JP5973293B2 - Electrostatic speaker - Google Patents

Description

  The present invention relates to an electrostatic speaker that is excellent in flexibility, does not require a high voltage, can maintain excellent sound quality even when used for a long time, and can provide stable sound quality in various environments.

  Conventionally, an electrostatic speaker is known as one of the speakers. This electrostatic loudspeaker is composed of a vibrating membrane and planar electrodes that are arranged in parallel across a predetermined gap so as to face both surfaces of the vibrating membrane. When a driving current is passed through the planar electrode, the vibrating membrane vibrates and generates sound. The vibration film is used by forming a conductive thin film on the surface of a thin polymer film of about 10 μm by a method such as vacuum deposition or sputtering. A characteristic of the electrostatic speaker is that power consumption can be reduced because a high voltage is applied to the vibrating membrane to efficiently vibrate and generate sound by charging the vibrating membrane. Furthermore, since sound is propagated by plane waves, there is almost no attenuation due to distance. Moreover, since the sound source is wide, it has various excellent features such as that the peak of feedback does not concentrate on a specific frequency and the housing does not occur.

  However, since the conventional electrostatic speaker applies a high voltage to the diaphragm, a safety problem remains, and a transformer for applying a high voltage is also required. Furthermore, when used for a long time in a dry environment, dust adheres to the surface of the vibration film and the buffer member, which disturbs the vibration of the vibration film and causes discharge, affecting the sound quality and sound volume. Further, when left in a high humidity environment for a long time, there is a problem that the charged vibrating membrane is discharged and the charge is lowered, making it difficult to produce sound.

As a method for solving such a problem, a method of suppressing the influence of humidity using a film obtained by treating a polymer film surface with a conductive polymer as a vibration membrane (Patent Document 1), or a member having a dust collecting function A method of installing and suppressing the adhesion of dust (Patent Document 2), a method of making it difficult for discharge to occur by not forming a conductive film formed on the surface of the vibration film on the edge (Patent Documents 3 and 4), etc. Has been proposed.
Japanese Unexamined Patent Publication No. 7-046697 JP 2008-148195 A JP 2010-016603 A JP 2010-021646 A

  However, in the method of suppressing the influence of humidity by using a film obtained by treating the surface of the polymer film with a conductive polymer as a vibrating membrane, it is possible to take measures against humidity. Dust adhesion occurs. In addition, it is necessary to apply a high potential for charging, which is not a fundamental measure. In addition, in a method of suppressing the adhesion of dust and dust by installing a member having a dust collecting function, or a method of making it difficult for discharge to occur by not forming a conductive film on the edge of the vibrating membrane, The structure becomes complicated and the speaker system becomes thick. Moreover, although discharge can be partially mitigated, it is impossible to prevent discharge from the vibrating membrane surface. Furthermore, since it is necessary for the system to apply a high voltage, the current situation is that there is no fundamental improvement.

  Accordingly, the present invention has been made to solve the above-described problems, and provides an electrostatic speaker in which an applied voltage that needs to be applied to a vibrating membrane in order to generate sound is lower. Objective.

  That is, the first invention is a vibration membrane made of a thin film-like member, a planar electrode having conductive sound permeability disposed opposite to the vibration membrane, and disposed between the vibration membrane and the planar electrode. And a buffer member for charging the diaphragm by contact with the diaphragm, wherein the buffer member has a cationic functional group at least on its surface.

  Further, the second invention is characterized in that the cationic functional group of the buffer member is any one of an amino group, an ammonium group, a sulfonium group, and a phosphonium group. It is an electric speaker.

  Furthermore, the third invention is the first or second invention, wherein the amount of the cationic functional group per unit mass of the buffer member is 0.5 mmol / g or more and 3.0 mmol / g or less. This is an electrostatic speaker.

Furthermore, a fourth invention is any one of the first to third inventions, wherein the cushioning member has an air permeability of 150 cm ³ / cm ² / sec or more and 400 cm ³ / cm ² / sec or less. The electrostatic speaker described in 1.

Furthermore, the fifth invention, wherein the surface opposing at least the vibration film of the cushioning member, and the inorganic particles or polymeric particles, a binder component and / or silane monomer, a thin film containing a is formed Tei Rukoto An electrostatic speaker according to any one of the first to fourth inventions.

Furthermore, the sixth invention is the vibration film according to any one of the first to fifth inventions, wherein a layer containing a fluorine-based polymer is formed on at least a part of the surface of the vibration film. This is an electrostatic speaker.

  In the electrostatic loudspeaker according to the present invention, since the buffer member has a cationic functional group, the charge amount of the vibration film is further increased by frictional charging due to vibration of the vibration film. Therefore, the same effect as when a high potential is applied can be obtained, and the acoustic characteristics particularly on the low frequency range side are excellent. From this, it is possible to lower the applied voltage necessary for outputting sound, to eliminate the possibility of electric shock due to a high potential, and to significantly improve the sound in the low sound range.

  In addition, the formation of a fine particle layer composed of inorganic fine particles and polymer fine particles on the buffer member surface and the formation of fine irregularities on the vibration film surface suppress the adhesion of dust and dust to the surface, Even if dust or dirt adheres, the contact area is extremely low, and it is easily detached from the surface of the diaphragm due to vibration of the diaphragm. it can. Therefore, it is possible to provide an electrostatic speaker that is less susceptible to the influence of dust and dirt even when used for a long time.

Schematic cross-sectional view of an electrostatic speaker according to the present invention Cross-sectional schematic diagram of the buffer member of the electrostatic speaker of the present embodiment Cross-sectional schematic diagram of another example of the buffer member of the electrostatic speaker of the present embodiment Cross-sectional schematic diagram of diaphragm of electrostatic speaker of this embodiment Cross-sectional schematic diagram of another example of the diaphragm of the electrostatic speaker according to the present embodiment The graph which shows the frequency characteristic of an Example and a comparative example

  The electrostatic speaker according to the embodiment of the present invention will be described in detail below.

