Porous film, air-permeable member, and sheet for member supply

Abstract

The porous film contains a fluorine-free thermoplastic resin as a main component and has a main surface that has been subjected to liquid repellent treatment by a liquid-repelling agent. The liquid-repelling agent includes at least one selected from the group consisting of silicone resins having an alkoxy group directly bonded to a silicon atom and polymethylpentene resins. The porous film, for example, has ratio (A2 / A1×100) of the air permeability A2 expressed by the Gurley number after a heat resistance test A to the air permeability A1 expressed by the Gurley number in the 50-150% range and a ratio (B2 / B1×100) of the insertion loss B2 after a heat resistance test A to the insertion loss B1 of a 1 kHz sound in the 70-130% range. The heat resistance test A involves heating for 3 minutes at 160°C.

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 films have also been proposed for use in these applications.

[0003] For example, Patent Document 1 discloses a porous polyethylene film used in an acoustic device, and describes that the porous polyethylene film is oil-repellent treated with a fluorine-based oil-repellent agent (Examples 3 and 7).

[0004] International Publication No. 2023 / 034730

[0005] Attaching a porous film to a device such as a smartphone may involve a heat treatment. Furthermore, the porous film may reach a high temperature (e.g., 60°C or higher) due to heat generated by the attached device itself or due to a temperature rise in the location where the attached device is placed. It is desirable to minimize changes in the properties of the porous film, such as breathability, sound permeability, and liquid repellency, caused by a temperature rise.

[0006] Therefore, an object of the present invention is to provide a fluorine-free porous film, a ventilation member, and a member-supplying sheet that are suitable for suppressing changes in properties due to temperature rise.

[0007] The present invention provides a porous film containing a fluorine-free thermoplastic resin as a main component, having a main surface that has been treated with a liquid-repellent agent to provide liquid repellency, wherein the liquid-repellent agent includes at least one selected from the group consisting of a silicone resin having an alkoxy group directly bonded to a silicon atom and a polymethylpentene resin.

[0008] From another aspect, the present invention provides a porous film containing a fluorine-free thermoplastic resin as a main component, having a main surface that has been treated with a liquid repellent agent to provide a liquid repellent effect, wherein a ratio (A2 / A1×100) of an air permeability A2 expressed in Gurley number after heat resistance test A to an air permeability A1 expressed in Gurley number is in the range of 50 to 150%, and a ratio (B2 / B1×100) of an insertion loss B2 of a sound at a frequency of 1 kHz after heat resistance test A to an insertion loss B1 of the sound at the frequency of 1 kHz is in the range of 70 to 130%, and the heat resistance test A is a test in which the film is heated at 160°C for 3 minutes.

[0009] 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.

[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 a tacky-adhesive layer bonded to the porous film, and the porous film is the porous film of the present invention described above.

[0011] According to the present invention, it is possible to provide a fluorine-free porous film, a ventilation member, and a member-supplying sheet that are suitable for suppressing changes in properties due to temperature rise.

[0012] FIG. 1 is a cross-sectional view schematically showing an example of a porous film of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a film member of the present invention. FIG. 3 is a cross-sectional view schematically showing a first modified example of the film member of FIG. 2. FIG. 4 is a cross-sectional view schematically showing a second modified example (rolled body) of the film member of FIG. 2. FIG. 5 is a cross-sectional view schematically showing an example of a ventilation member of the present invention. FIG. 6 is a cross-sectional view schematically showing a first modified example of the ventilation member of FIG. 5. FIG. 7 is a cross-sectional view schematically showing a second modified example of the ventilation member of FIG. 5. FIG. 8 is a cross-sectional view schematically showing a third modified example of the ventilation member of FIG. 5. FIG. 9 is a cross-sectional view schematically showing a fourth modified example of the ventilation member of FIG. 5. FIG. 10 is a cross-sectional view schematically showing a fifth modified example of the ventilation member of FIG. 5. FIG. 11 is a cross-sectional view schematically showing an example of a member supply sheet of the present invention. FIG. 12 is a cross-sectional view schematically showing a first modified example of the member supply sheet of FIG. 11. Fig. 13 is a cross-sectional view schematically showing a second modification of the member supply sheet of Fig. 11. Fig. 14 is a view illustrating the state of a liquid-repellent layer after heating a porous film that has been subjected to a liquid-repellent treatment with a liquid-repellent agent. Fig. 15 is a cross-sectional view schematically showing a sample body for evaluating the air resistance (Gurley air permeability) of a porous film. Fig. 16A is a cross-sectional view schematically showing a sample body for evaluating the insertion loss of a porous film. Fig. 16B is a cross-sectional view showing the sample body of Fig. 16A attached to a mock housing that simulates the housing of a mobile phone. Fig. 17 is a schematic view illustrating a method for evaluating the insertion loss of a porous film. Fig. 18 is a view illustrating an example of a method for applying a liquid-repellent treatment to a main surface of a porous film.

[0013] A porous film according to a first aspect of the present invention is a porous film containing a fluorine-free thermoplastic resin as a main component, and has a main surface that has been treated with a liquid-repellent agent to provide liquid repellency, and the liquid-repellent agent includes at least one selected from the group consisting of a silicone resin having an alkoxy group directly bonded to a silicon atom and a polymethylpentene resin.

[0014] In the second aspect of the present invention, for example, in the porous film according to the first aspect, the ratio (A2 / A1×100) of the air permeability A2 expressed in Gurley number after the heat resistance test A to the air permeability A1 expressed in Gurley number is in the range of 50 to 150%, the ratio (B2 / B1×100) of the sound insertion loss B2 after the heat resistance test A to the sound insertion loss B1 of a frequency of 1 kHz is in the range of 70 to 130%, and the heat resistance test A is a test in which the film is heated at 160°C for 3 minutes.

[0015] In the third aspect of the present invention, for example, in the porous film according to the second aspect, the ratio (B2 / B1 x 100) is in the range of 75 to 125%.

[0016] In a fourth aspect of the present invention, for example, in the porous film according to the second or third aspect, the ratio (C2 / C1 × 100) of the contact angle C2 of liquid paraffin on the main surface after heat resistance test B to the contact angle C1 of liquid paraffin on the main surface is 80% or more, and the heat resistance test B is a test in which the film is heated at 160°C for 10 minutes.

[0017] In a fifth aspect of the present invention, for example, in the porous film according to the fourth aspect, the contact angle C2 is 45° or more.

[0018] A porous film according to a sixth aspect of the present invention is a porous film containing a fluorine-free thermoplastic resin as a main component, having a main surface that has been treated with a liquid repellent agent, wherein the ratio (A2 / A1 x 100) of the air permeability A2 expressed in Gurley number after heat resistance test A to the air permeability A1 expressed in Gurley number is in the range of 50 to 150%, the ratio (B2 / B1 x 100) of the sound insertion loss B2 after heat resistance test A to the sound insertion loss B1 of a frequency of 1 kHz is in the range of 70 to 130%, and the heat resistance test A is a test in which the film is heated at 160°C for 3 minutes.

[0019] In a seventh aspect of the present invention, for example, in the porous film according to the sixth aspect, the ratio (C2 / C1 × 100) of the contact angle C2 of liquid paraffin on the main surface after heat resistance test B to the contact angle C1 of liquid paraffin on the main surface is 80% or more, and the heat resistance test B is a test in which the film is heated at 160°C for 10 minutes.

[0020] In an eighth aspect of the present invention, for example, in the porous film according to the sixth or seventh aspect, the contact angle C2 is 45° or more.

[0021] In a ninth aspect of the present invention, for example, in the porous film according to any one of the first to eighth aspects, the thermoplastic resin includes at least one selected from the group consisting of polyolefin resins and polyimide resins.

[0022] In a tenth aspect of the present invention, for example, the porous film according to any one of the first to ninth aspects is a stretched film.

[0023] A ventilation member according to an eleventh aspect of the present invention includes, for example, the porous film according to any one of the first to tenth aspects, and an adhesive layer bonded to the porous film.

[0024] A component supply sheet according to a twelfth 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 tenth aspects.

[0025] 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.

