Patent Abstract:
An organic electroluminescence display has data, gate, and signal lines arranged on a substrate. Pixel regions are defined by the gate and signal lines. Switching elements provided in the pixel regions are electrically connected to the signal lines and the gate lines. Switching blocks open and close an electrical connection between the signal lines and the pixels. A driving unit drives the switching elements by supplying scanning signals to the gate lines. The driving unit also supplies a first control signal before the scanning signals are supplied and a second control signal when the scanning signals are supplied. The second control signal makes the switching blocks sequentially conductive, during which time image signals are supplied to the data lines. The first control signal permits the signal lines to be set at a predetermined voltage.

Full Description:
CLAIM FOR PRIORITY  
       [0001]     This application claims the benefit of priority to Korean Patent Application No. 2004-039353, filed on May 31, 2004 which is hereby incorporated by reference as if fully set forth herein.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to an organic electroluminescence display that prevents a lighting emitting element from malfunctioning by retaining image signals upon applying each scanning signal by applying a set voltage to pixels and driving the same before applying scanning signals, and a method of driving the same.  
       DESCRIPTION OF THE BACKGROUND ART  
       [0003]     Generally, a cathode ray tube (CRT) has been one of widely used display devices. The CRT is mainly used for television monitors, in measuring instruments, information terminal equipment, etc. However, with the demand for miniaturization and lightweight design of electronic products, the CRT is problematic due to the weight and size of the products.  
         [0004]     Therefore, to replace the above cathode ray tube, various flat panel display (FPD) devices such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission display (FED) devices and electroluminescence display (ELD) devices have been researched and developed. The FPD devices thin, lightweight and have low power consumption, compared with CRTs.  
         [0005]     Among these display devices, the organic electroluminescence display is a display device that electrically excites fluorescent organic compounds to emit light, which can display an image by voltage-driving or current-driving an array of M×N organic light emitting pixels.  
         [0006]     The organic electroluminescence display can display colors close to natural colors since it can express visible light such as blue. The organic electroluminescence display has a high brightness and low power consumption. Moreover, the organic electroluminescence display does not have a limited viewing angle and is stable under low temperature conditions, unlike a liquid crystal display device provided with a liquid crystal layer. In addition, because the organic electroluminescence display is self luminescent, it is suitable for an ultra-thin type display device, and its production cost can be lowered because it has a simple manufacturing process. The organic electroluminescence display is also suitable for displaying moving images device as the response time is a few microseconds (μs).  
         [0007]     As an organic electroluminescence display, an active matrix type in which a plurality of pixels is arranged in a matrix form and image information is selectively supplied to each pixel through a switching element, such as a thin film transistor, has been widely applied.  
         [0008]      FIG. 1  is an exemplary view showing a general active matrix organic electroluminescence display.  
         [0009]     Referring to  FIG. 1 , the organic electroluminescence display includes a plurality of gate lines GL 1  to GLm and data lines DL 1  to DLn arranged on a substrate  1  in longitudinal and transverse directions, a plurality of pixels P 1  provided on areas defined by the gate lines GL 1  to GLm and the data lines DL 1  to DLn crossing each other, a data driving unit  30  for supplying an image signal to the pixels P 1  via the data lines DL 1  to DLn, and a gate driving unit  20  for applying scanning signals to the pixels P 1  via the gate lines GL 1  to GLm.  
         [0010]     The gate driving unit  20  applies scanning signals to the gate lines GL 1  to GLm in sequence. Switching elements electrically connected to the gate lines GL 1  to GLm to which the scanning signals are applied are conductive, and the data driving unit  30  applies image signals to the data lines DL 1  to DLn, thereby applying the image signals to the pixels P 1  via the conductive switching elements. Each pixel P 1  generates light by an organic electroluminescence device (not shown) according to the voltage level of input image signals.  
         [0011]     With recent improvement of the resolution of organic electroluminescence displays, it is possible to realize sharper images. However, this is restricted by a limited space of the substrate  1  because a great deal of data lines DL 1  to DLn has to be formed on the substrate  1  in order to realize a high resolution. Therefore, intervals between the lines to be formed get narrower and thus, signal interference occurs between the lines, thereby resulting in degradation of image quality.  
