Resin film, metal-clad laminate, and method for producing resin film

Abstract

The purpose of the present invention is to provide a resin film which is less likely to undergo blocking even when stored in a roll-like form for a long period of time. Provided is a long resin film containing at least a fluororesin. On at least one surface of the resin film, the ratio A2 / A1 of the absorbance A2 of a second peak to the absorbance A1 of a first peak is 0.006 or less when measured by infrared spectroscopy attenuated total reflection method (IR-ATR), wherein the first peak is a peak of CF2 symmetric stretching vibration in the wavenumber range of 1130 cm-1 to 1180 cm-1 inclusive and the second peak is a maximum peak in the wavenumber range of 1700 cm-1 to 1750 cm-1 inclusive. The ratio N2／N1 of the absorbance N2 of a fourth peak to the absorbance N1 of a third peak is 0.05 to 0.5 inclusive when measured by nano-infrared spectroscopy (nano-IR), wherein the third peak is a peak of CF2 symmetric stretching vibration in the wavenumber range of 1130 cm-1 to 1180 cm-1 inclusive and the fourth peak is a maximum peak in the wavenumber range of 1600 cm-1 to 1800 cm-1 inclusive. The average value of water contact angles is 55° to 105° inclusive, and the variation coefficient of the water contact angles is 30% or less.

Description

Resin film, metal-clad laminate, and method for manufacturing a resin film

[0001] This disclosure relates to a resin film, a metal-clad laminate, and a method for manufacturing a resin film.

[0002] To realize high-speed communication using next-generation information and communication technologies (e.g., high-frequency 5G), the dielectrics of printed circuit boards used in antennas and transmission lines are required to have low transmission loss characteristics. Against this backdrop, fluororesin materials with excellent electrical properties are attracting attention as insulating materials for printed circuit boards. Since fluororesin materials generally have poor adhesion to other materials, surface modification technology is used to improve adhesion. For example, Patent Document 1 describes performing corona discharge treatment on a long roll film. Patent Document 2 describes manufacturing a surface-coated fluororesin substrate in an inert gas plasma atmosphere and under atmospheric pressure by corona discharge. Patent Document 3 describes plasma treatment of a tetrafluoroethylene polymer in an atmosphere near atmospheric pressure.

[0003] Japanese Patent Publication No. 2022-112028, Japanese Patent Publication No. 2008-019393, International Publication No. 2021 / 187456

[0004] However, Patent Documents 1 to 3 do not describe the aspect of blocking. The present disclosure aims to provide a resin film that is less prone to blocking even when stored in a roll for a long period of time, and a method for manufacturing the same. The present disclosure also aims to provide a metal-clad laminate equipped with a resin film that is less prone to blocking even when stored in a roll for a long period of time.

[0005] This disclosure relates to a long resin film comprising at least a fluororesin, wherein at least one surface of the resin film has a first peak absorbance A measured by infrared total internal reflection (IR-ATR) spectroscopy. １ Absorbance A of the second peak relative to ２ Ratio A ２ / A １ However, it is less than 0.006, and the first peak is at wavenumber 1130 cm. －１ 1180cm or more －１ CF within the following range ２It is the peak of symmetric stretching vibration, and the second peak is at a wavenumber of 1700 cm －１ or more and 1750 cm －１ or less, and is the maximum peak within the range measured by nano-infrared spectroscopy (nano-IR). The absorbance N of the third peak １ with respect to the absorbance N of the fourth peak ２ The ratio N ２ / N １ is 0.05 or more and 0.5 or less. The third peak is a CF －１ symmetric stretching vibration peak within the range of 1130 cm －１ or more and 1180 cm ２ or less. The fourth peak is the maximum peak within the range of 1600 cm －１ or more and 1800 cm －１ or less. The average value of the water contact angle is 55° or more and 105° or less, and the coefficient of variation of the water contact angle is 30% or less. It is a resin film.

[0006] It is preferable that the rate of change of the water contact angle of the surface of the resin film, measured before and after annealing the resin film at 150°C for 30 minutes, is 150% or less. It is preferable that the rate of change of the water contact angle of the surface of the resin film, measured before and after immersing the resin film in tetrahydrofuran for 100 hours, is 150% or less. It is preferable that the amount of components eluted from the resin film into the tetrahydrofuran, measured by immersing the resin film in tetrahydrofuran for 100 hours, is 900 ppm or less relative to the mass of the resin film. It is preferable that the oxygen element ratio of the surface of the resin film, measured by scanning X-ray photoelectron spectroscopy (XPS), is 1 atomic% or more. It is preferable that the resin film comprises a fluororesin layer containing the fluororesin and a polymer layer formed by polymerization of monomers. It is preferable that the monomers include aliphatic vinyl compounds. It is preferable that the polymer layer is a layer formed by plasma treatment under a monomer-containing inert gas atmosphere containing the monomers. In multipoint measurements of the surface modulus of the resin film using a scanning atomic force microscope, it is preferable that the cumulative relative frequency reaching 1.3 GPa is 0.98 or less. It is preferable that the rate of change in the oxygen element ratio on the surface of the resin film, measured by scanning X-ray photoelectron spectroscopy (XPS) before and after storing the rolled resin film at 40°C for one month, is -20% or more and 0% or less. The resin film comprises a fluororesin layer containing the fluororesin and a polymer layer, wherein the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the polymer layer is a plasma polymerization layer of vinyl acetate, and the ratio A ２ / A １ However, it is 0.00001 or more and 0.006 or less, and the ratio N ２ / N １Preferably, the ratio is 0.1 to 0.45, the average value of the water contact angle is 55° to 105°, the coefficient of variation of the water contact angle is 0.1% to 10.0%, and the oxygen element ratio on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 1.0 atomic% to 20.0 atomic%.

[0007] The present disclosure also relates to a metal-clad laminate comprising the resin film described above and a metal foil. Preferably, the surface roughness (Rz) of the metal foil is 1.5 μm or less. The metal foil is provided directly on the resin film, the average value of the adhesive strength between the metal foil and the resin film is 2 N / cm or more, and the coefficient of variation of the adhesive strength between the metal foil and the resin film is 35% or less. Preferably, the metal-clad laminate further comprises a substrate.

[0008] This disclosure relates to a method for manufacturing a long resin film containing at least a fluororesin, comprising a plasma treatment step of plasma-treating at least one surface of the fluororesin layer while conveying the fluororesin-containing fluororesin layer under predetermined conditions in a monomer-containing inert gas atmosphere, wherein the predetermined conditions are: applied voltage frequency of 1 to 100 kHz, electric field strength of 5 to 50 kV / mm, and discharge degree of 1 to 5 W / cm. ２ The present invention relates to a method for manufacturing a resin film, wherein the ratio of the flow rate of monomers contained in the monomer-containing inert gas atmosphere to the transport speed of the fluororesin layer is 0.003 to 0.02 L / m.

[0009] On at least one surface of the resin film, the absorbance of the first peak A, measured by infrared total internal reflection (IR-ATR) spectroscopy, is １ Absorbance A of the second peak relative to ２ Ratio A ２ / A １ However, it is less than 0.006, and the first peak is at wavenumber 1130 cm. －１ 1180cm or more －１ CF within the following range ２ This is the peak of the symmetric stretching vibration, and the second peak corresponds to a wavenumber of 1700 cm⁻¹. －１ 1750cm or more－１ The maximum peak within the following range, measured by nano-infrared spectroscopy (nano-IR), is the absorbance N of the third peak. １ Absorbance of the fourth peak relative to N ２ Ratio N ２ / N １ However, it is between 0.05 and 0.5, and the third peak is at wavenumber 1130 cm. －１ 1180cm or more －１ CF within the following range ２ This is the peak of the symmetric stretching vibration, and the fourth peak corresponds to a wavenumber of 1600 cm⁻¹. －１ More than 1800cm －１ The maximum peak is within the following range, the average value of the water contact angle is 55° to 105°, and the coefficient of variation of the water contact angle is preferably 30% or less. It is preferable that the plasma treatment is continuously performed on the surface of the fluororesin layer while the fluororesin layer is conveyed by roll to roll. The plasma treatment is continuously performed on the surface of the fluororesin layer while the fluororesin layer is conveyed by roll to roll, and the monomer contained in the monomer-containing inert gas atmosphere polymerizes due to the plasma treatment, thereby forming a polymer layer on the fluororesin layer, the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, the monomer contained in the monomer-containing inert gas atmosphere is vinyl acetate, the concentration of vinyl acetate in the monomer-containing inert gas atmosphere is 0.30 to 1.0 volume%, and the predetermined conditions are an applied voltage frequency of 20 to 40 kHz, an electric field strength of 5 to 40 kV / mm, and a discharge degree of 1 to 3 W / cm. ２ Furthermore, it is preferable that the ratio of the flow rate of monomers contained in the monomer-containing inert gas atmosphere to the transport speed of the fluororesin layer is 0.003 to 0.010 L / m.

[0010] The resin film of this disclosure, and the resin film manufactured by the manufacturing method of this disclosure, are less prone to blocking even when stored in roll form for a long period of time. Furthermore, the metal-clad laminate of this disclosure comprises a resin film that is less prone to blocking even when stored in roll form for a long period of time.

[0011] This is an electron microscope image showing a cross-section of the resin film of Example 3. This is an electron microscope image showing the surface of the resin film of Comparative Example 1 before annealing. This is an electron microscope image showing the surface of the resin film of Comparative Example 1 after annealing. This is an electron microscope image showing the surface of the resin film of Example 3 before annealing. This is an electron microscope image showing the surface of the resin film of Example 3 after annealing.

[0012] The present disclosure will be explained in detail below. Fluororesin materials generally have poor adhesion to other materials. Surface-modified resin films that have been plasma-treated to improve adhesion have a problem in that when stored in a roll after surface modification treatment, the film surfaces tend to stick together, making it difficult to unwind the surface-modified resin film smoothly. In this disclosure, the phenomenon of "film surfaces sticking together when stored in a roll" may be referred to as "blocking." In particular, blocking of surface-modified resin films is likely to occur in surface modification treatments carried out under a monomer-containing inert gas atmosphere. One possible cause, though not definitive, is the accumulation of monomer-derived by-products (e.g., monomer decomposition products and / or aggregates of monomer homopolymers, etc.) on the resin film during the surface modification treatment process.

