JP2021059683A - Resin sheet - Google Patents

Abstract

To provide a resin sheet containing a heat-resistant resin as a main component which can be stably used under high temperature.SOLUTION: A resin sheet contains a heat-resistant resin as a main component, has no air permeability in a thickness direction, and has permeability A in a surface direction on at least one main surface of 1 mL/min or more. The permeability A is a characteristic represented by an air flow quantity per minute permeating from outside toward inside of a measurement region between the main surface and a smooth surface when a ring-like measurement region with an outer diameter of 47 mm and an inner diameter of 20 mm is set in the main surface, the sheet is pressed to the smooth surface of a member having no air permeability in the thickness direction with a load of 654.5 gf so that the main surface is brought into contact with the smooth surface in the whole measurement region and the pressure in the inside of the measurement region is reduced compared with that in the outside by 15 kPa.SELECTED DRAWING: Figure 1

Description

The present invention relates to a resin sheet.

A resin sheet containing a heat-resistant resin as a main component (heat-resistant resin sheet) is known. Patent Document 1 discloses a sheet of polytetrafluoroethylene (hereinafter referred to as "PTFE"). Patent Document 2 discloses a polyimide sheet. The heat-resistant resin sheet is expected to be used at high temperatures.

Japanese Unexamined Patent Publication No. 3-197122 Japanese Unexamined Patent Publication No. 4-283246

The heat-resistant resin sheet is used, for example, by arranging it on an object. After passing through a high temperature, the heat-resistant resin sheet may be peeled off from the state where it is placed on the object. If the heat-resistant resin sheet does not have air permeability in the thickness direction, air bubbles caught between the heat-resistant resin sheet and the object during placement may remain after placement, or it may be difficult to peel off from the state of being in close contact with the object. May become. In addition, the remaining bubbles may expand due to the high temperature, which may adversely affect the object. When the heat-resistant resin sheet has air permeability in the thickness direction, the above-mentioned problems are less likely to occur, but shrinkage and deformation are likely to occur when used at a high temperature.

An object of the present invention is to provide a resin sheet containing a heat-resistant resin as a main component, which can be used stably at a high temperature.

The present invention
Contains heat-resistant resin as the main component
Not breathable in the thickness direction,
A resin sheet having an air permeability A in the plane direction on at least one main surface of 1 mL / min or more.
I will provide a.
However, the air permeability A is
A ring-shaped measurement area having an outer diameter of 47 mm and an inner diameter of 20 mm is set on the main surface.
The sheet is pressed against the smooth surface with a load of 654.5 gf so that the main surface is in contact with the smooth surface of the member having no air permeability in the thickness direction in the entire measurement region, and the measurement region is pressed. When the inside is decompressed by 15 kPa compared to the outside,
It is a characteristic represented by the amount of airflow per minute that permeates between the main surface and the smooth surface from the outside to the inside of the measurement region.

The resin sheet of the present invention does not have air permeability in the thickness direction. In other words, the resin sheet does not have pores or through holes that provide breathability in the thickness direction. Therefore, shrinkage and deformation during use at high temperatures can be suppressed. On the other hand, the resin sheet of the present invention has an air permeability A in the surface direction on at least one main surface. Therefore, by using the main surface so as to face the object, for example, the entrainment of air bubbles due to the arrangement is suppressed, and the peelability from the state of being in close contact with the object is improved. Therefore, the resin sheet of the present invention can be used stably at a high temperature.

FIG. 1 is a cross-sectional view schematically showing an example of the resin sheet of the present invention. FIG. 2 is a plan view schematically showing the state of the main surface in an example of the resin sheet of the present invention. FIG. 3 is a schematic view showing an example of a mode in which the resin sheet of the present invention is used. FIG. 4 is a schematic view showing another example of the mode in which the resin sheet of the present invention is used. FIG. 5 is a schematic view for explaining a method of evaluating the air permeability A in the surface direction with respect to the resin sheet. FIG. 6 is a schematic view for explaining the surface processing template used in the examples. FIG. 7 is a graph showing the maximum height Rz and the air permeability A in the plane direction of the resin sheets produced in Examples and Comparative Examples. FIG. 8 is a graph showing the arithmetic mean roughness Ra and the air permeability A in the plane direction of the resin sheets produced in Examples and Comparative Examples.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Resin sheet]
An example of the resin sheet of the present invention is shown in FIG. The resin sheet 1 shown in FIG. 1 contains a heat-resistant resin as a main component. The resin sheet 1 is a single layer. The resin sheet 1 has heat resistance derived from a heat resistant resin. As used herein, the term "main component" means the component having the highest content. The content of the main component is, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, 80% by weight or more, and further 90% by weight or more. The resin sheet 1 may be made of a heat-resistant resin.

