Porous membrane, filter element and element supply assembly

Abstract

Provided is a porous membrane which contains, as a main component, a thermoplastic resin having a melting point of 180-300°C and has a tortoiseshell structure configured of a plurality of nodes and a plurality of fibrils. Alternatively, provided is a porous membrane which contains, as a main component, a thermoplastic resin having a melting point of 180-300°C and which, when a pressure of 2.5 N / mm2 is applied thereto, has a compressibility along the thickness direction of the porous film of 20% or less. The thermoplastic resin includes, for example, a polymethylpentene resin. When a section of the porous membrane is examined, there are, for example, a plurality of nodes arranged along the thickness direction.

Description

[Technical Field]

[0001] The present invention relates to a porous membrane, a filter element, and an element supply assembly. [Background technology]

[0002] Fluororesin porous membranes are used in a variety of applications, such as filters, sound-permeable membranes, air-permeable membranes, diaphragms, liquid absorbents, 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, characterized in that the biaxially stretched olefin-based resin microporous film has a puncture strength of 0.7 N or more and an air permeability of 75 to 400 s / 100 mL. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-095576 Summary of the Invention [Problem to be solved by the invention]

[0005] Even if a porous membrane has excellent mechanical strength such as puncture resistance, it may not be possible to ensure an appropriate attachment pressure when attaching it to, for example, a device housing.

[0006] Therefore, an object of the present invention is to provide a porous membrane that is suitable for attachment to a housing or the like of a device. [Means for solving the problem]

[0007] The present invention provides A porous film containing, as a main component, a thermoplastic resin having a melting point of 180°C or more and 300°C or less, The porous membrane has a tortoiseshell structure formed by a plurality of nodes and a plurality of fibrils. porous membrane, to provide.

[0008] From another aspect, the present invention provides a method for manufacturing a semiconductor device comprising: A porous film containing, as a main component, a thermoplastic resin having a melting point of 180°C or more and 300°C or less, 2.5N / mm 2 The compressibility of the porous membrane in the thickness direction when a pressure of 20% or less is applied. porous membrane, to provide.

[0009] From another aspect, the present invention provides The porous membrane of the present invention; A pressure-sensitive adhesive layer bonded to the porous film, Filter members, to provide.

[0010] From yet another aspect, the present invention provides a method for manufacturing a semiconductor device comprising: A member supply assembly including: a filter member to be placed on a surface of an object having an opening; and a base sheet having the filter member placed on a surface thereof, The filter member is a porous membrane having a shape that covers the opening when placed on the surface; a pressure-sensitive adhesive layer bonded to the porous membrane, The porous membrane is the porous membrane of the present invention. material supply assembly, to provide. [Effects of the Invention]

[0011] According to the present invention, a porous film suitable for attachment to a housing or the like of a device can be provided. [Brief explanation of the drawings]

[0012] [Figure 1A] FIG. 1A is a cross-sectional view schematically showing an example of the porous membrane of the present invention. [Figure 1B] FIG. 1B is a diagram schematically illustrating an example of the surface of the porous membrane of the present invention. [Figure 2] FIG. 2 is a cross-sectional view that schematically shows an example of the ventilation member of the present invention. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a first modification of the ventilation member of FIG. [Figure 4] FIG. 4 is a cross-sectional view that schematically shows a second modified example (wound body) of the ventilation member of FIG. [Figure 5] FIG. 5 is a cross-sectional view schematically showing an example of the filter member of the present invention. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a first modification of the filter member 4 of FIG. [Figure 7] FIG. 7 is a cross-sectional view schematically showing a second modification of the filter member 4 of FIG. [Figure 8] FIG. 8 is a cross-sectional view schematically showing a third modification of the filter member 4 of FIG. [Figure 9] FIG. 9 is a cross-sectional view schematically showing an example of a member supply assembly of the present invention. [Figure 10] FIG. 10 is a diagram (2500x magnification) showing the results of observing the surface of the porous membrane of Example 1 with a scanning electron microscope (SEM). [Figure 11] FIG. 11 is a diagram (2500x magnification) showing the results of observing the surface of the porous film of Example 2 with an SEM. [Figure 12A] FIG. 12A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the porous membrane of Example 3. [Figure 12B] FIG. 12B is a partial enlargement (10,000 times) of FIG. 12A. [Figure 12C] FIG. 12C is a diagram (1500x magnification) showing the results of SEM observation of the cross section of the porous membrane of Example 3. [Figure 13] FIG. 13 is a photograph (2500x magnification) showing the results of observing the surface of the porous film of Example 4 with an SEM. [Figure 14A]FIG. 14A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the porous membrane of Example 5. [Figure 14B] FIG. 14B is a partial enlargement (10,000 times) of FIG. 14A. [Figure 15A] FIG. 15A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the film of Comparative Example 1. [Figure 15B] FIG. 15B is a partial enlargement (10,000 times) of FIG. 15A. [Figure 15C] FIG. 15C is a diagram (2000x magnification) showing the results of SEM observation of the cross section of the film of Comparative Example 1. [Figure 16] FIG. 16 is a diagram (2500x magnification) showing the results of observing the surface of the film of Comparative Example 2 with an SEM. [Figure 17] FIG. 17 is a diagram (2500x magnification) showing the results of observing the surface of the film of Comparative Example 3 with an SEM. [Figure 18A] FIG. 18A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the film of Reference Example 2. [Figure 18B] FIG. 18B is a partial enlargement (20,000 times) of FIG. 18A. [Figure 19] FIG. 19 is a graph showing the results of measuring the actual film temperatures from after hot pressing to cooling with a thermocouple at intervals of 100 ms for Example 1, Examples 6 and 7, and Comparative Example 4. [Figure 20] FIG. 20 is a schematic diagram for explaining how to determine the distance between the island regions of the porous film of FIG. [Figure 21] FIG. 21 is a schematic cross-sectional view for explaining the compression test. DETAILED DESCRIPTION OF THE INVENTION

[0013] The porous membrane according to the first aspect of the present invention comprises: A porous film containing, as a main component, a thermoplastic resin having a melting point of 180°C or more and 300°C or less, The porous membrane has a tortoiseshell structure formed by a plurality of nodes and a plurality of fibrils.

[0014] In the second aspect of the present invention, for example, the porous membrane according to the first aspect has a resistance of 2.5 N / mm 2 When a pressure of 1000 kJ / cm is applied, the compressibility of the porous membrane in the thickness direction is 20% or less.

