Fluororesin sheet-like material and laminate including the same

Abstract

To provide a fluororesin sheet-like material having excellent adhesiveness without fluctuation in-plane uniformity, and further, to provide a fluororesin sheet-like material in which when a sheet-like material is formed in roll, transportation is excellent, and also roll appearance is improved.SOLUTION: A sheet-like material contains a fluororesin, wherein on at least one surface, when the oxygen atomic ratio is measured by scanning X-ray photoelectron spectroscopy (XPS) at 10 points each in the longitudinal, transverse, and diagonal directions of a 10 cm square sheet-like material, the average oxygen atomic ratio in any direction is 1.35 atomic% or more, and (MAX-MIN) / Avg. is 40% or less, forming the fluororesin sheet-like material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] Patent Document 2 describes a long film that is made of a heat-fusible polymer containing PFA, contains spherulites of the heat-fusible polymer, and has a radius of 10 μm or less, and has excellent adhesion and high-temperature stability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-181735 [Patent Document 2] International No. 2021 / 006258 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a fluororesin sheet material that has uniform, consistent adhesion within its surface and excellent adhesion to other materials. It is also an object of the present disclosure to provide a fluororesin sheet material that, when rolled, allows for good transportability of the sheet material and improves the appearance of the roll. Another object of the present disclosure is to provide a laminate that maintains low transmission loss characteristics and has excellent properties when used as a circuit board. [Means for solving the problem]

[0006] The present disclosure provides a sheet-like material containing a fluororesin, the sheet-like material having at least one surface comprising: When the oxygen element ratio is measured by scanning X-ray photoelectron spectroscopy (XPS) at the following 10 points in each of the longitudinal, transverse, and diagonal directions of a 10 cm square sheet material, the average oxygen element ratio is 1.35 atomic% or more in all directions, and (MAX-MIN) / Avg. is 40% or less. This is a fluororesin sheet material (A). 10 vertical points: 1.5cm from the left edge, 1.5cm from the top, 10 points at 8mm intervals 10 horizontal points: 1.5 cm from the top edge, 1.5 cm from the left edge, 10 points at 8 mm intervals 10 points diagonally: In both the vertical and horizontal directions, from the bottom right corner of the sheet material, a straight line connecting the points on each side of 6.5 cm vertically and 6.5 cm horizontally is the long side, and on a straight line 5 mm above the long side of a rectangle with a short side of 1 cm, the first point is 1.5 cm from the top of the long side of the rectangle, and 10 points are placed at 8 mm intervals.

[0007] It is preferable that the average value of the oxygen element ratio is 1.35 atomic % or more and 20 atomic % or less, and the (MAX-MIN) / Avg. is 3% or more and 40% or less, and the fluororesin is tetrafluoroethylene-perfluoroalkylvinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

[0008] The present disclosure also provides a laminate (A1) comprising the above-mentioned fluororesin sheet material (A) and a metal layer, in which the adhesive strength between the oxygen element ratio measurement surface of the above-mentioned fluororesin sheet material and the metal layer obtained by a 90-degree peel test in each of the vertical, horizontal and diagonal directions of a 10 cm square laminate is σ / Avg.≦35% in any direction. The present disclosure also provides a laminate (A2) comprising the above-mentioned fluororesin sheet material (A) and a metal layer, in which the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by a 90-degree peel test in each of the vertical, horizontal and diagonal directions of a 10 cm square laminate is (MAX-MIN) / Avg.≦150% in any direction.

[0009] The present disclosure also provides a laminate (A3) comprising the above-mentioned fluororesin sheet material (A) and a metal layer, in which the adhesive strength between the oxygen element ratio measurement surface of the above-mentioned fluororesin sheet material and the metal layer obtained by a 90-degree peel test in each of the vertical, horizontal and diagonal directions of a 10 cm square laminate is σ / Avg.≦35% and (MAX-MIN) / Avg.≦150% in any direction.

[0010] In the laminate, it is preferable that the adhesive strength is 1%≦σ / Avg.≦20% and 3%≦(MAX-MIN) / Avg.≦100% in any direction, and the fluororesin is tetrafluoroethylene-perfluoroalkylvinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP). In the laminate, the adhesive strength is preferably 0.5 N / cm or more in any direction.

[0011] The present disclosure provides a sheet-like material containing a fluororesin, the sheet-like material having at least one surface comprising: The specimen is divided into a horizontal (X) and b vertical (Y) sections every 10 cm, and the average oxygen element ratio measured at the center of each divided section is 1.35 atomic% or more, and The fluororesin sheet material (B) satisfies the following formulas (1) and (2). σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1 and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided region.

[0012] The present disclosure also provides a laminate comprising the fluororesin sheet material (B) and a metal layer, The laminate (B) is also a laminate that satisfies the following formulas (3) and (4), which are obtained from the average adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer, measured in the horizontal direction (X) and the vertical direction (Y) at 10 cm intervals within each 10 cm square region by a 90-degree peel test in the horizontal direction, vertical direction, and diagonal direction. σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb)≦35% (3) {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B (X1Y1~XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1 and satisfy the condition ab≧50. In this case, XaYb is the average of the average adhesive strength in three directions in the divided area corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y).

[0013] The present disclosure provides a sheet-like material having a surface of 10 cm square, in which, when the oxygen element ratio is measured by scanning X-ray photoelectron spectroscopy (XPS) at 10 points in each of the longitudinal, transverse, and diagonal directions, the average oxygen element ratio is 1.35 atomic% or more in all directions, and (MAX-MIN) / Avg. is 40% or less, Furthermore, the specimen is divided into a horizontal (X) and b vertical (Y) sections every 10 cm, and the average oxygen element ratio measured at the center of each divided section is 1.35 atomic% or more, and It is also a fluororesin sheet material (C) that satisfies the following formulas (1) and (2). σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1 and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided region. 10 vertical points: 1.5cm from the left edge, 1.5cm from the top, 10 points at 8mm intervals 10 horizontal points: 1.5 cm from the top edge, 1.5 cm from the left edge, 10 points at 8 mm intervals 10 points diagonally: In both the vertical and horizontal directions, from the bottom right corner of the sheet material, a straight line connecting the points on each side of 6.5 cm vertically and 6.5 cm horizontally is the long side, and on a straight line 5 mm above the long side of a rectangle with a short side of 1 cm, the first point is 1.5 cm from the top of the long side of the rectangle, and 10 points are placed at 8 mm intervals.

[0014] The present disclosure also provides a laminate comprising the above-mentioned fluororesin sheet material (C) and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the above-mentioned fluororesin sheet material and the metal layer obtained by a 90-degree peel test in each of the longitudinal direction, transverse direction, and diagonal direction of a 10 cm square laminate is σ / Avg.≦35% and (MAX-MIN) / Avg.≦150% in all directions; Furthermore, the laminate is divided into a section in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and within each divided 10 cm square area, a 90-degree peel test is carried out to measure the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer in the horizontal direction, vertical direction, and diagonal direction, and the laminate satisfies the following formulas (3) and (4). σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb)≦35% (3) {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B (X1Y1~XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1 and ab≧50. In this case, XaYb is the average of the average adhesive strength in three directions in the divided area corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y). It is preferable that the laminate (A3) is divided into a sections in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and within each divided 10 cm square area, the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer is measured in the horizontal direction, vertical direction, and oblique direction by a 90-degree peel test, and that the following formulas (3) and (4) are satisfied: σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb)≦35% (3) {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B(X1Y1~XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1 and satisfy the condition ab≧50. In this case, XaYb is the average of the average adhesive strength in three directions in the divided area corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y).

[0015] The laminates (A1) to (A3) and (B) further have a layer other than the fluororesin sheet material and the metal layer, The layers other than the fluororesin sheet material and the metal layer are preferably at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, and polybutadiene. [Effects of the Invention]

[0016] The fluororesin sheet material of the present disclosure has uniform, consistent adhesion to other materials, and excellent adhesion. Furthermore, because the surface treatment is uniform, when the fluororesin sheet material is in roll form, the transportability of the fluororesin sheet material is improved and the appearance of the roll is also improved. Furthermore, the laminate of the present disclosure maintains low transmission loss characteristics and has excellent properties when used as a circuit board. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an explanatory diagram showing an outline of the measurement position of the oxygen element ratio in a 10 cm square fluororesin sheet material and the position where a sample for a peel test was obtained. [Figure 2] FIG. 1 is an explanatory diagram showing an outline of the positions for measuring the oxygen element ratio and the positions for obtaining samples for peel tests in one embodiment when a fluororesin sheet material is divided into 10 cm squares. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present disclosure will be described in detail below. In the past, when modifying the surface of fluororesin sheets using plasma treatment, there have been a number of patents that specify the amount of oxygen element or the amount of specific functional groups as requirements for achieving good adhesion, but conventional plasma surface-treated sheets had the problem of unstable adhesive strength due to uneven surface modification. Furthermore, conventional plasma surface-treated sheets were only evaluated for the amount of functional groups in a very small area, so the variation across the entire sheet was not taken into consideration. Due to the above, it was not possible to achieve uniform adhesion to other materials, which led to issues such as peeling in later processes and reduced reliability of the board. Furthermore, when the sheet is in a roll form, problems may arise in the transportability of the roll and in the appearance of the roll.

