Speaker system and its application method

Abstract

This application discloses a speaker system applied to a television, which includes a piezoelectric speaker and an electromagnetic speaker, in which the crossover frequency between the piezoelectric speaker and the electromagnetic speaker is 500 Hz or higher, the piezoelectric speaker is provided on the back of a display device, and the electromagnetic speaker is provided on the bottom of the display device, and a method of using the same.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application filed with the China Patent Office on September 7, 2021, and accepted under application number 202111042000.4, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of speaker manufacturing, for example, a speaker system and its application method. [Background technology]

[0003] The television industry has been transitioning from the rise of display devices using the cathode ray tube system to thin televisions, which are thin display devices using plasma and liquid crystal systems. In recent years, ultra-thin televisions with self-emitting display functions using organic light-emitting semiconductors and the like have been widely accepted in the market, and most cathode ray tube television manufacturers have stopped production. The transition from cold cathode fluorescent tube light-emitting devices to light-emitting diode (LED) light-emitting devices has made LCD televisions thinner. The ideal form is a wall-mounted television product combined with the added value of light weight after heavy devices such as cold cathode fluorescent tubes are removed, and among them, organic light-emitting diodes (OLEDs), which are self-emitting display devices, are 0.5mm to 0.7mm thick and do not require external light-emitting devices such as LEDs, so there is a possibility of realizing ultra-thin televisions that are even thinner than conventional LCD displays. In addition, since there is no need for space to install LEDs, narrow-frame televisions have also been commercialized. Although OLEDs have the advantage of being overwhelmingly thin (less than 1 mm), only narrow-framed displays are currently in practical use, and it is still difficult to put them to practical use in wall-mounted flat-screen TVs.

[0004] The basic functions of a television are to display images and output sound. The display of images is realized by the added value of the OLED having a narrow frame structure. Sound output is mainly realized by attaching an electromagnetic speaker to the back of the television case, but the uneven shape of the electromagnetic speaker makes it too thick. Currently, the limit diameter of a thin electromagnetic speaker is about 20 mm, and the minimum diameter of an electromagnetic speaker actually used to realize the reproduction frequency required for a television is about 25 mm. If a speaker of this size, as shown in Figure 22, is attached to the back of a television, the advantage of the thickness of less than 1 mm obtained by the OLED is offset, and the television case becomes thick. In addition, a protrusion is created on the back of the television, making it difficult to realize a wall-mounted speaker from the standpoint of design. If the speaker is attached to the side of the television, the back of the television will be flat, making wall-mounting possible, but the design of the narrow frame will be lost.

[0005] Here we will briefly introduce the principle of movie theater video playback, which maximizes the added value of the sense of liveliness. At movie theaters, speakers are installed on the back of the mesh screen facing the viewer to output sound to them, and because sound is transmitted directly to the viewer through this mesh, the viewer feels as if the voices of the characters are coming from the screen and that sound effects are coming directly from the image, creating a strong sense of liveness. However, when speakers are placed on the back, as in the TV mentioned above, sound cannot be output directly to the viewer, resulting in a spatial deviation between the image and sound, resulting in an image display that lacks the sense of liveness.

[0006] A flat panel speaker in the related art generates sound by vibrating a thin panel with an excitation element, and has a function of generating sound by an excited panel that is attached with a driving source, such as an electromagnetic solenoid or piezoelectric ceramics, on a thin plate-like member. Since sound can be emitted directly from the display, it is possible to play images with a sense of realism.

[0007] However, the flat panel speaker device in the related art does not consider the vibration influence on the current ultra-thin display device such as OLED during the use process. The sound volume P obtained from the excited object is determined by the width size X, and the relationship P∝X can usually be established. Furthermore, X establishes Hooke's law X=F / K based on the relationship between the force F of the exciting object and the rigidity K of the excited object. In the case of a liquid crystal panel that requires an LED, the overall thickness of the display panel including the liquid crystal panel and the light guide plate is 3mm to 4mm, including the light guide plate on the back. The thickness of the OLED liquid crystal panel is 0.5mm to 0.7mm as mentioned above. The rigidity of the overall display panel of this display device is K, its Young's modulus is E, its second moment of area is I, the width of the display panel is a, its length is L, and its thickness is h, then I=ah 3 / 3, so K=48EI / L 3 =16Eah 3 / L 3 It can be seen that for structures of the same length, the stiffness K of the display panel is determined by the cube of the thickness of the display panel. If the thickness of the OLED is 0.7 mm and the thickness of the LCD panel is 3 mm, JPEG0007639181000001.jpg625 is obtained, and it is stated that the stiffness of OLED and LED liquid crystal panels is significantly different. The force required for equivalent bending of OLED and LED liquid crystal panels is JPEG0007639181000002.jpgThere is a difference of 621 times.

[0008] In related technology, a structure in which a vibration actuator is attached to the back of an OLED has been proposed. An OLED is an excited object with a display function, and can display images and videos by generating relatively large vibrations with a small force from an excitation element. Therefore, if a large sound can be obtained by exciting the excitation element, vibration must be applied to the OLED, but if the display device vibrates, there is a problem that screen blur occurs in the video or image being viewed by the viewer. Summary of the Invention

[0009] This application proposes a speaker system and its application method, which is particularly applicable to televisions, that combines a piezoelectric speaker that produces sound by vibration of an OLED self-luminous display device and an electromagnetically driven speaker that is installed separately from the display device, thereby reducing the spatial deviation between images and audio and providing an image display with a live feel.

[0010] An embodiment of the present application provides a speaker system including a piezoelectric speaker and an electromagnetic speaker, in which the crossover frequency between the piezoelectric speaker and the electromagnetic speaker is 500 Hz or more, the piezoelectric speaker is disposed on the rear side of the display device, and the electromagnetic speaker is disposed on the bottom side of the display device.

