Display device

Abstract

To improve sound quality in a display device emitting sound from a display panel.SOLUTION: A display device includes: a piezoelectric element that vibrates according to an input audio signal; a display panel that displays an image; and an elastic member connecting a part of the piezoelectric element and the display panel so as to transmit the vibration of the piezoelectric element to the display panel, in which at least one end of the piezoelectric element is not connected to the elastic member.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a display device. [Background technology]

[0002] 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Korean Patent Publication No. 10-2018-0077582 Summary of the Invention [Problem to be solved by the invention]

[0004] To improve the sense of realism, a display device in which the display panel itself functions as a speaker to emit sound has been studied. However, even if the display panel is made to function as a speaker using the structure described in Patent Document 1, the sound quality may not be sufficient.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to improve sound quality in a display device that emits sound from a display panel. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a display device comprising a piezoelectric element that vibrates in response to an input audio signal, a display panel that displays an image, and an elastic member that connects a portion of the piezoelectric element to the display panel so as to transmit the vibration of the piezoelectric element to the display panel, wherein at least one end of the piezoelectric element is not connected to the elastic member.

[0007] According to another aspect of the present invention, there is provided a display device comprising: a piezoelectric element having a first vibration portion and a second vibration portion extending in different directions in a planar view, the piezoelectric element vibrating in response to an input audio signal; a display panel that displays an image; and an elastic member that connects a portion of the first vibration portion to the display panel so as to transmit the vibration of the piezoelectric element to the display panel.

[0008] According to another aspect of the present invention, there is provided a display device comprising a plurality of piezoelectric elements that vibrate in response to an input audio signal, a display panel that displays an image, and an elastic member that connects a portion of each of the plurality of piezoelectric elements to the display panel so as to transmit the vibration of each of the plurality of piezoelectric elements to the display panel, wherein a first piezoelectric element and a second piezoelectric element among the plurality of piezoelectric elements have different frequency characteristics, and at least one end of the piezoelectric element is not connected to the elastic member. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the sound quality in a display device that emits sound from a display panel. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a schematic configuration of a display device according to a first embodiment. [Figure 2] 1 is a plan view showing a schematic configuration of a piezoelectric element according to a first embodiment. [Figure 3] 1 is a cross-sectional view showing a schematic configuration of a piezoelectric element according to a first embodiment. [Figure 4] FIG. 2 is a cross-sectional view showing the structure of the piezoelectric element according to the first embodiment in more detail. [Figure 5] 3A and 3B are schematic diagrams showing deformation when a voltage is applied to the piezoelectric element according to the first embodiment. [Figure 6] 3A and 3B are schematic diagrams showing deformation when a voltage is applied to the piezoelectric element according to the first embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing the structure of a piezoelectric element according to a comparative example. [Figure 8] FIG. 10 is a schematic diagram showing a vibration model according to a comparative example. [Figure 9] FIG. 2 is a schematic diagram showing a vibration model according to the first embodiment. [Figure 10] FIG. 10 is a plan view showing a schematic configuration of a piezoelectric element according to a second embodiment. [Figure 11] FIG. 10 is a cross-sectional view showing the structure of a piezoelectric element according to a third embodiment. [Figure 12] FIG. 10 is a plan view showing a schematic configuration of a piezoelectric element according to a fourth embodiment. [Figure 13] FIG. 10 is a cross-sectional view showing a schematic configuration of a piezoelectric element according to a fourth embodiment. [Figure 14] FIG. 10 is a cross-sectional view showing the structure of the piezoelectric element according to the fourth embodiment in more detail. [Figure 15] FIG. 10 is a plan view showing a schematic configuration of a piezoelectric element according to a fifth embodiment. [Figure 16] FIG. 10 is a plan view showing a schematic configuration of a piezoelectric element according to a sixth embodiment. [Figure 17] FIG. 13 is a plan view showing a schematic configuration of a piezoelectric element according to a seventh embodiment. [Figure 18] FIG. 13 is a plan view showing an arrangement of piezoelectric elements according to an eighth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Elements having common functions throughout the drawings will be designated by the same reference numerals, and duplicate descriptions may be omitted or simplified.

[0012] [First embodiment] 1 is a schematic diagram of a display device 1 according to a first embodiment. The display device 1 of this embodiment can be used, for example, as an image output device for a computer, a television receiver, a smartphone, a game console, etc., but is not particularly limited thereto.

[0013] 1, the display device 1 includes a piezoelectric element 10, a display panel 20, an elastic member 30, a first control unit 40, a second control unit 50, a data drive circuit 60, and a gate drive circuit 70. The display device 1 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.