[0013] In light of the above issues, the resin film manufacturing method of this disclosure involves surface modification treatment under predetermined conditions. As a result, the amount of monomer-derived by-products can be reduced, and a resin film that is less prone to blocking can be manufactured even when stored in roll form for a long period of time.

[0014] Furthermore, in resin films manufactured under the above-mentioned predetermined conditions, the modification treatment tends to proceed thinly and uniformly across the surface, unlike in the conventional method. Based on this finding, the resin film of this disclosure shall satisfy at least the following conditions (1) and (2). Since the resin film of this disclosure satisfies at least conditions (1) and (2), it has fewer monomer-derived by-products accumulated on its surface and is less prone to blocking even when stored in roll form for a long period of time.

[0015] [Resin Film] First, the resin film of the present disclosure will be described in detail. The resin film of the present disclosure is elongated and contains at least a fluororesin. The resin film of the present disclosure satisfies the following conditions (1) and (2), and further the following condition (3), on at least one surface of the resin film. (1) Absorbance of the first peak as measured by IR-ATR A １ Absorbance A of the second peak relative to ２ Ratio A ２ / A １ However, it is less than 0.006. The first peak is at wavenumber 1130 cm. －１ 1180cm or more －１ CF within the following range ２ This is the peak of symmetrical stretching vibration. The second peak is at wavenumber 1700 cm. －１ 1750cm or more －１ The maximum peak is within the following range: (2) Absorbance N of the third peak measured by nano-IR １ Absorbance of the fourth peak relative to N ２ Ratio N ２ / N １ However, it is between 0.05 and 0.5. The third peak is at wavenumber 1130 cm. －１ 1180cm or more －１ CF within the following range ２ This is the peak of symmetrical stretching vibration. The fourth peak is at wavenumber 1600 cm. －１ More than 1800cm －１ The maximum peak is within the following range: (3) The average value of the water contact angle is 55° or more and 105° or less, and the coefficient of variation of the water contact angle is 30% or less.

[0016] The measurement depth of IR-ATR shown in condition (1) is about a few micrometers. On the other hand, the measurement depth of nano-IR shown in condition (2) is about a few tens of nanometers. The measurement depth of nano-IR is shallower than that of IR-ATR, and nano-IR is much more suitable for measuring surface regions than IR-ATR. Hereinafter, the "region measurable by IR-ATR" may be referred to as the "deep surface region," and the "region measurable by nano-IR" may be referred to as the "extreme surface region."

[0017] The above condition (1) will be explained. The first peak is at wavenumber 1130 cm. －１1180cm or more －１ CF within the following range ２ This is the peak of the symmetric stretching vibration. The first peak is CF ２ The peak originates from symmetrical stretching vibrations. If the resin film has a fluororesin layer, the first peak is, for example, a peak originating from the fluororesin layer. The second peak is at wavenumber 1700 cm. －１ 1750cm or more －１ The maximum peak appearing within the following range is the peak that occurs when the resin film has a surface modification layer. If the resin film has a surface modification layer, the second peak is, for example, a peak derived from a substituent in the surface modification layer. Specifically, the peak derived from a substituent in the surface modification layer is a peak derived from one or both of a carbonyl group (-COOH) and / or an ester bond (-COO-). In this disclosure, the maximum peak means the peak with the highest absorbance.

[0018] Ratio A ２ / A １ This serves as an indicator of the degree of progress of surface modification treatment in the deep surface region of the resin film. Ratio A ２ / A １ The higher the value, the more likely it is that surface modification treatment is progressing in the deeper layers of the resin film's surface. Ratio A ２ / A １ When the ratio exceeds 0.006, the surface modification treatment is excessively advanced in the deep surface region of the resin film. As a result, monomer-derived by-products tend to accumulate on the surface of the resin film, and blocking occurs when stored in roll form for a long period of time. Therefore, in order to suppress blocking, in this disclosure, ratio A ２ / A １ Set it to 0.006 or less.

[0019] The above condition (2) will be explained. The third peak is wavenumber 1130 cm. －１ 1180cm or more －１ CF within the following range ２ This is the peak of symmetrical stretching vibration. If the resin film has a fluororesin layer, the third peak is, for example, a peak originating from the fluororesin layer. The fourth peak is at wavenumber 1600 cm. －１ More than 1800cm －１The maximum peak appearing within the following range is the peak that occurs when the resin film has a surface modification layer. If the resin film has a surface modification layer, the fourth peak is, for example, a peak that originates from a substituent in the surface modification layer. Specifically, the peak that originates from a substituent in the surface modification layer is a peak that originates from one or both of the carbonyl group (-COOH) and / or the ester bond (-COO-).

[0020] Ratio N ２ / N １ This serves as an indicator of the degree of progress of surface modification treatment in the extreme surface region of the resin film. Ratio N ２ / N １ The higher the value, the more the surface modification treatment tends to be progressing in the extreme surface region of the resin film. Ratio N ２ / N １ When the value is between 0.05 and 0.5, the surface modification treatment proceeds favorably in the extreme surface region of the resin film, and the advantages associated with the surface modification treatment are fully obtained.

[0021] Conventional surface modification methods tend to generate by-products and have poor surface modification efficiency, resulting in a tendency for scattered, island-like surfaces with by-products to be observed on a thin surface treatment layer. Therefore, in IR-ATR measurements with a large measurement area, information originating from such by-products is also picked up, A ２ / A １ A high ratio does not necessarily mean that surface modification is progressing favorably. On the other hand, as shown in (1) and (2) above, the resin film of this disclosure undergoes surface modification in the extreme surface region, and since there are almost no by-products in the deep surface region, even if the measurement area is large, it is not affected and only the modified layer in the extreme surface region is observed, A ２ / A １ The ratio tends to be close to that of the unmodified state. As a result, the resin film of this disclosure can reduce monomer-derived by-products accumulated on its surface and is less prone to blocking even when stored in roll form for a long period of time.

[0022] Condition (3) will be described. The average value of the water contact angle is 55° or more and 105° or less, and the coefficient of variation of the water contact angle is 30% or less. When the resin film is subjected to a surface modification treatment, the water contact angle of the surface of the resin film tends to be 105° or less. By the average value of the water contact angle being 55° or more and 105° or less, appropriate wettability can be imparted to the resin film. Also, by the coefficient of variation of the water contact angle being 30% or less, the variation in the water contact angle on the surface of the resin film can be reduced.

[0023] Hereinafter, the surface characteristics of the resin film of the present disclosure will be described in more detail. On at least one surface (one-sided or both-sided) of the resin film of the present disclosure, the ratio A ２ / A １ is measured by IR-ATR. In the present disclosure, the surface of the resin film on which the following parameters are measured is the same surface as the surface on which the ratio A ２ / A １ is measured. It is preferable that at least one surface (one-sided or both-sided) of the resin film of the present disclosure is a measurement surface and satisfies the following parameters. When a surface treatment such as plasma treatment is applied to the resin film, it is preferable that the surface treatment surface is a measurement surface and satisfies the following parameters.

[0024] <IR-ATR> The IR-ATR analysis is performed using a Fourier transform infrared spectrometer (Thermo Fisher Scientific's "Nicolet 6700"). As already described, the ratio A ２ / A １ is 0.006 or less. From the viewpoint of suppressing blocking when stored in a roll shape for a long period of time, the ratio A ２ / A １ is preferably 0.005 or less, more preferably 0.004 or less, still more preferably 0.003 or less, even more preferably 0.002 or less, and particularly preferably 0.001 or less. The lower limit of the ratio A ２ / A １ is not particularly limited, but is, for example, 0.00001 or more.

[0025] <nano-IR> Nano-IR analysis is performed using a nano-IR analyzer (neaSCOPE, a scattering-type near-field infrared microscope manufactured by attocube). Nano-IR is also called AFM-IR (Atomic Force Microscope - Infrared Spectroscopy), and it is possible to obtain a spectrum at any point from the AFM observation image. To confirm the modification state of the resin film, the measurement site is selected from a flat area within the observation field that does not contain any protrusions (corresponding to aggregates).

[0026] As already mentioned, ratio N ２ / N １ The ratio N is between 0.05 and 0.5. From the viewpoint of fully imparting the benefits associated with surface modification treatment to the resin film, ２ / N １ It is preferable that the ratio N is 0.1 or higher. From the viewpoint of suppressing blocking when stored in roll form for a long period of time, ２ / N １ It is preferable that it be 0.45 or less.

[0027] <Water Contact Angle> In this disclosure, the water contact angle refers to the static contact angle of water. The water contact angle in this disclosure is measured using a fully automatic contact angle meter DropMaster 700 (manufactured by Kyowa Interface Chemical Co., Ltd.) by dropping 1 μL of water from a microsyringe onto a resin film placed horizontally and capturing a still image 1 second after dropping with a video microscope. The water contact angle is measured at 50 locations on the surface of the resin film, and the average value (numerical mean, Ave.) and its standard deviation (σ) are determined.

[0028] As already mentioned, the average water contact angle on at least one surface of the resin film is 55° or higher. More preferably, the average water contact angle on the surface of the resin film is 60° or higher, even more preferably 70° or higher, even more preferably 80° or higher, and even more preferably 85° or higher. If the water contact angle is 55° or higher, the resin film can be given appropriate wettability. Furthermore, when a polymer layer is formed by the polymerization of monomers as described later, if the water contact angle is 55° or higher, excessive self-polymerization of monomers is suppressed, and a sufficient amount of monomer-derived substituents that contribute to adhesion can be present on the surface of the resin film. Therefore, the adhesive strength of the resin film is less likely to decrease. On the other hand, as already mentioned, the average water contact angle on at least one surface of the resin film is 105° or lower. In terms of giving the resin film appropriate wettability, it is preferable that the average water contact angle on the surface of the resin film is 100° or lower.