[0011] The present application further provides an application method of the speaker system in a television, in which an electromagnetic speaker is adopted to broadcast sound when it is determined that the thickness range of the television is 0.5mm to 2.0mm and the audio signal output by the television is less than 500Hz, and a piezoelectric speaker is adopted to broadcast sound when it is determined that the thickness range of the television is 0.5mm to 2.0mm and the audio signal output by the television is greater than 3000Hz. [Brief description of the drawings]

[0012] [Figure 1] 1A to 1C are schematic diagrams illustrating the attachment positions of piezoelectric ceramic elements of different sizes on an OLED screen in one embodiment of the present application. [Diagram 2] FIG. 1 is a schematic diagram of a simulation analysis of harmonic vibration at a frequency of 10 KHz after excitation of a display in the related art. [Diagram 3] 4 shows the resonant frequency when vibration occurs for different television screen sizes according to one embodiment of the present application. [Figure 4] 1 is a schematic diagram of sound output from a television that employs an OLED as a display according to an embodiment of the present application; [Diagram 5]FIG. 2 is a schematic diagram of the positions of people and a television when a viewer is watching television according to an embodiment of the present application. [Figure 6] 13 shows frequency data in which viewers in their teens perceived image blurring for different sizes of television according to an embodiment of the present application. [Figure 7] 11 is a graph showing the frequency with which viewers in their teens perceived image blurring for different sizes of televisions according to an embodiment of the present application. [Figure 8] 11 is a graph showing the frequency with which viewers in their 20s perceived image blurring of different sizes of televisions according to an embodiment of the present application. [Figure 9] 11 is a graph showing the frequency with which viewers in their 40s perceived image blurring of different sizes of televisions according to an embodiment of the present application. [Figure 10] 11 is a graph showing the frequency with which viewers in their 60s perceived image blurring of different sizes of televisions according to an embodiment of the present application. [Figure 11] 1 is a graph of viewer-perceived frequencies of image blur for different television sizes according to one embodiment of the present application. [Figure 12] FIG. 1 is a schematic diagram showing a low-frequency speaker according to an embodiment of the present application mounted at the bottom of a television facing the viewer. [Figure 13] FIG. 2 is a schematic diagram of a digital audio processing and driving circuit employing a flat panel speaker and an electromagnetic speaker according to an embodiment of the present application. [Figure 14] 13 shows frequency data of the sense of presence of viewers of different age groups for different programs broadcast on a 19-inch television according to an embodiment of the present application. [Figure 15] 13 shows frequency data of the sense of presence of viewers of different age groups for different programs broadcast on a 50-inch television according to an embodiment of the present application. [Figure 16] 13 shows frequency data of the sense of presence of viewers of different age groups for different programs broadcast on an 80-inch television according to an embodiment of the present application. [Figure 17]1 is a structural schematic diagram of a piezoelectric speaker vibrator according to an embodiment of the present application. [Figure 18] FIG. 2 is a schematic diagram showing a piezoelectric element attached to the rear side of an OLED according to an embodiment of the present application. [Figure 19] 2 is a schematic diagram of a lead electrode of a piezoelectric speaker transducer according to an embodiment of the present application. FIG. [Figure 20] 2A-2C are schematic diagrams illustrating the configuration of an OLED display panel in different signal states according to an embodiment of the present application. [Figure 21] 4 is a frequency response graph of an OLED display panel according to an embodiment of the present application. [Figure 22] 1 is a schematic diagram showing the structure of a bass reflex speaker system according to an embodiment of the present application; [Diagram 23] 1 is a frequency response graph of a bass reflex speaker system according to an embodiment of the present application. [Figure 24] 4 is a frequency response graph showing a piezoelectric speaker and an electromagnetic speaker system driven simultaneously according to an embodiment of the present application; [Diagram 25] FIG. 13 is a schematic diagram of an attachment method of an OLED display panel after a piezoelectric element is added according to another embodiment of the present disclosure. [Figure 26] 4 is a frequency response graph of an OLED display panel in a structure of multiple piezoelectric elements according to an embodiment of the present application; [Figure 27] 4 is a frequency response graph of a piezoelectric speaker according to an embodiment of the present application after low-pass filtering is applied; [Figure 28] 4 is a frequency response graph showing a piezoelectric speaker and an electromagnetic speaker system according to an embodiment of the present application; [Figure 29] FIG. 13 is a structural schematic diagram of a piezoelectric speaker vibrator according to another embodiment of the present application. [Diagram 30] FIG. 2 is a schematic diagram of the strain of a piezoelectric element after being poled at different voltages according to an embodiment of the present application. [Diagram 31] FIG. 4 is a schematic diagram of displacement distortion when an AC voltage is applied to a piezoelectric element after being polarized according to an embodiment of the present application. [Diagram 32]1 is a schematic diagram showing how a vibration element according to an embodiment of the present application is curved and deformed up and down around a support member; [Diagram 33] 1 is a schematic diagram illustrating a vibration element according to an embodiment of the present application that vibrates vertically and curvedly around a support member. [Diagram 34] 10 is a structural schematic diagram of a flat panel piezoelectric speaker vibrator according to another embodiment of the present application. FIG. [Diagram 35] 10 is a structural schematic diagram of a flat panel piezoelectric speaker vibrator according to another embodiment of the present application. FIG. [Diagram 36] 10 is a structural schematic diagram of a flat panel piezoelectric speaker vibrator according to another embodiment of the present application. FIG. [Explanation of symbols]

[0013] First piezoelectric element 1, first external electrode 2, third external electrode 3, high voltage electric field direction 4, second external electrode 5, solder 6, first lead 7, second lead 8, transparent glass substrate 9, organic EL panel 10, second piezoelectric element 11, reflective speaker system 12, opening 13, subwoofer 14, housing 15, polarization direction 16, thin metal plate 17, support member 18. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present application will now be further described with reference to the drawings and examples.