[0015] The porous membrane according to the third aspect of the present invention is A porous film containing, as a main component, a thermoplastic resin having a melting point of 180°C or more and 300°C or less, 2.5N / mm 2 When a pressure of 1000 kJ / cm is applied, the compressibility of the porous membrane in the thickness direction is 20% or less.

[0016] In a fourth aspect of the present invention, for example, in the porous membrane according to any one of the first to third aspects, the thermoplastic resin comprises a polymethylpentene resin.

[0017] In a fifth aspect of the present invention, for example, in the porous film according to any one of the first to fourth aspects, when a cross section of the porous film is observed, a plurality of the nodes are included along the thickness direction.

[0018] In a sixth aspect of the present invention, for example, the porous membrane according to any one of the first to fifth aspects has an air permeability expressed in Gurley number of 1000 seconds / 100 mL or less.

[0019] In a seventh aspect of the present invention, for example, in the porous film according to any one of the first to sixth aspects, the porosity of the porous film is 25% or more.

[0020] A filter member according to an eighth aspect of the present invention comprises: A porous membrane according to any one of the first to seventh aspects; and a pressure-sensitive adhesive layer bonded to the porous film.

[0021] A member supply assembly according to a ninth aspect of the present invention comprises: A member supply assembly including: a filter member to be placed on a surface of an object having an opening; and a base sheet having the filter member placed on a surface thereof, The filter member is a porous membrane having a shape that covers the opening when placed on the surface; a pressure-sensitive adhesive layer bonded to the porous membrane, The porous membrane is a porous membrane according to any one of the first to seventh aspects.

[0022] 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.

[0023] [Porous membrane] An example of a porous membrane of the present invention is shown in FIG. 1A. The porous membrane 1 in FIG. 1A contains, as a main component, a thermoplastic resin having a melting point of 180°C or higher and 300°C or lower. The "main component" refers to the component that is contained in the porous membrane in the largest amount by weight. With this configuration, the porous membrane 1 can be adhered to a device housing or the like, for example, not only by using an adhesive layer but also by heat fusion.

[0024] FIG. 1B is a schematic diagram showing an example of the surface of a porous membrane 1. The porous membrane 1 has a tortoiseshell structure formed by multiple nodes 1a and multiple fibrils 1b. As shown in FIG. 1B, the tortoiseshell structure is present throughout the porous membrane 1. This structure can prevent the porous membrane 1 from being compressed when attached to a device housing or the like, thereby ensuring appropriate attachment pressure. The tortoiseshell structure can be confirmed, for example, by observing the main surface of the porous membrane 1 from a vertical direction. In this disclosure, the term "main surface" refers to the surface of a sheet-like or film-like member having the largest area. In this disclosure, the terms "main surface" and "surface" of the porous membrane 1 are used interchangeably.

[0025] In the present disclosure, the term "hexagonal structure formed by multiple nodes 1a and multiple fibrils 1b" refers to a structure that can be confirmed by observing the surface of the porous membrane 1 with a scanning electron microscope (SEM). The island regions 1c formed by multiple nodes 1a are irregularly connected, and these island regions 1c are connected to each other by multiple fibrils 1b. Examples of island regions 1c include polygonal regions. The polygonal region does not necessarily have to have an outer shape composed of only straight lines, and also includes approximately polygonal regions in which some sides are curved, such as arcs. The polygon is, for example, a hexagon, but is not limited thereto and may be, for example, a pentagon or a rectangle. The hexagonal structure may include multiple island regions 1c and multiple fibrils 1b extending from each island region 1c in multiple directions. The island regions 1c may be connected to each other or overlap without the intervention of multiple fibrils 1b (see part I in Figure 1B). That is, there may not be multiple fibrils 1b between adjacent island regions 1c. Island regions 1c, which are aggregates of multiple nodes 1a, may be present together with nodes 1a (see part II in Figure 1B). Planar regions 1d may be present, formed by the dense collection of multiple fibrils 1b extending in multiple directions from each island region 1c (see part III in Figure 1B). When the surface of the porous membrane 1 is observed by SEM, it may not be clear at first glance whether the planar region 1d formed by the dense collection of multiple fibrils 1b is different from the island regions 1c formed by multiple nodes 1a. However, even in such cases, it is possible to distinguish between the island regions 1c and the planar region 1d by magnifying the observation image, for example, up to about 10,000 times. The island regions 1c may have a shape that is higher than the planar region 1d. When the surface of the porous membrane 1 is observed by SEM, the longest diameter of the island regions 1c may be 0.5 μm or more, 1 μm or more, or even 2 μm or more.

[0026] In this disclosure, the term "tortoiseshell-like" is a term that focuses on the island-like regions 1c and describes how the island-like regions 1c are irregularly arranged like a turtle shell, but does not necessarily mean that the island-like regions 1c are densely arranged like a turtle shell.

[0027] The average spacing between adjacent island regions 1c is, for example, 0.1 μm or more and 30 μm or less. The lower limit of the average spacing between island regions 1c may be 0.5 μm or more, 1 μm or more, 2 μm or more, or even 4 μm or more. The upper limit of the average spacing between island regions 1c may be 20 μm or less, 15 μm or less, 10 μm or less, or even 8 μm or less.

[0028] The average area of ​​the island regions 1c is, for example, 0.1 μm 2 More than 100μm 2 The lower limit of the average area of ​​the island regions 1c is 0.5 μm 2 It may be more than 1 μm 2 May be more than 5 μm 2 It may be more than 10 μm 2 It may be 14 μm or more, 2 The upper limit of the average area of ​​the island regions 1c is 75 μm 2 May be less than 65 μm 2 May be less than 55 μm 2 It may be less than 50 μm 2 It may be the following:

[0029] The average spacing between island regions of the porous membrane 1 can be determined by the method described below. Figure 20 is a schematic diagram illustrating how to determine the distance between island regions of the porous membrane 1 of Figure 1A. First, the surface of the porous membrane 1 is observed with an SEM (see, for example, Figure 1B). Next, the obtained SEM observation image (or a part thereof) is binarized using image analysis software. Island regions are identified from the obtained binarized image, and the area of ​​each island region contained in the image is calculated. For each island region, the circle equivalent diameter is calculated from the calculated area. The circle equivalent diameter is the diameter of a perfect circle having the same area as the area of ​​the island region being measured. As shown in Figure 20, the distance L between island regions A and B is AB can be calculated as the distance between the center of gravity c of island region A and the center of gravity c of island region B minus the circle equivalent diameter x 1 / 2 of island region A and the circle equivalent diameter x 1 / 2 of island region B. In this way, the distance between the island regions (L AB , L AC and L AD ) is calculated. That is, the distance between island region A and the fourth or subsequent island region (island region E) is calculated. AE ) is not used. However, the island region (island region F) that overlaps with island region A in the image is excluded from the three island regions that are first to third closest to island region A. The average of the distances between the island regions and the three island regions closest to island region A obtained in this way is considered to be the distance between island regions of island region A. The distance between island regions is obtained in the same manner for each island region included in the image. The average of the obtained distances between island regions can be considered to be the average spacing between island regions of the porous membrane 1. When identifying island regions, island regions that fall on the edges of the image are excluded from the analysis. As image analysis software, for example, ImageJ can be used.

