Patent Publication Number: US-2021181847-A1

Title: Display device and haptic feedback method of the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2019-0168431, filed on Dec. 17, 2019, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     Field 
     Exemplary embodiments of the invention relate generally to a display device and a haptic feedback method of the same. 
     Discussion of the Background 
     As the information society develops, the demand for display devices for displaying images is increasing in various forms. For example, display devices may be implemented as various electronic devices such as smartphones, digital cameras, notebook computers, navigation devices, and smart televisions. 
     As display devices are implemented as various electronic devices, display devices with various designs are being required. For example, when a display device is implemented as a smartphone, physical buttons such as a power button and a sound button disposed on a side surface of the display device may be removed to increase the aesthetic appeal of the smartphone. In this case, an area for recognizing the pressure applied by a user may be provided instead of a physical button to provide the same function as the physical button. However, since it is difficult for the user to tactually feel the area to apply pressure, it may be difficult for the user to find the area to apply pressure. In addition, when the user applies pressure, if mechanical deformation does not occur as when a physical button is pressed, it may be difficult for the user to recognize whether the user has properly applied pressure. 
     The above information disclosed in this Background section is only for understanding of the background of the inventive concepts, and, therefore, it may contain information that does not constitute prior art. 
     SUMMARY 
     Exemplary embodiments provide a display device including a tactile pattern that can be tactually felt by a user to enable the user to easily find an area to apply pressure to perform a desired function, and a feedback provision method of the display device. 
     Exemplary embodiments also provide a display device which cannot only sense pressure applied by a user but also provide haptic feedback using an actuator so that the user can easily recognize whether a desired function is properly performed by the pressure applied by the user, and a feedback provision method of the display device. 
     Additional features of the inventive concepts will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the inventive concepts. 
     An exemplary embodiment of the invention provides a display device including a display panel which displays an image; a cover window on a first surface of the display panel and including a tactile pattern; and an actuator which is disposed on a second surface opposite the first surface of the display panel and overlaps the tactile pattern in a width direction of the display panel. The actuator outputs a sensing voltage according to applied pressure and generates vibrations according to applied driving voltages. 
     Another exemplary embodiment of the invention provides a display device including a display layer which displays an image; a sensor electrode layer which is disposed on the display unit and senses a touch of a user; and an actuator under the display layer, outputs a sensing voltage according to applied pressure, and generates vibrations according to applied driving voltages. 
     Another exemplary embodiment of the invention provides a display device including a display layer which displays an image; a sensor electrode layer which is disposed on the display unit and senses a touch of a user; and a plurality of actuators which are disposed under the display layer and spaced apart from each other. Each of the actuators outputs a sensing voltage according to applied pressure and generates vibrations according to applied driving voltages. 
     Another exemplary embodiment of the invention provides a display device including a display panel which displays an image; a cover window on a first surface of the display panel; and first and second actuators disposed on a second surface opposite the first surface of the display panel and spaced apart from each other. Each of the first and second actuators outputs a sensing voltage according to applied pressure and generates vibrations according to applied driving voltages. 
     Another exemplary embodiment of the invention provides a haptic feedback method of a display device including applying pressure to a first surface of a display device by a user; calculating a touch position of the user and calculating a position threshold value according to the touch position of the user; converting a sensing voltage sensed from the actuator in response to the pressure into sensing data and comparing the sensing data with the position threshold value; and applying driving voltages to the actuator to vibrate the actuator when the sensing data is greater than the position threshold value. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are include to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention, and together with the description serve to explain the inventive concepts. 
         FIG. 1  is a perspective view illustrating a display device according to an exemplary embodiment. 
         FIG. 2  is an exploded perspective view illustrating the display device in accordance with  FIG. 1 . 
         FIG. 3  is a cross-sectional view illustrating a side of a display panel of the display device in accordance with  FIG. 1 . 
         FIG. 4  is a cross-sectional view illustrating the other side of the display panel of the display device in accordance with  FIG. 1 . 
         FIG. 5  is a cross-sectional view illustrating a display unit of the display panel in accordance with exemplary embodiments. 
         FIG. 6  is a view illustrating an actuator according to an exemplary embodiment. 
         FIG. 7  is a diagram illustrating an inverse piezoelectric effect of the actuator in accordance with  FIG. 6 . 
         FIG. 8  is a diagram illustrating a piezoelectric effect of the actuator in accordance with  FIG. 6 . 
         FIG. 9  is a block diagram illustrating the display panel, the actuator and a main processor of the display device according to an exemplary embodiment. 
         FIG. 10  is a flowchart illustrating a haptic feedback method of the display device according to exemplary embodiments. 
         FIG. 11  is a graph illustrating a sensing voltage sensed by the actuator according to pressure applied to a side surface of the display device in exemplary embodiments. 
         FIG. 12  is a graph illustrating vibration acceleration according to the vibration of the actuator when haptic feedback is provided to a user in exemplary embodiments. 
         FIG. 13  is a side view illustrating a display device according to an exemplary embodiment. 
         FIG. 14  is a side view illustrating a display device according to an exemplary embodiment. 
         FIG. 15  is a side view illustrating a display device according to exemplary an embodiment. 
         FIG. 16  is a side view illustrating a display device according to an exemplary embodiment. 
         FIG. 17  is a cross-sectional view illustrating a cover window of  FIG. 13  and an exemplary tactile pattern. 
         FIG. 18  is a cross-sectional view illustrating the cover window of  FIG. 13  and an exemplary tactile pattern. 
         FIG. 19  is a cross-sectional view illustrating the cover window of  FIG. 13  and an exemplary tactile pattern. 
         FIG. 20  is a cross-sectional view illustrating the cover window of  FIG. 13  and an exemplary tactile pattern. 
         FIG. 21  is a cross-sectional view illustrating the cover window of  FIG. 13  and an exemplary tactile pattern. 
         FIG. 22  is a cross-sectional view illustrating the cover window of  FIG. 13  and an exemplary tactile pattern. 
         FIG. 23  is a flowchart illustrating a haptic feedback method of a display device according to an exemplary embodiment. 
         FIG. 24  is a graph illustrating a sensing voltage sensed by an actuator according to pressure applied to a side surface of the display device in accordance with  FIG. 23 . 
         FIG. 25  is a graph illustrating vibration acceleration according to the vibration of the actuator when haptic feedback is provided to a user in accordance with  FIG. 23 . 
         FIG. 26  illustrates an actuator and tactile patterns on a side surface of a display device according to an exemplary embodiment. 
         FIG. 27  illustrates an actuator and tactile patterns on a side surface of a display device according to an exemplary embodiment. 
         FIG. 28  illustrates an actuator and tactile patterns on a side surface of a display device according to an exemplary embodiment. 
         FIG. 29  illustrates an actuator and tactile patterns on a side surface of a display device according to an exemplary embodiment. 
         FIG. 30  is a flowchart illustrating a haptic feedback method of a display device according to an exemplary embodiment. 
         FIG. 31  is a graph illustrating vibration acceleration according to the vibration of an actuator when haptic feedback is provided to a user in accordance with  FIG. 30 . 
         FIG. 32  is a flowchart illustrating a haptic feedback method of a display device according to an exemplary embodiment. 
         FIG. 33  is a graph illustrating sensing voltages sensed by actuators according to pressure applied to a side surface of the display device in accordance with  FIG. 32 . 
         FIG. 34  is a graph illustrating vibration acceleration according to the vibration of the actuators when haptic feedback is provided to a user in t accordance with  FIG. 32 . 
         FIG. 35  is a flowchart illustrating a haptic feedback method of a display device according to an exemplary embodiment. 
         FIG. 36  is a graph illustrating sensing voltages sensed by actuators according to pressure applied to a side surface of the display device in accordance with  FIG. 35 . 
         FIG. 37  is a graph illustrating vibration acceleration according to the vibration of the actuators when haptic feedback is provided to a user in accordance with  FIG. 35 . 
         FIG. 38  is a flowchart illustrating a haptic feedback method of a display device according to an exemplary embodiment. 
         FIG. 39  illustrates dragging on a side surface of the display device with a finger in an exemplary embodiment. 
         FIG. 40  is a flowchart illustrating a haptic feedback method of a display device according to an exemplary embodiment. 
         FIG. 41  illustrates zooming in or zooming out on a side surface of a display panel with a finger in an exemplary embodiment. 
         FIG. 42  is a flowchart illustrating a haptic feedback method of a display device according to an exemplary embodiment. 
         FIG. 43  is a flowchart illustrating a haptic feedback method of a display device according to an exemplary embodiment. 
         FIG. 44  is an exploded perspective view illustrating a display device according to an exemplary embodiment. 
         FIG. 45  is a block diagram illustrating a display panel, an actuator, and a main processor of the display device in accordance with  FIG. 44 . 
         FIG. 46  illustrates tactile patterns and actuators of a display device according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention, and together with the description serve to explain the inventive concepts. 
     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 is a part. 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 should not be interpreted in an idealized or overly formal sense, unless expressly so defined herein. 
       FIG. 1  is a perspective view illustrating a display device  10  according to an exemplary embodiment.  FIG. 2  is an exploded perspective view of the display device  10  in accordance with  FIG. 1 . 
     The display device  10  according to an exemplary embodiment is a device configured to display moving images or still images. The display device  10  may be used as a display screen in portable electronic devices such as mobile phones, smartphones, tablet personal computers (PCs), smart watches, watch phones, mobile communication terminals, electronic notebooks, electronic books, portable multimedia players (PMPs), navigation devices and ultra-mobile PCs (UMPCs), as well as in various products such as televisions, notebook computers, monitors, billboards and the Internet of things (IoT). Alternatively, the display device  10  may be used as a display screen applied to a center fascia of a vehicle. Although a case where the display device  10  according to the embodiment is a smartphone is mainly described below, embodiments are not limited to this case. 
     The display device  10  may be an organic light emitting display device using organic light emitting diodes, a quantum dot light emitting display device including quantum dot light emitting layers, an inorganic light emitting display device including inorganic semiconductors, or a micro light emitting diode display device using micro light emitting diodes. Although a case where the display device  10  is an organic light emitting display device is mainly described below, embodiments are not limited to this case. 
     Referring to  FIGS. 1 and 2 , the display device  10  according to the exemplary embodiments includes a cover window  100 , a display panel  300 , a display circuit board  310 , a display driver  320 , a bracket  600 , a main circuit board  700 , and a bottom cover  900 . 
     In the present specification, a first direction (X-axis direction) may be a width direction parallel to short sides of the display device  10  in plan view, for example, a horizontal direction of the display device  10 . A second direction (Y-axis direction) may be a length direction parallel to long sides of the display device  10  in plan view, for example, a vertical direction of the display device  10 . A third direction (Z-axis direction) may be a thickness direction of the display device  10 . 
     The display device  10  may be rectangular in plan view. For example, the display device  10  may have a rectangular planar shape having short sides in the first direction (X-axis direction) and long sides in the second direction (Y-axis direction) as illustrated in  FIGS. 1 and 2 . Each corner where a short side extending in the first direction (X-axis direction) meets a long side extending in the second direction (Y-axis direction) may be rounded with a predetermined curvature or may be right-angled. The planar shape of the display device  10  is not limited to the rectangular shape, but may also be another polygonal shape, a circular shape, or an oval shape. 
     The cover window  100  may be disposed on the display panel  300  to cover an upper surface of the display panel  300 . The cover window  100  may function to protect the upper surface of the display panel  300 . The cover window  100  may include alight transmitting portion DA 100  which transmits light and a light shielding portion NDA 100  which blocks light. The light shielding portion NDA 100  may include a decorative layer having a predetermined pattern. 
     The cover window  100  may include an upper surface portion  100 U that forms an upper surface of the display device  10 , a left side surface portion  100 L that forms a left side surface of the display device  10 , and a right side surface portion  100 R that forms a right side surface of the display device  10 . The left side surface portion  100 L of the cover window  100  may extend from a left side of the upper surface portion  100 U, and the right side surface portion  100 R may extend from a right side of the upper surface portion  100 U. 