         [0012]     To solve such problem, a block driving method was employed, which can supply image signals to the entire pixels P 1  by limiting the number of data lines DL 1  to DLn to be formed on the substrate  1  and repeatedly using the formed data lines DL 1  to DLN many times.  
         [0013]     The aforementioned block driving method will now be described in detail with reference to the accompanying drawings.  
         [0014]      FIG. 2  is an exemplary view showing a block-driven organic electroluminescence display.  
         [0015]     Referring to  FIG. 2 , the organic electroluminescence display includes a plurality of gate lines GL 11  and GL 12  and data lines DL 11  to DL 1   n  arranged on a substrate at regular intervals, a plurality of signal lines  140  arranged on the substrate at regular intervals, crossing the gate lines GL 11  and GL 12 , and connected to the data lines DL 11  to DL 12 , a plurality of pixels P 11  provided on areas defined by the signal lines  140  and the gate lines GL 11  and GL 12  crossing each other, and a plurality of switching blocks BL 1  to BLk provided on the signal lines  140 , respectively, and controlling image signals delivered to the pixels P 11  via the data lines DL 11  to DL 1   n.    
         [0016]     In the block driving method, the display device is driven by dividing the entire screen of the display device and supplying image signals to pixels P 11  via each switching block BL 1  to BLk. In  FIG. 2 , a multiplicity of switching blocks BL 1  to BLk for dividing the entire screen perpendicularly is shown.  
         [0017]     In the drawing, the data lines DL 11  to DL 1   n  are formed on the substrate in a horizontal direction which is the same as the direction of the gate lines GL 11  and GL 12 . As above, the number of the data lines DL 11  to DL 1   n  formed on the substrate is consistent with the, number of the signal lines  140  connected to each of the switching block BL 1  to BLk. That is, only the number of the data lines DL 11  to DL 1   n  required for simultaneously transmitting an image signal to one switching block BL 1  to BLk are formed. The switching blocks BL 1  to BLk consist of a plurality of switches  111 , and each switch  111  is electrically connected to the data lines DL 11  to DL 1   n , respectively, via the signal lines  140 .  
         [0018]     The signal lines  140  and the gate lines GL 11  and GL 12  define a plurality of pixels P 11  by crossing each other perpendicularly. The pixels P 11  are arranged in a matrix on the substrate.  
         [0019]     Each of the pixels P 11  is provided with a device, such as a thin film transistor. This thin film transistor is electrically connected to the gate lines GL 11  and GL 12  and the signal lines  140 .  
         [0020]     One side of the signal lines  140  is electrically connected to one of the plurality of data lines DL 11  to DL 1   n , while the other side thereof is electrically connected to one of the plurality of pixels P 11 . Each of the signal lines is provided with a switch  111  for conducting or blocking signals from the pixels P 11  to the data lines DL 11  to DL 1   n.    
         [0021]     In the thus constructed organic electroluminescence display, when scanning signals are applied to the gate lines GL 11  and GL 12 , the thin film transistors connected to the corresponding gate lines GL 11  and GL 12  are turned on. An image signal applied to the data lines DL 11  to DL 1   n  during the turn-on period is applied to the pixels P 11  in units of the switching blocks BL 1  to BLk via the signal lines  140 .  
         [0022]     Because the plurality of data lines DL 11  to DL 1   n  are commonly connected to each switching block BL 1 , they do not need to be formed so as to correspond to the entire substrate and the number of data lines to be formed can be reduced.  
         [0023]      FIG. 3  is an exemplary view showing the timing of signals upon block driving.  
         [0024]     Firstly, though a low voltage driving or high voltage driving may be selected according to the type of thin film transistors provided in the pixels, a description thereof will be based on a p-type thin film transistor that is turned on at a low voltage level.  
         [0025]     As shown in  FIG. 3 , a scanning signal GS 11  supplied from a gate driving unit (not shown) to gate lines is changed from a high voltage level to a low voltage level, block driving signals BE 11  to BE 1   k  are sequentially applied to switching blocks in a low voltage level section.  
