KR20100080037A - Blue phase mode liquid crystal display device and method of driving thereof - Google Patents

Abstract

PURPOSE: A driving method of the liquid crystal display device and a blue page mode liquid crystal display device which effectively prevents the degradation of the picture quality is provided to prevent hysteresis by inserting black data signal into real data signal. CONSTITUTION: A liquid crystal panel(102) includes a blue phase mode liquid crystal. A gate driver(104) and a data driver(106) drive the liquid crystal panel. A timing controller(108) generates black signal inserted into real data signal of the data signal and real data signal. A black data generator generates the black data signal. The black data signal is provided to data driver.

Description

BLUE PHASE MODE LIQUID CRYSTAL DISPLAY DEVICE AND METHOD OF DRIVING THEREOF

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue page mode liquid crystal display device and a driving method thereof, and more particularly, to a blue page mode liquid crystal display device and a driving method thereof capable of effectively preventing deterioration of image quality.

Recently, with increasing interest in information display and increasing demand for using a portable information carrier, a lightweight flat panel display (FPD), which replaces a conventional display device, a cathode ray tube (CRT), is used. The research and commercialization of Korea is focused on. In particular, the liquid crystal display (LCD) of the flat panel display device is an image representing the image using the optical anisotropy of the liquid crystal, is excellent in resolution, color display and image quality, and is actively applied to notebooks or desktop monitors have.

The liquid crystal display is largely composed of a color filter substrate as a first substrate, an array substrate as a second substrate, and a liquid crystal layer formed between the color filter substrate and the array substrate.

In this case, the color filter substrate is formed between a color filter composed of a plurality of sub-color filters for implementing red (R), green (G), and blue (B) colors and the sub-color filter. A black matrix for dividing and blocking light passing through the liquid crystal layer, and a transparent common electrode for applying a voltage to the liquid crystal layer.

The array substrate may include a plurality of gate lines and data lines arranged vertically and horizontally to define a plurality of pixel regions, a thin film transistor (TFT) which is a switching element formed at an intersection of the gate lines and the data lines, and the The pixel electrode is formed on the pixel region.

The color filter substrate and the array substrate configured as described above are joined to face each other by sealants formed on the outer side of the image display area to form a liquid crystal display panel. The color filter substrate and the array substrate are bonded to each other by the color filter substrate or the substrate. It is made through a bonding key formed on the array substrate.

In this case, the above-described liquid crystal display device represents a twisted nematic (TN) type liquid crystal display device which drives the nematic liquid crystal molecules in a direction perpendicular to the substrate, and the liquid crystal display device of the type has a viewing angle of 90 degrees. It has the disadvantage of being too narrow. This is due to the refractive anisotropy of the liquid crystal molecules because the liquid crystal molecules oriented horizontally with the substrate are oriented almost perpendicular to the substrate when a voltage is applied to the liquid crystal display panel.

In this regard, an in-plane switching (IPS) type liquid crystal display device has been developed in which the liquid crystal molecules are driven in a horizontal direction with respect to the substrate to improve the viewing angle to 170 degrees or more. Meanwhile, a blue phase mode liquid crystal display device having a response speed of about 1 ms and a high speed image of 240 Hz or more has been developed. Hereinafter, the blue phase mode liquid crystal display device will be described in detail with reference to the accompanying drawings.

1 is an exemplary diagram showing a phase conversion of a liquid crystal according to temperature, and FIG. 2 is an exemplary diagram showing a driving method of a blue phase mode.

Referring to FIG. 1, the blue phase mode is a phase observed only in a high chiral liquid crystal material first discovered by Reinitzer in 1888, and isotropic and chiral nematic phases are generated by electric fields. Switching device.

Referring to FIG. 2, such a blue phase mode applies an IPS technology in view of driving characteristics.

That is, in the off state, the blue phase is black in the polarizers perpendicular to each other in an isotropic state, and when the on phase is in the on state, the blue phase liquid crystal is rearranged in a horizontal electric field direction by applying voltage. White can be realized using the birefringence property of.

