JP2016066895A - Waterproof sound passing membrane, and waterproof sound passing member, electronic apparatus, electronic apparatus case and waterproof sound passing structure including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waterproof sound passing membrane having a higher degree of freedom for controlling sound passing ability and waterproofness than the conventional ones, for example, capable of achieving both sound passing ability and waterproofness at a higher level.SOLUTION: A waterproof sound passing membrane comprises a polymer film having through holes extending from one main surface to the other main surface. In the waterproof sound passing membrane, each through hole is a straight hole in which the central axis of the through hole extends linearly, has a shape in which an area of a cross section that is perpendicular in a direction where the central axis extends increases from the one main surface of the polymer film toward the other main surface, the opening diameter (a) of the through hole at the one main surface is 12.0 μm or less, and the permeability from the other main surface to the one main surface is 2.0 cm/(cms) or more and 80 cm/(cms) or less as shown in a Frazier number measured in accordance with JIS standard L1096.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a waterproof sound-permeable membrane having both waterproof and sound-permeable properties, and a waterproof sound-permeable member, an electronic device, an electronic device case, and a waterproof sound-permeable structure provided with the waterproof sound-permeable membrane.

  In recent years, electronic devices such as mobile phones, tablet computers, digital cameras, and game devices are generally provided with a voice function. A sound generation unit such as a speaker and / or a sound reception unit such as a microphone is accommodated as an acoustic unit in a housing of an electronic device having an audio function. An opening is usually provided at a position corresponding to the acoustic unit in the casing of the electronic device, and sound is transmitted between the outside of the electronic device and the acoustic unit through the opening.

  Intrusion of water into the housing must be prevented due to the nature of electronic equipment, but the opening for transmitting sound can easily be a path for water to enter. In particular, portable electronic devices are often exposed to rain and water in daily life, and the direction of the opening cannot be fixed in a certain direction that can avoid water (for example, the downward direction in which rain is difficult to blow). The risk of intrusion increases. Therefore, a waterproof sound-permeable membrane that transmits sound between the acoustic unit and the outside and prevents water from entering the housing through the opening from the outside is disposed so as to close the opening.

  An example of a waterproof sound-permeable membrane is a stretched porous membrane having a dispersed structure of innumerable pores generated by stretching. Patent Document 1 discloses a waterproof sound-permeable membrane made of a stretched porous membrane of polytetrafluoroethylene (PTFE) or ultrahigh molecular weight polyethylene. Another example of the waterproof sound-permeable membrane is a non-porous polymer film in which a plurality of through holes penetrating in the thickness direction are formed (see Patent Document 2). The waterproof sound-permeable membrane of Patent Document 2 is formed by chemical etching after irradiating a non-porous polymer film with an ion beam.

JP 2003-53872 A JP 2012-195928

  In recent years, there has been a demand for a waterproof sound-permeable membrane having a high degree of freedom in controlling sound permeability and waterproofness. For example, by making the contradictory characteristics of sound permeability and waterproof properties compatible at a high level, more specifically, by making a waterproof sound-permeable membrane that can achieve high waterproofness while having high sound permeability The degree of freedom in designing electronic devices, particularly portable information terminals, is improved.

  The waterproof sound-permeable membrane of Patent Document 1 has a membrane structure composed of innumerable fine PTFE fibrils generated by stretching and innumerable pores generated between the fibrils by stretching. The entire sound membrane is three-dimensionally dispersed and is continuous with each other. For this reason, in the waterproof sound-permeable membrane of Patent Document 1, there is a large variation in the size and shape of the pores in the membrane, and the degree of freedom of control of sound permeability and waterproofness is increased. It is difficult to achieve a high level of compatibility.

  On the other hand, the waterproof sound-permeable membrane of Patent Document 2 has high uniformity in the size and shape of the through holes, and the size (diameter) of the through holes can be changed depending on the conditions of chemical etching. Compared to sound-permeable membranes, the degree of freedom in controlling sound-permeability and waterproofness is high. However, it is still inadequate for the recent demand for the degree of freedom.

  One of the objects of the present invention is to provide a waterproof sound-permeable membrane having a higher degree of freedom of sound permeability and waterproof control than before, and a waterproof sound-permeable member including the waterproof sound-permeable membrane, an electronic device, and an electronic device The provision of equipment cases and waterproof sound-permeable structures.

The waterproof sound-permeable membrane of the present invention is composed of a polymer film having a through hole extending from one main surface to the other main surface, and the through hole is a straight hole in which the central axis of the through hole extends linearly. The through hole has a shape in which an area of a cross section perpendicular to the direction in which the central axis extends increases from one main surface to the other main surface of the polymer film, and the one main surface In which the opening diameter a of the through-hole is 12.0 μm or less, and the air permeability from the other principal surface to the one principal surface is expressed by the number of fragiles measured in accordance with JIS L1096. It is 0.0 cm ³ / (cm ² · sec) or more and 80 cm ³ / (cm ² · sec) or less.

  The waterproof sound-permeable member of the present invention includes the waterproof sound-permeable film of the present invention and a support joined to the waterproof sound-permeable film.

  The electronic device according to the present invention includes a housing in which an acoustic unit is accommodated and an opening for transmitting sound between the acoustic unit and the outside, and the acoustic unit and the outside that are arranged so as to close the opening. A waterproof sound-permeable membrane that transmits sound to and from the outside and prevents water from entering the housing through the opening, and the waterproof sound-permeable membrane is the waterproof sound-permeable membrane of the present invention. is there.

  The electronic device case of the present invention is an electronic device case that houses an electronic device having an acoustic part, and is provided with an opening for transmitting sound between the acoustic part of the electronic device and the outside. Provided with a waterproof sound-permeable membrane that is disposed so as to close and transmits sound between the acoustic part of the electronic device and the outside and prevents water from entering the case through the opening from the outside, The waterproof sound-permeable membrane is the above-described waterproof sound-permeable membrane of the present invention.

  The waterproof sound-transmitting structure of the present invention transmits sound between a housing provided with an opening for transmitting sound between the inside and the outside, and the inside and the outside disposed so as to close the opening. And a waterproof sound-permeable membrane that prevents water from entering the inside through the opening, and the waterproof sound-permeable membrane is the waterproof sound-permeable membrane of the present invention.

  According to the present invention, it is possible to obtain a waterproof sound-permeable membrane having a higher degree of freedom in sound permeability and waterproof control than conventional waterproof sound-permeable membranes.

It is sectional drawing which shows typically an example of the waterproof sound-permeable membrane of this invention. It is sectional drawing which shows typically another example of the waterproof sound-permeable membrane of this invention. It is sectional drawing which shows typically another example of the waterproof sound-permeable membrane of this invention. In the waterproof sound-permeable membrane of this invention, it is a top view which shows typically an example of the relationship between the said through-holes of the direction where a through-hole extends. In the waterproof sound-permeable membrane of this invention, it is a top view which shows typically another example of the relationship between the said through-holes of the direction where a through-hole extends. It is sectional drawing which shows typically another example of the waterproof sound-permeable membrane of this invention. It is sectional drawing which shows typically an example different from the above of the waterproof sound-permeable membrane of this invention. It is a method for forming a polymer film constituting the waterproof sound-permeable membrane of the present invention, and is a schematic diagram for explaining an outline of ion beam irradiation in a method using ion beam irradiation and subsequent chemical etching. It is a schematic diagram for demonstrating an example of ion beam irradiation in the method of forming the polymer film which comprises the waterproof sound-permeable membrane of this invention, and the method using ion beam irradiation and subsequent chemical etching. (A)-(c) is a method of forming the polymer film which comprises the waterproof sound-permeable membrane of this invention, Comprising: An example of progress of chemical etching in the method using ion beam irradiation and subsequent chemical etching It is process drawing shown typically. It is a perspective view which shows typically an example of the waterproof sound-permeable member of this invention. It is a top view which shows typically another example of the waterproof sound-permeable member of this invention. It is a perspective view which shows typically an example of the electronic device of this invention. It is sectional drawing which shows typically an example of arrangement | positioning of the waterproof sound-permeable membrane in the electronic device of this invention. It is a perspective view which shows typically an example of the case for electronic devices of this invention. It is sectional drawing which shows typically an example of arrangement | positioning of the waterproof sound-permeable membrane in the case for electronic devices of this invention. It is sectional drawing which shows typically an example of the waterproof sound-permeable structure of this invention. It is sectional drawing which shows typically the arrangement | positioning of the simulation housing | casing used in order to evaluate the sound pressure loss of a waterproof sound-permeable membrane, and the speaker in the said housing | casing. It is sectional drawing which shows typically the state which has arrange | positioned the waterproof sound-permeable member produced in order to evaluate the sound pressure loss of a waterproof sound-permeable film, and the said member in the simulation housing | casing.

[Waterproof sound-permeable membrane]
FIG. 1 shows an example of the waterproof sound-permeable membrane of the present invention. A waterproof sound-permeable membrane 1 shown in FIG. 1 includes a polymer film 2 and a liquid repellent layer 3 formed on the main surface of the polymer film 2. The polymer film 2 has a through-hole 5 extending from one main surface 4a of the film 2 to the other main surface 4b. The through-hole 5 is a straight hole in which the central axis (axis) 6 of the through-hole 5 extends linearly, and the area of the cross section 7 perpendicular to the direction in which the central axis 6 extends has one main surface of the polymer film 2. It has a shape that increases from 4a toward the other main surface 4b. The diameter (opening diameter) a of the opening 8a of the through hole 5 on one main surface is 12 μm or less. The liquid repellent layer 3 is also formed on the surface of the through hole 5 (the surface of the film 2 in the through hole 5). The liquid repellent layer 3 formed on the main surface of the polymer film 2 has openings at positions corresponding to the through holes 5 of the film 2 (positions corresponding to the openings 8a and 8b). The air permeability from the other main surface 4b of the waterproof sound-permeable membrane 1 to the one main surface 4a is 2.0 cm ³ / (cm ² · sec), expressed as the number of fragiles measured in accordance with JIS L1096. It is 80 cm ³ / (cm ² · sec) or less. The polymer film 2 is, for example, a non-porous film that does not have a path other than the through-hole 5 that can be vented in the thickness direction, and is typically non-porous except for the through-hole 5. (Solid) film. In the waterproof sound-permeable membrane 1, sound is transmitted through the through-hole 5 that is a ventilation path of the polymer film 2 and by vibration of the waterproof sound-permeable membrane 1 itself. In FIG. 1, the diameter of the through hole 5 is exaggerated for easy understanding. The same applies to the subsequent drawings.

  The waterproof sound-permeable membrane 1 shown in FIG. 1 is different in at least the shape of the through-hole from the waterproof sound-permeable membrane disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2012-195928). More specifically, the through-hole of the waterproof sound-permeable membrane of Patent Document 2 is a “straight hole that linearly penetrates the resin film with a constant cross-sectional shape” (paragraph 0014), whereas in FIG. The through-hole 5 of the waterproof sound-permeable membrane 1 is a straight hole whose central axis extends in a straight line, but the area of the cross section 7 perpendicular to the direction in which the central axis 6 extends differs from the one main surface 4a of the film 2 to the other. It has a shape that increases toward the main surface 4b. In the waterproof sound-permeable membrane 1, the opening diameter a of the through hole 5 on one main surface 4a of the film 2 is not equal to the opening diameter b of the through hole 5 on the other main surface 4b based on the shape of the through hole 5. For example, the opening diameter a is 80% or less of the opening diameter b.

  Based on at least the shape of the through-hole 5, the waterproof sound-permeable membrane 1 has a higher degree of freedom in controlling sound permeability and waterproofness than conventional waterproof sound-permeable membranes. For example, in contrast to the stretched porous membrane of Patent Document 1 in which pores that are three-dimensionally distributed throughout the membrane and are continuous with each other are used as ventilation paths, the polymer film 2 constituting the waterproof sound-permeable membrane 1 is In addition, the non-porous film does not have a ventilation path in the thickness direction other than the through hole that is a straight hole, and the uniformity of the size and shape of the through hole that becomes the ventilation path is higher. The shape of the through-hole 5, the opening diameter, and the ratio a / b can be changed according to the manufacturing conditions in the manufacturing method. For this reason, compared with the stretched porous membrane of patent document 1, the freedom degree of control of sound permeability and waterproofness of the waterproof sound-permeable membrane 1 is high, for example, to make both sound permeability and waterproof property at a high level. Can do.