[0015] In the related art, an actuator for excitation can be attached to a display device such as a liquid crystal display to generate sound. FIG. 1 is a schematic diagram of the attachment positions of piezoelectric ceramic elements of different sizes on an OLED screen in one embodiment of the present application. FIG. 2 is a schematic diagram of a simulation analysis of harmonic vibration at a frequency of 10 KHz after a display in the related art is excited, and the excited display has a divided vibration of 10 kHz frequency as shown in FIG. 2, and the divided vibration vibrates the air and is transmitted to the human ear as sound. The sound intensity I when a vibration displacement occurs in the vibrating body to generate a sound output is: In the formula, ρ and c slightly differ depending on the temperature and pressure of the gas, but here, the discussion can be made with ρ and c as constants.

[0016] In such a case, the intensity of the sound, I, is This means that the sound intensity I is determined by the frequency and the displacement of the vibrator, and that at high frequencies, a desired sound intensity can be obtained without a large displacement. However, in order to maintain a certain sound intensity in a wide frequency range, especially in the low frequency range, in the actual use of a television, a larger displacement is required than in the high frequency range.

[0017] Since the display described in this application is a device for displaying television images, if a large vibration occurs in the display itself, the image being viewed will also shake significantly, causing the image to blur (hereinafter referred to as screen blur), which will impair the basic functions of the television. Therefore, when generating sound by vibration of the television display, it is not realistic to reproduce sound over the entire frequency range from low to high frequencies by vibration of the display alone.

[0018] Therefore, this application simultaneously uses a piezoelectric speaker that generates sound from the vibration of the display, and an electromagnetic speaker that is effectively driven to reproduce low-frequency bands in order to prevent image blurring due to the above-mentioned low-frequency vibrations, and both are key elements for the practical application of piezoelectric speakers for televisions.

[0019] Generally, the screen size of a television used at home is about 19 inches to 80 inches. When an image is output by an OLED, the resonance frequency of vibration varies depending on the screen size of the television. FIG. 3 shows the resonance frequency when vibration occurs in different television screen sizes according to an embodiment of the present application. The result is obtained by calculating the resonance frequency of different sizes from 19 inches to 80 inches. In FIG. 3, t represents the thickness of the television screen, x represents the length of the television screen, and y represents the width of the television screen. Here, an analytical model of the outer periphery of the OLED is created, and the thickness is set to 0.3 mm to 1 mm. As can be seen from FIG. 3, the resonance frequency is determined by the size and thickness of the screen.

[0020] In addition, in the range of screen thickness of 0.3 mm to 1 mm, the primary resonance frequency of most televisions is 100 Hz or less. Generally, the reproduction band of television speakers is 100 Hz to 12 kHz, so that it is necessary to excite the OLED to increase its resonance frequency in order to reproduce sound.

[0021] Here, it is necessary to understand the vibration frequency of the panel that causes the human eye to sense screen blur. To this end, the following experiment was conducted.

[0022] (1) Divide viewers aged 10 to 60 into six groups based on age, and randomly select 10 viewers.

[0023] (2) Allowing viewers to watch a television on which an OLED LCD screen is the display.

[0024] (3) The television display device used in this case has an OLED LCD screen that is 0.6 mm thick and inputs the standard Society of Motion Picture and Television Engineers (SMPTE) color bar signal as the image signal.

[0025] (4) A vibrator with a diameter of 50 mm and a thickness of 30 mm is attached to the back of the display device of (3) above, as shown in Fig. 4, and vibration is applied to generate sound from the display device. In this case, the excitation signal generated by the signal generation controller is a sine wave sweep signal that is gradually lowered from 10 kHz to 100 Hz. Among them, Fig. 4 is a schematic diagram of sound generation from a television that uses an OLED as a display screen according to one embodiment of the present application.

[0026] (5) As shown in Fig. 5, the distance between the viewer and the television is L, where L is 0.5 m, 1.0 m, 2.0 m, and 5.0 m, and the viewer sees the SMPTE color bar in step (3) above at different positions and hears the audio output in step (4) above. Fig. 5 is a schematic diagram of the positions of the viewer and the television when the viewer is watching television according to an embodiment of the present application.

[0027] (6) During the viewing period in step (5), the frequency at which the image begins to blur due to the vibration of the display device is recorded. Figure 6 shows frequency data obtained by selecting viewers in their teens according to an embodiment of the present application and having them sense image blur on different TV sizes.

[0028] (7) The experiments in steps (1) to (6) above were conducted for image sizes of 19 inches, 32 inches, 50 inches, 65 inches, and 80 inches, and further classified based on age groups: teens, 20s, 40s, and 60s.

[0029] Through the above series of experiments, we can understand the frequencies at which different age groups perceive image blur on televisions of different sizes.

[0030] FIG. 6 shows data showing detailed results of this experiment conducted on teenage viewers. FIG. 7 shows a graph of the frequency at which viewers in the teenage age group, according to an embodiment of the present application, perceived image blur for different TV sizes. The average value of 10 viewers was collected for all data. As can be seen from FIG. 6, viewers tend to feel that the frequency of screen blur increases as the size of the TV increases. Also, the frequency at which screen blur is perceived decreases as the distance between the person and the TV increases, and FIG. 7 shows a graph of this data. Even for a large 80-inch TV, vibrations of about 400 Hz or more do not cause people to feel screen blur.

