Patent Publication Number: US-2023161546-A1

Title: Display device

Description:
This application is a continuation of U.S. patent application Ser. No. 16/841,680, filed on Apr. 7, 2020, which claims priority to Korean Patent Application No. 10-2019-0062683, filed on May 28, 2019, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which in its entirety is herein incorporated by reference. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments of the disclosure relate to a display device. 
     2. Description of the Related Art 
     With the development of information society, demands for display devices for displaying images are increasing in various forms. For example, display devices are widely used for various electronic devices such as smart phones, tablet personal computers (“PC”s), digital cameras, laptop computers, navigators, and televisions. The display device may be a flat panel display device such as a liquid crystal display device, a field emission display device, an organic light emitting display device, or a quantum dot light emitting display device. 
     SUMMARY 
     The display device may include a display panel for displaying an image, a sound generator for outputting a high sound by vibrating the display panel, and a woofer for outputting a low sound. Since the woofer is typically disposed behind the display device while the high sound generated by vibrating the display panel by the sound generator is output in a front direction of the display device, the low sound may be output in a direction other than the front direction of the display device. Therefore, the high and low sounds of the display device may not be effectively or realistically provided to a user. 
     Embodiments of the disclosure including a display device capable of improving sound quality by outputting a low sound and a high sound in the front direction of the display device. 
     However, embodiments of the disclosure are not restricted to those set forth herein. The above and other embodiments of the disclosure will become more apparent to one of ordinary skill in the art to which the disclosure pertains by referencing the detailed description of the disclosure given below. 
     According to an embodiment of the disclosure, a display device includes: a display panel; a first sound generator disposed on a surface of the display panel, where the first sound generator vibrates the display panel to output a first sound; and a first vibration damping member disposed between the display panel and the first sound generator, where the first vibration damping member reduces a vibration displacement of the display panel. 
     In an embodiment, the first vibration damping member may include a first metal plate and a second metal plate facing each other, and an adhesive layer disposed between the first metal plate and the second metal plate. 
     In an embodiment, a thickness of the first metal plate and a thickness of the second metal plate may be less than a thickness of the adhesive layer. 
     In an embodiment, the first vibration damping member may include a corner having a curvature in a plan view. 
     In an embodiment, the first vibration damping member may have a circular shape in a plan view. 
     In an embodiment, the first vibration damping member may include a heat radiation pin protruding in a thickness direction of the display panel. 
     In an embodiment, the heat radiation pin may be disposed to surround the first sound generator. 
     In an embodiment, the display device may further include blocking members disposed on the surface of the display panel, disposed to surround the first sound generator, where the blocking members define a first area in which the first sound generator is disposed, where an area of the first vibration damping member may be smaller than an area of the first area. 
     In an embodiment, the display device may further include a lower chassis disposed on the surface of the display panel, where a through hole may be defined in the lower chassis, and the through hole may be in the first area in the plan view. 
     In an embodiment, the first sound generator may include a bobbin disposed on the first vibration damping member; a voice coil surrounding the bobbin; and a magnet disposed on the bobbin and spaced apart from the bobbin. 
     In an embodiment, the display device may further include a second sound generator disposed on the surface of the display panel, where the second sound generator may output a second sound by vibrating the display panel, and the second sound may be in a higher frequency band than the first sound. 
     In an embodiment, the second sound generator may not overlap the first vibration damping member in a thickness direction of the display panel. 
     In an embodiment, the display device may further include a third sound generator disposed on the surface of the display panel, where the third sound generator may output a third sound by vibrating the display panel, and the third sound may be in a higher frequency band than the first sound. 
     In an embodiment, the display device may further include blocking members disposed on the surface of the display panel and disposed between the first sound generator and the second sound generator and between the first sound generator and the third sound generator. 
     In an embodiment, each of the second sound generator and the third sound generator includes a first electrode to which a first driving voltage is applied; a second electrode to which a second driving voltage is applied; and a vibration layer disposed between the first electrode and the second electrode, where the vibration layer may include a piezoelectric material, which contracts and expands in response to the first driving voltage applied to the first electrode and the second driving voltage applied to the second electrode. 
     In an embodiment, the display device may further include a lower chassis disposed on the surface of the display panel; a flexible film attached to a side portion of the display panel; and a control circuit board disposed on the lower chassis and electrically connected to the flexible film. 
     In an embodiment, the first sound generator may not overlap the control circuit board in a thickness direction of the display panel. 
     In an embodiment, the control circuit board may be disposed on the first sound generator, and the control circuit board may be fixed to a connection supporting portion disposed on the lower chassis. 
     In an embodiment, the display device may further include a fourth sound generator disposed on the surface of the display panel, where the fourth sound generator may output a fourth sound by vibrating the display panel, and the fourth sound may be in a lower frequency band than the second sound. 
     In an embodiment, the fourth sound generator may be disposed on the first vibration damping member. 
     In an embodiment, the display device may further include a second vibration damping member disposed between the display panel and the fourth sound generator, where the second vibration damping member may reduce the vibration displacement of the display panel. 
     In an embodiment, the display device may further include a fifth sound generator disposed on the surface of the display panel, where the fifth sound generator may output a fifth sound by vibrating the display panel, and the fifth sound may be in a higher frequency band than the first sound; and a sixth sound generator disposed on the surface of the display panel, where the sixth sound generator may output a sixth sound by vibrating the display panel, and the sixth sound may be in a higher frequency band than the first sound. 
     In an embodiment, the display device may further include blocking members disposed on the surface of the display panel between the first sound generator and the second sound generator, between the first sound generator and the third sound generator, between the fourth sound generator and the fifth sound generator, between the fourth sound generator and the sixth sound generator, between the second sound generator and the fifth sound generator, and between the third sound generator and the sixth sound generator. 
     According to embodiments of the disclosure, the first sound generator can output a sound having a low-frequency band by using the display panel as a vibration plate, and the second sound generator and the third sound generator can output a sound having a high-frequency band by using the display panel as a vibration plate. In such embodiments, the display device may output a sound having a low-frequency band and a sound having a high-frequency band in the front direction of the display device, thereby improving sound quality. 
     In such embodiments, since a vibration damping member having high rigidity is disposed between the display panel and the first sound generator, the vibration displacement of the display panel caused by the first sound generator can be reduced. Therefore, it is possible to prevent the vibration of the display panel from being visually recognized to the user seeing an image. 
     Other features and embodiments may be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the invention will become more apparent by describing in more detail embodiments thereof with reference to the attached drawings, in which: 
         FIG.  1    is an exploded perspective view of a display device according to an embodiment; 
         FIG.  2    is a bottom view showing an embodiment of a display panel of  FIG.  1    in a state where flexible films are unfolded; 
         FIG.  3    is a bottom view showing an embodiment of a display panel coupled with a lower chassis when flexible films are bent toward the lower portion of the lower chassis; 
         FIG.  4 A  is a cross-sectional view taken along line I-I′ of  FIG.  2   ; 
         FIG.  4 B  is an enlarged view of the encircled portion of  FIG.  4 A ; 
         FIG.  5    is a cross-sectional view taken along line II-IP of  FIG.  2   ; 
         FIG.  6    is a side view showing an embodiment of a vibration damping member; 
         FIG.  7    is a graph showing the vibration displacement of the display panel by a first sound generator according to the presence or absence of the vibration damping member; 
         FIG.  8    is a graph showing the sound pressure level with respect to the frequency of a first sound according to the presence or absence of the vibration damping member; 
         FIG.  9    is a cross-sectional view showing an embodiment of a first substrate, a second substrate, and a pixel array layer of a display panel; 
         FIGS.  10  and  11    are exemplary views showing the vibration of the display panel by the first sound generator; 
         FIG.  12    is an exemplary view showing the vibration of the display panel by the second sound generator of  FIG.  5   ; 
         FIG.  13    is an exemplary view showing a method of vibrating a vibration layer disposed between the first branch electrode and second branch electrode of a second sound generator; 
         FIG.  14    is a bottom view showing an alternative embodiment of a display panel of  FIG.  1    where flexible films are unfolded; 
         FIG.  15    a bottom view showing another alternative embodiment of a display panel of  FIG.  1    where flexible films are unfolded; 
         FIG.  16    a bottom view showing another alternative embodiment of a display panel of  FIG.  1    where flexible films are unfolded; 
         FIG.  17    is a cross-sectional view taken along line of  FIG.  16   ; 
         FIG.  18    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis of  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis; 
         FIG.  19    is a cross-sectional view taken along line IV-IV′ of  FIG.  18   ; 
         FIG.  20    a bottom view showing another alternative embodiment of a display panel of  FIG.  1    where flexible films are unfolded; 
         FIG.  21    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis of  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis; 
         FIG.  22    is a cross-sectional view taken along line V-V′ of  FIG.  21   ; 
         FIG.  23    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded; 
         FIG.  24    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis; 
         FIG.  25    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded; 
         FIG.  26    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis; 
         FIG.  27    a bottom view showing another alternative embodiment of a display panel when flexible films are unfolded; 
         FIG.  28    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis; 
         FIG.  29    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded; 
         FIG.  30    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis; 
         FIG.  31    is a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded; and 
         FIG.  32    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis. 
     
    
    
     DETAILED DESCRIPTION 
     The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. 
     It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. As used herein, the phrase “at least one of” modifying listed items includes any and all combinations of one or more of the listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     “About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. 
       FIG.  1    is an exploded perspective view of a display device according to an embodiment. 
     Referring to  FIG.  1   , an embodiment of a display device  10  includes an upper set cover  101 , a lower set cover  102 , a display panel  110 , source driving circuits  121 , flexible films  122 , a heat radiation film  130  (shown in  FIG.  2   ), source circuit boards  140 , first cables  150 , a control circuit board  160 , a timing control circuit  170 , a sound driving circuit  171 , a lower chassis  180 , a first sound generator  210 , a second sound generator  220 , and a third sound generator  230 . In an embodiment, the display device  10  may further include a functional layer  114  (shown in  FIGS.  4 A and  5   ) disposed on the display panel  110 . The functional layer  114  may include, for example, a touch sensing layer, a haptic layer or an optical layer (e.g., an antireflective layer such as a polarization film), but not being limited thereto. 
     In this specification, the “on”, “over”, “top”, “upper side”, or “upper surface” refers to a direction in which a second substrate  112  is disposed with respect to a first substrate  111  of the display panel  110 , that is, a thickness direction of the display panel  110  or the Z-axis direction, and the “beneath”, “under”, “bottom”, “lower side”, or “lower surface” refers to a direction in which the heat radiation film  130  is disposed with respect to the first substrate  111  of the display panel  110 , that is, a direction opposite to the Z-axis direction. Further, the “left”, “right”, “upper”, and “lower” refer to directions when the display panel  110  is viewed in a top plan view or a plan view in the Z-axis direction. For example, the “left” refers to the first direction (X-axis direction), the “right” refers to a direction opposite to the first direction (X-axis direction), the “upper” refers to the second direction (Y-axis direction), and the “lower” refers to a direction opposite to the second direction (Y-axis direction). 
     The upper set cover  101  may be disposed to cover edge portions of the upper surface of the display panel  110 . The upper set cover  101  may cover the non-display area of the display panel  110  other than the display area of the display panel  110 . The lower set cover  102  may be disposed under the lower chassis  180 . When the flexible films are bent to allow the source circuit boards  140 , the first cables  150 , and the control circuit board to be disposed under the display panel  110 , the lower set cover  102  may be disposed to cover the source circuit boards  140 , the first cables  150 , and the control circuit board  160 . Although it is shown in  FIG.  1    that the length of the lower set cover  102  in the second direction (Y-axis direction) is shorter than the length of the lower chassis  180  in the second direction (Y-axis direction), the invention is not limited thereto. Alternatively, the length of the lower set cover  102  in the second direction (Y-axis direction) may be greater than or substantially equal to the length of the lower chassis  180  in the second direction (Y-axis direction). The upper set cover  101  and the lower set cover  102  may include a plastic or a metal, or a combination thereof. 
     The display panel  110  may have a rectangular shape in a plan view. In one embodiment, for example, as shown in  FIG.  2   , the display panel  110  may have a rectangular planar shape having long sides in the first direction (X-axis direction) and short sides in the second direction (Y-axis direction). The corner where the long side in the first direction (X-axis direction) meets the short side in the second direction (Y-axis direction) may be formed to have a right angle shape or have a round shape of a predetermined curvature. The planar shape of the display panel  110  is not limited to a rectangular shape, and may be variously modified in another polygonal shape, a circular shape, or an elliptical shape. 
