Fluororesin sheet-like material and laminate containing same

Abstract

A purpose of the present invention is to provide a fluororesin sheet-like material which has in-plane uniformity and excellent adhesiveness without variation. Another purpose of the present invention is to provide a fluororesin sheet-like material which has good conveyability in cases where the sheet-like material is in a roll shape, while having an improved appearance of the roll. Provided is a fluororesin sheet-like material containing a fluororesin, wherein, on at least one surface thereof, if the oxygen element ratio is determined by scanning X-ray photoelectron spectroscopy (XPS) at 10 points in each of the longitudinal direction, the lateral direction, and the diagonal direction of a 10 cm square of the sheet-like material, the average value of the oxygen element ratio in any direction is 1.35 atomic% or more and (MAX – MIN) / Avg. is 40% or less. 10 points in the longitudinal direction: On a straight line at a distance of 1.5 cm from the left end, a first point is set at a distance of 1.5 cm from the top, and ten points are set at intervals of 8 mm. 10 points in the lateral direction: On a straight line at a distance of 1.5 cm from the upper end, a first point is set at a distance of 1.5 cm from the left end, and ten points are set at intervals of 8 mm. 10 points in the diagonal direction: As is the case in the longitudinal direction and the lateral direction, on a straight line 5 mm above the long side of a rectangle, which has a straight line connecting a point at a distance of 6.5 cm in the longitudinal direction from the bottom-right corner of the sheet-like material and a point at a distance of 6.5 cm in the lateral direction from the bottom-right corner of the sheet-like material as a long side, and has a short side of 1 cm, a first point is set at a distance of 1.5 cm from the upper end of the long side of the rectangle, and ten points are set at intervals of 8 mm.

Description

Fluororesin sheet material and laminate containing same

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

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

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

[0004] JP 2019-181735 A

[0005] The present disclosure aims to provide a fluororesin sheet material that is uniform in its surface, has no variations, and has excellent adhesion to other materials. It also aims to provide a fluororesin sheet material that, when rolled, allows for good transportability of the sheet material and improves the appearance of the roll. It also aims to provide a laminate that maintains low transmission loss and has excellent properties when used as a circuit board.

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

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

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

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

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

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

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

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

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

[0015] The laminates (A1) to (A3) and (B) each further comprise a layer other than the fluororesin sheet material and the metal layer, and it is preferable that the layer other than the fluororesin sheet material and the metal layer is at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, and polybutadiene.

[0016] The fluororesin sheet material of the present disclosure has in-plane uniformity, no variation, and excellent adhesion to other materials. Furthermore, the uniform surface treatment improves the transportability of the fluororesin sheet material when it is in roll form, and also improves the appearance of the roll. Furthermore, the laminate of the present disclosure maintains low transmission loss characteristics and has excellent properties when used as a circuit substrate.

[0017] 1 is a schematic diagram showing the measurement positions of the oxygen element ratio in a 10 cm square fluororesin sheet material and the position of obtaining a sample for a peel test. 2 is a schematic diagram showing the measurement positions of the oxygen element ratio in a 10 cm square fluororesin sheet material and the position of obtaining a sample for a peel test.

[0018] The present disclosure is described in detail below. Conventionally, in the surface modification of fluororesin sheets by plasma treatment, patents specifying the amount of oxygen element or the amount of specific functional groups as requirements for achieving good adhesion have been found. However, conventional plasma surface-treated sheets have had the problem of unstable adhesive strength due to uneven surface modification. Furthermore, conventional plasma surface-treated sheets have only evaluated the amount of functional groups in a very small area, so they lack consideration of variations throughout the sheet. As a result, they have not been able to be sufficiently uniformly bonded to other materials, leading to issues such as peeling in subsequent processes and reduced substrate reliability. Furthermore, when the sheet is rolled, problems can arise with the transportability and appearance of the roll.

