KR20080023578A - Liquid crystal display and draiving methid thereof - Google Patents

Abstract

A liquid crystal display device and a driving method thereof are provided to decrease an image blurring at a moving caption by adding a white color to an edge between an image and a caption. A liquid crystal display device includes an LCD(Liquid Crystal Display) panel(100), a light source(400), first and second data driving units(200,210), and a controller(500). The LCD panel includes an image region and a caption region. The light source irradiates light with different colors on the LCD panel. The first data driving unit applies image data to the image region. The second data driving unit applies caption data to the caption region. The controller sequentially supplies 3-color light on the image region for respective frames. The controller sequentially supplies 4-color light on the caption region for respective frames.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY AND DRAIVING METHID THEREOF}

1 is a control block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a graph illustrating signal waveforms of a liquid crystal display according to an exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: liquid crystal panel 110: image area

120: caption area 200: first data driver

210: second data driver 300: first gate driver

310: second gate driver 400: light source

410: first light source unit 420: second light source unit

500: control unit 510: signal conversion unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof, and more particularly, to a liquid crystal display device driven by a color sequential display method and a driving method thereof.

Recently, the liquid crystal display device most widely used includes a liquid crystal panel including a thin film transistor substrate on which a thin film transistor is formed and a color filter substrate on which a color filter layer is formed, and a liquid crystal layer between the thin film transistor substrate and the color filter substrate. Is located.

In general, most liquid crystal display devices form a color filter layer composed of three primary colors of red (R), green (G), and blue (B) on a color filter substrate, and adjust a desired color by controlling the amount of the color filter layer. Display. In the liquid crystal display, white light emitted from a light source is transmitted to the R, G, and B color filter layers, and the amount of light transmitted through the R, G, and B color filter layers is adjusted to synthesize R, G, and B colors. Is displayed.

Recently, independent light sources of R, G, and B colors are periodically turned on one conventional pixel, and a full color image can be obtained by applying a color signal corresponding to each pixel in synchronization with the lighting cycle. A liquid crystal display of a color sequential display (CSD) type using a three-color light source has been proposed. This method does not divide the pixel into subpixels, thereby facilitating the improvement of the aperture ratio and yield, and has the advantage of reducing the number of driving circuits required for each subpixel by 1/3.

However, in the case of CSD driving, since light of different colors of red, green, and blue is provided to the liquid crystal panel at different times, there is a problem of color dispersion in which colors are not properly mixed and broken. In addition, there is a problem that image blurring occurs more clearly than a region displaying an image in a region in which a subtitle having a high contrast is displayed.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a driving method thereof in which color dispersion and image blur are prevented.

In particular, the present invention provides a liquid crystal display and a driving method thereof in which an image blur generated in a moving caption is reduced in the case of an image displayed on the caption.

According to the present invention, there is provided a liquid crystal panel including an image region and a caption region; A light source unit providing light of different colors to the liquid crystal panel; A first data driver for applying image data to the image area; A second data driver for applying caption data to the caption area; And a control unit for controlling the light source unit to sequentially supply different tricolor light to one frame periodically in the image area, and to sequentially supply different four-color light to one subframe periodically in the caption area. Is achieved.

In the case where different four-color light is provided in the caption area, the controller may further include a signal converter for converting the input three-color video signal into four-color signals in order to provide caption data in synchronization with the caption area.

The controller outputs image data corresponding to an image from among input image signals to the first data driver, and outputs caption data corresponding to a subtitle to the signal converter.

The tricolor light may include red, green, and blue light, but is not limited thereto.

In addition, the four-color light may include red, green, blue and white light, it is preferable to include white light to prevent color dispersion.

The light source unit may include a plurality of point light sources emitting red, green, and blue light.

The light source unit includes a first light source unit providing light to the image area and a second light source unit providing light to the caption area, and the second light source unit provides white light to provide white light to the caption area where caption data is displayed. It is preferable to further include the point light source which emits light.

It is preferable that the number of frame repetitions per second in the image region in which tricolor light is periodically repeated is 180 or more.

In addition, since four-color light is periodically repeated in the caption area, the number of repeated frames per second of the caption area is preferably 240 or more.

On the other hand, the above object is, according to the present invention, in the method of driving a liquid crystal display device comprising a liquid crystal panel having a video region and a caption region, the four-color video signal of the caption data corresponding to the caption of the input video signal; Converting to a color signal; The video data of the video signal is applied to the video area, and the converted caption data is applied to the caption area, and the video area is sequentially supplied with three different colors of light every one frame, and different four-color light is supplied to the caption area. It can also be achieved by a method of driving a liquid crystal display device comprising the step of sequentially supplying a frame every cycle.

The tricolor light may include red, green, and blue light.