     Although it is illustrated in  FIG.  2    that the display panel  110  is formed to be flat, the invention is not limited thereto. The display panel  110  may be formed to be bent at a predetermined curvature. 
     The display panel  110  may include a first substrate  111  and a second substrate  112 . The second substrate  112  may be disposed to face the first surface of the first substrate  111 . The first substrate  111  and the second substrate  112  may be rigid or flexible. The first substrate  111  may include or be formed of a glass or a plastic. The second substrate  112  may include or be formed of a glass, a plastic, an encapsulation film, or a barrier film. Alternatively, the second substrate  112  may be omitted. In an embodiment, where the first substrate  111  and the second substrate  112  are formed of a plastic, the plastic may be polyethersulphone (“PES”), polyacrylate (“PA”), polyarylate (“PAR”), polyetherimide (“PEI”), polyethylenenapthalate (“PEN”), polyethyleneterepthalate (“PET”), polyphenylenesulfide (“PPS”), polyallylate, polyimide (“PI”), polycarbonate (“PC”), cellulose triacetate (“CAT”), cellulose acetate propionate (“CAP”), or a combination thereof. The encapsulation film or the barrier film may be a film in which a plurality of inorganic films are laminated one on another. 
     The display panel  110  may be an organic light emitting display panel using an organic light emitting diode including a first electrode, an organic light emitting layer, and a second electrode; an inorganic light emitting display panel using an inorganic light emitting diode including a first electrode, an inorganic semiconductor layer, and a second electrode; or a quantum dot light emitting display panel using a quantum dot light emitting diode including a first electrode, a quantum dot light emitting layer, and a second electrode. 
     Hereinafter, for convenience of description, embodiments where the display panel  110  includes a thin film transistor TFTL, a light emitting element layer EML, a filler FL, an optical wavelength conversion layer QDL, and a color filter layer CFL, which are disposed between the first substrate  111  and the second substrate  112 , as shown in  FIG.  9   , will be described in detail. In such embodiments, the first substrate  111  may be a thin film transistor substrate on which the thin film transistor TFTL, the light emitting element layer EML, and the thin film encapsulation layer TFEL are disposed, the second substrate  112  may a color filter substrate on which the optical wavelength conversion layer QDL and the color filter layer CFL are disposed, and the filler FL may be disposed between the thin film encapsulation layer TFEL of the first substrate  111  and the optical wavelength conversion layer QDL of the second substrate  112 . 
     Alternatively, the second substrate  112  of the display panel  110  may be omitted, and the thin film encapsulation layer may be disposed on the light emitting element layer EML. In such an embodiment, the filler FL may be omitted, and the optical wavelength conversion layer QDL and the color filter layer CFL may be disposed on the thin film encapsulation layer. 
     A surface of each of the flexible films  122  may be attached on a surface of the first substrate  111  of the display panel  110 , and an opposing surface of each of the flexible films  122  may be attached to a surface of the source circuit board  140 . In an embodiment, as shown in  FIG.  1   , the size of the first substrate  111  is larger than that of the second substrate  112 , such that one side of the first substrate  111  may be exposed without being covered by the second substrate  112 . The flexible films  122  may be attached to one side portion of the first substrate  111  exposed without being covered by the second substrate  112 . Each of the flexible films  122  may be attached to one surface of the first substrate  111  and one surface of the source circuit board  140  using an anisotropic conductive film. 
     Each of the flexible films  122  may be a flexible film such as a tape carrier package or a chip on film. In an embodiment, each of the flexible films  122  may be bent toward the lower portion of the first substrate  111  as shown in  FIGS.  3 ,  4 , and  5   . In such an embodiment, the source circuit boards  140 , the first cables  150 , and the control circuit board  160  may be disposed on the lower surface of the lower chassis  180 . Although it is illustrated in  FIG.  1    that eight flexible films  122  are attached onto the first substrate  111  of the display panel  110 , the number of the flexible films  122  in embodiments is not limited thereto. 
     The source driving circuit  121  may be disposed on one surface of each of the flexible films  122 . The source driving circuits  121  may be formed of or defined by an integrated circuit (“IC”). Each of the source driving circuits  121  converts digital video data into analog data voltages based on the source control signal of the timing control circuit  170 , and supplies the analog data voltages to the data lines of the display panel  110 . 
     The display panel  110  may include scan lines intersecting the data lines, and pixels arranged in the areas defined by the data lines and the scan lines. The scan lines may receive scan signals from a scan driver formed on the display panel  110 . The scan driver may include a plurality of thin film transistors to generate scan signals based on a scan control signal of the timing control circuit  170 . Each of the pixels is connected to at least one data line and at least one scan line, and receives a data voltage of the data line when the scan signal is supplied to the scan line. 
     Each of the source circuit boards  140  may be connected to the control circuit board  160  through the first cables  150 . Each of the source circuit boards  140  may include first connectors  151   a  for connection thereof to the first cables  150 . Each of the source circuit boards  140  may be a flexible printed circuit board or a printed circuit board. The first cables  150  may be flexible cables. 
     In an embodiment, the control circuit board  160  may be connected to the source circuit boards  140  through the first cables  150 . In such an embodiment, the control circuit board  160  may include second connectors  152   a  for connection thereof to the first cables  150 . The control circuit board  160  may be fixed on one surface of the lower chassis  180  through a fixing member such as a screw. The control circuit board  160  may be a flexible printed circuit board or a printed circuit board. 
     Although it is illustrated in  FIG.  2    that four first cables  150  connect the source circuit boards  140  and the control circuit board  160 , the number of the first cables  150  in embodiments is not limited thereto. Further, although it is illustrated in  FIG.  2    that two source circuit boards are provided, the number of the source circuit boards  140  in embodiments is not limited thereto. 
     Alternatively, when the number of the flexible films  122  is small, the source circuit boards  140  may be omitted. In such an embodiment, the flexible films  122  may be directly connected to the control circuit board  160 . 
     The timing control circuit  170  may be disposed on one surface of the control circuit board  160 . The timing control circuit  170  may be defined by or formed as an IC. The timing control circuit  170  may receive digital video data and timing signals from the system-on-chip of a system circuit board, and may generate a source control signal for controlling the timing of the source driving circuits based on the timing signals. 
     The sound driving circuit  171  may be disposed on one surface of the control circuit board  160 . The sound driving circuit  171  may be defined by or formed as an IC. The sound driving circuit  171  may receive sound data from a system circuit board. The sound driving circuit  171  may convert the sound data, which is digital data, into a first sound signal, a second sound signal and a third sound signal, which are analog signals. The sound driving circuit  171  may output the first sound signal to the first sound generator  210 , may output the second sound signal to the second sound generator  220 , and may output the third sound signal to the third sound generator  230 . 
     The system-on-chip may be mounted on a system circuit board that is connected to the control circuit board  160  through another flexible cable, and may be formed as an IC. The system-on-chip may be a processor of a smart television (“TV”), a central processing unit (“CPU”) or a graphic card of a desktop or laptop computer, or an application processor of a smart phone or a tablet PC. The system circuit board may be a flexible printed circuit board or a printed circuit board. 
     A power supply circuit may be additionally attached to one surface of the control circuit board  160 . The power supply circuit may generate voltages used for driving the display panel  110  from a main power source applied from the system circuit board, and may supply the voltages to the display panel  110 . In one embodiment, for example, the power supply circuit may generate a high-potential voltage, a low-potential voltage, and an initialization voltage for driving the organic light emitting element, and may supply the generated voltages to the display panel  110 . In an embodiment, the power supply circuit may generate and supply driving voltages for driving the source driving circuits  121 , the timing control circuit  170 , and the like. The power supply circuit may be defined by or formed as an IC. Alternatively, the power supply circuit may be disposed on another power supply circuit board separately formed from the control circuit board  160 . The power supply circuit board may be a flexible printed circuit board or a printed circuit board. 
     The first sound generator  210 , the second sound generator  220 , and the third sound generator  230  may be disposed on a second surface of the first substrate  111  opposite to the first surface of the first substrate  111 . The first sound generator  210  may be a vibrating device capable of vibrating the display panel  110  in the third direction (Z-axis direction) corresponding to the first sound signal of the sound driving circuit  171 . The second sound generator  220  may be a vibrating device capable of vibrating the display panel  110  in the third direction (Z-axis direction) corresponding to the second sound signal of the sound driving circuit  171 . The third sound generator  230  may be a vibrating device capable of vibrating the display panel  110  in the third direction (Z-axis direction) corresponding to the third sound signal of the sound driving circuit  171 . 
     In an embodiment, the first sound generator  210  may be an exciter for vibrating the display panel  110  by generating a magnetic force using a voice coil as shown in  FIGS.  10  and  11   . In an embodiment, each of the second sound generator and the second sound generator may be a piezoelectric element or piezoelectric actuator for vibrating the display panel  110  using a piezoelectric material that contracts and expands based on the applied voltage as shown in  FIGS.  12  and  13   . 
     The first sound generator  210  may serve as a low sound generator for outputting a sound of a low frequency band. The second sound generator  220  may serve as a high sound generator for outputting a sound of a high frequency band. The third sound generator  230  may serve as a high sound generator for outputting a sound of a high frequency band. The sound of a low frequency band may indicate a sound of a low frequency band having a frequency of about 800 megahertz (MHz) or less, and the sound of a high frequency band may indicate a sound of a high frequency band having a frequency higher than about 800 MHz. However, the embodiment of the invention is not limited thereto. Further, when the sound of a low frequency band is a sound of a low frequency band having a frequency of about 800 MHz or less, both a low sound and a middle sound may be included. 
     The lower chassis  180  may be disposed on the second surface of the first substrate  111 . A hole H, in which the first sound generator  210  is disposed, may be defined or formed in an area of the lower chassis  180  corresponding to the first sound generator  210 . In such an embodiment, the lower chassis  180  may be provided with a first cable hole CH 1  through which the first sound circuit board  251  for connecting the control circuit board  160  to the second sound generator  220  and the control circuit board  160  are passed, and a second cable hole CH 2  through which the second sound circuit board  252  for connecting the third sound generator  230  is disposed. The lower chassis  180  may include or be made of a metal or a reinforced glass. 
     As described above, according to an embodiment of the display device  10  shown in  FIG.  1   , the first sound generator  210  may output a sound of a low frequency band by using the display panel  110  as a vibration plate, and the second sound generator  220  and the third sound generator  230  may output a sound of a high frequency band by using the display panel  110  as a vibration plate. In such an embodiment, since the sound of a low frequency band and the sound of a high frequency band may be output in the front direction (or Z-axis direction) of the display device  10 , sound quality may be improved. 
     In an embodiment, as illustrated in  FIG.  1   , the display device  10  is a middle- or large-sized display device including a plurality of source driving circuits  121 , but the invention is not limited thereto. Alternatively, the display device  10  may be a small-sized display device including a single source driving circuit  121 . In such an embodiment, the flexible films  122 , the source circuit boards  140 , and the first cables  150  may be omitted. In such an embodiment, the source driving circuit  121  and the timing control circuit  170  may be integrated into a single IC to be attached onto one flexible circuit board, or may be attached onto the first substrate  111  of the display panel  110 . Herein, middle- and large-sized display devices may include monitors and TVs, for example, and small-sized display devices may include smart phones and table PCs, for example. 
       FIG.  2    is a bottom view showing an embodiment of a display panel of  FIG.  1    in a state where flexible films are unfolded,  FIG.  3    is a bottom view showing an embodiment of a display panel coupled with a lower chassis when flexible films are bent toward the lower portion of the lower chassis,  FIG.  4 A  is a cross-sectional view taken along line I-I′ of  FIG.  2   ,  FIG.  4 B  is an enlarged view of the encircled portion of  FIG.  4 A , and  FIG.  5    is a cross-sectional view taken along line II-IP of  FIG.  2   . 
     Referring to  FIGS.  2  to  5   , the first surface of the first substrate  111  and the first surface of the second substrate  112  may face each other. A pixel array layer  113  may be disposed between the first surface of the first substrate  111  and the first surface of the second substrate  112 . The pixel array layer  113 , as shown in  FIG.  9   , may include a plurality of pixels PX 1 , PX 2 , and PX 3  that emit light. The pixel array layer  113  will be described later in greater detail with reference to  FIG.  9   . 
     The heat radiation film  130  may be disposed on the second surface of the first substrate  111 . The first sound generator  210  may be disposed on one surface of the heat radiation film  130 . The heat radiation film  130  serves to radiate the heat generated by the first sound generator  210 . In an embodiment, the heat radiation film  130  may include a graphite layer or a metal layer such as a silver (Ag) layer, a copper (Cu) layer, or an aluminum (Al) layer, each having high thermal conductivity. 
