Fluororesin sheet-like material and laminate including 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 is a sheet-like material including fluororesin and the following general formula (A) holds for at least one surface. O≥E+0.5 ... (A) where O is an oxygen element ratio obtained by measurement by a scanning X-ray photoelectron spectrometer, and E is a difference between a surface elastic modulus when a cumulative relative frequency reaches 0.99 and a surface elastic modulus when the cumulative relative frequency reaches 0.01 in multipoint measurement of surface elastic modulus by a scanning atomic force microscope at 120°C.SELECTED DRAWING: None

Description

[Technical Field]

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

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

[0003] Patent Document 2 describes that by subjecting a fluororesin film to a surface treatment and an annealing treatment and adjusting the dimensional change rate and oxygen atom 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.

[0004] Furthermore, Patent Document 3 describes that by subjecting the surface of a heat-resistant film such as aramid to a surface modification treatment by corona discharge to make the surface elastic modulus 1.5 GPa or more, the adhesion between the heat-resistant film and the adhesive resin is improved, enabling the film to be made thinner. Furthermore, Patent Document 4 describes that by setting the surface elastic modulus of a release polyester film for semiconductor encapsulation process within a specific range, the occurrence of cracks in the release polyester film can be suppressed and the transfer of resin flow marks to the surface of the release film can be avoided. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-181735 [Patent Document 2] International Publication No. 2022 / 158524 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2004-123928 [Patent Document 4] Japanese Unexamined Patent Application Publication No. 2023-116512 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] An object of the present disclosure is to provide a fluororesin sheet-like material having excellent adhesiveness to a metal layer even when adhered at a temperature below the melting point of the fluororesin. [Means for Solving the Problems]

[0007] The present disclosure is a sheet-like material containing a fluororesin, and is a fluororesin sheet-like material in which the following general formula (A) holds on at least one surface. O≧E + 0.5 (A) O: Oxygen element ratio obtained when measured by a scanning X-ray photoelectron spectrometer (XPS) E: The difference between the surface elastic modulus when the cumulative relative frequency reaches 0.99 and the surface elastic modulus when the cumulative relative frequency reaches 0.XXX in the multi-point measurement of the surface elastic modulus by a scanning atomic force microscope at 120°C.

[0008] Furthermore, it is preferable that the difference E between the surface elastic modulus when the cumulative relative frequency reaches 0.99 and the surface elastic modulus when the cumulative relative frequency reaches 0.01 is 0.35 GPa ≦ E ≦ 3.0 GPa. Furthermore, it is preferable that the oxygen element ratio O is 1.35 atomic% < O < 20 atomic%.

[0009] The present disclosure is a sheet-like material containing a fluororesin, and on at least one surface When heated from 25°C to 120°C, the intermediate value of the surface elastic modulus (the value when the cumulative relative frequency reaches 0.50) decreases by 20% or more in multi-point measurements of the surface elastic modulus using a scanning atomic force microscope at 25°C and 120°C.

[0010] The present disclosure relates to a sheet-like material containing a fluororesin, the sheet-like material having at least one surface represented by the following general formula (A), and further comprising, on at least one surface: When heated from 25°C to 120°C, the intermediate value of the surface elastic modulus (the value when the cumulative relative frequency reaches 0.50) decreases by 20% or more in multi-point measurements of the surface elastic modulus using a scanning atomic force microscope at 25°C and 120°C. O≧E+0.5 (A) O: Oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS) E: In multipoint measurement of surface elastic modulus using a scanning atomic force microscope at 120°C, the difference between the surface elastic modulus when the cumulative relative frequency reaches 0.99 and the surface elastic modulus when the cumulative relative frequency reaches 0.01.

[0011] The fluororesin is preferably tetrafluoroethylene-perfluoroalkylvinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

[0012] The present disclosure also relates to a laminate including a fluororesin sheet material and a metal layer. 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.

[0013] The laminate further comprises a layer other than the fluororesin sheet material and the metal layer, The layer other than the fluororesin sheet material and the metal layer provided on the surface of the fluororesin sheet material is preferably a layer made of at least one material selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, and polybutadiene. [Effects of the Invention]

[0014] 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. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present disclosure will be described in detail below. In the past, there have been patents specifying the amount of oxygen or specific functional groups required to achieve good adhesion in surface modification of fluororesin sheets using plasma treatment, but these requirements alone are not enough to achieve satisfactory adhesion when bonding below the melting point. Insufficient adhesion can lead to peeling in subsequent processes and reduced reliability of the substrate.

