Patent Publication Number: US-8115880-B2

Title: Liquid crystal display panel and display apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 2008-114873 filed in Japan on Apr. 25, 2008, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a liquid crystal display (LCD) panel and a display apparatus. 
     2. Related Art 
     According to the development of the LCD technology, which has the advantages of light and non-radiation, the LCD apparatus has been widely applied to various kinds of electronic products to replace the traditional CRT (cathode ray tube) display apparatus. The LCD panel includes a TFT (thin-film transistor) substrate, a CF (color filter) substrate and a liquid crystal layer, which is disposed between the TFT substrate and the CF substrate. The TFT substrate has a storage capacitor electrode and a plurality of pixel unit, and the CF substrate has a common electrode. 
       FIG. 1A  is a schematic illustration showing a portion of the conventional TFT substrate B, and  FIG. 1B  is a schematic illustration showing an equivalent circuit of the conventional LCD panel. As shown in  FIG. 1A , each pixel unit  11  of the TFT substrate B includes a switching element  111  and a pixel electrode  112 . As shown in  FIGS. 1A and 1B , the pixel electrode  112  and the storage capacitor electrode  12  form a storage capacitance Cs. The pixel electrode  112  and the common electrode  13  of the CF substrate (not shown) form a liquid crystal capacitance Clc. The switching elements  111  are electrically connected to the data lines D i , D i+1  and the scan lines S j , S j+1 . The storage capacitor electrode  12  and the common electrode  13  are electrically connected to a storage capacitor electrode driving circuit  14  and a common electrode driving circuit  15 , respectively. 
     When the switching element  111  is turned on by the scan signal Sg j  transmitted through the scan line S j , the image voltage signal Vg i  can be written into the pixel electrode  112  of each pixel unit  11  through the data line D i . At the same time, the storage capacitor electrode driving circuit  14  outputs a storage capacitor voltage level signal Vs to the storage capacitor electrode  12 , and the common electrode driving circuit  15  outputs a common voltage level signal Vcom to the common electrode  13 , thereby maintaining the storage capacitor electrode  12  and the common electrode  13  at a constant voltage value or a preset AC voltage. 
       FIG. 1C  is a schematic illustration showing the variations of the conventional storage capacitor voltage level signal Vs and common voltage level signal Vcom when the image voltage signal Vg i  is written. As shown in  FIGS. 1B and 1C , the voltage of the data line D i  is changed during the period that the image voltage signal Vg i  is written into the data line D i . The voltage change of the data line D i  can make the pixel electrode  112 , the storage capacitor electrode  12  and the common electrode  13  generate voltage variation through the capacitance coupling effect. Herein, the voltage variation of the storage capacitor voltage level signal Vs is represented by the symbol Vd 2 . In addition, the image voltage signal Vg i  is written into the pixel unit  11  on the same scan line S j  through the data line D i . Thus, the storage voltage level signal Vs and the common voltage level signal Vcom of the storage capacitor electrode  12  and the common electrode  13  on the same scan line S j  can generate voltage variation through the capacitance coupling effect, which can make the pixel electrode voltage generate voltage variation. Then, the voltage variation Vd 1  of the storage voltage level signal Vs may exist, which leads to the lateral crosstalk issue of the display screen on the LCD panel  1 . 
     Therefore, it is an important subject to provide an LCD panel that can improve the lateral crosstalk issue. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, the invention is to provide an LCD panel that can improve the lateral crosstalk issue. 
     To achieve the above, the invention discloses an LCD panel including a first substrate, a second substrate, a common electrode driving circuit and a reverse gain circuit. The first substrate includes a storage capacitor electrode, and the second substrate, which is disposed oppositely to the first substrate, includes a common electrode. The common electrode driving circuit is electrically connected with the common electrode and outputs a common voltage level signal to the common electrode. The reverse gain circuit is electrically connected to the storage capacitor electrode through a connecting terminal and outputs a reverse gain voltage signal to the common electrode according to a voltage signal of the storage capacitor electrode. 
     In addition, the invention further discloses an LCD panel including a first substrate, a second substrate, a storage capacitor electrode driving circuit and a reverse gain circuit. The first substrate includes a storage capacitor electrode, and the second substrate, which is disposed oppositely to the first substrate, includes a common electrode. The storage capacitor electrode driving circuit is electrically connected with the storage capacitor electrode and outputs a storage capacitor voltage level signal to the storage capacitor electrode. The reverse gain circuit is electrically connected to the storage capacitor electrode through a connecting terminal and outputs a reverse gain voltage signal to the storage capacitor electrode according to a voltage signal of the storage capacitor electrode. 
