Abstract:
A transflective liquid crystal display (LCD) includes at least a transmission pixel region and at least a reflection pixel region positioned in a pixel region. The transmission region includes at least a transmissive electrode connected to a first switching element. The reflection pixel region includes at least a reflective electrode connected to a second switching element. The transmissive and the reflective electrodes are controlled respectively by independent switching elements.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a liquid crystal display (LCD), and more particularly to a transflective LCD.  
           [0003]    2. Description of the Prior Art  
           [0004]    LCDs have been popularly applied to various IT products such as notebooks, personal digital assistants (PDAs), and cellular phones. Since LCDs are passive luminous devices, an external light source is required. According to different types of external light sources, LCDs are generally classified into reflective LCDs, transmissive LCDs, and transflective LCDs. In a reflective LCD, an external light in front of the panel enters the panel, and is reflected by a reflective layer (such as a aluminum layer) so that users can see what the LCD displays on the screen. In a transmissive LCD, a back light module is installed behind the panel for radiating light, and the radiating light will pass through the panel so that users can see what the LCD displays on the screen. In a transflective LCD, an external light and a back light module are used simultaneously as light sources to illuminate the transflective LCD.  
           [0005]    Please refer to FIG. 1. FIG. 1 is a schematic diagram of a pixel region  100  of a prior art transflective LCD, wherein the pixel region  100  is a red color, green color, or blue color pixel region. As shown in FIG. 1, the pixel region  100  comprises a reflection pixel region  110  and a transmission region  120 , wherein the reflection pixel region  110  includes a reflective electrode (not shown), and the transmission pixel region  120  comprises a transmissive electrode (not shown). The transmissive electrode (not shown) and the reflective electrode of a pixel region are connected to a pixel driving circuit  101  controlled by a scan line SL 1  and a data line DL 1 , and the luminance of the transmission pixel and the reflective pixel are controlled by the pixel driving circuit  101  simultaneously.  
           [0006]    The transmission mode of the prior art transflective LCD uses an internal back light module, while the reflection mode uses an external light. However, in the prior art a pixel driving circuit is used to control both a transmission pixel region and a reflection pixel region in the same pixel region, so only the transmission region or the reflection region can be controlled to its best color display. Therefore the total color display of the transflective LCD is reduced.  
         SUMMARY OF INVENTION  
         [0007]    It is therefore a primary objective of the claimed invention to provide a transflective LCD using two independent switching elements to control the transmission pixel region and the reflection pixel region so that both the transmission mode and the reflection mode can achieve best color display with any light sources.  
           [0008]    According to the claimed invention, the transflective LCD comprises a reflection region and a transmission region installed in a pixel region. The reflection region includes a reflective electrode connected to a first switching element, and the transmission region comprises a transmissive electrode connected to a second switching element, wherein the first switching element and the second switching element respectively control the function of reflection mode and transmission mode.  
           [0009]    It is an advantage of the claimed invention that the best color display of the transflective LCD can be achieved because the luminance of the reflection region and the transmission region are controlled separately by the first switching element and the second switching element.  
           [0010]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]    [0011]FIG. 1 is a schematic diagram of a pixel region of a prior art transflective LCD.  
         [0012]    [0012]FIG. 2 to FIG. 5 are schematic diagrams of a pixel region of a transflective LCD along the radiation direction of a back light module in the first embodiment of the present invention.  
         [0013]    [0013]FIG. 6 is a schematic diagram of a pixel region of a transflective LCD along the radiation direction of a back light module in the second embodiment of the present invention.  
         [0014]    [0014]FIG. 7 to FIG. 10 are schematic diagrams of a pixel region of a transflective LCD along the radiation direction of a back light module in the third embodiment of the present invention.  
         [0015]    [0015]FIG. 11 is a schematic diagram of a pixel region of a transflective LCD along the radiation direction of a back light module in the fourth embodiment of the present invention.  
         [0016]    [0016]FIG. 12 to FIG. 17 are cross-section diagrams of a transflective LCD of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]    Please refer to FIG. 2. FIG. 2 is a schematic diagram of a pixel region  200  of a transflective LCD along the radiation direction of a back light module in the first embodiment of the present invention, wherein the pixel region  200  is a red color pixel region, a green color pixel region, or a blue color pixel region. As shown in FIG. 2, the pixel region  200  includes a reflection region  210  and a transmission region  220 , the luminance of the reflection region  210  is controlled by a first switching element  201 , and the luminance of the transmission region  220  is controlled by a second switching element  202 . The switching elements  201  and  202  can be driving circuits sharing a scan line SL 1 , connect to data lines DL 1  and DL 2  by contact holes  203  and  204 , and receive image data signals from data lines DL 1  and DL 2  respectively. Furthermore, the first switching element  201  is connected to a reflective electrode (not shown) by a contact hole  205  for controlling the luminance of the reflection region  210 , and the second switching element  202  is connected to a transmissive electrode (not shown) by a contact hole  206  for controlling the luminance of the transmission region  220 . In this embodiment of the present invention, the data line DL 1 , DL 2  and the switching element  201 ,  202  are located below the reflection region  210  for not affecting the aperture ratio. It is worth noticing that the relative location and ratio of the reflection pixel region and the transmission pixel region can be modified according to circuit designs as shown in FIG. 3, FIG. 4, and FIG. 5.  