[0031] 8 to 10 are results for people in their 20s, 40s, and 60s. FIG. 8 is a graph of the frequency at which viewers in their 20s, according to an embodiment of the present application, perceive image blurring of different TV sizes. FIG. 9 is a graph of the frequency at which viewers in their 40s, according to an embodiment of the present application, perceive image blurring of different TV sizes. FIG. 10 is a graph of the frequency at which viewers in their 60s, according to an embodiment of the present application, perceive image blurring of different TV sizes. As can be seen from FIGS. 7 to 10, viewers' perception of image blurring of different TV sizes is basically independent of age, and all of them show the same tendency. In addition, the frequency at which viewers perceive the screen as blurry decreases with age. Teenagers have the highest sensitivity to picture style. When all the data in FIGS. 8 to 10 are superimposed, it is shown in FIG. 11. FIG. 11 is a graph of the frequency at which viewers can perceive image blurring of different TV sizes according to an embodiment of the present application. The hatched area is the frequency range where image blurring due to panel vibration is felt. These results show that by driving an OLED at a frequency of 500Hz or higher, most viewers can see images without any screen blurring.

[0032] However, reproducing only frequencies above 500Hz as audio signals does not provide sufficient information. Low-frequency frequencies based on guitars, drums, etc. are essential for playing music, and frequencies from 300 to 500Hz are the reproduction band necessary for identifying human voices. Therefore, in order to compensate for frequencies below 500Hz, it is necessary to configure a speaker system in which an electromagnetic drive separate from the display device is driven simultaneously.

[0033] If sound is reproduced using only piezoelectric speakers based on the above conditions, it will not be possible to reproduce frequencies below 500 Hz, resulting in insufficient low-frequency sound pressure. Therefore, this application must mainly consider electromagnetic speakers that reproduce sound at low frequencies. In principle, electromagnetic speakers are installed in a completely different position from the video display device, so there is no need to worry about image blurring due to voice output. In addition, electromagnetic speakers have a wider reproduction band than piezoelectric speakers, and therefore can cover the reproduction of the entire sound of a television, and viewers watch television from a distance three times the height of the television screen. This distance is within the distance of step (2) above, which is considered to be the ideal position for watching television, and a microphone is installed at the height of the center of the television screen to collect noise. However, as mentioned above, the sense of realism obtained in a movie theater is obtained by the sound coming from the screen of the displayed image, so in order to obtain realistic sound on television, it is necessary to use piezoelectric speakers to reproduce the sound.

[0034] In particular, the system produces a sense of realism that is felt by the viewer by emitting sound directly from the video image, similar to that of a movie theater, and this differs from systems that produce a stereo surround effect by increasing the number of piezoelectric speakers or obtain a simulated surround effect by outputting a signal that performs phase manipulation. To verify this, the following experiment was conducted.

[0035] In step 1, the vibrator of FIG. 4 is attached to the back of the OLED display screen to apply vibration, and the OLED of the display device outputs sound to broadcast the screen, thereby realizing the television viewing function (i.e., providing a piezoelectric speaker in the speaker system described in this application), where 19-inch, 50-inch, and 80-inch televisions are used.

[0036] In step 2, the viewer watches the television from a position that is three times the height from the television screen. Experience has shown that this distance is the ideal position for watching television.

[0037] In step 3, a microphone is placed at the distance 2) above, which is considered to be the ideal position for watching television, and at the height of the center of the television screen, as shown in Fig. 12. Among them, Fig. 12 is a schematic diagram showing a low-frequency speaker according to an embodiment of the present application being placed at the bottom of a television facing the viewer.

[0038] In step 4, the low frequency speaker in FIG. 12 (ie, the electromagnetic speaker in the speaker system described in this application) is placed at the bottom of the television facing the viewer.

[0039] In step 5, pink noise is input to the piezoelectric speaker in step 1 and the electromagnetic speaker in step 4, respectively. At this time, the noise is measured by the microphone in step 3 and the magnitude of the input signal to each speaker is adjusted to make the noise levels of the piezoelectric speaker (flat panel speaker) and the electromagnetic speaker equal.

[0040] In step 6, a digital audio processing and driving circuit is configured as shown in Fig. 13, and a high-pass filter is connected to the piezoelectric speaker (Piezo Driver), and its cutoff frequency is set to 500Hz, so that the OLED image does not blur. Wherein, Fig. 13 is a schematic diagram of a digital audio processing and driving circuit using a flat panel speaker and an electromagnetic speaker according to an embodiment of the present application.

[0041] In step 7, similarly, a low-pass filter is connected to the electromagnetic speaker (SUB WOOWER) of FIG. 13 (ie, bass speaker), and its cut-off frequency can be varied below 3 kHz.

[0042] In step 8, the video signal is input to the OLED having the audio driving circuit shown in FIG. 13, and the audio signal is simultaneously input to the piezoelectric speaker (represented as a piezoelectric ceramic actuator in FIG. 13) and the electromagnetic speaker (represented as a bass speaker in FIG. 13) by the driving system shown in FIG. 13, so that audio can be generated from the piezoelectric speaker and the electromagnetic speaker in synchronization with the image of the OLED.

[0043] In step 9, 10 viewers are randomly selected from viewers in their 20s, 40s, and 50s, and these viewers watch images and sounds through the OLED display screen and driving system. Here, as shown in Figs. 14 to 16, a movie (a fight scene from Star Wars), a musician's concert, and a sports broadcast (FIFA World Cup) are shown in the sample images, respectively. Among them, Fig. 14 shows frequency data of the sense of presence of viewers of different age groups for different programs broadcasted by a 19-inch TV according to an embodiment of the present application. Fig. 15 shows frequency data of the sense of presence of viewers of different age groups for different programs broadcasted by a 50-inch TV according to an embodiment of the present application. Fig. 16 shows frequency data of the sense of presence of viewers of different age groups for different programs broadcasted by an 80-inch TV according to an embodiment of the present application.