[0016] The present inventors have discovered that, when surface treating a fluororesin sheet material, increasing the in-plane uniformity of the surface treatment improves adhesion to metals such as copper foil when bonding is performed at a temperature below the melting point of the fluororesin. In addition to evaluating the oxygen element content of the fluororesin sheet material, the in-plane uniformity of the surface elastic modulus was also evaluated, and two parameters that can be used to obtain high adhesion were identified.

[0017] One of them is that the following general formula (A) is satisfied on at least one surface of the sheet-shaped material containing a fluororesin. O≧E+0.5 (A) O: Oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS) E: In multipoint measurement of surface elastic modulus using a scanning atomic force microscope at 120°C, the difference between the surface elastic modulus when the cumulative relative frequency reaches 0.99 and the surface elastic modulus when the cumulative relative frequency reaches 0.01.

[0018] A fluororesin sheet material having a specific relationship between the oxygen element ratio O and the difference E in surface elastic modulus, as shown in the above general formula (A), exhibits good adhesion to metal foil when bonded at a temperature below the melting point of the fluororesin, resulting in no poor appearance or peeling and improved reliability as a circuit substrate. By enabling bonding at temperatures below the melting point of the fluororesin, warping of the metal foil is less likely to occur, resulting in a good appearance. Furthermore, by preventing peeling, surface smoothness is maintained, maintaining low transmission loss characteristics. Furthermore, lowering the bonding temperature makes manufacturing easier and improves production efficiency.

[0019] Here, the oxygen element ratio is determined by the following method. (Method for measuring oxygen element ratio) The oxygen element ratio on the surface of the fluororesin sheet material was measured under the conditions below using a scanning X-ray photoelectron spectrometer (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.) The detection targets were carbon, oxygen, fluorine, nitrogen, and silicon, and the oxygen element ratio was calculated from the composition ratio of C1s, O1s, F1s, N1s, and Si2p. Source: Monochromated AlKα Beam diameter: 100 μm X-ray output: 25W Measurement area: 1000μm x 300μm Pass energy: 23.5 eV Detection angle: 45°

[0020] The surface elasticity values ​​were obtained by measuring 64 points x 32 points in a 20 μm x 10 μm area using a scanning atomic force microscope AFM5300E (manufactured by Hitachi High-Tech Science Corporation) in force curve mapping mode. A histogram was created for the surface elasticity at a total of 2,048 points obtained in this way, with a class pitch of 0.01 GPa, and the difference between the class value when the cumulative relative frequency reached 0.99 and the class value when the cumulative relative frequency reached 0.01 was defined as the width of the distribution. The above E is the width of the distribution at a measurement temperature of 120° C., and the smaller the value, the higher the uniformity of the treated surface.

[0021] The mechanism by which the above results are obtained is not clear, but in order to form a bond with a metal, it is important, for example, to bring as many functional groups on the surface of the metal into close proximity. It is thought that by making the surface elastic modulus of the fluororesin sheet material uniform within the plane when heated and eliminating the gap between hard and soft areas, adhesion to the metal foil surface is improved without having to soften it by heating it to near the melting point of the fluororesin, and adhesive strength is improved even at low temperatures. Furthermore, in addition to the uniformity of the surface elastic modulus when heated, adhesiveness is improved when the relationship with the oxygen element ratio of the fluororesin sheet material is specific.

[0022] Furthermore, the difference E between the surface elastic modulus when the cumulative relative frequency reaches 0.99 and the surface elastic modulus when the cumulative relative frequency reaches 0.01 in the general formula (A) is preferably 0.35 GPa≦E≦3.0 GPa. The lower limit of E is more preferably 0.4 GPa or more, even more preferably 0.5 GPa or more, and most preferably 0.6 GPa or more. The upper limit of E is more preferably 2.0 GPa or less, even more preferably 1.5 GPa or less, and most preferably 1.0 GPa or less. If E is within the above range, there is no difference in the surface elastic modulus within the plane, and it can be said that in-plane uniformity is ensured, resulting in good adhesion to metals such as copper foil when bonding is performed at a temperature below the melting point of the fluororesin.

