Electrostatic electroacoustic transducer

Abstract

The present disclosure provides a flexible electrostatic electroacoustic transducer having a pair of conductive layers facing each other and a dielectric layer disposed between the pair of conductive layers facing each other. In the electrostatic electroacoustic transducer, one or both of the pair of conductive layers facing each other are a fiber structure containing conductive fibers or a fiber structure having a conductive material-containing layer on one surface or both surfaces. The conductive layer has a resin layer on one surface or both surfaces and has a plurality of non-resin parts in which the resin layer is not present on the surface having the resin layer. The average area of the non-resin parts is 20 mm2 or less.

Description

Electrostatic electroacoustic transducer

[0001] This disclosure relates to an electrostatic electroacoustic transducer.

[0002] Conventionally, flexible electrostatic electroacoustic transducers are known as one type of acoustic device. Flexible electrostatic electroacoustic transducers generally have a dielectric layer and a pair of conductive layers arranged opposite each other on both sides of the dielectric layer. By applying an electrical signal to the pair of conductive layers, the dielectric layer and the conductive layers vibrate together to generate sound waves. By using thin, flexible materials for the dielectric layer and the conductive layer, the electrostatic electroacoustic transducer as a whole can be made flexible.

[0003] For example, Patent Document 1 describes an electrostatic speaker characterized by comprising: a vibrating membrane made of a thin film member; a conductive, acoustically transparent planar electrode positioned opposite the vibrating membrane; and a buffer member positioned between the vibrating membrane and the planar electrode, formed by including a material that is at least opposite the vibrating membrane in the triboelectric series.

[0004] Japanese Patent Publication No. 2012-182684

[0005] The present disclosure aims to provide a flexible electrostatic electroacoustic transducer that has high sound pressure while reducing short-circuit failures.

[0006] Examples of embodiments of the present disclosure are listed below. [1] A flexible electrostatic electroacoustic transducer having a pair of opposing conductive layers and a dielectric layer disposed between the pair of opposing conductive layers, wherein one or both of the pair of opposing conductive layers are a fibrous structure containing conductive fibers, or a fibrous structure having a conductive material-containing layer on one or both sides, the conductive layer which is a fibrous structure has a resin layer on one or both sides, the conductive layer which is a fibrous structure has a plurality of non-resin portions on the side having the resin layer where the resin layer is absent, and the average area of ​​the non-resin portions is 20 mm² ２ [2] An electrostatic electroacoustic transducer having a minimum of 1 mm² of non-resin parts. ２[3] An electrostatic electroacoustic transducer as described in item 1, wherein the number of non-resin parts is less than or equal to [number]. [4] An electrostatic electroacoustic transducer as described in item 2, wherein multiple non-resin parts are randomly arranged. [5] An electrostatic electroacoustic transducer as described in any one of items 1 to 3, wherein the total area ratio of the non-resin parts to the area of ​​the conductive layer which is the fibrous structure is 0.5% or more and 35% or less. [6] 1 cm ２ [6] An electrostatic electroacoustic transducer according to any one of items 1 to 4, wherein the number of independent non-resin parts per unit is 1 or more and 200 or less. [7] An electrostatic electroacoustic transducer according to any one of items 1 to 5, wherein the thickness of the resin layer is 100 μm or less. [8] An electrostatic electroacoustic transducer according to any one of items 1 to 6, wherein the resin constituting the resin layer is at least one selected from the group consisting of acrylic, polyurethane, and polyvinyl chloride. [9] An electrostatic electroacoustic transducer according to any one of items 1 to 7, wherein the melting point of the resin constituting the resin layer is 150°C or higher.

[10] An electrostatic electroacoustic transducer according to any one of items 1 to 8, wherein the heat resistance of the electrostatic electroacoustic transducer is 100°C or higher. ２

[11] An electrostatic electroacoustic transducer according to any one of items 1 to 9, wherein the resistance of the conductive layer which is a fiber structure is 5Ω□ or less, according to any one of items 1 to 10, according to any one of items 1 to 11, according to any one of items 1 to 11, wherein the conductive layer which is a fiber structure has the conductive material containing layer on one or both sides, and the conductive material containing layer is made by plating, according to any one of items 1 to 11, according to any one of items 1 to 12, according to any one of items 1 to 12, wherein the conductive layer which is a fiber structure has the resin layer on the surface facing the dielectric layer side, according to any one of items 1 to 12, according to any one of items 1 to 12.

[0007] According to this disclosure, it is possible to provide a flexible electrostatic electroacoustic transducer that has high sound pressure while reducing short-circuit failures.

[0008] Figure 1 is a schematic diagram showing a preferred laminated structure of the electrostatic electroacoustic transducer of the present disclosure.

[0009] The embodiments of this disclosure will be described in detail below, but this disclosure is not limited to the embodiments described below. The upper and lower limits in each numerical range of the embodiments described below can be arbitrarily combined to form any numerical range.