[0044] In the case of step 9 above, the cutoff frequency of the low-pass filter connected to the electromagnetic speaker (bass speaker) is gradually lowered from 10 kHz to 100 Hz, and basically, the higher the cutoff frequency, the more dominant the sound produced by the electromagnetic speaker becomes. Therefore, by lowering the cutoff frequency, the influence of the sound produced by the piezoelectric speaker becomes dominant. The frequency at which the listener feels a sense of realism is obtained as the cutoff frequency changes.

[0045] From the above sensing results, it is possible to grasp the degree of dependency between the cutoff frequencies of the piezoelectric speaker and the electromagnetic speaker and the sense of realism felt by the listener.

[0046] The results of these experiments are summarized in Figures 14 to 16. Although it depends on the type of listening tendency, people of all ages can feel a sense of realism if the frequency is 2000 Hz to 3000 Hz or less.

[0047] Therefore, in a piezoelectric speaker in which a displacement element attached to a self-luminous display device vibrates the display device to produce sound, and in an electromagnetically driven speaker system separated from the display device and driven simultaneously, the crossover frequency between the piezoelectric speaker and the electromagnetic speaker must be 500 Hz or more and 3000 Hz or less, which is the frequency condition that prevents screen shaking and provides a sense of realism.

[0048] 17 to 24, an embodiment of a piezoelectric speaker using an OLED based on the above-mentioned optimization conditions for the cutoff frequency will be described. In the following description, the direction in which the OLED piezoelectric speaker generates sound will be the front side of the OLED piezoelectric speaker, and the opposite side will be the rear side. The piezoelectric speaker includes a piezoelectric speaker transducer, and the piezoelectric speaker transducer includes a piezoelectric element.

[0049] FIG. 17(a) is a structural external view of a piezoelectric speaker transducer, FIG. 17(b) is a schematic diagram of the piezoelectric speaker transducer structure connected to an external electrode, and FIG. 17(c) is a structural schematic diagram of the piezoelectric speaker transducer with a high voltage electric field applied. FIG. 18 is a schematic diagram of a piezoelectric element according to an embodiment of the present application attached to the back side of an OLED. Here, the piezoelectric element used is made of a piezoelectric material of lead zirconate titanate. After being made into a powder compact, 10 to 20 sheets of 30 μm are laminated, then pressed and sintered. The sintering temperature is 1050° C. The first external electrode 2 and the second external electrode 5 are printed on the upper and lower surfaces of the sintered first piezoelectric element 1, respectively, and sintered. A third external electrode 3, which is not electrically connected to the first external electrode 2, is formed at the same time on one side of the first external electrode 2, and the third external electrode 3 is connected to the second external electrode 5 on the back surface of the first piezoelectric element 1 by an electrode on the side surface of the first piezoelectric element 1 as shown in FIG. 17(b). The sintering temperatures of the first external electrode 2, the third external electrode 3, and the second external electrode 5 are all 600° C. Then, as shown in FIG. 17(c), a high voltage electric field is applied between the first external electrode 2, the second external electrode 5, and the third external electrode 3 on the upper and lower surfaces, so that the first piezoelectric element 1 is polarized, and the high voltage electric field direction 4 is oriented from the first external electrode 2 to the second external electrode 5. After being polarized, the first piezoelectric element 1 extends in the vertical direction by applying a voltage to the first external electrode 2 located on the upper part of the first piezoelectric element 1 and the second external electrode 5 located on the lower part of the first piezoelectric element 1. In this embodiment, after firing, a rectangular piezoelectric speaker vibrator of 90 mm x 30 mm x 0.5 mm is produced.

[0050] As shown in FIG. 19, the piezoelectric speaker transducer in FIG. 17(a) is attached to the back of an OLED display screen. The OLED display screen used in the present application is configured such that an organic electroluminescence (EL) panel 10, in which a transparent electrode layer, an organic light-emitting layer, and a reflective layer are laminated, is attached to a transparent glass substrate 9 as shown in FIG. 18 from the glass substrate side. Here, an OLED of 420 mm×240 mm×0.7 mm is used. As described with reference to FIG. 18 to FIG. 20, a first piezoelectric element 1 is attached to the center of the back of this OLED with an epoxy adhesive. FIG. 19 is a schematic diagram of a lead electrode of a piezoelectric speaker transducer according to an embodiment of the present application. FIG. 20 shows the form of an OLED display panel in different signal states according to an embodiment of the present application. At this time, as shown in FIG. 19, the first lead 7 is provided by solder 6 to the first external electrode 2 of the first piezoelectric element 1, and the second lead 8 is similarly provided by solder 6 to the third external electrode 3. When a voltage is applied between the first lead 7 and the second lead 8, the first piezoelectric element 1 expands, but the surface fixed by the epoxy adhesive is restrained by the OLED, so it cannot expand. Therefore, as shown in FIG. 20, FIG. 20(a) shows the form of the OLED display panel when there is no external signal input, and FIG. 20(b) shows the form of the OLED display panel when there is an external signal input, and it can be seen that the OLED is curved and deformed when an external signal is input. For example, when an AC voltage is applied between the first lead 7 and the second lead 8, the OLED curves and vibrates up and down, vibrating the air and generating sound.