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

[0020] One of them relates to a relatively small region of a fluororesin sheet material, and is as follows: (A) The fluororesin-containing sheet material of the present disclosure is characterized in that, on at least one surface, when the oxygen element ratio is measured by scanning X-ray photoelectron spectroscopy (XPS) at the following 10 points in each of the longitudinal, transverse, and diagonal directions of a 10 cm square sheet material, the average value (Avg.) of the oxygen element ratio is 1.35 atomic% or more, and (MAX-MIN) / Avg. is 40% or less in all directions. 10 points in the vertical direction: 10 points at 8mm intervals on a line 1.5cm from the left edge, with the first point being 1.5cm from the top. 10 points in the horizontal direction: 10 points at 8mm intervals on a line 1.5cm from the top edge, with the first point being 1.5cm from the left edge. 10 points in the diagonal direction: Following the vertical and horizontal directions, from the bottom right corner of the sheet material, a line connecting points on each side of 6.5cm vertically and 6.5cm horizontally is used as the long side, and a line 5mm above the long side of a rectangle with a short side of 1cm is used as the first point, with the first point being 1.5cm from the top of the long side of the rectangle.

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

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

[0023] Here, the oxygen element ratio is a value measured using a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) PHI5000VersaProbe II (manufactured by ULVAC-PHI, Inc.). Carbon, oxygen, fluorine, nitrogen, and silicon were detected, and the oxygen element ratio was determined from the composition ratios of C1s, O1s, F1s, N1s, and Si2p. The (MAX-MIN) / Avg. value was calculated using the maximum (MAX), minimum (MIN), and average (Avg.) values ​​of the measurements taken at 10 points in each of the vertical, horizontal, and diagonal directions obtained above.

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

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

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

[0027] The present disclosure also relates to a laminate including the fluororesin sheet material and a metal layer. The laminate is preferably laminated so that the surface of the fluororesin sheet material that satisfies the oxygen element ratio requirement is in contact with the metal layer. When only one surface of the fluororesin sheet material satisfies the oxygen element ratio requirement, it is preferable that this surface be in contact with the metal layer. Furthermore, when both surfaces of the fluororesin sheet material satisfy the oxygen element ratio requirement, it is preferable that at least one surface be in contact with the metal layer. In the laminate (A1) including the fluororesin sheet material and a 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, as obtained by 90-degree peel tests in each of the longitudinal, transverse, and diagonal directions, is σ / Avg.≦35% in all directions.

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

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

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

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

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

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

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

[0035] The laminates (A1) to (A3) of the present disclosure preferably have an adhesive strength of 0.5 N / cm or more in any direction. By setting the adhesive strength to more preferably 1 N / cm or more, even more preferably 2 N / cm or more, and most preferably 6 N / cm or more, the laminates can be suitably used as metal laminates or circuit boards. The upper limit is not particularly specified, but, for example, a strength of 20 N / cm or less can be suitably used as metal laminates or circuit boards. This adhesive strength is a value obtained by the peel test method described above.

[0036] Next, another parameter relates to a relatively large region of the fluororesin sheet material, and is as follows: (B) At least one surface of the sheet material containing fluororesin is divided into a regions in the horizontal direction (X) and b regions in the vertical direction (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 more, and is characterized by satisfying the following formulas (1) and (2): σ(X1Y1 to XaYb) / Avg.(X1Y1 to XaYb)≦20% (1) {MAX(X1Y1 to XaYb)-MIN(X1Y1 to XaYb)} / Avg. (X1Y1 to XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1 and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided regions.) There is no particular upper limit for ab, and it can be said that the fluororesin sheet material satisfies the above specification as long as ab≦1000.

