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

Abstract

The objective is to provide a resin film with minimal variation in surface properties along its length and excellent adhesion to other materials. [Solution] A long resin film comprising at least a fluororesin, wherein the average value of the first water contact angle in a first region of at least one surface of the resin film is 50° or more and 105° or less, and the rate of change of the coefficient of variation of the second water contact angle in a second region located 200m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation of the first water contact angle in the first region, is 40% or less.

Description

[Technical Field]

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

[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. For example, Patent Document 1 describes a circuit board having a metal-clad laminate in which metal foil and fluororesin film are essential layers.

[0003] On the other hand, fluororesin materials generally have poor adhesion to other materials, so surface modification techniques such as plasma treatment are used to improve adhesion. For example, Patent Document 2 describes the production of a surface-coated fluororesin substrate in an inert gas plasma atmosphere and under atmospheric pressure by corona discharge. Patent Document 3 describes the plasma treatment of a tetrafluoroethylene polymer in an atmosphere near atmospheric pressure. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2024 / 019177 [Patent Document 2] Japanese Patent Publication No. 2008-019393 [Patent Document 3] International Publication No. 2021 / 187456 [Overview of the project] [Problems that the invention aims to solve]

[0005] This disclosure aims to provide a resin film with minimal variation in surface properties along its length and excellent adhesion to other materials. Furthermore, this disclosure aims to provide a metal-clad laminate with minimal variation in surface properties along its length and excellent adhesion between the resin film and metal foil. Finally, this disclosure aims to provide a method for manufacturing a resin film that exhibits minimal processing unevenness along its length, even when the resin film is continuously plasma-treated, corresponding to the direction of processing. [Means for solving the problem]

[0006] This disclosure relates to a long resin film comprising at least a fluororesin, wherein the average value of the first water contact angle in a first region of at least one surface of the resin film is 50° or more and 105° or less, and the rate of change of the coefficient of variation of the second water contact angle in a second region located 200m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation of the first water contact angle in the first region, is 40% or less.

[0007] The fluororesin is preferably a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. It is preferable that the coefficient of variation of the second water contact angle in the second region is 6.0% or less. Preferably, the rate of change of the coefficient of variation of the second adhesive strength with the copper foil in the second region relative to the coefficient of variation of the first adhesive strength with the copper foil in the first region, as measured by a 90-degree peel test with the copper foil, is 100% or less. Preferably, the coefficient of variation of the second adhesive strength with the copper foil in the second region, as measured by a 90-degree peel test with the copper foil, is 35% or less. It is preferable that the fluorine element ratio on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is between 40 atomic% and 68 atomic%. It is preferable that the oxygen element ratio on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 1.0 atomic% or more. Preferably, the area ratio of the peaks corresponding to COO bonds on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 2.0% or more of the sum of the areas of the peaks corresponding to CC bonds and CH bonds, the area of ​​the peaks corresponding to CO bonds, the area of ​​the peaks corresponding to C=O bonds, the area of ​​the peaks corresponding to COO bonds, and the area of ​​the peaks corresponding to CF2 bonds. Preferably, the area ratio of peaks corresponding to CC bonds and CH bonds on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 2.0% or more and 60% or less of the sum of the areas of peaks corresponding to CC bonds and CH bonds, peaks corresponding to CO bonds, peaks corresponding to C=O bonds, peaks corresponding to COO bonds, and peaks corresponding to CF2 bonds. It is preferable that the rate of change of the coefficient of variation of the third water contact angle in the third region, which is located 1000 m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation of the first water contact angle in the first region, is 40% or less. It is preferable that the rate of change of the coefficient of variation of the fourth water contact angle in the fourth region, which is located 2000 m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation of the first water contact angle in the first region, is 40% or less. Preferably, the rate of change of the coefficient of variation of the third adhesive strength with the copper foil in the third region, located 1000 m away from the first region, relative to the coefficient of variation of the first adhesive strength with the copper foil in the first region, as measured by a 90-degree peel test with the copper foil, is 100% or less. Preferably, the rate of change of the coefficient of variation of the fourth adhesive strength with the copper foil in the fourth region, located 2000 m away from the first region, relative to the coefficient of variation of the first adhesive strength with the copper foil in the first region, as measured by a 90-degree peel test with the copper foil, is 100% or less. Preferably, it includes a fluororesin layer containing the fluororesin and a polymer layer formed by polymerization of a monomer. Preferably, the monomer contains an aliphatic vinyl compound. Preferably, the polymer layer is a layer formed by plasma treatment in a monomer-containing inert gas atmosphere containing the monomer. In the multi-point measurement of the surface elastic modulus of the resin film by a scanning atomic force microscope, it is preferable that the cumulative relative frequency reaching 1.3 GPa is 0.98 or less. Preferably, the value of the dielectric tangent of the resin film at 10 GHz is less than 0.0015. It includes a fluororesin layer containing the fluororesin and a polymer layer. The fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. The polymer layer is a plasma polymerization layer of vinyl acetate. The average value of the first water contact angle in the first region is 85° or more and 105° or less. The change rate of the coefficient of variation of the second water contact angle in the second region with respect to the coefficient of variation of the first water contact angle in the first region is 0% or more and 35% or less. The fluorine element ratio on the surface of the second region of the resin film measured by scanning X-ray photoelectron spectroscopy measurement (XPS) is 50 atomic% or more and 68 atomic% or less. Preferably, the oxygen element ratio on the surface of the second region of the resin film measured by scanning X-ray photoelectron spectroscopy measurement (XPS) is 1.2 atomic% or more and 7.0 atomic% or less.

[0008] This disclosure is also a metal-clad laminate including the above-described resin film and a metal foil. Preferably, the surface roughness (Rz) of the metal foil is 1.5 μm or less. The metal foil is directly provided on the resin film, and preferably, the adhesive strength between the metal foil and the resin film is 2 N / cm or more. Preferably, the metal foil laminate further includes a base material.

[0009] The present disclosure relates to a method for manufacturing a long resin film containing at least a fluororesin, including a plasma treatment step of subjecting at least one surface of a fluororesin layer containing the fluororesin to plasma treatment under predetermined conditions in a monomer-containing inert gas atmosphere. The predetermined conditions are a frequency of the applied voltage of 1 to 100 kHz, an electric field strength of 5 to 50 kV / mm, and a discharge density of 1 to 500 W·min / m 2 This is also a method for manufacturing a resin film.

[0010] The average value of the first water contact angle in the first region of the plasma-treated surface of the resin film is 50° or more and 105° or less, and the change rate of the coefficient of variation of the second water contact angle in the second region 200 m away from the first region in the length direction of the resin film with respect to the coefficient of variation of the first water contact angle in the first region is preferably 40% or less. Preferably, the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Preferably, a polymer layer is formed on the fluororesin layer by polymerization of the monomer contained in the monomer-containing inert gas atmosphere by the plasma treatment. The monomer contained in the monomer-containing inert gas atmosphere is an aliphatic vinyl compound, and the concentration of the vinyl compound in the monomer-containing inert gas atmosphere is preferably 0.1 to 5% by volume. Preferably, the inert gas contained in the monomer-containing inert gas atmosphere is one or more selected from the group consisting of nitrogen, argon, and helium. Preferably, the plasma treatment is continuously performed on the surface of the fluororesin layer while the fluororesin layer is being conveyed roll-to-roll. The plasma treatment is continuously performed on the surface of the fluororesin layer while the fluororesin layer is being conveyed roll-to-roll, The plasma treatment causes polymerization of monomers contained in the monomer-containing inert gas atmosphere, thereby forming a polymer layer on the fluororesin layer. The aforementioned 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% by volume. The aforementioned predetermined conditions are: applied voltage frequency of 15-50 kHz, electric field strength of 5-30 kV / mm, and discharge density of 15-250 W·min / m². 2 It is preferable that the following conditions are met. [Effects of the Invention]

[0011] The resin film of this disclosure exhibits minimal variation in surface properties along the length of the resin film and excellent adhesion to other materials. Furthermore, the metal-clad laminate of this disclosure exhibits minimal variation in surface properties along the length of the resin film and excellent adhesion between the resin film and the metal foil. Moreover, the method for manufacturing the resin film of this disclosure allows for the production of a resin film with minimal processing unevenness along the length of the resin film, even when the resin film is continuously plasma-treated. [Brief explanation of the drawing]

[0012] [Figure 1] This is an electron microscope image showing the surface of the resin film in Reference Example 1. [Figure 2] This is an electron microscope image showing the surface of the resin film of Comparative Example 1. [Figure 3] This is an electron microscope image showing the surface of the resin film of Example 2. [Figure 4] This is an electron microscope image showing the surface of the resin film of Example 8. [Figure 5] This is an electron microscope image showing a cross-section of the resin film of Example 2. [Figure 6] This is an electron microscope image showing a cross-section of the resin film of Example 8. [Modes for carrying out the invention]

[0013] The following provides a detailed explanation of this disclosure. Conventional plasma surface resin films have the problem of unstable adhesive strength due to uneven surface modification, as continuous and stable surface treatment is not possible. Uneven adhesive strength prevents uniform adhesion with other materials, leading to peeling in subsequent processes and a decrease in the reliability of the substrate. In particular, in plasma treatment performed under a monomer-containing inert gas atmosphere, the discharge becomes unstable as the treatment progresses, making continuous and stable surface treatment difficult. Specifically, as the treatment progresses, the unevenness of the treatment gradually increases, and the unevenness of adhesive strength with other materials also tends to increase. The cause is speculative and not definitive, but it is thought that under conventional discharge conditions, some of the monomers contained in the monomer-containing inert gas atmosphere carbonize, and the carbides adhere to the electrodes, causing the discharge of the plasma treatment to become unstable.

[0014] Based on the above issues, by performing surface treatment under discharge conditions that suppress monomer carbonization, the resin film of this disclosure exhibits less unevenness in treatment and less variation in surface properties in the longitudinal direction of the resin film corresponding to the direction of surface treatment.

[0015] Furthermore, taking the above problems into consideration, the resin film manufacturing method of this disclosure, by performing plasma treatment under predetermined conditions, can suppress monomer carbonization and enable stable discharge for a long period of time. As a result, even when the resin film is processed continuously, it is possible to manufacture a resin film with less processing unevenness in the longitudinal direction of the resin film corresponding to the direction of processing.

[0016] [Resin film] The resin film of this disclosure will be described in detail below. The resin film of this disclosure is elongated and contains at least a fluororesin. Differences in the surface properties of the resin film, caused by unstable discharge as the process progresses, tend to occur between two regions separated in the longitudinal direction of the resin film, corresponding to the direction of surface treatment. The further apart the two regions are in the longitudinal direction of the resin film, the greater the difference in the surface properties of the resin film tends to be.

