Fluororesin sheet-like material and laminate containing same

Abstract

The present invention provides a fluororesin sheet-like material that has excellent adhesiveness to a metal layer even when bonded at a temperature equal to or lower than the melting point of a fluororesin. The fluororesin sheet-like material satisfies, on at least one surface thereof, at least one of the following (1) and (2): (1) The maximum peak height (Rp) when the surface state is measured by an atomic force microscope is 30-150 nm. (2) The maximum peak depth (Rv) when the surface state is measured by an atomic force microscope is -30 to 120 nm.

Description

Fluororesin sheet material and laminate containing same

[0001] The present disclosure relates to a fluororesin sheet material and a laminate including the same.

[0002] To realize high-speed communication by next-generation information communication (high-frequency 5G), printed circuit boards used in antennas and transmission paths are required to have low transmission loss characteristics. Against this background, fluororesin materials (PTFE, PFA, etc.) with excellent electrical properties have attracted attention as insulating materials for printed circuit boards. However, since fluororesin materials generally have poor adhesion to other materials, surface modification techniques such as plasma treatment are used to improve adhesion (see, for example, Patent Document 1).

[0003] Patent Document 1 describes a method for producing a laminate in which both the inorganic layer surface and the fluororesin layer surface are surface-treated and then thermocompression-bonded at a temperature equal to or higher than the melting point of the fluororesin, in which the fluororesin layer is surface-treated by plasma treatment. It also describes suitable ranges for the arithmetic mean roughness Ra of the surface-treated inorganic layer and the fluororesin layer.

[0004] Patent Document 2 describes suitable ranges 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 a surface treatment and an annealing treatment and adjusting the dimensional change rate and oxygen atomic ratio of the fluororesin film to specific ranges, defects during lamination of the fluororesin film and copper foil can be reduced and a fluororesin film with excellent adhesion to the copper foil can be obtained.

[0006] JP 2019-181735 A International Publication No. 2019 / 230569 International Publication No. 2022 / 158524

[0007] An object of the present disclosure is to provide a fluororesin sheet material that has excellent adhesion to a metal layer even when bonded at a temperature below the melting point of the fluororesin.

[0008] The present disclosure provides a fluororesin sheet material that satisfies at least one of the following conditions (1) and (2) on at least one surface: (1) the maximum peak height (Rp) when the surface state is measured by an atomic force microscope is 30 to 150 nm, and (2) the maximum peak depth (Rv) when the surface state is measured by an atomic force microscope is −30 to −120 nm.

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

[0010] The present disclosure also provides a laminate including a metal layer and a fluororesin sheet material, the surface of which in contact with the metal layer satisfies at least one of the following conditions (3) and (4): (3) a maximum peak height (Rp) of 30 to 150 nm when the surface condition is measured by an atomic force microscope; and (4) a maximum peak depth (Rv) of −30 to −120 nm when the surface condition is measured by an atomic force microscope.

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

[0012] In the laminate, it is preferable that the fluororesin sheet 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 material is 1.5 μm or less.

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

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

[0015] The present disclosure also relates to a laminate including a fluororesin sheet material and a metal layer, 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 oxygen element ratio measured on the measured surface of the fluororesin sheet material by a scanning X-ray photoelectron spectroscopy (XPS) is 1.35 atomic % or more: (5) The ratio (Rp (fluororesin sheet material) / Rp (metal foil)) of the maximum peak height (Rp) measured by an atomic force microscope on the surface of at least one of the surfaces in contact with the metal layer before lamination of the fluororesin sheet material to the maximum peak height (Rp) measured by an atomic force microscope on the surface of the metal foil in contact with the fluororesin sheet material before lamination of the metal foil is 50 to 250%. (6) The ratio (Rv (fluororesin sheet material) / Rp (metal foil)) of the absolute value of the maximum peak depth (Rv) when the surface condition of at least one of the surfaces in contact with the metal layer before lamination of the fluororesin sheet material is measured by atomic force microscope to the maximum peak height (Rp) when the metal foil surface on the surface in contact with the fluororesin sheet material before lamination of the metal foil is measured by atomic force microscope is 50 to 200%.

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

[0017] The present disclosure also relates to a laminate including a fluororesin sheet material and a metal layer, wherein 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 of at least one of the surfaces in contact with the metal layer before lamination of the fluororesin sheet material 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 before lamination of the metal foil is 50 to 250%. (6) The ratio (Rv (fluororesin sheet material) / Rp (metal foil)) of the absolute value of the maximum peak depth (Rv) when the surface condition of at least one of the surfaces in contact with the metal layer before lamination of the fluororesin sheet material is measured by atomic force microscope to the maximum peak height (Rp) when the metal foil surface on the surface in contact with the fluororesin sheet material before lamination of the metal foil is measured by atomic force microscope is 50 to 200%.

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

[0019] In the laminate, the fluororesin is preferably tetrafluoroethylene-perfluoroalkylvinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP). In the laminate, the Rz of the surface of the metal layer that contacts the fluororesin sheet material is preferably 1.5 μm or less.

[0020] In the laminate, 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. The present disclosure also relates to a circuit board having the fluororesin sheet material or the laminate.

[0021] The fluororesin sheet material of the present disclosure has excellent adhesiveness to a metal layer even when bonded at a temperature below the melting point of the fluororesin.

[0022] The present disclosure is described in detail below. Conventionally, in the surface modification of fluororesin sheets by plasma treatment, there have been a number of patents specifying the amount of oxygen element or the amount of specific functional groups as requirements for achieving good adhesion. However, in adhesion below the melting point, these requirements alone do not provide satisfactory adhesion. Insufficient adhesion can lead to peeling in subsequent processes and reduced reliability of the substrate.

