Fluororesin film, metal-clad laminate and board for circuit

Abstract

To provide a fluororesin film having high uniformity of adhesive strength of a film.SOLUTION: A fluororesin film is a film composed of a composition containing a fluororesin, wherein an average value of contact angles to water measured at 5 positions, at intervals of 100 mm in a travel direction, in a place separated from a center, a right end and a left end in at least one surface by 100 mm is 105° or less, an average value of contact angles to n-hexadecane measured at 5 positions, at intervals of 100 mm in the travel direction, is 45° or less, and the film is long.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a fluororesin film, a metal-clad laminate, and a circuit board. [Background technology]

[0002] Epoxy resins and polyimide resins are widely used as insulating layers for circuit boards. In recent years, for high-frequency circuit boards used in applications in the high-frequency range of several tens of gigahertz, several configurations have been proposed in which an insulating layer of fluororesin is formed on a metal foil from the viewpoints of dielectric properties and moisture absorption.

[0003] In such printed wiring boards, the fluororesin film is sometimes subjected to a surface treatment to improve adhesion to the metal foil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication 2019-11413 [Patent Document 2] Patent Publication 2008-200991 [Patent Document 3] International Publication 2020 / 066457 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a fluororesin film having high uniformity in the adhesive strength of the film. [Means for solving the problem]

[0006] The present disclosure relates to The fluororesin film is made of a composition containing a fluororesin, and on at least one surface, at locations 100 mm from the center and each of the left and right ends, the average contact angle with water measured at five locations 100 mm apart in the running direction is 105° or less, and the average contact angle with n-hexadecane measured at five locations 100 mm apart in the running direction is 45° or less.

[0007] The fluororesin film preferably has a film width of 400 mm or more. The fluororesin preferably contains tetrafluoroethylene-perfluoroalkylvinylether (PFA) and / or tetrafluoroethylene-hexafluoropropylene (FEP).

[0008] The fluororesin film preferably has a dielectric loss tangent at 10 GHz of less than 0.0015. The number of unstable functional groups in the above fluororesin film is 1 × 10 6 It is preferable that there are less than 10 per unit.

[0009] The fluororesin film preferably has an adhesive strength of 0.8 N / mm or more between the metal foil having a surface roughness Rz of 1.5 μm or less and locations 100 mm from the center and each of the left and right ends of the fluororesin film.

[0010] The fluororesin film preferably has an adhesive strength of 0.8 N / mm or more between the prepreg containing epoxy resin and / or polyphenylene ether and locations 100 mm from the center and each of the left and right ends of the fluororesin film.

[0011] The fluororesin film preferably has an adhesion temperature to a metal foil of at least 200° C. The fluororesin film is preferably used for a metal-clad laminate.

[0012] The present invention also relates to a metal clad laminate having a metal foil and the above-mentioned fluororesin film as essential layers. The present invention also relates to a metal clad laminate comprising a metal foil having a surface roughness Rz of 1.5 μm or less and a fluororesin film, characterized in that the contact angle with water at the center and at locations 100 mm from each of the left and right ends of the surface of the fluororesin film not facing the metal foil is 105° or less, and the contact angle with n-hexadecane is 45° or less.

[0013] In the above metal clad laminate, the metal foil preferably has a surface roughness Rz of 1.5 μm or less. In the metal clad laminate of the present disclosure, the adhesive strength between the prepreg and locations 100 mm from the center and each of the left and right ends of the laminate is preferably 0.8 N / mm or more.

[0014] The metal clad laminate of the present disclosure further has a layer other than the metal foil and the fluororesin film, and the layer other than the metal foil and the fluororesin film is preferably at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, and polybutadiene.

[0015] The present disclosure also relates to a circuit board comprising the above-mentioned metal clad laminate. Effect of the Invention

[0016] The fluororesin film of the present disclosure exhibits the effect of having high uniformity in the adhesive strength of the film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present disclosure will now be described in detail. When a fluororesin film is used as a substrate for a metal-clad laminate, a metal foil, other resins, etc. may be laminated on the substrate. Since fluororesins are resins that inherently have low adhesive properties, there are cases where it is required to improve the adhesive properties in this case.

[0018] In order to improve such adhesiveness, it is known that the fluororesin film is subjected to surface treatment such as plasma treatment, corona treatment, sputtering treatment, etc. However, in such treatments, it is difficult to perform a uniform surface treatment, and unevenness in the treatment often occurs.

[0019] However, when a fluororesin film is used in a printed wiring board, uneven adhesion is a major problem from the viewpoint that metal wiring is formed in areas where the surface treatment is weak, which may cause peeling after circuit formation and raise concerns that the quality may not meet customer requirements. For this reason, there has been a demand for a fluororesin film with a uniform surface condition that can improve this problem.

[0020] In consideration of the problems described above, the present disclosure provides a fluororesin film having a uniform surface condition, in which a contact angle with water is 105° or less, and a contact angle with n-hexadecane is 45° or less, at locations 100 mm from the center and each of the left and right ends, due to a uniform surface treatment being performed. Each of these points will be explained in detail below.

[0021] (Surface condition of fluororesin film) The fluororesin film of the present disclosure satisfies the requirements that the contact angle with water is 105° or less and the contact angle with n-hexadecane is 45° or less at locations 100 mm from the center and each of the left and right ends.

[0022] When a surface treatment is performed to improve the adhesiveness of a fluororesin film, the contact angle of the film surface with water or n-hexadecane decreases. However, depending on the state of the surface treatment, the contact angle of the surface varies, and there are some places where the contact angle is not sufficiently reduced. The present disclosure improves this point by performing a highly uniform surface treatment, and is characterized by selecting a treatment method and treatment conditions that sufficiently reduce the surface tension with respect to both water and organic solvents.

[0023] The state of the surface treatment of the film is likely to differ between the ends and the center of the film, and therefore the present disclosure is characterized in that the above-mentioned contact angle is satisfied in both the ends and the center.

[0024] The surface condition of the fluororesin film of the present disclosure is such that, at all three locations 100 mm from the center and each of the left and right ends, the arithmetic mean of contact angles with water measured at five locations 100 mm apart in the running direction is 105° or less, and the arithmetic mean of contact angles with n-hexadecane measured at five locations 100 mm apart in the running direction is 45° or less.

[0025] The fluororesin film of the present disclosure may have both sides satisfying the above-mentioned parameters, or only one side may satisfy the above-mentioned parameters.

[0026] (Fluororesin film) The fluororesin film of the present disclosure is preferably a long film. In the case of a long film, there are a width direction and a length direction, and the length direction is the long direction. The measurement positions are three positions in the width direction: the center and positions 100 mm from both ends.

