Display device

Abstract

The present disclosure aims to improve the sound quality of a display device that emits sound from a display panel. The display device includes a piezoelectric element that vibrates in response to an input audio signal; a display panel configured to display an image; and an elastic member configured to connect a portion of the piezoelectric element to the display panel to transmit the vibration of the piezoelectric element to the display panel.

Description

[0001] This case is a divisional application, and its parent case is an application with an application date of December 3, 2020 (priority date of December 4, 2019), application number 202011407749.X, and invention name “Display Device”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit under 35 U.S.C. §119(a) of Japanese Patent Application No. 2019-219414 filed in the Japan Patent Office on December 4, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0004] The present disclosure relates to a display device. Background Art

[0005] Patent Document 1 discloses a display device including a display panel and an actuator. The display device of Patent Document 1 has a function of vibrating the display panel by controlling the actuator.

[0006] [Related technical literature]

[0007] [Patent Document]

[0008] (Patent Document 1) Patent Application No. 10-2018-0077582 Summary of the Invention

[0009] In order to improve the sense of reality, a display panel that emits sound by using the display panel itself as a speaker is being considered. However, although the structure disclosed in Patent Document 1 can use the display panel as a speaker, the sound quality may not be good enough.

[0010] The present disclosure is directed to improving the sound quality of a display device that emits sound from a display panel.

[0011] According to one aspect of the present disclosure, a display device is provided, including: a piezoelectric element that vibrates according to an input audio signal; a display panel that is configured to display an image; and an elastic member that is configured to connect a portion of the piezoelectric element with the display panel to transmit the vibration of the piezoelectric element to the display panel.

[0012] According to another aspect of the present disclosure, a display device is provided, including: a piezoelectric element, the piezoelectric element including a first vibration portion and a second vibration portion extending in different directions when viewed from above, the piezoelectric element vibrating according to an input audio signal; a display panel, the display panel being configured to display an image; and an elastic member configured to connect a portion of the piezoelectric element to the display panel to transmit the vibration of the piezoelectric element to the display panel.

[0013] According to another aspect of the present disclosure, a display device is provided, including: a plurality of piezoelectric elements, which vibrate according to an input audio signal; and a display panel, which is configured to display an image, wherein each of the plurality of piezoelectric elements is connected to the display panel to transmit the vibration to the display panel, and a first piezoelectric element and a second piezoelectric element among the plurality of piezoelectric elements have different frequency characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification. They illustrate embodiments of the disclosure and together with the description serve to explain the principles of embodiments of the disclosure.

[0015] Figure 1 is a schematic block diagram of a display device according to a first embodiment.

[0016] Figure 2 is a plan view showing a schematic configuration of a piezoelectric element according to the first embodiment.

[0017] Figure 3 is a cross-sectional view showing a schematic configuration of a piezoelectric element according to the first embodiment.

[0018] Figure 4 is a cross-sectional view showing the structure of the piezoelectric element according to the first embodiment in more detail.

[0019] Figure 5 is a schematic diagram illustrating deformation of the piezoelectric element to which voltage is applied according to the first embodiment.

[0020] Figure 6 is a schematic diagram illustrating deformation of the piezoelectric element to which voltage is applied according to the first embodiment.

[0021] Figure 7 is a cross-sectional view showing the structure of a piezoelectric element according to a comparative example.

[0022] Figure 8 is a schematic diagram illustrating a vibration model according to a comparative example.

[0023] Figure 9 is a schematic diagram illustrating a vibration model according to the first embodiment.

[0024] Figure 10 is a plan view showing a schematic configuration of a piezoelectric element according to a second embodiment.

[0025] Figure 11 is a cross-sectional view showing the structure of a piezoelectric element according to a third embodiment.

[0026] Figure 12 is a plan view showing a schematic configuration of a piezoelectric element according to a fourth embodiment.

[0027] Figure 13 is a cross-sectional view showing a schematic configuration of a piezoelectric element according to a fourth embodiment.

[0028] Figure 14 is a cross-sectional view showing the structure of a piezoelectric element according to the fourth embodiment in more detail.

[0029] Figure 15 is a plan view showing a schematic configuration of a piezoelectric element according to a fifth embodiment.

[0030] Figure 16 is a plan view showing a schematic configuration of a piezoelectric element according to a sixth embodiment.

[0031] Figure 17 is a plan view showing a schematic configuration of a piezoelectric element according to a seventh embodiment.

[0032] Figure 18 is a plan view showing the design of a piezoelectric element according to an eighth embodiment. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In each figure, the same reference numerals are assigned to elements having common functions, and their repeated descriptions will be omitted or simplified.

[0034] <First embodiment>

[0035] Figure 1 1 is a schematic block diagram of a display device 1 according to the first embodiment. For example, the display device 1 of this embodiment can be used for an image output device of a computer, a television receiver, a smartphone, a game console, etc., but the present disclosure is not particularly limited thereto.

[0036] like Figure 1 As shown, the display device 1 includes a piezoelectric element 10, a display panel 20, an elastic member 30, a first controller 40, a second controller 50, a data driving circuit 60, and a gate driving circuit 70. The display device 1 is a device that displays an image on the display panel 20 based on input RGB data and the like and generates sound based on input audio signals and the like.

