Patent Publication Number: US-2010128065-A1

Title: Driving method and display utilizing the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of Taiwan Patent Application No. 97145667, filed on Nov. 26, 2008, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a driving method and a display. 
     2. Description of the Related Art 
     Because cathode ray tubes (CRTs) are inexpensive and provide high definition, they are utilized extensively in televisions and computers. With technological development, new flat-panel displays are continually being developed. When a larger display panel is required, the weight of the flat-panel display does not substantially change when compared to CRT displays. 
     BRIEF SUMMARY OF THE INVENTION 
     Displays are provided. An exemplary embodiment of a display comprises a scan driver, a data driver, a first pixel, and a second pixel. The scan driver provides a first scan signal and a second scan signal. The data driver provides a data signal. The first pixel receives the first scan signal and displays a first color. The second pixel receives the second scan signal and displays a second color. The frequency of the first scan signal and the frequency of the second scan signal relate to the first color and the second color. 
     A driving method for a display is provided. An exemplary embodiment of a driving method for a display comprising a scan driver, a data driver, a first pixel displaying a first color, and a second pixel displaying a second color is described in the following. The scan driver is activated to provide a first scan signal to the first pixel. The scan driver is activated to provide a second scan signal to the second pixel. The frequency of the first scan signal and the frequency of the second scan signal relate to the first color and the second color. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1A  is a schematic diagram of an embodiment of a display; 
         FIG. 1B  is a structure diagram of an embodiment of the display; 
         FIG. 2  is a timing chart of scan signals; 
         FIG. 3  is a timing chart of another embodiment of scan signals 
         FIG. 4A  is a schematic diagram of another embodiment of the display; 
         FIGS. 4B-4D  are structure diagrams of other embodiments of the display; 
         FIG. 5  is a timing chart of an embodiment of scan signals shown in  FIG. 4A ; and 
         FIG. 6  is a flowchart of an embodiment of a driving method. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
       FIG. 1A  is a schematic diagram of an embodiment of a display. The display  100  comprises a scan driver  110 , a data driver  120 , and pixels P 11 ˜P mn . In this embodiment, the pixels P 11 ˜P mn  are not stacked together. The display  100  may be a cholesteric liquid crystal display (ChLCD), an electrophoresis display (EPD), an electro chromic display (ECD), or a twisting ball display (TBD). 
     The scan driver  110  provides scan signals SS 1 ˜SS n  to the pixels P 11 ˜P mn  via scan lines SL 1 ˜SL n . The frequencies of scan signals SS 1 ˜SS n  relate to the color displayed by the pixels P 11 ˜P mn . Assume the color displayed by a first pixel among is the pixels P 11 ˜P mn  is different from the color displayed by a second pixel among the pixels P 11 ˜P mn , then in this embodiment, the frequency of a first scan signal received by the first pixel is different from the frequency of a second scan signal received by the second pixel. 
     For example, if the color (such as red) displayed by the pixels P 11 , P 21 , . . . , and P m1  is different from the color (such as green) displayed by the pixels P 12 , P 22 , . . . , and P m2 , the frequency of the scan signal SS 1  is different from the frequency of the scan signal SS 2 . Similarly, if the color (such as red) displayed by the pixels P 11 , P 21 , . . . , and P m1  is different from the color (such as blue) displayed by the pixels P 13 , P 23 , . . . , and P m3 , the frequency of the scan signal SS 1  is different from the frequency of the scan signal SS 3 . 
     In another embodiment, the frequency of a first scan signal among the scan signals SS 1 ˜SS n  is the same as the frequency of a second scan signal among the scan signals SS 1 ˜SS n  when the color displayed by a first pixel among the pixels P 11 ˜P mn  is the same as the color displayed by a second pixel among the pixels P 11 ˜P mn . In this case, the first pixel receives the first scan signal and the second pixel receives the second scan signal. For example, the pixels P 13 , P 23 , . . . , P m3 , P 1n , P 2n , . . . , and P mn  display the same color, such as blue. Thus, the frequency of the scan signal SS 3  is the same as the frequency of the scan signal SS n . 
