Electrostatic speaker

Abstract

To provide a technology that increases the flexibility of an electrostatic type speaker and enables more effective use of the electrostatic type speaker.SOLUTION: An electrostatic type speaker 101 includes a first conductive cloth 111 that is a conductive cloth, second and third conductive cloths 121 and 131, which are conductive cloths arranged to sandwich the first conductive cloth 111 and are insulated from the first conductive cloth, and first and second exterior cloths 140, 150 that are arranged to cover the first to third conductive cloths 111, 121, 131, are thicker than the first to third conductive cloths 111, 121, 131, and are made of an insulating cloth. These first to third conductive cloths 111, 121, 131 and first and second exterior cloths 140, 150 are sewn with insulating thread.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This invention relates to an electrostatic speaker, and particularly to an electrostatic speaker having excellent flexibility.

Background Art

[0002] An electrostatic speaker is known as a speaker that generates sound corresponding to an electrical signal. An electrostatic speaker generally includes a pair of electrodes facing each other with a gap therebetween, and a sheet-like vibrating body having conductivity inserted between the pair of electrodes. Then, with a predetermined bias voltage applied to the vibrating body, by changing the voltage applied to the electrodes according to the electrical signal, the vibrating body is displaced according to the electrical signal, and sound is generated. In recent years, various techniques that enable bending have been proposed for such electrostatic speakers (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the electrostatic speaker proposed in Patent Document 1, since an elastic member is inserted between a pair of electrodes made of conductive cloth and the vibrating body, the flexibility of the obtained electrostatic speaker is not necessarily sufficient.

[0005] Further, even if it is possible to give a certain degree of flexibility to the electrostatic speaker, if wrinkles or the like occur in the electrostatic speaker, it becomes difficult to effectively utilize the electrostatic speaker.

[0006] The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a technique for increasing flexibility and enabling more effective utilization of an electrostatic speaker in an electrostatic speaker.

Means for Solving the Problems

[0007] In order to achieve at least a part of the above object, the present invention can be realized in the following forms or application examples.

[0008] [Application Example 1] An electrostatic speaker, comprising: a first conductive cloth which is a conductive fabric; second and third conductive cloths which are conductive fabrics arranged so as to sandwich the first conductive cloth and are insulated from the first conductive cloth; and first and second outer cloths which are arranged so as to cover the first to third conductive cloths, are thicker than the first to third conductive cloths, and are made of an insulating fabric, wherein the first to third conductive cloths and the first and second outer cloths are made of insulating yarns It is sewn, and at each end of each of the first to third conductive fabrics, fraying prevention processing is performed, and an insulating protective fabric is attached so as to wrap the ends of each of the first to third conductive fabrics. An electrostatic speaker characterized by the above.

[0009] According to this application example, since the first to third conductive cloths and the first and second outer cloths can move in the plane direction within a range allowed by their deformation, expansion and contraction, and the bending of the sewing thread, the flexibility of the electrostatic speaker can be further increased. And by forming the first and second outer cloths with a cloth thicker than the first to third conductive cloths, the occurrence of wrinkles and the like in the electrostatic speaker is suppressed, so that the electrostatic speaker can be utilized more effectively. Moreover, according to this application example, it is possible to suppress the occurrence of a short circuit between the first to third conductive fabrics by the conductive threads frayed from the first to third conductive fabrics. Furthermore, according to this application example, even if fraying occurs due to repeated bending of the electrostatic speaker, the influence of the frayed conductive threads is suppressed, so that the durability of the electrostatic speaker can be further improved.

[0010] [Application Example 2] The electrostatic speaker according to Application Example 1, wherein the electrostatic speaker is configured to be wound in a state where the first outer covering cloth is located on the inner peripheral side of the second outer covering cloth, the first outer covering cloth has elasticity in the winding direction in which the electrostatic speaker is wound, and the ends of the first and second outer covering cloths are sewn in such a way that the length of the first outer covering cloth in the winding direction becomes the natural length in the state where the electrostatic speaker is wound.

[0011] According to this application example, in each of the wound state wound for storage or the like and the deployed state pulled out for use or the like, wrinkles or the like are more surely suppressed from occurring on the outer surface of the electrostatic speaker. Therefore, it becomes easier to more effectively utilize the electrostatic speaker in which the inner peripheral side and the outer peripheral side in the wound state are predetermined.

[0012] [Application Example 3] The electrostatic speaker according to Application Example 2, wherein the first to third conductive cloths have elasticity in the winding direction, and the ends of the first to third conductive cloths and the first and second outer covering cloths are sewn in such a way that the length of the first to third conductive cloths in the winding direction becomes the natural length in the state where the electrostatic speaker is wound.

[0013] According to this application example, the occurrence of wrinkles in the first to third conductive cloths involved in the generation of sound is suppressed. Therefore, it becomes possible to more surely radiate sound as a plane wave from the electrostatic speaker.

[0018] [Application Example 6] The electrostatic speaker according to any one of Application Examples 1 to 3, wherein the first and second outer covering cloths are formed of fibers located on the positive side of paper in the charging series.

[0019] Generally, since the fibers positioned more positively than paper in the charging series have hygroscopicity, static electricity is less likely to accumulate. Therefore, according to this application example, with the application of a high-voltage DC voltage, the accumulation of static electricity in the surface layer fabric 140 and the base fabric 150 is suppressed, so that the possibility of discharge occurring between the user who has contacted the electrostatic speaker due to the accumulated static electricity can be reduced.

