Patent Publication Number: US-2012044272-A1

Title: Display apparatus and driving method of display panel thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Korean Patent Application No. 10-2010-0080380, filed on Aug. 19, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with the exemplary embodiments relate to a display apparatus which displays an image based on an image signal received from the outside, and a driving method of a display panel thereof, and more particularly, to a display apparatus and a driving method of a display panel thereof which minimize an after image displayed on a display panel if a predetermined image is displayed thereon for a long time. 
     2. Description of the Related Art 
     A display apparatus processes an image signal received from the outside to display an image on a display panel based on the processed image signal. The display apparatus may be a TV, a computer monitor for general users, and a digital information display (DID) to provide image information for unspecific users in a public place. 
     The display apparatus such as the DID tends to fixedly display a specific image, such as a logo, a motto, etc., for a long time according to characteristics of the provided image information. Such a display apparatus employs a liquid crystal display (LCD) panel in general, and if a specific image is displayed on the panel for a long time, a liquid crystal in a location where the image is displayed is stressed. If liquid crystal stress is excessive, the liquid crystal cannot react to an image signal received corresponding to another image, and an after image is generated on the panel. If the after image is generated, the LCD should be replaced, causing massive expenses. 
     SUMMARY 
     According to an aspect of an exemplary embodiment, there is provided: a backlight unit which generates and emits light; a display panel which includes a plurality of unit pixels, and displays a first image using the light emitted by the backlight unit; and a panel driver which sets a total number of unit pixel groups including a preset number of unit pixels, from among the plurality of unit pixels, to be different from a total number of pixels of the first image, and selectively drives different unit pixels of a unit pixel group among the total number of unit pixel groups, at different times, to transmit the light therethrough. 
     The panel driver may set a number of pixels of a horizontal resolution of the first image to be different from a number of unit pixel groups in a single row of the display panel. 
     The panel driver may divide and apply a pixel value of the first image to a unit pixel, of the unit pixel group, through which the light is transmitted. 
     The preset number of unit pixels of the unit pixel group may be even. 
     The unit pixel group may include a first sub group and a second sub group, and a number of unit pixels in the first and second sub groups may be the same. 
     The panel driver may alternately drive the first sub group and the second sub group to transmit the light therethrough. 
     The panel driver may select the different unit pixels, through which the light is transmitted, by field or frame of the first image. 
     The panel driver may change a degree of light transmittance of the unit pixels by turning on and off the unit pixels, linearly or non-linearly, on a unit time basis. 
     The panel driver may select the different unit pixels, through which the light is transmitted, for every unit time according to a preset pattern, and may change the preset pattern at a preset interval. 
     The display panel may not include a color filter, and the backlight unit may sequentially supply light in red, green and blue colors to the display panel. 
     According to an aspect of another exemplary embodiment, there is provided a driving method of a display panel, the driving method including: receiving an image signal corresponding to a first image; setting a total number of unit pixel groups including a preset number of unit pixels, from among a plurality of unit pixels of the display panel, to be different from a total number of pixels of the first image; and selectively driving different unit pixels of a unit pixel group among the total number of unit pixel groups, at different times, to transmit light therethrough to display the first image. 
     The setting the unit pixel group may include setting a number of pixels of a horizontal resolution of the first image to be different from a number of unit pixel groups in a single row of the display panel. 
     The selectively driving the different unit pixels may include dividing and applying a pixel value of the first image to a unit pixel, of the unit pixel group, through which the light is transmitted. 
     The preset number of unit pixels of the unit pixel group may be even. 
     The unit pixel group may include a first sub group and a second sub group, and a number of unit pixels in each of the first sub group and the second subgroup may be the same. 
     The selectively driving the different unit pixels may include alternately driving the first sub group and the second sub group to transmit the light therethrough. 
     The selectively driving the different unit pixels may include selecting the different unit pixels, through which the light is transmitted, by field or frame of the first image. 
     The selectively driving the different unit pixels may include changing a degree of light transmittance of the unit pixels by turning on and off the unit pixels, linearly or non-linearly, on a time basis. 
     The selectively driving the different unit pixels may include selecting the different unit pixels, through which the light is transmitted, for every unit time according to a preset pattern, and changing the preset pattern at a preset interval. 