[0014] The display panel 20 includes a plurality of pixels P arranged in a plurality of rows and a plurality of columns. The display device 1 may be, for example, an OLED display that uses organic light-emitting diodes (OLEDs) as light-emitting elements of the pixels P. If the display device 1 is capable of displaying color images, the pixels P may be sub-pixels that display any of a plurality of colors (e.g., RGB) that make up the color image.

[0015] The piezoelectric element 10 is an element that is displaced by the inverse piezoelectric effect when a voltage based on an input audio signal is applied. The piezoelectric element 10 may be, for example, a bimorph, unimorph, or other element that undergoes bending displacement in response to a voltage. Since the input audio signal is usually an AC voltage, the piezoelectric element 10 functions as a vibration element that vibrates in response to the input audio signal.

[0016] The elastic member 30 is a member made of an elastic material. The material of the elastic member 30 is typically a material such as rubber that has a smaller elastic modulus than 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 by the elastic member 30. This allows vibrations of the piezoelectric element 10 to be transmitted to the display panel 20, and the display panel 20 emits sound based on the input audio signal.

[0017] The host system 2 is a device or a system including multiple devices that controls the display device 1 by supplying image signals (e.g., RGB data), audio signals, and timing signals (vertical synchronization signal, horizontal synchronization signal, data enable signal, etc.). The host system 2 may be, for example, a television system, a set-top box, a navigation system, an optical disc player, a computer, a home theater system, a video telephone system, etc. The display device 1 and the host system 2 may be an integrated device or separate devices.

[0018] The first control unit 40 supplies a voltage to the piezoelectric element 10 based on the audio signal and timing signal input from the host system 2.

[0019] The second control unit 50 controls the data drive circuit 60 and the gate drive circuit 70 based on image data and timing signals input from the host system 2. The data drive circuit 60 supplies data voltages and the like to the pixels P via drive lines 61 arranged for each column of the pixels P. The gate drive circuit 70 supplies control signals to the pixels P via drive lines 71 arranged for each row of the pixels P. Note that each of the drive lines 61 and the drive lines 71 may be configured with multiple wirings.

[0020] Each of the first control unit 40, the second control unit 50, the data drive circuit 60, and the gate drive circuit 70 may be configured as one or more semiconductor integrated circuits. In addition, some or all of the first control unit 40, the second control unit 50, the data drive circuit 60, and the gate drive circuit 70 may be integrated into a single semiconductor integrated circuit.

[0021] Fig. 2 is a plan view showing a schematic configuration of the piezoelectric element 10 according to the first embodiment. Fig. 3 is a cross-sectional view showing a schematic configuration of the piezoelectric element 10 according to the first embodiment. The arrangement of the piezoelectric element 10 will be described with mutual reference to Fig. 2 and Fig. 3. The rectangular outer frame of the display panel 20 in Fig. 2 schematically shows the outer shape of the display panel 20.

[0022] As shown in Fig. 3, the surface of the display panel 20 on which an image is displayed is referred to as the image display surface 20a, and the surface opposite to the image display surface 20a is referred to as the back surface 20b. Here, Fig. 2 is a plan view of the display panel 20 as seen from the back surface 20b side. Fig. 2 shows coordinate axes in which the horizontal direction of the image display surface 20a is the x-axis, the vertical direction of the image display surface 20a is the z-axis, and the depth direction of the image display surface 20a is the y-axis. The direction from the back surface 20b toward the image display surface 20a is the positive direction of the y-axis. Fig. 3 is a cross-sectional view taken along line A-A' in Fig. 2.

[0023] The piezoelectric element 10 has a flat plate shape. As shown in Fig. 2, the piezoelectric element 10 has a rectangular shape with a longitudinal direction (z direction in the figure) and a lateral direction (x direction in the figure) in a plan view. This causes deformation such that the piezoelectric element 10 bends when viewed from a cross section (line A-A') along the longitudinal direction. The piezoelectric element 10 is arranged so that the longitudinal direction is perpendicular to the edge of the display panel 20.

[0024] The elastic member 30 is connected at a position including the longitudinal center of the piezoelectric element 10. Since the longitudinal center of the piezoelectric element 10 is the portion that becomes the antinode of vibration, vibration is transmitted to the display panel 20 efficiently.

[0025] 3, 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 to the rear surface 20b of the display panel 20. In this way, 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.