[0027] For each of the three measurement positions, an arbitrary position is designated as the first measurement point, and the contact angle is measured at five positions 100 mm apart in the longitudinal direction from that measurement point, and the average of these measured values ​​is defined as the contact angle in this disclosure.

[0028] The contact angles are measured at five points at each of three positions in the width direction, but in terms of the length direction, the contact angles are measured at five points at the same position and the average is taken.

[0029] In this way, when the contact angles with water and n-hexadecane are measured at five points, the contact angles are 105° or less and 45° or less, respectively. By doing so, the above-mentioned problems are solved. Although the details of the relationship between water and n-hexadecane and the adhesive strength are unknown, it is presumed that it is preferable to set the contact angles within a certain range from the following viewpoints.

[0030] A lower contact angle with water suggests that there is a lot of polar components (functional groups) on the film surface that have a strong interaction with water, and a lower contact angle with n-hexadecane suggests that there is a lot of non-polar components on the surface that have a strong interaction with n-hexadecane. Adhesion requires high wettability to increase the contact area with the opposing material, and strong adhesion between the substrates through chemical bonds and anchor effects. Fluorine has low wettability with all materials, so it is speculated that increasing its interaction with both polar and non-polar components to increase wettability is a factor in improving adhesive strength.

[0031] In this disclosure, the contact angle refers to a static contact angle, and the static contact angle was measured using a fully automatic contact angle meter DropMaster700 (manufactured by Kyowa Interface Science Co., Ltd.) in the following manner. 2 μL of solution was dropped from a microsyringe onto a horizontally placed substrate, and a still image was taken 1 second after the drop using a video microscope to determine the static contact angle. The static contact angle was measured at a specified location, and the average value was calculated and used.

[0032] The average contact angle with water is more preferably 105° or less, more preferably 100° or less, and even more preferably 90° or less. The average contact angle with n-hexadecane is more preferably 45° or less, more preferably 40° or less, and even more preferably 35° or less. A method for producing a fluororesin film having such a contact angle will be described in detail below.

[0033] The fluororesin film of the present disclosure preferably has a thickness of 5 to 150 μm. A thickness within this range is preferable from the viewpoint of having sufficient performance as a substrate film. The lower limit of the thickness is more preferably 5 μm, and even more preferably 10 μm. The upper limit of the thickness is more preferably 150 μm, and even more preferably 100 μm.

[0034] In the present disclosure, the thickness of the film is measured at 12 locations every 5 mm in the width direction and every 200 mm in the running direction. Then, for the same width direction, the thicknesses at 12 locations in the running direction are arithmetically averaged. These values ​​are the average film thickness in the running direction measured every 5 mm in the width direction. The arithmetic mean of all the average film thickness values ​​in the running direction measured every 5 mm in the width direction in this way is the average film thickness of the entire surface.

[0035] When comparing the average film thickness thus obtained with the average film thickness in each running direction for every 5 mm in the width direction, it is preferable that the average film thickness in each running direction for every 5 mm in the width direction is all within the range of the average value ±2 μm.

[0036] This means that the film has extremely high thickness uniformity, and if the film has such high uniformity, when a long film is wound up, the difference in thickness is small, so that a highly uniform film can be wound up in a good condition. This is preferable in that problems are less likely to occur during the subsequent lamination with metal foil. Furthermore, the characteristic impedance can be kept within a good range.

[0037] A film that is highly uniform in terms of both the state of the surface treatment and the thickness of the film is preferred in that it can achieve uniform adhesion, particularly in applications where it is to be bonded to a metal foil.

[0038] The fluororesin film of the present disclosure is preferably a long film. More specifically, the width is preferably 400 mm or more and the length is preferably 3 m or more. From the viewpoint of productivity, the width is more preferably 500 mm or more. Also, the length is more preferably 10 m or more. Such a long film is preferably a roll film.

[0039] (Fluorine resin) The fluororesin constituting the fluororesin film of the present disclosure should preferably have a smaller number of unstable functional groups, and such a fluororesin can be produced by adjusting the conditions during production (polymerization reaction), or by subjecting the fluororesin after polymerization to fluorine gas treatment (fluorination treatment), heat treatment, supercritical gas extraction treatment, etc. Fluorine gas treatment is preferred because it has excellent treatment efficiency and because some or all of the unstable functional groups are converted to -CF3 to become stable terminal groups. The use of a fluororesin with a reduced number of unstable functional groups in this way is preferred because it reduces the electrostatic dissipation factor and reduces the loss of electrical signals. The fluororesin disclosed in the present disclosure has a number of unstable functional groups equal to 1×10 6 It is preferable that the number of unstable functional groups is less than 350 per unit area. By having such a small number of unstable functional groups, gas generation during melt molding is suppressed, and thickness deviation due to drift of the molten resin caused by gas remaining near the slit of the T-die can be suppressed.

[0040] The number of unstable functional groups is 1 x 10 6 More preferably, there are less than 250 per molecule, even more preferably, there are less than 100 per molecule, even more preferably, there are less than 20 per molecule, and most preferably, there are less than 10 per molecule.

[0041] Specific examples of the unstable functional group include -COF, -COOH free, -COOH bonded, -CH2OH, -CONH2, and -COOCH3.

[0042] Specifically, the number of unstable functional 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 unstable functional groups in the main chain of 1×10 carbon atoms in the fluororesin is calculated according to the following formula (A): 6 The number of unstable functional groups per unit is calculated. N=I×K / t (A) I: Absorbance K: Correction coefficient t: film thickness (mm)

[0043] For reference, the absorption frequencies, molar absorption coefficients, and correction coefficients for the unstable functional 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.

[0044] [Table 1]

[0045] The fluorination treatment can be carried out by contacting a non-fluorination-treated fluororesin with a fluorine-containing compound.

[0046] The fluorine-containing compound is not particularly limited, but may be a fluorine radical source that generates fluorine radicals under fluorination treatment conditions, such as F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, halogen fluorides (e.g., IF5, ClF3), etc.

[0047] The fluorine radical source such as F2 gas may be of 100% concentration, but is preferably mixed with an inert gas and diluted to 5 to 50% by mass, more preferably 15 to 30% by mass. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, with nitrogen gas being preferred from an economical standpoint.

[0048] The conditions for the fluorination treatment are not particularly limited, and the fluorine-containing compound may be contacted with the molten fluororesin, 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 preferably carried out by contacting the unfluorinated fluororesin with fluorine gas (F2 gas).

[0049] 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.

