KR100937847B1 - A method for driving an LCD - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method of a liquid crystal display device which improves an impulsive driving method, wherein a unit frame is divided into a plurality of sections on an axis with time, and a start division section and an end division section among the plurality of division sections. The black data is inserted or the backlight is turned off during the interval. In the odd frame, the black data is inserted during the start division period and the backlight is turned off during the end division period. The backlight is turned off and the black data is inserted during the end division period, and the start division period and the end division period have the same size with respect to time. Backlight control room while minimizing excessive loss It is possible to eliminate unevenness and synchronization error of the blinking area per line of the diet and to finely control the blinking area.

Liquid Crystal Display, Driving Method, Impulsive Driving, Backlight Control, Data Addressing

Description

A method for driving an LCD}

1 is a view for explaining the light intensity (Light intensity) over time in a typical CRT,

2 is a view for explaining the density of light with time in a typical liquid crystal display;

3 is a schematic diagram of a panel configuration for a general liquid crystal display device;

4 is a diagram illustrating a method of applying a gate pulse as a frame-by-frame timing chart in a general liquid crystal display device.

FIG. 5 is a view illustrating a frame-by-frame image information configuration method of a conventional hold type liquid crystal display device; FIG.

FIG. 6 is a diagram illustrating a screen configuration method of the liquid crystal display of FIG. 5.

FIG. 7 illustrates light emission profiles of a typical CRT display.

8 is a view illustrating a light operating curve of a general liquid crystal display device.

FIG. 9 is a diagram illustrating a frame unit image information configuration method of a conventional impulsive liquid crystal display device.                 

FIG. 10 is a view for explaining impulsive driving of the data addressing (or data blocking) method.

11 is a view for explaining impulsive driving of the backlight control method;

12 is a view for explaining a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

* Explanation of symbols on the main parts of the drawings

I: Black data insertion section in unit frame

II: liquid crystal holding section in unit frame

III: Backlight Off Interval in Unit Frame

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method of a liquid crystal display device, and more particularly to a driving method of a liquid crystal display device having an improved impulsive driving method.

In general, a liquid crystal display device (LCD) is a device for displaying an image by selectively transmitting the light generated from the light source at the rear surface of each pixel of the LCD panel at the front surface by acting as a kind of optical switch. That is, the conventional cathode ray tube (CRT) controls the brightness by adjusting the intensity of the electron beam to be scanned, whereas the LCD controls the brightness of the screen by controlling the intensity of light generated from the light source.

With the development of technology, not only the technology of displaying still images but also the technology of displaying moving images is in the spotlight. However, it is difficult to realize a moving picture in a liquid crystal display device used for various display media because the response speed of the liquid crystal is slower than one frame period, so that a voltage charged in the liquid crystal, for example, an image signal or data voltage, is applied for one frame. After holding, if a new voltage is applied in the next frame, a drag phenomenon occurs on the screen.

FIG. 1 is a view for explaining the light intensity over time in a typical CRT, and FIG. 2 is a view for explaining the density of light over time in a general liquid crystal display.

As shown in FIG. 1, the CRT is driven by an impulse method, while the general liquid crystal display shown in FIG. 2 is driven by a hold method, and thus a screen drag occurs when a video is implemented.

In order to eliminate the screen drag phenomenon in the liquid crystal display, an impulse driving method for inputting data in a portion of a frame and black or white data in the other portion, such as a CRT, has been proposed.

Hereinafter, a schematic structure of a conventional liquid crystal display device and a driving method thereof will be described in more detail.

3 is a schematic diagram of a panel configuration for a general liquid crystal display device.

As shown in the figure, a liquid crystal between the upper substrate 4 having a common electrode (not shown), the lower substrate 6 having a pixel electrode (not shown), and the upper and lower substrates 4 and 6. The liquid crystal display panel 2 (hereinafter, abbreviated as liquid crystal panel) with the layer 8 interposed therebetween and positioned on the left side and the upper side of the liquid crystal panel 2, and the gate and data signals on the liquid crystal panel 2; Gates and data integrated circuits 10 and 12 for applying the are connected respectively.

The lower substrate 6 has a plurality of scan lines gi (i; i) as positive integers, 1 ≦ i ≦ n, and a plurality of pixel regions defined by crossing the scan lines gi. A plurality of signal lines dj (j; j are positive integers), and 1 ≦ i ≦ m, to which a signal is applied, are formed, and a plurality of thin film transistors T are formed in an area where the scan lines gi and the signal lines dj cross. Is formed.

One pixel unit equivalent circuit of the liquid crystal panel 2 includes a liquid crystal capacitance CLC, which is a liquid crystal charging capacity, and a storage capacitance CST, which is a pixel charging capacity, connected in parallel to the thin film transistor T.

Next, the driving method of the liquid crystal display device will be briefly described.