         [0026]     When each block driving signal BE 11  to BE 1   k  is sequentially applied to each switching block corresponding to the entire panel in a first horizontal period during which the scanning signal GS 11  maintains a low potential level, every switching block is conductive once and image signals are supplied to corresponding pixels via the connected switching blocks. In this manner, the pixels connected to the gate lines, to which the scanning signal GS 11  is applied in the first horizontal period, are all supplied with the image signals. As shown therein, the first block driving signal BE 11  to the K-th block driving signal BE 1   k  are applied at a low potential level pulse.  
         [0027]     Generally, a resistance component, a capacitor component and a conductance component exist on a line to which an electric signal is delivered. Likewise, a capacitor component exists on the aforementioned signal lines, and thus the problem of signal distortion may occur.  
         [0028]     In a case where block driving signals BE 11  to BE 1   k  are sequentially supplied to the switching blocks during the first horizontal period, the signal lines electrically connected to each switch of the switching blocks switched on are supplied with image signals from the data lines. Consequently, these image signals are supplied to the pixels. Since the scanning signal GS 11  sequentially applied to the gate lines is generated at regular intervals so that each signal does not overlap with each other, it is not until a predetermined (dummy) time passes after the scanning signal GS 11  becomes a low voltage level that the next scanning signal GS 11  is generated.  
         [0029]     However, a portion of the electric charge corresponding to the image signals remain on the signal lines even during this dummy time, and may affect the driving of the pixels. Moreover, as shown therein, as each switching block is conductive during the previous horizontal period, the image signals applied to the signal lines cannot be supplied with new image signal until each switching block is conductive in the next horizontal period. For example, the image signals applied in the previous horizontal period still remain on the signal lines during a dummy time A from the falling edge of the scanning signal GS 11  to the first block driving signal BE 11 , a dummy time B from the falling edge of the scanning signal GS 11  to the second block driving signal BE 12 , and a dummy time C from the falling edge of the scanning signal GS 11  to the k-the block driving signal BE 1   k . Therefore, the image signals corresponding to the previous horizontal period may be supplied to the organic electroluminescence device of the pixels during the dummy times A, B and C of the next horizontal period. The above organic electroluminescence device may generate undesired light emission by maintaining components of the image signals applied during the short dummy times A, B and C because it has a fast reaction speed. This problem may not be serious in a liquid crystal display using liquid crystal with relatively low reaction speed, but may lead to picture quality degradation in the organic electroluminescence device. Especially, in a case where white images with a high brightness are displayed in the pixels in the previous horizontal period and black images with a low brightness are displayed in the same pixels in the next horizontal period, the light emission of the luminescence device caused by the remaining components of the image signals will degrade the picture quality greatly.  
       SUMMARY OF THE INVENTION  
       [0030]     By way of introduction only, an organic electroluminescence display and method of display are presented which prevent picture quality degradation by suppressing light emission from a light emitting element caused by components of image signals remaining on signal lines by supplying a lowest gray level voltage to each of the signal lines prior to supplying a new image signal.  
         [0031]     In one aspect, an organic electroluminescence display comprises: a plurality of data lines and gate lines arranged on a substrate in a first direction; a plurality of signal lines arranged on the substrate in a second direction and electrically connected to the data lines, respectively; a plurality of pixel regions defined by the gate lines and the signal lines crossing each other; switching elements provided in the pixel regions, respectively, and electrically connected to the signal lines and the gate lines; a plurality of switching blocks that open and close an electrical connection between the signal lines and the pixels; a second driving unit that makes conductive the switching elements connected to the corresponding gate lines and the signal lines by outputting scanning signals to the gate lines; a first driving unit that outputs a first control signal for each horizontal period before the second driving unit outputs scanning signals, sequentially making conductive the switching blocks by a second control signal, and outputting image signals to the data lines; and a pre-charging unit connected between the signal lines and the first driving unit, the pre-charging unit being made conductive according to the first control signal of the first driving unit for setting the signal lines at a set voltage supplied from the first driving unit.  