[0050] The resin constituting the fluororesin film of the present disclosure is not particularly limited, and may be a polymer containing fluorine atoms in part. The fluororesin is more preferably a melt-moldable fluororesin, and examples thereof include tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), copolymer having chlorotrifluoroethylene (CTFE) units (CTFE copolymer), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV), tetrafluoroethylene-vinylidene fluoride copolymer, etc. Among these melt-moldable fluororesins, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are preferred.

[0051] By using the above melt-moldable fluororesin, melt molding can be performed, so the processing cost can be reduced compared to the case of using PTFE. Furthermore, the adhesiveness when bonding with metal foil can be improved.

[0052] The melting point of the PFA is preferably 180 to 340° C., more preferably 230 to 330° C., and further preferably 280 to 320° C. The melting point is the temperature corresponding to the maximum value on the heat of fusion curve when the temperature is increased at a rate of 10° C. / min using a differential scanning calorimeter [DSC].

[0053] The PFA is not particularly limited, but is preferably a copolymer in which the molar ratio of TFE units to PAVE units (TFE units / PAVE units) is 70 / 30 or more and less than 99.5 / 0.5. A more preferred molar ratio is 70 / 30 or more and 98.9 / 1.1 or less, and an even more preferred molar ratio is 80 / 20 or more and 98.5 / 1.5 or less. If the TFE units are too few, the mechanical properties tend to decrease, and if the TFE units are too many, the melting point tends to become too high and moldability tends to decrease. The PFA may be a copolymer consisting of only TFE and PAVE, or it is also preferable that the monomer units derived from monomers copolymerizable with TFE and PAVE are 0.1 to 10 mol %, and the TFE units and PAVE units are 90 to 99.9 mol % in total. Examples of monomers copolymerizable with TFE and PAVE include HFP, CZ3Z4=CZ5(CF2) n Z6 (wherein Z3, Z4 and Z5 are the same or different and each represents a hydrogen atom or a fluorine atom, Z6 represents a hydrogen atom, a fluorine atom or a chlorine atom, and n is an integer of 2 to 10) represents an integer.) and alkyl perfluorovinyl ether derivatives represented by CF2=CF-OCH2-Rf7 (wherein Rf7 represents a perfluoroalkyl group having 1 to 5 carbon atoms). Other copolymerizable monomers include, for example, cyclic hydrocarbon monomers having an acid anhydride group, and examples of acid anhydride monomers include itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, and maleic anhydride. The acid anhydride monomers may be used alone or in combination of two or more.

[0054] The PFA preferably has a melt flow rate (MFR) of 0.1 to 100 g / 10 min, more preferably 0.5 to 90 g / 10 min, and even more preferably 1.0 to 85 g / 10 min. In this specification, the MFR is a value measured according to ASTM D3307 under conditions of a temperature of 372° C. and a load of 5.0 kg.

[0055] The FEP is not particularly limited, but is preferably a copolymer in which the molar ratio of TFE units to HFP units (TFE units / HFP units) is 70 / 30 or more and less than 99 / 1. A more preferred molar ratio is 70 / 30 or more and 98.9 / 1.1 or less, and an even more preferred molar ratio is 80 / 20 or more and 97 / 3 or less. If the TFE units are too few, the mechanical properties tend to decrease, and if the TFE units are too many, the melting point tends to become too high and the moldability tends to decrease. It is also preferred that the FEP is a copolymer in which the monomer units derived from a monomer copolymerizable with TFE and HFP are 0.1 to 10 mol %, and the total of the TFE units and HFP units is 90 to 99.9 mol %. Examples of the monomers copolymerizable with TFE and HFP include alkyl perfluorovinyl ether derivatives.

[0056] The melting point of the FEP is preferably 150 to 320° C., more preferably 200 to 300° C., and further preferably 240 to 280° C. The melting point is the temperature corresponding to the maximum value on the heat of fusion curve when the temperature is increased at a rate of 10° C. / min using a differential scanning calorimeter [DSC]. The FEP has an MFR of preferably 0.01 to 100 g / 10 min, more preferably 0.1 to 80 g / 10 min, further preferably 1 to 60 g / 10 min, and particularly preferably 1 to 50 g / 10 min.

[0057] The fluororesin film of the present disclosure may contain components other than 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 fluororesin is preferably 5% by mass or less (more preferably 3% or less, 1% or less, etc.).

[0058] The composition containing the fluororesin of the present disclosure may contain spherical silica particles, which improves the flowability of the resin and makes it easy to mold even when a large amount of silica is blended.

[0059] The spherical silica particles refer to particles whose particle shape is close to a perfect sphere. Specifically, the sphericity is preferably 0.80 or more, more preferably 0.85 or more, even more preferably 0.90 or more, and most preferably 0.95 or more. The sphericity is calculated by taking a photograph with an SEM and calculating the value calculated from the area and perimeter of the observed particle as (sphericity) = {4π x (area) ÷ (perimeter) 2}. The closer to 1, the closer to a perfect sphere. Specifically, the arithmetic average value measured for 100 particles using an image processing device (Spectris Corporation: FPIA-3000) is used.

[0060] The spherical silica particles preferably have a D90 / D10 of 2 or more (preferably 2.3 or more, 2.5 or more) and a D50 of 10 μm or less when the volume is calculated from the smallest particle size. Furthermore, it is preferable that the D90 / D50 is 1.5 or more (more preferably 1.6 or more). It is preferable that the D50 / D10 is 1.5 or more (more preferably 1.6 or more). Since the small particle size spherical silica particles can enter the gaps between the large particle size spherical silica particles, it is possible to achieve excellent filling properties and high fluidity. In particular, it is preferable that the particle size distribution has a high frequency on the small particle size side compared to a Gaussian curve. The particle size can be measured by a laser diffraction scattering type particle size distribution measuring device. It is also preferable that coarse particles having a particle size of a predetermined size or more are removed by a filter or the like.

[0061] The spherical silica particles preferably have a water absorption of 1.0% or less, more preferably 0.5% or less. The water absorption is based on the mass of the silica particles when dry. The water absorption is measured by leaving a sample in a dry state at 40°C and 80% RH for 1 hour, and measuring the water generated by heating at 200°C using a Karl Fischer water content meter, and then calculating the water absorption.

[0062] Alternatively, the spherical silica particles can be prepared by heating the fluororesin composition at 600° C. for 30 minutes in an air atmosphere to burn off the fluororesin, and then extracting the spherical silica particles, after which the above-mentioned parameters can be measured using the above-mentioned method.

[0063] The silica powder of the present invention may be surface-treated. By previously performing the surface treatment, aggregation of the silica particles can be suppressed, and the silica particles can be well dispersed in the resin composition.