[0023] The present disclosure relates to a method for surface-treating a fluororesin sheet material, by improving the in-plane uniformity of the surface treatment, thereby improving adhesion to a metal layer such as copper foil when bonded at temperatures below the melting point of the fluororesin. While conventional methods for improving adhesion have evaluated the Rz of the metal foil surface and the Ra and Rz of the fluororesin film surface, the present inventors focused on the maximum peak height (Rp) and maximum peak depth (Rv) of the fluororesin sheet material surface and demonstrated that when at least one of these is within a specific range, excellent adhesion to a metal layer is achieved even when bonded at temperatures below the melting point of the fluororesin. Furthermore, they found that when the relationship between the Rp of the metal foil and the Rp or Rv of the fluororesin sheet material is specific, good adhesion is achieved, low transmission loss characteristics are maintained, and a laminate with excellent properties is obtained when used as a circuit board.

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

[0025] When the maximum peak height (Rp) is 30 to 150 nm, the functional groups present on the surface of the metal foil and the fluororesin sheet material are likely to be at an appropriate distance to form bonds at an adhesion temperature below the melting point of the fluororesin, resulting in good adhesion to the metal foil. As a result, poor appearance and peeling are eliminated, improving the reliability of the circuit substrate. By enabling adhesion below the melting point of the fluororesin, warping of the metal foil is less likely to occur, resulting in a good appearance. Furthermore, the resistance to peeling maintains surface smoothness, thereby maintaining low transmission loss characteristics. Furthermore, lowering the adhesion temperature facilitates manufacturing and improves production efficiency.

[0026] The fluororesin sheet material of the present disclosure is also characterized in that the maximum peak depth (Rv) of at least one surface is −30 to −120 nm when measured by an atomic force microscope (2).

[0027] By having the maximum peak depth (Rv) be -30 to -120 nm and the maximum peak height (Rp) be -30 to -120 nm, the functional groups present on the surface of the metal foil and the fluororesin sheet material are likely to be at an appropriate distance to form bonds at bonding temperatures below the melting point of the fluororesin, resulting in good adhesion to the metal foil. As a result, poor appearance and peeling are eliminated, improving the reliability of the circuit board. By enabling bonding below the melting point of the fluororesin, warping of the metal foil is less likely to occur, resulting in a good appearance. Furthermore, by reducing peeling resistance, surface smoothness is maintained, thereby maintaining low transmission loss characteristics. Furthermore, lowering the bonding temperature facilitates manufacturing and improves production efficiency.

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

[0029] The fluororesin sheet material of the present disclosure preferably has a maximum peak height (Rp) of 30 to 150 nm (1) and a maximum peak depth (Rv) of −30 to −120 nm (2) when the surface condition of at least one of the surfaces is measured by atomic force microscopy. By satisfying both of these conditions, the distance between the metal foil and the fluororesin sheet material becomes more appropriate for forming bonds between functional groups present on the surface of the metal foil and the fluororesin sheet material at an adhesion temperature below the melting point of the fluororesin.

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

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

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

[0033] The (per)fluoro(alkyl vinyl ether) (PAVE) may be either a fluoroalkyl vinyl ether or a perfluoro(alkyl vinyl ether). In the present disclosure, the term "perfluoro(alkyl vinyl ether)" refers to an alkyl vinyl ether that does not contain a C—H bond. Examples of the PAVE constituting the PAVE unit include those represented by the general formula (1): CF ２ = CFO (CF ２ CFY １ O) ｐ -(CF２ CF ２ CF ２ O) ｑ -R ｆ (1) (wherein, Y １ is F or CF ３ represents R ｆ represents a perfluoroalkyl group having 1 to 5 carbon atoms, p represents an integer of 0 to 5, and q represents an integer of 0 to 5.) and a monomer represented by the general formula (2): CFX=CXOCF ２ OR １ (2) (Wherein, X may be the same or different and is H, F or CF ３ represents R １ represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms which may contain 1 to 2 atoms of at least one type 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 of at least one type selected from the group consisting of H, Cl, Br and I.

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

[0035] The content of PAVE units in the TFE / PAVE copolymer is preferably 1.0 to 10% by mass, more preferably 2.0% by mass or more, even more 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, even more preferably 7.0% by mass or less, particularly preferably 6.5% by mass or less, and most preferably 6.0% by mass or less, based on the total amount of the PAVE units. １９ The TFE / PAVE copolymer may be a copolymer consisting of only TFE units and PAVE units.

[0036] When the fluororesin sheet 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 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 glass transition temperature is a value obtained by measuring dynamic viscoelasticity.

[0038] The TFE / HFP copolymer contains TFE units and HFP units. The content of the TFE units in the TFE / HFP copolymer is preferably 70% by mass or more, more preferably 85% by mass or more, and is 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 TFE / HFP copolymer preferably has a mass ratio of TFE units to HFP units (TFE / HFP) of 70 to 99 / 1 to 30 (mass %), more preferably 85 to 95 / 5 to 15 (mass %).

[0040] The TFE / HFP copolymer can further contain (per)fluoro(alkyl vinyl ether) (PAVE) units.The PAVE units contained in the TFE / HFP copolymer can be the same as the PAVE units described above.The TFE / PAVE copolymer does not contain HFP units, so in this respect it is different from the TFE / HFP / PAVE copolymer.

[0041] When the TFE / HFP copolymer is a copolymer containing TFE units, HFP units, and PAVE units (hereinafter also referred to as "TFE / HFP / PAVE copolymer"), the mass ratio (TFE / HFP / PAVE) is preferably 70-99.8 / 0.1-25 / 0.1-25 (mass%). The mass ratio (TFE / HFP / PAVE) is more preferably 75-98 / 1.0-15 / 1.0-10 (mass%). The TFE / HFP / PAVE copolymer preferably contains 1 mass% or more of HFP units and PAVE units in total relative to all monomer units.

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

[0043] The content of PAVE units is more preferably 20% by mass or less, further preferably 10% by mass or less, and particularly preferably 3% by mass or less. The content of PAVE units is preferably 0.1% by mass or more, more preferably 1% by mass or more. The content of PAVE units is １９ It can be measured by F-NMR.

