COLOR SEQUENTIAL LIQUID CRYSTAL DISPLAY

Abstract

A color sequential LCD display is disclosed. In addition to three base color lights including red, green and blue, the display also utilizes at least one additional color light whose color space coordinate is different from any of the three base color lights as additional light source for backlight. By doing so, and objective of expanding gamut ratio of the display can be achieved.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a color sequential LCD in accordance with one embodiment of the present invention;

FIG. 2 shows a structure of a sidelight type backlight module;

FIG. 3 shows a timing diagram of ON/OFF statuses of the respective color lights in sub-frames of a frame in accordance with an embodiment of the present invention; and

FIG. 4 shows color gamut ranges achieved by the conventional color sequential LCD displaying method and the method of the present invention, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be further described in details in conjunction with the accompanying drawings.

FIG. 1 schematically shows a color sequential LCD in accordance with one embodiment of the present invention. As shown, the color sequential LCD comprises an LCD panel 10, an LED backlight device 20, a conversion device 30 and an image data control device 40. The details will be described as follows.

The LCD panel 10 has an upper substrate and a lower substrate. A pixel array composed of a plurality of pixel electrodes is provided on one of the upper and lower substrates. Liquid crystal is disposed between the upper and lower substrates.

In accordance with an embodiment of the present invention, the LED backlight device 20 can be implemented by a sidelight type backlight module, of which the basic structure is shown in FIG. 2. The backlight device 20 comprises a plurality of light sources 201, 202, 203, 211, 213, the details will be further described later. The backlight device 20 further has a reflective plate 21 for reflecting incident light toward the upper direction, a light-guide plate 22 for spreading the incident light over the whole light-guide plate through multiple refractions and reflections to form a plane light source, a diffusion plate 23 for further spreading light illuminated from the light-guide plate over the whole surface more uniformly, so as to achieve uniform light output, and a prism plate 24 for receiving incident light beams of different directions and outputting emergent light in the upper direction through refractions and reflections.

In addition to three base light sources 201, 202, 203 of red (R), green (G), blue (B) lights, the backlight device 20 has additional light sources 211 and 213. In the present embodiment, the additional light sources 211 and 213 are another red light source and another blue light source with main wavelengths different from the base red and blue light sources, respectively. That is, the LED backlight device 20 of the present embodiment has five light sources. The five light sources are R1, R2 light sources 201, 211 with different main wavelengths, G light source 202, and B1, B2 light sources 203, 213 with different main wavelengths. It is noted that although the additional red light source and blue light source, which are of the same colors but having different main wavelengths with the base color lights, are used as the additional light sources, the choice for the additional light sources is not limited thereto. Here, the definition of “same color” is similar to general chromatics. For example, a light source of a color other than the three base colors can be used, such as a cyan light source or a yellow (Y) light source. Further, a color light which has a main wavelength the same as that of one of the base lights but has a color coordinate in the color space different from said base light can also be used. In addition, the number of the additional light sources is not limited. In the present embodiment, two additional color light sources are used. However, one or more than two additional color light sources are also possible as required. White balance generally made by RGB color lights should be achieved by five color lights of R1, R2, G, B1 B2, for example.

As described above, the color sequential LCD in accordance with the present invention further has the conversion device 30. Externally inputting image data is set based on R, G, B. However, the light sources have increased to include R1, R2, G, B1, B2. Data signals fed to the LCD panel are also decomposed into R1, R2, G, B1, B2. Accordingly, in the present embodiment, the conversion device 30 converts the image data, adjusts the voltage applied to the liquid crystal by the pixel electrode for each color light so as to control the light intensity passing through the liquid crystal. Thus, correct color tones and gray scales can be displayed.