     According to an aspect of another exemplary embodiment, there is provided a display apparatus including: a display panel which includes a plurality of unit pixels, and displays a first image using light; and a panel driver which sets a total number of unit pixel groups including a preset number of unit pixels, from among the plurality of unit pixels, to be different from a total number of pixels of the first image, and selectively drives different unit pixels of a unit pixel group among the total number of unit pixel groups, at different times, to transmit the light therethrough. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a display apparatus according to a first exemplary embodiment; 
         FIG. 2  is a block diagram of the display apparatus in  FIG. 1 ; 
         FIG. 3  illustrates image fields displayed by light in each color on a time basis from the display apparatus in  FIG. 1 ; 
         FIG. 4  illustrates pixels which form a first image in the display apparatus in  FIG. 1 ; 
         FIG. 5  illustrates a grouping of unit pixels of a display panel of the display apparatus in  FIG. 1 ; 
         FIG. 6  illustrates a driving method of unit pixels with respect to a single unit pixel group in  FIG. 5 ; 
         FIG. 7  is a graph which illustrates the driving method of the unit pixels in  FIG. 6  with respect to time; 
         FIG. 8  illustrates a method of applying a pixel value to the unit pixels in the display apparatus in  FIG. 1 ; 
         FIG. 9  is a graph which illustrates a driving method of unit pixels with respect to time according to a second exemplary embodiment; 
         FIG. 10  is a graph which illustrates a driving method of unit pixels with respect to time according to a third exemplary embodiment; and 
         FIG. 11  is a control flowchart of a driving method of a display panel according to a fourth exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Below, exemplary embodiments will be described in detail with reference to accompanying drawings so as to be easily realized by a person having ordinary knowledge in the art. The exemplary embodiments may be embodied in various forms without being limited to the exemplary embodiments set forth herein. Descriptions of well-known parts are omitted for clarity, and like reference numerals refer to like elements throughout. However, it is appreciated that it is not meant to exclude such omitted components from a display apparatus  1  to which the spirit of the exemplary embodiments are applied. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
       FIG. 1  is an exploded perspective view of a display apparatus  1  according to a first exemplary embodiment. As shown therein, the display apparatus  1  according to the present exemplary embodiment includes a large-screen digital information display (DID). However, the spirit of the present exemplary embodiment is not limited to the foregoing, and may apply to other general display apparatuses as long as they display an image based on an image signal received from the outside. 
     The display apparatus  1  includes a display panel  100 , a panel driver  200  to drive the display panel  100 , and a backlight unit  300  to supply light to a rear side of the display panel  100  to thereby display an image on the display panel  100 . 
     According to the present exemplary embodiment, the display panel  100  does not include a color filter, and the backlight unit  300  sequentially emits light in a plurality of colors to the display panel  100 , though it is understood that another exemplary embodiment is not limited thereto. An image corresponding to each color is accumulated sequentially within a user&#39;s field of view, and thus a user recognizes a final image in combined colors. 
     Directions in  FIG. 1  will now be described. Directions X, Y and Z refer to horizontal, vertical and height directions, respectively. The display panel  100  is disposed along a plane X-Y, and the backlight unit  300  and the display panel  100  are accumulated in the direction Z. Description will be made on the basis of the definition of the above directions. Opposite directions of the directions X, Y and Z refer to directions −X, −Y and −Z, respectively, and the plane X-Y refers to a plane which is formed by axes of the direction X and the direction Y. 
     The display panel  100  may be a liquid crystal display (LCD) panel according to the present exemplary embodiment, though it is understood that another exemplary embodiment is not limited thereto. As liquid crystals are filled between two substrates (not shown) and the arrangement of such liquid crystals is adjusted by a driving signal applied by the panel driver  200 , the display panel  100  displays an image thereon. The display panel  100  does not emit light itself, and receives light from the backlight unit  300  to display an image in a display area. The display area refers to an area that is parallel with the plane X-Y and displays an image therein from the display panel  100 . 
     A plurality of unit pixels (not shown) of the display panel  100  is arranged in a horizontal direction and a vertical direction, i.e., in the directions X and Y, and liquid crystals are provided with respect to each of the unit pixels. 
     The panel driver  200  includes a printed circuit board (PCB) (not shown) in which a chipset and a wiring are mounted corresponding to various functions. A flexible PCB (not shown) is provided between the PCB and the display panel  100  to transmit a driving signal from the panel driver  200  to the display panel  100 . 
     The panel driver  200  applies a voltage to each of the unit pixels of the display panel  100 , to thereby individually rotate liquid crystals of the unit pixels. Furthermore, light transmittance of the unit pixels is controlled differently, and an image is displayed on the display panel  100 . A detailed configuration of the panel driver  200  according to the present exemplary embodiment will be described below. 