[0064] The surface treatment is not particularly limited, and any known surface treatment can be used. Specific examples include treatment with a silane coupling agent such as epoxysilane, aminosilane, vinylsilane, acrylicsilane, hydrophobic alkylsilane, phenylsilane, or fluorinated alkylsilane having a reactive functional group, plasma treatment, and fluorination treatment. It is possible.

[0065] Examples of the silane coupling agent include epoxy silanes such as γ-glycidoxypropyltriethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, amino silanes such as aminopropyltriethoxysilane and N-phenylaminopropyltrimethoxysilane, vinyl silanes such as vinyltrimethoxysilane, and acrylic silanes such as acryloxytrimethoxysilane.

[0066] The spherical silica may be commercially available silica particles that satisfy the above-mentioned properties. Examples of commercially available silica particles include Denka fused silica FB grade (manufactured by Denka Co., Ltd.), Denka fused silica SFP grade (manufactured by Denka Co., Ltd.), Excelica (manufactured by Tokuyama Corporation), high-purity synthetic spherical silica Admafine (manufactured by Admatechs Co., Ltd.), Admanano (manufactured by Admatechs Co., Ltd.), and Admafuse (manufactured by Admatechs Co., Ltd.).

[0067] When the spherical silica is blended, the blending amount is preferably 5% by mass or less (more preferably 3% or less, 1% or less, etc.) relative to the mass of the fluororesin long film.

[0068] (Oxygen element ratio on the surface) The film of the present disclosure preferably has an oxygen atomic ratio of 1.35 atomic % or more when the surface condition of one or both sides of the film is measured by ESCA after heat treatment at 180° C. for 3 minutes. The oxygen atomic 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.

[0069] In order for the fluororesin film of the present disclosure to have a predetermined contact angle on the surface, it is preferable to increase the oxygen element ratio by performing a surface treatment such as plasma treatment, etc. Therefore, the fluororesin film of the present disclosure may be a film obtained by extrusion molding, or a film obtained by applying a liquid composition containing a fluororesin powder to a substrate and drying the film, and the oxygen element ratio of the surface may be increased and improved in adhesion, so that the oxygen element ratio of the surface falls within the above-mentioned range.

[0070] The film of the present disclosure may be a fluorine film in which the difference between the oxygen element ratio when the surface state is measured by a scanning X-ray photoelectron spectroscopy (XPS / ESCA) and the oxygen element ratio when the film is etched in the depth direction for 15 minutes with an argon gas cluster ion beam at an incidence angle of 45° and then measured by a scanning X-ray photoelectron spectroscopy (XPS / ESCA) is 1.0 atomic % or more. By increasing only the oxygen element ratio of the surface that contributes to adhesion in this way, sufficient adhesive strength can be obtained without impairing the dielectric properties.

[0071] The above heat treatment at 180°C for 3 minutes means that the film was placed on a metal tray and treated in an electric furnace in an air atmosphere.

[0072] The fluororesin film of the present disclosure is preferably such that the absolute value of the dimensional change rate in MD and TD before and after the heat treatment is 2.0% or less when the film is cooled to 25°C after heat treatment for 10 minutes at 180°C and measured. The dimensional change rate is more preferably 1.8% or less, and most preferably 1.5% or less. In the present disclosure, the dimensional change rate is calculated from the change in the gauge interval in each of the MD and TD directions of the film cut into a 300 mm square, marked with marks at 180 mm intervals, heat treated for 10 minutes without applying a load in an electric furnace in an air atmosphere set at 180°C, and cooled to 25°C.

[0073] In order to obtain a fluororesin film having such a rate of dimensional change, it is preferable to carry out an annealing treatment as described in detail below.

[0074] The resin film of the present disclosure preferably has a dielectric loss tangent at 10 GHz of less than 0.0015. By keeping the dielectric loss tangent within this range, it is preferable that the loss of electrical signals in the circuit can be kept low. The dielectric loss tangent is more preferably less than 0.0013, and even more preferably less than 0.0010. In order to keep the dielectric loss tangent within the above range, it is preferable to use a resin with few unstable functional groups, and it is more preferable to use a fluororesin that has been subjected to terminal fluorination treatment.

[0075] The above-mentioned fluororesin film preferably has an adhesive strength of 0.8 N / mm or more at locations 100 mm from the center and each of the left and right ends when bonded to a metal foil having a surface roughness Rz of 1.5 μm or less using a vacuum heat press under conditions of a temperature of not less than the melting point of the fluororesin but not more than the melting point +30°C, a pressure of 1.5 to 3.0 MPa, and a time of 300 to 600 seconds. That is, the film has sufficient adhesive strength at both the center and the ends, and the adhesiveness is highly uniform. In the present specification, the adhesive strength refers to the arithmetic average of measurements taken at five points at 100 mm intervals in the running direction, similar to the contact angle measurements.

[0076] The fluororesin film preferably has an adhesive strength of 0.8 N / mm or more between the prepreg, which is a thermosetting resin, and the center and each of the left and right ends of the fluororesin film at points 100 mm apart, where the adhesive strength here refers to the adhesive strength when bonded by the method described in the examples. As in the contact angle measurement, the adhesive strength also means the average value of measurements taken at five points at 100 mm intervals in the running direction.

[0077] The fluororesin film preferably has an adhesive strength of more than 30 N / m on one or both sides when the films are bonded together within the same plane at 200° C. By having such an adhesive strength, the fluororesin film has excellent adhesiveness even after heat treatment when used in combination with various other substrates, and the adhesive strength is more preferably more than 50 N / m, and even more preferably more than 100 N / m.

[0078] (Method of producing fluororesin film of the present disclosure) The fluororesin film of the present disclosure is generally produced by extrusion melt molding, in which molten resin is extruded through a T-die to form it into a film shape, which is then cooled and wound up.

[0079] The fluororesin film of the present disclosure is mainly characterized by the method of surface treatment. However, when the resin film to be surface-treated is itself a film with high uniformity, it is preferable in that the film as a whole has high uniformity. Therefore, it is particularly preferable to use a method for producing a fluororesin film with little thickness unevenness.

[0080] From this viewpoint, in extrusion melt molding, the thickness of the resin film is particularly influenced by the air gap distance from the end of the T-die where the resin flows out to the first roll, the MFR of the resin used, the melting temperature during film production, the pressure, the slit width of the T-die, the gap width, etc. Therefore, by appropriately adjusting these, a smooth resin film that satisfies the above-mentioned parameters can be obtained.