Under the control of the image data control device 40, the respective light sources in the backlight device 20 of the color sequential LCD emit lights in sequence to achieve an effect of color display. A specific ratio of the light intensities of the respective color lights is obtained by adjusting the light transmittance of the liquid crystal. In the present embodiment, one frame is divided into six sub-frames. The R1 light source emits light during the interval of the first sub-frame; the R2 light source emits light during the interval of the second sub-frame; the G light source emits light during the intervals of the third and fourth sub-frames; the B1 light source emits light during the interval of the fifth sub-frame; the B2 light source emits light during the interval of the sixth sub-frame, as shown in FIG. 3. In this case, the intervals of the respective sub-frames are the same. As described, the concept of the same color is similar to the that of chromatics. In the present embodiment, the timing for the light sources emit lights according to the sequence of R1, R2, G, G, B1, B2. That is, color light sources emitting color lights of the same color but with different wavelengths are turned on/off in succession. For example, R1 and R2 light sources successively emit light. When each color light source emits light, the pixels of the LCD panel 10 are fed with corresponding data signals synchronously, so that the liquid crystal appears a predetermined transmittance to control the mixing ratio of the respective color lights, thereby an image can be correctly displayed. The above five colors are basic colors for constructing a single pattern. Other arrangements are also possible. For example, in the condition that the single frame is divided into six sub-frames, the sequence of emitting lights can be R1, G, B1, R2, G, Bs, or R1, B1, R2, B2, G, G or B1, R2, B2, G, R1, G or the like. In another case, one frame is divided into three sub-frames, and emitting of the color light sources R1, G, B1, R2, G, B2 emit lights in any proper sequence is completed in two frames. For example, R1, G, B1 light sources are turned on in the first frame, while R2, G, B2 light sources are turned on in the second frame. The division of the sub-frames can be arranged as required. The LED backlight device 20 emits the color lights according to any determined sequence. That is, it is not necessary to follow a specific light emitting sequence. Preferably, the respective sub-frames of one frame occupy the equal time period, so that control is easy to be done. However, it is also possible that the respective sub-frames occupy different time periods. Intervals and frequencies of the sub-frame and sub-frames are controlled by the image data control device 40.

In the present embodiment, the R1 color light has the main wavelength of 610 nm, the CIE colorimetric value (i.e. color coordinate) thereof is (0.664, 0.336); the R2 color light has the main wavelength of 630 nm, the color coordinate thereof is (0.685, 0.315); the G color light has the main wavelength of 525 nm, the color coordinate thereof is (0.166, 0.735); the B1 color light has the main wavelength of 470 nm, the color coordinate thereof is (0.124, 0.075); the B2 color light has the main wavelength of 455 nm, the color coordinate thereof is (0.148, 0.040). Referring to FIG. 4, the color gamut of the LCD indicated by the triangle range circumscribed by the real lines is 109.1% when only three color lights including R1, G, B1 are used. The color gamut of the LCD indicated by the pentagon range circumscribed by the dotted lines is up to 115.2% when five color lights including R1, R2, G, B1, B2 are used.

In the present embodiment, additional color lights having the different main wavelengths with the three base color lights are used to expand the gamut. However, as described, even the color lights having the same main wavelengths as the base color lights can also be used. There is a phenomenon called “metamerism” in chromatics. Color lights of the same color have the same main wavelength but different spectrums, results in the color coordinates thereof are different. For example, two red lights both have the main wavelength of 615 mm. However, due to different spectrums, the color coordinates of the two red lights are respectively (0.6207, 0.3204) and (0.6278, 0.3204). If one of these two red lights is used as one of the three base color lights, then the other red light can be used as the additional color light. It is noted that no matter the additional color light has the same or different wavelength with the base color lights, the color coordinate thereof should be different to that of any of the three base color lights. In addition, the color coordinate of the additional color light should fall outside the gamut range defined by the three base color lights in the color space to expand the color gamut.

While the preferred embodiments of the present invention have been illustrated and described in details, various modifications and alterations can be made by persons skilled in this art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention should not be limited to the particular forms as illustrated, and that all modifications and alterations which maintain the spirit and realm of the present invention are within the scope as defined in the appended claims.

Claims

1. A color sequential liquid crystal display comprising: a liquid crystal display (LCD) panel having liquid crystal and a pixel array for controlling the liquid crystal transmittance by applying voltages;a backlight device having three base color light sources for emitting three base color lights and an additional light source for emitting an additional color light, the additional color light having a color coordinate which is different from color coordinates of the three base color lights, the base color light source and the additional light source being turned on and off to emit color lights according to a predetermined sequence; andan image data control device for controlling the backlight device according to timings and intervals of each frame and each sub-frame, and synchronously transmitting corresponding scanning signal and data signal to the LCD panel in coordination with on/off of the respective color light sources.

