Porous membrane, porous composite body, ventilation member, member supply assembly, and method for producing porous membrane

Abstract

Disclosed is a porous membrane which comprises a first microporous layer, a second microporous layer, and a porous layer that is positioned between the first microporous layer and the second microporous layer, the porous membrane containing a fluorine-free resin as a main component. The porous layer has rod-shaped voids that extend in the thickness direction of the porous membrane. In a cross section of the porous membrane parallel to the thickness direction, the inclination angle of the major axis of the rod-shaped voids with respect to the thickness direction is within the range of ±20°, and the ratio of the length (µm) of the rod-shaped voids along the thickness direction to the thickness (µm) of the porous membrane is 0.7 or more.

Description

Porous membrane, porous composite, ventilation member, member supply assembly, and method for manufacturing a porous membrane

[0001] The present invention relates to a porous membrane, a porous composite, a ventilation member, a member supply assembly, and a method for manufacturing a porous membrane.

[0002] Porous fluororesin membranes are used in a variety of applications, including filters, sound-transmitting membranes, ventilation membranes, and diaphragms. For these applications, fluorine-free porous membranes have also been proposed. For example, polyimide porous membranes, due to their excellent heat resistance, are particularly suitable for use in semiconductor devices such as micro electro-mechanical systems (MEMS) that involve heat treatment such as solder reflow during manufacturing.

[0003] For example, Patent Document 1 describes a porous polyimide film with a three-layer structure having a macrovoid layer sandwiched between two surface layers, in which the average pore diameter of the macrovoids, the thickness of the surface layer, the average pore diameter of the surface layer, the total film thickness, and the porosity are adjusted to a predetermined range. In Patent Document 1, the porous polyimide film is mainly used to improve the permeability (air permeability) of substances such as gases.

[0004] International Publication No. 2010 / 038873

[0005] The technology described in Patent Document 1 has room for reconsideration from the viewpoint of achieving both breathability and water resistance. Therefore, the present invention aims to provide a porous membrane and a method for manufacturing a porous membrane that are suitable for achieving both breathability and water resistance.

[0006] The present invention provides a porous membrane comprising a first microporous layer, a second microporous layer, and a porous layer located between the first microporous layer and the second microporous layer, wherein the porous layer mainly comprises a fluorine-free resin, the porous layer has rod-shaped voids extending in the thickness direction of the porous membrane, and in a cross-section of the porous membrane parallel to the thickness direction, when the straight line connecting the first end of the rod-shaped void on the first microporous layer side and the second end on the second microporous layer side is defined as the long axis of the rod-shaped void, the inclination angle of the long axis with respect to the thickness direction is within ±20°, and the ratio of the length (μm) of the rod-shaped void along the thickness direction to the thickness (μm) of the porous membrane is 0.7 or more.

[0007] From another perspective, the present invention provides a porous composite comprising the porous membrane of the present invention described above and a porous substrate, wherein the porous membrane is disposed in at least a portion of the voids of the porous substrate.

[0008] From yet another perspective, the present invention provides a breathable member comprising the porous membrane of the present invention described above and an adhesive layer bonded to the porous membrane.

[0009] From yet another perspective, the present invention provides a component supply assembly comprising: a ventilation member disposed on the surface of an object having an opening; and a base sheet on which the ventilation member is disposed, wherein the ventilation member comprises: a porous membrane having a shape that covers the opening when disposed on the surface; and an adhesive layer bonded to the porous membrane, and the porous membrane is the porous membrane of the present invention described above.

[0010] From yet another perspective, the present invention provides a method for producing a porous film, comprising the steps of: applying a solution containing a fluorine-free resin and a solvent onto a substrate to form a coating film; immersing the coating film in water; and drying the coating film, wherein the solvent comprises at least one selected from the group consisting of lactone-based solvents, sulfone-based solvents, ketone-based solvents, cyclic ether-based solvents, and amide-based solvents, and the polyethylene glycol content in the solution is less than 0.1 wt%.

[0011] According to the present invention, it is possible to provide a porous membrane suitable for achieving both breathability and water resistance, and a method for manufacturing a porous membrane.

[0012] Figure 1A is a schematic cross-sectional view showing an example of a porous membrane according to the present invention. Figure 1B is a partially enlarged view of Figure 1A. Figure 2A is a schematic cross-sectional view showing another example of a porous membrane according to the present invention. Figure 2B is a partially enlarged view of Figure 2A. Figure 3 is a schematic cross-sectional view showing a modified example 1 of the porous membrane. Figure 4 is a schematic cross-sectional view showing a modified example 2 of the porous membrane. Figure 5 is a schematic cross-sectional view showing an example of a porous composite according to the present invention. Figure 6 is a schematic cross-sectional view showing an example of a membrane member according to the present invention. Figure 7 is a schematic cross-sectional view showing a modified example 1 of the membrane member. Figure 8 is a schematic cross-sectional view showing a modified example 2 (winding body) of the membrane member. Figure 9 is a schematic cross-sectional view showing an example of a ventilation member according to the present invention. Figure 10 is a schematic cross-sectional view showing a modified example 1 of the ventilation member of Figure 9. Figure 11 is a schematic cross-sectional view showing a modified example 2 of the ventilation member of Figure 9. Figure 12 is a schematic cross-sectional view showing a modified example 3 of the ventilation member of Figure 9. Figure 13 is a schematic cross-sectional view showing modification 4 of the ventilation member in Figure 9. Figure 14 is a schematic cross-sectional view showing modification 5 of the ventilation member in Figure 9. Figure 15 is a schematic cross-sectional view showing another example of the ventilation member according to the present invention. Figure 16 is a schematic cross-sectional view showing a modification of the ventilation member in Figure 15. Figure 17 is a schematic cross-sectional view showing an example of a member supply assembly according to the present invention. Figure 18 is a schematic cross-sectional view showing modification 1 of the member supply assembly. Figure 19 is a schematic cross-sectional view showing modification 2 of the member supply assembly. Figure 20A is a scanning electron microscope (SEM) image of a cross section parallel to the thickness direction of the porous membrane according to Example 1. Figure 20B is an SEM image of the surface of the upper layer of the porous membrane in Figure 20A. Figure 20C is an SEM image of the surface of the lower layer of the porous membrane in Figure 20A. Figure 21A is an SEM image of a cross section parallel to the thickness direction of the porous membrane according to Example 2. Figure 21B is an SEM image of the surface of the upper layer of the porous membrane in Figure 21A. Figure 21C is an SEM image of the surface of the lower layer of the porous membrane in Figure 21A. Figure 22A is an SEM image of a cross-section parallel to the thickness direction of the porous membrane according to Example 3. Figure 22B is an SEM image of the surface of the upper layer of the porous membrane in Figure 22A. Figure 22C is an SEM image of the surface of the lower layer of the porous membrane in Figure 22A. Figure 23A is an SEM image of a cross-section parallel to the thickness direction of the porous membrane according to Comparative Example 1.Figure 23B is an SEM image of the surface of the upper layer of the porous membrane in Figure 23A. Figure 23C is an SEM image of the surface of the lower layer of the porous membrane in Figure 23A. Figure 24A is an SEM image of a cross-section parallel to the thickness direction of the porous membrane according to Comparative Example 2. Figure 24B is an SEM image of the surface of the upper layer of the porous membrane in Figure 24A. Figure 24C is an SEM image of the surface of the lower layer of the porous membrane in Figure 24A. Figure 25A is an SEM image of a cross-section parallel to the thickness direction of the porous membrane according to Comparative Example 3. Figure 25B is an SEM image of the surface of the upper layer of the porous membrane in Figure 25A. Figure 25C is an SEM image of the surface of the lower layer of the porous membrane in Figure 25A. Figure 26A is an SEM image of a cross-section parallel to the thickness direction of the porous membrane according to Comparative Example 4. Figure 26B is an SEM image of the surface of the upper layer of the porous membrane in Figure 26A. Figure 26C is an SEM image of the surface of the lower layer of the porous membrane shown in Figure 26A.

[0013] A porous membrane according to a first aspect of the present invention is a porous membrane comprising a first microporous layer, a second microporous layer, and a porous layer located between the first microporous layer and the second microporous layer, wherein the porous membrane mainly contains a fluorine-free resin, the porous layer has rod-shaped voids extending in the thickness direction of the porous membrane, and when the straight line connecting the first end of the rod-shaped void on the first microporous layer side and the second end on the second microporous layer side is defined as the major axis of the rod-shaped void in a cross-section of the porous membrane parallel to the thickness direction, the inclination angle of the major axis with respect to the thickness direction is within ±20°, and the ratio of the length (μm) of the rod-shaped void along the thickness direction to the thickness (μm) of the porous membrane is 0.7 or more.

[0014] In a second embodiment of the present invention, for example, in the porous membrane according to the first embodiment, the resin comprises at least one selected from the group consisting of polyimide resin, polysulfone resin, polyethersulfone resin, polystyrene resin, polyacrylonitrile resin, vinyl chloride resin, polycarbonate resin, polyamideimide resin, and polyetherimide resin.

[0015] In a third embodiment of the present invention, for example, in a porous membrane according to the first or second embodiment, the length of the rod-shaped voids along the plane direction perpendicular to the thickness direction in a cross-section of the porous membrane parallel to the thickness direction is 1 μm or more and 10 μm or less.

[0016] In a fourth embodiment of the present invention, for example, in a porous membrane according to any one of the first to third embodiments, in a cross-section of the porous membrane parallel to the thickness direction, the ratio of the length of the rod-shaped voids along the thickness direction (μm) to the length of the rod-shaped voids along the plane direction perpendicular to the thickness direction (μm) is 2 or more and 10 or less.

[0017] In a fifth embodiment of the present invention, for example, in a porous membrane according to any one of the first to fourth embodiments, in a cross-section of the porous membrane parallel to the thickness direction, the length of the rod-shaped voids along the planar direction perpendicular to the thickness direction decreases from the first microporous layer side toward the second microporous layer side.

[0018] In a sixth aspect of the present invention, for example, in a porous membrane according to any one of the first to fifth aspects, the average pore diameter on the surface of the first microporous layer is larger than the average pore diameter on the surface of the second microporous layer.

[0019] In a seventh aspect of the present invention, for example, in a porous membrane according to any one of the first to sixth aspects, the porous membrane has a thickness of 10 μm or more and 100 μm or less.

