, is 30 to 150 nm (3) and the maximum peak depth (Rv) is -30 to -120 nm (4).

[0093] (metal layer) Examples of metal species constituting the metal layer in this disclosure include copper, aluminum, stainless steel, nickel, and gold. Alloys of these can be used. From the viewpoint of conductivity and circuit processability, copper foil is preferred.

[0094] The metal foil forming the above-mentioned metal layer preferably has an Rz of 1.5 μm or less on the surface in contact with the fluororesin sheet-like material described above. That is, the fluororesin sheet-like material of this disclosure has excellent adhesion to metal foils with a high degree of smoothness, such as an Rz of 1.5 μm or less. The metal foil only needs to have an Rz of 1.5 μm or less on at least the surface in contact with the fluororesin sheet-like material described above, and the Rz value of the other surface is not particularly limited.

[0095] The above Rz is the sum of the highest point (maximum peak height: Rp) and the deepest point (maximum valley depth: Rv). The above surface roughness is the ten-point average roughness specified in JIS-B0601. In this specification, the above Rz is the value measured using a surface roughness meter (product name: Surfcom 470A, manufactured by Tokyo Seiki Co., Ltd.) with a measurement length of 4 mm.

[0096] The thickness of the copper foil is not particularly limited, but is preferably in the range of 1 to 100 μm, more preferably in the range of 5 to 50 μm, and even more preferably in the range of 9 to 35 μm.

[0097] The copper foils mentioned above are not particularly limited; for example, rolled copper foil, electrolytic copper foil, etc., are examples.

[0098] The copper foil with an Rz of 1.5 μm or less is not particularly limited, and commercially available foils can be used. Examples of commercially available copper foils with an Rz of 1.5 μm or less include electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.).

[0099] The copper foil described above may be surface-treated to enhance its adhesive strength with the fluororesin sheet material of this disclosure.

[0100] The above surface treatment is not particularly limited, but may include silane coupling treatment, plasma treatment, corona treatment, UV treatment, electron beam treatment, etc. The reactive functional group of the silane coupling agent is not particularly limited, but from the viewpoint of adhesion to the fluororesin sheet material, it is preferable that it has at least one selected from amino groups, (meth)acrylic groups, mercapto groups, and epoxy groups at its terminal end. The hydrolyzable group is not particularly limited, but may include alkoxy groups such as methoxy groups and ethoxy groups. The copper foil used in this disclosure may have a rust-preventive layer (such as an oxide film like chromate), a heat-resistant layer, etc. formed on it.

[0101] Surface-treated copper foil having a surface treatment layer of the above-mentioned silane compound on the surface of the copper foil can be manufactured by preparing a solution containing the silane compound and then surface-treating the copper foil with this solution.

[0102] The copper foil described above may have a roughened layer on its surface, for example, to improve adhesion with the fluororesin sheet material. Furthermore, if the roughening treatment is likely to degrade the performance required in this disclosure, the amount of roughening particles electrodeposited onto the copper foil surface may be reduced or the roughening treatment may be omitted as necessary.

[0103] Between the copper foil and the surface treatment layer, one or more layers selected from the group consisting of a heat-resistant treatment layer (nickel plating, titanium plating, etc.), a rust-preventive treatment layer, and a chromate treatment layer may be provided from the viewpoint of improving various properties. These layers may be a single layer or multiple layers.

[0104] In the laminate of this disclosure, the maximum peak height (Rp) measured by the atomic force microscope is The range is 30-150 nm. It is preferable to use a fluororesin sheet material in which the oxygen element ratio of the surface of a plane with a maximum peak depth (Rv) of -30 to -120 nm is measured by scanning X-ray photoelectron spectroscopy (XPS) and is 1.35 atomic% or more. Furthermore, in the laminate of this disclosure, the maximum peak height (Rp) measured by the above atomic force microscope is The range is 30-150 nm. It is preferable to use a fluororesin sheet material in which the amount of functional groups (C=O) is 2.0 atomic% or more, as measured by scanning X-ray photoelectron spectroscopy (XPS) on the surface of a surface with a maximum peak depth (Rv) of -30 to -120 nm.

[0105] Furthermore, the present disclosure also relates to a laminate comprising a fluororesin sheet-like material and a metal layer, wherein, in the state prior to lamination of the fluororesin sheet-like material, the ratio (Rp(fluororesin sheet-like material) / Rp(metal foil)) of the maximum peak height (Rp) measured by atomic force microscope on the surface state prior to lamination of the fluororesin sheet-like material and the maximum peak height (Rp) measured by atomic force microscope on the surface of the metal foil in contact with the fluororesin sheet-like material is 50-250% (5), and the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS) on the same surface of the fluororesin sheet-like material is 1.35 atomic% or more.