[0029] As already mentioned, the coefficient of variation of the water contact angle is 30% or less on at least one surface of the resin film. The coefficient of variation of the water contact angle (σ / Ave.) is an indicator of the variation in the water contact angle on the surface of the resin film. In terms of reducing the variation in the water contact angle of the resin film, the coefficient of variation of the water contact angle is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 6.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, and even more preferably 3.5% or less. The lower limit of the coefficient of variation of the water contact angle is not particularly limited, but for example, it is 0.1% or more. The coefficient of variation of the water contact angle (unit: %) is calculated from the mean value (Ave.) of the water contact angle and the standard deviation (σ) of the water contact angle based on the following formula: Coefficient of variation of water contact angle (σ / Ave.) = 100 × (σ) / (Ave.)

[0030] The rate of change in the water contact angle of the surface of the resin film, measured before and after annealing the resin film at 150°C for 30 minutes, is preferably 150% or less, more preferably 140% or less, even more preferably 130% or less, even more preferably 120% or less, and particularly preferably 110% or less. Hereinafter, "annealing the resin film at 150°C for 30 minutes" may be referred to as "predetermined annealing treatment." Also, "the rate of change in the water contact angle of the surface of the resin film, measured before and after annealing the resin film at 150°C for 30 minutes" may be referred to as "the rate of change in the water contact angle before and after the predetermined annealing treatment." The lower limit of the rate of change in the water contact angle before and after the predetermined annealing treatment is not particularly limited, but is, for example, 100% or more.

[0031] The rate of change in the water contact angle before and after a predetermined annealing treatment serves as an indicator of the amount of monomer-derived by-products accumulated on the surface of the resin film. A lower rate of change in the water contact angle before and after a predetermined annealing treatment tends to indicate less monomer-derived by-products accumulated on the surface of the resin film.

[0032] The rate of change in the water contact angle before and after a predetermined annealing treatment can be measured by the following method. Using the above method for measuring the water contact angle, measure the water contact angle of the resin film surface before the predetermined annealing treatment (water contact angle before predetermined annealing treatment) and the water contact angle of the resin film surface after the predetermined annealing treatment (water contact angle after predetermined annealing treatment). The rate of change in the water contact angle before and after the predetermined annealing treatment (in %) is calculated using the following formula: Rate of change = 100 × Water contact angle after predetermined annealing treatment / Water contact angle before predetermined annealing treatment

[0033] From the viewpoint of suppressing blocking when the resin film is stored in a roll for a long period of time, it is preferable that the rate of change in the water contact angle of the surface of the resin film, measured before and after immersing the resin film in tetrahydrofuran (THF) for 100 hours, is 150% or less. Hereinafter, "immersing the resin film in THF for 100 hours" may be referred to as "predetermined immersion." Also, "the rate of change in the water contact angle of the surface of the resin film, measured before and after immersing the resin film in THF for 100 hours" may be referred to as "the rate of change in the water contact angle before and after predetermined immersion." Predetermined immersion is performed by immersing an amount of resin film with a concentration of 100 g / L in THF at 25°C for 100 hours.

[0034] The rate of change in the water contact angle before and after a predetermined immersion is an indicator of the amount of monomer-derived by-products accumulated on the surface of the resin film. The lower the rate of change in the water contact angle before and after a predetermined immersion, the less monomer-derived by-products tend to accumulate on the surface of the resin film.

[0035] The rate of change in the water contact angle before and after a predetermined immersion can be measured by the following method. Using the above method for measuring the water contact angle, the water contact angle of the resin film surface before predetermined immersion (water contact angle before predetermined immersion) and the water contact angle of the resin film surface after predetermined immersion (water contact angle after predetermined immersion) are measured. The rate of change in the water contact angle before and after predetermined immersion (unit: %) is calculated using the following formula: Rate of change = 100 × Water contact angle after predetermined immersion / Water contact angle before predetermined immersion

[0036] The amount of components leached from the resin film into the THF (hereinafter sometimes referred to as the leached amount), measured by immersing the resin film in a predetermined amount of water, is preferably 900 ppm or less, more preferably 800 ppm or less, even more preferably 700 ppm, even more preferably 600 ppm or less, even more preferably 500 ppm or less, even more preferably 400 ppm or less, and particularly preferably 300 ppm or less, relative to the mass of the resin film.

[0037] The elution rate is an indicator of the amount of monomer-derived by-products accumulated on the surface of the resin film. A lower elution rate tends to result in a lower amount of monomer-derived by-products accumulated on the resin film surface. If the elution rate is 900 ppm or less, the amount of monomer-derived by-products accumulated on the resin film surface can be reduced, further suppressing blocking during long-term storage in roll form. While there is no particular lower limit to the elution rate, it is, for example, 0 ppm or higher.

[0038] The amount of elution is measured after a predetermined immersion period using the method described below. After the predetermined immersion period, the resin film is removed from the THF. The liquid containing the immersed THF is concentrated under reduced pressure using an evaporator, and then dried at 90°C for 96 hours to collect the components (elutes) eluted from the resin film into the THF. The collected elutes are dried until they are completely dry, and the mass of the elutes is measured. The amount of elution (in %) is calculated using the formula "Amount of elution = 100 × Mass of elutes / Mass of resin film before predetermined immersion," and then converted to the amount of elution (in ppm).

[0039] <Oxygen Element Ratio> The oxygen element ratio is measured by scanning X-ray photoelectron spectroscopy (XPS). Specifically, the oxygen element ratio is determined using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.), detecting carbon, oxygen, fluorine, and nitrogen, and calculating the composition ratio of C1s, O1s, F1s, and N1s.

[0040] In terms of having a suitable amount of functional groups that contribute to adhesion, the oxygen element ratio on the surface of the resin film is preferably 1.0 atomic% or more, more preferably 1.2 atomic% or more, even more preferably 1.5 atomic% or more, even more preferably 1.8 atomic% or more, even more preferably 2.0 atomic% or more, even more preferably 3.0 atomic% or more, and particularly preferably 4.0 atomic% or more. The upper limit of the oxygen element ratio on the surface of the resin film is not particularly limited, but for example it may be 25.0 atomic% or less, or 20.0 atomic% or less.

[0041] From the viewpoint of suppressing blocking when the resin film is stored in a roll for a long period of time, it is preferable that the rate of change in the oxygen element ratio on the surface of the resin film, measured by scanning X-ray photoelectron spectroscopy (XPS) before and after storing the rolled resin film at 40°C for one month, be -20% or more, more preferably -15% or more, and even more preferably -10% or more. Hereinafter, "storing the rolled resin film at 40°C for one month" may be referred to as "prescribed storage." In this disclosure, "one month" is defined as 30 days. The upper limit of the rate of change in the oxygen element ratio on the surface of the resin film, measured by scanning X-ray photoelectron spectroscopy (XPS) before and after prescribed storage, is not particularly limited, but is, for example, 0% or less.

[0042] The rate of change in the oxygen element ratio on the surface of a resin film, measured by scanning X-ray photoelectron spectroscopy (XPS) before and after predetermined storage, is measured, for example, by the following method. The oxygen element ratio on the surface of the resin film before predetermined storage (oxygen element ratio before predetermined storage) and the oxygen element ratio on the surface of the resin film after predetermined storage (oxygen element ratio after predetermined storage) are measured using the above oxygen element ratio measurement method. The rate of change in the oxygen element ratio before and after predetermined storage (unit: %) is calculated using the following formula. Note that the oxygen element ratio before predetermined storage is measured from the resin film before predetermined storage and before it is wound into a roll. Rate of change = 100 × {(oxygen element ratio after predetermined storage / oxygen element ratio before predetermined storage) - 1}

[0043] <Surface Modulus> In multi-point measurements of the surface modulus of a resin film using a scanning atomic force microscope, the cumulative relative frequency at which the resin film reaches 1.3 GPa (the cumulative relative frequency when 1.3 GPa is reached) is preferably 0.98 or less. When the cumulative relative frequency at which the resin film reaches 1.3 GPa is 0.98 or less, an appropriate adhesive layer is formed on the resin film, improving the adhesive strength. The cumulative relative frequency at which the resin film reaches 1.3 GPa is more preferably 0.96 or less, and even more preferably 0.95 or less. From the viewpoint of uniformity of the adhesive layer, the cumulative relative frequency at which the resin film reaches 1.3 GPa is preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more.

[0044] The cumulative relative frequency of a resin film reaching 1.3 GPa can be determined from a histogram obtained by multi-point measurement of the surface modulus of the resin film using a scanning atomic force microscope. Multi-point measurement of the surface modulus of the resin film can be performed by the method described in the examples. In the histogram, the horizontal axis shows the surface modulus (unit: GPa), and the vertical axis shows the frequency. In the histogram, the higher the frequency of regions where the surface modulus exceeds 1.3 GPa, the lower the cumulative relative frequency of reaching 1.3 GPa. The lower the cumulative relative frequency of reaching 1.3 GPa, the more regions with high surface modulus, in other words, regions with high rigidity, are increasing on the surface of the resin film. In one example, when a polymer layer with higher rigidity than the fluororesin layer (for example, a hydrocarbon-based layer) is formed on the surface of a low-rigidity fluororesin layer, the cumulative relative frequency of the resin film reaching 1.3 GPa tends to decrease and easily become a value of 0.98 or less. Furthermore, the cumulative relative frequency of the resin film reaching 1.3 GPa tends to decrease as the amount of polymer layer formed on the surface of the fluororesin layer increases.

[0045] <Fluororesin> The resin film of this disclosure comprises at least a fluororesin. The fluororesin is not particularly limited and may be any polymer that partially contains fluorine atoms. Preferably, the fluororesin is a melt-mold fluororesin. Examples of fluororesins include tetrafluoroethylene (TFE)-perfluoroalkyl vinyl ether (PAVE) copolymer [PFA], copolymers having chlorotrifluoroethylene (CTFE) units (CTFE copolymers), tetrafluoroethylene (TFE)-hexafluoropropylene (HFP) copolymer [FEP], tetrafluoroethylene (TFE)-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride copolymer (THV), and tetrafluoroethylene (TFE)-vinylidene fluoride copolymer. By using a melt-mold fluororesin, melt molding can be performed, thus reducing processing costs compared to using PTFE. Furthermore, adhesion to metal foil can be improved.

[0046] In particular, the fluororesin is preferably PFA or FEP, and more preferably PFA.