  On the other hand, compared to the waterproof sound-permeable membrane of Patent Document 2 having a through-hole penetrating the resin film with a constant cross-sectional shape, the waterproof sound-permeable membrane 1 has a change in the shape of the cross-section 7 of the through-hole 5 and the polymer film. The difference in the diameters of the openings 8a and 8b in each of the main surfaces 4a and 4b of 2 improves the sound permeability of the waterproof sound-permeable membrane 1 and the degree of freedom of control of the waterproof property. Both can be achieved at a high level. As a more specific and typical example, the main surface having an opening 8b having a relatively large opening diameter is more waterproof to prevent water from entering from the main surface 4a having the opening 8a having a relatively small opening diameter. The water permeability from the main surface 4b is better than the water resistance to prevent water from entering from the 4b, and the sound permeability from the main surface 4b is better than the sound permeability from the main surface 4a. That is, the waterproof sound-permeable membrane 1 is a film having anisotropy between the main surfaces (between the front and back) with respect to its waterproofness and sound permeability, and such anisotropy is sound-permeable as a waterproof sound-permeable membrane. And contributes to the high degree of freedom of waterproof control. Further, the ability to change the shape, opening diameter, and ratio a / b of the through hole 5 according to the manufacturing conditions in the manufacturing method described later also works in the direction of increasing the degree of freedom.

  As shown in FIG. 1, the through hole 5 has an asymmetric shape in the film thickness direction of the waterproof sound-permeable membrane 1 in which the shape of the cross section 7 changes in the direction in which the central axis 6 extends (the direction in which the through hole 5 extends). It is a through hole.

  The shape of the through-hole 5 is a straight hole in which the central axis 6 extends linearly, and the area of the cross section 7 perpendicular to the direction in which the central axis 6 extends varies from one main surface 4a to the other main surface 4b. As long as it increases towards, it is not limited. The area of the cross section 7 may increase continuously from the main surface 4a to the main surface 4b or may increase stepwise (that is, there may be a region where the area of the cross section 7 is constant). The area of the cross section 7 preferably increases continuously from the main surface 4a to the main surface 4b as in the example shown in FIG. 1 (the through hole 5 has an area of the cross section 7 from one main surface 4a. It is preferable to have a shape that continuously increases to the other main surface 4b), and it is more preferable that the increase rate is substantially constant or constant. According to the manufacturing method described later, the waterproof sound-permeable membrane 1 including the polymer film 2 having the through holes 5 in which the area of the cross section 7 continuously increases from the main surface 4a toward the main surface 4b, and The waterproof sound-permeable membrane 1 having an area increase rate that is substantially constant or constant can be formed.

  The shape of the cross section 7 of the through hole 5 is not particularly limited, and is, for example, a circle or an ellipse. At this time, the shape of the cross section 7 does not need to be a strict circle or ellipse, and for example, some shape disturbance due to unevenness of chemical etching performed by the manufacturing method described later can be allowed. The through-hole 5 has an area of the cross section 7 that continuously increases from the main surface 4a to the main surface 4b at a substantially constant or constant increase rate, and has a shape of the cross section 7 that is a circle or an ellipse. In this case, the shape of the through hole 5 is a cone or an elliptical cone having the central axis 6 as a center line, or a part thereof. According to the manufacturing method described later, it is possible to form the waterproof sound-permeable membrane 1 including the polymer film 2 having the through hole 5 whose cross section 7 is a circle or an ellipse.

  The ratio a / b of the diameter of the opening 8a (opening diameter a) and the diameter of the opening 8b (opening diameter b) in the through hole 5 is, for example, 80% or less, and the degree of freedom in controlling sound transmission and waterproofing is reduced. Since it can be made higher, it is preferably 75% or less, more preferably 70% or less. The lower limit of the ratio a / b is not particularly limited and is, for example, 10%.

  The diameter (opening diameter a) of the opening 8a which is a relatively small opening is 12.0 μm or less. When the opening diameter a exceeds 12.0 μm, sufficient waterproofness as a waterproof sound-permeable membrane is not ensured. When the degree of freedom of control of sound permeability and waterproofness can be increased, more specifically, when waterproofness and sound permeability can be compatible at a higher level, and the effective area of the waterproof sound-permeable membrane 1 is reduced In addition, the through hole a is preferably 1.0 μm or more, that is, the opening diameter a is preferably 1.0 μm or more and 12.0 μm or less. When the opening diameter a is excessively small, there is a possibility that sufficient sound permeability cannot be ensured particularly when the effective area of the waterproof sound-permeable membrane 1 is reduced. The opening diameter “a” is more preferably 2.0 μm or more and 10.0 μm or less, and further preferably 3.0 μm or more and 8.0 μm or less.

  On the other hand, the diameter (opening diameter b) of the opening 8b which is a relatively large opening is not limited as long as it is larger than the opening diameter a. The opening diameter b is preferably 4.0 to 20.0 μm, more preferably 5.0 to 15.0 μm, and more preferably 6.0 to 13.0 μm. When the opening diameter b is within these ranges, the degree of freedom of control of sound permeability and waterproofness can be increased. More specifically, waterproofness and sound permeability can be compatible at a higher level, and Even when the effective area of the sound membrane 1 is reduced, good sound permeability can be secured.

  For the through-hole 5, the diameter of the circle when the shape of the openings 8a and 8b is regarded as a circle, in other words, the diameter of a circle having the same area as the cross-sectional area (opening area) of the openings 8a and 8b It is set as the opening diameter of opening 8a, 8b. Although the opening diameter of the through-hole 5 in each main surface of the polymer film 2 does not have to coincide with all the openings existing in the main surface, the effective portion of the polymer film 2 (as the waterproof sound-permeable membrane 1) It is preferable to match the extent that can be regarded as substantially the same value (for example, the standard deviation is 10% or less of the average value). According to the manufacturing method described later, the waterproof sound-permeable membrane 1 having the same opening diameter on each main surface can be formed.

  In addition, the opening shape of the through-hole 5 extended in the direction inclined from the direction perpendicular | vertical to the main surfaces 4a and 4b of the polymer film 2 can be an ellipse. However, even in such a case, the shape of the cross section 7 of the through-hole 5 in the film 2 can be regarded as a circle, and the diameter of this circle is equal to the minimum diameter of the ellipse that is the opening shape. For this reason, in the case of the through hole 5 extending in the inclined direction and having an elliptical opening shape, the minimum diameter can be set as the opening diameter of the through hole.

The density (hole density) of the through holes 5 in the polymer film 2 is not particularly limited, and is, for example, 1 × 10 ³ pieces / cm ² or more and 1 × 10 ⁹ pieces / cm ² or less. When the pore density is within this range, it is easy to control sound permeability and waterproofness within a range that is preferable for the waterproof sound-permeable membrane 1. Pore density, 1 × 10 ⁵ / cm ² or more 1 × 10 ⁸ / cm ² or less being more preferred. The pore density need not be constant throughout the polymer film 2, but in the effective portion of the polymer film 2, it is constant so that the maximum pore density is not more than 1.5 times the minimum pore density. It is preferable.

  The opening ratio of the opening 8a in the main surface 4a of the polymer film 2 (ratio of the opening area to the area of the main surface) is preferably 50% or less, preferably 10% or more and 45% or less, more preferably 20% or more and 40% or less. preferable. When the aperture ratio is within these ranges, it is easy to control sound permeability and waterproofness within a range preferable for the waterproof sound-permeable membrane 1. In addition, the effective area of the waterproof sound-permeable membrane 1 is reduced by setting the aperture ratio and the opening diameter a of the opening 8a in the main surface 4a to these preferable ranges and setting the air permeability of the waterproof sound-permeable membrane 1 to the above range. Better sound transmission (characteristics of sound transmitted through the waterproof sound-permeable membrane) can be ensured. Note that a stretched porous membrane having a dispersed structure of innumerable pores generated by stretching cannot be a waterproof sound-permeable membrane having such a low porosity.

The waterproof sound-permeable membrane 1 is 2.0 cm ³ / (cm ² · sec) or more and 80 cm ³ / (cm ² ) as indicated by the number of fragiles measured in accordance with JIS L1096 (hereinafter simply referred to as “fragile number”). Second) The following air permeability is provided as the air permeability in the thickness direction from the main surface 4b to the main surface 4a. Considering that the liquid repellent layer 3 does not substantially affect the air permeability, the air permeability from the main surface 4b to 4a of the polymer film 2 is 2.0 cm ³ / (cm ² · sec) in terms of Frazier number. ) Or more and 80 cm ³ / (cm ² · sec) or less. In order to obtain a waterproof sound-permeable membrane 1 with a high degree of freedom in controlling sound permeability and waterproofness, in addition to the opening diameter a of the through-hole 5 being 12.0 μm or less, the main surface 4b to 4a The air permeability needs to be in this range. When the air permeability expressed in terms of the number of fragiles is less than 2.0 cm ³ / (cm ² · sec), the waterproof sound-permeable membrane and the degree of freedom of control of the sound-permeable property decrease, and the waterproof sound-permeable membrane is particularly effective. It is difficult to ensure sound transmission when the area is reduced. If the air permeability exceeds 80 cm ³ / (cm ² · sec), the risk of water from the outside increases depending on the aperture ratio of the waterproof sound-permeable membrane. The air permeability from the main surface 4b to 4a is preferably 5.0 cm ³ / (cm ² · sec) or more and 60 cm ³ / (cm ² · sec) or less, expressed as the number of fragile, and 10 cm ³ / (cm ² · sec). ) To 50 cm ³ / (cm ² · sec) or less.

  In the waterproof sound-permeable membrane 1 shown in FIG. 1, the central axis 6 of the through hole 5 extends in a direction perpendicular to the main surfaces 4a and 4b of the polymer film 2, but the extending direction of the central axis 6 of the through hole 5 is You may incline from the direction perpendicular | vertical to main surface 4a, 4b. That is, the waterproof sound-permeable membrane 1 may be composed of a polymer film 2 having a through hole 5 extending in a direction inclined from a direction perpendicular to the main surfaces 4a and 4b. An example of such a waterproof sound-permeable membrane 1 is shown in FIG. In FIG. 2, the liquid repellent layer 3 is not shown (the same applies to FIGS. 3 and 6).

  In the waterproof sound-permeable membrane 1, through-holes 5 having different extending directions of the central axis 6 may be mixed. More specifically, for example, in the polymer film 2, a through hole 5 in which the central axis 6 extends in a direction perpendicular to the main surfaces 4 a and 4 b, and a through hole 5 in which the central axis 6 extends in a direction inclined from the direction. May be mixed. Further, for example, the polymer film 2 has a through hole 5 in which the central axis 6 extends in a direction inclined from a direction perpendicular to the main surfaces 4 a and 4 b of the film 2, and the through holes 5 having different directions extending in the inclined direction are provided. It may be mixed in the polymer film 2. An example of the latter is shown in FIG.

  In the waterproof sound-permeable membrane 1 shown in FIG. 3, the polymer film 2 includes through holes 5 a to 5 g having different directions extending with the central axis 6 inclined from a direction perpendicular to the main surfaces 4 a and 4 b. In other words, the through hole 5 in the waterproof sound-permeable membrane 1 in FIG. 3 extends in a direction inclined with respect to the direction perpendicular to the main surfaces 4a and 4b of the polymer film 2 (through the polymer film 2). There are combinations of through holes 5 that extend in different directions. The polymer film 2 may have a combination of through holes 5 that extend in the same direction. In the example shown in FIG. 3, for example, the extending directions of the through holes 5a, 5b, and 5c are different from each other, and the extending directions of the through holes 5a and 5e are the same. Hereinafter, “combination” is also simply referred to as “set” in the present specification. The “set” is not limited to the relationship (pair) between one through hole and one through hole, and means a relationship between one or two or more through holes. Having a set of through holes having the same characteristics means that there are a plurality of through holes having the characteristics.