     The data driver  120  provides data signals SD 1 ˜SD m  to the pixels P 11 ˜P mn  via data lines DL 1 ˜DL m . The brightness or gray levels of the pixels P 11 ˜P mn  relates to the duration of data signals SD 1 ˜SD mn . Taking the pixel P 11  as an example, when the duration of the data signal SD 1  provided by the data driver  120  becomes longer, the brightness of the pixel P 11  becomes brighter. Similarly, when the duration of the data signal SD 1  provided by the data driver  120  becomes shorter, the brightness of the pixel P 11  becomes darker. Thus, the brightness of the pixels P 11 ˜P mn  can be controlled according to the duration of the data signals SD 1 ˜SD mn . 
       FIG. 1B  is a structure diagram of an embodiment of the display. The display comprises two panels stacked together. Each panel comprises a plurality of pixels. The pixels in one panel are stacked with the pixels in another panel. Taking a ChLCD as an example, each pixel may comprise a levorotary cholesteric liquid component or a dextrorotatory cholesteric liquid component to increase reflectivity. For example, the pixel P 11  comprises the levorotary cholesteric liquid component and the pixel P′ 11  comprises the dextrorotatory cholesteric liquid component. In this embodiment, when the color of a first pixel is different from the color of a second pixel, the frequency of a first scan signal is different from the frequency of a second scan signal, wherein he first scan signal is provided to the first pixel and the second scan signal is provided to the second pixel. 
       FIG. 2  is a timing chart of scan signals. For clarity, only four scan signals SS 1 , SS 2 , SS 3 , and SS n  are shown. Referring to  FIG. 1A , since the pixels P 11 , P 12 , and P 13  display the different colors, the frequencies of scan signals SS 1 , SS 2 , and SS 3  are different. In this embodiment, the frequency of the scan signal SS 1  is higher than the frequencies of scan signals SS 2 , and SS 3 . The frequency of the scan signal SS 2  is higher than the frequency of the scan signal SS 3 . In some embodiments, the frequency of the scan signal SS 1  may be less than the frequency of the scan signal SS 2  or the frequency of the scan signal SS 3 . 
     Since the color displayed by the pixel P 13  is the same as the color displayed by the pixel P 1n , the frequency of the scan signal SS 3  is the same as the frequency of the scan signal SS n . In this embodiment, the amplitudes of the scan signals SS 1 , SS 2 , SS 3 , and SS n  are the same, but the disclosure is not limited thereto. The amplitudes of the scan signals SS 1 , SS 2 , SS 3 , and SS n  can be changed according to the kind of the display. For example, if the display is a ChLCD, each pixel comprises cholesteric liquid crystal molecules. The arrangement of cholesteric liquid crystal molecules is determined by the voltage difference between a scan signal and a data signal. 
     In one embodiment, the frequency of the data signal SD 1  received by the pixel P 11  is the same as or different from the frequency of the scan signal SS 1 . In some embodiments, a phase difference arises between the data signal SD 1  and the scan signal SS 1 . The phase difference may be 180°. 
       FIG. 3  is a timing chart of another embodiment of scan signals  FIG. 3  is similar to  FIG. 2  except for the addition of a reset period. The reset period is composed of periods TR 1  and TR 2 . 
     During the period TR 1 , the scan signals SS 1 , SS 2 , SS 3 , and SS n  with amplitude Vp are provided to the pixels. During the period TR 2 , the scan signals SS 1 , SS 2 , SS 3 , and SS n  with amplitude 0V are provided to the pixels P 11 ˜P mn . Thus, the arrangement of the pixels is a planar type. For example, the arrangement of the pixels may be changed from a focal conic type to the planar type or may be maintained in the planar type. At this time, the pixels P 11 ˜P mn  are lighted. In this embodiment, the amplitude Vscan of the scan signal after the period TR 2  is less than the amplitude Vp of the scan during the period TR 1 . 
       FIG. 4A  is a schematic diagram of another embodiment of the display.  FIG. 4A  is similar to  FIG. 1  with the exception of the arrangement of the pixels P 11 ˜P mn . As shown in  FIG. 4A , the pixels displaying the same color are coupled to the different scan lines. For example, the pixels P 11 , P 12 , . . . , and P 1n  display red and are coupled to the scan lines SL 1 , SL 2 , . . . , and SL n  respectively. 