[0020] In the eighth aspect of the present invention, for example, in a porous membrane according to any one of the first to seventh aspects, the rod-shaped voids do not penetrate the porous layer.

[0021] In the ninth aspect of the present invention, for example, in a porous membrane according to any one of the first to eighth aspects, the second microporous layer has a thickness of 100 nm to 3000 nm.

[0022] In the tenth aspect of the present invention, for example, a porous membrane according to any one of the first to ninth aspects comprises at least one selected from the group consisting of lactone solvents, sulfone solvents, ketone solvents, cyclic ether solvents, and amide solvents.

[0023] In the 11th aspect of the present invention, for example, in the porous membrane according to the 10th aspect, the lactone-based solvent contains γ-butyrolactone.

[0024] In the 12th aspect of the present invention, for example, in the porous membrane according to any one of the 1st to 11th aspects, the air permeability of the porous membrane, expressed in Gurley number, is 25 seconds / 100 cm 3 or less.

[0025] In the 13th aspect of the present invention, for example, in the porous membrane according to any one of the 1st to 12th aspects, the water pressure resistance of the porous membrane measured according to the water resistance test B method (high water pressure method) defined in JIS L1092:2009 is 100 kPa or more.

[0026] The porous composite according to the 14th aspect of the present invention includes, for example, a porous membrane according to any one of the 1st to 13th aspects and a porous substrate, and the porous membrane is disposed in at least a part of the voids of the porous substrate.

[0027] The ventilation member according to the 15th aspect of the present invention includes, for example, a porous membrane according to any one of the 1st to 13th aspects and an adhesive layer bonded to the porous membrane.

[0028] The member supply assembly according to the 16th aspect of the present invention is a member supply assembly including a ventilation member disposed on the surface of an object having a surface with an opening, and a base sheet on which the ventilation member is disposed. The ventilation member has a porous membrane having a shape that covers the opening when disposed on the surface, and an adhesive layer bonded to the porous membrane, and the porous membrane is a porous membrane according to any one of the 1st to 13th aspects.

[0029] The method for manufacturing a porous membrane according to the 17th aspect of the present invention includes, in this order, a step of forming a coating film by applying a solution containing a resin not containing fluorine and a solvent onto a substrate, a step of immersing the coating film in water, and a step of drying the coating film. The solvent contains at least one selected from the group consisting of a lactone-based solvent, a sulfone-based solvent, a ketone-based solvent, a cyclic ether-based solvent, and an amide-based solvent. The content of polyethylene glycol in the solution is less than 0.1 wt%.

[0030] In the 18th aspect of the present invention, for example, in the method for manufacturing a porous membrane according to the 17th aspect, the resin includes at least one selected from the group consisting of a polyimide resin, a polysulfone resin, a polyethersulfone resin, a polystyrene resin, a polyacrylonitrile resin, a vinyl chloride resin, a polycarbonate resin, a polyamideimide resin, and a polyetherimide resin.

[0031] In the 19th aspect of the present invention, for example, in the method for manufacturing a porous membrane according to the 17th or 18th aspect, the lactone-based solvent includes γ-butyrolactone.

[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

[0033] [Porous Membrane] FIG. 1A is a cross-sectional view schematically showing an example of the porous membrane according to the present invention. FIG. 2A is a cross-sectional view schematically showing another example of the porous membrane according to the present invention. As shown in FIGS. 1A and 2A, the porous membrane 1A includes a first microporous layer 10, a second microporous layer 20, and a porous layer 30 located between the first microporous layer 10 and the second microporous layer 20. The porous layer 30 has a plurality of rod-shaped voids 31 extending in the thickness direction TD of the porous membrane 1A. The first microporous layer 10 has a plurality of first pores 11. The second microporous layer 20 has a plurality of second pores 21. The porous membrane 1A mainly contains a resin not containing fluorine.

[0034] Figure 1B is an enlarged view of portion IB in Figure 1A. Figure 2B is an enlarged view of portion IIB in Figure 2A. In a cross-section of the porous membrane 1A parallel to the thickness direction TD, the straight line connecting the first end 31a on the first microporous layer 10 side and the second end 31b on the second microporous layer 20 side of the rod-shaped void 31 is defined as the major axis 31L of the rod-shaped void 31. In this case, in the porous membrane 1A, the inclination angle θ31 of the major axis 31L with respect to the thickness direction TD is within ±20°, and the ratio of the length L3 (μm)1 of the rod-shaped void 31 along the thickness direction TD to the thickness T1 (μm) of the porous membrane 1A is 0.7 or more.

[0035] Through diligent research, the inventors have discovered that a porous membrane 1A having the above-described structure achieves not only excellent breathability but also excellent water resistance. This is thought to be because water resistance is ensured by the first microporous layer 10 and the second microporous layer 20 constituting the outermost layer of the porous membrane 1A, while excellent breathability is exhibited by the porous layer 30 having a plurality of rod-shaped voids 31. The porous membrane 1A of this embodiment is suitable for achieving both breathability and water resistance.

[0036] In this specification, "rod-shaped void" means a void having an elongated shape in the thickness direction TD in a cross-section of a porous membrane 1A parallel to the thickness direction TD, as shown in Figures 1A and 2A. "Rod-shaped void" does not necessarily mean that the void has a constant pore diameter in the plane direction SD perpendicular to the thickness direction TD. As will be described later, "rod-shaped voids" may include, for example, those in which the pore diameter decreases from the first microporous layer 10 side to the second microporous layer 20 side.

[0037] As described above, the porous membrane 1A mainly contains a fluorine-free resin. "Main component" means the component that is present in the most abundant amount by weight in the porous membrane 1A.

[0038] The fluorine-free resin includes, for example, at least one selected from the group consisting of polyimide resin, polysulfone resin, polyethersulfone resin, polystyrene resin, polyacrylonitrile resin, vinyl chloride resin, polycarbonate resin, polyamideimide resin, and polyetherimide resin.

[0039] The above resin may include at least one selected from the group consisting of polyimide resins and polysulfone resins.

[0040] The above resin may be a polyimide resin. That is, the porous film 1A may contain polyimide resin as its main component. Since the porous film 1A containing polyimide resin as its main component has excellent heat resistance, it can be used particularly suitably in applications such as semiconductor devices such as MEMS that involve heat treatment such as solder reflow during manufacturing.

[0041] The polyimide resin may be a soluble polyimide. A soluble polyimide is a polyimide that is soluble in an organic solvent. Examples of organic solvents include those used in the porous film manufacturing method described later. As the soluble polyimide, for example, a soluble polyimide that has already undergone imidization can be suitably used.

[0042] The above resin may be a polysulfone resin. That is, the porous film 1A may contain a polysulfone resin as its main component.

[0043] As described above, in the porous membrane 1A, the inclination angle θ31 of the major axis 31L with respect to the thickness direction TD in a cross-section of the porous membrane 1A parallel to the thickness direction TD is within the range of ±20°. In this specification, "±20°" means 0°±20°, in other words, an absolute value of 20° or less. The same notation as above can be interpreted similarly. For example, "±5°" means an absolute value of 5° or less. In the example of Figure 1B, the absolute value of the inclination angle θ31 of the major axis 31L with respect to the thickness direction TD is 0°. That is, the major axis 31L extends parallel to the thickness direction TD. On the other hand, in the example of Figure 2B, the absolute value of the inclination angle θ31 of the major axis 31L with respect to the thickness direction TD is greater than 0° and within the range of 20° or less.

[0044] The inclination angle θ31 of the major axis 31L with respect to the thickness direction TD may be within the range of ±15°, ±12°, ±10°, ±8°, and even ±5°. The smaller the absolute value of the inclination angle θ31, the shorter the length of the ventilation path along the thickness direction TD may be. Therefore, the permeability of the porous membrane 1A may be further improved.

[0045] In this specification, the first end 31a of the rod-shaped void 31 on the first microporous layer 10 side refers to the outermost point of the rod-shaped void 31 on the first microporous layer 10 side, as shown in Figures 1B and 2B, and means the point of contact between the rod-shaped void 31 and the straight line Lsd1 on the first microporous layer 10 side, which is parallel to the plane direction SD. However, if there are multiple such outermost points, if the number of outermost points is odd, the central point is defined as the first end 31a, and if the number of outermost points is even, the midpoint of the two central points is defined as the first end 31a. The second end 31b of the rod-shaped void 31 on the second microporous layer 20 side refers to the outermost point of the rod-shaped void 31 on the second microporous layer 20 side, as shown in Figures 1B and 2B, and means the point of contact between the rod-shaped void 31 and the straight line Lsd2 on the second microporous layer 20 side, which is parallel to the plane direction SD. However, if there are multiple such endpoints, if the number of endpoints is odd, the central point is designated as the second endpoint 31b; if the number of endpoints is even, the midpoint of the two central points is designated as the second endpoint 31b.

[0046] The inclination angle θ31 of the major axis 31L with respect to the thickness direction TD can be determined, for example, based on two SEM images of different fields of view of the cross-section of the porous membrane 1A parallel to the thickness direction TD. For each SEM image, three rod-shaped voids 31 are selected from the rod-shaped voids 31 that include the first end 31a and the second end 31b within the SEM image, in descending order of their length L31 (μm) along the thickness direction TD, and the inclination angle θ31 of the major axis 31L is measured for these three rod-shaped voids 31. The inclination angle θ31 of the major axis 31L may be the average of six measured values ​​obtained from the two SEM images. The length L31 (μm) of the rod-shaped voids 31 along the thickness direction TD can be measured based on the method described later.

[0047] As described above, in the porous membrane 1A, in a cross-section of the porous membrane 1A parallel to the thickness direction TD, the ratio of the length L31 (μm) of the rod-shaped voids 31 along the thickness direction TD to the thickness T1 (μm) of the porous membrane 1A is 0.7 or more.

[0048] The lower limit of the ratio of length L31 to thickness T1 may be 0.75 or more, 0.77 or more, 0.8 or more, or even 0.84 or more. The upper limit of the ratio of length L31 to thickness T1 is, for example, 0.99 or less. The upper limit of the ratio of length L31 to thickness T1 may be 0.95 or less, or even 0.9 or more.

[0049] The thickness T1 (μm) of the porous membrane 1A can be determined, for example, based on an SEM image of a cross-section of the porous membrane 1A parallel to the thickness direction TD. The thickness T1 is measured at arbitrary locations (e.g., 6 locations) of the porous membrane 1A in the SEM image. The thickness T1 may be the average of these measured values.