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

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

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

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

[0048] The fluororesin can be produced by a conventionally known method, such as emulsion polymerization or suspension polymerization, by appropriately mixing monomers that constitute the fluororesin and additives such as a polymerization initiator. Of these, emulsion polymerization is more preferred.

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

[0050] The fewer functional groups the fluororesin has, the less unstable terminal groups it has. Such fluororesins can be produced by adjusting the conditions during production (polymerization reaction), or by subjecting the fluororesin after polymerization to fluorine gas treatment, heat treatment, supercritical gas extraction treatment, etc. The number of unstable terminal groups can be reduced by using methods such as: excellent treatment efficiency; ３ The fluorine gas treatment is preferable because the fluorine resin having a reduced number of unstable terminal groups is converted to a stable terminal group. The use of such a fluororesin having a reduced number of unstable terminal groups is preferable because it reduces the electrostatic dissipation factor and the loss of electrical signals.

[0051] The number of unstable terminal groups is not particularly limited, but is preferably 10 or more, and more preferably 10 or more, and most .... ６ The number per particle is preferably 450 or less, more preferably 250 or less, even more preferably 100 or less, and most preferably 50 or less. In consideration of the effect of reducing the dielectric loss tangent, the number per particle is preferably less than 10, and more preferably 5 or less.

[0052] Specific examples of unstable terminal groups include -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), and hydroxyl groups (-CH ２ OH, etc.), -CONH ２ , -COOR(R=CH ３ etc.), -CF ２ Examples of functional groups include H and —OCOO—R (normal propyl carbonate, etc.).

[0053] Specifically, the number of unstable terminal groups is measured by the following method. First, the fluororesin is melted and compression-molded to produce a film having a thickness of 0.25 to 0.3 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain an infrared absorption spectrum of the fluororesin, and a difference spectrum is obtained from a base spectrum in which the fluororesin is completely fluorinated and no functional groups are present. From the absorption peaks of specific functional groups that appear in this difference spectrum, the number of carbon atoms in the fluororesin is calculated according to the following formula (A): ６The number of unstable terminal groups per unit is calculated as follows: N = I x K / t (A) I: absorbance K: correction coefficient t: film thickness (mm)

[0054] For reference, the absorption frequencies, molar absorption coefficients, and correction coefficients for the unstable terminal groups in this specification are shown in Table 1. The molar absorption coefficients were determined from the FT-IR measurement data of low molecular weight model compounds.

[0055]

[0056] The fluorination treatment can be carried out by contacting a non-fluorination-treated fluororesin with a fluorine-containing compound.

[0057] The fluorine-containing compound is not particularly limited, but may be a fluorine radical source that generates fluorine radicals under fluorination treatment conditions. ２ Gas, CoF ３ , AgF ２ , U.F. ６ , OF ２ , N ２ F ２ , C.F. ３ OF, halogen fluorides (e.g., IF ５ , ClF ３ ) etc.

[0058] Above F ２ The fluorine radical source such as a gas may be of 100% concentration, but is preferably mixed with an active gas and diluted to 5 to 50 mass %, more preferably 15 to 30 mass % for use. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, with nitrogen gas being preferred from an economical standpoint.

[0059] The conditions for the fluorination treatment are not particularly limited, and the molten fluororesin may be brought into contact with the fluorine-containing compound, but the treatment is usually carried out at a temperature below the melting point of the fluororesin, preferably 20 to 220°C, more preferably 100 to 200°C. The fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 25 hours. The fluorination treatment is carried out by exposing an unfluorinated fluororesin to fluorine gas (F ２ It is preferable to contact the catalyst with a gas.

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

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

[0062] The oxygen element ratio measured on at least one surface of the fluororesin sheet material of the present disclosure using a scanning X-ray photoelectron spectroscopy (XPS) is preferably 1.35 atomic% or more. The oxygen element ratio is more preferably 1.5 atomic% or more, even more preferably 1.8 atomic% or more, and most preferably 2.0 atomic% or more. 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. An oxygen element ratio within the above range is advantageous in that it contains an appropriate amount of functional groups that contribute to adhesiveness.

[0063] Here, the oxygen element ratio was determined by the following method. (Method for measuring oxygen element ratio) Using a scanning X-ray photoelectron spectroscopic analyzer (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.), the oxygen element ratio on the surface of the fluororesin sheet material was measured under the conditions shown 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: Monochromated AlKα Beam diameter: 100 μm X-ray output: 25 W Measurement area: 1000 μm × 300 μm Pass energy: 23.5 eV Detection angle: 45°

[0064] Furthermore, the amount of functional groups (C=O) measured on at least one surface of the fluororesin sheet material of the present disclosure using a scanning X-ray photoelectron spectroscopy (XPS) is preferably 2.0% or more. The amount of functional groups (C=O) is more preferably 3% or more, even more preferably 4% or more, and most preferably 5% or more. The upper limit of the amount of functional groups (C=O) is not particularly limited, but is preferably 35% or less, more preferably 30% or less, and even more preferably 20% or less. A functional group (C=O) amount within the above range provides an appropriate amount of functional groups that contribute to adhesion, which is advantageous in terms of improving adhesion and durability.

[0065] Here, the amount of functional groups (C═O) was 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 (manufactured by ULVAC-PHI) under the conditions shown below, and the amount of functional groups (C═O) was determined from the ratio between these peaks. The half-widths of peaks 1 to 4 were unified to 1.83, and the half-width of peak 5 was adjusted to match the shape of the original spectrum.

[0066]

[0067] The fluororesin sheet material of the present 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 fluororesin sheet material is a value measured by reflection spectroscopy using a film thickness measurement system F20 (manufactured by Filmetrics).

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

[0070] Furthermore, the fluororesin sheet material of the present disclosure preferably has a difference of 1.0 atomic % or more between the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS / ESCA) for the surface state thereof and the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS / ESCA) for the fluororesin sheet material after etching the fluororesin sheet material in the depth direction at an incident angle of 45° with an argon gas cluster ion beam for 15 minutes. A larger difference in the oxygen element ratio from the surface to the depth direction is preferable in terms of being able to obtain a predetermined transmission loss while maintaining adhesion.