[0081] Furthermore, it is preferable to adjust the MFR as well, that is, by shortening the air gap, the amount of air between the melt and the first roll is reduced, thereby reducing unevenness in the thickness of the film.

[0082] The specific method of the surface modification is not particularly limited, and can be carried out by any known method. The surface modification of the fluororesin film can be carried out by conventional discharge treatments such as corona discharge treatment, glow discharge treatment, plasma discharge treatment, and sputtering treatment. For example, the surface free energy can be controlled by introducing oxygen gas, nitrogen gas, hydrogen gas, etc. into the discharge atmosphere, and 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 cause discharge, thereby generating active species on the surface, and then the functional group of the organic compound can be introduced or a polymerizable organic compound can be graft-polymerized to perform surface modification. Examples of the inert gas include nitrogen gas, helium gas, and argon gas.

[0083] The organic compound in the organic compound-containing inert gas includes 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, etc. Among these, vinyl esters, acrylic esters, and ketones are preferred because the modified surface is less likely to be deactivated, that is, because they have a long life and are easy to handle, and particularly vinyl acetate and glycidyl methacrylate are preferred.

[0084] 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. 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. Usually, the discharge amount is 50 to 1500 W·min / m2 , preferably 70 W·min / m 2 More than 1400W min / m 2 Discharge treatment is carried out within the following range. The treatment temperature can be any temperature within the range of 0° C. to 100° C. A temperature of 80° C. or less is preferable to prevent stretching or wrinkling of the film.

[0085] In the above surface modification, the discharge power, which indicates the output per unit area, is set to 1.0 to 10 (W / cm 2 ) and the gas concentration / line speed ratio during discharge is preferably adjusted to a range of 0.005 to 0.05 (L / m). The gas concentration / line speed ratio here refers to the ratio of the concentration of the organic compound in the organic compound-containing inert gas divided by the line speed. If it is lower than 0.005 (L / m), the space is not filled with enough gas for the conveying speed, making it difficult for the activated gas to contact the film surface, and the uniformity within the surface decreases. If it is higher than 0.05 (L / m), the surface is overtreated and damaged, and low molecular weight compounds are generated on the surface, forming a brittle layer, which leads to a decrease in adhesive strength. Therefore, it is presumed that the film surface is treated more uniformly and a predetermined adhesion can be obtained, so treatment within such a range is particularly preferable.

[0086] Considering that the adhesive ability of the surface is reduced by heat during post-processing, the degree of surface modification is such that the abundance ratio of oxygen element is 2.0% or more when observed by ESCA, preferably 2.5% or more, more preferably 3.0% or more, and even more preferably 3.5% or more. There is no particular upper limit, but in consideration of the influence on productivity and other physical properties, it is preferably 25.0% or less. There is no particular limit to the abundance ratio of nitrogen element, but it is preferably 0.1% or more. In addition, the thickness of one fluororesin film is preferably 2.5 to 1000 μm, more preferably 5 to 500 μm, and even more preferably 7 to 150 μm.

[0087] Such treatment may be performed on only one side of the film or on both sides.

[0088] (Annealing treatment) The fluororesin film of the present disclosure may be subjected to an annealing treatment after the above-mentioned surface treatment. As described above, the fluororesin film of the present disclosure is preferably one that has dimensional stability when laminated with a metal foil. Therefore, it is preferable that the fluororesin film has a low shrinkage rate when heated.

[0089] Fluororesin films obtained by extrusion melt molding often undergo thermal shrinkage due to residual internal stress, and such thermal shrinkage adversely affects dimensional stability when laminated with a metal foil. Therefore, it is preferable to relieve the internal stress by performing an annealing treatment. The annealing treatment can be performed by heat treatment. The heat treatment can be performed, for example, by passing the film through a heating furnace using a roll-to-roll method.

[0090] In the production of the fluororesin film of the present disclosure, it is preferable to carry out an annealing treatment after the corona discharge treatment. In addition, a heat treatment may be carried out in the process of laminating the film to another material such as a metal foil. Therefore, the amount of oxygen on the surface of the fluororesin film decreases by undergoing these heat treatments. Therefore, it is preferable to carry out the surface modification under conditions that will obtain a sufficient amount of surface oxygen at the time when the fluororesin film is actually laminated to another material such as a metal foil.

[0091] The annealing temperature is preferably the glass transition temperature −20° C. or more and less than the melting point, more preferably the glass transition temperature or more and less than the melting point −20° C., and even more preferably the glass transition temperature or more and less than the melting point −60° C. The annealing time is not particularly limited, but may be appropriately adjusted within a range of, for example, 0.5 to 60 minutes.

[0092] When heating is performed by the roll-to-roll method, the tension may be adjusted appropriately depending on the thickness of the film, the set temperature, etc., but is preferably 20 N / m or less. Heating under such conditions is preferable in that the internal stress can be sufficiently relaxed and no dimensional changes occur.

[0093] The order of the above surface treatment and annealing treatment is not particularly limited, and the number of times each step is performed is not limited to once, but each step may be performed twice or more.

[0094] The present disclosure also provides a laminate characterized by having a metal foil adhered to one or both sides of the above-mentioned fluororesin film. As described above, the film containing the fluororesin of the present disclosure has excellent adhesiveness. The metal foil preferably has an Rz of 1.5 μm or less. That is, the fluororesin composition of the present disclosure also has excellent adhesiveness to a highly smooth metal foil having an Rz of 1.5 μm or less. Furthermore, the metal foil only needs to have a surface that is adhered to the above-mentioned fluororesin film of 1.5 μm or less, and the Rz value of the other surface is not particularly limited.

[0095] The thickness of the metal 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 9 to 35 μm.

[0096] The metal foil is not particularly limited, but is particularly preferably a copper foil. Specific examples of the copper foil include rolled copper foil and electrolytic copper foil.

[0097] The copper foil having Rz of 1.5 μm or less is not particularly limited, and commercially available products can be used. Examples of commercially available copper foil having 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.).

[0098] The metal foil may be surface-treated to enhance the adhesive strength with the fluororesin film of the present disclosure.

[0099] The surface treatment is not particularly limited, but may be a silane coupling treatment, a plasma treatment, a corona treatment, a UV treatment, an electron beam treatment, etc., and the reactive functional group of the silane coupling agent is not particularly limited, but from the viewpoint of adhesion to the resin substrate, it is preferable to have at least one selected from an amino group, a (meth)acrylic group, a mercapto group, and an epoxy group at the end. In addition, the hydrolyzable group is not particularly limited, but may be an alkoxy group such as a methoxy group or an ethoxy group. The metal foil used in the present disclosure may have an anti-rust layer (such as an oxide film such as chromate), a heat-resistant layer, etc. formed thereon.