[0019] The present inventors have found that, when surface-treating a fluororesin sheet material, improving the in-plane uniformity of the surface treatment can achieve uniform adhesion to metals such as copper foil. Furthermore, when the fluororesin sheet material is rolled, improving the in-plane uniformity of the surface treatment makes the fluororesin sheet material less likely to wrinkle, preventing shrinkage in width, improving the transportability of the roll, and improving the appearance of the roll. Furthermore, the long-term storage stability of the roll is also improved. It has also been clarified that, in order to obtain high adhesion to other materials, it is effective for the fluororesin sheet material to have specific properties in relatively small and large areas.It has also been clarified that, in the laminate having the fluororesin sheet material of the present disclosure and a metal layer, it is effective for the fluororesin sheet material to have specific properties in relatively small and large areas.

[0020] One of them concerns a relatively small area of ​​fluororesin sheet material and is as follows. (A) The sheet material containing the fluororesin of the present disclosure has, on at least one surface, When the oxygen element ratio is measured by scanning X-ray photoelectron spectroscopy (XPS) at 10 points in each of the vertical, horizontal, and diagonal directions of a 10 cm square sheet material, the average value (Avg.) of the oxygen element ratio is 1.35 atomic% or more in all directions, and (MAX-MIN) / Avg. is 40% or less. 10 vertical points: 1.5cm from the left edge, 1.5cm from the top, 10 points at 8mm intervals 10 horizontal points: 1.5 cm from the top edge, 1.5 cm from the left edge, 10 points at 8 mm intervals 10 points diagonally: In both the vertical and horizontal directions, from the bottom right corner of the sheet material, a straight line connecting the points on each side of 6.5 cm vertically and 6.5 cm horizontally is the long side, and on a straight line 5 mm above the long side of a rectangle with a short side of 1 cm, the first point is 1.5 cm from the top of the long side of the rectangle, and 10 points are placed at 8 mm intervals.

[0021] The specific positions of the 10 points in the vertical, horizontal, and diagonal directions of the 10 cm square fluororesin sheet material are outlined in Figure 1. In Figure 1, the black circles shown in the vertical, horizontal, and diagonal directions indicate the positions where the oxygen element ratio was measured by XPS.

[0022] The fluororesin sheet material (A) satisfying the above requirements ensures in-plane uniformity and exhibits good adhesion to metals such as copper foil. Furthermore, when the fluororesin sheet material is in the form of a roll, transportability is improved and the appearance of the roll is also improved.

[0023] The oxygen element ratios mentioned above were measured using a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.) The detection targets were carbon, oxygen, fluorine, nitrogen, and silicon, and the oxygen element ratio was determined from the composition ratios of C1s, O1s, F1s, N1s, and Si2p. The (MAX-MIN) / Avg. value is calculated using the maximum value (MAX), minimum value (MIN), and average value (Avg.) of the 10 measurement values ​​obtained above in the vertical, horizontal, and diagonal directions.

[0024] The average value (Avg.) of the oxygen element ratio is more preferably 1.5 atomic % or more, even more preferably 1.8 atomic % or more, and most preferably 2.0 atomic % or more. The upper limit of the average value (Avg.) of the oxygen element ratio is not particularly limited, but is preferably 25 atomic % or less, more preferably 20 atomic % or less, and even more preferably 15 atomic % or less. If the average value (Avg.) of the oxygen element ratio is within the above range, it is advantageous in that the amount of functional groups that contribute to adhesion is suitable.

[0025] Furthermore, the (MAX-MIN) / Avg. is preferably 40% or less, more preferably 30% or less, and even more preferably 20% or less. The lower limit of the (MAX-MIN) / Avg. is not particularly limited, but is preferably 3% or more, more preferably 4% or more, and even more preferably 5% or more. If (MAX-MIN) / Avg. is within the above range, there are no locations where the oxygen element ratio differs significantly, which is advantageous in that the surface treatment is uniform within the surface.

[0026] Furthermore, it is preferable that the average value (Avg.) of the oxygen element ratio is 1.35 atomic % or more and 20 atomic % or less, and the (MAX-MIN) / Avg. is 3% or more and 40% or less.

[0027] The present disclosure also relates to a laminate including the above-mentioned fluororesin sheet material and a metal layer. The laminate is preferably laminated so that the surface of the above-mentioned fluororesin sheet material that satisfies the oxygen element ratio requirement is in contact with the metal layer. In the fluororesin sheet material, if only one surface satisfies the oxygen element ratio requirement, it is preferable that this surface be in contact with the metal layer. In addition, in the fluororesin sheet material, if both surfaces satisfy the oxygen element ratio requirement, it is preferable that at least one surface be in contact with the metal layer. In the laminate (A1) comprising the fluororesin sheet material and the metal layer, it is preferable that the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer, obtained by 90-degree peel tests in each of the longitudinal direction, transverse direction and oblique direction, is σ / Avg.≦35% in any direction.

[0028] In the laminate (A2) comprising the fluororesin sheet material and the metal layer, it is preferable that the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer, obtained by 90-degree peel tests in each of the longitudinal direction, transverse direction and oblique direction, is (MAX-MIN) / Avg.≦150% in any direction.

[0029] Here, the adhesive strength is a value obtained by taking peel test samples (1 cm × 9 cm) from predetermined positions on the fluororesin sheet material in each of the vertical, horizontal, and diagonal directions as shown in FIG. 1, and using these samples to perform a 90-degree peel test on a laminate obtained as described below.

[0030] (90 degree peel test) (Method for preparing laminate) Using a fluororesin sheet material and metal foil, the metal foil, fluororesin sheet material, and metal foil are layered in that order, and heat-pressed in a vacuum heat press (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 200°C, a preheat time of 120 seconds, a pressure of 3 MPa, and a press time of 600 seconds to obtain a laminate. (Peel test method) In the peel test, one side of the laminate obtained by the above method was attached to an aluminum plate with adhesive tape, and a Tensilon universal testing machine (manufactured by Shimadzu Corporation) was used to measure the peel strength of the metal foil by grasping and pulling a 10 mm wide piece of metal foil in a direction 90° to the plane of the laminate at a speed of 50 mm per minute, and the obtained value was taken as the adhesive strength. For each laminate, the standard deviation of the adhesive strength in the section starting from 10 mm from the start of peeling to 40 mm, a total stroke distance of 30 mm, is defined as σ, the average as Avg., the maximum as MAX, and the minimum as MIN, and σ / Avg. and (MAX-MIN) / Avg. are calculated.

[0031] In this way, the adhesion between the surface of the fluororesin sheet material in the laminate that satisfies the above-mentioned oxygen element ratio characteristics and the metal layer is good, making it difficult to peel off, and the surface smoothness of the adhesive surface is maintained, so low transmission loss characteristics are maintained and the laminate has excellent properties when used as a circuit board.

[0032] The above σ / Avg. is preferably σ / Avg.≦35%, and more preferably σ / Avg.≦25%. The lower limit is not particularly limited, but is preferably 1%≦σ / Avg., and more preferably 3%≦σ / Avg. If σ / Avg. is within the above range, the in-plane adhesive strength will be stable and close to the value, which is advantageous for the stability of electrical properties when formed into a substrate.

[0033] Furthermore, the above (MAX-MIN) / Avg. is preferably (MAX-MIN) / Avg.≦150%, and more preferably (MAX-MIN) / Avg.≦100%. The lower limit is not particularly limited, but is preferably 3%≦(MAX−MIN) / Avg., and more preferably 5%≦(MAX−MIN) / Avg. If (MAX-MIN) / Avg. is within the above range, not only is the average value of the adhesive strength stable, but the range of variation in adhesive strength is also small, so that the in-plane adhesive strength is more stable and has a similar value, which is advantageous for the stability of the electrical properties when made into a substrate.

[0034] In the present disclosure, the laminate (A3) preferably satisfies both the requirements for σ / Avg. and (MAX-MIN) / Avg. of the adhesive strength. In the laminate (A3), the adhesive strength is preferably 1%≦σ / Avg.≦35% and 3%≦(MAX−MIN) / Avg.≦150%.

[0035] The laminates (A1) to (A3) of the present disclosure preferably have an adhesive strength of 0.5 N / cm or more in any direction. By adjusting the adhesive strength to more preferably 1 N / cm or more, even more preferably 2 N / cm or more, and most preferably 6 N / cm or more, the laminates can be suitably used as metal laminates or circuit boards. There is no particular upper limit, but for example, a strength of 20 N / cm or less can be suitably used as metal laminates or circuit boards. This adhesive strength is a value obtained by the above-mentioned peel test method.

[0036] Next, another parameter relates to a relatively large area of ​​the fluororesin sheet material, and is as follows: (B) On at least one surface of a sheet material containing a fluororesin, The specimen is divided into a horizontal (X) and b vertical (Y) sections every 10 cm, and the average value (Avg.) of the oxygen element ratio measured at the center of each divided section is 1.35 atomic% or more, and It is characterized by satisfying the following formulas (1) and (2). σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1 and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided region. The upper limit of ab is not particularly limited, and if ab≦1000, it can be said that the fluororesin sheet material satisfies the above-mentioned requirement.

[0037] One embodiment of a specific measurement method is shown in Fig. 2. Fig. 2 shows the case where a is 10 and b is 5. The oxygen element ratio was measured by XPS at the center of each 10cm square sheet material (marked with a black circle).

[0038] Here, the oxygen element ratio is a value measured using a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.) The detection targets are carbon, oxygen, fluorine, nitrogen, and silicon, and the oxygen element ratio is determined from the composition ratio of C1s, O1s, F1s, N1s, and Si2p.

