A thin-film electret electroacoustic conversion device, its manufacturing method and speaker

Abstract

This invention provides a thin-film electret electroacoustic conversion device, its manufacturing method, and a speaker. The thin-film electret electroacoustic conversion device includes a first electrode, an electret diaphragm, and a second electrode arranged sequentially along the thickness direction. Both the first and second electrodes are electrically isolated from the electret diaphragm. The electret diaphragm carries a permanent charge, which is distributed in a patterned array within its surface. The thin-film electret electroacoustic conversion device provided by this invention arranges the charge on the electret diaphragm in an array, so that when the electret diaphragm vibrates under the action of an electric field, it forms an arrayed vibration source. The sound waves emitted by the vibration source are transmitted within the thin film and simultaneously into the air outside the film. This avoids the concentration of the sound field perpendicular to the film direction caused by full-surface sound emission, resulting in a moderately diffused sound field distribution. This reduces the difficulty of sound effect setting and avoids the problem of significant sound effect degradation caused by angular setting deviations.

Description

Technical Field

[0001] This invention belongs to the field of thin-film electroacoustic conversion technology, specifically relating to a thin-film electret electroacoustic conversion device, its manufacturing method, and a speaker. Background Technology

[0002] Electrostatic loudspeakers operate based on Coulomb's law, which states that two conductors with equal and opposite charges can generate a push-pull force between them. This push-pull electrostatic force causes a diaphragm to vibrate, thereby producing sound. A typical electrostatic loudspeaker consists of two porous electrodes and a diaphragm positioned between the electrodes to form a series of capacitors. The electrodes and diaphragm can be separated by an air gap to provide space for the diaphragm to vibrate. The diaphragm is typically light and thin, thus giving electrostatic loudspeakers advantages over other types of loudspeakers, such as electrodynamic, moving-coil, or piezoelectric loudspeakers, in terms of transient response, high-frequency extension, sound smoothness, sound fidelity, and slight distortion. Furthermore, the diaphragm must be charged with static electrons, which, when a signal is supplied to the electrode plates, induce a static force that drives the diaphragm under the electric field created by the electrode plates.

[0003] Several existing technologies provide thin, lightweight, and high-quality electret film-based electrostatic loudspeakers. For example, Chinese invention patent CN103313174A provides a double-layer electret electroacoustic conversion device and an electronic device with an electret loudspeaker, and Chinese invention patent CN116112851A provides a thin-film electroacoustic conversion device and an audio-visual system. Although electret film electrostatic loudspeakers have the advantages of being thin, lightweight, high-quality, and low-power, the sound emission of such loudspeakers has a very significant directionality. In the direction perpendicular to the film, there is often a concentrated sound field distribution, while the sound field is weaker in the tilt direction. This directionality will bring great difficulties in the sound effect layout, and even a slight deviation will seriously affect the sound performance. Summary of the Invention

[0004] The main objective of this invention is to provide a thin-film electret electroacoustic conversion device, its manufacturing method, and a speaker, so as to overcome the shortcomings of the prior art.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a thin-film electret electroacoustic conversion device, which includes a first electrode, an electret diaphragm and a second electrode arranged sequentially along the thickness direction, wherein the first electrode and the second electrode are electrically isolated from the electret diaphragm. The electret diaphragm carries a permanent charge, and the permanent charge is distributed in a patterned array within the plane of the electret diaphragm.

[0006] Secondly, the present invention also provides a method for manufacturing the above-mentioned thin-film electret electroacoustic conversion device, comprising: Provide polymer films; Under the cover of a patterned shielding mask, the polymer film is subjected to corona polarization treatment so that the polymer film carries a permanent charge distributed in an array patterned manner, thereby obtaining an electret vibrating film. The electret diaphragm is combined with the first electrode and the second electrode to form a thin-film electret electroacoustic conversion device.

[0007] Thirdly, the present invention provides a speaker, the speaker including a modulation power supply and the aforementioned thin-film electret electroacoustic conversion device, wherein the output terminal of the modulation power supply is electrically connected to the first electrode and the second electrode of the thin-film electret electroacoustic conversion device.

[0008] Compared with the prior art, the beneficial effects of the present invention include at least the following: The thin-film electret electroacoustic conversion device provided by this invention sets the charge of the electret diaphragm to an array arrangement, so that when the electret diaphragm vibrates under the action of an electric field, it forms an array of vibration sources. The sound waves emitted by the vibration sources are transmitted into the air outside the film while being conducted inside the film. This avoids the concentration of the sound field perpendicular to the film direction caused by the whole surface sound generation, and makes the sound field distribution moderately divergent, which reduces the difficulty of sound effect setting and avoids the problem of significant sound effect degradation caused by angle setting deviation.

[0009] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the structure of a thin-film electret electroacoustic conversion device provided in a typical embodiment of the present invention; Figure 2 This is a schematic diagram of the planar charge distribution of a thin-film electret electroacoustic conversion device provided in a typical embodiment of the present invention; Figure 3 This is a schematic diagram of the speaker provided in a typical embodiment of the present invention.