[0050] In this specification, the length L31 (μm) of the rod-shaped void 31 along the thickness direction TD is the distance in the thickness direction TD between a straight line (straight line Lsd1) passing through the first end 31a of the rod-shaped void 31 and parallel to the surface direction SD, and a straight line (straight line Lsd2) passing through the second end 31b of the rod-shaped void 31 and parallel to the surface direction SD.

[0051] The length L31 (μm) of the rod-shaped voids 31 along the thickness direction TD can be determined, for example, based on an SEM image of a cross-section of the porous membrane 1A parallel to the thickness direction TD. The length L31 is measured for 50% or more of the rod-shaped voids 31 that include the first end 31a and the second end 31b in the SEM image. The length L31 of the rod-shaped voids 31 may be the average of these measured values.

[0052] In the porous membrane 1A, the length S31 of the rod-shaped voids 31 along the surface direction SD in a cross-section of the porous membrane 1A parallel to the thickness direction TD may be 1 μm or more and 10 μm or less. A porous layer 30 that satisfies the above numerical range makes it easier to achieve high permeability in the porous membrane 1A.

[0053] The lower limit of the length S31 of the rod-shaped void 31 along the planar direction SD may be 2 μm or more, 3 μm or more, 4 μm or more, or even 5 μm or more. The upper limit of the length of the short axis 31S of the rod-shaped void 31 may be 9 μm or less, 8 μm or less, or even 7 μm or less.

[0054] In this specification, the length S31 (μm) of the rod-shaped void 31 along the surface direction SD is the average of the lengths S311, S312, and S313 of the rod-shaped void 31 along the surface direction SD at positions where the length L31 of the rod-shaped void 31 along the thickness direction TD is divided into four equal parts.

[0055] The length S31 (μm) of the rod-shaped voids 31 along the planar direction SD can be determined, for example, based on an SEM image of a cross-section of the porous membrane 1A parallel to the thickness direction TD. For each of the rod-shaped voids 31 that make up 50% or more of the rod-shaped voids 31 that include the first end 31a and the second end 31b in the SEM image, the lengths S311, S312, and S313 are measured. The average of lengths S311, S312, and S313 is taken as the length S31 of each rod-shaped void 31. The length S31 of the rod-shaped voids 31 may also be the average of these calculated values.

[0056] In the porous membrane 1A, in a cross-section of the porous membrane 1A parallel to the thickness direction TD, the ratio of the length S31 (μm) of the rod-shaped voids 31 along the thickness direction TD to the length S31 (μm) of the rod-shaped voids 31 along the surface direction SD may be 2 or more and 10 or less. If the rod-shaped voids 31 satisfy the above numerical range, high permeability is easily achieved in the porous membrane 1A.

[0057] The lower limit of the ratio of the length L31 of the rod-shaped void 31 to the length S31 of the rod-shaped void 31 may be 2.5 or more, 3 or more, 3.5 or more, or even 4 or more. The upper limit of the ratio of the length L31 of the rod-shaped void 31 to the length S31 of the rod-shaped void 31 may be 9 or less, 8 or less, 7 or less, or even 6 or less.

[0058] The porous membrane 1A may be in the form of a sheet or a film. The porous membrane 1A may have a thickness T1 of 10 μm or more and 100 μm or less. A porous membrane 1A that satisfies the above numerical range is particularly suitable for achieving both breathability and water resistance.

[0059] The lower limit of the thickness T1 of the porous membrane 1A may be 12 μm or more, 15 μm or more, 17 μm or more, or even 20 μm or more. The upper limit of the thickness T1 of the porous membrane 1A may be 90 μm or less, 80 μm or less, 70 μm or less, or even 60 μm or less.

[0060] The method for determining the thickness T1 of the porous membrane 1A is as described above.

[0061] The porous layer 30 may have a thickness T30 of 5 μm or more and 80 μm or less. The lower limit of the thickness T30 may be 10 μm or more. The upper limit of the thickness T30 may be 70 μm or less.

[0062] The thickness T30 of the porous layer 30 can be determined by the same method as described for the thickness T1 of the porous membrane 1A. However, if the boundary line B1 between the porous layer 30 and the first microporous layer 10 is unclear in the cross-sectional SEM image, a straight line passing through the first end 31a closest to the first microporous layer 10 and parallel to the plane direction SD can be considered as the boundary line B1. If the boundary line B2 between the porous layer 30 and the second microporous layer 20 is unclear in the cross-sectional SEM image, a straight line passing through the second end 31b closest to the second microporous layer 20 and parallel to the plane direction SD can be considered as the boundary line B2. In this case, the first end 31a closest to the first microporous layer 10 and the second end 31b closest to the second microporous layer 20 do not have to be the first end 31a and second end 31b of the same rod-shaped void 31. Furthermore, the rod-shaped void 31 having a first end 31a closest to the first microporous layer 10 and the rod-shaped void 31 having a second end 31b closest to the second microporous layer 20 do not necessarily need to be entirely included in the SEM image.

[0063] In this embodiment, it is preferable that the rod-shaped void 31 does not communicate with at least the second pore 21 of the second microporous layer 20. Specifically, the rod-shaped void 31 may communicate with the first pore 11 of the first microporous layer 10, but it is preferable that it does not communicate with the second pore 21 of the second microporous layer 20. However, as shown in Figures 1A to 2B, it is more preferable that the rod-shaped void 31 does not communicate with either the first pore 11 of the first microporous layer 10 or the second pore 21 of the second microporous layer 20.

[0064] In other words, it is preferable that the rod-shaped voids 31 do not penetrate the porous layer 30. Having such a structure for the rod-shaped voids 31 prevents the porous membrane 1A from becoming too permeable and reducing its water resistance.

[0065] In other words, it is preferable that the rod-shaped void 31 is closed at both ends in the thickness direction TD in the porous layer 30. In this case, as shown in Figures 1A and 2A, the porous layer 30 may have a first partition wall 32a located on the side of the first microporous layer 10 and a second partition wall 32b located on the side of the second microporous layer 20. The first partition wall 32a is in contact with the first microporous layer 10. The second partition wall 32b is in contact with the second microporous layer 20.

[0066] As shown in Figures 1A and 2A, the porous layer 30 extends in the thickness direction TD and may further have a third partition wall 32c located between adjacent rod-shaped voids 31. The third partition wall 32c may be connected to the first partition wall 32a on the first microporous layer 10 side. The third partition wall 32c may be connected to the second partition wall 32b on the second microporous layer 20 side.

[0067] Although not shown in the figures, the first partition wall 32a, the second partition wall 32b, and the third partition wall 32c may contain pores with a diameter smaller than that of the rod-shaped voids 31. In a cross-section of the porous membrane 1A parallel to the thickness direction TD, the average pore diameter of the above pores may be in the range of 10 nm to 1000 nm. A porous layer 30 that satisfies the above numerical range makes it easier to maintain excellent permeability in the porous membrane 1A. In this specification, the average pore diameter is the number average pore diameter.

[0068] As described above, the first microporous layer 10 has a plurality of first pores 11. The second microporous layer 20 has a plurality of second pores 21. The average pore diameter D10 on the surface 10s of the first microporous layer 10 may be greater than the average pore diameter D20 on the surface 20s of the second microporous layer 20. That is, D10 > D20 may be satisfied. With the first microporous layer 10 and the second microporous layer 20 satisfying this relationship, the desired water resistance is easily achieved.

[0069] The average pore size D10 on the surface 10s of the first microporous layer 10 is, for example, in the range of 0.5 μm or more and 10 μm or less. The lower limit of the average pore size D10 may be 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or even 1 μm or more. The upper limit of the average pore size D10 may be 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, or even 2 μm or less.

[0070] The average pore diameter D10 on the surface 10s of the first microporous layer 10 can be determined, for example, based on an SEM image of the first surface 1a (the surface 10s of the first microporous layer 10) of the porous membrane 1A on the side of the first microporous layer 10. The pore diameters of the six largest first pores 11 in the SEM image are measured. However, if there are exceptionally large voids with a pore diameter exceeding 20 μm in the SEM image, such voids are excluded from the pore diameter measurement. The average pore diameter D10 can be calculated by averaging these measurements.

[0071] The average pore size D20 on the surface 20s of the second microporous layer 20 is, for example, in the range of 50 nm to 400 nm. The lower limit of the average pore size D20 may be 55 nm or more, 60 nm or more, 65 nm or more, or even 70 nm or more. The upper limit of the average pore size D20 may be 350 nm or less, 300 nm or less, 250 nm or less, or even 200 nm or less.

[0072] The average pore diameter D20 on the surface 20s of the second microporous layer 20 can be determined, for example, based on an SEM image of the second surface 1b (the surface 20s of the second microporous layer 20) of the porous membrane 1A on the second microporous layer 20 side. The pore diameters of six second pores 21 with large diameters among the second pores 21 in the SEM image are measured. However, if there are exceptionally large voids with a pore diameter exceeding 20 μm in the SEM image, such voids are excluded from the pore diameter measurement. The average pore diameter D20 can be calculated by averaging these measurements.

[0073] When the porous membrane 1A of this embodiment is used, for example, to ensure ventilation through an opening in the housing of a device while preventing the passage of foreign matter, the second surface 1b on the second microporous layer 20 side may be positioned so that it faces the side to which pressure such as water pressure is applied. With such an arrangement, the desired water resistance is easily achieved. However, the first surface 1a on the first microporous layer 10 side may also be positioned so that it faces the side to which pressure such as water pressure is applied.

[0074] The first microporous layer 10 may have a thickness T10 of 50 nm or more and 8000 nm or less. The lower limit of the thickness T10 may be 100 nm or more. The upper limit of the thickness T10 may be 7500 nm or less.

[0075] The second microporous layer 20 may have a thickness T20 of 100 nm or more and 3000 nm or less. The upper limit of the thickness T20 may be 2750 nm or less, 2500 nm or less, 2250 nm or less, and further 2000 nm or less.

[0076] The thickness T10 of the first microporous layer 10 and the thickness T20 of the second microporous layer 20 can be obtained by the same method as that described for the thickness T1 of the porous membrane 1A and the thickness T30 of the porous layer 30.

[0077] The air permeability of the porous membrane 1A may be 25 seconds / 100 cm 3 or less in Gurley number. Thus, the porous membrane 1A has high air permeability. In this specification, the "Gurley number" is the air permeability resistance (Gurley air permeability) measured in accordance with the King Research type tester method defined in JIS P8117:2009.

