Waterproof film, waterproof member with the same and electronic apparatus

Abstract

To provide a waterproof film capable of responding to further reduction of a transmission region of sounds.SOLUTION: In a waterproof film, when an area of a transmission region is 1.3 mm2, an insertion loss with respect to a sound of 1 kHz frequency is 5.0 dB or less and an insertion loss with respect to a sound of 10 kHz frequency is 5.0 dB or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a waterproof membrane, and a waterproof member and an electronic device that include the waterproof membrane. [Background technology]

[0002] An opening for passing sound or gas may be provided in the housing of an electronic device. For example, electronic devices such as wearable devices including smart watches, smartphones, mobile phones, and cameras have an audio function and have an audio conversion unit such as a microphone and a speaker inside the housing. In order to transmit sound between the audio conversion unit and the outside, an opening (external sound passage) is usually provided in the housing of the electronic device, and the audio conversion unit is accommodated in the housing so that sound can be transmitted between the audio conversion unit and the outside through the opening. In addition, an opening (air vent) for the purpose of eliminating the pressure difference between the inside and outside of the housing may be provided in the housing. On the other hand, water must be prevented from entering the inside of the housing of the electronic device. For this purpose, a waterproof membrane that prevents water from entering is arranged so as to prevent water from entering from the outside of the housing to the inside through the opening.

[0003] Patent Documents 1 and 2 disclose a polytetrafluoroethylene (hereinafter, referred to as "PTFE") porous membrane that can be used as a waterproof membrane. The waterproof membranes of Patent Documents 1 and 2 can be arranged to prevent water from entering through the external sound vent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-165787 [Patent Document 2] JP 2018-19222 A Summary of the Invention [Problem to be solved by the invention]

[0005] Electronic devices with audio functions, such as wearable devices such as smart watches, are becoming more and more diverse and smaller. This may necessitate a further reduction in the sound transmission area (sound-permeable area) of the waterproof membrane, but Patent Documents 1 and 2 do not take this into consideration.

[0006] An object of the present invention is to provide a waterproof membrane that can also accommodate further reductions in the sound transmission area. [Means for solving the problem]

[0007] The present invention relates to The area of ​​the sound transmission area is 1.3 mm 2 At the time, The insertion loss for a sound with a frequency of 1 kHz is 5.0 dB or less. The insertion loss for a sound frequency of 10 kHz is 5.0 dB or less. waterproof membrane, to provide.

[0008] In another aspect, the present invention provides a method for producing a composition comprising: The waterproof membrane of the present invention; A waterproof member comprising: a support joined to the waterproof membrane; to provide.

[0009] In yet another aspect, the present invention provides a method for producing a method for manufacturing a pharmaceutical composition comprising: A housing having an opening; an electronic device comprising: the waterproof membrane of the present invention attached to the housing and / or an internal member of the housing so as to prevent water from entering the housing from the outside through the opening; to provide. Effect of the Invention

[0010] According to the present invention, a waterproof membrane that can accommodate even further reduction in the sound transmission area is achieved. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a cross-sectional view that illustrates a schematic example of a waterproof membrane of the present invention. [Figure 2A] FIG. 2A is a perspective view that illustrates an example of the waterproof member of the present invention. [Figure 2B] FIG. 2B is a plan view showing the surface on which the support 2 is arranged in the waterproof member of FIG. 2A, as viewed from a direction perpendicular to the main surface of the waterproof membrane. [Diagram 3] FIG. 3 is a cross-sectional view showing an example of a state in which the waterproof film of the present invention is disposed in an electronic device. [Figure 4] FIG. 4 is a cross-sectional view showing another example of the waterproof film of the present invention disposed in an electronic device. [Diagram 5] FIG. 5 is a plan view showing an example of an electronic device of the present invention. [Figure 6] FIG. 6 is a schematic diagram for explaining a method for evaluating the maximum velocity Vmax for a waterproof membrane. [Figure 7] FIG. 7 is a schematic diagram for explaining a method for evaluating the sound transmission characteristics (insertion loss) of a waterproof membrane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiment.

[0013] [Waterproof membrane] An example of the waterproof membrane of the present invention is shown in Fig. 1. The waterproof membrane 1 in Fig. 1 has a sound transmission area (sound passing area) of 1.3 mm 2 When the insertion loss for a sound with a frequency of 1 kHz is 5.0 dB or less, and the insertion loss for a sound with a frequency of 10 kHz is 5.0 dB or less. In this specification, the sound transmission area in the waterproof membrane 1 means an area through which sound mainly transmits in the waterproof membrane 1 when the waterproof membrane 1 is placed on an object (for example, the housing of an electronic device or a member inside the housing). The transmission area can typically be defined as an area surrounded by a joint (for example, joint 3 described later) of the waterproof membrane 1 to the surface on which the waterproof membrane 1 is to be placed, as viewed from a direction perpendicular to the main surface of the waterproof membrane 1. However, when both main surfaces of the waterproof membrane 1 are joined to the respective surfaces on which the waterproof membrane 1 is to be placed, that is, when both main surfaces of the waterproof membrane 1 each have a joint, and when the areas of the areas surrounded by the joints between one main surface and the other main surface are different, the smaller area is defined as the area of ​​the transmission area. Note that, when the shape of the transmission area is a circle as viewed from a direction perpendicular to the main surface of the waterproof membrane 1, the area of ​​the transmission area is defined as a circle having a width of 1.3 mm. 2 The above area corresponds to the area of ​​a transparent region having a circular diameter of 1.3 mm.

[0014] Conventionally, the sound transmission characteristics (e.g., insertion loss) of waterproof membranes have been evaluated mainly for sounds with a frequency of 1 kHz, which is considered to be the median of the human vocal range, since the electronic devices in which the waterproof membranes are placed are mainly mobile phones and emphasis has been placed on ensuring the speech characteristics of the phone. However, according to the inventors' research, it has been found that when the area of ​​the transmission area is further reduced, while there is not much change in the sound transmission characteristics for sounds with a frequency of 1 kHz, there is a tendency for the sound transmission characteristics for high-pitched sounds, typically sounds with a frequency of 10 kHz, to decrease significantly. In recent electronic devices equipped with audio functions, there is often a demand for high-quality playback and recording of videos and music, and in order to be able to accommodate further reductions in the transmission area, high It is important to ensure sound transmission characteristics in the sound range. Under such circumstances, the waterproof membrane of the present invention has a transmission area of ​​1.3 mm2, which is the area assuming the further reduction. 2 At a frequency of 1k In the waterproof membrane according to the present invention, both the insertion loss for a sound of 20 Hz and the insertion loss for a sound of 10 kHz are equal to or less than a predetermined value. Therefore, the waterproof membrane according to the present invention can also accommodate a further reduction in the transmission area.

[0015] The area of ​​the transmission area is 1.3 mm 2 The insertion loss of waterproof membrane 1 for a sound with a frequency of 1 kHz when Insertion loss (hereinafter referred to as "IL 1.3 / 1kHz ") may be 4.0 dB or less, 3.5 dB or less, 3.1 dB or less, 2.7 dB or less, or even 2.0 dB or less. 2 The insertion loss of waterproof membrane 1 for a sound with a frequency of 10 kHz when (hereinafter referred to as "insertion loss IL 1.3 / 10kHz ") is 4.5dB or less, 4.0dB or less , 3.6 dB or less, 3.0 dB or less, or even 2.5 dB or less. 1.3 / 1kHz and the above-mentioned insertion loss IL 1.3 / 10kHz Preferred The ranges may be simultaneously satisfied in any combination.