[0026] [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. In this specification, the term "main component" refers to the component that is contained in the porous film 1 in the largest amount by weight. By containing a thermoplastic resin as a main component, the porous film 1 can be adhered to the housing of a smart watch or the like by heat fusion without using an adhesive or pressure-sensitive adhesive, for example.

[0027] The porous film 1 has a main surface that has been treated with a liquid-repellent agent. In other words, at least one main surface of the porous film 1 has been treated with a liquid-repellent agent. In this specification, the term "main surface" refers to the surface of a film-like or sheet-like member having the largest area. The liquid-repellent agent may contain at least one selected from the group consisting of a silicone resin having an alkoxy group directly bonded to a silicon atom and a polymethylpentene resin. In a porous film 1 having such a configuration, changes in properties due to temperature increase are suppressed.

[0028] The present inventors have discovered that while conventional fluorine-containing liquid repellents contribute to improving the liquid repellency of porous films, they also have issues with high-temperature resistance. Figure 14 illustrates the state of the liquid repellent layer after heating a porous film treated with a fluorine-containing liquid repellent agent. When a porous film 9 treated with a fluorine-containing liquid repellent agent is heated, the liquid repellent layer 91 tends to flow and penetrate into the porous film 9, or the surface 9s of the porous film 9 becomes exposed (see Figure 14 (A)). Such structural changes can cause changes in the properties of the porous film 9, such as breathability, sound permeability, and liquid repellency. The flow of the liquid repellent layer 91 with increasing temperature is thought to be related to the intermolecular interactions of the fluorine-containing liquid repellent agent. Generally, fluorine-containing organic compounds have low intermolecular interactions. Therefore, it is thought that the side chains contained in the fluorine-containing liquid repellent agent tend to tilt with increasing temperature, causing the liquid repellent layer 91 to flow. When a liquid repellent agent with stronger intermolecular interactions than a fluorine-containing liquid repellent agent is used, the liquid repellent layer 91 is less likely to flow even with increasing temperature. This is thought to suppress changes in the properties of the porous film 1 (see FIG. 14B).

[0029] The porous film 1 has a first main surface 1a and a second main surface 1b. At least one of the first main surface 1a and the second main surface 1b is treated with a liquid-repellent agent. In the example shown in FIG. 1, the first main surface 1a is treated with a liquid-repellent agent. However, both the first main surface 1a and the second main surface 1b may be treated with a liquid-repellent agent. With this configuration, for example, there is no need to be careful about confusing the main surface with higher liquid repellency, improving ease of handling.

[0030] As described above, the porous film 1 contains a fluorine-free thermoplastic resin as a main component. Examples of the fluorine-free thermoplastic resin include polyolefin resins and polyimide resins. The fluorine-free thermoplastic resin may contain at least one selected from the group consisting of polyolefin resins and polyimide resins. The fluorine-free thermoplastic resin may be one selected from the group consisting of polyolefin resins and polyimide resins.

[0031] The fluorine-free thermoplastic resin may include a polyolefin resin.The fluorine-free thermoplastic resin may be a polyolefin resin.

[0032] The polyolefin resin includes polyethylene (PE) resin, polypropylene (PP) resin, and polymethylpentene (PMP) resin.

[0033] The polyolefin resin may be a polyethylene resin or a polypropylene resin. When the porous film 1 contains a polyethylene resin or a polypropylene resin as a main component, the liquid repellent agent preferably contains a polymethylpentene resin.

[0034] The polyolefin resin may be a polymethylpentene resin. 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. When the porous film 1 contains a polymethylpentene resin as a main component, the liquid repellent agent preferably contains a silicone resin having an alkoxy group directly bonded to a silicon atom.

[0035] 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.

[0036] The fluorine-free thermoplastic resin may include a polyimide resin.The fluorine-free thermoplastic resin may be a polyimide resin.

[0037] 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.

[0038] 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.

[0039] The porous film 1 may contain additives such as a plasticizer and an antioxidant in addition to the thermoplastic resin.

[0040] As described above, the liquid repellent agent may contain at least one selected from the group consisting of a silicone resin having an alkoxy group directly bonded to a silicon atom and a polymethylpentene resin. Such a liquid repellent agent can impart excellent liquid repellency to the porous film 1.

[0041] Examples of silicone resins having alkoxy groups directly bonded to silicon atoms include polydimethylsiloxane, polydimethyldiphenylsiloxane, polymethylphenylsiloxane, oligomers thereof, etc. The silicone resin may also be a polymer containing the above-mentioned structural units, such as a copolymer.

[0042] As the polymethylpentene resin, the same polymethylpentene resins as those explained above for the thermoplastic resin can be used.

[0043] The porous film 1 can suppress changes in air permeability and sound permeability due to temperature rise. For example, in the porous film 1, the ratio (A2 / A1×100) of the air permeability A2 (sec / 100 mL) expressed as a Gurley number after heat resistance test A to the air permeability A1 (sec / 100 mL) expressed as a Gurley number is in the range of 50 to 150%, and the ratio (B2 / B1×100) of the sound insertion loss B2 after heat resistance test A to the sound insertion loss B1 of a frequency of 1 kHz is in the range of 70 to 130%. The heat resistance test A is a test in which the film is heated at 160°C for 3 minutes.

[0044] (Method for measuring air permeability expressed in Gurley number) In this specification, "Gurley number" refers to the air resistance (Gurley air permeability) measured in accordance with the Oken type testing machine method specified in JIS P8117: 2009. In addition, when the size of the porous film 1 is smaller than the recommended size (50 mm × 50 mm) of the test piece in the Oken type testing machine method, the air resistance (Gurley air permeability) can be evaluated in accordance with the Oken type testing machine method by using a measuring jig as described below.

[0045] 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 when measuring air permeability resistance. An example of a measurement jig is a 2 mm thick, 47 mm diameter SUS disk. Figure 15 is a schematic cross-sectional view of a sample 1A for evaluating the air permeability resistance (Gurley air permeability) of a porous film 1. A through-hole with an opening 51a smaller than the porous film 1 to be evaluated is provided at the center of the surface of the SUS disk 51 used as the measurement jig. The through-hole typically has a circular cross-section, and its diameter is such that the opening 51a of the through-hole is completely covered by the porous film 1 to be evaluated. In this embodiment, the diameter of the through-hole is 3 mm. Next, the porous film 1 to be evaluated is fixed to one side of the disk 51 so as to cover the opening 51a. If only the first main surface 1a of the porous film 1 has been treated with a liquid repellent agent, the second main surface 1b is fixed so that it faces the opening 51a. The fixation is performed so that during the air permeability resistance measurement, air passes only through the opening 51a and the effective test portion of the porous film 1 to be evaluated (the portion overlapping the opening 51a when viewed perpendicular to the main surface of the fixed porous film 1), and the fixation portion does not obstruct the passage of air through the effective test portion of the porous film 1. The porous film 1 can be fixed using double-sided adhesive tape 55 with a vent hole 55a (4 mm diameter) punched in the center. The double-sided adhesive tape 55 is simply placed between the disk 51 and the porous film 1 so that the central axis of the vent hole 55a coincides with the central axis of the opening 51a. In this manner, the sample 1A is obtained. As shown in FIG. 15 , the sample 1A has a bonded region R1 where the porous film 1 and the double-sided adhesive tape 55 are bonded, and a non-bonded region R2 surrounded by the bonded region R1 when viewed perpendicular to the main surface of the porous film 1.

[0046] Next, the sample body 1A is set in the air permeability measurement section of the Oken type testing machine so that the fixed surface of the porous film 1 is downstream of the air flow during measurement, and a test is carried out using the Oken type testing machine method, and the air permeability resistance indicated value t shown by the testing machine is recorded. Next, the recorded air permeability resistance indicated value t is used to measure the effective test area of ​​6.452 [cm2] as defined in the Oken type testing machine method. 2 ] per value tK 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 K can 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.

[0047] 15, the air permeability A1 (sec / 100 mL) expressed in Gurley number of the porous film 1 is measured, and then the air permeability A2 (sec / 100 mL) expressed in Gurley number after the heat resistance test A is measured. The ratio (A2 / A1 × 100) can be calculated from the air permeability A1 and the air permeability A2.

