Fluororesin sheet material and laminate containing 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] This disclosure relates to a fluororesin sheet material and a laminate containing the same. [Background technology]

[0002] To realize high-speed communication using next-generation information and communication (high-frequency 5G), the dielectric (insulating material) of printed circuit boards used in antennas and transmission lines is required to have low transmission loss characteristics. Against this backdrop, fluoropolymer materials (PTFE, PFA, etc.) with excellent electrical properties are attracting attention as insulating materials for printed circuit boards. On the other hand, fluoropolymer materials generally have poor adhesion to other materials, so surface modification technologies such as plasma treatment are used to improve adhesion (Patent Document 1, etc.).

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

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-181735 [Patent Document 2] International No. 2021 / 006258 [Overview of the project] [Problems that the invention aims to solve]

[0005] This disclosure aims to provide a fluororesin sheet material that is uniform in plane, consistent, and has excellent adhesion to other materials. Furthermore, when the sheet material is in roll form, it aims to provide a fluororesin sheet material that has good transportability and an improved appearance of the roll. Furthermore, this disclosure aims 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] This disclosure relates to a sheet-like material containing a fluororesin, wherein at least one surface has The fluororesin sheet material (A) is one in which, when the oxygen element ratio is measured at 10 points each in the longitudinal, transverse, and diagonal directions of a 10 cm square sheet material using scanning X-ray photoelectron spectroscopy (XPS), the average value of the oxygen element ratio in all directions is 1.35 atomic% or more, and (MAX-MIN) / Avg. is 40% or less. Ten points in the vertical direction: Starting from the first point 1.5 cm from the top of a straight line 1.5 cm from the left edge, ten points are placed at 8 mm intervals. Ten horizontal points: Starting from the first point 1.5 cm from the left edge, along a straight line 1.5 cm from the top edge, ten points are placed at 8 mm intervals. Ten points in a diagonal direction: Following the vertical and horizontal directions, starting from the bottom right corner of the sheet material, the longer side is a line connecting points 6.5 cm vertically and 6.5 cm horizontally, and the shorter side is 1 cm. On a line 5 mm above the longer side of a rectangle, the first point is 1.5 cm from the top edge of the longer side of the rectangle, and ten points are placed at 8 mm intervals.

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

[0008] This disclosure relates to a laminate (A1) comprising the above-mentioned fluororesin sheet material (A) 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 the longitudinal, transverse, and diagonal directions of a 10 cm square laminate, is σ / Avg. ≤ 35% in all directions. Furthermore, this disclosure also relates to a laminate (A2) comprising the above-mentioned fluororesin sheet material (A) 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 the longitudinal, transverse, and diagonal directions of a 10 cm square laminate, is (MAX-MIN) / Avg. ≤ 150% in all directions.

[0009] Furthermore, this disclosure also relates to a laminate (A3) comprising the above-mentioned fluororesin sheet material (A) 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 the longitudinal, transverse, and diagonal directions of a 10 cm square laminate, is σ / Avg. ≤ 35% and (MAX-MIN) / Avg. ≤ 150% in all directions.

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

[0011] This disclosure relates to a sheet-like material containing a fluororesin, wherein at least one surface has The area is divided into 'a' sections horizontally (X) and 'b' sections vertically (Y) every 10 cm, and the average value of the oxygen element ratio measured at the center of each divided area is 1.35 atomic% or higher, and The fluororesin sheet material (B) satisfies the following equations (1) and (2). σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦30% (2) (In the formula, a and b are integers 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 column a horizontally (X) and row b vertically (Y) within the divided area.

[0012] Furthermore, this disclosure relates to a laminate comprising the above-mentioned fluororesin sheet material (B) and a metal layer, The material is divided into 10cm sections, a horizontally (X) and b vertically (Y), and within each divided 10cm square area, a 90-degree peel test is performed to measure the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet-like material and the metal layer. This is obtained from the average values ​​of the adhesive strength between the metal layer and the oxygen element ratio measurement surface, and is also a laminate (B) that satisfies the following equations (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) (In the formula, a and b are integers greater than or equal to 1, and ab ≥ 50.) In this case, XaYb is the average of the adhesive strengths in three directions within the divided region corresponding to column a in the horizontal direction (X) and row b in the vertical direction (Y).

[0013] This disclosure describes a method in which, when the oxygen element ratio is measured at 10 points each in the longitudinal, transverse, and diagonal directions of a 10 cm square sheet material on at least one surface using scanning X-ray photoelectron spectroscopy (XPS), the average value of the oxygen element ratio is 1.35 atomic% or more in all directions, and (MAX-MIN) / Avg. is 40% or less. Furthermore, the region is divided into 'a' sections horizontally (X) and 'b' sections vertically (Y) every 10 cm, and the average value of the oxygen element ratio measured at the center of each divided region is 1.35 atomic% or higher, and It is also a fluororesin sheet material (C) that satisfies the following equations (1) and (2). σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦30% (2) (In the formula, a and b are integers 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 column a horizontally (X) and row b vertically (Y) within the divided area. Ten points in the vertical direction: Starting from the first point 1.5 cm from the top of a straight line 1.5 cm from the left edge, ten points are placed at 8 mm intervals. Ten horizontal points: Starting from the first point 1.5 cm from the left edge, along a straight line 1.5 cm from the top edge, ten points are placed at 8 mm intervals. Ten points in a diagonal direction: Following the vertical and horizontal directions, starting from the bottom right corner of the sheet material, the longer side is a line connecting points 6.5 cm vertically and 6.5 cm horizontally, and the shorter side is 1 cm. On a line 5 mm above the longer side of a rectangle, the first point is 1.5 cm from the top edge of the longer side of the rectangle, and ten points are placed at 8 mm intervals.

[0014] The present disclosure also relates to a laminate comprising the above fluororesin sheet-like material (C) and a metal layer, wherein for each of the longitudinal direction, transverse direction, and diagonal direction of a 10 cm square laminate, the adhesion strength between the oxygen element ratio measurement surface of the above fluororesin sheet-like material and the metal layer obtained by a 90-degree peel test satisfies σ / Avg.≦35% and (MAX-MIN) / Avg.≦150% in any direction. Furthermore, the laminate is also one that satisfies the following formulas (3) and (4), which are obtained from the average value of the adhesion strength between the oxygen element ratio measurement surface of the above fluororesin sheet-like material and the metal layer measured in the transverse direction, longitudinal direction, and diagonal direction by a 90-degree peel test within each divided 10 cm square region after dividing the laminate into a parts in the transverse direction (X) and b parts in the longitudinal direction (Y) every 10 cm. σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb)≦35% (3) {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B (X1Y1~XaYb)≦150% (4) (In the formula, a and b are each an integer of 1 or more, and ab≧50 holds. At this time, XaYb is a value obtained by further averaging the average value of the adhesion strengths in three directions of the region corresponding to the a-th column in the transverse direction (X) and the b-th row in the longitudinal direction (Y) among the divided regions.) In the above laminate (A3), it is preferable to satisfy the following formulas (3) and (4), which are obtained from the average value of the adhesion strength between the oxygen element ratio measurement surface of the above fluororesin sheet-like material and the metal layer measured in the transverse direction, longitudinal direction, and diagonal direction by a 90-degree peel test within each divided 10 cm square region after dividing the laminate into a parts in the transverse direction (X) and b parts in the longitudinal direction (Y) every 10 cm. σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb)≦35% (3) {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B(X1Y1~XaYb)≦150% (4) (In the formula, a and b are integers greater than or equal to 1, and ab ≥ 50.) In this case, XaYb is the average of the adhesive strengths in three directions within the divided region corresponding to column a in the horizontal direction (X) and row b in the vertical direction (Y).