[0106] The present disclosure relates to a laminate comprising a fluororesin sheet-like material and a metal layer, wherein, in the state prior to lamination of the fluororesin sheet-like material, the ratio (Rv(fluororesin sheet-like material) / Rp(metal foil)) of the absolute value of the maximum peak depth (Rv) when the surface state of at least one surface in contact with the metal layer is measured by atomic force microscopy is 50 to 200% (6), and the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS) on the same surface of the fluororesin sheet-like material is 1.35 atomic% or more.

[0107] Furthermore, the present disclosure relates to a laminate comprising a fluororesin sheet-like material and a metal layer, wherein the ratio (Rp(fluororesin sheet-like material) / Rp(metal foil)) between the maximum peak height (Rp) measured by atomic force microscope on the surface state of at least one surface of the fluororesin sheet-like material in contact with the metal layer before lamination, and the maximum peak height (Rp) measured by atomic force microscope on the surface of the metal foil in contact with the fluororesin sheet-like material before lamination, is 50-250% (5), and, Preferably, the laminate is such that the ratio (Rv(fluororesin sheet material) / Rp(metal foil)) between the absolute value of the maximum peak depth (Rv) when the surface condition of the same side of the fluororesin sheet material is measured by atomic force microscopy and the maximum peak height (Rp) when the surface of the metal foil in contact with the fluororesin sheet material is measured by atomic force microscopy is 50-200% (6), and the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS) on the surface of the same side of the fluororesin sheet material is 1.35 atomic% or more.

[0108] The present disclosure relates to a laminate comprising a fluororesin sheet-like material and a metal layer, wherein, in the state prior to lamination of the fluororesin sheet-like material, the ratio (Rp(fluororesin sheet-like material) / Rp(metal foil)) of the maximum peak height (Rp) measured by atomic force microscope on the surface state prior to lamination of the metal foil, on the surface of the metal foil in contact with the fluororesin sheet-like material, is 50-250% (5), and the amount of functional groups (C=O) measured by scanning X-ray photoelectron spectroscopy (XPS) on the same surface of the fluororesin sheet-like material is 2.0% or more.

[0109] This disclosure relates to a laminate comprising a fluororesin sheet-like material and a metal layer, wherein, in the state prior to lamination of the fluororesin sheet-like material, the ratio (Rv(fluororesin sheet-like material) / Rp(metal foil)) of the absolute value of the maximum peak depth (Rv) when the surface state of at least one surface in contact with the metal layer is measured by atomic force microscopy is 50 to 200% (6), and the amount of functional groups (C=O) measured on the same surface of the fluororesin sheet-like material by scanning X-ray photoelectron spectroscopy (XPS) is 2.0% or more.

[0110] Furthermore, the present disclosure relates to a laminate comprising a fluororesin sheet-like material and a metal layer, wherein the ratio (Rp(fluororesin sheet-like material) / Rp(metal foil)) between the maximum peak height (Rp) measured by atomic force microscope on the surface state of at least one surface of the fluororesin sheet-like material in contact with the metal layer before lamination, and the maximum peak height (Rp) measured by atomic force microscope on the surface of the metal foil in contact with the fluororesin sheet-like material before lamination, is 50-250% (5), and, Preferably, the laminate is such that the ratio (Rv(fluororesin sheet material) / Rp(metal foil)) between the absolute value of the maximum peak depth (Rv) when the surface condition of the same side of the fluororesin sheet material is measured by atomic force microscopy and the maximum peak height (Rp) when the surface of the metal foil in contact with the fluororesin sheet material is measured by atomic force microscopy is 50-200% (6), and the amount of functional groups (C=O) measured by scanning X-ray photoelectron spectroscopy (XPS) on the surface of the same side of the fluororesin sheet material is 2.0% or more.

[0111] The laminate of this disclosure is advantageous in that, by satisfying the above requirements, the functional groups present on the surface of the metal foil and the fluororesin sheet material in the micro-region tend to be at an appropriate distance for bonding, and the amount of functional groups contributing to adhesion is within a suitable range.