[0051] The OLED is fixed to a holder, and the digital audio processing and driving circuit shown in FIG. 13 is adopted. FIG. 21 is a frequency response graph of an OLED display panel according to an embodiment of the present application, in which curve A in FIG. 21 is a sound pressure characteristic measured at a distance of 1 m by shorting a high pass filter (HPF) in such a case. The effective sound frequency is about 300 Hz to about 6 kHz. However, in the frequency characteristic of curve A, the high frequency sound pressure is insufficient, and a relatively low sound is generated in the auditory sense. The resonance frequency of the bending vibration in FIG. 20 is derived from the size of the first piezoelectric element 1, and the larger the size of the piezoelectric element, the lower the resonance frequency. Therefore, as shown in FIG. 1, a second piezoelectric element 11 of a different size is attached. At this time, the size of the second piezoelectric element 11 is 45 mm×15 mm×0.5 mm. The sound pressure characteristic when driving the OLED by the above method is shown in curve B in FIG. 21. The characteristics at low frequencies are the same as curve A in FIG. 21, but the sound pressure is higher at 5kHz to 10kHz. From the viewpoint of hearing, high frequency sounds can also be clearly extended. However, since effective sound is generated at 400Hz, image blurring of the OLED can be confirmed. Therefore, if the frequency of the signal applied to the first piezoelectric element 1 and the second piezoelectric element 11 is cut at 6dB / Oct, the image blurring disappears, using a high-pass filter in the digital audio processing and driving circuit shown in FIG. 13.

[0052] As described above, if sound is generated only by the OLED, low-frequency sound cannot be heard, so low-frequency correction is performed using an electromagnetic bass. Here, a bass reflection type speaker system 12 as shown in FIG. 22 is used. FIG. 22 is a structural schematic diagram of a bass reflection type speaker system according to an embodiment of the present application. The reflective speaker system 12 includes an opening 13, a subwoofer 14, and a housing 15. The bass speaker among these is a moving coil type with an impedance of 8Ω and a diameter of 160 mm. FIG. 23 is a frequency response graph of the bass reflection type speaker system according to an embodiment of the present application. Curve A in FIG. 23 shows its frequency characteristics (measured at 1 m). In the driving circuit shown in FIG. 13, the input to the SUB WOOWER side is gain-controlled by the Audio Amp so that the sound pressure is approximately equal to the sound pressure around 1 kHz in the frequency characteristics of curve A in FIG. 21. The reproduction band generally has a characteristic of 20 Hz to 10 kHz. In order to obtain the above-mentioned sense of realism, as shown by curve B in FIG. 23, the low-pass filter in the driver circuit shown in FIG. 13 is set to an attenuation of −6 dB / Oct from 1 kHz.

[0053] Fig. 24 is a frequency response graph in which a piezoelectric speaker and an electromagnetic speaker system according to an embodiment of the present application are driven simultaneously, and is a measurement result obtained by simultaneously driving these piezoelectric speaker and electromagnetic speaker system 12 in the drive circuit shown in Fig. 13. The flatness from 20 Hz to 10 kHz indicates that a video signal including audio is added to this piezoelectric speaker system to check viewing, and that viewing can be performed without image blurring and with a sense of realism.

[0054] The embodiment shown in Figs. 25 to 28 uses the first piezoelectric element 1 and the second piezoelectric element 11 in the above embodiment, and adopts an OLED of 1770 mm x 996 mm x 0.7 mm as a display panel. Since the size of the OLED is larger than that of the above embodiment, the first piezoelectric element 1 and the second piezoelectric element 11 are attached in increased quantities as shown in Fig. 25. Fig. 25 is a schematic diagram of the attachment method of the OLED display panel after the piezoelectric element according to another embodiment 2 of the present application is added, and a total of four elements are attached to three equal positions in each of the long side direction and the short side direction of the OLED display panel. Fig. 26 is a frequency response graph of the OLED display panel in the structure of multiple piezoelectric elements according to one embodiment of the present application. Compared to the above embodiment, the area of ​​the OLED display panel is larger and the volume of the air removed is increased, so the overall sound pressure is increased. In addition, the reproduction band is also lowered to around 300 Hz. A video signal having a music signal is input to this OLED display panel, and the screen blur is checked after broadcasting. Therefore, as in the above embodiment, by using a high-pass filter (HPF) in the driving circuit shown in Figure 13 to cut the frequency of the signals applied to the first piezoelectric element 1 and the second piezoelectric element 11 at 6 dB / Oct, image blurring will be eliminated.

[0055] As in the previous embodiment, if sound is generated only from the OLED display panel, low-frequency sound cannot be heard, so an electromagnetic speaker is used to correct low frequencies, for example, an electromagnetic subwoofer is used. Here, too, a bass reflection type speaker system 12 as shown in FIG. 22 is used. FIG. 27 is a frequency response graph of a piezoelectric speaker according to an embodiment of the present application after low-pass filtering is adopted. Curve A in FIG. 27 shows its frequency characteristics (measured at a distance of 1 m). As in the related embodiment, the Audio Amp controls the output to the SUB WOOWER side so that it is almost equal to the sound pressure around 1 kHz in the frequency characteristics of FIG. 26. The reproduction band generally has a characteristic of 20 Hz to 10 kHz. In order to obtain the above-mentioned sense of realism, as shown in curve B in FIG. 27, the low-pass filter in the drive circuit shown in FIG. 13 is set to attenuate from 1 kHz by -6 dB / Oct.

[0056] Fig. 28 is a frequency response graph of the piezoelectric speaker and the electromagnetic speaker system according to an embodiment of the present application. That is, Fig. 28 shows the measurement results when the piezoelectric speaker and the electromagnetic speaker system 12 are simultaneously driven in the circuit of Fig. 13. From the flatness from 20Hz to 10kHz, it has already been discovered that even when using a large OLED, it is possible to enjoy realistic images without blurring.