         [0032]     In another aspect, a method of driving an organic electroluminescence display is presented. The organic electroluminescence display comprises a plurality of data lines and gate lines arranged on a substrate in a first direction, a plurality of signal lines electrically connected to the data lines, respectively, a plurality of pixels electrically connected to the gate lines and the signal lines, and a plurality of switching blocks for conducting or blocking image signals supplied to the pixels via the signal lines. The method comprises providing a pre-charging unit electrically connected to the signal lines; applying a set voltage to the signal lines through the pre-charging unit; maintaining the set voltage on the signal lines; applying scanning signals to the pixels via the gate lines; making the switching blocks conductive one by one; supplying image signals to the pixels via the signal lines by applying the image signals to the signal lines through the conductive switching blocks; and displaying images according to the image signals by the pixels.  
         [0033]     In another aspect, an organic electroluminescence display comprises: a plurality of data lines and gate lines arranged on a substrate in a first direction; a plurality of signal lines arranged on the substrate in a second direction and electrically connected to the data lines, respectively; a plurality of pixel regions defined by the gate lines and the signal lines crossing each other; a plurality of switching blocks for opening and closing an electrical connection between the signal lines and the pixels; a first driving unit for outputting a first image signal and a second image signal to the data lines, setting the signal lines to a voltage level of the first image signal by making the switching blocks conductive by a first control signal and a second control signal and supplying the second image signal to the pixel regions via the signal lines; and a second driving unit for outputting scanning signals to the gate lines after the first driving unit outputs the first control signal.  
         [0034]     In another aspect, a method of driving an organic electroluminescence display is presented. The organic electroluminescence display comprises a plurality of data lines and gate lines arranged on a substrate in a first direction, a plurality of signal lines electrically connected to the data lines, respectively, a plurality of pixels electrically connected to the gate lines and the signal lines, and a plurality of switching blocks for conducting or blocking image signals supplied to the pixels via the signal lines. The method comprises applying a first control signal to every switching block to make every switching block conductive; applying a first image signal of a set voltage level to the signal lines through the conductive switching blocks; terminating the first control signal; applying scanning signals to the pixels via the gate lines; sequentially applying a second control signal to the switching blocks to make the switching blocks sequentially conductive; supplying a second image signal to the pixels via the signal lines by applying the second image signal to the signal lines through the conductive switching blocks; and displaying images according to the second image signal at the pixels.  
         [0035]     In another aspect, a method of driving an organic electroluminescence display is presented. The organic electroluminescence display comprises a plurality of data lines and gate lines arranged on a substrate in a first direction, a plurality of signal lines electrically connected to the data lines, respectively, a plurality of pixels electrically connected to the gate lines and the signal lines, and a plurality of switching blocks that supply signals to the pixels via the signal lines when the switching blocks are conductive. In each display cycle the method comprises: supplying a set voltage level to all of the signal lines prior to applying scanning signals to the pixels via the gate lines; applying scanning signals to the pixels via the gate lines; sequentially applying a control signal to first switching blocks of the plurality of switching blocks to make the first switching blocks sequentially conductive; supplying image signals to the signal lines through the conductive first switching blocks; and terminating supply of the image and scanning signals to the pixels after all pixels have been supplied with the image signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]     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 embodiments of the invention and together with the description serve to explain the principles of the invention.  
         [0037]     In the drawings:  
         [0038]      FIG. 1  is an exemplary view showing a general active matrix organic electroluminescence display;  
         [0039]      FIG. 2  is an exemplary view showing a block-driven organic electroluminescence display;  
         [0040]      FIG. 3  is an exemplary view showing the timing of signals upon block driving;  
         [0041]      FIG. 4  is a view showing an organic electroluminescence display according to a first embodiment of the present invention;  
         [0042]      FIG. 5  is a timing diagram showing the driving waveform of a signal of  FIG. 4 ;  
         [0043]      FIG. 6  is a view showing an organic electroluminescence display according to a second embodiment of the present invention; and  
         [0044]      FIG. 7  is a timing diagram showing the driving waveform of a signal of  FIG. 6 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]      FIG. 4  is a view showing an organic electroluminescence display according to a first embodiment of the present invention.  