  FIG. 1 is an enlarged schematic view of a part of a cross section of an electrostatic speaker 100 according to an embodiment of the present invention. The electrostatic speaker 100 according to the present embodiment includes a planar electrode 1, a buffer member 2, and a vibrating membrane 3 that is a thin film member.

  The planar electrode 1 is a pair of electrodes that apply a voltage to the vibrating membrane 3. The planar electrode 1 is a conductive member provided to face the vibration film 3 and has sound permeability. By supplying electric power from the AC power source to the planar electrode 1, a voltage is applied between the planar electrode 1 and the vibrating membrane 3, and the vibrating membrane 3 can be vibrated to produce sound. For planar electrodes, for example, metallic materials such as copper, stainless steel, iron and aluminum, conductive materials such as carbon, and conductive materials are applied to the base material of resin and ceramics by applying or sputtering to impart conductivity. Any material may be used as long as it has conductivity.

  For the buffer member 2, the vibrating membrane 3 and the planar electrode 1 are in direct contact with each other, and the electric charge charged to the vibrating membrane 3 is discharged or the vibrating membrane 3 and the planar electrode are avoided for the purpose of avoiding scraping and breakage due to friction. 1 between the two. Further, the buffer member 2 is frictionally charged with the vibration film 3 and has sound permeability, vibration damping properties, and electrical insulation properties. Since the buffer member 2 and the vibration film 3 need to be triboelectrically charged, the buffer member 2 is disposed in contact with the vibration film 3, or at least in a positional relationship in contact when the vibration film 3 vibrates. . It is desirable that the buffer member 2 is made of a material separated from the material of the vibration film 3 on the charging train. The buffer member 2 is not limited to the case where the entire buffer member is separated from the vibrating membrane 3 on the charged column, and at least the surface portion of the buffer member 2 facing the vibrating membrane 3 is separated from the vibrating membrane 3 on the charged column. It may be formed including other materials. For example, even if the base material of the buffer member 2 and the vibration film 3 are the same material, a layer of a material separated from the vibration film 3 and the charged column is formed on the side of the buffer member 2 facing the vibration film 3. Further, a material separated from the charged column may be included. Similarly, when the surface portion of the vibration film 3 facing the buffer member 2 is formed of a material different from the other portions, the buffer member 2 is the surface portion of the vibration film 3 facing the buffer member. What is necessary is just to form with the material which left | separated the electrification row | line | column.

  Here, the charged column of the material is the one in which the polarity generated by charging is arranged in the order of positive and negative with respect to the phenomenon that one is charged positively when the polymer film or fiber is rubbed against each other, and the other is charged negatively. It is. As the charge train, the charge train of Lehmicke and the charge train of J. Henniker are known and widely used for countermeasures against static electricity.

  The ones on the positive side of the charge train are acrylic (PMMA), polyamide (nylon), wool and formalin resin, and those on the negative side are well known to be polyethylene and polyvinyl chloride. Tetrafluoroethylene (PTFE) is considered to be one of the most strongly negatively charged materials.

  Since the buffer member 2 is made of a material different from that of the vibration film 3 on the charging train, when the vibration film 3 vibrates, the vibration film 3 is charged by friction with the buffer member 2. If the buffer member 2 is further away from the vibration film 3 on the charging train, the charge amount of the vibration film becomes larger, and the same effect as when a high potential is applied can be obtained. Therefore, if the buffer member 2 and the vibration film 3 are formed using materials separated from each other on the charge train, it is possible to generate sound even at a lower applied voltage, and an electric shock due to a high potential. The risk of being lost.

  The buffer member 2 used in the present embodiment is not particularly limited as long as it is made of a material that is separated from the vibrating membrane 3 and the charge train. For example, a polyethylene resin, a polypropylene resin, a polystyrene resin, Polymethylpentene resin, polyvinylidene chloride resin, polymethyl acrylate resin, polyamide resin, polyimide resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyarylate resin, polyether phenyl ether sulfone resin Polymer materials such as polyvinylidene fluoride resin, thermoplastic resins such as PVF, FEP, ETFE, PTFE, and PVDF, molten liquid crystal polymers such as polyarylate and PPTA, and inorganic materials such as glass and ceramics Materials such as carbon, bamboo, silk and cotton Natural materials may be used. These materials may be used singly or may be used by combining two or more of them or by combining them by coating, impregnation, kneading, etc. Especially, it is desirable to use them by combining them with inorganic materials.

  And the buffer member 2 of this embodiment has a cationic functional group at least on the surface. The presence of a functional group having a chemically positive charge on the surface or inside of the buffer member 2 makes it possible to increase the amount of positive charge of the buffer member 2. If the buffer member 2 has a cationic functional group, the method for introducing the cationic functional group is not particularly limited. Examples thereof include a surface modification method using a chemical reaction of monomers, a chemical graft polymerization method, and a radiation graft polymerization method. In particular, the use of the radiation graft polymerization method is particularly preferable because many cationic functional groups can be uniformly applied not only to the surface of the buffer member 2 but also to the inside thereof.

  The buffer member 2 having a cationic functional group is improved in charging performance as compared with a buffer member having no cationic functional group. Therefore, it is possible to obtain the same effect as using a member that is further away on the charged column. That is, when equivalent friction is performed with the same vibrating membrane 3, the buffer member 2 having a cationic functional group has more charge than a buffer member of the same material and not having a cationic functional group. It will be charged. As the chargeability is improved, the amount of charge of the vibrating membrane 3 is also increased, and an effect that the applied voltage exhibits excellent acoustic characteristics can be obtained.

  Examples of the cationic functional group that the buffer member 2 of this embodiment has include an amino group, an ammonium group, a sulfonium volatilization, and a phosphonium group. An amino group is particularly preferred as the cationic functional group from the viewpoints of productivity, charge amount and ease of introduction of the organic polymer fiber.

  In the present embodiment, the amount of the cationic functional group per unit mass of the buffer member is preferably 0.5 mol / g or more and 3.0 mol / g or less. When the amount of the cationic functional group is less than 0.5 mol / g, since the amount of the functional group is small, the effect of increasing the charge amount due to friction is not sufficient, and the effect of charging the vibrating membrane, that is, the effect of improving the acoustic characteristics is low. On the other hand, if the functional group amount is more than 3.0 mol / g, the base material becomes brittle or hard, resulting in a decrease in mechanical properties and loss of flexibility.