The resin sheet 1 does not have air permeability in the thickness direction. In the present specification, "not having air permeability in the thickness direction" is defined in the air permeability measurement method B (Garley type method) defined in Japanese Industrial Standards (hereinafter referred to as "JIS") L1096: 2010. Expressed by the air permeability (Garley air permeability) obtained in accordance with this, it means that the air permeability in the thickness direction exceeds 10,000 seconds / 100 mL. The resin sheet 1 usually does not have pores and / or through holes connecting both main surfaces 2A and 2B of the sheet. The resin sheet 1 is typically a non-porous sheet made of a non-porous base material.

The air permeability A in the plane direction on one main surface 2A of the resin sheet 1 is 1 mL / min or more. The air permeability A may be 2 mL / min or more, 5 mL / min or more, 9 mL / min or more, 15 mL / min or more, and further 30 mL / min or more. The upper limit of the air permeability A is, for example, 100 mL / min or less. The other main surface 2B of the resin sheet 1 may or may not have the air permeability A in the surface direction in each of the above ranges. In the resin sheet of the present invention, the air permeability A in the surface direction on at least one main surface is in each of the above ranges.

For the air permeability A, a ring-shaped measurement region having an outer diameter of 47 mm and an inner diameter of 20 mm is set on the main surface, and the resin sheet 1 is loaded with a load of 654.5 gf so that the main surface is in contact with the smooth surface in the entire measurement region. When pressed against the smooth surface and the inside of the measurement area is depressurized by 15 kPa compared to the outside, the air flow rate per minute permeates between the main surface and the smooth surface from the outside to the inside of the measurement area. It is a characteristic represented. The smooth surface on which the resin sheet 1 is pressed is, for example, a surface having an arithmetic average roughness Ra (hereinafter, referred to as “arithmetic mean roughness Ra”) defined in JIS B0601: 2001 of 0.1 μm or less. Further, the smooth surface is a surface of a member that does not have air permeability in the thickness direction, is not deformed at the time of evaluation of the air permeability A, and is a surface that does not adhere or adhere to the sheet to be evaluated. The smooth surface is, for example, the surface of a resin plate or a metal plate having a sufficient thickness so as not to be deformed when the air permeability A is evaluated. Examples of resin plates are acrylic plates and polycarbonate plates. An example of a metal plate is a stainless steel plate. The above load is a load sufficient to evaluate the air permeability A without excessively deforming the surface shape of the main surface.

The air permeability A in the plane direction on each main surface of the resin sheet manufactured by a general molding method such as melt molding or cast molding is usually 0 mL / min. Further, as shown in Examples described later, when the surface roughness of the main surface, for example, the arithmetic surface roughness Ra, is large, the air permeability A in the surface direction on the main surface automatically becomes 1 mL / min or more. Do not mean.

The heat-resistant resin contained in the resin sheet 1 is typically a resin having a melting point of 150 ° C. or higher. The melting point of the heat-resistant resin may be 160 ° C. or higher, 200 ° C. or higher, and further 300 ° C. or higher. Examples of heat-resistant resins are fluororesins, polyimides, polyamideimides, and polyphenylene sulfides.

The heat-resistant resin is preferably a fluororesin. In other words, the resin sheet 1 is preferably a fluororesin sheet. Fluororesin generally has high heat resistance and peelability. Further, the fluororesin is softer than other heat-resistant resins such as polyimide. Therefore, it is possible to more reliably and efficiently impart the air permeability A by the surface processing described later.

Examples of fluororesins are PTFE, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE). .. The fluororesin is preferably PTFE. PTFE is particularly excellent in heat resistance and peelability. The fluororesin sheet 1 may not contain a component other than the fluororesin, or may substantially not contain a component other than the fluororesin. As used herein, "substantially free" means that the content is less than 0.1% by weight, preferably less than 0.01% by weight.

