Porous film, ventilation member, and member supply sheet

Abstract

This porous film contains a fluorine-free thermoplastic resin as a main component, has an air permeability of 200 seconds / 100 mL or less in terms of Gurley number, and has a cohesive force of 1.0 N / 20 mm or more. This ventilation member comprises a porous film and an adhesive layer that is bonded to the porous film. This member supply sheet comprises: a ventilation member which is disposed on a surface of an object, the surface having an opening; and a base material sheet that has a surface on which the ventilation member is disposed. The ventilation member comprises: a porous film which has a shape that covers the opening when disposed on the surface; and an adhesive layer which is bonded to the porous film.

Description

Porous film, ventilation member, and member supply sheet

[0001] The present invention relates to a porous film, a ventilation member, and a member-supplying sheet.

[0002] Fluorine resin porous films are used in various applications such as filters, sound-permeable membranes, air-permeable membranes, diaphragms, etc. Fluorine-free porous membranes have also been proposed for use in these applications.

[0003] For example, Patent Document 1 discloses a biaxially stretched olefin-based resin microporous film having micropores and containing an olefin-based resin, the biaxially stretched olefin-based resin microporous film having a puncture strength of 0.7 N or more and an air permeability of 75 to 400 s / 100 mL.

[0004] Japanese Patent Application Laid-Open No. 2017-095576

[0005] Porous films used to prevent the penetration of foreign matter through openings in the housing of a device or the like while ensuring ventilation through the opening are sometimes provided as components laminated with a release liner. When such porous films are placed on a surface having an opening in a housing or the like, they are peeled off from the release liner and used. However, according to the inventors' studies, when a fluorine-free porous film is imparted with practical breathability (air permeability), it can break when peeled off from the release liner. Breakage of fluorine-free porous films can also be a problem after placement on a surface having an opening. Fluorine-free porous films with practical breathability have limited handleability due to the risk of breakage, and this point leaves room for improvement.

[0006] Therefore, an object of the present invention is to provide a porous film, a ventilation member, and a member-supplying sheet that are suitable for achieving both handleability and breathability.

[0007] The present invention provides a porous film comprising a fluorine-free thermoplastic resin as a main component, having an air permeability expressed as a Gurley number of 200 seconds / 100 mL or less, and a cohesive strength of 1.0 N / 20 mm or more.

[0008] From another aspect, the present invention provides a ventilation member comprising: the porous film of the present invention; and an adhesive layer bonded to the porous film.

[0009] A ventilation member is provided, the ventilation member being placed on a surface of an object having an opening, the ventilation member comprising: a porous film shaped to cover the opening; and a first adhesive layer bonded to a first main surface of the porous film, the ventilation member being fixed to the surface of the object using the first adhesive layer; the porous film containing a thermoplastic resin that does not contain a fluororesin as a main component; the porous film having an air permeability, expressed as a Gurley number, of 200 seconds / 100 mL or less; and the porous film not undergoing cohesive failure up to at least 0.03 N / 2.0 mm when subjected to the following handling evaluation test. <Handling Evaluation Test> A double-sided adhesive tape is bonded to the second main surface of the porous film, and a release liner is bonded to the double-sided adhesive tape. Next, a roller is reciprocated once on the release liner while applying a load of 2 kg. Next, the ventilation member is subjected to an aging treatment at 60°C for 5 minutes. After the aging treatment, the ventilation member is left in an environment at room temperature for 15 minutes, and then the release liner is picked up with tweezers and lifted up to be peeled off.

[0010] From yet another aspect, the present invention provides a member supply sheet comprising: a ventilation member to be placed on a surface of an object having an opening; and a base sheet with the ventilation member placed on a surface thereof, wherein the ventilation member comprises: a porous film having a shape that covers the opening when placed on the surface; and an adhesive layer bonded to the porous film, and the porous film is the porous film of the present invention described above.

[0011] From yet another aspect, the present invention provides a component supply sheet comprising: a ventilation member to be placed on a surface of an object having an opening; and a base sheet having the ventilation member placed on a surface thereof, wherein the ventilation member comprises: a porous film having a shape that covers the opening when placed on the surface; a first adhesive layer bonded to a first main surface of the porous film; a second adhesive layer bonded to a second main surface of the porous film; and a release liner bonded to the second adhesive layer, wherein the second adhesive layer is placed between the release liner and the porous film; the ventilation member is fixed to the surface of the base sheet using the first adhesive layer; the porous film contains a thermoplastic resin that does not contain a fluororesin as a main component; the porous film has an air permeability, expressed in Gurley number, of 200 seconds / 100 mL or less; and when the following handleability evaluation test is carried out, the porous film does not undergo cohesive failure. <Handling Efficiency Evaluation Test> The first adhesive layer was peeled from the base sheet, and the ventilation member was placed on a stainless steel test plate with the first adhesive layer in contact with the test plate. Next, the ventilation member was fixed to the test plate by rolling a roller back and forth once on the release liner while applying a load of 2 kg. Next, the ventilation member was subjected to an aging treatment for 5 minutes in an environment at 60°C. After the aging treatment, the ventilation member was left in an environment at room temperature for 15 minutes, and then the release liner was picked up with tweezers and lifted up to be peeled off.

[0012] According to the present invention, it is possible to provide a porous film, a ventilation member, and a member-supplying sheet that are suitable for achieving both ease of handling and breathability.

[0013] FIG. 1 is a cross-sectional view schematically showing an example of a porous film of the present invention. FIG. 2 is a schematic view showing a method of a T-peel test for measuring the cohesive strength of the porous film of FIG. 1. FIG. 3 is a cross-sectional view schematically showing an example of a film member of the present invention. FIG. 4 is a cross-sectional view schematically showing a first modified example of the film member of FIG. 3. FIG. 5 is a cross-sectional view schematically showing a second modified example (rolled body) of the film member of FIG. 3. FIG. 6 is a cross-sectional view schematically showing an example of a ventilation member of the present invention. FIG. 7 is a cross-sectional view schematically showing a first modified example of the ventilation member of FIG. 6. FIG. 8 is a cross-sectional view schematically showing a second modified example of the ventilation member of FIG. 6. FIG. 9 is a cross-sectional view schematically showing a third modified example of the ventilation member of FIG. 6. FIG. 10 is a cross-sectional view schematically showing a fourth modified example of the ventilation member of FIG. 6. FIG. 11 is a cross-sectional view schematically showing a fifth modified example of the ventilation member of FIG. 6. FIG. 12 is a cross-sectional view schematically showing another example of a ventilation member of the present invention. FIG. 13 is a schematic cross-sectional view illustrating a handling evaluation test of the ventilation member of FIG. 12. FIG. 14 is a cross-sectional view illustrating a modified example of the ventilation member of FIG. 12. FIG. 15 is a cross-sectional view illustrating a schematic example of a member supply sheet of the present invention. FIG. 16 is a cross-sectional view illustrating a modified example 1 of the member supply sheet of FIG. 15. FIG. 17 is a schematic cross-sectional view illustrating a handling evaluation test of the member supply sheet of FIG. 16. FIG. 18 is a cross-sectional view illustrating a modified example 2 of the member supply sheet of FIG. 15. FIG. 19A is a diagram (2500x magnification) showing the results of observation of the surface of the porous film of Example 5 with a scanning electron microscope (SEM). FIG. 19B is a partial enlarged view (10000x magnification) of FIG. 19A. FIG. 19C is a diagram (1500x magnification) showing the results of observation of the cross section of the porous film of Example 5 with an SEM. Fig. 20A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the porous film of Comparative Example 2. Fig. 20B is a partially enlarged view (10000x magnification) of Fig. 20A. Fig. 20C is a diagram (1500x magnification) showing the results of SEM observation of the cross section of the porous film of Comparative Example 2.

[0014] The porous film according to the first aspect of the present invention comprises a fluorine-free thermoplastic resin as a main component, and has an air permeability expressed in Gurley number of 200 seconds / 100 mL or less, and a cohesive strength of 1.0 N / 20 mm or more.

[0015] In a second aspect of the present invention, for example, in the porous film according to the first aspect, the thermoplastic resin is a polyolefin resin.

[0016] In a third aspect of the present invention, for example, the porous film according to the first or second aspect has a thickness of 40 μm or more and 100 μm or less.

[0017] In a fourth aspect of the present invention, for example, the porous film according to any one of the first to third aspects has a water pressure resistance of 200 kPa or more.

[0018] In a fifth aspect of the present invention, for example, the porous film according to any one of the first to fourth aspects is a stretched film.

[0019] A ventilation member according to a sixth aspect of the present invention includes, for example, the porous film according to any one of the first to fifth aspects, and an adhesive layer bonded to the porous film.

[0020] In a seventh aspect of the present invention, for example, in the ventilation member according to the sixth aspect, the adhesive layer includes a first adhesive layer bonded to a first main surface of the porous film and a second adhesive layer bonded to a second main surface of the porous film.

[0021] In an eighth aspect of the present invention, for example, the ventilation member according to the seventh aspect further comprises a release liner, the second adhesive layer being disposed between the release liner and the porous film, and the second adhesive layer being bonded to the release liner.