[0016] As the area of ​​the transmission region becomes smaller, the sound transmission characteristics of the waterproof membrane usually decrease (the insertion loss usually increases). However, the waterproof membrane 1 has a transmission region of 1.3 mm 2 If we shrink it further from It is preferable that the area of ​​the transmission region is 0.79 mm2 or less. 2 The insertion loss of waterproof membrane 1 for a sound with a frequency of 1 kHz when 0.79 / 1kHz ") is, for example, 8.5 dB or less, and may be 8.2 dB or less, 6.0 dB or less, 5.1 dB or less, 4.0 dB or less, or even 3.0 dB or less. 2 The insertion loss of waterproof membrane 1 for a sound with a frequency of 10 kHz when Insertion loss (hereinafter referred to as "IL 0.79 / 10kHz") is, for example, less than 8.0 dB, and may be 7.5 dB or less, 7.0 dB or less, 6.5 dB or less, 6.0 dB or less, 5.6 dB or less, 5.0 dB or less, or even 4.6 dB or less. The waterproof membrane 1 has an insertion loss IL 0.79 / 1kHz and the above-mentioned insertion loss IL 0.79 / 10kHz and a preferred range of If the shape of the transparent area is a circle when viewed from a direction perpendicular to the main surface of the waterproof membrane 1, the thickness of the transparent area is 0.79 mm. 2 The above area is the diameter of the circle is 1.0 mm. It corresponds to the area of ​​a certain transparent region.

[0017] The area of ​​the transmission area is 1.3 mm 2 When the frequency is between 200Hz and 10kHz, The maximum insertion loss IL of the waterproof membrane 1 against sound 1.3 / max and minimum insertion loss IL 1.3 / min Difference between IL and 1.3 / max -IL 1.3 / min is, for example, 5.0 dB or less, and may be 4.2 dB or less, 4.0 dB or less, 3.0 dB or less, 2.0 dB or less, 1.5 dB or less, 1.0 dB or less, or even 0.5 dB or less. 2 When The maximum insertion loss IL of waterproof membrane 1 for sounds in the range of several hundred Hz to 10 kHz 0.79 / max and minimum insertion loss IL 0.79 / min Difference between IL and 0.79 / max -IL 0.79 / min is, for example, 7.0 dB or less, and may be 6.0 dB or less, 5.6 dB or less, 5.0 dB or less, 4.0 dB or less, 3.6 dB or less, 3.0 dB or less, 2.5 dB or less, 2.0 dB or less, 1.0 dB or less, or even 0.5 dB or less. max and IL min Difference between IL and max -IL min The smaller the difference IL, the flatter the sound transmission characteristics of the waterproof membrane 1 are over a wide range of sound. 1.3 / max -IL1.3 / min and / or difference IL 0.79 / max -IL 0.79 / min However, a waterproof membrane 1 falling within these ranges has flat sound transmission characteristics over a wide range of sound even if the transmission area is further reduced, and in this respect can more reliably accommodate further reductions in the transmission area.

[0018] The area of ​​the transmission area is 1.3 mm 2 When sound with a frequency of 100Hz to 10kHz is transmitted The maximum velocity V of the waterproof membrane 1 in the out-of-plane vibration direction max (Hereafter, simply "Maximum speed V max ") is, for example, 100 μm / sec or more, 110 μm / sec or more, 120 μm / sec or more The maximum velocity V may be 200 μm / sec or more, 300 μm / sec or more, 400 μm / sec or more, 500 μm / sec or more, 600 μm / sec or more, 700 μm / sec or more, or even 800 μm / sec or more. max The upper limit of the speed is, for example, 1300 μm / sec or less. According to the study, it was found that the transmission of high-frequency sound (typically 10 kHz) through a waterproof membrane is significantly affected by the state of vibration of the membrane that occurs during transmission, unlike the transmission of 1 kHz sound, which was the conventional evaluation standard for waterproof membranes, and mid-low frequency sounds that include the 1 kHz sound (typically 8 kHz or less). More specifically, the maximum speed V max but The larger the value, the better the sound transmission characteristics for sounds with a frequency of 10 kHz. max According to the waterproof membrane 1 that satisfies the above range, the permeable area can be further reduced. This can be done with certainty. Maximum speed of waterproof membrane 1 V max The laser dot vibrometer is a non-contact type. It can be measured using a puller vibrometer.

[0019] The thickness direction air permeability of the waterproof membrane 1 is expressed as the Frazier air permeability measured in accordance with the air permeability measurement method A (Fragile type method) defined in the Japanese Industrial Standards (hereinafter referred to as "JIS") L1096:2010, and is 3.0 cm 3 / (cm 2 sec) or less, and 3 / (cm 2 ·seconds) or less, 2.2cm 3 / (cm 2 ·seconds) or less, 2.0cm 3 / (c m 2 ·seconds) or less, 1.8cm 3 / (cm 2 ·seconds) or less, 1.6cm 3 / (cm 2 ·Seconds) or less, 1.0cm 3 / (cm 2 ·seconds) or less, 0.8cm 3 / (cm 2 ·seconds) or less, 0.5cm 3 / ( cm 2 seconds) or even 0.3 cm 3 / (cm 2 The present inventor According to the study by et al., when the thickness-wise air permeability of the waterproof membrane is within these ranges, expressed as Frazier air permeability, the maximum velocity V max This can increase the area of ​​the transmission area. Even when the size is further reduced, sound transmission characteristics in the high frequency range can be more reliably ensured.

[0020] Even if the size of the waterproof membrane 1 is less than the size of the test piece in the Frazier method (approximately 200 mm x 200 mm), it is possible to evaluate the Frazier air permeability of the waterproof membrane 1 by using a measuring tool that limits the area of ​​the measurement area. One example of the measuring tool is a resin plate with a through hole formed in the center with a cross-sectional area corresponding to the area of ​​the desired measurement area. For example, a measuring tool with a through hole formed in the center with a circular cross-section with a diameter of 1 mm or less can be used.

[0021] The water pressure resistance of the waterproof membrane 1 is, for example, 80 kPa or more. The water pressure resistance of the waterproof membrane 1 may be 100 kPa or more, 150 kPa or more, 180 kPa or more, 200 kPa or more, 230 kPa or more, 250 kPa or more, or even 270 kPa or more. The upper limit of the water pressure resistance is not limited, and is, for example, 3000 kPa or less. The water pressure resistance of the waterproof membrane 1 can be measured as follows using a measuring tool in accordance with the JIS L1092:2009 water resistance test method A (low water pressure method) or B (high water pressure method).

[0022] An example of the measurement tool is a stainless steel disk with a diameter of 47 mm and a through hole (with a circular cross section) with a diameter of 1 mm in the center. This disk has a thickness that does not deform due to the water pressure applied when measuring the water resistance. Measurement of the water resistance using this measurement tool can be carried out as follows.

[0023] The waterproof membrane 1 to be evaluated is fixed to one side of the measuring jig so as to cover the opening of the through hole of the measuring jig. Fixing is performed so that water does not leak from the fixed part of the membrane during the measurement of water pressure resistance. The waterproof membrane 1 can be fixed using double-sided adhesive tape with a water passage hole punched in the center, whose shape matches the shape of the opening. The double-sided adhesive tape can be placed between the measuring jig and the waterproof membrane 1 so that the circumference of the water passage hole and the circumference of the opening match. Next, the measuring jig with the waterproof membrane 1 fixed is set in the test device so that the surface opposite the fixing surface of the waterproof membrane 1 becomes the water pressure application surface during measurement, and the water pressure resistance is measured according to the water resistance test method A (low water pressure method) or method B (high water pressure method) of JIS L1092:2009. However, the water pressure resistance is measured when water comes out from one point on the membrane surface of the waterproof membrane 1. The measured water resistance can be regarded as the water resistance of the waterproof membrane 1. The test device can have the same configuration as the water resistance test device exemplified in JIS L1092:2009 and have a test piece mounting structure to which the above-mentioned measuring tool can be set.

[0024] The surface density of the waterproof membrane 1 is, for example, 1 to 30 g / m 2 The upper limit of surface density is 20 g / m 2 Below 15g / m2 Below 10g / m 2 Below 5g / m 2 The following may be acceptable: The lower limit of the strength is 2 g / m 2 The surface density is calculated by dividing the mass of the waterproof membrane 1 by the area (the main surface It can be calculated by dividing the area by the square footage.