     In an embodiment, the heat radiation film  130  may include a plurality of graphite layers or a plurality of metal layers, which are formed in the first direction (X-axis direction) and the second direction (Y-axis direction). In such an embodiment, since the heat generated by the first sound generator  210  may be diffused in the first direction (X-axis direction) and the second direction (Y-axis direction), the heat may be discharged more effectively. Therefore, the influence of the heat generated by the first sound generator  210  due to the heat radiation film  130  on the display panel  110  may be minimized. In an embodiment, the thickness D 1  of the heat radiation film  130  may be thicker than the thickness D 2  of the first substrate  111  and the thickness D 3  of the second substrate  112  to further reduce the influence of the heat generated by the first sound generator  210  on the display panel  110 . In this specification, the first direction (X-axis direction) may be a width direction of the display panel  110 , the second direction (Y-axis direction) may be a height direction of the display panel  110 , and the third direction (Z-axis direction) may be a thickness direction of the display panel  110 . 
     The size of the heat radiation film  130  may be smaller than that of the first substrate  111 , and thus the edge of one surface of the first substrate  111  may be exposed without being covered by the heat radiation film  130 . 
     In an alternative embodiment, the heat radiation film  130  may be omitted, and in such an embodiment, the components arranged on one surface of the heat radiation film  130  may be arranged on the second surface of the first substrate  111 . 
     The flexible films  122  may be bent toward the lower portion of the lower chassis  180 , and may be attached to the source circuit board  140  on one surface of the lower chassis  180 . The source circuit board  140  and the control circuit board  160  may be disposed on one surface of the lower chassis  180 , and may be connected to each other through the first cables  150 . 
     The first sound generator  210  may be disposed closer to the center of the display panel  110  as compared with the second sound generator  220  and the third sound generator  230 . The second sound generator  220  may be disposed closer to one side of the display panel  110 , for example, the right side of the display panel  110 . The third sound generator  230  may be disposed close to the other side of the display panel, for example, the left side of the display panel  110 . 
     In an embodiment, as shown in  FIGS.  10  and  11   , the first sound generator  210  may include a magnet  211 , a bobbin  212 , a voice coil  213 , and a plate  215 . The bobbin  212  may be attached to one surface of the heat radiation film  130  by an adhesive member. The adhesive member may be a double-sided adhesive or a double-sided tape. The voice coil  213  may be wound (or rolled) on the outer peripheral surface of the bobbin  212 . Since the bobbin  212  is formed to have a cylindrical shape, a central protrusion of the magnet  211  is disposed inside the bobbin  212 , and the side wall of the magnet  211  may be disposed outside the bobbin  212 . The plate  215  may be disposed on the lower surface of the magnet  211 . The plate  215  may be fixed to one surface of the control circuit board  160  through a fixing member  216  such as a screw. 
     The magnet  211  and the bobbin  212  are disposed in the hole H of the lower chassis  180 , and the plate  215  is disposed on one surface of the lower chassis  180  and is not disposed in the hole H of the lower chassis  180 . The size of the hole H may be smaller than the size of the plate  215 . 
     In an embodiment, as shown in  FIGS.  3  to  5   , the magnet  211  and the bobbin  212  may have a circular shape in a plan view, the plate  215  has a rectangular shape in a plan view, and the hole has a circular shape in a plan view. However, the shapes of the plate  215 , the bobbin  212 , and the hole H in a plan view are not limited to those shown in  FIGS.  3  to  5   . In one alternative embodiment, for example, the bobbin  212  and the hole H may have an elliptical shape or a polygonal shape in a plan view. In another alternative embodiment, the plate  215  may have a circular shape, an elliptical shape, or a polygonal shape in a plan view. 
     The bobbin  212  of the first sound generator  210  may be fixed on one surface of the heat radiation film  130 , and the magnet  211  may be fixed to the lower chassis  180 . Therefore, the bobbin  212  on which the voice coil  213  is wound may reciprocate in the third direction (Z-axis direction) according to the applied magnetic field formed around the voice coil  213 , and thus the display panel  110  may vibrate. 
     Each of the second sound generator  220  and the third sound generator  230  may be attached onto one surface of the heat radiation film  130  by an adhesive member such as a pressure-sensitive adhesive. The second sound generator  220  may be electrically connected to the control circuit board  160  by the first sound circuit board  251 , and the third sound generator  230  may be electrically connected to the control circuit board  160  by the second sound circuit board  252 . Each of the first sound circuit board  251  and the second sound circuit board  252  may be a flexible printed circuit board or a flexible cable. 
     A first pad and a second pad may be disposed on one side of each of the first sound circuit board  251  and the second sound circuit board  252 . The first pad of the first sound circuit board  251  may be connected to the first electrode of the second sound generator  220 , and the second pad of the first sound circuit board  251  may be connected to the second electrode of the second sound generator  220 . The first pad of the second sound circuit board  252  is connected to the first electrode of the third sound generator  230 , and the second pad of the second sound circuit board  252  may be connected to the second electrode of the third sound generator  230 . 
     A connection portion for connecting to a second-B connector  152   b  of the control circuit board  160  may be disposed on the other side of each of the first sound circuit board  251  and the second sound circuit board  252 . The second sound generator  220  may be connected to the second-B connector  152   b  of the control circuit board  160  by the connection portion of the first sound circuit board  251 . The third sound generator  230  may be connected to another second-B connector  152   b  of the control circuit board  160  by the connection portion of the second sound circuit board  252 . 
     The timing control circuit  170  and the sound driving circuit  171  may be disposed on the control circuit board  160 . The sound driving circuit  171  may be disposed on another circuit board other than the control circuit board  160 . In one embodiment, for example, the sound driving circuit  171  may be disposed on a system circuit board, a power supply circuit board, or a sound circuit board. The sound circuit board refers to a circuit board on which only the sound driving circuit  171  is disposed without other ICs. 
     The sound driving circuit  171  may include a digital signal processor (“DSP”) for digital-processing sound signals, a digital-analog converter DAC for converting the digital signals processed from the digital signal processor into driving voltages as analog signals, and an amplifier (“AMP”) for amplifying and outputting the analog driving voltages converted from the digital-analog converter. 
     The sound driving circuit  171  may generate a first sound signal including a first-A voltage (or a first first voltage) and a first-B voltage (or a second first voltage) for driving the first sound generator  210  based on stereo signals. The sound driving circuit  171  may generate a second sound signal including a second-A voltage (or a first second voltage) and a second-B voltage (or a second second voltage) for driving the second sound generator  220  based on stereo signals. The sound driving circuit  171  may generate a third sound signal including a third-A voltage (or a first third voltage) and a third-B voltage (or a second third voltage) for driving the third sound generator  230  according to stereo signals. 
     The first sound generator  210  may receive a first sound signal including the first-A driving voltage and the first-B driving voltage from the sound driving circuit  171 . The first sound generator  200  may output a sound by vibrating the display panel  110  based on the first-A driving voltage and the first-B driving voltage. In an embodiment, where the lower plate  215  of the first sound generator  210  is disposed on the lower chassis  180 , one end and the other end of the voice coil  213  of the first sound generator  210  may be electrically connected to a first sound wiring WL 1  and a second sound wiring WL 2 . The first sound wiring WL 1  and the second sound wiring WL 2  may be electrically connected to metal lines of the control circuit board  160 . 
     The second sound generator  220  may receive a second sound signal including the second-A driving voltage and the second-B driving voltage from the sound driving circuit  171 . The second sound generator  220  may output a sound by vibrating the display panel  110  based on the second-A driving voltage and the second-B driving voltage. The second sound signal of the sound driving circuit  171  may be transmitted to the second sound generator  220  through the first sound circuit board  251 . 
     The third sound generator  230  may receive a third sound signal including the third-A driving voltage and the third-B driving voltage from the sound driving circuit  171 . The third sound generator  230  may output a sound by vibrating the display panel  110  based on the third-A driving voltage and the third-B driving voltage. The third sound signal of the sound driving circuit  171  may be transmitted to the third sound generator  230  through the second sound circuit board  252 . 
     In an embodiment, the second sound generator  220  and the third sound generator  230  may be disposed on one surface of the heat radiation film  130 . In such an embodiment, the first sound circuit board  251  connected to the second sound generator  220  may be connected to the second-B connector  152   b  of the control circuit board  160  through the first cable hole CH 1  defined in the lower chassis  180 . In an embodiment, the second sound circuit board  252  connected to the third sound generator  230  may be connected to another second-B connector  152   b  of the control circuit board  160  through the second cable hole CH 2  defined in the lower chassis  180 . The first cable hole CH 1  may be formed between one side of the control circuit board  160  and the second sound generator  220  when seen in a plan view. The second cable hole CH 2  may be disposed between the other side of the control circuit board  160  and the third sound generator  230  when seen in a plan view. 
     A first blocking member  191 , a second blocking member  192 , and a third blocking member  193  may serve to block the propagation of vibration of the display panel  110  generated by the sound generators  210 ,  220 , and  230  or block the transmission of a sound generated by the vibration of the display panel  110 . The first blocking member  191 , the second blocking member  192 , and the third blocking member  193  may be attached to one surface of the heat radiation film  130  and the other surface of the lower chassis  180 . Alternatively, the heat radiation film  130  is omitted, and the first blocking member  191 , the second blocking member  192  and the third blocking member  193  may be attached to one surface of the first substrate  111  and the other surface of the lower chassis  180 . 
     In an embodiment, the first blocking member  191  may be disposed on four side edges of the heat radiation film  130  as shown in  FIG.  2   . The second blocking member  192  may extend in the second direction (Y-axis direction), and may be disposed between the first sound generator  210  and the second sound generator  220 . The third blocking member  193  may extend in the second direction (Y-axis direction), and may be disposed between the first sound generator  210  and the third sound generator  230 . Thus, the vibration plane of the display panel  110  may be divided into three areas A 1 , A 2 , and A 3  as shown in  FIG.  2   . 
     The first sound generator  210  may be disposed in the first area A 1  surrounded by the first blocking member  191 , the second blocking member  192 , and the third blocking member  193 . The second sound generator  220  may be disposed in the second area A 2  surrounded by the first blocking member  191  and the second blocking member  192 . The third sound generator  230  may be disposed in the third area A 3  surrounded by the first blocking member  191  and the third blocking member  193 . Since the first sound generator  210 , the second sound generator  220  and the third sound generator  230  are disposed in different areas A 1 , A 2  and A 3  surrounded by the first blocking member  191 , the second blocking member  192  and the third blocking member  193 , it may be reduced that the vibration of the display panel  110  generated by the first sound generator  210 , the vibration of the display panel  110  generated by the second sound generator  220 , and the vibration of the display panel  110  generated by the third sound generator  230  influence each other. 
     The first sound generator  210 , the second sound generator  220  and the third sound generator  230  may be disposed in different areas by the first blocking member  191 , the second blocking member  192  and the third blocking member  193 . In one embodiment, for example, as shown in  FIG.  2   , the first sound generator  210  may be disposed in the first area A 1 , the second sound generator  220  may be disposed in the second area A 2 , and the third sound generator  230  may be disposed in the third area A 3 . Therefore, in such an embodiment, the first sound generator  210  may output a first sound of a low frequency band by vibrating the first area A 1  of the display panel  110 . In such an embodiment, the second sound generator  220  may output a second sound, which is a right stereo sound of a high frequency band, by vibrating the second area A 2  of the display panel  110 . In such an embodiment, the third sound generator  230  may output a third sound, which is a left stereo sound of a high frequency band, by vibrating the third area A 3  of the display panel  110 . Accordingly, in such an embodiment, the display device  10  may provide a stereo sound of a 2.1 channel to the user. 
     In an embodiment, as shown in  FIG.  4 B , each of the first blocking member  191 , the second blocking member  192 , and the third blocking member  193  may include a base film  191   a , a buffer layer  191   b , a sacrificial layer  191   c , a first adhesive layer  191   d , and a second adhesive layer  191   e.    
     The base film  191   a  may include or be formed of a plastic. In one embodiment, for example, the base film  191   a  may be formed of PET, but the material thereof is not limited thereto. 
     The buffer layer  191   b  may be disposed on one surface of the base film  191   a . The buffer layer  191   b  may include or be formed of a foam having elasticity. In one embodiment, for example, the buffer layer  191   b  may be formed of polyurethane, silicone, a rubber, or an aerogel, but the material thereof is not limited thereto. 