[0037] The display panel 20 includes a plurality of pixels P arranged to form a plurality of rows and a plurality of columns. For example, the display device 1 may be an organic light-emitting diode (OLED) display using OLED as a light-emitting element of the pixel P. When the display device 1 is capable of displaying a color image, the pixel P may be a sub-pixel that displays any one of a plurality of colors (e.g., red (R), green (G), and blue (B)) constituting the color image.

[0038] The piezoelectric element 10 is an element that moves due to the inverse piezoelectric effect when a voltage based on an input audio signal is applied. For example, the piezoelectric element 10 may be an element such as a bimorph element or a unimorph element that bends and moves in response to the voltage. Since the input audio signal is typically an alternating current (AC) voltage, the piezoelectric element 10 functions as a vibrating element that vibrates in response to the input audio signal.

[0039] The elastic member 30 is made of an elastic material. Typically, a material such as rubber is used as the material for the elastic member 30, whose elastic modulus is smaller than that of the piezoelectric element 10 and the display panel 20. A portion of the piezoelectric element 10 and a portion of the display panel 20 are connected via the elastic member 30. As a result, the vibration of the piezoelectric element 10 is transmitted to the display panel 20, and the display panel 20 produces sound based on the input audio signal.

[0040] The host system 2 is a system comprising one or more devices that controls the display device 1 by providing image signals (e.g., RGB data), audio signals, and timing signals (vertical synchronization signal, horizontal synchronization signal, data enable signal, etc.). For example, the host system 2 may be a television system, a set-top box, a navigation system, an optical disc player, a computer, a home theater system, a video phone system, etc. Furthermore, the display device 1 and the host system 2 may be integrated devices or separate devices.

[0041] The first controller 40 supplies a voltage to the piezoelectric element 10 according to the audio signal and the timing signal input from the host system 2 .

[0042] The second controller 50 controls the data driving circuit 60 and the gate driving circuit 70 based on the image data and timing signals input from the host system 2. The data driving circuit 60 supplies data voltages and the like to the plurality of pixels P via a driving line 61 provided for each column of the plurality of pixels P. The gate driving circuit 70 supplies control signals to the plurality of pixels P via a driving line 71 provided for each row of the plurality of pixels P. In addition, each of the driving lines 61 and the driving lines 71 may be provided in plurality.

[0043] Each of the first controller 40, the second controller 50, the data driving circuit 60, and the gate driving circuit 70 may be configured as one or more semiconductor integrated circuits. In addition, some or all of the first controller 40, the second controller 50, the data driving circuit 60, and the gate driving circuit 70 may be integrally configured as one semiconductor integrated circuit.

[0044] Figure 2 1 is a plan view showing a schematic configuration of a piezoelectric element 10 according to the first embodiment. Figure 3 1 is a schematic cross-sectional view showing the configuration of the piezoelectric element 10 according to the first embodiment. Figure 2 and Figure 3 The design of the piezoelectric element 10 is described below. Figure 2 , the rectangular outline of the display panel 20 schematically illustrates the exterior of the display panel 20 .

[0045] like Figure 3 As shown, the surface of the display panel 20 on which an image is displayed is the image display surface 20a, and the surface of the display panel 20 opposite to the image display surface 20a is the rear surface 20b. In this case, Figure 2 is a plan view of the display panel 20 viewed from the rear surface 20 b . Figure 2 The coordinate axes are shown, wherein the horizontal direction of the image display surface 20a corresponds to the x-axis, the vertical direction of the image display surface 20a corresponds to the z-axis, and the depth direction of the image display surface 20a corresponds to the y-axis. In addition, the direction from the rear surface 20b toward the image display surface 20a is the positive direction of the y-axis. Figure 3 It is along Figure 2 A cross-sectional view taken along line AA' in FIG.

[0046] The piezoelectric element 10 has a flat plate shape. Figure 2 As shown, when viewed from above, the piezoelectric element 10 has a rectangular shape having a long side direction (z direction in the figure) and a short side direction (x direction in the figure). Therefore, when viewed from the long side direction of the cross section (line AA'), deformation such as bending occurs. The piezoelectric element 10 is arranged so that the long side direction is perpendicular to the end of the display panel 20.

[0047] The elastic member 30 is connected at a position including the center in the longitudinal direction of the piezoelectric element 10. Since the center in the longitudinal direction of the piezoelectric element 10 becomes the center of vibration, the vibration is effectively transferred to the display panel 20.

[0048] like Figure 3As shown, the piezoelectric element 10 has a first main surface 10a and a second main surface 10b. The elastic member 30 connects the first main surface 10a of the piezoelectric element 10 and the rear surface 20b of the display panel 20. As described above, the piezoelectric element 10 and the elastic member 30 are arranged on the rear surface 20b of the display panel 20 so as not to interfere with the user's viewing of the image display surface 20a.

[0049] The elastic member 30 is connected to only a portion of the first major surface 10a of the piezoelectric element 10. Since both ends of the piezoelectric element 10 in the longitudinal direction are suspended, the displacement of the bending vibration at both ends in the longitudinal direction is large, and thus the vibration of the piezoelectric element 10 is less likely to be hindered.