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

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

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

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

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

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

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

[0044] Similarly to the laminate (A), the laminate (B) containing the fluororesin sheet material (B) and a metal layer is preferably laminated so that the surface of the fluororesin sheet material that satisfies the oxygen element ratio specification is in contact with the metal layer. In the fluororesin sheet material, if only one surface satisfies the oxygen element ratio specification, it is preferable that this surface be in contact with the metal layer. In the fluororesin sheet material, if both surfaces satisfy the oxygen element ratio specification, it is preferable that at least one surface be in contact with the metal layer. The laminate (B) of the fluororesin sheet material (B) and a metal layer is preferably divided into a section a in the horizontal direction (X) and b in the vertical direction (Y) every 10 cm, and each divided 10 cm square area is preferably subjected to a 90-degree peel test to measure the average adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer in the horizontal, vertical, and diagonal directions. σ Ｂ (X1Y1~XaYb) / Avg. Ｂ (X1Y1~XaYb)≦35% (3) {MAX Ｂ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ (X1Y1 to XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the average of the average adhesive strengths in three directions of the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided regions.) The above Avg. Ｂ (X1Y1 to XaYb) represent further average values ​​(X1Y1, XaYb, etc.) of the average values ​​of adhesive strength in three directions (horizontal, vertical, and diagonal directions) in each 10 cm square area of ​​a × b (pieces). Note that there is no particular upper limit for ab, and if ab≦1000, it can be said that the laminate satisfies the above definition.

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

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

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

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

[0049] In addition, in the above formula (4), {MAX Ｂ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ It is preferable that (X1Y1 to XaYb)≦150%, and {MAX Ｂ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ It is more preferable that (X1Y1 to XaYb)≦100%. The lower limit is not particularly limited, and 5%≦{MAX Ｂ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ (X1Y1 to XaYb), and 10%≦{MAXＢ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ It is more preferable that the group is (X1Y1 to XaYb). Ｂ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ If (X1Y1 to XaYb) are in the above range, not only is the average value of adhesive strength stable over a wide range, but the range of variation in adhesive strength is also small, so that the adhesive strength within the plane is more stable and has similar values, which is advantageous for the stability of electrical properties when the laminate is made into a substrate regardless of the position from which it is sampled. In addition, the average value (Avg.) of the "average adhesive strength within the region" Ｂ (X1Y1 to XaYb)) is preferably 0.5 N / cm or more. There is no particular upper limit, but it may be, for example, 20 N / cm or less.

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

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

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

[0053] The (per)fluoro(alkyl vinyl ether) (PAVE) may be either a fluoroalkyl vinyl ether or a perfluoro(alkyl vinyl ether). In the present disclosure, the term "perfluoro(alkyl vinyl ether)" refers to an alkyl vinyl ether that does not contain a C—H bond. Examples of the PAVE constituting the PAVE unit include those represented by the general formula (1): CF ２ = CFO (CF ２ CFY １ O) ｐ -(CF ２ CF ２ CF ２ O) ｑ -R ｆ (1) (wherein, Y １ is F or CF ３ represents R ｆ represents a perfluoroalkyl group having 1 to 5 carbon atoms, p represents an integer of 0 to 5, and q represents an integer of 0 to 5.) and a monomer represented by the general formula (2): CFX=CXOCF ２ OR １ (2) (Wherein, X may be the same or different and is H, F or CF ３ represents R １ represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms which may contain 1 to 2 atoms of at least one type selected from the group consisting of H, Cl, Br and I, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms which may contain 1 to 2 atoms of at least one type selected from the group consisting of H, Cl, Br and I.

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

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

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

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

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

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

[0060] The TFE / HFP copolymer can further contain (per)fluoro(alkyl vinyl ether) (PAVE) units.The PAVE units contained in the TFE / HFP copolymer can be the same as the PAVE units described above.The TFE / PAVE copolymer does not contain HFP units, so in this respect it is different from the TFE / HFP / PAVE copolymer.