[0026] The elastic member 30 is connected to only a part of the first main surface 10a of the piezoelectric element 10. By keeping both longitudinal ends of the piezoelectric element 10 in a floating state, the vibration of the piezoelectric element 10 is less likely to be hindered at both longitudinal ends where the displacement of the bending vibration is large.

[0027] Fig. 4 is a cross-sectional view showing the structure of the piezoelectric element 10 according to the first embodiment in more detail. Fig. 4 is oriented in a different direction from Fig. 3, but like Fig. 3, shows a cross-sectional view taken along line A-A' in Fig. 2. Fig. 4 also shows a schematic circuit diagram of the connections between the electrodes included in the piezoelectric element 10, in order to explain how an audio signal is input to the piezoelectric element 10.

[0028] The piezoelectric element 10 shown in FIG. 4 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) provided closest to the display panel 20 is connected to the elastic member 30. The electrode 101 and the electrode 103 (second electrode) are arranged to sandwich the piezoelectric layer 102 (first piezoelectric layer) in the thickness direction. The electrode 103 and the electrode 105 (third electrode) are arranged to sandwich the piezoelectric layer 104 (second piezoelectric layer) in the thickness direction. The arrows shown inside the piezoelectric layers 102 and 104 indicate the polarization directions of the piezoelectric layers 102 and 104. In other words, the polarization directions of the piezoelectric layer 102 and the piezoelectric layer 104 are the same. Wiring for applying a voltage to each electrode may be connected to the electrodes 101, 103, and 105 by soldering or the like, but the wiring is not shown in FIG.

[0029] The voltage applied to the piezoelectric element 10 is based on an audio signal, and can therefore be thought of as an AC voltage corresponding to the frequency of the audio to be generated. In FIG. 4, this AC voltage is represented by the circuit symbol for AC power supply V. One terminal of AC power supply V is connected to electrodes 101 and 105, and the other terminal is connected to electrode 103. In other words, an in-phase voltage is applied to electrodes 101 and 105, an out-of-phase voltage is applied to electrodes 101 and 103, and an out-of-phase voltage is also applied to electrodes 103 and 105. As a result, voltages in opposite directions are applied to piezoelectric layers 102 and 104.

[0030] The material of the piezoelectric layers 102 and 104 is not particularly limited, but is preferably a material with good piezoelectric properties such as lead zirconate titanate, which can increase the amount of displacement. Although not shown in the configuration of Fig. 4, the outer periphery of the piezoelectric element 10 may be covered with an insulator such as resin to prevent short circuits with other components.

[0031] 5 and 6 are schematic diagrams showing deformation when a voltage is applied to the piezoelectric element 10 according to the first embodiment. As shown in Fig. 4, the polarization directions of the piezoelectric layers 102 and 104 are the same, and the voltages applied to the piezoelectric layers 102 and 104 are opposite in direction. As a result, the piezoelectric layers 102 and 104 expand and contract in opposite directions.

[0032] 5, at the same time that the piezoelectric layer 102 deforms so as to contract laterally, the piezoelectric layer 104 deforms so as to expand laterally. As a result, the end of the piezoelectric element 10 bends in a direction approaching the display panel 20. At this time, the display panel 20 receives stress directed toward the piezoelectric element 10 and deforms.

[0033] 6, at the same time that the piezoelectric layer 102 deforms to expand laterally, the piezoelectric layer 104 deforms to contract laterally. This causes the end of the piezoelectric element 10 to bend in a direction away from the display panel 20. At this time, the display panel 20 is deformed by receiving stress in a direction away from the piezoelectric element 10.

[0034] When an AC voltage based on an audio signal is applied to the piezoelectric element 10, the state shown in Figure 5 and the state shown in Figure 6 are alternately repeated at the frequency of the audio. In this way, the vibration of the piezoelectric element 10 is transmitted to the display panel 20, causing the display panel 20 to vibrate. Therefore, sound based on the audio signal is emitted from the display panel 20, and the display panel 20 functions as a speaker.

[0035] 7 to 9, the effects obtained by connecting a part of the piezoelectric element 10 and the display panel 20 by the elastic member 30 in this embodiment will be described in more detail. FIG. 7 is a cross-sectional view showing the configuration of the piezoelectric element 10 according to a comparative example. FIG. 8 is a schematic diagram showing a vibration model according to the comparative example. FIG. 9 is a schematic diagram showing the vibration model according to the first embodiment.

[0036] 7, in the comparative example, the entire 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 can be transmitted to the display panel 20, causing the display panel 20 to function as a speaker.