[0071] The oxygen element ratio after etching is the oxygen element ratio on the surface of the fluororesin sheet material before the surface treatment, and therefore the difference in the oxygen element ratio represents the increase in the oxygen element ratio due to the surface treatment.

[0072] The fluororesin sheet material preferably has an adhesive strength of more than 30 N / m on one or both sides when the sheet materials are bonded together in the same plane at 200° C. By having such an adhesive strength, the fluororesin sheet material will have excellent adhesiveness when used in combination with various other substrates even after heat treatment, and the adhesive strength is more preferably more than 50 N / m, and even more preferably more than 100 N / m.

[0073] More specifically, the adhesive strength was measured by overlapping the surface-treated surfaces of the fluororesin sheet material together and heat pressing (200°C, 0.1 MPa, 60 s) to produce a sample, which was then cut into a 10 mm wide strip. Using a precision universal testing machine Autograph AGS-X 100N (manufactured by Shimadzu Corporation), the unbonded portion of the strip sample was gripped between the upper and lower chucks of the Autograph and pulled at a rate of 100 mm per minute to measure the peel strength, and the obtained value was taken as the adhesive strength.

[0074] The resin sheet material of the present disclosure preferably has a dielectric dissipation factor of less than 0.0015 at 10 GHz. A dielectric dissipation factor within this range is preferable because it can minimize electrical signal loss in circuits. The dielectric dissipation factor is more preferably less than 0.0013, even more preferably less than 0.0010, and most preferably 0.00050 or less. Furthermore, considering signal transmission and antenna transmission / reception at higher frequencies, the dielectric dissipation factor 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. To achieve a dielectric dissipation factor within the above range, it is preferable to use a resin with few unstable terminal groups, and it is more preferable to use a fluororesin that has been subjected to a terminal fluorination treatment.

[0075] (Method for manufacturing fluororesin sheet material) An example of a method for manufacturing the fluororesin sheet material of the present disclosure described above will be described in detail below. Note that the fluororesin sheet material of the present disclosure is not limited to those manufactured by the following manufacturing method. The fluororesin sheet material of the present disclosure is not particularly limited to a method for forming into a sheet, but examples include a melt molding method such as extrusion molding, and a casting method in which a solution or dispersion containing a fluororesin is prepared, then coated on a substrate, and dried. Furthermore, the sheet may be stretched by a uniaxial or biaxial stretching method, or may be an unstretched sheet. Furthermore, the fluororesin sheet material may have a laminate structure partially including a fluororesin layer.

[0076] By subjecting one or both sides of the fluororesin sheet material obtained by this method to surface treatment under appropriate conditions, it is possible to produce a fluororesin sheet material having the above-mentioned specific maximum peak height (Rp) and maximum peak depth (Rv).

[0077] The specific method for the surface modification is not particularly limited, but specific examples are described in detail below. Conventional discharge treatments such as corona discharge, glow discharge, plasma discharge, and sputtering can be used to modify the surface of fluororesin sheet materials. 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, or ethylene gas into a discharge atmosphere. Alternatively, the surface to be modified can be exposed to an atmosphere of an organic compound-containing inert gas, which is an inert gas containing an organic compound, and a high-frequency voltage is applied between electrodes to generate a discharge, thereby generating active species on the surface. Surface modification can then be achieved by introducing functional groups from the organic compound or graft-polymerizing a polymerizable organic compound. Examples of 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 it is not certain, it is thought that by setting the Ar ratio in a suitable range, discharge becomes stable and more uniform surface modification can be achieved. Furthermore, it is preferable that the carbon dioxide gas is 0.05 to 5% by volume of nitrogen gas / argon gas, and more preferably 0.1 to 2% by volume. Although it is not certain, it is thought that by mixing an appropriate amount of carbon dioxide gas, the functional groups on the surface of the fluororesin sheet material that contribute to adhesiveness will be in a suitable range.

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

[0080] The concentration of the organic compound in the organic compound-containing inert gas varies depending on the type of organic compound, 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 may be appropriately selected depending on the desired degree of surface modification, the type of fluororesin, the type and concentration of the organic compound, etc. The discharge rate is usually 50 to 1500 W·min / m ２ , preferably 70 W·min / m ２ More than 1400W・min / m２ The discharge treatment is performed within the following range. The treatment temperature can be any temperature in the range of 0°C to 100°C. Due to concerns about stretching and wrinkling of the fluororesin sheet material, a temperature of 80°C or less is preferable. Considering that oxygen elements on the surface are deactivated by heat applied during lamination with metal foil or the like, resulting in a decrease in adhesive ability, the degree of surface modification of the fluororesin sheet material is such that the oxygen element abundance ratio observed by ESCA is 1.5% or more, preferably 1.75% or more, more preferably 2.0% or more, and even more preferably 2.5% or more. There is no particular upper limit, but in consideration of the impact on productivity and other physical properties, it is preferably 25.0% or less. The nitrogen element abundance ratio is not particularly specified, but is preferably 0.1% or more.

[0081] During the surface modification, the discharge degree, which indicates the output per unit area, is 1.0 to 10 W / cm ２ It is preferable to perform discharge treatment within this range, adjusting the gas concentration / line speed ratio to a range of 0.005 to 0.05 L / m. The gas concentration / line speed ratio here refers to the ratio of the organic compound concentration in the organic compound-containing inert gas divided by the line speed. If the gas concentration / line speed ratio is lower than 0.005 L / m, the space is not filled with sufficient gas relative to the transport speed, making it difficult for the activated gas to contact the surface of the fluororesin sheet material, which tends to reduce in-plane uniformity. If the gas concentration is higher than 0.05 L / m, the surface is over-treated and damaged, resulting in the formation of low-molecular-weight compounds on the surface, forming a brittle layer and, in turn, reducing adhesive strength. Therefore, treatment within this range is particularly preferred because it is expected to result in more uniform treatment within the surface of the fluororesin sheet material and achieve the desired adhesiveness.