The liquid crystal display device using the blue phase mode has the advantage of not needing rubbing and fast response speed. On the other hand, hysteresis occurs in the voltage and luminance characteristic curves and the luminance increases in the black state.

That is, as shown in FIG. 3, the same luminance cannot be exhibited at the same voltage due to the shift of the characteristic curve during the voltage rise and the voltage fall. In Fig. 3, hysteresis of about 5-6V occurs at voltage rise R and voltage drop F at a transmittance T of about 50% so that voltage rise R and voltage drop at the same voltage ( Since different luminance is implemented in F), image quality is distorted.

In addition, there is a problem in that the black brightness is increased at a certain viewing angle rather than the front, so that contrast is lowered and image quality is lowered.

An object of the present invention is to provide a blue phase mode liquid crystal display device and a driving method thereof, which can prevent hysteresis by inserting a black data signal into a real data signal.

Another object of the present invention is to provide a blue phase mode liquid crystal display device and a method of driving the same, which increases the gray value of the data signal applied to the liquid crystal panel and decreases the brightness of the backlight to prevent black brightness from increasing and the contrast ratio is improved. .

In order to achieve the above object, a liquid crystal display device according to an aspect of the present invention is a liquid crystal panel comprising a blue phase mode liquid crystal; A gate driver and a data driver for driving the liquid crystal panel; And a timing controller which generates a real data signal supplied to the liquid crystal panel and a black signal inserted in front of the real data signal of the data signal and provides the data signal to the data driver.

The timing controller may include a data alignment unit for arranging a real data signal supplied from a system to supply the data driver to the data driver; A black data generator which generates a black data signal having a gray level of 0 and supplies the black data signal to the data driver; And a control signal generator for generating a control signal, wherein the black data signal is 5-90% of one frame.

In addition, a blue phase mode liquid crystal display device according to another aspect of the present invention includes a liquid crystal panel including a blue phase mode liquid crystal; A gate driver and a data driver for driving the liquid crystal panel; And a timing controller that increases the gray level of the data signal supplied to the liquid crystal panel and decreases the brightness of the backlight when the brightness of the black state increases due to the data signal supplied to the liquid crystal panel. do.

The timing controller includes a data alignment unit for aligning the data signal supplied from the system and supplying the data signal to the data driver; A control signal generator for generating a control signal; And a backlight controller configured to apply a control signal to the data driver and the backlight to control the gray level of the data signal applied to the liquid crystal panel and to control the brightness of the backlight.

In the present invention, hysteresis can be prevented by inserting the black data signal into the real data signal. In addition, in the present invention, the gray level of the data signal applied to the liquid crystal panel is increased, and the brightness of the backlight is decreased, thereby preventing black brightness from increasing and improving the contrast ratio.

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

Hysteresis occurs in the blue phase mode liquid crystal display device due to the phenomenon of structural change of the bulk region due to the intermolecular cooperation due to the addition of the polymer network and the chiral dopant of the liquid crystal in the blue phase. . In addition, the increase in the black luminance in the blue phase mode liquid crystal display device is caused by light scattering in the polymer domain of the polymerization crosslinking, and the scattered light is transmitted through the liquid crystal panel in the black state.

Therefore, in order to prevent such an increase in hysteresis and black luminance, the liquid crystal layer is formed by finding an optimal combination condition of materials, thereby changing the structure of the bulk region by intermolecular cooperation due to the addition of polymer crosslinking and chiral dopant. It is possible to eliminate the increase in black brightness due to the hysteresis and the scattering of the polymer domain.

However, even if the combination of materials is optimal, it is impossible to completely prevent the increase in hysteresis and black brightness, and it is very difficult to find the conditions of the optimum combination of materials.

In the present invention, the hysteresis is not eliminated by changing the combination of materials as described above, but the data voltage applied to the liquid crystal panel is configured differently to prevent the increase in hysteresis and black brightness.

In the luminance and voltage curves shown in FIG. 3, the hysteresis causes the luminance to increase and decrease, so that the voltage can be applied only in the voltage increasing direction or the voltage decreasing direction, so as to increase or decrease the voltage. It is possible to eliminate the hysteresis that occurs in the.