[0078] The upper limit of the air permeability of the porous membrane 1A may be 24 seconds / 100 cm 3 or less, 23 seconds / 100 cm 3 or less, 22 seconds / 100 cm 3 or less, 21 seconds / 100 cm 3 or less, 20 seconds / 100 cm 3 or less, 19 seconds / 100 cm 3 or less, 18 seconds / 10,0 cm 3 or less, 15 seconds / 100 cm 3 or less, and further 10 seconds / 100 cm 3 or less. The lower limit of the air permeability of the porous membrane 1A is, for example, 1.5 seconds / 100 cm 3 or more in Gurley number.

[0079] In addition, even when the size of the porous membrane 1A does not meet the recommended dimensions (50 mm × 50 mm) of the test piece of the King Research type tester method, it is possible to evaluate the air permeability resistance (Gurley air permeability) in accordance with the King Research type tester method by using a measuring jig.

[0080] The measuring jig has a shape and size that can be placed in the air permeability measuring section of the Wangyan type testing machine, and has a thickness and material that does not deform due to the differential pressure applied to the test piece when measuring air permeability resistance. An example of a measuring jig is a SUS disc with a thickness of 2 mm and a diameter of 47 mm. A through hole with an opening smaller in size than the membrane to be evaluated is provided at the center of the surface of the measuring jig. The cross-section of the through hole is typically circular, and its diameter is such that the opening of the through hole is completely covered by the membrane to be evaluated. For example, the diameter of the through hole can be 1 mm or 2 mm. Next, the porous membrane 1A to be evaluated is fixed so that the first surface 1a faces one surface of the measuring jig so as to cover the opening. The fixing is done so that during the measurement of air permeability resistance, air passes only through the opening and the effective test portion of the porous membrane 1A to be evaluated (the portion that overlaps with the opening when viewed from a direction perpendicular to the main surface of the fixed porous membrane 1A), and the fixing portion does not obstruct the passage of air in the effective test portion of the porous membrane 1A. To fix the porous membrane 1A, double-sided adhesive tape with a vent punched out in the center that matches the shape of the opening can be used. The double-sided adhesive tape should be placed between the measuring jig and the porous membrane 1A so that the circumference of the vent coincides with the circumference of the opening. Next, the measuring jig with the porous membrane 1A fixed to it is set in the air permeability measurement section of the Wang-Lan testing machine so that the fixed surface of the porous membrane 1A is on the downstream side of the airflow during measurement, and the test is performed according to the Wang-Lan testing machine method, and the air permeability resistance indicator value t shown by the testing machine is recorded. Next, the recorded air permeability resistance indicator value t is set to the effective test area of ​​6.452 [cm²] specified in the Wang-Lan testing machine method. 2 ] Value t K In equation t, K = {t × (area of ​​the effective test portion of porous membrane 1A [cm²] 2 ]) / 6.452 [cm 2 Converted using ]}, the obtained converted value t KThis can be considered the air permeability resistance (Gurley air permeability) of the porous membrane 1A measured in accordance with the Wang-Lan testing machine method. It has been confirmed that the air permeability resistance measured without using a measuring jig for a porous membrane 1A that meets the recommended dimensions of the test specimen for the Wang-Lan testing machine method (50 mm x 50 mm) agrees well with the air permeability resistance measured using a measuring jig after the porous membrane 1A has been cut into pieces, meaning that the use of a measuring jig does not substantially affect the measured value of air permeability resistance.

[0081] The water pressure resistance of porous membrane 1A, as measured according to the water resistance test method B (high water pressure method) specified in JIS L1092:2009, may be 100 kPa or more.

[0082] The lower limit of the water pressure resistance of the porous membrane 1A may be 105 kPa or more, 110 kPa or more, 120 kPa or more, 130 kPa or more, or even 140 kPa or more. The upper limit of the water pressure resistance of the porous membrane 1A is, for example, 500 kPa or less.

[0083] The above water pressure resistance can be measured using a measuring jig in accordance with the above water pressure resistance test method, as follows. An example of a measuring jig is a 47 mm diameter stainless steel (SUS) disc with a 1.0 mm diameter through hole (having a circular cross-section) in the center. This disc has a thickness that does not deform under the water pressure applied when measuring water pressure resistance. The measurement of water pressure resistance using this measuring jig can be carried out as follows.

[0084] The porous membrane 1A to be evaluated is fixed to one side of the measuring jig so that its first surface 1a faces the opening of the through-hole in the measuring jig. The fixing is done in a way that prevents water from leaking from the fixed part of the membrane during water pressure resistance measurement. For fixing the porous membrane 1A, double-sided adhesive tape with a water inlet punched out in the center that matches the shape of the opening can be used. The double-sided adhesive tape should be placed between the measuring jig and the porous membrane 1A so that the circumference of the water inlet coincides with the circumference of the opening. Next, the measuring jig with the porous membrane 1A fixed to it is set in the test apparatus so that the side of the porous membrane 1A opposite to the fixing surface becomes the water pressure application surface during measurement, and the water pressure resistance is measured according to the water pressure resistance test method B (high water pressure method) specified in JIS L1092:2009. However, the water pressure resistance is measured based on the water pressure when water is released from one point on the membrane surface of the porous membrane 1A. The measured water pressure resistance can be used as the water pressure resistance of the porous membrane 1A. The test apparatus can be one that has a configuration similar to the water resistance test apparatus exemplified in JIS L1092:2009, and also has a test specimen mounting structure that allows the above-mentioned measuring jig to be set.

[0085] Surface modification treatment may be applied to at least one main surface of the porous film 1A. Examples of surface modification treatments include chemical treatment, sputter etching, oil-repellent treatment, and plasma treatment. In the region where surface modification treatment has been applied, the bonding properties of the porous film 1A are improved.

[0086] [Method for Manufacturing Porous Membrane] The method for manufacturing the porous membrane 1A described above is not limited to a specific method. The porous membrane 1A can be manufactured, for example, according to a phase separation method. Examples of phase separation methods include non-solvent-induced phase separation (NIPS method) and drying-induced phase separation (DIPS method). In the NIPS method, a porous membrane is obtained when a non-solvent such as water is incorporated into the coating film of the polymer solution or polymer precursor solution. In the DIPS method, a porous membrane is obtained when a phase separation is induced in the coating film of the polymer solution or polymer precursor solution due to solvent evaporation.

[0087] An example of a method for manufacturing the porous membrane 1A is described below. The method for manufacturing the porous membrane 1A includes, for example, a step of applying a solution containing a fluorine-free resin and a solvent onto a substrate to form a coating film (step 1), a step of immersing the coating film in water (step 2), and a step of drying the coating film (step 3), in this order. The solvent includes at least one selected from the group consisting of lactone-based solvents, sulfone-based solvents, ketone-based solvents, cyclic ether-based solvents, and amide-based solvents. The polyethylene glycol content in the solution is less than 0.1 wt%.

[0088] In step 1, the above solution is applied to a predetermined substrate to form a coating film. An example of the above substrate is a porous material containing fluororesin. Examples of substrates include a predetermined polytetrafluoroethylene (PTFE) porous membrane (manufactured by Nitto Denko Corporation, TEMISH® registered trademark), PET nonwoven fabric, etc. For example, the air permeability of a PTFE porous membrane, measured according to the air permeability measurement method B (Gurley method) specified in JIS L1096:2010, is 30 seconds / 100 cm. 3 ~50 seconds / 100cm 3 The PTFE porous membrane has a thickness of, for example, 50 to 100 μm. The average pore size on the surface of the PTFE porous membrane is, for example, 100 to 200 nm. In the production of the porous membrane 1A, a first microporous layer 10 can be formed in contact with the substrate surface of the coating film of the above solution. By using the above-described substrate, it is easy to form a first microporous layer 10 that satisfies the above-described requirements.

[0089] As described above, the fluorine-free resin includes, for example, at least one selected from the group consisting of polyimide resin, polysulfone resin, polyethersulfone resin, polystyrene resin, polyacrylonitrile resin, vinyl chloride resin, polycarbonate resin, polyamideimide resin, and polyetherimide resin. The above resin may also include at least one selected from the group consisting of polyimide resin and polysulfone resin. As the above resin, for example, soluble polyimide varnish (manufactured by Mitsubishi Gas Chemical Co., Ltd., NeoPrim S100 (solid content concentration: 20 wt%)), polysulfone resin (manufactured by Synsqo, Inc., Udel P-3500LCD), etc. can be used.

[0090] The above solvent includes, for example, at least one selected from the group consisting of lactone solvents, sulfone solvents, ketone solvents, cyclic ether solvents, and amide solvents. A lactone solvent includes, for example, γ-butyllactone. The lactone solvent may also be γ-butyllactone. A sulfone solvent includes, for example, sulfolane. A ketone solvent includes, for example, cyclopentanone. A cyclic ether solvent includes, for example, 1,3-dioxolane. An amide solvent includes, for example, dimethylformamide (DMF). The amide solvent may also be DMF.

[0091] It should be noted that in this embodiment, the solution is substantially free of polyethylene glycol (PEG). In this specification, "substantially free of PEG" means that the PEG content in the solution is less than 0.1 wt%. Conventionally, PEG is used as a porosity-forming agent when manufacturing porous membranes. Therefore, in this art, the usual idea is to use PEG to adjust the size of the voids in the porous membrane and improve its permeability. However, contrary to expectations, PEG is not used in this embodiment. As a result, characteristic rod-shaped voids 31 tend to be formed in step 2.

[0092] In step 2, the coating film of the above solution is immersed in water. This promotes phase separation in the coating film, accelerates porosity, and extracts the solvent from the coating film. The coating film of the above solution is immersed in a water bath at, for example, 20°C to 40°C. The water used in the water bath is typically pure water. The immersion time is, for example, 1 minute to 30 minutes. In step 2, the phase separation rate increases as you approach the outermost layer of the coating film, and the solvent is rapidly extracted. As a result, a second microporous layer 20 with a denser structure is formed on the surface side of the coating film, and a first microporous layer 10 is formed in contact with the contact surface of the coating film with the substrate. Due to the formation of the first microporous layer 10 and the second microporous layer 20, the solvent is less likely to be extracted from the inside of the coating film, and as a result, a porous layer 30 having rod-shaped voids 31 is formed on the inside of the coating film.

[0093] In step 3, the porous coating is dried. After drying, the resulting film is peeled off the substrate to obtain a porous film 1A. The drying time is, for example, 1 to 30 minutes.