     The sacrificial layer  191   c  may be disposed on one surface of the buffer layer  191   b . In an embodiment, the sacrificial layer  191   c  serves to a layer which is separated in the case where the blocking member  190  is desired to be detached when the blocking member  190  is erroneously attached. In such an embodiment, a part of the first adhesive layer  191   d  and a part of the sacrificial layer  191   c  may remain on the other surface of the lower chassis  180 . The sacrificial layer  191   c  may include or be formed of a material having low elasticity. In one embodiment, for example, the sacrificial layer  191   c  may include or be formed of polyurethane, but the material thereof is not limited thereto. Alternatively, the sacrificial layer  191   c  may be omitted. 
     The first adhesive layer  191   d  may be disposed on one surface of the sacrificial layer  191   c . The first adhesive layer  191   d  may be attached to another surface (e.g., a surface opposite to the one surface) of the lower chassis  180 . The second adhesive layer  191   e  may be disposed on the another surface of the second base film  201 . The second adhesive layer  191   e  may be attached to one surface of the heat radiation film  130 . The first adhesive layer  191   d  and the second adhesive layer  191   e  may be an acrylic adhesive or a silicone adhesive, but are not limited thereto. 
     In an embodiment, as shown in  FIGS.  10  and  11   , the first sound generator  210  may be an exciter for vibrating the display panel  110  by generating a magnetic force using a voice coil. In an embodiment, as shown in  FIGS.  12  and  13   , each of the second sound generator and the second sound generator may be a piezoelectric element or piezoelectric actuator for vibrating the display panel  110  using a piezoelectric material that contracts and expands based on the applied voltage. The first sound outputted by vibrating the display panel  110  using the first sound generator  210  may be a sound of a low frequency band. Therefore, the vibration displacement of the display panel  110  generated by the first sound generator  210  may be larger than the vibration displacement of the display panel  110  generated by the second sound generator device  220  or the vibration displacement of the display panel  110  generated by the third sound generator device  230 . When the vibration displacement of the display panel  110  generated by the first sound generator  210  may be large, the vibration of the display panel  110  may be recognized by a viewer. 
     In an embodiment, a vibration damping member  400  may be disposed on one surface of the display panel  110 , and the first sound generator  210  may be disposed on the vibration damping member  400  to reduce the vibration displacement of the display panel  110  generated by the first sound generator  210 . The vibration damping member  400  may be attached onto the heat radiation film  130  disposed on the second surface of the first substrate  111 . The first sound generator  210  may be disposed at the center of the vibration damping member  400 . The vibration damping member  400  may not overlap the second sound generator  220  and the third sound generator  230  in the thickness direction of the display panel  110 . 
     The vibration damping member  400  may have high rigidity. Rigidity refers to the degree of resistance to deformation when the vibration damping member  400  receives a load and deforms. The vibration damping member  400  may include a metal material having low density to have high rigidity. In one embodiment, for example, the vibration damping member  400  may be an aluminum metal sheet, or may be a composite steel sheet including a first metal plate  410 , a second metal plate  420 , and an adhesive layer  430  disposed between the first metal plate  410  and the second metal plate  420 , as shown in  FIG.  6   . In such an embodiment, since the rigidity of the composite steel sheet is proportional to an elastic force, the thickness D 6  of the adhesive layer  430  may be greater than the thickness D 4  of the first metal plate  410  and the thickness D 5  of the second metal plate  420  to increase the elastic force. 
     The vibration damping member  400  may have a rectangular shape in a plan view. The corners of the vibration damping member  400  may be formed in a round shape having a curvature in a plan view. In an embodiment, as shown in  FIG.  2   , where the bobbin  212  of the first sound generator  210  is formed in a circular shape in a plan view, the vibration generated by the first sound generator  210  may be spread in a circular shape in a plan view. In an embodiment, where the corners of the vibration damping member  400  is formed in a rectangular shape in a plan view, the shape of spreading vibration is different from the shape of the corner of the vibration damping member  400 , such that vibration may be substantially reduced at the corners of the vibration damping member  400  or the form of vibration may be deformed. In a case where the corners of the vibration damping member  400  are formed in a round shape having a curvature, the vibration generated by the first sound generator  210  may be spread as it is. The curvature of each of the corners of the vibration damping member  400  may be substantially equal to the curvature of the bobbin  212  of the first sound generator  210 . 
     The vibration damping member  400  may be disposed in the first area A 1  surrounded by the first blocking member  191 , the second blocking member  192 , and the third blocking member  193 . The area of the vibration damping member  400  may be smaller than the area of the first area A 1 . The vibration damping member  400  may not be disposed in the second area A 2  surrounded by the first blocking member  191  and the second blocking member  192  and in the third area A 3  surrounded by the first blocking member  191  and the third blocking member  193 . 
     In an embodiment, as shown in  FIG.  2    that the length L 1  of the vibration damping member  400  in the first direction (X-axis direction) is substantially the same as the length L 2  of the vibration damping member  400  in the second direction (Y-axis direction), but the invention is not limited thereto. Alternatively, the length L 1  of the vibration damping member  400  in the first direction (X-axis direction) may be different from the length L 2  of the vibration damping member  400  in the second direction (Y-axis direction). In an embodiment, as shown in  FIG.  4 A , the vibration damping member  400  may overlap the control circuit board  160  in the third direction (Z-axis direction) which is the thickness direction of the display panel  110 . 
     According to an embodiment shown in  FIGS.  2  to  5   , since the vibration damping member  400  having high rigidity is disposed between the display panel  110  and the first sound generator  210 , the vibration displacement of the display panel  110  generated by the first sound generator  210  may be reduced such that the vibration of the display panel  110  may be effectively prevented from being recognized by a viewer seeing an image displayed thereon. 
     According to an embodiment shown in  FIGS.  2  to  5   , since the first sound circuit board  251  connected to the second sound generator  220  is connected to the control circuit board  160  through the first cable hole CH 1  defined in the lower chassis  180 , even when the second sound generator  220  is disposed on one surface of the heat radiation film  130  and the control circuit board  160  is disposed on one surface of the lower chassis  180 , the control circuit board  160  and the second sound generator  220  may be effectively electrically connected to each other. 
       FIG.  7    is a graph showing the vibration displacement of the display panel by the first sound generator according to the presence or absence of the vibration damping member. 
     In  FIG.  7   , X-axis indicates a length from the center of the first sound generator  210  in the first direction (X-axis direction) or the second direction (Y-axis direction), and Y-axis indicates a vibration displacement of the display panel  110 . 
     Referring to  FIG.  7   , in a case where the vibration damping member  400  is omitted, the vibration displacement of the display panel  110  in the third direction (Z-axis direction) may be at most about 0.45 millimeter (mm). In contrast, in a case where the vibration damping member  400  is disposed between the display panel  110  and the first sound generator  210 , the vibration displacement of the display panel  110  in the third direction (Z-axis direction) may be at most about 0.15 mm. The difference in vibration displacement of the display panel  110  in the third direction (Z-axis direction) may be at most about 0.3 mm according to the presence or absence of the vibration damping member  400 . That is, as shown in  FIG.  7   , the vibration displacement of the display panel  110  generated by the first sound generator  210  may be reduced due to the vibration damping member  400 . 
       FIG.  8    is a graph showing the sound pressure level with respect to the frequency of a first sound according to the presence or absence of the vibration damping member. 
     In  FIG.  8   , X-axis indicates a frequency of a first sound output by vibrating the display panel  110  using the first sound generator  210 , and Y-axis indicates a sound pressure level of the first sound. 
     Referring to  FIG.  8   , in a case where the vibration damping member  400  is omitted and when the vibration damping member  400  is disposed between the display panel  110  and the first sound generator  210 , there is little difference in sound pressure level of the first sound according to frequency. That is, since the vibration damping member  400  disperses the force of vibrating the display panel  110  by the first sound generator  210  to reduce the vibration displacement of the display panel  110 , the sound pressure level of the first sound according to frequency is not reduced even when the vibration displacement of the display panel  110  generated by the first sound generator  210  is reduced. Accordingly, the vibration energy applied to the display panel  110  by the first sound generator  210  may be maintained substantially as it is. 
       FIG.  9    is a cross-sectional showing an embodiment of a first substrate, a second substrate, and a pixel array layer of a display panel. 
     Referring to  FIG.  9   , an embodiment of the display panel  110  may include a first substrate  111 , a second substrate  112 , and a pixel array layer  113 . The pixel array layer  113  may include a thin film transistor layer TFTL and a light emitting element layer EML. 
     A buffer film  302  may be disposed on one surface of the first substrate  111  facing the second substrate  112 . The buffer film  302  may be disposed on the first substrate  111  to protect the thin film transistors  335  and the light emitting elements from moisture permeating through the first substrate  111  that is vulnerable to moisture permeation. The buffer film  302  may include or be formed of a plurality of alternately laminated inorganic films. In one embodiment, for example, the buffer film  302  may be a multilayer film in which one or more inorganic films of a silicon oxide film (SiOx), a silicon nitride film (SiNx), and a SiON film are alternately laminated. Alternatively, the buffer film may be omitted. 
     The thin film transistor layer TFTL is disposed on the buffer film  302 . The thin film transistor layer TFTL includes thin film transistors  335 , a gate insulating film  336 , an interlayer insulating film  337 , a protective film  338 , and a planarization film  339 . 
     The thin film transistor  335  is disposed on the buffer film  302 . The thin film transistor  335  includes an active layer  331 , a gate electrode  332 , a source electrode  333 , and a drain electrode  334 . Although it is illustrated in  FIG.  9    that the thin film transistor  335  has a top gate structure in which the gate electrode  332  is located over the active layer  331 , but the invention is not limited thereto. That is, the thin film transistors  335  may have a bottom gate structure in which the gate electrode  332  is located under the active layer  331  or in a double gate structure in which the gate electrode  332  is located both over and under the active layer  331 . 
     The active layer  331  is disposed on the buffer film  302 . The active layer  331  may include or be formed of a silicon-based semiconductor material or an oxide-based semiconductor material. A light blocking layer for blocking external light incident on the active layer  331  may be disposed between the buffer film and the active layer  331 . 
     The gate insulating film  336  may be disposed on the active layer  331 . The gate insulating film  316  may include or be formed of an inorganic film, for example, a silicon oxide film (SiOx), a silicon nitride film (SiNx), or a multilayer film thereof. 
     The gate electrode  332  and the gate line may be disposed on the gate insulating film  316 . The gate electrode  332  and the gate line may include or be formed of a single layer or multiple layers including any one of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or an alloy thereof. 
     The interlayer insulating film  337  may be disposed on the gate electrode  332  and the gate line. The interlayer insulating film  337  may include or be formed of an inorganic film, for example, a silicon oxide film (SiOx), a silicon nitride film (SiNx), or a multilayer film thereof. 
     The source electrode  333 , the drain electrode  334  and the data line may be disposed on the interlayer insulating film  337 . Each of the source electrode  333  and the drain electrode  334  may be connected to the active layer  331  through a contact hole defined through the gate insulating film  336  and the interlayer insulating film  337 . The source electrode  333 , the drain electrode  334  and the data line may have a single layer structure or a multilayer structure with one or more layers, each including molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or a combination (e.g., an alloy) thereof. 
     The protective film  338  for insulating the thin film transistor  335  may be disposed on the source electrode  333 , the drain electrode  334 , and the data line. The protective film  338  may include or be formed of an inorganic film, for example, a silicon oxide film (SiOx), a silicon nitride film (SiNx), or a multilayer film thereof. 
     The planarization film  339  may be disposed on the protective film  338  to planarize a step due to the thin film transistor  335 . The planarization film  339  may include or be formed of an organic film including an acryl resin, an epoxy resin, a phenolic resin, a polyamide resin, or a polyimide resin. 
     The light emitting element layer EML is disposed on the thin film transistor layer TFTL. The light emitting element layer EML includes light emitting elements and a pixel defining film  344 . 
     The light emitting elements and the pixel defining film  344  are disposed on the planarization film  339 . In an embodiment, the light emitting element may be an organic light emitting element. In such an embodiment, the light emitting element may include an anode electrode  341 , light emitting layers  342 , and a cathode electrode  343 . 
     The anode electrode  341  may be disposed on the planarization film  339 . The anode electrode  341  may be connected to the source electrode  333  of the thin film transistor  335  through a contact hole defined through the protective film  338  and the planarization film  339 . 
     The pixel defining film  344 , which defines pixels, may be disposed on the planarization film  339  to cover the edges of the anode electrode  341 . That is, the pixel defining film  344  serves to define sub-pixels PX 1 , PX 2 , and PX 3 . Each of the sub-pixels PX 1 , PX 2  and PX 3  has a structure in which the anode electrode  341 , the light emitting layer  342 , and the cathode electrode  343  are sequentially laminated one on another, and thus holes from the anode electrode  341  and electrons from the cathode electrode  343  are combined with each other in the light emitting layer  342  to emit light. 