[0082] Furthermore, in the above-mentioned method, it is preferable that the fluororesin sheet material is surface-treated so that the difference between the oxygen element ratio when the surface condition of one or both sides is measured by a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) and the oxygen element ratio when the fluororesin-containing layer is etched in the depth direction with an argon gas cluster ion beam at an incident angle of 45° for 15 minutes and then measured by a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) is 1.0 atomic % or more.

[0083] In the above method, surface treatment with a gas containing an organic compound is also preferable in that it can impart localized unevenness to the resin surface, thereby making the dynamic friction coefficient between the metal foil surface and the fluororesin sheet material surface 0.4 or less. That is, in addition to improving the adhesive strength, the dynamic friction coefficient can be made small. This is preferable in that when a long laminate is made, poor winding performance is not generated.

[0084] The fluororesin sheet material surface-treated by the above method may be annealed to remove residual stress in advance. This reduces dimensional changes in the fluororesin sheet material due to heat from the pressure roll during the process of laminating it with metal foil to produce a laminate, allowing it to be bonded without wrinkles, thereby suppressing poor appearance of the laminate. Because 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 at the time the fluororesin sheet material and metal foil are bonded together.

[0085] The annealing treatment can be carried out by heat treatment. The heat treatment can be carried out, for example, by passing the material through a heating furnace using a roll-to-roll method. The heat treatment can also be carried out by placing the material in a batch-type drying furnace.

[0086] The annealing temperature is preferably not less than the glass transition temperature of the fluororesin minus 20° C. and less than the melting point, more preferably not less than the glass transition temperature of the fluororesin minus 20° C., and even more preferably not less than the glass transition temperature of the fluororesin minus 60° C. The annealing time is not particularly limited, but may be adjusted as appropriate within the range of, for example, 0.5 to 60 minutes.

[0087] When heating is performed by the roll-to-roll method, the tension may be adjusted appropriately depending on the thickness of the fluororesin sheet material, the set temperature, etc., but is preferably 20 N / m or less. Heating under such conditions is preferable in that it can sufficiently relieve internal stress and does not cause dimensional changes, etc.

[0088] The order of the surface treatment and annealing treatment is not particularly limited, and the number of times each step is performed is not limited to one, but each step may be performed two or more times.

[0089] (Laminate) The fluororesin sheet material of the present disclosure is suitable for use in forming a laminate with a metal or resin substrate. The present disclosure also relates to a laminate including a metal layer and a fluororesin sheet material (3), in which the maximum peak height (Rp) of at least one of the surfaces in contact with the metal layer is 30 to 150 nm when measured by atomic force microscopy on the surface state of at least one of the surfaces in contact with the metal layer. The present disclosure also relates to a laminate including a metal layer and a fluororesin sheet material (4), in which the maximum peak depth (Rv) of at least one of the surfaces in contact with the metal layer is −30 to −120 nm when measured by atomic force microscopy on the surface state of at least one of the surfaces in contact with the metal layer.

[0090] The laminate described above is excellent in that the metal foil and the functional groups present on the surface of the fluororesin sheet material in the microscopic region are easily at an appropriate distance to form a bond, thereby improving adhesion and durability.

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

[0092] Furthermore, it is preferable that the laminate is a laminate including a metal layer and a fluororesin sheet material, the maximum peak height (Rp) of which is 30 to 150 nm (3) and the maximum peak depth (Rv) of which is −30 to −120 nm (4) when the surface state of at least one of the surfaces in contact with the metal layer is measured by an atomic force microscope.

[0093] (Metal Layer) In the present disclosure, examples of metal species constituting the metal layer include copper, aluminum, SUS, nickel, and gold. Alloys of these metals can also be used. From the viewpoints of conductivity and circuit processability, it is preferable to use copper foil.

[0094] The metal foil forming the metal layer preferably has an Rz of 1.5 μm or less on the surface that contacts the fluororesin sheet material. That is, the fluororesin sheet material of the present disclosure also has excellent adhesion to metal foil with a high smoothness of 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 that contacts the fluororesin sheet material, and the Rz value of the other surface is not particularly limited.

[0095] The Rz is the sum of the values ​​of the highest point (maximum peak height: Rp) and the deepest point (maximum valley depth: Rv). The surface roughness is the ten-point average roughness specified in JIS-B0601. In this specification, the Rz is a 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 foil is not particularly limited, and specific examples include rolled copper foil and electrolytic copper foil.

[0098] The copper foil having an Rz of 1.5 μm or less is not particularly limited, and commercially available products can be used. Examples of commercially available copper foils having 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 Co., Ltd.).

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

[0100] The surface treatment is not particularly limited, but may be a 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 the reactive functional group has at least one selected from an amino group, a (meth)acrylic group, a mercapto group, and an epoxy group at the terminal. Furthermore, the hydrolyzable group is not particularly limited, but may include alkoxy groups such as a methoxy group and an ethoxy group. The copper foil used in the present disclosure may have a rust prevention layer (such as an oxide film such as chromate), a heat-resistant layer, etc. formed thereon.

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

[0102] The copper foil may have a roughened layer on its surface from the viewpoint of improving adhesion to the fluororesin sheet material, etc. If the roughening treatment is likely to deteriorate the performance required in the present disclosure, the amount of roughening particles electrodeposited on the copper foil surface may be reduced as needed, or the copper foil may not be roughened at all.

[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-proofing treatment layer, and a chromate treatment layer may be provided in order to improve various properties. These layers may be a single layer or multiple layers.