[0022] A ninth aspect of the present invention provides a ventilation member disposed on a surface of an object having an opening, the ventilation member comprising: a porous film shaped to cover the opening; and a first adhesive layer bonded to a first main surface of the porous film, the ventilation member being fixed to the surface of the object using the first adhesive layer; the porous film containing a thermoplastic resin that does not contain a fluororesin as a main component; the porous film having an air permeability, expressed in Gurley numbers, of 200 seconds / 100 mL or less; and, when subjected to the following handling evaluation test, the porous film does not undergo cohesive failure up to at least 0.03 N / 2.0 mm. <Handling Evaluation Test> Double-sided adhesive tape is bonded to the second main surface of the porous film, and a release liner is bonded to the double-sided adhesive tape. Next, a roller is reciprocated once on the release liner while applying a load of 2 kg. Next, the ventilation member is subjected to an aging treatment at 60°C for 5 minutes. After the aging treatment, the ventilation member is left in an environment at room temperature for 15 minutes, and then the release liner is picked up with tweezers and lifted up to be peeled off.

[0023] In a tenth aspect of the present invention, for example, the ventilation member according to the ninth aspect includes a second adhesive layer bonded to the second main surface of the porous film.

[0024] A component supply sheet according to an eleventh aspect of the present invention is a component supply sheet comprising: a ventilation member to be placed on a surface of an object having an opening; and a base sheet having the ventilation member placed on its surface, wherein the ventilation member comprises: a porous film having a shape that covers the opening when placed on the surface; and an adhesive layer bonded to the porous film, and the porous film is, for example, a porous film according to any one of the first to fifth aspects.

[0025] In a twelfth aspect of the present invention, for example, in the member supplying sheet according to the eleventh aspect, a plurality of the ventilation members are arranged on the surface of the base sheet.

[0026] a first adhesive layer bonded to a first main surface of the porous film; a second adhesive layer bonded to a second main surface of the porous film; and a release liner bonded to the second adhesive layer, wherein the second adhesive layer is disposed between the release liner and the porous film; the ventilation member is fixed to the surface of the base sheet using the first adhesive layer; the porous film contains a thermoplastic resin that does not contain fluororesin as a main component; the porous film has an air permeability, expressed in Gurley number, of 200 seconds / 100 mL or less; and the porous film does not undergo cohesive failure when subjected to the following handleability evaluation test. <Handling Efficiency Evaluation Test> The first adhesive layer was peeled from the base sheet, and the ventilation member was placed on a stainless steel test plate with the first adhesive layer in contact with the test plate. Next, the ventilation member was fixed to the test plate by rolling a roller back and forth once on the release liner while applying a load of 2 kg. Next, the ventilation member was subjected to an aging treatment for 5 minutes in an environment at 60°C. After the aging treatment, the ventilation member was left in an environment at room temperature for 15 minutes, and then the release liner was picked up with tweezers and lifted up to be peeled off.

[0027] In a fourteenth aspect of the present invention, for example, in the member supplying sheet according to the thirteenth aspect, a plurality of the ventilation members are arranged on the surface of the base sheet.

[0028] A method for producing a porous film according to a fifteenth aspect of the present invention includes the steps of: kneading a composition containing a fluorine-free thermoplastic resin and a plasticizer to obtain a kneaded mixture; performing a pressing or extrusion process; performing a cooling process; performing a stretching process; and performing a plasticizer extraction process, and further includes a pressing process after the stretching process.

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings, but is not limited to the following embodiments.

[0030] [Porous Film] An example of the porous film of the present invention is shown in Figure 1. The porous film 1 in Figure 1 contains a fluorine-free thermoplastic resin as a main component. The "main component" refers to the component that is contained in the largest amount by weight in the porous film 1. With this configuration, the porous film 1 can be adhered to an object such as a device housing by heat fusion, for example, without using an adhesive layer.

[0031] The air permeability in the thickness direction of the porous film 1, expressed as a Gurley number, is 200 seconds / 100 mL or less. Thus, the porous film 1 has high breathability. In this specification, the "Gurley number" refers to the air resistance (Gurley air permeability) measured in accordance with the Oken testing machine method specified in JIS P8117:2009.

[0032] The upper limit of the air permeability of the porous film 1, expressed in Gurley number, may be 190 seconds / 100 mL or less, 180 seconds / 100 mL or less, 170 seconds / 100 mL or less, 160 seconds / 100 mL or less, or even 150 seconds / 100 mL or less. The lower limit of the air permeability of the porous film 1, expressed in Gurley number, may be 0.1 seconds / 100 mL or more, 1 second / 100 mL or more, 10 seconds / 100 mL or more, or even 15 seconds / 100 mL or more. The air permeability of the porous film 1 may be 0.1 sec / 100 mL or more and 190 sec / 100 mL or less, 0.1 sec / 100 mL or more and 180 sec / 100 mL or less, 0.1 sec / 100 mL or more and 170 sec / 100 mL or less, 0.1 sec / 100 mL or more and 160 sec / 100 mL or less, or even 0.1 sec / 100 mL or more and 150 sec / 100 mL or less.

[0033] Even if the size of the porous film 1 does not meet the recommended dimensions (50 mm x 50 mm) of the test piece for the Oken Testing Machine Method, it is possible to evaluate the air resistance (Gurley air permeability) in accordance with the Oken Testing Machine Method by using a measuring jig.

[0034] The measurement jig has a shape and size that can be placed in the air permeability measurement section of the Oken testing machine, and is made of a thickness and material that will not deform due to the differential pressure applied to the test piece during air permeability resistance measurement. An example of the measurement jig is a 2 mm thick, 47 mm diameter SUS disk. A through-hole with an opening smaller than the membrane to be evaluated is provided in the center of the surface of the measurement jig. The cross section of the through-hole is typically circular, and the diameter is such that the opening of the through-hole is completely covered by the membrane to be evaluated. The diameter of the through-hole can be, for example, 1 mm or 2 mm. Next, the porous film 1 to be evaluated is fixed to one side of the measurement jig so as to cover the opening. The fixation is performed so that during air permeability resistance measurement, air passes only through the opening and the effective test portion of the porous film 1 to be evaluated (the portion overlapping with the opening when viewed perpendicular to the main surface of the fixed porous film 1), and the fixed portion does not obstruct the passage of air through the effective test portion of the porous film 1. To fix the porous film 1, double-sided adhesive tape with a vent hole punched in the center, having a shape that matches the shape of the opening, can be used. The double-sided adhesive tape can be placed between the measurement jig and the porous film 1 so that the periphery of the vent hole matches the periphery of the opening. Next, the measurement jig with the porous film 1 fixed is set in the air permeability measurement section of the Oken tester so that the fixed surface of the porous film 1 is downstream of the air flow during measurement, and a test is performed using the Oken tester method, and the air permeability resistance indicated value t shown by the tester is recorded. Next, the recorded air permeability resistance indicated value t is measured using an effective test area of ​​6.452 [cm2] as specified in the Oken tester method. 2 ] per value t K In equation t K = {t × (area of ​​the effective test portion of the porous film 1 [cm 2 ]) / 6.452 [cm 2 ]}, and the resulting converted value t Kcan be regarded as the air resistance (Gurley air permeability) of the porous film 1 measured in accordance with the Oken type testing machine method. It has been confirmed that the air resistance measured without using a measuring jig for a porous film 1 that meets the recommended dimensions (50 mm x 50 mm) of the test piece for the Oken type testing machine method is in good agreement with the air resistance measured using a measuring jig after cutting the porous film 1 into small pieces, that is, the use of a measuring jig does not substantially affect the measured value of the air resistance.

[0035] The cohesive strength of the porous film 1 is 1.0 N / 20 mm or more. With this configuration, the porous film 1 is prevented from undergoing cohesive failure when attached to a device housing or the like, and has appropriate handleability.

[0036] The upper limit of the cohesive strength of the porous film 1 may be 4.0 N / 20 mm or less, 3.5 N / 20 mm or less, or 3.0 N / 20 mm or less.

[0037] The cohesive strength of the porous film 1 can be measured in accordance with JIS Z0237:2009 by the method described below.

[0038] FIG. 2 is a schematic diagram showing a method of a T-peel test for measuring the cohesive strength of a porous film 1. First, the porous film 1 is cut to a size of 100 mm long x 20 mm wide. Next, two pieces of double-sided adhesive tape 51 (manufactured by Nitto Denko Corporation, No. 5610) having the same shape as the cut porous film 1 are prepared. Each double-sided adhesive tape 51 is bonded to one side and the other side of the porous film 1, respectively, with the outer peripheries aligned. Next, two pieces of PET film 52 (25 μm thick) having a length of 150 mm x width of 20 mm are prepared. Each PET film 52 is bonded to one side and the other side of the porous film 1, respectively, with the double-sided adhesive tape 51. The PET films 52 are bonded together so that both widthwise ends of each PET film 52 coincide with both widthwise ends of the porous film 1, and so that both longitudinal ends of each PET film 52 do not overlap the porous film 1 or the double-sided adhesive tape 51 when viewed perpendicular to the main surface of the PET film 52. However, the length (longitudinal direction) of the free end of each PET film 52 must be long enough (e.g., 25 mm) to allow the chuck of the tensile tester to stably grip the PET film 52. Next, a roller is moved back and forth once while applying a load of 2 kg so that a pressure is applied in the thickness direction to the laminate 50 of PET film 52 / double-sided adhesive tape 51 / porous film 1 / double-sided adhesive tape 51 / PET film 52. The laminate is then aged for 2 hours at 60°C. The laminate is left to cool at room temperature for 30 minutes, and used as the test piece 50.