         [0018]    Please refer to FIG. 6. FIG. 6 is a schematic diagram of a pixel region  230  of a transflective LCD along the radiation direction of a back light module in the second embodiment of the present invention, wherein the pixel region  230  is a red color pixel region, a green color pixel region, or a blue color pixel region. As shown in FIG. 6, the pixel region  230  includes a reflection region  240  and a transmission region  250 , the luminance of the reflection region  230  is controlled by a first switching element  231 , and the luminance of the transmission region  250  is controlled by a second switching element  232 . The switching elements  231  and  232  are driving circuits sharing a scan line SL 1 , connect to data lines DL 12  and DL 21  by contact holes  233  and  234 , and receive image data signals from data lines DL 12  and DL 21  respectively. Furthermore, the first switching element  231  is connected to a reflective electrode (not shown) by a contact hole  235  for controlling the luminance of the reflection region  240 , and the second switching element  232  is connected to a transmissive electrode (not shown) by a contact hole  236  for controlling the luminance of the transmission region  250 . In this embodiment of the present invention, the data line DL 12  and the first switching element  231  are located below the reflection region  240 , while the data line DL 21  and the second switching element  232  are located below a reflection pixel region of a neighboring pixel region for not affecting the aperture ratio.  
         [0019]    Please refer to FIG. 7. FIG. 7 is a schematic diagram of a pixel region  300  of a transflective LCD along the radiation direction of a back light module in the third embodiment of the present invention, wherein the pixel region  300  is a red color pixel region, a green color pixel region, or a blue color pixel region. As shown in FIG. 7, the pixel region  300  includes a reflection region  310  and a transmission region  320 , the luminance of the reflection region  310  is controlled by a first switching element  301 , and the luminance of the transmission region  320  is controlled by a second switching element  302 . The switching elements  301  and  302  are respectively connected to a data line DL 1  by contact holes  303  and  304 . Furthermore, the first switching element  301  is connected to a reflective electrode (not shown) by a contact hole  305 , and the reflective electrode (not shown) receives a signal from the scan line SL 1  to switch the reflection region  310 . The second switching element  302  is connected to a transmissive electrode (not shown) by a contact hole  306 , and the transmissive electrode (not shown) receives a signal from the scan line SL 2  to switch the transmission region  320 . In this embodiment of the present invention, the scan lines SL 1 , SL 2  and the switching elements  301 ,  302  are located below the reflection region  310  for not affecting the aperture ratio. It is worth noticing that the relative location and ratio of the reflection pixel region and the transmission pixel region can be modified according to circuit designs as shown in FIG. 8, FIG. 9, and FIG. 10.  
         [0020]    Please refer to FIG. 11. FIG. 11 is a schematic diagram of a pixel region  350  of a transflective LCD along the radiation direction of a back light module in the fourth embodiment of the present invention, wherein the pixel region  350  is a red color pixel region, a green color pixel region, or a blue color pixel region. As shown in FIG. 11, the pixel region  350  includes a reflection region  360  and a transmission region  370 , the luminance of the reflection region  360  is controlled by a first switching element  351 , and the luminance of the transmission region  370  is controlled by a second switching element  352 . The switching elements  351  and  352  are respectively connected to a data line DL 1  by contact holes  353  and  354 . Furthermore, the first switching element  351  is connected to a reflective electrode (not shown) by a contact hole  355 , and the reflective electrode (not shown) receives a signal from the scan line SL 1  to switch the reflection region  360 . The second switching element  352  is connected to a transmissive electrode (not shown) by a contact hole  356 , and the transmissive electrode (not shown) receives a signal from the scan line SL 2  to switch the transmission region  370 . In this embodiment of the present invention, the scan lines SL 1  and the first switching element  351  are located below the reflection region  360 , while the scan line SL 2  and the second switching element  352  are located below a reflection pixel region of a neighboring pixel region for not affecting the aperture ratio.  
         [0021]    All embodiments of the present invention can be modified as follows. Please refer to FIG. 12 to FIG. 17. FIG. 12 to FIG. 17 are cross-section diagrams of a transflective LCD  400  of the present invention. As shown in FIG. 12 to FIG. 14, the transflective LCD  400  comprises a reflective electrode  410 , a transmissive electrode  420 , a first switching element  401 , and a second switching element  402 . The first switching element  401  is connected to a data line by a via hole  403  and is connected to the reflective electrode  410  by a via hole  405 , and the second switching element  402  is connected to a data line by a via hole  404 . The material of the transmissive electrode  420  can be doped or non-doped polysilicon, or doped or non-doped amorphous silicon. Furthermore, the transmissive electrode  420  can be connected directly to an active layer (source/drain) of the second switching element  402  as shown in FIG. 12 and FIG. 13, or the transmissive electrode  420  can be connected to the active layer of the second switching element  402  by the via hole  406  as shown in FIG. 14. Additionally, the transmissive electrode  420  can be an ITO or an IZO material, and is connected to the second switching element  402  by a via hole  406 , wherein the location of the transmissive electrode  420  can be modified as shown in FIG. 15 to FIG. 17. As shown in FIG. 15, the transmissive electrode  420  is located on the bottom layer of the second switching element  402 . As shown in FIG. 16, the transmissive electrode  420  and the scan line are located in the same layer. As shown in FIG. 17, the transmissive electrode  420  and the data line are located in the same layer.  
         [0022]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.