In general, during the selection period in which the gate signal is turned on in the scan line, a voltage higher than that of the signal line is applied to the gate connected to the scan line, so that the resistance between the drain and source channels forming the thin film transistor becomes smaller, so that the voltage across the signal line is reduced. It is caught by the liquid crystal layer through the pixel electrode. During the non-selection period, a voltage lower than that of the signal line is applied to the gate connected to the scan line, and the drain and the source are electrically disconnected to maintain the charge charged in the liquid crystal layer during the selection period. That is, the first scan line and the last scan line all have a selection period and a non-selection period once to form one frame, which is the minimum unit for implementing the screen.

4 is a diagram illustrating a method of applying a gate pulse in a frame type timing chart in a general liquid crystal display device.

As shown in the figure, in a typical liquid crystal display device, a gate pulse is sequentially applied from the first scan line g1 to the nth scan line gn in an on / off manner for one frame to select all the scan lines. Done. For example, for successive first and second frames, the first gate pulse 14a of the first frame and the second gate pulse 14b of the second frame are pixels of the corresponding scan line only once in each frame. Is applied to.

That is, in this manner, the first scan line g1 passes through the gate pulse 14 on and off, and then, until the gate pulse 14 is applied to the i th scan line gi, the liquid crystal layer (FIG. 1). The arrangement of 8) should be kept constant for one frame. This driving method is called a hold type driving method.

FIG. 5 is a view illustrating a frame-by-frame image information configuration method of a conventional hold type liquid crystal display device. As shown in the drawing, in the hold type driving method, constant image information must be maintained for one frame. This is possible when the response speed of the liquid crystal maintains the image information processing speed level.

However, TN (Twisted Nematic) liquid crystal mode is mainly used in a general liquid crystal display device. The TN liquid crystal mode has a response speed of about 20 msec, and the response speed of a liquid crystal suitable for moving images is required at least 5 msec. In a commercial hold type liquid crystal display device, the image information processing speed does not match the response speed of the liquid crystal, so that the image information of the previous screen remains to some extent in the next frame, resulting in deterioration of image quality such as motion blur.

In FIG. 5, the height difference between the image information areas for each frame is based on the gray level difference of each image information.

FIG. 6 is a diagram illustrating a screen configuration method of the liquid crystal display of FIG. 5. As shown in FIG. 5, when the screen is viewed at any time, only image information by data on the selected scan line 17 is refreshed. do.

The selected scan line 17 receives image information on a new frame. If the response speed of the liquid crystal does not follow the image information processing speed, the image of the previous frame remains in the corresponding pixels of the selected scan line 17. As a result, an image blur phenomenon occurs.

In addition, the data signal voltage applied through the data integrated circuit has an error in the amount of pixel voltage substantially applied to the pixel due to the resistance between the wiring lines and the parasitic capacitance in the thin film transistor unit in the process of reaching the pixel. .

This results in a difference between the image information of the design value and the actual image information. This error brings about an image blur phenomenon in the visual perception.

FIG. 7 is a diagram illustrating light emission profiles of a typical CRT display, and FIG. 8 is a diagram showing a lighting operation curve of a typical liquid crystal display, and based on one pixel. Not shown.

In the CRT display of FIG. 7, the light divergence profile is individually implemented for each frame with a black image section I having zero light intensity in one frame, whereas the liquid crystal display of FIG. Because of the hold-type driving method which maintains a fixed image, a continuous light operating curve is formed, wherein the error region II between the light operating high line and the data voltage is visually and cognitively blurred as frames are repeated. do.

Therefore, in order to improve the problems of the hold type driving method, an impulsive type driving method has been proposed.

FIG. 9 is a diagram illustrating a frame-by-frame image information configuration method of a conventional impulsive type liquid crystal display device. In order to prevent an influence on the black image area III, a predetermined period is allocated in units of frames.

The impulsive driving method is classified into a data addressing method and a backlight control method.

FIG. 10 is a diagram for describing impulsive driving based on the data addressing (or data blinking) method. One gate pulse width as shown in FIGS. 10A and 10B is shown. The width is divided into half between the real data input line (B-line) and the black data input line (A-line), and one frame as shown in (a) and (c) of FIG. 10. Is divided into a specific ratio (for example, 7: 3, 6: 4, ..., etc.), and the real data is held in each divided part of the frame, and the black data is input in the remaining part. Secure time.

FIG. 11 is a view for explaining the impulsive driving of the backlight control method, by sequentially turning on / off a plurality of lamps (lamp 1-6) included in the backlight device of the LCD as shown in FIG. Implement impulsive driving. At this time, as shown in (b) of FIG. 11, the input of real data is the same as the conventional hold type method, and as shown in (c) of FIG. 11, one frame is assigned a specific ratio (for example, 7: 3, 6: 4, .. And the like to control on / off each lamp 1-6 in accordance with the divided ratio for one frame period.

However, the conventional impulsive driving method described above has the following problems.

