This application claims the priority benefit of Taiwan patent application serial no. 98111841, filed on Apr. 9, 2009. This application is also related to patent application Ser. No. 12/175,467, filed on Jul. 18, 2008, entitled “STRUCTURE AND MANUFACTURING METHOD OF ELECTROSTATIC SPEAKER”, now pending. This application is also related to patent application Ser. No. 12/370,598, filed on Feb. 13, 2009, entitled “SPEAKER DEVICES”, now pending. The entire disclosures, including the claims, of aforesaid applications are hereby incorporated by reference herein and made a part of this specification.
1. Technical Field
The disclosure relates to a structure of a flat speaker.
2. Background Art
The two most direct sensory systems of human being are visual and audible systems, so for a long time, scientists have given great effort to developing related elements or system techniques. Currently, electro-acoustic speakers are mainly classified into direct and indirect radiating types, and are approximately classified into dynamic, piezoelectric, and electrostatic speakers according to driving methods.
Electrostatic speakers mainly include hi-end earphones and loudspeakers in the current market. The operating principle for conventional electrostatic speakers is that two electrodes which are fixated and have holes are used to clamp a conductive membrane to form a capacitor, a DC bias is applied to the membrane and an AC voltage of sound frequencies is applied to the two fixated electrodes, and electrostatic forces generated by positive and negative electric fields are used to drive the conductive membrane to vibrate and to radiate sounds. The bias of the conventional electrostatic speakers is as high as hundreds to thousands of volts, so that expensive and bulky amplifiers need to be externally connected. Hence, the above is the reason that the conventional electrostatic speakers are not popular. If the electrostatic speakers cooperate with structural designs of membranes that are ferroelectric, although the AC voltage of the sound frequencies is lowered, the electrostatic effects of the membrane causes the electrode and the membrane to contact each other and thereby inhibiting sound production.
Relating to electrostatic speakers, U.S. Pat. No. 3,894,199 discloses an electro-acoustic transducer, as shown in
As illustrated in the related art, the frame holding member 110 is only used to hold the electrodes 120, and there are no supporting members between the membrane 130 and the electrodes 120, so that unintended contact between the electrodes 120 and the membrane 130 cannot be prevented. It can be known that present flat speakers do not provide design descriptions relevant to supporting members.
In addition, the conventional electrostatic speaker have weaker capacity for generating sounds of lower frequencies (<500 Hz), so that the electrostatic speakers on the market are mostly collocated with a dynamic speaker having low frequency response. Hence, it is known that improving low sound pressures at low frequencies of the conventional electrostatic speakers is an important issue in the field.
The embodiment provides a flat speaker structure. According to an embodiment, the speaker structure provided by the embodiment includes a membrane, an electrode, a frame holding member and at least one set of supporting members. The electrode has a plurality of holes, and the frame holding member forms an exterior shape of the speaker structure and holds the membrane and the electrode at two opposite sides. Each of the sets of the supporting members is disposed between non-porous areas of the electrode and the membrane and forms at least one ring-shaped geometric structure
The accompanying drawings are included to provide a further understanding of the embodiment, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the embodiment.
An embodiment may provide flat electrostatic speakers or speaker chamber structures that may be light, thin and/or flexible. Such embodiments may suit the current demand for flat or thin electrostatic speakers and may occupy less space or provide flexibility in the speaker structures themselves.
In some embodiments, a flat electrostatic speaker structure may include a frame, a diaphragm or membrane, an electrode above the membrane, a set of supporting members installed in a chamber space formed in the speaker structure. The chamber is enclosed between the electrode and the membrane. The supporting members are provided in the chamber space, which may be called a sound-chamber.
The electrode has a plurality of holes as soniferous holes for the sound generated by the speaker. The frame forms an exterior shape of the speaker structure and holds the membrane and the electrode at two opposite sides. Each of the sets of the supporting members is disposed between non-porous areas of the electrode and the membrane and forms at least one geometric structure.
An embodiment provides designs of the geometric structure for the supporting members to prevent the electrode from contacting the membrane due to electrostatic force, since the improper contact of the electrode and the membrane may inhibit sound production from the flat speaker. The designs can also simultaneously improve sound pressures when the flat speaker operates at low frequencies.
In some embodiments, the geometric structure for the supporting members of a flat electrostatic speaker can be fabricated by being integrated into the existing processes of making flat electrostatic speakers and therefore may be suitable for mass production.
Some embodiments of the structures of the flat electrostatic speakers, the electrode, and the membrane can be found in co-pending patent application Ser. No. 12/175,467, filed on Jul. 18, 2008, entitled “STRUCTURE AND MANUFACTURING METHOD OF ELECTROSTATIC SPEAKER” and patent application Ser. No. 12/370,598, filed on Feb. 13, 2009, entitled “SPEAKER DEVICES”, which are hereby incorporated by reference herewith and made a part of this specification.