     The light emitting layers  342  are disposed on the anode electrode  341  and the pixel defining film  344 . The light emitting layer  342  may be an organic light emitting layer. The light emitting layer  342  may emit light having a short wavelength such as blue light or ultraviolet light. The peak wavelength range of blue light may be about 450 nanometers (nm) to 490 nm, and the peak wavelength range of ultraviolet light may be less than 450 nm. In an embodiment, the light emitting layer  342  may be a common layer formed commonly for or to cover the sub-pixels PX 1 , PX 2 , and PX 3 . In such an embodiment, the display panel  110  may include an optical wavelength conversion layer (not shown) for converting light of a short wavelength such as blue light or ultraviolet light emitted from the light emitting layer  342  into red light, green light, and blue light, and a color filter layer CFL for transmitting red light, green light, and blue light. 
     The light emitting layer  342  may include a hole transporting layer, a light emitting layer, and an electron transporting layer. Further, the light emitting layer  342  may be in a tandem structure of two stacks or more, and in this case, a charge generating layer may be formed between the stacks. 
     The cathode electrode  343  is disposed on the light emitting layer  342 . The cathode electrode  343  may be disposed to cover the light emitting layer  342 . The cathode electrode  343  may be a common layer formed commonly in the pixels. 
     The light emitting element layer EML is formed in a top emission manner in which light is emitted in a direction toward the second substrate  112 , that is, in an upward direction. In such an embodiment, the anode electrode  341  may include or be formed of a high-reflectance metal material such as a laminate structure (Ti/Al/Ti) of aluminum and titanium, a laminate structure (ITO/Al/ITO) of aluminum and indium tin oxide (“ITO”), an APC alloy, or a laminate structure (ITO/APC/ITO) of an APC alloy and ITO. The APC alloy may be an alloy of silver (Ag), palladium (Pd), and copper alloy (Cu). The cathode electrode  263  may include or be formed of a transparent conductive material (“TCO”) such as ITO or indium zinc oxide (“IZO”), which is light-transmissive, or a semi-transmissive conductive material such as magnesium (Mg), silver (Ag), or an alloy of magnesium (Mg) and silver (Ag). In an embodiment, where the cathode electrode  343  is formed of a semi-transmissive conductive material, light emission efficiency may be increased by microcavity effects. 
     The encapsulation layer  345  is disposed on the light emitting element layer EML. The encapsulation layer  305  serves to prevent oxygen or moisture from permeating the light emitting layer  342  and the cathode electrode  343 . In such an embodiment, the encapsulation layer  345  may include at least one inorganic film. The inorganic film may include or be formed of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, or titanium oxide. The encapsulation layer  345  may further include at least one organic film. The organic film may be formed to have a sufficient thickness to prevent foreign matter (particles) from penetrating the encapsulation layer  305  and entering the light emitting layer  342  and the cathode electrode  343 . The organic film may include at least one of epoxy, acrylate and urethane acrylate. 
     The color filter layer CFL is disposed on one surface of the second substrate  112  facing the first substrate  111 . The color filter layer CFL may include a black matrix  360  and color filters  370 . 
     The black matrix  360  may be disposed on one surface of the second substrate  112 . The black matrix  360  may be disposed not to overlap the sub-pixels PX 1 , PX 2 , and PX 3  but to overlap the pixel defining film  344 . The black matrix  360  may include a black dye that may block light without transmitting the light, or may include an opaque metal material. 
     The color filters  370  may be arranged to overlap the sub-pixels PX 1 , PX 2 , and PX 3 . In an embodiment, first color filters  371  may be arranged to overlap the first sub pixels PX 1 , second color filters  372  may be arranged to overlap the second sub-pixels PX 2 , and third color filters  373  may be arranged to overlap the third sub-pixels PX 3 . In such an embodiment, the first color filter  371  may be a light transmitting filter of a first color that transmits light of the first color, the second color filter  372  may be a light transmitting filter of a second color that transmits light of the second color, and the third color filter  373  may be a light transmitting filter of a third color that transmits light of the third color. In one embodiment, for example, the first color may be red, the second color may be green, and the third color may be blue, but the invention is not limited thereto. In such an embodiment, the peak wavelength range of red light transmitted through the first color filter  371  may be about 620 nm to about 750 nm, the peak wavelength range of green light transmitted through the second color filter  372  may be about 500 nm to about 570 nm, and the peak wavelength range of blue light transmitted through the third color filter  373  may be about 450 nm to about 490 nm. 
     The edges of the two color filters adjacent to each other may overlap the black matrix  360 . Thus, the color mixture that may occur when light emitted from the light emitting layer  342  of any one sub-pixel moves to the color filter of the sub-pixel adjacent thereto may be effectively prevented by the black matrix  360 . 
     An overcoat layer may be disposed on the color filters  370  to planarize a step due to the color filters  370  and the black matrix  360 . Alternatively, the overcoat layer may be omitted. 
     The optical wavelength conversion layer QDL is disposed on the color filter layer CFL. The optical wavelength conversion layer QDL may include a first capping layer  351 , a first wavelength conversion layer  352 , a second wavelength conversion layer  353 , a third wavelength conversion layer  354 , a second capping layer  355 , an interlayer organic film  356 , and a third capping layer  357 . 
     The first capping layer  351  may be disposed on the color filter layer CFL. The first capping layer  351  serves to prevent external moisture or oxygen from penetrating the first wavelength conversion layer  352 , the second wavelength conversion layer  353 , and the third wavelength conversion layer  354  through the color filter layer CFL. The first capping layer  351  may include or be formed of an inorganic film including silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, or titanium oxide. 
     The first wavelength conversion layer  352 , the second wavelength conversion layer  353 , and the third wavelength conversion layer  354  may be arranged on the first capping layer  351 . 
     The first wavelength conversion layer  352  may be disposed to overlap the first sub-pixel PX 1 . The first wavelength conversion layer  352  may convert short-wavelength light such as blue light or ultraviolet light emitted from the light emitting layer  342  of the first sub-pixel PX 1  into light of the first color. In an embodiment, the first wavelength conversion layer  352  may include a first base resin, a first wavelength shifter, and a first scatterer. 
     In an embodiment, the first base resin is a material having high light transmittance and high dispersion characteristics for the first wavelength shifter and the first scatterer. In one embodiment, for example, the first base resin may include an organic material such as an epoxy resin, an acrylic resin, a cardo-based resin, or an imide resin. 
     The first wavelength shifter may convert or shift the wavelength range of the incident light. The first wavelength shifter may be a quantum dot, a quantum rod, or a phosphor. In an embodiment, where the first wavelength shifter is a quantum dot, the first wavelength shifter may have a specific band gap depending on its composition and size as a semiconductor nanocrystal material. Therefore, the first wavelength shifter may absorb incident light and then emit light having a specific wavelength. In an embodiment, the first wavelength shifter may have a core-shell structure including a core including nanocrystals and a shell surrounding the core. In such an embodiment, the nanocrystals constituting the core may include IV group nanocrystals, II-VI group compound nanocrystals, III-V group compound nanocrystals, IV-VI group nanocrystals, or a combination thereof, for example. The shell may serve as a protective layer for preventing the chemical denaturation of the core to maintain semiconductor characteristics and/or as a charging layer for imparting electrophoretic characteristics to the quantum dots. The shell may have a single layer structure or a multilayer structure, and the shell may include a metal or nonmetal oxide, a semiconductor compound, or a combination thereof, for example. 
     The first scatterer may have a different refractive index different from the first base resin, and may form an optical interface together with the first base resin. In one embodiment, for example, the first scatterer may be light scattering particles. In one embodiment, for example, the first scatterer may be metal oxide particles such as titanium oxide (TiO 2 ) particles, silicon oxide (SiO 2 ) particles, zirconium oxide (ZrO 2 ) particles, aluminum oxide (Al 2 O 3 ) particles, indium oxide (In 2 O 3 ) particles, or zinc oxide (ZnO) particles. Alternatively, the first scatterer may be organic particles such as acrylic resin particles or urethane resin particles. 
     The first scatterer may scatter incident light in a random direction without substantially changing the wavelength of light passing through the first wavelength conversion layer  352 . Accordingly, since the length of a path of light passing through the first wavelength conversion layer  352  may be increased, the color conversion efficiency by the first wavelength shifter may be increased. 
     In an embodiment, the first wavelength conversion layer  352  may overlap the first color filter  371 . Therefore, a part of short-wavelength light such as blue light or ultraviolet light provided from the first sub-pixel PX 1  may not be converted into light of the first color by the first wavelength shifter, but may be directly transmitted through the first wavelength conversion layer  352 . However, short wavelength light such as blue light or ultraviolet light, which is not converted by the first wavelength conversion layer  352  and is incident on the first color filter  371 , may not be transmitted through the first color filter  371 . In contrast, the light of the first color converted by the first wavelength conversion layer  352  may be transmitted through the first color filter  371  and emitted toward the second substrate  112 . 
     The second wavelength conversion layer  353  may be disposed to overlap the second sub-pixel PX 2 . The second wavelength conversion layer  353  may convert short-wavelength light such as blue light or ultraviolet light emitted from the light emitting layer  342  of the second sub-pixel PX 2  into light of the second color. In an embodiment, the second wavelength conversion layer  353  may include a second base resin, a second wavelength shifter, and a second scatterer. Since the second base resin, second wavelength shifter and second scatterer of the second wavelength conversion layer  353  are substantially the same as those described with respect to the first wavelength conversion layer  352 , any repetitive detailed description thereof will be omitted. In an embodiment, where the first wavelength shifter and the second wavelength shifter are quantum dots, the diameter of the second wavelength shifter may be smaller than the diameter of the first shifter diameter. 
     In an embodiment, the second wavelength conversion layer  353  may overlap the second color filter  372 . Therefore, a part of short-wavelength light such as blue light or ultraviolet light provided from the second sub-pixel PX 2  may not be converted into light of the second color by the second wavelength shifter, but may be directly transmitted through the second wavelength conversion layer  353 . However, short wavelength light such as blue light or ultraviolet light, which is not converted by the second wavelength conversion layer  353  and is incident on the second color filter  372 , may not be transmitted through the second color filter  372 . In contrast, the light of the second color converted by the second wavelength conversion layer  353  may be transmitted through the second color filter  372  and emitted toward the second substrate  112 . 
     The third wavelength conversion layer  354  may be disposed to overlap the third sub-pixel PX 3 . The third wavelength conversion layer  354  may convert short-wavelength light such as blue light or ultraviolet light emitted from the light emitting layer  342  of the third sub-pixel PX 3  into light of the third color. For this purpose, the third wavelength conversion layer  354  may include a third base resin and a third scatterer. Since the third base resin and third scatterer of the third wavelength conversion layer  354  are substantially the same as those described with respect to the first wavelength conversion layer  352 , any repetitive detailed description thereof will be omitted. 
     In an embodiment, the third wavelength conversion layer  354  may overlap the third color filter  373 . Therefore, short-wavelength light such as blue light or ultraviolet light provided from the third sub-pixel PX 3  may be directly transmitted through the third wavelength conversion layer  354 , and the light having passed through the third wavelength conversion layer  354  may be transmitted through the third color filter  373  and emitted toward the second substrate  112 . 
     The second capping layer  355  may be disposed on the first wavelength conversion layer  352 , the second wavelength conversion layer  353 , the third wavelength conversion layer  354 , and the first capping layer  351  exposed without being covered by the first to third wavelength conversion layers  352 ,  353 , and  354 . The second capping layer  355  serves to prevent external moisture or oxygen from penetrating the first wavelength conversion layer  352 , the second wavelength conversion layer  353 , and the third wavelength conversion layer  354 . The second capping layer  355  may include or be formed of an inorganic film including silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, or titanium oxide. 
     The interlayer organic film  356  may be disposed on the second capping layer  355 . The interlayer organic film  356  may be a planarization layer for planarizing a step due to the wavelength conversion layers  352 ,  353 , and  354 . The interlayer organic film  356  may be an organic film such as an acryl resin film, an epoxy resin film, a phenolic resin film, a polyamide resin film, or a polyimide resin film. 
     The third capping layer  357  may be disposed on the interlayer organic film  356 . The third capping layer  357  may include or be formed of an inorganic film including silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, or titanium oxide. 
     The filler FL may be disposed between the thin film encapsulation layer TFEL disposed on the first substrate  111  and the third capping layer  357  disposed on the second substrate  112 . The filler FL may include or be made of a material having a buffering function. In one embodiment, for example, the filler FL may be an organic film such as an acryl resin film, an epoxy resin film, a phenolic resin film, a polyamide resin film, or a polyimide resin film. 