[0050] Figure 4 is a cross-sectional view showing the structure of the piezoelectric element 10 according to the first embodiment in more detail. Figure 4 Direction and Figure 3 The direction is different, similar to Figure 3 , Figure 4 It is along Figure 2 In addition, Figure 4 A connection relationship between electrodes included in the piezoelectric element 10 is schematically shown using a circuit diagram in order to describe a method of inputting an audio signal to the piezoelectric element 10 .

[0051] Figure 4 The piezoelectric element 10 shown in has a structure called a bimorph in which two piezoelectric layers are stacked. The piezoelectric element 10 includes electrodes 101, 103 and 105 and piezoelectric layers 102 and 104. The electrode 101 (first electrode) installed on the side closest to the display panel 20 is connected to the elastic member 30. The electrode 101 and the electrode 103 (second electrode) are arranged so that the piezoelectric layer 102 (first piezoelectric layer) is interposed between them in the thickness direction. The electrode 103 and the electrode 105 (third electrode) are arranged so that the piezoelectric layer 104 (second piezoelectric layer) is interposed between them in the thickness direction. The arrows shown inside the piezoelectric layers 102 and 104 represent the polarization directions of the piezoelectric layers 102 and 104. That is, the polarization directions of the piezoelectric layer 102 and the piezoelectric layer 104 are the same. In addition, the wires for applying voltage to the electrodes can be connected to the electrodes 101, 103 and 105 by welding or the like, but in Figure 4 These lines are omitted from the illustration.

[0052] Since a voltage is applied to the piezoelectric element 10 based on the audio signal, the voltage can be regarded as an AC voltage according to the frequency of the sound to be generated. Figure 4, the AC voltage is represented by the circuit symbol V of the AC power supply. One terminal of the AC power supply V is connected to the electrodes 101 and 105, and the other terminal thereof is connected to the electrode 103. In other words, voltages having the same phase are applied to the electrodes 101 and 105, voltages having opposite phases are applied to the electrodes 101 and 103, and voltages having opposite phases are also applied to the electrodes 103 and 105. Therefore, voltages having opposite directions are applied to the piezoelectric layer 102 and the piezoelectric layer 104.

[0053] The material of the piezoelectric layers 102 and 104 is not particularly limited, but a material such as lead zirconate titanate having excellent piezoelectricity can be used because it can increase the displacement amount. Figure 4 Although not shown in the configuration, the periphery of the piezoelectric element 10 may be covered with an insulator such as resin to avoid short circuits with other members.

[0054] Figure 5 and Figure 6 1 is a schematic diagram showing a deformation of the piezoelectric element 10 to which a voltage is applied according to the first embodiment. Figure 4 As shown, the polarization directions of the piezoelectric layers 102 and 104 are the same, and voltages in opposite directions are applied to the piezoelectric layers 102 and 104. Therefore, the expansion and contraction directions of the piezoelectric layers 102 and 104 are opposite.

[0055] like Figure 5 As shown, when the piezoelectric layer 102 deforms and contracts in the lateral direction, the piezoelectric layer 104 deforms and expands in the lateral direction. As a result, the end of the piezoelectric element 10 bends toward the display panel 20. In this case, the display panel 20 deforms due to the stress applied in the direction toward the piezoelectric element 10.

[0056] like Figure 6 As shown in FIG. 1 , when the piezoelectric layer 102 is deformed and expanded in the short-side direction, the piezoelectric layer 104 is deformed and contracted in the short-side direction. As a result, the end of the piezoelectric element 10 is bent in a direction away from the display panel 20. In this case, the display panel 20 is deformed by the stress applied in the direction away from the piezoelectric element 10.

[0057] When an AC voltage based on an audio signal is applied to the piezoelectric element 10, Figure 5 Status and Figure 6 The state is repeated alternately at the frequency of the sound. As described above, the vibration of the piezoelectric element 10 is transmitted to the display panel 20, and the display panel 20 vibrates. Therefore, since the sound based on the audio signal is emitted from the display panel 20, the display panel 20 functions as a speaker.

[0058] In this embodiment, reference will be made to Figures 7 to 9Effects obtained by connecting a portion of the piezoelectric element 10 and the display panel 20 through the elastic member 30 are described in more detail. Figure 7 is a cross-sectional view showing the configuration of a piezoelectric element 10 according to a comparative example. Figure 8 is a schematic diagram illustrating a vibration model according to a comparative example. Figure 9 is a schematic diagram illustrating a vibration model according to the first embodiment.

[0059] like Figure 7 As shown, in the comparative example, the front surface of the piezoelectric element 10 is directly connected to the display panel 20. Even in this configuration, the displacement of the piezoelectric element 10 is transmitted to the display panel 20, thereby allowing the display panel 20 to function as a speaker.

[0060] In the vibration model according to the comparative example, as Figure 8 As shown, springs S1 and S2 are connected to both ends of mass points representing the piezoelectric element 10 and the display panel 20. The piezoelectric element 10 having mass m1 and the display panel 20 having mass m2 are directly connected.