[0025] The waterproof membrane 1 has a thickness of, for example, 3 to 30 μm. The upper limit of the thickness may be 25 μm or less, 20 μm or less, or even 15 μm or less. The lower limit of the thickness may be 5 μm or more.

[0026] The waterproof membrane 1 may satisfy at least two ranges selected from the above-mentioned range of thickness-wise air permeability, range of water pressure resistance, range of areal density, and range of thickness in any combination.

[0027] The waterproof membrane 1 is made of resin such as polyester, such as polyethylene terephthalate (PET), polycarbonate, polyethylene, polyimide, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE), polyurethane, silicone, etc. However, the resin constituting the waterproof membrane 1 is not limited to the above examples. PTFE is suitable as a material for the waterproof membrane 1. A membrane made of PTFE (PTFE membrane) has a good balance between mass and strength.

[0028] The waterproof membrane 1 may be a porous membrane. The PTFE membrane may be a porous membrane (PTFE porous membrane) formed by stretching a paste extrudate or cast membrane containing PTFE particles.

[0029] When it is expected that the electronic device in which the waterproof membrane 1 is disposed will be exposed to high water pressure, the waterproof membrane 1 may be a microporous membrane or a non-porous membrane. The microporous membrane and the non-porous membrane can have high water pressure resistance and are only slightly deformed by water pressure. The microporous membrane may be a PTFE microporous membrane made of PTFE. The non-porous membrane may be a PTFE non-porous membrane made of PTFE.

[0030] In the present specification, the microporous membrane means a membrane having an air permeability in the thickness direction of 10 sec / 100 mL or more and 10,000 sec / 100 mL or less, expressed by air permeability (Gurley air permeability) determined in accordance with the air permeability measurement method B (Gurley type method) specified in JIS L1096:2010. The lower limit of the Gurley air permeability of the microporous membrane may be 20 sec / 100 mL or more, 30 sec / 100 mL or more, 40 sec / 100 mL or more, 50 sec / 100 mL or more, or even 70 sec / 100 mL or more. The upper limit of the Gurley air permeability of the microporous membrane may be 5,000 sec / 100 mL or less, 1,000 sec / 100 mL or less, or even 300 sec / 100 mL or less. In the present specification, the non-porous membrane means a membrane having an air permeability in the thickness direction of more than 10,000 sec / 100 mL, expressed by the above Gurley air permeability. The air permeability in the thickness direction of the porous membrane is usually less than 10 seconds / 100 mL, expressed by the above-mentioned Gurley air permeability.

[0031] Even if the size of the waterproof membrane 1 is smaller than the size of the test piece in the Gurley method (approximately 50 mm x 50 mm), the Gurley air permeability can be evaluated by using a measuring tool. One example of the measuring tool is a polycarbonate disk with a thickness of 2 mm and a diameter of 47 mm, with a through hole (having a circular cross section with a diameter of 1 mm or 2 mm) provided in the center. Measurement of the Gurley air permeability using this measuring tool can be carried out as follows.

[0032] The waterproof membrane 1 to be evaluated is fixed to one surface of the measuring jig so as to cover the opening of the through hole of the measuring jig. The fixing is performed so that air passes only through the opening and the effective test part of the waterproof membrane 1 to be evaluated (the part overlapping with the opening when viewed from a direction perpendicular to the main surface of the fixed waterproof membrane 1) during the measurement of the Gurley air permeability, and the fixing part does not hinder the passage of air through the effective test part of the waterproof membrane 1. To fix the waterproof membrane 1, a double-sided adhesive tape with an air vent hole punched in the center having a shape that matches the shape of the opening can be used. The double-sided adhesive tape may be placed between the measuring jig and the waterproof membrane 1 so that the circumference of the air vent hole and the circumference of the opening match. Next, the measuring jig with the waterproof membrane 1 fixed thereto is set in a Gurley type air permeability tester so that the fixing surface of the waterproof membrane 1 is downstream of the air flow during measurement, and the time t1 for 100 mL of air to pass through the waterproof membrane 1 is measured. Next, the measured time t1 was calculated based on the effective test area of ​​642 [mm2] as specified in the JIS L1096:2010 air permeability measurement method B (Gurley type method). 2 ] per unit of water resistance, the formula t = {(t1) × (waterproof membrane Effective test area [mm 2 ]) / 642[mm 2 ]} and the converted value t obtained is It can be regarded as the Gurley air permeability of the waterproof membrane 1. When the above-mentioned circular plate is used as the measuring tool, the area of ​​the effective test portion of the waterproof membrane 1 is the area of ​​the cross section of the through hole. It has been confirmed that the Gurley air permeability measured without using the measuring tool for the waterproof membrane 1 that satisfies the size of the above-mentioned test piece is well matched with the Gurley air permeability measured using the measuring tool after cutting the waterproof membrane 1 into small pieces, that is, the use of the measuring tool does not substantially affect the measured value of the Gurley air permeability.

[0033] When the temperature of the housing drops due to use or wearing of an electronic device underwater, condensation may occur inside the housing. Condensation can be prevented by reducing the amount of water vapor remaining inside the housing. When the waterproof membrane 1 is a non-porous membrane, such as a PTFE non-porous membrane, the intrusion of water vapor into the housing through the waterproof membrane 1 is prevented. Therefore, by selecting a non-porous membrane as the waterproof membrane 1, the amount of water vapor remaining inside the housing can be reduced, and condensation can be prevented from occurring inside the housing.

[0034] On the other hand, even if water vapor does not penetrate into the inside of the housing through the waterproof membrane 1, there are cases where water vapor cannot be avoided from staying inside the housing. For example, this is the case when the housing is made of a resin having moisture absorption properties, such as polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene resin (ABS), polymethyl methacrylate (PMMA), polypropylene (PP) or polycarbonate (PC). In a housing made of a resin having moisture absorption properties, the external water vapor absorbed by the housing itself is released into the inside of the housing by heat from a heat source inside the housing, and tends to stay there. In this case, in order to prevent the occurrence of condensation inside the housing, it is preferable to select a waterproof membrane 1 that can release the water vapor staying inside the housing to the outside. One example of the selectable waterproof membrane 1 is a porous membrane or a microporous membrane, for example, a PTFE porous membrane or a PTFE microporous membrane. When the waterproof membrane 1 is a porous membrane or a microporous membrane, the water vapor staying inside the housing can be discharged to the outside by the moderate breathability of the waterproof membrane 1, and the occurrence of condensation inside the housing can be prevented. Furthermore, if the waterproof membrane 1 is a microporous membrane, even higher waterproof properties are expected.

[0035] The average pore size of the waterproof membrane 1, for example, a PTFE membrane, may be 0.01 to 1 μm. The upper limit of the average pore size may be 0.85 μm or less, 0.75 μm or less, 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, or even 0.2 μm or less. The maximum pore size of the waterproof membrane 1, for example, a PTFE membrane, may be 0.01 to 3 μm. The upper limit of the maximum pore size may be 1.0 μm or less, 0.8 μm or less, 0.5 μm or less, or even 0.25 μm or less. The ratio of the maximum pore size to the average pore size in the waterproof membrane 1, for example, a PTFE membrane, may be 2 or less, 1.8 or less, 1.6 or less, 1.4 or less, 1.3 or less, or even 1.2 or less. The membrane structure of the waterproof membrane 1 in which the ratio of the maximum pore size to the average pore size is 2 or less can have high homogeneity. Therefore, even when the permeation area is reduced, the membrane structure arranged to block the opening can be used. It is possible to reduce the variation in characteristics under different conditions and to achieve the maximum speed V max Further improvement is expected The average pore size and maximum pore size of the waterproof membrane 1 can be measured in accordance with ASTM (American Society for Testing and Materials) F316-86.