     In an embodiment, a sealing material for attaching the first substrate  111  to the second substrate  112  may be disposed in the non-display area of the display panel  110 , and the filler FL may be surrounded by the sealing material when viewed on the plane. The sealing material may be a glass frit or a sealant. 
     According to an embodiment shown in  FIG.  9   , the first to third sub-pixels PX 1 , PX 2  and PX 3  emit short-wavelength light such as blue light or ultraviolet light. In such an embodiment, the light of the first sub-pixel PX 1  may be converted into light of the first color through the first wavelength conversion layer  352  and then output through the first color filter CF 1 , the light of the second sub-pixel PX 1  may be converted into light of the second color through the second wavelength conversion layer  353  and then output through the second color filter CF 2 , and the light of the third sub-pixel PX 3  may be output through the third wavelength conversion layer  354  and the third color filter CF 3 , so that white light may be output. 
     In an embodiment, where the sub-pixels PX 1 , PX 2 , and PX 3  has a top emission manner in which light is emitted toward the second substrate  112 , that is, in an upward direction, as shown in  FIG.  9   , the heat radiation film  130  including an opaque material such as graphite or aluminum may be disposed on one surface of the first substrate  111 . 
       FIGS.  10  and  11    are exemplary views showing the vibration of the display panel by the first sound generator. 
     Referring to  FIGS.  10  and  11   , an embodiment of the first sound generator  210  may be an exciter for vibrating the display panel  110  by generating a magnetic force using a voice coil. In such an embodiment, a hole may be defined or formed in an area where the first sound generator  210  is disposed in the lower chassis  180 . 
     The first sound generator  210  may include a magnet  211 , a bobbin  212 , a voice coil  213 , a damper  214 , a plate  215 , a first fixing members  216 , and second fixing members  217 . 
     The magnet  211  may be a permanent magnet, and a sintered magnet such as barium ferrite may be used as the magnet  211 . The magnet  211  may be a ferric trioxide (Fe 2 O 3 ) magnet, a barium carbonate (BaCO 3 ) magnet, a neodymium magnet, or an alloy cast magnet of strontium ferrite having improved magnetic properties, aluminum (Al), nickel (Ni), or cobalt (Co), but is not limited thereto. The material of neodymium magnet may be, for example, neodymium-iron-boron (Nd—Fe—B). 
     The magnet  211  may include a flat portion  211   a , a central protrusion portion  211   b  protruding from the center of the flat portion  211   a , and a side wall portion  211   c  protruding from the edge of the flat portion  211   a . The central protrusion portion  211   b  and the side wall portion  211   c  may be spaced apart from each other by a predetermined distance, and thus a predetermined space may be formed between the central protrusion portion  211   b  and the side wall portion  211   c . In an embodiment, the magnet  211  has a cylindrical shape, and a circular space may be formed at a bottom surface of the cylindrical shape. 
     The central protrusion portion  211   b  of the magnet  211  may have magnetic properties of the N pole, and the flat portion  211   a  and the sidewall portion  211   c  may have magnetic properties of the S pole, so that an external magnetic field may be formed between the central protrusion portion  211   b  and plate  215  of the magnet  211  and between the central protrusion portion  211   b  and side wall portion  211   c  of the magnet  211 . 
     The bobbin  212  may be in a cylindrical shape. The central protrusion portion  211   b  of the magnet  211  may be disposed inside the bobbin  212 . In an embodiment, the bobbin  212  may be disposed to surround the central protrusion portion  211   b  of the magnet  211 . In such an embodiment, the side wall portion  211   c  of the magnet  211  may be disposed outside the bobbin  212 . In such an embodiment, the side wall portion  211   c  of the magnet  211  may be disposed to surround the bobbin  212 . A space may be formed between the bobbin  212  and the central protrusion portion  211   b  of the magnet  211  and between the bobbin  212  and the side wall portion  211   c  of the magnet  211 . 
     The bobbin  212  may include or be formed of a pulp or paper processed material; aluminum, magnesium, or an alloy thereof; synthetic resin such as polypropylene; or polyamide-based fiber. One end of the bobbin  212  may be bonded to the heat radiation film  130  using an adhesive member. The adhesive member may be a double-sided tape. 
     The voice coil  213  is wound (or rolled) on the outer peripheral surface of the bobbin  212 . One end of the voice coil  213  may be electrically connected to the first sound wiring WL 1 , and the other end thereof may be electrically connected to the second sound wiring WL 2 . Thus, the voice coil  213  may receive a first-A driving voltage (or a first first driving voltage) and a first-B driving voltage (or a second first driving voltage) from the sound driving circuit  171 . 
     The damper  214  is disposed between the bobbin  212  and the plate  215 . One side of the damper  214  may be fixed to the bobbin  212 , and the other side thereof may be fixed to the plate  215  by a second fixing member  217  such as a screw. Each of the second fixing members  217  may be inserted into and fixed to the damper hole of the damper  214  and the second fixing hole of the plate  215 . The damper hole of the damper  214  and the second fixing hole of the plate  215  may be screw holes into which the screw can be fixed. The damper hole of the damper  214  may be a hole defined through the damper  214 , and the second fixing hole of the plate  215  may be a hole defined through the plate  215  or a hole formed by boring a part of the plate  215 . 
     The damper  214  may have elasticity, and may include or be formed of a conductive material. The damper  214  regulates the vertical vibration of the bobbin  212  while contracting and relaxing in accordance with the vertical movement of the bobbin  212 . In such an embodiment, since the damper  214  is connected to the bobbin  212  and the plate  215 , the vertical movement of the bobbin  212  may be restricted by the restoring force of the damper  214 . In one embodiment, for example, when the bobbin  212  vibrates at a predetermined height or higher, or vibrates at a predetermined height or lower, the bobbin  212  may be restored to its original position by the restoring force of the damper  214 . 
     The plate  215  may be disposed on the lower surface of the magnet  211 . The plate  215  may be integrally formed with the magnet  211  as a single unitary unit or may be formed separately from the magnet  211 . In an embodiment, where the plate  215  is formed separately from the magnet  211 , the magnet  211  may be attached to the plate  215  through an adhesive member such as a double-sided tape. The plate  215  may be fixed to the lower chassis  180  through a fixing member  216  such as a screw. 
     The fixing direction of each of the first fixing members  216  and the fixing direction of each of the second fixing members  217  may be opposite to each other. In one embodiment, for example, as shown in  FIGS.  10  and  11   , each of the first fixing members  216  may be fixed in the second direction (Y-axis direction), whereas each of the second fixing members  217  may be fixed in the opposite direction of the second direction (Y-axis direction). 
     The plate  215  may have a bent shape between an area  215   a , in which the magnet  211  is disposed, and an area  215   b , in which the first fixing members  216  and the second fixing members  217  are disposed. The area  215   a  in which the magnet  211  is disposed may be concave compared to the area  215   b  in which the first fixing members  216  and the second fixing members  217  are disposed. Thus, the distance between the area  215   a  in which the magnet  211  is disposed and the area  215   b  in which the first fixing members  216  and the second fixing members  217  are disposed may be greater than the area  215   b  in which the first fixing members  216  and the second fixing members  217  are disposed and the first substrate  111  or the heat radiation film  130 . Thus, even when the height of the first sound generator  210  is not reduced, the distance between the lower chassis  180  and the first substrate  111  may be minimized, and thus the thickness of the display device  10  may be reduced. The height of the first sound generator  210  indicates a distance between one end of the bobbin  212  contacting the heat radiation film  130  and the plate  215  contacting the magnet  211 . 
     One end of the voice coil  213  may be electrically connected to the sound driving circuit  171  through the first sound wiring WL 1 , thereby receiving the first-A driving voltage from the sound driving circuit  171 . The other end of the voice coil  213  may be electrically connected to the sound driving circuit  171  through the second sound wiring WL 2 , thereby receiving the first-B driving voltage from the sound driving circuit  171 . A current may flow through the voice coil  213  in response to the first driving voltage and the first driving voltage. An applied magnetic field may be formed around the voice coil  213  in accordance with the current flowing through the voice coil  213 . When the first-A driving voltage is a positive polarity voltage and the first-B driving voltage is a negative polarity voltage and when the first-A driving voltage is a negative polarity voltage and the first-B driving voltage is a positive polarity voltage, the direction of the current flowing through the voice coil  213  is reversed. Therefore, the N pole and S pole of the applied magnetic field formed around the voice coil  213  are changed according to the alternate current (“AC”) driving of the first-A driving voltage and the first-B driving voltage, and thus attractive force and repulsive force are alternately applied to the magnet  211  and the voice coil  213 . Therefore, the bobbin  212  on which the voice coil  213  is wound may reciprocate in the third direction (Z-axis direction) as shown in  FIGS.  10  and  11   . Accordingly, the display panel  110  vibrates in the third direction (Z-axis direction) as shown in  FIGS.  10  and  11   , and thus a sound may be output. 
     In an embodiment, as described above, the magnet  211  and the plate  215  are fixed to the lower chassis  180 , but the embodiment of the invention is not limited thereto. Alternatively, the magnet  211  and the plate  215  may be fixed to a system circuit board, a power supply circuit board, or a dummy circuit board instead of the lower chassis  180 . In such an embodiment, a hole corresponding to the hole H of the lower chassis  180  may be defined or formed in the control circuit board  160 , the system circuit board, the power supply circuit board, or the dummy circuit board. The dummy circuit board refers to a circuit board in which components other than the magnet  211  and plate  215  of the first sound generator  210  and the amplifier for amplifying the first sound signal provided to the first sound generator  210  are not arranged. The dummy circuit board may be a flexible printed circuit board or a printed circuit board. 
     According to an embodiment, as shown in  FIGS.  10  and  11   , the bobbin  212  is fixed to the first substrate  111  or the heat radiation film  130 , and the plate  215  to which the magnet  211  is coupled is fixed to the lower chassis  180 . Since the lower chassis  180  supporting the magnet  211  is rigid as compared with the display panel  110 , the bobbin  212  wound with the voice coil  213  may reciprocate from the fixed magnet  211  based on the applied magnetic field. The display panel  110  may be vibrated in the third direction (Z-axis direction) as shown in  FIGS.  10  and  11    in accordance with the reciprocation of the bobbin  212 , and thus a sound may be output. 
     According to an embodiment, as shown in  FIGS.  10  and  11   , the plate  215  may have a bent shape between an area  215   a  in which the magnet  211  is disposed and an area  215   b  in which the first fixing members  216  and the second fixing members  217  are disposed. Thus, even when the height of the first sound generator  210  is not reduced, the distance between the lower chassis  180  and the first substrate  111  may be minimized, and thus the thickness of the display device  10  may be reduced. 
       FIG.  12    is an exemplary view showing the vibration of the display panel by the second sound generator of  FIG.  5   , and  FIG.  13    is an exemplary view showing a method of vibrating a vibration layer disposed between the first branch electrode and second branch electrode of a second sound generator. 
     Referring to  FIGS.  12  and  13   , an embodiment of the second sound generator  220  may be a piezoelectric element or a piezoelectric actuator that vibrates the display panel  110  by contracting or expanding based on an applied voltage. In one embodiment, for example, the second sound generator  220  may include a vibration layer  221 , a first electrode  222 , and a second electrode  223 . 
     The first electrode  222  may include a first stem electrode  2221  and first branch electrodes  2222 . In an embodiment, the first stem electrode  2221  may be disposed on at least one side surface of the vibration layer  221  as shown in  FIG.  12   . Alternatively, the first stem electrode  2221  may be disposed through a part of the vibration layer  221 . The first stem electrode  2221  may be disposed on the upper surface of the vibration layer  221 . The first branch electrodes  2222  may be branched from the first stem electrode  2221 . The first branch electrodes  2222  may be arranged in parallel with each other. 
     The second electrode  223  may include a second stem electrode  2231  and second branch electrodes  2232 . The second electrode  223  may be disposed to be spaced apart from the first electrode  222 . Thus, the second electrode  223  may be electrically separated from the first electrode  222 . In an embodiment, the second stem electrode  2231  may be disposed on at least one side surface of the vibration layer  221 . In such an embodiment, the first stem electrode  2221  may be disposed on the first side surface of the vibration layer  221 , and the second stem electrode  2231  may be disposed on the second side surface of the vibration layer  221 . Alternatively, the second stem electrode  2231  may be disposed to penetrate a part of the vibration layer  221 . The second stem electrode  2231  may be disposed on the upper surface of the vibration layer  221 . The second branch electrodes  2232  may be branched from the second stem electrode  2231 . The second branch electrodes  2232  may be arranged in parallel with each other. 