[0012] Explanation of reference numerals in the attached figures: 1. First electrode; 2. First electret film; 3. First dielectric layer; 4. Central metal layer; 5. Second dielectric layer; 6. Second electret film; 7. Second electrode; 8. Modulation power supply; 9. First array point; 10. Second array point. Detailed Implementation

[0013] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0014] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0015] The present invention first provides a thin-film electret electroacoustic conversion device, which includes a first electrode, an electret diaphragm and a second electrode arranged sequentially along the thickness direction. The first electrode and the second electrode are electrically isolated from the electret diaphragm. The electret diaphragm carries a permanent charge, and the permanent charge is distributed in a patterned array in the plane of the electret diaphragm.

[0016] Typically, the number of rows and columns in the array distribution is 5-10, such as a 5x5 array or a 10x10 array. By converting the vibration of the entire surface into the vibration of the array, the central enhancement caused by the overall resonance of the diaphragm is avoided, and the central peak is eliminated. This makes the sound field distribution in the angular direction more gentle. Although it still has the advantage direction perpendicular to the diaphragm, there is no concentrated peak in the axial direction. Therefore, the actual sound effect experience is more balanced, the sound effect design and arrangement are simpler, and it is less likely to have the problem of local focus that affects the experience.

[0017] The material constituting the electret diaphragm can be a fluorinated polymer, as fluorine has the strongest negative charge. Of course, other polymers can also be used, as long as they can anchor the charge, to achieve the same purpose. The primary method of charging this electret film is corona polarization, although other charging methods are also possible. The fluorinated polymers include expanded polytetrafluoroethylene (ePTFE), perfluoroalkoxy (PFA) with side chains, fluorinated ethylene propylene (FEP), ethylene-tetrafluoroethylene polymer (ETFE), and ethylene-trifluoroethylene (ECTFE) copolymer, etc., and are not limited to these.

[0018] For details on the specific structure, please refer to [link / reference]. Figure 1As shown, in some embodiments, the electret diaphragm has a multilayer structure, including a first electret film 2, a first dielectric layer 3, a central metal layer 4, a second dielectric layer 5, and a second electret film 6 arranged sequentially along the thickness direction; the charge distribution in the first electret film 2 forms a first lattice, and the charge distribution in the second electret film 6 forms a second lattice, with the first lattice and the second lattice being misaligned with each other.

[0019] In a typical embodiment, see [link to relevant documentation]. Figure 1 As shown, in the thin-film electret electroacoustic conversion device provided by the present invention, the two sides are respectively the first electrode 1 and the second electrode 7. The first electrode 1 and the second electrode 7 can be any one of metal mesh, perforated metal film or perforated metal plate or a combination thereof. The first electrode 1 and the second electrode 7 can be the same or different. The first electrode 1 and the first electret film 2 can be separated by air, or they can be separated by filling with some porous material, columnar body or other spacer medium. Similarly, it can be seen that the second electrode 7 and the second electret provide space for the vibration of the electret film while transmitting the electric field.

[0020] The first dielectric layer 3, the central metal layer 4, and the second dielectric layer 5 can be configured with reference to several existing technologies, and can serve the functions of fixing, insulating, and reinforcing the field plate.

[0021] In this embodiment, by setting two electret films and misaligning the charge concentration points on both sides, the sound field distribution is made smoother, avoiding sound field spikes and problems such as resonance points in the sound effect layout.

[0022] For more detailed information on the two-sided dot matrix distribution, please refer to [link / reference]. Figure 2 As shown, in some embodiments, when viewed in the thickness direction, four adjacent first array points 9 in the first lattice form a quadrilateral, and the second array point 10 in the second lattice is projected onto the center of the quadrilateral.

[0023] Furthermore, embodiments of the present invention provide a more optimized charge distribution method, namely, in some embodiments, the charge density of the permanent charge exhibits a gradient increasing trend from the center to the edge of the electret vibrating membrane.

[0024] Specifically, in some implementations, the edge charge density of the permanent charge is 1.2-1.5 times that of the central charge density.

[0025] In some embodiments, the average charge density of the first electret film 2 and the second electret film 6 are equal, and the charge density gradient of the first electret film 2 from the center to the edge varies by 1.5 to 3 times that of the second electret film 6.

[0026] Of course, the above-mentioned gradient ratio and the distribution difference of the two thin films are the preferred implementation scope of the present invention, and do not mean that the purpose of the present invention is limited to the above parameters.

[0027] In a typical embodiment, by setting the above-mentioned technical features, a thin-film electret electroacoustic conversion device is obtained. Sound field tests were conducted at different azimuth angles with a thin-film electret electroacoustic conversion device provided by the prior art. The results are shown in the table below: Azimuth 0° 2.5° 5° 15° 25° 30° This invention 55dB 52dB 45dB 40dB 10dB 10dB Comparison Samples 60dB 53dB 40dB 28dB 10dB 10dB It can be observed that the thin-film electret electroacoustic conversion device provided by the present invention no longer has a spike phenomenon in the central axial direction, and the sound field distribution is more gentle and uniform in different azimuth angles.