[0015] The above laminates (A1) to (A3) and (B) further have layers other than the fluororesin sheet material and the metal layer. Preferably, 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. [Effects of the Invention]

[0016] The fluororesin sheet material of this disclosure is uniform in surface, free from variation, and has excellent adhesion to other materials. Furthermore, due to the uniform surface treatment, 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 this disclosure maintains low transmission loss characteristics and has excellent properties when used as a circuit board. [Brief explanation of the drawing]

[0017] [Figure 1] An explanatory diagram showing the approximate locations for measuring the oxygen element ratio and acquiring samples for peeling tests in a 10cm square sheet of fluororesin material. [Figure 2] An explanatory diagram illustrating the schematic positions for measuring the oxygen element ratio and acquiring samples for peeling tests in one embodiment of dividing a fluororesin sheet material into 10 cm square sections. [Modes for carrying out the invention]

[0018] The details of this disclosure are described below. Conventionally, while there are patents specifying the amount of oxygen element and the amount of specific functional groups as requirements for obtaining good adhesion in the surface modification of fluororesin sheets by plasma treatment, conventional plasma surface-treated sheets have had the problem of unstable adhesive strength due to uneven surface modification. Furthermore, conventional plasma-surface-treated sheets only underwent evaluation of functional group content in extremely small areas, lacking consideration of variability across the entire sheet. As a result of the above, uniform adhesion with other materials was not sufficiently achieved, leading to issues such as peeling in subsequent processes and a decrease in the reliability of the substrate. Furthermore, when the sheets were in roll form, problems sometimes arose with the transportability of the rolls and their appearance.

[0019] The Disclosers have found that by improving the in-plane uniformity of the surface treatment when surface-treating a fluororesin sheet material, uniform adhesion to metals such as copper foil can be obtained. Furthermore, when the fluororesin sheet material is in the form of a roll, improving the in-plane uniformity of the surface treatment makes it less likely for wrinkles to form in the fluororesin sheet material, thus preventing shrinkage in width, improving the transportability of the roll, and improving the appearance of the roll. In addition, the long-term storage life of the roll is also improved. Furthermore, it was revealed that in order to obtain high adhesion with other materials, it is effective for the fluororesin sheet material to have specific properties in relatively small and large regions. Similarly, it was revealed that in a laminate having the fluororesin sheet material of this disclosure and a metal layer, it is effective for the material to have specific properties in relatively small and large regions.

[0020] One example relates to a relatively small area of ​​a fluororesin sheet material, and is as follows: (A) The sheet material containing the fluororesin of this disclosure has at least one surface, The oxygen element ratio is measured at 10 points each in the longitudinal, transverse, and diagonal directions of a 10cm square sheet-like material using scanning X-ray photoelectron spectroscopy (XPS). In all directions, the average value (Avg.) of the oxygen element ratio is 1.35 atomic% or higher, and (MAX-MIN) / Avg. is 40% or lower. Ten points in the vertical direction: Starting from the first point 1.5 cm from the top of a straight line 1.5 cm from the left edge, ten points are placed at 8 mm intervals. Ten horizontal points: Starting from the first point 1.5 cm from the left edge, along a straight line 1.5 cm from the top edge, ten points are placed at 8 mm intervals. Ten points in a diagonal direction: Following the vertical and horizontal directions, starting from the bottom right corner of the sheet material, the longer side is a line connecting points 6.5 cm vertically and 6.5 cm horizontally, and the shorter side is 1 cm. On a line 5 mm above the longer side of a rectangle, the first point is 1.5 cm from the top edge of the longer side of the rectangle, and ten points are placed at 8 mm intervals.

[0021] The approximate locations of the 10 specific points in the vertical, horizontal, and diagonal directions of the 10cm square fluororesin sheet material described above are shown in Figure 1. In Figure 1, the black circles indicated in the vertical, horizontal, and diagonal directions represent the locations where the oxygen element ratio was measured using XPS.

[0022] A fluororesin sheet material (A) that satisfies the above conditions ensures uniformity within the plane and exhibits good adhesion to metals such as copper foil. Furthermore, when the fluororesin sheet material is in roll form, its transportability improves, and the appearance of the roll is also improved.

[0023] Here, the oxygen element ratios mentioned above were measured using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.). Carbon, oxygen, fluorine, nitrogen, and silicon were detected, and the oxygen element ratio was determined from the composition ratio of C1s, O1s, F1s, N1s, and Si2p. Furthermore, the above (MAX-MIN) / Avg. is a value calculated using the maximum value (MAX), minimum value (MIN), and average value (Avg.) of the 10 measured points in each of the vertical, horizontal, and diagonal directions obtained as described above.

[0024] The average value (Avg.) of the above oxygen element ratio is more preferably 1.5 atomic% or higher, even more preferably 1.8 atomic% or higher, and most preferably 2.0 atomic% or higher. Furthermore, the upper limit of the average value (Avg.) of the above oxygen element ratio is not specifically 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 falls within the above range, it is advantageous in that the amount of functional groups contributing to adhesion is suitable.

[0025] Furthermore, the above (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 above (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, it is advantageous because there are no areas with extremely different oxygen element ratios, and the surface treatment is uniform across the plane.

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

[0027] Furthermore, this disclosure also relates to a laminate comprising the above-mentioned fluororesin sheet material and a metal layer. Preferably, the laminate is constructed such that the metal layer is in contact with a surface of the fluororesin sheet material that satisfies the specified oxygen element ratio. If, in the fluororesin sheet material, only one surface satisfies the specified oxygen element ratio, it is preferable that this surface is in contact with the metal layer. If, in the fluororesin sheet material, both surfaces satisfy the specified oxygen element ratio, it is preferable that at least one surface is in contact with the metal layer. In the laminate (A1) containing the above-mentioned fluororesin sheet material and 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 a 90-degree peel test in the longitudinal, transverse, and diagonal directions, is σ / Avg. ≤ 35% in all directions.

[0028] Furthermore, in the laminate (A2) containing the above-mentioned fluororesin sheet material and 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 a 90-degree peel test in the longitudinal, transverse, and diagonal directions, is (MAX-MIN) / Avg. ≤ 150% in all directions.

[0029] Here, the adhesive strength mentioned above is the value obtained by taking peel test samples (1 cm × 9 cm) at predetermined positions on the fluororesin sheet material in the vertical, horizontal, and diagonal directions, as shown in Figure 1, and then performing a 90-degree peel test on the laminate obtained as described below using these samples.

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

[0031] Thus, in the laminate, the adhesion between the surface of the fluororesin sheet material that satisfies the above-mentioned oxygen element ratio characteristics and the metal layer is good and difficult to peel off, and the surface smoothness of the adhesive surface is maintained, so low transmission loss characteristics are maintained and it 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%. Furthermore, 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 is stable and close to a similar value, which is advantageous for the stability of electrical properties when the material is formed into a substrate.