[0020] In addition, the present invention can be realized in various aspects. For example, it can be realized in aspects such as an electrostatic speaker, a speaker system including the electrostatic speaker and a drive unit of the electrostatic speaker, a projector screen using the electrostatic speaker, a sound insulation system using those electrostatic speakers and speaker systems, and the like.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0022] Hereinafter, the modes for carrying out the present invention will be described in the following order. A. First Embodiment: A1. Usage Mode of Speaker System: A2. Electrical Configuration of Speaker System: A3. Specific configuration of electrostatic speaker: B. Second embodiment: C. Third embodiment: D. Modification:

[0023] A. First embodiment: A1. Usage mode of speaker system: FIG. 1 is an explanatory diagram showing the usage mode of a speaker system 10 as the first embodiment of the present invention. As shown in FIG. 1, the speaker system 10 of the first embodiment includes a pull-out type projector screen 100 having a winding mechanism (hereinafter, also simply referred to as "screen") and a drive unit 200 connected to the screen 100.

[0024] In the usage mode shown in FIG. 1, an audio signal AS is supplied from a video disc player 900 that plays a video disc on which an image is recorded to the drive unit 200. Also, a video signal VS is supplied from the video disc player 900 to a projector (not shown). Then, by irradiating the projection surface 101 of the screen 100 with modulated light modulated by the video signal VS from the projector, a projected image PIM is displayed on the projection surface 101 of the screen 100.

[0025] On the other hand, although details will be described later, the drive unit 200 vibrates and drives the projection surface 101 of the screen 100 based on the supplied audio signal AS. As a result, sound corresponding to the audio signal AS supplied from the video disc player 900 is radiated from the projection surface 101 of the screen 100 in the direction normal to the projection surface 101.

[0026] A2. Electrical configuration of speaker system: FIG. 2 is an explanatory diagram showing the electrical configuration of the speaker system 10 of the first embodiment. As shown in FIG. 2, in the speaker system 10, a drive unit 200 is connected to the projection surface 101 of the screen 100 (FIG. 1) that radiates sound.

[0027] The projection surface 101 has a diaphragm 110 that radiates sound by vibrating, and two electrode films 120 and 130 arranged to face the diaphragm 110 with a gap therebetween. The drive unit 200 connected to the projection surface 101 of the screen 100 has an amplifier circuit 210, a transformer output circuit 220, and a high voltage generation circuit 230.

[0028] The amplifier circuit 210 is constituted by a differential amplifier U1 that amplifies the input single-ended signal and outputs a differential signal combining signals of opposite polarities of + and -. The single-ended audio signal AS input to the amplifier circuit 210 is amplified by the differential amplifier U1 and supplied as a differential audio signal DAS from the amplifier circuit 210 to the transformer output circuit 220.

[0029] In the first embodiment, the differential amplifier U1 that outputs a differential signal is used in the amplifier circuit 210, but it is also possible to use an amplifier that outputs a single-ended signal similar to the input audio signal AS. However, since the high voltage generation circuit 230 constituting the drive unit 200 has a chopper circuit as will be described later, there is a possibility of generating large noise. In order to reduce the influence of the noise generated in the high voltage generation circuit 230 in this way, it is preferable to use a differential amplifier that outputs a differential signal as the amplifier circuit 210 so as to output a differential audio signal DAS.

[0030] The transformer output circuit 220 has two transformers T1 and T2 of the same configuration. These two transformers T1 and T2 are connected in parallel on the primary side connected to the amplifier circuit 210. On the other hand, on the secondary side connected to the projection surface 101 of the screen 100, the two transformers T1 and T2 are connected in series. Also, the number of turns on the secondary side of the transformers T1 and T2 is set higher than the number of turns on the primary side. Thereby, the differential audio signal DAS supplied from the amplifier circuit 210 is boosted to a voltage twice the turns ratio of the transformers T1 and T2 at both ends of the transformers T1 and T2 connected in series and transmitted to the two electrode films 120 and 130 constituting the projection surface 101.

[0031] The high-voltage generation circuit 230 is a circuit that generates a DC voltage higher than the power supply voltage Vdd, and the generated high-voltage DC voltage is supplied to the transformer output circuit 220 connected to the high-voltage generation circuit 230. In the first embodiment, as the high-voltage generation circuit 230, a boost chopper circuit that turns on and off the drain-source of the MOS field-effect transistor Q1 by the rectangular wave generated by the oscillator OSC and generates a high voltage by the back electromotive force of the choke coil L, and a Cockcroft-Walton circuit that boosts using diodes D1 to D6 and capacitors C1 to C6 are combined. However, as the high-voltage generation circuit, various boost circuits such as a boost chopper circuit or a Cockcroft-Walton circuit used alone, or a boost circuit using an oscillator and a flyback transformer can also be used.

[0032] The high-voltage DC voltage generated by the high-voltage generation circuit 230 is supplied between two transformers T1 and T2 connected in series in the transformer output circuit 220. Then, by connecting both ends of the transformers T1 and T2 connected in series to the two electrode films 120 and 130 on the projection plane 101 and connecting the vibrating film 110 to the ground electrode of the transformer output circuit 220 to ground, a state where a high-voltage DC voltage is applied to the two electrode films 120 and 130 with respect to the vibrating film 110 is obtained.