     The upper surface portion  100 U, the left side surface portion  100 L and the right side surface portion  100 R of the cover window  100  may all include the light transmitting portion DA 100  and the light shielding portion NDA 100 . The light transmitting portion DA 100  may occupy most of the upper surface portion  100 U, the left side surface portion  100 L and the right side surface portion  100 R of the cover window  100 . The light shielding portion NDA 100  may be disposed at an upper edge and a lower edge of the upper surface portion  100 U of the cover window  100 , at an upper edge, a left edge and a lower edge of the left side surface portion  100 L of the cover window  100 , and at an upper edge, a right edge and a lower edge of the right side surface portion  100 R of the cover window  100 . 
     A tactile pattern  110  may be disposed on the right side surface portion  100 R of the cover window  100  as illustrated in  FIG. 2 . The tactile pattern  110  may be an embossed pattern protruding from the right side surface portion  100 R of the cover window  100  or an intaglio pattern cut into the right side surface portion  100 R of the cover window  100 . The embossed pattern may be a carve, mold, or stamp of a design on the right side surface portion  100 R of the cover window  100  so that the embossed pattern stands out in relief. The intaglio pattern may be a design incised or engraved into the right side portion  100 R of the cover window  100 . The tactile pattern  110  may be a pattern felt by a user as being different from a surface the cover window  100 . Therefore, the user may recognize the tactile pattern  110  as a physical button. 
     The display panel  300  may be disposed under the cover window  100 . The display panel  300  may include a main area MA and a sub area SA. The main area MA may include a display area DA in which pixels are formed to display an image and a non-display area NDA located around the display area DA. 
     The display area DA may occupy most of the main area MA. The display area DA may be disposed at a center of the main area MA. 
     The non-display area NDA may be an area outside the display area DA. The non-display area NDA may be defined as an edge area of the display panel  300 . 
     The sub area SA may protrude in the second direction (Y-axis direction) from a side of the main area MA. As illustrated in  FIG. 2 , a length of the sub area SA in the first direction (X-axis direction) may be smaller than a length of the main area MA in the first direction (X-axis direction), and a length of the sub area SA in the second direction (Y-axis direction) may be smaller than a length of the main area MA in the second direction (Y-axis direction). However, embodiments are not limited to this case. 
     The sub area SA may be bendable and may be disposed on a lower surface of the display panel  300  as illustrated in  FIG. 3 . The sub area SA may overlap the main area MA in the third direction (Z-axis direction). In the sub area SA, display pads (not illustrated) and the display driver  200   320  be disposed. 
     The display area DA of the display panel  300  may be overlapped by the light transmitting portion DA 100  of the cover window  100  in the thickness direction (Z-direction) of the display panel  300 . The non-display area NDA of the display panel  300  may be overlapped by the light shielding portion NDA 100  of the cover window  100  in the thickness direction (Z-direction) of the display panel  300 . 
     The display panel  300  may include an upper surface portion corresponding to the upper surface portion of the cover window  100 , a left side surface portion corresponding to the left side surface portion of the cover window  100 , and a right side surface portion corresponding to the right side surface portion of the cover window  100 . The left side surface portion of the display panel  300  may extend from a left side of the upper surface portion, and the right side surface portion of the display panel  300  may extend from a right side of the upper surface portion. 
     The upper surface portion, the left side surface portion and the right side surface portion of the display panel  300  may all include the display area DA and the non-display area NDA. The display area DA may occupy most of the upper surface portion, the left side surface portion and the right side surface portion of the display panel  300 . The non-display area NDA may be disposed at an upper edge and a lower edge of the upper surface portion of the display panel  300 , at an upper edge, a left edge and a lower edge of the left side surface portion of the display panel  300 , and at an upper edge, a right edge and a lower edge of the right side surface portion of the display panel  300 . 
     An actuator  510  may be disposed on a lower surface of the right side surface portion of the display panel  300 . The actuator  510  may be attached to the lower surface of the right side surface portion of the display panel  300  using an adhesive member such as a pressure sensitive adhesive (PSA). The actuator  510  may be a piezoelectric element or a piezoelectric actuator including a piezoelectric material that has a piezoelectric effect in which a voltage is generated in response to applied mechanical pressure and has an inverse piezoelectric effect in which mechanical deformation occurs in response to an applied voltage. 
     The actuator  510  may overlap the tactile pattern  110  of the cover window  100  in the width direction (X-direction) of the display panel  300  as illustrated in  FIGS. 2 and 4 . Therefore, when a user applies pressure to the tactile pattern  110  with a finger, the pressure may be applied to the actuator  510 . For example, when the user applies pressure to the tactile pattern  110  by recognizing the tactile pattern  110  as a physical button, the actuator  510  may generate a voltage due to the piezoelectric effect. In addition, when the actuator  510  generates vibrations due to mechanical deformation of the inverse piezoelectric effect, the vibrations may be transmitted to the user&#39;s finger touching the tactile pattern  110 . Therefore, the user may feel haptic feedback. 
     The display circuit board  310  and the display driver  320  may be attached to the subarea SA of the display panel  300 . An end of the display circuit board  310  may be attached onto display pads (not illustrated) disposed at a lower edge of the sub area SA of the display panel  300  by using an anisotropic conductive film. The display circuit board  310  may be a flexible printed circuit board that can be bent, a rigid printed circuit board that is rigid and not easily bent, or a composite printed circuit board including both a rigid printed circuit board and a flexible printed circuit board. 
     The display driver  320  receives control signals and power supply voltages through the display circuit board  310  and generates and outputs signals and voltages configured to drive the display panel  300 . The display driver  320  may be formed as an integrated circuit and attached to the sub area SA of the display panel  300  using a chip-on glass (COG) method, a chip-on plastic (COP) method, or an ultrasonic method. However, embodiments are not limited to this case. For example, the display driver  320  may be attached onto the display circuit board  310 . 
     A sensor driver  330  and an actuator driver  340  may be disposed on the display circuit board  310 . The sensor driver  330  and the actuator driver  340  may be formed as integrated circuits. 
     The sensor driver  330  may be attached to an upper surface of the display circuit board  310 . The sensor driver  330  may be electrically connected to sensor electrodes of a sensor electrode layer of the display panel  300  through the display circuit board  310 . The sensor driver  330  may transmit touch driving signals to driving electrodes among the sensor electrodes and determine a touch or proximity of a user by detecting amounts of charge change in capacitances between the driving electrodes and sensing electrodes among the sensor electrodes through the sensing electrodes. The touch of the user indicates that an object such as a finger of the user or a pen directly touches an upper surface of the cover window  100  disposed on the sensor electrode layer. The proximity of the user indicates that an object such as a finger of the user or a pen hovers above the upper surface of the cover window  100 . The sensor driver  330  may output touch data including touch coordinates of the user to a main processor  710 . 
     The actuator driver  340  may be attached to the upper surface of the display circuit board  310 . The actuator driver  340  may be electrically connected to the actuator  510 . A connection member may be disposed to connect the display circuit board  310  and the actuator  510 . The connection member may be a flexible printed circuit board or a flexible cable. 
     When the actuator  510  generates a voltage due to the piezoelectric effect, the actuator driver  340  may sense the voltage through the connection member. The actuator driver  340  may determine whether pressure has been applied to the actuator  510  by comparing the sensed voltage with a threshold voltage. 
     In addition, the actuator driver  340  may generate driving voltages according to driving data input from the main processor  710  of the main circuit board  700  to vibrate the actuator  510  through the inverse piezoelectric effect and may output the driving voltages to the actuator  510 . The driving voltages may be applied as sine waves or square waves. Here, when the driving voltages are applied as square waves, a user can clearly receive different haptic feedback even if the different haptic feedback is successively implemented using the actuator  510 . 
     The bracket  600  may be disposed under the display panel  300 . The bracket  600  may include plastic, metal, or both plastic and metal. The bracket  600  may include a first camera hole CMH 1  into which a camera device  720  is inserted, a battery hole BH in which a battery  790  is disposed, and a cable hole CAH through which a cable  314  connected to the display circuit board  310  passes. 
     The main circuit board  700  and the battery  790  may be disposed under the bracket  600 . The main circuit board  700  may be a printed circuit board or a flexible printed circuit board. 
     The main circuit board  700  may include the main processor  710 , the camera device  720 , and a main connector  730 . The main processor  710  may be formed as an integrated circuit. 
     The camera device  720  may be disposed on both upper and lower surfaces of the main circuit board  700 , the main processor  710  may be disposed on the upper surface of the main circuit board  700 , and the main connector  730  may be disposed on the lower surface of the main circuit board  700 . 
     The main processor  710  may control all the functions of the display device  10 . For example, the main processor  710  may output digital video data to the display driver  320  through the display circuit board  310  so that the display panel  300  can display an image. In addition, the main processor  710  may receive touch data including touch coordinates of a user from the sensor driver  330 , determine a touch or proximity of the user, and then perform an operation corresponding to the touch input or proximity input of the user. For example, the main processor  710  may execute an application indicated by an icon touched by the user or may perform an operation. 
     When the main processor  710  determines that pressure has been applied from the actuator  510  by the actuator driver  340 , it may provide haptic feedback to a user by using the actuator  510 . When determining that pressure has been applied from the actuator  510  by the actuator driver  340 , the main processor  710  may receive pre-stored driving data from a memory and output the driving data to the actuator driver  340 . 
     The main processor  710  may be an application processor, a central processing unit, or a system chip formed as an integrated circuit. 
     The camera device  720  may process an image frame such as a still image or a moving image obtained by an image sensor in a camera mode and output the processed image frame to the main processor  710 . 
     The cable  314  passing through the cable hole CAH of the bracket  600  may be connected to the main connector  730 . Therefore, the main circuit board  700  may be electrically connected to the display circuit board  310 . 
     The battery  790  may be disposed not to overlap the main circuit board  700  in the third direction (Z-axis direction). The battery  790  may be overlapped by the battery hole BH of the bracket  600  in the third direction (Z-axis direction). 
     In addition, the main circuit board  700  may further include a mobile communication module capable of transmitting or receiving a wireless signal to or from at least one of a base station, an external terminal, and a server over a mobile communication network. The wireless signal may include a voice signal, a video call signal, or various types of data according to transmission/reception of text/multimedia messages. 
     The bottom cover  900  may be disposed under the main circuit board  700  and the battery  790 . The bottom cover  900  may be fastened and fixed to the bracket  600 . The bottom cover  900  may form an upper side surface, a lower side surface and a lower surface of the display device  10 . The bottom cover  900  may include plastic, metal, or both plastic and metal. 
     A second camera hole CMH 2  exposing a lower surface of the camera device  720  may be formed in the bottom cover  900 . The position of the camera device  720  and the positions of the first and second camera holes CMH 1  and CMH 2  corresponding to the camera device  720  are not limited to the embodiment illustrated in  FIG. 2 . 
       FIG. 3  is a cross-sectional view of a lower side of a display module of the display device  10  according to the embodiment.  FIG. 4  is a cross-sectional view of the other upper side of the display module of the display device  10  according to the embodiment. 
     Referring to  FIGS. 3 and 4 , the display panel  300  may include a substrate SUB 1 , a display layer PAL, and a sensor electrode layer SENL. 
     The substrate SUB 1  may be made of an insulating material such as glass, quartz, or polymer resin. The substrate SUB 1  may be a rigid substrate or a flexible substrate that can be bent, folded, and rolled. The display layer PAL and the sensor electrode layer SENL may be disposed on the main area MA of the substrate SUB 1 . The subarea SA of the substrate SUB 1  may be bent onto the lower surface of the display panel  300  and attached to a lower surface of an bottom panel cover  400  by an adhesive member  390 . 
     The display layer PAL may be disposed on the substrate SUB 1 . The display layer PAL may be a layer including pixels to display an image. As illustrated in  FIG. 5 , the display layer PAL may include a buffer layer  302 , a thin-film transistor layer  303 , a light emitting element layer  304 , and an encapsulation layer  305 . 
     The sensor electrode layer SENL may be disposed on the display layer PAl. The sensor electrode layer SENL may include sensor electrodes and may be a layer configured to sense a user&#39;s touch. 
     A polarizing film PF (illustrated in  FIGS. 3 and 4 ) may be disposed on the sensor electrode layer SENL to prevent a decrease in visibility due to reflection of external light. The polarizing film PF may include a linear polarizer and a retardation film such as a quarter-wave (λ/4) plate. The retardation film may be disposed on the sensor electrode layer SENL, and the linear polarizer may be disposed on the retardation film. 