[0010] 《Electrostatic Electroacoustic Transducer》 The electrostatic electroacoustic transducer of this disclosure is a flexible electrostatic electroacoustic transducer having a pair of opposing conductive layers and a dielectric layer disposed between the pair of opposing conductive layers. By applying a voltage to the pair of conductive layers, the dielectric layer becomes charged, and an electrostatic force (Coulomb force) can be generated between the dielectric layer and the conductive layer. Then, by applying an electrical signal to the pair of conductive layers, the attractive or repulsive force due to the electrostatic force changes, and the dielectric layer and the conductive layer vibrate together to generate sound waves. In this disclosure, "sound waves" are not limited to sounds that can be heard by humans, but include sound waves and ultrasound. The applications are not limited, but when the electrostatic electroacoustic transducer emits sound waves that can be heard by humans, it can be used for music / voice playback, communication, notification, and alarms, etc. When it generates ultrasound, it can be used for detection (sonar), measurement, diagnosis, treatment, and pest control (insect repellent), etc.

[0011] The electrostatic electroacoustic transducer described herein is flexible. The degree of flexibility is not limited, but the rigidity of the electrostatic electroacoustic transducer as a whole, as measured according to JIS L1096:2010, Method A (45° cantilever method), is preferably 300 mm or less. By using relatively thin and flexible materials for the conductive layer, dielectric layer, and optional spacer layer and sealing layer that constitute the electrostatic electroacoustic transducer, the electrostatic electroacoustic transducer as a whole can be made flexible. Because the electrostatic electroacoustic transducer is flexible, it can be made in a small space and conform to any shape, thus offering a very high degree of design freedom. In addition, the sound waves generated from a flexible electrostatic electroacoustic transducer are close to plane waves and have high directivity. Therefore, flexible electrostatic electroacoustic transducers can be suitably used, for example, on surfaces in spaces such as inside vehicles and rooms, as well as on clothing and accessories. More specifically, flexible electrostatic electroacoustic transducers can be attached to the flat and curved surfaces of various items, such as car seats, front pillars, dashboards, sun visors, ceilings, door panels, and floors; interior walls, floors, ceiling columns, and curtains; and the surface of clothing, such as the inside of a hood.

[0012] <Dielectric Layer> The dielectric layer can be charged and vibrated by applying voltage and electrical signals, thereby generating sound waves. The dielectric layer is preferably a sheet or film of a non-conductive material.

[0013] The lower limit of the dielectric layer thickness is greater than 0 μm, for example, 1 μm or more, 5 μm or more, 10 μm or more, or 20 μm or more. The upper limit of the dielectric layer thickness, which can be arbitrarily combined with these lower limits, is 500 μm or less, preferably 400 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, or 100 μm or less.

[0014] It is preferable that the conductive layer and the dielectric layer are made of different materials in the triboelectric series. In an electrostatic electroacoustic transducer, the dielectric layer is charged by application of a voltage, and can vibrate by generating an electrostatic force (Coulomb force) between the dielectric layer and the conductive layer. In this case, since the conductive layer and the dielectric layer are made of different materials in the triboelectric series, frictional electrification occurs due to the vibration of the dielectric layer, whereby the charge amount of the dielectric layer is further increased, the same effect as that obtained when a high potential is applied can be achieved, and the sound pressure can be increased. The farther apart the materials of the conductive layer and the dielectric layer are in the triboelectric series, the more preferable it is. Note that the triboelectric series refers to a list in which polarities generated by electrification are arranged in positive-to-negative order for the phenomenon that, for example, when polymer films or fibers are rubbed against each other, one is positively charged and the other is negatively charged. As triboelectric series, Lehmicke's triboelectric series and J. Henniker's triboelectric series are known, and any triboelectric series may be used. When one or both of the conductive layer and the dielectric layer are not clear in terms of their position in the triboelectric series, or when the conductive layer or the dielectric layer is a composite material using two or more materials, the phrase that the conductive layer and the dielectric layer are "different in the triboelectric series" means that, when rubbed against each other in an environment of 25°C and 40% RH, a bias occurs in the electrostatic force of the conductive layer and the dielectric layer.

[0015] The dielectric breakdown voltage of the dielectric layer is preferably 3 kV or more, more preferably 5 kV or more. A higher dielectric breakdown voltage of the dielectric layer is more preferable because it means a wider allowable range of applicable voltage. In addition, this is preferable because it can prevent electric shock caused by leakage of current supplied to the conductive layer to the outside. The upper limit value of the dielectric breakdown voltage of the dielectric layer, which can be arbitrarily combined with any of these lower limit values, is not limited, but may be 20 kV or less.

[0016] Preferably, the dielectric layer material is at least one selected from the group consisting of silicone, fluororesin, polyolefin, and rubber. These materials allow for easy adjustment of the dielectric layer thickness and electrostatic force (charge amount) within the above range. Examples of fluororesins include tetrafluoroethylene resin (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and ethylenetetrafluoroethylene (ETFE). Preferably, polyolefins have 2 to 10 or 2 to 5 carbon atoms, are substituted or unsubstituted, and are linear or branched, such as polyethylene, polypropylene, and polybutylene. Examples of rubbers include natural rubber or synthetic rubber, such as nitrile rubber, butadiene rubber, styrene rubber, chloroprene rubber, acrylic rubber, and urethane rubber. Silicone is more preferably used as the material constituting the dielectric layer. Silicone allows for easier adjustment of the dielectric layer thickness, electrostatic force (charge amount), dielectric breakdown voltage, and melting point to the above ranges. The dielectric layer material may be used individually or in combination of two or more.