         [0046]     Referring to  FIG. 4 , the organic electroluminescence display includes; a plurality of data lines DL 21  to DL 2   n  arranged at regular intervals on a substrate in a transverse direction; a plurality of gate lines GL 21  to GL 2   n  arranged on the substrate in the same direction as the data lines DL 21  to DL 2   n ; a plurality of signal lines  240  electrically connected to the data lines DL 21  to DL 2   n  and the gate lines GL 21  to GL 2   m ; a plurality of pixels P 21  provided on areas defined by the gate lines GL 21  to GL 2   m  and the data lines DL 21  to DL 2   n  crossing each other; a plurality of switching blocks BL 21  to BL 2   k  provided on the signal lines  240 , respectively, and conductive or blocked by block driving signals BE 21  to BE 2   k  for applying image signals D 1  to Dn applied from the data lines DL 21  to DL 2   n  to the pixels P 21 ; a first driving unit  230  for supplying an image signal DATA to the signal lines  240  via the data lines DL 21  to DL 2   n ; a second driving unit  220  for supplying scanning signals GS 21  to GS 2   m  to the gate lines GL 21  to GL 2   m ; and a pre-charging block PBL connected to the ends of the signal lines  240 , respectively, and made conductive by a pre-charge signal PCS 11  of the first driving unit  230  for applying a setting voltage PV to the signal lines  240 .  
         [0047]     The data lines DL 21  to DL 2   n  are electrically connected to the pixels P 21  via the signal lines  240 . The signal lines  240  are formed at regular intervals on the substrate in a perpendicular direction, thus they cross the data lines DL 21  to DL 2   n  and the gate lines GL 21  to GL 2   m . The pixels P 21  are provided on areas defined by the gate lines GL 21  to GL 2   m  and the data lines DL 21  to DL 2   n  crossing each other.  
         [0048]     The pixels P 21  are arranged in a matrix on the substrate, and are provided with thin film transistors (not shown), respectively. The thin film transistors are electrically connected to the data lines DL 21  to DL 2   n  and the gate lines GL 21  to GL 2   m , so they are driven by signal delivered via the data lines DL 21  to DL 2   n  and the gate lines GL 21  to GL 2   m.    
         [0049]     A plurality of signal lines  240  are electrically connected to each of the plurality of switching blocks BL 21  to BL 2   k  formed on the substrate, and the switching blocks BL 21  to BL 2   k  are commonly connected to the data lines DL 21  to DL 2   n  via the signal lines  240 . Thus, the same image signals can be supplied to any switching blocks BL 21  to BL 2   k  via the signal lines  240  by only a small number of data lines DL 21  to DL 2   n . The switching blocks BL 21  to BL 2   k  consist of a plurality of switches  211 . The switches  211  are devices that are turned on or turned off by block driving signals BE 21  to BE 2   k . The switches  211  correspond to the signal lines  240 , respectively, and the switches  211  provided on the same switching blocks BL 21  to bL 2   k  are simultaneously turned on or turned off by the block driving signals BE 21  to BE 2   k . That is, because the switches  211  perform the same operation even if the switching blocks BL 21  to BL 2   k  are provided with the plurality of switches  211 , the switching blocks BL 21  to BL 2   k  perform one of integrated operations including conducting and blocking.  
         [0050]     One side of each switch  211  provided on the switching blocks BL 21  to BL 2   k  is connected to the data lines DL 21  to DL 2   n  via the signal lines  240 , while the other side of each switch  211  is connected to the pre-charging block PBL via the signal lines  240 .  
         [0051]     The first driving unit  230  supplies image signals D 1  to DN to the data lines DL 21  to DL 2   n , and sequentially applies block driving signals BE 21  to BE 2   k  to the switching blocks BL 21  to BL 2   k . Since every switching block BL 21  to BL 2   k  is commonly connected to the data lines DL 21  to DL 2   n , only one of the switching blocks BL 21  to BL 2   k  is made conductive by the block driving signals BE 21  to BE 2   k . The block driving signals BE 21  to BE 2   k  are supplied once to every switching block BL 221  to BL 2   k  within the first horizontal period.  