[0048] (Method for Measuring Insertion Loss) A method for measuring the insertion loss of the porous film 1 for a sound of a specific frequency will be described with reference to Figures 16A to 17. The insertion loss can be measured by the following method using a simulated housing that imitates the housing of a mobile phone.

[0049] FIG. 16A is a cross-sectional view schematically illustrating a sample 1B for evaluating the insertion loss of a porous film 1. The sample 1B includes a measurement jig and a porous film 1. An example of the measurement jig is a 2 mm thick, 47 mm diameter stainless steel disk. A through-hole having an opening 52a smaller than the porous film 1 to be evaluated is provided at the center of the surface of the SUS disk 52 serving as the measurement jig. The through-hole typically has a circular cross-section and a diameter such that the opening 52a of the through-hole is completely covered by the porous film 1 to be evaluated. In this embodiment, the diameter of the through-hole is 0.7 mm. Next, the porous film 1 to be evaluated is fixed to one side of the disk 52 so as to cover the opening 52a. If only the first main surface 1a of the porous film 1 has been treated with a liquid-repellent agent, the second main surface 1b is fixed so as to face the opening 52a. To secure the porous film 1, a double-sided adhesive tape 56 with a vent hole 56a (diameter 1.6 mm) punched in the center can be used. The double-sided adhesive tape 56 is placed between the disk 52 and the porous film 1 so that the central axis of the vent hole 56a coincides with the central axis of the opening 52a. Next, a double-sided adhesive tape 57 for securing the microphone is placed on the other main surface of the porous film 1 (the second main surface 1b in FIG. 15A ). The double-sided adhesive tape 57 has the same shape as the double-sided adhesive tape 56 and a vent hole 57a (diameter 1.6 mm) punched in the center. In this manner, sample 1B is obtained. As shown in FIG. 16A , sample 1B has a bonded region r1 where the porous film 1 and the double-sided adhesive tape 56 are bonded, and a non-bonded region r2 surrounded by the bonded region r1 when viewed perpendicular to the main surface of the porous film 1.

[0050] Next, sample body 1B was attached to a simulated housing simulating the housing of a mobile phone. FIG. 17 is a schematic diagram illustrating a method for evaluating the insertion loss of porous film 1. First, as shown in FIGS. 17A and 17B, a speaker unit 135 to be housed in the simulated housing was prepared. Specifically, the process is as follows: a speaker 140 (Star Micronics, SCC-16A) serving as a sound source, and fillers 130a, 130b, and 130c made of urethane sponge were prepared to house speaker 140 and prevent unnecessary diffusion of sound from the speaker (to minimize the generation of sound that is input to the evaluation microphone without passing through porous film 1, which is the evaluation target). A sound-passing hole 132 having a circular cross section with a diameter of 2 mm was provided in filler 130a in the thickness direction. Filler 130b has a cutout having a shape corresponding to the shape of speaker 140, and a cutout for accommodating speaker cable 142 and leading speaker cable 142 out of speaker unit 135. Next, fillers 130c and 130b are placed on top of each other, and speaker 140 and speaker cable 142 are placed in the cutout of filler 130b (FIG. 17A). Next, filler 130a is placed on top of filler 130b so that sound is transmitted from speaker 140 to the outside of speaker unit 135 through sound passage 132, thereby completing speaker unit 135 (FIG. 17B).

[0051] Next, as shown in FIG. 17C , the speaker unit 135 prepared above is housed inside a simulated housing 160 (made of polystyrene, outer dimensions 60 mm × 50 mm × 28 mm) that resembles the housing of a mobile phone. Specifically, the process is as follows. The prepared simulated housing 160 consists of two parts 160a and 160b, which can be fitted together. Part 160a is provided with a sound vent 162 (having a circular cross section with a diameter of 2 mm) that transmits sound emitted from the speaker unit 135 housed therein to the outside of the simulated housing 160, and a conductive hole 164 that leads the speaker cable 142 to the outside of the simulated housing 160. By fitting parts 160a and 160b together, a space with no openings other than the sound vent 162 and the conductive hole 164 is formed inside the simulated housing 160. After placing the manufactured speaker unit 135 on part 160b, parts 160a and 160b are fitted together to house the speaker unit 135 inside the simulated housing 160. At this time, the sound vent 132 of the speaker unit 135 and the sound vent 162 of part 160a are aligned so that sound is transmitted from the speaker 140 to the outside of the simulated housing 160 through both sound vents 132, 162. The speaker cable 142 is pulled out to the outside of the simulated housing 160 through the conducting hole 164, which is then sealed with putty.

[0052] Next, as shown in Fig. 17(D), sample body 1B is fixed to sound vent hole 162 of simulated housing 160. Fig. 16B is a cross-sectional view showing the state in which the sample body of Fig. 16A is attached to simulated housing 160. As shown in Fig. 16B, sample body 1B can be fixed using double-sided adhesive tape 58 with a vent hole (diameter 2.5 mm) punched in the center. When viewed from a direction perpendicular to the main surface of porous film 1, sample body 1B is fixed so that the entire non-bonded region r2 is located within the opening of sound vent hole 162.

[0053] Next, as shown in FIG. 17E, a microphone 150 (Knowles Acoustics, SPU0410LR5H) is fixed to the second main surface 1b of sample body 1B so as to cover the non-bonded region r2 of sample body 1B. As shown in FIG. 16B, microphone 150 is fixed using an adhesive layer 57 on the second main surface 1b of sample body 1B. The distance between speaker 140 and microphone 150 when fixed varies by up to about 2 mm depending on the thickness of sample body 1B to be evaluated, but is generally in the range of 22 to 24 mm. Finally, as shown in FIG. 16B, a weight 151 (344 g) is placed on microphone 150 (not shown in FIG. 17E).

[0054] The speaker 140 and microphone 150 are connected to an acoustic evaluation device (B&K Multi-analyzer System 3560-B-030), and the SSR (Solid State Response) mode (test signal 20 Hz to 20 kHz, sweep up) is selected and executed as the evaluation method to evaluate the insertion loss of the porous film 1 for sound of a specific frequency (for example, 1 kHz). The insertion loss is automatically determined from the test signal input to the speaker 140 from the acoustic evaluation device and the signal received by the microphone 150. When evaluating the insertion loss of the porous film 1, the value of the insertion loss when the sample body 1B is removed (blank value) is determined in advance. The blank value is -22 dB at a frequency of 1 kHz. The insertion loss of the porous film 1 for sound of a specific frequency is the value obtained by subtracting this blank value from the measurement value in the acoustic evaluation device. The smaller the insertion loss value, the better the level (volume) of the sound output from the speaker 140 is maintained.

[0055] 16B, the insertion loss B1 (dB) of the porous film 1 for a sound with a frequency of 1 kHz is measured, and then the insertion loss B2 (dB) for a sound with a frequency of 1 kHz is measured after the heat resistance test A. From the insertion loss B1 and the insertion loss B2, the ratio (B2 / B1 × 100) can be calculated.

[0056] In this embodiment, heat resistance test A can be performed, for example, by placing sample body 1A or sample body 1B inside a drying furnace (e.g., DKM300 manufactured by Yamato Scientific Co., Ltd.) whose temperature inside the furnace has been raised to a predetermined temperature for a predetermined period of time.

[0057] In the porous film 1, the air permeability ratio (A2 / A1×100) may be in the range of 60 to 120%, 70 to 130%, 80 to 120%, or even 90 to 110%.

[0058] In the porous film 1, the air permeability A2 expressed as a Gurley number after heat resistance test A is, for example, 500 seconds / 100 mL or less. The upper limit of the air permeability A2 may be 250 seconds / 100 mL, 100 seconds / 100 mL, or even 65 seconds / 100 mL. The lower limit of the air permeability A2 is, for example, 0.1 seconds / 100 mL. The lower limit of the air permeability A2 may be 1 second / 100 mL or 5 seconds / 100 mL.

[0059] In the porous film 1, the air permeability A1 expressed by the Gurley number in the initial state before the heat resistance test A is, for example, 0.1 sec / 100 mL or more and 500 sec / 100 mL or less.

[0060] In the porous film 1, the insertion loss ratio (B2 / B1×100) of a sound having a frequency of 1 kHz may be in the range of 75 to 125%. The insertion loss ratio (B2 / B1×100) may be in the range of 77 to 120%.