[0033] Furthermore, the above (MAX-MIN) / Avg. is preferably (MAX-MIN) / Avg. ≤ 150%, and more preferably (MAX-MIN) / Avg. ≤ 100%. Furthermore, 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. This results in more stable and consistent in-plane adhesive strength, which is advantageous for the stability of electrical properties when the material is formed into a substrate.

[0034] Furthermore, in this disclosure, it is preferable that the laminate (A3) satisfies both the σ / Avg. and (MAX-MIN) / Avg. requirements for the adhesive strength. Furthermore, in the laminate (A3), it is preferable that the adhesive strength is 1% ≤ σ / Avg. ≤ 35% and 3% ≤ (MAX-MIN) / Avg. ≤ 150%.

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

[0036] Next, the other 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-like material containing fluororesin, The area is divided into 'a' sections horizontally (X) and 'b' sections vertically (Y) every 10 cm, and the average value (Avg.) of the oxygen element ratio measured at the center of each divided area is 1.35 atomic% or higher, and The invention is characterized by satisfying the following equations (1) and (2). σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦30% (2) (In the formula, a and b are integers 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 column a horizontally (X) and row b vertically (Y) within the divided area. Furthermore, there is no particular upper limit to ab; if ab ≤ 1000, it can be said that it is a fluororesin sheet material that meets the above specifications.

[0037] Figure 2 shows one embodiment of the specific measurement method. Figure 2 shows the case where a is 10 and b is 5. The oxygen element ratio is measured by XPS at the center of each divided 10cm square sheet-like material (indicated by the black circle).

[0038] Here, the oxygen element ratio was measured using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000VersaProbeII (manufactured by ULVAC-PHI, Inc.). Carbon, oxygen, fluorine, nitrogen, and silicon were detected, and the oxygen element ratio was determined from the composition ratio of C1s, O1s, F1s, N1s, and Si2p.

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

[0040] In a relatively large area of ​​such a sheet-like material, the fluororesin sheet material (B) that satisfies the above conditions results in better in-plane stability of adhesion when bonded to a metal such as copper foil. Furthermore, when the fluororesin sheet material is in roll form, its transportability improves, and the appearance of the roll is also further improved.

[0041] The average value (Avg.) of the above oxygen element ratio is more preferably 1.5 atomic% or higher, even more preferably 1.8 atomic% or higher, and most preferably 2.0 atomic% or higher. Furthermore, the upper limit of the average value (Avg.) of the above 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 falls within the above range, it is advantageous in that the amount of functional groups contributing to adhesion is suitable.

[0042] Furthermore, in formula (1) above, it is preferable that σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb) ≤ 20%, and more preferably that σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb) ≤ 10%. The lower limit of the above σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb) is not particularly limited, but it 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 ratio of oxygen elements in the plane is stable and close to a similar value, which is advantageous for the stability of the adhesive strength when the material is laminated.

[0043] Furthermore, in equation (2) above, it is preferable that {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦40% or less, and more preferably 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 it 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). If {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. Therefore, the in-plane oxygen element ratio is more stable and close to a specific value, which is advantageous for the in-plane stability of the adhesive strength when formed into a laminate.

[0044] Furthermore, similar to the laminate (A) described above, it is preferable that the laminate (B) containing the fluororesin sheet material (B) and the metal layer is laminated such that the surface of the fluororesin sheet material that satisfies the specified oxygen element ratio is in contact with the metal layer. If, in the fluororesin sheet material, there is only one surface that satisfies the specified oxygen element ratio, it is preferable that this surface is in contact with the metal layer. Also, if, in the fluororesin sheet material, there are surfaces on both sides that satisfy the specified oxygen element ratio, it is preferable that at least one surface is in contact with the metal layer. In the laminate (B) of the fluororesin sheet material (B) and the metal layer, It is preferable that the fluororesin sheet material be divided into 'a' sections horizontally (X) and 'b' sections vertically (Y) every 10 cm, and that the following formulas (3) and (4) are satisfied, obtained from the average values ​​of the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer, measured in the horizontal, vertical, and diagonal directions by a 90-degree peel test within each divided 10 cm square area. σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb)≦35% (3) {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B(X1Y1~XaYb)≦150% (4) (In the formula, a and b are integers greater than or equal to 1, and ab ≥ 50.) In this case, XaYb is the average of the adhesive strengths in three directions within the divided region corresponding to column a in the horizontal direction (X) and row b in the vertical direction (Y). The above Avg. B (X1Y1~XaYb) represents the further average value (X1Y1, XaYb, etc.) obtained by averaging the average adhesive strength in three directions (horizontal, vertical, and diagonal) within each 10cm square area of ​​a×b (pieces). Furthermore, there is no particular upper limit to ab; if ab ≤ 1000, it can be said that the laminate meets the above specifications.

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

[0046] (90-degree peel test) (Method for preparing laminates) Using a fluororesin sheet material and metal foil, the metal foil, fluororesin sheet material, and metal foil are layered in that order, and a laminate is obtained by heat pressing in a vacuum heat press machine (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 200°C, a preheating time of 120 seconds, a pressing pressure of 3 MPa, and a pressing time of 600 seconds. (Peel test method) In the peel test, one side of the laminate obtained by the method described above is attached to an aluminum plate with adhesive tape, and a Tensilon universal testing machine (manufactured by Shimadzu Corporation) is used to measure the peel strength of the metal foil by gripping and pulling a 10 mm wide metal foil at a 90° angle to the plane of the laminate at a speed of 50 mm per minute, and the obtained value is taken as the adhesive strength. For each laminate, the average adhesive strength is calculated over a total stroke distance of 30 mm, starting from 10 mm from the start of delamination to 40 mm. The average values ​​of the adhesive strengths obtained in the horizontal, vertical, and diagonal directions are further averaged (X1Y1, XaYb, etc.) and this average value is taken as the "average adhesive strength within each divided region". The standard deviation of the "average value of adhesive strength within each region" for the number of measurements m = a × b (items) is σ B (X1Y1~XaYb), average value is Avg. B (X1Y1~XaYb), maximum value is MAX B (X1Y1~XaYb), minimum value is MIN B Let (X1Y1~XaYb), and in equation (3) above, σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb) and {MAX in equation (4) above B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B Calculate (X1Y1~XaYb).

[0047] Thus, by having a laminate that satisfies the above conditions over a relatively large area, the adhesion between the fluororesin sheet material and the metal layer is good over a wider area, making it less prone to peeling. As a result, the surface smoothness of the adhesive surface is maintained, lower transmission loss characteristics are preserved, and it has excellent properties when used as a circuit board.

[0048] In equation (3) above, σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb) ≤ 35%, and σ B (X1Y1~XaYb) / Avg. B It is more preferable that (X1Y1~XaYb)≦25% Furthermore, the lower limit is not particularly restricted, and is 1% ≤ σ B (X1Y1~XaYb) / Avg. B (X1Y1~XaYb) is preferred, and 3%≦σ B (X1Y1~XaYb) / Avg.B (X1Y1~XaYb) is more preferable. σ B (X1Y1~XaYb) / Avg. B If (X1Y1~XaYb) falls within the above range, the average adhesive strength is stable over a wide area, which is advantageous because it reduces the likelihood of problems such as delamination occurring during subsequent substrate fabrication, regardless of the location from which the laminate is taken.

