Patent Publication Number: US-9852706-B2

Title: Thin film transistor array substrate, display panel thereon, and method of testing single color image of display panel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Chinese Patent Application No. 201510696175.5 filed on Oct. 21, 2015, the contents of which are incorporated by reference herein. 
     FIELD 
     The present disclosure relates to display panels, and particularly to a thin film transistor (TFT) array substrate, for a display panel having a TFT array substrate, and a method of testing single color image of a display panel. 
     BACKGROUND 
     TFT display panels have become popular since they have advantages of compactness, low heat generation, long life, and ease of viewing. In general a display panel includes a backlight module, a first polarizer, a TFT array substrate, a color filter, and a second polarizer. The TFT array substrate forms a plurality of pixels thereon. Each pixel includes three sub-pixels, i.e., a red sub-pixel, a green sub-pixel, and a blue sub-pixel. For such an RGB TFT display panel, the backlight module consumes inordinate amounts of power in order to have sufficient light passing through the color filter. 
     An RGBW TFT display panel, in which each pixel includes a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel, avoids some disadvantages of the RGB TFT display panel. A transparent area corresponding to a white sub-pixel is defined in the color filter, whereby light transmittance of the color filter is improved, and the amount of power consumed by the backlight module can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is an exploded, cross-sectional view of a display panel in accordance with the present disclosure. 
         FIG. 2  is a schematic diagram of a TFT array substrate of the display panel of  FIG. 1 . 
         FIG. 3  is a schematic diagram of the TFT array substrate of the display panel of  FIG. 1  in concordance with a first embodiment of the present disclosure. 
         FIG. 4  is a schematic diagram of the TFT array substrate of the display panel of  FIG. 1  in concordance with a second embodiment. 
         FIG. 5  is a flow chart of a method of testing signal red color image of the display panel. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “substantially” is defined to be essentially conforming to the particular dimension, shape, or other feature that the term modifies, such that the component need not be exact. For example, “substantially cylindrical” means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series and the like. 
     The present disclosure is described in relation to an RGBW (red-green-blue-white) display panel, which can be used in a display screen, for example the screen of a smart phone, a monitor of a computer, a screen of a laptop, a screen of a television set, or a screen of a tablet computer. The display panel can be a Liquid Crystal Display (LCD) panel or an Organic Light Emitting Display (OLED) panel. 
       FIG. 1  illustrates an embodiment of a display panel  1 , which is a LCD panel. The display panel  1  can have, from the base to the top, a backlight module  10 , a first polarizer  20 , a thin film transistor (TFT) array substrate  30 , a liquid crystal layer  40 , a color filter  50 , and a second polarizer  60 . The TFT array substrate  30 , the liquid crystal layer  40 , the color filter  50 , and a driver circuit assembly (not shown) in combination construct an LCD module  70 . 
     The backlight module  10  can include a plurality of light emitting diodes (LEDs) or a plurality of cold cathode fluorescent lamps (CCFLs) as a light source for generating white light emitted through the first polarizer  20 , the TFT array substrate  30 , the liquid crystal layer  40 , the color filter  50 , and the second polarizer  60 . The first polarizer  20  can polarize the light, which means that only orthogonal light is allowed to pass through the first polarizer  20  to reach the TFT array substrate  30 . The liquid crystal layer  40  can include a plurality of liquid crystal molecules therein. An arrangement of the liquid crystal molecules can be changed in accordance with a change of a bias across the liquid crystal layer  40 , to adjust the amount of light passing through the liquid crystal layer  40 . In the illustrated embodiment, the color filter  50  is an RGBW color filter and has a plurality of pixels, each pixel a green sub-pixel, a red sub-pixel, a blue sub-pixel, and a white sub-pixel. The white sub-pixels are transparent whereby the light passing through the color filter  50  is increased. In comparison with an RGB color filter, the power needed by the backlight module  10  is decreased. The function of the second polarizer  60  can be similar to that of the first polarizer  20  and it allows only orthogonal light to pass through. 
       FIG. 2  illustrates an equivalent circuit  31  of the TFT array substrate  30  of the display panel  1 . The circuit  31  can include a plurality of pixels  311  arranged in a matrix, such as a 1920×1080 matrix of 5.5 inches in size. 
     For the sake of illustration,  FIG. 3  illustrates a pixel array of a 2×2 matrix. In fact, the actual pixel array can be more than the 2 rows and/or 2 columns shown in  FIG. 2 . 