[0057] Although a piezoelectric element that generates a simple expansion and contraction displacement such as the first piezoelectric element 1 has been described, examples of other piezoelectric elements will also be described with reference to Figs. 29 to 33. Fig. 29 is a structural schematic diagram of a piezoelectric speaker vibrator according to another embodiment of the present application. Fig. 29(a) is a structural external view of another piezoelectric speaker vibrator, Fig. 29(b) is a schematic diagram of the structure of another piezoelectric speaker vibrator connected to an external electrode, and Fig. 29(c) is a structural schematic diagram of the other piezoelectric speaker vibrator to which a high voltage electric field is applied. As shown in Fig. 29(b), a first piezoelectric element 1 (which may be, for example, a piezoelectric ceramic plate) has a first external electrode 2 that is not conductive on both the upper and lower surfaces. As shown in Fig. 29(c), when a circuit is connected and a high voltage is applied to the first external electrode 2 on the upper and lower surfaces, the high voltage electric field direction 4 is shown to be directed from the first external electrode 2 on the upper surface of the first piezoelectric element 1 to the first external electrode 2 on the lower surface. FIG. 30 is a schematic diagram of the distortion of a piezoelectric element after polarization at different voltages according to an embodiment of the present application. FIG. 30(a) is a structural schematic diagram of a piezoelectric element after polarization when no current is applied, and FIG. 30(b) is a schematic diagram of the distortion of a piezoelectric element after polarization when current is applied. As shown in FIG. 30(a), with reference to the polarization direction 16, two first piezoelectric elements 1 are attached to the upper and lower two surfaces of a metal thin plate 17 using a conductive adhesive, respectively, to form a circuit. When the circuit is energized, as shown in FIG. 30(b), the first piezoelectric element 1 on the upper surface of the metal thin plate 17 contracts, and the first piezoelectric element 1 on the lower surface of the metal thin plate 17 expands. Due to this action, the two first piezoelectric elements 1 form an interface with the metal thin plate 17, and are each deformed into a curved shape. This action is deformed into an opposite shape by reversing the direction in which the voltage is applied. Fig. 31 is a schematic diagram of displacement distortion when an AC voltage is applied to a piezoelectric element after polarization according to an embodiment of the present application. As can be seen from Fig. 31, the first piezoelectric elements on the upper and lower surfaces of the metal thin plate 17 repeatedly expand and contract in different directions, generating a curved vibration. The metal thin plate 17 and the first piezoelectric element 1 sandwiched between the upper and lower surfaces thereof together constitute one vibration element. Fig. 32 is a schematic diagram of the vibration element according to an embodiment of the present application curved and deformed up and down around the support member.As shown in FIG. 32, the support member 18 is fixed to two ends of the vibration element. This causes the vibration element to curve up and down around the support member 18. FIG. 32(a) is a structural diagram of the vibration element around the support member when no current is applied, and FIG. 32(b) is a schematic diagram of the distortion of the vibration element around the support member when current is applied. FIG. 33 is a schematic diagram of the displacement distortion when an AC voltage is applied to the vibration element around the support member according to one embodiment of the present application. As shown in FIG. 33, when the support member 18 of the vibration element is connected to the back of the OLED display panel and a drive signal is input, the curved vibration is transmitted to the surface of the OLED display panel through the support member 18, and vibration is generated on the surface of the OLED display panel as in the above embodiment. Therefore, the form of the first piezoelectric element may adopt a unimorph type structure and a bimorph type structure that automatically induces curved vibration.

[0058] The embodiment of the present application provides a flat panel piezoelectric speaker vibrator applied to the above speaker system, and Fig. 34 is a structural schematic diagram of a flat panel piezoelectric speaker vibrator according to another embodiment of the present application. As shown in Fig. 34, nine layers of single piezoelectric ceramic sheets are provided, and the fifth layer is an internal isolation layer, and the polarization direction of the single piezoelectric ceramic sheet above the internal isolation layer is opposite to the direction of the electric field applied during use, thereby generating a shortening displacement, and the polarization direction of the single piezoelectric ceramic sheet below the internal isolation layer is the same as the direction of the electric field applied during use, thereby generating an expansion / contraction displacement, and further increasing the overall displacement amount.

[0059] 35 and 36 are structural schematic diagrams of a flat panel piezoelectric speaker vibrator according to another embodiment of the present application. Among them, the aspect ratios of the piezoelectric ceramic sheets shown in FIG. 35 and FIG. 26 are different. As shown in FIG. 35 and FIG. 36, the piezoelectric ceramic sheet in the flat panel piezoelectric speaker vibrator is rectangular, and the aspect ratio is 3:1 to 10:1. The flat panel piezoelectric speaker vibrator includes a flat panel piezoelectric speaker vibrator used for mid-high frequency sound production and a flat panel piezoelectric speaker vibrator used for mid-low frequency sound production. Among them, the area of ​​the piezoelectric ceramic sheet in the flat panel piezoelectric speaker vibrator used for mid-high frequency sound production is 1 / 10 of the area of ​​the piezoelectric ceramic sheet in the flat panel piezoelectric speaker vibrator used for mid-low frequency sound production.

[0060] During polarization, the electrode added to 3-1 is the negative electrode, that of 3-2 is the positive electrode, and that of 3-3 is the ground GND electrode, so that the polarization direction is ensured to be downward in the first, third, seventh and ninth piezoelectric ceramic sheets, and upward in the second, fourth, sixth and eighth piezoelectric ceramic sheets, as shown in FIG. 34. When the piezoelectric ceramics function normally, the negative electrode 3-1 and the positive electrode 3-2 are soldered and turned on by using conductive leads, so that the electric field positive electrode is introduced, and 3-3 is the GND electrode circuit is accessed. The direction of the electric field generated inside the piezoelectric ceramic sheet is downward in the first, third, sixth and eighth piezoelectric ceramic sheets, and upward in the second, fourth, seventh and ninth piezoelectric ceramic sheets, as shown in FIG. 34. As a result, the polarization direction of the upper half of the piezoelectric ceramic sheet, located above the fifth internal isolation layer, is opposite to the direction of the applied electric field, and the polarization direction of the lower half of the piezoelectric ceramic sheet, located below the fifth internal isolation layer, is the same as the direction of the applied electric field, thereby generating a displacement form and increasing the amount of displacement, which in turn increases the phase amplitude and improves the sound volume.

