WO2013010398A1

WO2013010398A1 - Flexible and transparent acoustic apparatus

Info

Publication number: WO2013010398A1
Application number: PCT/CN2012/075313
Authority: WO
Inventors: Tianling Ren; He Tian; Dan XIE; Yi Yang
Original assignee: Tsinghua University
Priority date: 2011-07-21
Filing date: 2012-05-10
Publication date: 2013-01-24

Abstract

A flexible and transparent acoustic apparatus (20) is provided. The flexible and transparent acoustic apparatus (20) comprises: a thermoacoustic element, comprising a flexible and transparent substrate (26), at least one conductive film structure (24) and one or a plurality of pairs of electrodes, in which one end of a first electrode (28) and one end of a second electrode (30) in each pair are connected with the conductive film structure (24) respectively; and a signal input device (22), connected with the other end of the first electrode (28) and the other end of the second electrode (30) in each pair respectively to allow the conductive film structure (24) to change a density of a surrounding medium to generate an acoustic wave.

Description

FLEXIBLE AND TRANSPARENT ACOUSTIC APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefits of the following applications:

(1) Chinese Patent Application Serial No. 201110204478.2 filed with the State Intellectual

Property Office of P. R. China on July 21, 2011; and

(2) Chinese Patent Application Serial No. 201210030702.5 filed with the State Intellectual

Property Office of P. R. China on Feb. 10, 2012.

The entire contents of the above applications are incorporated herein by reference.

FIELD

The present disclosure relates to acoustic apparatus field, and more particularly to a flexible and transparent acoustic apparatus based on thermoacoustic effect. BACKGROUND

An acoustic apparatus generally consists of an acoustic element and a signal input device, and generates a corresponding sound by applying an electrical excitation signal to drive the acoustic element. A conventional acoustic element is generally a loudspeaker which is an electroacoustic device for converting an electrical signal into an acoustic signal. According to a working principle thereof, types of the conventional loudspeaker may be classified into an electromagnetic type, an electrostatic type, an electrodynamic type and a piezoelectric type. Although working principles of these loudspeakers are different, a self-generated mechanical vibration of these loudspeakers affects a surrounding air to cause a fluctuation, thus realizing conversion of an electricity into the mechanical vibration and conversion of the mechanical vibration to the sound. All these types of loudspeakers generate sound by a vibration of diaphragm, which are complicated in structure and belong to a hard device which may not be bended.

An earliest conventional acoustic apparatus based on thermoacoustic effect may date from the beginning of the last century, referring to "The Thermophone", C. W. Edward, Vol. XIX, No. 4, pp333-345 and "On some thermal effects of electric currents", H.P William, Proceedings of the royal society of London, Vol.30 (1879-1881), pp408-411, in which the acoustic apparatus generates the sound by applying an alternating current to a metal sheet or a metal wire. When the current flows through the metal sheet or the metal wire, a Joule heat may be generated with a change of current strength and conducted to a surrounding medium rapidly to allow the surrounding medium to expand or contract due to a periodical heating, thus generating an acoustic wave.

In 1917, H. D. Arnld and I. B. Crandall presented an acoustic apparatus based on thermoacoustic effect (referring to H. D. Arnld; I. B. Crandall. "The thermophone as a precision source of sound, Phys". Rev. L. 10, 22-38 (1917)). As shown in Fig. 1, an acoustic apparatus 10 uses a Pt sheet as an acoustic element 12 which is fixed by a clamp 14. Both the acoustic element 12 and the clamp 14 are fixed on a substrate 18. The acoustic signal is consequently generated when the current flows through the acoustic element 12 via a lead wire 16. An acoustic intensity of the acoustic element 12 is closely related to a thermal capacity per unit area of the Pt sheet. If the thermal capacity per unit area of the Pt sheet is large, a sound generated by the acoustic apparatus has a narrow frequency range and a low intensity. If the thermal capacity per unit area of the Pt sheet is small, the sound generated by the acoustic apparatus has a wide frequency range and a high intensity. In order to obtain a wide acoustic frequency range and a high acoustic intensity, the smaller the thermal capacity per unit area of the Pt sheet, the wider the acoustic frequency range is and the higher the acoustic intensity is, that is, the thinner the Pt sheet, the wider the acoustic frequency range is and the higher the acoustic intensity is. However, because of a restriction of a technical level at that time, a minimum thickness of the Pt sheet could merely reach 0.7 microns, so that the thermal capacity per unit area thereof is large and a maximum acoustic frequency is merely 4 KHz. Consequently, the acoustic element 12 with a narrow acoustic frequency range and a low acoustic intensity at that time has not been applied in practice for a long time.