[0017] Therefore, in this disclosure, at least a first region and a second region are set on the surface of the resin film. The second region is a region located 200 m away from the first region in the longitudinal direction of the resin film. From the viewpoint of further reducing variations in surface properties in the longitudinal direction of the resin film, it is preferable to further set a third region on the surface of the resin film. The third region is a region located 1000 m away from the first region in the longitudinal direction of the resin film. From the viewpoint of further reducing variations in surface properties in the longitudinal direction of the resin film, it is preferable to further set a fourth region on the surface of the resin film. The fourth region is a region located 2000 m away from the first region in the longitudinal direction of the resin film.

[0018] The first region is set at any location on the surface of the resin film. When the resin film is subjected to surface treatment, it is preferable that the first region be set at the starting point of the surface treatment on the resin film.

[0019] When the resin film is in roll form, the first region is closer to the beginning (inside) side of the roll than the second, third, and fourth regions. On the other hand, the second, third, and fourth regions are closer to the end (outside) side of the roll than the first region. The first, second, third, and fourth regions are arranged in this order from the beginning to the end of the roll.

[0020] When a resin film is subjected to surface treatment, the first region is closer to the starting point of the surface treatment on the resin film than the second, third, and fourth regions. On the other hand, the second, third, and fourth regions are closer to the ending point of the surface treatment on the resin film than the first region. The first, second, third, and fourth regions are arranged in this order from the upstream side (starting point of surface treatment) to the downstream side (ending point of surface treatment) in the direction of surface treatment.

[0021] If slitting or rewinding is performed after surface treatment, the relative positions from the starting point will naturally be reversed depending on the number of slits or rewindings.

[0022] Next, the surface properties of the resin film of this disclosure will be described. In a first region of at least one surface (one or both sides) of the resin film of this disclosure, a predetermined first water contact angle is satisfied. In this disclosure, the surface of the resin film on which the following parameters are measured is the same surface on which the first water contact angle in the first region is measured. It is preferable that at least one surface (one or both sides) of the resin film of this disclosure is the measurement surface and satisfies the following parameters. If the resin film is subjected to a surface treatment such as plasma treatment, it is preferable that the surface-treated surface is the measurement surface and satisfies the following parameters.

[0023] <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, DropMaster700 (manufactured by Kyowa Interface Chemical Co., Ltd.), by dropping 2 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 40 locations within each region, and the average value (numerical mean) is taken as the average water contact angle (ave). The water contact angle is measured at 40 locations within each region, and the standard deviation is taken as the standard deviation of the water contact angle (σ).

[0024] In the resin film of this disclosure, the average value (ave0m) of the first water contact angle in a first region of at least one surface of the resin film is 50° or more and 105° or less, and the rate of change of the coefficient of variation (σ / ave200m) of the second water contact angle in a second region located 200m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation (σ / ave0m) of the first water contact angle in the first region, is 40% or less. A resin film that satisfies this numerical range has less processing unevenness in the longitudinal direction even when it is in a long form, and can suppress the increase in variation of the water contact angle in the longitudinal direction.

[0025] As already mentioned, the average value of the first water contact angle (ave0m) in the first region is between 50° and 105°. If the average value of the first water contact angle (ave0m) in the first region is 50° or higher, the resin film can be given appropriate wettability. Furthermore, when a polymer layer is formed by monomer polymerization as described later, if the average value of the first water contact angle (ave0m) in the first region is 50° or higher, excessive self-polymerization of monomers is suppressed, and a sufficient amount of monomer-derived substituents that contribute to adhesion can be present, thus preventing a decrease in the adhesive strength of the resin film.

[0026] In terms of imparting appropriate wettability to the resin film, the average value of the first water contact angle (ave0m) in the first region is preferably 100° or less. In terms of imparting appropriate wettability to the resin film, the average value of the first water contact angle (ave0m) in the first region is preferably 60° or more, more preferably 70° or more, even more preferably 80° or more, and even more preferably 85° or more.

[0027] The coefficient of variation of the first water contact angle (σ / ave0m) is an indicator of the variation in the water contact angle within the first region. In terms of reducing the variation in the water contact angle of the resin film, the coefficient of variation of the first water contact angle (σ / ave0m) in the first region is preferably 6.0% or less, 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 first water contact angle (σ / ave0m) is not particularly limited, but for example, it is 0.1% or more. The coefficient of variation of the first water contact angle (σ / ave0m, unit: %) is calculated from the mean value of the first water contact angle (ave0m) and the standard deviation of the first water contact angle (σ0m) based on the following formula. The coefficient of variation of the first water contact angle is (σ / ave0m) = 100 × (σ0m) / (ave0m).

[0028] In terms of imparting appropriate wettability to the resin film, the average value of the second water contact angle (ave200m) in the second region is preferably 105° or less, and more preferably 100° or less. In terms of imparting appropriate wettability to the resin film, the average value of the second water contact angle (ave200m) in the second region is preferably 50° or more, even more preferably 60° or more, more preferably 70° or more, even more preferably 80° or more, and even more preferably 85° or more.

[0029] The coefficient of variation of the second water contact angle (σ / ave200m) is an indicator of the variation in the water contact angle within the second region. In terms of reducing the variation in the water contact angle of the resin film, the coefficient of variation of the second water contact angle (σ / ave200m) in the second region is preferably 6.0% or less, 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 second water contact angle (σ / ave200m) is not particularly limited, but for example, it is 0.1% or more. The coefficient of variation of the second water contact angle (σ / ave200m, unit: %) is calculated from the mean value of the second water contact angle (ave200m) and the standard deviation of the first water contact angle (σ200m) based on the following formula. The coefficient of variation of the second water contact angle is (σ / ave200m) = 100 × (σ200m) / (ave200m).

[0030] The rate of change of the coefficient of variation of the second water contact angle in the second region (σ / ave200m) relative to the coefficient of variation of the first water contact angle in the first region (σ / ave0m) serves as an indicator of the variation in the water contact angle along the length of the resin film. As already mentioned, the rate of change of the coefficient of variation of the second water contact angle in the second region (σ / ave200m) relative to the coefficient of variation of the first water contact angle in the first region (σ / ave0m) on the surface of the resin film is 40% or less. In terms of reducing the variation in the water contact angle along the length of the resin film, the rate of change of the coefficient of variation of the second water contact angle (σ / ave200m) is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, even more preferably 20% or less, and particularly preferably 15% or less. The lower limit of the rate of change of the coefficient of variation of the second water contact angle (σ / ave200m) is not particularly limited, but for example, it is 0% or more. The rate of change (σ / ave change rate, in %) of the coefficient of variation of the second water contact angle (σ / ave200m) relative to the coefficient of variation of the first water contact angle (σ / ave0m) is calculated from the coefficient of variation of the second water contact angle (σ / ave200m) and the coefficient of variation of the first water contact angle (σ / ave0m) based on the following formula. The rate of change of the coefficient of variation of the second water contact angle (σ / ave rate of change) = 100 × [(σ / ave 200m) - (σ / ave 0m)] / (σ / ave 0m)

[0031] In terms of imparting appropriate wettability to the resin film, the average value (ave1000m) of the third water contact angle in the third region of the surface of the resin film is preferably 105° or less, and more preferably 100° or less. In terms of imparting appropriate wettability to the resin film, the average value (ave1000m) of the third water contact angle in the third region is preferably 50° or more, even more preferably 60° or more, more preferably 70° or more, even more preferably 80° or more, and even more preferably 85° or more.

[0032] The coefficient of variation of the third water contact angle (σ / ave1000m) is an indicator of the variation in the water contact angle within the third region. In terms of reducing the variation in the water contact angle of the resin film, the coefficient of variation of the third water contact angle (σ / ave1000m) in the third region is preferably 6.0% or less, 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 third water contact angle (σ / ave1000m) is not particularly limited, but for example, it is 0.1% or more. The coefficient of variation of the third water contact angle (σ / ave1000m, unit: %) is calculated from the mean value of the third water contact angle (ave1000m) and the standard deviation of the third water contact angle (σ1000m) based on the following formula. The coefficient of variation of the third water contact angle is (σ / ave1000m) = 100 × (σ1000m) / (ave1000m).

[0033] The rate of change of the coefficient of variation of the third water contact angle in the third region (σ / ave1000m) relative to the coefficient of variation of the first water contact angle in the first region (σ / ave0m) serves as an indicator of the variation in the water contact angle along the length of the resin film. The rate of change of the coefficient of variation of the third water contact angle in the third region (σ / ave1000m) relative to the coefficient of variation of the first water contact angle in the first region (σ / ave0m) is preferably 40% or less, preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, and even more preferably 20% or less. The lower limit of the rate of change of the coefficient of variation of the third water contact angle (σ / ave1000m) is not particularly limited, but for example, it is 0% or more. The rate of change (σ / ave change rate, in %) of the coefficient of variation of the third water contact angle (σ / ave1000m) relative to the coefficient of variation of the first water contact angle (σ / ave0m) is calculated from the coefficient of variation of the third water contact angle (σ / ave1000m) and the coefficient of variation of the first water contact angle (σ / ave0m) based on the following formula. The rate of change of the coefficient of variation of the third water contact angle (σ / ave rate of change) = 100 × [(σ / ave 1000m) - (σ / ave 0m)] / (σ / ave 0m)

[0034] In terms of imparting appropriate wettability to the resin film, the average value (ave2000m) of the fourth water contact angle in the fourth region of the surface of the resin film is preferably 105° or less, and more preferably 100° or less. In terms of imparting appropriate wettability to the resin film, the average value (ave2000m) of the fourth water contact angle in the fourth region is preferably 50° or more, even more preferably 60° or more, more preferably 70° or more, even more preferably 80° or more, and even more preferably 85° or more.