[0023] Also, it is preferable that the above oxygen element ratio O satisfies 1.35 atomic% < O < 20 atomic%. The lower limit of the above oxygen element ratio O is more preferably 1.5 atomic% or more, still more preferably 1.8 atomic% or more, and most preferably 2.0 atomic% or more. Also, the upper limit of the above oxygen element ratio O is more preferably 25 atomic% or less, still more preferably 20 atomic% or less, and most preferably 15 atomic% or less. If the oxygen element ratio is within the above range, it is advantageous in that the functional groups contributing to adhesion are in a suitable amount.

[0024] Another parameter found in the present disclosure is that at least one surface of the fluororesin sheet-like material, in the multi-point measurement of the surface elastic modulus by a scanning atomic force microscope at 25°C and 120°C when heated from 25°C to 120°C, the median value of the surface elastic modulus (the value when the cumulative relative frequency reaches 0.50) decreases by 20% or more. Thus, the median value of the surface elastic modulus when the fluororesin sheet-like material is heated from room temperature level to 120°C decreases by 20% or more. That is, it is presumed that even at an adhesion temperature below the melting point of the fluororesin, the surface tends to become soft and is more likely to be at an appropriate distance for forming bonds with the functional groups present on the surface of the adhesion target.

[0025] Also, it is preferable that the fluororesin sheet-like material of the present disclosure simultaneously satisfies the above two parameters because it is more likely to be close to the adhesion target surface, and thereby the functional groups present on each other's surfaces can be efficiently utilized for bond formation.

[0026] 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.

[0027] (Fluorine resin) 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 these, tetrafluoroethylene (TFE)-(per)fluoro(alkyl vinyl ether) copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene (HFP) copolymer (FEP) is preferred.

[0028] (Per)fluoro(alkyl vinyl ether) (PAVE) may be either a fluoroalkyl vinyl ether or a perfluoro(alkyl vinyl ether). In the present disclosure, a "perfluoro(alkyl vinyl ether)" is an alkyl vinyl ether that does not contain a C-H bond. The PAVE constituting the PAVE unit is represented 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 of 0 to 5, and q represents an integer of 0 to 5.) and a monomer represented by general formula (2): CFX=CXOCF2OR 1 (2) (wherein X may be the same or different and represents H, F or CF3; R 1represents 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.

[0029] 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.

[0030] 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 monomer units. 19 The TFE / PAVE copolymer may be a copolymer consisting of only TFE units and PAVE units.

[0031] 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.

[0032] 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.

[0033] 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 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.

[0034] The TFE / HFP copolymer preferably has a mass ratio (TFE / HFP) of TFE units to HFP units of 70 to 99 / 1 to 30 (mass %), more preferably 85 to 95 / 5 to 15 (mass %).

[0035] The TFE / HFP copolymer may further contain (per)fluoro(alkyl vinyl ether) (PAVE) units. Examples of PAVE units contained in the TFE / HFP copolymer include the same PAVE units as those described above. The TFE / PAVE copolymer does not contain HFP units, and in this respect, it differs from the TFE / HFP / PAVE copolymer.

[0036] 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.

[0037] In the TFE / HFP / PAVE copolymer, the HFP unit preferably accounts for 25% by mass or less of the total monomer units. The content of HFP units 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 HFP units 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 HFP units is 19 It can be measured by F-NMR.

[0038] The content of PAVE units is more preferably 20% by mass or less, even more 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.

[0039] 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.

[0040] 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 70-98 / 0.1-25 / 0.1-25 / 0.1-25 (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.

[0041] The melting point of the TFE / HFP copolymer is preferably 200 to 322°C, more preferably over 200°C, even more preferably 220°C or higher, more preferably 300°C or lower, and even more preferably 280°C or lower.

[0042] 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.

[0043] 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.

[0044] The fluororesin preferably has a melt flow rate of 1 to 50 g / 10 min at 372° C. and a load of 49 N.

[0045] The fewer functional groups the fluororesin has, the fewer 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, or other methods to reduce the number of unstable terminal groups. Fluorine gas treatment is preferred because it has excellent treatment efficiency and converts some or all of the unstable terminal groups to —CF3, resulting in stable terminal groups. The use of fluororesins with a reduced number of unstable terminal groups is preferred because it reduces the electrostatic dissipation factor and reduces electrical signal loss.

[0046] The number of unstable terminal groups is not particularly limited, but is preferably 10 or more when the main chain carbon number of the fluororesin is 10. 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.

[0047] Specific examples of unstable terminal groups include functional groups such as -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), hydroxyl groups (such as -CHOH), -CONH, -COOR (such as R = CH), -CFH, and -OCOO-R (such as normal propyl carbonate).