     The backlight unit  300  sequentially generates and emits, to the display panel  100 , light in a plurality of colors, e.g., RGB colors. The backlight unit  300  includes a light source module  310  which generates light in RGB colors, a light guiding plate  320  which is disposed in parallel with the display panel  100  and receives light from the light source module  310 , and an optical sheet  330  which is provided between the light guiding plate  320  and the display panel  100 . 
     According to the present exemplary embodiment, the light source module  310  is a direct type that is arranged below the light guiding plate  320  to be in parallel therewith, but the spirit of the present exemplary embodiment is not limited to the foregoing. The spirit of the present exemplary embodiment may apply to an edge type light source module that is arranged in an edge of the light guiding plate to be in parallel therewith. 
     The light source module  310  includes a plurality of light sources  311 ,  313  and  315  which is arranged below the light guiding plate  320  to be in parallel therewith, and a light source substrate  317  in which the plurality of light sources  311 ,  313  and  315  is mounted. 
     The light sources  311 ,  313  and  315  include light emitting diodes (LED), and receive a driving power signal and a lighting control signal from the light source substrate  317 . In the present exemplary embodiment, the light sources  311 ,  313  and  315  include a red LED  311 , a green LED  313  and a blue LED  315 . 
     The light source substrate  317  supplies driving power to the light sources  311 ,  313 , and  315  mounted in an upper surface by being connected to an additional power source (not shown). The light sources  311 ,  313  and  315  in the light source substrate  317 , i.e., the red LED  311 , the green LED  313  and the blue LED  315 , are selectively turned on/off according to a control of a light source driver  400  (to be described below). 
     The light guiding plate  320  may be a plastic mold lens including acryl, and uniformly transmits the light from the light source module  310  to the entire display area of the display panel  100 . The light guiding plate  320  has a size and shape corresponding to the display panel  100 , and is arranged in the rear side of the display panel  100 . 
     In a lower side of the light guiding plate  320 , a light guiding pattern or an optical pattern dispersing light may be provided to improve uniformity of light guided by the light guiding plate  320  and adjust the volume of transmitted light. That is, a brightness of the display area may depend upon the optical pattern. 
     At least one optical sheet  330  is provided between the display panel  100  and the light guiding plate  320  in parallel with the display panel  100 . The optical sheet  330  includes at least one of a prism sheet, a diffusion sheet and a protection film, and transmits light guided by the light guiding plate  320  to the display panel  100 . 
     Hereinafter, a control configuration of the display apparatus  1  will be described with reference to  FIG. 2 .  FIG. 2  is a block diagram of the display apparatus  1 . 
     As shown therein, the display apparatus  1  includes an image receiver  10  which receives an image signal, an image processor  20  which processes an image signal received from the image receiver  10  to display an image, the display panel  100  which displays an image thereon, the panel driver  200  which drives the display panel  100  corresponding to the results of processing the image signal by the image processor  10 , the light source module  310  which generates light, and the light source driver  400  that controls the light source module  310  corresponding to the results of processing the image signal by the image processor  20 . 
     The light source driver  400  may be integrated with the light source substrate  317 . 
     The image receiver  10  may correspond to image signals according to various standards. For example, the image receiver  10  may receive a radio frequency (RF) signal in a wireless manner from a broadcasting station (not shown), or receive an image signal according to at least one of composite video, component video, super video, SCART, and high definition multimedia interface (HDMI) standards. The image receiver  10  may receive an image signal according to D-SUB transmitting an RGB signal by VGA or digital video interactive (DVI) and HDMI standards. 
     The image processor  20  processes the image signal transmitted from the image receiver  10 . The image processing by the image processor  20  includes, without limitation to, decoding and encoding for various image formats, deinterlacing, converting a frame refresh rate, scaling, reducing noise from an image for improving a picture quality, and enhancing details. 
     The image processor  20  may include individual configurations to perform each process individually, or include an integrated configuration to integrate several processes. The image processor  20  may be integrated to the panel driver  200 , or installed in the same PCB as the panel driver  200 . 
     The image processor  20  processes the image signal as described above, and controls the panel driver  200  and the light source driver  400  to drive the display panel  100  and the light source module  310 , respectively, corresponding to the result. The panel driver  200  and the light source driver  400  control to rotate liquid crystals and generate light according to the processing result of the image processor  20 , to thereby display an image on the display panel  100 . 
     According to the present exemplary embodiment, the display panel  100  does not include a color filter, but a user recognizes a final color image as the display panel  100  sequentially displays an image corresponding to RGB colors. This will be described with reference to  FIG. 3 .  FIG. 3  illustrates image fields R 01 , G 01 , B 01 , R 02 , G 02  and B 02  by light in RGB colors on a time basis in the display apparatus  1 . 