[0033] On one hand, as described above, the differential audio signal DAS is boosted at both ends of the transformers T1 and T2 connected in series and transmitted to the two electrode films 120 and 130 that constitute the projection surface 101. Therefore, voltages with opposite polarities corresponding to the differential audio signal DAS or the audio signal AS are applied to the electrode films 120 and 130 with respect to the vibrating film 110, and the voltages of the two electrode films 120 and 130 with respect to the vibrating film 110 vary in opposite directions. The vibrating film 110 vibrates as a whole in the opposing direction of the electrode films 120 and 130 in response to the voltage variations of these electrode films 120 and 130, and sound corresponding to the differential audio signal DAS (audio signal AS) is radiated from the vibrating film 110. Note that since the projection surface 101 composed of the vibrating film 110 and the two electrode films 120 and 130 has the function of radiating sound by electrostatic action in this way, it can also be called an "electrostatic speaker".

[0034] A3. Specific configuration of the electrostatic speaker: FIG. 3 is an explanatory diagram showing the specific configuration of the electrostatic speaker 101 (hereinafter simply referred to as the "speaker 101") of the first embodiment. As described above, the speaker 101 has, as an electrical configuration, a vibrating film 110 and two electrode films 120 and 130 arranged to face the vibrating film 110 with a gap therebetween. The speaker 101 also has, in addition to these vibrating film 110 and electrode films 120 and 130, a surface layer cloth 140 on which the projection video PIM is displayed on the screen 100 (FIG. 1), and a base cloth 150 as a base on which the speaker (projection surface) 101 is attached on the screen 100.

[0035] The vibrating film 110 is composed of a conductive cloth 111 that is a woven cloth having conductivity, and insulating films 112 and 113 adhered to both surfaces of the conductive cloth 111. The conductive cloth 111 is formed by plating a metal such as copper or aluminum on the raw yarn and weaving the plated raw yarn using a well-known weaving technique.

[0036] As the raw yarn for weaving the conductive cloth 111, chemical fibers such as polyester and acrylic, natural fibers such as cotton and wool, or blended fibers obtained by mixing multiple types of fibers can be used. However, in order to ensure flame retardancy, it is preferable to use flame-retardant polyamide fibers, aramid fibers, or various fibers subjected to flame-retardant treatment as the raw yarn.

[0037] In addition, as the conductive cloth 111, in addition to the woven fabric woven from the plated raw yarn, a woven fabric woven from fine metal wires or metal yarns such as copper, a net-like body made of a metal such as copper, a woven fabric woven from a raw yarn containing fine metal wires such as copper, or a carbon fiber woven fabric woven using conductive fibers such as carbon fibers as the raw yarn can also be used. However, in terms of suppressing a decrease in the flexibility of the conductive cloth 111, it is preferable to use a woven fabric woven from the plated raw yarn as the conductive cloth 111. Incidentally, since the plated raw yarn, the raw yarn containing fine metal wires, and the raw yarn using conductive fibers such as carbon fibers all have conductivity, they can also be referred to as "conductive raw yarns".

[0038] As the insulating films 112 and 113 adhered to the conductive cloth 111, films made of various resins such as polyester, epoxy, polyimide, or aramid such as polyethylene terephthalate (PET) can be used. Since these insulating films 112 and 113 are adhered to the conductive cloth 111, it is not necessary for them to guarantee strength by themselves. Therefore, if they have sufficient withstand voltage against the high-voltage DC voltage applied to the electrode films 120 and 130, it is preferable to use thinner ones.

[0039] The electrode films 120 and 130 are each composed of a conductive cloth 121 and 131 which are woven fabrics having conductivity, and insulating films 122 and 132 adhered to the vibration film 110 side. The conductive cloths 121 and 131 are formed in the same manner as the conductive cloth 111 constituting the vibration film 110. Also, the insulating films 122 and 132 are formed in the same manner as the insulating films 112 and 113 constituting the vibration film 110.

[0040] Note that the conductive fabrics 121 and 131 facilitate the external emission of the sound generated by the vibration of the diaphragm 110 through the electrode film 120, and also suppress the suppression of the vibration of the diaphragm 110 by the back pressure between the diaphragm 110 and the electrode film 130. Therefore, it is preferable to set the weaving density lower than that of the conductive fabric 111 of the diaphragm 110.

[0041] The surface fabric 140 and the base fabric 150 are insulating woven fabrics appropriately selected based on mechanical properties such as strength and other properties so that the function as the screen 100 (FIG. 1) can be realized. These surface fabric 140 and base fabric 150 are woven fabrics provided outside the diaphragm 110 and the electrode films 120 and 130 so as to cover them, and thus can also be called "outer fabrics".

[0042] As the surface fabric 140 and the base fabric 150, thicker woven fabrics than the conductive fabrics 111, 121, and 131 are used. Here, the thicker woven fabric refers to a woven fabric having thickness and tension. As such a thicker woven fabric, for example, denim, canvas, or the like is used. In order to give thickness to these surface fabric 140 and base fabric 150, the surface fabric 140 and the base fabric 150 may be formed by weaving thick yarns such as 7.5-count or 10-count, or may be formed by performing multi-layer weaving such as double weaving or triple weaving.

[0043] As the yarns for weaving the surface fabric 140 and the base fabric 150, various fibers can be used, but it is preferable to use fibers that are easily positively charged, that is, fibers located on the positive side of paper in the charging series. It is also possible to form the surface fabric 140 and the base fabric 150 by weaving a yarn obtained by blending a plurality of types of fibers that are easily positively charged. Examples of the fibers that are easily positively charged include natural fibers such as hemp, cotton, or wool, and polyamide fibers such as acetate fibers and nylon.