         [0052]     The first driving unit  230  applies a pre-charge signal PCS 11  to the pre-charging block PBL. A plurality of switches  215  of the pre-charging block PBL are simultaneously turned on by this pre-charge signal PCS 11 . A thin film transistor may be applicable to the switches  215 . As above, in a case where the pre-charging block PBL is made conductive by the pre-charge signal PCS 11 , the first driving unit  230  applies an initialization voltage PV to the pre-charging block PBL via the line commonly connected to the switches  215  of the pre-charging block PBL. The initialization voltage PV is applied to the signal lines  240  through the pre-charging block PBL.  
         [0053]     Meanwhile, the second driving unit  220  sequentially applies scanning signals GS 21  to GS 2   m  to the gate lines GL 21  to GL 2   m  in each frame. While the scanning signals GS 21  to GS 2   m  are applied to the gate lines GL 21  to GL 2   m , a plurality of thin film transistors electrically connected to the corresponding gate lines GL 21  to GL 2   m  enter a turned-on state. The first driving unit  230  supplies image signals D 1  to DM to the data lines DL 21  to DL 2   m , and sequentially applies block driving signals BE 21  to BE 2   k  to the switching blocks BL 21  to BL 2   k . Therefore, only one of the switching blocks BL 21  to BL 2   k  is made conductive, to thus deliver the image signals D 1  to Dn of the data lines DL 21  to DL 2   n  to the pixels P 21 . Though not shown in the drawings, a light emitting element (not shown) provided in the pixels P 21  emits light according to the input image signals D 1  to DN. The aforesaid driving of the first driving unit  230  and second driving unit  220  is all performed during the first horizontal period, and is repeated in each horizontal period.  
         [0054]     The first driving unit  230  and the second driving unit  220  may be constructed as separate circuits, but also may be constructed as an integrated circuit.  
         [0055]     The pixels P 21  are supplied with image signals D 1  to Dn in units of switching blocks BL 21  to BL 2   k . Because the switching blocks BL 21  to BL 2   k  are conductive only once in the first horizontal period, the image signals D 1  to Dn are applied to the signal lines  240  through the conducted switching blocks BL 21  to BL 2   k . If every switch  211  of the switching blocks BL 21  to BL 2   k  is blocked after a predetermined time, the signal lines  240  enter a floating state, and thus a portion of the remaining charge of the image signals D 1  to DN are left on the signal lines  240 . That is, the signal lines  240  have a constant voltage level, and this voltage level is introduced into the pixels P 21  until the corresponding switching blocks BL 21  to BL 2   k  are made conductive to apply new image signals D 1  to DN to the signal lines  240  even if the next horizontal period has arrived.  
         [0056]     To prevent degradation of picture quality caused by remaining components of the image signals D 1  to Dn left on the signal lines  240 , the pre-charging block PBL is provided. A detailed description of the driving of the organic electroluminescence display of  FIG. 4  will be presented, including  FIG. 5  in which a driving waveform is shown.  
         [0057]      FIG. 5  is a timing diagram showing the driving waveform of a signal of  FIG. 4 .  
         [0058]     The driving waveform of  FIG. 5  is shown under the assumption that a p-type transistor, which is turned on at a low voltage level, is applied to both switches  211  of the switching blocks BL 21  to BL 2   k  of  FIG. 4  and the switches  215  of the pre-charging block PBL. Hence, in a case where the p-type transistor of the switches  211  and  215  is replaced by an n-type, the potential of the driving waveform of  FIG. 5  has to be replaced by an opposite potential.  
         [0059]     The organic electroluminescence display displays images at a plurality of gray levels like a liquid crystal display does. The gray levels mean brightness levels of an image. The organic electroluminescence device has a different light emission brightness according to the size of a supplied current or voltage. Thus, remaining components of image signals D 1  to Dn are left on the signal lines  240 , the gray level of an image can be varied by changing the intensity of light emitting from the organic electroluminescence device. Hence, in order to prevent an image of an undesired gray level from being displayed, a voltage corresponding to the lowest gray level is applied to the signal lines  240  before the organic electroluminescence device emits light by new image signals D 1  to Dn, thereby driving the corresponding pixels P 21  to display black.  