[0030] The average area of ​​the island regions of the porous membrane 1 can be determined by the method described below. First, a binarized image is obtained using the same method as that described for the distance between island regions of the porous membrane 1, and nodes are identified from the binarized image. Island regions are identified from the obtained binarized image, and the area of ​​each island region contained in the image is calculated. The average value of the determined island region areas can be considered the average area of ​​the island regions of the porous membrane 1. However, the average area of ​​the island regions of the porous membrane 1 should be determined by measuring 30 or more island regions, for example, 50 to 200 island regions.

[0031] 10 to 12B and 13 to 14B are diagrams showing the results of SEM observation of the surfaces of the porous membranes of Examples 1 to 5 described below. As shown in these observation images, the surfaces of the porous membranes of Examples 1 to 5 have a hexagonal structure formed by a plurality of nodes and a plurality of fibrils. Specifically, island-like regions 1c formed by a plurality of nodes 1a are irregularly connected, and these island-like regions 1c are connected to each other by a plurality of fibrils 1b.

[0032] When observing a cross section of the porous membrane 1, a plurality of nodes may be included along the thickness direction. The plurality of nodes may be present throughout the entire thickness direction of the porous membrane 1. With such a structure, a reduction in the thickness of the membrane due to compression when attached to a device housing or the like can be suppressed.

[0033] The nodes present in the thickness direction may be lumpy. That is, when a cross section of the porous membrane 1 is observed, multiple lumpy nodes may be present along the thickness direction. The lumpy nodes present in the thickness direction correspond to island regions when the surface of the porous membrane 1 is observed with an SEM.

[0034] The multiple agglomerated nodes may be uniformly present across the thickness direction of the porous membrane 1. Adjacent agglomerated nodes may be connected by multiple fibrils, or adjacent agglomerated nodes may be directly linked to each other without being connected by multiple fibrils.

[0035] 12C shows the results of SEM observation of the cross section of the porous membrane of Example 3, which will be described later. As shown in FIG. 12C, when the cross section of the porous membrane of Example 3 is observed, multiple cluster nodes are present along the thickness direction. The multiple cluster nodes are present throughout the entire thickness direction of the porous membrane.

[0036] The porous membrane 1 has a resistance of 2.5 N / mm 2 The compressibility Rc of the porous membrane 1 in the thickness direction when a pressure of 1000 kJ / cm is applied is 20% or less. The compressibility Rc is a value per unit amount of resin. In this way, the porous membrane 1 is prevented from reducing in thickness due to compression when attached to a device housing or the like, so that an appropriate attachment pressure can be ensured.

[0037] The compressibility Rc can be determined by a compression test using a thermomechanical analyzer (TMA). Fig. 21 is a schematic cross-sectional view for explaining the compression test. First, the porous membrane 1 is cut into a strip of 10 mm in width and 10 mm in length to form a sample piece S. Next, in an environment of 25°C, a cylindrical indenter 90 of the TMA with a tip diameter of 1 mm is used to gradually apply a load from an initial load P1 (gf) (see Fig. 21(A)) to a maximum load P max (gf) (see FIG. 21(B)), the sample piece S was compressed at a loading rate of 50 gf / min while applying a load P n The function F1 of the load (gf) and the deformation rate (%) in the compression direction is obtained. n The deformation rate (%) at (gf) is the load P1 (gf) relative to the thickness T1 (μm) of the sample piece S. n (gf) Thickness T of sample piece S n (μm), and 100×T n Next, the function F1 is calculated by the area of ​​the indenter 90 (0.785 mm 2 ) to calculate the load per unit area Pa (gf / mm 2 ) and deformation rate (%) to convert it into a function F2 (load Pa (gf / mm 2 ) = load P n (gf) / 102 / indenter 90 area (mm2 )) Furthermore, taking into consideration the pores present in the porous membrane 1, the function F2 is converted to a value per unit resin amount, and the load Pb (gf / mm 2 ) to obtain the function F3 of the deformation rate (%) at the load Pb (gf / mm 2 ) = Load Pa (gf / mm 2 ) / {(100-porosity) / 100}). In function F3, the load Pb is 2.5 gf / mm 2 The deformation rate (%) at time is the rate of change R 2.5 When defined as 100-R 2.5 The value obtained by the above is regarded as the compression ratio Rc (%). The measurement conditions for the above compression test are as follows: <Measurement conditions> Initial load P1: 2gf Maximum load P max :500gf Loading rate: 50gf / min

[0038] The compression ratio Rc may be 19.5% or less, or may be 19% or less. The lower limit of the compression ratio Rc is, for example, 5%.

[0039] As described above, the melting point of the thermoplastic resin contained in the porous membrane 1 is 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 membrane 1. When the melting point of the thermoplastic resin is 300°C or lower, the porous membrane 1 can be produced by melt molding, for example.

[0040] The melting point of the thermoplastic resin may be 200°C or higher and 280°C or lower, or may be 220°C or higher and 260°C or lower.

[0041] The thermoplastic resin having a melting point of 180°C or higher and 300°C or lower may be a fluorine-free thermoplastic resin. The fluorine-free thermoplastic resin may be a polyolefin resin. Polyolefin resins include polyethylene (PE) resin, polypropylene (PP) resin, and polymethylpentene (PMP) resin.

[0042] Examples of thermoplastic resins include polymethylpentene resins such as poly(4-methylpentene-1) resin (polymethylpentene resin) and poly(3-methylbutene-1) resin; polyethylene terephthalate resin; polybutylene terephthalate resin; polyethylene naphthalate resin; polyacetal resin; polyphenylene sulfide resin; polyether ether ketone resin; syndiotactic polystyrene resin; ethylene-carbon monoxide copolymer resin; polyamide resins such as nylon 6 resin and nylon 66 resin; cycloolefin polymer (COP) resin; polyphenylene ether (PPE) resin; polyetherimide (PEI) resin; polyphenylene oxide (PPO) resin, etc.