[0036] The porosity of the waterproof membrane 1, for example, a PTFE membrane, may be 1 to 99%. The upper limit of the porosity may be 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, 60% or less, or even 50% or less. The lower limit of the porosity may be 5% or more, 10% or more, 15% or more, or even 20% or more. The porosity of the waterproof membrane 1 can be calculated by substituting the mass, thickness, area (area of ​​the main surface) and true density of the membrane into the following formula. The true density of PTFE is 2.18 g / cm 3 It is. Formula: Porosity (%) = {1 - (mass [g] / (thickness [cm] x area [cm 2 ]×true density[ g / cm 3 ]))}×100

[0037] The specific surface area of ​​the waterproof membrane 1, e.g., a PTFE membrane, is 6 m 2 / g or more, 2 / g or more, 30m 2 / g or more, 50m 2 / g or more, even 75m 2 / g or more. The upper limit of the specific surface area is, for example, 200 m 2 / g or less. The specific surface area is 8m 2 The waterproof membrane 1 has a membrane structure in which fine pores are uniformly distributed throughout the membrane, even though they are dense. max Further improvement is expected. The specific surface area of ​​waterproof membrane 1 is: It can be measured in accordance with ASTM F316-86.

[0038] When the waterproof membrane 1 is a PTFE porous membrane or a PTFE microporous membrane, the membrane 1 may be composed of countless PTFE fine fibers (fibrils). The membrane 1 may also have PTFE aggregated parts (nodes) in which a plurality of fibrils are connected. The fibrils and nodes are typically formed by stretching a PTFE sheet, which is an aggregate of PTFE. The average fibril diameter in the waterproof membrane 1 may be, for example, 0.2 μm or less, 0.16 μm or less, 0.1 μm or less, or even 0.075 μm or less. The lower limit of the average fibril diameter is, for example, 0.02 μm or more. The average inter-node distance in the waterproof membrane 1 may be, for example, 10 μm or less, 7.5 μm or less, 5 μm or less, 2.5 μm or less, or even 1.5 μm or less. The lower limit of the average inter-node distance is, for example, 0.1 μm or more. The average fibril diameter and the average inter-node distance can be evaluated by analyzing magnified observation images of the surface and / or cross section of the waterproof membrane 1 obtained using a scanning electron microscope (SEM) or the like. The average values ​​of measurements evaluated at at least 10 or more measurement points are defined as the average fibril diameter and the average inter-node distance.

[0039] The waterproof membrane 1 may be a single-layer membrane or a laminate of two or more membranes. The waterproof membrane 1 may be composed of a single-layer PTFE membrane or a laminate of two or more PTFE membranes.

[0040] The waterproof membrane 1 may be a colored membrane. The waterproof membrane 1 may be colored, for example, gray or black. A gray or black waterproof membrane 1 can be formed, for example, by mixing a gray or black colorant with the material constituting the membrane. The black colorant is, for example, carbon black. Note that, in terms of the "achromatic color brightness NV" defined in JIS Z8721:1993, a color in the range of 1 to 4 can be defined as "black," and a color in the range of 5 to 8 can be defined as "gray."

[0041] The waterproof film 1 may be subjected to a water-repellent treatment, an oil-repellent treatment, or a liquid-repellent treatment. The liquid-repellent treatment is a treatment that imparts both water-repellent and oil-repellent properties to the waterproof film 1. Furthermore, the surface of the waterproof film 1, particularly the waterproof film 1 containing a PTFE film, may be subjected to a physical treatment such as a sputtering treatment, or a chemical treatment such as a sodium treatment. These treatments can, for example, increase the adhesiveness and adhesion of the treated surface.

[0042] The shape of the waterproof membrane 1 is, for example, a polygon including a circle (including an approximate circle), an ellipse (including an approximate ellipse), a square, and a rectangle, when viewed from a direction perpendicular to the main surface of the waterproof membrane 1. The corners of the polygon may be rounded. However, the shape of the waterproof membrane 1 is not limited to the above examples.

[0043] The waterproof membrane 1 can be distributed in the shape in which it is actually used, or as a roll of a strip-shaped membrane. When distributed in the shape in which it is actually used, it may be distributed as a sheet in which one or more waterproof membranes 1 having that shape are arranged on a base film. The surface of the base film on which the waterproof membrane 1 is arranged may be an adhesive surface. The roll of the waterproof membrane 1 is used after being punched into a predetermined shape, for example.

[0044] The waterproof membrane 1 can be attached to the housing and / or the internal member of the housing so as to prevent water from entering the housing from the outside through the opening, for example, for an electronic device having a housing in which an audio conversion unit that converts between electric signals and sound is housed and an opening (external sound passage) for transmitting sound between the audio conversion unit and the outside is provided. In this case, the waterproof membrane 1 is typically disposed in a sound transmission path between the opening and the audio conversion unit corresponding to the opening. The waterproof membrane 1 may be attached so as to block the opening. The opening is located between the audio conversion unit and the outside of the housing. The internal member of the housing is, for example, the audio conversion unit. The waterproof membrane 1 may be attached so as to block the sound passage hole of the audio conversion unit. However, the arrangement of the waterproof membrane 1 is not limited to the above example, and the internal member of the housing in which the waterproof membrane 1 can be disposed is not limited to the above example. This arrangement of the waterproof membrane 1 can prevent water from entering the inside of the housing and / or the audio conversion unit from the outside through the opening, while allowing sound transmission between the audio conversion unit and the outside through the opening. However, the use of the waterproof membrane 1 is not limited to this example. The sound conversion unit is typically a microphone, a speaker, or an electro-acoustic converter having the functions of both a microphone and a speaker.

[0045] An example of a method for forming the waterproof membrane 1 will be described using a case in which the waterproof membrane 1 is a PTFE membrane.

[0046] The waterproof membrane 1, which is a PTFE porous membrane, can be formed, for example, by forming a mixture of unsintered PTFE powder and a liquid lubricant into a sheet by a method such as extrusion and / or rolling, removing the liquid lubricant from the obtained unsintered PTFE sheet, and stretching the PTFE sheet to make it porous. The stretching may be a multi-stage stretching that combines stretching in the MD direction (longitudinal direction) of the PTFE sheet and stretching in the TD direction (width direction). After forming the unsintered PTFE sheet, the sheet may be treated in an atmosphere at or above the melting point of PTFE to sinter the PTFE, and in this case, a PTFE porous membrane, which is a sintered membrane, is obtained. The above treatment includes stretching for porosity. The liquid lubricant is not limited as long as it can wet the surface of the PTFE particles and can be removed later, and is, for example, a hydrocarbon oil such as naphtha, white oil, and liquid paraffin. In this specification, the term "calcination" refers to treatment of a PTFE molded body in an atmosphere at or above 327°C, which is the melting point of PTFE.

[0047] The waterproof membrane 1, which is a PTFE microporous membrane, can be formed, for example, by removing the liquid lubricant from the unsintered PTFE sheet obtained for forming the PTFE porous membrane, rolling the sheet in a predetermined in-plane direction (typically the MD direction), and then stretching the sheet in another in-plane direction (typically the TD direction) to make it microporous.

[0048] The waterproof membrane 1, which is a non-porous PTFE membrane, can be formed, for example, by rolling a PTFE sheet formed by any method such as a casting method or a skiving method.

[0049] [Waterproof materials] An example of the waterproof member of the present invention is shown in Figures 2A and 2B. The member 11 includes a waterproof membrane 1 and a support 2 joined to the waterproof membrane 1. Fig. 2B shows the surface of the waterproof member 11 in Fig. 2A on which the support 2 is arranged, as viewed from a direction perpendicular to the main surface of the waterproof membrane 1. In the waterproof member 11, the waterproof membrane 1 is reinforced by joining the support 2, and the handleability of the waterproof member 11 as a whole is improved. Also, in the waterproof member 11, the support 2 can be used as an attachment margin to a portion where the waterproof membrane 1 is arranged, such as the inner surface of the housing or the surface of the audio conversion unit.

