Patent Publication Number: US-2007109468-A1

Title: Systems with reduced color lines at edges of associated display devices

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to display devices.  
      2. Description of the Related Art  
      Flat panel display devices, such as liquid crystal displays (LCDs), electroluminescent (EL) displays and plasma display panels (PDPs), have been rather popular and have widely replaced conventional cathode ray tube (CRT) display devices. Flat panel display devices have been adapted with electronic apparatuses, such as television sets, computer systems, mobile phones, game players and the like. The mechanism to display an image for such a flat panel display device is the dot mechanism. Thus, the image displayed by a flat panel display device is composed of an array of color dots. One color dot is also called a pixel, which usually includes three sub-pixels with each sub-pixel being characterized by a different one of the three primary colors of red (R), green (G), and blue (B). Since any color can be formed from these three primary color sub-pixels, a desired color at the corresponding pixel can be obtained by controlling the illumination intensity of the sub-pixels. If the intensities of the three primary color sub-pixels are equal, a white color (W) can appear after light mixing.  
       FIG. 1  is a schematic view showing a conventional display panel. As shown in  FIG. 1 , the display panel has a display area  110  and a non-display area  112 . A plurality of pixels are formed in the display area  110 , and each pixel includes three sub-pixels with respect to three primary colors, R, G and B. For example, pixel  100  includes sub-pixels  101 R,  101 G and  101 B. For a stripe-type display panel, each of the R, G and B sub-pixels is arranged in a column with other sub-pixels of like color, thus forming colored stripes. In this manner, the display area  110  usually includes a middle region  106  and side regions  102  and  104 . Therefore, only one of the primary colors is disposed in each of the side regions  102  and  104 . Here, the colors for the side regions  102 ,  104  are red and blue. Notably, in such a configuration the middle region  106  can display a white color because of a color mixing effect. However, the side regions  102  and  104  exhibit a poor color mixing effect, and therefore the red and blue color lines can be noticeable at the two edges of the display panel.  
      In order to reduce the foregoing phenomenon of the color lines being noticeable at the two edges of the display panel, another sub-pixel arrangement has been proposed as shown in  FIG. 2 . In  FIG. 2 , pixel  200  at the first row has the same sub-pixel sequence (RGB) as that of pixel  100  in  FIG. 1 . However, pixel  220  at the second row has another sub-pixel sequence (BGR). In this conventional design, the side region  122  exhibits an alternating sub-pixel sequence of R, B and side region  124  exhibits an alternating sub-pixel sequence of B, R to increase the color mixing effect. However, this design in  FIG. 2  still cannot completely eliminate the color lines at the edges of the display panel.  
     SUMMARY OF THE INVENTION  
      Systems for reducing color lines at edges of a display are provided. An exemplary embodiment of such a system comprises a display comprising a peripheral region and a non-peripheral region, with the non-peripheral region including at least a central image-displaying portion of the display, and the peripheral region including at least one image-displaying edge portion of the display. The peripheral region and the non-peripheral region comprise sub-pixels, wherein the sub-pixels disposed in the peripheral region have a brightness lower than that of the sub-pixels disposed in the non-peripheral region.  
      Another embodiment of a system for reducing color lines at edges of a display comprises a display. The display comprises pixels having sub-pixels arranged in a striped configuration such that sub-pixels of a first color are located in an outermost column of the sub-pixels. A brightness of the sub-pixels of the outermost column is lower than a brightness of other sub-pixels located closer to a center of a display portion of the display.  
      It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  and  FIG. 2  are schematic top views showing two conventional display panels.  
       FIG. 3  is a schematic top view showing a display panel according to an embodiment of the present invention.  
       FIGS. 4-9  are schematic top views each showing one pixel near the edge of a corresponding display panel according to several embodiments of the present invention.  
       FIG. 10  is a schematic view of a system incorporating an embodiment of a display device.  
       FIG. 11  is a schematic view of another system incorporating another embodiment of a display device. 
    