The present invention prevents hysteresis from occurring in the luminance and voltage curves as described above, and the present invention will be described in detail below.

4 is a view showing the structure of a blue phase mode liquid crystal display device according to a first embodiment of the present invention.

As shown in FIG. 4, the blue phase mode liquid crystal display device according to the first embodiment of the present invention includes a liquid crystal panel 102 displaying a predetermined image and a gate driver for driving the liquid crystal panel 102. 104 and the data driver 106, the timing controller 108 controlling the gate driver 104 and the data driver 106, and the backlight 110 generating predetermined light and irradiating the liquid crystal panel 102. It is configured to include).

In the liquid crystal panel 102, a plurality of gate lines GL0 to GLn and data lines DL1 to DLm are arranged, and a thin film transistor TFT and a pixel electrode (not shown) are formed at an intersection thereof. The liquid crystal panel 102 includes first and second substrates and liquid crystals (not shown) injected between the first and second substrates. The plurality of gate lines GL0 to GLn, the data lines DL1 to DLm, and the thin film transistor TFT are formed on a first substrate, and a color filler layer is formed on the second substrate.

The liquid crystal injected between the first substrate and the second substrate is a blue phase mode liquid crystal, which is an intermediate phase liquid crystal between nematic phase and isotropic.

In this case, an electric field horizontal to the surfaces of the first and second substrates is applied to the liquid crystal layer. That is, the pixel electrode and the common electrode which are arranged in parallel to each other are arranged on the pixels of the first substrate of the liquid crystal panel so that the gate signal is applied to the thin film transistor TFT through the gate lines GL0 to GLn. ) Is activated, the data signal is applied to the pixel electrode of the pixel through the data lines DL1 to DLm, and a transverse electric field parallel to the surface of the first substrate is applied to the liquid crystal layer.

The timing controller 108 includes a data alignment unit 112 for arranging data signals supplied from a system (not shown), a black data generation unit 114 for generating a black data signal having a gray level of 0, and a predetermined control signal. It consists of a control signal generation unit 116 for generating a.

The data sorter 112 sorts and supplies a real data signal supplied from the system to the data driver 106. The real data signal refers to a data signal displayed as an actual image on the liquid crystal panel 102.

The black data generator 114 generates a black data signal having a gray level of 0 and supplies it to the data driver 106. The black data signal is displayed on the liquid crystal panel 102 for about 5% to 90% of one frame.

The control signal generator 116 generates a gate control signal and a data control signal using a vertical / horizontal synchronization signal (Vsync / Hsync), a data enable (DE) signal, and a predetermined clock signal supplied from the system. . The gate control signal controls the gate driver 104, and the data control signal controls the data driver 106.

The gate control signal controls to sequentially drive the plurality of gate lines GL0 to GLn. When the gate control signal is supplied to the gate driver 104, the gate driver 104 supplies a scan signal to the plurality of gate lines GL0 to GLn for one horizontal section 1H.

The black data signal is supplied to the plurality of data lines DL1 to DLm for a predetermined time of one horizontal section 1H to which the scan signal is supplied, and the real data signal is supplied for the remaining time. That is, a real data signal and a black data signal are supplied to the plurality of data lines DL1 to DLm during one horizontal section 1H, which is one scan signal width.

As a result, by dividing one frame by a specific ratio, a real data signal is input to a predetermined part of one frame and a black data signal is input to the other part to secure a holding time of the data lines DL1 to DLm.

In the present invention, the black data signal is included in the data signal of one frame as described above in order to apply the signal only in a direction in which the voltage always increases to the pixel. That is, as shown in FIG. 5, the black data is included in the front of the data signal of one frame so that the black data voltage is applied before the actual data voltage is applied.

As the black data signal is included, the voltage is always applied only in the increasing direction. That is, as shown in FIG. 6A, when 64 gray voltage is applied to the liquid crystal panel and 250 gray voltage is applied to the liquid crystal panel, the voltage increases and then decreases, and thus the voltage increases. In this case, luminance is implemented along the rising curve R, and when falling, the luminance is implemented along the falling curve F. Even when the same 64 gray voltage is applied, other luminance is implemented in the image.