     As shown therein, the image fields R 01 , G 01 , BO 1 , R 02 , G 02  and B 02  are sequentially displayed as time T elapses. The image field R 01  corresponding to a red color, the image field G 01  corresponding to a green color, and the image field B 01  corresponding to a blue color are sequentially displayed, and a user views an image field in a final color that combines R 01 , G 01  and B 01  by recognizing R 01 , G 01  and B 01  overlapping each other. 
     According to the same principle, the image fields R 02 , G 02  and B 02  corresponding to the RGB colors are sequentially displayed, and a user may recognize a color image by the repetition of such processes. 
     To display the image field R 01 , the light source driver  400  turns on the red LED  311  among the red, green and blue LEDs  311 ,  313  and  315 , and generates a red light from the light source module  310 . The panel driver  200  controls the liquid crystals of the display panel  100  according to image data corresponding to the red color. 
     To display the image field G 01 , the light source driver  400  turns off the red LED  311 , and turns on the green LED  313  to generate a green light from the light source module  310 . The panel driver  200  controls the liquid crystals of the display panel  100  according to image data corresponding to the green color. 
     The display apparatus  1  according to the present exemplary embodiment may display a color image by the repetition of the above process. 
     In some cases, however, the display apparatus fixedly displays a first image for a long time. Hereinafter, for convenience of description, the expression “fixedly display” indicates that a location of the first image does not move substantially and the shape of the first image is not changed. Furthermore, hereinafter, for convenience of description, the expression “the first image” refers to an image that is fixedly displayed. 
     According to the present exemplary embodiment, the panel driver  200  sets a unit pixel group including a number of unit pixels (not shown) when driving the display panel  100  having a plurality of unit pixels, and sets the total number of the unit pixel groups to be different from the total number of pixels of the first image. The panel driver  200  selectively drives different unit pixels, through which light is transmitted, in a single unit pixel group as time elapses, and divides and applies a pixel value of the first image to the unit pixels through which light is transmitted. 
     Accordingly, liquid crystal stress of the display panel  100  is minimized, and an after image may be prevented, though a user may perceive the first image as if the first image is fixedly displayed. 
     Regarding the relationship between the total number of the unit pixel groups and the total number of pixels of the first image, the number of pixels in a single column of the first image is the same as the number of the unit pixels included in a single column of the display panel  100 . Accordingly, the panel driver  200  sets the number of pixels of a horizontal resolution in the first image, i.e., the number of pixels in a single row of the first image, to be different from the number of the unit pixel groups of a single row of the display panel  100 . 
     Hereinafter, a method of setting the unit pixel group by the panel driver  200  according to an exemplary embodiment will be described with reference to  FIGS. 4 and 5 . 
       FIG. 4  illustrates pixels MP 1 , MP 2 , MP 3 , MP 1918 , MP 1919  and MP 1920  forming a first image V. 
     As shown therein, the first image V includes a plurality of pixels MP 1 , MP 2 , MP 3 , MP 1918 , MP 1919  and MP 1920 , and each of the pixels MP 1 , MP 2 , MP 3 , MP 1918 , MP 1919  and MP 1920  are arranged in a two-dimensional manner along a column and a row.  FIG. 4  illustrates part of the pixels MP 1 , MP 2 , MP 3 , MP 1918 , MP 1919  and MP 1920  in the first row of the first image V. 
     For example, if a horizontal resolution of the first image V is 1920 pixels, then 1920 pixels MP 1 , MP 2 , MP 3 , MP 1918 , MP 1919  and MP 1920  are arranged in a single row of the first image V. 
       FIG. 5  illustrates a grouping of unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  of the display panel  100 . 
     As shown therein, the display panel  100  includes the plurality of unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  arranged along a column and a row.  FIG. 5  illustrates the unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  of the first row of the display panel  100 . For example, 5760 unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  are arranged in a single row of the display panel  100  of  FIG. 5 . The number of the unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  which are arranged in the single row of the display panel  100  may vary and does not limit the spirit of the present exemplary embodiment. 