  In this embodiment, examples of the method for introducing a cationic functional group into the buffer member 2 include a chemical graft polymerization method and a radiation graft polymerization method. Legal is particularly suitable. In the radiation graft polymerization method, when an organic polymer base material is used as the material of the buffer member 2, graft side chains can be introduced from the surface to the inside of the organic polymer base material, and cationic functional groups are introduced. This is because the amount can be significantly improved. Here, examples of the radiation used in the graft polymerization include α rays, β rays, γ rays, electron rays, ultraviolet rays, and the like. However, γ rays and electron rays are particularly suitable for use in the present invention. Yes. In the radiation graft polymerization method, a functional group can be suitably introduced by the method described below. As a first preferred method, there is a simultaneous irradiation polymerization method in which radiation is irradiated in the presence of a substrate and a monomer, and as a second preferred method, radiation such as γ rays, electron beams, etc. is previously applied to the substrate surface. There is a pre-irradiation graft polymerization method in which the reaction is carried out by contacting with a monomer after irradiation.

The method of introducing a cationic functional group is such that a monomer having a cationic functional group is graft-polymerized, or a monomer having a functional group that can be converted into a cationic functional group is graft-polymerized and then converted to a cationic functional group. Any of the methods can be used.

  Examples of the monomer having a cationic functional group include diethylamine, diethanolamine, and trimethylamine. Examples of the monomer having a functional group that can be converted into a cationic functional group include glycidyl methacrylate, styrene, chloromethylstyrene, acrylonitrile, and acrolein.

  The buffer member 2 only needs to be able to electrically insulate the planar electrode 1 and the diaphragm 3 from each other, and a through-hole is formed by a film shape, a sheet shape, a nonwoven fabric shape, a woven fabric shape, a mesh shape, a knitted shape, or a punching process. Can be used in any shape. Among these, from the viewpoint of flexibility and uniformity of sound transmission, an organic polymer fiber structure such as a nonwoven fabric, a fabric, or a mesh is preferable.

The buffer member 2 needs to have a function of transmitting air vibration, which is the sound generated by the vibration of the diaphragm, to the outside, and the air permeability of the buffer member is 150 cm ³ / cm ² / sec or more and 400 cm ³ / cm as an index. Those of ² / sec or less are preferable. When the air permeability is higher than 400 cm ³ / cm ² / sec, the density as the buffer member is low, so that the air permeability, that is, the sound permeability is excellent, but the insulation and vibration damping properties are lowered. Also, when the air permeability is lower than 150 cm ³ / cm ² / sec, the density becomes too high as a buffer member, so that the insulation is excellent, but the sound permeability is low because it is difficult for air to permeate, making it suitable as a buffer member. Absent.

  Further, at least the surface of the buffer member 2 having a cationic functional group on the surface according to the present embodiment can form minute irregularities due to inorganic fine particles or polymer fine particles. FIG. 2 is a schematic cross-sectional view of the buffer member 2 used in the electrostatic speaker 100 of the present embodiment. FIG. 2 illustrates an example in which a thin film containing inorganic fine particles 12a and polymer fine particles 12b is formed on the surface of the base 11 of the buffer member using the binder component 14. Although a cationic functional group is not shown in FIG. 2, the buffer member 2 has a cationic functional group at least on its surface, and a thin film of inorganic fine particles 12a and polymer fine particles 12b is formed thereon. It is formed.

  Due to the irregularities formed by the inorganic fine particles 12a and the polymer fine particles 12b, the dust and dirt adhering to the surface of the buffer member 2 have a reduced area with the buffer member 2 that comes into contact, and the effect of vibration of the vibration film 3 Synergistically, it is possible to suppress dust and dust accumulation by easily detaching. Furthermore, by using the inorganic fine particles 12a and the polymer fine particles 12b as dielectric materials, charging due to friction between the buffer member 2 and the vibration film 3 becomes easier, and the charged charges are difficult to discharge, and excellent acoustics can be obtained. There is an effect that the permeability can be maintained for a long time.

As the inorganic fine particles 12a used for the thin film formed on the surface of the buffer member 2, for example, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , Sb ₂ O _{3, PbO, CuO, Cu 2} O, NiO, Ni 3 O 4, Ni 2 O 3, CoO, Co 3 O 4, Co 2 O 3, WO 3, a single inorganic oxide such as CeO ₂ and the like . Further, as inorganic fine particles, for example, BaTiO ₃ , SrTiO ₃ , ZnFe ₂ O ₄ , SiO ₂ · Al ₂ O ₃ , SiO ₂ · B ₂ O ₃ , SiO ₂ · P ₂ O ₅ , SiO ₂ · TiO ₂ , SiO _{2 · ZrO 2, Al 2 O} 3 · TiO 2, Al 2 O 3 · ZrO 2, Al 2 O 3 · CaO, Al 2 O 3 · B 2 O 3, Al 2 O 3 · P 2 O 5, Al 2 O ₃・ CeO ₂ , Al ₂ O ₃・ Fe ₂ O ₃ , TiO ₂・ CeO ₂ , TiO ₂・ ZrO ₂ , SiO ₂・ TiO ₂・ ZrO ₂ , Al ₂ O ₃・ TiO ₂・ ZrO ₂ , SiO ₂・ Al ₂ O ₃・ TiO ₂ , SiO ₂・ TiO ₂・ CeO ₂ , TiC, TaC, KNbO ₃ -NaNbO ₃ ferroelectric ceramics, (Bi _1/2 Na _1/2 ) TiO ₃ ferroelectric ceramics And composite oxides such as tungsten-bronze type ferroelectric ceramics.

  These inorganic fine particles 12a can be used alone or in combination of two or more. Further, the particle diameter of these inorganic fine particles is preferably 10 nm to 500 nm in order to form minute irregularities.