[0048] 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 with 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 the base spectrum, which is completely fluorinated and has no functional groups. 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): 6 The number of unstable terminal groups per unit is calculated. N=I×K / t (A) I: Absorbance K: Correction coefficient t: film thickness (mm)

[0049] 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 FT-IR measurement data of low molecular weight model compounds.

[0050] [Table 1]

[0051] The fluorination treatment can be carried out by contacting a non-fluorination-treated fluororesin with a fluorine-containing compound.

[0052] The fluorine-containing compound is not particularly limited, but examples thereof include fluorine radical sources that generate fluorine radicals under fluorination treatment conditions, such as F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and halogen fluorides (e.g., IF5, ClF3).

[0053] The fluorine radical source such as F2 gas may be 100% concentrated, but is preferably mixed with an active gas and diluted to 5 to 50 mass %, more preferably 15 to 30 mass %. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, with nitrogen gas being preferred from an economical standpoint.

[0054] 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, and 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 preferably carried out by bringing an unfluorinated fluororesin into contact with fluorine gas (F2 gas).

[0055] 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.

[0056] 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 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.

[0057] 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.

[0058] The thickness of the fluororesin sheet material is a value measured by reflection spectroscopy using a film thickness measurement system F20 (manufactured by Filmetrics).

[0059] The fluororesin sheet material of the present disclosure preferably has an arithmetic mean roughness (Ra) of 30 μm × 30 μm of 30 nm or less, more preferably 20 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 the Ra is within the above range, the smoothness is high and the surface treatment is performed more uniformly within the surface, which is preferable in that the adhesion to the surface to be bonded is enhanced when bonding. The above Ra is a value obtained by the measurement method described below. (Ra (arithmetic mean roughness) of fluororesin sheet material) Using a scanning atomic force microscope AFM5000 (manufactured by Hitachi High-Technologies Corporation), the surface Ra of the surface-treated film surface and the copper foil in a 30 μm×30 μm area was measured under the conditions shown below. Cantilever: SI-DF20 (tip R<10nm, spring constant 15N / m) Measurement mode: AC mode Scanning frequency: 1Hz Number of pixels: 256 x 256

[0060] Furthermore, it is preferable that the difference between the oxygen element ratio of the fluororesin sheet material of the present disclosure when its surface condition is measured using a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) and the oxygen element ratio when the fluororesin sheet material 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 using a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) is 1.0 atomic % or more. The greater the difference in oxygen element ratio from the surface to the depth direction, the more preferable it is in that a predetermined transmission loss can be obtained while maintaining adhesiveness.

[0061] 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.

[0062] 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 being heat-treated, and the adhesive strength is more preferably more than 50 N / m, and even more preferably more than 100 N / m.

[0063] More specifically, the adhesive strength was measured by overlapping the surface-treated surfaces of two fluororesin sheet materials together and heat pressing (200°C, 0.1 MPa, 60 s) to create a sample, cutting it into 10 mm wide strips, and using a precision universal testing machine, Autograph AGS-X 100N (Shimadzu Corporation), the unbonded part of the strip sample was gripped between the top and bottom chucks of the Autograph and pulled at a rate of 100 mm per minute to measure the peel strength, and the value obtained was taken as the adhesive strength.

[0064] The resin sheet material of the present disclosure preferably has a dielectric loss tangent at 10 GHz of less than 0.0015. A dielectric loss tangent within this range is preferable because it can minimize loss of electrical signals in circuits. 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 signal transmission and antenna transmission / reception will be performed at higher frequencies, 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 terminal groups, and it is more preferable to use a fluororesin that has been subjected to a terminal fluorination treatment.

[0065] (Method of manufacturing fluororesin sheet material) An example of a method for producing the fluororesin sheet material of the present disclosure will be described in detail below. Note that the fluororesin sheet material of the present disclosure is not limited to those produced by the following production method. The fluororesin sheet material of the present disclosure is not particularly limited in the molding method for forming it into a sheet, but examples thereof include a melt molding method such as extrusion molding, a casting method in which a solution or dispersion containing a fluororesin is prepared, and then coated on a substrate and dried, etc. Furthermore, the sheet may be stretched by a uniaxial or biaxial stretching method, or may be an unstretched sheet.

[0066] By performing a surface treatment on one or both sides of the fluororesin sheet material obtained in this manner under appropriate conditions, a fluororesin sheet material that satisfies the above two parameters can be obtained.