     The cover window  100  may be disposed on the polarizing film PF. The cover window  100  may be made of a transparent material and may include glass or plastic. For example, the cover window  100  may include ultra-thin glass (UTG) having a thickness of 0.1 mm or less. The cover window  100  may include a transparent polyimide film. The cover window  100  may be attached onto the polarizing film PF by a transparent adhesive member such as an optically clear adhesive (OCA) film. 
     The bottom panel cover  400  may be disposed under the substrate SUB 1 . The bottom panel cover  400  may be attached to a lower surface of the substrate SUB 1  by an adhesive member. The adhesive member may be a PSA. The bottom panel cover  400  may include at least one of a light absorbing member configured to absorb light incident from the outside, a buffer member configured to absorb external impact, and a heat dissipating member configured to efficiently dissipate the heat of the display panel  300 . 
     The light absorbing member (not illustrated) may be disposed under the display panel  300 . The light absorbing member blocks transmission of light to prevent elements disposed under the light absorbing member, for example, the display circuit board  310 , etc. from being seen from above the display panel  300 . The light absorbing member may include a light absorbing material such as a black pigment or dye. 
     The buffer member (not illustrated) may be disposed under the light absorbing member. The buffer member absorbs external impact to prevent the display panel  300  from being damaged. The buffer member may be composed of a single layer or a plurality of layers. For example, the buffer member may be made of polymer resin such as polyurethane, polycarbonate, polypropylene or polyethylene or may be made of an elastic material such as sponge formed by foaming rubber, a urethane-based material or an acrylic-based material. 
     The heat dissipating member (not illustrated) may be disposed under the buffer member. The heat dissipating member may include a first heat dissipating layer containing graphite or carbon nanotubes and a second heat dissipating layer formed of a metal thin film (such as copper, nickel, ferrite or silver) capable of shielding electromagnetic waves and having excellent thermal conductivity. 
     When the actuator  510  is disposed on the heat dissipating member of the bottom panel cover  400 , a first heat dissipating layer (not illustrated) of the heat dissipating member may be broken by the vibration of the actuator  510 . Therefore, the heat dissipating member of the bottom panel cover  400  may be removed from an area where the actuator  510  is disposed, and the actuator  510  may be attached to a lower surface of the buffer member of the bottom panel cover  400 . 
     Alternatively, when the actuator  510  is disposed on the buffer member of the bottom panel cover  400 , the magnitude of vibration of the actuator  510  may be reduced by the buffer member. Therefore, the buffer member and the heat dissipating member may be removed from the area where the actuator  510  is disposed, and the actuator  510  may be attached to a lower surface of the light absorbing member. 
     Alternatively, as illustrated in  FIG. 4 , the bottom panel cover  400  may be removed from the area where the actuator  510  is disposed, and the actuator  510  may be attached to the lower surface of the substrate SUB 1  of the display panel  300 . That is, the actuator  510  and the bottom panel cover  400  may not overlap each other in the width direction of the display panel  300 . 
       FIG. 5  is a detailed cross-sectional view of the display layer PAL and the sensor electrode layer SENL of the display panel  300  according to an exemplary embodiment. 
     Referring to  FIG. 5 , the display panel  300  may include the substrate SUB 1 , the display layer PAL, and the sensor electrode layer SENL. The display layer PAL may include the buffer layer  302 , the thin-film transistor layer  303 , the light emitting element layer  304 , and the encapsulation layer  305 . 
     The buffer layer  302  may be formed on the substrate SUB 1 . The buffer layer  302  may be formed on the substrate SUB 1  to protect thin-film transistors  335  and light emitting elements from moisture introduced through the substrate SUB 1  which is vulnerable to moisture penetration. The buffer layer  302  may be composed of a plurality of inorganic layers stacked alternately. For example, the buffer layer  302  may be a multilayer in which one or more inorganic layers selected from a silicon oxide (SiO x ) layer, a silicon nitride (SiN x ) layer, and SiON are alternately stacked. The buffer layer  302  can be omitted. 
     The thin-film transistor layer  303  is formed on the buffer layer  302 . The thin-film transistor layer  303  includes the thin-film transistors  335 , a gate insulating layer  336 , an interlayer insulating film  337 , a protective layer  338 , and an organic layer  339 . 
     Each of the thin-film transistors  335  includes an active layer  331 , a gate electrode  332 , a source electrode  333 , and a drain electrode  334 . In  FIG. 5 , each of the thin-film transistors  335  is formed as a top-gate type in which the gate electrode  332  is located above the active layer  331 . However, it should be noted that embodiments are not limited to this case. That is, each of the thin-film transistors  335  may also be formed as a bottom-gate type in which the gate electrode  332  is located under the active layer  331  or a double-gate type in which the gate electrode  332  is located both above and under the active layer  331 . 
     The active layers  331  are formed on the buffer layer  302 . The active layers  331  may be made of a silicon-based semiconductor material or an oxide-based semiconductor material. For example, the active layers  331  may be made of polysilicon, amorphous silicon, or an oxide semiconductor. A light shielding layer may be formed between the buffer layer  302  and the active layers  331  to block external light from entering the active layers  331 . 
     The gate insulating layer  336  may be formed on the active layers  331 . The gate insulating layer  336  may be an inorganic layer, for example, a silicon oxide (SiO x ) layer, a silicon nitride (SiN x ) layer, or a multilayer composed of these layers. 
     The gate electrodes  332  may be formed on the gate insulating layer  336 . Each of the gate electrodes  332  and the gate lines may be a single layer or a multilayer made of any one or more of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Ne), copper (Cu), and alloys of the same. 
     The interlayer insulating film  337  may be formed on the gate electrodes  332  and the gate lines. The interlayer insulating film  337  may be an inorganic layer, for example, a silicon oxide (SiO x ) layer, a silicon nitride (SiN) layer, or a multilayer composed of these layers. 
     The source electrodes  333  and the drain electrodes  334  may be formed on the interlayer insulating film  337 . Each of the source electrodes  333  and the drain electrodes  334  may be connected to an active layer  331  through a contact hole passing through the gate insulating layer  336  and the interlayer insulating film  337 . Each of the source electrodes  333  and the drain electrodes  334  may be a single layer or a multilayer made of any one or more of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Ne), copper (Cu), and alloys of the same. 
     The protective layer  338  configured to insulate the thin-film transistors  335  may be formed on the source electrodes  333  and the drain electrodes  334 . The protective layer  338  may be an inorganic layer, for example, a silicon oxide (SiO x ) layer, a silicon nitride (SiN) layer, or a multilayer composed of these layers. 
     The organic layer  339  may be formed on the protective layer  338  to planarize steps due to the thin-film transistors  335 . The organic layer  339  may be made of an organic layer such as acryl resin, epoxy resin, phenolic resin, polyamide resin, or polyimide resin. 
     The light emitting element layer  304  is formed on the thin-film transistor layer  303 . The light emitting element layer  304  includes the light emitting elements and a bank  344 . 
     The light emitting elements and the bank  344  are formed on the organic layer  339 . The light emitting elements may be organic light emitting devices, each including an anode  341 , a light emitting layer  342 , and a cathode  343 . 
     The anodes  341  may be formed on the organic layer  339 . The anodes  341  may be connected to the source electrodes  333  or the drain electrodes  334  of the thin-film transistors  335  through contact holes passing through the protective layer  338  and the organic layer  339 . 
     The bank  344  may be formed on the organic layer  339  and may cover edges of the anodes  341  to define light emitting areas EA of pixels PX. That is, the bank  344  defines the light emitting areas EA of the pixels PX. Each of the pixels PX is an area in which the anode  341 , the light emitting layer  342  and the cathode  343  are sequentially stacked so that holes from the anode  341  and electrons from the cathode  343  combine together in the light emitting layer  342  to emit light. 
     The light emitting layers  342  are formed on the anodes  341  and the bank  344 . The light emitting layers  342  may be organic light emitting layers. Each of the light emitting layers  342  may emit one of red light, green light, and blue light. Alternatively, the light emitting layers  342  may be white light emitting layers which emit white light. In this case, the light emitting layers  342  may be a stack of a red light emitting layer, a green light emitting layer and a blue light emitting layer and may be a common layer common to all of the pixels PX. In this case, the display panel  300  may further include color filters configured to display red, green and blue. 
     Each of the light emitting layers  342  may include a hole transporting layer, an emitting layer, and an electron transporting layer. In addition, each of the light emitting layers  342  may be formed in a tandem structure of two or more stacks, in which case a charge generating layer may be formed between the stacks. 
     The cathode  343  is formed on the light emitting layers  342 . The cathode  343  may be formed to cover the light emitting layers  342 . The cathode  343  may be a common layer common to all of the pixels PX. 
     When the light emitting element layer  304  is formed as a top emission type which emits light in an upward direction, the anodes  341  may be made of a metal material having high reflectivity, such as a stacked structure (Ti/Al/Ti) of aluminum and titanium, a stacked structure (ITO/Al/ITO) of aluminum and indium tin oxide, an APC alloy, or a stacked structure (ITO/APC/ITO) of an APC alloy and indium tin oxide. The APC alloy is an alloy of silver (Ag), palladium (Pd), and copper (Cu). In addition, the cathode  343  may be made of a transparent conductive material (TCO) capable of transmitting light, such as indium tin oxide (ITO) or indium zinc oxide (IZO), or a semi-transmissive conductive material such as magnesium (Mg), silver (Ag) or an alloy of Mg and Ag. When the cathode  343  is made of a semi-transmissive conductive material, the light output efficiency may be increased by a microcavity. 
     When the light emitting element layer  304  is formed as a bottom emission type which emits light in a downward direction, the anodes  341  may be made of a transparent conductive material (TCO) such as indium tin oxide (ITO) or indium zinc oxide (IZO) or a semi-transmissive conductive material such as magnesium (Mg), silver (Ag) or an alloy of Mg and Ag. The cathode  343  may be made of a metal material having high reflectivity, such as a stacked structure (Ti/Al/Ti) of aluminum and titanium, a stacked structure (ITO/Al/ITO) of aluminum and indium tin oxide, an APC alloy, or a stacked structure (ITO/APC/ITO) of an APC alloy and indium tin oxide. When the anodes  341  are made of a semi-transmissive conductive material, the light output efficiency may be increased by a microcavity. 
     The encapsulation layer  305  is formed on the light emitting element layer  304 . The encapsulation layer  305  serves to prevent oxygen or moisture from penetrating into the light emitting layers  342  and the cathode  343 . To this end, the encapsulation layer  305  may include at least one inorganic layer. The inorganic layer may be made of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, or titanium oxide. In addition, the encapsulation layer  305  may further include at least one organic layer. The organic layer may be formed to a sufficient thickness so as to prevent particles from penetrating the encapsulation layer  305  and entering the light emitting layers  342  and the cathode  343 . The organic layer may include any one of epoxy, acrylate, and urethane acrylate. 
     The sensor electrode layer SENL may be formed on the encapsulation layer  305 . When the sensor electrode layer SENL is formed directly on the encapsulation layer  305 , a thickness of the display device  10  can be reduced as compared with when a separate touch panel is attached onto the encapsulation layer  305 . 
     The sensor electrode layer SENL may include sensor electrodes configured to sense a user&#39;s touch using a capacitance method and touch lines configured to connect pads and the sensor electrodes. For example, the sensor electrode layer SENL may sense a user&#39;s touch using a self-capacitance method or a mutual capacitance method. In  FIG. 5 , a case where the sensor electrode layer SENL is a double layer formed using the mutual capacitance method and including driving electrodes TE, sensing electrodes RE and connecting portions BE connecting the driving electrodes TE is mainly described. 
     The connecting portions BE may be formed on the encapsulation layer  305 . The connecting portions BE may be made of, but are not limited to, a stacked structure (Ti/Al/Ti) of aluminum and titanium, a stacked structure (ITO/Al/ITO) of aluminum and indium tin oxide, an APC alloy, or a stacked structure (ITO/APC/ITO) of an APC alloy and indium tin oxide. For example, each of the connecting portions BE may be formed as a single layer of molybdenum (Mo), titanium (Ti), copper (Cu), aluminum (Al), or indium tin oxide (ITO). 
     A first sensing insulating layer TINS 1  is formed on the connecting portions BE. The first sensing insulating layer TINS 1  may be made of an inorganic layer, for example, a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, a titanium oxide layer, or an aluminum oxide layer. 