[0049] Furthermore, in equation (4) above, {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B It is preferable that (X1Y1~XaYb)≦150%, and {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B It is more preferable that (X1Y1~XaYb)≦100%. Furthermore, the lower limit is not particularly limited, and 5% ≤ {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B (X1Y1~XaYb) is preferable, and 10%≦{MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B (X1Y1~XaYb) is more preferable. {MAX B (X1Y1~XaYb)-MIN B (X1Y1~XaYb)} / Avg. B If (X1Y1~XaYb) falls within the above range, not only is the average adhesive strength stable over a wide range, but the variation in adhesive strength is also small. This results in more stable and consistent in-plane adhesive strength, which is advantageous for the stability of electrical properties when the laminate is formed into a substrate, regardless of the position from which the laminate is taken. Also, the average value of "average adhesive strength within the region" (Avg. B (X1Y1~XaYb)) is preferably 0.5 N / cm or more. There is no specific upper limit, but for example, it should be 20 N / cm or less.

[0050] Furthermore, in this disclosure, it is preferable that both conditions (A) and (B) above are met. In the fluororesin sheet material of this disclosure, it is preferable that at least one surface satisfies both conditions (A) and (B) above. A fluororesin sheet material (C) whose oxygen element ratio satisfies conditions (A) and (B) above exhibits better adhesion between the fluororesin sheet material and the metal. Furthermore, when the fluororesin sheet material is in the form of a roll, the transportability is improved, and the appearance of the roll is also improved. In addition, the long-term storage life of the roll is also improved. The fluororesin sheet material (C) has an average value (Avg.) of oxygen element ratio of 1.35 atomic% or more in all directions when the oxygen element ratio is measured at 10 points each in the longitudinal, transverse, and diagonal directions of a 10 cm square sheet material on at least one surface using scanning X-ray photoelectron spectroscopy (XPS), and (MAX-MIN) / Avg. is 40% or less. Furthermore, the region is divided into 'a' sections horizontally (X) and 'b' sections vertically (Y) every 10 cm, and the average value (Avg.) of the oxygen element ratio measured at the center of each divided region is 1.35 atomic% or higher, and The material is a fluororesin sheet that satisfies the following equations (1) and (2). σ(X1Y1~XaYb) / Avg.(X1Y1~XaYb)≦20% (1) {MAX(X1Y1~XaYb)-MIN(X1Y1~XaYb)} / Avg.(X1Y1~XaYb)≦30% (2) (In the formula, a and b are integers 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 column a horizontally (X) and row b vertically (Y) within the divided area. Furthermore, in the laminate of this disclosure, by making the laminate (C) satisfy all of the above conditions (A) and (B), the adhesive strength becomes more uniform in the plane, resulting in less peeling in subsequent processes and improved reliability of the substrate. The above laminate (C) is a laminate comprising a fluororesin sheet-like material (C) and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet-like material and the metal layer, obtained by a 90-degree peel test in the longitudinal, transverse, and diagonal directions of a 10 cm square laminate, is σ / Avg. ≤ 35% and (MAX-MIN) / Avg. ≤ 150% in all directions. Furthermore, the laminate is obtained from the average values ​​of the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet-like material and the metal layer, which are measured in the horizontal, vertical, and diagonal directions by a 90-degree peel test within each divided 10cm square area, and from 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) (In the formula, a and b are integers greater than or equal to 1, and ab ≥ 50.) In this case, XaYb is the average of the adhesive strengths in three directions within the divided region corresponding to column a in the horizontal direction (X) and row b in the vertical direction (Y).

[0051] Fluororesin sheet materials that satisfy the above-described physical properties can be surface-treated by corona discharge, for example, by using nitrogen gas, argon, and carbon dioxide as inert gases, and by imparting functional groups with carbon dioxide, thereby improving the in-plane uniformity of the surface treatment. Details of the surface treatment method will be described later.

[0052] (Fluororesin) The fluororesin contained in the fluororesin sheet material of this disclosure is not particularly limited as long as it is a fluorine-containing resin, and known fluororesins can be used. In particular, it is preferable that the copolymer consists of tetrafluoroethylene (TFE)-perfluoro(alkyl vinyl ether) copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene (HFP) copolymer (FEP).

[0053] (Per)fluoro(alkyl vinyl ether) (PAVE) may be a fluoroalkyl vinyl ether or a perfluoro(alkyl vinyl ether). In this disclosure, "perfluoro(alkyl vinyl ether)" means an alkyl vinyl ether that does not contain a CH bond. The PAVE that constitutes the above PAVE unit is given 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 from 0 to 5, and q represents an integer from 0 to 5. ) Monomers represented by general formula (2): CFX=CXOCF2OR 1 (2) (In the formula, X represents the same or different H, F, or CF3, and R represents the same or different H, F, or CF3.) 1 This represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms, which may contain 1 to 2 atoms 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 selected from the group consisting of H, Cl, Br, and I.) A possible example is at least one selected from the group consisting of monomers represented by ).

[0054] In particular, 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 PAVE unit content in the above 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, with respect to the total monomer units. The amount of the above PAVE units is 19 Measurement is performed by 1F-NMR. The above TFE / PAVE copolymer may be a copolymer consisting only of TFE units and PAVE units.

[0056] When the above-mentioned 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 above-mentioned 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 above glass transition temperature is a value obtained by dynamic viscoelasticity measurement.

[0058] The above TFE / HFP copolymer contains TFE units and HFP units. The TFE unit content in the above TFE / HFP copolymer is preferably 70% by mass or more, more preferably 85% by mass or more, 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 above TFE / HFP copolymer preferably has a mass ratio (TFE / HFP) of 70-99 / 1-30 (mass%) of TFE units to HFP units. More preferably, the above mass ratio (TFE / HFP) is 85-95 / 5-15 (mass%).

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

[0061] When the above TFE / HFP copolymer is a copolymer containing TFE units, HFP units, and PAVE units (hereinafter also referred to as "TFE / HFP / PAVE copolymer"), it is preferable that the mass ratio (TFE / HFP / PAVE) is 70-99.8 / 0.1-25 / 0.1-25 (mass%). It is more preferable that the above mass ratio (TFE / HFP / PAVE) is 75-98 / 1.0-15 / 1.0-10 (mass%). It is preferable that the above TFE / HFP / PAVE copolymer contains 1% by mass or more of HFP units and PAVE units in total with respect to the total monomer units.

[0062] The above TFE / HFP / PAVE copolymer preferably contains 25% by mass or less of HFP units relative to the total monomer units. More preferably, the HFP unit content is 20% by mass or less, even more preferably 18% by mass or less, and particularly preferably 15% by mass or less. Furthermore, the HFP unit content is preferably 0.1% by mass or more, more preferably 1% by mass or more, and particularly preferably 2% by mass or more. Note that the HFP unit content is... 19 It can be measured by the 1F-NMR method.