[0037] 8, the vibration model according to the comparative example has a configuration in which springs S1 and S2 are connected to both ends of a mass point representing the piezoelectric element 10 and the display panel 20. The piezoelectric element 10 having a mass m1 and the display panel 20 having a mass m2 are directly connected.

[0038] 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 models the elasticity of the piezoelectric element 10. The spring S2 models the display panel 20 itself or a member that restrains the display panel 20, such as a housing. Note that both ends of this vibration model are typically fixed ends.

[0039] In the vibration model of the comparative example, the piezoelectric element 10 and the display panel 20 can be replaced by a single mass point having a mass (m1+m2). When a voltage is applied to the piezoelectric element 10, the force generated by the piezoelectric element 10 vibrates the entire piezoelectric element 10 and the display panel 20, each having a mass (m1+m2). Here, the display panel 20 is much larger than the piezoelectric element 10, so the mass (m1+m2) is much larger than the mass m1. Because the force generated by the piezoelectric element 10 is applied to an object with a very large mass, the acceleration that the piezoelectric element 10 and the display panel 20 experience due to this force is small. Therefore, the displacement of the piezoelectric element 10 and the display panel 20 is not very large, and the sound pressure of the sound emitted from the display panel 20 may not be sufficient in the configuration of the comparative example.

[0040] 9, the vibration model according to this embodiment has a configuration in which 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 S1 models the elasticity 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.

[0041] In the vibration model of this embodiment, the piezoelectric element 10 and the display panel 20 are displaced independently. The force generated when a voltage is applied to the piezoelectric element 10 vibrates the piezoelectric element 10, which has a mass m1. Because the mass of the object to which the force is applied is smaller than in the comparative example, the acceleration experienced by the piezoelectric element 10 due to this force is larger than in the comparative example. This causes the piezoelectric element 10 to resonate with a large displacement. Because the displacement of the piezoelectric element 10 is gradually transmitted to the display panel 20 via the spring S3, the mass of the display panel 20 is less likely to inhibit the displacement, as in the comparative example. Therefore, in this embodiment, the displacement can be made larger than in the comparative example, and the sound pressure is improved.

[0042] As described above, according to this embodiment, a display device 1 is provided that can improve sound quality by increasing the sound pressure of the sound emitted by the display panel 20 when the display panel 20 is made to function as a speaker.

[0043] 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 to a configuration in which sound is emitted directly from the piezoelectric element 10 or a configuration in which sound is emitted from a member with a high natural frequency, such as by connecting the piezoelectric element 10 to a small diaphragm separate from the display panel 20, the sound pressure in the low frequency range can be improved.

[0044] [Second embodiment] In this embodiment, a modified example of the arrangement of the piezoelectric elements 10 according to the first embodiment will be described. The basic configuration of the display device 1 and the structure of the piezoelectric elements 10 are the same as those in the first embodiment, and therefore will not be described again.

[0045] 10 is a plan view showing a schematic configuration of a piezoelectric element 10 according to the second embodiment. As shown in FIG. 10, in this embodiment, the piezoelectric element 10 is arranged so that the longitudinal direction of the piezoelectric element 10 is not perpendicular to any of the edges of the display panel 20.

[0046] When the piezoelectric element 10 has a rectangular shape, the distribution of vibrations generated in the display panel 20 is dominated by components directed in the longitudinal direction of the piezoelectric element 10. When the longitudinal direction of the piezoelectric element 10 is perpendicular to the edges of the display panel 20, as in the first embodiment, the vibrations generated by the piezoelectric element 10 and the vibrations reflected at the edges of the display panel 20 may reinforce each other, causing resonance. This resonance can be a source of noise. In contrast, in this embodiment, the longitudinal direction of the piezoelectric element 10 is not perpendicular to any of the edges of the display panel 20, making it less likely that resonance due to the above-mentioned factors will occur, thereby reducing noise.

[0047] Therefore, according to this embodiment, the same effects as those of the first embodiment can be obtained, and a display device 1 is provided in which noise caused by resonance due to reflection at the end surface of the display panel 20 is reduced and sound quality is improved.

[0048] In the configuration of the first embodiment, since vibrations reinforce each other, it may be possible to utilize this to improve sound pressure, adjust frequency characteristics, etc. Therefore, depending on design conditions such as required characteristics and design constraints, it may be desirable to make the longitudinal direction of the piezoelectric element 10 perpendicular to the edge of the display panel 20 as in the first embodiment.

[0049] [Third embodiment] In this embodiment, a modified example of the cross-sectional structure of the piezoelectric element 10 according to the first embodiment will be described. The basic configuration of the display device 1, the arrangement of the piezoelectric element 10, etc. are the same as those in the first embodiment, so the description will be omitted.