[0043] The thermoplastic resin may be a polymethylpentene resin. The polymethylpentene resin is a homopolymer or copolymer such as poly(4-methylpentene-1) resin and 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. The polymethylpentene resin has a melting point of 230°C to 240°C. Therefore, this configuration makes it easy to obtain a porous film suitable for suppressing thickness reduction due to compression when attached to a device housing, etc.

[0044] The thermoplastic resin may be 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 180°C or higher.

[0045] The porous film 1 may contain additives such as a plasticizer and an antioxidant in addition to the thermoplastic resin.

[0046] The air permeability in the thickness direction of the porous membrane 1, expressed as a Gurley number, may be 0.1 / 100 mL or more and 10,000 seconds / 100 mL or less. In this specification, the "Gurley number" refers to the air resistance (Gurley air permeability) measured in accordance with the Oken testing method specified in JIS P8117:2009. The lower limit of the air permeability of the porous membrane 1, expressed as a Gurley number, may be 10 seconds / 100 mL or more, 30 seconds / 100 mL or more, 50 seconds / 100 mL or more, or even 70 seconds / 100 mL or more. The upper limit of the air permeability of the porous membrane 1, expressed as a Gurley number, may be 5,000 seconds / 100 mL or less, 1,000 seconds / 100 mL or less, or even 500 seconds / 100 mL or less.

[0047] Furthermore, even if the size of the porous membrane 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.

[0048] 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 thick and made of a material that will not deform due to the differential pressure applied to the test piece during air permeability resistance measurement. An example of a measurement jig is a 2 mm thick, 47 mm diameter stainless steel disk. A through-hole with an opening smaller than the membrane to be evaluated is provided in the center 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 porous membrane 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 membrane 1 to be evaluated (the portion overlapping with the opening when viewed perpendicular to the main surface of the fixed porous membrane 1), and the fixed portion does not obstruct air passage through the effective test portion of the porous membrane 1. To fix the porous membrane 1, double-sided adhesive tape with a vent hole punched in the center, whose shape matches the shape of the opening, can be used. The double-sided adhesive tape can be placed between the measurement jig and the porous membrane 1 so that the periphery of the vent hole matches the periphery of the opening. Next, the measurement jig with the porous membrane 1 fixed is set in the air permeability measurement section of the Oken tester so that the fixed surface of the porous membrane 1 is downstream of the air flow during measurement, and a test is performed using the Oken tester method, and the air permeability resistance reading t indicated by the tester is recorded. Next, the recorded air permeability resistance reading 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 part of the porous membrane 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 membrane 1 measured in accordance with the Oken Tester Method. It has been confirmed that the air resistance measured without using a measuring jig for a porous membrane 1 that meets the recommended dimensions (50 mm × 50 mm) of a test piece for the Oken Tester Method closely matches the air resistance measured using a measuring jig after cutting the porous membrane 1 into small pieces, i.e., that the use of a measuring jig does not substantially affect the measured value of air resistance.

[0049] The water pressure resistance of the porous membrane 1 may be 10 kPa or more, as evaluated by water resistance test method B (high water pressure method) specified in JIS L1092:2009. The lower limit of the water pressure resistance of the porous membrane 1 may be 100 kPa or more, 130 kPa or more, or even 150 kPa or more. The upper limit of the water pressure resistance of the porous membrane 1 is, for example, 2000 kPa or less.

[0050] The water pressure resistance of the porous membrane 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 stainless steel (SUS) disk with a diameter of 47 mm and a through-hole (with a circular cross section) with a diameter of 2.0 mm at the center. This disk has a thickness that does not deform due to the water pressure applied when measuring the water pressure. Measurement of the water pressure resistance using this measuring jig can be carried out as follows.

[0051] The porous membrane 1 to be evaluated is fixed to one side of the measurement jig so as to cover the opening of the through-hole. The porous membrane 1 is fixed to prevent water leakage from the fixed part of the membrane during water pressure measurement. Double-sided adhesive tape with a water passage hole punched in the center, whose shape matches the opening, can be used to fix the porous membrane 1. The double-sided adhesive tape is simply placed between the measurement jig and the porous membrane 1 so that the circumference of the water passage hole coincides with the circumference of the opening. Next, the measurement jig with the porous membrane 1 fixed is set in the testing device so that the surface opposite the fixed surface of the porous membrane 1 becomes the surface to which water pressure is applied during measurement. The water pressure resistance is measured according to Water Resistance Test Method B (high water pressure method) specified in JIS L1092:2009. However, the water pressure resistance is measured based on the water pressure when water leaks from one point on the membrane surface of the porous membrane 1. The measured water pressure resistance can be used as the water pressure resistance of the porous membrane 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 to which the above-mentioned measuring jig can be set.

[0052] The porosity of the porous membrane 1 is, for example, 25% or more. The porosity of the porous membrane 1 may be 20% or more, or 35% or more. The porosity can be calculated by substituting the mass, thickness, area (area of ​​the main surface) and true density of the porous membrane 1 into the following formula (1).

[0053] Porosity (%) = {1 - (mass [g] / (thickness [cm] × area [cm 2 ] × true density [g / cm 3 ]))}×100...Equation (1)

[0054] The upper limit of the porosity of the porous membrane 1 is, for example, 95%. The upper limit of the porosity of the porous membrane 1 may be 90%.

[0055] The porous membrane 1 may be in the form of a sheet or a film. The thickness of the porous membrane 1 is, for example, 1 μm or more and 100 μm or less. Such a structure makes it easy to suppress a decrease in the thickness of the membrane due to compression when it is attached to a device housing or the like. The thickness of the porous membrane 1 may be 5 μm or more and 80 μm or less, or 10 μm or more and 70 μm or less.

[0056] The thickness of the porous membrane 1 can be determined by measuring the thickness at any five points on the porous membrane 1 using, for example, a dial gauge, and calculating the average value of these measured values. The thickness of the porous membrane 1 can also be determined by measuring the thickness at any five points on an SEM observation image of the cross section of the porous membrane 1 and calculating the average value of these measured values.

[0057] At least one of the main surfaces of the porous membrane 1 may be subjected to a surface modification treatment. Examples of the surface modification treatment include chemical treatment, sputter etching treatment, liquid repellent treatment, and plasma treatment. In the area subjected to the surface modification treatment, the bonding property of the porous membrane 1 is improved.