In addition, the four-color light may include red, green, blue and white light.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

In various embodiments, like reference numerals refer to like elements, and like reference numerals refer to like elements in the first embodiment and may be omitted in other embodiments.

1 is a control block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

As illustrated, the liquid crystal display according to the present embodiment includes a liquid crystal panel 100 and a light source unit 400 and a liquid crystal panel 100 including a point light source 401 that provides light to the liquid crystal panel 100. The control unit 500 controls the applied signal and the light source unit 400. In addition, the liquid crystal display includes a plurality of data drivers 200 and 210 for applying a data signal and a plurality of gate drivers 300 and 310 for applying a gate signal to the liquid crystal panel 100.

The liquid crystal panel 100 includes a first substrate on which a thin film transistor is formed, a second substrate provided to face the first substrate, and a liquid crystal layer injected between both substrates. The first substrate includes a gate line (not shown), a data line insulated from the gate line, a pixel defined by an intersection thereof, and a thin film transistor formed on the pixel. The gate drivers 300 and 310 are connected to the gate line to apply a gate signal including a gate on voltage and an off voltage to the gate line. When the gate-on voltage is applied to the gate line, the thin film transistor is turned on, and an image signal output from the data driver 200 or 210 is applied to the pixel to form an image on the liquid crystal panel 100. In the second substrate according to the present exemplary embodiment, color filters for implementing colors are not formed, and light of different colors is sequentially provided by the light source unit 400. That is, the image is realized by temporal mixing, not spatial mixing of red, green, and blue light.

The liquid crystal panel 100 according to the present exemplary embodiment includes an image region 110 in which image data as shown in the figure is displayed, and a caption region 120 in which caption data such as letters and symbols are displayed. In the present invention, a signal corresponding to a picture among the image signals displayed on the liquid crystal panel 100 is defined as image data and a subtitle data as subtitle data. As such, the liquid crystal panel 100 including the caption area may be mainly used for a public information display installed indoors or outdoors, and may be applied to a liquid crystal display device provided with a caption for the disabled.

The gate drivers 300 and 310 include a first gate driver 300 for applying a gate signal to the image region 110 and a second gate driver 310 for applying a gate signal to the subtitle region 120. The first gate driver 300 and the second gate driver 310 are independently driven by the control of the controller 500. In general, when 60 frames are formed in one second, 60 gate signals are applied to one gate line per second. However, according to the present exemplary embodiment, subframes are formed by the number of different colors provided by the light source unit 400 to form one frame. That is, the light source unit 400 provides light of a specific color, and data corresponding to the specific color is applied to the pixel to implement an image. Since three different colors of light are provided in the image region 110 according to the present embodiment, 180 subframes are formed in the image region 110 in order to form 60 frames per second. Therefore, the first gate driver 300 applies 180 gate signals per second to one gate line. On the other hand, since the light of different colors is provided in the caption area 120, 240 subframes are formed in the caption area 120 in 1 second to form 60 frames in 1 second. Accordingly, the second gate driver 310 applies 240 gate signals per second to one gate line. That is, the first gate driver 300 and the second gate driver 400 apply a gate signal to the gate line so that the corresponding region is driven at a different frequency.

The data drivers 200 and 210 include a first data driver 200 for applying image data to the image region 110 and a second data driver 210 for applying caption data to the subtitle region 120. The first data driver 200 receives red, green, and blue image data from the controller 500 and applies it to the image region 110 in synchronization with the gate-on voltage. On the other hand, the second data driver 210 receives four-color caption data consisting of red, green, blue, and white colors instead of three colors from the controller 500 and applies it to the caption area 120.

The controller 500 includes a signal converter 510 for converting an input three-color image signal into a four-color image signal. The controller 500 extracts a signal corresponding to the caption data from the image signal and outputs it to the signal converter 510.

The signal converter 510 extracts the white components from the three-color RGB video signals, and generates the four-color RGBW video signals through the half-tone processor, and increases the three-color RGB video signals. Among the values, a known method such as subtracting a pixel value from an increase value and using it as an input value of a white component and using an increment of an RGB image signal other than the white subtraction amount as an output signal of the remaining image signal RGB To convert the three-color subtitle data into red, green, blue, and white four-color subtitle data. The four-color caption data output from the signal converter 510 is transferred to the second date driver 210 and displayed on the caption area 120.

The light source unit 400 provides light of different colors to the liquid crystal panel 100 and includes a point light source 401 emitting red, green, and blue light. The point light sources 401 are arranged in four point light source units consisting of one red, two greens, and one blue. The point light source 401 according to the present embodiment is formed of a light emitting diode. The light source unit 400 includes a first light source unit 410 for providing different tricolor light to the image area 110 and a second light source unit 420 for providing four different color light to the subtitle area 120.