[0050] 11 is a cross-sectional view showing the structure of a piezoelectric element 10 according to the third embodiment. The cross-sectional position is the same as in FIGS.

[0051] 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) located closest to the display panel 20 is connected to the elastic member 30. The electrode 111 and the electrode 113 (second electrode) are arranged to sandwich the piezoelectric layer 112 (first piezoelectric layer) in the thickness direction. The electrode 115 (third electrode) and the electrode 117 (fourth electrode) are arranged to sandwich the piezoelectric layer 116 (second piezoelectric layer) in the thickness direction. The insulating layer 114 is arranged between the electrodes 113 and 115. The insulating layer 114 is a layer that ensures insulation between the electrode 113 and the electrode 115. Arrows illustrated inside the piezoelectric layers 112 and 116 indicate 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 to each other.

[0052] One terminal of AC power supply V, which indicates a voltage based on an audio signal, is connected to electrodes 111 and 115, and the other terminal is connected to electrodes 113 and 117. In other words, a voltage of the same phase is applied to electrodes 111 and 115. A voltage of opposite phase to the voltage input to electrodes 111 and 115 is applied to electrodes 113 and 117. As a result, a voltage of the same direction is applied to piezoelectric layer 112 and piezoelectric layer 116.

[0053] In this embodiment, when one of the two piezoelectric layers contracts laterally, the other expands laterally, resulting in flexural vibrations similar to those in the first embodiment. Therefore, the same effects as those in the first embodiment can be obtained in this embodiment. As such, the structures of the piezoelectric layers, electrodes, etc. in the piezoelectric element 10 are not limited to those in the first embodiment, and various structures can be applied.

[0054] For example, the piezoelectric element 10 may have a structure called a unimorph, which is a laminate of one piezoelectric layer, a pair of electrodes sandwiching the piezoelectric layer, and a diaphragm. However, to improve the conversion efficiency between voltage and displacement, it is desirable to employ a bimorph structure as shown in FIG. 4 or FIG. 11.

[0055] [Fourth embodiment] 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 of the display device 1 is the same as that of the first embodiment, and therefore a description thereof will be omitted.

[0056] Fig. 12 is a plan view showing a schematic configuration of a piezoelectric element 10 according to a fourth embodiment. Fig. 13 is a cross-sectional view showing a schematic configuration of a piezoelectric element 10 according to the fourth embodiment. The arrangement of the piezoelectric element 10 will be described with reference to Fig. 12 and Fig. 13.

[0057] As shown in FIG. 12 , the piezoelectric element 10 of this embodiment has a first vibrating portion 12 and a second vibrating portion 14 that extend in different directions in a plan view. The configuration of the first vibrating portion 12 is the same as that of the piezoelectric element 10 of the first embodiment. That is, the first vibrating portion 12 has a rectangular shape with a longitudinal direction (z direction in the figure) and a lateral direction (x direction in the figure) in a plan view. The second vibrating portion 14 extends in a direction different from that of the first vibrating portion 12. That is, the second vibrating portion 14 has a rectangular shape with a longitudinal direction (x direction in the figure) and a lateral direction (z direction in the figure) in a plan view. The longitudinal direction of the first vibrating portion 12 and the longitudinal direction of the second vibrating portion 14 are perpendicular to each other. Furthermore, the longitudinal direction of the first vibrating portion 12 and the longitudinal direction of the second vibrating portion 14 are both arranged perpendicular to the edge of the display panel 20.

[0058] 13, the first vibrating section 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 section 12 to the back surface 20b of the display panel 20. The elastic member 30 is connected to only a portion of the first main surface 12a of the first vibrating section 12. In this way, the piezoelectric element 10 and the elastic member 30 are arranged on the back surface 20b of the display panel 20 so as not to interfere with the user's viewing of the image display surface 20a.

[0059] The second vibrating section 14 is connected to only a portion of the second main surface 12b of the first vibrating section 12. This causes both longitudinal ends of the first vibrating section 12 to be in a floating state, and further causes both longitudinal ends of the second vibrating section 14 to be in a floating state. By causing both longitudinal ends of the piezoelectric element 10 to be in a floating state, the vibration of the piezoelectric element 10 is less likely to be hindered at both longitudinal ends where the displacement of the bending vibration is large.