[0035] The coefficient of variation of the fourth water contact angle (σ / ave2000m) is an indicator of the variation in the water contact angle within the fourth region. In terms of reducing the variation in the water contact angle of the resin film, the coefficient of variation of the fourth water contact angle (σ / ave2000m) in the fourth region is preferably 6.0% or less, 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 fourth water contact angle (σ / ave2000m) is not particularly limited, but for example, it is 0.1% or more. The coefficient of variation of the fourth water contact angle (σ / ave2000m, unit: %) is calculated from the mean value of the fourth water contact angle (ave2000m) and the standard deviation of the fourth water contact angle (σ2000m) based on the following formula. The coefficient of variation of the fourth water contact angle (σ / ave2000m) = 100 × (σ2000m) / (ave2000m)

[0036] The rate of change of the coefficient of variation of the fourth water contact angle in the fourth region (σ / ave2000m) relative to the coefficient of variation of the first water contact angle in the first region (σ / ave0m) serves as an indicator of the variation in the water contact angle along the length of the resin film. The rate of change of the coefficient of variation of the fourth water contact angle in the fourth region (σ / ave2000m) relative to the coefficient of variation of the first water contact angle in the first region (σ / ave0m) is preferably 40% or less, preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, and even more preferably 20% or less. The lower limit of the rate of change of the coefficient of variation of the fourth water contact angle (σ / ave2000m) is not particularly limited, but for example, it is 0% or more. The rate of change (σ / ave change rate, in %) of the coefficient of variation of the fourth water contact angle (σ / ave2000m) relative to the coefficient of variation of the first water contact angle (σ / ave0m) is calculated from the coefficient of variation of the fourth water contact angle (σ / ave2000m) and the coefficient of variation of the first water contact angle (σ / ave0m) based on the following formula. The rate of change of the coefficient of variation of the fourth water contact angle (σ / ave rate of change) = 100 × [(σ / ave 2000m) - (σ / ave 0m)] / (σ / ave 0m)

[0037] <Adhesive strength> Adhesion strength is measured by a 90-degree peel test with copper foil. The average value (Ave.) and its standard deviation (σ) of the adhesive strength are calculated over a total stroke distance of 65 mm, starting from 10 mm from the beginning of each peel and extending to 75 mm. The 90-degree peel test is described in detail in the examples.

[0038] In terms of improving adhesion to other materials, the average value of the first adhesive strength (ave0m) with the copper foil in the first region 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. The upper limit of the average value of the first adhesive strength (ave0m) with the copper foil in the first region is not particularly limited, but for example, it is 20 N / cm or less.

[0039] The coefficient of variation (σ / ave0m) of the first adhesive strength with copper foil is an indicator of the variation in adhesive strength within the first region. In terms of reducing the variation in the adhesive strength of the resin film, the coefficient of variation (σ / ave0m) of the first adhesive strength with copper foil in the first region is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, even more preferably 20% or less, still even more preferably 15% or less, and particularly preferably 10% or less. The lower limit of the coefficient of variation (σ / ave0m) of the first adhesive strength with copper foil is not particularly limited, but for example, it is 1% or more. The coefficient of variation (σ / ave0m, unit: %) of the first adhesive strength with copper foil in the first region is calculated from the mean value (ave0m) of the first adhesive strength and the standard deviation (σ0m) of the first adhesive strength based on the following formula. The coefficient of variation of the first adhesive strength (σ / ave0m) = 100 × (σ0m) / (ave0m)

[0040] In terms of improving adhesion to other materials, the average value of the second adhesive strength with copper foil in the second region (ave200m) 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, and particularly preferably 4 N / cm or more. The upper limit of the average value of the second adhesive strength with copper foil in the second region (ave200m) is not particularly limited, but for example, it is 20 N / cm or less.

[0041] The coefficient of variation (σ / ave200m) of the second adhesive strength with copper foil is an indicator of the variation in adhesive strength within the second region. In terms of reducing the variation in adhesive strength of the resin film, the coefficient of variation (σ / ave200m) of the second adhesive strength with copper foil in the second region is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, even more preferably 20% or less, even more preferably 15% or less, and particularly preferably 10% or less. The lower limit of the coefficient of variation (σ / ave200m) of the second adhesive strength with copper foil is not particularly limited, but for example, it is 1% or more. The coefficient of variation (σ / ave200m, unit: %) of the second adhesive strength with copper foil in the second region is calculated from the mean value (ave200m) of the second adhesive strength and the standard deviation (σ200m) of the second adhesive strength based on the following formula. The coefficient of variation of the second adhesive strength (σ / ave200m) = 100 × (σ200m) / (ave200m)

[0042] The rate of change between the average value of the second adhesive strength (ave200m) with the copper foil in the second region and the average value of the first adhesive strength (ave0m) in the first region serves as an indicator of the increase or decrease in adhesive strength along the length of the resin film. If the rate of change of the average value of the second adhesive strength (ave200m) with the copper foil is negative, the average value of the second adhesive strength (ave200m) is lower than the average value of the first adhesive strength (ave0m). The rate of change between the average value of the second adhesive strength (ave200m) with the copper foil in the second region and the average value of the first adhesive strength (ave0m) in the first region is preferably -15% or more, more preferably -10% or more, and even more preferably -5% or more. The upper limit of the rate of change of the average value of the second adhesive strength (ave200m) is not particularly limited, but for example, it is 0% or less. The percentage change (ave change rate, in units of %) between the average value of the first adhesive strength (ave0m) and the average value of the first adhesive strength (ave200m) is calculated from the average value of the second adhesive strength (ave200m) and the average value of the first adhesive strength (ave0m) based on the following formula. The rate of change of the average value of the second adhesive strength (ave change rate) = 100 × [(ave 200m) - (ave 0m)] / (ave 0m)

[0043] The rate of change of the coefficient of variation of the second adhesive strength with copper foil in the second region (σ / ave200m) relative to the coefficient of variation of the first adhesive strength with copper foil in the first region (σ / ave0m) serves as an indicator of the variation in adhesive strength along the length of the resin film. In terms of reducing the variation in adhesive strength along the length of the resin film, the rate of change of the coefficient of variation of the second adhesive strength with copper foil in the second region (σ / ave200m) relative to the coefficient of variation of the first adhesive strength with copper foil in the first region (σ / ave0m) is preferably 100% or less, more preferably 50% or less, even more preferably 30% or less, even more preferably 10% or less, and particularly preferably 5% or less. The lower limit of the rate of change of the coefficient of variation of the second adhesive strength (σ / ave200m) is not particularly limited, but for example, it is 0% or more. The rate of change (σ / ave change rate, in %) of the coefficient of variation of the second adhesive strength (σ / ave200m) relative to the coefficient of variation of the first adhesive strength (σ / ave0m) is calculated from the coefficient of variation of the second adhesive strength (σ / ave200m) and the coefficient of variation of the first adhesive strength (σ / ave0m) based on the following formula. The rate of change of the coefficient of variation of the second adhesive strength (σ / ave change rate) = 100 × [(σ / ave 200m) - (σ / ave 0m)] / (σ / ave 0m)

[0044] In terms of improving adhesion to other materials, the average value of the third adhesive strength with copper foil in the third region (ave1000m) 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. The upper limit of the average value of the third adhesive strength with copper foil in the third region (ave1000m) is not particularly limited, but for example, it is 20 N / cm or less.

[0045] The coefficient of variation (σ / ave1000m) of the third adhesive strength with copper foil is an indicator of the variation in adhesive strength within the third region. In terms of reducing the variation in adhesive strength of the resin film, the coefficient of variation (σ / ave1000m) of the third adhesive strength with copper foil in the third region is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, even more preferably 20% or less, still even more preferably 15% or less, and particularly preferably 10% or less. The lower limit of the coefficient of variation (σ / ave1000m) of the third adhesive strength with copper foil is not particularly limited, but for example, it is 1% or more. The coefficient of variation (σ / ave1000m, unit: %) of the third adhesive strength with copper foil in the third region is calculated from the mean value (ave1000m) of the third adhesive strength and the standard deviation (σ1000m) of the third adhesive strength based on the following formula. Third, the coefficient of variation of adhesive strength (σ / ave1000m) = 100 × (σ1000m) / (ave1000m)

[0046] The rate of change of the average value of the third adhesive strength with copper foil in the third region (ave1000m) relative to the average value of the first adhesive strength with copper foil in the first region (ave0m) serves as an indicator of the increase or decrease in adhesive strength along the length of the resin film. If the rate of change of the average value of the third adhesive strength with copper foil (ave1000m) is negative, it means that the average value of the third adhesive strength (ave1000m) is lower than the average value of the first adhesive strength (ave0m). The rate of change of the average value of the third adhesive strength with copper foil in the third region (ave1000m) relative to the average value of the first adhesive strength with copper foil in the first region (ave0m) is preferably -15% or more, more preferably -10% or more, and even more preferably -5% or more. The upper limit of the rate of change of the average value of the third adhesive strength (ave1000m) is not particularly limited, but for example, it is 0% or less. The percentage change (ave change rate, in %) between the average value of the first adhesive strength (ave0m) and the average value of the first adhesive strength (ave1000m) is calculated from the average value of the third adhesive strength (ave1000m) and the average value of the first adhesive strength (ave0m) based on the following formula. The percentage change in the average value of the third bond strength (average change rate) = 100 × [(average 1000m) - (average 0m)] / (average 0m)

[0047] The rate of change of the coefficient of variation of the third adhesive strength with copper foil in the third region (σ / ave1000m) relative to the coefficient of variation of the first adhesive strength with copper foil in the first region (σ / ave0m) serves as an indicator of the variation in adhesive strength along the length of the resin film. In terms of reducing the variation in adhesive strength along the length of the resin film, the rate of change of the coefficient of variation of the third adhesive strength with copper foil in the third region (σ / ave1000m) relative to the coefficient of variation of the first adhesive strength with copper foil in the first region (σ / ave0m) is preferably 100% or less, more preferably 50% or less, even more preferably 30% or less, and most preferably 10% or less. The lower limit of the rate of change of the coefficient of variation of the third adhesive strength (σ / ave1000m) is not particularly limited, but for example, it is 0% or more. The rate of change (σ / ave change rate, in %) of the coefficient of variation of the third adhesive strength (σ / ave1000m) relative to the coefficient of variation of the first adhesive strength (σ / ave0m) is calculated from the coefficient of variation of the third adhesive strength (σ / ave1000m) and the coefficient of variation of the first adhesive strength (σ / ave0m) based on the following formula. The rate of change of the coefficient of variation of the third adhesive strength (σ / ave change rate) = 100 × [(σ / ave 1000m) - (σ / ave 0m)] / (σ / ave 0m)

[0048] In terms of improving adhesion to other materials, the average value of the fourth adhesive strength with copper foil in the fourth region (ave2000m) 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. The upper limit of the average value of the fourth adhesive strength with copper foil in the fourth region (ave2000m) is not particularly limited, but for example, it is 20 N / cm or less.