     The panel driver  200  sets unit pixel groups G 1 , G 2 , G 1339  and G 1440  including the plurality of preset unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760 . The number of the unit pixel groups G 1 , G 2 , G 1339  and G 1440  of a single row of the display panel  100  is set to be different from the number of pixels of the horizontal resolution of the first image V, and the number of the unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  within the single unit pixel group G 1 , G 2 , G 1339  and G 1440  is adjusted properly corresponding to the number of the unit pixel groups. For example, if the number of the unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  in a single row of the display panel  100  is 5760 pixels, and a horizontal resolution of the first image V is 1920 pixels, the number of the unit pixel groups G 1 , G 2 , G 1339  and G 1440  may be set as 1440 pixels. In this case, the single unit pixel group G 1 , G 2 , G 1339  and G 1440  includes four unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760 . 
     The number of the unit pixel groups G 1 , G 2 , G 1339  and G 1440  and the number of unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  belonging to the single unit pixel group G 1 , G 2 , G 1339  and G 1440  may vary depending on the design type, and does not limit the spirit of the present exemplary embodiment. 
     In the present exemplary embodiment, the panel driver  200  forms the unit pixel groups G 1 , G 2 , G 1339  and G 1440  by grouping the unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  per four unit pixels in a single row. The unit pixel group G 1  includes four unit pixels SP 1 , SP 2 , SP 3  and SP 4  which are adjacent to each other in a single row. 
     If the unit pixel groups G 1 , G 2 , G 1339  and G 1440  are set as above, the panel driver  200  selectively drives different unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  through which light is transmitted, among those included in the respective unit pixel groups G 1 , G 2 , G 1339  and G 1440 , as the unit time elapses. That is, the panel driver  200  shifts the unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5757 , SP 5758 , SP 5759  and SP 5760  through which light is transmitted, within the single unit pixel group G 1 , G 2 , G 1339  and G 1440 . 
     The unit time may vary, e.g., may be applicable by field of the first image, frame of the first image, etc. 
     Hereinafter, a method of selectively driving the unit pixels SP 1 , SP 2 , SP 3  and SP 4  by the panel driver  200  will be described with reference to  FIG. 6 .  FIG. 6  illustrates the method of driving the unit pixels SP 1 , SP 2 , SP 3  and SP 4  with respect to a single unit pixel group G 1  in  FIG. 5 . 
     The present exemplary embodiment describes only the single unit pixel group G 1 , though it is understood that the description is applicable to the driving of other unit pixel groups G 2 , G 1339  and G 1440 . 
     As shown in  FIG. 6 , the unit pixel group G 1  includes four unit pixels SP 1 , SP 2 , SP 3  and SP 4 . ( 1 ) to ( 6 ) in  FIG. 6  indicate light transmittance stages of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  as the unit time elapses. Hereinafter, hatched unit pixels refer to unit pixels SP 1 , SP 2 , SP 3  and SP 4  in a light transmittance state and unhatched unit pixels refer to unit pixels SP 1 , SP 2 , SP 3  and SP 4  in a non-light transmittance state. 
     In ( 1 ) in  FIG. 6 , the panel driver  200  classifies the unit pixels SP 1 , SP 2 , SP 3  and SP 4  within the unit pixel group G 1  into two sub-groups, i.e., a first sub-group SP 1  and SP 3  and a second sub group SP 2  and SP 4 . The panel driver  200  drives the first sub group SP 1  and SP 3  to transmit light therethrough, and operates so that the second sub group SP 2  and SP 4  does not transmit light therethrough. 
     The first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4  are termed for convenience in classifying the unit pixels SP 1 , SP 2 , SP 3  and SP 4  within the unit pixel group G 1 , and the term and number of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  described herein does not limit the spirit of the present exemplary embodiment. The unit pixels SP 1 , SP 2 , SP 3  and SP 4  in the first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4  according to the present exemplary embodiment are alternately arranged, but the method of classifying the first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4  is not limited to the foregoing and may vary. 
     Meanwhile, the number of unit pixels SP 1 , SP 2 , SP 3  and SP 4  which belong to the first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4  is set equally, which will be described below. 
     In ( 2 ) in  FIG. 6 , the panel driver  200  operates so that the first sub group SP 1  and SP 3  does not transmit light therethrough, and drives the second sub groups SP 2  and SP 4  to transmit light therethrough. 
     In ( 3 ) in  FIG. 6 , the panel driver  200  drives the first sub group SP 1  and SP 3  to transmit light therethrough, and operates so that the second sub group SP 2  and SP 4  does not transmit light therethrough. 
     In ( 4 ) in  FIG. 6 , the panel driver  200  operates so that the first sub group SP 1  and SP 3  does not transmit light therethrough, and drives the second sub group SP 2  and SP 4  to transmit light therethrough. 