[0104] The laminate of the present disclosure preferably uses a fluororesin sheet material having an oxygen element ratio of 1.35 atomic % or more, as measured by a scanning X-ray photoelectron spectroscopy (XPS) on a surface having a maximum peak height (Rp) and / or a maximum peak depth (Rv) of −30 to −120 nm when measured by the atomic force microscope. The laminate of the present disclosure preferably uses a fluororesin sheet material having a functional group (C═O) content of 2.0 atomic % or more, as measured by a scanning X-ray photoelectron spectroscopy (XPS) on a surface having a maximum peak height (Rp) and / or a maximum peak depth (Rv) of −30 to −120 nm when measured by the atomic force microscope.

[0105] The present disclosure also provides a laminate including a fluororesin sheet material and a metal layer, wherein the ratio (Rp (fluororesin sheet material) / Rp (metal foil)) of the maximum peak height (Rp) measured by atomic force microscope on the surface of at least one of the surfaces that contact the metal foil before lamination of the fluororesin sheet material to the maximum peak height (Rp) measured by atomic force microscope on the surface of the metal foil on the surface that contacts the fluororesin sheet material before lamination of the metal foil is 50 to 250% (5), and the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS) on the same surface of the fluororesin sheet material is 1.35 atomic % or more.

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

[0107] The present disclosure also provides a laminate including a fluororesin sheet material and a metal layer, wherein the ratio of the maximum peak height (Rp) of the surface of at least one of the surfaces in contact with the metal layer measured by an atomic force microscope before lamination of the fluororesin sheet material to the maximum peak height (Rp) of the metal foil surface in contact with the fluororesin sheet material measured by an atomic force microscope before lamination of the metal foil (Rp (fluororesin sheet material) / Rp (metal foil)) is 50 to 250% (5), and It is preferable that the ratio (Rv (fluororesin sheet material) / Rp (metal foil)) of 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 an atomic force microscope to the maximum peak height (Rp) when the surface of the metal foil on the side in contact with the fluororesin sheet material is measured by an atomic force microscope is 50 to 200% (6), and that the oxygen element ratio measured on the same side of the surface of the fluororesin sheet material by a scanning X-ray photoelectron spectroscopy (XPS) is 1.35 atomic % or more.

[0108] The present disclosure relates to a laminate including a fluororesin sheet material and a metal layer, wherein the ratio (Rp (fluororesin sheet material) / Rp (metal foil)) of the maximum peak height (Rp) of at least one surface of the fluororesin sheet material in contact with the metal layer measured by atomic force microscope before lamination to the maximum peak height (Rp) of the metal foil surface in contact with the fluororesin sheet material measured by atomic force microscope before lamination of the metal foil is 50 to 250% (5), 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.

[0109] The present disclosure relates to a laminate including a fluororesin sheet material and a metal layer, wherein the ratio (Rv (fluororesin sheet material) / Rp (metal foil)) of the absolute value of the maximum peak depth (Rv) when the surface state of at least one of the surfaces in contact with the metal layer before lamination of the fluororesin sheet material is measured by atomic force microscope to the maximum peak height (Rp) when the metal foil surface on the surface in contact with the fluororesin sheet material before lamination of the metal foil is measured by atomic force microscope is 50 to 200% (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.

[0110] The present disclosure also provides a laminate including a fluororesin sheet material and a metal layer, wherein the ratio of the maximum peak height (Rp) of the surface of at least one of the surfaces in contact with the metal layer measured by an atomic force microscope before lamination of the fluororesin sheet material to the maximum peak height (Rp) of the metal foil surface in contact with the fluororesin sheet material measured by an atomic force microscope before lamination of the metal foil (Rp (fluororesin sheet material) / Rp (metal foil)) is 50 to 250% (5), and It is preferable that the ratio (Rv (fluororesin sheet material) / Rp (metal foil)) of 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 an atomic force microscope to the maximum peak height (Rp) when the surface of the metal foil on the side in contact with the fluororesin sheet material is measured by an atomic force microscope is 50 to 200% (6), and that the amount of functional groups (C═O) measured on the same side of the surface of the fluororesin sheet material by a scanning X-ray photoelectron spectroscopy (XPS) is 2.0% or more.

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

[0112] In the case of a laminate in which one side of a fluororesin sheet material is in contact with a metal layer, it is sufficient that the contacting surface satisfies the above-mentioned physical properties. In the case of a laminate in which both sides of a fluororesin sheet material are in contact with a metal layer, it is sufficient that at least one side satisfies the above-mentioned physical properties, and it is particularly preferable that both sides satisfies the above-mentioned physical properties.

[0113] In the laminate of the present disclosure, the adhesive strength between the measurement surface of the fluororesin sheet material and the metal layer is preferably 0.5 N / cm or more. That is, it is preferable that each of the above-mentioned laminates has an adhesive strength of 0.5 N / cm or more at least at the surface where the fluororesin sheet material and the metal layer contact, which satisfies the above-mentioned physical properties. By satisfying the above-mentioned requirements, such adhesive strength can be achieved. By increasing the adhesive strength to 1 N / cm or more, or even 2 N / cm or more, the laminate can be suitably used as a copper-clad laminate or a circuit board. The adhesive strength here refers to the adhesive strength measured under the conditions described in the examples.

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

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

[0116] When the laminate of the present disclosure has the layer (X), the layer structure can be a metal layer / fluororesin sheet material layer / layer (X). A fluororesin sheet material layer / metal layer laminate may be provided on one or both sides of the layer (X).

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

[0118] Heating is required to bond the metal foil and the fluororesin sheet material. In the production of the laminate of the present disclosure, the heating temperature is preferably set to a temperature below the melting point of the fluororesin. Specifically, a temperature of 70 to 300°C is preferred. A temperature of 70 to 250°C is preferred, and a temperature of 70 to 200°C is even more preferred. The fluororesin sheet material of the present disclosure exhibits excellent adhesion to the metal layer even when bonded at a temperature below the melting point of the fluororesin. The heat treatment process may be a roll-to-roll lamination method or a method in which a fluororesin coated on a metal foil is heat-treated. In other words, a low heating temperature is preferred in that it suppresses warping of the metal foil and minimizes loss of smoothness of the bonding surface during the process of bonding the metal foil and the fluororesin sheet material. As a result, poor appearance and peeling are eliminated, improving the reliability of the circuit board.