[0060] Fig. 14 is a cross-sectional view showing the structure of the piezoelectric element 10 according to the fourth embodiment in more detail. Fig. 14 is oriented in a different direction from Fig. 13, but like Fig. 13, it shows a cross-sectional view taken along line B-B' in Fig. 12. In addition, Fig. 4 shows a schematic circuit diagram of the connection relationships between the electrodes included in the piezoelectric element 10 in order to explain how an audio signal is input to the piezoelectric element 10.

[0061] The piezoelectric element 10 shown in Fig. 14 has a structure in which two bimorphs are stacked. The piezoelectric element 10 includes a first vibration portion 12 and a second vibration portion 14. The structure of the first vibration portion 12 is similar to that of the piezoelectric element 10 of the first embodiment. In Fig. 14, an insulating layer 120 is provided between the first vibration portion 12 and the second vibration portion 14, but this is not essential.

[0062] The second vibrating section 14 includes electrodes 121, 123, 125 and piezoelectric layers 122, 124. The electrode 121, which is provided closest to the first vibrating section 12, is connected to the insulating layer 120. The electrodes 121 and 123 are arranged to sandwich the piezoelectric layer 122 in the thickness direction. The electrodes 123 and 125 are arranged to sandwich the piezoelectric layer 124 in the thickness direction. Arrows shown inside the piezoelectric layers 122 and 124 indicate the polarization directions of the piezoelectric layers 122 and 124. In other words, the polarization directions of the piezoelectric layers 122 and 124 are the same.

[0063] One terminal of the AC power supply V, which indicates a voltage based on an audio signal, is connected to electrodes 101, 105, 121, and 125, and the other terminal is connected to electrodes 103 and 123. In other words, voltages of the same phase are applied to electrodes 101, 105, 121, and 125. A voltage of opposite phase to the voltage input to electrodes 101, 105, 121, and 125 is applied to electrodes 103 and 123. As a result, voltages of the same direction are applied to piezoelectric layers 102, 104, 122, and 124.

[0064] In both the first vibrating section 12 and the second vibrating section 14, when one of the two piezoelectric layers contracts laterally, the other expands laterally. Therefore, both the first vibrating section 12 and the second vibrating section 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 section 12 and the second vibrating section 14 vibrate in phase in response to an audio signal. As a result, the vibrations generated in the first vibrating section 12 and the second vibrating section 14 reinforce each other, improving vibration efficiency.

[0065] According to this embodiment, similar to the first embodiment, a display device 1 is provided that can improve sound quality by increasing the sound pressure of the sound emitted by the display panel 20. Furthermore, since the piezoelectric element 10 of this embodiment uses two vibration parts, it is possible to further improve the sound pressure compared to the configuration of the first embodiment that uses one vibration part.

[0066] Furthermore, in the first embodiment, since there is only one vibrating section, the vibration distribution is concentrated in the longitudinal direction of the piezoelectric element 10, that is, one-dimensionally. As a result, resonance is likely to occur in the display panel 20, and noise caused by the resonance may increase. In contrast, in the present embodiment, since the piezoelectric element 10 has the first vibrating section 12 and the second vibrating section 14 extending in different directions, the vibration distribution is two-dimensional and is less likely to concentrate in a specific location. As a result, resonance is less likely to occur in the display panel 20. Therefore, in the present embodiment, noise caused by resonance in the display panel 20 is reduced, and a display device 1 with further improved sound quality is provided.

[0067] [Fifth embodiment] In this embodiment, a modified example of the arrangement of the piezoelectric element 10 according to the fourth embodiment will be described. The basic configuration of the display device 1 and the structure of the piezoelectric element 10 are the same as those in the fourth embodiment, and therefore description thereof will be omitted.

[0068] 15 is a plan view showing a schematic configuration of a piezoelectric element 10 according to the fifth embodiment. As shown in Fig. 15, in this embodiment, the piezoelectric element 10 is arranged so that the longitudinal directions of the first vibrating section 12 and the second vibrating section 14 are not perpendicular to any of the ends of the display panel 20.

[0069] As described in the description of the second embodiment, there are cases where the vibrations generated by the first vibrating section 12 and the second vibrating section 14 and the vibrations reflected at the edges of the display panel 20 reinforce each other, causing resonance. This resonance can be a source of noise. In contrast, in this embodiment, the longitudinal directions of the first vibrating section 12 and the second vibrating section 14 are not perpendicular to either edge of the display panel 20, making it difficult for resonance to occur and reducing noise.

[0070] Therefore, according to this embodiment, the same effects as those of the fourth embodiment can be obtained, and a display device 1 is provided in which noise caused by resonance due to reflection at the end surface of the display panel 20 is reduced and sound quality is improved.