[0067] The specific method for the surface modification is not particularly limited, but specific examples are described in detail below. The surface of the fluororesin sheet material can be modified by conventional discharge treatments such as corona discharge treatment, glow discharge treatment, plasma discharge treatment, sputtering treatment, etc. Corona discharge treatment is particularly preferred. For example, the 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, 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 the electrodes to generate an electric discharge, thereby generating active species on the surface. The surface can then be modified by introducing functional groups of the organic compound or graft-polymerizing a polymerizable organic compound. Examples of the inert gas include nitrogen gas, helium gas, and argon gas.

[0068] It is particularly preferable to use nitrogen gas and argon gas in combination, and it is further preferable to use carbon dioxide gas. The ratio (by volume) of nitrogen gas to argon gas is preferably 30 / 70 to 100 / 0, more preferably 40 / 60 to 80 / 20, and even more preferably 50 / 50 to 70 / 30. If the ratio of nitrogen gas to argon gas is within the above range, the discharge is stable, which is advantageous in that more uniform in-plane surface modification can be achieved. The carbon dioxide gas content is preferably 0.05 to 5% by volume, more preferably 0.1 to 2% by volume, relative to the nitrogen gas / argon gas. If the carbon dioxide content is within the above range, it is advantageous in that functional groups that contribute to adhesiveness on the surface of the fluororesin sheet material are imparted within a suitable range.

[0069] 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; and 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.

[0070] The concentration of the organic compound in the organic compound-containing inert gas varies depending on the type of the 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 can be selected appropriately depending on the desired degree of surface modification, the type of fluororesin, the type and concentration of organic compounds, etc. The discharge rate is usually 50 to 1500 W·min / m 2 , preferably 100 W·min / m 2 More than 1400W min / m 2 Less than or equal to 200W·min / m 2 More than 1300W min / m 2 Discharge treatment is performed within the following range. The treatment temperature can be any temperature in the range of 0° C. to 100° C. In view of concerns about stretching and wrinkling of the fluororesin sheet material, a temperature of 80° C. or less is preferred. Considering that oxygen elements on the surface are deactivated by heat applied during lamination with metal foil or the like, and adhesive ability is reduced, the degree of surface modification of the fluororesin sheet material is such that the abundance ratio of oxygen elements 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 effect on productivity and other physical properties, it is preferably 25.0% or less. The abundance ratio of the nitrogen element is not particularly limited, but it is preferably 0.1% or more.

[0071] In the above surface modification, the discharge intensity, which indicates the output per unit area, is 1.0 to 10 W / cm 2 It is preferable to carry out the discharge treatment within this range, and adjust the gas concentration / line speed ratio during this treatment to within the range of 0.005 to 0.05 L / m. The gas concentration / line speed ratio referred to here indicates the ratio obtained by dividing the organic compound concentration in the organic compound-containing inert gas by the line speed. If the flow rate is lower than 0.005 L / m, the space will not be filled with enough gas relative to the conveying speed, making it difficult for the activated gas to contact the surface of the fluororesin sheet material, and the in-plane uniformity will tend to decrease. If the flow rate is higher than 0.05 L / m, the surface will be over-treated and damaged, and low-molecular-weight compounds will be generated on the surface, forming a brittle layer and tending to reduce the adhesive strength. Therefore, processing within this range is particularly preferred, as it is assumed that the in-plane treatment of the fluororesin sheet material will be more uniform and the desired adhesiveness will be obtained.

[0072] 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.

[0073] 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 film caused by 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 carry out 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.

[0074] 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.

[0075] The annealing temperature is preferably at least 20° C. below the glass transition temperature of the fluororesin and less than the melting point, more preferably at least 20° C. above the glass transition temperature of the fluororesin and less than the melting point, and even more preferably at least 60° C. above the glass transition temperature of the fluororesin and less than the melting point. The annealing time is not particularly limited, but may be adjusted as appropriate within the range of, for example, 0.5 to 60 minutes.

[0076] When heating is performed by the roll-to-roll method, the tension may be adjusted as appropriate 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.

[0077] 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.

[0078] (Laminate) The fluororesin sheet material of the present disclosure is suitably used to form a laminate with a metal or resin substrate, etc. The present disclosure also relates to a laminate including the above-mentioned fluororesin sheet material and a metal layer. The laminate of the present disclosure is preferably configured so that the surface of the fluororesin sheet material having the above-described properties is in contact with a metal layer.