[0044] Generally, fibers that are prone to positive charging have hygroscopic properties, so it is difficult for static electricity to accumulate. Therefore, by forming the surface layer fabric 140 and the base fabric 150 using fibers that are prone to positive charging, the accumulation of static electricity in the surface layer fabric 140 and the base fabric 150 is suppressed as a high-voltage DC voltage is applied to the electrode films 120, 130 (conductive fabrics 121, 131). Thus, it is possible to reduce the likelihood of discharge occurring between the user who has come into contact with the speaker 101 due to the accumulated static electricity.

[0045] In the above description, as an example of the usage mode of the speaker 101 of the first embodiment, an example of applying the speaker 101 to the projector screen 100 is shown. Thus, when applying the speaker 101 to the projector screen 100, in order to realize the function as the screen 100 in the speaker 101, for example, various processes for favorably reflecting the irradiated light are applied to the outer surface of the surface layer fabric 140, that is, the surface on the side opposite to the electrode film 120 as needed.

[0046] The diaphragm 110, the electrode films 120, 130, the surface layer fabric 140, and the base fabric 150 that constitute the speaker 101 are sewn together with insulating threads in their stacking direction (the vertical direction in the plane of FIG. 3). Thereby, the speaker 101 in which the diaphragm 110, the electrode films 120, 130, the surface layer fabric 140, and the base fabric 150 are integrated is formed.

[0047] The connection between the speaker 101 formed in this way and the drive unit 200 is made by sewing the wiring 119, 129, 139 extending from both ends of the ground electrode of the transformer output circuit 220 (FIG. 2) and the serially connected transformers T1, T2 to the diaphragm 110 and the electrode films 120, 130, respectively. In the example of FIG. 3, the wiring 119, 129, 139 is sewn to the ends of the diaphragm 110 and the electrode films 120, 130, but the location where the wiring is sewn can be changed as appropriate.

[0048] In the first embodiment, the wirings 119, 129, and 139 extending from the transformer output circuit 220 are sewn to the diaphragm 110 and the electrode films 120 and 130, respectively. However, it is also possible to connect the speaker 101 and the drive unit 200 by other methods. For example, the wirings 119, 129, and 139 extending from the transformer output circuit 220 may be attached to the diaphragm 110 and the electrode films 120 and 130 using a conductive paste or the like. However, in terms of making the connection between the wirings 119, 129, and 139 and the diaphragm 110 and the electrode films 120 and 130 more reliable and increasing the strength of the connection portion, it is preferable that the wirings 119, 129, and 139 be sewn to the diaphragm 110 and the electrode films 120 and 130.

[0049] In the speaker 101 of the first embodiment configured as described above, the diaphragm 110, the electrode films 120 and 130, the surface layer cloth 140, and the base cloth 150 are in a state of being sewn to each other. Therefore, the diaphragm 110, the electrode films 120 and 130, the surface layer cloth 140, and the base cloth 150 can move in the plane direction, that is, in the direction orthogonal to the stacking direction, within a range allowed by their deformation, expansion, and contraction and the bending of the sewing thread. Since the diaphragm 110, the electrode films 120 and 130, the surface layer cloth 140, and the base cloth 150 can move in the plane direction in this way, the flexibility of the speaker 101 is increased, so that the radius of curvature when winding up the cloth portion of the screen including the speaker 101 can be made smaller. Therefore, the size of the screen 100 during storage can be made smaller, and the portability and storability of the screen 100 can be increased.

[0050] Furthermore, in the speaker 101 of the first embodiment, the surface layer cloth 140 and the base cloth 150 are made of a thick woven cloth that is thicker and more taut than the conductive cloths 111, 121, and 131. Therefore, in the use state of the projector screen 100 (FIG. 1), the occurrence of wrinkles on the projection surface (speaker) 101 is suppressed, so that the projection video PIM can be more appropriately displayed.

[0051] In addition, by making the surface fabric 140 and the base fabric 150 thick woven fabrics, the insulation between the conductive fabrics 121 and 131 to which a high-voltage DC voltage is applied and the outer surface of the speaker 101 is enhanced. Therefore, the risk of the high-voltage DC voltage applied to the conductive fabrics 121 and 131 leaking to the outside can be reduced.

[0052] Also, by using the speaker 101 of the first embodiment, as shown in FIG. 1, on the projection surface 101 of the screen 100, a projection video PIM corresponding to the video signal VS supplied from the video disc player 900 is displayed, and sound corresponding to the audio signal AS supplied from the video disc player 900 is radiated from the projection surface (speaker) 101. Therefore, it is possible to conduct a presentation video or a remote conference without preparing a speaker separate from the screen 100.

[0053] In the speaker 101 of the first embodiment, since sound is radiated by the entire diaphragm 110 vibrating, the sound is radiated as a plane wave in the stacking direction of the diaphragm 110 and the electrode films 120 and 130, that is, in the normal direction of the speaker 101. As a result, since the sound is intensively radiated in the normal direction of the speaker 101, according to the speaker 101 of the first embodiment, it is possible to limit the target viewers during the screening of a presentation video or the like.

[0054] Furthermore, since the sound corresponding to the audio signal AS is radiated from the projection surface (speaker) 101 on which the projection video PIM is displayed, when the projection video PIM includes an image of a speaker or the like as shown in FIG. 1, the viewers of the projection video PIM can feel as if the speaker is actually speaking. Therefore, the sense of presence of a presentation video or a remote conference can be further enhanced.