  As shown in FIG. 3, in the waterproof sound-permeable membrane 1 composed of the polymer film 2 in which through-holes 5 having different directions extending at an inclination are mixed, the inclination degree and the ratio of the through-holes 5 extending in a certain direction are changed. Therefore, the sound permeability as the waterproof sound-permeable membrane 1 and the degree of freedom of waterproof control are further increased.

  2 and 3, the angle θ1 formed by the direction D1 inclined and extending with respect to the direction D2 perpendicular to the main surface of the polymer film 2 is preferably 45 ° or less, and more preferably 30 ° or less. When the angle θ1 is within these ranges, the level at which both sound permeability and waterproofness as the waterproof sound-permeable membrane 1 can be achieved becomes higher. Although the minimum of angle (theta) 1 is not specifically limited, For example, it is 10 degrees or more, and 20 degrees or more are preferable. If the angle θ1 is excessively large, the mechanical strength of the waterproof sound-permeable membrane 1 tends to be weakened. In the through hole 5 shown in FIG. 3, there are pairs having different angles θ1.

  As shown in FIG. 3, in the waterproof sound-permeable membrane 1 composed of the polymer film 2 in which the through holes 5 having different directions extending at an inclination are mixed, when viewed from a direction perpendicular to the main surface of the polymer film 2. (When the direction in which the through-hole 5 extends is projected onto the main surface), the directions in which the through-holes 5 extend may be parallel to each other, but the polymer film 2 has a set in which the extending directions are different from each other (the relevant It is preferable that the through holes 5 having different extending directions exist in the polymer film 2). In the case of the latter, the level which can make sound permeability and waterproof property as the waterproof sound-permeable membrane 1 compatible becomes higher.

  FIG. 4 shows an example in which the directions in which the through holes 5 extend are parallel to each other when viewed from a direction perpendicular to the main surface of the polymer film 2. In the example shown in FIG. 4, three through-holes 5 (5h, 5i, 5j) are visible, but the direction in which each through-hole 5 extends when viewed from a direction perpendicular to the main surface of the polymer film 2 (paper surface) D3, D4, and D5 are parallel to each other (the direction from the opening 8a of the through hole 5 on the front main surface to the opening 8b of the through hole 5 on the opposite main surface) (θ2 described later is 0 °). . However, the angle θ1 of each through hole 5h, 5i, 5j is different from each other, the angle θ1 of the through hole 5j is the smallest, and the angle θ1 of the through hole 5h is the largest. For this reason, the direction in which each through-hole 5h, 5i, 5j extends is three-dimensionally different.

  FIG. 5 shows an example in which the through-holes 5 extend in different directions when viewed from a direction perpendicular to the main surface of the polymer film 2. In the example shown in FIG. 5, three through holes 5 (5k, 5l, 5m) are visible, but the direction D6 in which each through hole 5 extends when viewed from a direction perpendicular to the main surface of the polymer film 2. D7 and D8 are different from each other. Here, the through holes 5k and 5l form an angle θ2 of less than 90 ° when viewed from a direction perpendicular to the main surface of the polymer film 2, and extend from the main surface in different directions. On the other hand, the through holes 5k and 5m form an angle θ2 of 90 ° or more when viewed from a direction perpendicular to the main surface of the polymer film 2, and extend from the main surface in different directions. Like the latter, the polymer film 2 has a set of through-holes 5 extending in different directions from the main surface at an angle θ2 of 90 ° or more when viewed from a direction perpendicular to the main surface of the film. It is preferable to have. In other words, when the polymer film 2 is viewed from a direction perpendicular to the main surface of the film, the polymer film 2 has a through hole 5k extending in a certain direction D6 from the main surface and 90 ° with respect to the certain direction D6. It is preferable to have a pair with the through hole 5m extending from the main surface in the direction D8 forming the angle θ2. At this time, the level that can achieve both sound permeability and waterproof property as the waterproof sound-permeable membrane 1 is further increased. The angle θ2 is preferably 90 ° or more and 180 ° or less, that is, may be 180 °.

  As shown in FIG. 3, in the waterproof sound-permeable membrane 1 composed of the polymer film 2 in which through-holes 5 having different directions extending at an inclination are mixed, two or more through-holes 5 intersect each other in the polymer film 2. It may be. That is, the polymer film 2 may have a set of through holes 5 that intersect with each other in the film 2. At this time, the level that can achieve both sound permeability and waterproof property as the waterproof sound-permeable membrane 1 is further increased. Such an example is shown in FIG. In the example shown in FIG. 6, the through holes 5 p and 5 q intersect with each other in the polymer film 2.

  The direction in which the through-hole 5 extends (in the waterproof sound-permeable membrane 1) in the polymer film 2 (the direction in which the central axis 6 of the through-hole 5 extends) is, for example, a scanning electron microscope (with respect to the main surface and cross section of the film). This can be confirmed by observation by SEM.

  The polymer film 2 may have through-holes that are straight holes whose cross-sectional shape perpendicular to the direction in which the central axis extends is constant in the thickness direction of the film 2.

  The waterproof sound-permeable membrane 1 may be subjected to a liquid repellent treatment. In the waterproof sound-permeable membrane 1 subjected to the liquid repellent treatment, the liquid repellent layer 3 is formed on at least a part of the surface of the polymer film 2. In the example shown in FIG. 1, the liquid repellent layer 3 is formed on both main surfaces 4 a and 4 b of the polymer film 2 and the surface of the through hole 3. The liquid repellent layer 3 may be formed only on one main surface of the polymer film 2 or may be formed only on one main surface and the surface of the through hole 3. It is preferable that the liquid repellent layer 3 is formed on the main surface 4a having the opening 8a having a relatively small diameter.

  The liquid repellent layer 3 is a layer having water repellency, and preferably also has oil repellency. The liquid repellent layer 3 has an opening at a position corresponding to the through hole 5 of the polymer film 2.

  The liquid repellent layer 3 can be formed, for example, by thinly applying a treatment liquid prepared by diluting a water repellent or a hydrophobic oil repellent with a diluent and drying it on the polymer film 2. The water repellent and the hydrophobic oil repellent are, for example, fluorine compounds such as perfluoroalkyl acrylate and perfluoroalkyl methacrylate. The thickness of the liquid repellent layer 3 is preferably less than ½ of the diameter of the through hole 5.

  When the liquid repellent layer 3 is formed by thinly applying the treatment liquid on the polymer film 2, the surface (inner peripheral surface) of the through hole is also the main surface of the film 2 depending on the diameter of the through hole 5. It is possible to cover the surface continuously with the liquid repellent layer 3 (this is the case in the example shown in FIG. 1).

  The thickness of the polymer film 2 is, for example, 5 μm to 100 μm, and preferably 15 μm to 50 μm.

  The material which comprises the polymer film 2 is a material which can form the through-hole 5 in the original film which is a non-porous polymer film, for example in the below-mentioned manufacturing method. The polymer film 2 is made of, for example, an alkaline solution, an acidic solution, or a resin that is decomposed by an alkaline solution or an acidic solution to which at least one selected from an oxidizing agent, an organic solvent, and a surfactant is added. In this case, it becomes easier to form the through holes 5 in the original film by ion beam irradiation and chemical etching in the manufacturing method described later. These solutions are typical etching processing solutions. Viewed from another aspect, the polymer film 2 is made of a resin that can be etched by hydrolysis or oxidative decomposition, for example. A commercially available film can be used for the original film.

  The polymer film 2 is made of, for example, at least one resin selected from polyethylene terephthalate (PET), polycarbonate, polyimide, polyethylene naphthalate, and polyvinylidene fluoride.

  The waterproof sound-permeable membrane 1 may include a polymer film 2 having two or more layers. Such a waterproof sound-permeable membrane 1 can be formed by, for example, ion beam irradiation and chemical etching on a laminate having two or more original films.

  The waterproof sound-permeable membrane 1 is disposed, for example, so as to close the opening of the housing of the electronic device, prevents water from entering the inside of the housing from the opening, and between the outside and the inside of the housing. The sound is transmitted with. As a more specific example, the waterproof sound-permeable membrane 1 has an acoustic part such as a sound generating part such as a speaker and / or a sound receiving part such as a microphone as an electronic device, and an opening that can transmit sound to the acoustic part ( When an opening) is provided in the housing, it is arranged so as to close the opening (sound passage), and prevents water from entering the inside of the electronic device from the opening. It is a film | membrane which transmits a sound between an acoustic part.

  The waterproof sound-permeable membrane 1 preferably has a water pressure of 3 kPa or more, more preferably 5 kPa or more, more preferably 10 kPa or more, measured according to the provisions of the water resistance test method B (high water pressure method) of JIS L1092. Further, it is preferably 15 kPa or more. The water pressure resistance of 10 kPa means that the water pressure can withstand a water depth of 1 m. In this case, waterproofness corresponding to “water protection class 7 (IPX7)” defined in JIS C0920 is ensured. Even when the electronic device equivalent to IPX7 is accidentally dropped into the water, it can avoid inundation into the device within a predetermined depth and time. Further, it is empirically known that when the water pressure resistance is about 5 kPa, waterproofing equivalent to “water protection class 4 (IPX4)” defined in JIS C0920 is secured. IPX4 is also one of the waterproof properties required for electronic devices in recent years. When the water pressure resistance of the waterproof sound-permeable membrane 1 is 5 kPa or more or 10 kPa or more, it is possible to achieve both IPX4 or IPX7 equivalent waterproofness and high sound permeability. There are few electronic devices with a high degree of design and design freedom, such as being small and / or thin.

  The waterproof sound-permeable membrane 1 is different in the diameters of the openings 8a and 8b of the through-holes 5 in both main surfaces 4a and 4b of the polymer film 2 constituting the membrane 1, so that one main surface 4a of the polymer film 2 is provided. The waterproof property from the main surface 4b side to the other main surface 4b, for example, the water pressure resistance, and the waterproof property from the other main surface 4b side to the one main surface 4a side are different. More specifically, the waterproof property from the main surface 4a side where the opening diameter of the through-hole 5 is relatively small is larger than the waterproof property from the main surface 4b side where the opening diameter is relatively large. The waterproof property from the main surface 4a side where the opening diameter of the through hole 5 is relatively small is preferably the above-mentioned preferable water pressure resistance. The difference between the water pressure resistance of the waterproof sound-permeable membrane 1 from the main surface 4a side and the water pressure resistance of the waterproof sound-permeable membrane 1 from the main surface 4b side is preferably 5 kPa or more, and more preferably 10 kPa or more. The degree of the difference in waterproofness of the waterproof sound-permeable membrane 1 due to the main surfaces 4a and 4b is determined by the shape of the through-hole 5 of the polymer film 2, more specifically, the opening diameter of the through-hole 5, and the above It can be controlled by the ratio a / b. Further, when the waterproof sound-permeable membrane 1 has two or more polymer films 2, the configuration of each polymer film 2 and the laminated state of the two or more polymer films 2 (each polymer film 2 in a laminated state). The main surfaces 4a and 4b of the waterproof sound-permeable membrane 1 can be controlled). The fact that such control is possible also contributes to the high degree of freedom in waterproof control of the waterproof sound-permeable membrane 1.