[0050] In the example shown in Figures 2A and 2B, the shape of the waterproof membrane 1 is a circle when viewed from a direction perpendicular to the main surface of the membrane 1. However, as described above, the shape of the waterproof membrane 1 is not limited to this example. The support 2 has a shape corresponding to the shape of the peripheral portion of the waterproof membrane 1 when viewed from a direction perpendicular to the main surface of the waterproof membrane 1. Specifically, the shape of the support 2 is ring-shaped. The support 2 is joined to the peripheral portion of the waterproof membrane 1. According to this embodiment, it is possible to reduce the size of the waterproof member 11 while ensuring the area of ​​the permeable region of the waterproof membrane 1 as much as possible.

[0051] In the waterproof member 11, the area of ​​the transmission region (sound-permeable region) 4 of the waterproof member 11, which is defined as the region surrounded by the joint 3 between the waterproof membrane 1 and the support 2, is 1.3 mm 2 It may be less than or equal to 0.79 mm. 2 or less. The waterproof member 11 including the waterproof membrane 1 can have good sound transmission characteristics for high-frequency sounds, for example, sounds of 10 kHz, even when the area of ​​the transmission region 4 is within these ranges. In other words, the waterproof member 11 can also accommodate further reductions in the transmission region 4. Note that, when the shape of the transmission region 4 is a circle when viewed from a direction perpendicular to the main surface of the waterproof membrane 1, the waterproof member 11 can have a sound transmission characteristic of 1.3 mm or less. 2 and 0. 79mm 2 The areas of the transparent regions 4, which have circular diameters of 1.3 mm and 1.0 mm, respectively, are Corresponds to the area.

[0052] 2A and 2B includes one support 2, and the one support 2 is joined to one main surface of the waterproof membrane 1. The waterproof member 11 may include two or more supports 2, and a support 2 may be joined to each of the main surfaces of the waterproof membrane 1. When the areas of the transmissive regions 4 differ between the two main surfaces, the smaller area can be used as the area of ​​the transmissive region 4 of the waterproof member 11.

[0053] The waterproof member 11 can have each of the properties that the waterproof membrane 1 can have, which were described above in the description of the waterproof membrane 1.

[0054] The material constituting the support 2 is, for example, a resin, a metal, or a composite material thereof. The resin is, for example, a polyolefin such as polyethylene or polypropylene; a polyester such as PET; a polycarbonate; a polyimide, or a composite material thereof. The metal is, for example, a metal having excellent corrosion resistance such as stainless steel or aluminum. The support 2 may be made of a resin foam.

[0055] The support 2 may be a double-sided adhesive tape. By using the support 2, which is a double-sided adhesive tape, as a fixing means, the waterproof membrane 1 and the waterproof member 11 can be fixed more reliably to the surface on which they are to be placed, and this makes it possible to further improve the waterproofing provided by the waterproof membrane 1 and the waterproof member 11.

[0056] A known double-sided adhesive tape can be used as the double-sided adhesive tape that can constitute the support 2. The substrate of the double-sided adhesive tape is, for example, a resin film, nonwoven fabric, or foam. Resins that can be used for the substrate are not limited, and examples include polyesters such as PET; polyolefins such as polyethylene; and polyimides. Various adhesives such as acrylic adhesives and silicone adhesives can be used for the adhesive layer of the double-sided adhesive tape. It is preferable to use an acrylic adhesive for the adhesive layer, since this can improve the adhesive strength to the waterproof membrane 1 and / or the surface on which it is to be placed. The double-sided adhesive tape may be a thermal adhesive tape. The double-sided adhesive tape may be a substrate-less double-sided adhesive tape that does not have a substrate.

[0057] The thickness of the support 2 is, for example, 5 to 500 μm, and may be 25 to 200 μm. In addition, the width of the support 2, which has a shape corresponding to the shape of the peripheral edge of the waterproof membrane 1, may be about 0.5 to 2 mm, focusing on its function as an attachment margin.

[0058] The waterproof membrane 1 and the support 2 can be joined by various methods, such as various welding methods, such as heat welding and ultrasonic welding; adhesion using an adhesive and / or a pressure sensitive adhesive; and adhesion using a double-sided pressure sensitive adhesive tape. In the case of the support 2 being a double-sided pressure sensitive adhesive tape, the support 2 and the waterproof membrane 1 may be joined by the pressure sensitive adhesive layer. However, the method for joining the waterproof membrane 1 and the support 2 is not limited to these examples.

[0059] The waterproof member 11 can be attached to the housing and / or the member inside the housing so as to prevent water from entering the housing from the outside through the opening, for example, for an electronic device having a housing in which a sound conversion unit that converts between electric signals and sound is housed and an opening (external sound passage) for transmitting sound between the sound conversion unit and the outside is provided. In this case, the waterproof member 11 is typically disposed in a sound transmission path between the opening and the sound conversion unit corresponding to the opening. The waterproof member 11 may be attached so as to block the opening. The opening is located between the sound conversion unit and the outside of the housing. The member inside the housing is, for example, the sound conversion unit. The waterproof member 11 may be attached so as to block the sound passage of the sound conversion unit. However, the arrangement of the waterproof member 11 is not limited to the above example, and the member inside the housing in which the waterproof member 11 can be disposed is not limited to the above example. When the support 2 is a double-sided adhesive tape, the adhesive layer of the support 2 may be used to fix the waterproof member 11 to the surface on which the waterproof member 11 is to be disposed. This arrangement of the waterproof member 11 makes it possible to prevent water from entering the inside of the housing and / or the audio conversion unit from the outside through the opening while allowing sound to be transmitted between the audio conversion unit and the outside through the opening. However, the use of the waterproof member 11 is not limited to this example.

[0060] [Placement of waterproof membrane and / or waterproof material on electronic equipment] FIG. 3 shows an example of a state in which the waterproof membrane 1 is disposed in an electronic device. In the example shown in FIG. 3, the waterproof membrane 1 is disposed inside a housing 51 of the electronic device. The housing 51 contains an electroacoustic transducer 53, which is a sound conversion unit, and is provided with an opening (external sound port) 52 for transmitting sound between the electroacoustic transducer 53 and the outside of the housing 51. The electroacoustic transducer 53 has a sound port 54 on one surface 56. The opening 52 and the sound port 54 are in a positional relationship in which sound can be transmitted between the outside of the housing 51 and the electroacoustic transducer 53, and in the example shown in FIG. 3, they overlap each other in their entirety when viewed from a direction perpendicular to the inner surface 55 of the housing 51. The electroacoustic transducer 53 is typically a microphone that converts sound transmitted from the sound port 54 into an electric signal, a speaker that converts the electric signal into sound and outputs it from the sound port 54, or a transducer that has both the functions of a microphone and a speaker. The electroacoustic transducer 53 may be configured by a micromechanical system (MEMS). The waterproof membrane 1 is disposed in a sound transmission path between the opening 52 of the housing 51 and the sound passage 54 of the electroacoustic transducer 53. More specifically, the waterproof membrane 1 is bonded to the inner surface 55 of the housing 51 so as to cover the opening 52 via the support 2 (2B) which is a double-sided adhesive tape. The waterproof membrane 1 is also bonded to the surface 56 of the electroacoustic transducer 53 so as to cover the sound passage 54 via the support 2 (2A) which is a double-sided adhesive tape. The laminate of the waterproof membrane 1 and the supports 2A and 2B is also a waterproof member 11. The waterproof membrane 1 prevents water from entering while allowing sound to pass through. In the electronic device of FIG. 3, the arrangement of the waterproof membrane 1 allows sound to be transmitted between the electroacoustic transducer 53 and the outside of the housing 51 via the opening 52, while preventing water from entering the inside of the housing 51 and the electroacoustic transducer 53 via the opening 52.

