Repeated-scan driving method for field sequential color liquid crystal display

The present invention discloses a REPEATED-SCAN driving method, which applies to a field sequential color liquid crystal display, wherein each sequential-color cycle of the multiplex-scan signal has at least two stages of scans to increase the luminous fluxes of all colors of backlights and bring closer the total amounts of fluxes, whereby is achieved higher color saturation and better flux uniformity between the rows. Further, the method of the present invention controls the backlights to form dark stages between the intervals respectively of two different colors of the backlights and controls the dark stage to coincide with a color-mixing interval, which is caused by response delay of liquid crystal, to prevent from color distortion caused by color mixing. Therefore, the present invention can generate the pure colors and the designed derived colors accurately.

FIELD OF THE INVENTION

The present invention relates to a REPEATED-SCAN driving method for an FSC LCD, particularly to an FSC LCD driving method, which can increase luminous flux and color saturation.

BACKGROUND OF THE INVENTION

In FSC LCD (Field Sequential Color Liquid Crystal Display), multi-color backlights are sequentially switched and pass through liquid crystal optical gates. FSC LCD opens and closes the liquid crystal optical gates to sequentially generate pure-color fields, and then the visual persistence of human eyes mixes the pure colors to present various colors. Refer toFIG. 1. The control signal1is used to open and close the liquid crystal optical gates. However, the light transmission curve2cannot instantly reflect the control signal1because the delayed response of liquid crystal molecules. Thus, there are response delays3appearing in the light transmission curve2.

Refer toFIG. 2a timing diagram of a conventional FSC LCD technology. In the timing diagram, the duty ratio is 1/4; C0, C1, and C3(C2is neglected) are the signals4scanning the common (row) electrodes of an LCD panel in a time-sharing multiplex mode; Sn is the signal4scanning the segment (column) electrodes of the LCD panel. The abovementioned signals4C0, C1, C3and Sn cooperate with the multi-color backlights5—a red backlight6(R), a green backlight7(G), and a blue backlight8(B), which sequentially and cyclically switch—to work.

Refer toFIG. 3a diagram schematically showing the luminous fluxes of colored lights of a conventional FSC LCD driven by the signals shown inFIG. 2. InFIG. 3, the integral areas (the fluxes) of the red backlight6(R), a green backlight7(G), and a blue backlight8(B) are small and inconsistent, and the latter color may mix with the former color. Thus, the row luminous fluxes9have problems of dimness and color distortion, as shown inFIG. 4.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a REPEATED-SCAN driving method for an FSC LCD to increase the luminous fluxes, bring closer the total amounts of the fluxes, and decrease flux difference between rows, whereby is achieved higher color saturation and better flux uniformity between the rows.

Another objective is to increase the luminous fluxes with the purity of colors maintained and without color mixing occurring, whereby is improved the problem of color distortion.

To achieve the abovementioned objectives, the present invention proposes a REPEATED-SCAN driving method for an FSC LCD and a device for realizing the same method. The method of the present invention comprises steps:

providing at least two colors of backlights, which sequentially switch; and

providing at least one multiplex-scan signal with the cycle of the color sequence corresponding to the timing of switching backlight colors, wherein each cycle of the multiplex-scan signal has at least two stages of scans.

In the present invention, a dark stage is arranged between the intervals respectively of two different colors of backlights and coincides with the color-mixing interval, which is caused by the response delay of liquid crystal, to prevent from mixing of different colors of backlights.

In the present invention, at least two stages of scans are arranged within every sequential-color cycle to increase the luminous fluxes, bring closer the total amounts thereof, and decrease flux variation between the rows, whereby colors may have higher saturation and uniformity. Further, the present invention provides a dark stage to prevent from mixing of different colors of backlights. Therefore, the present invention not only can prevent from color distortion of pure colors but also can present the correct derived colors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, the embodiments are described in detail in cooperation with the drawings to demonstrate the objectives, characteristics and efficacies of the present invention.

Refer toFIG. 5andFIG. 6. The present invention proposes a REPEATED-SCAN driving method for an FSC LCD60(Field Sequential Color Liquid Crystal Display). The method of the present invention provides at least two colors of backlights20, which sequentially switch. In the method, a dark stage21is arranged between the intervals respectively of two different colors of backlights20. The backlights20can include a red backlight201, a green backlight202and a blue backlight203, which sequentially switch. Besides, the dark stage21can be arranged in the very beginning of the backlights20.

The present invention provides at least one multiplex-scan signal30. The sequential-color cycles31of the scan signals30are corresponding to the timing of switching the colors of backlights20. Each sequential-color cycle31has at least two stages of scans32. In the drawings, the duty ratio of the multiplex-scan signal30is exemplified by 1/4. In the drawings, C0, C1, and C3(C2is neglected) are the signals scanning the common (row) electrodes of the LCD panel in a time-sharing mode, and Sn is the signal scanning the segment (column) electrodes of the LCD panel. In the drawings, the sequential-color cycle31having four stages of scans32is used as the exemplification.

Refer toFIG. 7. The multiplex-scan signal30inFIG. 6drives the FSC LCD60to output the luminous fluxes of the red backlight201, the green backlight202, and the blue backlight203shown inFIG. 7. FromFIG. 7, it is known that at least two stages of scans32are arranged within every sequential-color cycle31to increase the luminous fluxes, bring closer the total amounts of fluxes, and decrease flux variation between the rows. Thus, the present invention can increase color saturation and promote flux uniformity between the rows. Further, the method of the present invention can control the dark stage21to coincide with the color-mixing interval40, which is caused by the response delay of liquid crystal. Thus, none color mixing occurs in the effective luminous interval50, and color distortion is prevented. Therefore, the present invention can generate pure colors and derived colors accurately.

In conclusion, the method of the present invention provides at least two stages of scans32for each sequential-color cycle31to increase row fluxes70, bring closer the total amounts of the fluxes, and decrease flux variation between the rows, as shown inFIG. 8. Further, the method of the present invention controls the backlights20to form the dark stages21to prevent from the unwanted color mixing. Therefore, the present invention can generate the pure colors and the designed derived colors accurately.