[0061] In the porous film 1, the insertion loss B2 for a sound having a frequency of 1 kHz after the heat resistance test A is, for example, 20 dB. The upper limit of the insertion loss B2 may be 15 dB, 13 dB, or even 11 dB. The lower limit of the insertion loss B2 is, for example, 0 dB.

[0062] In the porous film 1, the insertion loss B1 for a sound with a frequency of 1 kHz in the initial state before the heat resistance test A is, for example, 0 dB or more and 20 dB or less.

[0063] Heat resistance test A may be a test of heating at 160° C. for 3 minutes and a test of heating at 60° C. for 7 days. In this case, the porous film 1 has excellent heat resistance not only against short-term, high-temperature heating such as when attached to a device using a thermosetting adhesive, but also against long-term, high-temperature heating such as caused by heat generation from the attached device itself or a temperature rise in the location where the attached device is placed.

[0064] Heat resistance test A may be a test of heating at 160°C for 1 minute, a test of heating at 160°C for 3 minutes, and a test of heating at 60°C for 7 days.

[0065] In the porous film 1, the ratio (B2 / B1×100) of the insertion loss B2 (dB) of the sound after the heat resistance test A to the insertion loss B1 (dB) of a sound with a frequency of 100 Hz may be in the range of 70 to 130%. The blank value at a frequency of 100 Hz when calculating the insertion loss for a sound with a frequency of 100 Hz is −31 dB.

[0066] In the porous film 1, the ratio (B2 / B1×100) of the insertion loss B2 (dB) of the sound after heat resistance test A to the insertion loss B1 (dB) of a sound with a frequency of 5 kHz may be in the range of 70 to 130%. The blank value for the frequency of 5 kHz when calculating the insertion loss for the sound with a frequency of 5 kHz is −34 dB.

[0067] In the porous film 1, the ratio (B2 / B1×100) of the insertion loss B2 (dB) of the sound after heat resistance test A to the insertion loss B1 (dB) of a sound with a frequency of 8 kHz may be in the range of 70 to 130%. The blank value for the 8 kHz frequency when calculating the insertion loss for the 8 kHz frequency sound is −35 dB.

[0068] The porous film 1 can suppress changes in liquid repellency due to temperature rise. For example, the porous film 1 has a main surface that has been treated with a liquid repellent agent, and the ratio (C2 / C1 x 100) of the contact angle C2 of liquid paraffin on the main surface after heat resistance test B to the contact angle C1 of liquid paraffin on the main surface that has been treated with the liquid repellent agent (first main surface 1a in the example of Figure 1) can be 80% or more. Heat resistance test B is a test in which the film is heated at 160°C for 10 minutes. Heat resistance test B can be performed, for example, by placing the porous film 1 in a drying oven (e.g., DKM300, manufactured by Yamato Scientific Co., Ltd.) for a predetermined time, with the temperature inside the oven increased to a predetermined temperature.

[0069] In this embodiment, the liquid paraffin used to measure the contact angle has a kinematic viscosity of 64.5 to 69.7 mm at 40°C. 2 / sec. The kinematic viscosity at 40°C is in the range of 64.5 to 69.7 mm 2 An example of a liquid paraffin having an oil repellency in the range of 0.1 / sec is Kaydol (manufactured by Sonneborn), which is used in the AATCC (American Association of Textile Chemists and Colorists) TM118 method (1997) for oil repellency grade 0.1. Using a fully automatic contact angle meter (e.g., Dmo-702, manufactured by Kyowa Interface Science Co., Ltd.), the contact angle C1 (°) of liquid paraffin on the liquid-repellent-treated main surface of porous film 1 is measured, and then the contact angle C2 (°) of liquid paraffin on the main surface after heat resistance test B is measured. The ratio (C2 / C1 x 100) can be calculated from the contact angles C1 and C2. When measuring the contact angle, the amount of liquid paraffin dropped is 3 μL. The measurement is performed three times, with the drop point changed, and the average of the three measurements is taken as the contact angle.

[0070] In the porous film 1, the contact angle ratio (C2 / C1×100) may be in the range of 80 to 130%. The contact angle ratio (C2 / C1×100) may be in the range of 80 to 125%.

[0071] In the porous film 1, the contact angle C2 after the heat resistance test B may be 45° or more. The lower limit of the contact angle C2 may be 46°, 47°, 48°, 49°, or even 50°. The upper limit of the contact angle C2 is, for example, 75°.

[0072] In the porous film 1, the contact angle C1 in the initial state before the heat resistance test B is, for example, 40° or more and 75° or less.

[0073] Heat resistance test B may be a test of heating at 160° C. for 10 minutes and a test of heating at 60° C. for 7 days. In this case, the porous film 1 has excellent heat resistance not only against short-term, high-temperature heating such as when attached to a device using a thermosetting adhesive, but also against long-term, high-temperature heating such as caused by heat generation from the attached device itself or a temperature rise in the location where the attached device is placed.

[0074] The porous film 1 is in the form of a film or a sheet. The thickness of the porous film 1 is preferably 200 μm or less.

[0075] 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.

[0076] The upper limit of the thickness of the porous film 1 may be 200 μm, 150 μm, 125 μm, or even 100 μm. The lower limit of the thickness of the porous film 1 is, for example, 1 μm.

[0077] The porous film 1 may be a stretched film. When the porous film 1 is a stretched film, properties such as breathability and sound permeability can be easily controlled. The stretched film may be a biaxially stretched film or a uniaxially stretched film.

[0078] At least one of the main surfaces of the porous film 1 may be subjected to a surface modification treatment other than the liquid-repellent treatment. Examples of the surface modification treatment include chemical treatment, sputter etching treatment, and plasma treatment. The bonding property of the porous film 1 is improved in the area subjected to the surface modification treatment.

[0079] [Method for Producing Porous Film] When the fluorine-free thermoplastic resin is a polyolefin resin such as a polyethylene resin or a polymethylpentene resin, the porous film 1 described above can be produced, for example, by the following method.

[0080] 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 S1), heat-pressing the kneaded mixture to obtain a pressed body (step S2), cooling the pressed body to obtain a molded body (step S3), stretching the molded body to obtain a porous sheet body (step S4), removing the plasticizer from the porous sheet body to obtain a porous film body (step S5), applying a liquid-repellent treatment to at least one main surface of the porous film body with a liquid-repellent agent (step S6), and drying the liquid-repellent treated porous film body (step S7).

[0081] Steps S1 to S3 correspond to a process for producing a precursor of the porous film 1. Steps S4 to S5 correspond to a process for growing a porous structure. Step S6 corresponds to a process for imparting liquid repellency to the porous film 1.

[0082] Step S1 is carried out, for example, at a temperature of 130° C. to 260° C. for 5 to 30 minutes.

[0083] 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.

[0084] The plasticizer is a non-volatile solvent that, when mixed with a thermoplastic resin such as a polyolefin resin, e.g., a polyethylene resin or a polymethylpentene resin, forms a mixture at or above the melting point of the resin, and exhibits 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. A single plasticizer may be used, or two or more types of plasticizers may be mixed and used. Examples of such plasticizers include those having a kinematic viscosity at 40°C of 5 to 1000 mm 2 / s can be used.

[0085] 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.

[0086] 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.

[0087] Step S2 is carried out for 2 to 30 minutes at a temperature of, for example, 130 to 260° C. The thickness of the pressed body obtained in step S2 is, for example, 0.1 mm.

[0088] In step S3, the pressed body obtained in step S2 may be cooled to a temperature sufficiently lower than the crystallization temperature of the thermoplastic resin and solidified by contacting it with a thermal conductor, for example. Examples of the thermal conductor used for cooling include metal, water, air, and a plasticizer.

[0089] 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. By step S4, voids are generated in the molded body.

[0090] The stretching temperature may be 20°C to 130°C, 50°C to 120°C, or even 70°C to 100°C in each of the longitudinal and transverse directions.

[0091] The stretching ratio in the longitudinal and / or transverse uniaxial directions may be 1.1 to 50.0 times, 2.0 to 30.0 times, or even 4.0 to 20.0 times.