     Each pixel  311  consists of a red sub-pixel  312 , a green sub-pixel  314 , a blue sub-pixel  316 , and a white sub-pixel  318 . The four sub-pixels  312 ,  314 ,  316 , and  318  are arranged in a substantially square matrix (i.e., 2×2 matrix). The red and green sub-pixels  312 ,  314  can be arranged as green-red pairs along one row (i.e., an odd row) and the blue and white sub-pixels  316 ,  318  can be arranged as blue-white pairs along a neighboring or an adjacent row (i.e., an even row). Thus the red and white sub-pixels  312 ,  318  can be arranged as red-white pairs in one column (i.e., an even column) and the green and blue sub-pixels  314 ,  316  arranged as green-blue pairs in a neighboring or an adjacent column (i.e., an odd column). In their row, the red and green sub-pixels  312 ,  314  alternate, and the blue and white sub-pixels  316 ,  318  also alternate. In their respective columns, the red and white sub-pixels  312 ,  318  alternate, and the green and blue sub-pixels  314 ,  316  also alternate. 
     In a vertical direction, a data line  332  and a data line  334  are arranged between some adjacent columns of sub-pixels of each pixel column. Thus, the data line  332  and the data line  334  are located between the sub-pixels  312 ,  314 ,  316 , and  318  of the pixel  311 . Another two data lines  336 ,  338  are arranged between the next adjacent columns of pixels. Thus, the data line  336  and the data line  338  are located between adjacent pixels along the row. A horizontal first scan line  320  is arranged between adjacent rows of sub-pixels of each pixel. Thus, the first scan line  320  is located between sub-pixels  312 ,  314 ,  316 , and  318  of the pixel  311 . A horizontal second scan line  322  is arranged between adjacent rows of pixels. Thus, the second scan line  322  is located between adjacent pixels along the column. The first and second scan lines  320 ,  322  can be orthogonal to the data lines  332 ,  334 ,  336 ,  338 . The data lines  332 ,  334 ,  336 ,  338  and the scan lines  320 ,  322  are electrically coupled to the red sub-pixel  312 , the green sub-pixel  314 , the blue sub-pixel  316 , and the white sub-pixel  318 . 
     For example, the red sub-pixel  312  of a first pixel (i.e., the pixel towards top left corner of the circuit  31  shown in  FIG. 3 ) can be electrically coupled to the first scan line  320  and the data line  336  via a thin film transistor (TFT)  313 . The TFT  313  can have a source electrode (not labeled) electrically coupled with the data line  336 , a gate electrode (not labeled) coupled with the first scan line  320 , and a drain electrode (not labeled) coupled with a pixel electrode (not labeled) of the red sub-pixel  312 . The red sub-pixel  312  of a second pixel (i.e., the pixel at top right corner of the circuit  31  shown in  FIG. 3 ), arranged in same row as the first pixel, can be electrically coupled to the first scan line  320  and the data line  334  adjacent to the red sub-pixel  312  via a thin film transistor (TFT). The red sub-pixels  312  of other pixels in same row as the first and second pixels can be electrically coupled to the first scan line  320  and one of the data lines  334 ,  336  in a similar way as with the red sub-pixel of the first pixel and the red sub-pixel of the second pixel. The red sub-pixel  312  of a third pixel (i.e. the pixel towards bottom left corner of the circuit  31  shown in  FIG. 3 ), arranged in same column as the first pixel, can be electrically coupled to the first scan line  320  and the data line  336  adjacent to the red sub-pixel  312  via a thin film transistor (TFT). The red sub-pixel  312  of a fourth pixel (i.e., the pixel towards bottom right corner of the circuit  31  shown in  FIG. 3 ), arranged in same column as the second pixel, can be electrically coupled to the first scan line  320  and the data line  334  adjacent to the red sub-pixel  312  via a thin film transistor (TFT). The red sub-pixels  312  of other pixels in same row as the third and fourth pixels can be electrically coupled to the first scan line  320  and one of the data lines  334 ,  336  in a similar way as with the red sub-pixel  312  of the third pixel and the red sub-pixel  312  of the fourth pixel. 
     Thus, the red sub-pixels  312  of the pixels of odd columns can be each electrically coupled to the first scan line  320  and the adjacent data line  336 , and the red sub-pixels of the pixels of even columns can be each electrically coupled to the first scan line  320  and the adjacent data line  334 . 