  Examples of the polymer fine particles 12b used for the thin film formed on the surface of the buffer member 2 include, for example, polyethylene resin, polypropylene resin, polystyrene resin, polymethylpentene resin, polyvinylidene chloride resin, and polyimide resin. And polyethylene terephthalate resin, polybutylene terephthalate resin, polyarylate resin, polyvinylidene fluoride resin, PVF, FEP, ETFE, PTFE, PVDF, and other thermoplastic resins. These polymer fine particles are used alone or in admixture of two or more. The particle diameter of these polymer fine particles is preferably 10 nm to 1.0 μm in order to form minute irregularities.

A binder component may be included in the thin film in order to fix the inorganic fine particles 12a and the polymer fine particles 12b to the surface of the buffer member 2, or to impart water repellency, hydrophilicity, and oil repellency. Examples of the binder component 14 include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, N- (vinylbenzyl). Hydrochloride of 2-aminoethyl-3-aminopropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxy Silane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methyl Examples of the silane monomer include tacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane.

  When the electrostatic speaker is used in a high humidity environment or in an environment where condensation is likely to occur due to a rapid temperature change, it is more preferable to use a water repellent compound as the binder component 14. Examples of the water-repellent binder component 14 include stearic acid acrylate, reactive silicone oil, dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, reactive silicone oligomer, and the like. For example, Matsushita Electric Works, Ltd. Fressela D ("Fressera" is a registered trademark) manufactured by Co., Ltd. is used.

  Furthermore, as the binder component 14 having water repellency, an acrylic monomer having a perfluoroalkyl group, such as 2- (perfluoropropyl) ethyl acrylate, 2- (perfluorobutyl) ethyl acrylate, 2- ( Perfluoropentyl) ethyl acrylate, 2- (perfluorohexyl) ethyl acrylate, 2- (perfluoroheptyl) ethyl acrylate, 2- (perfluorooctyl) ethyl acrylate, 2- (perfluoronolyl) ethyl acrylate 2- (perfluorodecyl) ethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, perfluorooctylethyl methacrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate , Fluorine-based compounds such as 3-perfluorodecyl-2-hydroxypropyl acrylate are used.

  Furthermore, as the binder component 14 having water repellency, for example, 2-perfluorooctylethanol, 2-perfluorodecylethanol, 2-perfluoroalkylethanol, perfluoro (propyl vinyl ether), perfluoroalkyl iodide, and the like. Alternatively, fluorine compounds such as perfluorooctylethylene and 2-perfluorooctylethylphosphonic acid may be used.

Further, as the binder component 14 having water repellency, a silane coupling agent having a perfluoroalkyl group, such as CF ₃ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ or CF ₃ (CF ₂ ) ₅ (CH ₂ ). ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₁₁ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₁₅ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (OC ₂ H ₅ ) ₃ , CF ₃ (CH ₂ ) ₂ SiCH ₃ (OCH ₃ ) ₂ , CF ₃ (CF ₂ ) ₂ (CH ₂ ) ₂ SiCH ₃ (OCH ₃ ) ₂ , CF ₃ (CF ₂ ) ₅ (CH ₂ ) ₂ SiCH ₃ (OCH ₃ ) ₂ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ SiCH ₃ (OCH ₃ ) ₂ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ SiCH ₃ (OC ₂ H5) ₂ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si _{(OCH 3) 3 and, CF 3 (CF 2) 7} (CH 2) and _{2 Si (OC 2 H5) 3} , CH 3 (CF 2) 9 (CH 2) 8Si (OC 2 H5) 3 and, CF _{3 (CF 2) 7 CONH (CH} 2) 3 Si (OCH 3) 3 and _has a _{CF 3 (CF 2) 7 CONH} (CH 2) 2 SiCH 3 (OCH 3) 2 or a perfluoroalkyl group and a silanol group Even if an oligomer, for example, KP-801M (manufactured by Shin-Etsu Chemical Co., Ltd.), X-24-7890 (manufactured by Shin-Etsu Chemical Co., Ltd.), perfluorobuter vinyl ether or a polymer thereof is used. There.

  Further, as another method for fixing the inorganic fine particles 12a on the surface of the buffer member 2 of the present embodiment, the surface of the inorganic fine particles 12a is made of silane having an unsaturated bond portion without using the binder component 14. It may be coated with a monomer, and the inorganic fine particles 12a may be fixed to the surface of the base 11 of the buffer member 2 by the silane monomer.

  FIG. 3 is a schematic cross-sectional view of the buffer member 2 in which the inorganic fine particles 12a are fixed to the base 11 of the buffer member by the silane monomer 13 chemically bonded to the surface of the inorganic fine particles 12a.

  By using the inorganic fine particles 12 a coated with the silane monomer, the inorganic fine particles 12 a can be firmly fixed to the surface of the base 11 of the buffer member 2. This is because the unsaturated bonds or reactive functional groups of the silane monomers 13 are chemically bonded to the inorganic fine particles 12a in the thin film, and the unsaturated bonds or reactions of the silane monomer 13 bonded to the inorganic fine particles 12a in the thin film. This is because the functional functional group chemically bonds to the surface portion of the base 11 of the buffer member 2.

  Here, the reason why the silane monomer 13 aligns and bonds the unsaturated bond portion or the reactive functional group toward the outside of the inorganic fine particles 12a will be described in detail. This is because the silanol group at one end of the silane monomer 13 is hydrophilic, so it is easily attracted to the surface of the inorganic fine particle 12a, which is also hydrophilic, while the unsaturated bond portion or reactive functional group at the reverse end is This is because it is hydrophobic and tends to leave the surface of the inorganic fine particles 12a. For this reason, since the silanol group of the silane monomer 13 is covalently bonded to the surface of the inorganic fine particle 12a by a dehydration condensation reaction, the silane monomer 13 is easily oriented with the unsaturated bond portion or the reactive functional group facing outward. Therefore, many silane monomers 13 are covalently bonded to the inorganic fine particles with the unsaturated bond portion or reactive functional group facing outward.