[0061] Another example of the waterproof membrane 1 disposed on an electronic device is shown in Fig. 4. The example shown in Fig. 4 is the same as the example shown in Fig. 3 except for the following points. A circuit board 57 with a sound vent 58 formed therein is housed inside the housing 51, and the electroacoustic transducer 53 is fixed to one surface 59 of the circuit board 57 by a socket 61. The opening 52, the sound vent 58, and the sound vent 54 are in a positional relationship that allows sound to be transmitted between the outside of the housing 51 and the electroacoustic transducer 53, and in the example shown in FIG. 4, they entirely overlap each other when viewed from a direction perpendicular to the inner surface 55 of the housing 51. The waterproof membrane 1 is bonded to the one surface 59 of the circuit board 57 via the support 2 (2B) which is a double-sided adhesive tape so as to cover the sound hole 58. The waterproof membrane 1 is also bonded to the surface 56 of the electro-acoustic transducer 53 via the support 2 (2A) which is a double-sided adhesive tape so as to cover the sound hole 54. The waterproof membrane 1 is fixed to the circuit board 57 in a state where it is inserted inside the opening of a socket 61, which is a member of the circuit board 57. Also, the waterproof member 11 including the waterproof membrane 1 and the support 2 (2A, 2B) is fixed to the circuit board 57 in a state where it is inserted inside the opening of the socket 61, which is a member of the circuit board 57. The waterproof membrane 1 and / or the waterproof member 11 may be fixed to the circuit board 57 in a state where it is inserted into a sound hole 58 of the circuit board 57. A seal 60 is disposed between the circuit board 57 and the housing 51. The seal 60 has, for example, the same configuration as the support body 2.

[0062] By arranging the waterproof membrane 1 in the electronic device of Figure 4, sound can be transmitted between the electro-acoustic transducer 53 and the outside of the housing 51 through the opening 52, while preventing water from entering the inside of the housing 51 and the electro-acoustic transducer 53 through the opening 52.

[0063] The arrangement of the waterproofing member relative to the electronic device is not limited to those shown in the above examples.

[0064] [Electronic equipment] An example of the electronic device of the present invention is shown in FIG. 5. The electronic device shown in FIG. 5 is a smartphone 62. An audio conversion unit that converts between electric signals and sound is disposed inside a housing 51 of the smartphone 62. The housing 51 is provided with an opening 52 (52A) and an opening 52 (52B) that are external sound passages. The smartphone 62 includes a waterproof membrane 1 and / or a waterproof member 11. The arrangement of the waterproof membrane 1 and / or the waterproof member 11 in the smartphone 62 is as shown in FIG. 3 or FIG. 4, for example. However, the arrangement is not limited as long as the waterproof membrane 1 is disposed in the sound transmission path between the opening 52A and / or the opening 52B and the audio conversion unit corresponding to each opening 52A, 52B, thereby enabling the transmission of sound between each audio conversion unit and the outside via the opening 52A and / or the opening 52B, while preventing the intrusion of water from the outside into the inside of the housing 51 and / or each audio conversion unit via the opening 52A and / or the opening 52B.

[0065] The electronic device including the waterproof film 1 and / or the waterproof member 11 is not limited to the smartphone 62. Examples of the electronic device include wearable devices such as smart watches and wristbands, various cameras including action cameras and security cameras, communication devices such as mobile phones and smartphones, virtual reality (VR) devices, augmented reality (AR) devices, sensor devices, and the like.

[0066] When the waterproof membrane 1 has breathability in the thickness direction, the waterproof membrane 1 and waterproof member 11 described above can be attached to a housing and / or a member inside the housing for use in an electronic device having a housing with an opening (e.g., an air vent, ventilation opening, pressure adjustment opening, etc.) for the purpose of gas circulation, so as to prevent water from entering the housing from the outside to the inside through the opening. In this case, the waterproof membrane 1 and waterproof member 11 function as a waterproof membrane and waterproof member that respectively prevent water from entering while allowing gas to pass through, and this function allows ventilation between the inside and outside of the housing in the electronic device through the opening, while preventing water from entering the inside of the housing through the opening. The waterproof film 1 and the waterproof member 11 may be used without being directly combined with the voice conversion unit.

[0067] Examples of electronic devices that have a housing with an opening for the purpose of gas flow include sensor devices such as pressure sensors, flow rate sensors, and gas concentration sensors (O2 sensors). The electronic device may be an electronic device having a sound function such as a smartphone. In this case, the opening is typically provided in the housing separately from the external sound passage. However, the electronic device having a housing provided with an opening for the purpose of gas flow is not limited to the above example. EXAMPLES

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0069] (Preparation of waterproof membrane) The following five types of waterproof membranes, A, B, C, D, and E, were prepared.

[0070] [Waterproof membrane A (Example 1)] 100 parts by weight of PTFE fine powder (Polyflon F-104, Daikin Industries, Ltd.) was mixed with 20 parts by weight of liquid lubricant (n-dodecane, Japan Energy Co., Ltd.) uniformly, compressed into a cylinder, and then extruded with a ram extruder to obtain a sheet-like molded body extending in the longitudinal direction. This sheet-like molded body, still containing the liquid lubricant, was passed between metal rolling rolls and rolled to a thickness of 0.2 mm. Thereafter, the sheet-like molded body was heated to 150°C to remove the liquid lubricant, and the sheet-like molded body was dried. Thereafter, the sheet-like molded body was stretched at 2.5 times the longitudinal direction at 300°C, stretched at 20 times the width direction at 200°C, and then fired at 400°C, which is a temperature above the melting point of PTFE, to obtain a waterproof membrane A, which is a PTFE porous membrane with a thickness of 15 μm.

[0071] [Waterproof membrane B (Example 2)] A sheet-like molded body having a thickness of 0.2 mm (before removing the liquid lubricant) obtained in the same manner as in Example 1 was stretched at room temperature by 4.5 times in the width direction. Next, the stretched sheet-like molded body was heated to 150°C to remove the liquid lubricant, and then dried. Thereafter, the sheet-like molded body was stretched at 2.0 times in the longitudinal direction at 300°C, stretched at 20 times in the width direction at 100°C, and then fired at 400°C, which is a temperature higher than the melting point of PTFE, to obtain a waterproof membrane B, which is a PTFE porous membrane having a thickness of 6 μm.

[0072] [Waterproof membrane C (Example 3)] A fluorosurfactant (MEGAFAC F-142D, manufactured by DIC) was added in an amount of 1 part by mass per 100 parts by mass of PTFE to a dispersion of PTFE particles (PTFE particle concentration 40% by mass, average particle size of PTFE particles 0.2 μm, containing 6 parts by mass of nonionic surfactant per 100 parts by mass of PTFE). Next, a coating film (thickness 20 μm) of the above PTFE dispersion to which the fluorosurfactant was added was formed on the surface of a strip-shaped polyimide substrate (thickness 125 μm). The coating film was formed by immersing the polyimide substrate in the PTFE dispersion and then pulling it up. Next, the entire substrate and coating film were heated to form a cast film of PTFE. The heating was performed in two stages: a first heating (100° C., 1 minute) and a second heating (390° C., 1 minute). The first heating removed the dispersion medium contained in the coating film, and the second heating promoted the formation of a cast film based on the binding of the PTFE particles contained in the coating film. The above immersion and subsequent heating were repeated two more times, and then the formed PTFE cast film (thickness 25 μm) was peeled off from the polyimide substrate. Next, the peeled cast film was rolled in the MD direction (longitudinal direction) and further stretched in the TD direction (width direction). The rolling in the MD direction was performed by roll rolling. The stretching ratio (area ratio) was 2.0 times, and the temperature (roll temperature) was 170°C. Stretching in the TD direction was performed using a tenter stretching machine. The stretching ratio in the TD direction was 2.0 times, and the temperature (temperature of the stretching atmosphere) was 300°C. In this way, a film with a thickness of 10 μm and an areal density of 15 g / m 2 of A waterproof membrane C, which was a PTFE microporous membrane, was obtained.