The electrode can be made of metal material or other conductive materials. The membrane may include an electret layer and a conductive electrode, in which the electret layer is made of, for example, electret materials. The conductive material can be metal (e.g., iron, copper, aluminum or an alloy thereof), conductive cloths (e.g., metal fiber, oxide metal fiber, carbon fiber or graphite fiber), etc., or any combination of these materials or other materials. To provide good tension and/or vibration effects of the membrane, the conductive electrode can be a metal film electrode such as a thin metal film electrode. As an example, its thickness may be between 0.2 micron and 0.8 micron. It may be about 0.3 micron in some embodiments. The scale range illustrated is usually identified as “ultra-thin.” Considering that the ultra-thin metal thin film electrode may be used when being exposed in the air and would be oxidized into a complete nonconductor, thereby affecting input of an audio signal, an insulating layer may be produced on a surface of the metal thin film electrode, but a position for an input end of the audio signal must be preserved.
When the conductive electrode is made of a nonconductive material layer plated with a metal film layer, the nonconductive material can be plastic, rubber, paper, a nonconductive cloth (cotton fiber or polymer fiber) or other nonconductive materials; and the metal film can be aluminum, gold, silver, copper, Ni/Au bimetal, indium tin oxide (ITO), indium zinc oxide (IZO), macromolecule conductive material PEDOT (polyethylenedioxythiophene), an alloy, any combination of the listed materials or equivalents thereof.
The designs of the supporting members of the speaker of the embodiment are a considerable issue for the flat speaker. The supporting members are disposed between the electrode and the membrane, so as to prevent the membrane having electrostatic effects from being improperly contacted by the electrode, which may cause the flat electrostatic speaker to fail in generating sounds. The specific designs of the supporting members can also improve the sound pressures when the flat electrostatic speaker operates at low frequencies.
The supporting members disposed between the electrode and the membrane form at least one geometric structure, in which a working area of the speaker is enclosed by the geometric structure of the supporting members. In some embodiments, the supporting members may be designed into different arrangements according to intensities of electrostatic effects of the membrane. For example, the geometric structure of the supporting member may be designed as a shape of a circle, oval, hexagon, square, rhombus, rectangle, triangle or any combination of the above. The geometric structures may be substantially concentric, meaning that the centers of the geometric structures may substantially overlap. Alternatively, the geometric structures may be disposed non-concentrically. For explanation, a supporting member with a ring-shaped geometric structure is introduced hereinafter, but some other shapes in different embodiments can be used and the embodiment is not limit thereto.
In some embodiments, the supporting members may have different patterns in placing the members or heights, which can be varied based on different applications or specifications. The ring-shaped geometric structures may be arranged by adjusting distances between the supporting members or heights of the supporting members. For example, the distances between the ring-shaped geometric structures may be equal or unequal, and the heights of the supporting members may be uniform or non-uniform. In addition, the ring-shaped geometric structures may be a closed figure structure formed by a continuous line or an open figure structure formed by broken lines, as shown. Differences of the distances between the supporting members or the heights of the supporting members are considerable issues in designing the overall frequency response of the speaker structure. For example, the different distances or heights are adjusted according to the optimal frequency range for using the speaker.
The supporting members provided by the embodiment may be directly produced on the electrode or directly produced on the membrane. In some embodiments, the supporting members may adhere to or not adhere to the membrane or the electrode, or the supporting members may be produced in advance and then inserted between the electrode and the membrane after completion.
In some embodiments, the supporting members may be fabricated on a substrate using transfer printing, direct printing such as inkjet printing or screen plane printing. In another embodiment, the supporting members may be fabricated by direct adhesion. As an example, the supporting members may be fabricated in advance, followed by placing the pre-fabricated supporting members between a metal electrode with holes and the membrane. The supporting members may be placed on the membrane or the electrode with holes with direct adhesion or without direct adhesion to the underlying membrane or electrode. In other embodiments, the supporting members can be fabricated using etching, photolithography, and/or adhesive-dispensing techniques.
The flat electrostatic speaker uses the principle of properties of charges in the material of the membrane and effects of electrostatic forces. When the membrane is stimulated by external voltages, a surface of the membrane is deformed, thereby driving the air near the membrane to produce sound. As known from the electrostatic force equation and energy laws, the force exerted on the membrane equals the capacitance value of the where speaker multiplied by the intensity of the internal electric field and the externally-input sound voltage signal. When the force exerted on the membrane is larger, the output sound generated accordingly is louder. According to Coulomb's law, the product of the electric charges of two charged objects is in direct proportion to the electrostatic forces exerted on each other and is in inverse proportion to the square of the distance between the two objects. If the charges of the objects are both positive or negative, the objects would repel each other, if the charges on one of the objects are positive and the charges on the other of the objects are negative, the objects would attract each other. The equation for electrostatic forces may be represented by Equation 1.