  That is, the buffer member 2 on which the thin film of the inorganic fine particles 12a used in the present embodiment is formed uses a highly reactive silane monomer having an unsaturated bond portion or a reactive functional group. The inorganic fine particles 12a on the buffer member 2 are bonded to each other by bonding, and a chemical bond is formed between the silane monomer on the surface of the inorganic fine particles 12a facing the buffer member 2 and the surface of the buffer member 2 to thereby form the inorganic fine particles. Can be firmly fixed on the buffer member 2.

  Examples of the unsaturated bond portion or reactive functional group of the silane monomer 13 covalently bonded to the inorganic fine particles 12a by dehydration condensation include a vinyl group, an epoxy group, a styryl group, a methacrylo group, an acryloxy group, and an isocyanate group.

  In the buffer member 2 on which the thin film composed of the inorganic fine particles 12a used in the present embodiment is formed, examples of the silane monomer that covers the inorganic fine particles 12a include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, N -Β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 2- (3,4 epoxy) (Cyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyl Methyldimethoxysilane, 3 -Methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane and the like.

  The amount of the silane monomer coated on the surface of these inorganic fine particles 12a may be supported by 0.1% by mass or more and 10% by mass or less with respect to the inorganic fine particles 12a. When the content is 0.1% by mass or more, the bonding strength of the inorganic fine particles 12a onto the buffer member 2 becomes higher. Even if it is supported in an amount of more than 10% by mass, the bond strength is almost constant.

  Next, the manufacturing method of the buffer member 2 shown in FIG. 3 to which the inorganic fine particles 12a whose surface is coated with a silane monomer is fixed will be described. First, inorganic fine particles in which a silane monomer is chemically bonded to the surface are mixed and dispersed in a dispersion medium such as methanol, ethanol, MEK, acetone, xylene, or toluene. Here, in order to promote the dispersion, a surfactant, a mineral acid such as hydrochloric acid or sulfuric acid, a carboxylic acid such as acetic acid or citric acid, or the like may be added as necessary. Subsequently, the inorganic fine particles are crushed and dispersed in a dispersion medium using an apparatus such as a bead mill, a ball mill, a sand mill, a roll mill, a vibration mill, or a homogenizer to produce a slurry containing inorganic fine particles.

  The covalent bond between the inorganic fine particles and the unsaturated bond portion or the silane monomer having a reactive functional group can be formed by an ordinary method. For example, the silane monomer is added to the dispersion of the inorganic fine particles, and then the mixture is refluxed. A method of forming a thin film composed of a silane monomer by covalently bonding a silane monomer to a surface of an inorganic fine particle by dehydration condensation reaction while adding the silane monomer to a dispersion obtained by micronization by pulverization, Alternatively, after adding silane monomer to form fine particles by pulverization, solid-liquid separation and heating at 100 to 180 ° C., the silane monomer is covalently bonded to the surface of the inorganic fine particles by dehydration condensation reaction, and then pulverized and disintegrated And re-dispersing.

  Here, after adding a silane monomer to a dispersion obtained by microparticulation under reflux or by pulverization, or after adding silane monomer to microparticles by pulverization, solid-liquid separation is performed, and the temperature is 100 ° C. to 180 ° C. When the silane monomer is covalently bonded to the surface of the inorganic fine particles by a dehydration condensation reaction by heating at a temperature of 0.01% by mass with respect to the mass of the inorganic fine particles, although depending on the average particle size of the inorganic fine particles The amount may be 40.0% by mass or less, and particularly preferably 0.1% by mass or more and 10% by mass or less from the viewpoint of the bonding strength between the inorganic fine particles and the buffer member 2. There may also be an excess of silane monomer that is not deposited in the bond.

  Subsequently, the slurry in which the inorganic fine particles obtained as described above are dispersed is applied to the surface of the buffer member 2 that fixes the inorganic fine particles. As a specific method for applying a slurry in which inorganic fine particles are dispersed, a commonly used spin coating method, dip coating method, spray coating method, cast coating method, bar coating method, micro gravure coating method, and gravure coating method are used. There is no particular limitation as long as it can be applied according to the purpose.

  Next, if necessary, after removing the dispersion medium by heat drying or the like, the buffer member 2 and the inorganic fine particles are chemically bonded. Specifically, the inorganic fine particles are bonded together by forming a chemical bond between the silane monomers on the surface of the inorganic fine particles, and the bonded inorganic fine particles form a chemical bond between the silane monomer and the surface of the buffer member. To fix.

  In the present embodiment, it is preferable to use a bonding method by graft polymerization as a method for chemically bonding the buffer member 2 and the silane monomer.

  Examples of the graft polymerization that can be used in the present embodiment include graft polymerization using a peroxide catalyst, graft polymerization using heat and light energy, and graft polymerization by radiation (radiation graft polymerization). Are appropriately selected and used. A chemical bond between the surface of the inorganic fine particles 2a and the silane monomer can be formed by treatment with a peroxide catalyst, treatment with heat or light energy, and treatment with radiation.

  Here, in order to perform graft polymerization of the silane monomer efficiently and uniformly, the surface of the buffer member 2 is previously subjected to corona discharge treatment, plasma discharge treatment, flame treatment, chromic acid, perchloric acid, etc. Hydrophilic treatment such as chemical treatment with an alkaline aqueous solution containing an oxidizing acid aqueous solution or sodium hydroxide may be performed.

  As described above, when the silane monomer 13 is chemically bonded to the surface of the inorganic fine particle 12 a and the inorganic fine particle 12 a is fixed to the base 11 of the buffer member 2 through the silane monomer 13, the inorganic fine particle 12 a is absorbed by the silane monomer 13. Since it is firmly held on the buffer member 2, peeling or the like can be suppressed.

  In the present embodiment, a method of fixing the inorganic fine particles 12a to the buffer member 2 with the binder component 14 and a method of fixing to the buffer member 2 via the silane monomer 13 chemically bonded to the surface of the inorganic fine particles 12a are described. However, it is not limited to this. The inorganic fine particles 12a may be fixed to the base 11 of the buffer member 2 by using both the binder component 14 and the silane monomer 13 chemically bonded to the surface of the inorganic fine particles 12a. In this case, since the inorganic fine particles 12a are more firmly fixed to the base 11 of the buffer member 2, the buffer member 2 having high durability can be formed.