[0039] In addition, in the above formula (1), σ(X1Y1-XaYb) / Avg.(X1Y1-XaYb) is a value calculated by taking the standard deviation obtained from the measured values ​​of the number of measurements n=a×b (number of measurements) as σ and the average value as Avg. for the oxygen element ratio measured at the center of each divided region. In the above formula (2), {MAX(X1Y1 to XaYb)-MIN(X1Y1 to XaYb)} / Avg.(X1Y1 to XaYb) is a value calculated by taking the maximum value obtained from the measured values ​​of the same number of measurements n=a×b (number of measurements) as above as MAX and the minimum value as MIN.

[0040] When the fluororesin sheet material (B) satisfies the above requirements in such a relatively large area of ​​the sheet material, the in-plane stability of the adhesiveness when it is laminated to a metal such as copper foil becomes better. Furthermore, when the fluororesin sheet material is in the form of a roll, transportability is improved and the appearance of the roll is also improved.

[0041] The average value (Avg.) of the oxygen element ratio is more preferably 1.5 atomic % or more, even more preferably 1.8 atomic % or more, and most preferably 2.0 atomic % or more. The upper limit of the average value (Avg.) of the oxygen element ratio is not particularly limited, but is preferably 25 atomic % or less, more preferably 20 atomic % or less, and even more preferably 15 atomic % or less. If the average value (Avg.) of the oxygen element ratio is within the above range, it is advantageous in that the amount of functional groups that contribute to adhesiveness is suitable.

[0042] In the above formula (1), it is preferable that σ(X1Y1 to XaYb) / Avg.(X1Y1 to XaYb)≦20% or less, and it is more preferable that σ(X1Y1 to XaYb) / Avg.(X1Y1 to XaYb)≦10%. The lower limit of the above σ(X1Y1-XaYb) / Avg.(X1Y1-XaYb) is not particularly limited, but is preferably 1%≦σ(X1Y1-XaYb) / Avg.(X1Y1-XaYb), and more preferably 3%≦σ(X1Y1-XaYb) / Avg.(X1Y1-XaYb). If σ(X1Y1-XaYb) / Avg.(X1Y1-XaYb) is within the above range, the in-plane oxygen element ratio is a stable and close value, which is advantageous for the stability of adhesive strength when laminated.

[0043] In addition, in the above formula (2), it is preferable that {MAX(X1Y1-XaYb)-MIN(X1Y1-XaYb)} / Avg.(X1Y1-XaYb)≦40% or less, and it is more preferable that {MAX(X1Y1-XaYb)-MIN(X1Y1-XaYb)} / Avg.(X1Y1-XaYb)≦20%. The lower limit of the above {MAX(X1Y1-XaYb)-MIN(X1Y1-XaYb)} / Avg.(X1Y1-XaYb) is not particularly limited, but is preferably 1%≦{MAX(X1Y1-XaYb)-MIN(X1Y1-XaYb)} / Avg.(X1Y1-XaYb), and more preferably 3%≦{MAX(X1Y1-XaYb)-MIN(X1Y1-XaYb)} / Avg.(X1Y1-XaYb). When {MAX(X1Y1-XaYb)-MIN(X1Y1-XaYb)} / Avg.(X1Y1-XaYb) is within the above range, not only is the average value of the oxygen element ratio stable, but the range of variation is also small, so that the in-plane oxygen element ratio is a more stable and closer value, which is advantageous for the in-plane stability of the adhesive strength when formed into a laminate.

[0044] Similarly to the laminate (A), the laminate (B) comprising the fluororesin sheet material (B) and a metal layer is preferably laminated so that the surface of the fluororesin sheet material that satisfies the oxygen element ratio requirement is in contact with the metal layer. In the fluororesin sheet material, when one surface satisfies the oxygen element ratio requirement, it is preferable that this surface be in contact with the metal layer. In the fluororesin sheet material, when both surfaces satisfy the oxygen element ratio requirement, it is preferable that at least one surface be in contact with the metal layer. In the laminate (B) of the fluororesin sheet material (B) and a metal layer, The sheet is divided into a section in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and within each 10 cm square area, a 90-degree peel test is carried out to measure the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer in the horizontal direction, vertical direction, and diagonal direction. It is preferable that the following formulas (3) and (4) be satisfied. σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb)≦35% (3) {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B(X1Y1~XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1 and satisfy the condition ab≧50. In this case, XaYb is the average of the average adhesive strength in three directions in the divided area corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y). Above Avg. B (X1Y1 to XaYb) indicate the further average values ​​(X1Y1, XaYb, etc.) of the average adhesive strength in three directions (horizontal, vertical, diagonal) in each 10 cm square area of ​​a × b (pieces). The upper limit of ab is not particularly limited, and if ab≦1000, the laminate can be said to satisfy the above requirement.

[0045] Here, the adhesive strength is a value obtained by taking peel test samples (1 cm × 9 cm) of the fluororesin sheet material in each of the vertical, horizontal, and diagonal directions in a 10 cm square area, as shown in FIG. 2, in the same positions as those for taking the peel test samples shown in FIG. 1, and using these samples to perform a 90-degree peel test on a laminate obtained as described below.

[0046] (90 degree peel test) (Method for preparing laminate) Using a fluororesin sheet material and metal foil, the metal foil, fluororesin sheet material, and metal foil are layered in that order, and heat-pressed in a vacuum heat press (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 200°C, a preheat time of 120 seconds, a pressure of 3 MPa, and a press time of 600 seconds to obtain a laminate. (Peel test method) In the peel test, one side of the laminate obtained by the above method was attached to an aluminum plate with adhesive tape, and a Tensilon universal testing machine (manufactured by Shimadzu Corporation) was used to measure the peel strength of the metal foil by grasping and pulling a 10 mm wide piece of metal foil in a direction 90° to the plane of the laminate at a speed of 50 mm per minute, and the obtained value was taken as the adhesive strength. For each laminate, the average value of adhesive strength is calculated in the section from 10 mm from the start of peeling to 40 mm, for a total stroke distance of 30 mm. The average adhesive strength values ​​obtained in the three directions (horizontal, vertical, and diagonal) are further averaged to obtain the average value (X1Y1, XaYb, etc.) for each divided area. The standard deviation of the "average adhesive strength within the area" for the number of measurements m = a × b (pieces) is σ B (X1Y1~XaYb), the average value is Avg. B (X1Y1~XaYb), maximum value is MAX B (X1Y1~XaYb), minimum is MIN B (X1Y1 to XaYb), and σ in the above formula (3) B (X1Y1~XaYb) / Avg. B (X1Y1 to XaYb) and {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B Calculate (X1Y1~XaYb).

[0047] In this way, by having a laminate that satisfies the above requirements over a relatively large area, the adhesion between the fluororesin sheet material and the metal layer is good over a wider range, making them less likely to peel off, thereby maintaining the surface smoothness of the adhesive surface and maintaining lower transmission loss characteristics, resulting in excellent properties when used as a circuit substrate.

[0048] In the above formula (3), σ B (X1Y1~XaYb) / Avg. B It is preferable that (X1Y1 to XaYb)≦35%, and σ B (X1Y1~XaYb) / Avg. B It is more preferable that (X1Y1 to XaYb)≦25%. The lower limit is not particularly limited, and is 1%≦σ B (X1Y1~XaYb) / Avg. B (X1Y1 to XaYb) is preferable, and 3%≦σ B (X1Y1~XaYb) / Avg.B It is more preferable that the group is (X1Y1 to XaYb). σ B (X1Y1~XaYb) / Avg. B If (X1Y1 to XaYb) are within the above range, the average value of the adhesive strength is stable over a wide range, which is advantageous in that defects such as peeling are unlikely to occur when the laminate is subsequently made into a substrate, regardless of the position from which the laminate is taken.

[0049] In addition, in the above formula (4), {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B It is preferable that (X1Y1 to XaYb)≦150%, and {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B It is more preferable that (X1Y1 to XaYb)≦100%. The lower limit is not particularly limited, and is 5%≦{MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B (X1Y1 to XaYb), and 10%≦{MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B It is more preferable that the group is (X1Y1 to XaYb). {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B If (X1Y1 to XaYb) are within the above range, not only is the average value of the adhesive strength stable over a wide range, but the range of variation in adhesive strength is also small, so that the in-plane adhesive strength is more stable and has similar values, which is advantageous for the stability of the electrical properties when the laminate is made into a substrate regardless of the position from which the laminate is sampled. In addition, the average value of "average adhesive strength within the area" (Avg. B (X1Y1 to XaYb)) is preferably 0.5 N / cm or more. The upper limit is not particularly specified, but may be, for example, 20 N / cm or less.