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

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

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

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

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

[0068] The above-mentioned fluororesin can be produced by conventionally known methods, such as emulsion polymerization or suspension polymerization, by appropriately mixing monomers that form its constituent units and additives such as polymerization initiators. Among these, it is more preferable that it is obtained by emulsion polymerization.

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

[0070] The above-mentioned fluororesin is preferable to have fewer functional groups, and in particular, a lower number of unstable end groups. Such fluororesins can be produced by adjusting the conditions during manufacturing (polymerization reaction), or by reducing the number of unstable end groups by performing fluorine gas treatment, heat treatment, or supercritical gas extraction treatment on the polymerized fluororesin. Fluorine gas treatment is preferred because it offers excellent processing efficiency and some or all of the unstable end groups are converted to -CF3, which becomes a stable end group. Using a fluororesin with a reduced number of unstable end groups in this way is preferable because it lowers the electrostatic loss tangent and reduces the loss of electrical signals.

[0071] The number of unstable end groups mentioned above is not particularly limited, but for fluororesins with a main chain of 10 carbon atoms... 6 The value per unit is preferably 450 or less, more preferably 250 or less, even more preferably 100 or less, and most preferably 50 or less. Considering the effect of reducing dielectric loss tangent, it is preferably less than 10, and even more preferably 5 or less.

[0072] Examples of unstable end groups include functional groups such as -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), hydroxyl groups (-CH2OH, etc.), -CONH2, -COOR (R=CH3, etc.), -CF2H, and -OCOO-R (n-propyl carbonate, etc.).

[0073] The number of unstable end groups is measured specifically by the following method. First, the above-mentioned fluororesin is melted and compressed to produce a film with a thickness of 0.25 to 0.3 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the above-mentioned fluororesin, and a difference spectrum is obtained from the base spectrum, which is completely fluorinated and does not contain any functional groups. From the absorption peak of a specific functional group that appears in this difference spectrum, the number of carbon atoms in the above-mentioned fluororesin is calculated according to the following formula (A): 1 × 10 6 Calculate the number of unstable terminals per unit. N = I × K / t (A) I: Absorbance K: Correction coefficient t: Film thickness (mm)

[0074] For reference, Table 1 shows the absorption frequency, molar extinction coefficient, and correction factor for the unstable end groups used in this specification. The molar extinction coefficient was determined from FT-IR measurement data of a small molecule model compound.

[0075] [Table 1]

[0076] The above fluorination treatment can be carried out by bringing an unfluorinated fluororesin into contact with a fluorine-containing compound.

[0077] The fluorine-containing compounds mentioned above are not particularly limited, but include fluorine radical sources that generate fluorine radicals under fluorination treatment conditions. Examples of fluorine radical sources include F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and halogenated fluorides (e.g., IF5, ClF3).

[0078] The fluorine radical source, such as F2 gas, may be at 100% concentration, but it is preferable to mix it with an inert gas and dilute it to 5-50% by mass, and more preferably to 15-30% by mass. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, but nitrogen gas is preferred from an economic standpoint.

[0079] The conditions for the above fluorination treatment are not particularly limited, and the fluororesin may be brought into contact with a fluorine-containing compound in a molten state. However, it 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 above fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 25 hours. The above fluorination treatment preferably involves 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 this disclosure may contain components other than fluororesin. The components that can be contained are not particularly limited, but include silica particles, fillers such as glass short fibers, and thermosetting resins and thermoplastic resins that do not contain fluorine. The content of components other than fluororesin is not particularly limited, but is more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0082] The fluororesin sheet material of this 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 above-mentioned fluororesin sheet material was measured using the reflection spectroscopy method of the film thickness measurement system F20 (manufactured by Filmetrics).

[0084] 30 μm of the fluororesin sheet material disclosed herein 2 The Ra (arithmetic mean roughness) in this material 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 it is preferably 5 nm or greater. If Ra is within the above range, it is preferable because the raw material itself has high smoothness, and the surface treatment can be applied more uniformly within the plane. The above Ra value is obtained by atomic force microscopy (AFM).

[0085] Furthermore, it is preferable that the fluororesin sheet material of this disclosure has a difference of 1.0 atomic% or more between the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS / ESCA) on the surface state of the fluororesin-containing layer and the oxygen element ratio measured by scanning X-ray photoelectron spectroscopy (XPS / ESCA) after etching the fluororesin-containing layer with an argon gas cluster ion beam at an incident angle of 45° in the depth direction for 15 minutes. Increasing the difference in the oxygen element ratio from the surface to the depth direction is preferable because it allows for obtaining a predetermined transmission loss while maintaining adhesion.

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

[0087] The above-mentioned fluororesin sheet material preferably has an adhesive strength greater than 30 N / m when two sheets of the same surface are bonded together at 200°C, either on one side or both sides. Having such an adhesive strength ensures that the fluororesin sheet material maintains excellent adhesion when used in combination with various other substrates, even after heat treatment. The above adhesive strength is more preferably greater than 50 N / m, and even more preferably greater than 100 N / m.

[0088] More specifically, the above adhesive strength was determined by overlapping the surface-treated surfaces of two fluororesin sheet materials and preparing a sample using heat pressing (200°C, 0.1 MPa, 60 s). This sample was then cut into 10 mm wide strips, and the peel strength was measured using a precision universal testing machine, Autograph AGS-X 100N (manufactured by Shimadzu Corporation). The unbonded portion of the strip sample was grasped by the upper and lower chucks of the Autograph and pulled at a speed of 100 mm per minute. The resulting value was defined as the adhesive strength.

[0089] The fluororesin sheet material of this disclosure preferably has a dielectric loss tangent of less than 0.0015 at 10 GHz. This is preferable because it can keep the loss of electrical signals in the circuit low. 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 signals are transmitted at higher frequencies and antennas are transmitted and received, 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 end groups, and more preferably to use a fluororesin that has undergone end fluorination treatment.

[0090] (Long sheet) The fluororesin sheet material disclosed herein is preferably a long sheet. Long sheets are particularly preferable from the standpoint of production cost if they are produced continuously. The long sheet is preferably 200 mm or more in width. Furthermore, it is preferably 1 m or more in length. When the long sheet is made into a roll, the above-described effects can be obtained.

[0091] (Method for manufacturing fluororesin sheet material) The following details an example of a method for manufacturing the fluororesin sheet material of the present disclosure described above. However, the fluororesin sheet material of the present disclosure is not limited to those manufactured by the following manufacturing method. The fluororesin sheet material of this disclosure is not limited in terms of the molding method used to form the sheet material, but examples include a melt molding method such as extrusion molding, and a casting method in which a solution or dispersion containing fluororesin is prepared and then applied and dried on a substrate. Furthermore, the sheet may be stretched by a uniaxial stretching or biaxial stretching method, or it may be an unstretched sheet. Furthermore, the fluororesin sheet material may have a laminated structure that includes a fluororesin layer in part.

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

[0093] The specific methods for surface modification described above are not limited, but some specific examples are detailed below. Surface modification of fluororesin sheet materials can be performed using conventional discharge treatments such as corona discharge treatment, glow discharge treatment, plasma discharge treatment, and sputtering treatment. For example, 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, surface modification can be performed by exposing the surface to be modified to an atmosphere of an inert gas containing organic compounds, applying a high-frequency voltage between electrodes to induce a discharge, thereby generating active species on the surface, and then introducing functional groups of organic compounds or graft polymerization of polymerizable organic compounds. Examples of the above-mentioned inert gases include nitrogen gas, helium gas, and argon gas.