[0039] Next, a tensile tester (for example, a desktop precision universal testing machine, Autograph AGS-X, manufactured by Shimadzu Corporation) is prepared. The free end of one PET film 52 at one end in the longitudinal direction of the test piece 50 is fixed to the upper chuck 61 of the tensile tester. The free end of the other PET film 52 at the other end in the longitudinal direction of the test piece 50 is attached to the lower chuck 62. Next, a tensile test is performed in which the upper end of one PET film 52 is pulled upward under conditions of a measurement temperature of 25 ° C. and a tensile speed of 100 mm / min, causing cohesive failure in the porous film 1. After the start of the measurement, the stress between the chucks measured during the initial 25 mm displacement is ignored, and the average value of the measured stress values ​​(N) recorded continuously during the subsequent 50 mm displacement is taken as the cohesive strength (N / 20 mm) of the porous film 1.

[0040] As described above, the porous film 1 contains a fluorine-free thermoplastic resin as a main component. The fluorine-free thermoplastic resin may be a polyolefin resin. When the thermoplastic resin is a polyolefin resin, it is easy to obtain a porous film 1 that is suitable for achieving both handleability and breathability.

[0041] The polyolefin resin includes polyethylene (PE) resin, polypropylene (PP) resin, and polymethylpentene (PMP) resin.

[0042] The polyolefin resin may be a polymethylpentene resin. The polymethylpentene resin is a homopolymer or copolymer such as poly(4-methylpentene-1) resin or poly(3-methylpentene-1) resin. Examples of the copolymer include random copolymers and block copolymers. From the viewpoints of heat resistance and moldability, a homopolymer of poly(4-methylpentene-1) resin is preferred.

[0043] The polyolefin resin may be a poly(4-methylpentene-1) resin. Poly(4-methylpentene-1) resin refers to a homopolymer of 4-methylpentene-1 or a copolymer of 4-methylpentene-1 and at least one α-olefin. The composition ratio of 4-methylpentene-1 to the α-olefin contained in the copolymer can be adjusted so that the melting point is in the range of 180°C or higher.

[0044] The fluorine-free thermoplastic resin may be a thermoplastic resin having a melting point of 180° C. or higher and 300° C. or lower. When the melting point of the thermoplastic resin is 180° C. or higher, sufficient heat resistance can be ensured in the porous film 1. When the melting point of the thermoplastic resin is 300° C. or lower, the porous film 1 can be produced by melt molding, for example.

[0045] The melting point of the thermoplastic resin may be 200°C or higher and 280°C or lower, and may further be 220°C or higher and 260°C or lower.

[0046] The water pressure resistance of the porous film 1 is preferably 200 kPa or more when evaluated by the water resistance test method B (high water pressure method) specified in JIS L1092:2009.

[0047] The lower limit of the water pressure resistance of the porous film 1 may be 220 kPa or more, 240 kPa or more, or even 250 kPa or more. The upper limit of the water pressure resistance of the porous film 1 is, for example, 2000 kPa or less. The water pressure resistance of the porous film 1 may be 220 kPa or more and 2000 kPa or less, 240 kPa or more and 2000 kPa or less, or even 250 kPa or more and 2000 kPa or less.

[0048] The water pressure resistance of the porous film 1 can be measured using a measuring jig in accordance with the above-mentioned water resistance test method as follows. An example of the measuring jig is a 47 mm diameter stainless steel (SUS) disk with a 1.0 mm diameter through-hole (having a circular cross section) in the center. This disk has a thickness that does not deform due to the water pressure applied when measuring the water pressure resistance. Measurement of the water pressure resistance using this measuring jig can be carried out as follows.

[0049] The porous film 1 to be evaluated is fixed to one side of the measuring jig so as to cover the opening of the through-hole. Fixation is performed so that water does not leak from the fixed portion of the membrane during water pressure resistance measurement. The porous film 1 can be fixed using double-sided adhesive tape with a water passage hole (1.6 mm diameter) punched in the center, whose shape matches the opening. The double-sided adhesive tape is simply placed between the measuring jig and the porous film 1 so that the periphery of the water passage hole coincides with the periphery of the opening. Next, the measuring jig with the porous film 1 fixed thereto is set in the testing device so that the surface opposite the fixed surface of the porous film 1 becomes the water pressure application surface during measurement, and the water pressure resistance is measured according to Water Resistance Test Method B (high water pressure method) specified in JIS L1092:2009. Note that 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 film 1. The measured water pressure resistance can be used as the water pressure resistance of the porous film 1. The test device may have the same configuration as the water resistance test device exemplified in JIS L1092:2009 and have a test piece mounting structure on which the above-mentioned measuring jig can be set.

[0050] The porous film 1 may be in the form of a film or a sheet. The thickness of the porous film 1 is preferably 40 μm or more and 100 μm or less. When the thickness is in the above range, the handleability of the porous film 1 can be improved.

[0051] The thickness of the porous film 1 can be determined by measuring the thickness at any five points on the porous film 1 using, for example, a dial gauge, and calculating the average value of these measured values. The thickness of the porous film 1 can also be determined by measuring the thickness at any five points on an SEM image of the cross section of the porous film 1 and calculating the average value of these measured values.

[0052] The lower limit of the thickness of the porous film 1 may be 44 μm or more. The upper limit of the thickness of the porous film 1 may be 90 μm or less, 80 μm or less, or 70 μm or less.

[0053] The porous film 1 may have a hexagonal structure formed by a plurality of nodes and a plurality of fibrils. The hexagonal structure may exist throughout the entire porous film 1. A porous film 1 having such a structure is suitable for achieving both ease of handling and breathability. The hexagonal structure can be confirmed, for example, by observing the main surface of the porous film 1 from the vertical direction. In this disclosure, the term "main surface" refers to the surface of a film-like or sheet-like member having the largest area. In this disclosure, the terms "main surface," "surface," and "face" of the porous film 1 are used interchangeably.

[0054] In the present disclosure, the term "hexagonal structure formed by multiple nodes and multiple fibrils" refers to a structure that can be confirmed by observing the surface of the porous film 1 with a scanning electron microscope (SEM), in which island-like regions formed by multiple nodes are irregularly connected and these island-like regions are connected to each other by multiple fibrils. The island-like regions have, for example, a polygonal shape. Note that the polygonal-shaped region does not necessarily have to have an outer shape composed only of straight lines, and also includes approximately polygonal-shaped regions in which some sides are curved, such as circular arcs. Furthermore, the polygonal shape is not limited to a hexagon.

[0055] For example, Figure 19A shows the results of SEM observation of the surface of the porous film of Example 5 (described later) (2500x magnification). Figure 19B is a partial enlargement of Figure 19A (10000x magnification). As shown in Figures 19A and 19B, the surface of the porous film of Example 5 has a tortoiseshell structure formed by multiple nodes and multiple fibrils.

[0056] When the cross section of the porous film 1 is observed with an SEM, a plurality of nodes may be present along the thickness direction. The plurality of nodes may be present throughout the entire thickness direction of the porous film 1. The plurality of nodes may be uniformly present throughout the thickness direction of the porous film 1. Adjacent agglomerated nodes may be connected by a plurality of fibrils, or adjacent agglomerated nodes may be directly connected to each other without being connected by a plurality of fibrils.

[0057] It is preferable that the porous film 1 has small variation in the size of the gaps between the island regions formed by the multiple nodes in the thickness direction, and that the gaps are dispersed. A porous film 1 having such a cross-sectional structure tends to have improved cohesive strength while maintaining high breathability. The gaps in the thickness direction contribute to improving the breathability of the porous film 1. On the other hand, if there is variation in the size of the gaps in the thickness direction, for example, if large and small gaps are mixed, the cohesiveness of the porous film 1 is likely to decrease. However, if there is small variation in the size of the gaps in the thickness direction and the gaps are dispersed, the cohesiveness of the porous film 1 is improved, and therefore high breathability and high cohesiveness can be achieved at the same time.

[0058] For example, Figure 19C is a diagram (1500x magnification) showing the results of SEM observation of the cross section of the porous film of Example 5 described below. As shown in Figure 19C, when the cross section of the porous film of Example 5 was observed with an SEM, multiple nodes were found to be present along the thickness direction. The multiple nodes were present throughout the entire thickness direction of the porous film. The porous film of Example 5 had small variation in the size of the gaps between the island regions formed by the multiple nodes in the thickness direction, and the gaps were dispersed.

[0059] The porosity of the porous film 1 is, for example, 25% or more. The porosity of the porous film 1 may be 20% or more, or 35% or more. The porosity can be calculated by substituting the weight, thickness, area (area of ​​the main surface), and true density of the porous film 1 into the following formula (1).

[0060] Porosity (%) = {1 - (weight [g] / (thickness [cm] × area [cm 2 ]×True density [g / cm 3 ]))}×100 ...Formula (1)

[0061] The upper limit of the porosity of the porous film 1 is, for example, 95%. The upper limit of the porosity may be 90%.

[0062] The porous film 1 may be a stretched film. When the porous film 1 is a stretched film, it is easy to control the breathability and cohesive force. The stretched film may be a biaxially stretched film or a uniaxially stretched film.

[0063] At least one of the main surfaces of the porous film 1 may be subjected to a surface modification treatment. Examples of the surface modification treatment include an oil-repellent treatment, a chemical treatment, a sputter etching treatment, and a plasma treatment. The bonding property of the porous film 1 is improved in the area subjected to the surface modification treatment.

[0064] At least one of the main surfaces of the porous film 1 may be subjected to a liquid-repellent treatment. The liquid-repellent treatment is generally carried out by applying a liquid-repellent agent to the surface of the porous film 1 or by immersing the porous film 1 in the liquid-repellent agent. The liquid-repellent agent is not particularly limited, and may be a fluorine-based liquid-repellent agent, a silicone-based liquid-repellent agent, or an acrylic-based liquid-repellent agent. The fluorine-based liquid-repellent agent has, for example, a structure having an acrylic main chain and a hydrocarbon side chain saturated with fluorine (perfluoroalkyl group).