[0100] The surface-treated metal foil having a surface treatment layer of the above-mentioned silane compound on the surface of the metal foil can be produced by preparing a solution containing the silane compound and then surface treating the metal foil with this solution.

[0101] The metal foil may have a roughening treatment layer on the surface thereof from the viewpoint of improving adhesion to a resin substrate. In addition, if there is a risk that the roughening treatment will degrade the performance required in the present disclosure, the amount of roughening particles electrodeposited on the metal foil surface can be reduced as necessary, or the roughening treatment can be omitted.

[0102] Between the metal foil and the surface treatment layer, one or more layers selected from the group consisting of a heat-resistant treatment layer, 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.

[0103] The laminate preferably has an adhesive strength between the metal foil and the fluororesin film of 0.8 N / mm or more. Such an adhesive strength can be achieved by applying the method described above. By making the adhesive strength 0.9 N / mm or more, or even 1.0 N / mm or more, the laminate can be suitably used as a metal-clad laminate or a circuit board. The adhesive strength here means the adhesive strength measured under the conditions described in the examples. In addition, in the case of a laminate in which a metal foil is bonded to the surface-treated surface of a fluororesin film that has been surface-treated on only one side, a surface modification may be separately performed on the non-surface-treated surface of the fluororesin film in order to improve the adhesiveness between the laminate and other materials.

[0104] The laminate can be produced by laminating a metal foil on the surface of a film, vapor deposition, plating, etc. The metal foil can be laminated by hot pressing or roll-to-roll lamination.

[0105] When laminating by heat pressing, the temperature may be from the melting point of the dielectric film -150°C to the melting point of the dielectric film +40°C. The heat pressing time is, for example, 1 to 30 minutes. The pressure of the heat pressing can be 0.1 to 10 MPa.

[0106] When laminating by roll-to-roll lamination, the temperature may be from the melting point of the dielectric film −150° C. to the melting point of the dielectric film +40° C. The speed is preferably 0.5 m / min or more, and more preferably 1.0 m / min or more from the viewpoint of productivity. The pressure is preferably in the range of 10 kg / cm to 200 kg / cm, and more preferably 20 kg / cm or more to obtain good adhesive strength. There are no particular limitations on the roll-to-roll laminating device, but it is preferable that the device has one or more pairs of metal nip rolls, or a nip roll with one side being a rubber roll.

[0107] The laminate is preferably a long laminate. More specifically, the width is preferably 400 mm or more and the length is preferably 3 m or more. From the viewpoint of productivity, the width is more preferably 500 mm or more. Also, the length is more preferably 10 m or more. Such a long laminate is preferably a roll laminate.

[0108] The metal-clad laminate of the present disclosure may further include layers other than the metal foil and the fluororesin film. The layers other than the metal foil and the fluororesin film are preferably at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, and polybutadiene.

[0109] The layers other than the metal foil and the fluororesin film are not particularly limited as long as they are made of the above-mentioned resins, and the layers other than the metal foil and the fluororesin film preferably have a thickness in the range of 12 to 200 μm.

[0110] In the metal-clad laminate of the present disclosure, a metal layer is formed on the surface of the film of the present invention. The metal layer may be formed on one or both sides of the film. Methods for forming the metal layer include a method of laminating a metal foil on the surface of the film, a vapor deposition method, a plating method, and the like. Methods for laminating a metal foil include a method using a hot press and a method using roll-to-roll lamination.

[0111] The method for combining the metal foil, the base layer, and the fluororesin film is not particularly limited, but the following two methods can be mentioned, for example. (i) A method of laminating a metal foil, a substrate layer, and a preformed fluororesin film by applying pressure under heat using a roll-to-roll process or a press. The layer facing the metal foil may be either a substrate layer or a fluororesin layer. (ii) A method in which a laminate is produced by adhering a fluororesin film to one side of a metal foil, and then the fluororesin side not facing the metal foil and a base layer are laminated by applying pressure under heat.

[0112] The metal clad laminate of the present disclosure is not particularly limited in its application, and is used as a circuit board. A printed circuit board is a plate-shaped component for electrically connecting electronic components such as semiconductors and capacitor chips, while at the same time arranging and fixing them in a limited space. There is no particular limit to the configuration of the printed circuit board formed from the present metal clad laminate. The printed circuit board may be any of a rigid board, a flexible board, and a rigid-flexible board. The printed circuit board may be any of a single-sided board, a board, a double-sided board, and a multilayer board (such as a built-up board). In particular, it can be suitably used for flexible boards and rigid boards.

[0113] The circuit board is not particularly limited, and can be produced by a general method using the above-mentioned metal clad laminate plate.

[0114] The laminate for a circuit board is also a laminate having a metal foil layer, the above-mentioned fluororesin film, and a base layer. The base layer is not particularly limited, but preferably has a fabric layer made of glass fiber and a resin film layer.

[0115] The fabric layer made of glass fibers is a layer made of glass cloth, glass nonwoven fabric, or the like. Commercially available glass cloth can be used, and glass cloth treated with a silane coupling agent is preferable to enhance affinity with the fluororesin. Examples of glass cloth materials include E glass, C glass, A glass, S glass, D glass, NE glass, and low dielectric constant glass, and E glass, S glass, and NE glass are preferable because they are easily available. The weaving method of the fibers may be plain weave or twill weave. The thickness of the glass cloth is usually 5 to 90 μm, and preferably 10 to 75 μm, but it is preferable to use a glass cloth thinner than the fluororesin film to be used.

[0116] The laminate may use a glass nonwoven fabric as a fabric layer made of glass fibers. The glass nonwoven fabric is a fabric in which short glass fibers are fixed with a small amount of a binder compound (resin or inorganic substance), or a fabric in which the shape is maintained by entangling short glass fibers without using a binder compound, and a commercially available product can be used. The diameter of the short glass fibers is preferably 0.5 to 30 μm, and the fiber length is preferably 5 to 30 mm. Specific examples of the binder compound include resins such as epoxy resins, acrylic resins, cellulose, polyvinyl alcohol, and fluororesins, and inorganic substances such as silica compounds. The amount of the binder compound used is usually 3 to 15 mass % based on the short glass fibers. Examples of the material of the short glass fibers include E glass, C glass, A glass, S glass, D glass, NE glass, and low dielectric constant glass. The thickness of the glass nonwoven fabric is usually 50 μm to 1000 μm, and preferably 100 to 900 μm. In the present application, the thickness of the glass nonwoven fabric refers to a value measured in accordance with JIS P8118:1998 using a digital gauge DG-925 (load 110 grams, face diameter 10 mm) manufactured by Ono Sokki Co., Ltd. In order to increase the affinity with the fluororesin, the glass nonwoven fabric may be treated with a silane coupling agent.