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

[0120] The roll-to-roll method is also preferable in that it reduces costs and allows a long laminate to be obtained. When producing a laminate by such a method, the width of the laminate is not particularly limited, but is preferably 200 mm or more.

[0121] In addition, in the case of a laminate in which a metal foil is adhered to the surface-treated surface of a fluororesin sheet material that has been surface-treated on only one side, the surface of the fluororesin sheet material that has not been surface-treated may be separately surface-modified in order to improve the adhesion between the laminate and other materials.

[0122] The laminate of the present disclosure has good adhesion between the metal layer and the fluororesin sheet material, making them less likely to peel off. Therefore, the surface smoothness of the adhesive surface can be maintained, resulting in low transmission loss. This makes it suitable for use in circuit boards, etc. It is particularly suitable for use in circuit boards for high-frequency circuits. The present disclosure also relates to a circuit board having the above-described fluororesin sheet material or laminate of the present disclosure.

[0123] In this disclosure, the term "high-frequency circuit" refers not only to a circuit that simply transmits only high-frequency signals, but also to a circuit that also includes a transmission line that converts a high-frequency signal into a low-frequency signal and outputs the generated low-frequency signal to the outside, a transmission line for supplying power to drive high-frequency compatible components, and other transmission lines that transmit signals other than high-frequency signals, all of which are installed on the same plane.The circuit can also be used as a circuit board for an antenna, a filter, etc.

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

[0125] (Example 1) [Method for producing fluororesin sheet material] 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 terminal groups: main chain carbon number: 10) was used as the fluororesin. ６ The resulting rolled fluororesin sheet material was subjected to a surface treatment on both sides (a corona discharge device was used, and the discharged material was placed in an extruder at 360°C using 297 pieces per roll), extruded through a 1700 mm wide T-die, taken up on a metal cooling roll, and further wound up on a take-up core to obtain a 1300 mm wide, 12 μm thick fluororesin sheet material. [Surface treatment] Surface treatment was performed on both sides of the obtained rolled fluororesin sheet material (a corona discharge device was used, and the fluororesin sheet material was continuously passed along the rolled ground electrode while an inert gas (nitrogen / Ar ratio 60 / 40) containing 0.50 vol% vinyl acetate and 0.70 vol% carbon dioxide was flowed near the discharge electrode and the rolled ground electrode, and a discharge amount of 200 W min / m ２Both sides of the fluororesin sheet material were subjected to corona discharge (using a corona discharge tester), and the long fluororesin sheet material was wound into a roll to obtain a surface-treated sample, which was then evaluated.

[0126] (Example 2) Carbon dioxide gas 0.50% by volume, inert gas nitrogen / Ar ratio 70 / 30, discharge amount 80 W min / m ２ A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed.

[0127] (Example 3) Carbon dioxide gas 0.20% by volume, inert gas nitrogen / Ar ratio 60 / 40, discharge amount 70 W min / m ２ A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed.

[0128] (Example 4) Carbon dioxide gas 0.30% by volume, inert gas nitrogen / Ar ratio 50 / 50, discharge amount 80 W min / m ２ A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed.

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

[0130] (Example 6) Carbon dioxide gas 0.30% by volume, inert gas nitrogen / Ar ratio 80 / 20, discharge amount 70 W min / m ２ A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed.

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

[0132] (Example 8) 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 terminal groups: undetectable (main chain carbon number: 10 ６ A sample was prepared in the same manner as in Example 6 except that less than one particle per particle was used.

[0133] (Example 9) 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 terminal groups: undetectable (main chain carbon number: 10 ６ A sample was prepared in the same manner as in Example 6 except that less than one particle per particle was used.

[0134] (Comparative Example 1) An inert gas (nitrogen) containing 0.50% by volume of vinyl acetate was used, and the discharge amount was 100 W·min / m ２ A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed.

[0135] (Comparative Example 2) An inert gas (nitrogen / Ar ratio 35 / 65) containing 1.50% by volume of carbon dioxide gas and 0.50% by volume of vinyl acetate was used, and the discharge amount was 150 W·min / m ２ A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed.

[0136] (Comparative Example 3) An inert gas (nitrogen / Ar ratio 30 / 70) containing 0.50% by volume of vinyl acetate was used, and the discharge amount was 40 W·min / m ２ A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed.

[0137] (Method for measuring maximum peak height (Rp) and maximum peak depth (Rv)) The maximum peak height (Rp) and maximum peak depth (Rv) for each sheet and copper foil in the Examples and Comparative Examples were determined by the following method. For the fluororesin sheet, the inner surface of the roll after surface treatment was measured, and for the copper foil, the inner surface of the roll (unroughened surface) was measured. Using a scanning atomic force microscope AFM5000 (manufactured by Hitachi High-Technologies 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 shown below. Cantilever: SI-DF20 (tip R<10 nm, spring constant 15 N / m) Measurement mode: AC mode Scanning frequency: 1 Hz Number of pixels: 256 × 256 The results are shown in Table 3.

[0138] (Method for measuring oxygen element ratio) Using a scanning X-ray photoelectron spectrometer (XPS / ESCA) PHI5000 VersaProbe II (manufactured by ULVAC-PHI, Inc.), the oxygen element ratio of the inner surface of the wound fluororesin sheet material roll after surface treatment was measured under the conditions shown 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: Monochromated AlKα Beam diameter: 100 μm X-ray output: 25 W Measurement area: 1000 μm × 300 μm Pass energy: 23.5 eV Detection angle: 45° The results are shown in Table .