[0112] In the case of a laminate in which one surface of a fluororesin sheet material is in contact with a metal layer, it is sufficient that the above physical properties are satisfied on the contact surface. Furthermore, in the case of a laminate in which both surfaces of the fluororesin sheet material are in contact with a metal layer, it is sufficient that the above physical properties are satisfied on at least one surface, and it is particularly preferable that the above physical properties are satisfied on both surfaces.

[0113] In the laminate of the present disclosure, it is preferable that the adhesive strength between the measurement surface of the fluororesin sheet material and the metal layer is 0.5 N / cm or more. In other words, each of the laminates described above preferably has an adhesive strength of 0.5 N / cm or more at the surface where the fluororesin sheet material and the metal layer are in contact, provided that they satisfy all of the above physical properties. By satisfying the requirements described above, such adhesive strength can be achieved. By increasing the adhesive strength to 1 N / cm or higher, and even further to 2 N / cm or higher, the material can be suitably used as a copper-clad laminate or circuit board. Note that the adhesive strength referred to here means the adhesive strength measured under the conditions described in the examples.

[0114] (Layer structure of the laminate) The laminate of this disclosure may be a two-layer structure consisting of the fluororesin sheet material and the metal layer described above, or it may be a three-layer or more structure having two or more layers of either or both of these. Furthermore, it may be a three-layer or more structure having a layer (X) other than the metal layer and the fluororesin sheet material.

[0115] Examples of layers (X) other than the metal layer and the fluororesin sheet material include polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, and polystyrene. Examples of thermosetting resins include epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, and polybutadiene.

[0116] If the laminate of the present disclosure has the above layer (X), the layer configuration may be metal layer / fluororesin sheet-like material layer / layer (X). The laminate of the fluororesin sheet-like material layer / metal layer may be on one or both sides of layer (X).

[0117] (Method of manufacturing a laminate) The method for manufacturing the laminate of this disclosure is described in detail below. To obtain the laminate of this disclosure, it is preferable that the metal foil used as a material has high smoothness, and that the conditions in the process of bonding it with the fluororesin sheet material are adjusted.

[0118] When bonding the above-mentioned metal foil and fluororesin sheet material, heating is required. In the manufacture of the laminate according to this disclosure, it is preferable to set the heating temperature to a temperature below the melting point of the fluororesin. Specifically, it is preferable to set the temperature to 70 to 300°C. Preferably, it is preferable to set the temperature to 70 to 250°C, and even more preferably to 70 to 200°C. The fluororesin sheet material of this disclosure exhibits excellent adhesion to metal layers even when bonded at a temperature below the melting point of the fluororesin. The heat treatment process may involve a roll-to-roll lamination method, or a heat treatment method for a fluororesin coating applied to a metal foil. In other words, by using a low heating temperature, warping of the metal foil is suppressed, and the smoothness of the bonding surface is less likely to be impaired during the process of bonding the metal foil to the fluororesin sheet material, which is preferable. As a result, cosmetic defects and peeling are eliminated, improving the reliability of the circuit board.

[0119] In the manufacturing of the laminate according to this disclosure, the method for bonding the metal foil and the fluororesin sheet material is not particularly limited, but from the viewpoint of excellent manufacturing efficiency, a roll-to-roll lamination method is particularly preferred.

[0120] Manufactured by roll-to-roll is preferable because it reduces costs and allows for the production of long laminates. When manufacturing laminates in this way, the width of the laminate is not particularly limited, but it is preferable to have a width of 200 mm or more.

[0121] Furthermore, in the case of a laminate formed by bonding metal foil to the surface-treated surface of a fluororesin sheet material that has been surface-treated on only one side, surface modification may be performed separately on the untreated surface of the fluororesin sheet material to improve the adhesion between the laminate and other materials.

[0122] The laminate of this disclosure exhibits good adhesion between the metal layer and the fluororesin sheet-like material, making it resistant to peeling. Therefore, it has the advantage of low transmission loss because the surface smoothness of the adhesive surface can be maintained. For this reason, it can be suitably used in circuit boards and the like. In particular, it can be especially suitably used in circuit boards for high-frequency circuits. This disclosure is also a circuit board having the fluororesin sheet material or laminate described above.