Therefore, there is a need for an acoustic apparatus characteristic with large area, low cost, flexibility, transparency, wide acoustic frequency band, high acoustic intensity, high reliability and high practicality.

SUMMARY

The present disclosure is aimed to solve at least one of the problems. Accordingly, a flexible and transparent acoustic apparatus is provided, which has characteristics of large area, low cost, flexibility, transparency, wide acoustic frequency band, high acoustic intensity, high reliability and high practicality. According to an aspect of the present disclosure, a flexible and transparent acoustic apparatus is provided. The flexible and transparent acoustic apparatus comprises: a thermoacoustic element, comprising a flexible and transparent substrate, and at least one conductive film structure and one or a plurality of pairs of electrodes both disposed on the substrate, in which one end of a first electrode and one end of a second electrode in each pair are connected with the conductive film structure respectively; and a signal input device, connected with the other end of the first electrode and the other end of the second electrode in each pair respectively for transmitting an excitation signal to the conductive film structure through the electrodes connected with the conductive film structure, so as to allow the conductive film structure to change a medium density around the conductive film structure to generate an acoustic wave.

In one embodiment, a conductive film of the conducting film structure is a transparent film made from any material of graphene, indium tin oxide, silver nanowire and poly(3 ,4-ethylenedioxythiophene)/polystyrene sulfonate .

In one embodiment, an acoustic frequency of the acoustic apparatus is within a range from lOHz to 100MHz.

In one embodiment, the conductive film structure comprises one layer of conductive film or multilayers of conductive films.

In one embodiment, a total thickness of the conductive film structure is within a range from 0.3nm ίοΙΟΟμιη.

In one embodiment, the plurality of pairs of electrodes are made of a pair of interdigital electrodes, each branch of a first interdigital electrode and each branch of a second interdigital electrode in the pair of interdigital electrodes are connected with the conductive film structure respectively to form the plurality of pairs of electrodes, and one end of the first interdigital electrode and one end of the second interdigital electrode are connected with the signal input device, respectively.

In one embodiment, the flexible and transparent substrate is a flexible, transparent film made from any organic material of polyimide, polyethylene terephthalate and polydimethylsiloxane.

In one embodiment, the medium is a liquid medium or a gaseous medium around the conductive film structure.

In one embodiment, the signal input device is an audio electrical signal input device or an electrical signal input device. According to another aspect of the present disclosure, a flexible and transparent acoustic apparatus is provided. The flexible and transparent acoustic apparatus comprises: a thermoacoustic element, comprising a flexible and transparent substrate, and at least one conductive film structure; and an optical signal input device, directly irradiating the conductive film structure so as to allow the conductive film structure to change the medium density around the conductive film structure to generate an acoustic wave.

Compared with a conventional acoustic apparatus, the acoustic apparatus according to an embodiment of the present disclosure has following advantages.

The conductive film is used as the thermoacoustic element. A Joule heat generated by the conductive film is conducted to a surrounding air to cause a density change of the surrounding air, thus causing a change of an acoustic pressure and consequently generating a sound. A working principle of the acoustic apparatus according to an embodiment of the present disclosure is different from a working principle of a conventional loudspeaker in that a self mechanical vibration may be generated by a conventional acoustic apparatus, but a high acoustic pressure within an acoustic frequency range from 10Hz to 100MHz may be generated by the acoustic apparatus because no self mechanical vibration is generated.

The conductive film structure has a small thermal capacity per unit area and a large specific surface area, so that the thermoacoustic element has advantages of fast temperature rise, little thermal hysteresis, fast heat exchange speed. The thermoacoustic element having such a conductive film structure may realize strong acoustic intensity. Moreover, because the conductive film has high light transmittance and high mechanical strength, the thermoacoustic element has high reliability and high practicality.

The flexible and transparent material is used for forming the thermoacoustic element and the substrate. Therefore, the whole thermoacoustic element with the characteristics of tensility and transparency may cover a flexible display to be integrated with the flexible display, so as to realize multifunctions of sound generation and display at a same time.