[0073] [Waterproof membrane D (Example 4)] A sheet-like molded body having a thickness of 0.2 mm (before removing the liquid lubricant) obtained in the same manner as in Example 1 was stretched at room temperature by 4.5 times in the width direction. Next, the stretched sheet-like molded body was heated to 150°C to remove the liquid lubricant, and then dried. Thereafter, the sheet-like molded body was stretched at 3.0 times in the longitudinal direction at 300°C, stretched at 20 times in the width direction at 100°C, and then fired at 400°C, which is a temperature higher than the melting point of PTFE, to obtain a waterproof membrane D, which is a PTFE porous membrane having a thickness of 8 μm.

[0074] [Waterproof membrane E (comparative example)] The sheet-like molded body from which the liquid lubricant had been removed was stretched in the longitudinal direction at a temperature of 380°C and a stretch ratio of 4.5 times, and in the transverse direction at a temperature of 330°C and a stretch ratio of 10 times. Except for not performing baking after the transverse stretching, a waterproof membrane E, which was a PTFE porous membrane with a thickness of 25 μm, was obtained in the same manner as waterproof membrane A.

[0075] (Evaluation of waterproof membrane properties) The waterproof membrane prepared above was evaluated for the following properties.

[0076] [Porosity] The porosity of the waterproof membrane was determined by the method described above.

[0077] [Average pore diameter and maximum pore diameter] The average pore size and maximum pore size of the waterproof membrane were determined using an Automated Perm Porometer manufactured by Porous Materials Inc., which is capable of measuring in accordance with ASTM F316-86. From the average pore size and maximum pore size thus obtained, the ratio of the maximum pore size to the average pore size was calculated.

[0078] [Specific surface area] The specific surface area of ​​the waterproof membrane was determined using a Perm-Porometer manufactured by Porous Materials Inc., which is capable of measurements in accordance with ASTM F316-86.

[0079] [Average fibril diameter and average internode distance] The average fibril diameter and average inter-node distance of the waterproof membrane were determined by defining 10 measurement areas (50 μm x 50 μm squares) in a magnified observation image (magnification 1000 to 20000 times) obtained by observing the surface of the waterproof membrane to be evaluated using a SEM, determining the average diameter of the fibrils present in each measurement area, and the average distance between the nodes present in each measurement area, and then calculating the average values ​​between the measurement areas for each of the average diameter and average distance.

[0080] [Breathability through thickness (Fragile air permeability)] The breathability of the waterproof membrane in the thickness direction was evaluated as the Frazier air permeability by the above-mentioned method based on the air permeability measurement method A (Fragile type method) specified in JIS L1096:2010.

[0081] [Water pressure resistance] The water pressure resistance of the waterproof membrane was measured using the above-mentioned measuring jig in accordance with the water resistance test method A (low water pressure method) or method B (high water pressure method) of JIS L1092:2009.

[0082] [Maximum speed V max ] The area of ​​the transmission area is 1.3 mm 2 When sound with a frequency of 100Hz to 10kHz is transmitted The maximum velocity of out-of-plane vibration of the waterproof membrane at max was performed using a laser Doppler vibrometer. The evaluation method is described with reference to FIG.

[0083] The waterproof membrane to be evaluated was punched out into a circle with a diameter of 5.8 mm to obtain a test piece 71. Next, supports 72A and 72B (ring-shaped with an outer diameter of 5.8 mm and an inner diameter of 1.3 mm, thickness 0.2 mm) made of double-sided adhesive tape (manufactured by Nitto Denko, No. 57120B) were bonded to both main surfaces of the obtained test piece 71. The bonding of supports 72A and 72B to test piece 71 was carried out so that the outer circumference of each support 72A and 72B coincided with the circumference of test piece 71 by the adhesive layer of the double-sided adhesive tape. The shape and area of ​​the transmission region in test piece 71 were determined to be a circle when viewed perpendicular to the main surface of test piece 71, and a circle with a diameter of 1.3 mm when viewed perpendicular to the main surface of test piece 71, by bonding supports 72A and 72B having the above-mentioned predetermined shape and size. 2 Next, we made a plastic model that resembled the housing of an electronic device. A carbonate sheet 73 (circular with a diameter of 47 mm, thickness of 1.0 mm) and a polycarbonate sheet 75 (circular with a diameter of 47 mm, thickness of 1.0 mm) simulating the housing of the voice conversion unit were bonded to the surface of the support 72B opposite to the surface of the test piece 71 side, and to the surface of the support 72A opposite to the surface of the test piece 71 side. Sound holes 74, 76 (both of which have a cross-sectional shape of a circle with a diameter of 1.0 mm) are provided in the center of the polycarbonate sheets 73, 75, respectively, and the polycarbonate sheets 73, 75 were bonded to the test piece 71 so that the centers of the sound holes 74, 76 coincide with the center of the test piece 71 when viewed from a direction perpendicular to the main surface of the test piece 71. In addition, when the members were bonded to each other, no gap was generated between the two members to be bonded. This point is the same for the bonding of members described below.

[0084] Separately, a test sound transmitter 82 was prepared, which included a housing 78 (each wall of which was made of a 2.0 mm thick polycarbonate plate) having a rectangular parallelepiped outer shape with a width of 50 mm, a depth of 60 mm, and a height of 28 mm, and a speaker 79 (Star Micronics, SCC-16A) mounted on the inner surface of the bottom wall of the housing 78. A sound vent 80 (having a cross-sectional shape of a circle with a diameter of 2.0 mm) was provided in an upper wall 81 of the test sound transmitter 82, and the speaker 79 was mounted on the inner surface so that the center of the sound vent 80 coincided with the center of the cone which is the output part of the speaker 79 when viewed from a direction perpendicular to the surface of the upper wall 81.

[0085] Next, a laminate of the test piece 71, supports 72A and 72B, and polycarbonate sheets 73 and 75 was bonded to the outer surface of the upper wall 81 of the test sound generator 82 via a seal 77 (ring-shaped with an outer diameter of 5.8 mm and an inner diameter of 1.3 mm, thickness of 1.3 mm) made of double-sided adhesive tape (manufactured by Nitto Denko, No. 57120B). The laminate was bonded so that the center of the test piece 71 and the center of the sound hole 80 of the test sound generator 82 coincided when viewed from a direction perpendicular to the main surface of the test piece 71. In the above bonded state, the distance between the surface of the speaker 79 and the test piece 71 was about 21 mm.

[0086] Next, a sound having a frequency of 100 Hz to 10 kHz (sound pressure level at the sound passage 80 of 85 dB) was output from the speaker 79 while increasing the frequency from 100 Hz to pass through the test piece 71, and a laser oscillator / receiver 83 of a laser Doppler vibrometer (Polytec, NLV-2500) was fixed above the sound passage 74, and a laser 84 was irradiated onto the upper surface of the test piece 71 through the sound passage 74, and the laser 84 reflected by the upper surface was received by the laser oscillator / receiver 83. The irradiation direction of the laser 84 was perpendicular to the main surface of the test piece 71. According to the laser Doppler vibrometer, the laser 84 irradiated onto the test piece 71 and reflected by the upper surface of the test piece 71 was analyzed by the attached analysis software, and the state of vibration of the test piece 71 in the out-of-plane direction caused by the transmission of the sound (maximum velocity V max (including In this way, the maximum speed of the waterproof membrane V max The measurement environment was evaluated. The environmental temperature was 25±5°C and the relative humidity was 60±5%.

[0087] [Insertion loss] The insertion loss of the waterproof film was evaluated as follows using a mock housing that imitated the housing of an electronic device.

[0088] Maximum speed V max The test piece 71 and the supports 72A and 72B were laminated in the same manner as in the evaluation method of In addition, for the waterproof membranes A to E, the inner diameters of the ring-shaped supports 72A and 72B were changed to 1.5 mm and 1.0 mm, respectively, to increase the area of ​​the permeable region to 1.8 mm. 2 and 0 .79mm 2 A laminate in which the above was changed was also produced.