  With respect to sound permeability, the waterproof sound-permeable membrane 1 has a maximum sound pressure loss of, for example, 5 dB or less, 3 dB or less, or 1 dB or less in a sound range of a frequency of 100 Hz to 3 kHz because of its high degree of freedom of control. it can. The sound range of 100 Hz to 3 kHz corresponds to a sound range that humans use for normal utterances and conversations, and that can be felt most sensitively during music reproduction. The small sound pressure loss in this sound range improves the appeal in the market for electronic devices including the waterproof sound-permeable membrane 1. The maximum sound pressure loss of the waterproof sound-permeable membrane in the sound range of 100 Hz to 3 kHz is usually measured in the high sound range of 2.5 kHz to 3 kHz. Further, for example, the sound pressure loss at a frequency of 1 kHz considered to be the median value of the human voice range can be 5 dB or less, 3 dB or less, and further 1 dB or less.

Moreover, in the waterproof sound-permeable membrane 1, sound permeability can be ensured even when the effective area is reduced by selecting the through hole 5, for example. For example, the effective area of the waterproof sound-permeable membrane 1 may be 4.9 mm ² or less. The advantageous feature that the effective area can be reduced contributes to improvement in design and design flexibility such as downsizing and / or thinning of the electronic device including the waterproof sound-permeable membrane 1. The effective area of the waterproof sound-permeable membrane 1 is that when the membrane is arranged so as to close the opening of the housing, sound is actually input to the membrane, and the sound is output from the membrane through the membrane. For example, in order to arrange the waterproof sound-permeable membrane 1, it does not include the area such as the support and the bonding portion arranged and formed on the peripheral edge of the membrane. The effective area is typically the area of the opening in which the membrane is arranged or the area of the opening in the waterproof sound-permeable member in which the support is arranged at the periphery of the waterproof sound-permeable membrane. It is possible.

In the waterproof sound-permeable membrane 1, for example, when the effective area is 4.9 mm ² (for example, when it is a circle with a diameter of 2.5 mm), the maximum sound pressure loss in the sound range of 100 Hz to 3 kHz is 5 dB or less, 3 dB. Hereinafter, it can be further set to 1 dB or less.

The smaller the effective area, the lower the sound permeability of the waterproof sound-permeable membrane, for example, the sound pressure loss increases. In the waterproof sound-permeable membrane 1, for example, when the effective area is 0.8 mm ² (for example, when it is a circle having a diameter of 1 mm) or less, the maximum sound pressure loss in the sound range of 100 Hz to 3 kHz is 10 dB or less, Furthermore, it can be 5 dB or less.

  Of course, not only when the effective area of the waterproof sound-permeable membrane 1 is small, but also when the waterproof sound-permeable membrane 1 is large, it is possible to achieve both higher levels of sound permeability and waterproofness, but when the effective area of the waterproof sound-permeable membrane is small, Or when it must be made small, the waterproof sound-permeable membrane 1 becomes especially advantageous.

  The waterproof sound-permeable membrane 1 is different in the diameters of the openings 8a and 8b of the through-holes 5 in both main surfaces 4a and 4b of the polymer film 2 constituting the membrane 1, so that one main surface 4a of the polymer film 2 is provided. The sound transmission property from the main surface 4b side to the other main surface 4b side, for example, the degree of the sound pressure loss, and the sound transmission property from the other main surface 4b side to the one main surface 4a side are different. More specifically, the sound transmission property from the other main surface 4b side where the opening diameter of the through-hole 5 is relatively large is the sound transmission property from the one main surface 4a side where the opening diameter is relatively small. It is better than that. It is preferable that the value of the (maximum) sound pressure loss is satisfied with respect to sound permeability from the main surface 4b side where the opening diameter of the through hole 5 is relatively large. The degree of difference in sound permeability of the waterproof sound-permeable membrane 1 by the main surfaces 4a and 4b is determined by the shape of the through-hole 5 of the polymer film 2, more specifically, the opening diameter of the through-hole 5, and It can be controlled by the ratio a / b. The fact that such control is possible also contributes to a high degree of freedom in controlling the sound permeability of the waterproof sound-permeable membrane 1.

  The waterproof sound-permeable membrane 1 can achieve these preferable sound pressure loss and water pressure resistance at the same time.

  The waterproof sound-permeable membrane 1 may include any member and / or layer other than the polymer film 2 and the liquid repellent layer 3 as necessary. The member is, for example, a breathable support layer 9 shown in FIG. In the waterproof sound-permeable membrane 1 shown in FIG. 7, a breathable support layer 9 is disposed on the other main surface 4b of the polymer film 2 of the waterproof sound-permeable membrane 1 shown in FIG. By the arrangement of the air-permeable support layer 9, the strength as the waterproof sound-permeable membrane 1 is improved, and the handleability is also improved. The breathable support layer 9 may be disposed on one main surface 4a of the polymer film 2 or may be disposed on both main surfaces 4a and 4b.

  The breathable support layer 9 is a layer having a higher air permeability in the thickness direction than the polymer film 2. For the breathable support layer 9, for example, a woven fabric, a nonwoven fabric, a net, or a mesh can be used. The material constituting the air-permeable support layer 9 is, for example, polyester, polyethylene, or aramid resin. The liquid repellent layer 3 may or may not be formed on the main surface of the polymer film 2 on which the air-permeable support layer 9 is disposed. The shape of the air-permeable support layer 9 may be the same as or different from the shape of the polymer film 2. For example, the air-permeable support layer 9 has a shape that is arranged only at the peripheral edge of the polymer film 2 (specifically, when the polymer film is circular, it has a ring shape that is arranged only at the peripheral edge). It can be. The air-permeable support layer 9 is disposed by a technique such as thermal welding with the polymer film 2 or adhesion with an adhesive.

The surface density of the waterproof sound-permeable membrane 1 is preferably 5 to 100 g / m ^{2 and} more preferably 10 to 50 g / m ² from the viewpoint of the strength, handleability and sound permeability of the membrane. In addition, in the stretched porous membrane having a dispersed structure of innumerable pores generated by stretching, as disclosed in Patent Document 1, the surface density as a waterproof sound-permeable membrane is set from the viewpoint of ensuring sound permeability. It needs to be smaller. On the other hand, a membrane with a low surface density is advantageous in that the waterproof sound-permeable membrane 1 is also advantageous in terms of strength and handling properties including production yield and mounting accuracy.

  The thickness of the waterproof sound-permeable membrane 1 is, for example, 5 to 100 μm, and preferably 15 to 50 μm.

  The waterproof sound-permeable membrane 1 may be subjected to a coloring process. Depending on the type of material constituting the polymer film 2, the color of the waterproof sound-permeable membrane 1 that has not been colored is, for example, transparent or white. When such a waterproof sound-permeable membrane 1 is disposed so as to close the opening of the housing, the membrane 1 may be conspicuous. The conspicuous membrane stimulates the user's curiosity, and the function as a waterproof sound-permeable membrane may be impaired by piercing with a needle or the like. If the waterproof sound-permeable membrane 1 is colored, for example, the membrane 1 having the same color as or similar to the color of the housing can be used to relatively restrain the user's attention. In addition, a colored waterproof sound-permeable membrane may be required in designing a housing of an electronic device or the like, and such a design requirement can be met by a coloring process.

  The coloring process can be performed by, for example, dyeing the polymer film 2 or adding a colorant to the polymer film 2. For example, the coloring treatment may be performed so that light included in a wavelength range of 380 nm to 500 nm is absorbed. That is, the waterproof sound-permeable membrane 1 may be subjected to a coloring process that absorbs light included in a wavelength range of 380 nm to 500 nm. For this purpose, for example, the polymer film 2 contains a colorant having the ability to absorb light included in the wavelength range of 380 nm to 500 nm, or absorbs light included in the wavelength range of 380 nm to 500 nm. Dyed with a dye having the ability to In this case, the waterproof sound-permeable membrane 1 can be colored blue, gray, brown, pink, green, yellow, and the like. The waterproof sound-permeable membrane 1 may be colored in black, gray, brown or pink.

  The waterproof sound-permeable membrane 1 can be used for various applications, for example, a waterproof sound-permeable member, an electronic device, a case for an electronic device, and a waterproof sound-permeable structure.

  The manufacturing method of the waterproof sound-permeable membrane 1 comprised from the polymer film 2 which has the through-hole 5 is not specifically limited, For example, it can manufacture with the manufacturing method demonstrated below.

[Method of manufacturing waterproof sound-permeable membrane]
In the following manufacturing method, the polymer film 2 is formed by ion beam irradiation on the original film and subsequent chemical etching. The polymer film 2 formed by ion beam irradiation and chemical etching may be used as the waterproof sound-permeable membrane 1 as it is, or through a further process such as a liquid repellent treatment, a coloring treatment, or a step of laminating the air-permeable support layer 9. The sound membrane 1 may be used.

  In the method using ion beam irradiation and subsequent chemical etching, the opening diameters of the through holes 5 of the polymer film 2 can be made uniform to the above-described preferable degree on the respective main surfaces 4a or 4b.

  The original film is a non-porous polymer film that does not have a path that can be vented in the thickness direction in the region used as the waterproof sound-permeable membrane 1 after ion beam irradiation and chemical etching. The original film may be a non-porous film.

  When the original film is irradiated with an ion beam, the polymer chain constituting the polymer film is damaged due to collision with ions in a portion where the ions in the film pass. Damaged polymer chains are more susceptible to chemical etching than other portions of the polymer chain that are not colliding with ions. For this reason, by chemically etching the original film irradiated with the ion beam, a polymer film having pores (through-holes) extending along the trajectory of ion collision can be obtained. That is, the direction in which the central axis 6 of the through hole 5 extends is the direction in which ions have passed through the original film during ion beam irradiation. In addition, a pore is not normally formed in the part which the ion in the original film has not passed.

  As described above, in the manufacturing method of the present disclosure, the method of forming the polymer film 2 from the original film includes the step (I) of irradiating the original film with the ion beam and the portion where the ions collide with the original film after the ion beam irradiation. (II), in which at least a part of the film is chemically etched to form a through hole 5 extending along a trajectory (ion track) of ion collision in the film. And in process (II), by arrangement | positioning of the masking layer to one main surface in the original film after ion irradiation, compared with the etching of the said part from the said one main surface, the other in the original film after ion irradiation Chemical etching is performed with a large degree of etching of the portion from the main surface. In this chemical etching, the degree of etching of the ion track from the other main surface is larger than that of the ion track from the one main surface on which the masking layer is disposed. By performing such asymmetric etching, more specifically, etching with different traveling speeds from one main surface and the other main surface in the original film after ion irradiation, the central axis 6 The through-hole 5 having a shape in which the area of the cross section 7 perpendicular to the direction in which the length of the polymer film 2 increases from one main surface to the other main surface of the polymer film 2 can be formed. In Patent Document 2, since uniform etching proceeds as a result from both main surfaces of the original film after ion beam irradiation, the cross-sectional shape of the through hole is constant in the film thickness direction. A film is formed.

  Hereinafter, steps (I) and (II) will be described more specifically.

[Step (I)]
In step (I), the original film is irradiated with an ion beam. The ion beam is composed of accelerated ions. By irradiating the ion beam, an original film in which ions in the beam collide is formed.

  When the original film is irradiated with the ion beam, as shown in FIG. 8, the ions 21 in the beam collide with the original film 22, and the collided ions 21 leave a locus 23 (ion track) inside the film 22. When viewed on the size scale of the original film 22 that is the object to be irradiated, the ions 21 usually collide with the original film 22 in a substantially straight line, so that a linearly extending locus 23 is formed in the film 22. The ions 21 usually penetrate the original film 22.

  The method of irradiating the original film 22 with an ion beam is not limited. For example, after the original film 22 is accommodated in the chamber and the pressure in the chamber is reduced (for example, after a high vacuum atmosphere is set to suppress the attenuation of energy of the irradiated ions 21), the ions 21 are generated from the beam line. Irradiate the film 22. A specific gas may be added to the chamber, or the original film 22 may be accommodated in the chamber, but the pressure in the chamber may not be reduced, and for example, ion beam irradiation may be performed at atmospheric pressure.

