KR20100080038A - Blue phase mode liquid crystal display device and method of driving thereof - Google Patents

Abstract

PURPOSE: A blue phase mode liquid crystal display device and a driving method preventing the degradation of image quality by the generation of the hysteresis are provided to implement identical luminance by changing data signal according to blue phase mode liquid crystal display device. 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. The data signal provided to the liquid crystal panel is changed. A timing controller(108) applies identical voltage to the liquid crystal panel. A data signal converter controls the voltage applied to the liquid crystal.

Description

Blue phase mode liquid crystal display and its driving method {BLUE PHASE MODE LIQUID CRYSTAL DISPLAY DEVICE AND METHOD OF DRIVING THEREOF}

The present invention relates to a blue phase mode liquid crystal display device and a driving method thereof, and more particularly, to a blue phase mode liquid crystal display device and a driving method thereof capable of preventing hysteresis.

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 a fast response speed, while there is a problem in that hysteresis occurs in the voltage and luminance characteristic curves.

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.

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above, and an object of the present invention is to provide a blue phase mode liquid crystal display device and a method of driving the same, which can always achieve the same brightness by converting the data signal according to the application form of the data signal.

In order to achieve the above object, a blue phase mode liquid crystal display device according to the present invention comprises 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 for converting the data signal supplied to the liquid crystal panel to apply the same voltage to the liquid crystal panel when the gray voltage increases and when the gray voltage decreases.

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 data signal conversion unit for converting a signal according to a direction in which a gray voltage increases or decreases in a data signal to adjust a voltage applied to the liquid crystal panel; And a control signal generator for generating a control signal.

The data signal converter may include a signal analyzer configured to analyze a data signal applied to the liquid crystal panel; A signal determining unit determining whether a data signal is applied in a direction in which the gray voltage is increased or in a direction in which the gray voltage is increased based on the information analyzed by the signal analyzer; And a signal converting unit converting the voltage of the data signal in accordance with the rise and fall of the gray voltage of the data signal determined by the signal determining unit.

In addition, the driving method of the blue phase mode liquid crystal display device according to the present invention comprises the steps of analyzing a data signal applied to the liquid crystal panel; Determining whether a data signal applied to the liquid crystal panel is applied in a direction of increasing or decreasing a gray voltage based on the information input from the data signal analyzer; And converting the voltage of the data signal as the gray voltage of the data signal rises and falls.

In the present invention, since the same luminance can be realized at all times by converting the data signal in accordance with the application form of the data signal, it is possible to prevent deterioration in image quality due to hysteresis.

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. . 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. Hysteresis due to this can be eliminated.

However, even with the optimal combination of materials, it is impossible to completely eliminate hysteresis, and it is also very difficult to find the conditions for the optimal combination of materials.

In the present invention, the hysteresis is prevented by changing the data voltage applied to the liquid crystal panel rather than removing the hysteresis by changing the combination of materials as described above.

In the luminance and voltage curves shown in FIG. 3, hysteresis results in different luminance when the voltage increases and decreases. Therefore, if the voltage can be applied differently in the voltage increasing direction and the voltage decreasing direction, The hysteresis that occurs between the reductions can be eliminated.

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 the present invention.

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

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 a liquid crystal layer (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 of the liquid crystal layer injected between the first substrate and the second substrate is a blue phase mode liquid crystal and 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 detects an input direction of the data signal and a data alignment unit 112 for aligning a data signal supplied from a system (not shown), and transmits a control signal to the data driver 106 according to the application direction of the data signal. And a data signal converter 120 for converting the data signal and a control signal generator 116 for generating a predetermined control signal.

The data sorter 112 aligns the data signal supplied from the system and supplies the data signal to the data driver 106.

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.

By controlling the gate control signal and the data control signal, the gate driver 104 outputs a scan signal to the plurality of gate lines GL0 to GLn, and the data driver 106 generates a plurality of data lines DL1 to DLm. Through the data signal is output to each pixel.

The data signal converter 120 converts different data signals according to the input form of the data signal so that different data signals are applied to the liquid crystal panel 102. The structure of the data signal converter 120 is shown in FIG. have.

As shown in FIG. 5, the data signal converter 120 may include a storage unit 128 for storing voltage and luminance information of a rising curve and a falling curve of a voltage versus luminance curve, and data applied to the liquid crystal panel 102. A signal analyzing unit 122 analyzing a signal and a signal determining unit determining whether a data signal is applied in a direction in which a voltage increases or decreases based on the information analyzed by the signal analyzer 122 ( 124 and a signal conversion for converting the voltage of the data signal based on the information stored in the storage unit 128 and supplying the data driver 106 as the voltage rise and fall of the data signal determined by the signal determination unit 124. Section 126.

The signal analyzer 122 analyzes the voltage of the data signal applied to the liquid crystal panel 102, and the signal determiner 124 increases the voltage of the data signal based on the information input to the signal analyzer 122. Determine if it is or is it decreased. That is, when the gray voltage increases at an initial low gray state voltage, it is determined that the voltage is applied in a direction of increasing, and when the gray voltage decreases again to a low gray voltage, it is determined that the voltage is applied in a direction of decreasing. .