[0049] The coefficient of variation (σ / ave2000m) of the fourth adhesive strength with copper foil is an indicator of the variation in adhesive strength within the fourth region. In terms of reducing the variation in adhesive strength of the resin film, the coefficient of variation (σ / ave2000m) of the fourth adhesive strength with copper foil in the fourth region is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, even more preferably 20% or less, still even more preferably 15% or less, and particularly preferably 10% or less. The lower limit of the coefficient of variation (σ / ave2000m) of the fourth adhesive strength with copper foil is not particularly limited, but for example, it is 1% or more. The coefficient of variation (σ / ave2000m, unit: %) of the fourth adhesive strength with copper foil in the fourth region is calculated from the mean value (ave2000m) of the fourth adhesive strength and the standard deviation (σ2000m) of the fourth adhesive strength based on the following formula. Third, the coefficient of variation of adhesive strength (σ / ave2000m) = 100 × (σ2000m) / (ave1000m)

[0050] The rate of change between the average value of the fourth adhesive strength (ave2000m) with the copper foil in the fourth region and the average value of the first adhesive strength (ave0m) in the first region serves as an indicator of the increase or decrease in adhesive strength along the length of the resin film. If the rate of change of the average value of the fourth adhesive strength (ave2000m) with the copper foil is negative, the average value of the fourth adhesive strength (ave2000m) is lower than the average value of the first adhesive strength (ave0m). The rate of change between the average value of the fourth adhesive strength (ave2000m) with the copper foil in the fourth region and the average value of the first adhesive strength (ave0m) in the first region is preferably -15% or more, more preferably -10% or more, and even more preferably -5% or more. The upper limit of the rate of change of the average value of the fourth adhesive strength (ave2000m) is not particularly limited, but for example, it is 0% or less. The percentage change (ave change rate, in %) between the average value of the first adhesive strength (ave0m) and the average value of the first adhesive strength (ave2000m) is calculated from the average value of the fourth adhesive strength (ave2000m) and the average value of the first adhesive strength (ave0m) based on the following formula. 4. Percentage change of the average adhesive strength (ave change rate) = 100 × [(ave 2000m) - (ave 0m)] / (ave 0m)

[0051] The rate of change of the coefficient of variation of the fourth adhesive strength with copper foil in the fourth region (σ / ave2000m) relative to the coefficient of variation of the first adhesive strength with copper foil in the first region (σ / ave0m) serves as an indicator of the variation in adhesive strength along the length of the resin film. In terms of reducing the variation in adhesive strength along the length of the resin film, the rate of change of the coefficient of variation of the fourth adhesive strength with copper foil in the fourth region (σ / ave2000m) relative to the coefficient of variation of the first adhesive strength with copper foil in the first region (σ / ave0m) is preferably 100% or less, more preferably 50% or less, even more preferably 30% or less, and even more preferably 10% or less. The lower limit of the rate of change of the coefficient of variation of the fourth adhesive strength (σ / ave2000m) is not particularly limited, but for example, it is 0% or more. The rate of change (σ / ave change rate, in %) of the coefficient of variation of the fourth adhesive strength (σ / ave2000m) relative to the coefficient of variation of the first adhesive strength (σ / ave0m) is calculated from the coefficient of variation of the fourth adhesive strength (σ / ave2000m) and the coefficient of variation of the first adhesive strength (σ / ave0m) based on the following formula. The rate of change of the coefficient of variation of the 4th adhesive strength (σ / ave change rate) = 100 × [(σ / ave 2000m) - (σ / ave 0m)] / (σ / ave 0m)

[0052] <Element ratio> The ratio of each element is measured by scanning X-ray photoelectron spectroscopy (XPS). The ratio of each element is measured using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) analyzer (PHI5000VersaProbeII, manufactured by ULVAC-PHI, Inc.), detecting carbon, oxygen, fluorine, and nitrogen. The ratio of fluorine is determined from the composition ratio of C1s, O1s, F1s, and N1s. The ratio of oxygen is determined from the composition ratio of C1s, O1s, F1s, and N1s.

[0053] The fluorine element ratio on at least one surface of the resin film is preferably 40 atomic% or more, more preferably 45 atomic% or more, even more preferably 50 atomic% or more, even more preferably greater than 55 atomic%, and particularly preferably 60 atomic% or more. If the fluorine element ratio is 40 atomic% or more, when a polymer layer is formed by the polymerization of monomers, excessive self-polymerization of monomers is suppressed, and a sufficient amount of monomer-derived substituents that contribute to adhesion can be present. As a result, the adhesive strength of the resin film is less likely to decrease. On the other hand, the fluorine element ratio on the surface of the resin film is preferably 68 atomic% or less. If the fluorine element ratio is 68 atomic% or less, the amount of fluorine element on the surface of the resin film does not become too high, and the resin film can be sufficiently bonded to other materials. It is preferable that the fluorine element ratio in one or both of the first and second regions is within the above range. In particular, the plasma treatment conditions described later are monomer plasma treatment conditions that can efficiently and continuously form a thin modified polymer layer that is less dense than conventional methods. Therefore, by surface-treating the fluororesin layer under the plasma treatment conditions described later, a thin, non-overcrowded modified layer is formed, allowing for the measurement of fluorine elements in the fluororesin layer beneath the modified layer, and a resin film with a fluorine element ratio of 40 atomic% or higher tends to be obtained.

[0054] 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, still more preferably 1.8 atomic% or more, even more preferably 2.0 atomic% or more, still even more preferably 3.0 atomic% or more, and particularly preferably 4.0 atomic% or more. The oxygen element ratio on at least one surface of the resin film is not particularly limited in upper limits, but may be, for example, 25.0 atomic% or less, 10.0 atomic% or less, or 7.0 atomic% or less. It is preferable that the oxygen element ratio in one or both of the first and second regions is within the above range.

[0055] <Combination ratio> Each binding ratio is measured by scanning X-ray photoelectron spectroscopy (XPS). Each binding ratio is calculated from the ratio of the areas of the five peaks obtained by separating the C1s narrow spectrum in the spectrum obtained using XPS (horizontal axis: binding energy (unit eV), vertical axis: intensity (unit CPS)) into five peaks under the conditions shown below. Peak 1: Chemical bonds CC and CH, peak position 283.5~284.6 eV Peak 2: Chemical bond C-O, peak position 286.1 eV Peak 3: Chemical bond C=O, peak position 287.6eV Peak 4: Chemical bond COO, peak position 288.6 eV Peak 5: Chemical bond CF2, peak position 291.1 eV

[0056] The intensity ratio of the peak corresponding to the COO bond (peak 4) on at least one surface of the resin film is preferably 2.0% or more, more preferably 3% or more, even more preferably 4% or more, and most preferably 6% or more, relative to the sum of the intensities of the peaks corresponding to the CC bond and CH bond (peak 1), the CO bond (peak 2), the C=O bond (peak 3), the COO bond (peak 4), and the CF2 bond (peak 5). Hereinafter, the area ratio of the peak corresponding to the COO bond to the sum of the areas of the peaks corresponding to the CC bond and CH bond, the CO bond, the C=O bond, the COO bond, and the CF2 bond may be referred to as the "COO ratio". The upper limit of the COO ratio is not particularly limited, but is preferably 20% or less, more preferably 15% or less, and even more preferably 12% or less. If the COO ratio is within the above range, the amount of functional groups contributing to adhesion will be suitable, which is advantageous in that it improves adhesion and durability. It is preferable that the COO ratio is within the above range in one or both of the first and second regions.

[0057] The area ratio of peaks corresponding to CC bonds and CH bonds on at least one surface of the resin film is preferably 2.0% or more, more preferably 4% or more, even more preferably 6% or more, and most preferably 8% or more, relative to the sum of the areas of peaks corresponding to CC bonds and CH bonds, CO bonds, C=O bonds, COO bonds, and CF2 bonds. Hereinafter, the area ratio of peaks corresponding to CC bonds and CH bonds to the sum of the areas of peaks corresponding to CC bonds and CH bonds, CO bonds, C=O bonds, COO bonds, and CF2 bonds may be referred to as the "CC and CH ratio." The upper limit of the CC and CH ratio is not particularly limited, but is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. When the CC and CH ratio is within the above range, a polymer layer formed by monomer polymerization is suitably formed, which is advantageous in that it improves adhesion and durability. Furthermore, it is preferable that the CC and CH ratios in either or both of the first and second regions are within the above range.

[0058] <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 at which 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. It is preferable that the cumulative relative frequency at which 1.3 GPa is reached in the first, second, third, or fourth region of the resin film is within the above range. From the viewpoint of further reducing variations in surface properties in the longitudinal direction of the resin film, it is even more preferable that the cumulative relative frequency reaching 1.3 GPa in two to four regions selected from the group consisting of the first, second, third, and fourth regions of the resin film is within the above range.

[0059] 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. A lower cumulative relative frequency of reaching 1.3 GPa indicates that the region with a high surface modulus, i.e., a region with high rigidity, is increasing on the surface of the resin film. In one example, when a polymer layer with higher rigidity than the fluororesin layer (e.g., 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. Also, the more the amount of polymer layer formed on the surface of the fluororesin layer increases, the lower the cumulative relative frequency of the resin film reaching 1.3 GPa tends to be.

[0060] <Electrical Characteristics> In terms of minimizing the loss of electrical signals in the circuit, the dielectric loss tangent of the resin film at 10 GHz is preferably less than 0.0015, more preferably 0.0013 or less, even more preferably 0.0012 or less, even more preferably 0.0010 or less, and most preferably 0.0005 or less. The lower limit of the dielectric loss tangent of the resin film at 10 GHz is not particularly limited, but for example, it is 0.000001 or more. In order to keep the dielectric loss tangent within the above range, it is preferable to use a resin with few unstable end groups, and more preferably to use a fluororesin that has undergone end fluorination treatment. The dielectric constant of the resin film at 10 GHz is preferably 3.8 or less, more preferably 3.4 or less, and even more preferably 3.0 or less. The lower limit of the dielectric constant of the resin film at 10 GHz is not particularly limited, but for example, it is 0.1 or more. The dielectric loss tangent and dielectric constant of the resin film are measured at 10 GHz using split cylinder resonators CR-710 and CR-740 (EM Lab Co., Ltd.).

[0061] <Fluororesin> The resin film of this disclosure comprises at least a fluororesin. The fluororesin is not particularly limited and may be any polymer containing fluorine atoms as part of it. Preferably, the fluororesin is a melt-mold fluororesin. Examples of fluororesins include tetrafluoroethylene (TFE)-perfluoroalkyl vinyl ether (PAVE) copolymer [PFA], copolymer having chlorotrifluoroethylene (CTFE) units (CTFE copolymer), 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, it improves adhesion when bonding with metal foil.

[0062] In particular, the fluororesin is preferably PFA or FEP, and more preferably PFA.

[0063] 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).

[0064] 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 higher the number of TFE units, the better the mechanical properties of the PFA tend to be. The lower the number of TFE units, the less the melting point of the PFA tends to be, and the better the moldability tends to be. Examples of PAVE units include perfluoropropyl vinyl ether (PPVE) units.

[0065] 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 the total amount of TFE units and PAVE units is 90 to 99.9 mol%. Examples of monomers copolymerizable with TFE and PAVE include HFP, vinyl monomers represented as CZ3Z4=CZ5(CF2)nZ6 (wherein Z3, Z4, and Z5 are the same or different hydrogen atoms or fluorine atoms, Z6 is a hydrogen atom, fluorine atom, or chlorine atom, and n is an integer from 2 to 10), and alkyl perfluorovinyl ether derivatives represented as CF2=CF-OCH2-Rf7 (wherein Rf7 is a perfluoroalkyl group having 1 to 5 carbon atoms). 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. One acid anhydride monomer may be used alone, or two or more may be used in combination.