2. The color sequential liquid crystal display as claimed in claim 1, wherein the color coordinate of the additional color light falls outside a color gamut defined by the color coordinates of the three base color lights.

3. The color sequential liquid crystal display as claimed in claim 1, wherein the three base color lights are red (R), green (G), and blue (B) color lights.

4. The color sequential liquid crystal display as claimed in claim 1, wherein the main wavelength of the additional color light is different from the main wavelength of any of the three base color lights.

5. The color sequential liquid crystal display as claimed in claim 1, wherein the main wavelength of the additional color light is the same as the main wavelength of one of the three base color lights.

6. The color sequential liquid crystal display as claimed in claim 1, wherein the sequence for the color light sources to emit the color lights is to emit the base color light and the additional color light of the same color in succession.

7. The color sequential liquid crystal display as claimed in claim 1, wherein the sequence for the color light sources to emit the color lights is to emit the base color light and the additional color light of the same color at spaced intervals.

8. A light emitting diode (LED) backlight device comprising: three base light sources for respectively emitting three base color lights; andan additional light source for emitting an additional color light of which the color coordinate is different from the color coordinate of any of the three base color lights.

9. The LED backlight device as claimed in claim 8, further comprising: a reflective plate for reflecting incident lights toward a predetermined direction; a light-guide plate for spreading the incident lights over the whole light-guide plate guiding the lights toward the predetermined direction;a diffusion plate for spreading lights illuminated from the light-guide plate over the whole surface more uniformly, so as to achieve uniform light output; anda prism plate for receiving incident light beams of different directions from the diffusion plate and outputting emergent lights in the predetermined direction.

10. The LED backlight device as claimed in claim 8, wherein the color coordinate of the additional color light falls outside a color gamut defined by the color coordinates of the three base color lights.

11. The LED backlight device as claimed in claim 8, wherein the three base color lights are red (R), green (G) and blue (B) color lights.

12. The LED backlight device as claimed in claim 8, wherein the main wavelength of the additional color light is different to the main wavelength of any of the three base color lights.

13. The LED backlight device as claimed in claim 8, wherein the main wavelength of the additional color light is the same as the main wavelength of one of the three base color lights.

14. A displaying method for a color sequential liquid crystal display, said color sequential liquid crystal display comprising a liquid crystal display (LCD) panel, which has liquid crystal and a pixel array for applying a voltage to control the transmittance of the liquid crystal, said panel applying different voltages to the LCD panel pixels to control the light intensity of backlight passing through the liquid crystal according to data signals, said method comprising: providing backlight for the LCD panel to display an image, the backlight comprising three base color lights and an additional color light, the color coordinate of the additional color light being different from the color coordinate of any of the three base color lights, the base color lights and the additional color light being turned on and off to emit lights according to a predetermined sequence by a unit of a sub-frame which is divided from a frame;controlling timing and interval of each frame and each sub-frame and synchronously inputting corresponding scan signal and data signal to the LCD panel in coordination with on/off of the respective color lights; andcontrolling to sequentially apply voltages to pixel electrodes of the LCD panel in the sub-frames for different color lights.

15. The method as claimed in claim 14, wherein the color coordinate of the additional color light falls outside a color gamut defined by the color coordinates of the three base color lights.

16. The method as claimed in claim 14, wherein the three base color lights are red (R), green (G) and blue (B) color lights.

17. The method as claimed in claim 14, wherein the main wavelength of the additional color light is different from the main wavelength of any of the three base color lights.

18. The method as claimed in claim 14, wherein the main wavelength of the additional color light is the same as the main wavelength of one of the three base color lights.

19. The method as claimed in claim 14, wherein the sequence for emitting the color lights is to emit the base color light and the additional color light of the same color in succession.

20. The method as claimed in claim 14, wherein the sequence for emitting the color lights is to emit the base color light and the additional color light of the same color at spaced intervals.