     The green sub-pixel  314  of the first pixel can be electrically coupled to the first scan line  320  and the adjacent data line  338  via a thin film transistor (TFT)  315 . The TFT  315  can have a source electrode coupled with the data line  338 , a gate electrode coupled with the first scan line  320 , and a drain electrode coupled with a pixel electrode of the green sub-pixel  314 . The green sub-pixel  314  of the second pixel, which arranged in a neighboring same row of the first pixel, can be electrically coupled to the first scan line  320  and the data line  332  adjacent to the green sub-pixel  314  via a thin film transistor (TFT). The green sub-pixels  314  of other pixels in same row as the first and second pixel can be electrically coupled to the first scan line  320  and one of the data lines  338 ,  332  in a similar way as with the green sub-pixel of the first pixel and the green sub-pixel of the second pixel. The green sub-pixel  314  of the third pixel, which arranged in a neighboring same column of the first pixel, can be electrically coupled to the first scan line  320  and the data line  338  adjacent to the green sub-pixel via a thin film transistor (TFT). The green sub-pixel  314  of the fourth pixel, arranged in same column as the second pixel, can be electrically coupled to the first scan line  320  and the data line  332  adjacent to the green sub-pixel via a thin film transistor (TFT). The green sub-pixels  314  of other pixels in same row as the third and fourth pixels can electrically coupled to the first scan line  320  and one of the data lines  338 ,  332  in a similar way as with the green sub-pixel of the third pixel and the green sub-pixel of the fourth pixel. 
     Thus, the green sub-pixels of the pixels of odd columns can be each electrically coupled to the first scan line  320  and the adjacent data line  338 , and the green sub-pixels of the pixels of even columns can be each electrically coupled to the first scan line  320  and the adjacent data line  332 . 
     The blue sub-pixel  316  of the first pixel can be electrically coupled to the second scan line  322  and the adjacent data line  332  via a thin film transistor (TFT)  317 . The TFT  317  can have a source electrode coupled with the data line  332 , a gate electrode coupled with the second scan line  322 , and a drain electrode coupled with a pixel electrode of the blue sub-pixel  316 . The blue sub-pixel  316  of the second pixel, arranged in same row as the first pixel, can be electrically coupled to the second scan line  322  and the data line  338  adjacent to the blue sub-pixel  316  via a thin film transistor (TFT). The blue sub-pixels  316  of other pixels in same row as the first and second pixels can be electrically coupled to the second scan line  322  and one of the data lines  332 ,  338  in a similar way as with the blue sub-pixel of the first pixel and the blue sub-pixel of the second pixel. The blue sub-pixel  316  of the third pixel, arranged in same column as the first pixel, can be electrically coupled to the second scan line  322  and the data line  332  adjacent to the blue sub-pixel via a thin film transistor (TFT). The blue sub-pixel  316  of the fourth pixel, arranged in same column as the second pixel, can be electrically coupled to the second scan line  322  and the data line  338  adjacent to the blue sub-pixel via a thin film transistor (TFT). The blue sub-pixels  316  of other pixels in same row as the third and fourth pixels can electrically coupled to the second scan line  322  and one of the data lines  332 ,  338  in a similar way as with the blue sub-pixel of the third pixel and the blue sub-pixel of the fourth pixel. 
     Thus, the blue sub-pixels of the pixels of odd columns can be each electrically coupled to the second scan line  322  and the adjacent data line  332 , and the blue sub-pixels of the pixels of even columns can be each electrically coupled to the second scan line  322  and the adjacent data line  338 . 
     The white sub-pixel  318  of the first pixel can be electrically coupled to the second scan line  322  and the adjacent data line  334  via a thin film transistor (TFT)  319 . The TFT  319  can have a source electrode coupled with the data line  334 , a gate electrode coupled with the second scan line  322 , and a drain electrode coupled with a pixel electrode of the white sub-pixel  318 . The white sub-pixel  318  of the second pixel, arranged in same row as the first pixel, can be electrically coupled to the second scan line  322  and the data line  336  adjacent to the white sub-pixel  318  via a thin film transistor (TFT). The white sub-pixels  318  of other pixels in same row as the first and second pixels can be electrically coupled to the second scan line  322  and one of the data lines  334 ,  336  in a similar way as with the white sub-pixel of the first pixel and the white sub-pixel of the second pixel. The white sub-pixel  318  of the third pixel, arranged in same column of the first pixel, can be electrically coupled to the second scan line  322  and the data line  334  adjacent to the white sub-pixel via a thin film transistor (TFT). The white sub-pixel  318  of the fourth pixel, arranged in same column as the second pixel, can be electrically coupled to the second scan line  322  and the data line  336  adjacent to the white sub-pixel via a thin film transistor (TFT). The white sub-pixels  318  of other pixels in same row as the third and fourth pixels can electrically coupled to the second scan line  322  and one of the data lines  334 ,  336  in a similar way as with the white sub-pixel of the third pixel and the white sub-pixel of the fourth pixel. 