[0061] A spring S1 having a spring constant k1 is connected to the piezoelectric element 10, and a spring S2 having a spring constant k2 is connected to the display panel 20. The spring S1 is an elastic model of the piezoelectric element 10. The spring S2 is a model of the display panel 20 itself or a member such as a housing for restraining the display panel 20. In addition, the two ends in this vibration model are generally fixed ends.

[0062] In the vibration model of the comparative example, the piezoelectric element 10 and the display panel 20 can be replaced by a point mass of m1+m2. When a voltage is applied to the piezoelectric element 10, the force generated by the piezoelectric element 10 causes the piezoelectric element 10 and the display panel 20, which have a mass of m1+m2, to vibrate as a whole. Here, since the display panel 20 is much larger than the piezoelectric element 10, the mass m1+m2 is much larger than the mass m1. Since the force generated by the piezoelectric element 10 is applied to an object with a very large mass, the acceleration to which the piezoelectric element 10 and the display panel 20 are subjected due to the force is small. Therefore, the displacement of the piezoelectric element 10 and the display panel 20 is not very large, and in the configuration of the comparative example, the sound pressure of the sound emitted from the display panel 20 may be insufficient.

[0063] On the other hand, in the vibration model according to the present embodiment, as Figure 9 As shown, a spring S3 having a spring constant k3 is connected between mass points representing the piezoelectric element 10 and the display panel 20. The spring S3 is an elastic model of the elastic member 30. The piezoelectric element 10 having a mass m1 and the display panel 20 having a mass m2 are connected via the spring S3.

[0064] In the vibration model of the present embodiment, the piezoelectric element 10 and the display panel 20 move independently. The force generated when a voltage is applied to the piezoelectric element 10 causes the piezoelectric element 10 having a mass m1 to vibrate. Since the mass of the object to which the force is applied is smaller than that in the comparative example, the acceleration to which the piezoelectric element 10 is subjected due to the force is greater than that in the comparative example. Therefore, the piezoelectric element 10 resonates within a large displacement range. Since the displacement of the piezoelectric element 10 is gradually transmitted to the display panel 20 through the spring S3, it is difficult for the movement to be hindered by the mass of the display panel 20 as in the comparative example. Therefore, in the present embodiment, the displacement can be increased and the sound pressure can be increased when compared with the comparative example.

[0065] As described above, according to the present embodiment, when the display panel 20 functions as a speaker, the display device 1 capable of improving the sound quality by increasing the sound pressure of the sound generated by the display panel 20 is provided.

[0066] In addition, in this embodiment, the vibration source is the piezoelectric element 10, but the sound source is the display panel 20, which has a large mass and a low natural frequency. Therefore, compared with a configuration in which sound is generated directly from the piezoelectric element 10 or a configuration in which sound is generated from a member having a high natural frequency (for example, a configuration in which the piezoelectric element 10 is connected to a small partition separate from the display panel 20), the sound pressure in the bass range can be increased.

[0067] <Second embodiment>

[0068] In this embodiment, a modified example of the design of the piezoelectric element 10 according to the first embodiment will be described. Since the basic configuration of the display device 1, the structure of the piezoelectric element 10, etc. are the same as those in the first embodiment, their description will be omitted.

[0069] Figure 10 1 is a plan view showing a schematic configuration of a piezoelectric element 10 according to the second embodiment. Figure 10 As shown, in this embodiment, the piezoelectric element 10 is disposed such that the long side direction of the piezoelectric element 10 is not perpendicular to either end of the display panel 20 .

[0070] When the piezoelectric element 10 has a rectangular shape, in the distribution of vibrations generated in the display panel 20, the main component of the vibrations is the component directed in the long side direction of the piezoelectric element 10. As in the first embodiment, when the long side direction of the piezoelectric element 10 is perpendicular to the end of the display panel 20, the vibrations generated by the piezoelectric element 10 and the vibrations reflected from the end of the display panel 20 can be enhanced to generate resonance. Resonance may cause noise. On the other hand, in this embodiment, since the long side direction of the piezoelectric element 10 is not perpendicular to either end of the display panel 20, it is difficult to generate resonance due to the above factors, thereby reducing noise.

[0071] Therefore, according to the present embodiment, the same effects as in the first embodiment are obtained while reducing noise due to resonance caused by reflection from the end surface of the display panel 20, thereby providing the display device 1 with improved sound quality.

[0072] In addition, since vibration enhancement occurs in the configuration of the first embodiment, in some cases, it is possible to increase the sound pressure, adjust the frequency characteristics, etc. by utilizing vibration enhancement. Therefore, depending on design conditions such as required characteristics and design constraints, in some cases, it is appropriate to make the long side direction of the piezoelectric element 10 perpendicular to the end of the display panel 20 as in the first embodiment.

[0073] <Third embodiment>

[0074] In this embodiment, a modified example of the cross-sectional structure of the piezoelectric element 10 according to the first embodiment will be described. Since the basic configuration of the display device 1, the structure of the piezoelectric element 10, etc. are the same as those in the first embodiment, their description will be omitted.