     The driving electrodes TE and the sensing electrodes RE may be formed on the first sensing insulating layer TINS 1 . The driving electrodes TE and the sensing electrodes RE may be made of, but are not limited to, a stacked structure (Ti/Al/Ti) of aluminum and titanium, a stacked structure (ITO/Al/ITO) of aluminum and indium tin oxide, an APC alloy, or a stacked structure (ITO/APC/ITO) of an APC alloy and indium tin oxide. For example, each of the driving electrodes TE and the sensing electrodes RE may be formed as a single layer of molybdenum (Mo), titanium (Ti), copper (Cu), aluminum (Al), or indium tin oxide (ITO). 
     Contact holes penetrating the first sensing insulating layer TINS 1  to expose the connecting portions BE may be formed in the first sensing insulating layer TINS 1 . The driving electrodes TE may be connected to the connecting portions BE through the contact holes. 
     A second sensing insulating layer TINS 2  is formed on the driving electrodes TE and the sensing electrodes RE. The second sensing insulating layer TINS 2  may planarize steps formed by the driving electrodes TE, the sensing electrodes RE, and the connecting portions BE. The second sensing insulating layer TINS 2  may be made of an organic layer such as acryl resin, epoxy resin, phenolic resin, polyamide resin, or polyimide resin. 
     The connecting portions BE connecting adjacent driving electrodes TE may be disposed on the encapsulation layer  305 , and the driving electrodes TE and the sensing electrodes RE may be disposed on the first sensing insulating layer TINS 1 . Therefore, the driving electrodes TE and the sensing electrodes RE may be electrically insulated at their intersections. The sensing electrodes RE may be electrically connected in one direction, and the driving electrodes TE may be electrically connected in the other direction. 
       FIG. 6  is a detailed view of an actuator  510  according to an exemplary embodiment.  FIG. 7  is a diagram illustrating the inverse piezoelectric effect of the actuator  510  in accordance with  FIG. 6 .  FIG. 8  is a diagram illustrating the piezoelectric effect of the actuator  510  in accordance with  FIG. 6 . 
     Referring to  FIGS. 6 through 8 , the actuator  510  may be a piezoelectric element or a piezoelectric actuator that vibrates the display panel  300  using a piezoelectric material that contracts or expands according to an applied voltage. The actuator  510  may include a vibration layer  511 , a first electrode  512 , and a second electrode  513 . 
     The first electrode  512  may include a first stem electrode  5121  and first branch electrodes  5122 . The first stem electrode  5121  may be disposed on at least one side surface of the vibration layer  511  as illustrated in  FIG. 6 . Alternatively, the first stem electrode  5121  may penetrate a part of the vibration layer  511 . The first stem electrode  5121  may also be disposed on an upper surface of the vibration layer  511 . The first branch electrodes  5122  may branch from the first stem electrode  5121 . The first branch electrodes  5122  may be arranged parallel to each other. 
     The second electrode  513  may include a second stem electrode  5131  and second branch electrodes  5132 . The second electrode  513  may be spaced apart from the first electrode  512 . Therefore, the second electrode  513  may be electrically insulated from the first electrode  512  by the vibration layer  511 . The second stem electrode  5131  may be disposed on at least one side surface of the vibration layer  511 . In this case, the first stem electrode  5121  may be disposed on a first side surface of the vibration layer  511 , and the second stem electrode  5131  may be disposed on a second side surface of the vibration layer  511 . Alternatively, the second stem electrode  5131  may penetrate a part of the vibration layer  511 . The second stem electrode  5131  may be disposed on the upper surface of the vibration layer  511 . The second branch electrodes  5132  may branch from the second stem electrode  5131 . The second branch electrodes  5132  may be arranged parallel to each other. 
     The first branch electrodes  5122  and the second branch electrodes  5132  may be arranged parallel to each other in the horizontal direction (X-axis direction or Y-axis direction). In addition, the first branch electrodes  5122  and the second branch electrodes  5132  may be alternately arranged in the vertical direction (Z-axis direction). That is, the first branch electrodes  5122  and the second branch electrodes  5132  may be repeatedly arranged in the vertical direction (Z-axis direction) in the order of the first branch electrode  5122 , the second branch electrode  5132 , the first branch electrode  5122 , and the second branch electrode  5132 . 
     The first electrode  512  and the second electrode  513  may be connected to pads of a flexible circuit board. The pads of the flexible circuit board may be connected to the first electrode  512  and the second electrode  513  exposed on a surface of the actuator  510 . 
     The vibration layer  511  may be a piezoelectric element that is deformed according to a driving voltage applied to the first electrode  512  and a driving voltage applied to the second electrode  513 . In this case, the vibration layer  511  may be anyone of a piezoelectric material, such as a polyvinylidene fluoride (PVDF) film or plumbum ziconate titanate (PZT), and an electroactive polymer. 
     Because a production temperature of the vibration layer  511  is high, the first electrode  512  and the second electrode  513  may be made of silver (Ag) having a high melting point or an alloy of Ag and palladium (Pd). When the first electrode  512  and the second electrode  513  are made of an alloy of Ag and Pd, the Ag content may be higher than the Pd content in order to raise melting points of the first electrode  512  and the second electrode  513 . 
     The vibration layer  511  may be disposed between each pair of the first and second branch electrodes  5122  and  5132 . The vibration layer  511  may contractor expand according to a difference between the driving voltage applied to each first branch electrode  5122  and the driving voltage applied to a corresponding second branch electrode  5132 . 
     As illustrated in  FIG. 6 , when a polarization direction of the vibration layer  511  disposed between a first branch electrode  5122  and a second branch electrode  5132  disposed under the first branch electrode  5122  is an upward direction (?), the vibration layer  511  may have a positive polarity in an upper area adjacent to the first branch electrode  5122  and a negative polarity in a lower area adjacent to the second branch electrode  5132 . In addition, when the polarization direction of the vibration layer  511  disposed between a second branch electrode  5132  and a first branch electrode  5122  disposed under the second branch electrode  5132  is a downward direction ( 1 ), the vibration layer  511  may have a negative polarity in an upper area adjacent to the second branch electrode  5132  and a positive polarity in a lower area adjacent to the first branch electrode  5122 . The polarization direction of the vibration layer  511  may be determined by a poling process in which an electric field is applied to the vibration layer  511  using a first branch electrode  5122  and a second branch electrode  5132 . 
     As illustrated in  FIG. 7 , when the polarization direction of the vibration layer  511  disposed between a first branch electrode  5122  and a second branch electrode  5132  disposed under the first branch electrode  5122  is the upward direction (t), if a positive driving voltage is applied from a power source PSi to the first branch electrode  5122  and a negative driving voltage is applied from the power source PSi to the second branch electrode  5132 , the vibration layer  511  may contract according to a first force F 1 . The first force F 1  may be a contractile force. Also, if a negative driving voltage is applied from the power source PS 1  to the first branch electrode  5122  and a positive driving voltage is applied from the power source PSi to the second branch electrode  5132 , the vibration layer  511  may expand according to a second force F 2 . The second force F 2  may be a stretching force. 
     As illustrated in  FIG. 7B , when the polarization direction of the vibration layer  511  disposed between a second branch electrode  5132  and a first branch electrode  5122  disposed under the second branch electrode  5132  is the downward direction (↓), if a positive driving voltage is applied to the second branch electrode  5132  and a negative driving voltage is applied to the first branch electrode  5122 , the vibration layer  511  may expand according to a stretching force. Also, if a negative driving voltage is applied to the second branch electrode  5132  and a positive driving voltage is applied to the first branch electrode  5122 , the vibration layer  511  may contract according to a contractile force. 
     When the driving voltage applied to the first electrode  512  and the driving voltage applied to the second electrode  513  repeatedly alternate between the positive polarity and the negative polarity, the vibration layer  511  may repeatedly contract and expand, thus causing the actuator  510  to vibrate as illustrated by vibration lines  550 . Because the actuator  510  is disposed on a surface of the substrate SUB 1 , when the vibration layer  511  of the actuator  510  contracts and expands, the display panel  300  may vibrate in the third direction (Z-axis direction), which is the thickness direction of the display panel  300 , as well as the width direction (X-direction), due to stress. As the display panel  300  is vibrated by the actuator  510 , sound may be output. 
     A protective layer  519  may be additionally disposed on a lower surface and side surfaces of the actuator  510 . The protective layer  519  may be made of an insulating material or the same material as the vibration layer  511 . The protective layer  519  may be disposed on the first electrode  512 , the second electrode  513 , and the vibration layer  511  and may be exposed without being covered by the first electrode  512  and the second electrode  513 . The protective layer  519  may be disposed to surround the first electrode  512 , the second electrode  513 , and the vibration layer  511  and may be exposed without being covered by the first electrode  512  and the second electrode  513 . Therefore, the vibration layer  511 , the first electrode  512  and the second electrode  513  of the actuator  510  may be protected by the protective layer  519 , but embodiments are not limited thereto. In some embodiments, the protective layer  519  may be omitted. 
     In addition, as illustrated in  FIG. 8 , when mechanical deformation occurs in the actuator  510  due to pressure applied to the actuator  510 , the vibration layer  511  of the actuator  510  may contract according to a force F 1  resulting from the applied pressure. Accordingly, a voltage may be generated in at least any one of the first electrode  512  and the second electrode  513 . When a voltage is generated in at least any one of the first electrode  512  and the second electrode  513 , the actuator driver  340  may sense the voltage. 
     As illustrated in  FIGS. 6 through 8 , the actuator  510  may generate a sensing voltage in at least any one of the first electrode  512  and the second electrode  513  due to the piezoelectric effect when pressure is applied by a user and may generate vibrations due to the inverse piezoelectric effect when a driving voltage is applied to each of the first electrode  512  and the second electrode  513 . 
       FIG. 9  is a block diagram illustrating electrical connections between various modules including the display module, the actuator  510  and the main processor  710  of the display device  10  according to exemplary embodiments. 
     Referring to  FIG. 9 , the display device  10  includes the display panel  300 , the display driver  320 , the sensor driver  330 , the actuator driver  340 , a scan driver  350 , the actuator  510 , and the main processor  710 . 
     The display panel  300  may include the display layer PAL which may include data lines, scan lines intersecting the data lines, and pixels connected data lines and scan lines. Each pixel is connected to any one of the data lines and at least one of the scan lines. In addition, the display layer PAL of the display panel  300  may further include a first power supply voltage line to which a first power supply voltage is supplied and a second power supply voltage line to which a second power supply voltage lower than the first power supply voltage is supplied. In this case, the pixels may be electrically connected to the first power supply voltage line and the second power supply voltage line. Each of the pixels may include a light emitting element, a plurality of transistors configured to supply a light emitting current to the light emitting element, and at least one capacitor. 
     The display driver  320  receives digital video data DATA and timing signals from the main processor  710 . The display driver  320  converts the digital video data DATA into analog data voltages according to the timing signals and applies the analog data voltages to the data lines of the display panel  300 . In addition, the display driver  320  may generate a scan control signal SCS configured to control the operation timing of the scan driver  350  according to the timing signals. The display driver  320  may output the scan control signal SCS to the scan driver  350 . 
     The sensor driver  330  receives sensor sensing voltages TRV of the sensor electrodes of the sensor electrode layer SENL of the display panel  300 . The sensor driver  330  may convert the sensor sensing voltages TRV into touch row data which is digital data. The sensor driver  330  may analyze the touch row data to calculate touch coordinates at which a user&#39;s touch input has occurred. The sensor driver  330  may output touch data TD including the touch coordinates to the main processor  710 . 
     The actuator driver  340  receives a sensing voltage RV generated by the piezoelectric effect of the actuator  510 . The actuator driver  340  may convert the analog sensing voltage RV into sensing data RD which is digital data. The actuator driver  340  may output the sensing data RD to the main processor  710 . 
     The actuator driver  340  receives driving data DD from the main processor  710 . The actuator driver  340  may generate analog driving voltages ADV according to the driving data DD and output the analog driving voltages ADV to the actuator  510 . 
     The scan driver  350  receives the scan control signal SCS from the display driver  320 . The scan driver  350  generates scan signals SP according to the scan control signal SCS and transmits the scan signals SP to the scan lines of the display panel  300 . 