     Thus, the white sub-pixels of the pixels of odd columns can be each electrically coupled to the second scan line  322  and the adjacent data line  334 , and the white sub-pixels of the pixels of even columns can be each electrically coupled to the second scan line  322  and the adjacent data line  336 . 
     The green sub-pixels  314  of the first and third pixels can be electrically coupled to the data line  338 . The green sub-pixels  314  of the first and third pixels, and the blue sub-pixels  316  in same column as the green sub-pixels  314  of the first and third pixels can be electrically coupled to the data line  332 . The data line  338  coupling with the green sub-pixels  314  of the first column of the pixels  311 , and the data line  332  coupling with the blue sub-pixels  316  of the first column of the pixels  311  can be coupled to a node coupling with a first data test point D 1 . The green sub-pixels  314  of the second and fourth pixels can be coupled to the data line  332 . The green sub-pixels  314  of the second and fourth pixels, and the blue sub-pixels  316  of the second and fourth pixels, can be electrically coupled to the data line  338 . The data line  332  coupling with the green sub-pixels  314  of the second and fourth pixels and the data line  338  coupling with the blue sub-pixels  316  of the second and fourth pixels can be coupled to a node in electrical coupling with a third data test point D 3 . Similarly, other pixels  311  can be in same electrical coupling relationship as the above. Such as, the data line  338  in electrical coupling with the green sub-pixels  314  of the pixels of an odd column, and the data line  332  in electrical coupling with the blue sub-pixels  316  of the pixels of the odd column can be in electrical coupling with the first data test point D 1 . The data line  332  coupling with the green sub-pixels  314  of the pixels of an even column, and the data line  338  in electrical coupling with the blue sub-pixels  316  of the pixels of the even column can be in electrical coupling with the third data test point D 3 . 
     The red sub-pixels  312  of the first and third pixels can be electrically coupled to the data line  336 . The red sub-pixels  312  of the first and third pixels, and the white sub-pixels  318  in same column as the red sub-pixels  312  of the first and third pixels can be electrically coupled to the data line  334 . The data line  336  coupling with the red sub-pixels  312  of the first column of the pixels  311 , and the data line  334  coupling with the white sub-pixels  318  of the first column of the pixels  311  can be coupled to a node in electrical coupling with a second data test point D 2 . The red sub-pixels  312  of the second and fourth pixels can be electrically coupled to the data line  334 . The red sub-pixels  312  of the second and fourth pixels, and the white sub-pixels  318  of the second and fourth pixels can be electrically coupled to the data line  336 . The data line  334  in electrical coupling with the red sub-pixels  312  of the second and fourth pixels and the data line  336  in electrical coupling with the white sub-pixels  318  of the second and fourth pixels can be coupled to a node in electrical coupling with a fourth data test point D 4 . Similarly, other pixels  311  can be in same electrical coupling relationship as the above. Such as, the data line  336  in electrical coupling with the red sub-pixels  312  of the pixels of an odd column, and the data line  334  in electrical coupling with the white sub-pixels  318  of the pixels of the odd column can be in electrical coupling with the second data test point D 2 . The data line  334  in electrical coupling with the red sub-pixels  312  of the pixels of an even column, and the data line  336  in electrical coupling with the white sub-pixels  318  of the even column can be in electrical coupling with the fourth data test point D 4 . 
     The green sub-pixel  314  of the first pixel can be coupled to the first scan line  320  in electrical coupling with a first scan test point S 1 . The blue sub-pixel  316  of the first pixel can be coupled to the second scan line  322  in electrical coupling with a second scan test point S 2 . The green sub-pixel  314  of the third pixel can be coupled to the first scan line  320  in electrical coupling with a third scan test point S 3 . The blue sub-pixel  316  of the third pixel can be coupled to the second scan line  322  in electrical coupling with a fourth scan test point S 4 . For other pixels, the coupling relationship can be similar. Such as, the first scan line  320  in electrically coupling with the green and red sub-pixels of the pixels of an odd row can be coupled with a first scan test point S 1 , and the first scan line  320  in electrically coupling with the green and red sub-pixels of the pixels of an even row can be coupled with a third scan test point S 3 . The second scan line  322  in electrically coupling with the blue and white sub-pixels of the pixels of an odd row can be coupled with a second scan test point S 2 , and the second scan line  322  in electrically coupling with the blue and white sub-pixels of the pixels of an even row can be coupled with a fourth scan test point S 4 . 