[0089] Next, as shown in (a) and (b) of FIG. 7, a speaker unit 85 to be housed in a simulated housing was produced. Specifically, the process is as follows. A speaker 86 (Star Precision Co., Ltd., SCC-16A) which is a sound source, and fillers 87A, 87B, and 87C made of urethane sponge for housing the speaker 86 and preventing unnecessary diffusion of sound from the speaker (preventing as much sound as possible from being input to the evaluation microphone without passing through the test piece 71 to be evaluated) were prepared. A sound passage hole 88 having a circular cross section with a diameter of 5 mm is provided in the thickness direction of the filler 87A. A notch having a shape corresponding to the shape of the speaker 86 and a notch for housing the speaker cable 89 and for leading the speaker cable 89 out of the speaker unit 85 are provided in the filler 87B. Next, the fillers 87C and 87B are stacked, and the speaker 86 and the speaker cable 89 are housed in the notch of the filler 87B. Next, filler 87A was layered so that sound could be transmitted from speaker 86 to the outside of speaker unit 85 through sound passage hole 88, thereby obtaining speaker unit 85 (FIG. 7(b)).

[0090] Next, as shown in FIG. 7(c), the speaker unit 85 prepared above was housed inside a simulated housing 91 (made of polystyrene, outer dimensions 60 mm×50 mm×28 mm, plate thickness 2 mm) that imitates the housing of an electronic device. Specifically, the process is as follows. The prepared simulated housing 91 is composed of two parts 91A and 91B, and the parts 91A and 91B can be fitted together. The part 91A is provided with a sound passage 92 (having a circular cross section with a diameter of 2 mm) that transmits the sound emitted from the speaker unit 85 housed inside to the outside of the simulated housing 91, and a conductive hole 93 that leads the speaker cable 89 to the outside of the simulated housing 91. By fitting the parts 91A and 91B together, a space with no openings other than the sound passage 92 and the conductive hole 93 is formed inside the simulated housing 91. After placing the manufactured speaker unit 85 on part 91B, parts 91A and 91B were fitted together to house the speaker unit 85 inside the simulated housing 91. At this time, the sound passage 88 of the speaker unit 85 and the sound passage 92 of part 91A were overlapped so that sound was transmitted from the speaker 86 to the outside of the simulated housing 91 through both sound passages 88, 92. The speaker cable 89 was led out of the simulated housing 91 through the conducting hole 93, which was sealed with putty.

[0091] 7(d), a laminate 94 of the test piece 71 and the supports 72A and 72B was bonded to a surface 95 of the simulated housing 91 on which a sound passage hole 92 was formed, by the adhesive layer of the support 72A. The laminate 94 was bonded so that the transmission region of the test piece 71 covered the sound passage hole 92 and the support 72A did not overlap with the sound passage hole 92 when viewed from a direction perpendicular to the main surface of the test piece 71.

[0092] Next, as shown in FIG. 7(e), a microphone 96 (SPU0410LR5H, manufactured by Knowles Acoustics) was attached to the laminate of the test piece 71 and the supports 72A and 72B by the adhesive layer of the support 72B so as to cover the transmission area of ​​the test piece 71. When the microphone 96 was attached, the distance between the speaker 86 and the microphone 96 was 22 mm. Next, the speaker 86 and the microphone 96 were placed on an acoustic evaluation device (B The test piece 71 was connected to a multi-analyzer system (3560-B-030, manufactured by &K Co.), and the SSR (Solid State Response) mode (test signal 20 Hz to 20 kHz, sweep up) was selected and executed as the evaluation method to evaluate the insertion loss of the test piece 71. The insertion loss is automatically determined from the test signal input from the acoustic evaluation device to the speaker 86 and the signal received by the microphone 96. When evaluating the insertion loss of the test piece 71, the value of the insertion loss when the test piece 71 is removed (blank value) was previously determined. The blank value was -24 dB at a frequency of 1 kHz and -35 dB at a frequency of 10 kHz. The insertion loss of the test piece 71 is the value obtained by subtracting this blank value from the measurement value of the acoustic evaluation device. The smaller the insertion loss value, the better the sound transmission characteristics of the sound output from the speaker 86 are maintained.

[0093] The evaluation results are shown in Tables 1 to 5 below.

[0094] [Table 1]

[0095] [Table 2]

[0096] [Table 3]

[0097] [Table 4]

[0098] [Table 5]

[0099] As shown in Tables 3 to 5, in the waterproof membranes A, B, C, and D of the examples, the area of ​​the permeable region was set to 1.8 mm 2 Reduced from 1.3 mm 2 When the area of ​​the transmission area was 1.8 mm or less, the deterioration of the sound transmission characteristics (increase in insertion loss) for a sound with a frequency of 10 kHz was suppressed compared to the waterproof membrane E of the comparative example. 2 (No significant difference was observed when For waterproofing membranes A, B, C and D, the area of ​​the permeable area is 1.8 mm 2 Reduced from 1.3 mm 2 When the above conditions were met, the difference between the maximum insertion loss and the minimum insertion loss for sounds in the frequency range of 200 kHz or more and 10 kHz or less could be reduced compared to the comparative waterproof membrane E. [Industrial Applicability]

[0100] The technology of the present invention can be applied to various electronic devices, such as wearable devices such as smart watches; various cameras; communication devices such as mobile phones and smartphones; and sensor devices. [Explanation of symbols]

[0101] 1 Waterproof membrane 2,2A,2B Support 3 Joint 4 Transparent area 11 Waterproofing materials 51 Case 52, 52A, 52B openings (external sound vents) 53 Electroacoustic Transducer 54 Sound Inlet 55 Inside 56 Surface 57 Circuit Board 58 Sound Inlet 59 One side 60 Seals 61 Sockets 62 Smartphone

Claims

1. The area of ​​the sound transmission area is 1.3 mm 2 At the time, The insertion loss for a sound with a frequency of 1 kHz is 5.0 dB or less, The insertion loss for a sound having a frequency of 10 kHz is 5.0 dB or less. Waterproof membrane.

2. The area of ​​the transmission region is 1.3 mm 2 When the frequency is between 200 Hz and 10 kHz, Maximum insertion loss (IL) for the range of sounds 1.3 / max and the minimum insertion loss IL 1.3 / min Difference between IL and 1.3 / max -IL 1.3 / min 2. The waterproof membrane according to claim 1, wherein the noise level is 5.0 dB or less.

3. The air permeability in the thickness direction is expressed as the Frazier air permeability measured in accordance with the air permeability measurement method A (Fragile type method) specified in JIS L1096:2010, and is 3.0 cm 3 / (c m 2 3. The waterproof membrane according to claim 1 or 2, wherein the water resistance is less than 1.0 sec.

4. The area of ​​the transmission region is 1.3 mm 2 When this occurs, the transmission of sound with frequencies between 100Hz and 10kHz is The maximum velocity of vibration in the out-of-plane direction during max is 100 μm / sec or more 3. A waterproof membrane according to any one of claims 1 to 3.

5. The waterproof membrane according to any one of claims 1 to 4, comprising a polytetrafluoroethylene membrane.

6. Specific surface area is 6m 2 The waterproof membrane according to any one of claims 1 to 5, wherein the water resistance is 1 / g or more.

7. A waterproof membrane according to any one of claims 1 to 6; A waterproof member comprising: a support joined to the waterproof membrane.

8. The support has a shape corresponding to the shape of the peripheral portion of the waterproof membrane when viewed from a direction perpendicular to the main surface of the waterproof membrane, and is joined to the peripheral portion; When viewed from the above direction, the area of ​​the permeable region of the waterproof member, which is defined as the region surrounded by the joint between the waterproof membrane and the support, is 1.3 mm 2 The method according to claim 7, Waterproofing materials.

9. A housing having an opening; An electronic device comprising: a waterproof membrane according to any one of claims 1 to 6, attached to the housing and / or a member inside the housing so as to prevent water from entering the housing from the outside through the opening.

10. An audio conversion unit that converts between electrical signals and audio is housed in the housing, The electronic device according to claim 9 , wherein the opening is located between the sound conversion unit and an outside of the housing.

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