On the other hand, in the present invention, as shown in Fig. 6B, black data is inserted between the data voltages. In the blue phase mode, black data refers to an OV state where no voltage is applied. Therefore, the voltage is applied in the direction of increasing voltage from OV to 64 gray voltage, and is applied in the direction of increasing voltage to 250 gray voltage after the OV state of the black data is again applied. In addition, after the application of the 250 gray voltage, the voltage falls back to OV and is applied in the direction in which the voltage increases from OV to 64 gray voltage.

In other words, in the present invention, since the voltage is applied to the liquid crystal panel in a direction in which the voltage always increases as the black data is inserted, since the luminance is always implemented along the rising curve R in the luminance band voltage curve, the voltage rises and It is possible to prevent the occurrence of the luminance difference due to the fall.

7 is a view showing the structure of a blue phase mode liquid crystal display device according to a second embodiment of the present invention.

In this case, the description of the same configuration as in the first embodiment will be omitted, and only the other configuration will be described.

As shown in FIG. 7, the blue phase mode liquid crystal display device according to the second embodiment of the present invention includes a liquid crystal panel 202 for displaying a predetermined image and a gate driver for driving the liquid crystal panel 202. 204 and the data driver 206, the timing controller 208 controlling the gate driver 204 and the data driver 206, and the backlight 210 for generating predetermined light and irradiating the liquid crystal panel 202. It is configured to include).

The timing controller 208 includes a data alignment unit 212 for aligning data signals supplied from a system (not shown), a control signal generation unit 216 for generating a predetermined control signal, and a control signal in the backlight 210. It is composed of a backlight control unit 220 for controlling the backlight 210 by applying a.

The data sorter 212 aligns the data signals supplied from the system and supplies them to the data driver 206.

The control signal generator 216 generates a gate control signal and a data control signal using a vertical / horizontal synchronization signal (Vsync / Hsync), a data enable (DE) signal, and a predetermined clock signal supplied from the system. The gate control signal controls the gate driver 204, and the data control signal controls the data driver 206.

The backlight controller 220 adjusts the brightness of the backlight 210 according to the data signal supplied from the data driver 206 to the liquid crystal panel 202. Typically, in the blue phase mode liquid crystal display device, the luminance in the black state is increased, and the backlight controller 220 adjusts the brightness of the backlight 210 according to the data signal supplied to the liquid crystal panel 202.

8 is a diagram illustrating the structure of the backlight controller 220. As illustrated in FIG. 8, the backlight controller 220 may include a data signal analyzer 222 for analyzing a data signal applied to the liquid crystal panel 202, and the information input from the data signal analyzer 222. A signal converting unit 224 for converting a signal applied to the liquid crystal panel 202 to increase a gray value of the applied signal, a filtering unit 228 for filtering a signal output from the signal converting unit 224, and The backlight signal converter 226 converts a signal applied to the backlight based on the information input from the data signal analyzer 222 and adjusts the brightness of the backlight.

The data signal analyzer 222 analyzes the gray value of the input data signal of the liquid crystal panel 202 and outputs information indicating whether the luminance in the black state is increased to the signal converter 224, and the signal converter 224. ) Outputs a signal to the data driver 206 based on the information analyzed by the data signal analyzer 222 and applies a data signal having a gray scale value increased from the data driver 206 to the liquid crystal panel 202. Do it. In addition, the backlight signal converter 226 reduces the brightness of the backlight by outputting a signal to the backlight 210 based on the information analyzed by the data signal analyzer 222.

In the liquid crystal display device having the above-described configuration, when the data signal supplied to the liquid crystal panel 202 is analyzed and the data signal is a gray level of increasing black luminance, the data signal having the increased gray level value is supplied to the liquid crystal panel 202 so as to be blue. The transmittance of light passing through the phase mode liquid crystal panel 202 is improved to increase the luminance of light passing through the liquid crystal panel 202. At the same time, the control signal is output to the backlight to reduce the brightness of the backlight by the brightness of the light by improving the transmittance of the liquid crystal panel 202.