[0092] In step S5, the plasticizer is removed from the porous sheet using, for example, an extraction solvent.

[0093] The extraction solvent is preferably a poor solvent for thermoplastic resins such as polyethylene resins and polyolefin resins such as polymethylpentene resins, but a good solvent for plasticizers, and has a boiling point lower than the melting point of the porous sheet. 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.

[0094] Between step S4 and step S5, the porous 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 porous sheet after stretching. The heat-set temperature is, for example, 50°C to 130°C. The heat-set temperature may be 70°C to 120°C, or may be 80°C to 110°C.

[0095] 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.

[0096] FIG. 18 is a diagram illustrating an example of a method for applying a liquid-repellent treatment to a main surface of a porous film. In step S6, at least one main surface of the porous film 1p from which the plasticizer was removed in step S5 is subjected to a liquid-repellent treatment using a liquid-repellent agent. Examples of methods for the liquid-repellent treatment include slot die coating, gravure coating, spin coating, and bar coating. As shown in FIG. 18, a porous film 1p may be fixed using adhesive tape 63 on a glass plate 61 fixed on a flat table using adhesive tape 62, and a liquid-repellent treatment liquid containing a liquid-repellent agent may be applied from above the porous film 1p using a wireless bar coater 65 (e.g., KCN-OSP-04S, manufactured by Cortec Corporation).

[0097] In step S7, the porous film body 1p that has been subjected to the liquid repellent treatment is dried, for example, by air drying for 24 hours. In this way, the porous film 1 is obtained.

[0098] [Another Example of Method for Producing Porous Film] When the fluorine-free thermoplastic resin is a polyimide resin, the porous film 1 described above can be produced, for example, by the following method.

[0099] When the fluorine-free thermoplastic resin is a polyimide resin, the porous film 1 can be produced, for example, by a phase separation method. Examples of phase separation methods include non-solvent-induced phase separation (NIPS method) and drying-induced phase separation (DIPS method). In the NIPS method, a porous film is obtained by inducing phase separation in a coating of a polymer solution or a polymer precursor solution by incorporating a non-solvent such as water. In the DIPS method, a porous film is obtained by inducing phase separation in a coating of a polymer solution or a polymer precursor solution by solvent evaporation.

[0100] The method for producing the porous film 1 includes, for example, applying a soluble polyimide solution containing a soluble polyimide and a solvent onto a substrate to form a coating film (step ST1), immersing the coating film in water (step ST2), and drying the coating film (step ST3), in this order. The solvent includes at least one selected from the group consisting of lactone-based solvents, sulfone-based solvents, ketone-based solvents, and cyclic ether-based solvents. The polyethylene glycol content in the soluble polyimide solution is less than 0.1 wt %.

[0101] In step ST1, a soluble polyimide solution is applied to a predetermined substrate to form a coating film. An example of the soluble polyimide is a soluble polyimide varnish (Neoprim S100 (solid content: 20 wt%), manufactured by Mitsubishi Gas Chemical Company, Inc.). Examples of the solvent are lactone-based solvents, sulfone-based solvents, or ketone-based solvents. The solvent may also be a lactone-based solvent. An example of the substrate is a porous material containing a fluororesin. The substrate is preferably a predetermined polytetrafluoroethylene (PTFE) porous membrane (TEMISH (registered trademark), manufactured by Nitto Denko Corporation). For example, the air permeability of the PTFE porous membrane, measured according to the air permeability measurement method B (Gurley method) specified in JIS L1096:2010, is 30 seconds / 100 cm. 3 ~50 seconds / 100cm 3 The PTFE porous membrane has a thickness of, for example, 50 to 100 μm. The average pore size on the surface of the PTFE porous membrane is, for example, 100 to 200 nm. In producing the porous film 1, a first microporous layer can be formed in contact with the contact surface of the coating of the soluble polyimide solution with the substrate.

[0102] The solvent includes at least one selected from the group consisting of lactone solvents, sulfone solvents, ketone solvents, and cyclic ether solvents. The lactone solvent includes, for example, γ-butyl lactone. The lactone solvent may be γ-butyl lactone. The sulfone solvent includes, for example, sulfolane. The ketone solvent includes, for example, cyclopentanone. The cyclic ether solvent includes, for example, 1,3-dioxolane.

[0103] In this embodiment, the soluble polyimide solution is substantially free of polyethylene glycol (PEG). In this specification, "substantially free of polyethylene glycol" means that the polyethylene glycol content in the soluble polyimide solution is less than 0.1 wt%. Conventionally, PEG is used as a porosifying agent when producing porous films. Therefore, in this field, it is common knowledge that the use of PEG can adjust the pore size of the porous film and improve its breathability. However, contrary to expectations, PEG is not used in this embodiment. This tends to result in the formation of characteristic rod-shaped pores in step ST2.

[0104] In step ST2, the coating film of the soluble polyimide solution is immersed in water. This promotes phase separation in the coating film, promoting porosity, and extracting the solvent from the coating film. The coating film of the soluble polyimide solution is immersed, for example, in a water bath at 20°C to 40°C. The water used in the water bath is typically pure water. The immersion time is, for example, 1 minute to 30 minutes. In step ST2, the closer to the outermost layer of the coating film, the faster the phase separation rate becomes, and the more rapidly the solvent is extracted. Therefore, a second microporous layer having a denser structure is formed on the surface side of the coating film, and a first microporous layer is formed in contact with the surface of the coating film that comes into contact with the substrate. The formation of the first microporous layer and the second microporous layer makes it difficult for the solvent to be extracted from the inside of the coating film, and as a result, a porous layer with rod-shaped voids is formed inside the coating film.

[0105] In step ST3, the porous coating film is dried. The film obtained after drying is peeled off from the substrate to obtain the porous film 1. The drying time is, for example, 1 minute to 30 minutes.

[0106] [Film member] An example of the film member of the present invention is shown in Figure 2. The film member 2 (2A) in Figure 2 includes a porous film 1. A first modified example of the film member in Figure 2 is shown in Figure 3. The film member 2 (2B) in Figure 3 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.

[0107] 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.

[0108] The film member 2B in Fig. 3 includes one breathable support material 3 arranged on one main surface of the porous film 1. In the example shown in Fig. 3, the breathable support material 3 is arranged on the main surface (second main surface 1b) of the porous film 1 that has not been treated with a liquid repellent. However, the breathable support material 3 may also be arranged on the main surface (first main surface 1a) of the porous film 1 that has been treated with a liquid repellent. 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.

[0109] The film member 2 may include any layers and / or members other than those described above.

[0110] The thickness of the film member 2 is, for example, 1 to 300 μm, and may be 50 to 200 μm.

[0111] 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.

[0112] The film member 2 can have the same properties as the porous film 1, such as breathability and sound permeability.

[0113] The film member 2 may be subjected to a liquid-repellent treatment and / or a coloring treatment.

[0114] 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.

[0115] 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.

[0116] FIG. 4 shows a second modified example (roll) of the film member of FIG. 2 . The roll 10 shown in FIG. 4 includes the film member 2A and release liner 11 of FIG. 2 . 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 without the adhesive layer 12 formed on its surface. The release liner 11 may be disposed on the main surface of the porous film 1 that has not been subjected to the liquid-repellent treatment (second main surface 1b), or on the main surface of the porous film 1 that has been subjected to the liquid-repellent treatment (first main surface 1a).

[0117] As used herein, "adhesive" means "sticking" or "adhesion." For example, "adhesive layer" means "sticking layer" or "adhesive layer."

[0118] As used herein, "pressure-sensitive adhesive," as defined by JIS, refers to a type of adhesion that is temporary and can bond with only slight pressure. It also refers to a property that, while possessing cohesive strength and elasticity, provides strong adhesion, it can also be peeled off from hard, smooth surfaces. Pressure-sensitive adhesives are soft solids and do not undergo state changes like adhesives. Pressure-sensitive adhesives wet to the adherend in their original state and resist peeling, so when adherends are bonded together, they instantly exhibit practical adhesive strength. In other words, pressure-sensitive adhesives possess both the liquid properties (fluidity) that allow them to wet to the adherend and the solid properties (cohesive strength) that resist peeling. Because pressure-sensitive adhesives are soft solids, the contact area with the adherend gradually increases with the application of pressure or over time. Furthermore, because they can maintain this softness for a long period of time, they have the property of being easily removable.