[0075] Figure 11 is a cross-sectional view showing the structure of the piezoelectric element 10 according to the third embodiment. The position of the cross section is Figure 3 and Figure 4 The same as in .

[0076] The piezoelectric element 10 includes electrodes 111, 113, 115 and 117, piezoelectric layers 112 and 116, and an insulating layer 114. The electrode 111 (first electrode) mounted on the side closest to the display panel 20 is connected to the elastic member 30. The electrode 111 and the electrode 113 (second electrode) are arranged so that the piezoelectric layer 112 (first piezoelectric layer) is interposed between them in the thickness direction. The electrode 115 (third electrode) and the electrode 117 (fourth electrode) are arranged so that the piezoelectric layer 116 (second piezoelectric layer) is interposed between them in the thickness direction. The insulating layer 114 is arranged between the electrode 113 and the electrode 115. The insulating layer 114 is a layer that ensures the insulation performance between the electrode 113 and the electrode 115. The arrows shown inside the piezoelectric layers 112 and 116 represent the polarization directions of the piezoelectric layers 112 and 116. That is, the polarization directions of the piezoelectric layer 112 and the piezoelectric layer 116 are opposite.

[0077] One terminal of an AC power source V representing a voltage based on an audio signal is connected to the electrodes 111 and 115, and the other terminal thereof is connected to the electrodes 113 and 117. In other words, a voltage having the same phase is applied to the electrodes 111 and 115. A voltage having a phase opposite to that of the voltage input to the electrodes 111 and 115 is applied to the electrodes 113 and 117. Therefore, voltages in the same direction are applied to the piezoelectric layers 112 and 116.

[0078] Even in this embodiment, when one of the two piezoelectric layers contracts in the lateral direction, bending vibration occurs in the same manner as in the first embodiment. Therefore, even in this embodiment, the same effects as in the first embodiment can be achieved. As described above, the structure of the piezoelectric element 10, the structure of the electrodes, and the like are not limited to those in the first embodiment, and various structures can be applied.

[0079] For example, the piezoelectric element 10 may have a structure called a unimorph in which a piezoelectric layer, a pair of electrodes (the piezoelectric layer is interposed therebetween), and a vibration plate are stacked. However, in order to improve the conversion efficiency between voltage and displacement, a Figure 4 or Figure 11 The bimorph structure shown in is suitable.

[0080] <Fourth embodiment>

[0081] In this embodiment, a modified example of the structure of the piezoelectric element 10 according to the first embodiment will be described. Since the basic configuration and the like of the display device 1 are the same as those in the first embodiment, description thereof will be omitted.

[0082] Figure 12 is a plan view showing a schematic configuration of a piezoelectric element 10 according to a fourth embodiment. Figure 13 is a cross-sectional view showing a schematic configuration of a piezoelectric element 10 according to a fourth embodiment. Figure 12 and Figure 13 The design of the piezoelectric element 10 is described.

[0083] like Figure 12 As shown, the piezoelectric element 10 of this embodiment includes a first vibrating portion 12 and a second vibrating portion 14 extending in different directions when viewed from above. The configuration of the first vibrating portion 12 is the same as that of the piezoelectric element 10 of the first embodiment. When viewed from above, the first vibrating portion 12 has a rectangular shape having a long side direction (z direction in the figure) and a short side direction (x direction in the figure). The second vibrating portion 14 extends in a direction different from that of the first vibrating portion 12. That is, when viewed from above, the second vibrating portion 14 has a rectangular shape having a long side direction (x direction in the figure) and a short side direction (z direction in the figure). The long side direction of the first vibrating portion 12 and the long side direction of the second vibrating portion 14 are perpendicular to each other. In addition, the long side direction of the first vibrating portion 12 and the long side direction of the second vibrating portion 14 are both perpendicular to the end of the display panel 20.

[0084] like Figure 13As shown, the first vibrating portion 12 has a first main surface 12a and a second main surface 12b. The elastic member 30 connects the first main surface 12a of the first vibrating portion 12 and the rear surface 20b of the display panel 20. The elastic member 30 is only connected to a portion of the first main surface 12a of the first vibrating portion 12. As described above, the piezoelectric element 10 and the elastic member 30 are disposed on the rear surface 20b of the display panel 20 so as not to interfere with the user's viewing of the image display surface 20a.

[0085] The second vibrating portion 14 is connected to only a portion of the second major surface 12b of the first vibrating portion 12. Consequently, both ends of the first vibrating portion 12 in the longitudinal direction are suspended in the air, and both ends of the second vibrating portion 14 in the longitudinal direction are suspended in the air. When both ends of the piezoelectric element 10 in the longitudinal direction are suspended in the air, the displacement of the flexural vibration is greater at both ends in the longitudinal direction, and thus, the vibration of the piezoelectric element 10 is less likely to be hindered.

[0086] Figure 14 is a cross-sectional view showing the structure of the piezoelectric element 10 according to the fourth embodiment in more detail. Figure 14 Direction and Figure 13 The direction is different, similar to Figure 13 , Figure 14 It is along Figure 12 In addition, Figure 14 A connection relationship between electrodes included in the piezoelectric element 10 is schematically shown using a circuit diagram in order to describe a method of inputting an audio signal to the piezoelectric element 10 .