[0055] In the first embodiment shown in FIG. 1, a portable screen 100 used for presentations and remote conferences is employed. However, the present invention can also be applied to stationary screens used in home theaters and the like. Even in this case, since sound is radiated from the screen on which the video is displayed, it becomes more immersive, and thus a good sense of immersion can be given to the viewers of the video.

[0056] In addition, when the screen (speaker) to which the present invention is applied is used in a home theater or the like that performs audio reproduction in a surround system, the screen itself can be used as a center speaker arranged on the screen side. In this case, since the arrangement of a separate center speaker can be omitted, the degree of freedom in arranging the screen can be increased further.

[0057] Furthermore, by appropriately adjusting the weaving density of the conductive cloths 111, 121, 131 constituting the diaphragm 110 and the electrode films 120, 130, and the surface cloth 140 and the base cloth 150, it becomes possible to allow sound to pass well from the base cloth 150 side to the surface cloth 140 side. By doing so, the speaker can be arranged behind the screen, and thus the degree of freedom in arranging the screen can be increased even further.

[0058] B. Second Embodiment: FIG. 4 is an explanatory diagram showing a specific configuration of the speaker 101a in the second embodiment. The second embodiment is different from the first embodiment in that the configuration of the speaker 101a is different. Since the other configurations are the same as those in the first embodiment, the description thereof is omitted here.

[0059] Specifically, the speaker 101a in the second embodiment is different from the speaker 101 in the first embodiment shown in FIG. 3 in that protective cloths 114a, 124a, 134a, which are insulating woven fabrics, are attached to the respective ends of the diaphragm 110a and the electrode films 120a, 130a. In FIG. 4, for the sake of convenience, the illustration of the attachment portions of the wirings 119, 129, 139 (FIG. 3) to the diaphragm 110a and the electrode films 120a, 130a is omitted.

[0060] As shown in Fig. 4, the protective cloths 114a, 124a, and 134a are attached so as to wrap the respective ends of the diaphragm 110a and the electrode films 120a and 130a. The attachment of the protective cloths 114a, 124a, and 134a to the ends of the diaphragm 110a and the electrode films 120a and 130a is performed, for example, by sewing with insulating threads.

[0061] The protective cloths 114a, 124a, and 134a are formed by weaving a raw yarn using chemical fibers such as polyester and acrylic, natural fibers such as cotton and wool, or blended fibers obtained by mixing multiple types of fibers. However, in order to ensure flame retardancy, it is preferable to use flame-retardant polyamide fibers, aramid fibers, or various fibers subjected to flame-retardant treatment as the raw yarn.

[0062] With the use of the speaker 101a, there is a possibility that the ends of the conductive cloths 111, 121, and 131 constituting the diaphragm 110a and the electrode films 120a and 130a may fray. However, in the second embodiment, as shown in Fig. 4, the protective cloths 114a, 124a, and 134a suppress the exposure of frayed threads having conductivity from the conductive cloths 111, 121, and 131. Therefore, short-circuiting between the conductive cloths 111, 121, and 131 through the frayed threads is suppressed. In addition, by suppressing the exposure of the frayed threads, the risk of leakage of the high-voltage DC voltage applied to the conductive cloths 121 and 131 to the outside can be reduced.

[0063] In the example of FIG. 4, by wrapping the ends of the conductive fabrics 111, 121, 131 (vibrating membrane 110a and electrode membranes 120a, 130a) with the protective fabrics 114a, 124a, 134a, the exposure of the threads frayed from the conductive fabrics 111, 121, 131 is suppressed, short circuits between the conductive fabrics 111, 121, 131 are suppressed, and leakage of the high-voltage DC voltage applied to the conductive fabrics 121, 131 to the outside is suppressed. This reduces the influence of the threads frayed from the conductive fabrics 111, 121, 131. Therefore, in the speaker 101a of the second embodiment, it can be considered that fraying prevention processing for suppressing the fraying of the conductive fabrics 111, 121, 131 is performed.

[0064] Thus, from the viewpoint of suppressing the fraying of the conductive fabrics 111, 121, 131, it is also possible to realize fraying prevention processing by a configuration different from the configuration in which the ends of the conductive fabrics 111, 121, 131 shown in the example of FIG. 4 are wrapped with the protective fabrics 114a, 124a, 134a.

[0065] For example, by applying a fraying prevention liquid to the ends of the conductive fabrics 111, 121, 131, the fraying of the conductive fabrics 111, 121, 131 can be suppressed. As the fraying prevention liquid to be applied, for example, a commercially available fraying prevention liquid in which nylon is dissolved in ethanol can be used. Also, if the raw yarns from which the conductive fabrics 111, 121, 131 are woven are fibers having thermoplasticity, the fraying of the conductive fabrics 111, 121, 131 can also be suppressed by heating the respective ends of the conductive fabrics 111, 121, 131 to weld the raw yarns at the ends.

[0066] However, when applying the fraying prevention liquid to the ends of the conductive fabrics 111, 121, 131, or welding the raw yarns at the respective ends of the conductive fabrics 111, 121, 131, the number of bending times of the speaker increases. Therefore, the effect of suppressing fraying may decrease. For this reason, it is preferable that the fraying prevention process is performed by attaching the protective fabrics 114a, 124a, 134a to the conductive fabrics 111, 121, 131 so as to wrap the ends of the conductive fabrics 111, 121, 131 as in the second embodiment. By doing so, even if fraying occurs due to repeated bending of the speaker, the influence exerted by the frayed conductive yarns is suppressed, so that the durability of the speaker 101a can be further enhanced.