         [0060]     When a first scanning signal GS 21  of low voltage level is applied to gate lines GL 21  to GL 2   m , the thin film transistors of the pixels P 21  connected to the corresponding gate lines GL 21  to GL 2   m  are all turned on and thus are supplied with image signals D 1  to Dn through switching blocks BL 21  to BL 2   k  sequentially made conductive by block driving signals BE 21  to BE 2   k . However, since the block driving signals BE 21  to BE 2   k  are generated after a predetermined time from the point of time of the falling edge of the first scanning signal GS 21  as shown in the drawings, and each block driving signal BE 21  to BE 2   k  is periodically generated at regular time intervals, a predetermined dummy time exists until each block driving signal BE 21  to BE 2   k  is generated. The remaining components of the image signals D 1  to Dn remaining on the signal lines  240  are removed during this dummy time, so that the remaining components may not be introduced into the pixels P 21  through the thin film transistors turned on by the first scanning signal GS 21 .  
         [0061]     As above, in order to remove the image signal D 1  to Dn components left on the signal lines  240 , the first driving unit  230  outputs a pre-charge signal PCS 11  and applies it to the pre-charging block PBL before applying the first scanning signal GS 21 . The pre-charging block PBL is made conductive to thus apply an initialization voltage PV of the first driving unit  230  to the signal lines  240 . The initialization voltage PV is a voltage corresponding to the lowest gray level of an image. If the initialization voltage PV is applied to the organic electroluminescence device of the pixels P 21  through the thin film transistors, the organic electroluminescence emits light at the minimum level, and thus the pixels display black. As the initialization voltage PV, a ground voltage can be set. That is, at this time, as the pre-charging block PBL, is conducted, the signal lines  240  are grounded.  
         [0062]     After the block driving signals BE 21  to BE 2   k  are sequentially output from the first driving unit  230  during the low voltage level section of the first scanning signal GS 21 , the first scanning signal GS 21  is changed to a high voltage level. After the passage of a predetermined time, a second scanning signal GS 22  of low voltage level is applied to the gate lines GL 21  to GL 2   m . After the application of the first scanning signal GS 21  is finished, a pre-charge signal PCS 11  of low voltage level is re-generated before the second scanning signal GS 22  is generated. The first driving unit  230  outputs the pre-charge signal PCS 11  and applies it to the pre-charging block PBL before the second driving unit  220  outputs the second scanning signal G 32 . The pre-charge signal PCS 11  is generated in the same cycle as the scanning signals GS 21  to GS 2   m  of the second driving unit  220 , but at a different period within the cycle.  
         [0063]     In this way, the first driving unit  230  can remove image signals D 1  to Dn components that have been previously left on the signal lines  240  by presetting the signal lines  240  to a certain voltage level through the pre-charging block PBL before the second driving unit  220  outputs scanning signals GS 21  to GS 2   m.    
         [0064]     In the aforementioned first embodiment of the present invention, a pre-charging block PBL consisting of switches  215  each connected to one side of the signal lines  240  is provided. Additionally, to control the pre-charging block PBL, a circuit for outputting the pre-charge signal PCS 21  and the initialization voltage PV is added to the first driving unit  230 . Consequently, additional manufacturing costs may be incurred, and the construction may be more complicated than a conventional organic electroluminescence display.  
         [0065]     Accordingly,  FIG. 6  is a view showing an organic electroluminescence display according to a second embodiment of the present invention.  FIG. 7  is a timing diagram showing the driving waveform of a signal of  FIG. 6 .  
         [0066]     In the organic electroluminescence display according to the second embodiment, the pre-charge signal of the pre-charging block and the initialization voltage outputting circuit of the first driving unit in the first embodiment can be eliminated. Similar portions of the first and second embodiments will be briefly described.  
         [0067]     A plurality of signal lines  340  arranged on a substrate in a longitudinal direction and a plurality of gate lines GL 31  to GL 3   m  arranged in a transverse direction are crossed perpendicularly to define a plurality of pixels P 31 . The pixels P 31  are arranged in plural number on the substrate along the gate lines GL 31  to GL 3   m . Each pixel P 31  is provided with a thin film transistor (not shown) electrically connected to the gate lines GL 31  to GL 3   m  and the signal lines  340 .  