A capacitance ratio ∈o equals 8.85×10−12 F/m, ∈e is a dielectric constant of an electret, Se is a thickness of the electret, Sa is a thickness of an air layer, Vin is a voltage of an input signal, Ve is a voltage of the electret and P is a force per unit area of the membrane. Hence, at the same distance, if the electrostatic speakers contain large numbers of charges, audio voltage signals input into the speakers may be lowered to several volts to tens of volts, so that practicality of the flat electrostatic speaker is enhanced.
Hence, the embodiment provides an implementation method as the following. A material of the electrode having the holes may be metal or a conductive material. The holes in the metal material are advantageous to the spreading of sound. According to another embodiment, the same effect may be achieved by electroplating a conductive electrode layer on an extremely thin paper.
According to an embodiment, the membrane includes the electret material such as a dielectric material. The dielectric material maintains static charges for a long time after being electrized, generates ferroelectric effects in the material after being charged, and is thus called the electret membrane. The electret membrane may be a membrane which includes a single layer or multiple layers of dielectric material. The above dielectric material may be, for example, fluorinated ethylene propylene (FEP), poly tetra fluoro ethyene (PTFE), polyvinylidene fluoride (PVDF), fluorine polymers and other suitable materials. The electret membrane is a membrane capable of maintaining the static charges and piezoelectricity for a long time after the dielectric material is electrized, and includes micro nano-holes to increase transparency of light and piezoelectric characteristics. Thus, after being charged by corona, dipolar charges are generated in the material to generate the ferroelectric effect.
A transparent and flexible material, for example a plastic material, may be adopted as the material of the supporting members, so as to increase diversity of designs for using the supporting members.
According to the supporting members of the speaker, the following illustrates using an embodiment.
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In order to the prevent the electrostatic effect generated by the membrane 230 from causing the membrane 230 and the electrode 220 to contact each other, at least one set of supporting member 240 may be placed in a space opposite to a soniferous hole region. In various embodiments, the supporting members 240 may be produced on the electrode 220 or on the membrane 230. In some embodiments, the supporting members 240 may adhere to or not adhere to the membrane 230 or the electrode 220. Alternatively, the supporting members 240 may be produced first and then placed in the space between the electrode 220 and the membrane 230.
The supporting members 240 are disposed while taking into consideration the number of charges and the intensity of the electrostatic effect, so as to adopt an optimal disposition. In addition, different disposition distances of the supporting members are taken into consideration to adopt designs of the supporting members having different heights. Objectives of the above designs are to exclude possibilities of contact between the electrode 220 and the membrane 230 except for the supporting members 240, as shown in
Using the supporting members according to the above embodiment, the supporting members 240 may be produced on the electrode 220 or the membrane 230 by using transferring or decaling. According to another embodiment, the supporting members 240 may be produced using printing technologies including direct printing, screen plane printing or lamination. The above supporting members 240 may also be formed using a photoresist or etching.
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Alternatively, besides forming at least a set of ring-shaped geometric structures, the supporting members may additionally form a line-shaped or cross-shaped structure, as shown in
The above embodiments are only used for illustration and not for limiting the embodiment. The ring-shaped geometric structure formed by the supporting members may be hexagonal structures, square structures, rhombus structures, rectangular structures, triangular structures, polygon structures, any combination of the above or any geometric structures.
In order to enhance effects of frequency response of the speaker, the distances between the ring-shaped geometric structures formed by the supporting members may be arbitrarily adjusted, so as to obtain the best sound producing effects. The distances between the ring-shaped geometric structures may be equal or unequal. The heights of the supporting members may also be arbitrarily adjusted to achieve the best sound producing effects. The heights of the supporting members may be uniform or non-uniform. In addition, the ring-shaped geometric structures may be a closed figure structure formed by a continuous line or an open figure structure formed by broken lines.
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In summary, the embodiments the metal electrode and the membrane are prevented from contacting to each other due to the electrostatic forces and simultaneously increase sound pressures when the electrostatic speakers operate at low frequencies. The geometric structure for the supporting members of a flat electrostatic speaker can be fabricated by being integrated the existing processes of making flat electrostatic speakers and therefore may be suitable for mass production. The choice of the embodiments cooperating with flexible materials provides a breakthrough in flat speaker structures, thereby completing acoustic components required for the characteristics of flexible electronics.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the embodiment without departing from the scope or spirit of the embodiment. In view of the foregoing, it is intended that the embodiment cover modifications and variations of this embodiment provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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98111841 A | Apr 2009 | TW | national |
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Entry |
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“Office Action of Taiwan Counterpart Application”, issued on Dec. 17, 2012, p. 1-p. 7, in which the listed reference was cited. |
“First Office Action of China Counterpart Application”, issued on Jun. 25, 2012, p. 1-p. 5, in which the listed references were cited. |
Number | Date | Country | |
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20100260370 A1 | Oct 2010 | US |