[0066] 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 the value obtained by measuring under conditions of 372°C and a load of 5.0 kg in accordance with ASTM D3307.

[0067] Fluororesins are preferable to have fewer functional groups, and especially fewer unstable end groups. Such fluororesins can be produced by adjusting the conditions during manufacturing (polymerization reaction), or by reducing the number of unstable end groups by performing fluorine gas treatment, heat treatment, or supercritical gas extraction on the polymerized fluororesin. Fluorine gas treatment is preferred due to its excellent processing efficiency and the fact that some or all of the unstable end groups are converted to -CF3, becoming stable end groups. Fluorination treatment can be performed by contacting an unfluorinated fluororesin with a fluorine-containing compound. Using fluororesins 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.

[0068] 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.

[0069] Examples of unstable end groups include functional groups such as -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), hydroxyl groups (-CH2OH, etc.), -CONH2, -COOR (R=CH3, etc.), -CF2H, and -OCOO-R (n-propyl carbonate, etc.).

[0070] The number of unstable end groups is measured specifically by the following method. First, the above-mentioned fluororesin is melted and compressed to produce a film with a thickness of 0.25 to 0.3 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the above-mentioned fluororesin, and a difference spectrum is obtained from the base spectrum, which is completely fluorinated and does not contain any functional groups. From the absorption peak of a specific functional group that appears in this difference spectrum, the number of carbon atoms in the above-mentioned fluororesin is calculated according to the following formula (A): 1 × 10 6 Calculate the number of unstable terminals per unit. N = I × K / t (A) I: Absorbance K: Correction coefficient t: Film thickness (mm)

[0071] 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.).

[0072] 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.

[0073] <Composition of 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 200m or more, may be 1000m or more, may be 2000m or more, or may be 5000m or more. The upper limit of the length of the resin film is not particularly limited, but for example it is 100,000m or less. The lower limit of the width of the resin film is not particularly limited, but for example it may be 200mm or more, or may be 400mm or more. The upper limit of the width of the resin film is not particularly limited, but for example it is 2000mm or less.

[0074] 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 Filmetrics).

[0075] 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.

[0076] 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 fluororesin. The fluororesin content in the fluororesin layer may be 100% by mass.

[0077] The modified layer of this disclosure is extremely thin, and its thickness 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 the cross-section of the resin film with an electron microscope (a field emission transmission electron microscope JEM-ARM200F manufactured by JEOL Ltd.).

[0078] 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.

[0079] 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.

[0080] 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. From the viewpoint of achieving both polymerizability and adhesion to other materials, aliphatic vinyl compounds are preferred as monomers that can be used to form the polymer layer. The aliphatic vinyl compounds that can be used as monomers are similar to those found in the monomer-containing inert gas atmosphere described later.

[0081] 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.

[0082] [Method for manufacturing resin film] This disclosure also relates to a method for manufacturing a resin film. For example, the resin film described above can be manufactured by the manufacturing method of this disclosure. The manufacturing method of this disclosure is a method for manufacturing a long resin film containing at least a fluororesin. The manufacturing method of this disclosure includes a plasma treatment step. The manufacturing method of the resin film of this disclosure optionally includes a step for forming a fluororesin layer. However, if a commercially available fluororesin film is used as the fluororesin layer, the step for forming the fluororesin layer can be omitted.

[0083] <Fluororesin layer formation process> In the process of forming the fluororesin layer, 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.

[0084] <Plasma treatment process> In the plasma treatment process, at least one surface of a fluororesin layer containing fluororesin is plasma treated under predetermined conditions in a monomer-containing inert gas atmosphere. The predetermined conditions are an applied voltage frequency of 1 to 100 kHz, an electric field strength of 5 to 50 kV / mm, and a discharge density of 1 to 500 W·min / m 2 These are the conditions.

[0085] As already mentioned, in plasma treatment performed under a monomer-containing inert gas atmosphere, the discharge becomes unstable as the treatment progresses, making it difficult to achieve continuous and stable surface treatment. Specifically, as the treatment progresses, unevenness in the treatment gradually increases, and unevenness in the adhesion strength with other materials may increase. Although this is speculation and not definitive, it is thought that under conventional discharge conditions, some of the monomers contained in the monomer-containing inert gas atmosphere carbonize, and the carbides adhere to the electrodes, causing the discharge to become unstable. Based on the above problem, it is presumed that by performing plasma treatment under the discharge conditions specified above, the monomers are efficiently plasma-converted, and the carbonization of monomers that are not plasma-converted is suppressed. As a result, the adhesion of monomer carbides to the electrodes is suppressed, and stable discharge for a long time becomes possible. Consequently, even when a resin film is continuously plasma-treated, a resin film with uniform surface characteristics with less unevenness in the longitudinal direction of the resin film corresponding to the direction of treatment progress can be obtained. Such surface treatment may be performed on only one side of the fluororesin layer or on both sides.

[0086] It is preferable that the plasma-treated surface of the resin film has the surface characteristics of the resin film of this disclosure described above. By changing the predetermined conditions of the plasma treatment, the coefficient of variation and rate of change of the second water contact angle in the second region, the coefficient of variation and rate of change of the third water contact angle in the third region, and the coefficient of variation and rate of change of the fourth water contact angle in the fourth region can be appropriately adjusted. Furthermore, by changing the predetermined conditions of the plasma treatment, the coefficient of variation and rate of change of the second adhesive strength with the copper foil in the second region, the coefficient of variation and rate of change of the third adhesive strength with the copper foil in the third region, and the coefficient of variation and rate of change of the fourth adhesive strength with the copper foil in the fourth region can be appropriately adjusted.

[0087] The longitudinal direction of the resin film of the present disclosure described above corresponds to the direction of plasma treatment in the manufacturing method of the present disclosure. The winding start side of the resin film of the present disclosure described above corresponds to the start side of plasma treatment in the manufacturing method of the present disclosure. The winding end side of the resin film of the present disclosure described above corresponds to the end side of plasma treatment in the manufacturing method of the present disclosure.

[0088] Preferably, a polymer layer is formed on the fluororesin layer by polymerization of monomers contained in a monomer-containing inert gas through plasma treatment. Specifically, a plasma of monomers contained in the monomer-containing inert gas is generated by corona discharge. The generated monomer plasma polymerizes (e.g., graft polymerization), forming a polymer layer on the surface of the fluororesin layer. The surface free energy can be controlled by introducing an inert gas into the discharge atmosphere. Furthermore, by exposing the surface to be modified to a monomer-containing discharge atmosphere and applying a voltage between electrodes, a discharge is induced, thereby generating active species on the surface. Surface modification can then be performed by introducing monomer functional groups or graft polymerization of polymerizable organic compounds.

[0089] In terms of production efficiency and manufacturing cost, when the fluororesin layer is in a long shape, it is preferable to continuously perform plasma treatment on the surface of the fluororesin layer while conveying the long fluororesin layer by roll-to-roll, rather than by batch processing. 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.

[0090] 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.

[0091] Plasma treatment may be carried out, for example, under atmospheric pressure (equivalent to 1 atm, 1013 hPa) or pressures in the vicinity thereof. However, plasma treatment is not limited to the atmospheric pressure environment and may be carried out in an environment pressurized or depressurized within the range of 500 to 2000 hPa. By pressurizing, it is possible to prevent the inflow of unintended gases (for example, oxygen in the air) into the plasma atmosphere.

[0092] Examples of the monomer contained in the monomer-containing inert gas atmosphere include, for example, the same monomers as those for forming the polymer layer described above. From the viewpoints that the modified surface is difficult to be deactivated and has a long lifespan, and that it is easy to handle, the monomer contained in the monomer-containing inert gas atmosphere is preferably a vinyl compound. 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, still more preferably 98 mol% or more, even more preferably 99 mol% or more, and particularly preferably 100 mol%.

[0093] From the viewpoint of achieving both the polymerizability of the monomer and the adhesiveness with other materials, preferred examples of the vinyl compound that can be used as the monomer contained in the monomer-containing inert gas atmosphere include aliphatic vinyl compounds and the like. An aliphatic vinyl compound is an aliphatic compound having a vinyl group. The carbon atom chain possessed by the aliphatic compound may be linear or branched. Further, the carbon-carbon bond of the carbon atom chain possessed by the aliphatic compound may be a saturated bond or an unsaturated bond. Further, the carbon atom chain possessed by the aliphatic compound may have a hetero atom such as an oxygen atom in addition to carbon atoms. From the viewpoint of achieving both the polymerizability of the monomer and the adhesiveness with other materials, preferred examples of the aliphatic vinyl compound include a compound represented by the general formula (1) "H2C=CH-O-R 1 ". In the general formula (1), R 1 represents an alkyl group having 1 to 6 carbon atoms or a group represented by the general formula (2) "-CO-R 2 ". In the general formula (2), R 2R represents a hydrogen atom, a C1-C6 alkyl group, or a C2-C6 alkenyl group. C1-C6 alkyl groups are linear or branched. C2-C6 alkenyl groups are linear or branched and may have one or more (e.g., two or three) double bonds. In general formula (1), R represents a hydrogen atom, a C1-C6 alkyl group, or a C2-C6 alkenyl group. 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. 2 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. 2 As the alkenyl group having 2 to 6 carbon atoms represented by , an alkenyl group having 2 to 5 carbon atoms is preferred.

[0094] 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%.

[0095] The concentration of monomer in the monomer-containing inert gas atmosphere varies depending on the type of monomer and the type of fluororesin to be surface-modified, 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.

[0096] 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.

[0097] The monomer-containing inert gas atmosphere may contain carbon dioxide, but it is preferable that it does not contain carbon dioxide in order to suppress carbonization.

[0098] Plasma treatment can be performed, for example, using a corona discharge device. A corona discharge device comprises, for example, a discharge electrode and a ground electrode (for example, a roll-shaped ground electrode).

[0099] In terms of improving processing continuity, 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. In terms of improving processing continuity, the frequency of the applied voltage is 100 kHz or lower, preferably 80 kHz or lower, more preferably 50 kHz or lower, and even more preferably 40 kHz or lower. The above applied voltage frequency is relatively low, and this is presumed to contribute to processing continuity. The type of applied voltage is not particularly limited, but for example, it is an AC voltage.

[0100] In terms of improving processing continuity, the electric field strength, which is the discharge condition, is preferably 5kV / mm or higher, and more preferably 10kV / mm or higher. In terms of improving processing continuity, the electric field strength, which is the discharge condition, is preferably 50kV / mm or lower, more preferably 40kV / mm or lower, and more preferably 30kV / mm or lower.