[0065] [Method for Producing Porous Film] The porous film 1 described above can be produced, for example, by the following method.

[0066] The method for producing the porous film 1 includes, for example, kneading a composition containing a fluorine-free thermoplastic resin and a plasticizer to obtain a kneaded product (step S1), pressing the kneaded product to obtain a first pressed body (step S2), cooling the first pressed body to obtain a molded body (step S3), stretching the molded body to obtain a sheet body (step S4), pressing the sheet body a second time to obtain a second pressed body (step S5), and extracting the plasticizer from the second pressed body (step S6).

[0067] As another method, the method for producing the porous film 1 includes, for example, kneading a composition containing a fluorine-free thermoplastic resin and a plasticizer to obtain a kneaded mixture (step ST), extruding the kneaded mixture using a twin-screw extruder (step ST2), cooling the extruded kneaded mixture to obtain a molded body (step ST3), stretching the molded body to obtain a sheet body (step S4), pressing the sheet body to obtain a pressed body (step S5), and extracting the plasticizer from the pressed body (step S6).

[0068] Steps S1 to S3 correspond to a process for producing a precursor of the porous film 1. Steps S4 to S6 correspond to a process for growing a porous structure.

[0069] Step S1 is carried out, for example, at a temperature of 230° C. to 260° C. for 5 to 30 minutes.

[0070] As the fluorine-free thermoplastic resin, for example, polymethylpentene resin can be used.

[0071] The composition containing the thermoplastic resin and the plasticizer may be mixed with a resin such as polyethylene, polypropylene, poly-1-butene, or cyclic polyolefin, as long as the properties of the porous film 1 are not affected.

[0072] The plasticizer is a non-volatile solvent that, when mixed with a thermoplastic resin such as polymethylpentene resin, forms a mixture at or above the melting point of the resin, and that undergoes thermally induced phase separation when the mixture is cooled. The plasticizer may be in the form of a liquid or a solid at room temperature. The plasticizer may be used alone, or two or more types of plasticizers may be mixed and used.

[0073] The mixing ratio of the thermoplastic resin and the plasticizer is set so that a uniform kneaded product can be obtained in step S1 and a molded body can be formed in step S3. Specifically, the weight ratio of the thermoplastic resin in the composition containing the thermoplastic resin and the plasticizer is, for example, 20% by weight or more and 80% by weight or less, preferably 30% by weight or more and 70% by weight. When the weight ratio of the thermoplastic resin is 20% by weight or more, excessive reduction in viscosity of the composition can be avoided. When the weight ratio of the thermoplastic resin is 80% by weight or less, a good porous structure can be easily obtained.

[0074] The composition containing the thermoplastic resin and the plasticizer may further contain additives such as antioxidants, crystal nucleating agents, antistatic agents, flame retardants, lubricants, ultraviolet absorbers, colorants, and inorganic fillers for improving strength, depending on the purpose.

[0075] Step S2 is carried out for 2 to 30 minutes at a temperature of 230 to 260° C., for example. The thickness of the first pressed body obtained in step S2 is 0.1 mm, for example.

[0076] In step S3, the first press body obtained in step S2 is cooled to a temperature sufficiently lower than the crystallization temperature of the thermoplastic resin by contacting it with a thermal conductor, for example, and solidified. Examples of thermal conductors used for cooling include water, air, metal, and plasticizer.

[0077] The manufacturing method may include, instead of step S2, performing an extrusion process on the kneaded material using a twin-screw extruder (step ST2). In step ST2, the kneaded material may be extruded onto a metal roll whose surface temperature is controlled. A flat die (hanger coat die) may be used to extrude the kneaded material. By using a flat die, the kneaded material can be extruded in a wide width, so that a sheet-like molded product can be easily obtained in step ST2.

[0078] When step ST2 is included instead of step S2, the manufacturing method may include, instead of step S3, performing a cooling treatment on the extruded kneaded material to obtain a molded body (step ST3). In step ST3, for example, a metal roll with a controlled surface temperature may be used to roll out the kneaded material while cooling it to obtain a sheet-like molded body. The surface temperature of the metal roll is controlled to, for example, 120°C. A plurality of metal rolls may be used. A sheet-like molded body may be formed while cooling by passing the kneaded material through a plurality of metal rolls.

[0079] In step S4, the molded body is stretched at least once in at least one axial direction. Stretching in at least one axial direction includes uniaxial stretching in the machine direction, uniaxial stretching in the transverse direction, simultaneous biaxial stretching, and sequential biaxial stretching. The molded body may be biaxially stretched sequentially, or simultaneously. Step S4 generates pores in the molded body, and a tortoiseshell structure formed by a plurality of nodes and a plurality of fibrils is formed.

[0080] The stretching temperature may be 20°C to 240°C, 50°C to 230°C, or even 100°C to 220°C in each of the longitudinal and transverse directions.

[0081] The stretching ratio in the longitudinal and / or transverse uniaxial directions may be 2.0 to 10.0 times, 2.0 to 8.0 times, or even 2.0 to 5.0 times.

[0082] The strain rate in the stretching may be 1% / sec to 10% / sec, 1% / sec to 8% / sec, or even 1% / sec to 5% / sec in the machine direction and / or the transverse direction. When the strain rate is in the above range, a porous film exhibiting good breathability can be obtained.

[0083] Step S5 is carried out, for example, at a temperature of 80°C to 200°C and a pressure of 2 kPa to 10 kPa for 2 to 30 minutes. The heat pressing temperature in step S5 is preferably below the melting point of the thermoplastic resin. The thickness of the second pressed body obtained by step S5 is, for example, 100 μm or less. Step S5 suppresses variation in the size of gaps in the thickness direction of the second pressed body, dispersing the gaps. This improves the cohesive strength of the porous film 1 finally obtained.

[0084] In step S6, the plasticizer is extracted and removed from the second pressed body or sheet using, for example, an extraction solvent. After step S6, the second pressed body or sheet from which the plasticizer has been extracted and removed may be dried using a dryer or by natural drying. In this way, the porous film 1 is obtained.

[0085] The extraction solvent is preferably a poor solvent for thermoplastic resins such as polymethylpentene resins, but a good solvent for plasticizers, and has a boiling point lower than the melting point of the porous film 1. Examples of such extraction solvents include hydrocarbons such as n-hexane and cyclohexane; halogenated hydrocarbons such as methylene chloride and 1,1,1-trichloroethane; alcohols such as ethanol and isopropanol; ethers such as diethyl ether and tetrahydrofuran; and ketones such as acetone and 2-butanone. Considering safety and other factors, alcohols and ketones are preferably used. Methyl ethyl ketone (MEK) may also be used as the extraction solvent.

[0086] Between step S4 and step S5, the sheet may be heat-set. Heat-set may be performed, for example, using a hot air circulating oven. Heat-set may reduce the thermal shrinkage of the sheet after stretching. The heat-set temperature is, for example, 50°C to 240°C. The heat-set temperature may be 100°C to 230°C, or may be 150°C to 220°C.

[0087] Heat setting may be performed after step S4, between steps S4 and S5, or both after steps S4 and S5. Examples of the heat setting method include fixing the film in the width direction with a tenter and continuously passing it through a heat treatment furnace, applying an appropriate tension and continuously passing it through a heat treatment furnace without fixing it in the width direction, and winding the film around a roll and feeding it into a heat treatment furnace in batches.

[0088] [Film member] An example of the film member of the present invention is shown in Figure 3. The film member 2 (2A) in Figure 3 includes a porous film 1. A first modified example of the film member of Figure 3 is shown in Figure 4. The film member 2 (2B) in Figure 4 further includes an air-permeable support material 3. The air-permeable support material 3 is laminated on the porous film 1. The air-permeable support material 3 can improve the strength and handleability of the film member 2.

[0089] The breathable support material 3 usually has higher breathability in the thickness direction than the porous film 1. Examples of the breathable support material 3 include woven fabric, nonwoven fabric, net, and mesh. Examples of materials constituting the breathable support material 3 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene (PE) and polypropylene (PP), and aramid resin. The shape of the breathable support material 3, when viewed perpendicularly to the main surface of the film member 2, may be the same as or different from the shape of the porous film 1. The breathable support material 3 may have a peripheral edge corresponding to the peripheral edge of the porous film 1, when viewed perpendicularly to the main surface of the film member 2.

[0090] The film member 2B in Fig. 4 includes one breathable support material 3 arranged on one surface of the porous film 1. The film member 2 may include two or more breathable support materials 3. In the film member 2, the breathable support materials 3 may be arranged on both surfaces of the porous film 1. The porous film 1 and the breathable support material 3 may be joined by welding such as thermal welding or ultrasonic welding, an adhesive, a pressure-sensitive adhesive, or the like.

[0091] The film member 2 may include any layers and / or members other than those described above.

[0092] The thickness of the film member 2 is, for example, 1 to 300 μm, and may be 50 to 200 μm.

[0093] The basis weight of the film member 2 is, for example, 1.0 to 200.0 g / m 2 The basis weight of the film member 2 is 10.0 to 100.0 g / m 2 may be.

[0094] The film member 2 can have the same properties as the porous film 1, such as air permeability in the thickness direction and / or water pressure resistance.

[0095] The film member 2 may be subjected to a liquid-repellent treatment and / or a coloring treatment.

[0096] The film member 2 can be used as, for example, a filter member, but the uses of the film member 2 are not limited to the above example.

[0097] The shape of the film member 2, when viewed perpendicularly to the main surface of the film member 2, is, for example, a polygon including a square and a rectangle, a circle, an ellipse, or a strip. The corners of the polygon may be rounded. However, the shape of the film member 2 is not limited to the above examples. A strip-shaped film member 2 may be wound to form a wound body. Furthermore, if necessary, the film member 2 may be wound in a state where it is laminated with a release liner.

[0098] A second modification (roll) of the film member of Fig. 3 is shown in Fig. 5. The roll 10 shown in Fig. 5 includes the film member 2A and release liner 11 of Fig. 3. The film member 2A and the release liner 11 are bonded to each other by an adhesive layer 12. In the roll 10, a release surface 13 formed when the release liner 11 is peeled from the film member 2A is located between the film member 2A and the adhesive layer 12. That is, in the roll 10, when the release liner 11 is peeled off, the adhesive layer 12 is also peeled off from the film member 2A, resulting in a film member 2A that does not have the adhesive layer 12 formed on its surface.

[0099] The film member 2A supplied by the roll 10 and having no adhesive layer 12 formed on its surface can be bonded to the opening of the housing by any bonding method. That is, the film member 2A has a high degree of freedom in the method of bonding to the opening of the housing. Bonding methods include, for example, bonding using an adhesive layer newly disposed on the surface of the film member 2A, bonding by thermal welding, and bonding by ultrasonic welding.

[0100] The film member 2A supplied by the roll 10 can be processed into any shape as needed. That is, the film member 2A has a high degree of freedom in terms of shape. However, "shape" also includes "size." The above means that the roll 10 allows the film member 2A, which functions as a waterproof membrane, to be supplied with a high degree of freedom in terms of the joining method to the opening of the housing and / or the shape.

[0101] Furthermore, according to the wound body 10, misalignment between the film member 2A and the release liner 11 during winding is suppressed by the adhesive layer 12. The wound body 10 can suppress the occurrence of malfunctions (abnormal shape of the wound body) caused by tightness during winding, etc.

[0102] [Ventilation Member] An example of a ventilation member of the present invention is shown in FIG. 6. The ventilation member 4 (4A) in FIG. 6 has breathability in the thickness direction and includes the porous film 1 or film member 2 described above as a member that prevents the penetration of foreign matter in that direction. The ventilation member 4 is, for example, a member that is placed on a surface of an object having an opening, and ensures ventilation through the opening while preventing the penetration of foreign matter through the opening. In this case, the ventilation member 4 is typically placed so that the porous film 1 or film member 2 covers the opening of the object. The ventilation member 4A in FIG. 6 includes a porous film 1. Below, an example will be described in which the ventilation member 4 has breathability in the thickness direction and includes a porous film 1 as a member that prevents the penetration of foreign matter in that direction.

[0103] The ventilation member 4 (4A) has an adhesive layer 5 arranged on one side of the porous film 1. The porous film 1 and the adhesive layer 5 are directly bonded to each other. The ventilation member 4A can be placed on the surface of an object via the adhesive layer 5.

[0104] Examples of adhesives constituting the adhesive layer 5 include acrylic adhesives, silicone adhesives, urethane adhesives, epoxy adhesives, and rubber adhesives. When consideration must be given to using the ventilation member 4 at high temperatures, it is preferable to select an acrylic adhesive or a silicone adhesive, particularly a silicone adhesive, which have excellent heat resistance. The adhesive layer 5 may be a substrate-less double-sided adhesive tape. The adhesive may be a curable adhesive such as a phenolic resin, an epoxy resin, a urea resin, a polyurethane resin, a melamine resin, or a polyester resin.

[0105] The outer periphery of the porous film 1 and the outer periphery of the adhesive layer 5 coincide when viewed perpendicularly to the main surface of the porous film 1. The shape of the adhesive layer 5 corresponds to the peripheral edge of the porous film 1 when viewed perpendicularly to the main surface of the porous film 1. The region of the porous film 1 to which the adhesive layer 5 is not bonded can be used as the ventilation region of the ventilation member 4A. However, the shape of the adhesive layer 5 is not limited to the above example.

[0106] The area of ​​the ventilation area is, for example, 40 mm 2 The ventilation member 4 having a ventilation region area within this range is suitable for placement in an object having a small diameter opening, for example. The lower limit of the ventilation region area is, for example, 0.008 mm 2 However, the area of ​​the ventilation region may be larger depending on the type of object in which the ventilation member 4 is placed.

[0107] Fig. 7 shows a first modification of the ventilation member of Fig. 6. The ventilation member 4 (4B) of Fig. 7 has the same configuration as the ventilation member 4A of Fig. 6, except that it further includes an adhesive layer 5 (5B) arranged on the other surface of the porous film 1. The porous film 1 is sandwiched between a pair of adhesive layers 5 (5A, 5B).

[0108] As shown in Figure 7, the adhesive layer 5 may include a first adhesive layer 5A bonded to one surface (first main surface 1a) of the porous film 1 and a second adhesive layer 5B bonded to the other surface (second main surface 1b) of the porous film 1.

[0109] Fig. 8 shows a second variation of the ventilation member of Fig. 6. The ventilation member 4 (4C) of Fig. 8 further includes a base material layer 6 disposed on one side of the porous film 1, and has the same configuration as the ventilation member 4A of Fig. 6, except that the porous film 1 and the adhesive layer 5 are joined via the base material layer 6. The base material layer 6 can improve the strength and handleability of the ventilation member 4, and can prevent damage to the porous film 1 during handling or placement on an object.

[0110] Examples of materials constituting the base material layer 6 include polyolefins such as PE and PP, polyesters such as PET, silicone resins, polycarbonate, polyimide, polyamideimide, polyphenylene sulfide, polyether ether ketone (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 material layer 6 are not limited to the above examples.

[0111] The outer periphery of the porous film 1 and the outer periphery of the base material layer 6 coincide when viewed perpendicularly to the main surface of the porous film 1. The shape of the base material layer 6 corresponds to the peripheral edge of the porous film 1 when viewed perpendicularly to the main surface of the porous film 1. The region of the porous film 1 to which the base material layer 6 is not bonded can be used as the ventilation region of the ventilation member 4C. However, the shape of the base material layer 6 is not limited to the above example.

[0112] The porous film 1 and the base layer 6 may be joined by a pressure-sensitive adhesive or adhesive, or by welding such as thermal welding or ultrasonic welding. The porous film 1 and the base layer 6 may be joined by an adhesive layer. The adhesive layer may have the same structure as the adhesive layer 5. The base layer 6 may be a single-sided adhesive tape or a double-sided adhesive tape.

[0113] A third variation of the ventilation member of Fig. 6 is shown in Fig. 9. The ventilation member 4 (4D) of Fig. 9 has the same configuration as the ventilation member 4C of Fig. 8, except that it further includes a base material layer 6 (6B) arranged on the other side of the porous film 1. The porous film 1 is sandwiched between the pair of base material layers 6 (6A, 6B). This sandwiching structure can further improve the strength and handleability of the ventilation member 4.

[0114] As shown in Figure 9, the substrate layer 6 may include a first substrate layer 6A bonded to one surface (first main surface 1a) of the porous film 1 and a second substrate layer 6B bonded to the other surface (second main surface 1b) of the porous film 1.

[0115] Fig. 10 shows a fourth variation of the ventilation member of Fig. 6. The ventilation member 4 (4E) of Fig. 10 has the same configuration as the ventilation member 4B of Fig. 7, except that it further includes a release liner 7 and the porous film 1 and the release liner 7 are joined via an adhesive layer 5 (5B).

[0116] As shown in Figure 10, the ventilation member 4 (4E) may further include a release liner 7, with a second adhesive layer 5B disposed between the release liner 7 and the porous film 1, and the second adhesive layer 5B bonded to the release liner 7.

[0117] The release liner 7 has a tab that protrudes outward from the outer periphery of the porous film 1 when viewed perpendicularly to the main surface of the porous film 1. The ventilation member 4E can be handled or placed on the surface of an object by grasping the tab. The release liner 7 is usually removed when the ventilation member 4E is used. The release liner 7 can be made of, for example, the same material as the material that constitutes the base layer 6. The release liner 7 is usually removed by grasping the tab and lifting it up. At this time, a strong force is applied to the porous film 1 in the lifting direction. However, the ventilation member 4E prevents cohesive failure of the porous film 1 when the release liner 7 is peeled off.

[0118] Fig. 11 shows a fifth variation of the ventilation member of Fig. 6. The ventilation member 4 (4F) of Fig. 11 further includes a release liner 7, and has the same configuration as the ventilation member 4D of Fig. 9, except that the base material layer 6 (6B) and the release liner 7 are bonded via an adhesive layer 5 (5B). The ventilation member 4F prevents cohesive failure of the porous film 1 when the release liner 7 is peeled off.

[0119] Another example of a ventilation member of the present invention is shown in FIG. 12. The ventilation member 4 (4G) in FIG. 12 is placed on the surface 8s of an object 8, the surface 8s having an opening 8p. The ventilation member 4G includes a porous film 1 shaped to cover the opening 8p and an adhesive layer 5 bonded to the first main surface 1a of the porous film 1. The ventilation member 4G is fixed to the surface 8s of the object 8 using the adhesive layer 5. As described above, the porous film 1 contains a thermoplastic resin that does not contain fluororesin as a main component. The air permeability of the porous film 1, expressed in Gurley number, is 200 seconds / 100 mL or less. However, the object 8 to which the ventilation member 4 (4G) is bonded may be, for example, a plate-shaped member or a housing.