Compared with the conventional acoustic apparatus, the acoustic apparatus according to an embodiment of the present disclosure having advantages of high reliability, flexibility, transparency, low cost and high performance may be integrated with the display, so as to realize multifunctions of sound generation and display at a same time. Therefore, the acoustic apparatus may be widely used in electronic fields, such as mobile phones, MP3s, MP4s, TVs, computers, ultrasonic imaging and distance-measuring systems.

Additional aspects and advantages of the embodiments of the present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and advantages of the disclosure will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which:

Fig. 1 is a schematic perspective view of a conventional acoustic apparatus;

Fig. 2 is a schematic structural view of a flexible and transparent acoustic apparatus according to a first embodiment of the present disclosure;

Fig. 3 is a frequency response characteristic curve of the flexible and transparent acoustic apparatus according to the first embodiment of the present disclosure;

Fig. 4 is a light transmittance characteristic curve of the flexible and transparent acoustic apparatus within a visible light wavelength range according to the first embodiment of the present disclosure;

Fig. 5 is a schematic perspective view of the flexible and transparent acoustic apparatus integrated with a display according to the first embodiment of the present disclosure; and

Fig. 6 is a schematic structural view of a flexible and transparent acoustic apparatus according to a second embodiment of the present disclosure.

DETAILED DESCRIPTION

The flexible and transparent acoustic apparatus according to an embodiment of the present disclosure will be described below in detail with reference to the drawings.

Referring to Fig. 2, according to a first embodiment of the present disclosure, a flexible and transparent acoustic apparatus 20 is provided. The flexible and transparent acoustic apparatus 20 comprises a signal input device 22 and a thermoacoustic element. The thermoacoustic element comprises a conductive film structure 24, a flexible and transparent substrate 26, a first electrode 28, a second electrode 30 and conducting wires 32. The first electrode 28 and the second electrode 30 constitute a pair of electrodes. One end of the first electrode 28 and one end of the second electrode 30 are connected with two sides of the conductive film structure 24 respectively. The other end of the first electrode 28 and the other end of the second electrode 30 are electrically connected with the signal input device 22 respectively. The flexible and transparent substrate 26 is disposed on bottom surfaces of the first electrode 28, the second electrode 30 and the conductive film structure 24 for supporting and protecting the first electrode 28, the second electrode 30 and the conductive film structure 24.

In this embodiment, a conductive film of the conducting film structure 24 is a transparent conductive film made from any material of graphene, indium tin oxide, silver nanowire and poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate, which are commonly used for forming transparent electrodes in the prior art. The conductive film structure 24 may comprise one layer, double layers or multilayers of conductive films. A total thickness of the conductive film structure 24 may be adjusted within a range from 0.3nm ίοΙΟΟμιη according to practical applications if the conductive film structure 24 comprises at least one layer of conductive film. In this embodiment, the conductive film structure 24 is lxl cm² in size and 100 nm in thickness. Certainly, the size of the conductive film structure 24 may be changed according to practical applications.

A thermal capacity per unit area of the conductive film structure 24 is smaller than l x lO^"2 J/ (cm²-K). When the conductive film structure 24 is used in the thermoacoustic element, the larger the contact area between the conductive film structure 24 and an air, the higher an acoustic intensity of the thermoacoustic element is. Because the conductive film structure 24 consists of the conductive film, the conductive film structure 24 has high toughness and high mechanical strength.

As shown in Fig. 2, in some embodiments, the first electrode 28 and the second electrode 30 are electrically connected with two sides of the signal input device 22 via the conducting wires 32 respectively for transmitting a signal generated by the signal input device 22 to the conductive film structure 24. The first electrode 28 and the second electrode 30 are formed by conductive materials, and there are no special limits on material types, shapes and structures of the first electrode 28 and the second electrode 30. Specifically, a material of each of the first electrode 28 and the second electrode 30 may be a metal, a conductive adhesive, a metal oxide, etc. A shape of each of the first electrode 28 and the second electrode 30 may be any of a layered shape, a rod-like shape, a block shape and other shapes. In this embodiment, the first electrode 28 and the second electrode 30 are preferably layered shaped conductive adhesive electrodes respectively. Two sides of the conductive film structure 24 are electrically connected with the first electrode 28 and the second electrode 30 respectively, and fixed via the first electrode 28 and the second electrode 30.