[0067] C. Third Embodiment: FIG. 5 is an explanatory diagram showing a specific configuration of the speaker 101b in the third embodiment. The speaker 101b in the third embodiment is different from the speaker 101 in the first embodiment in that the configurations of the diaphragm 110b, the electrode films 120b, 130b, and the surface layer fabric 140b are different. Since the other configurations are the same as those in the first embodiment, the description thereof is omitted here. Also, in FIG. 5, for the sake of convenience, the illustration of the attachment portions of the wirings 119, 129, 139 (FIG. 3) to the diaphragm 110b and the electrode films 120b, 130b is omitted.

[0068] Specifically, the speaker 101b in the third embodiment is different from the speaker 101 in the first embodiment in that the conductive fabrics 111b, 121b, 131b constituting the diaphragm 110b and the electrode films 120b, 130b and the surface layer fabric 140b are knitted fabrics (knits) having stretchability.

[0069] The conductive fabrics 111b, 121b, 131b are formed by knitting the selected conductive raw yarns using a well-known knitting technique in the same manner as in the first embodiment. Also, the surface layer fabric 140b is formed by knitting the selected insulating raw yarns in the same manner as in the first embodiment.

[0070] Note that the conductive fabrics 111b, 121b, 131b and the surface fabric 140b are formed such that the highly stretchable direction coincides with the winding direction when the speaker 101b is wound, that is, they are formed to have stretchability in the winding direction.

[0071] As the insulating films 112b, 113b, 122b, 132b adhered to the conductive fabrics 111b, 121b, 131b, films made of easily stretchable resins such as polyurethane, polyurea, polyurethane urea, polybutadiene or silicone are used so that the stretchability of the conductive fabrics 111b, 121b, 131b is not inhibited and the diaphragm 110b and the electrode films 120b, 130b have stretchability. Thereby, in the speaker 101b of the third embodiment, the diaphragm 110b, the electrode films 120b, 130b and the surface fabric 140b constituting the speaker 101b have stretchability in the winding direction.

[0072] FIG. 6 is an explanatory view showing the state of the speaker 101b in each of the wound state and the unfolded state. FIG. 6(a) shows the state of the speaker 101b in the wound state, that is, the state in which the speaker 101b is wound for storage or the like, and FIG. 6(b) shows the state of the speaker 101b in the unfolded state, that is, the state in which the speaker 101b is pulled out for use or the like. Specifically, FIGS. 6(a) and 6(b) show the states of the diaphragm 110b, the electrode films 120b, 130b and the surface fabric 140b at the end portion surrounded by the dashed-dotted line and the middle portion surrounded by the double-dashed-dotted line in each of the wound state and the unfolded state. Note that, as can be seen from FIG. 6, in the third embodiment, the speaker 101b is wound such that the surface fabric 140b is on the inner peripheral side and the base fabric 150 is on the outer peripheral side.

[0073] In the wound state shown in FIG. 6(a), the diaphragm 110b, the electrode films 120b and 130b, the surface layer cloth 140b, and the base cloth 150 are sewn at their ends such that the lengths of the stretchable diaphragm 110b, electrode films 120b and 130b, and surface layer cloth 140b in the winding direction become their natural lengths. Therefore, in the wound state, the diaphragm 110b, electrode films 120b and 130b, surface layer cloth 140b, and base cloth 150 that constitute the speaker 101b all have their lengths in the winding direction as their natural lengths. As a result, when the speaker 101b is wound, the surface layer cloth 140b and the electrode film 120b on the inner peripheral side are prevented from bending, and wrinkles are prevented from occurring in the speaker 101b.

[0074] On the other hand, in the unfolded state in which the wound speaker 101b is pulled out, since the diaphragm 110b, the electrode films 120b and 130b, and the surface layer cloth 140b are stretchable, the diaphragm 110b, the electrode films 120b and 130b, and the surface layer cloth 140b extend in the winding direction due to the difference in the circumferences from the base cloth 150. Therefore, due to the difference in the circumferences, the base cloth 150 and the electrode film 130b on the outer peripheral side are prevented from bending, and wrinkles are prevented from occurring in the speaker 101b.

[0075] As described above, in the third embodiment, since the exterior cloth (i.e., the surface layer cloth 140b) located on the inner peripheral side in the wound state, the diaphragm 110b, and the electrode films 120b and 130b are stretchable in the winding direction, wrinkles are prevented from occurring in the speaker 101b in any of the wound state and the unfolded state.

[0076] In the third embodiment, since the speaker 101b is wound such that the surface layer cloth 140b is on the inner peripheral side, the surface layer cloth 140b is a knitted cloth having stretchability. However, when winding is performed such that the base cloth is on the inner peripheral side, the base cloth is a knitted cloth having stretchability.

[0077] Also, in the third embodiment, since the speaker 101b is applied to the pull-out type projector screen 100 (Fig. 1) having a winding mechanism, the inner peripheral side and the outer peripheral side in the wound state are determined in advance. However, when applying it to a projector screen without a winding mechanism, such as a vertical screen type or a hanging picture type projector screen, the inner peripheral side and the outer peripheral side in the wound state are not determined. In such a case, if both the surface fabric and the base fabric are knitted fabrics having stretchability, wrinkling of the speaker is suppressed in both the wound state and the unfolded state. In this case, in the unfolded state of the speaker, the diaphragm, the two electrode films, the surface fabric, and the base fabric are all sewn at the ends so that the length in the winding direction becomes the natural length.