     In the illustrated embodiment, the sub-pixels which are in connection with a same data line of the data lines  332 ,  334 ,  336 , and  338  have a same polarity (either positive electrode or negative electrode). 
       FIG. 5  constitutes a flow chart of a method of testing signal red color image of the display panel. The method is provided by way of example, as there are a variety of ways to carry out the method. The method of testing signal red color image of the display panel described below can be carried out using the configurations illustrated in  FIGS. 1 to 4 , for example, and various elements of these figures are referenced in explaining the example method. Each block shown in  FIG. 5  represents one or more processes, methods, or subroutines carried out in the example method. Furthermore, the illustrated order of blocks is by example only and the order of the blocks can be changed. Additional blocks may be added or fewer blocks may be utilized, without departing from this disclosure. The example method can begin at block  101 . 
     At block  101 , each of the first and the third scan test points S 1 , S 3  can apply a high level voltage. 
     At block  102 , each of the second and fourth scan test points S 2 , S 4  can apply a low level voltage. 
     At block  103 , each of the first and third data test points D 1 , D 3  can apply a low level voltage. 
     At block  104 , the second data test point D 2  can apply a positive high level voltage, and the fourth data test point D 4  can apply a negative high level voltage. 
     At block  105 , the display panel can display a single red color. At that moment, the electrode of the red sub-pixel of the first pixel can be positive, and the electrode of the red sub-pixel of the second pixel can be negative. Similarly, the electrode of the red sub-pixel of the third pixel can be positive, and the electrode of the red sub-pixel of the fourth pixel can be negative. In other words, the red sub-pixels of adjacent pixels in a same row have opposite polarities. 
     This is similar to when the display panel  1  displays other single colors. Each of the first and third scan test points S 1 , S 3  can apply voltages of different levels relative to a voltage applied to each of the second and fourth scan test points S 2 , S 4 . Each of the first and third data test points D 1 , D 3  can apply voltages of different levels relative to a voltage applied to each of the second and fourth data test points D 2 , D 4 . The first and third data test points D 1 , D 3 , or the second and fourth data test points D 2 , D 4 , which apply high level voltages have opposite voltage polarities. Thus, the green sub-pixels  314  of adjacent pixels in the same row have opposite polarities, and the blue sub-pixels  316  of adjacent pixels in the same row have opposite polarities, and the white sub-pixels  318  of adjacent pixels in the same row have opposite polarities. That is, a red (green, blue, white) sub-pixel  312  ( 314 ,  316 , and  318 ) and a neighboring red (green, blue, white) sub-pixel in the same row have opposite polarities. 
     By such arrangement, the coupling effects caused by capacitors (i.e., Cscs) of each two neighboring columns of the pixels  311  on the waveform of an common electrode can be offset from each other to obviate horizontal crosstalk, wherein the capacitor is a capacitor interconnecting a data line and a common electrode for supplying a bias across the liquid crystal layer  40 . Flicker of the single color display can thus be reduced. The common electrode of the pixels  311  and the capacitors are well known by those skilled in the art, thus detailed descriptions thereof are omitted here. 
       FIG. 4  illustrates a second embodiment of a circuit  31  of the TFT array substrate  30  of the display panel  1 . A structure of the TFT array substrate  30  of the second embodiment is similar to a structure of the TFT array substrate  30  of the first embodiment shown in  FIG. 3 . Differences in the second embodiment are as follows. 
     There are two data test points D 1  to D 4  and two scan test points S 1  to S 4 . The two groups of the data test points D 1  to D 4  are respectively positioned at opposite sides horizontally of the display panel  1 . The two groups of the scan test points S 1  to S 4  are respectively positioned at opposite sides vertically of the display panel  1 . 
     When testing single color image of the display panel  1 , a voltage can be applied by both of the two first data test points D 1 , by the two second data test points D 2 , by the two third data test points D 3 , and by the two fourth data test points. Such voltage can also be applied by two first scan test points S 1 , two second scan test points S 2 , two third scan test points S 3 , and two fourth scan test points S 4 . Thus, the electric current can be shared to the data test points D 1  to D 4  and the scan test points S 1  to S 4 . 
     The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in particular the matters of shape, size, and arrangement of parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims.