KR101405253B1 - Backlight driving method for liquid crystal display device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight driving method for a liquid crystal display (LCD), and more particularly, to a backlight driving method of a liquid crystal display, ) Color backlight and dividing the one-frame display time into a first sub-frame and a second sub-frame to display an image on the liquid crystal panel, the backlight driving method comprising:

(1) the light emission luminances of the red color backlight in the first sub-frame and the red color backlight in the second sub-frame are different from each other, (2) the light emission luminance of the first sub- (CBU) phenomenon in a display image, thereby providing a high-quality display image. The present invention also provides a backlight driving method of a liquid crystal display device, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight driving method for a liquid crystal display,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight driving method for a liquid crystal display, and more particularly, to a backlight driving method of a liquid crystal display (LCD), which applies field sequential driving and a color filter to improve color break- To a backlight driving method of the apparatus.

A widely used liquid crystal display (hereinafter, referred to as 'LCD') supplies a plurality of liquid crystal cells arranged in a matrix form and image data for controlling the light transmission amount by controlling the rotation angle of the liquid crystal in each of the liquid crystal cells A backlight unit (backlight unit) is transmitted to a liquid crystal panel provided with a TFT (thin film transistor) for displaying a desired image on a screen.

As a light source used in such a backlight unit, a cold cathode fluorescent lamp (CCFL) is mainly used. Such a backlight unit is in a trend of downsizing, thinning, and light weight, A light emitting diode (hereinafter, referred to as 'LED') which is advantageous in terms of power consumption, weight, and luminance has been newly proposed instead of the CCFL used in the backlight unit.

In addition, a field sequential color (FSC) driving method is proposed through a backlight unit using such an LED to obtain a better image quality.

The field sequential color (FSC) driving method sequentially drives LEDs of three primary colors (red, green, and blue) without using a color filter in displaying colors, And is a driving method capable of displaying mixed colors by using the afterimage effect by a human eye.

More specifically, the display time of one frame on the panel is divided into three periods of red, green, and blue, and each backlight is sequentially illuminated with intervals in time.

As shown in FIG. 1, this FSC driving method is divided into three subframes (1 Sub-frame) of red (R), green (G) and blue (B) frame = 5.56 ms).

Each subframe is divided into a data writing time (DW = 1.69 ms) through TFT scanning, a liquid crystal response time (LR = 1.5 ms) according to data writing, and a backlight emitting time (BL = 2.37 ms) The time BL during which the backlight can be turned on is the time excluding the data writing time DW and the liquid crystal response time LR.

This FSC driving will be described below. Data input to RGB is sequentially generated in the same ratio (R: G: B = 1: 1: 1) in one vertical synchronizing cycle in the liquid crystal panel, The light source is also synchronized in the same manner so that the red (R) light source, the green (G) light source, and the blue (B) light source are sequentially turned on. In this case, each light source is an LED lamp or a fluorescent lamp, and the red, green and blue light sources are sequentially arranged.

Since the FSC drive uses only the red, green, and blue light sources, the color gamut that can be expressed is limited, and since one frame is driven by time division into three sub-frames, a color break-up called a "rainbow effect" break up (CBU).

That is, when the viewer views the display image while moving left and right, the center of the human retina has a habit of moving in the direction in which the object moves, so that the colors of red, green, So that it looks like a rainbow.

SUMMARY OF THE INVENTION It is an object of the present invention to improve a color break-up (CBU) phenomenon in a display image and provide a high-quality display image.

In order to accomplish the above object, the present invention provides a color filter comprising a red filter, a green filter, a blue filter, a red filter, a green filter, a cyan filter, a blue filter, A backlight driving method of a liquid crystal display device in which a backlight is formed and an image is displayed on a liquid crystal panel by dividing one frame display time into a first sub-frame and a second sub-

(1) the light emission luminances of the red color backlight in the first sub-frame and the red color backlight in the second sub-frame are different from each other, (2) the light emission luminance of the first sub- The backlight driving method of the liquid crystal display device is characterized in that the light emission luminances of the blue color backlight of the liquid crystal display device are different from each other.

In the backlight driving method of the liquid crystal display device, the light emission luminance ratio of the red color backlight in the first sub-frame and the second sub-frame is 1: (1.05 to 1.6) .

In the backlight driving method of the liquid crystal display device, the light emission luminance ratio of the blue color backlight in the first sub-frame and the second sub-frame is 1: (1.1 to 2.0) .

In the backlight driving method of the liquid crystal display device, a backlight of red, cyan, and blue colors is emitted in the first sub-frame.

In the backlight driving method of the LCD, the red, green, and blue backlights are emitted in the second sub-frame.

In the backlight driving method of the liquid crystal display device, the backlight may be a light emitting diode (LED) or a fluorescent lamp.

According to a backlight driving method of a liquid crystal display according to the present invention, a liquid crystal display (LCD) having an RGB color filter and dividing one frame into a first sub-frame and a second sub- There is an advantage that a color break-up phenomenon in a device is improved and a high-quality display image can be provided.

First, to explain a backlight driving method of a liquid crystal display device according to the present invention, a liquid crystal display device will be briefly described.

A backlight driving method of a liquid crystal display device proposed in the present invention has recently been proposed in order to overcome the disadvantages of FSC driving of the related art and includes a color filter (C / F) , Green (G), cyan (Cyan), and blue (B) color light sources. Of course, the light source can be selected from LED or CCFL.

2, the one-frame display time is divided into two sub-frames. In the first sub-frame (sub1), the RCB light source is lit along with the writing of the RCB image data, In the sub-frame sub2, the RGB light source is turned on along with the writing of RGB image data. At this time, the light emission luminances of R, G, C, and B light sources in one sub-frame may be different. The light emission luminances of the respective color sources in the first sub-frame sub1 and the second sub-frame sub1 are the same. For example, when the R light source is taken as an example, if the light emission luminance of the R light source in the first sub-frame sub1 is 1.0, the light emission luminance of the R light source in the second sub-frame sub1 is also 1.0 will be.

Also, the one frame display time is suitable for a time corresponding to a drive frequency of about 180 Hz which does not visually cause flicker.

Referring to the chromaticity coordinates of FIG. 3, R (red), G (green), C (cyan), and B (blue) are substantially transmitted through the first sub-frame sub1 and the second sub- ) Color can be expressed and the color gamut can be expanded by the effect of expanding the color gamut, as compared with the FSC driving of the related art, and furthermore, one color can be further segmented and displayed to provide a higher quality display image There is an advantage to be able to do.

However, when the RCB color is displayed in the first sub-frame sub1 and the RGB color is displayed in the second sub-frame sub2, a color difference is generated between the two sub-frames sub1 and sub2 .

That is, when comparing the color coordinate X1 of the average color represented by the first sub-frame sub1 and the color coordinate X2 of the average color represented by the second sub-frame sub2, - It can be seen that the color coordinates of the average color between frames (sub1, sub2) are located at different coordinates. In this case, 'X' in the color coordinates of FIG. 3 is a color coordinate for a white color in R, G, C, and B 4 primary colors (60 Hz).

Therefore, when a display of a fast moving picture or a viewer moves left and right according to the color difference between the two sub-frames (sub1, sub2), the above-described color break-up (CBU) phenomenon occurs.

Accordingly, in order to improve the color break-up (CBU) phenomenon in the liquid crystal display device in which the color filter (C / F) and the FSC drive are performed as described above in the present invention, the first sub- the color coordinate X1 of the average color by the first sub-frame sub1 and the color coordinate X2 of the average color by the second sub-frame sub2 representing the RGB color are substantially the same color coordinates (i.e., X ' Position) of the R, G, C, and B light sources according to the sub-frame.

Referring to FIG. 4, one frame display time corresponding to a driving frequency of 180 Hz is divided into two sub-frames. In the first sub-frame sub1, an RCB light source is lit along with writing of RCB image data And in the second sub-frame sub2, the RGB light source is turned on along with the writing of the RGB image data.

At this time, the R light source and the B light source control different light emission luminance ratios for each sub-frame.