     When pressure is applied to the actuator  510 , the actuator  510  may output the sensing voltage RV to the actuator driver  340  due to the piezoelectric effect. The actuator  510  may receive the driving voltages ADV from the actuator driver  340 . When the driving voltages ADV are applied to the actuator  510 , mechanical deformation may occur due to the inverse piezoelectric effect. For example, the actuator  510  may vibrate according to the period of the driving voltages ADV. 
     The main processor  710  may convert the resolution of the digital video data DATA received from an external source to match the resolution of the display panel  300 . The main processor  710  may output the digital video data DATA and the timing signals to the display driver  320 . 
     The main processor  710  may receive the touch data TD from the sensor driver  330 . The main processor  710  may calculate touch coordinates according to the touch data TD. The main processor  710  may perform an operation corresponding to a user&#39;s touch. For example, the main processor  710  may execute an application or perform an operation indicated by an icon at touch coordinates determined to have been touched by a user. 
     The main processor  710  receives the sensing data RD from the actuator driver  340 . When the sensing data RD is greater than a threshold value, the main processor  710  may determine that a user has applied pressure. In this case, the main processor  710  may output the driving data DD to the actuator driver  340  in order to provide haptic feedback using the actuator  510 . 
       FIG. 10  is a flowchart illustrating a haptic feedback method of the display device  10  according to exemplary embodiments.  FIG. 11  is a graph illustrating the sensing voltage RV sensed by the actuator  510  according to pressure applied to a side surface of the display device  10  in exemplary embodiments.  FIG. 12  is a graph illustrating vibration acceleration according to the vibration of the actuator  510  when haptic feedback is provided to a user in exemplary embodiments. Vibration acceleration may be characterized as vibration intensity. 
     First, a user applies pressure to the tactile pattern  110  disposed on a side surface of the display device  10  to execute a predetermined function (operation S 101  of  FIG. 10 ). 
     The tactile pattern  110  may be an embossed pattern protruding from the right side surface portion of the cover window  100  or an intaglio pattern cut into the right side surface portion of the cover window  100 . The tactile pattern  110  may be a pattern that may be felt by the user as being different from the cover window  100 . Therefore, the user may recognize the tactile pattern  110  as a physical button. Hence, the user may apply pressure to the tactile pattern  110  as if pressing a physical button in order to execute a predetermined function. The predetermined function may be a power control function such as power on or power off or a volume control function configured to increase or decrease the volume. Although the tactile pattern  110  is disposed on an upper surface of the right side surface portion  100 R of the cover window  100  illustrated in  FIGS. 11 and 12 , the position of the tactile pattern  110  is not limited to this position. 
     In a second operation, it is determined whether the sensing data RD of the actuator  510  overlapping the tactile pattern  110  in the width direction (X-direction) of the display panel  300  is greater than a threshold value VTH (operation S 102  of  FIG. 10 ). 
     As illustrated in  FIG. 9 , when the user applies pressure to the tactile pattern  110 , the actuator  510  overlapping the tactile pattern  110  in the width direction of the display panel  300  may generate the sensing voltage RV due to the piezoelectric effect, and the actuator driver  340  may sense the sensing voltage RV of the actuator  510 . The actuator driver  340  may convert the analog sensing voltage RV into the sensing data RD which is digital data and output the sensing data RD to the main processor  710 . 
     The main processor  710  determines whether the sensing data RD is greater than a threshold value VTH. When the sensing data RD is greater than the threshold value VTH, the main processor  710  may determine that the user has applied pressure to the actuator  510 . That is, when the sensing data RD is greater than the threshold value VTH, the main processor  710  may determine that the user has applied sufficient pressure to the tactile pattern  110  in order to execute the predetermined function. 
     Third, when the sensing data RD is greater than the threshold value, the actuator  510  overlapping the tactile pattern  110  in the width direction of the display panel  300  may be vibrated to provide haptic feedback (operation S 103  of  FIG. 10 ). Thus when a user applies sufficient pressure to the tactile pattern  110 , the tactile pattern  110  may be activated to vibrate. 
     When the sensing data RD is greater than the threshold value VTH, the main processor  710  may execute the predetermined function assigned to the tactile pattern  110  such as the power control function or the volume control function while outputting the driving data DD stored in the memory to the actuator driver  340 . The actuator driver  340  may convert the driving data DD which is digital data into the driving voltages ADV which are analog data and output the driving voltages ADV to the actuator  510 . The actuator  510  may vibrate according to the driving voltages ADV due to the inverse piezoelectric effect. That is, the user may be provided with haptic feedback through the vibration of the actuator  510 . 
     As illustrated in  FIGS. 11 and 12 , the right side surface portion  100 R of the cover window  100  may include first through p th  areas A 1  through Ap (wherein p is an integer of 2 or more), and the tactile pattern  110  and the actuator  510  may be disposed in the second area A 2 . 
     As a position (along the Y-axis) to which the user applies pressure moves farther from the tactile pattern  110 , sensing data RD (Z-axis) sensed by the actuator  510  may be smaller. For example, as illustrated in  FIG. 11 , when the position to which the user applies pressure is the second area A 2 , the sensing data RD sensed by the actuator  510  may be largest. In addition, when the position to which the user applies pressure is the p th  area Ap, the sensing data RD sensed by the actuator  510  may be smallest. 
     In addition, the vibration acceleration of the actuator  510  may become smaller as the distance from the actuator  510  increases. For example, as illustrated in  FIG. 12 , when the actuator  510  is disposed in the second area A 2 , the vibration acceleration of the actuator  510  may be largest in the second area A 2  and smallest in the p th  area Ap. The vibration acceleration of the actuator  510  indicates a value measured by an accelerometer for vibration generated by the actuator  510 . 
     As illustrated in  FIGS. 10 through 12 , the tactile pattern  110  may be formed on an upper surface of the right side surface portion  100 R of the cover window  100 . As a result, due to the tactile pattern  110 , a user can easily find an area to apply pressure to perform a desired function. 
     In addition, when the user applies pressure to the tactile pattern  110  of the cover window  100 , the sensing data RD of the actuator  510  overlapping the tactile pattern  110  in the width direction of the display panel  300  may be sensed. As illustrated in  FIG. 11 , when the sensing data RD is greater than the threshold value VTH, a predetermined function such as the power control function or the volume control function may be executed, and at the same time, the actuator  510  may be vibrated by applying driving voltages to the actuator  510  to provide haptic feedback to the user. In an area such as A 1 , A 2 , or A 3 , the vibration acceleration may be felt more by a user. In the area Ap, the vibration acceleration may be smallest. Accordingly, the user can recognize whether a desired function is properly performed by the pressure applied to the tactile pattern  110 . 
       FIGS. 13 through 16  are side views of display devices  10  according to exemplary embodiments. 
     In each of  FIGS. 13 through 16 , a right side surface portion  100 R of a display device  10  is illustrated. In each of  FIGS. 13 through 16 , a bottom cover  900  is omitted for ease of description, and only a cover window  100  and a tactile pattern  110  are illustrated. 
     Although the tactile pattern  110  is disposed on the right side surface portion  100 R of the display device  10  in each of  FIGS. 13 through 16 , the position of the tactile pattern  110  is not limited to this position. For example, the tactile pattern  110  may also be disposed on a left side surface portion  100 L of the display device  10  or an upper surface portion  100 U of the display device  10 . 
     The tactile pattern  110  may be an embossed pattern protruding from a left or upper surface of the cover window  100  or an intaglio pattern cut into a part of the left or upper surface of the cover window  100 . 
     The tactile pattern  110  may be quadrangular in plan view as illustrated in  FIG. 13 . However, the planar shape of the tactile pattern  110  is not limited to the quadrangular shape and may also be a polygon other than a quadrangle, a circle, or an oval as illustrated in  FIG. 14 . 
     Alternatively, the tactile pattern  110  may be formed in the shape of a quadrangular frame or a quadrangular window frame in plan view as illustrated in  FIG. 15 . The tactile pattern  110  may be formed as a quadrangular border in plan view. Alternatively, the tactile pattern  110  may be formed in the shape of a polygonal frame other than a quadrangular frame, a circular frame, or an oval frame in plan view. 
     Alternatively, the tactile pattern  110  may include a plurality of dots that form a quadrangle in plan view as illustrated in  FIG. 16 . Alternatively, the tactile pattern  110  may include a plurality of dots that form a polygon other than a quadrangle, a circle, or an oval in plan view. 
     The planar shape of the tactile pattern  110  is not limited to the shapes described with reference to  FIGS. 13 through 16  and may be various. 
       FIGS. 17 through 22  are cross-sectional views of the cover window  100  of  FIG. 13  and a plurality of tactile patterns  110 . In  FIGS. 17 through 22 , only the cover window  100  and the tactile patterns  110  are illustrated for ease of description. 
     A tactile pattern  110  may be disposed on a first surface  100   a  of the cover window  100  as illustrated in  FIG. 17 . The first surface  100   a  may refer to the right, left, or upper surface of the cover window  100 . The first surface  100   a  of the cover window  100  may be a surface opposite a second surface  100   b  of the cover window  100  that faces the display panel  300 . The first surface  100   a  of the cover window  100  may be the upper surface of the cover window  100 , and the second surface  100   b  of the cover window  100  may be a lower surface of the cover window  100 . A thickness in the Z-direction of the tactile pattern  110  may be smaller than that of the cover window  100 . 
     The tactile pattern  110  may include an inorganic material or an organic-inorganic hybrid material. For example, the tactile pattern  110  may include a silicon (Si)-based inorganic material. Alternatively, the tactile pattern  110  may include transparent plastic such as polycarbonate (PC) or polymethyl methacrylate (PMMA) and an inorganic material. Alternatively, the tactile pattern  110  have a material in which an organic material such as ultraviolet-curable acrylic or heat-curable epoxy is covalently bonded with a silicon (Si)-based inorganic material. Here, the higher the proportion of the organic material in the tactile pattern  110 , the easier the printing of the tactile pattern  110  may be. In addition, the higher the proportion of the inorganic material in the tactile pattern  110 , the higher the strength of the tactile pattern  110  may be. Alternatively, the tactile pattern  110  may include frit glass. 
     A tactile pattern  110  may be disposed on a hole pattern HP (or a well pattern) formed in the first surface  100   a  of the cover window  100  as illustrated in  FIG. 18 . The hole pattern HP may be formed at the same time as when a through hole is formed in the cover window  100  by computerized numerically control processing. Alternatively, the hole pattern HP may be formed by forming a mask pattern on the first surface of the cover window  100  and etching the cover window  100  using a chemical as in wet etching or dry etching. Alternatively, the hole pattern HP may be formed using a laser. An upper surface of the hole pattern HP may not be even but may be rough as illustrated in  FIG. 18 . 
     The tactile pattern  110  may be integrally formed with the cover window  100  as illustrated in  FIG. 19 . The tactile pattern  110  may be an embossed pattern protruding from the first surface  100   a  of the cover window  100 . In this case, a thickness T 1  of the cover window  100  in an area where the tactile pattern  110  is disposed may be greater than a thickness T 2  of the cover window  100  in an area where the tactile pattern  110  is not disposed. 
     A tactile pattern  110  may be an intaglio pattern cut into the first surface of the cover window  100  as illustrated in  FIG. 20 . In this case, a thickness T 3  of the cover window  100  in an area where the tactile pattern  110  is disposed may be smaller than the thickness T 2  of the cover window  100  in an area where the tactile pattern  110  is not disposed. 
     A tactile pattern  110  may be a part of a bent portion  110  in which the cover window  100  is bent as illustrated in  FIGS. 21 and 22 . Each of upper and lower surfaces of the bent portion  111  may have a triangular cross-sectional shape as illustrated in  FIGS. 21 and 22 . When the bent portion  111  protrudes toward the upper surface of the cover window  100  as illustrated in  FIG. 21 , the tactile pattern  110  may be an embossed pattern. When the bent portion  111  protrudes toward the lower surface of the cover window  100  as illustrated in  FIG. 22 , the tactile pattern  110  may be an intaglio pattern. The bent portion  111  may be triangular as illustrated or may have rounded edges. 
       FIG. 23  is a flowchart illustrating a haptic feedback method of a display device  10  according to an exemplary embodiment.  FIG. 24  is a graph illustrating a sensing voltage RV sensed by an actuator  510  according to pressure applied to a side surface of the display device  10  in accordance with  FIG. 23 .  FIG. 25  is a graph illustrating vibration acceleration according to the vibration of the actuator  510  when haptic feedback is provided to a user in accordance with  FIG. 23 . 