[0079] (metal layer) In the present disclosure, examples of metals constituting the metal layer include copper, aluminum, SUS, nickel, and gold. Alloys of these metals can also be used. From the viewpoints of electrical conductivity and circuit processability, it is preferable to use copper foil.

[0080] The copper foil preferably has an Rz of 1.5 μm or less. That is, the fluororesin sheet material of the present disclosure also has excellent adhesion to copper foil, which has a high smoothness of Rz of 1.5 μm or less. Furthermore, it is sufficient for at least the surface of the copper foil that adheres to the fluororesin film to have an Rz of 1.5 μm or less, and the Rz value of the other surface is not particularly limited. The Rz is the sum 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.

[0081] 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.

[0082] The copper foil is not particularly limited, and specific examples include rolled copper foil and electrolytic copper foil.

[0083] 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.).

[0084] The copper foil may be surface-treated to enhance the adhesive strength with the fluororesin sheet material of the present disclosure.

[0085] The surface treatment is not particularly limited, but may be a silane coupling treatment, plasma treatment, corona treatment, UV treatment, electron beam treatment, or the like. 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-preventive layer (such as an oxide film such as chromate), a heat-resistant layer, or the like formed thereon.

[0086] 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.

[0087] The copper foil may have a roughened layer on the surface thereof from the viewpoint of improving adhesion to the fluororesin sheet material. If the roughening treatment is likely to degrade 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 roughening treatment may not be performed at all.

[0088] 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.

[0089] In the laminate of the present disclosure, the adhesive strength between the metal layer and the fluororesin sheet material is preferably 0.5 N / cm or more. Such adhesive strength can be achieved by adhering to the metal layer a surface of the fluororesin sheet material of the present disclosure where the general formula (A) is satisfied and / or a surface of the fluororesin sheet material of the present disclosure where the median value of the surface elastic modulus (the value when the cumulative relative frequency reaches 0.50) decreases by 20% or more when the surface elastic modulus is measured at multiple points by a scanning atomic force microscope at 25°C and 120°C when the material is heated from 25°C to 120°C. By increasing the adhesive strength to 1 N / cm or more, and further to 2 N / cm or more, the adhesive can be suitably used as a copper-clad laminate or a circuit board. The adhesive strength here means the adhesive strength measured under the conditions described in the examples.

[0090] (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 a metal layer, or may have a three-layer or more structure having two or more layers of either or both of these.Furthermore, it may have a three-layer or more structure having a layer (X) other than the metal layer and the fluororesin sheet material.

[0091] 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.

[0092] When the laminate of the present disclosure has the layer (X), the layer configuration can be 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 layer (X). In the present disclosure, it is preferable to provide a layer (X) on the surface of the fluororesin sheet material.

[0093] In addition, in the case of a laminate in which copper foil is bonded 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.

[0094] (Method of manufacturing laminate) The method for producing 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 in the step of bonding it to the fluororesin sheet material are adjusted.

[0095] Heating is required when bonding the metal foil and the fluororesin sheet material, and in producing the laminate of the present disclosure, it is preferable to set the temperature at or below the melting point of the fluororesin. Specifically, the heating temperature is preferably 70 to 300°C, more preferably 70 to 250°C, and even more preferably 70 to 200°C. The fluororesin sheet material of the present disclosure has excellent adhesion to a metal layer even when bonded at a temperature below the melting point of the fluororesin. The heat treatment step 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, by setting the heating temperature to a low temperature, warping of the metal foil is suppressed, and the smoothness of the bonding surface is less likely to be impaired in the process of bonding the metal foil layer and the fluororesin sheet material, which is preferable. As a result, defects in appearance and peeling are eliminated, improving the reliability of the circuit board.

[0096] 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.

[0097] 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.

[0098] 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. Therefore, it is suitable for use in circuit boards, etc., and is particularly suitable for use in circuit boards for high-frequency circuits.

[0099] 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. [Example]

[0100] 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.

[0101] Example 1 [Method of manufacturing fluororesin sheet material] PFA was charged into an extruder at 360°C, extruded through a 1700 mm wide T-die, taken up onto a metal cooling roll, and then wound onto a take-up core to obtain a 1300 mm wide, 12 μm thick roll sheet. The PFA was a TFE / PPVE copolymer, with a composition of TFE / PPVE=95.4 / 4.6 (mass%), MFR of 15.8 g / 10 min, a melting point of 305°C, and a main chain carbon number of 10. 6 297 pieces were used per piece.

[0102] [Number of unstable terminal groups] FT-IR Spectrometer 1760X (Perkin-Elmer) The analysis was carried out using

[0103] [Surface treatment] Surface treatment was performed on both sides of the roll sheet (a corona discharge device). An inert gas (nitrogen / Ar ratio 75 / 25) containing 0.50% by volume of vinyl acetate and 0.25% by volume of carbon dioxide was passed around the discharge electrode and roll-shaped ground electrode. The sheet was passed continuously along the roll-shaped ground electrode, and discharged at 150 W·min / m. 2 Both sides of the sheet were subjected to corona discharge treatment at 1000 W (at 1000 W), and the long sheet was wound into a roll to obtain a surface-treated sample. Thereafter, the oxygen element ratio and surface elastic modulus were evaluated as described below.

[0104] [Method of manufacturing laminate] The obtained fluororesin sheet material and electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) were used to cut out each, and then the copper foil, fluororesin sheet material, and copper foil were layered in this order, with the unroughened side 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 material was heat-pressed in a vacuum heat press (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 120°C, a preheat time of 120 seconds, a pressure of 10 MPa, and a press time of 600 seconds.

[0105] Example 2 Discharge rate: 200W·min / m2 A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed, and then the sample was evaluated.

[0106] Example 3 A surface-treated sample was obtained in the same manner as in Example 1, except that the carbon dioxide gas was changed to 0.5% by volume, and then evaluated.

[0107] Example 4 A surface-treated sample was obtained in the same manner as in Example 1, except that the nitrogen / Ar ratio was set to 65 / 35, and then evaluated.

[0108] Example 5 A surface-treated sample was obtained in the same manner as in Example 1, except that the nitrogen / Ar ratio was 65 / 35 and the carbon dioxide gas was 0.5% by volume, and then the sample was evaluated.

[0109] Example 6 Nitrogen / Ar ratio 65 / 35, carbon dioxide 0.5% by volume, discharge rate 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, and then the sample was evaluated.

[0110] Example 7 Fluorine resin: 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 surface-treated sample was obtained in the same manner as in Example 1, except that the nitrogen / Ar ratio was set to 55 / 45, and then evaluation was performed.

[0111] Example 8 Fluorine resin: 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 6The nitrogen / Ar ratio was set to 55 / 45, and the discharge rate was set to 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, and then the sample was evaluated.

[0112] Example 9 Fluorine resin: 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 The nitrogen / Ar ratio was set to 55 / 45 and the discharge rate was set to 250 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, and then the sample was evaluated.

[0113] Example 10 Fluorine resin: Fluorinated PFA2 (TFE / PPVE copolymer, composition: TFE / PPVE = 96.1 / 3.9 (mass%), MFR: 16.0 g / 10 min, melting point: 305 °C, number of unstable terminal groups: undetectable (main chain carbon number: 10 6 The nitrogen / Ar ratio was set to 55 / 45 and the discharge rate was set to 250 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, and then the sample was evaluated.

[0114] (Comparative Example 1) The nitrogen / Ar ratio was 100 / 0, vinyl acetate was not added, carbon dioxide was not added, and the discharge rate was 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, and then the sample was evaluated.

[0115] (Comparative Example 2) The nitrogen / Ar ratio was 100 / 0, vinyl acetate was not added, carbon dioxide was not added, and the discharge rate was 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, and then the sample was evaluated.

[0116] (Comparative Example 3) Nitrogen / Ar ratio 100 / 0, carbon dioxide 0.25% by volume, discharge rate 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, and then the sample was evaluated.

[0117] Comparative Example 4 The nitrogen / Ar ratio was set to 100 / 0, no carbon dioxide was added, and the discharge rate was 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, and then the sample was evaluated.

[0118] (Method for measuring oxygen element ratio) The measurement sample was obtained by cutting a 1cm x 1cm square from a location adjacent to the cut-out portion of the fluororesin sheet material used to manufacture the laminate. The oxygen element ratio on the inner surface of a roll of surface-treated fluororesin sheet material was measured using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000 VersaProbe II (manufactured by ULVAC-PHI, Inc.) under the conditions listed 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. Source: Monochromated AlKα Beam diameter: 100 μm X-ray output: 25W Measurement area: 1000μm x 300μm Pass energy: 23.5 eV Detection angle: 45°