     Furthermore, the invention also discloses an LCD panel including a first substrate, a second substrate, a storage capacitor electrode driving circuit and a reverse gain circuit. The first substrate includes a storage capacitor electrode, and the second substrate, which is disposed oppositely to the first substrate, includes a common electrode. The storage capacitor electrode driving circuit outputs a storage capacitor voltage level signal to the storage capacitor electrode. The reverse gain circuit is electrically connected to the common electrode through a connecting terminal and outputs a reverse gain voltage signal to the storage capacitor electrode according to a voltage signal of the common electrode. 
     To achieve the above, the invention also discloses a display apparatus including a display panel and an input unit. The display panel includes a first substrate, a second substrate, a common electrode driving circuit and a reverse gain circuit. The first substrate includes a storage capacitor electrode, and the second substrate, which is disposed oppositely to the first substrate, includes a common electrode. The common electrode driving circuit is electrically connected with the common electrode and outputs a common voltage level signal to the common electrode. The reverse gain circuit is electrically connected to the storage capacitor electrode through a connecting terminal and outputs a reverse gain voltage signal to the common electrode according to a voltage signal of the storage capacitor electrode. The input unit is coupled to the display panel for transmitting signals to the display panel for control the display panel to display image. 
     As mentioned above, the LCD panel of the invention has a reverse gain circuit electrically connected to the storage capacitor electrode. The reverse gain circuit can output a reverse gain voltage signal to the common electrode according to the voltage signal of the storage capacitor electrode so as to compensate the voltage variation of the common voltage level signal. The reverse gain voltage signal can not only compensate the voltage variation of the common voltage level signal, but also indirectly compensate the voltage variation of the storage capacitor voltage level signal. 
     In addition, the reverse gain circuit can output the reverse gain voltage signal to the storage capacitor electrode to compensate the voltage variation of the storage capacitor voltage level signal. Similarly, the reverse gain voltage signal can not only compensate the voltage variation of the storage capacitor voltage level signal, but also indirectly compensate the voltage variation of the common voltage level signal. 
     Furthermore, the reverse gain circuit can be electrically connected to the common electrode and output the reverse gain voltage signal to the storage capacitor electrode according to a voltage signal of the common electrode so as to compensate the voltage variation of the storage capacitor voltage level signal. The reverse gain voltage signal can not only compensate the voltage variation of the storage capacitor voltage level signal, but also indirectly compensate the voltage variation of the common voltage level signal. 
     Accordingly, the voltage variations of the common electrode and the storage capacitor electrode, which are caused by the writing of the image voltage signal, can be compensated by the reverse gain circuit. Thus, the lateral crosstalk issue of the LCD panel, which is caused by the voltage variations of the common electrode and the storage capacitor electrode, can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will become more fully understood from the detailed description and accompanying drawings, which are given for illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1A  is a schematic illustration showing a portion of the conventional TFT substrate; 
         FIG. 1B  is a schematic illustration showing an equivalent circuit of the conventional LCD panel; 
         FIG. 1C  is a signal waveform illustration showing the variations of the conventional storage capacitor voltage level signal and common voltage level signal when the image voltage signal is written; 
         FIG. 2A  is a sectional view of an LCD panel according to a first embodiment of the invention; 
         FIG. 2B  is a schematic illustration of an equivalent circuit of the LCD panel according to the first embodiment of the invention; 
         FIG. 2C  is a signal waveform illustration showing the variations of the storage capacitor voltage level signal and common voltage level signal of the invention; 
         FIG. 3  is a schematic illustration of an equivalent circuit of another LCD panel according to the first embodiment of the invention; 
         FIG. 4  is a schematic illustration of an equivalent circuit of an LCD panel according to a second embodiment of the invention; 
         FIG. 5  is a schematic illustration of an equivalent circuit of an LCD panel according to a third embodiment of the invention; and 
         FIG. 6  is a schematic illustration of a display apparatus of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
     First Embodiment 
       FIG. 2A  is a sectional view of an LCD panel  2  according to a first embodiment of the invention, and  FIG. 2B  is a schematic illustration of an equivalent circuit of the LCD panel  2 . With reference to  FIGS. 2A and 2B , the LCD panel  2  includes a first substrate B 1 , a second substrate B 2 , a common electrode driving circuit  25  and a reverse gain circuit  26 . 