  A roll around which the strip-shaped original film 22 is wound may be prepared, and the original film 22 may be continuously irradiated with an ion beam while the original film 22 is sent out from the roll. Thereby, the polymer film 2 can be formed efficiently. The roll (delivery roll) and the take-up roll that winds up the original film 22 after irradiation with the ion beam are arranged in the chamber described above, and the belt is stripped from the delivery roll in an arbitrary atmosphere such as reduced pressure or high vacuum. While the original film 22 is being fed out, the film may be continuously irradiated with an ion beam, and the original film 22 after the beam irradiation may be wound on a take-up roll.

  The resin constituting the original film 22 is the same as the resin constituting the polymer film 2 and is, for example, at least one selected from PET, polycarbonate, polyimide, polyethylene naphthalate, and polyvinylidene fluoride. The original film 22 composed of these resins has a feature that the chemical etching of the portion where the ions 21 collide proceeds smoothly but the chemical etching of the other portion is difficult to proceed. Control of the chemical etching of the portion corresponding to the locus 23 becomes easy. For this reason, use of such an original film 22 makes it easier to control the shape of the through-hole 5 of the polymer film 2, for example.

  The original film 22 may be composed of two or more kinds of resins, and may contain materials other than the resin as long as the polymer film 2 is formed through the steps (I) and (II). Examples of the material include additives such as a light stabilizer and an antioxidant, an oligomer component derived from a resin raw material, and a metal oxide (for example, white pigment: alumina, titanium oxide, and the like).

  The thickness of the original film 22 is, for example, 5 to 100 μm. Usually, the thickness of the original film 22 does not change depending on before and after the ion beam irradiation in the step (I).

  The original film 1 that is irradiated with an ion beam is, for example, a non-porous film. In this case, a portion other than the through holes 5 formed by the steps (I) and (II) is non-porous unless a further step of forming holes in the film other than the steps (I) and (II) is performed. A molecular film 2 can be formed. When the said further process is implemented, the polymer film 2 which has the through-hole 5 formed by process (I) and (II) and the hole formed by the said further process is formed.

  The type of ions 21 that are irradiated and collide with the original film 22 is not limited. However, since the chemical reaction with the resin constituting the original film 22 is suppressed, ions having a mass number greater than that of neon, specifically, argon. At least one ion selected from ions, krypton ions and xenon ions is preferred.

  The energy (acceleration energy) of the ions 21 is typically 100 to 1000 MeV. When a polyester film having a thickness of about 5 to 100 μm is used as the original film 22, the energy of the ions 21 when the ion species is argon ions is preferably 100 to 600 MeV. The energy of the ions 21 irradiated to the original film 22 can be adjusted according to the ion species and the type of resin constituting the original film 22.

  The ion source of the ions 21 irradiated to the original film 22 is not limited. The ions 21 emitted from the ion source are, for example, accelerated by an ion accelerator and then irradiated to the original film 22 through a beam line. The ion accelerator is, for example, a cyclotron, and a more specific example is an AVF cyclotron.

The pressure of the beam line serving as the path of the ions 21 is preferably a high vacuum of about 10 ⁻⁵ to 10 ⁻³ Pa from the viewpoint of suppressing energy attenuation of the ions 21 in the beam line. When the pressure of the chamber in which the original film 22 that irradiates the ions 21 is not high vacuum, the pressure difference between the beam line and the chamber may be maintained by a partition wall that transmits the ions 21. The partition is made of, for example, a titanium film or an aluminum film.

  The ions 21 are irradiated to the film from a direction perpendicular to the main surface of the original film 22, for example. In the example shown in FIG. 8, such irradiation is performed. In this case, since the trajectory 23 extends perpendicularly to the main surface of the original film 22, a through hole 5 extending the central axis 6 in a direction perpendicular to the main surface is formed by subsequent chemical etching, as shown in FIG. A polymer film 2 is obtained. The ions 21 may be applied to the film from a direction oblique to the main surface of the original film 22. In this case, the polymer film 2 as shown in FIG. 2 in which the through hole 5 is formed by extending the central axis 6 in the direction inclined from the direction perpendicular to the main surface is obtained by subsequent chemical etching. The direction in which the original film 22 is irradiated with the ions 21 can be controlled by a known means. 2 can be controlled by, for example, the incident angle of the ion beam with respect to the original film 22.

  For example, the ions 21 are irradiated on the original film 22 so that tracks of the plurality of ions 21 are parallel to each other. In the example shown in FIG. 8, such irradiation is performed. In this case, a polymer film 2 as shown in FIGS. 1 and 2 in which a plurality of through holes 5 extending in parallel with each other is formed by subsequent chemical etching.

  The ions 21 may be irradiated to the original film 22 so that the tracks of the plurality of ions 21 are not parallel to each other (for example, random to each other). Thereby, for example, a polymer film 2 as shown in FIGS. 3 to 6 is formed. More specifically, in order to form the polymer film 2 as shown in FIGS. 3 to 6, for example, the ion beam is irradiated while being tilted from a direction perpendicular to the main surface of the original film 22, and continuously or in stages. Alternatively, the direction of tilting may be changed. Since the ion beam is a beam in which a plurality of ions fly in parallel with each other, a set of through holes 5 extending in the same direction usually exists in the polymer film 2 (a plurality of through holes 5 extending in the same direction are present). Usually present in the polymer film 2).

  FIG. 9 shows an example of a method for changing the tilt direction continuously or stepwise. In the example shown in FIG. 9, the strip-shaped original film 22 is sent out from the delivery roll 31, passed through an irradiation roll 32 having a predetermined curvature, irradiated with an ion beam 33 while passing through the roll 32, and the original after irradiation. The film 22 is taken up on a take-up roll 34. At this time, since the ions 21 in the ion beam 33 fly one after another in parallel, the angle at which the ion film collides with the main surface of the original film 22 while the original film 22 moves on the irradiation roll 32 ( The incident angle θ1) will change. When the ion beam 33 is continuously irradiated, the tilt direction changes continuously, and when the ion beam 33 is intermittently irradiated, the tilt direction changes stepwise. This can be said to be control by the irradiation timing of the ion beam. The state of the locus 23 formed on the original film 22 (for example, the angle θ1) can also be controlled by the sectional shape of the ion beam 33 and the sectional area of the beam line of the ion beam 33 with respect to the irradiation surface of the original film 22.

  The pore density of the polymer film 2 can be controlled by ion beam irradiation conditions (ion species, ion energy, ion collision density (irradiation density), etc.) on the original film 22.

  The ions 21 may be irradiated to the original film 22 from two or more beam lines.

  Step (I) may be performed in a state where the masking layer is disposed on the main surface of the original film 22, for example, the one main surface.

[Step (II)]
In the step (II), at least a part of the portion of the original film 22 that has collided with the ions 21 in the step (I) is chemically etched to penetrate along the trajectory 23 of the collision of the ions 21. Holes 5 are formed in the film. The portions other than the through-holes 5 in the polymer film 2 thus obtained are basically the same as the original film 22 before the ion beam irradiation unless a step of changing the state of the film is further performed.

  Further, in the step (II), the chemical etching is performed in a state where the masking layer is disposed on one main surface of the original film 22 after the ion beam irradiation. In this chemical etching, the etching of the portion of the original film 22 where the ions 21 collide is greater in the degree of etching from the other main surface than in the etching from the one main surface where the masking layer is disposed. That is, in the step (II), chemical etching (asymmetric etching) in which etching from both main surfaces of the film proceeds asymmetrically with respect to the etching of the portion of the original film 22 where the ions 21 collide is performed. More specifically, “the degree of etching is large” means, for example, that the etching amount per unit time is large for the part, that is, the etching rate is high for the part.

  In the step (II), the above-mentioned portion from the one main surface is arranged on the one main surface of the original film 22 by disposing a masking layer that is hard to be chemically etched compared to the portion where the ions 21 collide with the original film 22. You may implement the chemical etching which advances the etching of the said part from the other main surface of the original film 22, suppressing etching. Such etching can be performed, for example, by selecting the type and thickness of the masking layer, disposing the masking layer, selecting etching conditions, and the like.

  Although the kind of masking layer is not specifically limited, It is preferable that it is a layer comprised from the material which is hard to be chemically etched compared with the part which the ion 21 collided in the original film 22. FIG. More specifically, “not easily etched” means, for example, that the amount etched per unit time is small, that is, the etching rate is small. Whether or not chemical etching is difficult can be determined based on the conditions of the asymmetric etching actually performed in the step (II) (the type of etching solution, etching temperature, etching time, etc.). As will be described later, when the asymmetric etching is performed a plurality of times in the step (II) while changing the type and / or arrangement surface of the masking layer, each etching may be determined based on the etching conditions.

  The masking layer may be either more or less likely to be chemically etched than the portion of the original film 22 where the ions 21 do not collide, but it is preferable that the masking layer is less likely to be. If it is difficult to do so, for example, the thickness of the masking layer required to perform asymmetric etching can be reduced.

  In the step (I), when the ion film is irradiated to the original film 22 on which the masking layer is arranged, ion tracks are also formed on the masking layer. Considering this, it is preferable that the material constituting the masking layer is a material in which the polymer chain is hardly damaged even by irradiation with an ion beam.

  The masking layer is composed of at least one selected from, for example, polyolefin, polystyrene, polyvinyl chloride, polyvinyl alcohol, and metal foil. These materials are difficult to be chemically etched and are not easily damaged by ion beam irradiation.

  What is necessary is just to arrange | position a masking layer in at least one part of one main surface of the original film 22 corresponded to the area | region which implements asymmetrical etching. Of course, it can arrange | position to the whole one main surface of the original film 22 as needed.

  The method of disposing the masking layer on the main surface of the original film 22 is not limited as long as the masking layer does not peel off from the main surface during the asymmetric etching. The masking layer is disposed on the main surface of the original film 22 with an adhesive, for example. That is, in the step (II), the chemical etching (asymmetric etching) may be performed in a state where the masking layer is bonded to the one main surface with an adhesive. The arrangement of the masking layer with the pressure-sensitive adhesive can be performed relatively easily. Further, by selecting the type of the pressure-sensitive adhesive, the masking layer can be easily peeled off from the original film 22 after the asymmetric etching.

  In step (II), asymmetric etching may be performed a plurality of times. Further, as long as at least one asymmetric etching is performed, symmetric etching may be performed in which the etching of the trajectory 23 progresses equally from both main surfaces of the original film 22. For example, the masking layer may be peeled off from the polymer film 1 in the course of etching to switch from asymmetric etching to symmetric etching. Alternatively, the asymmetric etching may be performed by arranging the masking layer after performing the symmetric etching.

  When asymmetric etching is performed a plurality of times, the etching conditions may be changed in each etching.

  FIG. 10 shows an example of the step (II).

  In the example shown in FIG. 10, a masking layer 41 is disposed on one main surface of the original film 22 after the ion beam irradiation (FIG. 10A), and chemical etching is performed in this state. As a result, etching proceeds along the locus 23 formed by ion beam irradiation from the other surface where the masking layer is not disposed, and the through-hole 5 extending along the locus 23 is formed (FIG. 10). (B)). As shown in FIG. 10B, the etching does not proceed from the main surface on which the masking layer 41 is disposed, and no pores are formed. The cross-section of the formed through-hole 5 has a conical shape, and the tip of the through-hole 5 opens on the one main surface of the original film 22. And the opening diameter in the said one main surface of the through-hole 5 and the opening diameter in the other main surface are mutually different, and the opening diameter in the said other main surface used as the etching origin is larger. That is, in the example shown in FIG. 10, a polymer film 2 having a through hole having a conical cross-sectional shape and having an opening diameter different between both main surfaces of the film is obtained. (FIG. 10 (c)). The ratio a / b between the opening diameter a of the through hole 5 in the one main surface and the opening diameter b of the through hole 5 in the other main surface is, for example, 80% or less, and is performed in the step (II). Depending on the etching conditions, this ratio can be further reduced.

  Thus, in process (II), the through-hole 5 in which the hole diameter is changing in the film thickness direction of the film can be formed. The direction in which the central axis 6 of the through hole 5 extends is the direction in which the locus 23 extends.