That is, assuming that the light emission luminances of the R light source and the B light source in the first sub-frame sub1 are 1.0 (R) and 1.0 (B), respectively, the R light source and the B light source in the second sub- The light emission luminance of each of the light sources is adjusted in the range of 1.05 to 1.6 (R light source) and 1.1 to 2.0 (B light source), and more preferably 1.1 to 1.3 (R light source) and 1.3 to 1.7 It is also acceptable. In particular, the experimental optimum ratio through the simulation was calculated to be 1.2 in the R light source and 1.5 in the B light source, which can be variously calculated within the above range.

Further, the adjustment of the light emission luminance can be realized by adjusting the on duty of the backlight control dimming signal of the liquid crystal display device in case of a PWM signal or adjusting the voltage level of the dimming signal in the case of an analog voltage signal .

In short,

In a liquid crystal display device provided with an RGB color filter and an RGCB light source to divide and display one frame display time into two sub-frames, a first sub-frame sub1 representing an RCB color and a second sub- In the sub-frame sub2,

(1) the R light emission luminance ratios at sub1 and sub2 are 1.0: 1.05 to 1.6,

(2) The B light source emission luminance ratio at sub1 and sub2 = 1.0: 1.1 to 2.0.

At this time, since the C light source in the first sub-frame sub1 and the G light source in the second sub-frame sub2 write different image data for each sub-frame, a separate control for the light emission luminance is performed Do not perform.

In this manner, the light emission luminances of the R light source and the B light source in the second sub-frame sub2 are higher than those of the R light source and the B light source in the first sub-frame sub1, The color coordinate X1 of the average color by the first sub-frame sub1 representing the RGB color and the color coordinate X2 of the average color by the second sub-frame sub2 representing the RGB color are shifted relative to each other .

3, the color coordinate X1 of the average color by the first sub-frame sub1 and the color coordinate X1 of the average color by the second sub-frame sub2 representing the RGB color, (I.e., the X 'position in FIG. 3), and the color break-up (CBU) phenomenon is improved in the displayed image.

In addition, since the light emission luminance ratios of the sub-frame R light source and the B light source shown in the above (1) and (2) can be calculated experimentally according to the type of the light source and the characteristics of the liquid crystal display, 2) may be varied depending on the type of the light source and the characteristics of the liquid crystal display device.

1 is a view for explaining a method of driving a field sequential color (FSC) of a liquid crystal display device;

2 is a view for explaining a backlight driving method applied to one liquid crystal display device;

FIG. 3 is a view showing a color coordinate system for explaining a color break-up phenomenon occurring in one liquid crystal display device described with reference to FIG.

4 is a view for explaining a backlight driving method of a liquid crystal display according to the present invention for improving a color break-up phenomenon in one liquid crystal display device described with reference to FIG.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

R: red G: green

C: cyan B: blue

CBU: color break up

Claims (7)

The backlight of the red, green, and blue color filters and the red, green, cyan, and blue colors are configured, A backlight driving method of a liquid crystal display device for displaying an image on a liquid crystal panel by dividing the sub-frame into a sub-frame and a second sub- Controlling the emission luminance of the red color backlight in the first sub-frame and the emission luminance of the red color backlight in the second sub-frame to be different from each other; Controlling the emission luminance of the blue color backlight in the first sub-frame and the emission luminance of the blue color backlight in the second sub-frame to be different from each other; A backlight driving method of a liquid crystal display device The method according to claim 1, Wherein the ratio of the light emission luminance of the red sub-frame to the red sub-frame in the first sub-frame is 1: 1.05 to 1.6. The method according to claim 1, Wherein the ratio of the light emission luminance of the first sub-frame to the blue color backlight in the second sub-frame is 1: (1.1 to 2.0). The method according to claim 1, Wherein a backlight of a red color, a cyan color, and a blue color is emitted in the first sub-frame, The method according to claim 1, And a backlight of red, green, and blue colors is emitted in the second sub-frame. The method according to claim 1, A backlight driving method of a liquid crystal display device, characterized in that the backlight is a light emitting diode (LED) or a fluorescent lamp The method according to claim 1, Frame, the light emission luminance of the red color backlight in the first sub-frame is smaller than the light emission luminance of the red color backlight in the second sub-frame, Wherein the light emission luminance of the blue color backlight in the first sub-frame is smaller than the light emission luminance of the blue color backlight in the second sub-frame.

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