The substrate 26 is disposed for achieving functions of supporting and protection, and there are no special limits on a specific shape of the substrate 26. In one embodiment, the substrate 26 is preferably a planar structure or a curved structure with a surface, so that the conductive film structure 24 may be directly disposed and attached on the surface of the substrate 26. Because the whole conductive film structure 24 is supported by the substrate 26, the conductive film structure 24 is able to receive a stronger signal, thus possessing a higher acoustic intensity.

A material of the substrate 26 may be a flexible and transparent organic material such as an organic material of polyimide, polyethylene terephthalate or polydimethylsiloxane. The material of the substrate 26 has good thermal insulation property, so as to prevent the substrate 26 from over-absorbing a heat generated by the conductive film structure 24 which may not heat a surrounding medium to generate a sound. In addition, the substrate 26 may have a rough surface so as to form a certain gap between the conductive film structure 24 disposed on the surface of the substrate 26 and the substrate 26, thus reducing heat dissipation to the substrate 26 and further improving an acoustic effect of the acoustic apparatus 20.

In this embodiment, the signal input device 22 may be a conventional audio electrical signal input device, a conventional optical signal input device or a conventional electrical signal input device. Accordingly, an input signal of the signal input device 22 may include, but are not limited to, an audio signal, an optical signal and an AC signal.

It can be understood that the first electrode 28, the second electrode 30 and the conducting wire 32 are optional elements according to different signal input devices 22. For example, if the input signal is the optical signal, the signal input devices 22 may directly input the signal to the conductive film structure 24 by directly irradiating the conductive film structure 24 without any electrode and any conducting wire.

In practical use, the total thickness of the conductive film structure 24 may be within the range from 0.3nm ίοΙΟΟμιη. Because such a conductive film structure has a smaller thermal capacity per unit area and a larger surface area for heat dissipation, when the signal is input, a temperature of the conductive film structure 24 may rapidly rise or fall, thus causing a periodic temperature change; and a rapid heat exchange between the conductive film structure 24 and the surrounding medium occurs, thus periodically change a density of the surrounding medium to allow the surrounding medium to expand or contract periodically to generate a sound. The thicker the conductive film structure 24, the larger a power of the conductive film structure 24 is. Moreover, since the conductive film structure 24 has high toughness and high mechanical strength, the acoustic apparatus 20 with any shape, such as a circle, a rectangle, a triangle or a polygon, and with any size may be formed by the conductive film structure 24. The acoustic apparatus 20 may be conveniently used in various acoustic apparatuses in electronic fields, such as mobile phones, MP3s, MP4s, TVs, computers, ultrasonic imaging and ranging systems, and acoustic apparatuses in other fields. The medium around the conductive film structure 24 may be a liquid medium or a gaseous medium. In this embodiment, the medium around the conductive film structure 24 is a gaseous medium.

In this embodiment, when a 5V AC electrical signal is applied to the acoustic element, a measurement may be carried out in a position which is 5cm away from the thermoacoustic element, as shown in Fig. 3. With reference to Fig. 3, a maximum and a minimum of an acoustic pressure of the thermoacoustic element may be 61dB and 49dB respectively, and an acoustic frequency is within a range from lKHz to 50KHz. Therefore, the acoustic apparatus 20 has good acoustic intensity, wide frequency range and ideal acoustic effect. It should be noted that due to a limit of a measuring instrument, an upper limit of the tested acoustic frequency is merely 50 KHz. However, it has been proved in theory that the acoustic apparatus 20 may generate a smooth acoustic pressure ranging from ΙΟΙΚΗζ to 100MHz.

In this embodiment, a light transmittance of the acoustic apparatus 20 within a visible light wavelength range from 390nm to 770nm has been tested with reference to Fig. 4. A test result shows that an average light transmittance of the visible light is 74.8%. Therefore, the flexible and transparent acoustic apparatus 20 has good transmittance, which may be integrated with a display and have high flexibility.

With reference to Fig. 5, an acoustic apparatus 40 integrated with a display is provided. The acoustic apparatus 40 comprises a thermoacoustic element, a display 50 and a signal input device (not shown). The thermoacoustic element comprises a conductive film structure 42, two electrodes 44, conducting wires 46 and a flexible and transparent substrate 48. The two electrodes 44 are disposed on two sides of the conductive film structure 42 respectively, and electrically connected with the signal input device via the conducting wires 46 respectively. The flexible and transparent substrate 48 is used for supporting and protecting the conductive film structure 24 and the two electrodes 44. The whole thermoacoustic element is mounted on the display 50.