[0101] In terms of improving processing continuity, the discharge density, which is a discharge condition, is 1 W·min / m 2 That's all. 5W·min / m 2Preferably, it should be 10 W·min / m 2 It is more preferable that the value be 15 W·min / m 2 It is even more preferable that the above conditions are met. In terms of improving processing continuity, the discharge density, which is a discharge condition, should be 500 W·min / m 2 The following applies: 400W·min / m 2 Preferably, the following: 300W·min / m 2 It is more preferable that the following conditions apply: 250W·min / m 2 The following is even more preferable:

[0102] The processing temperature can be any temperature within the range of 0°C to 100°C. To reduce elongation and wrinkles in 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.

[0103] <Annealing process> The method for manufacturing a fluororesin film according to this disclosure may, after the plasma treatment step described above, optionally be performed as an annealing step. If annealing is performed, it may be carried out by heat treatment. The heat treatment may be carried out, for example, by passing the film through a heating furnace in a roll-to-roll manner. The heat treatment may also be carried out by placing the film in a batch-type drying oven.

[0104] However, the manufacturing method of this disclosure does not require an annealing process. As described above, since the variation in surface properties in the longitudinal direction of the resin film can be reduced by performing the plasma treatment process under predetermined conditions, the manufacturing method of this disclosure can produce a resin film with less distortion and deformation even without performing an annealing process. Furthermore, if annealing is not performed, the manufacturing method of this disclosure can shorten the production time.

[0105] 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.

[0106] The resin film of this disclosure exhibits minimal variation in surface properties along its length and excellent adhesion to other materials. For this reason, the resin film of this disclosure is 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 particularly useful in various display devices (e.g., liquid crystal displays, organic EL displays, 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.

[0107] [Metal-clad laminate] The present disclosure also relates to 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. Because it comprises the resin film of the present disclosure, the metal-clad laminate of the present disclosure has less variation in surface properties in the longitudinal direction of the resin film and excellent adhesion between the resin film and the metal foil. The metal-clad laminate preferably further comprises a substrate.

[0108] <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.

[0109] 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, such as 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 specified 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.

[0110] The copper foils that can be used for metal foils are 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.).

[0111] When the metal foil is directly mounted on the resin film, the 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 these materials are suitable for use as metal-clad laminates and circuit boards. The upper limit of the adhesive strength between the metal foil and the resin film is not particularly limited, but is, for example, 20 N / cm or less. The adhesive strength between the metal foil and the resin film can be measured by the 90-degree peel test described above, except when the copper foil is replaced with metal foil.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] <Base material> The base material is not particularly limited, but examples include fabrics made of glass fibers, glass nonwoven fabrics, and resin film layers. The fabrics made of glass fibers may be in the form of a prepreg impregnated with resin. Examples of resin films used as the base material 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 base material is preferably in the range of 12 to 200 μm.

[0117] 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.

[0118] <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 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.

[0119] There are no particular limitations on the method for compounding metal foil, other layers, and resin films, but two examples include the following: (i) A method of laminating metal foil, other layers, and pre-formed resin films 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 a metal foil, and laminating the resin side not facing the metal foil with the other layers by applying pressure under heating.

[0120] The metal-clad laminate of this disclosure has the advantage of low transmission loss because it exhibits less variation in surface properties along the length of the resin film and excellent adhesion to other materials. For this reason, 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, while simultaneously arranging and fixing 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-layer 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 for transmitting non-high-frequency signals on the same plane, such as transmission lines that convert high-frequency signals to low-frequency signals and output the generated low-frequency signals to the outside, and transmission lines that supply power for driving high-frequency compatible components. Furthermore, the circuit board of this disclosure can also be used as a circuit board for antennas, filters, and the like.

[0121] 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. [Examples]

[0122] The present disclosure will be described below in detail 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 "%" represent "parts by mass" and "% by mass," respectively.

[0123] The fluororesins used in the examples, comparative examples, and reference examples are shown below. Fluorinated 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: Untreated TFE / PPVE copolymer (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)

[0124] [Example 1] <Manufacturing of fluororesin sheets> F-type PFA was fed into a 360°C extruder, extruded through a 1700mm wide T-die, taken up onto a metal cooling roll, and then wound onto a winding core to obtain a roll of fluororesin sheet (equivalent to a fluororesin layer) with a width of 1300mm and a thickness of 12μm.

[0125] <Plasma Treatment> A roll-shaped fluororesin sheet was plasma-treated on both sides while being conveyed by a roll-to-roll system. Specifically, under atmospheric pressure, a monomer-containing inert gas containing 0.5% by volume of 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 aligned with the roll-shaped ground electrode, was continuously passed between the electrodes. Discharge density: 143 W·min / m 2Both sides of the fluororesin sheet were plasma-treated by applying corona discharge to both sides of the fluororesin sheet under the conditions of an electric field strength of 7.1 kV / mm and an applied voltage frequency of 50 kHz. The plasma-treated fluororesin sheet was wound into a roll to obtain the resin film of Example 1.

[0126] [Examples 2-10 and Comparative Examples 1-4] Except for the fluororesin used in the manufacture of the fluororesin sheet, and the discharge density, electric field strength, and frequency of the applied voltage for plasma treatment, as described in Tables 1 to 3 below, resin films of Examples 2 to 10 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1.

[0127] [Reference example 1] For Reference Example 1, a fluororesin sheet prepared from the F-type PFA of Example 1 was used as the resin film without plasma treatment.

[0128] [Settings for Areas 1-4] A reference line parallel to the width direction of the resin film was established on the winding start side of the resin film (the starting point of atmospheric plasma treatment). In the measurements of the examples and comparative examples, the reference line was established on the point where atmospheric plasma treatment began on the resin film. The first region was set up so that the winding start end of the first region coincided with the reference line. The second region was set up so that the winding start end of the second region was 200 m away from the reference line. The third region was set up so that the winding start end of the third region was 1000 m away from the reference line. The fourth region was set up so that the winding start end of the fourth region was 2000 m away from the reference line. The width of each region from the first to the fourth region was defined as the width of the plasma treatment region, and the length of each region was set to 100 cm. The plasma treatment proceeded in the direction from the winding start side of the resin film toward the winding end side (the ending point of atmospheric plasma treatment).

[0129] [Method for measuring the water contact angle] The water contact angle was measured using a fully automatic contact angle meter, DropMaster700 (manufactured by Kyowa Interface Chemical Co., Ltd.), in the following manner: 2 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.

[0130] <Ave0m of water contact angle> The water contact angle was measured at 40 locations within the first region of the resin film (20 locations at 3 mm intervals in the width direction of the resin film, and 20 locations in two rows offset by 5 mm in the longitudinal direction and 1.5 mm in the width direction, for a total of 40 locations), and the average value (ave0m) was calculated.

[0131] <σ / ave0m of the water contact angle> The standard deviation (σ0m) of the water contact angles at 40 locations within the first region measured above was calculated. The σ / ave0m (in %) of the water contact angle was calculated using the formula "(σ / ave0m) = 100 × (σ0m) / (ave0m)".

[0132] <Water contact angle at ave200m, σ / ave200m> The water contact angle was measured at 40 locations within the second region of the resin film (20 locations at 3 mm intervals in the width direction of the resin film, and 20 locations in two rows offset by 5 mm in the longitudinal direction and 1.5 mm in the width direction, for a total of 40 locations), and the average value (ave200m) and its standard deviation (σ200m) were calculated. The σ / ave200m (unit: %) of the water contact angle was calculated using the formula "(σ / ave200m) = 100 × (σ200m) / (ave200m)".

[0133] <Rate of change of σ / ave of water contact angle> The rate of change of σ / ave (in %) of the water contact angle was calculated using the formula "(σ / ave change rate) = 100 × [(σ / ave 200m) - (σ / ave 0m)] / (σ / ave 0m)".

[0134] [Method for measuring adhesive strength] <90-degree peel test method A> A laminate for peel testing was obtained 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 the laminate was heat-pressed using a vacuum heat press (model: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 180°C, a preheating time of 120 seconds, a pressurizing pressure of 3 MPa, and a pressurizing time of 15 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). The resin film was cut from a point 1 cm in the longitudinal direction from the water contact angle measurement point.

[0135] (Peel test method) An aluminum plate was attached to the underside of the laminate for the peel test using adhesive tape. Using a precision universal testing machine Autograph AGS-X 100N (manufactured by Shimadzu Corporation), the copper foil was gripped 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.

[0136] (Adhesive strength) Using the peel test method described above, the average value (Ave.) and standard deviation (σ) of the adhesive strength were determined in a section from 10 mm to 75 mm from the start of peeling, for a total stroke distance of 65 mm.

[0137] <Adhesive strength ave0m> The adhesive strength within the first region of the resin film was measured using peel test method A, and the average value (ave0m) was calculated.

[0138] <Adhesive strength: average 200m> The adhesive strength within the second region of the resin film was measured using peel test method A, and the average value (ave200m) was determined.

[0139] <Rate of change in adhesive strength> The rate of change of ave (in %) of adhesive strength was calculated using the formula "(ave change rate) = 100 × [(ave 200m) - (ave 0m)] / (ave 0m)".

[0140] <Adhesive strength σ / ave0m> The standard deviation (σ0m) of the adhesive strength within the first region measured above was calculated. The adhesive strength σ / ave0m (in %) was calculated using the formula "(σ / ave0m) = 100 × (σ0m) / (ave0m)".

[0141] <Adhesive strength σ / ave200m> The standard deviation (σ200m) of the adhesive strength within the second region measured above was calculated. The σ / ave200m (unit: %) of the adhesive strength was calculated using the formula "(σ / ave200m) = 100 × (σ200m) / (ave200m)".

[0142] <Percentage change in adhesive strength σ / ave> The σ / ave change rate (in %) of the adhesive strength was calculated using the formula "(σ / ave change rate) = 100 × [(σ / ave 200m) - (σ / ave 0m)] / (σ / ave 0m)".

[0143] The measurement results for the water contact angle and adhesive strength of the resin films in Examples 1-10 and Comparative Examples 1-4 are shown in Tables 1-3. Additionally, the measurement results for the water contact angle of the resin film in Reference Example 1 are shown in Table 1.

[0144] [Table 1]

[0145] [Table 2]

[0146] [Table 3]

[0147] [Example 11] In Example 11, the adhesive strength of the resin film from Example 6 was measured using the 90-degree peel test method B described below. The measurement results are shown in Table 4.