[0119] (Method for measuring surface elastic modulus) The measurement sample was obtained by cutting out a 1 cm x 1 cm square from a location adjacent to the cut-out portion of the fluororesin sheet material used to manufacture the laminate. The surface elastic modulus was measured on the inner surface of a roll of the surface-treated fluororesin sheet material using a scanning atomic force microscope AFM5300E (manufactured by Hitachi High-Tech Science Corporation) under the following conditions. Cantilever: Si cantilever (Al coated on the back, Hitachi High-Tech Fielding, tip R≦10 nm, spring constant 2 N / m) Pressing load: 10nN Measurement mode: Force curve mapping (FCM) mode Measurement environment: Atmospheric, 120°C Measurement field of view: 20 μm x 10 μm (64 points x 32 points)

[0120] (Calculation method for surface elastic modulus distribution width) A histogram was created for the surface elastic modulus of 2,048 points obtained as described above, with a 0.01 GPa interval, and the difference between the class value when the cumulative relative frequency reached 0.99 and the class value when the cumulative relative frequency reached 0.01 was taken as the width of the distribution. The width of the distribution was evaluated at 120°C, which is the assumed bonding temperature.

[0121] (Calculation method for the reduction rate of surface elastic modulus) The class value (median value) when the cumulative relative frequency obtained from the histogram obtained above reached 0.50 was evaluated for the rate of decrease in the median value when heated from room temperature (25°C) to 120°C.

[0122] (Adhesion strength between copper foil and fluororesin sheet material) An aluminum plate was attached to the underside of the laminate with adhesive tape, and a Tensilon universal testing machine (Shimadzu Corporation) was used to measure the peel strength of the copper foil by gripping and pulling a 10 mm wide piece of copper foil in a direction 90° to the plane of the laminate at a speed of 50 mm per minute, and the obtained value was taken as the adhesive strength. The measurement results are shown in Table 2.

[0123] [Table 2]

[0124] From the results in Table 2, the fluororesin sheet materials of the examples had good adhesiveness at temperatures below the melting point of the fluororesin. [Industrial Applicability]

[0125] The fluororesin sheet material of the present disclosure can be suitably used as a circuit substrate.

Claims

1. A sheet-like material containing a fluororesin, wherein the following general formula (A) is satisfied on at least one surface of the sheet-like material: O≧E+0.5...(A) O: Oxygen element ratio measured by a scanning X-ray photoelectron spectrometer (XPS) E: In multipoint measurement of surface elastic modulus at 120°C using a scanning atomic force microscope, the difference between the surface elastic modulus when the cumulative relative frequency reaches 0.99 and the surface elastic modulus when the cumulative relative frequency reaches 0.

01.

2. 2. The fluororesin sheet material according to claim 1, wherein the difference E between the surface elastic modulus when the cumulative relative frequency reaches 0.99 and the surface elastic modulus when the cumulative relative frequency reaches 0.01 satisfies 0.35 GPa≦E≦3.0 GPa.

3. 3. The fluororesin sheet material according to claim 1, wherein the oxygen element ratio O satisfies the relationship 1.35 atomic %<O<20 atomic %.

4. A sheet-like material containing a fluororesin, at least one surface of which is A fluororesin sheet material in which, when heated from 25°C to 120°C, the median value of the surface elastic modulus (the value when the cumulative relative frequency reaches 0.50) decreases by 20% or more in multi-point measurements of the surface elastic modulus using a scanning atomic force microscope at 25°C and 120°C.

5. A sheet-like material containing a fluororesin, at least one surface of which is 2. The fluororesin sheet material according to claim 1, wherein when heated from 25°C to 120°C, in multipoint measurements of surface elasticity at 25°C and 120°C using a scanning atomic force microscope, the median value of the surface elasticity (the value when the cumulative relative frequency reaches 0.50) decreases by 20% or more.

6. 6. The fluororesin sheet material according to claim 5, wherein the fluororesin is tetrafluoroethylene-perfluoroalkylvinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

7. A laminate comprising the fluororesin sheet material according to claim 5 or 6 and a metal layer.

8. 8. The laminate according to claim 7, wherein the adhesive strength between the measurement surface of the fluororesin sheet material and the metal layer is 0.5 N / cm or more.

9. Furthermore, the sheet-like material has a layer other than the fluororesin sheet material and the metal layer, 8. The laminate according to claim 7, wherein the layer other than the fluororesin sheet material and the metal layer provided on the surface of the fluororesin sheet material is a layer made of at least one material selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, and polybutadiene.

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