[0047] The melting point of PFA is preferably 180 to 340°C, more preferably 230 to 330°C, and even more preferably 280 to 320°C. The melting point is the temperature corresponding to the maximum value in the heat of fusion curve when the temperature is increased at a rate of 10°C / min using a differential scanning calorimeter (DSC).

[0048] While there are no particular limitations on the PFA, copolymers with a molar ratio of TFE units to PAVE units (TFE units / PAVE units) of 70 / 30 or more and less than 99.5 / 0.5 are preferred. More preferably, the molar ratio of TFE units to PAVE units (TFE units / PAVE units) is 70 / 30 or more and 98.9 / 1.1 or less, and even more preferably 80 / 20 or more and 98.5 / 1.5 or less. The more TFE units there are, the better the mechanical properties of the PFA tend to be. The fewer TFE units there are, the less the melting point of the PFA tends to become too high, and the better the moldability tends to be. Examples of PAVE units include perfluoropropyl vinyl ether (PPVE) units.

[0049] PFA may be a copolymer containing only TFE and PAVE. Alternatively, PFA may be a copolymer in which monomer units derived from monomers copolymerizable with TFE and PAVE amount to 0.1 to 10 mol%, and TFE units and PAVE units total 90 to 99.9 mol%. Examples of monomers copolymerizable with TFE and PAVE include HFP and CZ. ３ Z ４ = CZ ５ (CF ２ )nZ ６ (In the formula, Z ３ Z ４ and Z ５ Z represents a hydrogen atom or a fluorine atom, either identical or different. ６ ) represents a vinyl monomer, and CF ２ = CF - OCH ２ -Rf ７ (wherein, Rf ７ ) represents a perfluoroalkyl group having 1 to 5 carbon atoms. Examples include alkyl perfluorovinyl ether derivatives represented by ). Other copolymerizable monomers include, for example, cyclic hydrocarbon monomers having an acid anhydride group. Examples of acid anhydride monomers include itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride, and maleic anhydride. Acid anhydride monomers may be used individually or in combination of two or more.

[0050] 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 obtained by measuring under conditions of 372°C and a load of 5.0 kg in accordance with ASTM D3307.

[0051] Fluoropolymers are preferable when they have fewer functional groups, and especially when they have fewer unstable end groups. Such fluoropolymers can be produced by adjusting the conditions during manufacturing (polymerization reaction), or by reducing the number of unstable end groups after polymerization through methods such as fluorine gas treatment, heat treatment, or supercritical gas extraction. These methods offer excellent processing efficiency, and some or all of the unstable end groups are -CF ３ Fluorine gas treatment is preferred because it converts to stable end groups. Fluorination treatment can be carried out by contacting an unfluorinated fluororesin with a fluorine-containing compound. Using a fluororesin with a reduced number of unstable end groups in this way is preferable because it reduces the electrostatic loss tangent and decreases the loss of electrical signals.

[0052] The number of unstable end groups mentioned above is not particularly limited, but for fluororesins with a main chain of 10 carbon atoms... ６ The value per unit is preferably 450 or less, more preferably 250 or less, even more preferably 100 or less, and most preferably 50 or less. Considering the effect of reducing dielectric loss tangent, it is preferably less than 10, and even more preferably 5 or less.

[0053] Unstable end groups include, specifically, -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), and hydroxyl groups (-CH ２ OH, etc.), -CONH ２ , -COOR(R=CH ３ etc.), -CF ２ Examples of functional groups include H,-OCOO-R (such as n-propyl carbonate).

[0054] The number of unstable end groups is measured specifically by the following method. First, the above-mentioned fluororesin is melted and compressed to produce a film with a thickness of 0.25 to 0.3 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the above-mentioned fluororesin, and a difference spectrum is obtained from the base spectrum, which is completely fluorinated and does not contain any functional groups. From the absorption peak of a specific functional group that appears in this difference spectrum, the number of carbon atoms in the above-mentioned fluororesin (1 × 10) is calculated according to the following formula (A). ６ Calculate the number of unstable end groups per unit. N = I × K / t (A) I: absorbance K: correction factor t: film thickness (mm)

[0055] The fluororesin film of this disclosure may contain components other than fluororesin. The components that can be contained are not particularly limited and include fillers such as silica particles and glass short fibers, fluorine-free thermosetting resins, and fluorine-free 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.).

[0056] Fluororesins can be produced by conventionally known methods, such as emulsion polymerization or suspension polymerization, by appropriately mixing monomers that form their constituent units and additives such as polymerization initiators as needed. Among these, fluororesins obtained by emulsion polymerization are preferred.

[0057] <Composition of the Resin Film> The resin film of this disclosure is elongated. The elongated shape is a shape in which the size in the length direction of the resin film is longer than the size in the width direction. The length of the resin film is 200 m or more, may be 1000 m or more, may be 2000 m or more, or may be 5000 m or more. The upper limit of the length of the resin film is not particularly limited, but for example it is 50000 m or less. The lower limit of the width of the resin film is not particularly limited, but for example it may be 200 mm or more, or may be 400 mm or more. The upper limit of the width of the resin film is not particularly limited, but for example it is 2000 mm or less.

[0058] The thickness of the resin film of this disclosure is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The thickness of the resin film of this disclosure is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. The thickness of the resin film can be measured by reflection spectroscopy using the film thickness measurement system F20 (manufactured by Filmtrics).

[0059] The resin film of this disclosure preferably comprises a fluororesin layer and a modified layer. It is preferable that the modified layer be on at least one surface (one side or both sides) of the resin film. The fluororesin layer and the modified layer will be described below.

[0060] The fluororesin layer contains a fluororesin. The fluororesin described above is preferred. The fluororesin content in the fluororesin layer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 99% by mass or more, and still more preferably 99.5% by mass or more. The fluororesin layer may also contain only a fluororesin. The fluororesin content in the fluororesin layer may be 100% by mass.

[0061] The modified layer in this disclosure is extremely thin, to the extent that it is not detected at the measurement depth of IR-ATR, but is detected at the measurement depth of nano-IR. The thickness of the modified layer is preferably 1 nm to 100 nm, more preferably 1 nm to 50 nm, and even more preferably 1 nm to 20 nm. The thickness of the modified layer is measured by observing a cross-section of the resin film using an electron microscope (a field emission transmission electron microscope JEM-ARM200F manufactured by JEOL Ltd.).

[0062] The modified layer is preferably a polymer layer. The polymer layer is a layer formed by the polymerization of monomers (monomer polymerization layer). Preferably, the polymer layer is a layer formed by plasma treatment in a monomer-containing inert gas atmosphere (monomer plasma polymerization layer). Details of the plasma treatment will be described later. The polymer layer is preferably provided directly on top of the fluororesin layer. The polymer layer also functions as an adhesive layer to bond other materials to the resin film.

[0063] The polymer layer may completely cover the surface of the fluororesin layer. However, in many cases, the polymer layer does not completely cover the surface of the fluororesin layer to the extent that the fluorine element concentration on the surface of the resin film can be measured, and a portion of the fluororesin layer is exposed on the surface of the resin film. One example of a state in which a portion of the fluororesin layer is exposed on the surface of the resin film is when the fluororesin layer is exposed through gaps between substituents derived from numerous monomers introduced on the surface of the fluororesin layer.

[0064] Examples of monomers for forming the polymer layer include polymerizable or nonpolymerizable organic compounds containing oxygen atoms. Specific examples of monomers for forming the polymer layer include vinyl compounds such as aliphatic vinyl compounds; acrylic acid esters such as glycidyl methacrylate; 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 acid esters such as ethyl acetate and ethyl formate; and acrylic acids such as acrylic acid and methacrylic acid. Of these, vinyl compounds, acrylic acid esters, and ketones are preferred, with vinyl compounds being more preferred, due to their resistance to deactivation of the modified surface, long lifespan, and ease of handling.

[0065] The resin constituting the polymer layer has units derived from the above-mentioned monomers as constituent units. Preferably, the resin constituting the polymer layer has units derived from vinyl compounds as constituent units, more preferably from aliphatic vinyl compounds, and even more preferably from vinyl acetate. In the resin constituting the polymer layer, the content of units derived from vinyl compounds is preferably 90 mol% or more, more preferably 95 mol% or more, even more preferably 98 mol% or more, even more preferably 99 mol% or more, and particularly preferably 100 mol% of the total number of constituent units.

[0066] From the viewpoint of achieving both polymerizability of monomers and adhesion to other materials, suitable examples of vinyl compounds that can be used as monomers include aliphatic vinyl compounds. Aliphatic vinyl compounds are aliphatic compounds having a vinyl group. The carbon chain of an aliphatic compound may be linear or branched. Furthermore, the carbon-carbon bond of the carbon chain of an aliphatic compound may be saturated or unsaturated. In addition, the carbon chain of an aliphatic compound may have heteroatoms such as oxygen atoms in addition to carbon atoms. From the viewpoint of achieving both polymerizability of monomers and adhesion to other materials, suitable examples of aliphatic vinyl compounds include those with the general formula (1) "H ２ C = CH - O - R １ Examples of compounds represented by " are shown. R in general formula (1) １ This is an alkyl group having 1 to 6 carbon atoms, or the general formula (2) "-CO-R ２ This represents the base represented by " in general formula (2). ２ R represents a hydrogen atom, a C1-C6 alkyl group, or a C2-C6 alkenyl group. The C1-C6 alkyl group is linear or branched. The C2-C6 alkenyl group is linear or branched and may have one or more (e.g., two or three) double bonds. １ The alkyl group having 1 to 6 carbon atoms represented by is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably an alkyl group having 1 or 2 carbon atoms. ２The alkyl group having 1 to 6 carbon atoms represented by is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably an alkyl group having 1 or 2 carbon atoms. ２ As the alkenyl group having 2 to 6 carbon atoms represented by , an alkenyl group having 2 to 5 carbon atoms is preferred.