[0094] In particular, it is preferable to use nitrogen gas and argon gas in combination. Furthermore, it is preferable to use carbon dioxide gas. The ratio (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, it is advantageous in that the discharge is stable and more uniform surface modification can be achieved within the plane. Furthermore, the amount of carbon dioxide is preferably 0.05 to 5% by volume, and 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 contributing to adhesion on the surface of the fluororesin sheet material are provided within a suitable range.

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

[0096] The concentration of the organic compound in the inert gas containing the organic compound varies depending on its type, 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 should be appropriately selected depending on the desired degree of surface modification, the type of fluororesin, and the type and concentration of organic compounds. Typically, the discharge rate is 50-1500 W·min / m 2 Preferably 70 W·min / m 2 More than 1400W min / m 2 The discharge treatment is performed within the following range. The treatment temperature can be any temperature within the range of 0°C to 100°C. However, it is preferable to keep the temperature below 80°C due to concerns about stretching and wrinkling of the fluororesin sheet material. The degree of surface modification of the fluororesin sheet material is such that, considering the deactivation of oxygen elements on the surface due to heat during lamination with metal foil, etc., and the resulting decrease in adhesive strength, the oxygen element abundance observed by ESCA is preferably 1.5% or more, more preferably 1.75% or more, more preferably 2.0% or more, and even more preferably 2.5% or more. There is no specific upper limit, but considering the impact on productivity and other physical properties, it is preferable that it be 25.0% or less. While there are no specific requirements regarding the relative abundance of nitrogen, it is preferable that it be 0.1% or higher.

[0097] In the above surface modification process, it is preferable to discharge the material within the range of 1.0 to 10 W / cm², where the discharge rate is the output per unit area, and to adjust the gas concentration / line velocity ratio to within the range of 0.005 to 0.05 L / m. The gas concentration / line velocity ratio referred to here is the ratio obtained by dividing the concentration of the organic compound in the organic compound-containing inert gas by the line velocity. If the flow rate is lower than 0.005 L / m, the space will not be sufficiently filled with gas relative to the transport speed, making it difficult for the activated gas to come into contact with the surface of the fluororesin sheet material, thus reducing the uniformity of the surface. If the flow rate is higher than 0.05 L / m, the surface will be overtreated and damaged, leading to the formation of a brittle layer due to the generation of low molecular weight compounds on the surface, which in turn leads to a decrease in adhesive strength. Therefore, it is presumed that the surface of the fluororesin sheet material will be treated more uniformly and the desired adhesive strength will be obtained, so treatment within such limits is particularly preferable.

[0098] Furthermore, in the above method, it is preferable that the difference between the oxygen element ratio measured on one or both sides of the surface state of the fluororesin sheet material using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) and the oxygen element ratio measured after etching the fluororesin-containing layer with an argon gas cluster ion beam at an incident angle of 45° in the depth direction for 15 minutes, and then measuring it using a scanning X-ray photoelectron spectroscopy (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 beforehand. This reduces dimensional changes in the fluororesin sheet material due to heat from the pressure roll during the lamination process with metal foil to manufacture a laminate, allowing for bonding without wrinkles and thus suppressing defects in the appearance of the laminate. Since 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 is obtained when the fluororesin sheet material and metal foil are bonded together.

[0100] Annealing can be carried out by heat treatment. This heat treatment can be performed, for example, by passing the material through a heating furnace in a roll-to-roll manner. Heat treatment may also be performed in a batch-type drying oven.

[0101] The annealing temperature is preferably above the glass transition temperature of the fluororesin - 20°C and below the melting point, more preferably above the glass transition temperature of the fluororesin and below the melting point - 20°C, and even more preferably above the glass transition temperature of the fluororesin and below the melting point - 60°C. The annealing time is not particularly limited, but can be appropriately adjusted, for example, between 0.5 and 60 minutes.

[0102] When heating using the roll-to-roll method described above, the tension can be adjusted appropriately depending on the thickness of the fluororesin sheet material and the set temperature, but it is preferable to keep it at 20 N / m or less. Heating under these conditions is preferable because it allows for sufficient relaxation of internal stress and prevents dimensional changes.

[0103] The above surface treatment and annealing treatments are not limited to any particular order, nor are they limited to being performed only once; they may be performed two or more times.

[0104] (Laminated structure) This disclosure also relates to a laminate comprising a fluororesin sheet-like material and a gold-retaining layer that satisfies the requirements described above.

[0105] (metal layer) Examples of metal species constituting the metal layer in this disclosure include copper, aluminum, stainless steel, nickel, and gold. Alloys of these can be used. From the viewpoint of conductivity and circuit processability, copper foil is preferred.

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

[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 foils mentioned above are not particularly limited; for example, rolled copper foil, electrolytic copper foil, etc., are examples.

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

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

[0111] The above surface treatment is not particularly limited, but may include silane coupling treatment, plasma treatment, corona treatment, UV treatment, electron beam treatment, etc. 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 it has at least one selected from amino groups, (meth)acrylic groups, mercapto groups, and epoxy groups at its terminal end. The hydrolyzable group is not particularly limited, but may include alkoxy groups such as methoxy groups and ethoxy groups. The copper foil used in this disclosure may have a rust-preventive layer (such as an oxide film like chromate), a heat-resistant layer, etc. formed on it.

[0112] Surface-treated copper foil having a surface treatment layer of the silane compound described above on the surface of the copper foil can be manufactured by preparing a solution containing the silane compound and then using this solution to surface-treat the copper foil.

[0113] The copper foil described above may have a roughened layer on its surface, for example, to improve adhesion with the fluororesin sheet material. Furthermore, if the roughening treatment is likely to degrade the performance required in this disclosure, the amount of roughening particles electrodeposited onto the copper foil surface may be reduced or the roughening treatment may be omitted as necessary.

[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-preventive treatment layer, and a chromate treatment layer may be provided from the viewpoint of improving various properties. These layers may be a single layer or multiple layers.

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

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

[0117] If the laminate of this disclosure has the above layer (X), the layer configuration may be metal / fluororesin sheet material / layer (X). The laminate of fluororesin sheet material / metal may be on one or both sides of layer (X). In this disclosure, it is preferable to provide a layer (X) on the surface of the fluororesin sheet material.

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

[0119] When bonding the metal foil and the fluororesin sheet material, heating is required. In the manufacture of the laminate according to this disclosure, the heating temperature is preferably 100 to 280°C. Preferably, it is 200 to 280°C, and more preferably 220 to 280°C. The heat treatment process may be a roll-to-roll lamination method, or a method of heat-treating the fluororesin coated on the metal foil. In other words, by using a low heating temperature, the smoothness of the bonding surface is less likely to be impaired during the process of bonding the metal foil and the fluororesin sheet material, which is preferable.

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

[0121] Manufactured by roll-to-roll is preferable because it reduces costs and allows for the production of long laminates. When manufacturing laminates in this way, the width of the laminate is not particularly limited, but it is preferable to be 200 mm or more.