     The first branch electrodes  2222  and the second branch electrodes  2232  may be arranged in parallel to each other in the horizontal direction (X-axis direction or Y-axis direction). Further, the first branch electrodes  2222  and the second branch electrodes  2232  may be arranged alternately in the vertical direction (Z-axis direction). That is, the first branch electrodes  2222  and the second branch electrodes  2232  may be arranged repeatedly in order of the first branch electrode  2222 , the second branch electrode  2232 , the first branch electrode  2222 , and the second branch electrode  2232  in the vertical direction (Z-axis direction). 
     The first electrode  222  and the second electrode  223  may be connected to the pads of the first sound circuit board  251  or the second sound circuit board  252 . The pads of the first sound circuit board  251  or the second sound circuit board  252  may be electrically connected to the first electrode  222  and second electrode  223  disposed on one surface of the second sound generator  220 . 
     The vibration layer  221  may be a piezoelectric element that is deformed based on a first driving voltage applied to the first electrode  222  and a second driving voltage applied to the second electrode  223 . In an embodiment, the vibration layer  511  may be at least one of a poly vinylidene fluoride (“PVDF”) film, a piezoelectric body of plumbum zirconate titanate (“PZT”), and an electroactive polymer. 
     Since the manufacturing temperature of the vibration layer  221  is high, each of the first electrode  222  and the second electrode  223  may include or be formed of silver (Ag) or an alloy of silver (Ag) and palladium (Pd) each having a high melting point. In an embodiment, where each of the first electrode  222  and the second electrode  223  is formed of an alloy of silver (Ag) and palladium (Pd), the content of silver (Ag) may be higher than the content of palladium (Pd) to increase the melting point of each of the first electrode  222  and the second electrode  223 . 
     The vibration layer  221  may be disposed between the first branch electrodes  2222  and the second branch electrodes  2232 . The vibration layer  221  contracts or expands based on a difference between the first driving voltage applied to the first branch electrode  2222  and the second driving voltage applied to the second branch electrode  2232 . 
     In an embodiment, as shown in  FIG.  13   , when the polar direction of the vibration layer  221  disposed between the first branch electrode  2222  and the second branch electrode  2232  disposed under the first branch electrode  2222  is an upward direction ( 1 ), the vibration layer  221  has a positive polarity in an upper area adjacent to the first branch electrode  2222  and has a negative polarity in a lower area adjacent to the second branch electrode  2232 . In such an embodiment, as shown in  FIG.  13   , when the polar direction of the vibration layer  221  disposed between the second branch electrode  2232  and the first branch electrode  2222  disposed under the second branch electrode  2232  is a downward direction (↓), the vibration layer  221  has a negative polarity in an upper area adjacent to the second branch electrode  2232  and has a positive polarity in a lower area adjacent to the first branch electrode  2222 . The polar direction of the vibration layer  221  may be determined by a poling process of applying an electric field to the vibration layer  221  using the first branch electrode  2222  and the second branch electrode  2232 . 
     As shown in  FIG.  13   , in a case where the polar direction of the vibration layer  221  disposed between the first branch electrode  2222  and the second branch electrode  2232  disposed under the first branch electrode  2222  is an upward direction (↑), when a second-A driving voltage of positive polarity is applied to the first branch electrode  2222  and a second-B driving voltage of negative polarity is applied to the second branch electrode  2232 , the vibration layer  221  may be contracted by a first force F 1 . The first force F 1  may be a contractile force. In such a case, when a second-A driving voltage of negative polarity is applied to the first branch electrode  2222  and a second-B driving voltage of positive polarity is applied to the second branch electrode  2232 , the vibration layer  221  may be expanded by a second force F 2 . The second force F 2  may be an extensible force. 
     Similarly, in a case where the polar direction of the vibration layer  221  disposed between the second branch electrode  2232  and the first branch electrode  2222  disposed under the second branch electrode  2232  is a downward direction (↓), when a second-A driving voltage of positive polarity is applied to the second branch electrode  2232  and a second-B driving voltage of negative polarity is applied to the first branch electrode  2222 , the vibration layer  221  may be expanded by an extensible force. Further, when a second-A driving voltage of negative polarity is applied to the second branch electrode  2232  and a second-B driving voltage of positive polarity is applied to the first branch electrode  2222 , the vibration layer  511  may be contracted by a contractile force. 
     In such a case, when the second driving voltage applied to the first electrode  222  and the second driving voltage applied to the second electrode  223  are alternately repeated in positive and negative polarities, the vibration layer  221  repeats contraction and expansion. Thus, the second sound generator  220  vibrates. Since the second sound generator  220  is disposed on one surface of the heat radiation film  130 , when the vibration layer  221  of the second sound generator  220  contracts and expands, the display panel  110  is vibrated in the third direction (Z-axis direction), which is a thickness direction of the display panel  110 , by stress. In an embodiment, since the display panel  110  may be vibrated by the second sound generator  220  as described above, the display device  10  may output a sound. 
     Since the third sound generator  230  is substantially the same as the second sound generator  220  described above with reference to  FIGS.  12  and  13   , any repetitive detailed description of the third sound generator  230  will be omitted. 
       FIG.  14    is a bottom view showing an alternative embodiment of a display panel of  FIG.  1    where flexible films are unfolded. 
     The embodiment shown in  FIG.  14    is substantially the same as the embodiment shown in  FIG.  2    except that the first blocking member  191 , the second blocking member  192  and the third blocking member  193  are omitted. Therefore, the display panel  110  is vibrated by the first sound generator  210 , the second sound generator  220 , and the third sound generator  230 , thereby outputting a sound. 
     Referring to  FIG.  14   , in an embodiment where the first blocking member  191 , the second blocking member  192 , and the third blocking member  193  are omitted, the display panel  110  has a single vibration surface. 
       FIG.  15    is a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded. 
     The embodiment shown in  FIG.  15    is substantially the same as the embodiment shown in  FIG.  2    except that the vibration damping member  400  has a circular shape in a plan view. 
     As shown in  FIG.  15   , in an embodiment where the bobbin  212  of the first sound generator  210  is formed in a circular shape in a plan view, the vibration generated by the first sound generator  210  may be spread in a circular shape in a plan view. If the corners of the vibration damping member  400  is formed in a rectangular shape in a plan view, the shape of spreading vibration is different from the shape of the corner of the vibration damping member  400 , such that vibration may be greatly reduced at the corners of the vibration damping member  400  or the form of vibration may be deformed. In an embodiment, the vibration damping member  400  has a circular shape in a plan view, such that the vibration generated by the first sound generator  210  may be spread as it is. 
       FIG.  16    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded, and  FIG.  17    is a cross-sectional view taken along line of  FIG.  16   . 
     The embodiment shown in  FIGS.  16  and  17    is substantially the same as the embodiment shown in  FIGS.  2  and  3    except that the vibration damping member  400  includes a plurality of heat radiation pins  401  protruding in the third direction (Z-axis direction). 
     Referring to  FIGS.  16  and  17   , in an embodiment, each of the plurality of heat radiation pins  401  may have a rectangular shape in a plan view. In an embodiment, as shown in  FIGS.  16  and  17   , the corners of each of the plurality of heat radiation pins  401  may be formed in a round shape having a planar curvature in a plan view, but the invention is not limited thereto. In one alternative embodiment, for example, the corners of each of the plurality of heat radiation pins  401  are formed in a rectangular shape in a plan view. The plurality of heat radiation pins  401  may be arranged in parallel with each other. 
     The first sound generator  210  may be disposed at a center portion of the vibration damping member  400 , and the plurality of heat radiation pins  401  may be disposed at edge portions of the vibration damping member  400 . The plurality of heat radiation pins  401  may be disposed to surround the first sound generator  210 . 
     In an embodiment, as shown in  FIG.  17   , each of the plurality of heat radiation pins  401  may protrude from one surface of the vibration damping member  400  in the third direction (Z-axis direction). Since the contact area of the vibration damping member  400  with air may be increased due to the plurality of heat radiation pins  401 , the heat generated by the vibration of the first sound generator  210  can be efficiently discharged through the vibration damping member  400 . 
       FIG.  18    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis, and  FIG.  19    is a cross-sectional view taken along line IV-IV′ of  FIG.  18   . 
     The embodiment shown in  FIGS.  18  and  19    is substantially the same as the embodiment shown in  FIGS.  2  and  3    except that a first through hole TH 1  and a second through hole TH 2  are defined in the lower chassis  180 . 
     Referring to  FIGS.  18  and  19   , in an embodiment, a first through hole TH 1  and a second through hole TH 2 , each defined through the lower chassis  189 , may be formed in the lower chassis  180 . In an embodiment, as shown in  FIG.  18   , the first through hole TH 1  is disposed at the right side of the first sound generator  210  and the second through hole TH 2  is disposed at the left side of the first sound generator  210 , but the invention is not limited thereto. In such an embodiment, the first through hole TH 1  may be disposed on one side of four sides of the first sound generator  210 , and the second through hole TH 2  may be disposed at another side of the four sides of the first sound generator  210 . Alternatively, the first through hole TH 1  and the second through hole TH 2  may be formed as a single unitary unit, and may be disposed to surround the four sides of the first sound generator  210 . 
     The first through hole TH 1  and the second through hole TH 2  are defined in the first area A 1  surrounded by the first blocking member  191 , the second blocking member  192 , and the third blocking member  193 . In such an embodiment, the first sound of a low frequency band, generated by the first sound generator  210 , may be outputted in the backward direction of the display panel  110  due to the first through hole TH 1  and the second through hole TH 2 . Accordingly, the user may feel a low sound more abundantly, and thus sound quality may be improved. 
       FIG.  20    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded,  FIG.  21    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis, and  FIG.  22    is a cross-sectional view taken along line V-V′ of  FIG.  21   . 
     The embodiment shown in  FIGS.  20  to  22    is substantially the same as the embodiment shown in  FIGS.  2  to  4    except that the first sound generator  210  is disposed to overlap the source circuit board  140  and the control circuit board  160  in the third direction (Z-axis direction). 
     Referring to  FIGS.  20  to  22   , in an embodiment, the first sound generator  210  is disposed adjacent to the lower side of the display panel  110 , and thus the first sound generator  210  may be disposed to overlap the source circuit board  140  and the control circuit board  160  in the third direction (Z-axis direction). In such an embodiment, the control circuit board  160  may not be effectively fixed directly to the lower chassis  180  due to the plate  215  of the first sound generator  210 . In such an embodiment, as shown in  FIG.  22   , a first connection supporting portion  181  and a second connection supporting portion  182 , each having a height higher than a thickness of the plate  215  of the first sound generator  210 , may be disposed on the lower chassis  180 . 
     The first connection supporting portion  181  and the second connection supporting portion  182  may be fixed to the surface of the lower chassis  180  facing the display panel and disposed opposite to each other. Each of the first connection supporting portion  181  and the second connection supporting portion  182  may include a screw groove, into which a fixing member such as a screw is fastened. The control circuit board  160  may be fixed to the first connection supporting portion  181  through a fixing member such as a screw. The source circuit board  140  may be fixed to the second connection supporting portion  182  through a fixing member such as a screw. In an embodiment, the distance between the lower chassis  180  and the source circuit board  140  is greater than the distance between the lower chassis  180  and the control circuit board  160 , such that the height of the second connection supporting portion  182  may be greater than the height of the first connection supporting portion  181 . 
     In an embodiment, as shown in  FIGS.  20  to  22    that the first sound generator  210  may overlap the source circuit board  140  and the control circuit board  160 , but the invention is not limited thereto. Alternatively, the first sound generator  210  may overlap one of the source circuit board  140  and the control circuit board  160 . 
       FIG.  23    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded, and  FIG.  24    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis.  FIG.  25    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded, and  FIG.  26    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis. 
     The embodiments shown in  FIGS.  23  to  26    are substantially the same as the embodiment shown in  FIGS.  2  and  3    except that the plurality of sound generators  210  and  240  are disposed on the vibration damping member  400 . 
     Referring to  FIGS.  23  and  24   , in an embodiment, the first sound generator  210  and the fourth sound generator  240  may be disposed on the vibration damping member  400 . Each of the first sound generator  210  and the fourth sound generator  240  may be an exciter for vibrating the display panel  110  by generating a magnetic force using a voice coil as shown in  FIGS.  10  and  11   . In such an embodiment, the fourth sound generator  240  may include a magnet, a bobbin  242 , a voice coil, and a plate. Since the first sound generator  210  and the fourth sound generator  240  are substantially the same as the first sound generator described above with reference to  FIGS.  2  to  5 ,  10 , and  11   , any repetitive detailed description thereof will be omitted. 