Therefore, since the supply of light by the backlight is reduced, the scattering of light by the polymer domain of the polymerization crosslinking is reduced, so that the leakage of light in the black state is reduced, thereby reducing the black luminance. At the same time, since the luminance of the light due to the improvement of the transmittance of the liquid crystal panel 202 is increased, the luminance in the entire liquid crystal panel 202 can be kept the same. In other words, the overall luminance is the same, but the black luminance is greatly reduced, so that the contrast ratio of the liquid crystal panel 202 is improved.

Another example or modified example of the present invention is that a liquid crystal display device using the basic concept of the present invention can be easily created by anyone in the technical field to which the present invention belongs, and should be included in the scope of the present invention.

1 is an exemplary view showing a phase conversion of a liquid crystal with temperature.

2 is an exemplary view showing a driving method of a blue phase mode.

3 is a graph showing hysteresis occurring in a conventional blue phase mode liquid crystal display device.

4 is a view showing the structure of a blue phase mode liquid crystal display device according to a first embodiment of the present invention;

5 is a waveform diagram showing a signal into which a black data signal is inserted.

6A is a diagram showing a signal application form in a conventional blue phase mode liquid crystal display device;

6B is a view showing a signal application form in a blue phase mode liquid crystal display device according to the present invention;

7 is a view showing the structure of a blue phase mode liquid crystal display device according to a second embodiment of the present invention;

8 is a block diagram illustrating a structure of a backlight control unit of FIG. 7.

Claims (9)

A liquid crystal panel including a blue phase mode liquid crystal; A gate driver and a data driver for driving the liquid crystal panel; And And a timing controller configured to generate a real data signal supplied to the liquid crystal panel and a black signal inserted in front of the real data signal of the data signal and provide the black signal to the data driver. The method of claim 1, wherein the timing controller, A data alignment unit for aligning the real data signals supplied from the system and supplying the real data signals to the data driver; A black data generator which generates a black data signal having a gray level of 0 and supplies the black data signal to the data driver; And Blue phase mode liquid crystal display device comprising a control signal generation unit for generating a control signal. The blue phase mode liquid crystal display of claim 1, wherein the black data signal is 5-90% of one frame. Generating a real data signal; Generating a black data signal; Inserting the black data signal in front of the real data signal; And A blue phase mode liquid crystal display device driving method comprising applying a data signal into which a black data signal is inserted into a blue phase mode liquid crystal panel. A liquid crystal panel including a blue phase mode liquid crystal; A gate driver and a data driver for driving the liquid crystal panel; And When the luminance of the black state is increased by the data signal supplied to the liquid crystal panel, the blue controller includes a timing controller that increases the gray level of the data signal supplied to the liquid crystal panel and decreases the brightness of the backlight to prevent an increase in the black luminance. Phase mode liquid crystal display device. The method of claim 5, wherein the timing controller, A data alignment unit for aligning the data signal supplied from the system and supplying the data signal to the data driver; A control signal generator for generating a control signal; And A blue phase mode liquid crystal display device comprising: a backlight controller configured to apply a control signal to a data driver and a backlight to control a gray value of a data signal applied to the liquid crystal panel and to control brightness of a backlight. The method of claim 6, wherein the backlight control unit, A data signal analyzer for analyzing a data signal applied to the liquid crystal panel; A signal converter for converting a signal applied to the liquid crystal panel based on the information input from the data signal analyzer to increase a gray value of the applied signal; And A blue phase mode liquid crystal display device comprising: a backlight signal converter configured to control a brightness of a backlight by converting a signal applied to the backlight based on information input from a data signal analyzer. The blue phase mode liquid crystal display of claim 7, wherein the backlight control unit further comprises a filtering unit filtering the signal output from the signal conversion unit. Analyzing a data signal applied to the liquid crystal panel; When the black luminance increases in the liquid crystal panel based on the information input from the data signal analyzer, converting a signal applied to the liquid crystal panel to increase a gray value of the applied signal; And And converting a signal applied to the backlight to reduce the brightness of the backlight when the black luminance increases in the liquid crystal panel based on the information input from the data signal analyzer.

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