[0058] [Method of manufacturing porous membrane] The porous membrane 1 described above can be produced, for example, by the following method.

[0059] The method for producing the porous membrane 1 includes kneading a composition containing a thermoplastic resin having a melting point of 180°C or more and 300°C or less 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 sheet body (step S4), and extracting and removing the plasticizer from the sheet body (step S5).

[0060] 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.

[0061] Step S1 is carried out, for example, at a temperature of 230° C. to 260° C. for 5 to 30 minutes.

[0062] As the thermoplastic resin having a melting point of 180° C. or more and 300° C. or less, a polymethylpentene resin can be used.

[0063] The composition containing a thermoplastic resin and a 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 membrane 1 are not affected.

[0064] A 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 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 of 50 to 150 mm at 40°C. 2 / s can be used.

[0065] The mixing ratio of the thermoplastic resin and the plasticizer is set so that a uniform mixture 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 wt% to 80 wt%, and preferably 30 wt% to 70 wt%. When the weight ratio of the thermoplastic resin is 20 wt% or more, excessive reduction in viscosity of the composition can be avoided. When the weight ratio of the thermoplastic resin is 80 wt% or less, a good porous structure can be easily obtained.

[0066] 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.

[0067] Step S2 is carried out for 2 to 30 minutes at a temperature of, for example, 230 to 260° C. The thickness of the pressed body obtained by step S2 is, for example, 0.1 mm.

[0068] In step S3, the pressed body obtained in step S2 may be solidified by being cooled to a temperature sufficiently lower than the crystallization temperature of the thermoplastic resin, for example, by contacting it with a thermal conductor. Examples of thermal conductors used for cooling include water, air, plasticizers, and metals. The thermal conductor used for cooling is preferably water.

[0069] 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. Pores are generated in the molded body by step S4.

[0070] 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.

[0071] 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.

[0072] The strain rate during stretching may be 1% / sec to 10% / sec in the machine direction and / or the transverse direction, or 2% / sec to 8% / sec, or even 3% / sec to 5% / sec. When the strain rate is within the above range, breakage is less likely to occur during stretching, further improving productivity. By having the strain rate within the above range, it is possible to stretch the film at a strain rate of 2.5 N / mm 2 It is easy to realize a porous film having a compressibility Rc of 20% or less in the thickness direction when a pressure of 1000 kJ / cm is applied.

[0073] In step S5, the plasticizer is extracted and removed from the sheet using, for example, an extraction solvent.

[0074] 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 membrane. 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, alcohols and ketones are preferably used. Methyl ethyl ketone (MEK) may also be used as the extraction solvent.

[0075] Between step S4 and step S5, the sheet may be heat-set. Heat-set can be performed, for example, using a hot air circulating oven. Heat-set can reduce the thermal shrinkage of the stretched sheet. 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.

[0076] Heat setting may be performed after step S4, between steps S4 and S5, or both after steps S4 and S5. Examples of heat setting methods 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.

[0077] [Ventilation material] An example of a ventilation member of the present invention is shown in Figure 2. The ventilation member 2 (2A) in Figure 2 comprises a porous membrane 1. A first modified example of the ventilation member of Figure 2 is shown in Figure 3. The ventilation member 2 (2B) in Figure 3 further comprises an air-permeable support material 3. The air-permeable support material 3 is laminated on the porous membrane 1. The air-permeable support material 3 can improve the strength and handleability of the ventilation member 2.

[0078] The breathable support material 3 usually has higher breathability in the thickness direction than the porous membrane 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 may be the same as or different from the shape of the porous membrane 1 when viewed perpendicularly to the main surface of the ventilation member 2. The breathable support material 3 may have a shape corresponding to the peripheral edge of the porous membrane 1 when viewed perpendicularly to the main surface of the ventilation member 2. When the shape of the porous membrane 1 is circular, the shape is ring-shaped. The configuration and shape of the breathable support material 3 are not limited to the above examples.

[0079] The ventilation member 2B in Fig. 3 includes one breathable support material 3 arranged on one side of the porous membrane 1. The ventilation member 2 may include two or more breathable support materials 3. In the ventilation member 2, breathable support materials 3 may be arranged on both sides of the porous membrane 1. The porous membrane 1 and the breathable support material 3 may be joined by welding such as thermal welding or ultrasonic welding, an adhesive, or a pressure-sensitive adhesive.

[0080] The ventilation member 2 may include any layers and / or members other than those described above.

[0081] The thickness of the ventilation member 2 is, for example, 1 to 300 μm, and may be 50 to 200 μm.

[0082] The weight of the ventilation member 2 is, for example, 1.0 to 200.0 g / m 2 and 10.0 to 100.0 g / m 2 may be.

[0083] The ventilation member 2 can have the same properties as the porous membrane 1, such as air permeability in the thickness direction and / or water pressure resistance.

[0084] The ventilation member 2 may be subjected to a liquid-repellent treatment and / or a coloring treatment.

[0085] The ventilation member 2 can be used as, for example, a filter member, but the uses of the ventilation member 2 are not limited to the above examples.

[0086] The shape of the ventilation member 2, when viewed perpendicularly to the main surface of the ventilation 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 ventilation member 2 is not limited to the above examples. The strip-shaped ventilation member 2 may be wound to form a wound body. Furthermore, if necessary, it may be wound in a state where it is laminated with a release liner.

[0087] FIG. 4 shows a second modified example (roll) of the ventilation member of FIG. 2. The roll 10 shown in FIG. 4 includes the ventilation member 2A and release liner 11 of FIG. 2. The ventilation member 2A and release liner 11 are bonded to each other by a pressure-sensitive adhesive layer 12. In the roll 10, a release surface 13 formed when the release liner 11 is peeled from the ventilation member 2A is located between the ventilation member 2A and the pressure-sensitive adhesive layer 12. That is, in the roll 10, when the release liner 11 is peeled off, the pressure-sensitive adhesive layer 12 is also peeled off from the ventilation member 2A, resulting in a ventilation member 2A that does not have the pressure-sensitive adhesive layer 12 formed on its surface.

[0088] The ventilation member 2A supplied by the roll 10 and having no adhesive layer 12 formed on its surface can be joined to the opening of the housing by any joining method. That is, the ventilation member 2A has a high degree of freedom in the method of joining to the opening of the housing. Joining methods include, for example, joining by an adhesive layer newly placed on the surface of the ventilation member 2A, joining by thermal welding, and joining by ultrasonic welding.