     As shown in  FIGS. 2A and 2B , the first substrate B 1  is, for example, a TFT substrate, which includes a storage capacitor electrode  22 . The first substrate B 1  has a plurality of pixel units  21 . Each pixel unit  21  includes a switching element  211  and a pixel electrode  212 , which are electrically connected with each other. The switching elements  211  are further electrically connected to the data lines D i , D i+1  and the scan lines S j , S j+1 , respectively. The pixel electrode  212  and the storage capacitor electrode  22  form a storage capacitance Cs. In the embodiment, the switching element  211  is, for example, a thin-film transistor. The source of the switching element  211  is electrically connected with the data line D i  or D i+1 , the gate thereof is electrically connected with the scan line S j  or S j+1 , and the drain thereof is electrically connected with the pixel electrode  212 . 
     The second substrate B 2  is, for example, a CF substrate, which has a common electrode  23  and is disposed oppositely to the first substrate B 1 . The common electrode  23  and the pixel electrode  212  form a liquid crystal capacitance Clc. In addition, the second substrate B 2  further includes a black matrix layer  27 , a color filter layer  28  and an insulation layer  29 . A spacer P is disposed between the first substrate B 1  and a second substrate B 2 . 
     The common electrode driving circuit  25  is electrically connected to the common electrode  23  and outputs a common voltage level signal Vcom to the common electrode  23 . 
     The reverse gain circuit  26  is electrically connected to the storage capacitor electrode  22  through a connecting terminal. The connecting terminal can be a monitoring terminal or a wire. In the embodiment, the connecting terminal is a wire W for example. 
     In addition, the LCD panel  2  further includes a storage capacitor electrode driving circuit  24 , which is electrically connected to the storage capacitor electrode  22  and outputs a storage capacitor voltage level signal Vs to the storage capacitor electrode  22 . 
     As mentioned above, the storage capacitor electrode  22  and the common electrode  23  are respectively driven by the storage capacitor voltage level signal Vs and the common voltage level signal Vcom, which are inputted from the storage capacitor electrode driving circuit  24  and the common electrode driving circuit  25 , respectively. Thus, the storage capacitor electrode  22  and the common electrode  23  can be maintained at a constant voltage value or a preset AC voltage. 
     When the switching element  211  is turned on by the scan signal Sg j  transmitted through the scan line S j , the image voltage signal Vg i  can be written into the pixel electrode  212  of the pixel unit  21  through the data line D i . 
       FIG. 2C  is a schematic illustration showing the variations of the storage capacitor voltage level signal and common voltage level signal of the invention. Referring to  FIGS. 2B and 2C , the reverse gain circuit  26  can detect the voltage signal V 1  (Vs) of the storage capacitor electrode  22 . When the voltage variation of the voltage signal V 1  (Vs), such as Vd 2  as shown in  FIG. 2C , is generated according to the capacitance coupling effect between the data line D i  and the storage capacitor electrode  22 , the reverse gain circuit  26  can output a reverse gain voltage signal R 1  with respect to the voltage variation. For example, if the voltage variation is −0.3V, the reverse gain circuit  26  can make a calculation with respect to the voltage variation as:
 
−(−0.3)× G= 0.3 G  
 
     The reverse gain circuit  26  firstly reverses the sign of the voltage variation and then multiplies the reversed voltage variation with a gain G. The gain G can be between 1 and 100. In the embodiment, the gain G is, for example but not limited to, 10. Thus, the reverse gain circuit  26  outputs the reverse gain voltage signal R 1  of 3V to the common electrode  23  so as to compensate the voltage variation of the common voltage level signal Vcom of the common electrode  23 . 
     By compensating the common voltage level signal Vcom, the voltage variation of the storage capacitor voltage level signal Vs of the storage capacitor electrode  22  can also be compensated (Vd 1  approaches 0) due to the electric charge transmission between the liquid crystal capacitance Clc and the storage capacitance Cs. Accordingly, the lateral crosstalk issue of the LCD panel  2  caused by the voltage variations of the storage capacitor electrode  22  and the common electrode  23  can be improved. 
       FIG. 3  is a schematic illustration of an equivalent circuit of another LCD panel, which includes another common electrode driving circuit  25   a , according to the first embodiment of the invention. With reference to  FIG. 3 , the common electrode driving circuit  25   a  includes a common electrode driving unit  251  and an adder  252 . The adder  252  is electrically connected to the common electrode driving unit  251  and the reverse gain circuit  26 . The adder  252  can adjust the common voltage level signal Vcom according to the reverse gain voltage signal R 1 . 