[0050] In the present disclosure, it is preferable to satisfy both of the above conditions (A) and (B). In the fluororesin sheet material of the present disclosure, it is preferable that at least one surface satisfies both the above conditions (A) and (B). Fluororesin sheet material (C) whose oxygen element ratio satisfies the above conditions (A) and (B) exhibits better adhesion between the fluororesin sheet material and metal. Furthermore, when the fluororesin sheet material is in roll form, it exhibits better transportability and improved appearance of the roll. Furthermore, the long-term storage stability of the roll is also improved. When the oxygen element ratio of the fluororesin sheet material (C) is measured on at least one surface by scanning X-ray photoelectron spectroscopy (XPS) at 10 points in each of the longitudinal, transverse and diagonal directions of a 10 cm square sheet material, the average value (Avg.) of the oxygen element ratio is 1.35 atomic% or more in all directions, and (MAX-MIN) / Avg. is 40% or less, Furthermore, the specimen is divided into a horizontal (X) and b vertical (Y) sections every 10 cm, and the average value (Avg.) of the oxygen element ratio measured at the center of each divided section is 1.35 atomic % or more, and The fluororesin sheet material satisfies the following formulas (1) and (2). σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1 and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided region. Furthermore, in the laminate of the present disclosure, by providing laminate (C) whose adhesive strength satisfies all of the above conditions (A) and (B), the in-plane adhesiveness becomes more uniform, which reduces peeling in later processes and leads to improved reliability of the substrate. The laminate (C) is a laminate including a fluororesin sheet material (C) and a metal layer, and the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by a 90-degree peel test in each of the longitudinal direction, transverse direction, and diagonal direction of a 10 cm square laminate is σ / Avg.≦35% and (MAX-MIN) / Avg.≦150% in all directions, Furthermore, the laminate is divided into a section in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and within each divided 10 cm square area, a 90-degree peel test is carried out to measure the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer in the horizontal direction, vertical direction, and diagonal direction, and the laminate satisfies the following formulas (3) and (4). σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb)≦35% (3) {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B (X1Y1~XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1 and ab≧50. In this case, XaYb is the average of the average adhesive strength in three directions in the divided area corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y).

[0051] The fluororesin sheet material having the above physical properties can be surface-treated by corona discharge, for example, using nitrogen gas, argon, and carbon dioxide gas as inert gases, and the carbon dioxide gas can be used to impart functional groups, thereby improving the in-plane uniformity of the surface treatment. Details of the surface treatment method will be described later.

[0052] (Fluorine resin) The fluororesin contained in the fluororesin sheet material of the present disclosure is not particularly limited as long as it is a resin containing fluorine, and any known fluororesin can be used. Among these, those made of tetrafluoroethylene (TFE)-perfluoro(alkyl vinyl ether) copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene (HFP) copolymer (FEP) are preferred.

[0053] (Per)fluoro(alkyl vinyl ether) (PAVE) may be either a fluoroalkyl vinyl ether or a perfluoro(alkyl vinyl ether). In the present disclosure, a "perfluoro(alkyl vinyl ether)" is an alkyl vinyl ether that does not contain a C-H bond. The PAVE constituting the PAVE unit is represented by the general formula (1): CF2=CFO(CF2CFY 1 O) p -(CF2CF2CF2O) q -R f (1) (In the formula, Y 1 represents F or CF3, and R f represents a perfluoroalkyl group having 1 to 5 carbon atoms, p represents an integer of 0 to 5, and q represents an integer of 0 to 5.) and a monomer represented by general formula (2): CFX=CXOCF2OR 1 (2) (wherein X may be the same or different and represents H, F or CF3; R 1 represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms which may contain 1 to 2 atoms of at least one type selected from the group consisting of H, Cl, Br and I, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms which may contain 1 to 2 atoms of at least one type selected from the group consisting of H, Cl, Br and I.

[0054] Among these, the PAVE is preferably a monomer represented by general formula (1), more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether) (PPVE), and even more preferably PPVE.

[0055] The content of PAVE units in the TFE / PAVE copolymer is preferably 1.0 to 10% by mass, more preferably 2.0% by mass or more, even more preferably 3.5% by mass or more, particularly preferably 4.0% by mass or more, most preferably 5.0% by mass or more, more preferably 8.0% by mass or less, even more preferably 7.0% by mass or less, particularly preferably 6.5% by mass or less, and most preferably 6.0% by mass or less, based on the total monomer units. 19 The TFE / PAVE copolymer may be a copolymer consisting of only TFE units and PAVE units.

[0056] When the fluororesin sheet material is made of a TFE / PAVE copolymer, the melting point is preferably 280 to 322°C, more preferably 290°C or higher, and more preferably 315°C or lower.

[0057] When the fluororesin sheet material is a TFE / PAVE copolymer, the glass transition temperature (Tg) is preferably 70 to 110° C., more preferably 80° C. or higher, and more preferably 100° C. or lower. The glass transition temperature is a value obtained by measuring dynamic viscoelasticity.

[0058] The TFE / HFP copolymer contains TFE units and HFP units. The content of the TFE units in the TFE / HFP copolymer is preferably 70% by mass or more, more preferably 85% by mass or more, and preferably 99.8% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less, based on the total monomer units.

[0059] The TFE / HFP copolymer preferably has a mass ratio (TFE / HFP) of TFE units to HFP units of 70 to 99 / 1 to 30 (mass %), more preferably 85 to 95 / 5 to 15 (mass %).

[0060] The TFE / HFP copolymer may further contain (per)fluoro(alkyl vinyl ether) (PAVE) units. Examples of PAVE units contained in the TFE / HFP copolymer include the same PAVE units as those described above. The TFE / PAVE copolymer does not contain HFP units, and in this respect, it differs from the TFE / HFP / PAVE copolymer.

[0061] When the TFE / HFP copolymer is a copolymer containing TFE units, HFP units, and PAVE units (hereinafter also referred to as "TFE / HFP / PAVE copolymer"), the mass ratio (TFE / HFP / PAVE) is preferably 70-99.8 / 0.1-25 / 0.1-25 (mass%). The mass ratio (TFE / HFP / PAVE) is more preferably 75-98 / 1.0-15 / 1.0-10 (mass%). The TFE / HFP / PAVE copolymer preferably contains 1 mass% or more of HFP units and PAVE units in total relative to all monomer units.

[0062] In the TFE / HFP / PAVE copolymer, the HFP unit preferably accounts for 25% by mass or less of the total monomer units. The content of HFP units is more preferably 20% by mass or less, even more preferably 18% by mass or less, and particularly preferably 15% by mass or less. The content of HFP units is preferably 0.1% by mass or more, more preferably 1% by mass or more, and particularly preferably 2% by mass or more. The content of HFP units is 19 It can be measured by F-NMR.

[0063] The content of PAVE units is more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 3% by mass or less. The content of PAVE units is preferably 0.1% by mass or more, more preferably 1% by mass or more. The content of PAVE units is 19 It can be measured by F-NMR.

[0064] The TFE / PAVE copolymer and the TFE / HFP copolymer may further contain other ethylenic monomer (α) units. The other ethylenic monomer (α) units are not particularly limited as long as they are monomer units copolymerizable with TFE, HFP, and PAVE, and examples thereof include fluorine-containing ethylenic monomers such as vinyl fluoride (VF), vinylidene fluoride (VdF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE), as well as non-fluorinated ethylenic monomers such as ethylene, propylene, and alkyl vinyl ethers. The content of the other ethylenic monomer (α) units is preferably 0 to 25% by mass, more preferably 0.1 to 25% by mass.

[0065] When the copolymer is a TFE / HFP / PAVE / other ethylenic monomer (α) copolymer, the mass ratio (TFE / HFP / PAVE / other ethylenic monomer (α)) is preferably 70-98 / 0.1-25 / 0.1-25 / 0.1-25 (mass%). The TFE / HFP / PAVE / other ethylenic monomer (α) copolymer preferably contains 1 mass% or more of monomer units other than TFE units in total.

[0066] The melting point of the TFE / HFP copolymer is preferably 200 to 322°C, more preferably over 200°C, even more preferably 220°C or higher, more preferably 300°C or lower, and even more preferably 280°C or lower.

[0067] The glass transition temperature (Tg) of the TFE / HFP copolymer is preferably 60 to 110° C., more preferably 65° C. or higher, and more preferably 100° C. or lower. The glass transition temperature is a value obtained by measuring dynamic viscoelasticity.

[0068] The fluororesin can be produced by a conventionally known method, for example, by appropriately mixing monomers that constitute the fluororesin and additives such as a polymerization initiator, followed by emulsion polymerization or suspension polymerization, etc. Among these, the fluororesin obtained by emulsion polymerization is more preferred.

[0069] The fluororesin preferably has a melt flow rate of 1 to 50 g / 10 min at 372° C. and a load of 49 N.

[0070] The fewer functional groups the fluororesin has, the fewer unstable terminal groups it has. Such fluororesins can be produced by adjusting the conditions during production (polymerization reaction), or by subjecting the fluororesin after polymerization to fluorine gas treatment, heat treatment, supercritical gas extraction, or other methods to reduce the number of unstable terminal groups. Fluorine gas treatment is preferred because it has excellent treatment efficiency and converts some or all of the unstable terminal groups to —CF3, resulting in stable terminal groups. The use of a fluororesin with a reduced number of unstable terminal groups is preferred because it reduces the electrostatic dissipation factor and reduces electrical signal loss.

[0071] The number of unstable terminal groups is not particularly limited, but is preferably 10 or more when the main chain carbon number of the fluororesin is 10. 6 The number per particle is preferably 450 or less, more preferably 250 or less, even more preferably 100 or less, and most preferably 50 or less. In consideration of the effect of reducing the dielectric loss tangent, the number per particle is preferably less than 10, and more preferably 5 or less.

[0072] Specific examples of unstable terminal groups include functional groups such as -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), hydroxyl groups (such as -CHOH), -CONH, -COOR (such as R = CH), -CFH, and -OCOO-R (such as normal propyl carbonate).