[0123] In this disclosure, a high-frequency circuit includes not only circuits that transmit only high-frequency signals, but also circuits that have transmission lines for transmitting non-high-frequency signals on the same plane, such as transmission lines that convert high-frequency signals to low-frequency signals and output the generated low-frequency signals to the outside, and transmission lines that supply power for driving high-frequency compatible components. It can also be used as a circuit board for antennas, filters, etc. [Examples]

[0124] The present disclosure will now be described in detail based on the following examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0125] (Example 1) [Method for manufacturing fluororesin sheet material] As a fluororesin, PFA (TFE / PPVE copolymer, composition: TFE / PPVE = 95.8 / 4.2 (mass%), MFR: 15.8 g / 10 min, melting point: 305°C, number of unstable end groups: 10 carbon atoms in the main chain) 6 Using 297 units per batch, the material was fed into a 360°C extruder, extruded from a 1700mm wide T-die, taken up onto a metal cooling roll, and then wound onto a winding core to obtain a fluororesin sheet-like material with a width of 1300mm and a thickness of 12μm. [Surface treatment] Surface treatment is applied to both sides of the obtained roll-shaped fluororesin sheet material (while flowing an inert gas (nitrogen / Ar ratio 60 / 40) containing 0.50% vinyl acetate and 0.70% carbon dioxide near the discharge electrode and roll-shaped ground electrode of the corona discharge device, the fluororesin sheet material is continuously passed along the roll-shaped ground electrode, and the discharge rate is 200 W·min / m 2 Corona discharge was performed on both sides of a fluororesin sheet material, and a long roll of the fluororesin sheet material was wound into a roll to obtain a surface-treated sample. The sample was then evaluated.

[0126] (Example 2) The system uses 0.50% carbon dioxide by volume, with a nitrogen / Ar ratio of 70 / 30 for the inert gas, and a discharge rate of 80 W·min / m². 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0127] (Example 3) The system uses 0.20% carbon dioxide by volume, a nitrogen / Ar ratio of 60 / 40 inert gases, and a discharge rate of 70 W·min / m². 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0128] (Example 4) The system uses 0.30% carbon dioxide by volume, a 50 / 50 ratio of nitrogen / Ar inert gases, and a discharge rate of 80 W·min / m². 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0129] (Example 5) Carbon dioxide at 0.50% by volume, inert gas nitrogen / Ar ratio at 90 / 10, discharge rate at 300 W·min / m 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0130] (Example 6) The carbon dioxide gas is 0.30% by volume, the nitrogen / Ar ratio of the inert gas is 80 / 20, and the discharge rate is 70 W·min / m². 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0131] (Example 7) Carbon dioxide at 0.80% by volume, inert gas nitrogen / Ar ratio at 80 / 20, discharge rate at 200 W·min / m 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0132] (Example 8) As a fluororesin, fluorinated PFA1 (TFE / PPVE copolymer, composition: TFE / PPVE = 94.1 / 5.9 (mass%), MFR: 16.2 g / 10 min, melting point: 305°C, number of unstable end groups: undetectable (main chain carbon number: 10) 6Samples were obtained in the same manner as in Example 6, except that less than one sample was used per sample.

[0133] (Example 9) As a fluororesin, fluorinated PFA2 (TFE / PPVE copolymer, composition: TFE / PPVE = 96.1 / 3.9 (mass%), MFR: 16.2 g / 10 min, melting point: 305°C, number of unstable end groups: undetectable (main chain carbon number: 10) 6 Samples were obtained in the same manner as in Example 6, except that less than one sample was used per sample.

[0134] (Comparative Example 1) Using an inert gas (nitrogen) containing 0.50% vinyl acetate, the discharge rate was set to 100 W·min / m². 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0135] (Comparative Example 2) Using an inert gas containing 1.50% by volume of carbon dioxide and 0.50% by volume of vinyl acetate (nitrogen / Ar ratio 35 / 65), the discharge rate was 150 W·min / m². 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0136] (Comparative Example 3) Using an inert gas containing 0.50% vinyl acetate by volume (nitrogen / Ar ratio 30 / 70), the discharge rate was 40 W·min / m². 2 A sample was obtained that was surface-treated in the same manner as in Example 1, except that the same procedure was followed.

[0137] (Method for measuring maximum peak height (Rp) and maximum peak depth (Rv)) For each sheet and copper foil in the examples and comparative examples, the maximum peak height (Rp) and maximum peak depth (Rv) were determined by the following method. Furthermore, for the fluororesin sheet, the measurement was taken on the inner surface of the roll after surface treatment, and for the copper foil, the measurement was taken on the inner surface (unroughened surface) of the copper foil roll. Using a scanning atomic force microscope (AFM5000, manufactured by Hitachi High-Tech Corporation), the surface Rp and surface Rv of the surface-treated sheet surface and copper foil in a 10 μm square area were measured under the conditions described below. Cantilever: SI-DF20 (tip radius < 10 nm, spring constant 15 N / m) Measurement mode: AC mode Scanning frequency: 1Hz Pixel count: 256 x 256 The results are shown in Table 3.