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

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

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

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

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

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

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

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

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

[0070] The fewer functional groups the fluororesin has, the less unstable terminal groups it has. Such fluororesins can be produced by adjusting the conditions during production (polymerization reaction), or by subjecting the fluororesin after polymerization to fluorine gas treatment, heat treatment, supercritical gas extraction treatment, etc. The number of unstable terminal groups can be reduced by using methods such as: excellent treatment efficiency; ３ The fluorine gas treatment is preferable because the fluorine resin having a reduced number of unstable terminal groups is converted into a stable terminal group. The use of such a fluororesin having a reduced number of unstable terminal groups is preferable because it reduces the electrostatic dissipation factor and the loss of electrical signals.

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

[0072] Specific examples of unstable terminal groups include -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), and hydroxyl groups (-CH ２ OH, etc.), -CONH ２ , -COOR(R=CH ３ etc.), -CF ２ Examples of functional groups include H and —OCOO—R (normal propyl carbonate, etc.).

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

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

[0075]

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

[0077] The fluorine-containing compound is not particularly limited, but may be a fluorine radical source that generates fluorine radicals under fluorination treatment conditions. ２ Gas, CoF ３ , AgF ２ , U.F. ６ , OF ２ , N ２ F ２ , C.F. ３ OF, halogen fluorides (e.g., IF ５ , ClF ３ ) etc.

[0078] Above F ２ The fluorine radical source such as a gas may be of 100% concentration, but is preferably mixed with an inert gas and diluted to 5 to 50 mass %, more preferably 15 to 30 mass % for use. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, with nitrogen gas being preferred from an economical standpoint.

[0079] The conditions for the fluorination treatment are not particularly limited, and the molten fluororesin may be brought into contact with the fluorine-containing compound, but the treatment is usually carried out at a temperature below the melting point of the fluororesin, preferably 20 to 220°C, more preferably 100 to 200°C. The fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 25 hours. The fluorination treatment is carried out by exposing an unfluorinated fluororesin to fluorine gas (F ２ It is preferable to bring the material into contact with a gas.

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

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

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

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

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

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

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

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

[0088] More specifically, the adhesive strength was measured by overlapping the surface-treated surfaces of the fluororesin sheet material together and heat pressing (200°C, 0.1 MPa, 60 s) to produce a sample, which was then cut into a 10 mm wide strip. Using a precision universal testing machine Autograph AGS-X 100N (manufactured by Shimadzu Corporation), the unbonded portion of the strip sample was gripped between the upper and lower chucks of the Autograph and pulled at a rate of 100 mm per minute to measure the peel strength, and the obtained value was taken as the adhesive strength.

[0089] The fluororesin sheet material of the present disclosure preferably has a dielectric dissipation factor of less than 0.0015 at 10 GHz. A dielectric dissipation factor within this range is preferable because it can minimize electrical signal loss in circuits. The dielectric dissipation factor is more preferably less than 0.0013, even more preferably less than 0.0010, and most preferably 0.00050 or less. Furthermore, considering signal transmission and antenna transmission / reception at higher frequencies, the dielectric dissipation factor 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. To achieve a dielectric dissipation factor within the above range, it is preferable to use a resin with few unstable terminal groups, and it is more preferable to use a fluororesin that has been subjected to a terminal fluorination treatment.

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

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

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

[0093] The specific method for the surface modification is not particularly limited, but specific examples are described in detail below. Surface modification of fluororesin sheet materials can be achieved by 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 a discharge atmosphere. Alternatively, the surface to be modified can be exposed to an atmosphere of an organic compound-containing inert gas, which is an inert gas containing an organic compound, and a high-frequency voltage is applied between electrodes to generate a discharge, thereby generating active species on the surface. Surface modification can then be achieved by introducing functional groups of the organic compound or graft polymerizing a polymerizable organic compound. Examples of 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. A ratio of nitrogen gas to argon gas within the above range is advantageous in that discharge is stable and more uniform in-plane surface modification is possible. Furthermore, the carbon dioxide gas content is preferably 0.05 to 5% by volume, more preferably 0.25 to 2% by volume, relative to the nitrogen gas / argon gas ratio. A carbon dioxide gas content within the above range is advantageous in that functional groups contributing to adhesiveness on the surface of the fluororesin sheet material are imparted within a suitable range.

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

[0096] The concentration of the organic compound in the organic compound-containing inert gas varies depending on the type of organic compound, the type of fluororesin to be surface-modified, etc., but is usually 0.1 to 3.0% by volume, preferably 0.1 to 1.0% by volume, more preferably 0.15 to 1.0% by volume, and even more preferably 0.30 to 1.0% by volume. The discharge conditions may be appropriately selected depending on the desired degree of surface modification, the type of fluororesin, the type and concentration of the organic compound, etc. The discharge rate is usually 50 to 1500 W·min / m ２ , preferably 70 W·min / m２ More than 1400W・min / m ２ The discharge treatment is performed within the following range. The treatment temperature can be any temperature in the range of 0°C to 100°C. Due to concerns about stretching and wrinkling of the fluororesin sheet material, a temperature of 80°C or less is preferable. Considering that oxygen elements on the surface are deactivated by heat applied during lamination with metal foil or the like, resulting in a decrease in adhesive ability, the degree of surface modification of the fluororesin sheet material is such that the oxygen element abundance ratio observed by ESCA is 1.5% or more, preferably 1.75% or more, more preferably 2.0% or more, and even more preferably 2.5% or more. There is no particular upper limit, but in consideration of the impact on productivity and other physical properties, it is preferably 25.0% or less. The nitrogen element abundance ratio is not particularly specified, but is preferably 0.1% or more.

[0097] During the surface modification, it is preferable to perform the discharge treatment at a discharge intensity (output per unit area) within the range of 1.0 to 10 W / cm², with the gas concentration / line speed ratio adjusted to a range of 0.005 to 0.05 L / m. The gas concentration / line speed ratio here refers to the ratio of the organic compound concentration in the organic compound-containing inert gas divided by the line speed. At a gas concentration below 0.005 L / m, the space is not filled with sufficient gas relative to the transport speed, making it difficult for the activated gas to contact the surface of the fluororesin sheet material, resulting in reduced in-plane uniformity. At a gas concentration above 0.05 L / m, the surface is overtreated and damaged, resulting in the formation of low-molecular-weight compounds on the surface, forming a brittle layer and ultimately reducing adhesive strength. Therefore, treatment within this range is particularly preferred, as it is believed that this results in more uniform in-plane treatment of the fluororesin sheet material and the desired adhesive properties.

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

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

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

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

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

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

[0104] (Laminate) The present disclosure also relates to a laminate that includes a fluororesin sheet material and a metal layer, and that satisfies the above-mentioned requirements.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0119] Heating is required when bonding the metal foil and the fluororesin sheet material, and in producing the laminate of the present disclosure, the heating temperature is preferably 100 to 280°C. A temperature of 200 to 280°C is more preferable, and a temperature of 220 to 280°C is even more preferable. The heat treatment step may be a roll-to-roll lamination method or a method in which a fluororesin coated on a metal foil is heat-treated. In other words, a low heating temperature is preferable in that the smoothness of the bonding surface is less impaired in the step of bonding the metal foil and the fluororesin sheet material.

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

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

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

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

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

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

[0126] (Example 1) [Method for producing a fluororesin sheet material] PFA was charged into an extruder at 360°C, extruded through a 1700 mm wide T-die, taken up on a metal cooling roll, and further wound around a winding core to obtain a roll sheet with a width of 1300 mm and a thickness of 12 μm. The PFA was a TFE / PPVE copolymer, with a composition of TFE / PPVE=95.4 / 4.6 (mass%), MFR of 15.8 g / 10 min, a melting point of 305°C, and a main chain carbon number of 10. ６ [Surface Treatment] Surface treatment was performed on both sides of the rolled fluororesin sheet material (a corona discharge device was used). While an inert gas (nitrogen / Ar ratio 95 / 5) containing 0.50% by volume of vinyl acetate and 0.5% by volume of carbon dioxide was flowed near the discharge electrode and rolled ground electrode, the sheet was passed continuously along the rolled ground electrode, and a discharge amount of 400 W min / m was obtained. ２ Both sides of the fluororesin sheet material were subjected to corona discharge (using a corona discharge tester), and the long fluororesin sheet material was wound into a roll to obtain a surface-treated sample, which was then evaluated.

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

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

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

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

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

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

[0133] (Method for measuring oxygen element ratio) (A) The above surface-treated fluororesin sheet material was cut into a 10 cm square, and the oxygen element ratio was measured on one side of the cut-out fluororesin sheet material at 10 points in each of the longitudinal, transverse, and diagonal directions as shown in Figure 1, using the method described below. Note that, to avoid the influence of heat pressing, 1 x 9 cm peel test samples were cut out in advance from the 10 cm square cut-out fluororesin sheet material in the longitudinal, transverse, and diagonal directions, and the oxygen element ratio was measured using the remaining fluororesin sheet material. Furthermore, if the measurement points can be set at the measurement positions specified below by marking or the like, the sample may be cut to an appropriate size to fit on the XPS sample stage. 10 points in the vertical direction: 10 points at 8mm intervals on a line 1.5cm from the left edge, with the first point being 1.5cm from the top. 10 points in the horizontal direction: 10 points at 8mm intervals on a line 1.5cm from the top edge, with the first point being 1.5cm from the left edge. 10 points in the diagonal direction: Following the vertical and horizontal directions, from the bottom right corner of the fluororesin sheet material, a line connecting points on each side of 6.5cm vertically and 6.5cm horizontally is used as the long side, and a line 5mm above the long side of a rectangle with a short side of 1cm is used as the first point, with the first point being 1.5cm from the top of the long side of the rectangle. 10 points at 8mm intervals.

[0134] The oxygen element ratio of the surface of the surface-treated fluororesin sheet material was measured using a scanning X-ray photoelectron spectrometer (XPS / ESCA) PHI5000 VersaProbe II (manufactured by ULVAC-PHI, Inc.) under the conditions shown 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: Monochromated AlKα Beam diameter: 100 μm X-ray output: 25 W Measurement area: 1000 μm × 300 μm Pass energy: 23.5 eV Detection angle: 45°

[0135] Furthermore, the maximum value (MAX), minimum value (MIN), and average value (Avg.) of the measured values ​​at 10 points in each of the vertical direction, horizontal direction, and oblique direction obtained as described above were used to calculate (MAX-MIN) / Avg.

[0136] (B) As shown in Figure 2, the fluororesin sheet material was divided into 10 sections in the horizontal direction (X) and 5 sections in the vertical direction (Y), every 10 cm. The oxygen element ratio was measured at the center of each divided area on the surface measured in (A) above using the above method. As in (A) above, 1 x 9 cm peel test samples were cut out in the vertical, horizontal, and diagonal directions from each 10 cm square fluororesin sheet material to avoid the influence of the heat press, and the oxygen element ratio was measured using the remaining fluororesin sheet material. For the oxygen element ratio measured at the center of each divided area, σ was used to calculate σ(X1Y1-X10Y5) / Avg.(X1Y1-X10Y5), where σ is the standard deviation and Avg. is the average value obtained from 50 measurements. In addition, the maximum value obtained from the 50 measurements similar to those described above was defined as MAX, and the minimum value obtained from the 50 measurements was defined as MIN, whereby {MAX(X1Y1 to X10Y5) - MIN(X1Y1 to X10Y5)} / Avg.(X1Y1 to X10Y5) was calculated.

[0137] (90-degree peel test method) (A) [Method for manufacturing laminate for peel test] A fluororesin sheet material and electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) were used, and the copper foil, fluororesin sheet material, and copper foil were stacked in this order, with the unroughened side of the copper foil in contact with the fluororesin sheet material and with the inner surface of the fluororesin sheet material after surface treatment facing up, and a laminate was 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 preheat time of 120 seconds, a pressure of 3 MPa, and a press time of 600 seconds. Specifically, the 1 cm x 9 cm peel test samples obtained above in the vertical, horizontal, and diagonal directions were arranged on copper foil cut to 3 cm x 12 cm so as not to overlap, and copper foil cut to 3 cm x 12 cm was further placed on top of them and hot 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) for peel test were taken from each direction.

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

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

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

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

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

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

[0145] (Method for evaluating roll appearance) The appearance of a 500 mm wide surface-treated fluororesin sheet material in a rolled state was visually judged according to the following criteria: ◯: 3 or less wrinkles along the outer periphery of the roll △: 5 or less wrinkles along the outer periphery of the roll ×: 6 or more wrinkles along the outer periphery of the roll

[0146] (Method for evaluating roll appearance after long-term storage) The appearance of a 500 mm wide surface-treated fluororesin sheet material in a rolled state after storage at room temperature for six months was visually judged according to the following criteria: ◯: 3 or less wrinkles along the outer periphery of the roll △: 5 or less wrinkles along the outer periphery of the roll ×: 6 or more wrinkles along the outer periphery of the roll

[0147] (Method for Measuring Dielectric Breakdown Strength) A fluororesin sheet material was placed on the lower electrode, and a 25 mm diameter, 500 g weight was placed on the upper electrode. The voltage at both ends was increased at 100 V / sec to measure the breakdown voltage. Sixteen measurements were made, with the top and bottom six removed to calculate the average value, and the average value was divided by the thickness to determine the dielectric breakdown strength. The results were evaluated according to the following criteria: ◯: During n10 measurements, n9 and above were within 400-500 V / μm. △: During n10 measurements, n8 and above were within 400-500 V / μm. ×: During n10 measurements, n7 and above were not within 400-500 V / μm. The results are shown in Tables 2 and 3.

[0148]

[0149]

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

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

Claims

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

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

3. A laminate comprising the fluororesin sheet material of claim 1 or 2 and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by 90-degree peel tests in each of the vertical, horizontal and diagonal directions of a 10 cm square laminate is σ / Avg.≦35% in any direction.

4. A laminate comprising the fluororesin sheet material of claim 1 or 2 and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by 90-degree peel tests in each of the vertical, horizontal, and diagonal directions of a 10 cm square laminate is (MAX - MIN) / Avg. ≦150% in all directions.