[0067] The compounds represented by general formula (1) that can be used as aliphatic vinyl compounds are preferably vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, and vinyl sorbate; and ethers such as vinyl ethyl ether and vinyl methyl ether. Among these, aliphatic vinyl compounds such as vinyl acetate, vinyl propionate, and vinyl formate are particularly preferred. When the vinyl compound contains aliphatic vinyl compounds such as vinyl acetate, vinyl propionate, and vinyl formate, the proportion of the aliphatic vinyl compound in the vinyl compound is preferably 90 mol% or more, more preferably 95 mol% or more, even more preferably 98 mol% or more, even more preferably 99 mol% or more, and particularly preferably 100 mol%.

[0068] [Method for Manufacturing Resin Film] This disclosure also relates to a method for manufacturing a resin film. The method for manufacturing a resin film comprising at least a fluororesin is a method for manufacturing a long resin film. By the method for manufacturing a resin film, for example, the resin film of this disclosure described above can be manufactured.

[0069] The manufacturing method of the present disclosure includes a plasma treatment step. The manufacturing method of the resin film of the present disclosure includes, if necessary, a step of forming a fluororesin layer. However, if a commercially available fluororesin film is used as the fluororesin layer, the step of forming the fluororesin layer can be omitted.

[0070] <Fluororesin Layer Formation Process> In the fluororesin layer formation process, a fluororesin layer containing fluororesin is formed. Examples of fluororesins used in forming the fluororesin layer include those described above. The fluororesin used in forming the fluororesin layer is preferably PFA or FEP, and more preferably PFA. The molding method for forming the fluororesin layer into a sheet is not particularly limited, but examples include a melt molding method and a casting method. An example of a melt molding method is extrusion molding. An example of a casting method is to prepare a solution or dispersion containing fluororesin, and then coat and dry it on a substrate such as metal such as copper foil or aluminum foil, or resin. The fluororesin layer formed on the substrate may be used together with the substrate or peeled off and used. Furthermore, the fluororesin layer may be formed by uniaxial stretching or biaxial stretching of the fluororesin, or it may be unstretched.

[0071] <Plasma Treatment Process> In the plasma treatment process, while transporting the fluororesin layer containing fluororesin, at least one surface of the fluororesin layer is plasma treated under predetermined conditions in a monomer-containing inert gas atmosphere. The predetermined conditions are: applied voltage frequency of 1 to 100 kHz, electric field strength of 5 to 50 kV / mm, and discharge degree of 1 to 5 W / cm. ２ Furthermore, the ratio of the flow rate of monomers in the monomer-containing inert gas atmosphere to the transport speed of the fluororesin layer is 0.003 to 0.02 L / m. Hereinafter, "the ratio of the flow rate of monomers in the monomer-containing inert gas atmosphere to the transport speed of the fluororesin layer" may be referred to as "gas concentration / line speed ratio".

[0072] The gas concentration / line speed ratio (L / m) is calculated from the monomer flow rate (in L / min) and the transport speed of the fluororesin layer to be processed (in m / min) based on the formula "Gas concentration / line speed ratio = monomer flow rate / transport speed". The monomer flow rate (in L / min) is calculated from the monomer-containing inert gas flow rate (in L / min) and the monomer concentration in the monomer-containing inert gas atmosphere (in volume %) based on the formula "Monomer flow rate = monomer-containing inert gas flow rate × monomer concentration / 100". The transport speed of the fluororesin layer corresponds to the line speed of the factory line.

[0073] It is presumed that by performing plasma treatment under the above-described conditions, the modification of the fluororesin layer surface (e.g., generation of carbon radicals by abstraction of fluorine atoms) proceeds uniformly within the plane, and the accompanying polymerization (e.g., graft polymerization) proceeds efficiently. As a result, the generation of monomer-derived by-products (e.g., monomer decomposition products and / or aggregates of monomer homopolymers) is suppressed. By suppressing the generation of monomer-derived by-products, it is possible to obtain a resin film that is less prone to blocking even when stored in roll form for a long period of time.

[0074] The plasma treatment may be performed on one side of the fluororesin layer or on both sides.

[0075] It is preferable to surface treat the surface by exposing the surface to be modified to an atmosphere of an organic compound-containing inert gas, which includes an organic compound and an inert gas, inducing a discharge by applying a high-frequency voltage between electrodes, thereby generating active species on the surface, and then introducing functional groups of the organic compound or graft polymerization of a polymerizable organic compound. For example, plasma treatment causes polymerization of monomers contained in the monomer-containing inert gas, forming a polymer layer on the fluororesin layer. Specifically, corona discharge generates plasma of monomers contained in the monomer-containing inert gas. The generated monomer plasma polymerizes (e.g., graft polymerization), forming a polymer layer on the surface of the fluororesin layer.

[0076] In terms of production efficiency and manufacturing cost, it is preferable to continuously perform plasma treatment on the surface of the fluororesin layer while conveying it by roll-to-roll, rather than using chamber treatment or batch treatment. Roll-to-roll is a processing method in which a roll of fluororesin layer is unwound, the unwound fluororesin layer is passed through a processing section (e.g., a plasma processing section), and the plasma-treated fluororesin layer, which is a resin film, is wound back into a roll shape.

[0077] In terms of improving processing continuity, the transport speed of the fluororesin layer is preferably 1 m / min or more and 100 m / min or less, more preferably 1 m / min or more and 50 m / min or less, and even more preferably 2.5 m / min or more and 25 m / min or less.

[0078] Plasma treatment may be carried out, for example, under atmospheric pressure (equivalent to 1 atmosphere, 1013 hPa) or a pressure close to it. However, plasma treatment is not limited to an atmospheric pressure environment, and may be carried out under a pressurized or depressurized environment in the range of 500 to 2000 hPa. Pressurization can prevent unintended gases (e.g., oxygen from the air) from flowing into the plasma atmosphere.

[0079] Examples of monomers included in the monomer-containing inert gas atmosphere include those similar to those used to form the polymer layer described above. From the standpoint of the modified surface being less prone to deactivation and having a long lifespan, and ease of handling, the monomers included in the monomer-containing inert gas atmosphere are preferably vinyl compounds (preferably aliphatic vinyl compounds). When the monomer contains a vinyl compound, the proportion of the vinyl compound in the monomer is preferably 90 mol% or more, more preferably 95 mol% or more, even more preferably 98 mol% or more, even more preferably 99 mol% or more, and particularly preferably 100 mol%. The vinyl compound is preferably an aliphatic vinyl compound. When the vinyl compound contains an aliphatic vinyl compound, the proportion of the aliphatic vinyl compound in the vinyl compound is preferably 90 mol% or more, more preferably 95 mol% or more, even more preferably 98 mol% or more, even more preferably 99 mol% or more, and particularly preferably 100 mol%.

[0080] The concentration of monomer in the monomer-containing inert gas atmosphere varies depending on the type of monomer, the type of fluororesin to be surface-modified, etc., but is preferably 0.1 to 5% by volume, more preferably 0.1 to 3.0% by volume, even more preferably 0.1 to 1.0% by volume, even more preferably 0.15 to 1.0% by volume, and particularly preferably 0.30 to 1.0% by volume.

[0081] Examples of inert gases included in the monomer-containing inert gas atmosphere include nitrogen gas, helium gas, and argon gas. In order to stabilize the discharge and enable more uniform surface modification within the plane, it is preferable that the inert gas be one or more (for example, one to three) selected from the group consisting of nitrogen, argon, and helium, and more preferably nitrogen gas.

[0082] The monomer-containing inert gas may contain carbon dioxide, but it is preferable that it does not contain carbon dioxide in order to suppress the carbonization of the monomer.

[0083] Plasma treatment can be performed, for example, using a corona discharge apparatus. A corona discharge apparatus comprises, for example, a discharge electrode and a ground electrode (for example, a roll-shaped ground electrode).

[0084] From the viewpoint of reducing by-products in the resin film and suppressing blocking when stored in roll form for a long period of time, the frequency of the applied voltage, which is the discharge condition, is 1 kHz or higher, preferably 10 kHz or higher, more preferably 15 kHz or higher, even more preferably 20 kHz or higher, and even more preferably 25 kHz or higher. From the viewpoint of reducing by-products in the resin film and suppressing blocking when stored in roll form for a long period of time, the frequency of the applied voltage is 100 kHz or lower, preferably 80 kHz or lower, more preferably 70 kHz or lower, even more preferably 60 kHz or lower, even more preferably 50 kHz or lower, and particularly preferably 40 kHz or lower. The above frequency of the applied voltage is relatively low, and this is presumed to contribute to the reduction of by-products in the resin film. The type of applied voltage is not particularly limited, but for example, it is an AC voltage.

[0085] From the viewpoint of reducing by-products in the resin film and suppressing blocking when stored in roll form for a long period of time, the electric field strength, which is the discharge condition, is preferably 5 kV / mm or more, and preferably 10 kV / mm or more. From the viewpoint of reducing by-products in the resin film and suppressing blocking when stored in roll form for a long period of time, the electric field strength, which is the discharge condition, is preferably 50 kV / mm or less, preferably 40 kV / mm or less, and more preferably 30 kV / mm or less.

[0086] To reduce by-products in the resin film and suppress blocking during long-term storage in roll form, the discharge condition, or discharge degree, is set to 5 W / cm². ２ The following is true: 4 W / cm ２ More preferably, the following is true: 3 W / cm ２ The following is even more preferable: From the viewpoint of reducing by-products in the resin film and suppressing blocking when stored in roll form for a long period of time, the discharge condition, which is the discharge degree, is 1 W / cm². ２That is all. 2 W / cm ２ It is more preferable that the above conditions are met.

[0087] From the viewpoint of reducing by-products in the resin film and suppressing blocking when stored in roll form for a long period of time, the gas concentration / line velocity ratio is preferably 0.003 L / m or higher, and more preferably 0.005 L / m or higher. From the viewpoint of reducing by-products in the resin film and suppressing blocking when stored in roll form for a long period of time, the gas concentration / line velocity ratio is preferably 0.02 L / m or lower, and more preferably 0.010 L / m or lower.

[0088] The processing temperature can be any temperature within the range of 0°C to 100°C. To reduce stretching and wrinkling of the resin film, the processing temperature is preferably 80°C or lower. Note that when heat treatment is performed when laminating the resin film with other materials such as metal foil, the amount of oxygen on the surface of the resin film may decrease due to the heat treatment. Therefore, it is preferable to perform surface modification under conditions that ensure a sufficient amount of surface oxygen at the time the resin film and other materials such as metal foil are bonded together.