  The method for forming minute irregularities is not limited to the method of forming a film containing inorganic fine particles 12a and polymer fine particles 12b on the base member 11 of the buffer member, but embossing, nanoimprinting, oxygen plasma, etc. The unevenness may be formed by a physical method such as, or may be formed by a chemical method such as chemical etching.

  Next, the vibrating membrane 3 changes the electrostatic force (Coulomb force) acting on the vibrating membrane 3 due to the change in the voltage applied from the planar electrode 1, and vibrates by the electrostatic force to generate sound. By applying a voltage corresponding to the acoustic signal, the vibrating membrane 3 emits sound corresponding to the acoustic signal. The diaphragm 3 of the present embodiment is a diaphragm that is self-charged by friction with the buffer member 2, and electrostatic force acts on the diaphragm 3 when a voltage is applied to the planar electrode 1 by friction charging. And vibrates.

  The vibration film 3 is preferably formed of a material having excellent chargeability, and for example, a film or sheet made of a polymer is preferable. Specific materials include, for example, polyethylene resin, polypropylene resin, polystyrene resin, polymethylpentene resin, polyvinylidene chloride resin, polymethyl acrylate resin, polyamide resin, polyimide resin, polyethylene terephthalate resin, , Polybutylene terephthalate resin, polyarylate resin, polyether phenyl ether sulfone resin, polyvinylidene fluoride resin, PVF (poly vinyl fluoride), FEP (fluorinated ethylene propylene copolymer), ETFE (ethylene tetra fluoroethylene) And thermoplastic resins such as PTFE (polytetrafluoroethylene) and PVDF (polyvinylidene difluoride), polyarylate, and molten liquid crystal polymers such as PPTA (Poly (p-phenylene terephthalamide)).

These materials may be used alone, or may be used as a substrate, and the surface thereof may be used by forming a polymer layer of another material. In particular, the vibration film needs to be thin and lightweight and strong in terms of durability against vibration, and a polymer film formed with a fluorine-based material or a fluorine-based polymer layer is desirable. Fluorine-based thin films have a strong tendency to be negatively charged due to friction. From this point, it is possible to configure a speaker with better acoustic characteristics by selecting a member that tends to be positively charged as a buffer member. .

  FIG. 4 is an enlarged view of a part of the cross section of the diaphragm 3 of the electrostatic speaker according to the embodiment of the present invention. The vibrating membrane 3 made of a thin film-like member is a polymer film formed of a material made of a material further separated from the buffer member 2 in which a cationic functional group is introduced on the surface of an organic polymer (fiber) substrate. The fluorine-based polymer layer 15 is formed on the surface of the film substrate 16. As a result, it is possible to construct a more excellent electrostatic speaker having characteristics such as high water repellency and low dielectric constant of the fluorine-based polymer.

  Examples of the fluorine-based polymer used for the fluorine-based polymer layer 15 of the vibration film 3 include thermoplastic resins such as polyvinylidene fluoride resin, PVF, FEP, ETFE, PTFE, and PVDF, and amorphous fluorine. Resins can be used. These fluorine-based polymers may be used alone, or two or more of non-fluorine-based polymers and fluorine-based polymers may be laminated or combined by coating or the like, and the surface may be a fluorine-based polymer. Any configuration may be used as long as the diaphragm 3 is coated with the above.

  Further, as shown in FIG. 5, the surface of the vibration film 3 is formed with minute irregularities having an arithmetic average roughness Ra of 5 nm or more and 500 nm or less, so that dust or dirt attached to the surface of the vibration film 3 is removed. By easily detaching, accumulation of dust and dust can be suitably suppressed. As a method for forming minute irregularities, embossing, nanoimprinting, physical methods such as oxygen plasma, and chemical methods such as chemical etching can be used.

  Further, as a method of forming irregularities on the surface of the vibration film 3, a thin film made of inorganic fine particles or polymer fine particles containing a binder component may be formed on the surface of the vibration film 3, as with the buffer member 2. Even in this case, the effect of suppressing the adhesion of dust and dust or easily detaching is exhibited. It is industrially difficult to control the arithmetic mean roughness Ra of the surface of the vibrating membrane 3 to be less than 5 nm, and when it is greater than 500 nm, dust-like dust that is generated daily in a living environment, so-called cotton linter, is generated. This is not preferable because it easily adheres and is difficult to detach. Further, by forming minute irregularities on the surfaces of the constituent materials of the vibration film 3 and the buffer member 2, it is difficult for dust and dirt to adhere, and even if it adheres, it is easily detached, so that even better acoustics can be obtained. Characteristics are maintained for a long time.

  The electrostatic loudspeaker 100 according to the embodiment of the present invention includes a planar electrode 1 having conductive sound transmission provided facing a vibration film 3 made of a thin film member, and a surface of an organic polymer (fiber) substrate. The buffer member 2 into which a cationic functional group is introduced is provided between the vibrating membrane 3 and the planar electrode 1. Here, the planar electrode 1 and the buffer member 2 may be configured independently, or may be configured integrally.

  According to the present embodiment described above, the vibration film 3 and the buffer member 2 are rubbed by the vibration of the vibration film, and the vibration film 3 is charged. In this embodiment, since the vibrating membrane 3 has a cationic functional group on the surface of the organic polymer (fiber) substrate, the amount of charge of the vibrating membrane 3 is further increased by frictional charging, and the planar electrode 1 The same effects as when a high potential is applied, and particularly the acoustic characteristics on the low sound range side are excellent. Thus, the applied voltage required for outputting sound can be further lowered, there is no risk of electric shock due to a high potential, and the sound in the low sound range is remarkably improved.

  Furthermore, the formation of a fine particle layer composed of inorganic fine particles and polymer fine particles on the surface of the buffer member 2 and the formation of fine irregularities on the surface of the vibrating membrane suppress the adhesion of dust and dust to the surface. Even if dust or dirt adheres, the contact area becomes extremely low, and it is easily detached from the surface of the diaphragm by the vibration of the diaphragm 3, so that even if it is used for a long time, the sound quality changes or the volume decreases. Can be suppressed. Therefore, it is possible to provide an electrostatic speaker that is less susceptible to the influence of dust and dirt even after long-term use.