     In such an embodiment, when the display panel  110  is vibrated using a plurality of sound generators, the vibration energy applied to the display panel  110  may be greater, compared to when the display panel  110  is vibrated using a single sound generator. Therefore, when the first sound of a low frequency band is output by vibrating the display panel  110  using the first sound generator  210  and the fourth sound generator  240 , the sound pressure level of the first sound may be increased. 
     In an embodiment, referring back to  FIG.  7   , the vibration damping member  400  may reduce the vibration displacement of the display panel  110  generated by the first sound generator  210  by a maximum of 0.3 mm. In an embodiment, where the vibration damping member  400  is disposed between the display panel  110  and the first sound generator  210 , the vibration displacement of the display panel  110  in the third direction (Z-axis direction), generated by the first sound generator  210 , is at most 0.15 mm. Therefore, even when the fourth sound generator  240  is added to vibrate the display panel  110  by the first sound generator  210  and the fourth sound generator  240 , the vibration displacement of the display panel  110  in the third direction (Z-axis direction) may be reduced as compared with a case where the vibration damping member  400  is omitted. 
     In an embodiment, as shown in  FIGS.  23  and  24   , the first sound generator  210  and the fourth sound generator  240  may be disposed in the first direction (X-axis direction) and the length L 3  of the vibration damping member  400  in the first direction (X-axis direction) may be longer than the length L 4  of the vibration damping member  400  in the second direction (Y-axis direction), but the invention is not limited thereto. Alternatively, as shown in  FIGS.  25  and  26   , the first sound generator  210  and the fourth sound generator  240  may be disposed in the second direction (Y-axis direction) and the length L 5  of the vibration damping member  400  in the second direction (Y-axis direction) may be longer than the length L 6  of the vibration damping member  400  in the first direction (X-axis direction). In such an embodiment, where the first sound generator  210  and the fourth sound generator  240  are disposed in the second direction (Y-axis direction), any one of the first sound generator  210  and the fourth sound generator  240  may overlap at least one of the source circuit board  140  and the control circuit board  160  as shown in  FIGS.  20  to  22   . Alternatively, the positions of the first sound generator  210  and the fourth sound generator  240  may be variously modified within the first area A 1 . 
       FIG.  27    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded, and  FIG.  28    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis.  FIG.  29    a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded, and  FIG.  30    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis. 
     The embodiments shown in  FIGS.  27  to  30    are substantially the same as the embodiment shown in  FIGS.  23  to  26    except that the first sound generator  210  is disposed on a first vibration damping member  440  and the fourth sound generator  240  is disposed on a second vibration damping member  450 . 
     Referring to  FIGS.  27  and  28   , in an embodiment, the first sound generator  210  may be disposed on a first vibration damping member  440 , and the fourth sound generator  240  may be disposed on a second vibration damping member  450 . Since each of the first vibration damping member  440  and the second vibration damping member  450  is substantially the same as the vibration damping member  400  described above with reference to  FIGS.  2  and  6  to  9   , any repetitive detailed description thereof will be omitted. Each of the first sound generator  210  and the fourth sound generator  240  may be an exciter for vibrating the display panel  110  by generating a magnetic force using a voice coil as shown in  FIGS.  10  and  11   . Since the first sound generator  210  and the fourth sound generator  240  are substantially the same as those described above with reference to  FIGS.  2  to  5 ,  10 , and  11   , any repetitive detailed description thereof will be omitted. 
     In such an embodiment, when the display panel  110  is vibrated using a plurality of sound generators, the vibration energy applied to the display panel  110  may be greater, compared to when the display panel  110  is vibrated using a single sound generator. Therefore, when the first sound of a low frequency band is output by vibrating the display panel  110  using the first sound generator  210  and the fourth sound generator  240 , the sound pressure level of the first sound may be increased. 
     In an embodiment, as shown in  FIGS.  27  and  28   , the first sound generator  210  and the fourth sound generator  240  are disposed in the first direction (X-axis direction), but the invention is not limited thereto. Alternatively, as shown in  FIGS.  29  and  30   , the first sound generator  210  and the fourth sound generator  240  may be disposed in the second direction (Y-axis direction). In such an embodiment, where the first sound generator  210  and the fourth sound generator  240  are disposed in the second direction (Y-axis direction), any one of the first sound generator  210  and the fourth sound generator  240  may overlap at least one of the source circuit board  140  and the control circuit board  160  as shown in  FIGS.  20  to  22   . Alternatively, the positions of the first sound generator  210  and the fourth sound generator  240  may be variously modified within the first area A 1 . 
       FIG.  31    is a bottom view showing another alternative embodiment of a display panel in  FIG.  1    where flexible films are unfolded, and  FIG.  32    is a bottom view showing another alternative embodiment of a display panel coupled with a lower chassis in  FIG.  1    where flexible films are bent toward the lower portion of the lower chassis. 
     The embodiment shown in  FIGS.  31  and  32    is substantially the same as the embodiment shown in  FIGS.  2  and  3    except that a fourth sound generator  240 , a fifth sound generator  250 , and a sixth sound generator  260  are further provided. 
     Referring to  FIGS.  31  and  32   , the first sound generator  210  may be disposed closer to the center of the display panel  110  as compared with the second sound generator  220  and the third sound generator  230 . The second sound generator  220  may be disposed closer to one side of the display panel  110 , for example, the right side of the display panel  110 . The third sound generator  230  may be disposed closer to another side of the display panel, for example, the left side of the display panel  110 . 
     The fourth sound generator  240  may be disposed closer to the center of the display panel  110  as compared with the fifth sound generator  250  and the sixth sound generator  260 . The fifth sound generator  250  may be disposed closer to one side of the display panel  110 , for example, the right side of the display panel  110 . The sixth sound generator  260  may be disposed closer to another side of the display panel, for example, the left side of the display panel  110 . 
     In an embodiment, as shown in  FIGS.  31  and  32   , the first sound generator  210  and the fourth sound generator  240  may be disposed in the second direction (Y-axis direction), but the invention is not limited thereto. Alternatively, the first sound generator  210  and the fourth sound generator  240  may be disposed in the first direction (X-axis direction), as shown in  FIG.  23   . In an embodiment, where the first sound generator  210  and the fourth sound generator  240  are disposed in the second direction (Y-axis direction), any one of the first sound generator  210  and the fourth sound generator  240  may overlap at least one of the source circuit board  140  and the control circuit board  160  as shown in  FIGS.  20  to  22   . Alternatively, the positions of the first sound generator  210  and the fourth sound generator  240  may be variously modified within the first area A 1 . 
     Each of the second sound generator  220 , the third sound generator  230 , the fifth sound generator  250 , and the sixth sound generator  260  may be a piezoelectric element or piezoelectric actuator for vibrating the display panel  110  using a piezoelectric material that contracts and expands according to the applied voltage as shown in  FIGS.  2  to  5 ,  12 , and  13   . Since the second sound generator  220 , the third sound generator  230 , the fifth sound generator  250 , and the sixth sound generator  260  are substantially the same as those described above with reference to  FIGS.  12  and  13   , any repetitive detailed description thereof will be omitted. 
     The first sound generator  210  may be disposed on the first vibration damping member  440 , and the fourth sound generator  240  may be disposed on the second vibration damping member  450 . Since the first vibration damping member  440  and the second vibration damping member  450  are substantially the same as those described with reference to  FIGS.  2  and  6  to  9   , any repetitive detailed description thereof will be omitted. 
     A first blocking member  191 , a second blocking member  192 , a third blocking member  193 , a fourth blocking member  194 , and a fifth blocking member  195  may serve to block the propagation of vibration of the display panel  110  generated by the sound generators  210 ,  220 ,  230 ,  240 , and  250  or block the transmission of a sound generated by the vibration of the display panel  110 . The first blocking member  191 , the second blocking member  192 , the third blocking member  193 , the fourth blocking member  194 , and the fifth blocking member  195  may be attached to one surface of the heat radiation film  130  and one surface of the lower chassis  180 , which are opposite to each other. Alternatively, the heat radiation film  130  may be omitted, and the first blocking member  191 , the second blocking member  192 , the third blocking member  193 , the fourth blocking member  194 , and the fifth blocking member  195  may be attached to one surface of the first substrate  111  and the one surface of the lower chassis  180 . 
     The first blocking member  191  may be disposed on four side edge portions of the heat radiation film  130  as shown in  FIG.  2   . The second blocking member  192  may extend in the second direction (Y-axis direction), and may be disposed between the first sound generator  210  and the second sound generator  220  and between the fourth sound generator  240  and the fifth sound generator  250 . The third blocking member  193  may extend in the second direction (Y-axis direction), and may be disposed between the first sound generator  210  and the third sound generator  230  and between the fourth sound generator  240  and the sixth sound generator  260 . The fourth blocking member  194  may extend in the first direction (X-axis direction), and may be disposed between the second sound generator  220  and the fifth sound generator  250 . The fifth blocking member  195  may extend in the first direction (X-axis direction), and may be disposed between the third sound generator  230  and the sixth sound generator  260 . Thus, the vibration plane of the display panel  110  may be divided into five areas A 1 , A 2 , A 3 , A 4 , and A 5  as shown in  FIG.  31   . 
     The first sound generator  210  and the fourth sound generator  240  may be disposed in the first area A 1  surrounded by the first blocking member  191 , the second blocking member  192 , and the third blocking member  193 . Each of the second sound generator  220  and the fifth sound generator  250  may be disposed respectively in the second area A 2  and the fourth area A 4  surrounded by the first blocking member  191 , the second blocking member  192 , and the fourth blocking member  194 . The third sound generator  230  and the sixth sound generator  260  may be disposed respectively in the third area A 3  and the fifth area A 5  surrounded by the first blocking member  191 , the third blocking member  193 , and the fifth blocking member  195 . 
     Since the first sound generator  210 , the second sound generator  220 , the third sound generator  230 , the fourth sound generator  240 , the fifth sound generator  250 , and the sixth sound generator  260  may be disposed in different areas A 1 , A 2 , A 3 , A 4 , and A 5  surrounded by the first blocking member  191 , the second blocking member  192 , the third blocking member  193 , the fourth blocking member  194  and the fifth blocking member  195 , it may be reduced that the vibration of the display panel  110  generated by the first sound generator  210 , the vibration of the display panel  110  generated by the second sound generator  220 , the vibration of the display panel  110  generated by the third sound generator  230 , the vibration of the display panel  110  generated by the fourth sound generator  240 , and the vibration of the display panel  110  generated by the fifth sound generator  250  influence each other. 
     The first sound generator  210 , the second sound generator  220 , the third sound generator  230 , the fourth sound generator  240 , the fifth sound generator  250 , and the sixth sound generator  260  may be disposed in different areas surrounded by the first blocking member  191 , the second blocking member  192 , the third blocking member  193 , the fourth blocking member  194 , and the fifth blocking member  195 . In one embodiment, for example, as shown in  FIG.  31   , the first sound generator  210  and the fourth sound generator  240  may be disposed in the first area A 1 , the second sound generator  220  may be disposed in the second area A 2 , and the third sound generator  230  may be disposed in the third area A 3 . In such an embodiment, the fifth sound generator  250  may be disposed in the fourth area A 4 , and the sixth sound generator  260  may be disposed in the fifth area A 5 . Therefore, the first sound generator  210  and the fourth sound generator  240  may output a first sound of a low frequency band by vibrating the first area A 1  of the display panel  110 . In such an embodiment, the second sound generator  220  may output a second sound, which is a right upper stereo sound of a high frequency band, by vibrating the second area A 2  of the display panel  110 . In such an embodiment, the third sound generator  230  may output a third sound, which is a left upper stereo sound of a high frequency band, by vibrating the third area A 3  of the display panel  110 . In such an embodiment, the fourth sound generator  240  may output a fourth sound, which is a right lower stereo sound of a high frequency band, by vibrating the fourth area A 4  of the display panel  110 . In such an embodiment, the fifth sound generator  250  may output a fifth sound, which is a left lower stereo sound of a high frequency band, by vibrating the fifth area A 5  of the display panel  110 . Accordingly, the display device  10  may provide a stereo sound of a 4.1 channel to the user. 
     In an embodiment, where a blocking member is additionally disposed between the first sound generator  210  and the fourth sound generator  240 , the first area A 1  may be divided into two areas. In such an embodiment, since each of the first sound generator  210  and the fourth sound generator  240  may output a low sound, the display device  10  may provide a stereo sound of a 4.1 channel to the user. 
     While the invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit or scope of the invention as defined by the following claims.