[0089] <Annealing Process> The method for manufacturing a fluororesin film according to the present disclosure may include an annealing process after the plasma treatment process described above, if necessary. Annealing further suppresses blocking of the resin film. If annealing is performed, it can be carried out by heat treatment. Heat treatment can be carried out, for example, by passing the film through a heating furnace in a roll-to-roll manner. Heat treatment may also be carried out by placing the film in a batch-type drying oven.

[0090] However, the manufacturing method of this disclosure does not require an annealing step. As described above, blocking of the resin film can be suppressed by performing a plasma treatment step under predetermined conditions, so the manufacturing method of this disclosure can obtain the desired benefit of suppressing blocking even without performing an annealing step. Furthermore, if annealing is not performed, the manufacturing method of this disclosure can shorten the production time.

[0091] The above describes an example of a method for manufacturing the resin film of this disclosure. However, the resin film of this disclosure described above is not limited to those manufactured by the above manufacturing method. For example, the resin film of this disclosure may be surface-treated by conventional methods such as corona discharge treatment, glow discharge treatment, plasma discharge treatment other than those described above, sputtering treatment, etc.

[0092] The resin film of this disclosure can suppress blocking when stored in roll form for a long period of time. For this reason, the resin film of this disclosure can be suitably used in metal-clad laminates and circuit boards. Furthermore, the resin film of this disclosure can be applied to various flexible devices, and is specifically useful as various display devices (e.g., liquid crystal display devices, organic EL display devices, touch panels, liquid crystal displays, organic EL displays, color filters, electronic paper, etc.), glass laminated transparent antennas, transparent antenna films, antenna-on displays, surface protective films for solar panels, substrate materials for solar cells, foldable displays, or components thereof.

[0093] [Metal-clad laminate] The present disclosure is also a metal-clad laminate. The metal-clad laminate of the present disclosure comprises the resin film of the present disclosure described above and a metal foil. The metal-clad laminate of the present disclosure comprises the resin film of the present disclosure which is less prone to blocking even when stored in roll form for a long period of time. Furthermore, even when the resin film is a surface-modified resin film, the metal-clad laminate of the present disclosure enables efficient production by allowing processing while smoothly unwinding the resin film. The metal-clad laminate preferably further comprises a base material.

[0094] <Metal Foil> The metal foil is provided directly or indirectly on the resin film. The metal foil may be provided on both sides of the resin film or on one side. Examples of metals that make up the metal foil include copper, aluminum, stainless steel (SUS), nickel, and gold. Alloys of these may also be used. From the viewpoint of conductivity and circuit processability, copper foil is preferred as the metal foil.

[0095] The surface roughness (Rz) of the metal foil is preferably 1.5 μm or less, and more preferably 1.0 μm or less. The resin film of this disclosure described above also exhibits excellent adhesion to metal foil with a high degree of smoothness, having an Rz of 1.5 μm or less. The metal foil only needs to have an Rz of 1.5 μm or less on at least the surface that adheres to the resin film described above, and the Rz of the other surface is not particularly limited. The lower limit of the Rz of the metal foil is not particularly limited, but for example, it is 0.1 μm or more. The Rz of the metal foil is the sum of the highest part (maximum peak height: Rp) and the deepest part (maximum valley depth: Rv). The Rz of the metal foil is the ten-point average roughness as defined in JIS-B0601. In this disclosure, the Rz of the metal foil is the value measured using a surface roughness meter (product name: Surfcom 470A, manufactured by Tokyo Seiki Co., Ltd.) with a measurement length of 4 mm.

[0096] The copper foil that can be used for metal foil is not particularly limited, and examples include rolled copper foil and electrolytic copper foil. The copper foil with an Rz of 1.5 μm or less is not particularly limited, and for example, unroughened copper foil that has not undergone roughening treatment can be used. Furthermore, the copper foil with 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 with an Rz of 1.5 μm or less include electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm, Rz 0.85 μm) (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.).

[0097] When the metal foil is directly mounted on the resin film, the average adhesive strength between the metal foil and the resin film is preferably 0.5 N / cm or more, more preferably 1 N / cm or more, even more preferably 2 N / cm or more, even more preferably 3 N / cm or more, even more preferably 4 N / cm or more, and particularly preferably 5 N / cm or more, as it is suitable for use as a metal-clad laminate and a circuit board. The upper limit of the average adhesive strength between the metal foil and the resin film is not particularly limited, but for example, it is 20 N / cm or less.

[0098] The coefficient of variation (σ / Ave.) of the adhesive strength between metal foil and resin film is an indicator of the variability in adhesive strength. It is preferable that the coefficient of variation of the adhesive strength between metal foil and resin film be 35% or less. While there is no particular lower limit to the coefficient of variation of the adhesive strength between metal foil and resin film, it is, for example, 0.1% or more. The coefficient of variation of the adhesive strength between metal foil and resin film (unit: %) is calculated from the average value (Ave.) of adhesive strength and the standard deviation (σ) of adhesive strength based on the following formula: Coefficient of variation of adhesive strength (σ / Ave.) = 100 × (σ) / (Ave.)

[0099] The adhesive strength between the metal foil and the resin film is measured by a 90-degree peel test. The adhesive strength is measured at five points on the surface of the resin film, and the average value (Ave.) and its standard deviation (σ) are calculated. Details of the measurement method will be described later in the examples.

[0100] 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 in the range of 9 to 35 μm.

[0101] The metal foil may be surface-treated to enhance its adhesive strength with the resin film of this disclosure. The surface treatment of the metal foil is not particularly limited, but examples include plasma treatment, corona treatment, UV treatment, electron beam treatment, etc.

[0102] From the viewpoint of improving adhesion with the resin film, the metal foil may have a roughened layer on its surface. However, if the roughening treatment may reduce the performance required in this disclosure, the amount of roughened particles electrodeposited on the metal foil surface may be reduced or the roughening treatment may be omitted as needed.

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

[0104] <Substrate> The substrate is not particularly limited, but examples include fabrics made of glass fibers, glass nonwoven fabrics, and resin film layers. Fabrics made of glass fibers may be in the form of prepregs impregnated with resin. Examples of resin films used as substrates include heat-resistant resin films and thermosetting resin films. Examples of heat-resistant resin films include polyimide, liquid crystal polymers, polyphenylene sulfide, cycloolefin polymers, and polystyrene. Examples of thermosetting resin films include epoxy resins, polyphenylene oxide, polyphenylene ethers, polybutadiene, and divinylbenzene. The heat-resistant resin film and thermosetting resin film may contain reinforcing fibers. The reinforcing fibers are not particularly limited, but examples include glass cloth, and low-dielectric types are particularly preferred. The thickness of the substrate is preferably in the range of 12 to 200 μm.

[0105] In the metal-clad laminate of this disclosure, the lamination order and manufacturing method of the metal foil layer, substrate layer, and the resin film described above are not particularly limited, and the layer configuration can be adapted to the purpose. Specifically, examples of lamination orders include those consisting of a substrate layer / resin film / metal layer, a metal layer / resin film / substrate layer / resin film / metal layer, a metal layer / substrate layer / resin film / substrate layer / metal layer, and a metal layer / substrate layer / resin film / metal layer. Alternatively, the lamination order may consist of a metal layer / resin film / metal layer. Furthermore, other layers may be included as needed.

[0106] <Method for Manufacturing Metal-Clad Laminates> The metal-clad laminate of this disclosure has a metal layer formed on the surface of a resin film. The metal layer may be formed on one side or both sides of the resin film. Examples of methods for forming the metal layer include laminating a metal foil onto the surface of the resin film, vapor deposition, and plating.

[0107] There are no particular limitations on the method for compounding metal foil, other layers, and resin films, but two examples are given below: (i) A method of laminating metal foil, other layers, and a pre-formed resin film by applying pressure under heating using a roll-to-roll process or a press. The layer facing the metal foil may be any other layer or a resin film. (ii) A method of manufacturing a laminate by adhering a resin film to one side of the metal foil, and laminating the resin side not facing the metal foil with the other layer by applying pressure under heating.

[0108] The metal-clad laminate of this disclosure comprises a resin film of this disclosure that is less prone to blocking even when stored in a roll for a long period of time. The metal-clad laminate of this disclosure can be suitably used as a circuit board. Examples of circuit boards include printed circuit boards. A printed circuit board is a plate-shaped component used to electrically connect electronic components such as semiconductors and capacitor chips, and to arrange and fix them within a limited space. The configuration of a printed circuit board is not particularly limited. A printed circuit board may be a rigid board, a flexible board, or a rigid-flexible board. Furthermore, a printed circuit board may be a single-sided board, a single-sided board, a double-sided board, or a multilayer board (such as a pull-up board). The circuit board of this disclosure can be suitably used as a circuit board for high-frequency circuits in particular. In this disclosure, a high-frequency circuit includes not only circuits that simply transmit high-frequency signals, but also circuits that have transmission lines that transmit signals other than high-frequency signals on the same plane, such as transmission lines that convert high-frequency signals into low-frequency signals and output the generated low-frequency signals to the outside, or transmission lines that supply power supplied for driving high-frequency compatible components. Furthermore, the circuit board of this disclosure can also be used as a circuit board for antennas, filters, and the like.

[0109] While embodiments of this disclosure have been described above, it will be understood that a variety of modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0110] The present disclosure will be described in detail below based on examples, but the present disclosure is not limited in any way to the examples. In the following examples, unless otherwise specified, "parts" and "%" refer to "parts by mass" and "% by mass," respectively.

[0111] The fluororesins used in the examples and comparative examples are shown below. F-type PFA: Terminally fluorinated TFE / PPVE copolymer (Composition: TFE / PPVE = 96.1 / 3.9 (mass%), MFR: 16.0 g / 10 min, Melting point: 305°C, Number of unstable end groups: Undetectable (Main chain carbon number 10) ６ (Less than 1 per unit) PFA: TFE / PPVE copolymer that has not undergone terminal fluorination treatment (Composition: TFE / PPVE = 95.4 / 4.6 (mass%), MFR: 15.8 g / 10 min, Melting point: 305°C, Number of unstable end groups: 10 carbon atoms in the main chain) ６ (297 pieces per unit)

[0112] [Example 1] <Manufacturing of fluororesin sheet> F-type PFA was put into an extruder at 360°C, extruded from a 1700 mm wide T-die, taken up onto a metal cooling roll, and further wound onto a winding core to obtain a roll of fluororesin sheet (corresponding to a fluororesin layer) with a width of 1300 mm and a thickness of 12 μm.