[0078] Furthermore, in the third embodiment, in addition to the surface fabric 140b, the diaphragm 110b (conductive fabric 111b) and the electrode films 120b, 130b (conductive fabrics 121b, 131b) are made stretchable, but it is also possible to make only the surface fabric 140b stretchable. Even in this case, wrinkling on the outer surface of the speaker is suppressed, so that the projected image PIM (Fig. 1) can be more appropriately displayed.

[0079] However, by making the diaphragm 110b (conductive fabric 111b) and the electrode films 120b, 130b (conductive fabrics 121b, 131b) stretchable, wrinkling of the diaphragm 110b and the electrode films 120b, 130b involved in sound generation is suppressed, and it becomes possible to more reliably radiate sound as a plane wave from the speaker 101b. Therefore, it is preferable to make the diaphragm 110b (conductive fabric 111b) and the electrode films 120b, 130b (conductive fabrics 121b, 131b) stretchable.

[0080] Also, in the third embodiment, in order to give elasticity to the conductive fabrics 111b, 121b, 131b and the surface fabric 140b, these fabrics 111b, 121b, 131b, 140b are made into knitted fabrics having elasticity. However, as long as the fabric has elasticity, it is also possible to make at least a part of these fabrics 111b, 121b, 131b, 140b into woven fabrics. When making a part of the elastic fabric into a woven fabric, it is preferable to make the surface fabric (the base fabric when giving elasticity to the base fabric) into a woven fabric. In this way, the outer surface of the speaker becomes a woven fabric that is resistant to snagging, so the durability of the speaker can be further increased.

[0081] In the speaker 101b of the third embodiment, fraying prevention processing is not performed on the ends of the conductive fabrics 111b, 121b, 131b. However, similar to the speaker 101a of the second embodiment, it is also possible to perform fraying prevention processing on the ends of the conductive fabrics 111b, 121b, 131b. When attaching an insulating protective fabric so as to wrap the ends of the conductive fabrics 111b, 121b, 131b which are knitted fabrics as the fraying prevention processing, it is preferable to use a knitted fabric as the protective fabric, similar to the conductive fabrics 111b, 121b, 131b.

[0082] D. Modification examples: The present invention is not limited to the above-described embodiments, and can be implemented in various aspects without departing from the gist thereof. For example, the following modifications are possible.

[0083] D1. Modification example 1: In each of the above embodiments, the insulating films 122, 122b, 132, 132b are provided on each of the electrode films 120, 120a, 120b, 130, 130a, 130b. However, it is also possible to omit these insulating films 122, 122b, 132, 132b. In this case, the emission of the sound generated by the vibration of the diaphragm 110, 110a, 110b to the outside becomes easier, and the suppression of the vibration of the diaphragm 110, 110a, 110b is further suppressed.

[0084] Alternatively, the insulating films 112, 112b, 113, 113b provided on the diaphragms 110, 110a, 110b may be omitted, and insulating films 122, 122b, 132, 132b may be provided only on each of the electrode films 120, 120a, 120b, 130, 130a, 130b. Generally, it is sufficient that the space between the diaphragms 110, 110a, 110b and the electrode films 120, 120a, 120b, 130, 130a, 130b can be insulated. The insulating films may be provided on at least one of the diaphragms 110, 110a, 110b and one of the electrode films 120, 120a, 120b, and on at least one of the diaphragms 110, 110a, 110b and the other electrode films 130, 130a, 130b, respectively.

[0085] However, by providing the insulating films 112, 112b, 113, 113b on both sides of the diaphragms 110, 110a, 110b and providing the insulating films 122, 122b, 132, 132b on each of the electrode films 120, 120a, 120b, 130, 130a, 130b, it is possible to reduce the possibility of a short circuit between the diaphragms 110, 110a, 110b and the electrode films 120, 120a, 120b, 130, 130a, 130b due to damage to a part of these insulating films 112, 112b, 113, 113b, 122, 122b, 132, 132b. Thus, as in each of the above embodiments, it is preferable to provide the insulating films 112, 112b, 113, 113b on both sides of the diaphragms 110, 110a, 110b and provide the insulating films 122, 122b, 132, 132b on each of the electrode films 120, 120a, 120b, 130, 130a, 130b.

[0086] D2. Modification 2: In addition, in order to insulate the conductive fabrics 111 and 111b that constitute the diaphragms 110, 110a, and 110b from the conductive fabrics 121, 121b, 131, and 131b that constitute the electrode films 120, 120a, 120b, 130, 130a, and 130b, insulating films 122, 122b, 132, and 132b are provided on each of the electrode films 120, 120a, 120b, 130, 130a, and 130b. However, it is also possible to insulate the conductive fabrics 111 and 111b from the conductive fabrics 121, 121b, 131, and 131b by other means.

[0087] For example, as such insulating means, instead of the insulating films 112, 112b, 113, 113b, 122, 122b, 132, and 132b, it is also possible to attach an insulating fabric to the conductive fabrics 111, 111b, 121, 121b, 131, and 131b. Note that the attachment of the insulating fabric to the conductive fabrics 111, 111b, 121, 121b, 131, and 131b can be performed using methods such as adhesion, sewing, or multi-woven techniques.