[0094] The porous membrane 1A produced by the above manufacturing method may contain the above solvent. That is, the porous membrane 1A may contain the above solvent. The porous membrane 1A may contain at least one selected from the group consisting of lactone-based solvents, sulfone-based solvents, ketone-based solvents, cyclic ether-based solvents, and amide-based solvents. The porous membrane 1A may contain at least one selected from the group consisting of lactone-based solvents and amide-based solvents. The lactone-based solvent may include, for example, γ-butyllactone. The amide-based solvent may include, for example, dimethylformamide (DMF).

[0095] The weight content of the solvent relative to the weight of the porous membrane 1A is, for example, in the range of 0.001 to 20% by weight.

[0096] The weight content of the solvent relative to the weight of the porous membrane 1A can be determined, for example, by pyrolysis GC / MS analysis. First, 0.2 mg of porous membrane 1A is prepared as a sample. The sample is placed in a glass tube and heated at 300°C for 10 minutes in a helium gas atmosphere in a thermal desorption unit (GERSTEL, TDU2) directly connected to a pyrolysis GC / MS instrument (Agilent Technologies, 8890 / 5977C) to perform instantaneous thermal decomposition. The gaseous components generated from the sample are cold-trapped at -150°C at the inlet of the thermal desorption unit cooled with liquid nitrogen, and then the inlet is rapidly heated to 300°C. The gaseous components are introduced into a column (Agilent Technologies, DB-HeavyWAX) and their mass is measured using a pyrolysis GC / MS instrument. Based on the measured value, the weight content of the solvent relative to the weight of the porous membrane 1A can be calculated. The column is heated from 40°C to 280°C at a rate of 20°C / min and held at 280°C. The ionization method used in the pyrolysis GC / MS instrument is the electron ionization method (EI). The conditions for the inlet temperature, interface temperature, carrier gas, ionization method, and scanning mass range of the pyrolysis GC / MS instrument are as follows: Inlet temperature: 280°C Interface temperature: 300°C (heating rate: 60°C / min) Carrier gas: Helium 1.8 mL / min Ionization method: EI 70 eV Scanning mass range: m / z = 10 to 800

[0097] In the examples shown in Figures 1A to 2B, the rod-shaped voids 31 have a substantially cylindrical shape. However, the shape of the rod-shaped voids 31 is not limited to the examples shown in Figures 1A to 2B. Also, in the examples shown in Figures 1A to 2B, there is one rod-shaped void 31 located in the direction of the thickness T30 of the porous layer 30. However, the number of rod-shaped voids 31 located in the direction of the thickness T30 of the porous layer 30 is not limited to the examples shown in Figures 1A to 2B. Below, modifications 1 and 2 of the porous membrane according to the present invention will be described. In the following, the same reference numerals may be used for components with the same structure as the porous membrane 1A described above, and their description may be omitted.

[0098] (Modification 1) Figure 3 is a schematic cross-sectional view of the porous membrane 1B of Modification 1. In the porous membrane 1B, the rod-shaped voids 31 have a substantially conical shape. Except for this point, the porous membrane 1B has the same structure as the porous membrane 1A described above. The porous membrane 1B of Modification 1 can be manufactured, for example, by controlling the speed of phase separation and the way in which phase separation proceeds by selecting a solvent and phase separation conditions in the manufacturing method.

[0099] As can be seen from Figure 3, in a cross-section of the porous membrane 1B parallel to the thickness direction TD, the length S31 of the rod-shaped voids 31 along the surface direction SD decreases from the first microporous layer 10 side to the second microporous layer 20 side. A porous membrane 1B having such a structure is also suitable for achieving both breathability and water resistance.

[0100] (Modification 2) Figure 4 is a schematic cross-sectional view of the porous membrane 1C of Modification 2. In the porous membrane 1C, the number of rod-shaped voids 31 existing in the direction of the thickness T30 of the porous layer 30 is not limited to one. Except for this point, the porous membrane 1C has the same structure as the porous membrane 1A described above. The porous membrane 1C having such a structure is also suitable for achieving both air permeability and water resistance. The porous membrane 1C of Modification 2 can be manufactured, for example, by controlling the speed of phase separation and the way in which phase separation proceeds by selecting a solvent and phase separation conditions in the manufacturing method.

[0101] As shown in Figure 4, two or more rod-shaped voids 31 (31A, 31B) may be present in the thickness T30 direction of the porous layer 30.

[0102] As shown in Figure 4, the major axes 31L of two or more rod-shaped gaps 31 (31A, 31B) may be offset from each other in the planar direction SD.

[0103] As shown in Figure 4, in the porous membrane 1C, a fourth partition wall 32d may exist between two or more rod-shaped voids 31 (31A, 31B) located in the direction of the thickness T30 of the porous layer 30.

[0104] As illustrated in Figure 4, in the porous membrane 1 (1A, 1B, 1C) of this embodiment, the porous layer 30 may have other voids 35 having a short-axis length similar to that of the rod-shaped voids 31. The other voids 35 are distinguished from the rod-shaped voids 31 in that they do not have an elongated shape in the thickness direction TD.

[0105] [Porous Composite] The porous membrane 1 (1A, 1B, 1C) of this embodiment can provide, for example, a porous composite 40 comprising the porous membrane 1. An example of a porous composite according to the present invention is shown in Figure 5. The porous composite 40 comprises a porous membrane 1 and a porous substrate 41. In the example of Figure 1, the porous composite 40 comprises the porous membrane 1A shown in Figure 1A as the porous membrane 1. In the porous composite 40, the porous membrane 1 is arranged in at least a portion of the voids 41v of the porous substrate 41.

[0106] The porous membrane 1 may be placed in a portion of the voids 41v of the porous substrate 41, or it may be placed in the entire voids 41v of the porous substrate 41. For example, one surface of the first microporous layer 10 in the thickness direction TD is in contact with at least a portion of the porous substrate 41, and the second microporous layer 20 is placed on the other surface of the porous layer 30 in the thickness direction TD.

[0107] The porous substrate 41 is not limited to a specific porous substrate. The porous substrate 41 is, for example, a nonwoven fabric. Examples of nonwoven fabrics include those mainly composed of resins such as polyethylene terephthalate (PET), liquid crystal polyester (LCP), polyimide (PI), polyphenylene sulfide (PPS), polyacrylonitrile, and polyamide. Another example of a nonwoven fabric is glass fiber and other silica fiber. The fiber diameter of the fibers contained in the nonwoven fabric is not limited to a specific value, but is, for example, about 50 nm to about 3000 nm. From the viewpoint of heat resistance, the nonwoven fabric preferably contains fibers such as PI, PPS, LCP, polyamide, and glass.

[0108] The thickness and basis weight of the porous substrate 41 are not limited to specific values. The thickness of the porous substrate 41 is, for example, 1 μm to 200 μm. The basis weight of the porous substrate 41 is, for example, 2 to 200 g / m². 2The porous substrate 41 has a thickness of 1 μm or more, which makes it easier to handle the porous substrate 41 when manufacturing the porous composite 40. The porous substrate 41 has a thickness of 200 μm or less, which makes it easier for the porous composite 40 to have the desired air permeability. The basis weight of the porous substrate 41 is 2 g / m². 2 As a result, handling of the porous substrate 41 is easier when manufacturing the porous composite 40. The basis weight of the porous substrate 41 is 200 g / m². 2 The porous composite 40 is more likely to have the desired breathability due to the following:

[0109] [Method for Manufacturing Porous Composites] The method for manufacturing the porous composite 40 described above is not limited to a specific method. For example, the porous composite 40 can be manufactured by using a nonwoven fabric as a base material in step 1 of the method for manufacturing the porous membrane 1A described above. Examples of nonwoven fabrics that can be used include PPS nonwoven fabric (HC#100, thickness 100 μm, basis weight 86 g / m²) provided by Toray Industries, Inc. 2 ) are examples. This allows for the creation of a porous composite 40 containing a porous membrane 1 in at least a portion of the voids in the nonwoven fabric.

[0110] [Membrane Member] An example of a membrane member according to the present invention is shown in Figure 6. The membrane member 2 (2A) in Figure 6 comprises a porous membrane 1 (1A, 1B, 1C). A modified example 1 of the membrane member in Figure 6 is shown in Figure 7. The membrane member 2 (2B) in Figure 7 further comprises a breathable support material 3. The breathable support material 3 is laminated on the porous membrane 1. The breathable support material 3 improves the strength and handling of the membrane member 2.

[0111] The breathable support material 3 typically has higher breathability in the thickness direction compared to the porous membrane 1. Examples of breathable support material 3 include woven fabrics, nonwoven fabrics, nets, and meshes. Examples of materials constituting the breathable support material 3 include polyester such as polyethylene terephthalate (PET), polyolefins such as polyethylene (PE) and polypropylene (PP), aramid resins, polyphenylene sulfide (PPS), and liquid crystal polyester (LCP). The shape of the breathable support material 3 may be the same as or different from the shape of the porous membrane 1 when viewed perpendicular to the main surface of the membrane member 2. The breathable support material 3 may have a peripheral portion that corresponds to the peripheral portion of the porous membrane 1 when viewed perpendicular to the main surface of the membrane member 2.

[0112] The membrane member 2B in Figure 7 includes one breathable support material 3 positioned on one surface (first surface 1a or second surface 1b) of the porous membrane 1. The membrane member 2 may include two or more breathable support materials 3. In the membrane member 2, breathable support materials 3 may be positioned on both surfaces (first surface 1a and second surface 1b) of the porous membrane 1. The porous membrane 1 and the breathable support material 3 may be joined by welding such as heat welding and ultrasonic welding, adhesives or other adhesives.

[0113] The film member 2 may include any other layers and / or members besides those described above.

[0114] The thickness of the film member 2 is, for example, 1 to 300 μm. The thickness of the film member 2 may also be 50 to 200 μm.

[0115] The basis weight of the film member 2 is, for example, 1.0 to 200.0 g / m². 2 The basis weight of the film member 2 is 10.0 to 100.0 g / m². 2 That's fine.

[0116] The membrane member 2 may have the same properties as the porous membrane 1, for example, air permeability in the thickness direction and / or water pressure resistance.

[0117] The film member 2 may be treated with a liquid-repellent treatment and / or a coloring treatment.

[0118] The membrane member 2 can be used, for example, as a filter member. However, the applications of the membrane member 2 are not limited to the above examples.

[0119] The shape of the membrane member 2, when viewed perpendicular to the main surface of the membrane member 2, may be, for example, a polygon including squares and rectangles, a circle, an ellipse, or a strip. The corners of the polygon may be rounded. However, the shape of the membrane member 2 is not limited to the above examples. A strip-shaped membrane member 2 may be wound to form a wound body. Also, if necessary, it may be wound in a laminated state with a release liner.

[0120] Figure 8 shows a modified example 2 (winding body) of the membrane member shown in Figure 6. The winding body 2C shown in Figure 8 includes the membrane member 2A of Figure 6 and a release liner 25. The membrane member 2A and the release liner 25 are joined to each other by an adhesive layer 26. In the winding body 2C, the release surface 27 formed when the release liner 25 is peeled off from the membrane member 2A is located between the membrane member 2A and the adhesive layer 26. That is, in the winding body 2C, when the release liner 25 is peeled off, the adhesive layer 26 is also peeled off from the membrane member 2A, resulting in a membrane member 2A in which the adhesive layer 26 is not formed on the surface.

[0121] The membrane member 2A, supplied by the wound body 2C and without an adhesive layer 26 formed on its surface, can be joined to the opening of the housing by any joining method. In other words, the membrane member 2A has a high degree of freedom in terms of how it can be joined to the opening of the housing. Joining methods include, for example, joining by a newly placed adhesive layer on the surface of the membrane member 2A, joining by heat welding, and joining by ultrasonic welding.

[0122] The membrane member 2A supplied by the wound body 2C can be processed into any shape as needed. In other words, the membrane member 2A has a high degree of freedom in shape. However, "shape" includes "size". The above point means that the wound body 2C can supply the membrane member 2A, which functions as a waterproof membrane, in a state with a high degree of freedom in the method of joining to the opening of the housing and / or in shape.

[0123] Furthermore, with the winding body 2C, the slippage between the film member 2A and the release liner 25 during winding is suppressed by the adhesive layer 26. The winding body 2C can suppress the occurrence of malfunctions (abnormal shape of the winding body) caused by winding tightness during winding.

[0124] [Ventilation Member] An example of a ventilation member according to the present invention is shown in Figure 9. The ventilation member 4 (4A) in Figure 9 has ventilation in the thickness direction and includes the porous membrane 1 or membrane member 2 described above as a member that prevents the passage of foreign matter in that direction. The ventilation member 4 is, for example, placed on the surface of an object having an opening, and is a member that ensures ventilation through the opening while preventing the passage of foreign matter through the opening. In this case, the ventilation member 4 is usually arranged such that the porous membrane 1 or membrane member 2 covers the opening of the object. In the example of Figure 9, the ventilation member 4A includes the porous membrane 1. Hereafter, the case in which the ventilation member 4 has ventilation in the thickness direction and includes the porous membrane 1 as a member that prevents the passage of foreign matter in that direction will be described as an example.

[0125] The ventilation member 4 (4A) comprises an adhesive layer 5 disposed on one side (first surface 1a or second surface 1b) of the porous membrane 1. The porous membrane 1 and the adhesive layer 5 are directly joined. The ventilation member 4A can be placed on the surface of an object via the adhesive layer 5.

[0126] Examples of adhesives constituting the adhesive layer 5 include acrylic adhesives, silicone adhesives, urethane adhesives, epoxy adhesives, and rubber adhesives. When it is necessary to consider the use of the ventilation member 4 at high temperatures, it is preferable to select an acrylic adhesive or a silicone adhesive, particularly a silicone adhesive, which has excellent heat resistance. The adhesive layer 5 may also be a substrate-less double-sided adhesive tape. The adhesive may also be a curable adhesive such as a phenolic resin, epoxy resin, urea resin, polyurethane resin, melamine resin, and polyester resin.

[0127] The outer periphery of the porous membrane 1 and the outer periphery of the adhesive layer 5 coincide when viewed perpendicular to the main surface of the porous membrane 1. Furthermore, the shape of the adhesive layer 5 corresponds to the peripheral edge of the porous membrane 1 when viewed perpendicular to the main surface of the porous membrane 1. Areas of the porous membrane 1 not joined by the adhesive layer 5 can be used as ventilation areas for the ventilation member 4A. However, the shape of the adhesive layer 5 is not limited to the above example.

[0128] The area of ​​the ventilation region is, for example, 40 mm². 2The following applies: A ventilation member 4 whose ventilation area falls within this range is suitable, for example, for placement on an object with a small-diameter opening. The lower limit of the ventilation area is, for example, 0.008 mm. 2 That concludes the explanation. However, the area of ​​the ventilation region may be larger depending on the type of object on which the ventilation member 4 is placed.

[0129] A modified example of the ventilation member in Figure 9 is shown in Figure 10. The ventilation member 4 (4B) in Figure 10 has the same configuration as the ventilation member 4A in Figure 9, except that it further comprises an adhesive layer 5 (5B) located on the other side of the porous membrane 1. The porous membrane 1 is sandwiched between the pair of adhesive layers 5 (5A, 5B).

[0130] As shown in Figure 10, the adhesive layer 5 may include a first adhesive layer 5A bonded to one surface of the porous film 1 (first surface 1a in Figure 10) and a second adhesive layer 5B bonded to the other surface of the porous film 1 (second surface 1b in Figure 10).

[0131] A modified example of the ventilation member in Figure 9, Part 2, is shown in Figure 11. The ventilation member 4 (4C) in Figure 11 further comprises a base layer 6 disposed on one side of the porous membrane 1 (first surface 1a or second surface 1b), and the porous membrane 1 and the adhesive layer 5 are joined via the base layer 6, except that it has the same configuration as the ventilation member 4A in Figure 9. The base layer 6 improves the strength and handling of the ventilation member 4 and suppresses damage to the porous membrane 1 during handling or placement on an object.

[0132] Examples of materials constituting the base layer 6 include polyolefins such as PE and PP, polyesters such as PET, silicone resins, polycarbonates, polyimides, polyamide-imides, polyphenylene sulfide, polyetheretherketone (PEEK), polyvinyl chloride, fluororesins, and metals such as aluminum and stainless steel. Examples of fluororesins include PTFE, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE). However, the materials constituting the base layer 6 are not limited to the above examples.

[0133] The outer periphery of the porous membrane 1 and the outer periphery of the base layer 6 coincide when viewed perpendicular to the main surface of the porous membrane 1. Furthermore, the shape of the base layer 6 corresponds to the peripheral edge of the porous membrane 1 when viewed perpendicular to the main surface of the porous membrane 1. Regions of the porous membrane 1 where the base layer 6 is not joined can be used as the ventilation region of the ventilation member 4C. However, the shape of the base layer 6 is not limited to the above example.

[0134] The porous membrane 1 and the base layer 6 may be joined by an adhesive or bonding agent, or by welding such as heat welding and ultrasonic welding. The porous membrane 1 and the base layer 6 may also be joined by an adhesive layer. The adhesive layer may have the same configuration as the adhesive layer 5. The base layer 6 may be a single-sided adhesive tape or a double-sided adhesive tape.

[0135] A modified example 3 of the ventilation member shown in Figure 9 is shown in Figure 12. The ventilation member 4 (4D) in Figure 12 has the same configuration as the ventilation member 4C in Figure 11, except that it further comprises a base material layer 6 (6B) arranged on the other side of the porous membrane 1. The porous membrane 1 is sandwiched between a pair of base material layers 6 (6A, 6B). This sandwiching structure further improves the strength and handling of the ventilation member 4.

[0136] As shown in Figure 12, the base layer 6 may include a first base layer 6A bonded to one surface of the porous film 1 (first surface 1a in Figure 12) and a second base layer 6B bonded to the other surface of the porous film 1 (second surface 1b in Figure 12).

[0137] A modified example 4 of the ventilation member in Figure 9 is shown in Figure 13. The ventilation member 4 (4E) in Figure 13 has the same configuration as the ventilation member 4B in Figure 10, except that it further includes a release liner 7 and the porous membrane 1 and the release liner 7 are joined via an adhesive layer 5 (5B).

[0138] As shown in Figure 13, the ventilation member 4 (4E) further comprises a peel-off liner 7, and a second adhesive layer 5B may be placed between the peel-off liner 7 and the porous membrane 1, with the second adhesive layer 5B being bonded to the peel-off liner 7.

[0139] The peel-off liner 7 has tabs that protrude outward from the outer circumference of the porous membrane 1 when viewed perpendicular to the main surface of the porous membrane 1. The ventilation member 4E can be handled and placed on the surface of an object by gripping the tabs. The peel-off liner 7 is usually removed when the ventilation member 4E is used. The peel-off liner 7 may be made of a material similar to the material that constitutes the base layer 6, for example.

[0140] A modified example 5 of the ventilation member in Figure 9 is shown in Figure 14. The ventilation member 4 (4F) in Figure 14 has the same configuration as the ventilation member 4D in Figure 12, except that it further includes a release liner 7 and is joined to the base layer 6 (6B) and the release liner 7 via an adhesive layer 5 (5B).

[0141] Another example of a ventilation member according to the present invention is shown in Figure 15. The ventilation member 4 (4G) in Figure 15 is positioned on the surface 8s of an object 8 having an opening 8p. The ventilation member 4G comprises a porous membrane 1 having a shape that covers the opening 8p, and an adhesive layer 5 bonded to one surface (first surface 1a or second surface 1b) of the porous membrane 1. The ventilation member 4G is fixed to the surface 8s of the object 8 using the adhesive layer 5.

[0142] As shown in Figure 15, the adhesive layer 5 may be bonded to the first surface 1a of the porous film 1.

[0143] A modified example of the ventilation member 4G in Figure 15 is shown in Figure 16. The ventilation member 4 (4H) in Figure 16 has the same configuration as the ventilation member 4G in Figure 15, except that it further comprises an adhesive layer 5 (5B) located on the other side of the porous membrane 1. The porous membrane 1 is sandwiched between a pair of adhesive layers 5 (5A, 5B).

[0144] As shown in Figure 16, the adhesive layer 5 may include a first adhesive layer 5A bonded to one surface of the porous film 1 (first surface 1a in Figure 16) and a second adhesive layer 5B bonded to the other surface of the porous film 1 (second surface 1b in Figure 16).

[0145] [Component Supply Assembly] The ventilation member 4 can be supplied, for example, by a component supply assembly. An example of a component supply assembly, which is a method of supplying the ventilation member 4, is shown in Figure 17. The component supply assembly 50 (50A) in Figure 17 comprises a ventilation member 4 (4A) which is placed on the surface of an object having an opening, and a base sheet 9 on which the ventilation member 4 (4A) is placed. The component supply assembly 50A includes a ventilation member 4A as the ventilation member 4. The ventilation member 4A comprises a porous membrane 1 which has a shape that covers the opening when placed on the surface of an object, and an adhesive layer 5 which is bonded to the porous membrane 1.

[0146] The ventilation member 4 (4A) is placed on the base sheet 9 via an adhesive layer 5. The member supply assembly 50 (50A) allows for efficient supply of the ventilation member 4 to, for example, a process of placing it on the surface of an object.

[0147] The ventilation member 4 may be placed on the base sheet 9 via an adhesive layer provided on the surface on which the ventilation member 4 is placed. The adhesive layer on the placement surface is preferably weakly adhesive.

[0148] Although not shown in the diagram, a plurality of ventilation members 4 may be arranged on the surface of the base sheet 9.

[0149] Examples of materials constituting the base sheet 9 include paper, metal, resin, and composite materials thereof. Examples of metals include stainless steel and aluminum. Examples of resins include polyester such as PET, and polyolefins such as PE and PP. However, the materials constituting the base sheet 9 are not limited to the above examples. The base sheet 9 may be in the form of a single sheet or a strip. If the base sheet 9 is in the form of a strip, the component supply assembly 50 may be wound to form a wound body.

[0150] Examples of objects on which the ventilation member 4 is placed include the housings of electronic devices and the housings of vehicle electrical components. The ventilation member 4 can be placed on the outer and / or inner surfaces of the housing. In this case, the opening may be a ventilation opening and / or sound vent provided in the housing. Examples of electronic devices include wearable devices such as smartwatches and wristbands; various cameras including action cameras and security cameras; information and communication devices such as mobile phones, smartphones and tablets; virtual reality (VR) devices; augmented reality (AR) devices; and sensor devices. Examples of vehicle electrical components include lamps and ECUs. However, the objects are not limited to the above examples.

[0151] Foreign matter whose passage is prevented by the arrangement of the ventilation member 4 includes, for example, particles such as dust and liquid water such as water droplets.

[0152] A modified example of the component supply assembly shown in Figure 17 is shown in Figure 18. The component supply assembly 50 (50B) in Figure 18 has the same configuration as the component supply assembly 50A in Figure 18, except that it includes the ventilation member 4E shown in Figure 13 as the ventilation member 4. That is, in the component supply assembly 50B, the ventilation member 4E comprises a porous membrane 1, a first adhesive layer 5A joined to the first surface 1a of the porous membrane 1, a second adhesive layer 5B joined to the second surface 1b of the porous membrane 1, and a release liner 7 joined to the second adhesive layer 5B. The second adhesive layer 5B is placed between the release liner 7 and the porous membrane 1, and the porous membrane 1 is fixed to the surface of the base sheet 9 using the first adhesive layer 5A.

[0153] A modified example 2 of the component supply assembly shown in Figure 17 is shown in Figure 19. The component supply assembly 50 (50C) in Figure 19 has the same configuration as the component supply assembly 50A in Figure 17, except that it is equipped with the ventilation member 4F shown in Figure 14 as the ventilation member 4.

[0154] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the examples shown below.

[0155] [Example 1] As a fluorine-free resin, a soluble polyimide varnish (NeoPrim S100, manufactured by Mitsubishi Gas Chemical Company, solid content concentration: 20 wt%) was prepared. As a solvent, a lactone-based solvent, γ-butyllactone (manufactured by Tokyo Chemical Industry Co., Ltd.), was prepared. 2.5 g of soluble polyimide varnish was mixed with 7.5 g of γ-butyllactone. This obtained the polyimide (PI) solution of Example 1. The polyimide concentration of the PI solution of Example 1 was 5 wt%.

[0156] A PTFE porous membrane (manufactured by Nitto Denko Corporation, TEMISH®) was prepared as the substrate. The PI solution from Example 1 was applied to the PTFE porous membrane using an applicator to a wet thickness of 125 μm to form a coating film.

[0157] Next, the coating film was immersed in a 20°C water bath for 10 minutes to allow porosity formation by phase separation and solvent extraction to proceed. Then, the coating film was fixed to a square-shaped SUS component with sides of 10 cm in plan view, and dried at 80°C for 10 minutes. This resulted in a porous film containing polyimide resin as the main component on the PTFE porous film. Finally, the polyimide porous film was peeled off from the PTFE porous film. In this way, the porous film of Example 1 was obtained.

[0158] Figure 20A is an SEM image (2500x magnification) of a cross-section parallel to the thickness direction of the porous membrane according to Example 1. Figure 20B is an SEM image (50000x magnification) of the surface of the upper layer (second microporous layer) of the porous membrane in Figure 20A. Figure 20C is an SEM image (10000x magnification) of the surface of the lower layer (first microporous layer) of the porous membrane in Figure 20A. Note that the lower layer in Figure 20A corresponds to the layer that was in contact with the PTFE porous membrane (first microporous layer). The same applies to the SEM images of cross-sections parallel to the thickness direction of the porous membranes according to Examples 2-3 and Comparative Examples 1-4.

[0159] [Example 2] 6.5 g of γ-butyllactone was added to 3.5 g of soluble polyimide varnish and mixed uniformly. This obtained the PI solution of Example 2. The polyimide concentration of the PI solution of Example 2 was 7 wt%. The porous film of Example 2 was obtained in the same manner as in Example 1.

[0160] Figure 21A is an SEM image (1500x magnification) of a cross-section parallel to the thickness direction of the porous membrane according to Example 2. Figure 21B is an SEM image (50000x magnification) of the surface of the upper layer (second microporous layer) of the porous membrane in Figure 21A. Figure 21C is an SEM image (10000x magnification) of the surface of the lower layer (first microporous layer) of the porous membrane in Figure 21A.

[0161] [Example 3] 6.5 g of γ-butyllactone was added to 3.5 g of soluble polyimide varnish and mixed uniformly. This obtained the PI solution of Example 3. The polyimide concentration of the PI solution of Example 3 was 7 wt%. The PI solution of Example 3 was applied to a PTFE porous membrane using an applicator to a wet thickness of 50 μm to form a coating film. The porous membrane of Example 3 was obtained in the same manner as in Example 1, except for these steps.

[0162] Figure 22A is an SEM image (2500x magnification) of a cross-section parallel to the thickness direction of the porous membrane according to Example 3. Figure 22B is an SEM image (50000x magnification) of the surface of the upper layer (second microporous layer) of the porous membrane in Figure 22A. Figure 22C is an SEM image (10000x magnification) of the surface of the lower layer (first microporous layer) of the porous membrane in Figure 22A.

[0163] [Comparative Example 1] PEG (polyethylene glycol 200, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was prepared as a porosizing agent. 5 g of soluble polyimide varnish was mixed with 3 g of γ-butyllactone to obtain a solution. 2 g of PEG as a porosizing agent was added to the above solution and mixed uniformly. This obtained the PI solution of Comparative Example 1. The polyimide concentration of the PI solution of Comparative Example 1 was 10 wt%. In the water immersion step, the coating film was immersed in a 60°C water bath for 10 minutes. The porous film of Comparative Example 1 was obtained in the same manner as in Example 1, except for these steps.

[0164] Figure 23A is an SEM image (1500x magnification) of a cross-section parallel to the thickness direction of the porous membrane according to Comparative Example 1. Figure 23B is an SEM image (50000x magnification) of the surface of the upper layer of the porous membrane in Figure 23A. Figure 23C is an SEM image (10000x magnification) of the surface of the lower layer of the porous membrane in Figure 23A.

[0165] [Comparative Example 2] In the water immersion step, the coating film was immersed in a 20°C water bath for 10 minutes. The porous film of Comparative Example 2 was obtained in the same manner as in Comparative Example 1.

[0166] Figure 24A is an SEM image (1500x magnification) of a cross-section parallel to the thickness direction of the porous membrane according to Comparative Example 2. Figure 24B is an SEM image (50000x magnification) of the surface of the upper layer of the porous membrane in Figure 24A. Figure 24C is an SEM image (10000x magnification) of the surface of the lower layer of the porous membrane in Figure 24A.

[0167] [Comparative Example 3] Prior to the water immersion process, the coating film was left to stand for 10 minutes inside a constant temperature and humidity chamber adjusted to a temperature of 30°C and a relative humidity of 90%, and a humidification process was carried out. In the water immersion process, the humidified coating film was immersed in a 20°C water bath for 10 minutes. The porous film of Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except for these steps.

[0168] Figure 25A is an SEM image (2500x magnification) of a cross-section parallel to the thickness direction of the porous membrane according to Comparative Example 3. Figure 25B is an SEM image (50000x magnification) of the surface of the upper layer of the porous membrane in Figure 25A. Figure 25C is an SEM image (10000x magnification) of the surface of the lower layer of the porous membrane in Figure 25A.

[0169] [Comparative Example 4] 3.5 g of soluble polyimide varnish was mixed uniformly with 1.6 g of γ-butyllactone and 4.9 g of dimethylacetamide. This yielded the PI solution of Comparative Example 4. The polyimide concentration of the PI solution of Comparative Example 4 was 7 wt%. In the water immersion step, the coating film was immersed in a 20°C water bath for 10 minutes. The porous film of Comparative Example 4 was obtained in the same manner as in Comparative Example 1, except for these steps.

[0170] Figure 26A is an SEM image (1500x magnification) of a cross-section parallel to the thickness direction of the porous membrane according to Comparative Example 4. Figure 26B is an SEM image (50000x magnification) of the surface of the upper layer of the porous membrane in Figure 26A. Figure 26C is an SEM image (10000x magnification) of the surface of the lower layer of the porous membrane in Figure 26A.

[0171] [Example 4] A polysulfone resin (Syensqo, Udel P-3500LCD) was prepared as a fluorine-free resin. DMF (Tokyo Chemical Industries, Ltd.) was prepared as the solvent. 1.2 g of polysulfone resin was mixed with 8.8 g of DMF. This obtained the polysulfone (PSU) solution of Example 4. The polysulfone concentration of the PSU solution of Example 4 was 12 wt%.

[0172] As a base material, PET nonwoven fabric (basis weight: 80 g / m²) 2 A PET nonwoven fabric (thickness: 100 μm) was prepared. The PSU solution from Example 4 was applied to the PET nonwoven fabric using an applicator to a wet thickness of 125 μm to form a coating film.

[0173] Next, the coating film was placed inside a constant temperature and humidity chamber adjusted to a temperature of 25°C and a relative humidity of 70% for 3 seconds to perform a humidification process. After that, the coating film was immersed in a 50°C water bath for 10 minutes to allow porosity formation by phase separation and solvent extraction to proceed. Next, the coating film was fixed to a square-shaped SUS component with sides of 10 cm in plan view and dried at 80°C for 10 minutes. As a result, a porous film mainly composed of polysulfone resin was obtained on a PET nonwoven fabric. In this way, the porous film of Example 4 was obtained.

[0174] Table 1 shows the manufacturing conditions for the porous membranes of Examples 1-3, Comparative Examples 1-4, and Example 4.

[0175]

[0176] Using the method described above for porous membranes, the porous membranes of Examples 1-3, Comparative Examples 1-4, and Example 4 were evaluated for the items listed in Table 2 below, using SEM images of the cross-section parallel to the thickness direction of the porous membrane, SEM images of the surface of the upper layer of the porous membrane, and SEM images of the surface of the lower layer of the porous membrane. The evaluation results are shown in Table 2. In the case of the porous membrane of Example 4, since the porous membrane and the PET nonwoven fabric were in contact, it was difficult to measure the average pore diameter on the surface of the lower layer and the thickness of the lower layer, so it is marked as "unmeasurable".

[0177]

[0178] Next, using the method described above for porous membranes, the solvent content relative to the weight of the porous membrane was determined for the porous membranes of Examples 1 to 3. The γ-butyllactone content of Example 1 was 0.61 wt% (6100 μg / g). The γ-butyllactone content of Example 2 was 1.5 wt% (15000 μg / g). The γ-butyllactone content of Example 3 was 1.2 wt% (12000 μg / g). From these results, it was confirmed that the porous membranes of Examples 1 to 3 contain γ-butyllactone. The DMF content of Example 4 was 0.8 wt% (8000 μg / g). From this result, it was confirmed that the porous membrane of Example 4 contains DMF.

[0179] Next, the air permeability and water pressure resistance of the porous membranes of Examples 1-3, Comparative Examples 1-4, and Example 4 were evaluated using the method described above for porous membranes. The evaluation results are shown in Table 3.

[0180]

[0181] As shown in Figures 20A, 21A, and 22A, the porous membranes of Examples 1 to 3 comprised a first microporous layer, a second microporous layer, and a porous layer located between the first and second microporous layers. The porous layer had rod-shaped voids extending in the thickness direction of the porous membrane. As shown in Table 2, in the porous membranes of Examples 1 to 3, the inclination angle of the major axis of the rod-shaped voids with respect to the thickness direction was within 20°, and the ratio of the length of the rod-shaped voids along the thickness direction to the thickness of the porous membrane was 0.7 or more.

[0182] As shown in Table 3, the porous membranes of Examples 1 to 4 had an air permeability of 25 seconds / 100 cm, expressed in Gurley numbers. 3 The following criteria were met, and the water pressure resistance was 100 kPa or higher, achieving both breathability and water resistance.

[0183] As shown in Figure 23A, the porous membrane of Comparative Example 1 had rod-shaped voids. However, as shown in Table 2, in the porous membrane of Comparative Example 1, the inclination angle of the long axis of the voids relative to the thickness direction exceeded 20°. Also, the length of the voids along the plane direction greatly exceeded 10 μm. Furthermore, the thickness of the second microporous layer greatly exceeded 3000 nm. This is thought to be partly due to the fact that the PI solution in Comparative Example 1 contained polyethylene glycol, which is a porosity-forming agent, as shown in Table 1. As a result, as shown in Table 3, although the porous membrane of Comparative Example 1 had a water pressure resistance of 100 kPa, its air permeability was 25 seconds / 100 cm. 3 It exceeded expectations.

[0184] As shown in Figure 24A, the porous membrane of Comparative Example 2 also contained rod-shaped voids. However, as shown in Table 2, in the porous membrane of Comparative Example 2, the ratio of the length of voids along the thickness direction to the thickness of the porous membrane was less than 0.7, indicating insufficient growth of voids in the thickness direction. Furthermore, the length of voids along the plane direction greatly exceeded 10 μm. Moreover, the ratio of the length of voids along the thickness direction to the length of voids along the plane direction was less than 2. Furthermore, the thickness of the second microporous layer greatly exceeded 3000 nm. This is thought to be partly due to the fact that the PI solution in Comparative Example 2 contained polyethylene glycol, which is a porosizing agent, as shown in Table 1. As a result, as shown in Table 3, the porous membrane of Comparative Example 2 had an air permeability of 98 seconds / 100 cm. 3 And, 25 seconds / 100cm 3 It far exceeded that.

[0185] As shown in Figure 25A, no rod-shaped voids were observed in the porous membrane of Comparative Example 3. Furthermore, as shown in Table 2, the average pore size on the surface of the upper layer was 0 (zero). This is largely attributed to the fact that in Comparative Example 3, a humidification process was carried out for a long period of 10 minutes at a high relative humidity of 90% prior to the water immersion process. As a result, as shown in Table 3, the porous membrane of Comparative Example 3 had extremely low air permeability.

[0186] As shown in Figure 26A, no rod-shaped voids were observed in the porous membrane of Comparative Example 4. Furthermore, as shown in Table 2, the thickness of the second microporous layer was less than 500 nm. As a result, the air permeability of the porous membrane of Comparative Example 4 was 18.8 seconds / 100 cm. 3 However, the water pressure resistance was less than 100 kPa. As shown in Table 2, in the porous membrane of Comparative Example 4, the length of the voids along the planar direction exceeded 10 μm, which made it easier to improve air permeability. On the other hand, the thickness of the second microporous layer was less than 500 nm, which made it difficult to ensure water resistance.

[0187] The technology of the present invention can be applied, for example, to waterproof and breathable membranes, waterproof and sound-permeable membranes, separators for energy storage devices, and the like.

Claims

1. A porous membrane comprising a first microporous layer, a second microporous layer, and a porous layer located between the first microporous layer and the second microporous layer, wherein the porous layer mainly contains a fluorine-free resin, the porous layer has rod-shaped voids extending in the thickness direction of the porous membrane, and in a cross-section of the porous membrane parallel to the thickness direction, when the straight line connecting the first end of the rod-shaped void on the first microporous layer side and the second end on the second microporous layer side is defined as the long axis of the rod-shaped void, the inclination angle of the long axis with respect to the thickness direction is within ±20°, and the ratio of the length (μm) of the rod-shaped void along the thickness direction to the thickness (μm) of the porous membrane is 0.7 or more.

2. The porous membrane according to claim 1, wherein the resin comprises at least one selected from the group consisting of polyimide resin, polysulfone resin, polyethersulfone resin, polystyrene resin, polyacrylonitrile resin, vinyl chloride resin, polycarbonate resin, polyamideimide resin, and polyetherimide resin.

3. The porous membrane according to claim 1, wherein, in a cross-section of the porous membrane parallel to the thickness direction, the length of the rod-shaped voids along the plane direction perpendicular to the thickness direction is 1 μm or more and 10 μm or less.

4. The porous membrane according to claim 1, wherein in a cross-section of the porous membrane parallel to the thickness direction, the ratio of the length of the rod-shaped voids along the thickness direction (μm) to the length of the rod-shaped voids along the plane direction perpendicular to the thickness direction (μm) is 2 or more and 10 or less.

5. The porous membrane according to claim 1, wherein, in a cross-section of the porous membrane parallel to the thickness direction, the length of the rod-shaped voids along the plane direction perpendicular to the thickness direction decreases from the first microporous layer side toward the second microporous layer side.

6. The porous membrane according to claim 1, wherein the average pore diameter on the surface of the first microporous layer is greater than the average pore diameter on the surface of the second microporous layer.

7. The porous membrane according to claim 1, wherein the porous membrane has a thickness of 10 μm or more and 100 μm or less.

8. The porous membrane according to claim 1, wherein the rod-shaped voids do not penetrate the porous layer.

9. The porous membrane according to claim 1, wherein the second microporous layer has a thickness of 100 nm to 3000 nm.

10. The porous membrane according to claim 1, comprising at least one selected from the group consisting of lactone solvents, sulfone solvents, ketone solvents, cyclic ether solvents, and amide solvents.

11. The porous membrane according to claim 10, wherein the lactone-based solvent contains γ-butyl lactone.

12. The permeability of the porous membrane is 25 seconds / 100 cm, expressed in Gurley numbers. 3 The porous membrane according to claim 1, which is as follows:

13. The porous membrane according to claim 1, wherein the water pressure resistance of the porous membrane, as measured according to the water resistance test method B (high water pressure method) specified in JIS L1092:2009, is 100 kPa or more.

14. A porous composite comprising a porous membrane according to claim 1 and a porous substrate, wherein the porous membrane is disposed in at least a portion of the voids of the porous substrate.

15. A ventilation member comprising a porous membrane according to any one of claims 1 to 13, and an adhesive layer bonded to the porous membrane.

16. A component supply assembly comprising: a ventilation member disposed on the surface of an object having an opening; and a base sheet on which the ventilation member is disposed, wherein the ventilation member comprises: a porous membrane having a shape that covers the opening when disposed on the surface; and an adhesive layer bonded to the porous membrane, and the porous membrane is the porous membrane according to any one of claims 1 to 13.

17. A method for producing a porous film, comprising the steps of: applying a solution containing a fluorine-free resin and a solvent onto a substrate to form a coating film; immersing the coating film in water; and drying the coating film, wherein the solvent comprises at least one selected from the group consisting of lactone-based solvents, sulfone-based solvents, ketone-based solvents, cyclic ether-based solvents, and amide-based solvents, and the polyethylene glycol content in the solution is less than 0.1 wt%.

18. The method for producing a porous membrane according to claim 17, wherein the resin comprises at least one selected from the group consisting of polyimide resin, polysulfone resin, polyethersulfone resin, polystyrene resin, polyacrylonitrile resin, vinyl chloride resin, polycarbonate resin, polyamideimide resin, and polyetherimide resin.

19. The method for producing a porous membrane according to claim 17, wherein the lactone-based solvent contains γ-butyllactone.

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