[0087] Figure 14 The piezoelectric element 10 shown in FIG has a structure in which two bimorphs are stacked. The piezoelectric element 10 includes a first vibrating portion 12 and a second vibrating portion 14. The structure of the first vibrating portion 12 is the same as that of the piezoelectric element 10 of the first embodiment. Figure 14 In the embodiment, the insulating layer 120 is provided between the first vibrating portion 12 and the second vibrating portion 14 , but this is not essential.

[0088] The second vibrating portion 14 includes electrodes 121, 123, and 125, and piezoelectric layers 122 and 124. Electrode 121, mounted on the side closest to the first vibrating portion 12, is connected to the insulating layer 120. Electrodes 121 and 123 are arranged so that the piezoelectric layer 122 is interposed between them in its thickness direction. Electrodes 123 and 125 are arranged so that the piezoelectric layer 124 is interposed between them in its thickness direction. The arrows shown within piezoelectric layers 122 and 124 indicate the polarization directions of the piezoelectric layers 122 and 124. In other words, the polarization directions of piezoelectric layers 122 and 124 are the same.

[0089] One terminal of an AC power source V representing a voltage based on an audio signal is connected to the electrodes 101, 105, 121, and 125, and the other terminal thereof is connected to the electrodes 103 and 123. In other words, voltages having the same phase are applied to the electrodes 101, 105, 121, and 125. A voltage having a phase opposite to that of the voltage input to the electrodes 101, 105, 121, and 125 is applied to the electrodes 103 and 123. Therefore, voltages in the same direction are applied to the piezoelectric layers 102, 104, 122, and 124.

[0090] Even in both the first vibrating portion 12 and the second vibrating portion 14, when one of the two piezoelectric layers contracts laterally, the other expands laterally. Therefore, both the first vibrating portion 12 and the second vibrating portion 14 flexurally vibrate in the same manner as in the first embodiment. Furthermore, by setting the polarization direction and voltage direction as described above, the first vibrating portion 12 and the second vibrating portion 14 vibrate in phase with the audio signal. Consequently, the vibrations generated by the first vibrating portion 12 and the second vibrating portion 14 are amplified, thereby improving vibration efficiency.

[0091] According to this embodiment, similar to the first embodiment, there is provided a display device 1 capable of improving sound quality by increasing the sound pressure of the sound generated by the display panel 20. In addition, since the piezoelectric element 10 of this embodiment uses two vibration parts, the sound pressure can be further increased compared to the configuration of the first embodiment in which one vibration part is provided.

[0092] In addition, in the first embodiment, since only one vibration portion is provided, the vibration distribution is concentrated in the long side direction of the piezoelectric element 10, that is, the vibration distribution is concentrated in one dimension. Therefore, resonance may occur in the display panel 20, and the noise caused by the resonance may increase. On the other hand, in the present embodiment, since the piezoelectric element 10 includes the first vibration portion 12 and the second vibration portion 14 extending in different directions, the vibration distribution is two-dimensional, and the vibration distribution is difficult to concentrate in a specific part. Therefore, it is difficult for resonance to occur in the display panel 20. Therefore, in the present embodiment, the noise caused by the resonance in the display panel 20 is reduced, and a display device 1 with improved sound quality is provided.

[0093] <Fifth embodiment>

[0094] In this embodiment, a modified example of the design of the piezoelectric element 10 according to the fourth embodiment will be described. Since the basic configuration of the display device 1, the structure of the piezoelectric element 10, etc. are the same as those of the fourth embodiment, their description will be omitted.

[0095] Figure 15 1 is a plan view showing a schematic configuration of a piezoelectric element 10 according to a fifth embodiment. Figure 15As shown, in this embodiment, the piezoelectric element 10 is disposed so that the long side directions of the first vibrating portion 12 and the second vibrating portion 14 are not perpendicular to either end of the display panel 20 .

[0096] As described in the second embodiment, the vibrations generated by the first and second vibrating parts 12 and 14 and the vibrations reflected from the ends of the display panel 20 can be enhanced, thereby generating resonance. Resonance can cause noise. In contrast, in this embodiment, the longitudinal directions of the first and second vibrating parts 12 and 14 are not perpendicular to either end of the display panel 20, making resonance less likely to occur, thereby reducing noise.

[0097] Therefore, according to the present embodiment, the same effects as in the fourth embodiment are obtained, and at the same time, noise due to resonance caused by reflection from the end surface of the display panel 20 is reduced, thereby providing the display device 1 with improved sound quality.

[0098] In addition, in the configuration of the fourth embodiment, in some cases, it is possible to design for improving sound pressure, adjusting frequency characteristics, etc. by utilizing vibration enhancement. Therefore, depending on design conditions such as required characteristics and design constraints, in some cases, it is appropriate to make the long side direction of the piezoelectric element 10 perpendicular to the end of the display panel 20 as in the fourth embodiment.

[0099] <Sixth embodiment>

[0100] In this embodiment, a modified example of the structure of the piezoelectric element 10 according to the fourth embodiment will be described. The basic configuration and the like of the display device 1 are the same as those of the fourth embodiment, and thus description thereof will be omitted.