[0139] (Method for measuring the amount of functional group (C═O)) The C1s narrow spectrum obtained by the XPS was separated into five peaks using MultiPak software (manufactured by ULVAC-PHI) 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 half-widths of peaks 1 to 4 were standardized to 1.83, and the half-width 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) A fluororesin sheet material and an electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) were used, and each was cut into a predetermined shape. The copper foil, fluororesin sheet material, and copper foil were stacked in this order, with the unroughened surface of the copper foil in contact with the fluororesin sheet material and with the inner surface of the fluororesin sheet material after surface treatment facing up, and the laminate was obtained by heat pressing in 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 pressure of 10 MPa, and a pressurizing time of 1200 seconds. The resulting laminate was cut into 10 mm wide pieces, and an aluminum plate was attached to the underside with adhesive tape. Using a Tensilon universal testing machine (Shimadzu Corporation), the peel strength of the copper foil was measured by gripping and pulling a 10 mm wide piece of copper foil at a 90° angle relative to the plane of the laminate at a speed of 50 mm per minute. The peel strength was measured using a Tensilon universal testing machine (Shimadzu Corporation). The measured value was taken as the adhesive strength. The laminate was fabricated and measured at five locations, 100 mm apart in the running direction, at three locations on the rolled fluororesin sheet material: the center and each of the left and right edges. The average of 15 measurements was taken. The results are shown in Table 3.

[0141] (Adhesion strength after thermal shock test) A fluororesin sheet material, 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 Co., Ltd.) and CF-V9S-SV-12 (thickness 12 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) were used, and each was cut into a predetermined shape. From the top, they were stacked in the order of CF-T9DA-SV-18 (unroughened surface on the bottom), fluororesin sheet material (the inner surface of the roll after surface treatment on the top), prepreg R-5680(J), and CF-V9S-SV-12 (rough lower surface on the top), and hot pressed under pressing conditions of a temperature of 200°C, a pressing time of 75 minutes, and a pressure of 3.0 MPa, to obtain a laminate. The resulting laminate was subjected to 500 cycles of thermal shock testing (low-temperature exposure at -55°C for 15 minutes, temperature transition time 5 minutes, high-temperature exposure at 125°C for 15 minutes), then cut into 10 mm widths. An aluminum plate was attached to the CF-V9S-SV-12 side with adhesive tape, and the adhesive strength was measured in the same manner as for measuring the adhesive strength with copper foil. The measured value was the average of 15 measurements taken at five locations, 100 mm apart in the running direction, at three random locations on the rolled fluororesin sheet material: the center and three locations 100 mm from each of the left and right edges. The results are shown in Table 3.

[0142]

[0143] From the results in Table 3, the fluororesin sheet materials of the examples had good adhesiveness at temperatures below the melting point of the fluororesin.

[0144] The fluororesin sheet material of the present disclosure can be suitably used as a circuit substrate.

Claims

1. A fluororesin sheet material that satisfies at least one of the following conditions (1) and (2) on at least one surface: (1) The maximum peak height (Rp) when the surface condition is measured by an atomic force microscope is 30 to 150 nm, or (2) The maximum peak depth (Rv) when the surface condition is measured by an atomic force microscope is -30 to -120 nm.

2. A fluororesin sheet material according to claim 1, which satisfies both of (1) and (2).

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

4. A laminate comprising a metal layer and a fluororesin sheet material, the surface of which in contact with the metal layer satisfies at least one of the following conditions (3) and (4): (3) The maximum peak height (Rp) when the surface condition is measured by an atomic force microscope is 30 to 150 nm, and (4) The maximum peak depth (Rv) when the surface condition is measured by an atomic force microscope is -30 to -120 nm.

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

6. The laminate according to claim 4, wherein the fluororesin sheet material satisfies both of (3) and (4).

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

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

9. A laminate according to any one of claims 4 to 7, wherein the amount of functional groups (C=O) measured on the surface of the fluororesin sheet material by scanning X-ray photoelectron spectroscopy (XPS) is 2.0% or more.

10. A laminate comprising a fluororesin sheet material and a metal layer, wherein the surface of at least one of the sides in contact with the metal layer satisfies at least one of the following (5) and (6), and the oxygen element ratio measured on the measured surface of the fluororesin sheet material by scanning X-ray photoelectron spectroscopy (XPS) is 1.35 atomic % 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 of the sides in contact with the metal layer before lamination of the fluororesin sheet material 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 before lamination of the metal foil is 50 to 250%. (6) The ratio (Rv (fluororesin sheet material) / Rp (metal foil)) of the absolute value of the maximum peak depth (Rv) when the surface condition of at least one of the surfaces in contact with the metal layer before lamination of the fluororesin sheet material is measured by atomic force microscope to the maximum peak height (Rp) when the metal foil surface on the surface in contact with the fluororesin sheet material before lamination of the metal foil is measured by atomic force microscope is 50 to 200%.

11. The laminate according to claim 10, which satisfies both of (5) and (6).

12. A laminate comprising a fluororesin sheet material and a metal layer, wherein the surface of at least one of the sides 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 of at least one of the sides in contact with the metal layer before lamination of the fluororesin sheet material 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 before lamination of the metal foil is 50 to 250%. (6) The ratio (Rv (fluororesin sheet material) / Rp (metal foil)) of the absolute value of the maximum peak depth (Rv) when the surface condition of at least one of the surfaces in contact with the metal layer before lamination of the fluororesin sheet material is measured by atomic force microscope to the maximum peak height (Rp) when the metal foil surface on the surface in contact with the fluororesin sheet material before lamination of the metal foil is measured by atomic force microscope is 50 to 200%.

13. The laminate according to claim 12, which satisfies both of (5) and (6).

14. The laminate according to any one of claims 10 to 13, wherein the fluororesin is tetrafluoroethylene-perfluoroalkylvinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

15. A laminate according to any one of claims 10 to 14, wherein the Rz of the surface of the metal layer in contact with the fluororesin sheet material is 1.5 µm or less.

16. The laminate according to any one of claims 10 to 15, wherein the adhesive strength between the measurement surface of the fluororesin sheet material and the metal layer is 0.5 N / cm or more.

17. A circuit board comprising the fluororesin sheet element according to any one of claims 1 to 3, or the laminate according to any one of claims 4 to 7 and 10 to 16.

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