[0138] (Method for measuring the oxygen element ratio) Using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.), the oxygen element ratio on the inner surface of a fluororesin sheet material roll after surface treatment was measured under the conditions described below. Carbon, oxygen, fluorine, nitrogen, and silicon were detected, and the oxygen element ratio was determined from the composition ratio of C1s, O1s, F1s, N1s, and Si2p. Radiation source: Monochromatized AlKα Beam diameter: 100 μm X-ray output: 25W Measurement area: 1000μm x 300μm Pass energy: 23.5 eV Detection angle: 45° The results are shown in the table.

[0139] (Method for measuring the amount of functional groups (C=O)) The C1s narrow spectrum obtained by the above XPS was separated into five peaks using MultiPak software (ULVAC-PHIE) under the conditions shown in Table 2 above, and the amount of functional group (C=O) was determined from the ratio of these peaks. The full width at half maximum (FMAX) of peaks 1 to 4 was standardized to 1.83, and the FMAX of peak 5 was adjusted to match the shape of the original spectrum. The results are shown in Table 3.

[0140] (Adhesion strength with copper foil) Using a fluororesin sheet material and electrolytic copper foil CF-T9DA-SV-18 (thickness 18μm / Rz 0.85μm) (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.), each was cut to a predetermined shape. The copper foil, fluororesin sheet material, and copper foil were stacked in that order, with the unroughened surface of the copper foil in contact with the fluororesin sheet material, and the inner surface of the fluororesin sheet material after surface treatment facing upwards. A laminate was obtained by heat pressing using a vacuum heat press machine (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 120°C, a preheating time of 120 seconds, a pressing pressure of 10 MPa, and a pressing time of 1200 seconds. The resulting laminate was cut to a width of 10 mm, and an aluminum plate was attached to the bottom surface with adhesive tape. Using a Tensilon universal testing machine (manufactured by Shimadzu Corporation), the peel strength of the copper foil was measured by gripping and pulling a 10 mm wide copper foil at a 90° angle to the plane of the laminate at a speed of 50 mm per minute, and the obtained value was defined as the adhesive strength. The measurement values ​​are the average of 15 measurements taken from a laminate created at 5 locations, 100 mm apart in the direction of travel, at three points (100 mm from the center and 100 mm from each end) of a roll-shaped fluororesin sheet material. The results are shown in Table 3.

[0141] (Adhesive strength after thermal shock test) A fluororesin sheet material, along with prepreg R-5680(J) (thickness 132 μm) (manufactured by Panasonic Corporation) as a prepreg material, and copper foils CF-T9DA-SV-18 (thickness 18 μm) (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.) and CF-V9S-SV-12 (thickness 12 μm) (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.) as copper foils, were used. Each material was cut into a predetermined shape, and the layers were stacked in the following order from top to bottom: CF-T9DA-SV-18 (unroughened surface facing down), fluororesin sheet material (inner surface of the roll after surface treatment facing up), prepreg R-5680(J), and CF-V9S-SV-12 (roughened bottom surface facing up). The layers were then hot-pressed under the following conditions: temperature 200°C, pressurization time 75 minutes, and pressure 3.0 MPa to obtain a laminate. The resulting laminate was subjected to a thermal shock test (low temperature exposure -55°C for 15 minutes, temperature transition time 5 minutes, high temperature exposure 125°C for 15 minutes) for 500 cycles. After that, it was cut into 10 mm wide strips, and an aluminum plate was attached to the CF-V9S-SV-12 side with adhesive tape. The adhesive strength was then measured using the same method as for measuring the adhesive strength with copper foil. The measurement values ​​are the average of 15 measurements taken from a laminate created at 5 locations, 100 mm apart in the direction of travel, at three points (100 mm from the center and 100 mm from each end) of a roll-shaped fluororesin sheet material. The results are shown in Table 3.

[0142] [Table 3]

[0143] The results in Table 3 show that the fluororesin sheet material of the example exhibited good adhesion at temperatures below the melting point of the fluororesin. [Industrial applicability]

[0144] The fluororesin sheet material of this disclosure can be suitably used as a circuit board.

