JP2009272978A - Flexible speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable flexible speaker which can be freely formed into a desired shape by using a flexible film-like sounding body and has no significant change in frequency characteristics even when bent.
SOLUTION: An elastic film made of a polymer material such as an elastomer is used as a base layer, and a pair of electrode layers is formed by applying an elastic conductive polymer material on both sides of the elastic film. By applying a DC bias voltage and superimposing an AC audio signal thereon, the attractive force generated between the electrode layers is changed, thereby causing a compression and expansion in the base layer to produce a flexible speaker that generates audio. The elastic material of the base layer and the electrode layer increases the flexibility of the shape of the flexible speaker and minimizes the frequency characteristic change due to bending.
[Selection] Figure 1

Description

  The present invention relates to a flexible speaker, and more particularly to a flexible speaker comprising a sounding body as a flexible film-like electroacoustic transducer.

  As a conventional film-like speaker, there is a piezoelectric speaker using PVDF (polyvinylidene fluoride) which is a piezoelectric element (see, for example, Patent Document 1). In that case, the PVDF piezo film is curved in a semi-cylindrical or substantially cylindrical shape, and an electric audio signal is applied to the electrodes made of metal films formed on both sides to expand and contract the film in the bending direction, and orthogonal to the bending direction. Generate sound that radiates in the axial direction. However, in order to generate a certain volume with this piezo film, it is necessary to give the film a certain degree of hardness. On the other hand, bending the film with hardness results in a significant change in the original frequency characteristics of the film. It is known that the width of the change exceeds a range that can be compensated by an electric circuit or the like. The use of a metal film as the electrode also facilitates this problem.

  On the other hand, there is an electrostatic speaker that superimposes an AC signal after applying a DC bias voltage between the electrodes (see, for example, Patent Documents 2 and 3), but can be formed because a metal electrode is used as a fixed electrode. There is a certain limit to the shape, and there is a problem that free deformation is not allowed. In addition, since only air exists between the electrodes, it is difficult to keep the distance between the electrode plates stable at the time of deformation.

Furthermore, there are speakers manufactured using an elastomer material for artificial muscles (see, for example, Non-Patent Documents 1 and 2), but since the elastomer material is tensioned, the speaker can be freely deformed. It has the problem of being difficult.
JP-A-10-224893 JP-A 64-71400 JP-A-11-178098 AES 13th Tokyo Section Paper “Acoustic Characteristics of Acrylic Elastomer and Its Application to Loudspeakers” by Takehiro Sugimoto et al., 2007 July 19-21 J.Acoust.Soc.Am.107 (2), February 2000 pp.833-839 “Acoustical performance of an electrostrictive polymer film loudspeaker” by Richard Heydt et al.

  The present invention shows a stable reproduction characteristic that can be freely formed into a desired shape by using a flexible sounding body as an electroacoustic transducer, and the frequency characteristic is not significantly changed by bending. The purpose is to provide a flexible speaker.

A flexible speaker according to the present invention includes a base layer made of a film-like polymer material having elasticity, a pair of electrode layers formed on both surfaces of the base layer with an electroconductive polymer material, and an electrode layer as described in claim 1 A pair of terminal wires connected to each of the two, and applying a DC bias voltage between both electrode layers through the terminal wires and generating sound by expanding and contracting a base layer generated by superimposing an AC audio signal .
The flexible speaker of the present invention according to claim 2 is characterized in that the polymer material forming the base layer in claim 1 is an elastomer.
A flexible speaker according to a third aspect of the present invention is characterized in that the flexible speaker according to the first or second aspect of the present invention is formed in a cylindrical shape, and enables almost omnidirectional directional characteristics in a horizontal plane.
A flexible speaker according to a fourth aspect of the present invention is characterized in that the radiation efficiency can be improved by molding the flexible speaker according to the first or second aspect so as to be a flat curved surface including a polyhedron, a cone, and a sphere. .
A flexible speaker according to a fifth aspect of the present invention is characterized in that, in the fourth aspect, the flat curved surface is formed into a cone.
A flexible speaker according to a sixth aspect of the present invention is characterized in that the flexible speaker according to the fourth aspect of the present invention has a disk shape with a flat curved surface and an annular frame on the outer periphery.

  Since the base layer is made of a flexible elastic film-like polymer material and the electrode layers on both sides thereof are also made of a flexible conductive polymer material, the film-like flexible speaker according to the present invention is excellent in flexibility and the speaker. It can be freely formed into a desired shape and can be attached to walls, ceilings, etc., and the degree of freedom of use is increased, and the desired acoustic radiation characteristic or directional characteristic improved according to the shape Is obtained.

  1 to 7 showing the basic configuration of a flexible speaker according to the present invention and Examples 1 and 2, the best mode for carrying out the invention will be described.

  FIG. 1 shows a flexible speaker 1a in the basic configuration of the present invention. In the figure, an elastomer film made of polypropylene, which is a polymer material having elasticity, is used as the base layer 1 of the film-like speaker, and a conductive polymer polyethylene dioxythiophene having elasticity is applied to both sides of the film, and the base layer 1 is interposed through the base layer 1. A pair of opposing electrode layers 2 and 3 are formed, and each of the terminal wires 4 and 5 is connected to each electrode layer. The thickness of the base layer 1 is approximately 100 μm to several hundred μm, and the electrode layers 2 and 3 may be less than that. FIG. 1 is a schematic perspective view of the flexible speaker 1a without bias.