       FIG. 5  is a timing chart of an embodiment of scan signals shown in  FIG. 4A . For clarity, only three scan signals SS 1 , SS 2 , and SS n  are shown. During a period T 1 , the scan signal SS 1  comprises a first frequency. At this time, the frequency and the amplitude of the data signals are controlled such that a portion of the pixels coupled to the scan line SL 1  display the same color. In one embodiment, the pixels comprising the pixel P 11  and coupled to the scan line SL 1  display red according to the voltage difference between the scan signal SS 1  and the data signal. 
     During a period T 2 , the scan signal SS 1  comprises a second frequency. At this time, the frequency and the amplitude of the data signals are controlled such that another portion of the pixels coupled to the scan line SL 1  display the same color. In one embodiment, the pixels comprising the pixel P 21  and coupled to the scan line SL 1  display green according to the voltage difference between the scan signal SS 1  and the data signal. 
     During a period T 3 , the scan signal SS 1  comprises a third frequency. At this time, the frequency and the amplitude of the data signals are controlled such that the other portion of the pixels coupled to the scan line SL 1  display the same color. In one embodiment, the pixels comprising the pixels P 31  and P m1  and coupled to the scan line SL 1  display blue according to the voltage difference between the scan signal SS 1  and the data signal. 
     During a period T 4 , the scan signal SS 2  comprises a first frequency. At this time, the frequency and the amplitude of the data signals are controlled such that a portion of the pixels coupled to the scan line SL 2  display the same color. In this embodiment, the frequency of the scan signal SS 2  during the period T 4  is the same as the frequency of the scan signal SS 1  during the period T 1 . Thus, the pixels comprising the pixel P 12  and coupled to the scan line SL 2  display red according to the voltage difference between the scan signal SS 2  and the data signal. 
     During a period T 5 , the scan signal SS 2  comprises a second frequency. At this time, the frequency and the amplitude of the data signals are controlled such that another portion of the pixels coupled to the scan line SL 2  display the same color. In this embodiment, the frequency of the scan signal SS 2  during the period T 5  is the same as the frequency of the scan signal SS 1  during the period T 2 . Thus, the pixels comprising the pixel P 22  and coupled to the scan line SL 2  display green according to the voltage difference between the scan signal SS 2  and the data signal. 
     During a period T 6 , the scan signal SS 2  comprises a third frequency. At this time, the frequency and the amplitude of the data signals are controlled such that the other portion of the pixels coupled to the scan line SL 2  display the same color. In this embodiment, the frequency of the scan signal SS 2  during the period T 6  is the same as the frequency of the scan signal SS 1  during the period T 3 . Thus, the pixels comprising the pixels P 32  and P m2  and coupled to the scan line SL 2  display blue according to the voltage difference between the scan signal SS 2  and the data signal. 
     During a period Tn, the scan signal SS n  comprises a first frequency. In this embodiment, the frequency of the scan signal SS n  during the period Tn is the same as the frequency of the scan signal SS 1  during the period T 1 . Thus, the pixels comprising the pixel P 1n  and coupled to the scan line SL n  display red according to the voltage difference between the scan signal SS n  and the data signal. 
     During a period Tn+1, the scan signal SS n  comprises a second frequency. In this embodiment, the frequency of the scan signal SS n  during the period Tn+1 is the same as the frequency of the scan signal SS 1  during the period T 2 . Thus, the pixels comprising the pixel P 2n  and coupled to the scan line SL n  display green according to the voltage difference between the scan signal SS n  and the data signal. 
     During a period Tn+2, the scan signal SS n  comprises a third frequency. In this embodiment, the frequency of the scan signal SS n  during the period Tn+2 is the same as the frequency of the scan signal SS 1  during the period T 3 . Thus, the pixels comprising the pixels P 3n  and P mn  and coupled to the scan line SL n  display blue according to the voltage difference between the scan signal SS n  and the data signal. 