The surface roughness of the main surface 2A having an air permeability A of 1 mL / min or more is indicated by the maximum height Rz (hereinafter, referred to as “maximum height Rz”) defined in JIS B0601: 2001, for example. It may be 30 μm or less, 25 μm or less, 23 μm or less, 20 μm or less, 18 μm or less, 15 μm or less, 13 μm or less, 10 μm or less, 9 μm or less, and further 8 μm or less. The lower limit of the maximum height Rz is, for example, 2 μm or more. The other main surface 2B may have a maximum height Rz in each of the above ranges.

The surface roughness of the main surface 2A having an air permeability A of 1 mL / min or more is, for example, 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, and further 2 μm or less, expressed by the arithmetic mean roughness Ra. You may. The lower limit of the arithmetic mean roughness Ra is, for example, 0.3 μm or more. The other main surface 2B may have an arithmetic mean roughness Ra in each of the above ranges.

The main surface 2A may have a groove portion composed of one or a plurality of grooves. The groove portion can serve as a permeation path for air that permeates between the main surface 2A and the smooth surface in a state where the resin sheet 1 is pressed against the smooth surface. The groove portion may have at least one groove connected to the periphery of the resin sheet 1 at one or both ends. The groove portion may have at least one groove in which both ends are connected to the circumference of the resin sheet 1. In this case, effects such as achieving a larger air permeability A and / or improving the uniformity of the air permeability A in the resin sheet 1 can be obtained. When the shape of the main surface of the resin sheet 1 is polygonal, the groove portion has at least one groove connecting one side of the polygon and one or two or more sides different from the side. May be good. The groove may extend over the entire main surface 2A. In this case, the uniformity of the air permeability A in the resin sheet 1 can be improved. The width of each groove constituting the groove portion is, for example, 10 to 200 μm, and may be 20 to 50 μm. The depth of each groove constituting the groove portion is, for example, 2 to 30 μm, and may be 10 to 30 μm. However, for one groove, the width and / or depth may not be constant throughout the groove. Further, the width and depth of each groove constituting the groove portion may not be the same, and the groove portion may have a plurality of grooves having different widths and / or depths. The groove forming the groove portion may extend linearly on the main surface 2A or may extend in a non-linear shape, for example, a curved line shape. The other main surface 2B may have the groove portion.

The groove portion may have grooves arranged in a grid pattern on the main surface 2A and / or the main surface 2B. FIG. 2 shows an example of the resin sheet 1 having the groove portion on the main surface 2A. The main surface 2A of the resin sheet 1 of FIG. 2 has groove portions 4 composed of a plurality of grooves 3 arranged in a square lattice pattern. Each groove 3 is connected to the circumference 5 of the resin sheet 1 at both ends thereof. The groove 4 extends over the entire main surface 2A. The grid in which the grooves 3 are arranged is not limited to the square grid. The grooves 3 may be arranged in various lattices such as a rectangular lattice, an orthorhombic lattice, a hexagonal lattice, a rhombic lattice, and a central rectangular lattice. In the grooves 3 arranged in a grid pattern, the pitch P1 which is the distance between the center lines of the adjacent grooves 3 is, for example, 50 to 1000 μm, and may be 200 to 1000 μm.

The thickness of the resin sheet 1 is, for example, 10 to 500 μm, and may be 20 to 300 μm, 30 to 200 μm, and further 50 to 100 μm.

The shape of the resin sheet 1 is, for example, a polygon including squares and rectangles, a circle, an ellipse, and a band. However, the shape of the resin sheet 1 is not limited to the above example. The polygonal, circular, and elliptical resin sheets 1 can be distributed as a single leaf, and the strip-shaped resin sheet 1 can be distributed as a winding body (roll) wound around a winding core. The width of the strip-shaped resin sheet 1 and the width of the wound body around which the strip-shaped resin sheet 1 is wound can be freely set.

The resin sheet 1 in FIG. 1 is a single layer. However, another layer may be arranged on the main surface 2A and / or the main surface 2B of the resin sheet 1.

[Manufacturing method of resin sheet]
The resin sheet 1 can be manufactured, for example, by the following method.

First, a precursor sheet containing a heat-resistant resin as a main component is prepared. The precursor sheet can be produced by a general sheet molding method such as melt molding and cast molding.

As an example, a method for producing a precursor sheet containing PTFE as a main component (PTFE precursor sheet) will be described.