The first light source unit 410 includes light source units 411 to 416 having a plurality of bar shapes, and sequentially sequentially red, green, and blue light with one frame in synchronization with a gate signal applied from the first gate driver 300. To the image area 110.

The second light source unit 420 is composed of a plurality of light source units (421, 422), The red, green, blue, and white light are sequentially provided to the caption area 120 at intervals of one frame in synchronization with the gate signal applied from the second gate driver 310. In order to emit white light, light may be emitted from all the point light sources 401 corresponding to the point light source unit, and may further include a white point light source that emits pure white light. In the case of the subtitle area 120 in which a subtitle is formed, a bright gray character having a large difference in brightness from black is usually provided on a black background while providing information while moving from one direction to the other. As such, when the image having a large brightness difference is moved, image blur occurs, and in particular, when the CSD is driven, the image quality deteriorates due to color dispersion. In the case of the liquid crystal display according to the present exemplary embodiment, four-color driving is performed in the subtitle area 120 where the subtitles are formed, not white, so that color dispersion caused by not mixing in white can be reduced.

In summary, the control unit 500 separates the input image signal and sets the first gate driver 300, the first data driver 200, and the first light source unit 410 into one set, and the second gate driver 310. The second data driver 210 and the second light source 420 are driven in one set.

2 is a graph illustrating signal waveforms of a liquid crystal display according to an exemplary embodiment of the present invention. Referring to FIG. 2, the image signal displayed on the liquid crystal panel 100 and the color of light provided from the light source unit 400 are as follows.

In the image region 110, as shown in (a), image data of red, green, and blue is applied for 1/60 second. In response, the first light source unit 410 turns on the red point light source 401 when the red image data is applied, and turns on the green point light source 401 when the green image data is applied, and the blue image data is turned on. When applied, the blue point light source 401 is turned on (b). That is, three subframes are formed in the image region 110 during 1/60 second when one frame is formed, and 180 subframes are formed in one second. Accordingly, the first light source 410 is also driven at 180 Hz.

On the other hand, as shown in (c), red, green, blue and white image data are applied to the caption area 120 for 1/60 seconds. In response, the second light source unit 420 turns on the point light source 401 of all colors when white caption data is applied in addition to the red point light source 401, the green point light source 401, and the blue point light source 401. Provide white light (d). Four subframes are formed in the subtitle area 120 during 1/60 second when one frame is formed, and 240 subframes are formed in one second. Accordingly, the second light source unit 420 is also driven at 240 Hz.

In the liquid crystal display according to the present invention, the CSD driving is performed by dividing the regions formed in the image and the subtitle, but the CSD driving is performed in which the white color is added to the portion where the color dispersion is severe, thereby preventing color dispersion and improving image blur.

Although some embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that modifications may be made to the embodiment without departing from the spirit or spirit of the invention. . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, there is provided a liquid crystal display device and a driving method thereof in which phase blur is prevented.

In addition, according to the present invention, in particular, in the case of an image in which a caption is displayed, a liquid crystal display device and a driving method thereof in which an image blur generated in a moving caption is reduced are provided.

Claims (12)

A liquid crystal panel including an image region and a subtitle region; A light source unit providing light of different colors to the liquid crystal panel; A first data driver for applying image data to the image area; A second data driver for applying caption data to the caption area; And a control unit which controls the light source unit to sequentially supply different tricolor light to one frame periodically in the image area, and sequentially supply different four-color light to one subframe periodically in the caption area. Display. The method of claim 1, The control unit further comprises a signal conversion unit for converting the input three-color image signal to a four-color signal. The method of claim 2, And the control unit outputs image data corresponding to an image among the input image signals to the first data driver, and outputs caption data corresponding to the subtitles to the signal converter. The method according to any one of claims 1 to 3, And the tricolor light includes red, green, and blue light. The method of claim 4, wherein Wherein the four-color light includes red, green, blue, and white light. The method of claim 5, The light source unit includes a plurality of point light sources emitting red, green, and blue light. The method of claim 6, The light source unit includes a first light source unit providing light to the image area and a second light source unit providing light to the caption area, The second light source unit further comprises a point light source for emitting white light. The method according to any one of claims 1 to 3, And a frame repetition frequency per second of the image area is 180 or more. The method of claim 8, And a repetition number of frames per second of the subtitle area is 240 or more. A driving method of a liquid crystal display device comprising a liquid crystal panel having an image region and a subtitle region, Converting the three-color video signal of the caption data corresponding to the caption among the input video signals into a four-color signal; The video data of the video signal is applied to the video area, and the converted caption data is applied to the caption area, and the video area is sequentially supplied with three different colors of light every one frame, and different four-color light is supplied to the caption area. And sequentially supplying one frame at a cycle. The method of claim 10, And wherein the tricolor light includes red, green, and blue light. The method of claim 11, And the four-color light includes red, green, blue, and white light.

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