[0089] The ventilation member 2A supplied by the wound body 10 can be processed into any shape as needed. That is, the ventilation member 2A has a high degree of freedom in terms of shape. However, "shape" also includes "size." The above means that the wound body 10 allows the ventilation member 2A that 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.

[0090] Furthermore, with the wound body 10, misalignment between the ventilation member 2A and the release liner 11 during winding is suppressed by the pressure-sensitive adhesive layer 12. With the wound body 10, the occurrence of malfunctions (abnormal shape of the wound body) due to tightness during winding or the like can be suppressed.

[0091] [Filter material] An example of a filter member of the present invention is shown in Fig. 5. The filter member 4 (4A) in Fig. 5 has the above-described ventilation member 2 as a ventilation member that is breathable in the thickness direction and prevents the passage of foreign matter in that direction. The filter member 4A is a member that is placed, for example, on the surface of an object having an opening, to ensure ventilation through the opening while preventing the passage of foreign matter through the opening. In this case, the filter member 4A is usually placed so that the ventilation member 2 covers the opening of the object.

[0092] The filter member 4A includes an adhesive layer 5 disposed on one side of the ventilation member 2. The ventilation member 2 and the adhesive layer 5 are directly bonded together. The filter member 4A can be placed on the surface of an object via the adhesive layer 5.

[0093] When handling the filter member 4 or placing it on an object, a strong force may be applied to the filter member 4 in a specific direction. However, the ventilation member 2 has a tortoiseshell structure formed by multiple nodes and multiple fibrils, and is equipped with a porous membrane 1 that can suppress a decrease in membrane thickness due to compression. Therefore, for example, the filter member 4 can be manufactured without limiting the direction in which the ventilation member 2 (or porous membrane 1) is assembled into the filter member 4.

[0094] Examples of adhesives constituting the adhesive layer 5 include acrylic adhesives, silicone adhesives, urethane adhesives, epoxy adhesives, and rubber adhesives. When it is necessary to consider using the filter 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.

[0095] The outer periphery of the ventilation member 2 and the outer periphery of the pressure-sensitive adhesive layer 5 are coincident when viewed perpendicularly to the main surface of the ventilation member 2. The shape of the pressure-sensitive adhesive layer 5 corresponds to the peripheral edge of the ventilation member 2 when viewed perpendicularly to the main surface of the ventilation member 2. The region of the ventilation member 2 to which the pressure-sensitive adhesive layer 5 is not bonded can be used as the ventilation region of the filter member 4A. However, the shape of the pressure-sensitive adhesive layer 5 is not limited to the above example.

[0096] The area of ​​the ventilation area is, for example, 40 mm 2 The filter member 4 having an area of ​​the ventilation region within this range is suitable for placement in an object having a small diameter opening, for example. The lower limit of the area of ​​the ventilation region is, for example, 0.008 mm 2 However, the area of ​​the ventilation region may be larger depending on the type of object on which the filter member 4 is placed.

[0097] Fig. 6 shows a first modified example of the filter member 4 in Fig. 5. The filter member 4 (4B) in Fig. 6 further includes a base material layer 6 disposed on one side of the ventilation member 2, and has the same configuration as the filter member 4A, except that the ventilation member 2 and the pressure-sensitive adhesive layer 5 are joined via the base material layer 6. The base material layer 6 can improve the strength and handleability of the filter member 4, and can prevent damage to the ventilation member 2 during handling or placement on an object.

[0098] Examples of materials constituting the base 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 layer 6 are not limited to the above examples.

[0099] The outer periphery of the ventilation member 2 and the outer periphery of the base material layer 6 are coincident when viewed perpendicularly to the main surface of the ventilation member 2. The shape of the base material layer 6 corresponds to the peripheral edge of the ventilation member 2 when viewed perpendicularly to the main surface of the ventilation member 2. The region of the ventilation member 2 to which the base material layer 6 is not joined can be used as the ventilation region of the filter member 4B. However, the shape of the base material layer 6 is not limited to the above example.

[0100] The ventilation member 2 and the base layer 6 may be joined with an adhesive or a bonding agent, or may be joined by welding such as thermal welding or ultrasonic welding. The ventilation member 2 and the base layer 6 may be joined with an adhesive layer. The adhesive layer may have the same structure as the adhesive layer 5. The base layer 6 and the adhesive layer 5 may be the base and adhesive layer of a single-sided adhesive tape or a double-sided adhesive tape, respectively.

[0101] FIG. 7 shows a second modification of the filter member 4 in FIG. 5. The filter member 4 (4C) in FIG. 7 has the same configuration as the filter member 4B, except that it further includes a base material layer 6 (6B) arranged on the other surface of the ventilation member 2. The ventilation member 2 is sandwiched between the pair of base material layers 6 (6A, 6B). This sandwiching structure can further improve the strength and handleability of the filter member 4.

[0102] FIG. 8 shows a third variation of the filter member 4 in FIG. 5. The filter member 4 (4D) in FIG. 8 further includes a tab film 7, and has the same configuration as the filter member 4C, except that the base layer 6 (6B) and the tab film 7 are bonded via an adhesive layer 5 (5B). The tab film 7 has a tab that protrudes outward beyond the outer periphery of the base layer 6B when viewed perpendicularly to the main surface of the base layer 6B. The filter member 4D can be handled or placed on the surface of an object by grasping the tab. The tab film 7 is typically removed when the filter member 4D is used. The tab film 7 can be made of the same material as the base layer 6. The tab film 7 is typically removed by grasping and lifting the tab. At this time, a strong force is applied to the ventilation member 2 in the lifting direction.

[0103] [Material supply assembly] The filter member 4 can be supplied by, for example, a member supply sheet. Fig. 9 shows an example of a member supply assembly, which is a mode of supplying the filter member 4. The member supply assembly 20 of Fig. 9 includes the filter member 4 to be placed on the surface of an object having an opening, and a base sheet 9 on whose surface the filter member 4 is placed. The member supply assembly 20 shown in Fig. 9 includes a filter member 4D as the filter member 4.

[0104] The filter member 4 (4D) is disposed on the base sheet 9 via the adhesive layer 5. The member supply assembly 20 can efficiently supply the filter member 4, for example, in the step of disposing it on the surface of an object.

[0105] The filter member 4 may be placed on the base sheet 9 via an adhesive layer provided on the surface of the base sheet 9 on which the filter member 4 is to be placed. The adhesive layer on the surface on which the filter member 4 is to be placed is preferably weakly adhesive.