     In some embodiments, the scan signals SS 1 , SS 2 , and SS n  as shown in  FIG. 5  also comprise the reset period as shown in  FIG. 3 . In addition, assuming the display is a ChLCD comprising a first pixel and a second pixel, then the color displayed by the first pixel will be different from the color displayed by the second pixel. If the frequency received by the first pixel is different from the frequency received by the second pixel, the R-V curve of the first pixel will approach the R-V curve of the second pixel, wherein R is a reflectivity of the cholesteric liquid component and V is a voltage difference between a scan signal and a data signal. Thus, the pixels displaying the different colors can be controlled by one voltage source. 
       FIG. 4B  is a structure diagram of an embodiment of the display. The display comprises two panels stacked together. Each panel comprises a plurality of pixels. The pixels in one panel are stacked with the pixels in another panel. Taking a ChLCD as an example, each pixel comprises a levorotary cholesteric liquid component and a dextrorotatory cholesteric liquid component to increase reflectivity. For example, the pixel P 11  comprises the levorotary cholesteric liquid component and the pixel P′ 11  comprises the dextrorotatory cholesteric liquid component. In this embodiment, when the color displayed by a first pixel is different from the color displayed by a second pixel, the frequency of a first scan signal received by the first pixel is different from the frequency of a second scan signal received by the second pixel. 
       FIG. 4C  is a schematic diagram of another embodiment of a display. The display comprises three panels  431 ˜ 433  stacked together. Each of the panels  431 ˜ 433  comprises a plurality of pixels. The pixels in the same panel display the same color. The pixels in one panel are stacked with the pixels in another panel. Taking a ChLCD as an example, assuming that the color displayed by the panel  431  is red, the color displayed by the panel  432  is green, and the color displayed by the panel  433  is blue. In this embodiment, the frequencies of the scan signals received by the panels  431 ˜ 433  are different because the panels  431 ˜ 433  display the different colors. 
       FIG. 4D  is a schematic diagram of another embodiment of a display. The display comprises six panels  441 ˜ 446  stacked together. Each of the panels  441 ˜ 446  comprises a plurality of pixels. The pixels in the same panel are capable of displaying a specific color and arranged into a specific rotational direction. The pixels in one panel are stacked with the pixels in another panel. The pixels in the different panels are capable of displaying the different colors and arranged into the different rotational directions. For example, the panel  441  comprises the levorotary cholesteric liquid component and displays red. The panel  442  comprises the dextrorotatory cholesteric liquid component and displays red. The panel  443  comprises the levorotary cholesteric liquid component and displays green. The panel  444  comprises the dextrorotatory cholesteric liquid component and displays green. The panel  445  comprises the levorotary cholesteric liquid component and displays blue. The panel  446  comprises the dextrorotatory cholesteric liquid component and displays blue. The reflectivity of the pixels can be increased by the levorotary cholesteric liquid components and the dextrorotatory cholesteric liquid components. 
       FIG. 6  is a flowchart of an embodiment of a driving method. The driving method can be applied in a display. The display comprises a scan driver, a data driver, a first pixel, and a second pixel. The first pixel displays a first color. The second pixel displays a second color. 
     First, the scan driver is activated to provide a first scan signal to the first pixel (step S 610 ). Then, the scan driver is activated to provide a second scan signal to the second pixel (step S 620 ). The frequency of the first scan signal and the frequency of the second scan signal relate to the first color and the second color. In one embodiment, if the first color is different from the second color, the frequency of the first scan signal is different from the frequency of the second scan signal. In another embodiment, if the first color is the same as the second color, the frequency of the first scan signal is the same as the frequency of the second scan signal. 
     Furthermore, the first and the second pixels receive the first and the second scan signals via the same scan line. In other embodiment, the first pixel receives the first scan signal via a first scan line and the second pixel receives the second scan signal via a second scan line different from the first scan line. Additionally, the first pixel is stacked or not stacked with the second pixel. 
     In one embodiment, the first pixel displays color according to the voltage difference between the first scan signal and a data signal. In this case, the brightness of the first pixel is determined by the duration of the data signal provided by the data driver. In another embodiment, the frequency of the data signal is equal to or not equal to the frequency of the first scan signal. Furthermore, the amplitude of the first scan signal is the same as or different from the amplitude of the second scan signal. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.