[0101] Figure 16 1 is a plan view showing a schematic configuration of a piezoelectric element 10 according to a sixth embodiment. Figure 16 As shown, the piezoelectric element 10 of this embodiment includes a first vibrating portion 12, a second vibrating portion 14, and a third vibrating portion 16 extending in different directions when viewed from above. Figure 14 , and only the number of layers is increased, so the description of the cross-sectional structure of the piezoelectric element 10 will be omitted.

[0102] In this embodiment, similar to the first embodiment, a display device 1 is provided that can increase the sound pressure of the sound generated by the display panel 20. Furthermore, since the piezoelectric element 10 of this embodiment uses three vibrating parts, it is possible to further increase the sound pressure compared to the configuration of the fourth embodiment having two vibrating parts. As described above, the number of vibrating parts is not limited to one or two, but can be three or more. As the number of vibrating parts increases, the sound pressure increases.

[0103] In addition, in this embodiment, the vibration distribution is more uniform in two dimensions compared to the configuration of the fourth embodiment. Therefore, it is more difficult for vibration to occur in the display panel 20. Therefore, according to this embodiment, the noise caused by resonance in the display panel 20 is further reduced, and a display device 1 with improved sound quality is provided.

[0104] <Seventh embodiment>

[0105] In this embodiment, a modified example of the structure of the piezoelectric element 10 according to the first embodiment will be described. The basic configuration and the like of the display device 1 are the same as those of the first embodiment, and thus description thereof will be omitted.

[0106] Figure 17 1 is a plan view showing a schematic configuration of a piezoelectric element 10 according to a seventh embodiment. The piezoelectric element 10 has a flat plate shape. Figure 17 As shown in FIG. 1 , the piezoelectric element 10 of this embodiment has a circular shape when viewed from above. The elastic member 30 is connected at a position including the center of the circle of the piezoelectric element 10. Figure 3 and Figure 4 , so their description will be omitted.

[0107] In the present embodiment, similarly to the first embodiment, the display device 1 capable of increasing the sound pressure of the sound generated by the display panel 20 is provided.

[0108] In addition, in this embodiment, since the piezoelectric element 10 has a circular shape, the vibration distribution is uniform in two dimensions. Therefore, for the same reason as in the fourth embodiment, resonance is less likely to occur in the display panel 20. Therefore, according to this embodiment, the noise caused by resonance in the display panel 20 is reduced, thereby providing a display device 1 with improved sound quality.

[0109] <Eighth Embodiment>

[0110] In this embodiment, a modified example of the structure of the piezoelectric element 10 according to the fifth embodiment will be described. The basic configuration and the like of the display device 1 are the same as those of the fifth embodiment, and thus description thereof will be omitted.

[0111] Figure 18 1 is a plan view showing the design of a piezoelectric element 10 according to an eighth embodiment. Figure 18 As shown, in this embodiment, a plurality of piezoelectric elements 10 are provided on the display panel 20. The plurality of piezoelectric elements 10 are arranged in a matrix along the x-direction and the z-direction. The piezoelectric elements 10 are the same as those of the fifth embodiment. Since the plurality of piezoelectric elements 10 are provided on the display panel 20, the sound pressure of the sound generated by the display panel 20 is increased compared to the case of a single piezoelectric element.

[0112] Display panel 20 includes region R1 and region R2. Piezoelectric element 10 in region R1 (first piezoelectric element) and piezoelectric element 10 in region R2 (second piezoelectric element) have different frequency characteristics. For example, the frequency characteristics of the two piezoelectric elements are made different from each other to reduce the deviation of the frequency characteristics of the sound generated by display panel 20.

[0113] Because piezoelectric elements 10 have natural frequencies due to their shape and other factors, they may exhibit frequency characteristic deviations, such as increased sound pressure at specific frequencies. When all piezoelectric elements 10 in display panel 20 have the same characteristics, the frequency characteristic deviations of the multiple piezoelectric elements 10 overlap, potentially resulting in frequency characteristic deviations across the entire display panel 20. In this embodiment, the frequency characteristics of piezoelectric elements 10 in region R1 and piezoelectric elements 10 in region R2 are made different and offset from each other, thereby reducing any potential frequency characteristic deviations that may occur due to these factors.

[0114] Variations in the frequency characteristics of piezoelectric element 10 are primarily caused by the natural frequency of piezoelectric element 10. Therefore, it is desirable to make the natural frequency of piezoelectric element 10 in region R1 different from the natural frequency of piezoelectric element 10 in region R2. For example, by making the natural frequency of piezoelectric element 10 in region R2 lower than that of piezoelectric element 10 in region R1, region R1 functions as a high-pitched sound generation region, while region R2 functions as a low-pitched sound generation region. This provides a display device 1 capable of producing balanced bass and treble.

[0115] The natural frequency of piezoelectric element 10 depends on its shape or material. Therefore, by making the shapes and sound velocities different from each other, piezoelectric element 10 in region R1 and piezoelectric element 10 in region R2 can have different natural frequencies. Examples of material properties that affect the sound velocity of a material include elastic modulus and density. Therefore, it is suitable to use a material that differs in any one of sound velocity, elastic modulus, and density. In addition, when the piezoelectric element 10 in region R1 and the piezoelectric element 10 in region R2 differ only in shape, it is suitable to use the same material.