[0113] <Plasma Treatment> A roll-shaped fluororesin sheet was plasma-treated on both sides while being conveyed roll-to-roll. Specifically, under atmospheric pressure, a monomer-containing inert gas containing 0.5 vol% vinyl acetate and nitrogen gas was flowed near the discharge electrode of the corona discharge device and the roll-shaped ground electrode, while the fluororesin sheet, which was attached to the roll-shaped ground electrode, was continuously passed between the electrodes. The vinyl acetate gas concentration / line velocity ratio was set to 0.010 L / m. The electric field strength was 11.4 kV / mm, the applied voltage frequency was 28 kHz, and the discharge degree was 2.9 W / cm. ２ Under these conditions, both sides of the fluororesin sheet were plasma-treated by applying corona discharge to both sides. The plasma-treated fluororesin sheet was wound into a roll to obtain the resin film of Example 1.

[0114] [Examples 2-7 and Comparative Examples 1-2] Resin films of Examples 2-7 and Comparative Examples 1-2 were obtained in the same manner as in Example 1, except that the gas concentration / line speed ratio, electric field strength, applied voltage frequency, and discharge degree for plasma treatment were as shown in Tables 2-3 described later.

[0115] [Method for Measuring IR-ATR] IR-ATR analysis was performed using a Fourier transform infrared spectrometer (ThermoFisher Scientific "Nicolet 6700") to measure the surface of the resin film under the following conditions, and the IR-ATR spectrum (horizontal axis: wavenumber / vertical axis: absorbance) was obtained. From the IR-ATR spectrum, the absorbance of the first peak A was obtained. １ And the absorbance of the second peak A ２ Find and ratio A ２ / A １ The following was calculated: • Analysis depth: approximately 2-3 μm • Measurement area: approximately 2 mmφ • Number of cumulative measurements: 32 • ATR prism: Ge • Incident angle: 45°

[0116] [Method for measuring nano-IR] Nano-IR analysis was performed using a nano-IR analyzer (neaSCOPE, a scattering-type near-field infrared microscope manufactured by attocube Co., Ltd.) to measure the surface of the resin film under the following conditions and obtain a nano-IR spectrum (horizontal axis: wavenumber / vertical axis: absorbance). To confirm the modification state of the resin film, the measurement site was selected from a flat area without convex parts (corresponding to aggregates) within the observation field. From the nano-IR spectrum, the absorbance of the third peak N １ And the absorbance of the fourth peak N ２ We find the ratio N ２ / N １ The following was calculated: • Analysis depth: approximately 30 nm • Measurement area: several tens of nm in diameter • Cantilever tip diameter: 20 nm • Probe amplitude: 40 nm

[0117] [Method for Measuring Water Contact Angle] The water contact angle was measured using a fully automatic contact angle meter, DropMaster 700 (manufactured by Kyowa Interface Chemical Co., Ltd.), in the following manner. 1 μL of water was dropped onto a horizontally placed resin film from a microsyringe, and a still image was captured 1 second after dropping using a video microscope. The water contact angle was measured at 50 locations on the surface of the resin film (25 locations x 2 rows at 3 mm intervals in the width direction of the resin film), and the average value (Ave.) and its standard deviation (σ) were calculated. The coefficient of variation (unit: %) of the water contact angle was calculated using the formula "Coefficient of Variation = 100 × (σ) / (Ave.)".

[0118] [Method for Measuring Oxygen Element Ratio] The oxygen element ratio on the surface of a resin film was measured using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC, PHI, Inc.) under the conditions shown below. Carbon, oxygen, fluorine, and nitrogen were detected, and the oxygen element ratio was determined from the composition ratio of C1s, O1s, F1s, and N1s. Radiation source: Monochromatic AlKα Beam diameter: 100 μm X-ray output: 25 W Measurement area: 1000 μm × 300 μm Pass energy: 23.5 eV Detection angle: 45°

[0119] [Cross-sectional observation method] A copper-clad laminate formed using a resin film was cross-sectionally prepared by ion milling and used as an observation sample. The cross-section was observed at a magnification of 1,000,000x using an electron microscope (field emission transmission electron microscope JEM-ARM200F manufactured by JEOL Ltd.), and the presence or absence of an adhesive layer (corresponding to a polymer layer) was confirmed by low-angle scattering dark-field spectroscopy. In addition, elemental mapping images of carbon and fluorine were obtained using an energy-dispersive X-ray analyzer of the same model. Since the adhesive layer has a high proportion of carbon, the adhesive layer was identified by elemental mapping.

[0120] [90-degree peel test] <Method for manufacturing laminate for peel test> Using a resin film and electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm, Rz 0.85 μm, unroughened copper foil) (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.), the copper foil, resin film, and copper foil were stacked in that order, and a laminate for the peel test was obtained by heat pressing with a vacuum heat press machine (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 200°C, a preheating time of 120 seconds, a pressing pressure of 3 MPa, and a pressing time of 10 minutes. The size of the resin film was 1 cm on the short side (length direction of the resin film) x 10 cm on the long side (width direction of the resin film).

[0121] <Peel Test Method> An aluminum plate was attached to the underside of the laminate for the peel test with adhesive tape. Using a precision universal testing machine Autograph AGS-X 100N (manufactured by Shimadzu Corporation), the copper foil was grasped and pulled at a speed of 50 mm per minute at a 90-degree angle to the plane of the laminate for the peel test and in the direction of the long side of the laminate (the width direction of the resin film). The peel strength of the copper foil was measured, and the obtained value was defined as the adhesive strength. The peel surface was the interface between the copper foil on the upper side of the peel test sample and the resin film.

[0122] <Adhesive Strength> The adhesive strength was measured at five locations on the surface of the resin film (5 locations at 200 mm intervals in the width direction of the resin film) using the peel test method described above, and the average value (Ave.) and its standard deviation (σ) were determined. The coefficient of variation of the adhesive strength (σ / Ave., unit: %) was calculated from the formula "Coefficient of Variation = 100 × (σ) / (Ave.)".

[0123] [Specified annealing treatment method] The resin film cut from the roll was heated in a 150°C oven (under an air atmosphere) for 30 minutes.

[0124] [Percentage Change Before and After Predetermined Annealing Treatment] The water contact angle of the surface of the resin film before the predetermined annealing treatment (water contact angle before predetermined annealing treatment) and the water contact angle of the surface of the resin film after the predetermined annealing treatment (water contact angle after predetermined annealing treatment) were measured using the water contact angle measurement method described above. The percentage change in the water contact angle before and after the predetermined annealing treatment (unit: %) was calculated using the following formula: Percentage change = 100 × Water contact angle after predetermined annealing treatment / Water contact angle before predetermined annealing treatment

[0125] [Specified immersion method] 20 g of resin film was immersed in 200 mL of THF at a 25°C atmosphere for 100 hours.

[0126] [Method for measuring elution amount] After predetermined immersion, the resin film was removed from the THF. The liquid containing the THF after immersion was concentrated under reduced pressure using an evaporator, and then dried in an oven at 90°C for 96 hours to completely remove the THF and obtain the eluate. The eluate was dried until it was completely dry, and its mass was measured. The elution amount (in %) was calculated using the formula "elution amount = 100 × mass of eluate / mass of resin film before predetermined immersion," and then converted to elution amount (in ppm).

[0127] [Percentage Change Before and After Predetermined Immersion] Using the water contact angle measurement method described above, the water contact angle of the resin film surface before predetermined immersion (water contact angle before predetermined immersion) and the water contact angle of the resin film surface after predetermined immersion (water contact angle after predetermined immersion) were measured. The percentage change in the water contact angle before and after predetermined immersion (unit: %) was calculated using the following formula: Percentage change = 100 × Water contact angle after predetermined immersion / Water contact angle before predetermined immersion

[0128] [Percentage Change Before and After Designated Storage (After Unwinding)] A roll of resin film was stored for one month at a temperature of 40°C and a relative humidity of 80% (designated storage). Using the oxygen element ratio measurement method described above, the oxygen element ratio on the surface of the resin film before rolling and designated storage (oxygen element ratio before designated storage) and the oxygen element ratio on the surface of the resin film after designated storage (oxygen element ratio after designated storage) were measured. The percentage change in the oxygen element ratio before and after designated storage (unit: %) was calculated using the following formula: Percentage change = 100 × {(oxygen element ratio after designated storage / oxygen element ratio before designated storage) - 1}

[0129] [Method for Evaluating Blocking Properties] <Blocking Coefficient> Using a resin film sampled immediately after surface treatment, the blocking coefficient (unit: mN / cm) was measured using a 2001 universal material tester (manufactured by Intesco) in accordance with JIS K7125;1999. Pretreatment: 65°C, 50% RH, 72 hours, load 10 kg Test piece width: 200 mm Load cell capacity: 10 kg Load cell guaranteed range: 200 mN or more Test speed: 200 mm / min Measurement fixture: Aluminum rod (length 270 mm, diameter 7 mm) Measurement direction: Film MD direction Test environment: 23°C, 50% RH

[0130] <Sensory Evaluation> A 1300 mm wide surface-treated fluororesin sheet material (the resin film prepared above) was wound onto a 6-inch core with a winding tension of 30 N and stored for one month at 40°C and 80% RH. The resistance to snagging when the sheet was unwound by hand perpendicular to the roll after storage was evaluated on a 10-point scale according to the criteria shown in Table 1 below.

[0131]

[0132] The measurement results for Examples 1 to 7 and Comparative Examples 1 to 2 are shown in Tables 2 to 3.

[0133]

[0134]

[0135] The results in Tables 2 and 3 show that the resin film of the example was less prone to blocking even when stored in roll form for a long period of time.