[0122] The laminate of this disclosure exhibits good adhesion between the metal layer and the fluororesin sheet-like material, making it resistant to peeling. Therefore, it has the advantage of low transmission loss because the surface smoothness of the adhesive surface can be maintained. For this reason, it can be suitably used in circuit boards and the like. In particular, it can be especially suitably used in circuit boards for high-frequency circuits.

[0123] Furthermore, in the case of a laminate formed by bonding metal foil to the surface-treated surface of a fluororesin sheet material that has been surface-treated on only one side, surface modification may be performed separately on the untreated surface of the fluororesin sheet material to improve the adhesion between the laminate and other materials.

[0124] In this disclosure, a high-frequency circuit includes not only circuits that transmit only high-frequency signals, but also circuits that have transmission lines for transmitting non-high-frequency signals on the same plane, such as transmission lines that convert high-frequency signals to low-frequency signals and output the generated low-frequency signals to the outside, and transmission lines that supply power for driving high-frequency compatible components. It can also be used as a circuit board for antennas, filters, etc. [Examples]

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

[0126] (Example 1) [Method for manufacturing fluororesin sheet material] PFA was fed into a 360°C extruder, extruded through a 1700mm wide T-die, taken onto a metal cooling roll, and then wound onto a winding core to obtain a roll sheet with a width of 1300mm and a thickness of 12μm. The above 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 end groups: 10 carbon atoms in the main chain. 6 297 items were used per unit. [Surface treatment] The surface treatment is applied to both sides of the roll-shaped fluororesin sheet material (while flowing an inert gas containing 0.50% vinyl acetate and 0.5% carbon dioxide (nitrogen / Ar ratio 95 / 5) near the discharge electrode and roll-shaped ground electrode of the corona discharge device, the sheet is continuously passed along the roll-shaped ground electrode, and the discharge rate is 400 W·min / m 2 Corona discharge was performed on both sides of a fluororesin sheet material, and a long roll of the fluororesin sheet material was wound into a roll to obtain a surface-treated sample. The sample was then evaluated.

[0127] (Example 2) Discharge amount 100W min / m 2Except for the above, a surface-treated sample was obtained in the same manner as in Example 1, and then evaluated.

[0128] (Example 3) As a fluororesin, F-modified 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 end groups: undetectable (main chain carbon number 10) 6 Using less than one unit per unit, and further specifying a nitrogen / Ar ratio of 85 / 15, carbon dioxide 1.0% by volume, and a discharge rate of 100 W·min / m², 2 Except for the above, a surface-treated sample was obtained in the same manner as in Example 1, and then evaluated.

[0129] (Example 4) As a fluororesin, F-modified 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 end groups: undetectable (main chain carbon number 10) 6 Using less than one unit per unit, and further specifying a nitrogen / Ar ratio of 85 / 15, carbon dioxide 1.0% by volume, and a discharge rate of 300 W·min / m², 2 Except for the above, a surface-treated sample was obtained in the same manner as in Example 1, and then evaluated.

[0130] (Example 5) As a fluororesin, F-modified 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 end groups: undetectable (main chain carbon number: 10) 6 Using less than one unit per unit, and further specifying a nitrogen / Ar ratio of 85 / 15, carbon dioxide 1.0% by volume, and a discharge rate of 300 W·min / m², 2 Except for the above, a surface-treated sample was obtained in the same manner as in Example 1, and then evaluated.

[0131] (Comparative Example 1) With a nitrogen / Ar ratio of 100 / 0, no carbon dioxide added, and a discharge rate of 45 W·min / m² 2Except for the above, a surface-treated sample was obtained in the same manner as in Example 1, and then evaluated.

[0132] (Comparative Example 2) The nitrogen / Ar ratio was set to 100 / 0, vinyl acetate was not added, and the discharge rate was 200 W·min / m 2 Except for the above, a surface-treated sample was obtained in the same manner as in Example 1, and then evaluated.

[0133] (Method for measuring the oxygen element ratio) (A) The above surface-treated fluororesin sheet material was cut into 10 cm squares, and on one side of the cut fluororesin sheet material, the oxygen element ratio was measured at 10 points each in the vertical, horizontal, and diagonal directions, as shown in Figure 1, using the method described below. To avoid the effects of heat pressing, 1 x 9 cm samples for peel testing were pre-cut from a 10 cm square sheet of fluororesin material in the vertical, horizontal, and diagonal directions. The oxygen element ratio was then measured using the remaining fluororesin sheet material. Alternatively, if measurement points can be set at the measurement positions defined below by marking, the material may be cut to an appropriate size to fit on the XPS sample stage. Ten points in the vertical direction: Starting from the first point 1.5 cm from the top of a straight line 1.5 cm from the left edge, ten points are placed at 8 mm intervals. Ten horizontal points: Starting from the first point 1.5 cm from the left edge, along a straight line 1.5 cm from the top edge, ten points are placed at 8 mm intervals. Ten points in a diagonal direction: Following the vertical and horizontal directions, starting from the bottom right corner of the fluororesin sheet material, the longer side is a line connecting points 6.5 cm vertically and 6.5 cm horizontally, and the shorter side is 1 cm. On a line 5 mm above the longer side of a rectangle, the first point is 1.5 cm from the top edge of the longer side of the rectangle, and ten points are placed at 8 mm intervals.

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

[0135] Furthermore, (MAX-MIN) / Avg. was calculated by using the maximum value (MAX), minimum value (MIN), and average value (Avg.) of the 10 measurement points obtained in the vertical, horizontal, and diagonal directions as described above.

[0136] (B) The above fluororesin sheet material was divided into 10 sections horizontally (X) and 5 sections vertically (Y) at 10 cm intervals, as shown in Figure 2. The oxygen element ratio was measured at the center of each divided region on the surface where (A) was measured, using the method described above. In addition, as with (A) above, to avoid the effects of heat pressing, 1 x 9 cm peel test samples were pre-cut from each fluororesin sheet material, which had been divided into 10 cm squares, in the vertical, horizontal, and diagonal directions. The oxygen element ratio was then measured using the remaining fluororesin sheet material. For the oxygen element ratio measured at the center of each divided region, the standard deviation obtained from 50 measurements was defined as σ, and the mean value as Avg., thereby calculating σ(X1Y1~X10Y5) / Avg.(X1Y1~X10Y5). Furthermore, by defining the maximum value obtained from 50 measurements (similar to those described above) as MAX and the minimum value as MIN, the formula {MAX(X1Y1~X10Y5)-MIN(X1Y1~X10Y5)} / Avg.(X1Y1~X10Y5) was calculated.

[0137] (90-degree peel test method) (A) [Method for manufacturing laminates for peel testing] Using a fluororesin sheet material and electrolytic copper foil CF-T9DA-SV-18 (thickness 18μm / Rz 0.85μm) (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.), the copper foil, fluororesin sheet material, and copper foil were stacked in that order, with the unroughened surface of the copper foil in contact with the fluororesin sheet material, and the inner surface of the fluororesin sheet material after surface treatment facing upwards. A laminate was obtained by heat pressing using a vacuum heat press machine (model number: MKP-1000HVWH-S7 / manufactured by Mikado Technos Co., Ltd.) at a press temperature of 200℃, preheating time of 120 seconds, pressurizing pressure of 3MPa, and pressurizing time of 600 seconds. Specifically, a 1cm x 9cm peel test sample obtained above, arranged in the vertical, horizontal, and diagonal directions without overlapping, was placed on a 3cm x 12cm piece of copper foil. Then, a 3cm x 12cm piece of copper foil was placed on top and heat-pressed to obtain a laminate.