[0071] In the configuration of the fourth embodiment, it may be possible to use vibration reinforcement to improve sound pressure, adjust frequency characteristics, etc. Therefore, depending on design conditions such as required characteristics and design constraints, it may be desirable to make the longitudinal direction of the piezoelectric element 10 perpendicular to the edge of the display panel 20 as in the fourth embodiment.

[0072] [Sixth embodiment] 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 of the display device 1 is the same as that of the fourth embodiment, and therefore a description thereof will be omitted.

[0073] Fig. 16 is a plan view showing a schematic configuration of a piezoelectric element 10 according to a sixth embodiment. As shown in Fig. 16, the piezoelectric element 10 of this embodiment has a first vibrating portion 12, a second vibrating portion 14, and a third vibrating portion 16 that extend in different directions in a plan view. The cross-sectional structure of the piezoelectric element 10 is simply the same as that of Fig. 14, except that a piezoelectric layer and an electrode corresponding to the third vibrating portion 16 have been added to increase the number of layers, and therefore a description thereof will be omitted.

[0074] In this embodiment, a display device 1 is provided that can improve the sound pressure of the sound emitted by the display panel 20, similar to the first embodiment. Furthermore, since the piezoelectric element 10 of this embodiment uses three vibration parts, the sound pressure can be improved even more than in the configuration of the fourth embodiment, which has two vibration parts. As such, the number of vibration parts is not limited to one or two, but may be three or more. The greater the number of vibration parts, the higher the sound pressure.

[0075] Furthermore, in this embodiment, the vibration distribution is more two-dimensionally uniform than in the configuration of the fourth embodiment. This makes it more difficult for resonance to occur in the display panel 20. Therefore, according to this embodiment, noise caused by resonance in the display panel 20 is further reduced, and a display device 1 with improved sound quality is provided.

[0076] [Seventh embodiment] 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 of the display device 1 is the same as that of the first embodiment, and therefore a description thereof will be omitted.

[0077] FIG. 17 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. As shown in FIG. 17, the piezoelectric element 10 of this embodiment has a circular shape in a plan view. The elastic member 30 is connected to a position including the center of the circle of the piezoelectric element 10. The cross-sectional structure of the piezoelectric element 10 is similar to that shown in FIGS. 3 and 4, and therefore description thereof will be omitted.

[0078] According to this embodiment, a display device 1 capable of improving the sound pressure of the sound emitted by the display panel 20 is provided, similar to the first embodiment.

[0079] Furthermore, in this embodiment, since the piezoelectric element 10 is circular, the vibration distribution is two-dimensionally uniform. 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, noise caused by resonance in the display panel 20 is reduced, and a display device 1 with improved sound quality is provided.

[0080] [Eighth embodiment] In this embodiment, a modified example of the structure of the piezoelectric element 10 according to the eighth embodiment will be described. The basic configuration of the display device 1 is the same as that of the fifth embodiment, and therefore a description thereof will be omitted.

[0081] FIG. 18 is a plan view showing an arrangement of piezoelectric elements 10 according to the eighth embodiment. As shown in FIG. 18, in this embodiment, a plurality of piezoelectric elements 10 are arranged on a display panel 20. The plurality of piezoelectric elements 10 are arranged in a matrix in the x and z directions. The piezoelectric elements 10 are the same as those in the fifth embodiment. By arranging a plurality of piezoelectric elements 10 on the display panel 20, the sound pressure of the sound emitted by the display panel 20 is improved compared to when a single piezoelectric element 10 is arranged.

[0082] The display panel 20 includes an area R1 and an area R2. The piezoelectric elements 10 (first piezoelectric elements) in the area R1 and the piezoelectric elements 10 (second piezoelectric elements) in the area R2 have different frequency characteristics. For example, by making the frequency characteristics of the two different, it is possible to reduce bias in the frequency characteristics of the sound emitted by the display panel 20.

[0083] Piezoelectric elements 10 have natural frequencies due to their shape, etc., and may have biased frequency characteristics, such as increased sound pressure at certain frequencies. If the characteristics of all piezoelectric elements 10 in the display panel 20 are the same, the biases in the frequency characteristics of multiple piezoelectric elements 10 may overlap, resulting in a biased frequency characteristic for the entire display panel 20. In this embodiment, the frequency characteristics of the piezoelectric elements 10 in region R1 and the piezoelectric elements 10 in region R2 are made different and equalized, thereby reducing the bias in frequency characteristics that may occur due to the factors described above.