    
     DETAILED DESCRIPTION  
      Systems with reduced color lines at edges of associated displays are provided. In some embodiments, such a system incorporates a display device that includes pixels and corresponding sub-pixels. The sub-pixels exhibit reduced effective brightness in the peripheral region of the display. Potentially, this configuration can effectively improve the color balance at edges of the display device and thereby improve the displaying quality. Several examples or embodiments will now be described.  
       FIG. 3  is a schematic top view showing a display panel according to an embodiment of the present invention. As shown in  FIG. 3 , the display panel includes a display area  310  and a non-display area  312 , wherein a plurality of pixels are disposed in the display area  310 . Each pixel, such as pixel  300 , includes three sub-pixels, such as sub-pixels  301 R,  301 G and  301 B, with respect to three primary colors R, G and B, for example. These sub-pixels are arranged in a two-dimensional array of columns and rows. The number of columns and the number of rows depicted in  FIG. 3  are merely exemplary. The sub-pixels are liquid crystal display sub-pixels in this embodiment. In other embodiments, however, various other types of pixels can be used, such as electroluminescent display sub-pixels (such as organic or inorganic light emitting diode sub-pixels) or plasma display sub-pixels, for example. In addition, several driving integrated circuits (ICs) (not shown) are located in the non-display area  310  for driving the sub-pixels. In other embodiments, at least some of the driving ICs can be located in other areas.  
      In  FIG. 3 , the display area  310  includes peripheral regions  302  and  303  and a non-peripheral region  306 . The R, G and B sub-pixels are arranged in a stripe-type configuration. That is, the sub-pixels arranged in the same column exhibit the same color. In this embodiment, the sub-pixel sequence is RGB, and thus the sub-pixels at the first column are red and the sub-pixels at the second column are green. However, in other embodiments, the sub-pixel sequence can be different. It should be noted that the arrangement of the peripheral regions  302  and  303  and the non-peripheral region  306  is not limited to the configuration shown in  FIG. 3  in other embodiments. For instance, in some embodiments, the peripheral regions can be disposed around the non-peripheral region.  
      Notably, the sub-pixels disposed in the peripheral regions  302  and  303  have a brightness lower than that of the sub-pixels disposed in the non-peripheral region  306 . In order to reduce the brightness of the sub-pixels  301  in the peripheral region  302  various techniques can be used, such as adjusting the sub-pixel size, forming an opaque or semiopaque material layer to at least partially obscure the sub-pixels, adjusting the sub-pixel thickness or material, and/or adjusting driving voltage.  
      In the embodiment of  FIG. 3 , the sub-pixels disposed in the peripheral regions  302  and  303  are smaller than the sub-pixels  301  in the non-peripheral region  306 . Because the sub-pixels in the peripheral regions  302  and  303  are smaller than the sub-pixels of the non-peripheral region  306 , the effective brightness at the peripheral region  302  is reduced.  
      Alternatively, under the same design principle, the sub-pixels in the peripheral regions are reduced in size by only one-dimension or “one-direction reducing,” as shown in  FIG. 4  and  FIG. 5 . In  FIG. 4 , a pixel  300 A, including three sub-pixels  301 R A ,  301 G A  and  3 O 1 B A  disposed near the edge of the display panel, is shown. The reducing direction is the column direction (as indicated by the arrows). In other words, the length of each of the sub-pixels in the peripheral region  302 A is reduced. Similarly, as shown in  FIG. 5 , the reduction in size can be achieved in the row direction (as indicated by the arrows). In that embodiment, the width of each of the sub-pixels in the peripheral region  302 B is reduced.  
      Basically, the reduction ratio can be, for example, about 30%-70%. In other words, the size of the sub-pixels in the peripheral regions can be reduced to about 30%-70% relative to the sub-pixels disposed in the non-peripheral region. Therefore, the brightness of the sub-pixels in the peripheral regions is reduced to about 30%-70% of the original brightness.  
       FIG. 6  schematically shows another example. The size of the sub-pixel  301 R C  in the peripheral region  302 C is identical to that of the sub-pixels in the non-peripheral region  306 C. In the peripheral region  302 C, a portion of the sub-pixel  301 R C  is covered by an opaque material  502  leaving a central portion of the sub-pixel exposed. As a result, the central portion can produce the desired brightness. In other words, the brightness of the peripheral region  302 C is reduced by the opaque material. Also, the pattern of the opaque material  502  is not limited to the frame configuration shown in  FIG. 6 .  
       FIG. 7  schematically shows another example. The sub-pixel  301 R D  in the peripheral region  302 D is covered by a semi-opaque material  602 . As a result, the transmittance of the sub-pixel  301 R D  in the peripheral region  302 D is lower than that of the sub-pixels in the non-peripheral region  306 D.  
      The material of an opaque or semi-opaque layer(s) of a sub-pixel in a peripheral region can be a dielectric layer, a conductive layer, an organic layer, an inorganic layer or a combination thereof.  
       FIG. 8  schematically shows another example. In this embodiment, a sub-pixel  301 R E  in the peripheral region  302 E incorporates a color filter  702  that exhibits a lower transmittance than a color filter of another sub-pixel located in non-peripheral region  306 E. For reducing transmittance, a material of the color filter  702  can be different from the color filter of another sub-pixels, or a thickness of the color filter  702  can be thicker than the color filter of another sub-pixels. As a result, the brightness of the sub-pixels in the peripheral region  302 E can be reduced. Alternatively, a thickness of the sub-pixels in peripheral region can be adjusted for reduced brightness thereof, such as by increasing the thickness of the sub-pixels.  
       FIG. 9  schematically shows another example. When the image is displayed, a set of driving voltages is respectively applied to the sub-pixels. In this embodiment, the sub-pixels in non-peripheral region  306 F are connected to a first driving voltage V 1  and the sub-pixels in the peripheral region  302 F are connected to a second driving voltage V 2 , wherein the first driving voltage V 1  is different from the second driving voltage V 2 . When driving voltage is increased, transmittance is reduced in normally white-type LCDs. Thus, the second driving voltage V 2  applied on the sub-pixels in the peripheral region  302 F is set higher than the first driving voltage V 1  for the sub-pixels in the non-peripheral region  306 F.  
      Embodiments of systems for reducing color lines can be implemented with a variety of devices that incorporate displays. In  FIG. 10 , an embodiment of such a system incorporates a display device that comprises a display panel  700  and a control circuit  702  electrically connected to the display panel. The circuit  702  controls imaging of the display panel  700 . The display panel  700  can include pixel configurations such as mentioned above. Additionally, the display panel  700  can be for example, a liquid crystal display (LCD) panel, an electroluminescent (EL) display panel, such as an organic light emitting diode (OLED) display panel or inorganic light emitting diode display panel or a plasma display panel (PDP).  
       FIG. 11  is a diagram illustrating another embodiment of a system, in this case, an electronic device. In  FIG. 11 , the electronic device comprises a display device  800  and an input device  802  for providing input data to the display device  800 . The electronic device can be, for example, a television set, a computer system, a mobile phone, or a gaming device.  
      It will be apparent to those skilled in the art that various modifications and variations can be made to the structures described herein without departing from the scope or spirit of the invention.