Claims

1. A fluororesin sheet material having at least one of the following conditions (1) and (2) on at least one of its surfaces, and the amount of functional groups (C=O) measured on the same surface by scanning X-ray photoelectron spectroscopy (XPS) being 2.0% or more. (1) The maximum peak height (Rp) when the surface condition is measured by atomic force microscopy is 30 to 150 nm. (2) The maximum peak depth (Rv) when the surface condition is measured by atomic force microscopy is -30 to -120 nm

2. The fluororesin sheet material according to claim 1, satisfying both (1) and (2) above.

3. The fluororesin sheet material according to claim 2, wherein the fluororesin is tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

4. A method for manufacturing a laminate comprising a fluororesin sheet-like material and a metal layer, A method for manufacturing a laminate by bonding a fluororesin sheet-like material to a metal layer, wherein at least one of the surfaces of the metal layer in contact with the metal layer satisfies at least one of the following conditions (3) and (4), and the amount of functional groups (C=O) measured on the same surface by scanning X-ray photoelectron spectroscopy (XPS) is 2.0% or more. (3) The maximum peak height (Rp) when the surface condition is measured by atomic force microscopy is 30 to 150 nm. (4) The maximum peak depth (Rv) when the surface condition is measured by atomic force microscopy is -30 to -120 nm

5. The method for manufacturing a laminate according to claim 4, wherein the Rz of the surface of the metal layer in contact with the fluororesin sheet material is 1.5 μm or less.

6. A method for manufacturing a laminate according to claim 4, wherein the fluororesin sheet material satisfies both of (3) and (4) above.

7. The method for manufacturing a laminate according to claim 6, wherein the Rz of the surface of the metal layer in contact with the fluororesin sheet material is 1.5 μm or less.

8. A method for manufacturing a laminate according to any one of claims 4 to 7, wherein the oxygen element ratio measured on the measurement surface of the above-mentioned fluororesin sheet-like material by scanning X-ray photoelectron spectroscopy (XPS) is 1.35 atomic% or more.

9. A method for manufacturing a laminate comprising a fluororesin sheet-like material and a metal layer, A method for manufacturing a laminate, wherein the surface of at least one of the surfaces in contact with the metal layer satisfies at least one of the following (5) and (6), and the amount of functional groups (C=O) measured on the same surface of the fluororesin sheet material by scanning X-ray photoelectron spectroscopy (XPS) is 2.0% or more. (5) The ratio (Rp(fluororesin sheet material) / Rp(metal foil)) of the maximum peak height (Rp) measured by atomic force microscope on the surface state of at least one surface of the fluororesin sheet material in contact with the metal layer in the state before lamination of the metal foil, to the maximum peak height (Rp) measured by atomic force microscope on the surface of the metal foil in contact with the fluororesin sheet material in the state before lamination of the metal foil, is 50 to 250%. (6) The ratio (Rv(fluororesin sheet material) / Rp(metal foil)) between the absolute value of the maximum peak depth (Rv) when the surface state of at least one surface of the fluororesin sheet material in contact with the metal layer is measured by atomic force microscope in the state before lamination of the metal foil and the maximum peak height (Rp) when the surface of the metal foil in contact with the fluororesin sheet material is measured by atomic force microscope in the state before lamination of the metal foil is 50 to 200%.

10. A method for manufacturing a laminate according to claim 9, which satisfies both of (5) and (6) above.

11. The method for manufacturing a laminate according to claim 9, wherein the oxygen element ratio measured on the measurement surface of the fluororesin sheet-like material by scanning X-ray photoelectron spectroscopy (XPS) is 1.35 atomic% or more.

12. The method for manufacturing a laminate according to claim 11, satisfying both (5) and (6) above.

13. A method for producing a laminate according to any one of claims 9 to 12, wherein the fluororesin is tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

14. A method for manufacturing a laminate according to any one of claims 9 to 12, wherein the Rz of the surface of the metal layer in contact with the fluororesin sheet material is 1.5 μm or less.

15. A method for manufacturing a laminate according to any one of claims 9 to 12, wherein the adhesive strength between the measuring surface of the fluororesin sheet material and the metal layer is 0.5 N / cm or more.

16. A laminate obtained by the method for manufacturing a laminate according to claim 4 or claim 9.

17. The laminate according to claim 16, wherein a fluororesin sheet material and a metal layer are bonded together at a temperature below the melting point of the fluororesin.

18. A circuit board having a fluororesin sheet-like material according to any one of claims 1 to 3.

Images