[0148] [Example 11: Method for measuring adhesive strength] <90-degree peel test method B> (Method of manufacturing a laminate for peel testing B) Using a fluororesin sheet material (the resin film produced above), and further using prepreg material, prepreg R-5680(J) (thickness 132μm) (manufactured by Panasonic Corporation), and copper foil, CF-T9DA-SV-18 (thickness 18μm, Rz 0.85μm, unroughened copper foil) (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.) and CF-V9S-SV-12 (thickness 12μm) (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.), each is cut into the specified shape, and then CF-T9D is applied from above. The layers were stacked in the following order: A-SV-18 (unroughened side facing down), fluororesin sheet material (inner surface of the roll after surface treatment facing up), prepreg R-5680(J), and CF-V9S-SV-12 (roughened side facing up). The layers were then hot-pressed under the following conditions: temperature 200°C, preheating time 120 seconds, pressurizing time 75 minutes, and pressure 3.0 MPa. The resulting laminate for peel testing had dimensions of 1 cm (lengthwise direction of the resin film) x 10 cm (widthwise direction of the resin film).

[0149] (Peel test method B) An aluminum plate was attached to the underside (CF-V9S-SV-12 side) of the peel test sample with adhesive tape. Using a precision universal testing machine Autograph AGS-X 100N (manufactured by Shimadzu Corporation), the copper foil was gripped and pulled at a speed of 50 mm per minute at a 90-degree angle to the plane of the peel test sample to measure the peel strength of the copper foil, and the obtained value was defined as the adhesive strength. The peel surface was the interface between the copper foil CF-T9DA-SV-18 of the peel test sample and the resin film.

[0150] (Adhesive strength) Using the peel test method described above, the average value (Ave.) and standard deviation (σ) of the adhesive strength were determined in a section from 10 mm to 75 mm from the start of peeling, for a total stroke distance of 65 mm.

[0151] <Adhesive strength at ave0m, ave200m, ave change rate, σ / ave0m, σ / ave200m, and σ / ave change rate> Using the same calculation method as for 90-degree peel test method A, the ave0m, ave200m, ave change rate, σ / ave0m, σ / ave200m, and σ / ave change rate of the adhesive strength measured by 90-degree peel test method B were calculated. Furthermore, to aid understanding, the measured water contact angle values ​​from Example 6 are again shown as the measured water contact angle values ​​from Example 11.

[0152] [Table 4]

[0153] [Example 12] In Example 12, the water contact angle and adhesive strength were measured for the third region of the resin film from Example 6 using the following method. The measurement results are shown in Table 5.

[0154] [Example 12: Method for measuring water contact angle] <σ / ave1000m of water contact angle> The water contact angle was measured at 40 locations within the third region of the resin film in Example 6 (20 locations at 3 mm intervals in the width direction of the resin film, and 20 locations in two rows offset by 5 mm in the longitudinal direction and 1.5 mm in the width direction, for a total of 40 locations), and the average value (ave1000m) and its standard deviation (σ1000m) were calculated. σ / ave1000m (unit: %) was calculated using the formula "(σ / ave1000m) = 100 × (σ1000m) / (ave1000m)".

[0155] <Rate of change of σ / ave of water contact angle> The rate of change of σ / ave (in %) was calculated using the formula "(σ / ave change rate) = 100 × [(σ / ave 1000m) - (σ / ave 0m)] / (σ / ave 0m)". For Example 12, the measured value of σ / ave 0m for the water contact angle was used.

[0156] [Example 12: Method for measuring adhesive strength] <Adhesive strength of ave1000m> The adhesive strength within the third region of the resin film was measured using peel test method A, and the average value (ave1000m) was determined.

[0157] <Rate of change in adhesive strength> The rate of change of ave (in %) of the adhesive strength was calculated using the formula "(ave change rate) = 100 × [(ave 1000m) - (ave 0m)] / (ave 0m)". For Example 12, the measured value of ave 0m of the adhesive strength in Example 6 was used as the ave 0m value for the adhesive strength.

[0158] <Adhesive strength σ / ave1000m> The standard deviation (σ1000m) of the adhesive strength within the third region measured above was calculated. The σ / ave1000m (unit: %) of the adhesive strength was calculated using the formula "(σ / ave1000m) = 100 × (σ1000m) / (ave1000m)".

[0159] <Percentage change in adhesive strength σ / ave> The percentage change in σ / ave of the adhesive strength (in units: %) was calculated using the formula "(σ / ave change rate) = 100 × [(σ / ave 1000m) - (σ / ave 0m)] / (σ / ave 0m)". For Example 12, the measured value of σ / ave 0m of the adhesive strength in Example 6 was used as the value of σ / ave 0m for the adhesive strength.

[0160] [Table 5]

[0161] [Example 13] In Example 13, the water contact angle and adhesive strength were measured for the fourth region of the resin film from Example 6 using the following method. The measurement results are shown in Table 6.

[0162] [Example 13: Method for measuring water contact angle] <σ / ave2000m of water contact angle> The water contact angle was measured at 40 locations within the fourth region of the resin film in Example 6 (20 locations at 3 mm intervals in the width direction of the resin film, and 20 locations in two rows offset by 5 mm in the longitudinal direction and 1.5 mm in the width direction, for a total of 40 locations), and the average value (ave2000m) and its standard deviation (σ2000m) were calculated. The water contact angle σ / ave2000m (unit: %) was calculated from the formula "(σ / ave2000m) = 100 × (σ2000m) / (ave2000m)".

[0163] <Rate of change of σ / ave of water contact angle> The rate of change of σ / ave (in %) was calculated using the formula "(σ / ave change rate) = 100 × [(σ / ave 2000m) - (σ / ave 0m)] / (σ / ave 0m)". For Example 13, the measured value of σ / ave 0m for the water contact angle was used.

[0164] [Example 13: Measurement of adhesive strength] <Adhesive strength averaged 2000m> The adhesive strength within the third region of the resin film was measured using peel test method A, and the average value (average 2000 m) was determined.

[0165] <Rate of change in adhesive strength> The rate of change of ave (in %) of the adhesive strength was calculated using the formula "(ave change rate) = 100 × [(ave 2000m) - (ave 0m)] / (ave 0m)". For Example 12, the measured value of ave 0m of the adhesive strength in Example 6 was used as the ave 0m value for the adhesive strength.

[0166] <Adhesive strength σ / ave2000m> The standard deviation (σ2000m) of the adhesive strength within the third region measured above was calculated. The σ / ave2000m (unit: %) of the adhesive strength was calculated using the formula "(σ / ave2000m) = 100 × (σ2000m) / (ave2000m)".

[0167] <Percentage change in adhesive strength σ / ave> The percentage change in σ / ave of adhesive strength (in %) was calculated using the formula "(σ / ave change rate) = 100 × [(σ / ave 2000m) - (σ / ave 0m)] / (σ / ave 0m)". For Example 12, the measured value of σ / ave 0m of adhesive strength from Example 6 was used as the value of σ / ave 0m of adhesive strength.

[0168] [Table 6]

[0169] From the results in Tables 1 to 6, the resin films of the examples showed little variation in surface properties along the length direction and excellent adhesion to other materials. Furthermore, from the results in Tables 1 to 6, the copper-clad laminates comprising the resin films of the examples showed little variation in surface properties along the length direction of the resin film and excellent adhesion between the resin film and the copper foil. In addition, from the results in Tables 1 to 6, the manufacturing method of the resin films of the examples, even when subjected to continuous plasma treatment, was able to produce resin films with minimal processing unevenness and little variation in surface properties along the length direction of the resin film corresponding to the direction of treatment progression.

[0170] [Method for measuring the ratio of fluorine and oxygen elements] As representative examples, the fluorine and oxygen element ratios were measured for the resin films of Reference Example 1, Examples 1-10, and Comparative Examples 2 and 4 using the following method. The measurement results are shown in Table 7.

[0171] Using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.), the fluorine and oxygen element ratios on the surface of the second region of a resin film were measured under the conditions described below. Carbon, oxygen, fluorine, and nitrogen were detected. The fluorine element ratio was determined from the composition ratio of C1s, O1s, F1s, and N1s, and the oxygen element ratio was determined from the composition ratio of C1s, O1s, F1s, and N1s. Radiation source: Monochromatized AlKα Beam diameter: 100 μm X-ray output: 25W Measurement area: 1000μm x 300μm Passage energy: 58.7 eV Detection angle: 45°

[0172] [Method for measuring COO ratio, and CC and CH ratios] As representative examples, the COO ratio and CC and CH ratios were measured within the first region of the resin films of Reference Example 1, Examples 5, 6, 8, 9, and 10, and Comparative Examples 2 and 4, using the following method. The measurement results are shown in Table 8.

[0173] The C1s narrow spectrum in the spectrum obtained by the above XPS / ESCA (horizontal axis: binding energy (unit eV), vertical axis: intensity (unit CPS)) was separated into five peaks using MultiPak software (manufactured by ULVAC-PHI, Inc.) under the conditions shown below. The full width at half maximum (FWHM) of peaks 1 to 4 was standardized to 1.83, and the FWHM of peak 5 was adjusted to match the shape of the original spectrum. The heights were adjusted so that the combined spectral shape of the original spectrum and the separated peaks matched, and the area of ​​each peak was calculated. From the area of ​​each peak, the COO ratio (unit: %) was calculated based on the following formula (i). From the area of ​​each peak, the CC and CH ratios (unit: %) were calculated based on the following formula (ii).

[0174] Peak 1: Chemical bonds CC and CH, peak position 283.5~284.6 eV Peak 2: Chemical bond C-O, peak position 286.1 eV Peak 3: Chemical bond C=O, peak position 287.6eV Peak 4: Chemical bond COO, peak position 288.6 eV Peak 5: Chemical bond CF2, peak position 291.1 eV

[0175] COO ratio = 100 × (Area of ​​peak corresponding to COO bond) / [(Area of ​​peak corresponding to CC bond and CH bond) + (Area of ​​peak corresponding to CO bond) + (Area of ​​peak corresponding to C=O bond) + (Area of ​​peak corresponding to COO bond) + (Area of ​​peak corresponding to CF2 bond)] ... (i) CC and CH ratio = 100 × (Area of ​​peaks corresponding to CC and CH bonds) / [(Area of ​​peaks corresponding to CC and CH bonds) + (Area of ​​peaks corresponding to CO bonds) + (Area of ​​peaks corresponding to C=O bonds) + (Area of ​​peaks corresponding to COO bonds) + (Area of ​​peaks corresponding to CF2 bonds)] ... (ii)

[0176] [Table 7]

[0177] [Table 8]

[0178] The fluorine atom ratio on the surface of the resin film in the examples shown in Table 7 was between 40 atomic% and 68 atomic%. The oxygen element ratio on the surface of the resin film in the examples shown in Table 7 was 1.0 atomic% or higher. The COO ratio on the surface of the resin film in the examples shown in Table 8 was 2.0% or higher. The CC and CH ratios on the surface of the resin film in the examples shown in Table 8 were between 2.0% and 60.0%.