[0017] <Conductive Layer> In this disclosure, one or both of a pair of opposing conductive layers are fibrous structures containing conductive fibers, or fibrous structures having conductive material-containing layers on one or both sides. The conductive layer, which is a fibrous structure, has a resin layer on one or both sides. The conductive layer also has a plurality of non-resin portions on the side having the resin layer, where the resin layer is absent, and the average area of ​​each of these non-resin portions is 20 mm². ２ / piece. The electrostatic electroacoustic transducer of this disclosure, by having the said configuration, can provide a flexible electrostatic electroacoustic transducer that has high sound pressure while reducing short-circuit failures. The reason for this is not limited to theory, but the inventors speculate as follows: That is, the conductive layer has a high degree of permeability because it is a fibrous structure, and thereby can have high sound pressure. In addition, by having a resin layer on one or both sides of the conductive layer, it is possible to reduce the occurrence of short-circuit failures caused by fibers coming loose (fraying) from the conductive layer, which is a fibrous structure, and coming into contact with the other conductive layer facing it. In the manufacturing process of electrostatic electroacoustic transducers, the conductive layer may be cut, for example, by punching out a roll-shaped conductive layer to an arbitrary size and shape and laminating it with other members such as a dielectric layer. In this case, by having a resin layer on one or both sides of the conductive layer, it is possible to prevent fibers from fraying from the cut ends of the conductive layer, and thus short-circuit failures can be reduced more effectively. Furthermore, the conductive layer has a plurality of non-resin parts on the surface having the resin layer where the resin layer does not exist, and the average area of ​​each of the non-resin parts is 20 mm² ２ Because of this single layer design, the permeability of the conductive layer is not excessively reduced compared to cases without a resin layer, thus allowing for the maintenance of high sound pressure.

[0018] It is more preferable that both of the pair of opposing conductive layers are fibrous structures. It is preferable that the conductive layer which is a fibrous structure has a resin layer at least on the surface facing the dielectric layer side (the inner side of the laminated structure). It is considered that the surface having the resin layer of the conductive layer is less prone to fraying, and by making the inner surface, which is at a close distance to the other conductive layer, less prone to fraying, short circuits can be prevented more effectively. It is preferable that the conductive layer has a conductive material-containing layer on the surface facing the dielectric layer side (inner side), has a resin layer on the conductive material-containing layer on the surface facing the dielectric layer side (inner side), and does not have a resin layer on the surface facing the opposite side to the dielectric layer (outer side). It is also preferable that the conductive layer has a conductive material-containing layer on both surfaces, has a resin layer on the conductive material-containing layer on the surface facing the dielectric layer side (inner side), and does not have a resin layer on the surface facing the opposite side to the dielectric layer (outer side). This can reduce the sheet resistance on the outer side while preventing fraying on the inner side, so that short circuits can be prevented more effectively and higher sound pressure can be obtained. Lower sheet resistance on the outer side is particularly advantageous in an embodiment in which wirings are respectively connected to the outer surfaces of the pair of conductive layers.

[0019] In one aspect, the conductive layer may have a conductive material-containing layer on the surface facing the opposite side to the dielectric layer. This increases the distance between conductive materials, so that short-circuit defects can be reduced more effectively. Further, the conductive layer may have a conductive material-containing layer on the surface facing the opposite side to the dielectric layer, and may have a resin layer on the conductive material-containing layer. This prevents fraying of fibers containing the conductive material, so that short-circuit defects can be reduced more effectively.

[0020] The resin layer only needs to be formed on at least a part of one surface or both surfaces of the conductive layer which is a fibrous structure. Since fiber fraying easily occurs at the end portions of the conductive layer, the resin layer is preferably provided over at least a part of the end portions of the conductive layer, more preferably over 50% or more, for example 70% or more, 80% or more, 90% or more, or 97% or more of the total length of the end portions. This enables more effective reduction of short-circuit defects.

[0021] The upper limit of the average area of the non-resin portions is 20 mm from the viewpoint of further reducing short-circuit defects ２ / unit, preferably 18 mm ２ / unit or less, more preferably 15 mm ２ / unit or less, still more preferably 10 mm ２ / unit or less, for example, 8 mm ２ / unit or less, 5 mm ２ / unit or less, 2 mm ２ / unit or less, 1 mm ２ / unit or less, or 0.5 mm ２ / unit or less. Further, the lower limit of the average area of the non-resin portions that can be arbitrarily combined with these upper limit values is not particularly limited, but from the viewpoint of obtaining higher sound pressure, 0.001 mm ２ / unit or more, 0.01 mm ２ / unit or more, or 0.1 mm ２ / unit or more.

[0022] The arrangement of the plurality of non-resin portions may be a pattern of any shape, or any shapes may be arranged randomly. By randomly arranging the plurality of non-resin portions, short-circuit defects can be reduced regardless of the direction in which the conductive layer is cut, no matter what shape the conductive layer is cut into (this is referred to as "free cuttability" in the present disclosure). In particular, when the average area of the non-resin portions is small to a certain extent, for example, 1 mm ２ / unit or less, and the plurality of non-resin portions are randomly arranged, the free cuttability is more excellent.