[0073] Specifically, the number of unstable terminal groups is measured by the following method. First, the fluororesin is melted and compression molded to produce a film with a thickness of 0.25 to 0.3 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain an infrared absorption spectrum of the fluororesin, and a difference spectrum is obtained from the base spectrum, which is completely fluorinated and has no functional groups. From the absorption peaks of specific functional groups that appear in this difference spectrum, the number of carbon atoms in the fluororesin is calculated according to the following formula (A): 6 The number of unstable terminal groups per unit is calculated. N=I×K / t (A) I: Absorbance K: Correction coefficient t: film thickness (mm)

[0074] For reference, the absorption frequencies, molar absorption coefficients, and correction coefficients for the unstable terminal groups in this specification are shown in Table 1. The molar absorption coefficients were determined from FT-IR measurement data of low molecular weight model compounds.

[0075] [Table 1]

[0076] The fluorination treatment can be carried out by contacting a non-fluorination-treated fluororesin with a fluorine-containing compound.

[0077] The fluorine-containing compound is not particularly limited, but examples thereof include fluorine radical sources that generate fluorine radicals under fluorination treatment conditions, such as F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and halogen fluorides (e.g., IF5, ClF3).

[0078] The fluorine radical source such as F2 gas may be 100% concentrated, but is preferably mixed with an inert gas and diluted to 5 to 50 mass %, more preferably 15 to 30 mass %. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, with nitrogen gas being preferred from an economical standpoint.

[0079] The conditions for the fluorination treatment are not particularly limited, and the molten fluororesin may be brought into contact with the fluorine-containing compound, but the treatment is usually carried out at a temperature below the melting point of the fluororesin, preferably 20 to 220°C, and more preferably 100 to 200°C. The fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 25 hours. The fluorination treatment is preferably carried out by bringing an unfluorinated fluororesin into contact with fluorine gas (F2 gas).

[0080] In this specification, the content of each monomer unit constituting the fluororesin can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer.

[0081] The fluororesin sheet material of the present disclosure may contain components other than the fluororesin. The components that can be contained are not particularly limited, and examples include fillers such as silica particles and short glass fibers, and fluorine-free thermosetting resins and thermoplastic resins. The content of components other than the fluororesin is not particularly limited, but is preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0082] The fluororesin sheet material of the present disclosure preferably has a thickness of 1 to 100 μm. The upper limit is more preferably 50 μm or less, and even more preferably 30 μm or less. The lower limit is more preferably 3 μm or more, and even more preferably 5 μm or more.

[0083] The thickness of the fluororesin sheet material is a value measured by reflection spectroscopy using a film thickness measurement system F20 (manufactured by Filmetrics).

[0084] 30 μm of the fluororesin sheet material of the present disclosure 2 The arithmetic mean roughness (Ra) in the above formula is preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 15 nm or less. The lower limit is not particularly limited, but is preferably 5 nm or more. If the Ra is within the above range, the raw sheet itself has high smoothness, which is preferable in that the surface treatment can be carried out more uniformly within the surface. The above Ra is a value obtained by an atomic force microscope (AFM).

[0085] Furthermore, in the fluororesin sheet material of the present disclosure, the difference between the oxygen element ratio when the surface state of the fluororesin-containing layer is measured by a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) and the oxygen element ratio when the fluororesin-containing layer is etched in the depth direction with an argon gas cluster ion beam at an incident angle of 45° for 15 minutes and then measured by a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) is preferably 1.0 atomic % or more. The greater the difference in oxygen element ratio from the surface to the depth direction, the more preferable it is in that a predetermined transmission loss can be obtained while maintaining adhesiveness.

[0086] The oxygen element ratio after etching is the oxygen element ratio on the surface of the fluororesin sheet that is the raw material for the fluororesin-containing layer before the surface treatment, and therefore the difference in the oxygen element ratio represents the increase in the oxygen element ratio due to the surface treatment.

[0087] The fluororesin sheet material preferably has an adhesive strength of more than 30 N / m on one or both sides when the sheet materials are bonded together in the same plane at 200° C. By having such an adhesive strength, the fluororesin sheet material will have excellent adhesiveness when used in combination with various other substrates, even after being heat-treated, and the adhesive strength is more preferably more than 50 N / m, and even more preferably more than 100 N / m.

[0088] More specifically, the adhesive strength was measured by overlapping the surface-treated surfaces of two fluororesin sheet materials together and heat pressing (200°C, 0.1 MPa, 60 s) to create a sample, cutting it into 10 mm wide strips, and using a precision universal testing machine, Autograph AGS-X 100N (Shimadzu Corporation), the unbonded part of the strip sample was gripped between the top and bottom chucks of the Autograph and pulled at a rate of 100 mm per minute to measure the peel strength, and the value obtained was taken as the adhesive strength.

[0089] The fluororesin sheet material of the present disclosure preferably has a dielectric loss tangent at 10 GHz of less than 0.0015. A dielectric loss tangent within this range is advantageous in that it can minimize loss of electrical signals in circuits. The dielectric loss tangent is more preferably less than 0.0013, even more preferably less than 0.0010, and most preferably 0.00050 or less. Furthermore, assuming that signal transmission and antenna transmission / reception will be performed at higher frequencies, the dielectric loss tangent at 40 GHz is preferably less than 0.0015, more preferably less than 0.0013, even more preferably less than 0.0010, and most preferably 0.00050 or less. In order to keep the dielectric loss tangent within the above range, it is preferable to use a resin with few unstable terminal groups, and it is more preferable to use a fluororesin that has been subjected to a terminal fluorination treatment.

[0090] (long sheet) The fluororesin sheet material of the present disclosure is preferably a long sheet. A continuously produced long sheet is particularly preferable from the viewpoint of production costs. The long sheet preferably has a width of 200 mm or more. Furthermore, the length is preferably 1 m or more. When the long sheet is rolled, the above-mentioned effects can be obtained.

[0091] (Method of manufacturing fluororesin sheet material) An example of a method for producing the fluororesin sheet material of the present disclosure will be described in detail below. Note that the fluororesin sheet material of the present disclosure is not limited to those produced by the following production method. The fluororesin sheet material of the present disclosure is not particularly limited in the molding method for forming it into a sheet, but examples include melt molding such as extrusion molding, and a casting method in which a solution or dispersion containing a fluororesin is prepared, then coated on a substrate and dried. Furthermore, the sheet may be uniaxially or biaxially stretched, or may be an unstretched sheet. Furthermore, the fluororesin sheet material may have a laminated structure partially including a fluororesin layer.

[0092] The fluororesin sheet material obtained by this method can be made into a fluororesin sheet material that satisfies the above requirements by performing a surface treatment on one or both sides under appropriate conditions.

[0093] The specific method for the surface modification is not particularly limited, but specific examples are described in detail below. The surface of the fluororesin sheet material can be modified by conventional discharge treatments such as corona discharge treatment, glow discharge treatment, plasma discharge treatment, and sputtering treatment. For example, the surface free energy can be controlled by introducing oxygen gas, nitrogen gas, hydrogen gas, carbon dioxide gas, methane gas, ethylene gas, etc. into the discharge atmosphere. Alternatively, the surface to be modified can be exposed to an atmosphere of an organic compound-containing inert gas, which is an inert gas containing an organic compound, and a high-frequency voltage is applied between the electrodes to generate an electric discharge, thereby generating active species on the surface. The surface can then be modified by introducing functional groups of the organic compound or graft-polymerizing a polymerizable organic compound. Examples of the inert gas include nitrogen gas, helium gas, and argon gas.

[0094] It is particularly preferable to use nitrogen gas and argon gas in combination, and it is further preferable to use carbon dioxide gas. The ratio (by volume) of nitrogen gas to argon gas is preferably 30 / 70 to 100 / 0, more preferably 40 / 60 to 95 / 5, and even more preferably 50 / 50 to 90 / 10. If the ratio of nitrogen gas to argon gas is within the above range, the discharge is stable, which is advantageous in that more uniform in-plane surface modification can be achieved. The carbon dioxide gas content is preferably 0.05 to 5% by volume, more preferably 0.25 to 2% by volume, relative to the nitrogen gas / argon gas. If the carbon dioxide content is within the above range, it is advantageous in that functional groups that contribute to adhesiveness on the surface of the fluororesin sheet material are imparted within a suitable range.

[0095] Examples of the organic compound in the organic compound-containing inert gas include polymerizable or non-polymerizable organic compounds containing oxygen atoms, such as vinyl esters such as vinyl acetate and vinyl formate; acrylic esters such as glycidyl methacrylate; ethers such as vinyl ethyl ether, vinyl methyl ether, and glycidyl methyl ether; carboxylic acids such as acetic acid and formic acid; alcohols such as methyl alcohol, ethyl alcohol, phenol, and ethylene glycol; ketones such as acetone and methyl ethyl ketone; carboxylic esters such as ethyl acetate and ethyl formate; and acrylic acids such as acrylic acid and methacrylic acid. Among these, vinyl esters, acrylic esters, and ketones are preferred because the modified surface is less likely to be deactivated, i.e., has a long life, and is easy to handle. Vinyl acetate and glycidyl methacrylate are particularly preferred.