[0117] Most nonwoven glass fabrics have a very high porosity of 80% or more, so it is preferable to use a sheet that is thicker than a sheet made of fluororesin and compress it by pressure.

[0118] The glass fiber fabric layer may be a layer in which a glass cloth and a glass nonwoven fabric are laminated together, whereby the properties of the two fabrics are combined to obtain suitable properties. The glass fiber fabric layer may be in the form of a prepreg impregnated with a resin.

[0119] In the above laminate, the glass fiber fabric layer and the fluororesin film may be bonded at the interface, or the glass fiber fabric layer may be partially or entirely impregnated with the fluororesin film. Furthermore, a prepreg may be prepared by impregnating a fabric made of glass fibers with the fluororesin composition. The prepreg thus obtained may be further laminated with the fluororesin film of the present disclosure. In this case, the fluororesin composition used in preparing the prepreg is not particularly limited, and the fluororesin film of the present disclosure may also be used.

[0120] The resin film used as the substrate is preferably a heat-resistant resin film or a thermosetting resin film. Examples of the heat-resistant resin film include polyimide, liquid crystal polymer, polyphenylene sulfide, etc. Examples of the thermosetting resin include those containing epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, polybutadiene, etc.

[0121] The heat-resistant resin film and the thermosetting resin film may contain reinforcing fibers. The reinforcing fibers are not particularly limited, but for example, glass cloth, particularly low dielectric type, is preferable.

[0122] The heat-resistant resin film and the thermosetting resin film are not particularly limited in terms of dielectric properties, linear expansion coefficient, water absorption rate, and other properties, but for example, the dielectric constant at 20 GHz is preferably 3.8 or less, more preferably 3.4 or less, and even more preferably 3.0 or less. The dielectric loss tangent at 20 GHz is preferably 0.0030 or less, more preferably 0.0025 or less, and even more preferably 0.0020 or less. The linear expansion coefficient is preferably 100 ppm / °C or less, more preferably 70 ppm / °C or less, and even more preferably 40 ppm / °C or less. The water absorption rate is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less. EXAMPLES

[0123] The present disclosure will now be described in detail with reference to examples. In the following examples, the ratios are expressed as molar ratios.

[0124] Example 1 PFA (TFE / PPVE copolymer, composition: TFE / PPVE=98.2 / 1.8, MFR: 15.8g / 10min, melting point 305°C, glass transition temperature 92°C) was fed into an extruder at 360°C, extruded from a 1700mm wide T-die, taken up on a metal cooling roll, and then wound around a take-up core to obtain a roll film 1300mm wide and 50μm thick. Both sides of the roll film were surface-treated (a corona discharge device was used to continuously pass the film along the roll-shaped ground electrode while nitrogen gas was flowed near the discharge electrode and roll-shaped ground electrode so that the ratio of the vinyl acetate gas concentration in the nitrogen gas to the line speed was 0.014 (L / m), and the film was continuously passed along the roll-shaped ground electrode, with a discharge intensity of 1.4W / cm. 2 Both sides of the film were subjected to a corona discharge treatment at 150.degree. C. The surface-treated long film was wound into a roll to obtain a surface-treated sample, which was then evaluated.

[0125] Example 2 Discharge intensity: 2.3W / cm 2 A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned procedure was changed to the above-mentioned procedure, and then the surface-treated sample was evaluated.

[0126] Example 3 Discharge intensity: 2.9W / cm 2 A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned procedure was changed to the above-mentioned procedure, and then the surface-treated sample was evaluated.

[0127] Example 4 Discharge intensity: 3.7W / cm 2 A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned procedure was changed to the above-mentioned procedure, and then the surface-treated sample was evaluated.

[0128] Example 5 A surface-treated sample was obtained in the same manner as in Example 3, except that the gas concentration / line speed ratio was set to 0.007 L / m, and then evaluation was performed.

[0129] Example 6 A surface-treated sample was obtained and then evaluated in the same manner as in Example 3, except that a long roll film having a width of 1,300 mm and a thickness of 50 μm obtained by the T-die method was slit into a width of 500 mm.

[0130] Example 7 A surface-treated sample was obtained and then evaluated in the same manner as in Example 3, except that the fluororesin was PFA (TFE / PPVE copolymer, composition: TFE / PPVE=97.7 / 2.3, MFR: 15.0 g / 10 min, melting point 300.9°C, glass transition temperature 93°C).

[0131] Comparative Example 1 A surface-treated sample was obtained in the same manner as in Example 3, except that the gas concentration / line speed ratio was set to 0.004 L / m, and then evaluation was performed.

[0132] Comparative Example 2 Discharge intensity: 0.6W / cm 2 A surface-treated sample was obtained in the same manner as in Example 3, except that the above-mentioned procedure was changed to the above-mentioned procedure, and then the surface-treated sample was evaluated.

[0133] Comparative Example 3 The evaluation was carried out using a sample that had not been subjected to a surface treatment.

[0134] (Static contact angle of water) The static contact angle of water was measured using a fully automatic contact angle meter DropMaster700 (Kyowa Interface Science Co., Ltd.) in the following manner. 2 μL of water was dropped from a microsyringe onto the horizontally placed substrate, and a still image was taken 1 second after the drop using a video microscope. The static contact angle of water was measured at five locations 100 mm apart in the running direction, at positions 100 mm from the center and each of the left and right ends. The average values ​​are shown in Table 2. The contact values ​​shown in Table 2 are initial values ​​measured immediately after the film was produced.

[0135] (Static contact angle of n-hexadecane) The static contact angle of n-hexadecane was measured using a fully automatic contact angle meter DropMaster700 (Kyowa Interface Science Co., Ltd.) in the following manner. 2 μL of n-hexadecane was dropped from a microsyringe onto a horizontally placed substrate, and a still image was taken 1 second after the drop using a video microscope. The static contact angle of n-hexadecane was measured at five locations 100 mm apart in the running direction, at positions 100 mm from the center and each of the left and right ends. The average values ​​are shown in Table 2. The contact values ​​shown in Table 2 are initial values ​​measured immediately after the film was produced.