First, the impulsive driving method of the data blinking method is secured by inserting (or referred to as black data) a blacking area, which is closely related to the operation characteristics of the liquid crystal. Nematic liquid crystals, which are currently commercialized, incorporate high-speed response technologies such as over driving and low cell gap technologies, but still lose luminance due to the response delay of the liquid crystals. In particular, for impulsive driving, the black liquid is inserted after the odd frame data is input to secure the blinking area, and the normal liquid crystal is input again from the beginning by inputting the same size data inverted polarity of the even frame. Since there is a need to operate, there is a problem that the unnecessary luminance loss due to the response delay becomes large.

Second, the impulsive driving method of the backlight control method is difficult to implement a precise impulsive driving method for each line, and there is an error in the liquid crystal driving of each line and synchronization of each lamp because the boundary line of the area covered by each lamp is ambiguous. There is no choice but to. That is, since the setting of the on / off duty ratio of each lamp is not the same for all lines, there is a problem in that the variation of the luminance and motion blur removal rate of the edge portion of each lamp area occurs. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to eliminate unnecessary luminance loss due to delay in response of liquid crystals between odd frames and even frames, which is a problem in the impulsive driving of the blinking method, and impulses of the backlight control method. It is an object of the present invention to provide a method of driving a liquid crystal display device which minimizes problems in driving a sieve.

In order to achieve the above object, a driving method of a liquid crystal display according to the present invention includes: turning off a backlight during a first switching period of changing from an odd frame to an even frame; And inserting black data during the second transition period from the even frame to the odd frame.

The first switching section includes an end section of the odd frame and a start section of the even frame, and the second switching section includes an end section of the even frame and a start section of the odd frame. The starting section has the same size with respect to time. In addition, when the odd frame is the first frame, black data is inserted into a start section of the odd frame.

That is, the present invention is characterized in that the unit frame is divided into a plurality of sections on the axis of time, and black data is inserted or the backlight is turned off during the start division section and the end division section among the plurality of division sections. Inserting the black data during the start division period and turning off the backlight during the end division period, turning off the backlight during the start division period and inserting the black data during the end division period in an even frame The start division section and the end division section have the same size based on time.

Hereinafter, a driving method of a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

12 is a view for explaining a method of driving a liquid crystal display according to an exemplary embodiment of the present invention, where (a) is a view showing application of a data voltage in units of frames of a liquid crystal display, and (b) and (c). ) Is a view showing a frame-by-frame configuration of image information of the liquid crystal display, (b) is an ideal state (c) is a view showing a real state.

First, referring to FIG. 12, an odd frame including the first start frame (first frame) includes a black data insertion section (black picture section) I, a liquid crystal holding section (real picture section) II, and a backlight off section ( Black image section) (III).

In addition, the even frame is sequentially divided into the backlight off section III, the liquid crystal holding section II, and the black data insertion section I. FIG.                     

The black data insertion section (I), the liquid crystal holding section (II), and the backlight off section (III) are divided by a specific ratio based on time, and the black data insertion section (I) and the backlight off section (III) ) Split into equal sizes. For example, the division ratio between the black data insertion section I and the liquid crystal holding section II and the backlight off section III may be 1.5: 7: 1.5 or 2: 6: 2 or 2.5: 5: 2.5, or the like. You can do it together.

According to the present invention, the backlight is turned off according to the impulsive driving method of the backlight control method during the first switching period III + III changing from the odd frame to the even frame, and the second switching period I + I changing from the even frame to the odd frame. Black data is inserted according to the impulsive driving method of the data addressing method.

That is, the present invention is a mixture of a backlight control type impulsive driving method and a data addressing type impulsive driving method, and inserts black data by resetting a gate line in the black data insertion section I based on a unit frame. In the liquid crystal holding section II, the actual image is displayed as it is, and in the backlight off section III, the corresponding lamp of the backlight device is turned off.

In the transition period from odd frame to even frame, only polarity reversal occurs and the data voltage is the same, thus minimizing luminance loss by securing a blinking area through the corresponding lamp-off of the backlight without inserting black data, and also for even frame After this is completed, the black data is inserted before the next data is input, thereby substantially minimizing the influence of the previous data image. In this case, black data of the same size (time interval) as the black data is inserted before the start of the odd frame and before the end of the even frame in order to balance the DC balance between the odd frame and the even frame.

According to the driving method of the liquid crystal display device as described above in detail, while minimizing excessive loss of luminance in the data blinking method, the backlight control method eliminates unevenness and synchronization error of the blinking area for each line and finely blocks the blinking area. Can be controlled.

Claims (9)

Dividing each odd and even frame into a start section, an image display section, and an end section, and inserting black data into the start section of the odd frame, which is the first frame; Turning off the backlight during the end of the odd frame and the start of the even frame; And  And inserting black data during an end period of the even frame and the start period of the odd frame. delete The method of claim 1, And the end section and the start section have the same size with respect to time. delete delete delete Dividing each odd and even frame into a start section, an image display section, and an end section, and turning off the backlight in the start section of the odd frame, which is the first frame; Inserting black data during an end period of the odd frame and a start period of the even frame; And  And turning off the backlight during the end of the even frame and the start of the odd frame. delete The method of claim 7, wherein The start division period and the end division period have the same size with respect to time.

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