[0106] Although not shown in the drawings, a plurality of filter members 4 may be arranged on the surface of the base sheet 9.

[0107] Examples of materials that make up 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 that make up 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. If the sheet 9 is in the form of a strip, the member supply assembly 20 may be wound to form a wound body.

[0108] Examples of objects on which the filter member 4 is to be placed include the housing of an electronic device and the housing of a vehicle electrical component. The filter member 4 can be placed 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.

[0109] The foreign matter that is prevented from passing through by the arrangement of the filter member 4 is, for example, particles such as dust, and liquid water such as water droplets. [Example]

[0110] 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.

[0111] [Example 1] As a thermoplastic resin, poly(4-methylpentene-1) resin (manufactured by Mitsui Chemicals, Inc., RT18, melting point: 232°C) was prepared. 2 Liquid paraffin (MORESCO) with a viscosity of 1 / s was prepared. Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (BASF Japan) was prepared as an antioxidant. 50.0 wt% of thermoplastic resin, 49.8 wt% of plasticizer, and 0.2 wt% of antioxidant were mixed to obtain a mixture. The mixture was kneaded at 260°C for 30 minutes using a Labo Plastomill (Toyo Seiki Seisakusho) to obtain a uniform kneaded product. The kneaded product was hot-pressed using a compression molding machine heated to 260°C to obtain a pressed body. The pressed body was sandwiched between a pair of polyimide plates and cooled by contacting it with 18°C ​​water to obtain a molded body.

[0112] Next, using a biaxial stretching machine, the molded body was subjected to simultaneous biaxial stretching under the conditions of a stretching temperature of 150°C and a stretching ratio of 2.5 times (longitudinal direction) x 2.5 times (transverse direction). The strain rate during stretching was 4% / sec (2.6 mm / sec) in both the longitudinal and transverse directions. This resulted in a sheet body. Finally, an extraction operation was performed by immersing the sheet body in MEK at room temperature for 2 minutes using methyl ethyl ketone (MEK) as the extraction solvent. This resulted in the extraction and removal of the plasticizer from the sheet body. The extraction operation was performed while the sheet body was fixed to a stainless steel frame to prevent shrinkage. In this way, the porous membrane of Example 1 was obtained.

[0113] FIG. 10 is a photograph (2500x magnification) showing the results of observing the surface of the porous film of Example 1 with an SEM.

[0114] [Example 2] As a plasticizer, it has a kinematic viscosity of 68mm at 40°C. 2 A 1000-kJ / s liquid paraffin (manufactured by MORESCO) was prepared. 70.0 wt% of thermoplastic resin, 29.8 wt% of plasticizer, and 0.2 wt% of antioxidant were mixed to obtain a mixture. The mixture was kneaded using a Labo Plastomill at 230°C for 30 minutes to obtain a uniform kneaded mixture. Except for these factors, the porous membrane of Example 2 was obtained by the same method as Example 1.

[0115] FIG. 11 is a diagram (2500x magnification) showing the results of observing the surface of the porous film of Example 2 with an SEM.

[0116] [Example 3] As a plasticizer, it has a kinematic viscosity of 92mm at 40°C. 2 / s of liquid paraffin (manufactured by MORESCO Corporation) was prepared. Except for these, the porous membrane of Example 3 was obtained in the same manner as in Example 1.

[0117] Fig. 12A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the porous membrane of Example 3. Fig. 12B is a partially enlarged diagram (10000x magnification) of Fig. 12A. Fig. 12C is a diagram (1500x magnification) showing the results of SEM observation of the cross section of the porous membrane of Example 3.

[0118] [Example 4] As a plasticizer, it has a kinematic viscosity of 68mm at 40°C. 2 A 1000-kJ / s liquid paraffin (manufactured by MORESCO) was prepared. A mixture was obtained by mixing 30.0 wt% thermoplastic resin, 69.8 wt% plasticizer, and 0.2 wt% antioxidant. The mixture was kneaded using a Labo Plastomill at 230°C for 30 minutes to obtain a uniform mixture. A biaxial stretching machine was used to perform simultaneous biaxial stretching at a stretching temperature of 150°C and a stretch ratio of 2.0 times (longitudinal direction) × 2.0 times (transverse direction). A porous membrane of Example 4 was obtained by the same method as in Example 1, except for the above.

[0119] FIG. 13 is a photograph (2500x magnification) showing the results of observing the surface of the porous film of Example 4 with an SEM.

[0120] [Example 5] Using a biaxial stretching machine, simultaneous biaxial stretching was carried out under the conditions of a stretching temperature of 150 ° C. and a stretching ratio of 2.0 times (longitudinal direction) × 2.0 times (transverse direction). Except for this, the porous membrane of Example 5 was obtained by the same method as in Example 1.

[0121] Fig. 14A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the porous membrane of Example 5. Fig. 14B is a partially enlarged diagram (10000x magnification) of Fig. 14A.

[0122] [Comparative Example 1] As a thermoplastic resin, poly(4-methylpentene-1) resin (manufactured by Mitsui Chemicals, Inc., MX002, melting point: 224°C) was prepared. 2 Liquid paraffin (MORESCO) with a viscosity of 1 / s was prepared. 30.0 wt% of thermoplastic resin, 69.8 wt% of plasticizer, and 0.2 wt% of antioxidant were mixed to obtain a mixture. The mixture was kneaded using a Labo Plastomill at 230°C for 30 minutes to obtain a uniform mixture. Except for these factors, the membrane of Comparative Example 1 was obtained in the same manner as in Example 1.

[0123] Fig. 15A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the film of Comparative Example 1. Fig. 15B is a partially enlarged diagram (10000x magnification) of Fig. 15A. Fig. 15C is a diagram (2000x magnification) showing the results of SEM observation of the cross section of the film of Comparative Example 1.

[0124] Comparative Example 2 A mixture was obtained by mixing 50.0 wt% of thermoplastic resin, 49.8 wt% of plasticizer, and 0.2 wt% of antioxidant, and the membrane of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except for this.

[0125] FIG. 16 is a diagram (2500x magnification) showing the results of observing the surface of the film of Comparative Example 2 with an SEM.

[0126] Comparative Example 3 A mixture was obtained by mixing 70.0 wt% of thermoplastic resin, 29.8 wt% of plasticizer, and 0.2 wt% of antioxidant, and the membrane of Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except for this.