[0119] In this specification, "adhesive" refers to the property of bonding and integrating solid surfaces of the same or different types, as defined by JIS. An adhesive is a fluid substance that wets and blends with the adherends when bonding them together. It then transforms into a solid through heating or chemical reaction, firmly binding the adherends at their interfaces and exerting resistance to peeling. In other words, an adhesive wets the fluid substance and adheres as a solid.

[0120] The film member 2A supplied by the roll 10 and not having the 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 by an adhesive layer newly disposed on the surface of the film member 2A, bonding by thermal welding, and bonding by ultrasonic welding.

[0121] 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 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 the joining method to the opening of the housing and / or the shape.

[0122] 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.

[0123] [Ventilation Member] An example of a ventilation member of the present invention is shown in FIG. 5. The ventilation member 4 (4A) in FIG. 5 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. 5 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.

[0124] The ventilation member 4 (4A) has an adhesive layer 5 disposed on one main surface 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 disposed on the surface of the object via the adhesive layer 5. In the example shown in Fig. 5, the adhesive layer 5 is disposed on the main surface (second main surface 1b) of the porous film 1 that has not been treated with a liquid repellent coating. However, the adhesive layer 5 may also be disposed on the main surface (first main surface 1a) of the porous film 1 that has been treated with a liquid repellent coating.

[0125] 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.

[0126] The outer periphery of the porous film 1 and the outer periphery of the adhesive layer 5 are coincident 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. A region of the porous film 1 to which the adhesive layer 5 is not bonded can be used as a ventilation region of the ventilation member 4A. However, the shape of the adhesive layer 5 is not limited to the above example.

[0127] 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.

[0128] Fig. 6 shows a first modification of the ventilation member of Fig. 5. The ventilation member 4 (4B) of Fig. 6 has the same configuration as the ventilation member 4A of Fig. 5, except that it further includes an adhesive layer 5 (5B) arranged on the other main surface of the porous film 1. The porous film 1 is sandwiched between a pair of adhesive layers 5 (5A, 5B).

[0129] As shown in Figure 6, the adhesive layer 5 may include a first adhesive layer 5A bonded to one main surface (first main surface 1a) of the porous film 1 and a second adhesive layer 5B bonded to the other main surface (second main surface 1b) of the porous film 1.

[0130] Fig. 7 shows a second variation of the ventilation member of Fig. 5. The ventilation member 4 (4C) of Fig. 7 has the same configuration as the ventilation member 4A of Fig. 5, except that it further includes a base material layer 6 arranged on one main surface of the porous film 1, and the porous film 1 and the adhesive layer 5 are bonded 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.

[0131] 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.

[0132] 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.

[0133] The porous film 1 and the base layer 6 may be bonded together with a pressure-sensitive adhesive or adhesive, or may be bonded together by welding such as thermal welding or ultrasonic welding. The porous film 1 and the base layer 6 may be bonded together with 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.

[0134] A third variation of the ventilation member of Fig. 5 is shown in Fig. 8. The ventilation member 4 (4D) of Fig. 8 has the same configuration as the ventilation member 4C of Fig. 5, except that it further includes a base material layer 6 (6B) arranged on the other main surface 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.

[0135] As shown in Figure 8, the substrate layer 6 may include a first substrate layer 6A bonded to one main surface (first main surface 1a) of the porous film 1 and a second substrate layer 6B bonded to the other main surface (second main surface 1b) of the porous film 1.

[0136] Fig. 9 shows a fourth modification of the ventilation member of Fig. 5. The ventilation member 4 (4E) of Fig. 9 has the same configuration as the ventilation member 4B of Fig. 6 except that it further includes a release liner 7 and the porous film 1 and the release liner 7 are bonded via an adhesive layer 5 (5B).

[0137] As shown in FIG. 9 , 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.

[0138] The release liner 7 has a tab that protrudes outward beyond 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 makes up the base layer 6.

[0139] Fig. 10 shows a fifth variation of the ventilation member of Fig. 5. The ventilation member 4 (4F) of Fig. 10 further includes a release liner 7, and has the same configuration as the ventilation member 4D of Fig. 8 except that the release liner 7 is bonded to the base material layer 6 (6B) via an adhesive layer 5 (5B).

[0140] [Component Supply Sheet] The ventilation member 4 can be supplied, for example, by 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. 11 . The component supply sheet 20 (20A) in FIG. 11 includes 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 includes the ventilation member 4A as the ventilation member 4. The ventilation member 4A includes 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. In the example shown in FIG. 11 , the base sheet 9 is arranged so as to face the main surface (second main surface 1b) of the porous film 1 that has not been treated with a liquid repellent coating. However, the base sheet 9 may also be arranged so as to face the main surface (first main surface 1a) of the porous film 1 that has been treated with a liquid repellent coating.

[0141] The ventilation member 4 (4A) is disposed on the base sheet 9 via the 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.

[0142] The ventilation member 4 may be disposed on the base sheet 9 via an adhesive layer provided on the surface of the base sheet 9 on which the ventilation member 4 is disposed. The adhesive layer on the surface on which the ventilation member 4 is disposed preferably has weak adhesive properties.

[0143] Although not shown in the drawings, a plurality of ventilation members 4 may be arranged on the surface of the base sheet 9 .

[0144] 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.

[0145] 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.

[0146] 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.

[0147] Fig. 12 shows a first modification of the member supply sheet of Fig. 11. The member supply sheet 20 (20B) of Fig. 12 has the same configuration as the member supply sheet 20A of Fig. 11, except that it is provided with the ventilation member 4E of Fig. 9 as the ventilation member 4.

[0148] A second modification of the member supply sheet of Fig. 11 is shown in Fig. 13. The member supply sheet 20 (20C) of Fig. 13 has the same configuration as the member supply sheet 20A of Fig. 11, except that it is provided with the ventilation member 4F of Fig. 10 as the ventilation member 4.

[0149] 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.

[0150] [Example 1] A porous film containing a polyethylene resin as a main component was prepared as a substrate. The porous film had a thickness of 30 μm, a pore diameter of 0.1 μm, a porosity of 80%, and a tensile elongation in the transverse direction (TD) T TD Tensile elongation T in the MD (Machine Direction) MD The ratio (T MD / T TD ) was 15 / 30, and the water flow rate at a differential pressure of 100 kPa in the flat membrane state was 17 mL / min / cm 2 In the flat membrane state, the ethanol flow rate at a differential pressure of 100 kPa was 12 mL / min / cm2 It was.

[0151] As a liquid repellent, a liquid repellent containing a silicone resin having an alkoxy group directly bonded to a silicon atom (manufactured by Shin-Etsu Chemical Co., Ltd., X-48-2316, viscosity 100 mm) was used. 2 1 / sec (25°C), specific gravity 1.07 (25°C)) was prepared. Isopropanol (IPA) was prepared as a diluent. 0.1 g of liquid-repellent agent and 9 g of diluent were mixed to prepare a 1.0 wt % liquid-repellent treatment liquid. Using the method described in FIG. 18, a liquid-repellent treatment was applied to one main surface of a porous film cut into a 50 mm x 50 mm size using a wireless bar coater (KCN-OSP-04S, manufactured by Cortec Co., Ltd.). Specifically, a 1 mL dropper was used to drop approximately 0.5 mL of liquid-repellent treatment liquid in front of the wireless bar coater, and the wireless bar coater was moved in the direction of the arrow in FIG. 18 to scrape off the liquid-repellent treatment liquid, thereby applying the liquid-repellent treatment liquid to a wet thickness of 54 μm on one main surface of the porous film. Nitto Denko No. 318 (thickness 50 μm) adhesive tapes 62 and 63 were used.

[0152] The porous film body after being coated with the liquid-repellent treatment liquid was left to stand for 30 minutes and then air-dried for 24 hours, thereby obtaining the porous film of Example 1.