[0023] The shape of the non-resin parts when multiple non-resin parts are arranged in a pattern or randomly is not limited, but examples include circles, ellipses, and polygons. Examples of patterns include dots, stripes, grids, and combinations thereof. Examples of dot arrangements include triangular grids, square grids, and honeycomb grids. The diameter and spacing of the dots are arbitrary and may be constant or a combination of multiple diameters and spacings. Examples of stripe shapes include straight lines, waves, and triangular waves. The arrangement (orientation) of the stripes may be parallel, perpendicular, or at a predetermined angle to the transport direction of the dielectric layer and conductive layer in the manufacturing process, and multiple arrangements may be combined. The width and spacing of the stripes may be constant or a combination of multiple widths and spacings. Examples of grid arrangements include triangular grids, square grids, and honeycomb grids. The width and spacing of the grid may be constant or a combination of multiple widths and spacings. The non-resin portion may be randomly arranged across one or both sides of the conductive layer, may consist of a single pattern, or may consist of any combination of random arrangement and one or more patterns.

[0024] The method for forming a resin layer and a non-resin portion on one or both sides of a conductive layer is not particularly limited, but examples include applying resin to a part of one or both sides of the conductive layer, and applying resin to at least a part or all of one or both sides of the conductive layer and removing a part of the formed resin layer. An example of a method for removing a part of the resin layer is to provide a plurality of through holes in a fiber structure. Fiber structures may or may not be present in the through-hole portions. An example of a method for providing through holes is needle punching. In one embodiment, it is preferable to form a resin layer on one or both sides of a conductive layer which is a fiber structure, and then to provide a plurality of random through holes in the resin layer by needle punching the fiber structure. The resin layer is removed from the punched portions, and these become non-resin portions. Fibers of the fiber structure may or may not be present in the punched portions.

[0025] The total area ratio of the non-resin portion to the area of ​​the conductive layer, which is a fibrous structure, is preferably 0.5% to 35%. The lower limit of the total area ratio of the non-resin portion is more preferably 1% or more, for example 5% or more, or 10% or more. The upper limit of the total area ratio of the non-resin portion, which can be arbitrarily combined with these lower limits, is more preferably 30% or less, for example 25% or less, 20% or less, or 15% or less. By having the total area ratio of the non-resin portion within the above preferred range, higher sound pressure can be obtained and short-circuit failures can be further reduced. In addition, if the average area of ​​the non-resin portion is relatively small and / or the non-resin portion is randomly arranged, the free-cut properties are better.

[0026] In a conductive layer which is a fibrous structure, 1 cm of the surface having a resin layer ２ The number of independent non-resin parts per unit is preferably 1 to 200. The lower limit of the number of independent non-resin parts is more preferably 5 or more, for example 10 or more, 15 or more, 20 or more, or 50 or more. The upper limit of the number of independent non-resin parts, which can be arbitrarily combined with these lower limits, is more preferably 180 or less, for example 150 or less, or 120 or less. By having the number of independent non-resin parts within the above preferred range, higher sound pressure can be obtained and short-circuit failures can be further reduced. In addition, the free-cut properties are better if one or more of the following are met: the average area of ​​the non-resin parts is relatively small; the non-resin parts are arranged randomly; and the total area ratio of the non-resin parts satisfies the above preferred range.

[0027] The upper limit of the resin layer thickness is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. The lower limit of the resin layer thickness, which can be optionally combined with these upper limits, is not limited but may be, for example, 0.1 μm or more, 1 μm or more, or 5 μm or more. When the resin layer thickness is within these preferred ranges, higher sound pressure can be obtained and short-circuit defects can be further reduced.

[0028] The resin constituting the resin layer is preferably at least one selected from the group consisting of thermoplastic resins and thermosetting resins, such as acrylic, polyurethane, and polyvinyl chloride. The melting point of the resin constituting the resin layer is preferably 150°C or higher, for example 160°C or higher, 170°C or higher, 180°C or higher, 190°C or higher, or 200°C or higher. By using the above-mentioned specific material and / or the above-mentioned melting point of the resin constituting the resin layer, short-circuit failures can be further reduced, and the heat resistance of the resin layer is improved. The heat resistance of the resin layer is preferably 100°C or higher, for example 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, or 150°C or higher. Here, "heat resistance of the resin layer" means that in the heat resistance test of the resin layer described later, when the constant temperature bath is set to the said temperature, the evaluation result is "A".

[0029] The air permeability of the conductive layer, which is a fibrous structure, is preferably 0.5 cc / cm². ２ / sec or more, more preferably 1 cc / cm³ ２ / sec or more, more preferably 5cc / cm ２ / sec or more, more preferably 10cc / cm ２ / sec or more, particularly preferably 15cc / cm ２ / sec or more, for example, 20cc / cm³ ２ / sec or more, 25cc / cm ２ / sec or more, 30cc / cm ２ / sec or more, 35cc / cm ２ / sec or more, or 40cc / cm³ ２ It may be greater than or equal to / sec. The upper limit of the permeability of the conductive layer, which can be arbitrarily combined with these lower limits, is not limited, but is 100 cc / cm². ２ / sec or less, 80cc / cm ２ / sec or less, 60cc / cm ２ Less than / sec, or 50cc / cm³ ２ It is less than / sec. By having the permeability of the conductive layer within the above preferred range, higher sound pressure can be obtained, and short-circuit failures can be further reduced.