[0084] The bias in the frequency characteristics of the piezoelectric element 10 is mainly due to the natural frequency of the piezoelectric element 10. Therefore, it is desirable to make the natural frequency of the piezoelectric element 10 in region R1 different from that of the piezoelectric element 10 in region R2. For example, by making the natural frequency of the piezoelectric element 10 in region R2 lower than the natural frequency of the piezoelectric element 10 in region R1, region R1 functions as a high-frequency sound generating region, and region R2 functions as a low-frequency sound generating region. This provides a display device 1 that can emit high-frequency and low-frequency sounds in a well-balanced manner.

[0085] The natural frequency of the piezoelectric element 10 depends on the shape or material of the piezoelectric element 10. Therefore, the natural frequency can be made different between the piezoelectric elements 10 in region R1 and the piezoelectric elements 10 in region R2 by making the shape or sound speed different. Examples of material properties that affect the sound speed in a material include elastic modulus and density. Therefore, it is desirable to use materials that differ in any of the sound speed, elastic modulus, and density. It is also desirable to make only the shape different between the piezoelectric elements 10 in region R1 and the piezoelectric elements 10 in region R2, as this has the advantage of allowing the use of a common material.

[0086] As described above, according to this embodiment, the display device 1 is provided that can improve the sound quality by reducing the bias in the frequency characteristics of the sound emitted by the display panel 20.

[0087] Although the piezoelectric element 10 of the fifth embodiment has been given as an example of a piezoelectric element 10 applicable to this embodiment, the present invention is not limited to this. Piezoelectric elements 10 having any structure or arrangement among those of the first to seventh embodiments may be used, and piezoelectric elements having a structure or arrangement different from those described in the first to seventh embodiments may also be used.

[0088] [Other embodiments] The above-described embodiments merely exemplify some aspects to which the present invention can be applied, and the technical scope of the present invention should not be interpreted as being limited by the above-described embodiments. Furthermore, the present invention can be implemented in various aspects by making appropriate modifications and variations without departing from the spirit of the present invention. For example, it should be understood that embodiments in which part of the configuration of any embodiment is added to or replaced with part of the configuration of another embodiment are also embodiments to which the present invention can be applied.

[0089] In the above-described embodiment, the device configuration of the display device 1 and the like is merely an example and is not limited to that shown in the drawings. For example, the display device 1 may be a liquid crystal display, a CRT display, or the like, instead of an OLED display. However, since it is desirable for the display device 1 to be able to efficiently transmit vibrations from the piezoelectric element 10 to the display panel 20, it is particularly desirable for the display device 1 to be an OLED display with few cavities. [Explanation of symbols]

[0090] 1 Display device 10 Piezoelectric element 20 Display panel 30 Elastic member

Claims

1. a display panel including a first region and a second region, the display panel configured to display an image; a plurality of piezoelectric elements arranged on the display panel; Equipped with the first region is configured to generate high-pitched sounds and the second region is configured to generate low-pitched sounds; each of the plurality of piezoelectric elements includes a first vibration portion and a second vibration portion each having a rectangular shape with a longitudinal direction and a lateral direction in a plan view; the first vibration portion and the second vibration portion extend in different directions in a plan view, At least one end portion in the longitudinal direction of the first vibration section and at least one end portion in the longitudinal direction of the second vibration section are in a floating state, the plurality of piezoelectric elements include a third vibration portion extending in a direction different from the first vibration portion and the second vibration portion extending in different directions in a plan view, the third vibration section has a rectangular shape having a longitudinal direction and a lateral direction in a plan view, positions including the centers of the first vibration section, the second vibration section, and the third vibration section in the longitudinal direction overlap each other; Display device.

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

3. The display device according to claim 1 , wherein the plurality of piezoelectric elements are arranged in a matrix in a first direction and a second direction perpendicular to the first direction.

4. The display device according to claim 1 , wherein the piezoelectric elements arranged in the first region and the piezoelectric elements arranged in the second region have different shapes.

5. The display device according to claim 1 , wherein the piezoelectric elements arranged in the first region and the piezoelectric elements arranged in the second region have frequency characteristics different from each other.

6. The display device according to claim 1 , wherein the piezoelectric elements arranged in the first region and the piezoelectric elements arranged in the second region have natural frequencies different from each other.

7. The display device according to claim 6 , 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.

8. The display device according to claim 7 , wherein the material constituting the first piezoelectric element differs from the material constituting the second piezoelectric element in at least one of sound velocity, elastic modulus, and density.

9. a position including a center of the first vibration part in the longitudinal direction is connected to a position including a center of the second vibration part in the longitudinal direction; The display device according to claim 1 .

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