[0028] To obtain the aforementioned thin-film electret electroacoustic conversion device, embodiments of the present invention also provide a method for manufacturing the thin-film electret electroacoustic conversion device provided in any of the above embodiments, which includes the following steps: Provide polymer films; Under the cover of a patterned shielding mask, the polymer film is subjected to corona polarization treatment so that the polymer film carries a permanent charge distributed in an array patterned manner, thereby obtaining an electret vibrating film. The electret diaphragm is combined with the first electrode 1 and the second electrode 7 to form a thin-film electret electroacoustic conversion device.

[0029] In some embodiments, the preparation method specifically includes the following steps: The first electret film 2 and the second electret film 6 are formed by using different patterned masks, or by using the same patterned mask to form the electret film, and then the first electret film 2 and the second electret film 6 are formed by different cutting methods. The electret diaphragm is formed by sequentially stacking the first electret film 2, the first dielectric layer 3, the central metal layer 4, the second dielectric layer 5, and the second electret film 6, such that the charge distribution in the first electret film 2 and the charge distribution in the second electret film 6 are misaligned.

[0030] In some embodiments, the corona polarization treatment uses multiple needle electrodes to form an electric field, with the distance between the needle electrode corresponding to the center of the electret diaphragm and the polymer film being greater than the distance between the needle electrode corresponding to the edge of the electret diaphragm and the polymer film.

[0031] Embodiments of the present invention also provide a speaker, such as Figure 3As shown, the speaker includes a modulation power supply 8 and a thin-film electret electroacoustic conversion device provided in any of the above embodiments. The output terminal of the modulation power supply 8 is electrically connected to the first electrode 1 and the second electrode 7 of the thin-film electret electroacoustic conversion device, respectively.

[0032] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A thin-film electret electroacoustic conversion device, characterized in that, It includes a first electrode, an electret diaphragm, and a second electrode arranged sequentially along the thickness direction, wherein the first electrode and the second electrode are electrically isolated from the electret diaphragm; The electret diaphragm carries a permanent charge, and the permanent charge is distributed in a patterned array within the plane of the electret diaphragm.

2. The thin-film electret electroacoustic conversion device according to claim 1, characterized in that, The electret diaphragm has a multilayer structure, including a first electret film, a first dielectric layer, a central metal layer, a second dielectric layer, and a second electret film arranged sequentially along the thickness direction; The charge distribution in the first electret film forms a first lattice, and the charge distribution in the second electret film forms a second lattice, with the first and second lattices being misaligned.

3. The thin-film electret electroacoustic conversion device according to claim 2, characterized in that, Viewed in the thickness direction, four adjacent array points in the first lattice form a quadrilateral, and the array points in the second lattice are projected onto the center of the quadrilateral.

4. The thin-film electret electroacoustic conversion device according to claim 2, characterized in that, The charge density of the permanent charge exhibits a gradient increasing trend from the center to the edge of the electret diaphragm.

5. The thin-film electret electroacoustic conversion device according to claim 4, characterized in that, The edge charge density of the permanent charge is 1.2-1.5 times that of the central charge density.

6. The thin-film electret electroacoustic conversion device according to claim 5, characterized in that, The average charge density of the first electret film and the second electret film are equal, and the charge density gradient of the first electret film from the center to the edge is 1.5-3 times that of the second electret film.

7. A method for manufacturing the thin-film electret electroacoustic conversion device according to any one of claims 1-6, characterized in that, include: Provide polymer films; Under the cover of a patterned shielding mask, the polymer film is subjected to corona polarization treatment so that the polymer film carries a permanent charge distributed in an array patterned manner, thereby obtaining an electret vibrating film. The electret diaphragm is combined with the first electrode and the second electrode to form a thin-film electret electroacoustic conversion device.

8. The manufacturing method according to claim 7, characterized in that, Specifically, it includes: The first electret film and the second electret film are formed by using different patterned masks, or by using the same patterned mask to form the electret film, and then the first electret film and the second electret film are formed by different cutting methods. The electret vibrating membrane is formed by sequentially stacking the first electret film, the first dielectric layer, the central metal layer, the second dielectric layer, and the second electret film, such that the charge distribution in the first electret film and the charge distribution in the second electret film are misaligned.

9. The manufacturing method according to claim 8, characterized in that, The corona polarization treatment uses multiple needle electrodes to form an electric field. The distance between the needle electrode corresponding to the center of the electret diaphragm and the polymer film is greater than the distance between the needle electrode corresponding to the edge of the electret diaphragm and the polymer film.

10. A speaker, the speaker comprising a modulation power supply and a thin-film electret electroacoustic conversion device as described in any one of claims 1-6, wherein the output terminal of the modulation power supply is electrically connected to a first electrode and a second electrode of the thin-film electret electroacoustic conversion device, respectively.

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