[0153] [Example 2] As a liquid repellent, a liquid repellent containing a silicone resin having an alkoxy group directly bonded to a silicon atom (KP611, manufactured by Shin-Etsu Chemical Co., Ltd., viscosity 550 mm) was used. 2 / sec (25°C), specific gravity 0.98 (25°C)). 0.19 g of the liquid repellent agent was mixed with 9 g of a diluent (IPA) to prepare a 1.0 wt% liquid repellent treatment liquid. After coating with the liquid repellent treatment liquid, the porous film was air-dried for 24 hours. Except for these factors, the porous film of Example 2 was obtained by the same method as in Example 1.

[0154] [Example 3] A liquid repellent agent containing polymethylpentene resin (manufactured by Mitsui Chemicals, Inc., RT18: high rigidity grade, density 0.833, MFR 26 g / 10 min) was used as the liquid repellent agent. A solvent obtained by mixing cyclohexane and tetrahydrofuran (THF) at a weight ratio of 1:1 was used as the diluent. 0.1 g of the liquid repellent agent and 9.9 g of the diluent were stirred at 60°C and 800 rpm for 6 hours to prepare a 1.0 wt% liquid repellent treatment liquid. The porous film body after coating with the liquid repellent treatment liquid was air-dried for 24 hours. Except for these, the porous film of Example 3 was obtained by the same method as Example 1.

[0155] [Example 4] A liquid repellent agent containing polymethylpentene resin (manufactured by Mitsui Chemicals, Inc., MX002: low rigidity grade, density 0.834, MFR 21 g / 10 min) was used. Except for this, a porous film of Example 4 was obtained by the same method as Example 3.

[0156] Comparative Example 1 The porous film of Example 1 was used as the porous film of Comparative Example 1. That is, the porous film of Comparative Example 1 was not subjected to a liquid-repellent treatment with a liquid-repellent agent.

[0157] Comparative Example 2: As a liquid repellent, a fluorine-based liquid repellent (X-70-262S, manufactured by Shin-Etsu Chemical Co., Ltd., viscosity 2.4 mm) was used. 2 The diluent used was Novec 7200 (viscosity: 0.4 mm / s (25°C), specific gravity: 1.67 (25°C)) manufactured by 3M. 2 / sec, specific gravity 1.43) was used. 0.65 g of the liquid repellent agent was mixed with 9 g of diluent to prepare a 1.0 wt % liquid repellent treatment liquid. The porous film body after coating with the liquid repellent treatment liquid was cured (hardened) at 130°C for 1 minute. A drying step was not carried out. Except for these, the porous film of Comparative Example 2 was obtained by the same method as in Example 1.

[0158] Comparative Example 3 A fluorine-based liquid repellent agent containing a polymer having a compound represented by the following chemical formula (a) as a monomer was used as the liquid repellent agent: CH2=CHCOOCH2CH2C6F 13 ...(a)

[0159] As a diluent, AE3000 manufactured by AGC (viscosity: 0.65 mPa s (25°C), specific gravity: 1.474) was used. 0.65 g of the liquid repellent agent and 9 g of the diluent were mixed to prepare a 1.0 wt% liquid repellent treatment liquid. After coating with the liquid repellent treatment liquid, the porous sheet was air-dried for 24 hours. Except for these, a porous film of Comparative Example 3 was obtained by the same method as in Example 1.

[0160] Comparative Example 4 A fluorine-based liquid repellent agent containing a polymer having a compound represented by the following chemical formula (b) as a monomer was used as the liquid repellent agent: CH2=C(CH3)COOCH2CH2C5F 10 CH2C4F9...(b)

[0161] Except for this, the porous film of Comparative Example 4 was obtained in the same manner as in Comparative Example 3.

[0162] [Example 5] Poly(4-methylpentene-1) resin (RT18, manufactured by Mitsui Chemicals, Inc.) was prepared as a fluorine-free thermoplastic resin. 2Liquid paraffin (manufactured by MORESCO) with a 1000-milliliter capacity (10 ... Next, using a longitudinal stretching machine, the sheet was longitudinally stretched under the conditions of a front roll temperature of 60°C, a rear roll temperature of 120°C, and a stretch ratio of 1.2 times (i.e., a line speed of the front roll feed side of 5 m / min, and a line speed of the rear roll of 6 m / min). This resulted in a longitudinally stretched film. Next, the longitudinally stretched film was transversely stretched under conditions of a stretching temperature of 100°C and a stretch ratio of 2.5 times, and then annealed at 150°C. This resulted in a porous sheet. Finally, the porous sheet was immersed in room temperature methyl ethyl ketone (MEK) as an extraction solvent for 140 seconds to remove the plasticizer from the porous sheet. In this way, a porous film containing polymethylpentene resin as the main component was produced.

[0163] The produced porous film was subjected to a liquid-repellent treatment using the liquid-repellent treatment liquid produced in Example 1 in the same manner as in Example 1. In this way, the porous film of Example 5 was obtained.

[0164] [Example 6] The porous film containing polymethylpentene resin as a main component prepared in Example 5 was used as the substrate. The porous film was subjected to a liquid-repellent treatment using the liquid-repellent treatment liquid prepared in Example 2 in the same manner as in Example 2. In this way, the porous film of Example 6 was obtained.

[0165] [Comparative Example 5] As the porous film of Comparative Example 5, a porous film containing polymethylpentene resin as a main component produced in Example 5 was used. That is, the porous film of Comparative Example 5 was not subjected to a liquid-repellent treatment with a liquid-repellent agent.

[0166] Example 7 Soluble polyimide varnish (Neoprim S100 (solid content: 20 wt%), manufactured by Mitsubishi Gas Chemical Company, Inc.) was prepared as a fluorine-free thermoplastic resin. γ-Butyllactone (manufactured by Tokyo Chemical Industry Co., Ltd.), a lactone solvent, was prepared as a dilution solvent. 6.5 g of γ-butyllactone was added to 3.5 g of the soluble polyimide varnish and mixed uniformly. This resulted in a soluble polyimide (PI) solution. The polyimide concentration of the soluble PI solution was 7.0 wt%.

[0167] A PTFE porous membrane (TEMISH (registered trademark), manufactured by Nitto Denko Corporation) was prepared as a substrate. The soluble PI solution was applied onto the PTFE porous membrane using an applicator to a wet thickness of 125 μm to form a coating film.

[0168] Next, the coating film was immersed in a water bath at 20 ° C for 10 minutes to allow porosity due to phase separation and solvent extraction to proceed. Next, the coating film was fixed to a square SUS member with a side length of 10 cm in plan view, and dried at 80 ° C for 10 minutes. This resulted in a porous film body on the PTFE porous film. Finally, the porous film body was peeled off from the PTFE porous film. In this way, a porous film body containing polyimide resin as the main component was produced.

[0169] The liquid-repellent treatment liquid prepared in Example 2 was applied to one main surface of the prepared porous film body to a wet thickness of 16 μm. Except for this, the liquid-repellent treatment was carried out in the same manner as in Example 2. In this way, the porous film of Example 7 was obtained.

[0170] [Example 8] As a substrate, a porous film containing polyimide resin as a main component prepared in Example 7 was used. The liquid-repellent treatment liquid prepared in Example 2 was applied to one main surface of the prepared porous film with a wet thickness of 20 μm. Except for this, the liquid-repellent treatment was performed in the same manner as in Example 2. In this way, the porous film of Example 8 was obtained.

[0171] Using the methods described above, the porous films of Examples 1 to 8 and Comparative Examples 1 to 5 were evaluated for the air permeability ratio (A2 / A1 x 100), insertion loss ratio (B2 / B1 x 100), and contact angle ratio (C2 / C1 x 100). Specifically, using Sample 1A shown in FIG. 15, the air permeability ratio (A2 / A1 x 100) was evaluated when Heat Resistance Test A involved heating at 160°C for 1 minute and heating at 160°C for 3 minutes. Using Sample 1B shown in FIG. 16A, the insertion loss ratio (B2 / B1 x 100) of a sound with a frequency of 1 kHz was evaluated when Heat Resistance Test A involved heating at 160°C for 1 minute and heating at 160°C for 3 minutes. Using Kaydol (manufactured by Sonneborn) as liquid paraffin, heat resistance test B involved heating at 160°C for 10 minutes, and evaluation was performed on the contact angle ratio (C2 / C1 x 100) and other parameters. A fully automatic contact angle meter (Dmo-702, manufactured by Kyowa Interface Science Co., Ltd.) was used to measure the contact angle. Heat resistance tests A and B were performed using a drying oven (DKM300, manufactured by Yamato Scientific Co., Ltd.). The evaluation results are shown in Tables 1 to 4.