  In the present embodiment, a speaker having a pair of electrodes (planar electrode 1) and a buffer member 2 is illustrated, but the present invention is not limited to this, and one electrode that is composed of the electrode, the buffer member, and the vibrating membrane 3 is provided. It may be a speaker having only.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

(Fabrication of vibration membrane and buffer member)
Example 1
First, the vibration film was diluted with CT-solv.100E (trade name: Asahi Glass Co., Ltd.) as a fluorine-based coating material for polyester film (Toray Industries, Inc., thickness 1.4 μm). A top (trade name: CTL-102AE manufactured by Asahi Glass Co., Ltd.) was applied by dipping and dried at 100 ° C. for 1 minute.

Next, the buffer member was produced as follows. First, a nylon nonwoven fabric (manufactured by Asahi Kasei Fibers, 40 g / m ² per unit area) is used in an atmosphere of nitrogen and an electron curtain type electron beam irradiation device, CB250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd., with an acceleration voltage of 200 kV. Irradiated with 20 Mrad. Subsequently, this nonwoven fabric was immersed in a 10% glycidyl methacrylate solution and graft polymerized. At this time, the graft ratio defined by weight increase rate ((weight of nonwoven fabric after graft polymerization−graph and weight of nonwoven fabric before polymerization) / weight of nonwoven fabric before graft polymerization × 100 (%)) was 134%. The obtained nonwoven fabric is called GMA graft polymerization nonwoven fabric. Thereafter, the obtained GMA graft nonwoven was immersed in a 10% diethylamine aqueous solution. By this reaction, the epoxy group in the graft polymer chain was converted to an amino group, and a buffer member into which the amino group was introduced was produced. The obtained buffer member is called an amino group introduction buffer member. The amount of the cationic functional group was calculated by the following formula (1) from the weight increase of the buffer member accompanying the reaction.
Amount of cationic functional group (mmol / g) = 1000 (W ₂ -W ₁ ) / 73 / W ₁ (1)
Here, W ₁ is the weight of the GMA grafted nonwoven fabric (buffer member before amino group introduction), and W ₂ is the weight of the amino group introduction buffer member. “73” is the molecular weight of diethylamine. From the above, the amount of the cationic functional group possessed by the buffer member of Example 1 was calculated to be 2.1 mmol / g.
When a monomer other than diethylamine is used as the cationic functional group, the molecular weight of the monomer may be used in place of “73” in calculating the amount of the cationic functional group in the formula (1).

(Example 2)
The vibration film is the same as that in the first embodiment. The buffer member is the same as that of Example 1 except that the irradiation amount of the electron beam to the nylon nonwoven fabric is 5 Mrad in Example 1. The graft ratio defined by the weight increase rate of the obtained GMA nonwoven fabric (buffer member before amino group introduction) was 60%, and the amount of cationic functional groups of the amino group introduction buffer member was 0.6 mmol / g.

(Example 3)
The vibration film was produced in the same manner as in Example 1 except that a PVDF film (manufactured by Kureha, thickness 4 μm) was used instead of the polyester film of Example 1.

The buffer member is made of polypropylene non-woven fabric (Asahi Kasei Fibers, 40 g / m ² per unit area) under an atmosphere of Iwasaki Electric Co., Ltd., an electro curtain type electron beam irradiation device, CB250 / 15 / 180L, and an electron beam of 200 kV. Irradiated with 20 Mrad at an acceleration voltage. Subsequently, this nonwoven fabric was immersed in a 10% glycidyl methacrylate solution and subjected to a graft polymerization reaction to obtain a polypropylene-made GMA graft nonwoven fabric having a graft rate of 140% defined by a weight increase rate. Furthermore, this GMA graft nonwoven fabric was immersed in a 10% diethylamine aqueous solution, and amino groups were introduced to prepare a buffer member. The amount of the cationic functional group was 2.8 mmol / g.

Example 4
The same vibration film as in Example 1 was used. In the electron beam irradiation process in Example 1, the buffer member had an electron beam irradiation amount of 30 Mrad. Otherwise, a buffer member was obtained by the same operation as in Example 1. In Comparative Example 2, the graft ratio of the GMA nonwoven fabric was 198%, and the amount of the cationic functional group of the amino group-introducing buffer member was 4.0 mmol / g.

(Example 5)
The same vibration film as in Example 1 was used. In the electron beam irradiation treatment in Example 1, the buffer member had an electron beam irradiation amount of 2 Mrad. Except for this, a cushioning material was obtained in the same manner as in Example 1. The graft ratio of the GMA nonwoven fabric obtained in Comparative Example 3 was 15%, and the amount of cationic functional groups in the amino group-introducing buffer material was 0.2 mmol / g.

(Example 6)
The same vibration film as in Example 1 was used. The buffer member is made of nylon non-woven fabric (Asahi Kasei Fibers, 100 g / m ² per unit area) made of Iwasaki Electric Co., Ltd., an electro curtain type electron beam irradiation device, CB250 / 15 / 180L in a nitrogen atmosphere, and an electron beam of 200 kV. 20 Mrad irradiation was performed at an acceleration voltage of. Subsequently, this nonwoven fabric was immersed in a 10% glycidyl methacrylate solution, and a graft polymerization reaction was performed to obtain a nylon GMA graft nonwoven fabric having a graft rate of 105% as defined by a weight increase rate. Further, this nonwoven fabric was immersed in a 10% diethylamine aqueous solution to introduce amino groups, a buffer member having a cationic functional group amount of 2.6 mmol / g was obtained, and the vibration membrane was the same as in Example 1.

(Comparative Example 1)
The same vibration film as in Example 1 was used. As the buffer member, the nylon nonwoven fabric (made by Asahi Kasei Fibers, basis weight 40 g / m ² ) used in Example 1 was directly used as the buffer member.