[0096] The concentration of the organic compound in the organic compound-containing inert gas varies depending on the type of the organic compound, the type of fluororesin to be surface-modified, etc., but is usually 0.1 to 3.0% by volume, preferably 0.1 to 1.0% by volume, more preferably 0.15 to 1.0% by volume, and even more preferably 0.30 to 1.0% by volume. The discharge conditions can be selected appropriately depending on the desired degree of surface modification, the type of fluororesin, the type and concentration of organic compounds, etc. The discharge rate is usually 50 to 1500 W·min / m 2 , preferably 70W·min / m 2 More than 1400W min / m 2 Discharge treatment is carried out within the following range. The treatment temperature can be any temperature within the range of 0°C to 100°C. Due to concerns about stretching and wrinkling of the fluororesin sheet material, it is preferable to keep the temperature below 80°C. Considering that oxygen elements on the surface are deactivated by heat applied during lamination with metal foil or the like, and adhesive ability is reduced, the degree of surface modification of the fluororesin sheet material is such that the abundance ratio of oxygen elements observed by ESCA is 1.5% or more, preferably 1.75% or more, more preferably 2.0% or more, and even more preferably 2.5% or more. There is no particular upper limit, but in consideration of the effect on productivity and other physical properties, it is preferably 25.0% or less. The abundance ratio of the nitrogen element is not particularly limited, but it is preferably 0.1% or more.

[0097] In the above surface modification, it is preferable to carry out discharge treatment with a discharge intensity, which indicates the output per unit area, in the range of 1.0 to 10 W / cm2, and to adjust the gas concentration / line speed ratio in the range of 0.005 to 0.05 L / m. The gas concentration / line speed ratio referred to here indicates the ratio obtained by dividing the organic compound concentration in the organic compound-containing inert gas by the line speed. If the flow rate is lower than 0.005 L / m, the space will not be filled with enough gas relative to the conveying speed, making it difficult for the activated gas to contact the surface of the fluororesin sheet material, resulting in reduced in-plane uniformity. If the flow rate is higher than 0.05 L / m, the surface will be over-treated and damaged, resulting in the formation of low-molecular-weight compounds on the surface, forming a brittle layer and actually reducing adhesive strength. Therefore, treatment within this range is particularly preferred, as it is believed that the in-plane treatment of the fluororesin sheet material will be more uniform and the desired adhesiveness will be obtained.

[0098] Furthermore, in the above-mentioned method, it is preferable that the difference between the oxygen element ratio when the surface condition of one or both sides of the fluororesin sheet material is measured by a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) and the oxygen element ratio when the fluororesin-containing layer is etched in the depth direction with an argon gas cluster ion beam at an incident angle of 45° for 15 minutes and then measured by a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) is 1.0 atomic % or more.

[0099] The fluororesin sheet material surface-treated by the above method may be annealed to remove residual stress in advance. This reduces dimensional changes in the fluororesin sheet material due to heat from the pressure roll during the process of laminating it with metal foil to produce a laminate, allowing it to be bonded without wrinkles, thereby suppressing poor appearance of the laminate. Because these heat treatments reduce the amount of oxygen on the surface of the fluororesin sheet material, it is preferable to perform surface modification under conditions that ensure a sufficient amount of surface oxygen at the time the fluororesin sheet material and metal foil are bonded together.

[0100] The annealing treatment can be carried out by heat treatment. The heat treatment can be carried out, for example, by passing the material through a heating furnace using a roll-to-roll method. The heat treatment can also be carried out by placing the material in a batch-type drying furnace.

[0101] The annealing temperature is preferably at least 20° C. below the glass transition temperature of the fluororesin and less than the melting point, more preferably at least 20° C. above the glass transition temperature of the fluororesin and less than the melting point, and even more preferably at least 60° C. above the glass transition temperature of the fluororesin and less than the melting point. The annealing time is not particularly limited, but may be adjusted as appropriate within the range of, for example, 0.5 to 60 minutes.

[0102] When heating is performed by the roll-to-roll method, the tension may be adjusted as appropriate depending on the thickness of the fluororesin sheet material, the set temperature, etc., but is preferably 20 N / m or less. Heating under such conditions is preferable in that it can sufficiently relieve internal stress and does not cause dimensional changes, etc.

[0103] The order of the surface treatment and annealing treatment is not particularly limited, and the number of times each step is performed is not limited to one, but each step may be performed two or more times.

[0104] (Laminate) The present disclosure also provides a laminate comprising a fluororesin sheet material and a metal layer, which satisfies the above requirements.

[0105] (metal layer) In the present disclosure, examples of metals constituting the metal layer include copper, aluminum, SUS, nickel, and gold. Alloys of these metals can also be used. From the viewpoints of electrical conductivity and circuit processability, it is preferable to use copper foil.

[0106] The copper foil preferably has an Rz of 1.5 μm or less. That is, the fluororesin sheet material of the present disclosure also has excellent adhesion to copper foil, which has a high smoothness of Rz of 1.5 μm or less. Furthermore, it is sufficient for at least the surface of the copper foil that adheres to the fluororesin sheet material described above to have an Rz of 1.5 μm or less, and the Rz value of the other surface is not particularly limited. The Rz is the sum of the highest point (maximum peak height: Rp) and the deepest point (maximum valley depth: Rv). The surface roughness is the ten-point average roughness specified in JIS-B0601. In this specification, the Rz is a value measured using a surface roughness meter (product name: Surfcom 470A, manufactured by Tokyo Seiki Co., Ltd.) with a measurement length of 4 mm.

[0107] The thickness of the copper foil is not particularly limited, but is preferably in the range of 1 to 100 μm, more preferably in the range of 5 to 50 μm, and even more preferably in the range of 9 to 35 μm.

[0108] The copper foil is not particularly limited, and specific examples include rolled copper foil and electrolytic copper foil.

[0109] The copper foil having an Rz of 1.5 μm or less is not particularly limited, and commercially available products can be used. Examples of commercially available copper foils having an Rz of 1.5 μm or less include electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.).

[0110] The copper foil may be surface-treated to enhance the adhesive strength with the fluororesin sheet material of the present disclosure.

[0111] The surface treatment is not particularly limited, but may be a silane coupling treatment, plasma treatment, corona treatment, UV treatment, electron beam treatment, or the like. The reactive functional group of the silane coupling agent is not particularly limited, but from the viewpoint of adhesion to the fluororesin sheet material, it is preferable that the reactive functional group has at least one selected from an amino group, a (meth)acrylic group, a mercapto group, and an epoxy group at the terminal. Furthermore, the hydrolyzable group is not particularly limited, but may include alkoxy groups such as a methoxy group and an ethoxy group. The copper foil used in the present disclosure may have a rust-preventive layer (such as an oxide film such as chromate), a heat-resistant layer, or the like formed thereon.

[0112] The surface-treated copper foil having a surface treatment layer of the above-mentioned silane compound on the copper foil surface can be produced by preparing a solution containing the silane compound and then surface treating the copper foil with this solution.

[0113] The copper foil may have a roughened layer on the surface thereof from the viewpoint of improving adhesion to the fluororesin sheet material. If the roughening treatment is likely to degrade the performance required in the present disclosure, the amount of roughening particles electrodeposited on the copper foil surface may be reduced as needed, or the roughening treatment may not be performed at all.

[0114] Between the copper foil and the surface treatment layer, one or more layers selected from the group consisting of a heat-resistant treatment layer (nickel plating, titanium plating, etc.), a rust-proofing treatment layer, and a chromate treatment layer may be provided in order to improve various properties. These layers may be a single layer or multiple layers.

[0115] (Layer structure of laminate) The laminate of the present disclosure may have a two-layer structure consisting of the above-mentioned fluororesin sheet material and a metal layer, or may have a three-layer or more structure having two or more layers of either or both of these.Furthermore, it may have a three-layer or more structure having a layer (X) other than the fluororesin sheet material and the metal layer. As described above, the laminate of the present disclosure is preferably laminated so that the surface of the fluororesin sheet material that satisfies the oxygen element ratio requirement is in contact with the metal layer. In the fluororesin sheet material, if only one surface satisfies the oxygen element ratio requirement, it is preferable that this surface be in contact with the metal layer. Furthermore, in the fluororesin sheet material, if both surfaces satisfy the oxygen element ratio requirement, it is preferable that at least one surface be in contact with the metal layer.

[0116] Examples of the layer (X) other than the fluororesin sheet material and the metal layer include polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, etc. Examples of the thermosetting resin include those containing epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, polybutadiene, etc.

[0117] When the laminate of the present disclosure has the layer (X), the layer structure can be metal / fluororesin sheet material / layer (X). A laminate of fluororesin sheet material / metal may be provided on one or both sides of layer (X). In the present disclosure, it is preferable to provide a layer (X) on the surface of the fluororesin sheet material.

[0118] (Method of manufacturing laminate) The method for producing the laminate of the present disclosure is described in detail below. To obtain the laminate of the present disclosure, it is preferable that the metal foil used as the material has high smoothness, and further that the conditions in the step of bonding it to the fluororesin sheet material are adjusted.

[0119] Heating is required when bonding the metal foil and the fluororesin sheet material, and in producing the laminate of the present disclosure, the heating temperature is preferably 100 to 280° C., more preferably 200 to 280° C., and even more preferably 220 to 280° C. The heat treatment step may be a roll-to-roll lamination method, or a method in which a fluororesin coated on a metal foil is heat-treated. That is, by using a low heating temperature, the smoothness of the bonding surface is not significantly impaired in the process of bonding the metal foil and the fluororesin sheet material, which is preferable.

[0120] In producing the laminate of the present disclosure, the method for bonding the metal foil and the fluororesin sheet material is not particularly limited, but from the viewpoint of excellent production efficiency, a roll-to-roll lamination method is particularly preferred.