[0030] The resistance of the conductive layer, which is a fibrous structure, is preferably 5 Ω□ or less, more preferably 2 Ω□ or less, and even more preferably 1 Ω□ or less. The lower the resistance of the conductive layer, the higher the sound pressure that can be obtained. The lower limit of the resistance of the conductive layer, which can be arbitrarily combined with these upper limits, is not limited, but may be, for example, 0.001 Ω□ or more. In this disclosure, "resistance of the conductive layer" means sheet resistance as described later, and if the value differs depending on the surface of the conductive layer being measured, the lower resistance value will be adopted.

[0031] Examples of fibrous structures include woven fabrics, knitted fabrics, and nonwoven fabrics, with nonwoven fabrics being preferred. Because the conductive layer is a nonwoven fabric, thread fraying (loosening) from the edges is less likely to occur, further suppressing short-circuit failures.

[0032] When the conductive layer is a fibrous structure containing conductive fibers, examples of conductive fibers include metal fibers, metal-coated fibers, conductive polymer-containing fibers, and carbon fibers. Examples of metal components in metal fibers and metal-coated fibers include metals such as gold, platinum, silver, copper, nickel, chromium, iron, zinc, aluminum, tungsten, stainless steel, titanium, magnesium, tin, vanadium, cobalt, molybdenum, and tantalum, as well as their alloys. As conductive fibers, fibers in which a metal film mainly composed of silver is formed on a chemical fiber are preferred from the viewpoint of conductivity and flexibility. Here, "main component" means the component that accounts for the largest mass % of the components constituting the metal film. Examples of conductive polymers include polyacetylene and polythiophene. Examples of carbon fibers include PAN-based carbon fibers, pitch-based carbon fibers, and carbon fibers spun from carbon nanotubes. Conductive fibers may be used individually or in combination of two or more. In addition, other fibers may be combined with the above conductive fibers.

[0033] When the conductive layer is a fibrous structure having a conductive material-containing layer, the fibers constituting the fibrous structure may be the conductive fibers listed above, other fibers, or a combination thereof. Examples of fibers include synthetic fibers and natural fibers, such as polyester, polyamide, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, polyacrylonitrile, polyethylene, polypropylene, polyurethane, aramid, cellulose, cotton, linen, wool, and silk. These fibers may be used individually or in combination of two or more.

[0034] Examples of conductive materials in the conductive material-containing layer include metals, conductive polymers, and carbon materials. Examples of metallic components include those similar to those in metal fibers and metal-coated fibers, and a conductive material-containing layer having at least one selected from the group consisting of copper, tin, nickel, aluminum, gold, silver, and zinc as the main component is preferred from the viewpoint of conductivity. Here, "main component" means the component that accounts for the largest mass % of the components constituting the conductive material-containing layer. Examples of conductive polymers include polyacetylene and polythiophene. Examples of carbon materials include carbon black, carbon nanotubes, and graphene. Conductive materials may be used individually or in combination of two or more.

[0035] The conductive material-containing layer can be formed on one or both sides of the fibrous structure. Methods for forming the conductive material-containing layer include coating, plating, sputtering, and vapor deposition. It is more preferable that the conductive material-containing layer is composed of plating (also called the "plated layer"). By making the conductive material-containing layer a plated layer, the resistance value of the conductive layer can be further reduced, and as a result, a higher sound pressure can be obtained.

[0036] Preferably, one or both of the pair of conductive layers and the dielectric layer are joined to each other at least in part. This allows the conductive and dielectric layers to adhere closely together, making it easier for electrostatic force (Coulomb force) to be generated, thus improving sound pressure. Furthermore, when the electrostatic electroacoustic transducer deforms or when frictional force is applied to the surface, the displacement of the conductive and dielectric layers in the planar direction is suppressed.

[0037] Examples of joining methods include sewing using non-conductive fibers, bonding using adhesives, and adhesion using adhesives. Preferably, the adhesive is a material that is fluid before joining and solidifies when applied to join the two materials. Preferably, the adhesive is a material that maintains a viscous semi-solid state before and after joining and can join the two materials. The joining method may be any one of these or a combination of two or more of them. Examples of adhesives used for bonding and adhesives used for adhesion include thermoplastic resins and thermosetting resins, such as acrylic, vinyl acetate, polyvinyl acetal, vinyl chloride, polyester, polyamide, cellulose, olefin, styrene, urethane, epoxy, and silicone adhesives. When the conductive layer has a resin layer on the surface facing the dielectric layer, the adhesive and adhesive may be placed between the resin layer and the dielectric layer.

[0038] The joint may consist of a single continuous joint region, or it may be a discrete joint containing two or more discontinuous joint regions. An example of a continuous joint is to continuously join the outer periphery of a stacked conductive layer and dielectric layer, leaving the inner portion unjoined. A discrete joint may be a pattern of any shape, such as a dot pattern, stripe pattern, grid pattern, or a combination thereof.

[0039] From the viewpoint of improving sound pressure, it is preferable that the bonding area be part of the region where the conductive layer and the dielectric layer face each other. For example, when one or both of a pair of conductive layers are bonded to a dielectric layer, it is preferable that the bonding area be greater than 0% and less than or equal to 70% of the area where the conductive layer and the dielectric layer face each other. This makes it easier for electrostatic force (Coulomb force) to be generated as the conductive layer and the dielectric layer are in close contact, and the bonding does not hinder the vibration of the conductive layer and the dielectric layer less, thus improving sound pressure and sound quality. The lower limit of the bonding area is more preferably 10% or more, and even more preferably 20% or more. The upper limit of the bonding area, which can be arbitrarily combined with these lower limits, is more preferably 60% or less.