  When a DC bias voltage of about 1 kV is first applied between the electrode layers 2 and 3 of the flexible speaker 1a configured as described above, an attractive force is generated between the opposing electrode layers due to Maxwell stress, and the electrode layers attract each other. As a result, the base layer 1 As shown by the arrows in FIG. 2, the elastomer forming the above is expanded in all directions in the surface direction of the base layer 1. In this extended state, as shown in FIG. 3, when an AC audio signal is superimposed on a DC bias voltage, the electrode interlayer attractive force changes according to the AC audio signal, and the elastomer expands and contracts. Will occur. According to this method, it is possible to produce a sound with a sufficient volume without applying significant tension to the elastomer film.

  Further, since the elastomer film has high flexibility like rubber, the flexible speaker 1a of the present invention having the elastomer film as the base layer 1 and the flexible polymer material as the electrode layers 2 and 3 can be freely deformed. It is possible to obtain a desired shape, and since excessive tension does not act on the material even after bending, the resonance frequency of the material used does not change significantly.

  FIG. 4 shows the flexible speaker 10 of the present invention in Example 1, which has a shape that is curved as a whole by using the flexibility of the polymer material to be used and projects toward the listener. The base layer 11 is an elastomer film made of polypropylene having an A4 size and a thickness of 150 μm, and has the same electrode layers 12 and 13 as the above basic configuration. A DC bias voltage of 1 kV is applied between the electrode layers of the flexible speaker 10, a sinusoidal AC voltage is superimposed as an audio signal, and the sound is reproduced by changing the frequency of the audio signal. When the frequency characteristics and directivity characteristics were measured, sufficient volume and frequency characteristics were obtained as shown in the characteristic diagram of FIG. In the figure, 0 °, 90 °, and 180 ° are frequency characteristics measured from the front, side, and back of the flexible speaker 10, respectively.

  FIG. 6 shows the flexible speaker 20 of the present invention in Example 2, and the film-like flexible speaker 20 having the same structure as that of Example 1 is formed in a cylindrical shape. The frequency characteristics and directivity characteristics measured under the same conditions are shown in the characteristic diagram of FIG. In the figure, 0 °, 90 °, and 180 ° are frequency characteristics measured from the front, side, and back of the flexible speaker 20, respectively. In particular, as can be seen from the comparison of the directivity characteristic at 1 kHz with the case of the first embodiment, it can be seen that the directivity characteristic in the horizontal plane is improved and the characteristic close to the almost all directivity can be obtained by the cylindricalization.

  In the present specification, polypropylene is described as the polymer material of the elastomer film, but it goes without saying that the present invention is also effective when other polymer materials are used. Moreover, although the use of polyethylenedioxythiophene was described as the electrode material, it goes without saying that the present invention is also effective when other conductive polymer materials are used. Further, the shape of the speaker may be a flat curved surface including a conical shape or a spherical shape other than the curved shape and the cylindrical shape shown in the first and second embodiments, and a disk shape whose outer periphery is reinforced with a frame.

It is a schematic perspective view of the fundamental structure of the flexible speaker of this invention, Comprising: The state at the time of no bias is shown. 1 shows a basic configuration of a flexible speaker of the present invention, in which a DC bias voltage is applied to the front and back electrode layers, and the flexible speaker extends in all directions. An explanatory view of a state in which an AC audio signal is superimposed on a DC bias voltage applied in the flexible speaker of the present invention is shown. 1 is a perspective view of a curved flexible speaker according to Embodiment 1. FIG. FIG. 3 is a frequency characteristic diagram of the flexible speaker according to the first embodiment. FIG. 6 is a perspective view of a cylindrical flexible speaker in Embodiment 2. FIG. 6 is a frequency characteristic diagram of the flexible speaker according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Flexible speaker 10, 20 Flexible speaker 1, 11, 21 Base layer 2, 12, 22 Electrode layer 3, 13, 23 Electrode layer 4, 14, 24 Terminal wire 5, 15, 25 Terminal wire

Claims (6)

  A base layer made of an elastic film-like polymer material, a pair of electrode layers formed on both sides of the base layer with a conductive polymer material, and a pair of terminal wires connected to each of the electrode layers, A flexible speaker, wherein a sound is generated by expansion and contraction of a base layer generated by applying a direct current bias voltage between both electrode layers and superimposing an alternating sound signal.   The flexible speaker according to claim 1, wherein the polymer material forming the base layer is an elastomer.   3. The flexible speaker according to claim 1 or 2, wherein the flexible speaker is formed in a cylindrical shape and enables omnidirectional directivity characteristics in a horizontal plane.   3. The flexible speaker according to claim 1, wherein the radiation efficiency can be improved by forming a flat curved surface including a polyhedron, a cone, and a sphere.   5. The flexible speaker according to claim 4, wherein the flat curved surface is formed into a cone.   5. The flexible speaker according to claim 4, wherein the flat curved surface has a disk shape having an annular frame at the outer peripheral edge.

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