     Second Embodiment 
       FIG. 4  is a schematic illustration of an equivalent circuit of an LCD panel  3  according to a second embodiment of the invention. With reference to  FIG. 4 , the difference between the LCD panel  3  and the LCD panel  2  of the first embodiment is in that the reverse gain circuit  36  of the LCD panel  3  outputs a reverse gain voltage signal R 1  to the storage capacitor electrode  32  so as to compensate the voltage variation of the storage capacitor voltage level signal Vs of the storage capacitor electrode  32 . 
     Similarly, after compensating the storage capacitor voltage level signal Vs, the voltage variation of the common voltage level signal Vcom of the common electrode  33  can be compensated due to the electric charge transmission between the storage capacitance Cs and the liquid crystal capacitance Clc. 
     In addition, the storage capacitor electrode driving circuit can also include a storage capacitor electrode voltage driving unit and an adder (not shown) as that of the first embodiment. The adder is electrically connected to the storage capacitor electrode driving unit and the reverse gain circuit  36 , so that it can adjust the storage capacitor voltage level signal Vs according to the reverse gain voltage signal R 1 . 
     Third Embodiment 
       FIG. 5  is a schematic illustration of an equivalent circuit of an LCD panel  4  according to a third embodiment of the invention. With reference to  FIG. 5 , the difference between the LCD panel  4  and the LCD panel  2  of the first embodiment is in that the reverse gain circuit  46  of the LCD panel  4  is electrically connected to the common electrode  43  and outputs a reverse gain voltage signal R 2  to the storage capacitor electrode  42  according to the voltage signal V 2  of the common electrode  43  so as to compensate the voltage variation of the storage capacitor voltage level signal Vs of the storage capacitor electrode  42 . 
     Similarly, after compensating the storage capacitor voltage level signal Vs, the voltage variation of the common voltage level signal Vcom of the common electrode  43  can be compensated due to the electric charge transmission between the storage capacitance Cs and the liquid crystal capacitance Clc. 
     In addition, the storage capacitor electrode driving circuit can also include a storage capacitor voltage driving unit and an adder (not shown) as that of the second embodiment. The adder is electrically connected to the storage capacitor electrode driving unit and the reverse gain circuit  46 , so that it can adjust the storage capacitor voltage level signal Vs according to the reverse gain voltage signal R 2 . 
     With reference to  FIG. 6 , a display apparatus  5  of the invention can be applied to a mobile phone, a digital camera, a personal digital assistant (PDA), a laptop computer, a desktop computer, a television, a vehicle display, a global positioning system (GPS), a flight display, a digital photo frame, or a portable DVD player. The display apparatus  5  includes a display panel  6  and an input unit  7 . The input unit  7  is coupled to the display panel  6  for transmitting signals I to the display panel  6  for control the display panel  6  to display image. 
     Herein, the display panel  6  includes the LCD panel  2  of the first embodiment. In addition, the display panel  6  may include the LCD panel  3  or  4  of the previous mentioned second or third embodiment. The structures of the LCD panels  2 ,  3  and  4  are described in the above-mentioned embodiments, so the detailed descriptions thereof will be omitted. 
     In summary, the LCD panel of the invention has a reverse gain circuit electrically connected to the storage capacitor electrode. The reverse gain circuit can output a reverse gain voltage signal to the common electrode according to the voltage signal of the storage capacitor electrode so as to compensate the voltage variation of the common voltage level signal. The reverse gain voltage signal can not only compensate the voltage variation of the common voltage level signal, but also indirectly compensate the voltage variation of the storage capacitor voltage level signal. 
     In addition, the reverse gain circuit can output the reverse gain voltage signal to the storage capacitor electrode to compensate the voltage variation of the storage capacitor voltage level signal. Similarly, the reverse gain voltage signal can not only compensate the voltage variation of the storage capacitor voltage level signal, but also indirectly compensate the voltage variation of the common voltage level signal. 
     Furthermore, the reverse gain circuit can be electrically connected to the common electrode and output the reverse gain voltage signal to the storage capacitor electrode according to a voltage signal of the common electrode so as to compensate the voltage variation of the storage capacitor voltage level signal. The reverse gain voltage signal can not only compensate the voltage variation of the storage capacitor voltage level signal, but also indirectly compensate the voltage variation of the common voltage level signal. 
     Accordingly, the voltage variations of the common electrode and the storage capacitor electrode, which are caused by the writing of the image voltage signal, can be compensated by the reverse gain circuit. Thus, the lateral crosstalk issue of the LCD panel, which is caused by the voltage variations of the common electrode and the storage capacitor electrode, can be improved. 
     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.