[0040] The thickness of the conductive layer is not particularly limited, but from the viewpoint of flexibility and space saving, it may be, for example, 1 μm or more and 1000 μm or less. The lower limit of the thickness of the conductive layer is, for example, 1 μm or more, 5 μm or more, 10 μm or more, 50 μm or more, or 100 μm or more. The upper limit of the thickness of the conductive layer, which can be arbitrarily combined with these lower limits, is, for example, 1000 μm or less, 500 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less.

[0041] <Spacer Layer> In addition to the conductive layer and dielectric layer described above, it is preferable that the electrostatic electroacoustic transducer further has a spacer layer disposed on one or both of the conductive layers. The spacer layer is flexible and can isolate the conductive layer from external people or other articles (or the sealing layer described later), while ensuring the amplitude of the conductive layer and dielectric layer. By further having a spacer layer in the electrostatic electroacoustic transducer, it is possible to prevent people or other articles from directly touching the conductive layer. Furthermore, if the electrostatic electroacoustic transducer has the sealing layer described later, it is possible to prevent the sealing layer from directly touching the conductive layer and interfering with the vibration of the conductive layer and dielectric layer.

[0042] The spacer layer is preferably made of a highly permeable material from the viewpoint of easily transmitting sound waves, and is preferably a fibrous structure. Examples of fibrous structures include woven fabrics, knitted fabrics, and nonwoven fabrics, and is preferably a nonwoven fabric from the viewpoint of permeability and adhesion between the spacer layer and the conductive layer, and between the spacer layer and the sealing layer.

[0043] From a safety standpoint, the fibrous structure of the spacer layer is preferably composed of non-conductive fibers. Examples of non-conductive fibers include synthetic fibers and natural fibers, such as polyester, polyamide, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, polyacrylonitrile, polyethylene, polypropylene, polyurethane, aramid, cellulose, cotton, linen, wool, and silk. These fibers may be used individually or in combination of two or more.

[0044] <Sealing Layer> In addition to the conductive layer, dielectric layer, and spacer layer described above, it is preferable that the electrostatic electroacoustic transducer further has a sealing layer disposed on the spacer layer. The sealing layer is flexible and electrically insulates the electrostatic electroacoustic transducer from the surrounding environment and prevents water, dust, etc. from entering the interior. By further having a sealing layer in the electrostatic electroacoustic transducer, safety and durability can be improved.

[0045] The sealing layer is preferably a sheet or film of a non-conductive material from the viewpoint of electrical insulation, waterproofing, and dustproofing. Examples of non-conductive materials for the sealing layer include polyurethane, silicone, and rubber, with polyurethane being preferred from the viewpoint of flexibility and safety. The sealing layer material may be one of these materials alone, or two or more may be used in combination.

[0046] Figure 1 is a schematic diagram showing a preferred laminated structure of the electrostatic electroacoustic transducer of the present disclosure. As schematically shown in Figure 1, the electrostatic electroacoustic transducer 10 has a pair of opposing conductive layers 2 and a dielectric layer 1 disposed between the pair of conductive layers 2. The electrostatic electroacoustic transducer 10 further has a spacer layer 3 disposed on both of the pair of conductive layers 2 and a sealing layer 4 disposed on the spacer layer 3.

[0047] Examples and comparative examples of the present disclosure are described below, but the present disclosure is not limited to the following examples and comparative examples.

[0048] <Measurement and Evaluation Method> <Average Area, Total Area Ratio, and Number of Non-Resin Parts per Unit Area> For the conductive layer of the electrostatic electroacoustic transducer, the surface having the resin layer and non-resin parts was photographed using an all-in-one digital microscope KH-8700 (manufactured by Hirox Co., Ltd.). From the images, the number and area of ​​independent non-resin parts were measured, and the average area (mm²) was calculated. ２ (per piece), total area ratio of non-resin parts (%), unit area (1 cm²) ２ Number of independent non-resin parts per unit area (pieces / cm²) ２ The following calculation was performed. Here, if the non-resin part is a through-hole randomly formed by needle punching, multiple through-holes may combine to form a single independent non-resin part. In that case, an independent non-resin part formed by the combination of multiple through-holes is counted as one.

[0049] <Average Thickness of Resin Layer> The average thickness (μm) of the resin layer was measured from images of the cross-section of the conductive layer taken with a microscope. The conductive layer was solidified by resin embedding as needed, then cut, and its cross-section was obtained. However, when the resin layer is a thin film at the level of a few μm, the irregularities of fibers may be visible in the area where the resin layer exists, making it difficult to measure the average thickness of the resin layer. In such cases, it is determined that a resin layer of 10 μm or less has been formed.

[0050] <Melting point of the resin layer> The resin layer was placed in a DSC (Differential Scanning Calorimetry, T.A. Instruments Japan Co., Ltd., part number Q-10), and the endothermic peak when the pressure was increased to 300°C at a rate of 10°C / min was measured as the melting point (°C).

[0051] <Thickness of Conductive and Dielectric Layers> The thickness of the conductive and dielectric layers was measured in accordance with JIS L1913 Method B. The thickness (μm) was measured at three or more locations at a pressure of 0.02 kPa, and the average value was calculated.