First, PTFE powder (molding powder) is introduced into a mold, and a predetermined pressure is applied to the powder in the mold for a predetermined time to preform. Premolding may be carried out at room temperature. The shape of the internal space of the mold is preferably cylindrical in order to enable cutting by a cutting lathe described later. In this case, a columnar premolded product and a PTFE block can be obtained. Next, the preformed product is taken out from the mold and fired at a temperature equal to or higher than the melting point of PTFE (327 ° C.) for a predetermined time to obtain a PTFE block. Next, the PTFE block is cut to a predetermined thickness to obtain a PTFE precursor sheet which is a cutting sheet (skive sheet). With a cylindrical PTFE block, it is possible to use a cutting lathe that continuously cuts the surface while rotating the block. Therefore, the PTFE precursor sheet can be efficiently obtained. Further, according to the cutting lathe, it is relatively easy to control the thickness of the PTFE precursor sheet to be formed, and it is also possible to obtain a strip-shaped PTFE precursor sheet.

The PTFE precursor sheet may be prepared by the following method.

First, a base sheet for applying the PTFE dispersion to the surface is prepared. The base sheet is composed of, for example, resin, metal, paper and a composite material thereof. The surface of the base sheet to which the PTFE dispersion liquid is applied may be subjected to a peeling treatment for facilitating the peeling of the PTFE sheet from the base sheet. A known method can be applied to the peeling treatment. Next, a coating film of the PTFE dispersion liquid is formed on the surface of the base sheet. Various known coaters can be used for applying the PTFE dispersion. The PTFE dispersion may be applied to the surface of the base sheet by immersion. Next, the formed coating film is dried and fired to form a PTFE sheet. Next, the formed PTFE sheet is peeled off from the base material sheet to obtain a PTFE precursor sheet which is a cast sheet. In this method, the thickness of the PTFE precursor sheet can be controlled by the coating thickness of the PTFE dispersion liquid on the base sheet.

The method for producing the PTFE precursor sheet is not limited to the above example.

Next, surface processing is performed to impart air permeability A to at least one main surface of the precursor sheet. In the surface processing, a surface shape that can serve as an air permeation path to and from the smooth surface when pressed against the smooth surface is given to the main surface. Examples of surface processing are scratch processing, etching processing by laser irradiation, and press processing in which a template having a specific surface shape on the pressing surface is pressed against the main surface and pressed. In the case of a precursor sheet of a relatively soft resin such as fluororesin, the template may be pressed against the main surface opposite to the main surface to be surface-processed. However, the surface processing method is not limited to the above example.

The rubbing process can be performed by rubbing the main surface with a rubbing member, for example. Examples of the rubbing member are a file, sandpaper, grindstone, steel wool, and a sheet, disc, belt, etc. having a rubbing surface composed of these members. However, the rubbing member is not limited to the above example.

The etching process can be performed by, for example, irradiation of energy rays such as a laser or chemical etching using masking such as a resist. However, the etching processing method is not limited to the above example.

The template used for stamping is composed of, for example, metal, resin, glass and a composite material thereof. It is also possible to use the above-mentioned rubbing member as a template. In order to form the resin sheet 1 having the groove portions 4 having the grooves 3 arranged in a grid pattern on the main surface, a surface shape complementary to the groove portions, for example, convex portions extending linearly are arranged in a grid pattern. A template having a surface shape, which is formed on the pressing surface, can be used.

[Use of resin sheet]
An example of the usage mode of the resin sheet 1 is shown in FIG. In FIG. 3, the resin sheet 1 is wound around the winding body (roll) 11 in a state of being laminated with the film 12. The resin sheet 1 is used as a protective sheet for the film 12. The air permeability A suppresses the entrainment of air bubbles when, for example, the resin sheet 1 is laminated on the film 12 and / or wound together with the film 12. Further, the resin sheet 1 can be more stably peeled off from the wound body 11 and / or after being fed out.

The film 12 is made of, for example, metal or resin. In the resin film 12, outgas may be generated after molding into the film. Outgas is likely to occur, for example, in the polycarbonate, polystyrene and acrylic resin films 12. The outgas generated after winding remains between the adjacent films 12 and may cause deformation or dents of the films 12. By laminating the resin sheet 1 with the film 12 and winding the film 12, the outgas generated after the winding can be more reliably released to the outside. Further, it is also possible to consider the implementation of the degassing treatment in which the winding body 11 is heated and the outgas is released to the outside in advance.