  In the example shown in FIG. 10, since asymmetric etching has already been performed once, chemical etching may be further advanced from the state where the masking layer 41 shown in FIG. Thereby, for example, the ratio a / b of the opening diameter of the through hole 5 or the opening diameter a of the through hole 5 on one main surface of the polymer film 2 and the opening diameter b of the through hole 5 on the other main surface. Can be controlled.

  The opening diameter of the through-hole 5 can also be controlled by etching conditions such as etching temperature, etching time, and composition of the etching treatment liquid.

  The polymer film 2 having the through holes 5 cannot be formed by a conventional method.

  The etching process liquid used for chemical etching is not specifically limited. The etching solution is, for example, an alkaline solution, an acidic solution, or an alkaline solution or an acidic solution to which at least one selected from an oxidizing agent, an organic solvent, and a surfactant is added. The alkaline solution is, for example, a solution (typically an aqueous solution) containing a base such as sodium hydroxide or potassium hydroxide. The acidic solution is, for example, a solution (typically an aqueous solution) containing an acid such as nitric acid or sulfuric acid. Examples of the oxidizing agent include potassium dichromate, potassium permanganate, and sodium hypochlorite. The organic solvent is, for example, methanol, ethanol, 2-propanol, ethylene glycol, amino alcohol, N-methylpyrrolidone, N, N-dimethylformamide. The surfactant is, for example, an alkyl benzene sulfonate or an alkyl sulfate.

  Except for the asymmetric etching using the masking layer 41, a specific etching method may follow a known method. For example, the beam-irradiated original film 22 in which the masking layer 41 is disposed may be immersed in an etching treatment solution at a predetermined temperature for a predetermined time.

  The etching temperature is, for example, 40 to 150 ° C., and the etching time is, for example, 10 seconds to 60 minutes.

  After step (II), part or all of the masking layer 41 can be left on the polymer film 2 as necessary. The remaining masking layer 41 can be used, for example, as a mark for distinguishing the one main surface (the main surface on which the masking layer is disposed) and the other main surface of the polymer film 2.

  The manufacturing method of the polymer film 2 may include any step other than the steps (I) and (II).

[Waterproof sound transmission member]
An example of the waterproof sound-permeable member of the present invention is shown in FIG. A waterproof sound-permeable member 11 shown in FIG. 11 is a waterproof sound-permeable membrane 1 having a circular shape when viewed from a direction perpendicular to the main surface of the membrane, and a ring-shaped sheet joined to the peripheral edge of the membrane 1. A support 51. The form in which the support body 51 is joined to the waterproof sound-permeable membrane 1 reinforces the waterproof sound-permeable membrane 1 and improves its handleability. Moreover, since the support body 51 becomes an allowance to the part in which the waterproof sound-permeable member 11 is arrange | positioned, such as opening of a housing | casing, the attachment operation | work of the waterproof sound-permeable membrane 1 becomes easy.

  The shape of the support body 51 is not limited. For example, as shown in FIG. 12, a support 51 that is a frame-like sheet joined to the peripheral edge of a waterproof sound-permeable membrane 1 having a rectangular shape when viewed from a direction perpendicular to the main surface of the membrane. Also good. As shown in FIGS. 11 and 12, by reducing the shape of the support 51 to the shape of the peripheral edge of the waterproof sound-permeable membrane 1, a decrease in sound permeability of the waterproof sound-permeable membrane 1 due to the arrangement of the support 51 is suppressed. The Moreover, the sheet-like support body 51 is preferable from the viewpoint of improving the handleability of the waterproof sound-permeable member 11 and the disposition property to the housing, particularly the disposition property within the housing.

  The material which comprises the support body 51 is resin, a metal, and these composite materials, for example. The resin is, for example, a polyolefin such as polyethylene or polypropylene; a polyester such as PET or polycarbonate; a polyimide or a composite material thereof. The metal is a metal having excellent corrosion resistance, such as stainless steel or aluminum.

  The thickness of the support 51 is, for example, 5 to 500 μm, and preferably 25 to 200 μm. When attention is paid to the function as an attachment margin, the ring width (frame width: difference between the outer shape and the inner diameter) is suitably about 0.5 to 2 mm. For the support 51, a foam made of the above resin may be used.

  The joining method of the waterproof sound-permeable membrane 1 and the support 51 is not particularly limited. For example, methods such as heat welding, ultrasonic welding, adhesion with an adhesive, and adhesion with a double-sided tape can be employed.

  The direction of the waterproof sound-permeable membrane 1 in the waterproof sound-permeable member 11 (the direction of the main surface of the polymer film 2 provided in the waterproof sound-permeable membrane 1) is not limited. For example, when the waterproof sound-permeable member 11 is fixed to the opening of the casing, the main surface 4a of the polymer film 2 (the opening diameter of the through-hole 5 is on the outside of the casing where water may enter). The waterproof sound-permeable membrane 1 and the support body 51 may be joined so that the relatively small main surface 4a) faces. In this case, it is possible to ensure higher waterproofness of the housing and higher sound transmission from the inside of the housing.

  The waterproof sound-permeable member 11 may include two or more waterproof sound-permeable membranes 1 and / or two or more supports 51.

  The waterproof sound-permeable member 11 can be used for the same application as the conventional waterproof sound-permeable member.

[Electronics]
An example of the electronic device of the present invention is shown in FIG. 13A. The electronic device illustrated in FIG. 13A is a smartphone that is a type of mobile phone. The housing 61 of the smartphone 65 includes an opening 62a provided in the vicinity of a transducer that is a kind of sound generation part and sound receiving part, and an opening 62b provided in the vicinity of a microphone that is a kind of sound receiving part, And an opening 62c provided in the vicinity of a speaker which is a kind of sound generation unit. Sound is transmitted between the outside of the smartphone 65 and each acoustic unit (transducer, microphone, and speaker) accommodated in the housing 61 via the openings 62a to 62c. As shown in FIG. 13B, in the smartphone 65, the waterproof sound-permeable membrane 1 is attached to the housing 61 from the inside so as to close these openings 62a to 62c. Thereby, while being able to transmit a sound between the exterior of the smart phone 65 and an acoustic part, it can prevent that water permeates into the housing | casing 61 via an opening from the exterior. In addition, the waterproof sound-permeable membrane 1 having a high degree of freedom in controlling sound permeability and waterproofness can achieve improvement in design and design freedom such as miniaturization and / or thinning of the smartphone 65.

  The place and method of disposing the waterproof sound-permeable membrane 1 in the electronic device 65 of the present invention are not limited as long as the opening (opening) provided in the housing 61 of the device 65 is closed by the waterproof sound-permeable membrane 1. . In the example shown in FIG. 13B, the waterproof sound-permeable membrane 1 is joined to the housing 61 via the support body 51 (that is, as a waterproof sound-permeable member). For the placement of the waterproof sound-permeable membrane 1 in the electronic device 65, a technique such as sticking using a double-sided tape, thermal welding, high-frequency welding, ultrasonic welding, or the like can be employed.

  The direction of the waterproof sound-permeable membrane 1 in the electronic device 65 (the direction of the main surface of the polymer film 2 included in the waterproof sound-permeable membrane 1) is not limited. For example, the waterproof sound-permeable membrane 1 is arranged so that the main surface 4a of the polymer film 2 (the main surface 4a having a relatively small opening diameter of the through hole 5) faces the outside of the housing 61 of the electronic device 65. It may be. In this case, higher waterproofness and higher sound transmission from the inside of the housing 81 can be ensured.

  The casing 61 is made of resin, metal, glass, and a composite material thereof. The display unit of the electronic device 65 may constitute a part of the housing 61 like a smartphone and a tablet computer.

  The electronic device of the present invention is not limited to the smartphone 65. An opening for transmitting sound between the outside and the sound section is provided in the housing, and it is necessary to prevent intrusion of water into the inside through the opening. This applies to all types of electronic devices that can be arranged to close the opening. The electronic apparatus of the present invention is, for example, a mobile phone such as a feature phone and a smartphone, a tablet computer, a wearable computer, a PDA, a game machine, a mobile computer such as a notebook computer, an electronic notebook, a digital camera, a video camera, and an electronic book reader. is there.

[Electronic case]
An example of the electronic device case of the present invention is shown in FIG. 14A. The case 75 shown in FIG. 14A is provided with openings 71 a to 71 c that transmit sound between the acoustic part of the electronic device housed in the case 75 and the outside of the case 75. A case 75 shown in FIG. 14A is a case of a smartphone of a type different from the smartphone 65 shown in FIG. 13A. The opening 71a transmits sound to the receiver of the smartphone, and the opening 71b transmits sound to the transmitter of the smartphone. In order to transmit the sound, the openings 71c are provided to transmit the sound from the speaker of the smartphone to the outside. As shown in FIG. 14B, the case 75 further includes a waterproof sound-permeable membrane 1 arranged so as to close the openings 71a (71b, 71c). With this waterproof sound-permeable membrane 1, sound is transmitted between the acoustic part of the electronic device housed in the interior 72 of the case 75 and the outside, and the case 75 through the opening 71a (71b, 71c) from the outside. Water can be prevented from entering the interior 72 and thus the electronic equipment. In addition, the waterproof sound-permeable membrane 1 having a high degree of freedom in controlling sound permeability and waterproofness is designed for electronic devices that are designed to be downsized and / or thinned and that are compatible with electronic devices with a high degree of design freedom. Case 75 can be used. Moreover, it can also be set as the case 75 for electronic devices with the small area of opening 71a (71b, 71c), and the improvement of design of case 75 itself and a design freedom can be achieved.

  The method of disposing the waterproof sound-permeable membrane 1 in the electronic device case 75 of the present invention is not limited as long as the openings (openings) 71a (71b, 71c) are closed by the membrane 1. In the example shown in FIG. 14B, the waterproof sound-permeable membrane 1 is joined from the inside 72 to the case 75 via the support body 51 (that is, as a waterproof sound-permeable member). For the placement of the waterproof sound-permeable membrane 1 on the case 75, a technique such as sticking using a double-sided tape, thermal welding, high-frequency welding, or ultrasonic welding can be employed. It is also possible to arrange the waterproof sound-permeable membrane 1 from the outside of the case 75.

  The direction of the waterproof sound-permeable membrane 1 in the electronic device case 75 (the direction of the main surface of the polymer film 2 provided in the waterproof sound-permeable membrane 1) is not limited. For example, the waterproof sound-permeable membrane 1 may be arranged so that the main surface 4a of the polymer film 2 (the main surface 4a having a relatively small opening diameter of the through hole 5) faces the outside of the case 75. In this case, higher waterproofness and higher sound transmission from the inside of the housing 81 can be ensured.

  The electronic device case 75 is made of resin, metal, glass, and a composite material thereof. The electronic device case 75 can have any configuration as long as the effects of the present invention can be obtained. For example, a case 75 shown in FIG. 14A is a case for a smartphone, and includes a film 73 that can operate a touch panel of a smartphone housed inside.

[Waterproof sound transmission structure]
An example of the waterproof sound-permeable structure of the present invention is shown in FIG. The waterproof sound-transmitting structure 12 shown in FIG. 15 is provided with a casing 81 provided with an opening 82 for transmitting sound between the inside 83 and the outside, and a waterproof sound-transmitting sound disposed so as to close the opening (opening) 82. A membrane 1. With this waterproof sound-permeable membrane 1, it is possible to prevent water from entering the housing 81 from the outside through the opening 82 while transmitting sound between the outside and the inside 83 of the housing 81. In the example shown in FIG. 15, the waterproof sound-permeable membrane 1 is joined to the housing 81 via the support 51. In other words, the waterproof sound-permeable member 11 including the waterproof sound-permeable membrane 1 and the support 51 is joined to the housing 81. In the example shown in FIG. 15, the waterproof sound-permeable membrane 1 is joined to the housing 81 from the inside 83 of the housing 81, but may be joined from the outside of the housing 81.

  The casing 81 is made of resin, metal, glass, and a composite material thereof.