The signal converter 126 converts the gray voltage of the data signal according to the information determined by the signal determiner 124. In this case, the signal converter 126 changes the signal using the information stored in the storage unit 128.

Table 1 shows the information stored in the storage unit 128 in detail. As shown in Table 1, the storage section stores the voltage band luminance information of the rising curve R and the falling curve F of the voltage versus luminance curve.

Voltage (V) Luminance R (nit) Luminance F (nit) 0 0.23 0.32 5 0.21 0.4 10 0.22 0.62 15 0.39 1.2 20 0.96 2.49 25 2.24 5.01 30 4.56 9.42 35 8.15 16.1 40 13.33 25.01 45 20.02 34.24 50 27.84 42.42 55 35.97 48.51 60 43.5 51.81 65 49.2 52.7 70 52.3 51.52 75 52.9 49.11 80 51.1 46.08 85 47.63 42.74 90 43.21 39.3 95 38.37 36.11 100 33.7

A method of removing hysteresis by converting a data signal using information stored in the storage unit 128 will now be described.

 The signal converter 126 converts the gray voltage of the data signal using the data of the voltage versus luminance curve. In this case, the signal converter 126 selects one of the rising curve R and the falling curve F of the voltage-to-brightness curve and converts the signal based on this.

For example, when the rising curve R is selected, if it is determined that the data signal is applied to the signal determining unit 124 in the direction in which the gray voltage of the data signal increases, the original signal, that is, the voltage in the rising state is left as it is. Is authorized. If the signal determining unit 124 determines that the data signal is applied in the direction in which the gray voltage of the data signal decreases, the voltage of the data signal is converted and applied. That is, the voltage corresponding to the falling curve F is converted into a voltage corresponding to the rising curve R and applied. For example, when a voltage corresponding to a luminance of 52.7 nits is applied, the voltage corresponding to the falling curve F is 65 V, but the data signal is converted to remove the hysteresis from the rising curve R to raise the rising curve ( In R), a voltage corresponding to a value (62.9 nits) similar to the luminance of 52.7 nits is applied to 75 V. As such, since the voltage corresponding to the rising curve R is always applied to the liquid crystal panel 102 as the data signal is converted, hysteresis can be suppressed.

On the contrary, in the case where the falling curve F is used as a reference, when the signal determining unit 124 determines that the data signal is applied in the direction in which the gray voltage of the data signal decreases, the original signal, that is, the voltage in the decreasing state is returned. Apply as is. If the signal determining unit 124 determines that the data signal is applied in the direction in which the gray voltage of the data signal increases, the signal decision unit 124 converts the voltage of the data signal into a voltage corresponding to the falling curve.

Thus, after determining the reference curve, by converting the data signal and applying the converted signal to the liquid crystal panel, the voltage-to-brightness curve is represented by only one of the rising curve R or the falling curve F, thereby preventing hysteresis. You can do it.

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 the present invention;

5 is a block diagram illustrating a structure of a signal converter of FIG. 4.

Claims (7)

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 for converting a data signal supplied to the liquid crystal panel to apply the same voltage to the liquid crystal panel when the gray voltage increases and when the gray voltage decreases. 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 data signal conversion unit for converting a signal according to a direction in which a gray voltage increases or decreases in a data signal to adjust a voltage applied to the liquid crystal panel; And Blue phase mode liquid crystal display device comprising a control signal generation unit for generating a control signal. The method of claim 1, wherein the data signal converter, A signal analyzer which analyzes a data signal applied to the liquid crystal panel; A signal determining unit determining whether a data signal is applied in a direction in which the gray voltage is increased or in a direction in which the gray voltage is increased based on the information analyzed by the signal analyzer; And And a signal converting unit converting the voltage of the data signal in accordance with the rise and fall of the gray voltage of the data signal determined by the signal determining unit. 4. The blue phase mode liquid crystal display of claim 3, wherein the data signal converter further includes a storage configured to store voltage and luminance information of a rising curve and a falling curve of a voltage-to-brightness curve. Analyzing a data signal applied to the liquid crystal panel; Determining whether a data signal applied to the liquid crystal panel is applied in a direction of increasing or decreasing a gray voltage based on the information input from the data signal analyzer; A method of driving a blue phase mode liquid crystal display device comprising converting a voltage of a data signal in response to a rising and falling gray voltage of a data signal. The method of claim 5, wherein the converting the voltage of the data signal comprises applying the original voltage as it is when the data signal is applied in a direction in which the gray voltage of the data signal increases. And converting the voltage of the data signal into a voltage corresponding to a rising curve when the data signal is applied in a direction in which the gray voltage of the data signal decreases. The method of claim 5, wherein the converting the voltage of the data signal comprises applying the original voltage as it is when the data signal is applied in a direction in which the gray voltage of the data signal decreases when the reference curve is a curve in which the gray voltage falls. And converting the voltage of the data signal into a voltage corresponding to a falling curve when the data signal is applied in a direction in which the gray voltage of the data signal is increased.

Images