When the acoustic apparatus 40 is used, the flexible and transparent material is used for forming the thermoacoustic element and the substrate. Therefore, the whole thermoacoustic element with characteristics of tensility and transparency may cover a flexible display to be integrated with the flexible display, so as to realize functions of sound generation and display at a same time.

With reference to Fig. 6, according to a second embodiment of the present disclosure, a flexible and transparent acoustic apparatus 60 having an interdigital electrode structure is provided. The flexible and transparent acoustic apparatus 60 comprises a signal input device 62 and a thermoacoustic element. The thermoacoustic element comprises a conductive film structure 64, a flexible and transparent substrate 66, a first interdigital electrode 68, a second interdigital electrode 70 and conducting wires 72. Each branch 681 of the first interdigital electrode 68 and each branch 701 of a second interdigital electrode 70 constitute a pair of interdigital electrodes, and are connected with the conductive film structure 64 respectively to form a plurality of pairs of electrodes. One end 682 of the first interdigital electrode 68 and one end 702 of the second interdigital electrode 70 are connected with the signal input device 62 respectively. The substrate 66 is disposed on bottom surfaces of the first interdigital electrode 68, the second interdigital electrode 70 and the conductive film structure 64 for supporting and protecting the first interdigital electrode 68, the second interdigital electrode 70 and the conductive film structure 64.

Compared with the first embodiment, in the second embodiment, the plurality of pairs of electrodes are used to further reduce an output resistance of the conductive film structure and increase an output power, thus enhancing the output strength of the acoustic pressure, improving a performance of the acoustic apparatus and increasing a reliability.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications may be made in the embodiments without departing from spirit and principles of the disclosure. Such changes, alternatives, and modifications all fall into the scope of the claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A flexible and transparent acoustic apparatus, comprising:

a thermoacoustic element, comprising a flexible and transparent substrate, and at least one conductive film structure and one or a plurality of pairs of electrodes both disposed on the substrate, wherein one end of a first electrode and one end of a second electrode in each pair are connected with the conductive film structure respectively; and

a signal input device, connected with the other end of the first electrode and the other end of the second electrode in each pair respectively for transmitting an excitation signal to the conductive film structure through the electrodes connected with the conductive film structure, so as to allow the conductive film structure to change a density of a medium around the conductive film structure to generate an acoustic wave.

2. The flexible and transparent acoustic apparatus according to claim 1, wherein a conductive film of the conducting film structure is a transparent film made from any material of graphene, indium tin oxide, silver nanowire and poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate.

3. The flexible and transparent acoustic apparatus according to any one of claims 1-2, wherein an acoustic frequency of the acoustic apparatus is within a range from 10Hz to 100MHz.

4. The flexible and transparent acoustic apparatus according to any one of claims 1-3, wherein the conductive film structure comprises one layer or multilayers of conductive films.

5. The flexible and transparent acoustic apparatus according to any one of claims 1-4, wherein a total thickness of the conductive film structure is within a range from 0.3nm ίοΙΟΟμιη.

6. The flexible and transparent acoustic apparatus according to any one of claims 1-5, wherein the plurality of pairs of electrodes are made of a pair of interdigital electrodes, each branch of a first interdigital electrode and each branch of a second interdigital electrode in the pair of interdigital electrodes are connected with the conductive film structure respectively to form the plurality of pairs of electrodes, and one end of the first interdigital electrode and one end of the second interdigital electrode are connected with the signal input device respectively.

7. The flexible and transparent acoustic apparatus according to any one of claims 1-6, wherein the flexible and transparent substrate is a flexible, transparent film made from any organic material of polyimide, polyethylene terephthalate and polydimethylsiloxane.

8. The flexible and transparent acoustic apparatus according to any one of claims 1-7, wherein the medium is a liquid medium or a gaseous medium around the conductive film structure.

9. The flexible and transparent acoustic apparatus according to any one of claims 1-8, wherein the signal input device is an audio electrical signal input device or an electrical signal input device.

10. A flexible and transparent acoustic apparatus, comprising:

a thermoacoustic element, comprising a flexible and transparent substrate, and at least one conductive film structure; and

an optical signal input device, directly irradiating the conductive film structure so as to allow the conductive film structure to change a density of a medium around the conductive film structure to generate an acoustic wave.