[0121] The roll-to-roll method is also preferable in that it reduces costs and allows a long laminate to be obtained. When producing a laminate by such a method, the width of the laminate is not particularly limited, but is preferably 200 mm or more.

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

[0123] In addition, in the case of a laminate in which a metal foil is adhered to the surface-treated surface of a fluororesin sheet material that has been surface-treated on only one side, the surface of the fluororesin sheet material that has not been surface-treated may be separately surface-modified in order to improve the adhesion between the laminate and other materials.

[0124] In this disclosure, the term "high-frequency circuit" refers not only to a circuit that simply transmits only high-frequency signals, but also to a circuit that also includes a transmission line that converts a high-frequency signal into a low-frequency signal and outputs the generated low-frequency signal to the outside, a transmission line for supplying power to drive high-frequency compatible components, and other transmission lines that transmit signals other than high-frequency signals, all of which are installed on the same plane.The circuit can also be used as a circuit board for an antenna, a filter, etc. [Example]

[0125] The present disclosure will be specifically described below based on examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass", respectively.

[0126] Example 1 [Method of manufacturing fluororesin sheet material] PFA was charged into an extruder at 360°C, extruded through a 1700mm wide T-die, taken up onto a metal cooling roll, and then wound around a winding core to obtain a roll sheet 1300mm wide and 12µm thick. The PFA is a TFE / PPVE copolymer, composition: TFE / PPVE=95.4 / 4.6 (mass%), MFR: 15.8 g / 10 min, melting point: 305°C, number of unstable terminal groups: main chain carbon number 10 6 297 pieces per piece were used. [Surface treatment] The rolled fluororesin sheet material was subjected to surface treatment on both sides (a corona discharge device). An inert gas containing 0.50% by volume of vinyl acetate and 0.5% by volume of carbon dioxide (nitrogen / Ar ratio 95 / 5) was passed around the discharge electrode and rolled ground electrode of the corona discharge device. The sheet was passed continuously along the rolled ground electrode, and a discharge rate of 400 W·min / m was achieved. 2 Both sides of the fluororesin sheet material were subjected to corona discharge (at 1000 W), and the long fluororesin sheet material was wound into a roll to obtain a surface-treated sample, which was then evaluated.

[0127] Example 2 Discharge amount 100W min / m 2A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed, and then the sample was evaluated.

[0128] Example 3 Fluorine resin: Fluorinated PFA1 (TFE / PPVE copolymer, composition: TFE / PPVE = 94.1 / 5.9 (mass%), MFR: 16.2 g / 10 min, melting point: 301 °C, number of unstable terminal groups: undetectable (main chain carbon number 10 6 The nitrogen / Ar ratio was 85 / 15, carbon dioxide was 1.0% by volume, and the discharge rate was 100 W min / m. 2 A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed, and then the sample was evaluated.

[0129] Example 4 Fluorine resin: Fluorinated PFA1 (TFE / PPVE copolymer, composition: TFE / PPVE = 94.1 / 5.9 (mass%), MFR: 16.2 g / 10 min, melting point: 301 °C, number of unstable terminal groups: undetectable (main chain carbon number 10 6 The nitrogen / Ar ratio was 85 / 15, carbon dioxide was 1.0% by volume, and the discharge rate was 300 W·min / m 2 A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed, and then the sample was evaluated.

[0130] Example 5 Fluorine resin: Fluorinated PFA2 (TFE / PPVE copolymer, composition: TFE / PPVE = 96.1 / 3.9 (mass%), MFR: 16.2 g / 10 min, melting point: 301 °C, number of unstable terminal groups: undetectable (main chain carbon number 10 6 The nitrogen / Ar ratio was 85 / 15, carbon dioxide was 1.0% by volume, and the discharge rate was 300 W·min / m 2 A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed, and then the sample was evaluated.

[0131] (Comparative Example 1) The nitrogen / Ar ratio was set to 100 / 0, no carbon dioxide was added, and the discharge rate was 45 W·min / m 2A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were met, and then the sample was evaluated.

[0132] (Comparative Example 2) The nitrogen / Ar ratio was 100 / 0, vinyl acetate was not added, and the discharge rate was 200 W·min / m 2 A surface-treated sample was obtained in the same manner as in Example 1, except that the above-mentioned conditions were met, and then the sample was evaluated.

[0133] (Method for measuring oxygen element ratio) (A) The above surface-treated fluororesin sheet material was cut into 10 cm squares, and the oxygen element ratio was measured on one side of the cut-out fluororesin sheet material at 10 points in each of the vertical, horizontal, and diagonal directions as shown in Figure 1, using the method described below. To avoid the effects of the heat press, 10cm square pieces of fluororesin sheet material were cut out in advance to obtain 1x9cm samples for the peel test in the vertical, horizontal, and diagonal directions, and the remaining fluororesin sheet material was used to measure the oxygen element ratio. Furthermore, if the measurement points can be set at the measurement positions specified below by marking or other methods, the material may be cut to an appropriate size to fit on the XPS sample stage. 10 vertical points: 1.5cm from the left edge, 1.5cm from the top, 10 points at 8mm intervals 10 horizontal points: 1.5 cm from the top edge, 1.5 cm from the left edge, 10 points at 8 mm intervals 10 points diagonally: From the bottom right corner of the fluororesin sheet material in both the vertical and horizontal directions, a straight line connecting the points on each side of the material is taken as the long side, and the short side is taken as 1 cm. On a straight line 5 mm above the long side of the rectangle, the first point is taken as 1.5 cm from the top of the long side of the rectangle, and 10 points are taken at 8 mm intervals.

[0134] The oxygen element ratio on the surface of the surface-treated fluororesin sheet material was measured under the conditions below using a scanning X-ray photoelectron spectrometer (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.) The detection targets were carbon, oxygen, fluorine, nitrogen, and silicon, and the oxygen element ratio was calculated from the composition ratio of C1s, O1s, F1s, N1s, and Si2p. Source: Monochromated AlKα Beam diameter: 100 μm X-ray output: 25W Measurement area: 1000μm x 300μm Pass energy: 23.5 eV Detection angle: 45°

[0135] In addition, (MAX-MIN) / Avg. was calculated using the maximum value (MAX), minimum value (MIN), and average value (Avg.) of the 10 measurement values ​​obtained in each of the vertical, horizontal, and diagonal directions.

[0136] (B) As shown in FIG. 2, the fluororesin sheet material was divided into 10 sections in the horizontal direction (X) and 5 sections in the vertical direction (Y) at 10 cm intervals, and the oxygen element ratio was measured at the center of each divided area on the surface measured in (A) above by the above method. As in (A) above, to avoid the influence of the heat press, 10 cm square samples for peel test were cut out in advance from each fluororesin sheet material in the vertical, horizontal, and diagonal directions, and the oxygen element ratio was measured using the remaining fluororesin sheet material. For the oxygen element ratio measured at the center of each divided region, σ(X1Y1~X10Y5) / Avg.(X1Y1~X10Y5) was calculated by taking the standard deviation obtained from 50 measurements as σ and the average value as Avg. In addition, the maximum value obtained from the same 50 measurements as above was defined as MAX, and the minimum value was defined as MIN, and {MAX(X1Y1 to X10Y5)-MIN(X1Y1 to X10Y5)} / Avg.(X1Y1 to X10Y5) was calculated.

[0137] (90 degree peel test method) (A) [Method of manufacturing laminate for peel test] A fluororesin sheet material and electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) were used, and the copper foil, fluororesin sheet material, and copper foil were layered in this order, with the unroughened side of the copper foil in contact with the fluororesin sheet material and the inner surface of the fluororesin sheet material after surface treatment facing up. A laminate was obtained by heat pressing in a vacuum heat press (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 200°C, a preheat time of 120 seconds, a pressure of 3 MPa, and a press time of 600 seconds. Specifically, the 1 cm x 9 cm peel test samples obtained above in the vertical, horizontal, and diagonal directions were arranged on top of copper foil cut to 3 cm x 12 cm so as not to overlap, and then copper foil cut to 3 cm x 12 cm was placed on top of them and hot pressed to obtain a laminate.

[0138] [Peel test method] The laminate obtained above was divided into three pieces, and laminates (1 cm x 12 cm) for peel test were taken from each direction.

[0139] An aluminum plate was attached to the underside of the laminate for the peel test with adhesive tape, and a Tensilon universal testing machine (manufactured by Shimadzu Corporation) was used to measure the peel strength of the copper foil by gripping and pulling a 10 mm wide piece of copper foil in a direction 90° to the plane of the laminate at a speed of 50 mm per minute, and the obtained value was taken as the adhesive strength.

[0140] For the laminates used in the peel test in each direction, the standard deviation of the adhesive strength in the section from 10 mm from the start of peeling to 40 mm, a total stroke distance of 30 mm, was defined as σ, the average as Avg., the maximum as MAX, and the minimum as MIN, and σ / Avg. and (MAX-MIN) / Avg. were calculated.

[0141] (B) Using the same method as in (A) above, laminates (1 cm x 12 cm) for peel test in three directions were taken from each divided area.

[0142] One side of the laminate for the peel test was attached to an aluminum plate with adhesive tape, and a Tensilon universal testing machine (manufactured by Shimadzu Corporation) was used to measure the peel strength of the copper foil by grasping and pulling a 10 mm wide piece of copper foil in a direction 90° to the plane of the laminate at a speed of 50 mm per minute, and the obtained value was taken as the adhesive strength.