[0116] As described above, according to the present embodiment, the deviation of the frequency characteristics of the sound generated by the display panel 20 is reduced, thereby providing the display device 1 with improved sound quality.

[0117] In addition, although the piezoelectric element 10 of the fifth embodiment has been described as an example of the piezoelectric element 10 applicable to the present embodiment, the present disclosure is not limited thereto. The piezoelectric element 10 having any structure or design in the first to seventh embodiments may be used, or a piezoelectric element having a structure or design different from that described in the first to seventh embodiments may be used.

[0118] <Other embodiments>

[0119] The above embodiments are merely exemplary aspects to which the present disclosure may be applied, and the technical scope of the present disclosure should not be construed as being limited by the above embodiments. Furthermore, without departing from the spirit and scope of the present disclosure, the present disclosure may be appropriately modified and altered to implement the present disclosure in various aspects. For example, it should be understood that embodiments in which some components of one embodiment are added to embodiments of another embodiment, or some components of one embodiment are replaced by some components of another embodiment, are also embodiments to which the present disclosure may be applied.

[0120] In the above-described embodiment, the device configurations of the display device 1 and the like are merely examples and are not limited to the one shown. For example, the display device 1 may not be an OLED display, but may be a liquid crystal display, a cathode ray tube (CRT) display, or the like. Since the display device 1 is preferably a display capable of efficiently transmitting vibrations from the piezoelectric element 10 to the display panel 20, it is particularly suitable for the display device 1 to be an OLED display having a small cavity.

[0121] According to the present disclosure, in a display device that emits sound from a display panel, the sound quality can be improved.

Claims

1. A display device, comprising: a display panel configured to display an image and comprising a first area and a second area; as well as a plurality of piezoelectric elements, wherein the plurality of piezoelectric elements are arranged on the display panel, The plurality of piezoelectric elements are arranged in a matrix in a first direction and in a second direction perpendicular to the first direction. wherein the first area is configured to generate sound in a high frequency band, and the second area is configured to generate sound in a low frequency band, and The first area is a central area of ​​the display panel, and the second area is a peripheral area surrounding the first area.

2. The display device according to claim 1, wherein Each of the plurality of piezoelectric elements is configured to vibrate based on an audio signal input thereto.

3. The display device according to claim 1, wherein Each of the plurality of piezoelectric elements has a different shape.

4. The display device according to claim 1, wherein Each of the plurality of piezoelectric elements has a different frequency characteristic.

5. The display device according to claim 1, wherein Each of the plurality of piezoelectric elements has a different natural frequency. The display device according to claim 5 , wherein: A natural frequency of a second piezoelectric element in the second region among the plurality of piezoelectric elements is lower than a natural frequency of a first piezoelectric element in the first region among the plurality of piezoelectric elements.

7. The display device according to claim 6, wherein: The material constituting the first piezoelectric element and the material constituting the second piezoelectric element are different in at least one of acoustic velocity, elastic modulus, and density.

8. The display device according to any one of claims 1 to 7, wherein: Each of the plurality of piezoelectric elements includes a first vibration portion having a rectangular shape including a long side direction and a short side direction in a plan view, and At least one end portion of the first vibration portion in the longitudinal direction is in a suspended state.

9. The display device according to any one of claims 1 to 7, wherein: Each of the plurality of piezoelectric elements includes a first vibration portion and a second vibration portion extending in different directions when viewed from above. wherein each of the first vibration portion and the second vibration portion has a rectangular shape including a long side direction and a short side direction when viewed from above, and The position including the center of the first vibration part in the longitudinal direction is connected to the position including the center of the second vibration part in the longitudinal direction.

10. The display device according to any one of claims 1 to 7, wherein: Each of the plurality of piezoelectric elements includes a first vibrating portion, a second vibrating portion, and a third vibrating portion extending in different directions in a plan view. wherein each of the first vibration portion, the second vibration portion, and the third vibration portion has a rectangular shape including a long side direction and a short side direction when viewed from above, and Here, positions including the center of each of the first vibrating portion, the second vibrating portion, and the third vibrating portion in the longitudinal direction overlap with each other.

11. The display device according to any one of claims 1 to 7, wherein: Each of the plurality of piezoelectric elements includes a first vibration portion having a circular shape when viewed from above, and The center of the circular shape including the first vibrating portion is connected to the display panel.

12. A display device comprising: a display panel configured to display an image and comprising a first area and a second area; a plurality of piezoelectric elements, wherein the plurality of piezoelectric elements have a circular shape when viewed from above; as well as an elastic member configured to connect a portion of the plurality of piezoelectric elements and the display panel, wherein the plurality of piezoelectric elements are arranged in a matrix in a first direction and in a second direction perpendicular to the first direction, and The first area is a central area of ​​the display panel, and the second area is a peripheral area surrounding the first area.

13. The display device according to claim 12, wherein: The elastic member is connected at a position of a center of the circular shape including the plurality of piezoelectric elements.

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