     The exemplary embodiment of  FIGS. 23 through 25  is different from the embodiment of  FIGS. 10 through 12  in that the display device  10  illustrated in  FIGS. 23 through 25  does not include a tactile pattern  110 . A user may apply pressure to a part of a side surface of the display device  10  instead of applying pressure to a designated area overlapping the actuator  510  in the width direction (X-direction) of a display panel  300 . 
     In the flowchart, first a user applies pressure to a side surface of the display device  10  to execute a predetermined function (operation S 201  of  FIG. 23 ). 
     The tactile pattern  110  may not be formed on the side surface of the display device  10 . When the user applies pressure to apart of the side surface of the display device  10 , the display device  10  may execute a predetermined function such as a power control function or a volume control function. 
     Second, a touch position of the user to which the user has applied pressure is calculated, and a position threshold value is calculated according to the touch position of the user (operation S 202  of  FIG. 23 ). 
     When the user touches the display device  10  to apply pressure, the sensor driver  330  may convert sensor sensing voltages of a sensor electrode layer SENL of the display panel  300  into touch row data and calculate touch coordinates of the user by analyzing the touch row data. For example, the sensor driver  330  may calculate coordinates of touch row data which is greater than a touch threshold value as the touch coordinates. The sensor driver  330  may output touch data TD including the touch coordinates of the user to a main processor  710 . The touch coordinates may be similar to the areas A 1  through Ap. 
     The main processor  710  may determine the touch position of the user according to the touch coordinates of the touch data TD. The main processor  710  may include a lookup table that stores a position threshold value VLTH for each of the touch coordinates. The lookup table may output the position threshold value VLTH by using the touch coordinates as an input address. The main processor  710  may output the touch coordinates to the lookup table and receive the position threshold value VLTH. The position threshold value VLTH is related to an amount of pressure applied by a user to an area of the window  100 . 
     As a position to which the user applies pressure is farther from the actuator  510 , sensing data RD sensed by the actuator  510  may be smaller. Therefore, a threshold value to be compared with the sensing data RD needs to be adjusted according to the position to which the user applies pressure. That is, the position threshold value VLTH may decrease as the distance from the actuator  510  increases. For example, as illustrated in  FIG. 24 , when the actuator  510  is disposed in a second area A 2  of a right side surface portion of the cover window  100 , the position threshold value VLTH may be largest in the second area A 2  and smallest in a p th  area Ap. 
     Third, it is determined whether the sensing data RD of the actuator  510  is greater than the position threshold value VLTH (operation S 203  of  FIG. 23 ). 
     When the user applies pressure to a part of the side surface of the display device  10 , the actuator  510  may generate the sensing voltage RV due to a piezoelectric effect, and an actuator driver  340  may sense the sensing voltage RV of the actuator  510 . The actuator driver  340  may convert the analog sensing voltage RV into the sensing data RD which is digital data and output the sensing data RD to the main processor  710 . 
     The main processor  710  determines whether the sensing data RD is greater than the position threshold value VLTH. When the sensing data RD is greater than the position threshold value VLTH, the main processor  710  may determine that the user has applied pressure to the actuator  510 . That is, when the sensing data RD is greater than the position threshold value VLTH, the main processor  710  may determine that the user has applied sufficient pressure to a part of the side surface of the display device  10  to execute the predetermined function. 
     Fourth, when the sensing data RD is greater than the threshold value VLTH, the actuator  510  may be vibrated to provide haptic feedback (operation S 204  of  FIG. 23 ). 
     When the sensing data RD is greater than the position threshold value VLTH, the main processor  710  may execute the predetermined function such as the power control function or the volume control function while outputting driving data DD stored in a memory to the actuator driver  340 . The actuator driver  340  may convert the driving data DD which is digital data into driving voltages ADV which are analog data and output the driving voltages ADV to the actuator  510 . The actuator  510  may vibrate according to the driving voltages ADV due to an inverse piezoelectric effect. That is, the user may be provided with haptic feedback through the vibration of the actuator  510 . 
     As illustrated in  FIG. 24 , when the display device  10  does not include the tactile pattern  110 , the sensing data RD of the actuator  510  may be smaller as the position to which a user applies pressure is farther from the actuator  510 . Therefore, the position threshold value VLTH may be variable and set to a smaller value as the distance from the actuator  510  increases, so that the pressure applied by the user can be sensed using the actuator  510  regardless of the position to which the user applies pressure. 
     The vibration acceleration of the actuator  510  may decrease as the distance from the actuator  510  increases. For example, as illustrated in  FIG. 25 , when the actuator  510  is disposed in the second area A 2 , the vibration acceleration of the actuator  510  may be largest in the second area A 2  and smallest in the p th  area Ap. Therefore, the haptic feedback felt by the user may decrease as the distance from the actuator  510  increases. Hence, compensation may be sought for a reduction in haptic feedback as the distance from the actuator  510  increases. 
       FIGS. 26 through 29  illustrate a cover window  100 , a display panel  300 , an actuator  510 , and a plurality of tactile patterns  110  according to exemplary embodiments. The plurality of tactile patterns  110  may be concentrated around the actuator  510  area, or may be spread out along a length of the cover window  100 . 
     In  FIGS. 26 through 29 , cross sections of only the cover window  100 , the display panel  300 , the actuator  510 , and the plurality of tactile patterns  110  are illustrated. 
     Referring to  FIG. 26 , lengths of the tactile patterns  110  in the second direction (Y-axis direction) may increase as the distance from the actuator  510  in the second direction (Y-axis direction) increases. As the lengths of the tactile patterns  110  in the second direction (Y-axis direction) increase, a contact area between a user&#39;s finger and a tactile pattern  110  may increase. An increased contact area between the user&#39;s finger and a tactile pattern  110  increases the area of vibration that can be felt by the user, thereby increasing the haptic feedback felt by the user. Therefore, even if the vibration acceleration of the actuator  510  decreases as the distance from the actuator  510  increases, because a contact area between a user&#39;s finger and a tactile pattern  110  increases as the distance from the actuator  510  increases, the haptic feedback felt by the user may be almost similar. That is, using tactile patterns  110  of increasingly longer lengths as they move farther from the actuator  510 , it is possible to prevent the haptic feedback felt by the user from being reduced as the distance from the actuator  510  increases. 
     Referring to  FIG. 27 , lengths of the tactile patterns  110  in the third direction (Z-axis direction) may increase as the distance from the actuator  510  in the second direction (Y-axis direction) increases. That is, heights of the tactile patterns  110  protruding from the cover window  100  may increase as the distance from the actuator  510  in the second direction (Y-axis direction) increases. As the lengths of the tactile patterns  110  in the third direction (Z-axis direction) increase, a user&#39;s finger may touch not only an upper surface of a tactile pattern  110  but also side surfaces of the tactile pattern  110 . That is, the area of vibration that can be felt by the user may increase, thereby increasing the haptic feedback felt by the user. Therefore, even if the vibration acceleration of the actuator  510  decreases as the distance from the actuator  510  increases, because the contact area between the user&#39;s finger and a tactile pattern  110  increases as the distance from the actuator  510  increases, the haptic feedback felt by the user may be almost similar. That is, it is possible to prevent the haptic feedback felt by the user from being reduced as the distance from the actuator  510  increases. 
     Referring to  FIG. 28 , lengths of the upper surfaces of the tactile pattern  110  may decrease as the distance from the actuator  510  in the second direction (Y-axis direction) increases. Therefore, the tactile patterns  110  may become sharper as the distance from the actuator  510  increases. For example, as the distance from the actuator  510  increases, cross-sectional shapes of the tactile patterns  110  overlapping the actuator  510  in the width direction of the display panel  300  may change to a rectangular shape, a trapezoidal shape, and a triangular shape. As the tactile patterns  110  become sharper, the haptic feedback felt by a user may become greater as the haptic feedback may become concentrated to a smaller area. Therefore, even if the vibration acceleration of the actuator  510  decreases as the distance from the actuator  510  increases, because the tactile patterns  110  are sharper as the distance from the actuator  510  increases, the haptic feedback felt by the user may be almost similar. That is, it is possible to prevent the haptic feedback felt by the user from being reduced as the distance from the actuator  510  increases. 
     Referring to  FIG. 29 , surface roughness of the tactile patterns  110  or the number of dot patterns of each tactile pattern  110  may increase as the distance from the actuator  510  in the second direction (Y-axis direction) increases. Here, the lengths of the tactile patterns  110  in the second direction (Y-axis direction), the lengths of the tactile patterns  110  in the third direction (Z-axis direction), and the cross-sectional shapes of the tactile patterns  110  may be substantially the same. As the surface roughness of the tactile patterns  110  or the number of dot patterns of each tactile pattern  110  increases, the haptic feedback felt by a user may increase. Therefore, even if the vibration acceleration of the actuator  510  decreases as the distance from the actuator  510  increases, because the surface roughness of the tactile patterns  110  or the number of dot patterns of each tactile pattern  110  increases as the distance from the actuator  510  increases, the haptic feedback felt by the user may be almost similar. That is, the haptic feedback of an increased roughness farther away from the actuator  510  may be similar to the haptic feedback of a decreased roughness closer to the actuator  510 . Thus, it is possible to prevent the haptic feedback felt by the user from being reduced as the distance from the actuator  510  increases. 
       FIG. 30  is a flowchart illustrating a haptic feedback method of a display device  10  according to an exemplary embodiment.  FIG. 31  is a graph illustrating vibration acceleration according to the vibration of an actuator  510  when haptic feedback is provided to a user in accordance with  FIG. 30 . 
     The embodiment of  FIGS. 30 and 31  is different from the embodiment of  FIGS. 23 through 25  in that the vibration acceleration of the actuator  510  is adjusted according to a touch position of a user in operation S 304 . Therefore, a description of operations S 301  through S 303  of  FIGS. 30 and 31  will be omitted. 
     Referring to  FIGS. 30 and 31 , haptic feedback is provided to a user by adjusting the vibration acceleration of the actuator  510  according to a touch position of the user (operation S 304  of  FIG. 30 ). 
     When sensing data RD is greater than a position threshold value VLTH, a main processor  710  may execute a predetermined function such as a power control function or a volume control function while outputting driving data DD stored in a memory to an actuator driver  340 . The main processor  710  may include a lookup table that stores the driving data DD for each touch coordinate. The lookup table may output the driving data DD by using touch coordinates as an input address. The main processor  710  may output the touch coordinates to the lookup table and receive the driving data DD. 
     The vibration acceleration of the actuator  510  may decrease as the distance from the actuator  510  increases. Therefore, the vibration acceleration of the actuator  510  may be adjusted according to the position to which the user applies pressure. That is, as the touch position of the user is farther from the actuator  510 , a swing width of each driving voltage applied to the actuator  510  may be increased to increase the vibration acceleration of the actuator  510 . 
     As illustrated in  FIG. 31 , when the user applies pressure to a second area A 2 , the actuator  510  may be vibrated according to the driving voltages having a first swing width, thus causing the second area A 2  to provide haptic feedback at first vibration acceleration G 1 . On the other hand, when the user applies pressure to a fourth area A 4 , the actuator  510  may be vibrated according to driving voltages having a second swing width greater than the first swing width, thus causing the second area A 2  to provide haptic feedback at second vibration acceleration G 2  greater than the first vibration acceleration G 1 . In this case, because the vibration acceleration caused by the actuator  510  decreases the haptic feedback as the distance from the actuator  510  increases, the user&#39;s finger located in the fourth area A 4  may feel haptic feedback with the first vibration acceleration G 1 . That is, the user may be provided with haptic feedback of substantially the same vibration acceleration when the user applies pressure to the second area A 2  and when the user applies pressure to the fourth area A 4 . 
     As illustrated in  FIGS. 30 and 31 , when the display device  10  does not include a tactile pattern  110 , because the vibration acceleration of the actuator  510  decreases as the position to which a user applies pressure is farther from the actuator  510 , the swing width of each driving voltage applied to the actuator  510  is increased as the distance from the actuator  510  increases. Therefore, haptic feedback of substantially the same vibration acceleration can be provided regardless of the position to which the user applies pressure. 