[0172]

[0173]

[0174]

[0175]

[0176] Furthermore, for the porous films of Examples 1, 4, 5-8 and Comparative Examples 1, 4, and 5, the air permeability ratio (A2 / A1 x 100) was evaluated using Sample 1A shown in Figure 15 when Heat Resistance Test A was performed at 60°C for 7 days. The insertion loss ratio (B2 / B1 x 100) was evaluated using Sample 1B shown in Figure 16A when Heat Resistance Test A was performed at 60°C for 7 days. Kaydol (manufactured by Sonneborn) was used as liquid paraffin, and the contact angle ratio (C2 / C1 x 100) and other properties were evaluated when Heat Resistance Test B was performed at 60°C for 7 days. The evaluation results are shown in Tables 5 to 7.

[0177]

[0178]

[0179]

[0180] As can be seen from the results in Tables 1 to 2 and Table 5, in Examples 1 to 4, changes in the properties of the porous films due to temperature increases were suppressed compared to Comparative Examples 1 to 4. Specifically, in Examples 1 to 4, the ratios of air permeability (A2 / A1 x 100) in Heat Resistance Test A, which involved heating at 160°C for 3 minutes and heating at 60°C for 7 days, were in the range of 50 to 150%, thereby suppressing changes in air permeability due to short-term and long-term temperature increases. Furthermore, in Examples 1 to 4, the ratios of insertion loss (B2 / B1 x 100) in Heat Resistance Test A, which involved heating at 160°C for 3 minutes and heating at 60°C for 7 days, were in the range of 70 to 130%, thereby suppressing changes in sound permeability due to short-term and long-term temperature increases. Furthermore, in Examples 1 to 4, when heat resistance test B was a test in which the sample was heated at 160°C for 10 minutes and a test in which the sample was heated at 60°C for 7 days, the contact angle ratio (C2 / C1 × 100) was 80% or more, and changes in liquid repellency due to temperature increases over short and long periods were suppressed.

[0181] As can be seen from the results in Tables 3 and 6, in Examples 5 and 6, changes in the properties of the porous film due to temperature increase were suppressed compared to Comparative Example 5. Specifically, in Examples 5 and 6, the ratios of air permeability (A2 / A1 x 100) in Heat Resistance Test A, which involved heating at 160°C for 3 minutes and at 60°C for 7 days, were in the range of 50 to 150%, indicating that changes in air permeability due to short-term and long-term temperature increases were suppressed. Furthermore, in Examples 5 and 6, the ratios of insertion loss (B2 / B1 x 100) in Heat Resistance Test A, which involved heating at 160°C for 3 minutes and at 60°C for 7 days, were in the range of 70 to 130%, indicating that changes in sound permeability due to short-term and long-term temperature increases were suppressed. Furthermore, in Examples 5 and 6, when heat resistance test B was a test in which the sample was heated at 160°C for 10 minutes and a test in which the sample was heated at 60°C for 7 days, the ratio of the contact angles (C2 / C1 × 100) was 80% or more, and changes in liquid repellency due to temperature increases over short and long periods were suppressed.

[0182] As can be seen from the results in Tables 4 and 7, in Examples 7 to 8, changes in the properties of the porous films due to temperature increases were suppressed. Specifically, in Examples 7 to 8, the ratios of air permeability (A2 / A1 x 100) in Heat Resistance Test A, which involved heating at 160°C for 3 minutes and at 60°C for 7 days, were in the range of 50 to 150%, indicating that changes in air permeability due to short-term and long-term temperature increases were suppressed. Furthermore, in Examples 7 to 8, the ratios of insertion loss (B2 / B1 x 100) in Heat Resistance Test A, which involved heating at 160°C for 3 minutes and at 60°C for 7 days, were in the range of 70 to 130%, indicating that changes in sound permeability due to short-term and long-term temperature increases were suppressed. Furthermore, in Examples 7 and 8, when heat resistance test B was a test in which the sample was heated at 160°C for 10 minutes and a test in which the sample was heated at 60°C for 7 days, the contact angle ratio (C2 / C1 × 100) was 80% or more, and changes in liquid repellency due to temperature increases over short and long periods were suppressed.

[0183] The porous films of Examples 1 to 8 had their main surfaces treated with a liquid-repellent agent containing at least one selected from the group consisting of a silicone resin having an alkoxy group directly bonded to a silicon atom and a polymethylpentene resin. On the other hand, the porous films of Comparative Examples 2 to 4 had their main surfaces treated with a fluorine-based liquid-repellent agent. The main surfaces of the porous films of Comparative Examples 1 and 5 were not treated with a liquid-repellent agent. The properties of the porous films of Comparative Examples 2 to 4 changed with increasing temperature. This is presumably due to changes in the structure of the porous film caused by heating, such as the liquid-repellent layer containing the liquid-repellent agent flowing and penetrating into the interior of the porous film or the surface of the porous film being exposed. The porous film of Comparative Example 1 had low contact angles C1 and C2, both of which were 30° or less, and did not have sufficient liquid repellency. The porous film of Comparative Example 5 had an insertion loss ratio (B2 / B1 x 100) of more than 130%, and its sound permeability changed with both short-term and long-term temperature increases.

[0184] From the above results, it can be seen that the porous films of Examples 1 to 8 are suitable for suppressing changes in properties due to temperature rise.

[0185] 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 a main component, having a main surface that has been treated with a liquid-repellent agent, the liquid-repellent agent including at least one selected from the group consisting of a silicone resin having an alkoxy group directly bonded to a silicon atom and a polymethylpentene resin.

2. The porous film according to claim 1, wherein the ratio (A2 / A1 x 100) of the air permeability A2 expressed in Gurley number after heat resistance test A to the air permeability A1 expressed in Gurley number is in the range of 50 to 150%, the ratio (B2 / B1 x 100) of the sound insertion loss B2 after heat resistance test A to the sound insertion loss B1 of a frequency of 1 kHz is in the range of 70 to 130%, and the heat resistance test A is a test in which the film is heated at 160°C for 3 minutes.

3. The porous film according to claim 2, wherein the ratio (B2 / B1 x 100) is in the range of 75 to 125%.

4. The porous film according to claim 2, wherein the ratio (C2 / C1 x 100) of the contact angle C2 of liquid paraffin on the main surface after heat resistance test B to the contact angle C1 of liquid paraffin on the main surface is 80% or more, and wherein heat resistance test B is a test in which the film is heated at 160°C for 10 minutes.

5. The porous film according to claim 4, wherein the contact angle C2 is 45° or more.

6. A porous film whose main component is a fluorine-free thermoplastic resin, the main surface of which has been treated with a liquid repellent agent, the ratio of the air permeability A2 expressed in Gurley number after heat resistance test A to the air permeability A1 expressed in Gurley number (A2 / A1 x 100) being in the range of 50-150%, the ratio of the sound insertion loss B2 after heat resistance test A to the sound insertion loss B1 of a frequency of 1 kHz (B2 / B1 x 100) being in the range of 70-130%, and the heat resistance test A being a test in which the film is heated at 160°C for 3 minutes.

7. The porous film according to claim 6, wherein the ratio (C2 / C1 x 100) of the contact angle C2 of liquid paraffin on the main surface after heat resistance test B to the contact angle C1 of liquid paraffin on the main surface is 80% or more, and wherein heat resistance test B is a test in which the film is heated at 160°C for 10 minutes.

8. The porous film according to claim 7, wherein the contact angle C2 is 45° or more.

9. The porous film according to claim 1 or 6, wherein the thermoplastic resin comprises at least one selected from the group consisting of polyolefin resins and polyimide resins.

10. The porous film according to claim 1 or 6, which is a stretched film.

11. A ventilation member comprising the porous film according to any one of claims 1 to 8 and an adhesive layer bonded to the porous film.

12. 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 8.

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