[0120] The air permeability of the porous film 1 in the ventilation member 4 (4G) may be measured by separating the porous film 1 from the object 8 to be joined, or may be measured while the porous film 1 is integrated with the object 8. The latter measurement can be performed in accordance with the above-mentioned measurement method using a SUS disk. However, when the inner diameter area of ​​the adhesive layer 5 is S [cm 2 ], the area of ​​the effective test portion of the porous film 1 in the above formula t [cm 2 ]" and S [cm 2 ] is used.

[0121] In the ventilation member 4G, when a handling evaluation test was carried out, the porous film 1 did not undergo cohesive failure up to at least 0.03 N / 2.0 mm.

[0122] <Handling Evaluation Test> Figure 13 is a schematic cross-sectional view illustrating a handling evaluation test for the ventilation member 4G. First, a double-sided adhesive tape 55 (manufactured by Nitto Denko Corporation, No. 5605) is bonded to the second main surface 1b of the porous film 1, and a release liner 71 (thickness: 38 µm) is bonded to the double-sided adhesive tape 55. The release liner 71 may be any tape that does not cause cohesive failure of the porous film 1 up to a peel strength of at least 0.03 N / 2.0 mm. For example, a polyester-based adhesive tape (No. 31B) manufactured by Nitto Denko Corporation that exhibits a peel strength of 0.6 N / 50 mm can be used as the release liner 71. Next, a roller is reciprocated once on the release liner 71 while applying a load of 2 kg. Next, the ventilation member 4G is subjected to an aging treatment at 60°C for 5 minutes. After the aging treatment, the ventilation member 4G is left in an environment at room temperature for 15 minutes, and then the release liner 71 is picked up with tweezers and lifted up to be peeled off.

[0123] When the above-described handling evaluation test was carried out on the ventilation member 4G, cohesive failure did not occur in the porous film 1 up to at least 0.03 N / 2.0 mm. Due to this configuration, the porous film 1 included in the ventilation member 4G is prevented from undergoing cohesive failure when attached to the housing of a device or the like, and has appropriate handleability.

[0124] Figure 14 shows a modified example of the ventilation member 4G of Figure 12. The ventilation member 4 (4H) of Figure 14 has the same configuration as the ventilation member 4G of Figure 12, except that it further includes an adhesive layer 5 (5B) arranged on the other surface of the porous film 1. The porous film 1 is sandwiched between a pair of adhesive layers 5 (5A, 5B).

[0125] In the handling evaluation test of the ventilation member 4H, the double-sided adhesive tape 55 is bonded to the adhesive layer 5B on the second main surface 1b side of the porous film 1, and the release liner 71 is bonded to the double-sided adhesive tape 55.

[0126] [Component supply sheet] The ventilation member 4 can be supplied by, for example, a component supply sheet. An example of a component supply sheet, which is a supply mode of the ventilation member 4, is shown in FIG. 15. The component supply sheet 20 (20A) of FIG. 15 comprises a ventilation member 4 (4A) to be placed on the surface of an object having an opening, and a base sheet 9 on whose surface the ventilation member 4 (4A) is placed. The component supply sheet 20A comprises a ventilation member 4A as the ventilation member 4. The ventilation member 4A comprises a porous film 1 having a shape that covers the opening when placed on the surface of the object, and an adhesive layer 5 bonded to the porous film 1.

[0127] The ventilation member 4 (4A) is disposed on the base sheet 9 via the pressure-sensitive adhesive layer 5. The member supply sheet 20 (20A) makes it possible to efficiently supply the ventilation member 4, for example, in the step of placing the ventilation member 4 on the surface of an object.

[0128] The ventilation member 4 may be placed on the base sheet 9 via an adhesive layer provided on the placement surface of the base sheet 9 on which the ventilation member 4 is placed. The adhesive layer on the placement surface preferably has weak adhesiveness.

[0129] Although not shown in the drawings, a plurality of ventilation members 4 may be arranged on the surface of the base sheet 9 .

[0130] Examples of materials constituting the base sheet 9 include paper, metal, resin, and composite materials thereof. Examples of metal include stainless steel and aluminum. Examples of resin 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 sheet or a strip. When the base sheet 9 is in the form of a strip, the member supply sheet 20 may be rolled up to form a roll.

[0131] Examples of objects in which the ventilation member 4 is disposed include the housing of an electronic device and the housing of a vehicle electrical component. The ventilation member 4 can be disposed on the outer surface and / or inner surface of the housing. In this case, the opening may be an air vent and / or a sound vent provided in the housing. Examples of electronic devices include wearable devices such as smart watches 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.

[0132] The foreign matter that is prevented from passing through by the arrangement of the ventilation member 4 is, for example, particles such as dust, and liquid water such as water droplets.

[0133] FIG. 16 shows a first modified example of the component supply sheet of FIG. 15 . The component supply sheet 20 (20B) of FIG. 16 has the same configuration as the component supply sheet 20A of FIG. 15 , except that the component supply sheet 20 (20B) of FIG. 16 includes the ventilation member 4E of FIG. 10 as the ventilation member 4. That is, in the component supply sheet 20B, the ventilation member 4E includes a porous film 1, a first adhesive layer 5A bonded to the first main surface 1a of the porous film 1, a second adhesive layer 5B bonded to the second main surface 1b of the porous film 1, and a release liner 7 bonded to the second adhesive layer 5B. The second adhesive layer 5B is disposed between the release liner 7 and the porous film 1, and the porous film 1 is fixed to the surface of the base sheet 9 using the first adhesive layer 5A. As described above, the porous film 1 contains, as a main component, a thermoplastic resin that does not contain a fluororesin. The air permeability of the porous film 1, expressed as a Gurley number, is 200 seconds / 100 mL or less.

[0134] Furthermore, even if the size of the porous film 1 provided in the component supply sheet 20B does not meet the recommended dimensions (50 mm x 50 mm) of the test piece for the Oken Testing Machine Method, it is possible to evaluate the air resistance (Gurley air permeability) in accordance with the Oken Testing Machine Method by using a measuring jig.

[0135] The measurement jig has a shape and size that can be placed in the air permeability measurement section of the Oken tester, and is made of a thickness and material that will not deform due to the differential pressure applied to the test piece during air permeability resistance measurement. An example of the measurement jig is a 2 mm thick, 47 mm diameter SUS disk. A through-hole with an opening smaller than the membrane to be evaluated is provided in the center of the surface of the measurement jig. The cross-section of the through-hole is typically circular, and the diameter is such that the opening is completely covered by the membrane to be evaluated. The diameter of the through-hole can be, for example, 1 mm or 2 mm. Next, the first adhesive layer 5A is peeled off from the base sheet 9, and the porous film 1 to be evaluated is fixed to one side of the measurement jig so as to cover the opening of the measurement jig. The fixation is performed so that during the air permeability resistance measurement, air passes only through the opening and the effective test portion of the porous film 1 to be evaluated (the portion overlapping with the opening when viewed perpendicular to the main surface of the fixed porous film 1), and the fixed portion does not obstruct the passage of air through the effective test portion of the porous film 1. The first adhesive layer 5A can be used to fix the porous film 1. The first adhesive layer 5A may be placed between the measuring jig and the porous film 1 so that the periphery of the ventilation hole coincides with the periphery of the opening. Next, the release liner 7 is peeled off from the porous film 1 to expose the porous film 1. Next, the measuring jig with the porous film 1 fixed thereto is set in the air permeability measuring section of the Oken Tester so that the fixed surface (first main surface 1a) of the porous film 1 is downstream of the air flow during measurement, and a test is performed using the Oken Tester method, and the air permeability indication value t indicated by the tester is recorded. Next, the recorded air permeability indication value t is calculated based on the effective test area of ​​6.452 [cm2] as specified in the Oken Tester method. 2 ] per value t K In equation t K = {t × (area of ​​the effective test portion of the porous film 1 [cm 2 ]) / 6.452 [cm 2 ]}, and the resulting converted value t Kcan be regarded as the air resistance (Gurley air permeability) of the porous film 1 measured in accordance with the Oken type testing machine method. It has been confirmed that the air resistance measured without using a measuring jig for a porous film 1 that meets the recommended dimensions (50 mm x 50 mm) of the test piece for the Oken type testing machine method is in good agreement with the air resistance measured using a measuring jig after cutting the porous film 1 into small pieces, that is, the use of a measuring jig does not substantially affect the measured value of the air resistance.

[0136] When the component supply sheet 20B was subjected to the following handling evaluation test, cohesive failure did not occur in the porous film 1. Therefore, the porous film 1 included in the component supply sheet 20B is prevented from undergoing cohesive failure when attached to the housing of a device or the like, and has appropriate handling properties.

[0137] <Handling Evaluation Test> Figure 17 is a schematic cross-sectional view illustrating a handling evaluation test of the member supply sheet 20B. First, the first adhesive layer 5A is peeled from the base sheet 9, and the first adhesive layer 5A is brought into contact with a stainless steel test plate 81, thereby placing the ventilation member 4E on the test plate 81. Next, the ventilation member 4E is fixed to the test plate 81 by moving a roller back and forth once on the release liner 7 while applying a load of 2 kg. Next, the ventilation member 4E is subjected to an aging treatment for 5 minutes in an environment at 60°C. After the aging treatment, the ventilation member 4E is left in an environment at room temperature for 15 minutes, and then the release liner 7 is picked up with tweezers and lifted up to be peeled off.

[0138] A second modification of the member supply sheet of Fig. 15 is shown in Fig. 18. The member supply sheet 20 (20C) of Fig. 18 has the same configuration as the member supply sheet 20A of Fig. 15, except that it is provided with the ventilation member 4F of Fig. 11 as the ventilation member 4.

[0139] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0140] The porous film having the configuration shown in FIG. 1 was evaluated for its breathability, cohesive strength, and the like.

[0141] [Example 1] Poly(4-methylpentene-1) resin (RT18, manufactured by Mitsui Chemicals, Inc.) was used as the thermoplastic resin. 2 Liquid paraffin (manufactured by MORESCO) with a viscosity of 1 / s was prepared. Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (manufactured by BASF Japan) was used as the antioxidant. A mixture was obtained by mixing 50.0 wt% thermoplastic resin, 49.8 wt% plasticizer, and 0.2 wt% antioxidant. The mixture was kneaded at 260°C for 30 minutes using a Labo Plastomill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to obtain a uniform kneaded product. 1.6 g of the kneaded product pellet was sandwiched between two polyimide plates (thickness 150 μm), then sandwiched between two stainless steel plates (thickness 3.0 mm). The pellet was then hot-pressed at 1.0 kN for 5 minutes using a compression molding machine heated to 260°C to obtain a first pressed body. The first pressed body was cooled by contacting it with water at 18°C ​​while sandwiched between polyimide plates, yielding a molded body. Next, using a biaxial stretching machine, simultaneous biaxial stretching was performed on the molded body at a stretching temperature of 150°C and a stretch ratio of 2x (longitudinal direction) x 2x (transverse direction). The strain rate during stretching was 1% / sec (0.655 mm / sec) in both the longitudinal and transverse directions. This resulted in a sheet body. Stretching was performed 5 minutes after placing the molded body in a furnace set at the stretching temperature. Next, as with the first heat pressing, the sheet body was sandwiched between polyimide and stainless steel plates, and then a compression molding machine heated to 180°C was used to perform a second heat pressing on the sheet body at 2 kPa for 5 minutes to obtain a second pressed body. Finally, an extraction operation was performed by immersing the second pressed body in room temperature MEK for 2 minutes using methyl ethyl ketone (MEK) as the extraction solvent. This resulted in the extraction and removal of the plasticizer from the second pressed body. The extraction operation was carried out in a state where the second press body was fixed to a stainless steel frame in order to prevent shrinkage of the second press body. In this way, the porous film of Example 1 was obtained.

[0142] [Example 2] The molded body was subjected to simultaneous biaxial stretching under the conditions of a stretching temperature of 100°C and a stretching ratio of 2 times (longitudinal direction) × 2 times (transverse direction) to obtain a sheet body. Except for this, a porous film of Example 2 was obtained by the same method as in Example 1.

[0143] [Example 3] A second heat press was performed on the sheet body at 2 kPa for 5 minutes using a compression molding machine heated to 80°C, to obtain a second pressed body. Except for this, a porous film of Example 3 was obtained in the same manner as in Example 2.

[0144] [Example 4] A second heat press was performed on the sheet body using a compression molding machine heated to 80°C under conditions of 10 kPa and 5 minutes to obtain a second pressed body. Except for this, a porous film of Example 4 was obtained in the same manner as in Example 2.

[0145] [Example 5] A second heat press was performed on the sheet body using a compression molding machine heated to 180°C under conditions of 10 kPa and 5 minutes to obtain a second pressed body. Except for this, a porous film of Example 5 was obtained in the same manner as in Example 2.

[0146] Figure 19A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the porous film of Example 5. Figure 19B is a partially enlarged diagram (10000x magnification) of Figure 19A. Figure 19C is a diagram (1500x magnification) showing the results of SEM observation of the cross section of the porous film of Example 5.

[0147] [Example 6] The molded body was subjected to simultaneous biaxial stretching under the conditions of a stretching temperature of 100°C and a stretching ratio of 2.5 times (longitudinal direction) x 2.5 times (transverse direction) to obtain a sheet body. Except for this, a porous film of Example 6 was obtained by the same method as in Example 5.

[0148] [Example 7] The molded body was subjected to simultaneous biaxial stretching under the conditions of a stretching temperature of 100 ° C. and a stretching ratio of 2 times (longitudinal direction) × 2 times (transverse direction) to obtain a sheet body. The strain rate in the stretching was 5% / sec (3.25 mm / sec) in both the longitudinal direction and the transverse direction. Except for these, the porous film of Example 7 was obtained by the same method as in Example 5.

[0149] Comparative Example 1 A porous film of Comparative Example 1 was obtained in the same manner as in Example 1, except that the sheet was not subjected to the second heat press and the plasticizer was extracted and removed from the sheet.

[0150] [Comparative Example 2] A porous film of Comparative Example 2 was obtained in the same manner as in Example 2, except that the sheet was not subjected to the second heat press and the plasticizer was extracted and removed from the sheet.

[0151] Fig. 20A is a diagram (2500x magnification) showing the results of SEM observation of the porous film surface of Comparative Example 2. Fig. 20B is a partially enlarged view (10000x magnification) of Fig. 20A. Fig. 20C is a diagram (1500x magnification) showing the results of SEM observation of the cross section of the porous film of Comparative Example 2.

[0152] [Comparative Example 3] A porous film of Comparative Example 3 was obtained in the same manner as in Example 6, except that the sheet was not subjected to the second heat pressing and the plasticizer was extracted and removed from the sheet.

[0153] Comparative Example 4 A porous film of Comparative Example 4 was obtained in the same manner as in Example 7, except that the sheet was not subjected to the second heat press and the plasticizer was extracted and removed from the sheet.

[0154] Comparative Example 5 The porous film of Comparative Example 5 was obtained in the same manner as in Comparative Example 4, except that the strain rate in the stretching was 20% / sec (13.1 mm / sec) in both the longitudinal and transverse directions.

[0155] Comparative Example 6: Poly(4-methylpentene-1) resin (MX002, manufactured by Mitsui Chemicals, Inc.) was used as the thermoplastic resin. 2Liquid paraffin (manufactured by MORESCO) with a viscosity of 1 / s was used. Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (manufactured by BASF Japan) was used as the antioxidant. A mixture was obtained by mixing 35.0 wt% thermoplastic resin, 64.5 wt% plasticizer, and 0.5 wt% antioxidant. The mixture was kneaded using a Labo Plastomill at 260°C for 30 minutes to obtain a uniform kneaded product. 1.6 g of a pellet of the kneaded product was sandwiched between two polyimide plates (thickness 150 μm), then sandwiched between a stainless steel plate (thickness 3.0 mm). The pellet was then hot-pressed at 1.0 kN for 5 minutes using a compression molding machine heated to 260°C to obtain a first pressed body. The first pressed body, while sandwiched between the polyimide plates, was cooled by contacting it with water at 18°C ​​to obtain a molded body. Prior to biaxial stretching, the molded body was annealed at 150°C for 30 minutes. The annealed molded body was then immersed in MEK at room temperature for 5 minutes to extract and remove the plasticizer from the molded body. Using a biaxial stretching machine, the molded body after extraction and removal of the plasticizer was subjected to simultaneous biaxial stretching at a stretching temperature of 150°C and a stretching ratio of 3 times (longitudinal direction) x 3 times (transverse direction). The strain rate during stretching was 1% / sec (0.655 mm / sec) in both the longitudinal and transverse directions. A sheet was thus obtained. A second heat press was not performed on the sheet. In this manner, the porous film of Comparative Example 6 was obtained.

[0156] [Comparative Example 7] The porous film of Comparative Example 6 was subjected to an annealing treatment at 165°C for 5 minutes. Except for this, the porous film of Comparative Example 7 was obtained in the same manner as in Comparative Example 6.

[0157] Comparative Example 8 Poly(4-methylpentene-1) resin (DX845, manufactured by Mitsui Chemicals, Inc.) was used as the thermoplastic resin. 2Liquid paraffin (manufactured by MORESCO) with a viscosity of 1 / s was used. Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (manufactured by BASF Japan) was used as the antioxidant. A mixture was obtained by mixing 55 wt% thermoplastic resin, 44.5 wt% plasticizer, and 0.5 wt% antioxidant. The mixture was kneaded using a Labo Plastomill at 260°C for 30 minutes to obtain a uniform kneaded product. A 1.6 g pellet of the kneaded product was sandwiched between two polyimide plates (thickness 150 μm), then sandwiched between a stainless steel plate (thickness 3.0 mm). The pellet was then hot-pressed at 1.0 kN for 5 minutes using a compression molding machine heated to 260°C to obtain a first pressed body. The first pressed body, while sandwiched between the polyimide plates, was cooled by contacting it with water at 18°C ​​to obtain a molded body. Next, the molded body was immersed in MEK at room temperature for 5 minutes to perform an extraction operation, and the plasticizer was extracted and removed from the molded body. Next, using a biaxial stretching machine, the molded body after the plasticizer was extracted and removed was subjected to simultaneous biaxial stretching under the conditions of a stretching temperature of 180 ° C and a stretching ratio of 3 times (longitudinal direction) × 3 times (transverse direction). The strain rate in the stretching was 1% / sec (0.655 mm / sec) in both the longitudinal and transverse directions. This resulted in a sheet body. The sheet body was not subjected to a second heat press, but was annealed at 170 ° C for 5 minutes. In this way, the porous film of Comparative Example 8 was obtained.

[0158] The manufacturing conditions for the porous films of Examples 1 to 7 and Comparative Examples 1 to 8 are shown in Table 1.

[0159]

[0160] The thickness, air permeability, water pressure resistance, cohesive strength, and handleability of the porous films of Examples 1 to 7 and Comparative Examples 1 to 8 were evaluated using the methods described above for porous films. The evaluation results are shown in Table 2. The handleability was evaluated as follows: A: When the release liner was picked up with tweezers, lifted up, and peeled off, no cohesive failure occurred in the porous film. B: When the release liner was picked up with tweezers, lifted up, and peeled off, cohesive failure occurred in the porous film.

[0161]

[0162] As can be seen from Table 2, the porous films of Examples 1 to 7 had an air permeability expressed in Gurley number of 200 seconds / 100 mL or less, a cohesive strength of 1.0 N / 20 mm or more, and also showed excellent handleability (A). Thus, the porous films of Examples 1 to 7 had both handleability and breathability.

[0163] As can be seen from a comparison of Figures 19A-19B with Figures 20A-20B, the surfaces of the porous film of the Example (Example 5) and the porous film of the Comparative Example (Comparative Example 2) both had a tortoiseshell structure formed by multiple nodes and multiple fibrils. However, as can be seen from a comparison of Figures 19C and 20C, in the thickness direction, the porous film of the Example (Example 5) had small variations in the size of the gaps between the island regions formed by multiple nodes, and the gaps were dispersed, whereas the porous film of the Comparative Example (Comparative Example 2) had variations in the size of the gaps, with a mixture of large and small gaps. From these results, it can be inferred that the porous film of the Example (Example 5) had small variations in the size of the gaps present in the thickness direction, and the gaps were dispersed, thereby improving the cohesion of the porous film.

[0164] From the above results, it can be seen that the porous films of Examples 1 to 7 are suitable for achieving both ease of handling and breathability.

[0165] Next, the ventilation member having the configuration shown in FIG. 12 was evaluated for its air permeability and handling properties.

[0166] [Example 8] The porous film of Example 1 was cut into a circle with a diameter of 5.8 mm and used as a ventilation member. A stainless steel (SUS) disk with a thickness of 2 mm and a diameter of 47 mm and a central opening with a circular cross-section of 1 mm diameter was used as the target object. A double-sided adhesive tape (Nitto Denko Corporation, No. 5605) with a vent hole (1.6 mm diameter) punched in the center with a shape matching the opening was used as the adhesive layer. A ventilation member was placed on the side of the disk with the opening. In this way, the ventilation member of Example 8 was obtained.

[0167] The breathability and handleability of the ventilation member of Example 8 were evaluated using the methods described above for ventilation member 4G. The evaluation results are shown in Table 3. The handleability was evaluated as follows: C: When the release liner was picked up with tweezers, lifted up, and peeled off, no cohesive failure occurred in the porous film up to a force of at least 0.03 N / 2.0 mm. D: When the release liner was picked up with tweezers, lifted, and peeled off, cohesive failure occurred in the porous film up to a force of 0.03 N / 2.0 mm.

[0168]

[0169] As can be seen from Table 3, in the ventilation member of Example 8, the air permeability of the porous film, expressed as a Gurley number, was 200 seconds / 100 mL or less. The porous film also had a peel strength of 0.03 N / 2.0 mm or more. Thus, in the ventilation member of Example 8, the porous film had both good handleability and good breathability.

[0170] In addition, since Example 8 is a ventilation member using the porous membrane of Example 1, it can be said that, based on the cohesive force of Example 1 in Table 2 and the results of the handling evaluation test of Example 8 in Table 3, the cohesive force of the porous membrane being 1.2 N / 20 mm is synonymous with the peel force of the porous membrane in the ventilation member using the porous membrane being 0.03 N / 2.0 mm.

[0171] Next, the breathability and handling properties of the member supplying sheet having the configuration shown in FIG. 16 were evaluated.

[0172] [Example 9] The porous film of Example 1 was cut into a circle with a diameter of 5.8 mm and used as a ventilation member. A base sheet (Nippa Corporation, release grade J0L) was used. A double-sided adhesive tape (Nitto Denko Corporation, No. 5605) with a vent hole (1.6 mm diameter) punched in the center and having a shape matching the opening shape was used as the first adhesive layer and second adhesive layer. A polyester base adhesive tape (Nitto Denko Corporation, No. 31B) with a release force of 0.6 N / 50 mm was used as the release liner. A second adhesive layer was disposed between the release liner and the porous film. The porous film was fixed to the surface of the base sheet using the first adhesive layer. In this way, the member supply sheet of Example 9 was obtained.

[0173] The breathability and handleability of the component supply sheet of Example 9 were evaluated using the method described above for component supply sheet 20B. The evaluation results are shown in Table 4. The handleability was evaluated as follows: E: When the release liner was picked up with tweezers, lifted up, and peeled off, no cohesive failure occurred in the porous film. F: When the release liner was picked up with tweezers, lifted, and peeled off, cohesive failure occurred in the porous film.

[0174]

[0175] As can be seen from Table 4, in the member supply sheet of Example 9, the air permeability of the porous film, expressed as a Gurley number, was 200 seconds / 100 mL or less. In addition, the porous film exhibited excellent handling properties (E). Thus, in the member supply sheet of Example 9, the porous film had both good handling properties and good air permeability.

[0176] The technology of the present invention can be applied to, for example, waterproof gas-permeable membranes, waterproof sound-permeable membranes, separators for electricity storage devices, and the like.

Claims

1. A porous film containing a fluorine-free thermoplastic resin as its main component, having an air permeability expressed in Gurley number of 200 seconds / 100 mL or less, and a cohesive strength of 1.0 N / 20 mm or more.

2. The porous film according to claim 1, wherein the thermoplastic resin is a polyolefin resin.

3. The porous film according to claim 1, having a thickness of 40 μm or more and 100 μm or less.

4. The porous film according to claim 1, having a water pressure resistance of 200 kPa or more.

5. The porous film according to claim 1, which is a stretched film.

6. A ventilation member comprising the porous film according to any one of claims 1 to 5 and an adhesive layer bonded to said porous film.

7. The ventilation member according to claim 6, wherein the adhesive layer includes a first adhesive layer bonded to a first main surface of the porous film, and a second adhesive layer bonded to a second main surface of the porous film.

8. The ventilation member according to claim 7, further comprising a release liner, the second adhesive layer being disposed between the release liner and the porous film, and the second adhesive layer being bonded to the release liner.

9. A ventilation member placed on a surface of an object having an opening, the ventilation member comprising: a porous film shaped to cover the opening; and a first adhesive layer bonded to a first main surface of the porous film, the ventilation member being fixed to the surface of the object using the first adhesive layer; the porous film containing a thermoplastic resin that does not contain fluororesin as a main component; the porous film having an air permeability, expressed in Gurley numbers, of 200 seconds / 100 mL or less; and the porous film not undergoing cohesive failure up to at least 0.03 N / 2.0 mm when subjected to the following handling evaluation test. <Handling Evaluation Test> Double-sided adhesive tape is bonded to the second main surface of the porous film, and a release liner is bonded to the double-sided adhesive tape. Next, a roller is moved back and forth on the release liner while applying a load of 2 kg. Next, the ventilation member is subjected to an aging treatment at 60°C for 5 minutes. After the aging treatment, the ventilation member is left in an environment at room temperature for 15 minutes, and then the release liner is picked up with tweezers and lifted up to be peeled off.

10. The ventilation member according to claim 9, further comprising a second adhesive layer bonded to the second main surface of the porous film.

11. A component supply sheet comprising a ventilation member to be placed on a surface of an object having an opening, and a base sheet with the ventilation member placed on its surface, wherein the ventilation member comprises: a porous film having a shape that covers the opening when placed on the surface; and an adhesive layer bonded to the porous film, and the porous film is the porous film described in any one of claims 1 to 5.

12. The member supply sheet according to claim 11, wherein a plurality of the ventilation members are arranged on the surface of the base sheet.

13. A component supply sheet comprising a ventilation member to be placed on a surface of an object having an opening, and a base sheet with the ventilation member placed on its surface, wherein the ventilation member comprises: a porous film shaped to cover the opening when placed on the surface; a first adhesive layer bonded to a first main surface of the porous film; a second adhesive layer bonded to a second main surface of the porous film; and a release liner bonded to the second adhesive layer, wherein the second adhesive layer is placed between the release liner and the porous film; the ventilation member is fixed to the surface of the base sheet using the first adhesive layer; the porous film contains a thermoplastic resin that does not contain fluororesin as a main component; the porous film has an air permeability, expressed in Gurley number, of 200 seconds / 100 mL or less; and the porous film does not undergo cohesive failure when subjected to the following handleability evaluation test. <Handling Efficiency Evaluation Test> The first adhesive layer was peeled from the base sheet, and the ventilation member was placed on a stainless steel test plate with the first adhesive layer in contact with the test plate. Next, the ventilation member was fixed to the test plate by rolling a roller back and forth once on the release liner while applying a load of 2 kg. Next, the ventilation member was subjected to an aging treatment for 5 minutes in an environment at 60°C. After the aging treatment, the ventilation member was left in an environment at room temperature for 15 minutes, and then the release liner was picked up with tweezers and lifted up to be peeled off.

14. The member supply sheet according to claim 13, wherein a plurality of the ventilation members are arranged on the surface of the base sheet.

15. A method for producing a porous film, comprising: a step of kneading a composition containing a fluorine-free thermoplastic resin and a plasticizer to obtain a kneaded mixture; a step of performing a pressing or extrusion treatment; a step of performing a cooling treatment; a step of performing a stretching treatment; and a step of performing a plasticizer extraction treatment, wherein the method further comprises a step of performing a pressing treatment after the step of performing the stretching treatment.

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