  For the arrangement of the waterproof sound-permeable membrane 1, techniques such as sticking using double-sided tape, thermal welding, high-frequency welding, and ultrasonic welding can be employed. The support 51 may be a double-sided tape.

  The direction of the waterproof sound-permeable membrane 1 in the waterproof sound-permeable structure 12 (the direction of the main surface of the polymer film 2 included in the waterproof sound-permeable membrane 1) is not limited. For example, the waterproof sound-permeable membrane 1 so that the main surface 4a of the polymer film 2 (the main surface 4a having a relatively small opening diameter of the through hole 5) faces the outside of the housing 81 having the waterproof sound-permeable structure 12. May be arranged. In this case, higher waterproofness and higher sound transmission from the inside of the housing 81 can be ensured.

  Parts, devices, devices, products, etc. having the waterproof sound-permeable structure 12 are not limited.

  The waterproof sound-permeable structure 12 can be applied to various uses as in the conventional waterproof sound-permeable structure.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.

  First, evaluation methods for polymer films and waterproof sound-permeable membranes produced in Examples and Comparative Examples will be described.

[Opening diameter of through hole]
Both main surfaces of the polymer film were observed with a scanning electron microscope (SEM), and the opening diameters of 10 through holes arbitrarily selected from the obtained SEM images were obtained from the images for each main surface, and the average The value was the opening diameter of the through hole in the polymer film.

[Aperture ratio]
The aperture ratio of each main surface of the polymer film was determined by image analysis of an SEM image obtained by observing the main surface with an SEM. The aperture ratio is a ratio (%) of the total area of the openings of the through holes existing in the portion to the area of the evaluation target portion on the main surface.

[Air permeability]
The air permeability in the thickness direction of the waterproof sound-permeable membrane was determined in accordance with the provisions of JIS L1096 (Breathability measurement method A: Frazier type method).

[Water pressure resistance]
The water pressure resistance of the waterproof sound-permeable membrane was determined in accordance with the provisions of the water resistance test method B (high water pressure method) of JIS L1092. However, since the membrane is significantly deformed in the area of the test piece indicated in this regulation, a stainless steel mesh (opening diameter 2 mm) is placed on the opposite side of the pressure surface of the membrane, and measurement is performed with the membrane deformed to some extent. did.

[Pore density]
The pore density of the polymer film is obtained by observing both main surfaces of the film with an SEM, visually counting the number of through holes in the obtained SEM image, and converting this to a value per unit area. It was.

[Oil repellency]
The oil repellency of the waterproof sound-permeable membrane was evaluated as follows. Place the waterproof sound-permeable membrane and copy paper (plain paper) so that the waterproof sound-permeable membrane is on top and the copy paper is on the bottom, and drop a drop of castor oil on the waterproof sound-permeable membrane with a dropper. Left for 1 minute. Thereafter, the waterproof sound-permeable membrane was removed and the state of the copy paper was confirmed. When the copy paper was wet with castor oil, the waterproof sound-permeable membrane was not oil-repellent, and when the copy paper was not wet, it was made oil-repellent.

[Acoustic characteristics]
As the sound permeability of the produced waterproof sound-permeable membrane, acoustic characteristics (sound pressure loss) were evaluated as follows.

  First, as shown in FIG. 16A, a simulated casing 91 (made of polystyrene, outer dimensions 60 mm × 50 mm × 28 mm) imitating the casing of a mobile phone was prepared. The simulated housing 91 is provided with a speaker mounting hole 92 (circular with a diameter of 2.5 mm) serving as an opening for transmitting the sound output from the speaker to the outside of the housing, and a speaker cable conduction hole 93. There is no opening other than that. Next, a speaker 95 (Star Precision Co., Ltd., SCG-16A) was embedded in a urethane sponge filler 94 in which a sound passage hole having a circular shape with a diameter of 5 mm was formed, and housed in the housing 91. The speaker cable 96 of the speaker 95 is led out of the housing 91 from the conduction hole 93, and then the conduction hole 93 is closed with putty.

Next, a double-sided tape 97 made of polyethylene foam (Nitto Denko, No. 57120B, thickness 0.2 mm), a PET film 98 (thickness 0.1 mm), and a double-sided tape 99 made of PET (Nitto Denko) , No.5603, thickness 0.03 mm), and a ring shape having an inner diameter of 2.5 mm and an outer diameter of 5.8 mm, and a ring shape having an inner diameter of 1.0 mm and an outer diameter of 5.8 mm, respectively. The ring was punched. Separately, the waterproof sound-permeable membrane 100 produced in each example and comparative example was punched into a circle having a diameter of 5.8 mm. Next, a ring-shaped double-sided tape 97 with an inner diameter of 2.5 mm, a circular waterproof sound-permeable membrane 100, a ring-shaped double-sided tape 99 with an inner diameter of 2.5 mm, and a ring-shaped PET film 98 with an inner diameter of 2.5 mm In order, the outer shapes were laminated to form a waterproof sound-permeable member A (effective area of the waterproof sound-permeable membrane is 4.9 mm ² ) for evaluating acoustic characteristics (see FIG. 16B). Separately, a ring-shaped double-sided tape 97 having an inner diameter of 1.0 mm, a circular waterproof sound-permeable membrane 100, a ring-shaped double-sided tape 99 having an inner diameter of 1.0 mm, and a ring-shaped PET film 98 having an inner diameter of 1.0 mm are provided. In this order, the outer shapes were aligned and laminated, and a waterproof sound-permeable member B (effective area of the waterproof sound-permeable membrane was 0.8 mm ² ) for evaluating acoustic characteristics was produced.

  Next, the produced waterproof sound-permeable member is attached to the outside of the simulated casing 91 using the polyethylene foam double-faced tape 97 provided in the member so that the waterproof sound-permeable membrane 100 completely covers the opening 92. It was. At that time, gaps were prevented from being formed between the waterproof sound-permeable membrane 100 and the double-sided tape 97 and between the double-sided tape 97 and the simulated casing 91.

  Next, the speaker cable 96 and the microphone (Knowles Acoustic, Spm0405Hd4H-W8) are connected to the acoustic evaluation device (B & K, Multi-analyzer System 3560-B-030), and 21 mm away from the opening 92 of the simulated housing 91. A microphone was placed at the position. Next, SSR analysis (test signal 20 Hz to 10 kHz, sweep) was selected and executed as the evaluation method, and the acoustic characteristics (THD, sound pressure loss) of the waterproof sound-permeable membrane 100 were evaluated. The sound pressure loss is automatically obtained from the signal input to the speaker 95 from the sound evaluation device and the signal detected via the microphone. Separately from this, the sound pressure loss of the blank was calculated in the same manner without placing the waterproof sound-permeable membrane, and the sound pressure loss when the waterproof sound-permeable membrane was placed was subtracted from the sound pressure loss of the blank. Was the sound pressure loss (insertion loss), which is a characteristic of the waterproof sound-permeable membrane. It can be determined that the smaller the insertion loss, the better the characteristics of the sound transmitted through the waterproof sound-permeable membrane. This was performed for each of the waterproof sound-permeable members A and B having different effective areas of the waterproof sound-permeable membranes produced in Examples and Comparative Examples.

Example 1
A non-porous commercially available PET film (it4ip, Track etched membrane, thickness 50 μm) in which a plurality of through holes penetrating in the thickness direction was formed was prepared. This film is a film produced by irradiating a non-porous PET film with an ion beam and chemically etching the irradiated film. When the surface and cross section of this film were observed by SEM, (1) the through hole had a diameter of 0.25 μm and the area of the cross section perpendicular to the direction in which the central axis extends did not change in the film thickness direction. It is a straight hole (constant), (2) the through hole extends in a direction perpendicular to the main surface of the film, and (3) the hole density is 2.0 × 10 ⁶ holes / cm ^2. It was confirmed that

  Next, a polyethylene film (thickness: 55 μm) was attached to one main surface of the prepared PET film with an acrylic adhesive as a masking layer. This was immersed in an etching treatment liquid maintained at 80 ° C. (aqueous solution having a potassium hydroxide concentration of 20 mass%) for 23 minutes. After completion of the etching, the film was taken out from the treatment liquid, immersed in RO water (reverse osmosis membrane filtered water), washed, and then dried in a drying oven at 50 ° C. Thereafter, the masking layer was peeled off to obtain the polymer film 2 in which the through holes 5 were formed.

  The polymer film obtained in Example 1 has a shape in which the area of the cross section perpendicular to the direction in which the central axis extends increases from one main surface (masking surface) to the other main surface (etching surface). It was confirmed that the film had holes. Moreover, the opening diameter of the through-hole in each main surface was 4.5 micrometers about the masking surface, and 6.4 micrometers about the etching surface. The thickness was 45 μm.

  Next, after the liquid repellent treatment liquid is applied to the entire surface including both main surfaces of the produced polymer film 2, it is left to dry at room temperature for 30 minutes, and the surface of the film 2 and the inner peripheral surface of the through-hole 5 A liquid-repellent layer 3 was formed on the film to obtain a waterproof sound-permeable membrane 1. The liquid repellent treatment liquid was prepared by diluting a liquid repellent (X-70-029C, manufactured by Shin-Etsu Chemical Co., Ltd.) with a diluent (manufactured by Shin-Etsu Chemical Co., Ltd., FS thinner) so as to have a concentration of 0.7% by weight.

The thus obtained waterproof sound-permeable membrane 1 has a fragile air permeability of 15 cm ³ / (cm ² · sec), water pressure of 20 kPa on the masking surface side, 15 kPa on the etched surface side, “Yes” for oil repellency, and masking ratio of opening. The surface side was 31.8%, and the etched surface side was 64.3%. The evaluation results of these characteristics (excluding water pressure resistance) are summarized in Table 1 below together with the evaluation results of the waterproof sound-permeable membranes produced in other examples and comparative examples. In the columns of Examples 1 to 3 in Table 1, the evaluation result on the masking surface side is shown on the left side of “/”, and the evaluation result on the etching surface side is shown on the right side of “/”.

  Further, regarding the waterproof sound-permeable membrane 1 thus obtained, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. Table 2 below shows. In the column of Examples 1 to 3 in Table 2, on the left side of “/”, the masking surface of the polymer film 2 (the main surface having a relatively small opening diameter of the through hole) is provided on the outside of the simulated housing. The (maximum) sound pressure loss and water pressure resistance (that is, the water pressure resistance on the masking surface side) when directed to the right side of “/” is the etching surface (through hole of the through-hole) on the outside of the simulated housing. The (maximum) sound pressure loss and water pressure resistance (that is, water pressure resistance on the etching surface side) when the main surface having a relatively large opening diameter is directed are shown.

(Comparative Example 1)
A chemical film was obtained in the same manner as in Example 1 except that the masking layer was not disposed and that the chemical etching was performed for 15 minutes. Thus, the opening diameter of the through-hole in each main surface of the obtained polymer film was 4.5 micrometers in any main surface. The thickness was 45 μm.

Next, the produced polymer film was subjected to a liquid repellent treatment in the same manner as in Example 1. The fragile air permeability of the waterproof sound-permeable membrane thus obtained is 8 cm ³ / (cm ² · sec), the water pressure resistance is 20 kPa on any main surface, the oil repellency is “present”, and the aperture ratio is any main surface. Was 31.8%.

  Moreover, in the waterproof sound-permeable membrane obtained in this way, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. It is shown in Table 2 below.

(Comparative Example 2)
A chemical film was obtained in the same manner as in Example 1 except that the masking layer was not disposed and that the chemical etching was performed for 20 minutes. Thus, the opening diameter of the through-hole in each main surface of the polymer film obtained was 6.0 micrometers about all the main surfaces. The thickness was 45 μm.

Next, the produced polymer film was subjected to a liquid repellent treatment in the same manner as in Example 1. The fragile air permeability of the waterproof sound-permeable membrane thus obtained is 18 cm ³ / (cm ² · sec), the water pressure is 15 kPa on any main surface, the oil repellency is “Yes”, and the aperture ratio is on any main surface. Was 56.5%.