[0136] (Adhesive strength with copper foil) Using a film and electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil and Powder Co., Ltd.), copper foil, fluororesin film, and copper foil were stacked in this order, and heat pressed with a vacuum heat press machine (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 320 ° C, a preheating time of 60 seconds, a pressure of 1.5 MPa, and a pressurization time of 300 seconds. An aluminum plate was attached to one side of the laminate with adhesive tape, and a Tensilon universal testing machine (manufactured by Shimadzu Corporation) was used to measure the peel strength of the copper foil by grasping and pulling a 10 mm wide 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 measured value was the average value of the measured values ​​at five locations, 100 mm apart in the running direction, at three locations 100 mm from the center and each of the left and right ends. The results are shown in Table 2.

[0137] (Adhesive strength with prepreg) Prepreg R-5680(J) (thickness 132μm) (manufactured by Panasonic Corporation) was used as the prepreg material, and samples were created under press conditions of 200℃ temperature, 75 minutes, and 3.0MPa pressure. The adhesive strength was then measured in the same manner as for the adhesive strength with copper foil. The measured value was the average value of measurements taken at five locations, 100mm apart in the running direction, at three locations 100mm from the center and each of the left and right ends. The results are shown in Table 2.

[0138] (Adhesive strength between fluororesin films) The treated surfaces of the fluororesin films were placed together, and a sample was prepared using a heat press (200°C, 0.1 MPa, 60 s). The sample was then cut into 10 mm-wide strips, and a Tensilon universal testing machine (Shimadzu Corporation) was used to measure the peel strength by gripping the unbonded portion of the strip sample with the top and bottom chucks of the Tensilon and pulling at a speed of 100 mm per minute, and the value obtained was taken as the adhesive strength. The measured value was the average of measurements taken at five locations, 100 mm apart in the running direction, at three locations 100 mm from the center and each of the left and right ends. The results are shown in Table 2.

[0139] For Examples 1 and 7, the dielectric constant and dielectric loss tangent were measured using a split cylinder resonator (10 GHz).

[0140] (Melting Point) The melting peak was calculated from the melting peak measured by heating at a rate of 10° C. / min using a DSC device.

[0141] (glass transition temperature) The values ​​were calculated from the tan δ peak measured using a solid dynamic viscoelasticity apparatus (DMA) at a frequency of 10 Hz, strain of 0.1%, and a temperature rise rate of 5° C. / min. The results are shown in Table 2.

[0142] (Number of unstable functional groups) The analysis was performed using an FT-IR Spectrometer 1760X (Perkin-Elmer). The results are shown in Table 2.

[0143] (Thickness of fluororesin film) The measurements were made using a micrometer. As shown in Figure 1, the thickness was measured at 12 locations, 5 mm apart in the width direction and 20 cm apart in the running direction. The average of all the thicknesses measured in this way is shown in the table as the "average thickness of the surface." Furthermore, the average thickness of the 12 locations measured in the running direction at the same value in the width direction was calculated, and the difference between the maximum value and the average value was shown in the table.

[0144] (ESCA analysis of fluororesin film surface) The measurements were performed using a scanning X-ray photoelectron spectrometer (XPS / ESCA) PHI5000VersaProbeII (ULVAC-PHI, Inc.) with a monochromated AlKα source and an incidence angle of 45°.

[0145] (Dielectric tangent) Using a fluororesin film, measurements were performed at 10 GHz (26 °C) using split cylinder resonators CR-710 and CR-740 (EM Labs, Inc.), and the measurements were analyzed using a vector network analyzer P5007A (Keysight Technologies, Inc.).

[0146] (Rz) Using a Keyence color 3D laser microscope VK-9700, 2 Rz was measured in the range of

[0147] [Table 2]

[0148] From the results in Table 2 above, it is clear that the fluororesin film of the present disclosure has high uniformity in adhesive strength. [Industrial Applicability]

[0149] The fluororesin film of the present disclosure can be used for metal-clad laminates for circuit boards, etc.

Claims

1. A film comprising a composition containing a fluororesin, A fluoropolymer film characterized in that, on at least one surface, the average value of the contact angle with water measured at five locations 100 mm apart in the direction of travel, at a distance of 100 mm from the center and each of the left and right edges, is 105° or less, and the average value of the contact angle with n-hexadecane measured at five locations 100 mm apart in the direction of travel is 45° or less, and the film is long in length.

2. The fluororesin film according to claim 1, wherein the film width is 400 mm or more.

3. The fluororesin film according to claim 1 or 2, wherein the fluororesin comprises tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) and / or tetrafluoroethylene-hexafluoropropylene (FEP).

4. A fluororesin film according to claim 1 or 2, wherein the dielectric loss tangent at 10 GHz is less than 0.0015.

5. A fluororesin film according to claim 1 or 2, wherein the dielectric loss tangent at 10 GHz is less than 0.0010.

6. The fluororesin film according to claim 1 or 2, wherein the number of unstable functional groups is less than 10 per 1 × 10⁶ carbon atoms in the main chain of the fluororesin.

7. The fluororesin film according to claim 1 or 2, wherein the adhesive strength between a metal foil with a surface roughness Rz of 1.5 μm or less and locations 100 mm from the center and each of the left and right edges of the fluororesin film is 0.8 N / mm or more.

8. The fluororesin film according to claim 1 or 2, wherein the adhesive strength between the prepreg containing epoxy resin and / or polyphenylene ether and locations 50 mm from the center and each of the left and right edges of the fluororesin film is 0.8 N / mm or more.

9. A fluororesin film according to claim 1 or 2, wherein the adhesive strength when two films are bonded together on the same surface at 200°C, either on one side or both sides, is greater than 30 N / m.

10. A fluororesin film according to claim 1 or 2, used in a metal-clad laminate.

11. A metal-clad laminate comprising a metal foil and a fluororesin film according to claim 1 or 2 as essential layers.

12. A long laminate comprising a metal foil having a surface roughness Rz of 1.5 μm or less and a long fluororesin film, characterized in that the contact angle with water at the center of the fluororesin film surface not facing the metal foil, and at a distance of 100 mm from each of the left and right ends, is 105° or less, and the contact angle with n-hexadecane is 45° or less.

13. The metal-clad laminate according to claim 12, wherein the metal foil has a surface roughness Rz of 1.5 μm or less.

14. The metal-clad laminate according to claim 12, wherein the adhesive strength between the prepreg and locations 100 mm from the center and each of the left and right edges of the laminate is 0.8 N / mm or more.

15. Furthermore, it has layers other than metal foil and fluororesin film, The metal-clad laminate according to claim 12, wherein the layer other than the metal foil and fluororesin film is at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, and polybutadiene.

16. A method for producing a metal-clad laminate according to claim 11, characterized by comprising the step of laminating a metal foil onto a fluororesin film according to claim 1.

17. A circuit board characterized by having a metal-clad laminate as described in claim 12.