[0127] FIG. 17 is a diagram (2500x magnification) showing the results of observing the surface of the film of Comparative Example 3 with an SEM.

[0128] Table 1 shows the production conditions for Examples 1 to 5 and Comparative Examples 1 to 3.

[0129] [Table 1]

[0130] Using the methods described above for the porous membranes, the Gurley air permeability, water pressure resistance, etc. were evaluated for the porous membranes of Examples 1 to 5 and the membranes of Comparative Examples 1 to 3. Table 2 shows the evaluation results.

[0131] [Table 2]

[0132] [Example 6] The pressed body was cooled by contacting it with water at 90°C while sandwiched between polyimide plates to obtain a molded body. Except for this, the membrane of Example 6 was obtained in the same manner as in Example 1.

[0133] [Example 7] The pressed body was cooled by contacting it with water at 5°C while sandwiched between polyimide plates to obtain a molded body. Except for this, the membrane of Example 7 was obtained in the same manner as in Example 1.

[0134] Comparative Example 4 The pressed body was cooled by being left to stand at room temperature to obtain a molded body. Except for this, the membrane of Comparative Example 4 was obtained in the same manner as in Example 1.

[0135] Table 3 shows the manufacturing conditions for Examples 6 to 7 and Comparative Example 4, along with the manufacturing conditions for Example 1. Fig. 19 shows the results of measuring the actual film temperatures from hot pressing to cooling with a thermocouple at intervals of 100 ms for Example 1, Examples 6 to 7, and Comparative Example 4.

[0136] Fig. 18A is a diagram (2500x magnification) showing the results of SEM observation of the surface of the film of Comparative Example 4. Fig. 18B is a partially enlarged diagram (20000x magnification) of Fig. 18A.

[0137] [Table 3]

[0138] As can be seen from a comparison of Figures 10 to 12B and 13 to 14B with Figures 15A to 15B and 16 to 17, the porous membranes of Examples 1 to 5 had a hexagonal structure formed by multiple nodes and multiple fibrils. Specifically, in the porous membranes of Examples 1 to 5, island regions formed by multiple nodes were irregularly connected, and these island regions were connected to each other by multiple fibrils. In contrast, the membranes of Comparative Examples 1 to 3 did not have such a hexagonal structure. Because the membranes of Comparative Examples 1 to 3 did not have island regions, it was not possible to determine the average spacing between the island regions and the average area of ​​the island regions.

[0139] The porous membranes of Examples 1 to 5 contained multiple island regions and multiple fibrils extending in multiple directions from each island region. It was also confirmed that the island regions were connected to each other or overlapped without the intervention of multiple fibrils (see, for example, Figure 14B). Some porous membranes contained a mixture of island regions, which were aggregates of multiple nodes, and nodes (see, for example, Figure 12B). Some porous membranes contained planar regions formed by the dense accumulation of multiple fibrils extending in multiple directions from each island region (see, for example, Figures 10 and 11).

[0140] On the other hand, the membranes of Comparative Examples 1 to 3 exhibited a structure that does not have clear nodes and fibrils, and is called a cell structure.

[0141] The reason why a hexagonal structure was formed in the porous membranes of Examples 1 to 5, while a hexagonal structure was not formed in the membranes of Comparative Examples 1 to 3, is presumed to be as follows: The thermoplastic resin (RT18) used in Examples 1 to 5 and the thermoplastic resin (MX002) used in Comparative Examples 1 to 3 contain ethylene units as polymer chain units. MX002 is known to contain more ethylene units than RT18. Due to the difference in ethylene unit content, the compatibility between the thermoplastic resin and the plasticizer and the temperature range at which the thermoplastic resin precipitates as a solid phase differ between Examples 1 to 5 and Comparative Examples 1 to 3, and it is believed that these differences caused differences in the structure after phase separation. As a result, a hexagonal structure was ultimately obtained in Examples 1 to 5, while a cell structure without a hexagonal structure was obtained in Comparative Examples 1 to 3.

[0142] Furthermore, among Examples 6 to 7 and Comparative Example 4, in which the same RT18 as in Example 1 was used as the thermoplastic resin but the cooling conditions were changed, the tortoiseshell structure was confirmed in Examples 6 and 7, just like in Example 1 (not shown). On the other hand, in Comparative Example 4, in which air cooling was performed, the tortoiseshell structure was not confirmed (see Figures 18A and 18B). As shown in Figure 19, in Comparative Example 4, the cooling rate of the thermoplastic resin was relatively slow, which is thought to have greatly promoted crystal growth and phase separation, preventing the tortoiseshell structure from being formed. From these results, it is thought that the cooling conditions also affect the formation of the tortoiseshell structure.

[0143] 12C and 15C, multiple clustered nodes were uniformly present throughout the thickness of the porous membrane of Example 3. In contrast, such structures were not observed in the membrane of Comparative Example 1.

[0144] As shown in Table 2, the porous membranes of Examples 1 to 5 had a resistance of 2.5 N / mm 2 In contrast, the films of Comparative Examples 1 to 3 exhibited compressibility Rc of 21.4% to 42.5%.

[0145] From these results, it can be seen that the porous films of Examples 1 to 5 can suppress a decrease in film thickness caused by compression when attached to a device housing or the like. [Industrial Applicability]

[0146] 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, as a main component, a thermoplastic resin having a melting point of 180°C or more and 300°C or less, The porous membrane has a tortoiseshell structure formed by a plurality of nodes and a plurality of fibrils, The thermoplastic resin includes a polymethylpentene resin. Porous membrane.

2. 2.5 N / mm 2 The compressibility of the porous membrane in the thickness direction when a pressure of 20% or less is applied to the porous membrane. The porous membrane of claim 1.

3. When a cross section of the porous film is observed, a plurality of the nodes are included along the thickness direction. The porous membrane of claim 1.

4. The air permeability is expressed as a Gurley number of 1000 seconds / 100 mL or less. The porous membrane of claim 1.

5. The porosity of the porous film is 25% or more. The porous membrane of claim 1.

6. The porous membrane according to any one of claims 1 to 5, A pressure-sensitive adhesive layer bonded to the porous film, Filter material.

7. A member supply assembly including: a filter member to be placed on a surface of an object having an opening; and a base sheet having the filter member placed on a surface thereof, The filter member is a porous membrane having a shape that covers the opening when placed on the surface; a pressure-sensitive adhesive layer bonded to the porous membrane, The porous membrane is the porous membrane according to any one of claims 1 to 5. Material supply assembly.

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