[0088] D3. Modification Example 3: In the above embodiments, the speakers 101, 101a, and 101b according to the present invention are applied to the screen 100. However, the speaker according to the present invention is not necessarily applicable only to the projector screen. The speaker according to the present invention can be applied to, for example, a soundproof system.

[0089] In one aspect of applying the speaker according to the present invention to a soundproof system, the speaker according to the present invention is used as wallpaper for a building. In this case, since it is possible to generate sound throughout the wallpaper, if sound is generated to cancel out voices such as conversations in a conference room or noise from adjacent rooms in an apartment building, a soundproof system can be constructed that suppresses the leakage of conversations in the conference room to the outside or effectively removes the noise from adjacent rooms. Also in this case, according to the speaker according to the present invention, which is mainly composed of a fabric, it is easy to construct according to the unevenness of the wall surface and can be used more appropriately as wallpaper.

[0090] In another aspect of applying the speaker according to the present invention to a sound insulation system, the speaker according to the present invention is used as a finishing such as a partition or a partition, or a tapestry attached to a partition or a partition. Also in this case, if sound is generated so as to cancel out voices such as conversations in the area partitioned by a partition or a partition, etc., it is possible to suppress the leakage of conversations, etc. in the area to the outside.

[0091] <Applications of Electrostatic Speakers> As described above, the electrostatic speaker of the present invention has good sound quality, high directivity, and flexibility. Therefore, it can be used for screens such as projectors, partitions, room dividers, folding screens, floors, ceilings, walls, wallpapers, curtains, desks, desk mats, doors, door leaves, stairs, toilets, office supplies, book covers, schedule boards, exhibition panels and sheets, explanatory signs and boards, whiteboards, furniture, chairs, chair covers, headrests of seats, chairs, seat surfaces of benches, lockers, pillars, window glasses, umbrellas of lighting fixtures, letter boxes, pillows, cushions, futons, blankets, mattresses, rugs, zabutons, bedding such as beds, tablecloths, chests of drawers, hangers, cupboards, bookshelves or bookshelves, magazine racks, various display shelves, benches, standing signs (made of wood or synthetic resin), canopies, draperies, funeral supplies, cradles, mannequins, bags, backpacks, shoes, clothing, sundries, hats, helmets, umbrellas, fans, folding fans, walking sticks, canes, tapestries, hanging scrolls, wall hangings, pictures, frames, sculptures, bronze statues, pedestals, Buddhist altars, calendars, posters, pet clothing, pet beds, pet houses, umbrella stands, clogs boxes, beds, toys, play equipment, sports equipment, electronic devices such as personal computers, business such as for mobile phones, home, interior, exterior, vehicles, ships, aircraft, medical, care, leisure, outdoor and other various applications. And by incorporating or attaching them to those articles, it can function as a speaker that allows only a specific person to hear the emitted sound (such as voices and music) (for example, a speaker that emits sound from the ceiling or headrest above a predetermined seat in a vehicle, but the sound cannot be heard by the users of other seats).

Description of Symbols

[0092] 10…Speaker system 100…Screen (projector screen) 101, 101a, 101b…Speaker (projection surface) 110, 110a, 110b…Diaphragm 111, 111b…Conductive cloth 112, 112b, 113, 113b…Insulating film 114a, 124a, 134a…Protective cloth 119…Wiring 120, 120a, 120b, 130, 130a, 130b…Electrode film 121, 121b, 131, 131b…Conductive cloth 122, 122b, 132, 132b…Insulating film 129, 139…Wiring 140, 140b…Surface layer cloth 150…Base cloth 200…Drive unit 210…Amplification circuit 220…Transformer output circuit 230…High voltage generation circuit 900…Video disc player AS…Audio signal C1~C6…Capacitor D1~D6…Diode DAS…Differential audio signal L…Choke coil OSC…Oscillator PIM…Projection video Q1…MOS field effect transistor T1, T2…Transformer U1…Differential amplifier VS…Video signal

Claims

1. An electrostatic speaker, comprising: a first conductive cloth which is a conductive fabric; second and third conductive cloths which are conductive fabrics arranged so as to sandwich the first conductive cloth and are insulated from the first conductive cloth; first and second exterior cloths which are arranged so as to cover the first to third conductive cloths, are thicker than the first to third conductive cloths, and are made of an insulating fabric; and the first to third conductive cloths and the first and second exterior cloths are sewn together with insulating threads, and fray prevention processing is performed on each end of the first to third conductive cloths, and an insulating protective cloth is attached so as to wrap each end of the first to third conductive cloths. The electrostatic speaker is characterized by this.

2. The electrostatic speaker according to Claim 1, wherein the electrostatic speaker is configured to be wound in a state where the first exterior cloth is located on the inner peripheral side of the second exterior cloth, the first exterior cloth has elasticity in the winding direction in which the electrostatic speaker is wound, and the ends of the first and second exterior cloths are sewn so that the length of the first exterior cloth in the winding direction becomes the natural length in a state where the electrostatic speaker is wound. An electrostatic speaker.

3. The electrostatic speaker according to Claim 2, wherein the first to third conductive cloths have elasticity in the winding direction, and the ends of the first to third conductive cloths and the first and second exterior cloths are sewn so that the lengths of the first to third conductive cloths in the winding direction become the natural lengths in a state where the electrostatic speaker is wound. An electrostatic speaker.

4. The electrostatic speaker according to any one of Claims 1 to 3, wherein the first and second exterior cloths are formed of fibers that are positioned on the positive side of paper in the charging series.

Images