[0052] <Dielectric Breakdown Voltage> The dielectric layer (5 cm x 5 cm) was measured in accordance with JIS C2110-1. A DC voltage was applied using a dielectric strength tester (TOS5101, manufactured by Kikusui Electronics Co., Ltd.), the current was checked after 20 seconds, and the voltage at which dielectric breakdown occurred (kV) was measured by gradually increasing the voltage.

[0053] <Resistance Value> The sheet resistance of the conductive layer of the electrostatic electroacoustic transducer, specifically the side with the resin layer, was measured using the four-probe method (product name: Lorestar GXII, manufactured by Nitto Seiko Analytech Co., Ltd.). Measurements were taken on both sides of the conductive layer, and the value with the lower resistance was adopted.

[0054] <Air Permeability> The air permeability of the conductive layer of the electrostatic electroacoustic transducer was measured in accordance with JIS-L-1096, 1018 Air Permeability Test Method (Method A: Air Volume). In the measurement, the air permeability that permeates through the flexible electrostatic electroacoustic transducer was measured using the FX3300 Lab Air IV air permeability tester manufactured by Takayama Reed Co., Ltd.

[0055] <Sound Pressure> In a room measuring 4m x 4m x 2m (25°C, 40% RH), a pure tone of 2000 Hz was reproduced from an electrostatic electroacoustic transducer (10cm x 10cm) suspended at a height of 1m, and the sound pressure was measured at a distance of 1m from the electrostatic electroacoustic transducer. The sound pressure of the electrostatic electroacoustic transducer in Comparative Example 2 (P ０ For (dB), the sound pressure (P) of each electrostatic electroacoustic transducer １ ) (dB) difference (=P ０ -P １ The sound pressure was measured in dB. The sound pressure was evaluated according to the following criteria: E (Excellent): P ０ -P １ ≦5dB G (acceptable): 5dB<P ０ -P １ ≦10dB P (not allowed): P ０ -P １ >10dB

[0056] <Short-circuit defects> Ten laminates of conductive layer-dielectric layer-conductive layer were fabricated. The ten laminates were punched out together into 10 cm squares using a die-cutting machine, and the presence or absence of short circuits in the conductive layers was checked. At this time, the resistance value between pairs of conductive layers was measured, and those in which continuity was confirmed were classified as short-circuit defects and judged according to the following criteria: E (Excellent): One or fewer short circuits occurred in the ten laminates. G (Acceptable): Two to three short circuits occurred in the ten laminates. P (Unacceptable): Four or more short circuits occurred in the ten laminates.

[0057] <Heat Resistance> After exposing an electrostatic electroacoustic transducer to a constant temperature chamber (100°C) for 5.5 hours, the change in sound pressure of the electrostatic electroacoustic transducer was observed. In a 4m x 4m x 2m room (25°C, 40% RH), a pure tone of 1000 Hz was reproduced from an electrostatic electroacoustic transducer (10cm x 10cm) suspended at a height of 1m, and the sound pressure (dB) was measured at a distance of 1m from the electrostatic electroacoustic transducer. The sound pressure (P) of the electrostatic electroacoustic transducer before high-temperature exposure was measured. ０ (dB) vs. the sound pressure of the electrostatic electroacoustic transducer after high-temperature exposure (P １ ) (dB) difference (=P ０ -P １ If the (dB) level exceeds 5 dB, it is classified as "B," and if it is 5 dB or less, it is classified as "A."

[0058] Examples and Comparative Examples Example 1 A woven fabric (U5500, manufactured by Urase Co., Ltd., basis weight 80 g / m) with Cu-Ni plating on both sides was used as the fibrous structure for the conductive layer. ２ A single-sided acrylic-coated material was used. The melting point of the acrylic coating is 140°C or higher. Through holes of approximately 0.2 mm in diameter were made in this fiber structure in a random arrangement by needle punching, thereby forming a non-resin portion in the acrylic coating. A pair of conductive layers were placed facing each other with the resin layer (acrylic coating) side facing inward, and a 30 μm thick, 120 mm square electret film (PoreFlon® membrane, manufactured by Sumitomo Electric Fine Polymer Co., Ltd., product number HP-010-30) made of a fluoropolymer was sandwiched between them as a dielectric layer, in contact with the conductive layer. At this time, an acrylic adhesive was applied in a stripe pattern to the surface of the dielectric layer, and then the conductive layer was bonded to it, obtaining a laminate of conductive layer-dielectric layer-conductive layer. Wiring was connected to the outer surfaces of the pair of conductive layers, respectively, to obtain a flexible electrostatic electroacoustic transducer.

[0059] <Example 2> A flexible electrostatic electroacoustic transducer was obtained in the same manner as in Example 1, except that the diameter of the through-holes formed by needle punching of the conductive layer was set to approximately 0.4 mm and the number of holes per unit area was changed as shown in Table 1.

[0060] <Example 3> As a fibrous structure for the conductive layer, a woven fabric (U5001W, manufactured by Urase Co., Ltd., basis weight 75 g / m) with Cu-Ni plating on both sides was used. ２ A non-coated material was used. On one side of the material, a 1 mm thick grid (mesh) pattern was applied using polyurethane resin by gravure printing, leaving a rhombus-shaped non-resin portion with a diagonal length of 5 mm x 6 mm. A flexible electrostatic electroacoustic transducer was obtained in the same manner as in Example 1.