     As described above, the panel driver  200  alternately drives the first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4 . As the light transmittance state of the particular unit pixels SP 1 , SP 2 , SP 3  and SP 4  is not fixed, liquid crystal stress is minimized while the first image V is displayed as if being fixed. 
     Accordingly, a user may recognize the first image V as if the image is fixedly displayed, and liquid crystal stress is minimized, thereby preventing an after image of the display panel  100 . 
     The pixel value applied to the unit pixels SP 1 , SP 2 , SP 3  and SP 4  within the unit pixel group G 1  will be described below. 
     In ( 5 ) in  FIG. 6 , the panel driver  200  operates so that the first sub group SP 1  and SP 3  does not transmit light therethrough, and drives the second sub group SP 2  and SP 4  to transmit light therethrough. In ( 6 ) in  FIG. 6 , the panel driver  200  drives the first sub group SP 1  and SP 3  to transmit light therethrough, and operates so that the second sub group SP 2  and SP 4  does not transmit light therethrough. 
     A selection pattern of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  changes at the time between ( 4 ) and ( 5 ) in  FIG. 6  to prevent liquid crystal stress due to a fixed pattern from occurring if the unit pixels SP 1 , SP 2 , SP 3  and SP 4  are selected to transmit light according to a preset pattern. Thus, the after image of the display panel  100  may be prevented by changing the selection pattern of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  at preset intervals. 
     As compared to the present exemplary embodiment, the number of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  included in the first sub group and the second sub group may differ, e.g., when the number of unit pixels of the first sub group is more than the number of unit pixels of the second sub group, according to another exemplary embodiment. In this case, the light transmittance by the first sub group generates higher brightness than that by the second sub group, and brightness becomes irregular over time while the first image V is displayed. 
     To prevent the above case, the number of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  included in the first and second sub groups may be the same, though it is understood that another exemplary embodiment is not limited thereto. Furthermore, the number of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  included in the single unit pixel group G 1  may, although not necessarily, be even. If the number of the unit pixels included in the single unit pixel group is odd, the number of the unit pixels included in the first and second sub groups may not be the same. 
       FIG. 7  is a graph which illustrates the driving method of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  in  FIG. 5  with respect to time. 
     As shown therein, a horizontal axis T of graphs (A) and (B) refers to time, and a vertical axis L refers to a digital brightness level. T and L are relative comparative values, and thus do not have any unit. 
     The graph (A) illustrates the case when the panel driver  200  controls the light transmittance of the first sub group SP 1  and SP 3 , and the graph (B) illustrates the case when the panel driver  200  controls the light transmittance of the second sub group SP 2  and SP 4 . In a vertical axis of the two graphs, L 1  indicates a particular target digital brightness value. 
     According to the graphs (A) and (B), as time elapses from areas ( 1 ) to ( 4 ), the first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4  are turned on and off correspondingly to each other to transmit light therethrough. A timing Tc which is located between the area ( 4 ) and an area ( 5 ), refers to an interval at which the selection pattern of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  changes as described above. 
     According to an exemplary embodiment, the number of pixels of the horizontal resolution of the first image V is set to be different from the number of the unit pixel groups in a single row of the display panel  100 . Thus, regarding a pixel value which is applied to the unit pixel through which light is transmitted, the pixels of the first image and the unit pixels of the display panel  100  do not correspond in a 1:1 relationship. The pixel value of the first image V is divided and applied to the unit pixels, as will now be described with reference to  FIG. 8 .  FIG. 8  illustrates a method of applying the pixel value to the unit pixels according to an exemplary embodiment. 
     As shown therein, if a horizontal resolution of the first image V is 1920 pixels and the number of unit pixel groups G 1 , G 2 , G 1339  and G 1440  in a single row of the display panel  100  is 1440 groups, three unit pixel groups G 1 , G 2  and G 3  adjacent to each other in the display panel  100  correspond to four adjacent pixels MP 1 , MP 2 , MP 3  and MP 4  of the first image V. 
     If light is transmitted by the unit pixels SP 1 , SP 3 , SP 5 , SP 7 , SP 9  and SP  11  among the units pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5 , SP 6 , SP 7 , SP 8 , SP 9 , SP 10 , SP 11  and SP 12  of the unit pixel groups G 1 , G 2  and G 3 , the pixel value of the pixels MP 1 , MP 2 , MP 3  and MP 4  of the first image V is divided and applied to the unit pixels SP 1 , SP 3 , SP 5 , SP 7 , SP 9  and SP 11 . 