5. A laminate comprising the fluororesin sheet material of claim 1 or 2 and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer obtained by 90-degree peel tests in each of the vertical, horizontal 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 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. A sheet material containing fluororesin, wherein on at least one surface, the material is divided into a sections in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and the average oxygen element ratio measured at the center of each divided section is 1.35 atomic% or more, and the following formulas (1) and (2) are satisfied: σ(X1Y1-XaYb) / Avg.(X1Y1-XaYb)≦20% (1) {MAX(X1Y1-XaYb)-MIN(X1Y1-XaYb)} / Avg. (X1Y1 to XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided regions.) 9. A laminate comprising the fluororesin sheet material of claim 8 and a metal layer, wherein the laminate is divided into a sections in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and within each divided 10 cm square area, a 90-degree peel test is carried out to measure the average adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer in the horizontal direction, vertical direction, and diagonal direction, and the laminate satisfies the following formulas (3) and (4): σ Ｂ (X1Y1~XaYb) / Avg. Ｂ (X1Y1~XaYb)≦35% (3) {MAX Ｂ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ (X1Y1 to XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the average of the average adhesive strengths in three directions of the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) among the divided regions.) 10. A fluororesin sheet material, on at least one surface, when the oxygen element ratio is measured by scanning X-ray photoelectron spectroscopy (XPS) at the following 10 points in each of the longitudinal, transverse, and diagonal directions of a 10 cm square sheet material, the oxygen element ratio is 1.35 atomic% or more in all directions, and (MAX - MIN) / Avg. is 40% or less, and further, when the sheet is divided into a sections in the transverse direction (X) and b sections in the longitudinal direction (Y) every 10 cm, the oxygen element ratio measured at the center of each divided section is all 1.35 atomic% or more, and also satisfies the following formulas (1) and (2): σ(X1Y1-XaYb) / Avg.(X1Y1-XaYb)≦20% (1) {MAX(X1Y1-XaYb)-MIN(X1Y1-XaYb)} / Avg. (X1Y1 to XaYb)≦30% (2) (wherein a and b are each an integer greater than or equal to 1 and ab≧50. In this case, XaYb is the value of the oxygen element ratio measured in the region that corresponds to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) of the divided region.) 10 points in the vertical direction: 10 points at 8 mm intervals on a line 1.5 cm from the left end, with the first point being a point 1.5 cm from the top 10 points in the horizontal direction: 10 points at 8 mm intervals on a line 1.5 cm from the top 10 points diagonally: In both the vertical and horizontal directions, from the bottom right corner of the sheet material, a straight line connecting points on each side of 6.5 cm vertically and 6.5 cm horizontally is the long side, and the short side is 1 cm. On a straight line 5 mm above the long side of the rectangle, the first point is 1.5 cm from the top of the long side of the rectangle, and 10 points are made at 8 mm intervals.

11. A laminate comprising the fluororesin sheet material of claim 10 and a metal layer, wherein the adhesive strength between the oxygen element ratio measurement surface of said fluororesin sheet material and the metal layer, obtained by a 90-degree peel test in each of the longitudinal, transverse and diagonal directions of a 10 cm square laminate, is σ / Avg.≦35% and (MAX-MIN) / Avg.≦150% in any direction, and further wherein the laminate is divided into a sections in the transverse direction (X) and b sections in the longitudinal direction (Y) every 10 cm, and the laminate satisfies the following formulas (3) and (4), which are obtained from the average adhesive strengths between the oxygen element ratio measurement surface of said fluororesin sheet material and the metal layer, measured in the transverse, longitudinal and diagonal directions within each divided 10 cm square area by a 90-degree peel test: σ Ｂ (X1Y1~XaYb) / Avg. Ｂ (X1Y1~XaYb)≦35% (3) {MAX Ｂ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ (X1Y1 to XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the average of the average adhesive strengths in three directions of the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) among the divided regions.) 12. The laminate according to claim 5 or 6, which is divided into a sections in the horizontal direction (X) and b sections in the vertical direction (Y) every 10 cm, and within each divided 10 cm square area, measurements are made in the horizontal direction, vertical direction, and diagonal direction by a 90-degree peel test to determine the average adhesive strength between the oxygen element ratio measurement surface of the fluororesin sheet material and the metal layer, and satisfies the following formulas (3) and (4): σ Ｂ (X1Y1~XaYb) / Avg. Ｂ (X1Y1~XaYb)≦35% (3) {MAX Ｂ (X1Y1~XaYb)-MIN Ｂ (X1Y1~XaYb)} / Avg. Ｂ (X1Y1 to XaYb)≦150% (4) (wherein a and b are each an integer greater than or equal to 1, and ab≧50. In this case, XaYb is the average of the average adhesive strengths in three directions of the region corresponding to the a-th column in the horizontal direction (X) and the b-th row in the vertical direction (Y) among the divided regions.) 13. A laminate according to any one of claims 3 to 7, 9, 11 and 12, further comprising a layer other than the fluororesin sheet material and the metal layer, wherein the layer other than the fluororesin sheet material and the metal layer is at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene and polybutadiene.

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