FIG. 4 shows another example of the usage mode of the resin sheet 1. In FIG. 4, the resin sheet 1 is wound around the winding body (roll) 13 in a state of being laminated with the adhesive tape 16. The adhesive tape 16 is a laminate of the base film 14 and the adhesive layer 15. The resin sheet 1 is in contact with the adhesive layer 15. The surface of the resin sheet 1 in contact with the adhesive layer 15 is, for example, a main surface 2A having a degree of air permeability A. The resin sheet 1 is used as a separator for the adhesive tape 16. The air permeability A suppresses the entrainment of air bubbles when, for example, the resin sheet 1 is laminated on the adhesive tape 16. Further, the resin sheet 1 can be peeled off more stably after being unwound from the winding body 13.

The adhesive tape 16 is usually aged after being wound around the winding body 13. The aging treatment stabilizes the adhesiveness of the adhesive layer 15. At that time, outgas may be generated from the adhesive layer 15. The outgas remains between the adjacent adhesive tapes 16 and may cause deformation, dents, etc. of the adhesive layer 15. By laminating the resin sheet 1 with the adhesive tape 16 and winding the resin sheet 1, the outgas generated during the aging treatment can be more reliably released to the outside.

The use and method of using the resin sheet 1 are not limited to the above examples. For example, the resin sheet 1 may be used for various purposes exposed to high temperatures. Further, the resin sheet 1 may be used by arranging it on a stage or a table.

The present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

First, a method for evaluating the characteristics of the resin sheets of Examples and Comparative Examples will be shown.

[Breathability in the thickness direction]
The air permeability (garley air permeability) in the thickness direction of the resin sheet was determined in accordance with the air permeability measurement method B (garley type method) specified in JIS L1096: 2010.

[Air permeability A in the plane direction]
The air permeability A on the main surface (evaluation surface) of the resin sheet was determined as follows using a measuring jig. The evaluation method of the air permeability A will be described with reference to FIG.

As measuring jigs, a ring-shaped acrylic resin plate 52 (thickness 2.0 mm) having an outer diameter of 47 mm and an inner diameter of 20 mm, a disc-shaped silicone rubber sheet 53 having a diameter of 47 mm (thickness 2.0 mm and a weight of 4.5 g), In addition, a columnar weight 54 (made of stainless steel, weight 650 g) having a diameter of 47 mm was prepared. Further, the resin sheet was cut into a circle having a diameter of 47 mm and used as a test piece 51. The arithmetic mean roughness Ra of the surface (smooth surface) of the acrylic resin plate 52 in contact with the test piece 51 was 0.03 μm. The acrylic resin plate 52 did not have air permeability in the thickness direction.

Next, the test piece 51, the silicone rubber sheet 53, and the weight 54 were placed on the acrylic resin plate 52 in this order so that their outer circumferences coincide with each other. The test piece 51 was arranged so that the evaluation surface was in contact with the acrylic resin plate 52. The silicone rubber sheet 53 was arranged so that the load by the weight 54 and the rubber sheet 53 itself was applied to the test piece 51 as evenly as possible. Next, a suction pipe connected to the pump was connected to the opening 55 of the through hole 56 located in the center of the acrylic resin plate 52 (the opening 55 on the surface opposite to the test piece 51 side). A pressure gauge was placed at the connection with the opening 55 in the suction pipe, and a flow meter was placed between the pump and the opening 55 in the suction pipe. Next, a decompression test was carried out in which the pump was operated to maintain the pressure inside the through hole 56 in a depressurized state 15 kPa lower than the external pressure (atmospheric pressure). Then, the value obtained by measuring the flow rate of air flowing through the suction pipe per minute with a flow meter at the time of the test was defined as the air permeability A on the evaluation surface of the resin sheet. The test was carried out at room temperature (25 ° C.). Further, after the decompression test was started, the measured value after the flow rate of the air flowing through the suction pipe became stable was defined as the air permeability A in the plane direction.

[Surface roughness (Rz and Ra)]
The surface roughness (maximum height Rz and arithmetic mean roughness Ra) of the evaluation surface of the resin sheet is evaluated by a surface texture measuring device (SURFCOM1400D, manufactured by Tokyo Seimitsu Co., Ltd.) capable of measuring in accordance with JIS B0601: 2001. did.

(Comparative Example 1)
PTFE powder (Polyflon PTFE M-12 manufactured by Daikin Industries, Ltd.) was introduced into a cylindrical mold and premolded under the conditions of a temperature of 23 ° C., a pressure of 60 MPa, and a pressure application time of 1 hour. Next, the formed preformed product was taken out from the mold and fired at 375 ° C. for 3 hours to obtain a columnar PTFE block having a height of 300 mm and an outer diameter of 200 mm. Next, the obtained PTFE block was cut with a cutting lathe to prepare a PTFE sheet having a thickness of 50 μm, which was used as the resin sheet of Comparative Example 1.