     That is, of four pixels MP 1 , MP 2 , MP 3  and MP 4  of the first image V, six unit pixels SP 1 , SP 3 , SP 5 , SP 7 , SP 9  and SP  11  should receive the pixel value. Thus, the pixel values of the first image V should be divided to the unit pixels SP 1 , SP 3 , SP 5 , SP 7 , SP 9  and SP  11  properly, which is called an interpolation. 
     For example, the panel driver  200  divides and applies the pixel value of the pixel MP 1  to the unit pixels SP 1  and SP 3 , and divides and applies the pixel value of the pixel MP 4  to the unit pixels SP 9  and SP 11 . In this case, the panel driver  200  calculates the average of the pixel values of the pixels MP 2  and MP 3  and applies the average pixel value to the unit pixels SP 5  and SP 7 . By this method, the panel driver  200  may apply pixel values to the unit pixels SP 1 , SP 2 , SP 3 , SP 4 , SP 5 , SP 6 , SP 7 , SP 8 , SP 9 , SP 10 , SP 11  and SP 12 . 
     The foregoing method is an exemplary embodiment, which does not limit the spirit of the present exemplary embodiment. By another method, the panel driver  200  may divide and apply the pixel value of the pixel MP 1  to the unit pixels SP 1  and SP 3 , divide and apply the pixel value of the pixel MP 4  to the unit pixels SP 9  and SP 11 , apply the pixel value of the pixel MP 2  to the unit pixel SP 5 , and apply the pixel value of the pixel MP 3  to the unit pixel SP 7 . Otherwise, the panel driver  200  may derive a change curve of the pixel value of the pixels MP 1 , MP 2 , MP 3  and MP 4 , and then set the pixel value to be similar to the derived change curve to apply the pixel value to the unit pixels SP 1 , SP 3 , SP 5 , SP 7 , SP 9  and SP 11 . 
     Moreover, though  FIG. 7  illustrates a change of a degree of light transmittance of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  by the panel driver  200  by turning on and off the unit pixels SP 1 , SP 2 , SP 3  and SP 4  on a time basis, it is understood that the spirit of the present exemplary embodiment is not limited thereto, and various driving controls are possible. 
       FIG. 9  is a graph which illustrates a driving method of unit pixels SP 1 , SP 2 , SP 3  and SP 4  with respect to time according to a second exemplary embodiment. 
     A graph (C) in  FIG. 9  illustrates the case when the panel driver  200  controls the light transmittance of the first sub group SP 1  and SP 3 , and a graph (D) illustrates the case when the panel driver  200  controls the light transmittance of the second sub group SP 2  and SP 4 . Other matters including horizontal and vertical axes are the same as those in  FIG. 7 . 
     According to the second exemplary embodiment, the panel driver  200  changes the degree of light transmittance of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  linearly on a time basis. 
     For example, in an area ( 1 ), the panel driver  200  decreases the degree of light transmittance of the first sub group SP 1  and SP 3  linearly and then increases the light transmittance linearly again after a light blocking operation. The panel driver  200  increases the degree of light transmittance of the second sub group SP 2  and SP 4  linearly and then decreases the light transmittance linearly after reaching a preset level L 1 . 
     In an area ( 2 ), the panel driver  200  increases the degree of light transmittance of the first sub group SP 1  and SP 3  linearly, and then decreases the degree of light transmittance again linearly after reaching a level L 1 . The panel driver  200  also decreases the degree of light transmittance of the second sub group SP 2  and SP 4  linearly and then increases the degree of light transmittance again linearly after the light blocking. 
     Even if the degree of light transmittance of the first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4  changes on a time basis, the total brightness value at the predetermined timing is still the same, i.e., L 1 . As time elapses, the entire brightness of the first image V may be uniform. 
     To change the selection pattern of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  at the timing Tc, the panel driver  200 , in an area ( 5 ), increases the degree of light transmittance of the first sub group SP 1  and SP 3  which was decreasing, and decreases the degree of light transmittance of the second sub group SP 2  and SP 4  which was increasing. The panel driver  200 , in an area ( 6 ), decreases the degree of light transmittance of the first sub group SP 1  and SP 3  linearly and then increases again the degree of light transmittance linearly, and increases the degree of light transmittance of the second sub group SP 2  and SP 4  linearly and then decreases the degree of light transmittance linearly after reaching the preset level L 1 . 
       FIG. 10  is a graph which illustrates a driving method of unit pixels SP 1 , SP 2 , SP 3  and SP 4  with respect to time according to a third exemplary embodiment. 