[0138] [Peel Test Method] The laminate obtained above was divided into three sections, and laminates (1 cm x 12 cm) were taken from each direction for peeling tests.

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

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

[0141] (B) Using the same method as in (A) above, laminated samples (1 cm × 12 cm) for peel testing were taken from each divided region in three directions.

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

[0143] For the laminates for the peel test in each direction, the average value of the adhesive strength in the section from 10 mm from the start of peeling to 40 mm, with a total stroke distance of 30 mm, was calculated. The average value obtained by further averaging the average values of the adhesive strengths in the three directions of the horizontal, vertical, and diagonal directions was taken as the "average value of the adhesive strength within the region" for each divided part. The standard deviation of 50 "average values of the adhesive strength within the region" was σ B (X1Y1~X10Y5), 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 B (X1Y1~X10Y5) was calculated.

[0144] (Evaluation method of transportability) In the surface treatment process of a 500 mm wide fluororesin sheet-like material, the quality of the appearance after passing through the electrode was judged according to the following definition. 〇... The width reduction of the fluororesin sheet-like material on the transport roll during transport is 1 mm or less. △... The width reduction of the fluororesin sheet-like material on the transport roll during transport exceeds 1 mm and is less than 2 mm. ×... The width reduction of the fluororesin sheet-like material on the transport roll during transport is 2 mm or more.

[0145] [ (Method for evaluating the appearance of rolls) The appearance quality of a 500mm wide surface-treated fluororesin sheet material in a rolled state was determined by visual inspection using the following definitions. ○... Three or fewer wrinkles along the outer edge of the roll. △...Five or fewer wrinkles along the outer edge of the roll. ×... More than 6 wrinkles along the outer edge of the roll

[0146] (Method for evaluating the appearance of rolls after long-term storage) The appearance of a 500mm wide surface-treated fluororesin sheet material in a rolled state was visually judged according to the following definition after being stored at room temperature for six months. ○... Three or fewer wrinkles along the outer edge of the roll. △...Five or fewer wrinkles along the outer edge of the roll. ×... More than 6 wrinkles along the outer edge of the roll

[0147] (Method for measuring dielectric breakdown strength) A fluororesin sheet material was placed as the lower electrode, and a φ25mm, 500g weight was placed as the upper electrode. The voltage across both ends was increased at 100V / sec, and the voltage at which the material broke was measured. Sixteen measurements were taken, and the top and bottom six were removed to calculate the average value. The dielectric breakdown strength was then determined by dividing this average value by the thickness. The results were then evaluated according to the following definition. ○...During n10 measurement, n9 or higher falls within 400-500V / μm. △...During n10 measurement, n8 or higher falls within 400-500V / μm. ×...During n10 measurement, n7 or higher does not fall within the 400-500V / μm range. The results are shown in Tables 2 and 3.

[0148] [Table 2]

[0149] [Table 3]

[0150] The results in Tables 2 and 3 show that the fluororesin sheet material in the examples had good transportability and roll appearance. [Industrial applicability]

[0151] The fluororesin sheet material disclosed herein can be suitably used as a circuit board.

Claims

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

2. The fluororesin sheet material according to claim 1, wherein the above oxygen element ratio is 1.35 atomic% or more and 25 atomic% or less, and the above (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 a fluororesin sheet-like material and a metal layer as described in claim 1, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet-like material and the metal layer, obtained by a 90-degree peel test in the longitudinal, transverse, and diagonal directions of a 10 cm square laminate, is σ / Avg. ≤ 35% in all directions.

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

5. A laminate comprising a fluororesin sheet-like material and a metal layer as described in claim 1, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet-like material and the metal layer, obtained by a 90-degree peel test in 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. The laminate according to claim 5, wherein the above 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. The laminate according to any one of claims 3 to 6, wherein the adhesive strength is 0.5 N / cm or more in any direction.

8. On at least one surface, when the oxygen element ratio is measured at 10 points each in the longitudinal, transverse, and diagonal directions of a 10 cm square sheet of material by scanning X-ray photoelectron spectroscopy (XPS), the average value of the oxygen element ratio in all directions is 1.35 atomic% or more, and (MAX-MIN) / Avg. is 40% or less. Furthermore, the region is divided into 'a' sections horizontally (X) and 'b' sections vertically (Y) every 10 cm, and the average value of the oxygen element ratio measured at the center of each divided region is 1.35 atomic% or higher, 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) (In the formula, a and b are integers 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 column a horizontally (X) and row b vertically (Y) within the divided area. Ten points in the vertical direction: Starting from the first point 1.5 cm from the top of a straight line 1.5 cm from the left edge, ten points are placed at 8 mm intervals. Ten points horizontally: Starting from the first point 1.5 cm from the left edge, along a straight line 1.5 cm from the top edge, ten points are placed at 8 mm intervals. Ten points in a diagonal direction: Following the vertical and horizontal directions, starting from the bottom right corner of the sheet material, the long side is a line connecting points 6.5 cm vertically and 6.5 cm horizontally, and the short side is 1 cm. On a line 5 mm above the long side of a rectangle, the first point is 1.5 cm from the top edge of the long side of the rectangle, and ten points are placed at 8 mm intervals.

9. A laminate comprising a fluororesin sheet-like material and a metal layer as described in claim 8, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet-like material and the metal layer, obtained by a 90-degree peel test in the longitudinal, transverse, and diagonal directions of a 10 cm square laminate, is such that in all directions, σ / Avg. ≤ 35% and (MAX-MIN) / Avg. ≤ 150%. Furthermore, the material is divided into 'a' sections horizontally (X) and 'b' sections vertically (Y) every 10 cm, and within each divided 10 cm square area, a 90-degree peel test is performed to measure the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet-like material and the metal layer. The laminate is obtained from the average values ​​of these values ​​and satisfies the following formulas (3) and (4). 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) (In the formula, a and b are integers greater than or equal to 1, and ab ≥ 50.) In this case, XaYb is the average of the adhesive strengths in three directions within the divided region corresponding to column a in the horizontal direction (X) and row b in the vertical direction (Y).

10. A laminate according to claim 5 or 6 that satisfies the following formulas (3) and (4), obtained from the average value of the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet-like material and the metal layer, measured in the horizontal, vertical, and diagonal directions by a 90-degree peel test within each divided 10 cm square area, divided into a 'a' section in the horizontal direction (X) and b section 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) (In the formula, a and b are integers greater than or equal to 1, and ab ≥ 50.) In this case, XaYb is the average of the adhesive strengths in three directions within the divided region corresponding to column a in the horizontal direction (X) and row b in the vertical direction (Y).

11. Furthermore, it has layers other than a fluororesin sheet material and a metal layer, The laminate according to claim 3, 4, 5, 6, or 9, 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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