[0061] The flat panel piezoelectric speaker transducer is manufactured by using lead zirconate titanate (PZT), potassium sodium niobate (KNN) or other series of lead-free or lead-containing materials, and the lamination process is carried out by using a press or some isostatic pressure equipment, and the pressure is 100-300 MPa / cm 2 The flat panel piezoelectric speaker vibrator is pressed using a pressure of 0.01 mm, and the internal electrodes of the flat panel piezoelectric speaker vibrator are manufactured using a metal material of silver / palladium (Ag / Pd), and the external electrodes are manufactured using a metal material such as gold (Au) or silver (Ag).

[0062] The speaker system according to the present invention has a small volume, has small distortion between video and audio, reduces spatial deviation between video and audio, and can provide video display with a more live feel.

Claims

1. a piezoelectric speaker and an electromagnetic speaker, the crossover frequency between the piezoelectric speaker and the electromagnetic speaker being 500 Hz or more, the piezoelectric speaker being provided on a rear surface of the display device, and the electromagnetic speaker being provided on a bottom surface of the display device; the display device is an OLED display; The piezoelectric speaker includes a piezoelectric speaker vibrator, and two different sized piezoelectric speaker vibrators are attached to the rear surface of the OLED display. The speaker system further comprises a digital audio processing and driving circuit, the digital audio processing and driving circuit comprising a high frequency left channel output circuit, a high frequency right channel output circuit and a low frequency output circuit each connected to an audio signal amplifier, the high frequency left channel output circuit and the high frequency right channel output circuit each being provided with a high pass filter, the output terminals of the high pass filters being respectively connected to the two different sized piezoelectric speaker transducers, the high pass filters performing a first order 6 dB / oct processing on the input audio signal, the low frequency output circuit being provided with a low pass filter, the output terminals of the low pass filter being connected to the electromagnetic speaker, the low pass filter performing a -6 dB / oct processing on the input audio signal, The piezoelectric speaker vibrator adopts a unimorph type structure or a bimorph type structure that is equipped with a piezoelectric element and automatically induces a curved vibration, the piezoelectric speaker vibrator is provided with a metal thin plate, and two piezoelectric elements are bonded and fixed to the upper and lower sides of the metal thin plate with a conductive adhesive, and external electrodes that are not conductive to each other are provided on both the upper and lower surfaces of the piezoelectric ceramic plate of each piezoelectric element, and the two piezoelectric elements are provided corresponding to the upper and lower sides of the metal thin plate along the polarization direction, and after an external drive signal is sent, the piezoelectric element on the upper side of the metal thin plate contracts and the piezoelectric element on the lower side of the metal thin plate expands, and support members for connecting and fixing to the OLED display are provided on both ends of the metal thin plate, and after an AC electric signal is sent from the outside, the piezoelectric elements on the upper and lower sides of the metal thin plate repeatedly expand and contract in different directions to realize up and down curved vibration of the piezoelectric speaker vibrator centered on the support member, thereby generating a curved vibration. Speaker system.

2. The crossover frequency between the piezoelectric speaker and the electromagnetic speaker is 3000 Hz or less.

2. The speaker system according to claim 1.

3. The size of the OLED display is 420 mm x 240 mm x 0.7 mm, and two different sizes of piezoelectric speaker transducers, a rectangular piezoelectric speaker transducer of 45 mm x 15 mm x 0.5 mm and a rectangular piezoelectric speaker transducer of 90 mm x 30 mm x 0.5 mm, are attached to the back surface of the OLED display.

2. The speaker system according to claim 1.

4. The size of the OLED display is 1770 mm x 996 mm x 0.7 mm, and two different sizes of piezoelectric speaker transducers, a rectangular piezoelectric speaker transducer of 45 mm x 15 mm x 0.5 mm and a rectangular piezoelectric speaker transducer of 90 mm x 30 mm x 0.5 mm, are attached to the rear surface of the OLED display.

2. The speaker system according to claim 1.

5. The piezoelectric speaker transducer comprises a piezoelectric element that has undergone a high-voltage electric field polarization process, the piezoelectric element comprises 10 to 20 layers of piezoelectric ceramic sheets made of lead zirconate titanate material and having a thickness of 30 μm, the first external electrode and the second external electrode are printed on the upper and lower sides of the piezoelectric element, respectively, the upper or lower side of the piezoelectric element is provided with a third external electrode that is not electrically connected to the external electrode on the same side, the third external electrode bypasses a side surface of the piezoelectric element and then connects to an external electrode on a different side, and the high-voltage electric field polarization process includes applying a high-voltage electric field to the first external electrode, the second external electrode, and the third external electrode.

5. A speaker system according to claim 3 or 4.

6. The speaker system according to any one of claims 1 to 4 is applied to a television, and when it is determined that the thickness range of the television is 0.5mm to 2.0mm and the audio signal output by the television is less than 500Hz, an electromagnetic speaker is adopted to broadcast sound; when it is determined that the thickness range of the television is 0.5mm to 2.0mm and the audio signal output by the television is greater than 3000Hz, the piezoelectric speaker is adopted to broadcast sound. How to apply speaker systems.

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