[0136] Figure 1 shows an electron microscope image of the cross-section of the resin film of Example 3, obtained by electron microscope observation using the above [Cross-sectional observation method]. As is clear from Figure 1, an adhesive layer (corresponding to a polymer layer) was formed on the resin film of Example 3.

[0137] Before and after the annealing treatment described in the above [Prescribed Annealing Treatment Method], the surfaces of the resin films of Comparative Example 1 and Example 3 were observed using an electron microscope (Hitachi High-Tech Corporation "SU8020"). The observation magnification was 2000x for the resin film of Comparative Example 1 and 1000x for the resin film of Example 3. Figure 2 shows an electron microscope image of the surface of the resin film of Comparative Example 1 before annealing treatment, and Figure 3 shows an electron microscope image of the surface of the resin film of Comparative Example 1 after annealing treatment. Figure 4 shows an electron microscope image of the surface of the resin film of Example 3 before annealing treatment, and Figure 5 shows an electron microscope image of the surface of the resin film of Example 3 after annealing treatment. A large amount of residue (aggregates) was present on the surface of the resin film of Comparative Example 1, and this was removed by the annealing treatment. Therefore, it is presumed that the contact angle of the resin film of Comparative Example 1 changed significantly before and after the annealing treatment. On the other hand, in the resin film of Example 3, even when the magnification was reduced and a wider area was observed, no irregularities resembling residue (aggregates) were seen, and no change in surface condition was observed before and after the annealing treatment.

[0138] [Surface Modulus] As representative examples, the surface modulus of the resin films of the Reference Example and Example 2 was measured using the following method. As the resin film of the Reference Example, the fluororesin sheet prepared in Example 2 was used without plasma treatment. The measurement results are shown in Table 4.

[0139] The measurement samples were obtained by cutting out 1 cm x 1 cm squares from the resin film. The surface modulus was measured on the inner surface of the roll of resin film using a scanning atomic force microscope AFM5300E (Hitachi High-Tech Science Corporation) under the following conditions: Cantilever: Si cantilever (with Al coating on the back, Hitachi High-Tech Fielding Corporation, tip R ≤ 10 nm, spring constant 2 N / m) Compression load: 10 nN Measurement mode: Force curve mapping (FCM) mode Measurement environment: Air, 120°C Measurement field of view: 20 μm x 10 μm (64 points x 32 points) Histograms were created for the 2048 surface moduli obtained as described above, with a class pitch of 0.01 GPa. From the obtained histograms, the cumulative relative frequency of the resin film reaching 1.3 GPa was determined.

[0140]

[0141] The cumulative relative frequency of the resin films in the examples shown in Table 4 that reached 1.3 GPa was 0.98 or less.

[0142] The resin film of this disclosure can be suitably used as a circuit board.

Claims

1. A long resin film containing at least a fluororesin, wherein on at least one surface of the resin film, the absorbance ratio A of the second peak to the first peak measured by infrared spectroscopic total reflection measurement (IR-ATR) is 0.006 or less, the first peak is a peak of symmetric stretching vibration of CF within the range of 1130 cm^-1 or more and 1180 cm^-1 or less, the second peak is the maximum peak within the range of 1700 cm^-1 or more and 1750 cm^-1 or less, the absorbance ratio N of the fourth peak to the third peak measured by nano-infrared spectroscopy (nano-IR) is 0.05 or more and 0.5 or less, the third peak is a peak of symmetric stretching vibration of CF within the range of 1130 cm^-1 or more and 1180 cm^-1 or less, the fourth peak is the maximum peak within the range of 1600 cm^-1 or more and 1800 cm^-1 or less, the average value of the water contact angle is 55° or more and 105° or less, and the coefficient of variation of the water contact angle is 30% or less. １ for the absorbance A of the second peak ２ to the absorbance A ２ / A １ is 0.006 or less, and the first peak is at a wavenumber of 1130 cm －１ or more and 1180 cm －１ or less within the range of CF ２ symmetric stretching vibration peak, the second peak is at a wavenumber of 1700 cm －１ or more and 1750 cm －１ or less within the range of the maximum peak, and the absorbance N of the third peak measured by nano-infrared spectroscopy (nano-IR) １ to the absorbance N of the fourth peak ２ ratio N ２ / N １ is 0.05 or more and 0.5 or less, the third peak is at a wavenumber of 1130 cm －１ or more and 1180 cm －１ or less within the range of CF ２ symmetric stretching vibration peak, the fourth peak is at a wavenumber of 1600 cm －１ or more and 1800 cm －１ or less within the range of the maximum peak, the average value of the water contact angle is 55° or more and 105° or less, and the coefficient of variation of the water contact angle is 30% or less, a resin film.

2. The resin film according to claim 1, wherein the rate of change of the water contact angle of the surface of the resin film, measured before and after annealing the resin film at 150°C for 30 minutes, is 150% or less.

3. The resin film according to claim 1 or 2, wherein the rate of change of the water contact angle of the surface of the resin film, measured before and after immersion of the resin film in tetrahydrofuran for 100 hours, is 150% or less.

4. The resin film according to any one of claims 1 to 3, wherein the amount of components eluted from the resin film into the tetrahydrofuran, as measured by immersing the resin film in tetrahydrofuran for 100 hours, is 900 ppm or less relative to the mass of the resin film.

5. The resin film according to any one of claims 1 to 4, wherein the oxygen element ratio on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 1 atomic% or more.

6. A resin film according to any one of claims 1 to 5, comprising a fluororesin layer containing the fluororesin and a polymer layer formed by polymerization of monomers.

7. The resin film according to claim 6, wherein the monomer comprises an aliphatic vinyl compound.

8. The resin film according to claim 6 or 7, wherein the polymer layer is a layer formed by plasma treatment in a monomer-containing inert gas atmosphere containing the monomer.

9. The resin film according to any one of claims 1 to 8, wherein, in multipoint measurements of the surface modulus of the resin film using a scanning atomic force microscope, the cumulative relative frequency reaching 1.3 GPa is 0.98 or less.

10. The resin film according to any one of claims 1 to 9, wherein the rate of change in the oxygen element ratio on the surface of the resin film, measured by scanning X-ray photoelectron spectroscopy (XPS) before and after storing the rolled resin film at 40°C for one month, is -20% or more and 0% or less.

11. The material comprises a fluororesin layer containing the fluororesin and a polymer layer, wherein the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the polymer layer is a plasma polymerization layer of vinyl acetate, and the ratio A ２ / A １ However, it is 0.00001 or more and 0.006 or less, and the ratio N ２ / N １ The resin film according to any one of claims 1 to 10, wherein the water contact angle is 0.1 or more and 0.45 or less, the average value of the water contact angle is 55° or more and 105° or less, the coefficient of variation of the water contact angle is 0.1% or more and 10.0% or less, and the oxygen element ratio of the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 1.0 atomic% or more and 20.0 atomic% or less.

12. A metal-clad laminate comprising a resin film according to any one of claims 1 to 11 and a metal foil.

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

14. The metal-clad laminate according to claim 12 or 13, wherein the metal foil is provided directly on the resin film, the average value of the adhesive strength between the metal foil and the resin film is 2 N / cm or more, and the coefficient of variation of the adhesive strength between the metal foil and the resin film is 35% or less.

15. A metal-clad laminate according to any one of claims 12 to 14, further comprising a base material.

16. A method for manufacturing a long resin film containing at least a fluororesin, comprising a plasma treatment step of plasma-treating at least one surface of the fluororesin layer while conveying the fluororesin-containing fluororesin layer under predetermined conditions in a monomer-containing inert gas atmosphere, wherein the predetermined conditions are: applied voltage frequency of 1 to 100 kHz, electric field strength of 5 to 50 kV / mm, and discharge degree of 1 to 5 W / cm. ２ A method for manufacturing a resin film, wherein the ratio of the flow rate of monomers contained in the monomer-containing inert gas atmosphere to the transport speed of the fluororesin layer is 0.003 to 0.02 L / m.

17. The absorbance of the first peak A, measured by infrared total internal reflection (IR-ATR) on at least one surface of the resin film. １ Absorbance A of the second peak relative to ２ Ratio A ２ / A １ However, it is less than 0.006, and the first peak is at wavenumber 1130 cm. －１ 1180cm or more －１ CF within the following range ２ This is the peak of the symmetric stretching vibration, and the second peak corresponds to a wavenumber of 1700 cm⁻¹. －１ More than 1750cm －１ The maximum peak within the following range, measured by nano-infrared spectroscopy (nano-IR), is the absorbance N of the third peak. １ Absorbance of the fourth peak relative to N ２ Ratio N ２ / N １ However, it is between 0.05 and 0.5, and the third peak is at wavenumber 1130 cm. －１ 1180cm or more －１ CF within the following range ２ This is the peak of the symmetric stretching vibration, and the fourth peak corresponds to a wavenumber of 1600 cm⁻¹. －１ More than 1800cm －１ The method for manufacturing a resin film according to claim 16, wherein the maximum peak is within the following range, the average value of the water contact angle is 55° or more and 105° or less, and the coefficient of variation of the water contact angle is 30% or less.

18. A method for manufacturing a resin film according to claim 16 or 17, wherein the plasma treatment is continuously performed on the surface of the fluororesin layer while the fluororesin layer is being conveyed by roll-to-roll.

19. The plasma treatment is continuously performed on the surface of the fluororesin layer while the fluororesin layer is conveyed by roll-to-roll, and the monomer contained in the monomer-containing inert gas atmosphere polymerizes due to the plasma treatment, thereby forming a polymer layer on the fluororesin layer, the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, the monomer contained in the monomer-containing inert gas atmosphere is vinyl acetate, the concentration of vinyl acetate in the monomer-containing inert gas atmosphere is 0.30 to 1.0 volume%, and the predetermined conditions are an applied voltage frequency of 20 to 40 kHz, an electric field strength of 5 to 40 kV / mm, and a discharge degree of 1 to 3 W / cm. ２ A method for manufacturing a resin film according to any one of claims 16 to 18, wherein the ratio of the flow rate of monomers contained in the monomer-containing inert gas atmosphere to the transport speed of the fluororesin layer is 0.003 to 0.010 L / m.

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