(Examples 1 to 3)
A stainless steel sheet having a surface shape in which the convex portions 61 extending linearly are arranged in a square lattice pattern was prepared as a template. The template had the above-mentioned surface shape on the entire pressing surface 62 (see FIG. 6). The width of the convex portion 61 was 0.02 to 0.03 mm. The pitch P2, which is the distance between the center lines of the adjacent convex portions 61, was set to 0.26 mm. The height of the convex portion 61 from the pressing surface 62 was set to 0.10 mm. The extending direction of each convex portion 61 was set to intersect one side of the template at 45 degrees. Next, the template was placed on one main surface of the resin sheet produced in Comparative Example 1, and press working was performed at 25 ° C. to press the template against the one main surface. The template was placed so as to cover the entire sheet when viewed from the direction perpendicular to the press surface. Further, the template was arranged so that the pressing surface 62 was in contact with one of the main surfaces and the extending direction of each of the convex portions 61 intersected one side of the resin sheet at 45 degrees. The pressure for pressing the template (press pressure) was 11.2 MPa (Example 1), 33.4 MPa (Example 2) and 55.6 MPa (Example 3). The arrangement surface of the template at the time of press working was used as the evaluation surface of the produced resin sheet.

(Examples 4 and 5 and Comparative Example 2)
Examples 1 to 3 except that the width of the convex portion 61 is changed to 0.01 to 0.02 mm, the pitch P2 is changed to 0.13 mm, and the height of the convex portion 61 from the pressing surface 62 is changed to 0.04 mm. Similarly, resin sheets of Comparative Example 2, Example 4 and Example 5 (press pressures 11.2 MPa, 33.4 MPa and 55.6 MPa, respectively) were obtained. The arrangement surface of the template at the time of press working was used as the evaluation surface of the produced resin sheet.

The evaluation results of the resin sheet are shown in Table 1 below.

A graph showing the maximum height Rz on the horizontal axis and the air permeability A on the vertical axis for each of the evaluation surfaces of Examples 1 to 5 and Comparative Examples 1 and 2 is shown in FIG. Further, for each of the evaluation surfaces of Examples 1 to 5 and Comparative Examples 1 and 2, a graph in which the arithmetic mean roughness Ra is on the horizontal axis and the air permeability A is on the vertical axis is shown in FIG. As shown in FIGS. 7 and 8, it was confirmed that the air permeability A on the evaluation surface of the resin sheet is not a characteristic automatically determined from the maximum height Rz of the surface and the arithmetic mean roughness Ra.

The resin sheet of the present invention can be used, for example, in various applications exposed to high temperatures.

1 Resin sheet 2A, 2B Main surface 3 Groove 4 Groove 5 circumference

Claims (6)

Contains heat-resistant resin as the main component
Not breathable in the thickness direction,
A resin sheet having an air permeability A in the surface direction on at least one main surface of 1 mL / min or more.
However, the air permeability A is
A ring-shaped measurement area having an outer diameter of 47 mm and an inner diameter of 20 mm is set on the main surface.
The sheet is pressed against the smooth surface with a load of 654.5 gf so that the main surface is in contact with the smooth surface of the member having no air permeability in the thickness direction in the entire measurement region, and the measurement region is pressed. When the inside is decompressed by 15 kPa compared to the outside,
It is a characteristic represented by the amount of airflow per minute that permeates between the main surface and the smooth surface from the outside to the inside of the measurement region. The resin sheet according to claim 1, wherein the surface roughness of the main surface is 10 μm or less, represented by the arithmetic average roughness Ra defined in JIS B0601: 2001. The main surface has a groove portion composed of one or a plurality of grooves, and the main surface has a groove portion.
The resin sheet according to claim 1 or 2, wherein the groove portion has at least one groove connected to the periphery of the resin sheet at one or both ends. The resin sheet according to claim 3, wherein the grooves have the grooves arranged in a grid pattern on the main surface. The resin sheet according to any one of claims 1 to 4, wherein the heat-resistant resin is a fluororesin. The resin sheet according to claim 5, wherein the fluororesin is polytetrafluoroethylene.

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