       FIG. 32  is a flowchart illustrating a haptic feedback method of a display device  10  according to an embodiment.  FIG. 33  is a graph illustrating sensing voltages RV sensed by actuators  510  according to pressure applied to a side surface of the display device  10  in accordance with  FIG. 32 .  FIG. 34  is a graph illustrating vibration acceleration according to the vibration of the actuators  510  when haptic feedback is provided to a user in accordance with  FIG. 32 . 
     The embodiment of  FIGS. 32 through 34  is different from the embodiment of  FIGS. 23 through 25  in that the display device  10  includes a plurality of actuators  510 . 
     First, a user applies pressure to a side surface of the display device  10  to execute a predetermined function (operation S 401  of  FIG. 32 ). 
     Second, a touch position to which the user has applied pressure is calculated, and an actuator  510  adjacent to the touch position of the user is selected from a plurality of actuators  510  (operation S 402  of  FIG. 32 ). 
     When the user touches the display device  10  to apply pressure, a sensor driver  330  may convert sensor sensing voltages of a sensor electrode layer SENL of a display panel  300  into touch row data and calculate touch coordinates of the user by analyzing the touch row data. For example, the sensor driver  330  may calculate coordinates of touch row data which is greater than a touch threshold value as the touch coordinates. The sensor driver  330  may output touch data TD including the touch coordinates of the user to a main processor  710 . 
     The actuators  510  may respectively be disposed in first through p th  areas A 1  through Ap of a right side surface portion  100 R of a cover window  100 . For example, one of the actuators  510  may be disposed in each of the first through p th  areas A 1  through Ap of the right side surface portion of the cover window  100 . Alternatively, the actuators  510  may be disposed in some of the first through p th  areas A 1  through Ap of the right side surface portion of the cover window  100 . For example, the actuators  510  may be disposed in the first through p th  areas A 1  through Ap of the right side surface portion of the cover window  100 , respectively. 
     When the user applies pressure to the side surface of the display device  10 , each of the actuators  510  generates the sensing voltage RV of varying levels due to a piezoelectric effect. An actuator driver  340  may sense various sensing voltages RV of each of the actuators  510 . The actuator driver  340  may convert the analog sensing voltages RV into sensing data RD which is digital data and output the sensing data RD to the processor  710 . 
     The main processor  710  may determine the touch position of the user according to the touch coordinates of the touch data TD. The main processor  710  may select an actuator  510  adjacent to the touch position of the user from the actuators  510 . For example, as illustrated in  FIG. 33 , when the user applies pressure to the (p−2) th  area Ap−2 of the right side surface portion of the cover window  100 , the main processor  710  may determine the (p−2) th  area Ap−2 as the touch position of the user and select an actuator  510  disposed in the (p−2) th  area Ap−2 from among the actuators  510 , but embodiments are not limited thereto. When pressure is applied to one or more actuators, the main processor may  710  may determine one or more actuators that is pressed. 
     Third, it is determined whether the sensing data RD of a selected actuator  510  is greater than a threshold value VTH (operation S 403  of  FIG. 32 ). 
     The main processor  710  determines whether the sensing data RD of the one or more selected actuators  510  is greater than the threshold value VTH. When the sensing data RD of the one or more selected actuators  510  is greater than the threshold value VTH, the main processor  710  may determine that the user has applied pressure to the side surface of the display device  10  to execute the predetermined function. 
     Fourth, when the sensing data RD of the one or more selected actuators  510  is greater than the threshold value VTH, the selected one or more actuators  510  may be vibrated to provide haptic feedback (operation S 404  of  FIG. 32 ). 
     When the sensing data RD is greater than the threshold value VTH, the main processor  710  may execute the predetermined function such as a power control function or a volume control function while outputting driving data DD configured to drive the one or more selected actuators  510  to the actuator driver  340 . The actuator driver  340  may convert the driving data DD which is digital data into driving voltages ADV which are analog data and output the driving voltages ADV to the one or more selected actuators  510 . The one or more selected actuators  510  may vibrate according to the driving voltages ADV due to an inverse piezoelectric effect. That is, the user may be provided with haptic feedback through the vibration of the one or more selected actuators  510 . As illustrated in  FIG. 34 , the actuator  510  disposed in the (p−2) th  area Ap−2 where the user&#39;s finger is located may be vibrated to provide haptic feedback to the user. 
     As illustrated in  FIGS. 32 through 34 , when a user applies pressure to an area of a side surface of the display device  10  to execute a predetermined function, an actuator  510  adjacent to the position to which the user applies pressure is selected from the actuators  510 , and the pressure applied by the user is sensed using the selected actuator  510 . Therefore, there is no need to apply a different threshold value according to the position to which the user applies pressure. In addition, because haptic feedback is provided to the user by vibrating the selected actuator  510 , there is no need to adjust the driving voltages of the actuator  510  according to the position to which the user applies pressure. 
       FIG. 35  is a flowchart illustrating a haptic feedback method of a display device  10  according to an exemplary embodiment.  FIG. 36  is a graph illustrating sensing voltages RV sensed by actuators  511  and  520  according to pressure applied to a side surface of the display device  10  in accordance with  FIG. 35 .  FIG. 37  is a graph illustrating vibration acceleration according to the vibration of the actuators  511  and  520  when haptic feedback is provided to a user in accordance with  FIG. 35 . 
     The embodiment of  FIGS. 35 through 37  is different from the embodiment of  FIGS. 23 through 25  in that the display device  10  includes a first actuator  511  and a second actuator  512 . 
     In the flowchart, first a user applies pressure to a side surface of the display device  10  to execute a predetermined function (operation S 501  of  FIG. 35 ). 
     Second, the first and second actuators  511  and  520  may be disposed on a right side surface portion of a cover window  100 . The first and second actuators  511  and  520  may be disposed in two of first through p th  areas A 1  through Ap of the right side surface portion of the cover window  100 , respectively. The position of the first actuator  511  and the position of the second actuator  512  may be symmetrical with respect to a center of the right side surface portion of the cover window  100 . That is, the first actuator  511  may be disposed adjacent to an upper side of the right side surface portion of the cover window  100 , and the second actuator  512  may be disposed adjacent to a lower side of the right side surface portion of the cover window  100 . For example, as illustrated in  FIGS. 36 and 37 , the first actuator  511  may be disposed in the second area A 2 , and the second actuator  512  may be disposed in the (p−1) th  area Ap−1. The positions of the first and second actuators  511  and  520  are not limited to those illustrated in  FIGS. 36 and 37 . 
     When the user applies pressure to the side surface of the display device  10 , each of the first and second actuators  511  and  520  generates the sensing voltage RV due to a piezoelectric effect. As illustrated, this may apply when a user does not touch an area that directly overlaps one of the first and second actuators  511  and  520 . An actuator driver  340  may sense a first sensing voltage of the first actuator  511  and a second sensing voltage of the second actuator  512 . The actuator driver  340  may convert the first sensing voltage into first sensing data RD 1  which is digital data and the second sensing voltage into second sensing data RD 2  which is digital data and output the first sensing data RD 1  and the second sensing data RD 2  to a main processor  710 . The main processor  710  may calculate final sensing data FRD by adding up the first sensing data RD 1  of the first actuator  511  and the second sensing data RD 2  of the second actuator  512 . 
     Third, it is determined whether the final sensing data FRD is greater than a threshold value VTH (operation S 503  of  FIG. 35 ). 
     The main processor  710  determines whether the final sensing data FRD is greater than the threshold value VTH. When the final sensing data FRD is greater than the threshold value VTH, the main processor  710  may determine that the user has applied pressure to the side surface of the display device  10  to execute the predetermined function. 
     As illustrated in  FIG. 36 , when the user applies pressure to the (p−2) th  area Ap−2 of the cover window  100 , because the first actuator  511  is disposed in the second area A 2  and the second actuator  512  is disposed in the (p−1) th  area Ap−1, both the first sensing data RD 1  of the first actuator  511  and the second sensing data RD 2  of the second actuator  512  may be smaller than the threshold value VTH. However, the final sensing data FRD obtained by adding up the first sensing data RD 1  of the first actuator  511  and the second sensing data RD 2  of the second actuator  512  may be greater than the threshold value VTH. That is, when the first and second actuators  511  and  520  are disposed on the right side surface portion  100 R of the cover window  100 , the final sensing data FRD obtained by adding up the first sensing data RD 1  of the first actuator  511  and the second sensing data RD 2  of the second actuator  512  may be compared with the threshold value VTH. Therefore, there is no need to apply a different threshold value according to the position to which the user applies pressure. 
     Fourth, when the final sensing data FRD is greater than the threshold value VTH, the first and second actuators  511  and  520  may be vibrated to provide haptic feedback (operation S 504  of  FIG. 35 ). 
     When the final sensing data FRD is greater than the threshold value VTH, the main processor  710  may execute the predetermined function such as a power control function or a volume control function while outputting first driving data configured to drive the first actuator  511  and second driving data configured to drive the second actuator  512  to the actuator driver  340 . The actuator driver  340  may convert the first driving data which is digital data into first sub-driving voltages which are analog data and output the first sub-driving voltages to the first actuator  511 . The actuator driver  340  may convert the second driving data which is digital data into second sub-driving voltages which are analog data and output the second sub-driving voltages to the second actuator  512 . The first actuator  511  may vibrate according to the first sub-driving voltages due to an inverse piezoelectric effect, and the second actuator  512  may vibrate according to the second sub-driving voltages due to the inverse piezoelectric effect. The user may be provided with haptic feedback through the vibration of the first actuator  511  and the vibration of the second actuator  512 . For example, as illustrated in  FIG. 37 , the user may be provided with haptic feedback in the (p−2) th  area Ap−2 according to final vibration acceleration FG obtained by adding up first vibration acceleration G 1  of the first actuator  511  and second vibration acceleration G 2  of the second actuator  512 . Vibration acceleration may be analogous to vibration intensity. Just as pressure must reach a certain threshold to be registered to provide haptic feedback, vibration intensity may have a maximum level as output from an actuator. 
     As illustrated in  FIGS. 35 through 37 , when a user applies pressure to an area of a side surface of the display device  10  to execute a predetermined function, the final sensing data FRD obtained by adding up the first sensing data RD 1  of the first actuator  511  and the second sensing data RD 2  of the second actuator  512  is compared with a threshold value to determine whether the user has applied pressure. Therefore, there is no need to apply a different threshold value according to the position to which the user applies pressure. In addition, because haptic feedback is provided to the user according to the final vibration acceleration FG obtained by adding up the first vibration acceleration G 1  of the first actuator  511  and the second vibration G 2  of the second actuator  512 , there is no need to adjust driving voltages of the first and second actuators  511  and  512  according to the position to which the user applies pressure. 
       FIG. 38  is a flowchart illustrating a haptic feedback method of a display device  10  according to an exemplary embodiment.  FIG. 39  illustrates dragging on a side surface of the display device  10  with a finger in an exemplary embodiment. 
     First, it is determined whether a user has dragged a finger or the like in a direction on aside surface of the display device  10  to execute a first function. For example, it may be determined whether the user has dragged a finger or the like in the direction on the side surface of the display device  10  to perform a function of increasing the volume (operation S 601  of  FIG. 38 ). 
     When the user touches the display device  10 , a sensor driver  330  may convert sensor sensing voltages of a sensor electrode layer SENL of a display panel  300  into touch row data and calculate touch coordinates of the user by analyzing the touch row data. For example, the sensor driver  330  may calculate coordinates of touch row data which is greater than a touch threshold value as the touch coordinates. The sensor driver  330  may output touch data TD including the touch coordinates of the user to a main processor  710 . The main processor  710  may determine whether the user has dragged a finger or the like in the direction on the side surface of the display device  10  by analyzing the touch data TD received during a plurality of frame periods. The direction may be a direction parallel to the second direction (Y-axis direction) and may be a direction from a lower side toward an upper side of a right side surface of the display device  10 . 
     Second, when it is determined that the user has dragged in the direction on the side surface of the display device  10 , vibration acceleration of an actuator  510  disposed on the side surface of the display device  10  is gradually increased (operation S 602  of  FIG. 38 ). 
     The main processor  710  may output driving data DD to an actuator driver  340  during a plurality of frame periods. The actuator driver  340  may convert the driving data DD which is digital data into driving voltages ADV which are analog data and output the driving voltages ADV to the actuator  510 . The actuator  510  may vibrate according to the driving voltages ADV due to an inverse piezoelectric effect. 