[0179] <Method for evaluating the presence or absence of unevenness> As representative examples, the surfaces of the resin films of Reference Example 1, Comparative Example 1, Example 2, and Example 8 were observed at a magnification of 5000x using an electron microscope (Hitachi High-Tech Corporation "SU8020"), and the presence or absence of irregularities (uniformity) was determined according to the definition below. The determination results are shown in Table 9. In addition, electron microscope images of the surfaces of the resin films of Reference Example 1, Comparative Example 1, Example 2, and Example 8 are shown in Figures 1, 2, 3, and 4, respectively. A (Good): No bumps or unevenness. B (Defective): Uneven surface

[0180] [Table 9]

[0181] The resin films of the examples shown in Table 9 had minimal surface unevenness and were uniformly surface-treated. Furthermore, a comparison between the resin film of Reference Example 1 shown in Figure 1 (a resin film that has not undergone plasma treatment) and the resin films of Examples 2 and 8 shown in Figures 3 and 4 (resin films that have undergone plasma treatment under predetermined conditions) confirmed that a polymer layer was formed on the surface of the resin films of Examples 2 and 8. In addition, a comparison between the resin films of Examples 2 and 8 shown in Figures 3 and 4 (resin films treated under predetermined discharge conditions) and the resin film of Comparative Example 1 shown in Figure 2 (a resin film treated under discharge conditions other than predetermined conditions) confirmed that the polymer layer formed on the surface of the resin films of Examples 2 and 8 was uniform with minimal surface unevenness.

[0182] <Method for evaluating the presence or absence of an adhesive layer> As representative examples, copper-clad laminates formed using the resin films of Examples 2 and 8 were cross-sectionally prepared by ion milling and used as observation specimens. The cross-sections were 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. The confirmation results are shown in Table 10. Furthermore, electron microscope images of the cross-sections of the resin films of Examples 2 and 8 are shown in Figures 5 and 6, respectively.

[0183] [Table 10]

[0184] As is clear from Table 10, Figures 5 and 6, the resin films of the examples shown in Table 10 had an adhesive layer (corresponding to a polymer layer) formed on them.

[0185] <Dielectric constant and dielectric loss tangent> As representative examples, the resin films of Examples 6 and 10 were measured at 10 GHz (26°C) using split-cylinder resonators CR-710 and CR-740 (EM Lab Co., Ltd.), and analyzed using a vector network analyzer P5007A (Keysight Technologies, Inc.) to obtain the dielectric constant and dielectric loss tangent. The measurement results are shown in Table 11.

[0186] [Table 11]

[0187] The dielectric loss tangent values ​​at 10 GHz for the resin films of the examples shown in Table 11 were less than 0.0015.

[0188] <Surface modulus> As representative examples, the surface modulus of the resin films of Reference Example 1, Example 2, and Example 8 was measured using the following method. The measurement results are shown in Table 12.

[0189] The measurement sample was obtained by cutting a 1cm x 1cm square from within the second region of 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, manufactured by Hitachi High-Tech Fielding Co., Ltd., tip radius R ≤ 10 nm, spring constant 2 N / m) Indentation load: 10nN Measurement mode: Force curve mapping (FCM) mode Measurement environment: Air, 120°C Measurement field of view: 20 μm × 10 μm (64 points × 32 points) Histograms were created for the 2048 surface modulus values ​​obtained as described above, with a class pitch of 0.01 GPa. From the resulting histograms, the cumulative relative frequency at which the resin film reaches 1.3 GPa was determined.

[0190] [Table 12]

[0191] The cumulative relative frequency of the resin films in the examples shown in Table 12 that reached 1.3 GPa was 0.98 or less. [Industrial applicability]

[0192] 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, The average value of the first water contact angle in the first region of at least one surface of the resin film is 50° or more and 105° or less. A resin film in which the rate of change of the coefficient of variation of the second water contact angle in a second region located 200 m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation of the first water contact angle in the first region, is 40% or less.

2. The resin film according to claim 1, wherein the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

3. The resin film according to claim 1 or 2, wherein the coefficient of variation of the second water contact angle in the second region is 6.0% or less.

4. The resin film according to claim 1 or 2, wherein the rate of change of the coefficient of variation of the second adhesive strength with the copper foil in the second region relative to the coefficient of variation of the first adhesive strength with the copper foil in the first region, as measured by a 90-degree peel test with the copper foil, is 100% or less.

5. The resin film according to claim 1 or 2, wherein the coefficient of variation of the second adhesive strength with the copper foil in the second region, as measured by a 90-degree peel test with the copper foil, is 35% or less.

6. The resin film according to claim 1 or 2, wherein the fluorine element ratio on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 40 atomic% or more and 68 atomic% or less.

7. The resin film according to claim 1 or 2, wherein the oxygen element ratio on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 1.0 atomic% or more.

8. The area ratio of peaks corresponding to COO bonds on the surface of the resin film, measured by scanning X-ray photoelectron spectroscopy (XPS), is the area of ​​the peaks corresponding to C-C bonds and C-H bonds, the area of ​​the peaks corresponding to C-O bonds, the area of ​​the peaks corresponding to C=O bonds, the area of ​​the peaks corresponding to COO bonds, and CF ２ The resin film according to claim 1 or 2, wherein the total area of ​​the peaks corresponding to the bonds is 2.0% or more.

9. The area ratio of peaks corresponding to C-C bonds and C-H bonds on the surface of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is the area of ​​the peaks corresponding to C-C bonds and C-H bonds, the area of ​​the peaks corresponding to C-O bonds, the area of ​​the peaks corresponding to C=O bonds, the area of ​​the peaks corresponding to COO bonds, and CF ２ The resin film according to claim 1 or 2, wherein the total area of ​​the peaks corresponding to the bonds is 2.0% or more and 60% or less.

10. The resin film according to claim 1 or 2, wherein the rate of change of the coefficient of variation of the third water contact angle in a third region located 1000 m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation of the first water contact angle in the first region, is 40% or less.

11. The resin film according to claim 1 or 2, wherein the rate of change of the coefficient of variation of the fourth water contact angle in a fourth region located 2000 m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation of the first water contact angle in the first region, is 40% or less.

12. The resin film according to claim 1 or 2, wherein the rate of change of the coefficient of variation of the third adhesive strength with the copper foil in a third region located 1000 m away from the first region, with respect to the coefficient of variation of the first adhesive strength with the copper foil in the first region, as measured by a 90-degree peel test with the copper foil, is 100% or less.

13. The resin film according to claim 1 or 2, wherein the rate of change of the coefficient of variation of the fourth adhesive strength with the copper foil in a fourth region located 2000 m away from the first region, with respect to the coefficient of variation of the first adhesive strength with the copper foil in the first region, as measured by a 90-degree peel test with the copper foil, is 100% or less.

14. A fluororesin layer containing the aforementioned fluororesin, A resin film according to claim 1 or 2, comprising a polymer layer formed by polymerization of monomers.

15. The resin film according to claim 14, wherein the monomer comprises an aliphatic vinyl compound.

16. The resin film according to claim 14, wherein the polymer layer is a layer formed by plasma treatment under a monomer-containing inert gas atmosphere containing the monomer.

17. The resin film according to claim 1 or 2, 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.

18. The resin film according to claim 1 or 2, wherein the dielectric loss tangent value of the resin film at 10 GHz is less than 0.0015.

19. The system comprises a fluororesin layer containing the aforementioned fluororesin and a polymer layer, The aforementioned fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, The polymer layer is a plasma-polymerized vinyl acetate layer. The average value of the first water contact angle in the first region is 85° or more and 105° or less. The rate of change of the coefficient of variation of the second water contact angle in the second region with respect to the coefficient of variation of the first water contact angle in the first region is 0% or more and 35% or less. The fluorine element ratio on the surface of the second region of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 50 atomic% or more and 68 atomic% or less. The resin film according to claim 1 or 2, wherein the oxygen element ratio of the surface of the second region of the resin film, as measured by scanning X-ray photoelectron spectroscopy (XPS), is 1.2 atomic% or more and 7.0 atomic% or less.

20. A metal-clad laminate comprising a resin film according to claim 1 or 2 and a metal foil.

21. The metal-clad laminate according to claim 20, wherein the surface roughness (Rz) of the metal foil is 1.5 μm or less.

22. The metal-clad laminate according to claim 20, wherein the metal foil is provided directly on the resin film, and the adhesive strength between the metal foil and the resin film is 2 N / cm or more.

23. The metal-clad laminate according to claim 20, further comprising a base material.

24. A method for producing a long resin film containing at least a fluororesin, The process includes a plasma treatment step in which at least one surface of the fluororesin layer containing the fluororesin is plasma treated under predetermined conditions in a monomer-containing inert gas atmosphere. The aforementioned predetermined conditions are: applied voltage frequency of 1 to 100 kHz, electric field strength of 5 to 50 kV / mm, and discharge density of 1 to 500 W・min / m². ２ A method for manufacturing a resin film, which meets the following conditions.

25. The average value of the first water contact angle in the first region of the plasma-treated surface of the resin film is 50° or more and 105° or less. A method for manufacturing a resin film according to claim 24, wherein the rate of change of the coefficient of variation of the second water contact angle in a second region located 200 m away from the first region in the longitudinal direction of the resin film, with respect to the coefficient of variation of the first water contact angle in the first region, is 40% or less.

26. The method for producing a resin film according to claim 24 or 25, wherein the fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

27. A method for producing a resin film according to claim 24 or 25, wherein a polymer layer is formed on the fluororesin layer by polymerization of monomers contained in the monomer-containing inert gas atmosphere through the plasma treatment.

28. The monomer contained in the monomer-containing inert gas atmosphere is an aliphatic vinyl compound. The method for producing a resin film according to claim 24 or 25, wherein the concentration of the aliphatic vinyl compound in the monomer-containing inert gas atmosphere is 0.1 to 5% by volume.

29. The method for producing a resin film according to claim 24 or 25, wherein the inert gas contained in the monomer-containing inert gas atmosphere is one or more selected from the group consisting of nitrogen, argon, and helium.

30. A method for manufacturing a resin film according to claim 24 or 25, 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.

31. While the fluororesin layer is being conveyed by a roll-to-roll mechanism, the plasma treatment is continuously performed on the surface of the fluororesin layer. The plasma treatment causes polymerization of monomers contained in the monomer-containing inert gas atmosphere, thereby forming a polymer layer on the fluororesin layer. The aforementioned 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% by volume. The predetermined conditions are an applied voltage frequency of 15 to 50 kHz, an electric field strength of 5 to 30 kV / mm, and a discharge density of 15 to 250 W・min / m². ２ A method for manufacturing a resin film according to claim 24 or 25, which is a condition of the present invention.

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