         [0068]     When a second driving unit  320  sequentially outputs scanning signals GS 41  to GS 4   m  to the gate lines GL 31  to GL 3   m , the thin film transistors of the pixels P 31  connected to the corresponding gate lines GL 31  to GL 3   m  to which the scanning signals GS 41  to GS 4   m  are applied are all turned on.  
         [0069]     The first driving unit  330  applies image signals D 11  to D 1   n  to the gate lines DL 31  to DL 3   n , and the image signals D 11  to D 1   n  are applied to the pixels P 31  conducted by the scanning signals GS 41  to GS 4   m  of the second driving unit  320  via the signal lines  340  connected to the data lines DL 31  to DL 3   n . That is, the driving timing of the first driving unit  330  is synchronized with the driving timing of the second driving unit  320 .  
         [0070]     In order for the image signals D 11  to D 1   n  output from the first driving unit  330  to be delivered to the pixels P 31 , the switching blocks BL 41  to BL 4   k  are sequentially made conductive. The first driving unit  330  sequentially applies block driving signals BE 41  to BE 4   k  to the switching blocks BL 41  to BL 4   k.    
         [0071]     However, while in the first embodiment, the signal lines are first set at a certain voltage by the first driving unit  230  outputting a pre-charge signal to make a pre-charging block conductive before the second driving unit  220  outputs scanning signals GS 21  to GS 2   m  in every horizontal period, in the second embodiment, the same driving as in the first embodiment is performed using block driving signals supplied to the switching blocks BL 41  to BL 4   k  without a pre-charging block.  
         [0072]     As shown therein, the first driving unit  330  increases the number of times of outputting block driving signals BE 41  to BE 4   k  for every horizontal period. That is, for every horizontal period, the first driving unit  330  simultaneously outputs every block driving signal BE 41  to BE 4   k  before the second driving unit  320  outputs scanning signals GS 41  to GS 4   m . Therefore, every switching block BL 41  to BL 4   k  formed on the substrate is simultaneously made conductive to thus conduct the signal lines  340  and data lines DL 31  to DL 3   n  at the pixels P 31  side through the switching blocks BL 41  to BL 4   k . The block driving signals BE 41  to BE 4   k  simultaneously generated from the first driving unit  330  are referred to as a pre-charge pulse PCP 31  for the convenience of explanation. The pre-charge pulse PCP 31  is output during a dummy section in which the previous scanning signals GS 41  to GS 4   m  are changed to a high voltage level and the next scanning signals GS 41  to GS 4   m  are not output yet.  
         [0073]     As above, in order to increase the number of times of outputting block driving signals BE 41  to BE 4   k , the output timing of the first driving unit  330  may be controlled. The first driving unit  330  and the second driving unit  320  are integrated, thus signals may be output by internal synchronization of the output timing of every signal.  
         [0074]     With every switching block BL 41  to BL 4   k  made conductive by the pre-charge pulse PCP 31  simultaneously output from the first driving unit  330 , all of the signal lines  340  are set to a predetermined voltage level. However, since no pre-charge block is provided in the second embodiment, the signal lines  340  can all be set to a certain voltage level by adjusting the voltage level of the image signals D 1  to D 1   n  delivered to the signal lines  340  via the data lines DL 31  to DL 3   n . That is, like the first embodiment, the voltage level of the image signals D 1  to D 1   n  are set to the lowest gray level voltage before the second driving unit  320  outputs scanning signals GS 41  to GS 4   k  so that the signal lines  340  may be set to the lowest gray level voltage. Alternatively, the signal lines  340  may be set to a ground voltage by applying a ground voltage to the data lines DL 31  to DL 3   n.    
         [0075]     As described above, it is possible to prevent the picture quality of the organic electroluminescence display from being degraded, due to the light emitting element of the pixels emitting light by a voltage left on the signal lines before new images are displayed from the pixels, by presetting the signal lines electrically connected to the pixels to a certain voltage before scanning signals are output to conduct the pixels according to the first embodiment and second embodiment.  
         [0076]     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Technology Classification (CPC): 6