[0061] <Example 4> Knitted fabric as the fibrous structure of the conductive layer (3D FINEX®, manufactured by Asahi Kasei Advance Co., Ltd., basis weight 330 g / m) ２ A material consisting of 62% polyester and 38% polyurethane was used, and Cu-Ni conductive material-containing layers were provided on both sides by electroless plating. A resin layer was provided on one side by heat laminating polyurethane hot melt (Mobilon®, manufactured by Nisshinbo Textile Co., Ltd., product number MF100T, 100 μm thick), and a non-resin portion was provided by randomly arranging through holes of approximately 0.4 mm in diameter using needle punching. A flexible electrostatic electroacoustic transducer was obtained in the same manner as in Example 1.

[0062] <Example 5> As the fibrous structure of the conductive layer, a nonwoven fabric (Presize®, manufactured by M.A. Life Materials Co., Ltd., model number AC1050, basis weight 50 g / m²) was used. ２ Using this material, Cu-Ni conductive material-containing layers were formed on both sides by electroless plating. On one side thereafter, 50 g / m² of polyvinyl chloride resin with a melting point of 160°C was applied wet. ２ A resin layer was created by coating, and then a non-resin portion was formed by creating through-holes with a diameter of approximately 0.4 mm in a random arrangement using needle punching. Aside from this, a flexible electrostatic electroacoustic transducer was obtained in the same manner as in Example 1.

[0063] <Comparative Example 1> Conductive layer: Cu-Ni plated fabric (U5500, manufactured by Urase Co., Ltd., basis weight 80 g / m) ２ A flexible electrostatic electroacoustic transducer was obtained in the same manner as in Example 1, except that a single-sided acrylic-coated product was used without needle punching.

[0064] <Comparative Example 2> Conductive layer: Cu-Ni plated fabric (U5001W, manufactured by Urase Co., Ltd., basis weight 75 g / m) ２ A flexible electrostatic electroacoustic transducer was obtained in the same manner as in Example 3, except that the uncoated product was used without resin processing.

[0065] <Comparative Example 3> Conductive layer Cu-Ni plated fabric (U5500, manufactured by Urase Co., Ltd., basis weight 80 g / m) ２ For a single-sided acrylic-coated product, a laser cutter was used to cut Φ6 (6 mm in diameter) openings at a rate of 130 per 100 mm square (1 cm ２ They were uniformly arranged so that there were 1.3 per unit. Otherwise, a flexible electrostatic electroacoustic transducer was obtained in the same manner as in Example 1.

[0066]

[0067] 1. Dielectric layer 2. Conductive layer 3. Spacer layer 4. Sealing layer 10. Electrostatic electroacoustic transducer

Claims

1. A flexible electrostatic electroacoustic transducer having a pair of opposing conductive layers and a dielectric layer disposed between the pair of opposing conductive layers, wherein one or both of the pair of opposing conductive layers are fibrous structures containing conductive fibers, or fibrous structures having conductive material-containing layers on one or both sides, the conductive layer which is a fibrous structure has a resin layer on one or both sides, and the conductive layer which is a fibrous structure has a plurality of non-resin portions on the side having the resin layer where the resin layer is absent, with an average area of ​​20 mm² ２ A electrostatic electroacoustic transducer with a quantity of one or less.

2. The average area of ​​the non-resin part is 1 mm ２ The electrostatic electroacoustic transducer according to claim 1, wherein the number is less than or equal to / .

3. The electrostatic electroacoustic transducer according to claim 2, wherein a plurality of the non-resin parts are arranged randomly.

4. The electrostatic electroacoustic transducer according to any one of claims 1 to 3, wherein the total area ratio of the non-resin portion to the area of ​​the conductive layer which is a fibrous structure is 0.5% or more and 35% or less.

5. 1 cm ２ The electrostatic electroacoustic converter according to any one of claims 1 to 3, wherein the number of independent non-resin parts per unit is 1 or more and 200 or less.

6. The electrostatic electroacoustic transducer according to any one of claims 1 to 3, wherein the thickness of the resin layer is 100 μm or less.

7. The electrostatic electroacoustic transducer according to any one of claims 1 to 3, wherein the resin constituting the resin layer is at least one selected from the group consisting of acrylic, polyurethane, and polyvinyl chloride.

8. The electrostatic electroacoustic transducer according to any one of claims 1 to 3, wherein the melting point of the resin constituting the resin layer is 150°C or higher.

9. The electrostatic electroacoustic transducer according to any one of claims 1 to 3, wherein the heat resistance of the electrostatic electroacoustic transducer is 100°C or higher.

10. The air permeability of the conductive layer, which is the fibrous structure, is 0.5 cc / cm². ２ An electrostatic electroacoustic converter according to any one of claims 1 to 3, wherein the frequency is / sec or greater.

11. The electrostatic electroacoustic transducer according to any one of claims 1 to 3, wherein the resistance value of the conductive layer, which is a fibrous structure, is 5Ω□ or less.

12. The electrostatic electroacoustic transducer according to any one of claims 1 to 3, wherein the conductive layer, which is a fibrous structure, has the conductive material-containing layer on one or both sides, and the conductive material-containing layer is formed by plating.

13. The electrostatic electroacoustic transducer according to any one of claims 1 to 3, wherein the conductive layer, which is a fibrous structure, has the resin layer on a surface facing the dielectric layer.

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