[0143] For the laminate for peel test in each direction, the average value of adhesive strength was calculated in the section from 10 mm from the start of peeling to 40 mm, a total stroke distance of 30 mm. The average values ​​of the obtained adhesive strengths in the three directions (horizontal, vertical and diagonal directions) were further averaged to obtain the "average adhesive strength value within each divided region." "Average adhesive strength within the area" Standard deviation of 50 (pieces) is σ B (X1Y1~X10Y5), the average value is Avg. B (X1Y1~X10Y5), maximum value is MAX B (X1Y1~X10Y5), minimum value is MIN B (X1Y1~X10Y5), and σ B (X1Y1~X10Y5) / Avg. B (X1Y1~X10Y5) and {MAX B (X1Y1~X10Y5)-MIN B (X1Y1~X10Y5)} / Avg. B (X1Y1~X10Y5) was calculated.

[0144] (Method for evaluating transportability) In the surface treatment process of a 500mm wide fluororesin sheet material, the appearance after passing through the electrodes was judged according to the following definitions. ○…The width of the fluororesin sheet material on the transport roll during transport is reduced by 1 mm or less △: The width of the fluororesin sheet material on the transport roll shrinks by more than 1 mm and less than 2 mm during transport. ×…The width of the fluororesin sheet material on the transport roll shrinks by 2 mm or more during transport

[0145] (Roll appearance evaluation method) The appearance of the 500mm wide surface-treated fluororesin sheet material in roll form was visually judged according to the following definitions. ○: Three or fewer wrinkles along the outer circumference of the roll △: 5 or less wrinkles along the outer circumference of the roll ×: Six or more wrinkles along the outer circumference of the roll

[0146] (Method for evaluating the appearance of rolls after long-term storage) The appearance of a 500mm wide rolled surface-treated fluororesin sheet material was visually inspected and judged according to the following criteria after storage at room temperature for six months. ○: Three or fewer wrinkles along the outer circumference of the roll △: 5 or less wrinkles along the outer circumference of the roll ×: Six or more wrinkles along the outer circumference of the roll

[0147] (Method for measuring dielectric breakdown strength) A fluororesin sheet material was placed on the lower electrode, and a 25mm diameter, 500g weight was placed on the upper electrode. The voltage at both ends was increased at 100V / sec to measure the breakdown voltage. 16 measurements were taken, with the top and bottom 6 removed to calculate the average value, and the value divided by the thickness was used to determine the dielectric breakdown strength. The results were judged using the following definitions. ○…While measuring n10, n9 or higher is within 400~500V / μm △…n10 measurement, n8 or more falls within 400~500V / μm ×…While measuring n10, n7 or more is not within 400 to 500V / μm The results are shown in Tables 2 and 3.

[0148] [Table 2]

[0149] [Table 3]

[0150] From the results in Tables 2 and 3, the fluororesin sheet materials of the examples had good transportability and roll appearance. [Industrial Applicability]

[0151] The fluororesin sheet material of the present disclosure can be suitably used as a circuit substrate.

Claims

1. A sheet-like material containing a fluororesin, at least one surface of which is A fluororesin sheet material in which the oxygen element ratio is measured by scanning X-ray photoelectron spectroscopy (XPS) at 10 points in each of the longitudinal, transverse, and diagonal directions of a 10 cm square sheet material, the average oxygen element ratio is 1.35 atomic% or more in all directions, and (MAX - MIN) / Avg. is 40% or less. 10 points in the vertical direction: 1.5 cm from the left edge, 1.5 cm from the top, 10 points at 8 mm intervals 10 horizontal points: 1.5 cm from the top edge, 1.5 cm from the left edge, 10 points at 8 mm intervals 10 points diagonally: In both the vertical and horizontal directions, from the bottom right corner of the sheet material, a straight line connecting points on each side of 6.5 cm vertically and 6.5 cm horizontally is the long side, and the short side is 1 cm. On a straight line 5 mm above the long side of the rectangle, the first point is 1.5 cm from the top of the long side of the rectangle, and 10 points are made at 8 mm intervals.

2. The fluororesin sheet material according to claim 1, wherein the oxygen element ratio is 1.35 atomic% or more and 20 atomic% or less, and the (MAX-MIN) / Avg. is 3% or more and 40% or less, and the fluororesin is tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

3. A laminate comprising the fluororesin sheet material of claim 1 and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by a 90-degree peel test in each of the vertical, horizontal and diagonal directions of a 10 cm square laminate is σ / Avg.≦35% in any direction.

4. A laminate comprising the fluororesin sheet material according to claim 1 and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by a 90-degree peel test in each of the longitudinal direction, transverse direction, and diagonal direction of a 10 cm square laminate is (MAX - MIN) / Avg. ≦150% in any direction.

5. A laminate comprising the fluororesin sheet material according to claim 1 and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by 90-degree peel tests in each of the longitudinal, transverse and diagonal directions of a 10 cm square laminate is σ / Avg.≦35% and (MAX−MIN) / Avg.≦150% in all directions.

6. 6. The laminate according to claim 5, wherein the adhesive strength is 1%≦σ / Avg.≦25% and 3%≦(MAX−MIN) / Avg.≦100% in any direction, and the fluororesin is tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) or tetrafluoroethylene-hexafluoropropylene (FEP).

7. 7. The laminate according to claim 3, wherein the adhesive strength is 0.5 N / cm or more in any direction.

8. A sheet-like material containing a fluororesin, at least one surface of which is The sample is divided into a sections in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and the average value of the oxygen element ratio measured at the center of each divided section is 1.35 atomic% or more, and A fluororesin sheet material that satisfies the following formulas (1) and (2). σ(X1Y1~XaYb) / Avg. (X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg. (X1Y1~XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided regions.

9. A laminate comprising the fluororesin sheet material according to claim 8 and a metal layer, A laminate that satisfies the following formulas (3) and (4), which are obtained from the average adhesive strengths between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer, measured in the horizontal direction, vertical direction, and diagonal direction by a 90-degree peel test within each 10 cm square region, which is divided into a section a in the horizontal direction (X) and a section b in the vertical direction (Y). σ Ｂ (XHY1~XaY｡) / Av6'. Ｂ (X1-1~Xa-｡)≦35% (3) {MAX Ｂ (X1Y1~XaY")-MIN Ｂ (X1-1~Xa-｡)} / B6'. Ｂ (X1-1~Xa-｡)≦150% (4) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the average of the average adhesive strengths in three directions in the divided area corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y).

10. When the oxygen element ratio is measured by scanning X-ray photoelectron spectroscopy (XPS) at the following 10 points in each of the longitudinal, transverse, and diagonal directions of a 10 cm square sheet material on at least one surface, the oxygen element ratio is 1.35 atomic% or more in all directions, and (MAX-MIN) / Avg. is 40% or less, Furthermore, the sample is divided into a sections in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and the oxygen element ratio measured at the center of each divided section is 1.35 atomic% or more in all cases, and A fluororesin sheet material that satisfies the following formulas (1) and (2). σ(X1Y1~XaYb) / Avg. (X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg. (X1Y1~XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided regions. 10 points in the vertical direction: 1.5 cm from the left edge, 1.5 cm from the top, 10 points at 8 mm intervals 10 horizontal points: 1.5 cm from the top edge, 1.5 cm from the left edge, 10 points at 8 mm intervals 10 points diagonally: In both the vertical and horizontal directions, from the bottom right corner of the sheet material, a straight line connecting points on each side of 6.5 cm vertically and 6.5 cm horizontally is the long side, and the short side is 1 cm. On a straight line 5 mm above the long side of the rectangle, the first point is 1.5 cm from the top of the long side of the rectangle, and 10 points are made at 8 mm intervals.

11. A laminate comprising the fluororesin sheet material according to claim 10 and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by a 90-degree peel test in each of the longitudinal direction, transverse direction and diagonal direction of a 10 cm square laminate is σ / Avg.≦35% and (MAX−MIN) / Avg.≦150% in all directions, Further, the laminate is divided into a section in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and within each divided 10 cm square area, a 90-degree peel test is carried out to measure the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer in the horizontal direction, vertical direction, and oblique direction, and the adhesive strength is calculated so that the following formulas (3) and (4) are satisfied: σ Ｂ (XHY1~XaY｡) / Av6'. Ｂ (X1-1~Xa-｡)≦35% (3) {MAX Ｂ (X1Y1~XaY")-MIN Ｂ (X1Y1~XaYb)} / B6'. Ｂ (X1-1~Xa-｡)≦150% (4) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the average of the average adhesive strengths in three directions in the divided area corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y).

12. 7. The laminate according to claim 5 or 6, wherein the laminate is divided into a sections in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and within each divided 10 cm square area, the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer is measured in the horizontal direction, vertical direction, and oblique direction by a 90-degree peel test, and the following formulas (3) and (4) are obtained by calculating the average adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer: σ Ｂ (XHY1~XaY｡) / Av6'. Ｂ (X1-1~Xa-｡)≦35% (3) {MAX Ｂ (X1Y1~XaY")-MIN Ｂ (X1-1~Xa-｡)} / B6'. Ｂ (X1-1~Xa-｡)≦150% (4) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the average of the average adhesive strengths in three directions in the divided area corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y).

13. Furthermore, the sheet-like material has a layer other than the fluororesin sheet material and the metal layer, 12. The laminate according to claim 3, 4, 5, 9 or 11, wherein the layers other than the fluororesin sheet material and the metal layer are at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, and polybutadiene.

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