     A graph (E) in  FIG. 10  illustrates the case when the panel driver  200  controls the light transmittance of the first sub group SP 1  and SP 3 , and a graph (F) illustrates the case when the panel driver  200  controls the light transmittance of the second sub group SP 2  and SP 4 . Other matters including horizontal and vertical axes are the same as those in  FIG. 7 . 
     According to the third exemplary embodiment, the panel driver  200  changes a degree of light transmittance of unit pixels SP 1 , SP 2 , SP 3  and SP 4  on a time basis in a non-linear type, e.g., in a sine wave. 
     For example, in an area ( 1 ), the panel driver  200  decreases the degree of light transmittance of the first sub group SP 1  and SP 3  in a non-linear manner and then increases the degree of light transmittance non-linearly after the light blocking operation, and increases the degree of light transmittance of the second sub group SP 2  and SP 4  in a non-linear manner and then decreases the degree of light transmittance non-linearly after the level L 1 . 
     Meanwhile, in an area ( 2 ), the panel driver  200  increases the degree of light transmittance of the first sub group SP 1  and SP 3  in a non-linear manner in an area ( 2 ) and then decreases the degree of light transmittance non-linearly after the level  1 , and decreases the degree of light transmittance of the second sub group SP 2  and SP 4  in a non-linear manner and then increases the degree of light transmittance non-linearly after the light blocking. 
     Even if the light transmittance of the first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4  changes on a time basis, the total brightness value at the predetermined timing is still the same, i.e., L 1 . As time elapses, the entire brightness of the first image V may be uniform. 
     To change the selection pattern of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  at the timing Tc, the panel driver  200 , in an area ( 5 ), increases the degree of light transmittance of the first sub group SP 1  and SP 3 , which was decreasing, in a non-linear manner, and decreases the degree of light transmittance of the second sub group SP 2  and SP 4 , which was increasing, in a non-linear manner. The panel driver  200 , in an area ( 6 ), decreases the degree of light transmittance of the first sub group SP 1  and SP 3  in a non-linear manner and then increases again the degree of light transmittance in the non-linear manner, and increases the degree of light transmittance of the second sub group SP 2  and SP 4  in a non-linear manner and then decreases the degree of light transmittance in the non-linear manner after reaching the preset level L 1 . 
     As described above, the method of changing the degree of light transmittance of the unit pixels SP 1 , SP 2 , SP 3  and SP 4  by the panel driver  200  may vary according to exemplary embodiments. 
       FIG. 11  is a control flowchart of a driving method of the display panel  100  according to a fourth exemplary embodiment. 
     The detailed configuration of the display apparatus  1  according to the fourth exemplary embodiment is substantially the same as that according to the first exemplary embodiment, and descriptions of the same configurations will be omitted herein. 
     As shown in  FIG. 11 , according to the present exemplary embodiment, if an image signal corresponding to the first image V is received by the display apparatus  1  (operation S 100 ), the panel driver  200  forms the unit pixel groups G 1 , G 2 , G 1339  and G 1440  corresponding to pixels MP 1 , MP 2 , MP 3 , MP 1338 , MP 1339  and MP 1440  (operation S 110 ). 
     The panel driver  200  sets the first sub group SP 1  and SP 4  and the second sub group SP 2  and SP 4  for each of the unit pixel groups G 1 , G 2 , G 1339  and G 1440  (operation S 120 ). 
     As the display of the first image V is initiated (operation S 130 ), the panel driver  200  selectively, e.g., alternately, drives the unit pixels SP 1 , SP 2 , SP 3  and SP 4  of the first sub group SP 1  and SP 3  and the second sub group SP 2  and SP 4  by unit time (operation S 140 ), thereby displaying the first image V. 
     Accordingly, if the first image V is fixedly displayed, liquid crystal stress is minimized and the after image may be prevented. 
     While not restricted thereto, an exemplary embodiment can be embodied as computer-readable code on a computer-readable recording medium. The computer-readable recording medium is any data storage device that can store data that can be thereafter read by a computer system. Examples of the computer-readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, and optical data storage devices. The computer-readable recording medium can also be distributed over network-coupled computer systems so that the computer-readable code is stored and executed in a distributed fashion. Also, an exemplary embodiment may be written as a computer program transmitted over a computer-readable transmission medium, such as a carrier wave, and received and implemented in general-use or special-purpose digital computers that execute the programs. Moreover, one or more units of the display apparatus  100  can include a processor or microprocessor executing a computer program stored in a computer-readable medium. 
     Although a few exemplary embodiments have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the inventive concept, the scope of which is defined in the appended claims and their equivalents.