(Comparative Example 2)
The same diaphragm as in Example 3 was used. As the buffer member, the polypropylene nonwoven fabric used in Example 3 (manufactured by Asahi Kasei Fibers, basis weight 40 g / m ² ) was directly used as the buffer member.

(Comparative Example 3)
The same vibration film as in Example 1 was used. The nylon nonwoven fabric used in Example 6 (manufactured by Asahi Kasei Fibers, basis weight 100 g / m ² ) was directly used as a buffer member.

  The samples prepared above are shown in Table 1.

(Measurement of air permeability)
The air permeability of the buffer member was measured according to JIS L 1096 (Fragile type method).

(Speaker frequency characteristics evaluation)
The vibration membrane and the buffer member were previously neutralized with a direct current blower type static eliminator (Kasuga Denki, KD-410) so that the charge amount of the vibration membrane and the buffer member was approximately 0.0 nC. Thereafter, the planar electrode was a SUS325 mesh plate, and each of the buffer members of Examples and Comparative Examples was provided between the planar electrodes as shown in FIG. The frequency characteristics were evaluated by supplying a voltage of 100 V with a sine wave of 20 Hz to 10 kHz between the electrodes of the produced speaker. The frequency was measured with a sound level meter (NL-20 manufactured by Lion Co., Ltd.) installed at a distance of 25 cm from the speaker.

(Charge measurement)
The measurement of the charge amount of the diaphragm and the buffer member was performed by supplying a 100 Hz and 1 kHz sine wave voltage of 100 V to the speaker manufactured for frequency characteristic evaluation, and then removing the diaphragm from the speaker. Using an electrostatic charge meter (Faraday cage type KQ-1400) connected to a meter (NK-1001), the charge amount at each frequency was measured.

  FIG. 6 shows the sound pressure characteristics with respect to the frequencies of Example 1 and Comparative Example 1 as the measurement results of the sound level meter. This frequency characteristic result shows that the frequency characteristic of the buffer member into which the cationic functional group is introduced is excellent particularly in a low frequency region of 1 kHz or less. Therefore, as a representative evaluation of the frequency characteristics, the sound pressure values at 100 Hz and 1 kHz are shown in Table 2 together with the measurement results of the charge amounts of the buffer member and the diaphragm.

  Table 3 shows the ranking of the materials used in this example on the charged column. The charge trains in Table 3 refer to Lehmicke's charge trains widely used in anti-static technology. Nylon is the most positively charged material, and Teflon (registered trademark) is the most negatively charged material. Was used as a reference material, and was measured by measuring the positive and negative charges and the amount of charge during mutual friction with the reference material.

  From the results of Table 2, comparing Examples 1 to 3 and Comparative Examples 1 and 2, by introducing an amino group that is a cationic functional group into the buffer member, the amount of charge of the buffer member due to frictional charging is increased, Along with this, the charge amount of the vibrating membrane also increases, and as a result, it can be seen that the sound pressure is improved. In particular, as shown by a frequency of 100 Hz as a representative value of the frequency characteristics, it can be seen that the acoustic effect is significantly improved by introducing a cationic functional group in a low frequency region.

  Here, although the introduction amount of the amino group which is a cationic functional group was increased in Example 4, the amount of charge and sound pressure were slightly improved as compared with Example 1. Although the amount of cationic functional groups is increased by increasing the amount of electron beam irradiation and the grafting ratio is increased, the flexibility of the base material is lost, and the cushioning properties as a buffer member are reduced by becoming harder. This is thought to be due to adverse effects on the chargeability due to friction. Also, increasing the amount of electron beam irradiation has a negative effect on the physical properties of the substrate, such as strength and elongation, so care must be taken with regard to the sustainability of the speaker's acoustic characteristics and handling during speaker construction. is there. Further, in Example 5, since the introduction amount of the cationic functional group is small, the effect of improving the charge amount of the buffer member is limited to some extent, the change in the charge amount of the vibrating membrane is not large, and the improvement in acoustic characteristics is also limited. It is thought that it became.

  Furthermore, as shown in Example 6, when using a cushion member having a low air permeability, the frictional charge amount and acoustic characteristics are improved as compared with Comparative Example 3 in which a cationic functional group is not introduced, It can be seen that the effect of introducing a cationic functional group is suppressed because the sound permeability is low.

  Therefore, the electrostatic loudspeaker obtained in the present invention can significantly improve the acoustic characteristics by increasing the triboelectric charge amount between the vibration membrane and the buffer member by introducing a cationic functional group into the buffer member. Was confirmed.

100 Electrostatic Speaker 2 Buffer Member 3 Vibration Film 11 Buffer Member Base 12a Inorganic Fine Particle 12b Polymer Fine Particle 13 Silane Monomer 14 Binder 15 Fluorine Polymer Layer 16 Vibration Film Base

Claims (6)

A vibrating membrane made of a thin-film member;
A planar electrode having conductive acoustic transparency disposed opposite to the vibrating membrane;
A buffer member disposed between the vibrating membrane and the planar electrode, and charging the vibrating membrane by contact with the vibrating membrane ;
The said buffer member has a cationic functional group at least on the surface, The electrostatic speaker characterized by the above-mentioned.   The electrostatic loudspeaker according to claim 1, wherein a cationic functional group of the buffer member is any one of an amino group, an ammonium group, a sulfonium group, and a phosphonium group.   The electrostatic loudspeaker according to claim 1 or 2, wherein the amount of the cationic functional group per unit mass of the buffer member is 0.5 mmol / g or more and 3.0 mmol / g or less. Electrostatic speaker according to any one of claims 1 to 3, wherein the air permeability of the cushioning member is 150cm ³ / cm ² / sec or more 400cm ³ / cm ² / sec or less. Wherein the surface opposing at least the vibration film of the cushioning member, and the inorganic particles or polymeric particles, a binder component and / or silane monomers, the Tei Rukoto thin film is formed containing from claim 1, wherein 4 The electrostatic speaker according to any one of the above. The vibrating membrane, electrostatic speaker according to claim 1, any one of 5, wherein that you layer is formed containing a fluorine-based polymer to at least a portion of the surface.

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