     Here, a swing width of each driving voltage ADV applied to the actuator  510  during the frame periods may gradually increase. Therefore, the user may be provided with haptic feedback with gradually increasing intensity of vibration. 
     Third, when it is determined that the user has not dragged in the direction on the side surface of the display device  10  to perform a second function, it is determined whether the user has dragged in the other direction on the side surface of the display device  10 . For example, it may be determined whether the user has dragged in the other direction on the side surface of the display device  10  to perform a function of reducing the volume (operation S 603  of  FIG. 38 ). 
     The main processor  710  may determine whether the user has dragged in the other direction on the side surface of the display device  10  by analyzing the touch data TD received during a plurality of frame periods. The other direction may be a direction parallel to the second direction (Y-axis direction) and may be a direction from the upper side toward the lower side of the right side surface of the display device  10 . 
     Fourth, when it is determined that the user has dragged in the other direction on the side surface of the display device  10 , the vibration acceleration of the actuator  510  disposed on the side surface of the display device  10  is gradually reduced (operation S 604  of  FIG. 38 ). 
     The swing width of each driving voltage ADV applied to the actuator  510  during the frame periods may gradually decrease. Therefore, the user may be provided with haptic feedback with gradually decreasing intensity of vibration. 
     As illustrated in  FIGS. 38 and 39 , when a user drags in a direction on a side surface of the display device  10  or when the user drags in the other direction on the side surface of the display device  10 , the vibration acceleration of the actuator  510  disposed on the side surface of the display device  10  may be increased or reduced, thereby providing different feedback to the user. 
       FIG. 40  is a flowchart illustrating a haptic feedback method of a display device  10  according to an exemplary embodiment.  FIG. 41  illustrates zooming in or zooming out on a side surface of a display panel  300  with a finger in an exemplary embodiment. 
     First, it is determined whether a user has performed a zoom-in touch on a surface of the display device  10  to perform a first function. For example, it may be determined whether the user has performed the zoom-in touch on the surface of the display device  10  to perform a zoom-in function (operation S 701  of  FIG. 40 ). 
     When the user touches the display device  10 , a sensor driver  330  may convert sensor sensing voltages of a sensor electrode layer SENL of the display panel  300  into touch row data and calculate touch coordinates of the user by analyzing the touch row data. For example, the sensor driver  330  may calculate coordinates of touch row data which is greater than a touch threshold value as the touch coordinates. The sensor driver  330  may output touch data TD including the touch coordinates of the user to a main processor  710 . The main processor  710  may determine whether the user has performed the zoom-in touch on the surface of the display device  10  by analyzing the touch data TD received during a plurality of frame periods. 
     Second, when it is determined that the user has performed the zoom-in touch on the surface of the display device  10 , vibration acceleration of an actuator  510  disposed on the surface of the display device  10  is gradually increased (operation S 702  of  FIG. 40 ). 
     The main processor  710  may output driving data DD to an actuator driver  340  during a plurality of frame periods. The actuator driver  340  may convert the driving data DD which is digital data into driving voltages ADV which are analog data and output the driving voltages ADV to the actuator  510 . The actuator  510  may vibrate according to the driving voltages ADV due to an inverse piezoelectric effect. 
     Here, a swing width of each driving voltage ADV applied to the actuator  510  during the frame periods may gradually increase. Therefore, the user may be provided with haptic feedback with gradually increasing intensity of vibration. 
     Third, when it is determined that the user has not performed the zoom-in touch on the surface of the display device  10  to perform a second function, it is determined whether a zoom-out touch has been performed on the surface of the display device  10 . For example, it may be determined whether the user has performed the zoom-out touch on the surface of the display device  10  to perform a zoom-out function (operation S 703  of  FIG. 40 ). 
     The main processor  710  may determine whether the user has performed the zoom-out touch on the surface of the display device  10  by analyzing the touch data TD received during a plurality of frame periods. 
     Fourth, when it is determined that the user has performed the zoom-out touch on the surface of the display device  10 , the vibration acceleration of the actuator  510  disposed on the surface of the display device  10  is gradually reduced (operation S 704  of  FIG. 40 ). 
     The swing width of each driving voltage ADV applied to the actuator  510  during the frame periods may gradually decrease. Therefore, the user may be provided with haptic feedback with gradually decreasing intensity of vibration. 
     As illustrated in  FIGS. 40 and 41 , when a user performs a zoom-in touch or a zoom-out touch on a surface of the display device  10 , the vibration acceleration of the actuator  510  disposed on a side surface of the display device  10  may be increased or reduced, thereby providing different feedback to the user. 
       FIG. 42  is a flowchart illustrating a haptic feedback method of a display device  10  according to an exemplary embodiment. 
     The embodiment of  FIG. 42  is different from the embodiment of  FIGS. 30 and 31  in that the display device  10  is controlled to wake up from a sleep mode when a user touches a side surface of the display device  10  to apply pressure to the side surface of the display device  10 . Therefore, a description of operations S 801  and S 803  through S 805  illustrated in  FIG. 42  will be omitted. 
     Referring to  FIG. 42 , when a user touches a side surface of the display device  10  to apply pressure to the side surface of the display device  10 , the display device  10  wakes up from the sleep mode. In the sleep mode, power is not supplied to a display layer PAL of a display panel  300  to reduce power consumption of the display device  10 . Therefore, an image may not be displayed on the display panel  300  (operation S 802  of  FIG. 42 ). 
     When the user touches the display device  10  to apply pressure, a sensor driver  330  may convert sensor sensing voltages of a sensor electrode layer SENL of the display panel  300  into touch row data and calculate touch coordinates of the user by analyzing the touch row data. For example, the sensor driver  330  may calculate coordinates of touch row data which is greater than a touch threshold value as the touch coordinates. The sensor driver  330  may output touch data TD including the touch coordinates of the user to a main processor  710 . 
     When the main processor  710  determines that the user&#39;s touch has occurred by analyzing the touch data TD, it may wake up the display device  10  from the sleep mode. For example, the main processor  710  may control the display device  10  to display an initial screen such as a lock screen when the display device  10  wakes up from the sleep mode. 
     As illustrated in  FIG. 42 , because the display device  10  may be driven in the sleep mode before a user touches a side surface of the display device  10 , the power consumption of the display device  10  can be reduced. 
       FIG. 43  is a flowchart illustrating a haptic feedback method of a display device  10  according to an exemplary embodiment. 
     The embodiment of  FIG. 43  is different from the embodiment of  FIGS. 30 and 31  in that the display device  10  is controlled to wake up from a sleep mode when a user approaches the display device  10  to apply pressure to aside surface of the display device  10 . Therefore, a description of operations S 903  through S 906  illustrated in  FIG. 43  will be omitted. 
     First, it is determined whether there is an object in proximity to a side surface of the display device  10  (operation S 901  of  FIG. 43 ). 
     When a user approaches a side surface of the display device  10  to apply pressure, a sensor driver  330  may convert sensor sensing voltages of a sensor electrode layer SENL of a display panel  300  into touch row data and calculate proximity coordinates of the user by analyzing the touch row data. For example, the sensor driver  330  may calculate coordinates of touch row data which is greater than a proximity threshold value as the proximity coordinates. The proximity threshold value may be smaller than a touch threshold value. The sensor driver  330  may output touch data TD including the proximity coordinates of the user to a main processor  710 . The main processor  710  may determine whether the user is in proximity to the side surface of the display device  10  by analyzing the touch data TD. 
     Second, when an object in proximity to the side surface of the display device  10  is detected, the display device  10  may be woken up from the sleep mode (operation S 902  of  FIG. 43 ). 
     When the main processor  710  determines that the user is in proximity to the side surface of the display device  10 , it may wake up the display device  10  from the sleep mode. For example, the main processor  710  may control the display panel  300  to display an initial screen such as a lock screen when the display device  10  wakes up from the sleep mode. 
     As illustrated in  FIG. 42 , because the display device  10  may be driven in the sleep mode before a user approaches the display device  10  to apply pressure to a side surface of the display device  10 , the power consumption of the display device  10  can be reduced. 
       FIG. 44  is an exploded perspective view of a display device  10  according to an embodiment.  FIG. 45  is a block diagram illustrating a display panel  300 , an actuator  510 , and a main processor  710  of the display device  10  according to the embodiment. 
     The embodiment of  FIGS. 44 and 45  is different from the embodiment of  FIGS. 2 and 9  in that an actuator driver  340  is integrated into a sensor driver  330 . When the actuator driver  340  is integrated into the sensor driver  330  as illustrated in  FIGS. 44 and 45 , the number of integrated circuits attached to a display circuit board  310  can be reduced, thereby reducing costs. 
       FIG. 46  illustrates tactile patterns  110  and actuators  510  of a display device  10  according to an exemplary embodiment. 
     In  FIG. 46 , the display device  10  is illustrated as a notebook computer including a main display portion MDA and an auxiliary display portion ADA. 
     Referring to  FIG. 46 , the display device  10  may include the main display portion MDA which displays a main image and the auxiliary display portion ADA which displays auxiliary images such as icons for volume control, screen brightness control, application switching, home screen switching, sound/vibration/silence switching, and auxiliary window on/off setting. In the auxiliary display portion ADA, a plurality of actuators  510  may be disposed, and a plurality of tactile patterns  110  respectively overlapping the actuators  510  may be disposed. 
     As illustrated in  FIG. 46 , a user may apply pressure to the tactile patterns  110  disposed on the icons to execute the icons displayed in the auxiliary display portion ADA. The display device  10  may not only sense the pressure of the user using the actuators  510  but also provide haptic feedback to the user by vibrating the actuators  510 . 
     In a display device and a haptic feedback method of the same according to an embodiment, a tactile pattern is formed on an upper surface of a side surface portion of a cover window. As a result, due to the tactile pattern, a user can easily find an area to apply pressure to perform a desired function. 
     In a display device and a haptic feedback method of the same according to an embodiment, when a user applies pressure to a tactile pattern, sensing data of an actuator overlapping the tactile pattern in a width direction of a display panel may be sensed. When the sensing data of the actuator is greater than a threshold value, a predetermined function such as a power control function or a volume control function may be executed while haptic feedback is provided to the user by vibrating the actuator. Accordingly, the user can recognize whether a desired function is properly performed by the pressure applied to the tactile pattern. 
     In a display device and a haptic feedback method of the same according to an embodiment, when the display device does not include a tactile pattern, sensing data of an actuator may be smaller as a position to which a user applies pressure is farther from the actuator. Therefore, a position threshold value may be set to a smaller value as the distance from the actuator increases, so that the pressure applied by the user can be sensed using the actuator regardless of the position to which the user applies pressure. 
     In a display device and a haptic feedback method of the same according to an embodiment, when the display device does not include a tactile pattern, vibration acceleration of an actuator may be smaller as a position to which a user applies pressure is farther from the actuator. Therefore, a swing width of each driving voltage applied to the actuator may be increased as the distance from the actuator increases. Accordingly, haptic feedback of substantially the same vibration acceleration may be provided to the user regardless of the position to which the user applies pressure. 
     In a display device and a haptic feedback method of the same according to an embodiment, when a user applies pressure to an area of a side surface of the display device to execute a predetermined function, an actuator adjacent to the position to which the user applies pressure is selected from a plurality of actuators, and the pressure of the user is sensed using the selected actuator. Therefore, there is no need to apply a different threshold value according to the position to which the user applies pressure. In addition, because haptic feedback is provided to the user by vibrating the selected actuator, there is no need to adjust driving voltages of an actuator according to the position to which the user applies pressure. 
     In a display device and a haptic feedback method of the same according to an embodiment, when a user applies pressure to an area of a side surface of the display device to execute a predetermined function, final sensing data obtained by adding up first sensing data of a first actuator and second sensing data of a second actuator is compared with a threshold value to determine whether the pressure has been applied by the user. Therefore, there is no need to apply a different threshold value according to the position to which the user applies pressure. In addition, because haptic feedback is provided to the user according to final vibration acceleration obtained by adding up first vibration acceleration of the first actuator and second vibration acceleration of the second actuator, there is no need to adjust driving voltages of an actuator according to the position to which the user applies pressure. 
     Although certain exemplary embodiments and implementations have been described herein, other embodiments and modifications will be apparent from this description. Accordingly, the inventive concepts are not limited to such embodiments, but rather to the broader scope of the appended claims and various obvious modifications and equivalent arrangements as would be apparent to a person of ordinary skill in the art.