  Moreover, in the waterproof sound-permeable membrane obtained in this way, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. It is shown in Table 2 below.

(Example 2)
Chemical etching was performed in the same manner as in Example 1 except that the pore density of the commercially available PET film prepared first was 4.0 × 10 ⁵ holes / cm ² and that the chemical etching time was 35 minutes. As a result, a polymer film 2 was obtained. The opening diameter of the through hole in each main surface of the polymer film thus obtained was 10.0 μm for the masking surface and 12.5 μm for the etching surface. The thickness was 45 μm.

Next, the produced polymer film was subjected to a liquid repellent treatment in the same manner as in Example 1. The thus obtained waterproof sound-permeable membrane has a fragile air permeability of 65 cm ³ / (cm ² · sec), water pressure is 7 kPa on the masking surface side, 5 kPa on the etching surface side, “Yes” is oil repellency, and the aperture ratio is the masking surface. The side was 31.4% and the etched surface side was 49.1%.

  Further, regarding the waterproof sound-permeable membrane 1 thus obtained, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. Table 2 below shows.

(Comparative Example 3)
Chemical etching was carried out in the same manner as in Example 2 except that the masking layer was not disposed and that the chemical etching was performed for 25 minutes to obtain a polymer film. Thus, the opening diameter of the through-hole in each main surface of the polymer film obtained was 10.0 micrometers about all the main surfaces. The thickness was 45 μm.

Next, the produced polymer film was subjected to a liquid repellent treatment in the same manner as in Example 1. The fragile air permeability of the waterproof sound-permeable membrane thus obtained is 50 cm ³ / (cm ² · sec), the water pressure is 7 kPa on all main surfaces, the oil repellency is “Yes”, and the aperture ratio is on any main surface. Was 31.0%.

  Moreover, in the waterproof sound-permeable membrane obtained in this way, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. It is shown in Table 2 below.

(Comparative Example 4)
A chemical film was obtained in the same manner as in Example 2 except that the masking layer was not disposed and that the chemical etching time was 33 minutes to obtain a polymer film. Thus, the opening diameter of the through-hole in each main surface of the polymer film obtained was 12.5 micrometers in any main surface. The thickness was 45 μm.

Next, the produced polymer film was subjected to a liquid repellent treatment in the same manner as in Example 1. The fragile air permeability of the waterproof sound-permeable membrane thus obtained is 75 cm ³ / (cm ² · sec), the water pressure is 5 kPa on any main surface, the oil repellency is “Yes”, and the aperture ratio is any main surface. Was 48.8%.

  Moreover, in the waterproof sound-permeable membrane obtained in this way, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. It is shown in Table 2 below.

(Example 3)
A polymer film 2 was obtained by performing chemical etching in the same manner as in Example 1 except that the chemical etching time was 16 minutes. Thus, the opening diameter of the through-hole in each main surface of the polymer film obtained was 3.0 micrometers about the masking surface, and 4.0 micrometers about the etching surface. The thickness was 45 μm.

Next, the produced polymer film was subjected to a liquid repellent treatment in the same manner as in Example 1. The fragile air permeability of the waterproof sound-permeable membrane thus obtained is 4.5 cm ³ / (cm ² · sec), the water pressure resistance is 35 kPa on the masking surface side, 21 kPa on the etching surface side, “Yes” is oil repellency, and the aperture ratio is The masking surface side was 14.1% and the etching surface side was 25.1%.

  Further, regarding the waterproof sound-permeable membrane 1 thus obtained, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. Table 2 below shows.

(Comparative Example 5)
A chemical film was obtained in the same manner as in Example 3 except that the masking layer was not disposed and that the chemical etching was performed for 12 minutes. Thus, the opening diameter of the through-hole in each main surface of the polymer film obtained was 3.0 micrometers about any main surface. The thickness was 45 μm.

Next, the produced polymer film was subjected to a liquid repellent treatment in the same manner as in Example 1. The thus obtained waterproof sound-permeable membrane has a fragile air permeability of 2.5 cm ³ / (cm ² · sec), a water pressure of 35 kPa on all main surfaces, an oil repellency of “Yes”, and an aperture ratio of any of the main surfaces. The main surface was also 14.0%.

  Moreover, in the waterproof sound-permeable membrane obtained in this way, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. It is shown in Table 2 below.

(Comparative Example 6)
A chemical film was obtained in the same manner as in Example 3 except that the masking layer was not disposed and that the chemical etching was performed for 14 minutes. Thus, the opening diameter of the through-hole in each main surface of the polymer film obtained was 4.0 micrometers in any main surface. The thickness was 45 μm.

Next, the produced polymer film was subjected to a liquid repellent treatment in the same manner as in Example 1. The fragile air permeability of the waterproof sound-permeable membrane thus obtained is 5 cm ³ / (cm ² · sec), the water pressure resistance is 21 kPa on any main surface, the oil repellency is “Yes”, and the aperture ratio is any main surface. Was 26.5%.

  Moreover, in the waterproof sound-permeable membrane obtained in this way, the sound pressure loss when the sound frequency is 1 kHz and 3 kHz and the maximum sound pressure loss in the sound range between 100 Hz and 3 kHz are combined with the result of the water pressure resistance. It is shown in Table 2 below.

As shown in Table 1, in the waterproof sound-permeable membrane of Example 1 as compared with Comparative Example 1, when the masking surface of the polymer film 2 is directed to the outside of the simulated housing, water enters from outside the housing. As a result, lower sound pressure loss was achieved while ensuring equivalent water pressure resistance. In particular, when the effective area of the waterproof sound-permeable membrane is small (when the effective area is 0.8 mm ² ), the effect of reducing sound pressure loss was great. Further, in the waterproof sound-permeable membrane of Example 1 as compared with Comparative Example 2, when the masking surface of the polymer film 2 is directed to the outside of the simulated housing, the equivalent low sound pressure loss is ensured. Higher water pressure resistance was achieved against water intrusion from outside the housing. The same relationship was confirmed between Example 2 and Comparative Examples 3 and 4 and between Example 3 and Comparative Examples 5 and 6.

  The waterproof sound-permeable membrane of the present invention can be used in various applications for preventing permeation of water while ensuring sound permeability. There are no particular limitations on devices, equipment, components, structures, etc. to which the waterproof sound-permeable membrane of the present invention can be applied.

DESCRIPTION OF SYMBOLS 1 Waterproof sound-permeable membrane 2 Polymer film 3 Liquid repellent layer 4a, 4b (Main surface of polymer film 2) 5 Through-hole 6 Central axis 7 (through-hole 5 central axis 6) Vertical section 8a (opening of the through hole 5 in the main surface 4a) 8b (opening of the through hole 5 in the main surface 4b) 9 breathable support layer 11 waterproof sound transmitting member 12 waterproof sound transmitting structure 21 ion 22 original film 23 ( Trajectory of ion 2 collision in polymer film 1 31 Delivery roll 32 Irradiation roll 33 Ion beam 34 Take-up roll 41 Masking layer 51 Support body 61 Case 62a, 62b, 62c Opening (of case 61) 63 (Housing) 61) internal 65 electronic equipment (smartphone)
71a, 71b, 71c Opening (in case 75) 72 Inside 73 (in case 75) 73 Film 75 Case for electronic device 81 Housing 82 Opening (in housing 81) 83 Inside (in housing 81) 91 Simulated housing 92 Speaker Mounting hole 93 Conductive hole 94 Filler 95 Speaker 96 Speaker cable 97 Double-sided tape 98 PET film 99 Double-sided tape 100 Waterproof sound-permeable membrane

Claims (19)

It is composed of a polymer film having a through hole extending from one main surface to the other main surface,
The through hole is a straight hole in which the central axis of the through hole extends linearly,
The through hole has a shape in which an area of a cross section perpendicular to a direction in which the central axis extends increases from one main surface to the other main surface of the polymer film,
The opening diameter a of the through hole in the one main surface is 12.0 μm or less,
The air permeability from the other principal surface to the one principal surface is represented by the number of fragiles measured in accordance with the provisions of JIS L1096, and is 2.0 cm ³ / (cm ² · sec) or more and 80 cm ³ / (cm Waterproof sound-permeable membrane that is less than ² seconds).   The waterproof sound-permeable membrane according to claim 1, wherein the through hole has a shape in which an area of the cross section continuously increases from the one main surface to the other main surface.   The waterproofing according to claim 1 or 2, wherein a ratio a / b between an opening diameter a of the through hole in the one main surface and an opening diameter b of the through hole in the other main surface is 80% or less. Sound-permeable membrane.   The polymer film has the through-hole extending in a direction in which a central axis is inclined with respect to a direction perpendicular to a main surface of the film, and the through-hole having different directions extending in an inclined manner is mixed in the polymer film. The waterproof sound-permeable membrane according to any one of claims 1 to 3.   The waterproof sound-permeable membrane according to any one of claims 1 to 4, which has been subjected to a liquid repellent treatment. The waterproof sound-permeable membrane according to any one of claims 1 to 5, wherein an effective area is 4.9 mm ² or less.   The waterproof sound-permeable membrane according to any one of claims 1 to 6, wherein the water-resistant pressure measured in accordance with JIS L1092 water resistance test B method (high water pressure method) is 3 kPa or more.   The polymer film is composed of an alkaline solution, an acidic solution, or a resin that decomposes with an alkaline solution or an acidic solution to which at least one selected from an oxidizing agent, an organic solvent, and a surfactant is added. The waterproof sound-permeable membrane according to any one of the above.   The waterproof sound-permeable membrane according to any one of claims 1 to 7, wherein the polymer film is composed of at least one selected from polyethylene terephthalate, polycarbonate, polyimide, polyethylene naphthalate, and polyvinylidene fluoride.   The waterproof sound-permeable membrane according to any one of claims 1 to 9, wherein a coloring treatment for absorbing light included in a wavelength range of 380 nm to 500 nm is applied.   The waterproof sound-permeable membrane according to any one of claims 1 to 9, which is colored black, gray, brown or pink.   The waterproof sound-permeable membrane according to any one of claims 1 to 11, further comprising a sound-permeable support layer laminated on the polymer film. The waterproof sound-permeable membrane according to any one of claims 1 to 12,
A waterproof sound-permeable member comprising a support joined to the waterproof sound-permeable film. A housing in which an acoustic unit is accommodated and an opening for transmitting sound between the acoustic unit and the outside is provided;
A waterproof sound-permeable membrane disposed so as to close the opening and transmitting sound between the acoustic unit and the outside and preventing water from entering the housing from the outside through the opening; ,
An electronic apparatus, wherein the waterproof sound-permeable membrane is the waterproof sound-permeable membrane according to any one of claims 1 to 12.   The electronic device according to claim 14, wherein the waterproof sound-permeable membrane is arranged in the housing such that the one main surface of the membrane faces the outside of the housing. An electronic device case for housing an electronic device having an acoustic part,
An opening for transmitting sound between the acoustic part of the electronic device and the outside is provided,
A waterproof sound-permeable membrane disposed so as to close the opening and transmitting sound between the acoustic part of the electronic device and the outside and preventing water from entering the case from the outside through the opening Prepared,
The case for electronic devices whose said waterproof sound-permeable membrane is the waterproof sound-permeable membrane in any one of Claims 1-12.   The case for electronic equipment according to claim 16, wherein the waterproof sound-permeable membrane is disposed such that the one main surface of the membrane faces the outside of the case. A housing provided with an opening for transmitting sound between the inside and the outside;
A waterproof sound-permeable membrane disposed so as to close the opening, and transmitting sound between the inside and the outside and preventing water from entering the inside through the opening from the outside,
A waterproof sound-permeable structure, wherein the waterproof sound-permeable film is the waterproof sound-permeable film according to any one of claims 1 to 12.   The waterproof sound-permeable structure according to claim 18, wherein the waterproof sound-permeable film is disposed in the housing such that the one main surface of the film faces the outside of the housing.

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